BE485599A - - Google Patents

Description

       

   <Desc / Clms Page number 1>
 



  "Heat-insulating materials and their manufacturing process *
The present invention relates to a new type of heat-insulating material, as well as to improved compositions and their preparation methods.



   In the manufacture and use of insulating materials and in particular heat insulators for maintaining high temperatures, it is necessary to provide a high temperature material "for those surfaces where high temperatures prevail, for example temperatures above 315 However, these high temperature insulating materials exhibit other characteristics. For example, they are, as a rule, of high density and are, therefore, heavy. Furthermore, they do not retain usually not their shape or their thermal conductivity is greater than desired, and the price is also comparatively high.

 <Desc / Clms Page number 2>

 



   It would be possible to employ a sufficient thickness of such "high temperature" insulating material so as to insulate high temperature surfaces. However, we do not. It is generally accepted that this would result in too much insulation weight, too thick a coating (with too large an outer surface in terms of radiation and heat loss) and too great an expense. This would therefore constitute an installation which, in general, would not be satisfactory.



   For these reasons, it has become common practice in the insulation of high temperature surfaces to apply a heat insulating material at high temperature, capable of withstanding the action of heat, and of sufficient thickness. so that the range or scale of temperatures, going from that of its sides where there is a high temperature to that where there is a low temperature, ensures a temperature of about 315 C, or a little less, on the low temperature side. This temperature is set as a criterion by the upper safe temperature limit for low or lower temperature insulating materials available, such as, for example, cast magnesia (85%).

   Insulating materials of the "lower temperature" type have the advantage of having a lower bulk density and lower heat conductivity.



  Consequently, they have a greater thermal or calorific power of insulation, with regard to surfaces or zones exposed to the outside temperature or to a lower temperature of heat insulating installations of this kind. However, these materials have poor shape retention or tensile strength and are not able to withstand high temperatures. Thus, for example, magnesia has 75%

 <Desc / Clms Page number 3>

 tends to calcine and weaken or disintegrate at temperatures above 315 C.



   In addition, the "high temperature" and "low temperature" types of heat insulating materials (but especially the latter), are weak and are also prone to weaken or soften and disintegrate further under the action. moisture such as water in ships' holds or condensate, water vapor, etc., in closed buildings or towers. Therefore, when it is used in such places, special precautions and constant care are necessary, if it is to be avoided or to prevent their rupture and ineffectiveness.



   It is therefore, among other things, an object of the present invention to provide an improved kind of insulating materials which can be applied to surfaces at high temperature, which retain their shapes, which are also of low conductivity. calorific and of low bulk density and which are capable of constituting the entire insulation. It also aims to provide an insulating material which is solid a. the dry state and which is also resistant to humidity, with the minimum loss or reduction of the other properties which it should possess.



   Other objects of the invention will emerge from the description which follows.



   In the heat insulation industry, it is assumed that, quite independently of the intrinsic heat conductivity of a material, it could see its effective conductivity drop when it had many voids or air spaces, especially if the voids individually are so small, that the convection air currents generated in these voids can be neglected, as in finely divided powders. Many heat insulators have also been manufactured using

 <Desc / Clms Page number 4>

 Porous Materials Such a structure is suitable for facilitating resistance to the free conductivity of heat through these materials.

   As a general rule, however, the volume of these agglutinated powders and the walls of porous structure is relatively large compared to the voids or air spaces they contain. It follows that such insulating materials have a relatively high bulk density. Obviously, this is the case in present-day types, in which heat insulators of an average weight have a bulk density of about 320 kg per cubic meter, while even heat insulators of a light weight " have a bulk density of 224 to 256 kg per cubic meter.



   Although heat insulators have sometimes been manufactured with a density as low as 192 kg per cubic meter, this has only been by sacrificing some of the basic requirements, even for low temperature insulation. As a result, such products can only be used for certain special applications.



   It has been proposed to employ as heat insulating materials various kinds of fibers in which the voids or air spaces are partially enclosed (rather than completely blocked) by the masses of interlaced fibers. When this type of heat-insulating material is used, the result obtained is necessarily limited by the type of fibers (such as natural or artificial fibers, etc.) and by the operations which are necessary to give these fibers the consistency and desired shapes. It was necessary to use binders or agglutinants to give the mass the desired shape and to keep the shaped mass its shape and (or) its volume.

   Until. presently, these binders have been employed usually in the liquid state and have, therefore, to a large extent negated the advantages of

 <Desc / Clms Page number 5>

 the fibrous structure. The liquid binder tends to fill the voids and spaces which exist between the fibers and to modify the nature of the solids, transforming the mass state of loose fibers and narrow capillary air spaces existing between these fibers, in that of round air spaces, closed by solid partition walls, formed of fiber and binder.

   In structural terms, these materials are, therefore, similar to the bound or agglutinated powders and porous wall structures which have been described above, thus adding both weight and greater weight. heat conductivity to the product obtained as a result.



   Therefore, it can be said, in general, that previously manufactured insulators fall into several categories which, based on their composition and physical structure, are as follows:.



   I - There are first those which are composed of distinct, finely divided particles, which tend to agglomerate loosely and enclose large propor- tions of area, distributed among them under the form of numerous thin films, more or less continuous.



   For example, in calories per square centimeter per second and per centimeter of thickness: - carbon black (C = 0.00007), lime (0.00029), magnesia (0.00016 to 0.00046), magnesium carbonate (0.00023 to 0.00025), see sand (0.00093), sawdust (0.00012), charcoal (0.00012),
 EMI5.1
 Silicon carbide (0.0006), psil-o-eel "(0.00011).



   But, as these are inconsistent powders, they therefore do not have the power to retain their shape and therefore do not have any compressive or tensile strength.

 <Desc / Clms Page number 6>

 



   II - There are insulators which are made up of small solid particles, packed freely or tightly, and bound or agglutinated together in this respective situation by various means, leaving some of the air spaces free. These air spaces serve to impart to the mass taken as a whole a lower heat conductivity than the heat conductivity of the solid particles or of the binder per se. However, the volumes of the air spaces existing between the loose particles and their individual sizes and shapes are considerably altered by the binder employed, as noted above. Therefore, such insulating materials have a considerably greater heat conductivity than inconsistent, unaggregated powders.



   These insulating materials are as follows: Magnesia brick ................. (0.0027 to 0.0072) Silicon carbide brick ...... (0.032 to 0.027) Concrete brick .................... (0.0022)
It will be noted that the fact of binding or agglutinating the particles together makes it possible to mold the product which, after setting of the binder has a mass often possessing a high tensile and compressive strength and is, therefore, capable of retaining the shape that was given to him.

   However, the increase in bulk density and thermal conductivity is so much greater than that of loose particles, in the unaggregated state in which they are independent and spaced apart from each other, than their usefulness as insulators, in terms of efficiency, enter an entirely different order.

 <Desc / Clms Page number 7>

 



   III - The third type of insulator is that which is characterized by a cellular or vesicular structure. Instead of being constituted by solid particles, spaced apart by an inconsistent packing or stuffing, or by particles more or less agglutinated in this inconsistent mass, they form a continuous solid wall or of a material forming a body in which some l air is dispersed in the form of bubbles. These air bubbles are, therefore, surrounded or enclosed, more or less, or even completely, by solid matter.



   These insulating materials are: diatomaceous earth (0.00013), plaster (0.0007), refractory brick (0.00028 to 0, 0011), pressed diatomaceous earth bricks (0.0003), and lime (0.002).



   This type of insulation is characterized by relatively low heat conductivity or high strength, but not both. In addition, these materials are either products of natural formation which would require special shaping or products of relatively high bulk density.



   In these different types of insulators - in which the structure is that of (I) finely divided particles, inconsistently packed, or (II) of those particles bound or agglutinated together to form a compact mass, 'or still (III) of a continuous solid matter, containing dispersed voids or bubble-shaped spaces filled with gas - the conductivity of the mass as a whole, is above all that of the solid matter and is, therefore - quent, relatively high.



   Although the air spaces are small, they are nevertheless enclosed or surrounded by solids and are, therefore, conductive with regard to the air.

 <Desc / Clms Page number 8>

 transmission of heat by convection of the gases they contain, by radiation through them, and by conductivity around and through their marginal surfaces. In addition, the free surfaces of matter, in those structures retaining their shape - whether internally or externally spherical and, therefore, of a generally concave or convex character - will tend to be of a dense formation, as an inherent result of the conditions in which they were assembled and integrated.



  Their union, in many cases, will be, by their generic character, of the kind obtained by wetting by capillary action of solids and liquids.



   It follows that the insulating materials of these categories, while acquiring the properties which allow them to retain the forms in which they have been molded or shaped, as well as a greater power of resistance to traction and compression, at the same time considerably increased their heat conductivity and consequently lost a great deal of their thermal power. These insulating materials also have relatively high bulk densities and installations which are made with these materials are of corresponding high weight.



   IV. There is also a group of insulating materials which are characterized by the fact that they consist of fine and loose fibers, have a very low heat conductivity and therefore a great insulating power; these are, for example:
Asbestos fiber (0.00019), cork (0.00073 to 0.00013), raw cotton (0.000043), felted (0.000033), down (0.000093), felt ( 0.000087), balsam wool (0.000093), horsehair insulation composed of 75% horsehair and 25% jute (0.000093 50% horsehair - 50% jute (0, 000089).

 <Desc / Clms Page number 9>

 



   It should be noted that these loose fibrous masses have very low heat conductivity.



   This can be attributed to the dispersion of the fibers and their irregular relationship with the tenuous, complex, but continuous system of free spaces which exist between the fibers and which are filled with air.



     Air has a very low heat conductivity, especially when it occurs in small volumes which cannot circulate efficiently to be able to transfer heat by convection, namely 0.000068 calories per square centimeter at the air. second and per centimeter of thickness. However, loose fiber masses have no ability to retain their shape and have no tensile or compressive strength. On the contrary, they may tend to sag, even by virtue of their own weight, become denser, better conductors of heat and less thermo-insulating, while leaving a space above them. uninsulated air.



   V. The loose fibrous insulation materials have been formed into sheets possessing some tensile strength, but still lacking in compressive strength, yet possessing the power to retain their shape. It should be observed that these fibrous sheet materials have a relatively low heat conductivity and therefore have a high insulating power, although in general these properties are somewhat inferior to those of loose fibers. and that their satisfactory application in actual practice be limited.

   For example, we can cite:
Asbestos paper (0.0004 to 0.0006) blotting paper (0.00015), felt (0.000087), flannel (0.00023), horsehair cloth felt (0 , 000042), the

 <Desc / Clms Page number 10>

 cowhide (0.00042), chamois (0.00016), capok between sackcloth or paper (0.000083), eelgrass between kraft paper (0.000086), felted cattle hair (0 , 0000895) flax fibers between paper (0.000096) felted jute and asbestos fibers (0.000127), felted horsehair and asbestos fibers (0.000096), flax fibers 0 , 000096), flax fiber (0.00011), flax and rye fiber (0.00011) rock wool or glass wool (0.00009).



   These sheeted fibrous materials also lack the ability to retain their shape and lack tensile and compressive strength. In addition, with the exception of asbestos, rock wool, mineral wool and glass wool, they are of organic origin and, as a result, disintegrate or are flammable to high temperatures. They cannot, therefore, be used where molded or shaped insulation is required, nor at high temperatures. In addition, under the action of pressure, they can easily be given a compactness which they can also acquire, over time, under the effect of their own weight, which increases their heat conductivity as well as their density. apparent, which is undesirable.



   VI. Attempts have been made to bind or agglutinate these fibrous materials in a manner analogous to that which has been employed to bind or agglutinate the granular insulating materials or powders of Groups II and III described above. However, the same results and the same consequences increase, in particular a more compact structure, which results in a considerably increased apparent density of mass and a large effective conductivity of heat.

   These changes can be attributed to the putting of the fibrous mass into a compact form during the agglutination operations,

 <Desc / Clms Page number 11>

 the introduction of fillers between the fibers other than freely spaced apart; and the formation, on the adjacent fibers and between them, of a meniscus wetting the binder or agglutinating which constitutes, in the finished product, a sealing wall or membrane which continues continuously throughout the volume of the mass and which increases both the weight and the calorific conductivity of the whole.



   The present invention offers a new kind of insulation which is first of all mineral composition, resists high temperatures and is characterized by a fibrous, open and inconsistent structure, in which the fibers are arranged, at random and separated. or spaced apart by a system of capillary, fine and continuous air spaces.



  This insulator has the power to retain its shape and, with a bulk density of 192.240 kg per cubic meter, the thermal conductivity "C" of this new product approaches 0.0002. The fibers are united together at their interstices or points of contact, but not by clogging liquid binders or binders which, starting from a liquid, have solidified and therefore tend to bring the fibers together. and to form, for the air spaces, obstructing rounded limits.



  The artificially obtained and crystallized fibers are brought together by direct inherent entanglement of the fibers with each other and by joining with other preformed organic fibers or mineral fibrous crystals, such as asbestos, which are of a similar nature and behave similarly. the same way.



   On the basis of the present invention, it has been found that reagents - and more particularly mineral reagents - which are capable of forming by reaction cultures in the form of crystals of a fibrous nature, could

 <Desc / Clms Page number 12>

 be induced or permitted to develop fibrous formations of this kind in a predominantly, if not exclusively, and complete manner, by the creation of a state of dispersion of the reactants and, concurrently therewith, of a dispersion of preformed, finely divided, or spike fibers (i.e. fibers which already possess and (or) which develop before or during their preparation, a fibrous form, characteristically finely divided, which will be defined in more detail below),

   having a large amount of free, fibrous and fine ends, which serve as nuclei for the crystallization of the fiber-forming reagents and provide or facilitate the development of the latter in the form of fine crystals , and fibrous separated.



   The preformed activating fibers or spicules, which thus serve as instigators for the initial crystallization of the reaction products (which are in themselves capable of giving rise to fibrous products) direct their development in the crystalline form and can be organic or mineral. In the latter case, if suitably dispersed, the preformed fibers and the segregating crystals derived from the fiber-forming reagents can crystallize with one another and thus integrate to form a dispersed, continuous but filamentous agglomeration of spaced fibrous crystals.



   The expression "spiculation" as used in the description and the summary denotes a treatment of naturally fibrous materials, for example asbestos, by means of which the bundles in which these materials are usually found are separated in the longitudinal direction of. sufficient so that the resulting individual fibrous filaments exhibit, in cross section,

 <Desc / Clms Page number 13>

 dimensions ranging from 1/10 of a micron to 3 microns, in width or in thickness, at their ends or over their entire length. The degree to which this treatment can be carried out and its nature can be governed, inter alia, by the fibrous material employed, by the type of apparatus used, by the viscosity of the agent in which the treatment is carried out, and by the yield obtained.



   The term "spicules" as used throughout the description and summary denotes fibrous particles (such as those obtained by the "spiculation" treatment), which are characterized by this They have, at their ends, cross-sectional dimensions of 1 / 10th of a micron to 3 miBrons in width or thickness, and which, in relation to length, may be of different sizes.

   For example: - (A) in the case of complete asbestos speculation ,. in a medium of low viscosity, such as air or dilute aqueous suspensions, - spicules of 10 to 1000 microns, in which the dimensions indicated above persist over their entire length; in the case of partial spiculation of asbestos, such as in heating the fiber in more concentrated aqueous suspensions (1% # la% by weight) in which the spicules are typically 100 to 2000 microns in length, and are usually associated with a slight proportion of fibers of category (A);

   and (C) in the case of spiculation under the action of rapid swirling with a high concentration of asbestos in a liquid medium (for example 1% to 10% by weight, in water), as obtained in the apparatus shown at. FIG. 2, spi- cules comprising a small proportion of fibers whose lengths are those of category (A) and a higher proportion of fibers of lengths greater than 1000 microns

 <Desc / Clms Page number 14>

 and further characterized by scalloped or "brushed" ends having a number of small fibrous filaments whose individual dimensions, in cross-section at their ends, regardless of the width, range from 1 / 10th of a micron at 3 microns.



   The viscosity of the resulting aqueous suspensions, when the solids present are at the same degree of concentration, is a measure of the degree of speculation obtained.



   As stated above, the preformed, finely divided, spiculated fibers can be of an organic nature. In this case, although they are capable of fulfilling the same physical purpose of initiating crystallization from their free ends and distinct formation and growth as mineral fibrous crystals, the organic fibers, in such cases, however, will not integrate with them, in a coherent way, in the sense of continuity in the inherent physical structure, although they / present some degree of integration, by virtue of their physical adhesion with them, especially at their free ends.



   However, in either of these cases, when it is a question of preformed mineral or organic fibers, the crystals which form as a result of the reaction of the reagents present, can also develop freely between them. , at the location of their original points of contact and thus form an integral fibrous mass, in the entire volume of the dispersion in which they are contained :. The strength of the integrated filament system, obtained as a result, consists of the inherent cumulative tensile strength possessed by the crystals themselves and the organic and inorganic fibers which served as nuclei in the fibrous crystal formation.

 <Desc / Clms Page number 15>

 



   In either case, the system is that of reactants molecularly dissolved and (or) dispersed by colloidal route, capable of reacting in such a way as to form mineral crystals in the shape of characteristic fine needles or having fibrous and growing properties. in the manner of the wolverine (resembling the downs of thistles), which are selectively caused to undergo this reaction and to propagate this kind of growth at many points (often in the form of clusters of radial circular crystals) scattered separately from one another others in three dimensions; From these points, the crystals are free and kept free to extend in all directions through the liquid dispersion medium, throughout their reaction.

   This growth will preferably be impeded only as a result of contact with similar crystals forming under similar conditions of instigation and growth, after which they may together continue to grow where they come into contact with each other. They can also come into contact with the surfaces of the preformed fibers, with which they can grow or develop concurrently (by adhering to each other), at the point or points of contact between them, to form fibrous, solid crystals. .

   In either case of this contact growth, the liquid phase and hence the viscosities and the attached meniscus formations are not prevented by solidification but are replaced by the separation of Inherent crystalline growth of the reactants giving rise to fibers, and usually by a gel which subsequently takes on much less bulk.



   The predominant feature of the reaction mass, therefore, is that the reactants

 <Desc / Clms Page number 16>

 are presented at so many and finely dispersed points (at which their initial reaction and subsequent crystal formation may take place) by the dispersed ends of the spiculated fibers, that the crystallization and growth of each Crystalline fiber is in principle one-dimensional and, in cross-section, of substantially colloidal dimensions only, both per se, and in their contacts and intergrowths with each other.



     This is why the present invention has made it possible to observe that if reagents exhibiting the characteristic of being able to form products of fibrous crystal growth are subjected to conditions such that these products will be formed and that these fibrous crystals will be able to grow freely. , starting from widely spaced and dispersed points of origin, and being kept dispersed for at least a period of substantial growth, they will tend to form a mass of fine-fiber crystals.

   These crystals will have a large proportion of spaces or voids, will unite directly with these points of origin and also with other fibrous materials (without inclusions or occlusions of other different binders, such as adhesive binders. sifers, cohesive fusions, etc.), will develop their individual characteristics, consisting of possessing high tensile and compressive strengths (by virtue of their large surface-to-volume ratio and their superficial action.), and will remain separated by thin, elongated, continuous capillary spaces, rather than spherical, enclosed air spaces with solid, opposing surfaces;

   they will therefore have a low bulk density, relatively high compressive and tensile strengths, low heat conductivity,

 <Desc / Clms Page number 17>

 and, reciprocally, a great thermal insulation capacity.



   For this purpose, it has been found that lime and silica, for example, if they are in a finely divided state and capable of reacting with each other, for example in the form of an aqueous solution or a colloidal suspension, active or hydrated lime and active or hydrated silica tend to react - for example by direct application of heat and pressure - to form hydrated calcium silicate which is capable of forming suitable needle-shaped or fibrous crystals.



   In ordinary mixtures of lime and silica (such as lime-lime bricks), the product obtained as a result will have a high bulk density (eg 1920 kg per cubic meter). Under these conditions the reaction will also be more or less incomplete, because much of the silica is not available to react with the lime.



   But, if the lime is used in the form of quicklime, hydrated lime, or milk of lime, preferably containing a high proportion of active lime (for example soluble in sugar), the reaction will take place of a much more active and more complete way. When silica is finely divided, it reacts more, but its chemical condition is also important. It is preferably used in the form of "active" silica, such as, for example, in the form of diatomaceous earth or hydrated silica. The reaction is initiated and facilitated by water, steam, an increase in pressure, etc., and also by the condition of the lime, as in the controlled hydration of lime to produce milk. lime with the maximum activity.

   The reaction of lime and silica can be promoted, in accordance with the present invention, by

 <Desc / Clms Page number 18>

 so as to give as a result a complete transformation of the two materials into a mass of calcium silicate, a considerable proportion of which is in the state of crystals, in the form of separate needles and of hydrated calcium silicate of a new molecular form. It has now been found that the distribution of these needle-shaped or fibrous crystals can be favored and governed by the presence of suitably preformed, fibrous, spiculated and dispersed particles, or spicules, as has been said above, such as asbestos, paper fibers, and the like.

   Further, crystallization will tend to develop outward from those points of origin which are the free ends, and preferably freshly fractured, of preformed fibers. By this means, the fibrous crystals which form disperse and are kept dispersed by their own growth and by the speculation of the preformed fibers as well as by water (and water vapor) in which and at means of which they are formed: After evaporation of water vapor and residual water from between the mass of fine needles formed and fully crystallized, the voids are occupied by air. (There is also a huge shrinkage in the gel which usually forms during the reaction).

   As a result, the mass as a whole will contain a considerable volume of air, so that the bulk density may correspondingly be low and be considerably less than that of 'heavy *, -middle-, insulating materials. .light. known so far in the industry.



   The preformed fibrous or "spiculated" component which is suitable for thus practicing the present invention may, as already stated, be of organic or inorganic origin or composition, and will possess properties.

 <Desc / Clms Page number 19>

 properties and corresponding application possibilities.



  It is characterized by the colloidal order of dimensions, in the cross section, namely from 1 to 3 microns, and dimensions in the length direction which are much larger than the dimensions in cross section, but which are still of the order of small dimensions, relative to untreated fibers, for example of the order of 10 to 1000 microns, from 100 to 2000 microns, or beyond 1000 microns.



  These fibers are, therefore, liable to disperse in a liquid medium such as water and to remain dispersed for a considerable period of time, without appreciable loss of uniformity or without spontaneous dehydration or segregation of the liquid. contained therein, under the effect of gravity, at rest.



   This spiculation of asbestos fibers or other fibers with a view to giving them a cross section of less than three microns and lengths equal to at least three times their diameter has a certain importance from the point of view of distribution, as will be discussed below. see :
Assuming each of the fibers is just three microns in diameter and 10 microns in length, these fibers will be able to settle or disperse relative to their ends (which are called to serve as centers to initiate the original crystallization of the needles. , prisms or calcium hydrosilicate fibers) in the manner of a crisscross. However, these fibers are solids, and it follows that any two fibers will not cross in the same plane. They will pile up.

   The distance between the surfaces of the free ends of these crossed spicules would be about 5 microns or a little more. However, the intercalation of a third fiber or preformed spicule, arranged at random, in three dimensions, with the greatest possible proximity of the first two, would be held

 <Desc / Clms Page number 20>

 vertically with respect to said first two.



   Its faces would then be spaced from at least one of the faces of the other two spicules by an amount less than about 2 microns or less than the thickness of the fiber.



   Therefore, with fibers whose lengths do not exceed about three times their diameters, the exposed, fractured, and hence susceptible to crystallization and generating, faces will be closer together than the cross-sectional dimensions of their own free ends. It follows that a crystal growing on one of said end faces will tend to merge with a crystal growing on an end face of a similar adjacent fiber, before it has grown over a distance as great as that over which it developed laterally beyond this face. This is the kind of crystallization that powders, as opposed to fibers, will produce.



   In this connection, it is also interesting and significant that, approximately, a 1% (by weight) pulp or suspension of spicules in water would correspond to a volume percentage of about 0.4 %, with asbestos with a specific gravity of 2.5.



    That is, in a thousand cubic microns of the suspension (that is, a cube of ten microns per side), there would be four cubic microns of asbestos which would be equivalent to one asbestos fiber one square micron and four microns in length.



   If this fiber occupied the middle of the ten micron cube assigned to it, it would be four and a half microns from the cube wall on each side, and three microns from the cube wall at each end. . As a result, it would present an aqueous film

 <Desc / Clms Page number 21>

 of a thickness equal to several times its diameter, on each side, and almost equal to its length, at the ends.

   If the immediately adjacent fibers, in similarly adjacent ten micron cubes of liquid, were similarly spaced and parallel to the first, these adjacent fibers would be spaced nine microns apart at the sides and six microns at the ends. (or an intermediate value between these numbers, if the spicules were turned in different directions perpendicular or angular to each other).



   If the fiber length exceeded four microns, there would obviously be less in a .1% suspension.



   The same would apply if these fibers were larger in cross section. For example, a spicule 2 microns in length, 2 microns in thickness and 8 microns in length would equal thirty-two cubic microns, and would occupy a space equal to eight ten-micron cubes, or a cube of 20 x 20 x 20, or eight thousand cubic microns.



   However, in such a cube there would be a greater spacing, for example eighteen microns from the neighboring fiber, oriented in a similar way (parallel) on each side, and twelve microns from the neighboring fiber. , oriented in a similar way, at each end.



  As a result, it would be freer and more likely to get rid of the suspension, or to become dehydrated. This is the characteristic of aqueous dispersions of asbestos or other fibrous agglomerates and suspensions, longer or less defibrated.



   On the other hand, if the dimensions of the cross sectional fiber are the same as before, for example 1 micron x 1 micron, but if the concentration increases,

 <Desc / Clms Page number 22>

 say by 2% by weight, increasing the length of each fiber, for example from four to eight microns, then it would happen that, in the distribution described above, the ends of these spicules would approach each other within the limits of four microns, while the sides would be the same average distance from each other as before.



   If the fibers remain 1 x 1 micron x 4 microns long (e.g. 4% by weight in the slurry), so that there are, for example, four of them that are parallel and equidistant one from the other, laterally, in the 10 micron liquid cube, as assumed above, they will then be / separated from each other (by water films) only four microns and four microns of parallel, analogously oriented spicules in adjacent ten micron cubes.



   It is obvious that if the spicules were to swell (laterally), they would reduce this distance even further. Thus, a 4% suspension of spicules constitutes the limit of the free working of the pulps of paper or of binder, as a rule, on a large scale. However, chrysotile asbestos pulps (which swell) form a solid jelly at a concentration of 4% to 6% by weight. As a result, the free working concentration of its pulp is about 1% by weight.



   In other words, in an aqueous suspension of the preformed asbestos (or cellulose) fibers or spicules, the water films surrounding these fibers, to a depth of two to six microns, appear to be vigorously adsorbed or held by the fibers. and strongly repel each other, so as to produce and maintain the

 <Desc / Clms Page number 23>

 uniform dispersion of the fibers throughout the volume of water in which they are suspended, even when the spiculated fibers do not swell.



   The spiculated, dispersed fibers can hydrolyze and swell under these conditions (or else this hydrolysis and swelling can be encouraged), for example in the case of some kinds of asbestos, such as asbestos. chrysotile, or finely divided organic fibers, such as cellulose and its derivatives. This further promotes the dispersion and the permanence of these dispersions.

   However, asbestos fibers of the prescribed dimensions, which do not swell, for example blue asbestos from Bolivia and amosite from Africa, will also disperse in large volumes of water and will remain dispersed for many years. long periods of time, without forming spontaneous deposits, and also give satisfaction when applied to the purposes sought by the present invention.

   The best conditions under which the fibrous material can present itself in order to achieve the objects of the present invention therefore appear to be those in which the fibers have many free ends, are of almost colloidal dimensions in cross section, and d 'a length sufficient to allow and propagate a free and uniform dispersion through an entire volume of liquid, after being mixed therewith in dilute proportions (e.g. 1% to 5%), head and continue to move at random throughout the liquid or liquid mixture (in which these free ends are kept predominantly spaced apart from each other) and which initiate the original formation of crystals at these points separated from each other,

   thus directing the progressive formation

 <Desc / Clms Page number 24>

 of crystals in fibrous form from the points in question instead of crystallization from closely contiguous solid surfaces or points, as is the case in dispersions of finely divided powders in which the three dimensions of each particle are all roughly the same.



   It should be noted in particular that the end faces of preformed spiculated fibers, whether mineral and crystalline or organic and non-crystalline, have free surfaces, freshly fractured, instead of surfaces of natural formations. and therefore more stabilized. They act, therefore, as the original centers for the crystallization of reactants producing fibrous crystals, in solution or dispersion.



  Given that these free ends are of limited or even colloidal dimensions, it follows that the dimensions of the crystals (seeds) whose formation they generate on themselves are also limited. The formation of outer crystals, on the natural side surfaces of the fibers or preformed crystals is not favored as much (if at all) as the gradual crystallization outward and radially from these fractured ends, once this crystallization has been initiated.



  Further, any crystallization from the sidewalls of the fibers would be subject to adhesion, as the growth of crystals from the end faces of these fractured fibers involves cohesive or valence forces of an interatomic combination.



   Although the ultimate formation of these preformed organic or mineral fibers cannot be considered to be determined in a consistent and certain way, it is commonly assumed that finely divided organic fibers,

 <Desc / Clms Page number 25>

 such as cellulose, which is commonly prepared, are formed from even finer and smaller entities, frequently referred to as micelles, which are also of a fibrous nature, i.e. which are long compared to their cross-sectional dimensions. It is also known that with mineral fibers, such as asbestos, the fibrous masses formed exhibit a high degree of two-dimensional cleavage resulting in easy separation of the mass into long crystalline and fibrous needles.

   Although the ultimate degree of separation which can be effected has not been determined, it is known that it can take place at extremely small dimensions, in both transverse directions. Although the lengths of these fine fibers will inevitably be greatly reduced by fracture, in operations of this kind the fibrous nature will persist and can be effectively maintained so as to have lengths significantly greater than the lengths. cross-sectional dimensions, as described above.



   A fundamental cause of this fibrous asbestos material is attributed to the fact that the silicon and oxygen atoms associated with it are proportioned and united in a chain form, in the longitudinal direction of the fibrous crystals. This union is of the order of a primary valence and therefore gives the fibers considerable tensile strength in the longitudinal direction, which contrasts with the weakness of the union between the fibers in the longitudinal direction. the transverse direction. However, after transverse fracture of the individual (or ultimate) fibrous crystal, it should be noted that there is thus a break in the chain of the silicon and oxygen atoms of the crystal structure.

 <Desc / Clms Page number 26>

 



  As a result, the cohesive or corresponding value forces of silicon and oxygen which formed the longitudinal tensile strength of the fibrous crystals are released to provide physical or chemical union on the fractured face.



   According to the present invention, these free faces of fibrous crystals are multiplied considerably and dispersed in a large volume (of water) by spiculation, as defined above, and thus constitute centers of crystallization of an amount. at least equal (or even greater) of the products of active lime and active silica (and of water), with a view to the formation thereon, by chemical union and growth, of fine crystals, needle-shaped or fibrous, hydrated calcium silicate.

   Now, it is in the nature of this culture of crystals that the growing silicate crystals form a silicon-oxygen chain constituting a real prolongation of the silicon-oxygen chain of fine fibrous crystals of spiculated asbestos which have been divided by the spiculation. They will also be kept separate at random by the random arrangement of the long, fine spicules and caused to form long, fibrous crystals themselves.



   Therefore, the formation and growth of these fibrous crystals from the ends of the preformed fiber spicules and their union with them and with each other, results in an entangled fibrous mass whose strength is not measured by the force of adhesion of the binders to each other or to each other and the preformed fibers (organic or inorganic), but by the integrated tensile strength of the cohesive forces of the crystallized fibers themselves. In fact, when two growing fibrous crystals come together and their intersection is formed by

 <Desc / Clms Page number 27>

 mutual crystallization as a result of the chemical reaction, the resulting product constitutes a unitary formation of an inherent cohesive chemical force and not a formation of external contact, inclusion or adhesion.



   For example, if the reactive, finely divided silicon component discussed above and dispersed or dissolved lime, in lime water for example, are dispersed in a very large volume of water, if the particles ( or solution) maintained in this state of wide dispersion with finely spiculated asbestos fibers and if the interaction to form hydrated calcium silicate takes place, needle-shaped crystals of hydrated calcium silicate will be caused to grow in a longer and finer form and to have a dispersed, entangled mass of fibrous crystals throughout the volume of water in which the reagents (and any such generative organs) have been kept in suspension during the reaction.

   Further, the segregating and forming crystals will unite to a considerable extent, during their growth, at the points of contact between two or more crystals and will then intertwine to form an openwork lath, interwoven. , a permanent layout and structure.

     After completion of crystallization and crystal growth and subsequent extraction of the waste water as well as any water-containing gels that are between these crystals, (which, in fact, is the case, according to observations made), the mass present, between the fibers (and through the gel films), innumerable voids or air spaces which are of a continuous and capillary nature and communicate with each other, instead of being completely surrounded or blocked by a solid material such as the agglutinants or continuous walls which

 <Desc / Clms Page number 28>

 characterize them and are inherent in the structures of the insulating materials used until now.



   By making use of a gel of a volumetric dispersion for the purpose of maintaining or promoting, during the reaction, the dispersion of the reactants and the growing fibers, it is possible to better retain the consistency, constitution and dispersing the composition employed in the reaction uniformly, as well as maintaining the latter in that state for such time as is necessary or suitable to complete the reaction. At the same time, this composition can, by gentle agitation, be subjected to a free flow of plastic liquid, or the like, which can give it any desired shape or size.

   If the formed mass is then kept at rest, the mixture can be returned to a gel state and allowed to react or be subjected to conditions suitable to initiate, promote and complete its reaction, with a view to formation, throughout the process. load, fibrous hydrated calcium silicate needles, which consequently assume the shapes, dimensions and volumes imposed on them. The developed crystal mass in part or in whole may be subjected to modified or entirely different treatments for special applications and results.



     This is how it can be removed from the molding device and the reaction can be completed by prolonging the treatment time, subjecting the mass to higher temperatures and pressures, etc., in a different vessel, with or without. drying, as appropriate.



   If desired, crystal development and complete reaction of all ingredients of the entire batch can take place in the original molding device prior to removal. In either case,

 <Desc / Clms Page number 29>

   The residual moisture will eventually be removed, in any suitable manner, after which the product is ready for use.



   The gel, whether formed during the reactions or added to the feed, may or may not enter the reaction in which the crystals are formed.



  If it does enter, subsequent molding or casting of the mass can interrupt crystal formation and therefore reduce the ultimate potential strength of the product. However, if the gel is added to the composition and to the crystallization reaction, the molding and pouring of the gel mass can proceed without affecting the crystal forming structure and the strength of the crystallized product. tallized if carried out and completed before abundant crystal intergrowth has occurred.



   A feature of this distinct, individual reaction which forms crystals is that the needles of hydrated calcium silicate, as they close with the help of the suspended medium in which the reactants are contained are of a much smaller volume than the total volume of the mass in which they are formed. The product therefore typically consists of a filamentous system of a network of unified crystals of small dimensions, usually colloidal in cross section, and when the lime and silica have substantially completed their reaction, the The main ingredient, or preferably the only ingredient remaining in the bulk of the load, is water or water vapor, both of which are permanently expelled, after drying, and replaced by air.



   When other materials are contained in the reaction charge, as described above, for example to serve as a suspending or gel agent, or for other purposes,

 <Desc / Clms Page number 30>

 they can stay there. Thus, finely divided fibrous cellulose, for example pulp, can serve as both spiculated fiber and gel. In this case, the cellulose fibers obviously remain between the crystallized needles of hydrated calcium silicate, even after the water and water vapor have been expelled.



  But, although cellulose fibers may increase the heat insulating properties of the mass, at ambient temperatures they will tend to be reduced at or above the temperature of boiling water, or else the cellulose will tend to be modified or destroyed. by charring and falling from the spaces in which it was previously held. This material would therefore not constitute a suitable permanent adjuvant to heat insulating materials intended for use at very high temperatures, although it would serve to facilitate the dispersed formation and crystallization of the needles of calcium silicate hydrate. the state of fibrous formation intermixed at random and integrated as a mass, so that it can be used at medium or low temperatures.



   On the other hand, it has been found that, by incorporating certain mineral substances, which are at the same time fibrous, capable of forming a gel and retaining their needle or fibrous form, for example chrysotile asbestos, a dispersed, interwoven structure of fibrous crystals of hydrated calcium silicate and fibrous asbestos crystals could form, constituting, throughout the mass, a fine continuous fibrous structure, a continuous integral sage existing between the two kinds of fibers and the gel, this structure being solid, of low volume and specific mass capable of withstanding high temperatures and arranged at random, while retaining the

 <Desc / Clms Page number 31>

 thin character,

   inconsistent and open to the fibrous structure of the mass as a whole and also possessing both the compressive and tensile strengths of the two ultimate individual fibrous constituents themselves.



   This fine fibrous structure of fibrous crystals intertwined and growing within each other is distinguished from the occlusive type of binder or agglutinant, fiber to fiber, obtained by wetting, fusion or impregnation and (or) agglutinants, or similar impregnations, which have been previously used in industry. The latter are distinguished from the intergrowth of fine crystalline fibers in that they present a continuous, more consolidated structure which is inherently of a much greater bulk density and which from surface to surface. It also contains a greater volume of solid, continuous structure through which heat can easily pass, dissipate and be lost.



  At the same time, since the voids or pores of the fibrous material obtained in accordance with the present invention are not blocked or closed, it follows that the openings existing between the fibers and the crystals themselves and their junctions with each other are attenuated and have small dimensions such that the spaces, bodies and surfaces oriented for the radiating and convective air currents which pass through them are broken up, effectively dispersed and prevented from spreading. gradually or rapidly transferring heat through the whole mass, in any direction, by convection, conduction or radiation.

   This system of formation of continuous, filamentous, fine crystals and small, attenuated, continuous capillary air spaces which intervene between these crystals and separate them, consequently constitutes a product which,

 <Desc / Clms Page number 32>

 as a whole, is of low thermal conductivity, but has, on the contrary, a great insulating power, while possessing, to a high degree, the power to retain its shapes, a great tensile strength and a very apparent density. low.



     As an example of the practical application of the invention to the manufacture of heat insulating materials, and more especially of those which have a low bulk density and a low conductivity, will be described with reference to the accompanying drawing in which:
Figure 1 shows a flow diagram, and
Figure 2 is a more or less schematic view of a suitable device for spiculating asbestos fiber.



   The asbestos component is preferably first treated by reducing it from approximately the raw state in which it is found in the mine to a degree of uniformity and purity in which it is relatively free of non-fibrous minerals and. other impurities. For example, untreated asbestos may consist of chrysotile asbestos fibers with the following dimensions:
25% passing through a 12.7 millimeter mesh screen and retained on a 6.35 millimeter mesh screen (Canadian asbestos specification),
50% retained on a 2-millimeter sieve
25% passing through a 2 mm sieve.



   This asbestos fiber is then mixed in the tank 1, Figure 1, with water constituting a liquid vehicle. In carrying out this operation, a relatively dilute sludge can advantageously be employed, obtained, for example, by mixing, by means of a mixer 2, 1 to 5 parts by weight of fiber, with 99 to 95 parts of water. , to form a uniform mixture. This mixture is then drawn off

 <Desc / Clms Page number 33>

 by the pipe 3, controlled by the valve 4, to bring it to the pump 5, from where it can return, through the outlet passage 6 and the pipe 7, as a result of the opening of the valve 8, in the tank 1, the valve 9 giving access to the spiculation device 10 remaining closed.



   The spiculation device 10 comprises a motor 11 (of the three-phase type, for example), intended to actuate the shaft 12 which passes into the closed chamber 13 and carries, on its inner end, a conical hardened steel plate 14, fitted with , on its conical face 16, of radial grooves 15 and maintained, in a precise and adjustable manner, at a distance from a circular scraper blade 17, the surface of which is parallel to the surface of the conical plate 14 and is maintained firmly in a fixed position. The clearance between the conical disc or plate and the scraper blade is of the order of approximately 3 to 5 tenths of a millimeter.

   The plate 14 preferably rotates at a high speed (for example at 3600 rpm) and preferably under a constant maximum load, as indicated by the ammeter 18 (for example 70 amps, on the motor employed in the present case. ), which indicates the most efficient spiculation of the entire mass.



   With the spiculation rotor running at full speed, the valve 9 is then opened, providing the passage through the inlet pipe and into the chamber 19 which is on the control side or the truncated side of the plate. The sludge then enters the chamber, first under the impulse of the pump 5, then under the effect of the centrifugal force of the rotor and of the plate 14 which drives it into and through the free space existing between the chamber. face of the disc or platen and the scraper blade.

   In this operation, the asbestos fibers are twisted and disintegrated or separated from each other according to their longitudinal cleavage planes and are also

 <Desc / Clms Page number 34>

 fractured and scalloped or "swept" transversely, resulting in a many-times-multiplied number at their ends of thin, distinct fibrous entities which are characterized, as a rule, by small diameters (e.g. / 10th to 3 microns), in which the ratio of length to cross-section characterizes them as fibers, unlike fine granules in which all three dimensions are substantially of the same order,

   as well as that category of fibers which are of such length as to cause interlacing and lump formation which characterizes untreated or unspiculated asbestos fibers of excessive length .



   As the sludge leaves the spiculator, it is collected in chamber 20, from where it can pass into outlet duct 21 and from there, through valve 22 and pipe 23, into a second tank 24 which is also equipped with a stirrer 25.



   When all the sludge prepared in tank 1 has thus passed through the spiculator and is collected in tank 24, the operation of the device is reversed. This result is obtained by closing the valves 4, 8 and 9, connected to the conduits connected to the tank 1 and by opening the corresponding valve 26 of the pipe 27, the valve 28 of the pipe 29 and, later, the valve 30 giving access to the tank. inlet duct in the spiculation device 10, and also by opening the valve 31 of the pipe 32 returning from the outlet passage 21 of the spiculator in the reservoir 1, all these valves having been previously closed.



   By then operating the pump and the spiculation device as previously done, the sludge load will undergo a second treatment similar to

 <Desc / Clms Page number 35>

 first and will then be discharged into tank 1, until the entire load has been treated in this way a second time.



   These operations can thus be reversed and repeated as many times as is deemed necessary or desirable.



  However, to ensure the effective reduction of fibers to a degree suitable for the proposed purpose, it has repeatedly been found that two or three passes are sufficient.



   When the sludge has acquired the desired degree of spiculation, all the previous valves are closed with the exception of the valve (4 or 26) of the pipe going from the tank containing the completed charge of spiculated asbestos sludge to pump 5 , and one opens the valve 33 which goes from the outlet passage of the pump, through the pipe 34, to the mixing tank 35. By operating the pump 5, the latter will then deliver all the load to the mixer 35.



   Mixer 35 consists of a horizontal cylinder of a common type with a pair of helical, ribbon-shaped, opposing pitch mixing vanes.



   Before introducing into the mixer, the prepared asbestos slurry, hydrate a finely pulverized quicklime suspension (for example which can pass through a sieve of 150 microns and even finer) using water which is at room temperature and in an amount sufficient to ensure a distinctly liquid suspension, preferably at a temperature of about 71 to .93 C. The amount of water employed is such that it will form, in the mixer, a composition having the desired consistency, dispersion and suspension. For example, five times as much water as quicklime, by weight, will give effective quenching, dispersion and satisfactory sludge as a result.



  When the lime is completely hydrated and dispersed in

 <Desc / Clms Page number 36>

 the water from the mixer, the slurry of spiculated asbestos fibers, is sucked in, mixed thoroughly, then added with the desired amount of finely divided silica, diatomaceous earth or other similar material into a fine and dry powder, the mixing being continued until a complete and uniform dispersion has been obtained.



   Typical and representative examples of compositions which can be prepared by proceeding according to the present invention are as follows:
I
 EMI36.1
 
<tb> Lime .................. <SEP> 30 <SEP>% <SEP> in <SEP> weight <SEP> by <SEP> example <SEP> 30 <SEP> kg
<tb>
 
 EMI36.2
 Quartz flour ........ 25 to .. 25 kg Diatomaceous earth ....... 35% '25 kg Asbestos (beaten) ......... 15 8 ... 15 kg
 EMI36.3
 
<tb> Asbestos <SEP> (not <SEP> treated) <SEP> 5 <SEP>% <SEP> "<SEP>" <SEP> 5 <SEP> kg
<tb>
 
 EMI36.4
 Water with asbestos ... 350, o of the ppids tō8 360 kg
 EMI36.5
 
<tb> tal <SEP> of <SEP> solid <SEP> materials
<tb>
 
 EMI36.6
 Water with lime 50% of the weight to-8 "150 kg
 EMI36.7
 
<tb> tal <SEP> of <SEP> solid <SEP> materials
<tb>
 II
 EMI36.8
 Lime ...... * #, ##.

     # s o # $ 30 by weight e.g. 30 kg Diatomaceous earth ...... 50 m v a u 50 kg
 EMI36.9
 
<tb> Asbestos <SEP> (as prepared <SEP>
<tb>
<tb> in <SEP> 1 device <SEP> of <SEP> the
<tb>
 
 EMI36.10
 figure 2) 20 j "u a a 20 kg
 EMI36.11
 
<tb> Water <SEP> with <SEP> of <SEP> asbestos <SEP> .. <SEP> 400 <SEP>% <SEP> of <SEP> weight <SEP> to- "<SEP>" < SEP> 400 <SEP> or
<tb> tal <SEP> of <SEP> materials <SEP> solids <SEP> up to <SEP> 470 <SEP> kg
<tb> Eu <SEP> with <SEP> of <SEP> the <SEP> lime .... <SEP> 150 <SEP>% <SEP> of <SEP> weight <SEP> to- "<SEP>" <SEP> 130 <SEP> or
<tb> tal <SEP> of <SEP> solid <SEP> materials <SEP> up to <SEP> 150 <SEP> kg
<tb>
 III
 EMI36.12
 
<tb> Lime ..................

   <SEP> 30 <SEP>% <SEP> in <SEP> weight <SEP> by <SEP> example <SEP> 30 <SEP> kg
<tb>
 
 EMI36.13
 Earth â, diatoms 50 p 50 kg
 EMI36.14
 
<tb> Asbestos <SEP> (as prepared <SEP>
<tb>
<tb> in <SEP> the <SEP> device of <SEP> the
<tb>
 
 EMI36.15
 figure 2) 20, it n # # 20 kg Water with asbestos .. 85o, br0 8 50 kg
 EMI36.16
 
<tb> Water <SEP> with <SEP> of <SEP> the <SEP> lime <SEP> ... <SEP> 150 <SEP>% <SEP> of <SEP> weight <SEP> to- <SEP> 150 <SEP> kg
<tb>
<tb>
<tb>
<tb>
<tb> tal <SEP> of <SEP> solid <SEP> materials
<tb>
 

 <Desc / Clms Page number 37>

 IV
 EMI37.1
 
<tb> Lime <SEP> ............... <SEP> 33 <SEP>% <SEP> in <SEP> weight <SEP> by <SEP> example <SEP> 33 <SEP> kg
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> Flour <SEP> of <SEP> quartz <SEP> ....

   <SEP> 60 <SEP>% <SEP> "<SEP>" <SEP> "<SEP>" <SEP> 60 <SEP> kg
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> Asbestos <SEP> (completely
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> spicule, <SEP> by <SEP> example
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> to <SEP> sec <SEP> in <SEP> a <SEP> suspen-
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> air <SEP> sion) <SEP> 7 <SEP>% <SEP> "<SEP>" <SEP> "<SEP> 7 <SEP> kg
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> Water <SEP> with <SEP> of <SEP> the <SEP> lime <SEP> 150 <SEP>% <SEP> of <SEP> weight <SEP> to- "<SEP>" <SEP> 150 <SEP> kg
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> tal <SEP> of <SEP> solid <SEP> materials
<tb>
<tb>
<tb>
<tb>
<tb> Water <SEP> .................. <SEP> 100 <SEP>% <SEP> of <SEP> weight <SEP> to- "<SEP> "<SEP> 100 <SEP> kg
<tb>
 tal of solids
The mixing operation usually takes 30 minutes to an hour.

   When it is completed, the mixing is stopped and the slurry is withdrawn which can be poured, under the action of gravity, into metal molds or basins 36 or other similar containers, which are preferably thin and good conductors. heat, which is then placed in a chamber 37 and which is subjected to the action of live, saturated steam at a pressure of 8.4 kg / cm2 for example for three hours to bring the load at the desired temperature, keeping them for a period of twelve hours under constant pressure, allowing them to cool and allowing the pressure to drop to atmospheric pressure for a period of about five hours. They can be removed or allowed to cool further.

   The molded filler will be found to have cured retaining its original size and shape, without appreciable water separation, or loss of its original size and shape.



   It is therefore possible to remove the molded product from the basins and remove the water it contains, by drying in a dryer / at a temperature varying between 1210 and 176 C approximately, which leaves a product having the shape and dimensions which were given to it by the molds, as well as a weight equal to that of the solid constituents of the reaction mixture only (plus

 <Desc / Clms Page number 38>

 crystallization in combination with absorbed moisture, as well as * absorbed water, if any) hence. water of dispersion has been removed and is therefore of low bulk density.



   For example a product of this kind (especially that obtained according to formula II), shows an apparent density of about 176 kg, per cubic meter, and has a conductivity of about 0.0002, at temperatures rising to about 205 C on the hot side, if the cold side is at a temperature of about 65.5 G.



   This bulk density can be determined from the concentration of solids contained in the original slurry from which it was taken and which has hardened. And since there has been no appreciable change in volume during the process, the product will, in kilograms per cubic meter, have substantially the same bulk density as the original slurry, based on its solid constituents (more water of crystallization and (or) water blocked in any other way), the voids being, in one case, filled with liquid water and, in the other case, with air.



   It is obvious that other products could be obtained by preparing spiculated asbestos slurries in which the markedly prolonged or permanent suspending power of this asbestos could be used for many other purposes. For example, this can be used to effect and maintain the dispersion of much heavier materials or large proportions of reactants, during the reaction or other treatments, whether the product is to be of low or high density. related.



   In accordance with the present invention, the degree of spiculation as well as the proportion of short fibers to long fibers are set and determine,

 <Desc / Clms Page number 39>

 in turn, the properties which it is desired to impart to the product. In this respect, the present invention differs fundamentally from other attempts which have been made.



   For example, to make structural materials of high density, containing a greater proportion of solid cementitious reagents and reaction products, it has been found that fully spiculated asbestos, of category (A) as defined above, was the most suitable material for increasing the ultimate flexural strength of these products.

   In order to manufacture products of low density for use as heat insulator capable of retaining its shape, containing a comparatively small amount of cement-forming reactants, solids, and reaction products, it has been found that the The partially spiculated asbestos, belonging to category (C) as defined above, imparted a relatively high flexural strength, compared to the low bulk density products obtained so far, as well as a high residual strength, after initial fracture of the binder or bond forming cement.



   Spiculated asbestos can be obtained from different kinds of commercial asbestos, by treating a suspension of this asbestos with a fluid (gaseous or liquid) in an instrument or apparatus which subdivides the fibers under the effect of l 'attrition of the cylindrical vortex of the fluid rotating at high angular speeds. This disintegration can be effected in various mills established to operate with compressed air, or by employing superheated, high pressure steam as the fluid agent, it can also be achieved by stirring a dilute suspension of about 5%, more or less, by weight (from 1 to 10%) of asbestos in water, using one or more propeller stirrers,

 <Desc / Clms Page number 40>

 rotating at high speed, or even by heating this suspension in a pulp pestle.

   However, in each of these operations, the treatment is carried out to a much more intense degree and extends well beyond what is customary with these methods and apparatus intended primarily for the preparation of pasta, with the aim of to obtain the desired degree of reduction in fiber dimensions and the desired proportion of fibrous material relative to the dimension or dimensions which characterize spiculated asbestos. In this way, it is possible to obtain, by prolonged or repeated treatment, in the apparatus shown, a fully spiculated asbestos fiber, with a suspension of 1% by weight.

   The net result of this treatment is to break up the spike bundles or the fiber content of the different kinds of commercial asbestos, to cause them to. their ultimate state of spicules, but without destroying their characteristics of fiber length relative to their dimensions in cross section.



   In accordance with what has just been said, the spiculated fibers or 'spicules' are characterized in that they are capable of forming a relatively permanent or static suspension in water; for example, those which are in concentrations of 1/10% to 2.5% (or more), by weight, or 1/25 to 1% (or more), by volume, are by themselves capable of resist segregation under the effect of gravity, for a period of several hours (or even several days).



   This static dispersion and prolonged suspension of fine spiculated fibers therefore constitute a dispersion system in which many unusual conditions and novel characteristic reactions and results can be obtained.

 <Desc / Clms Page number 41>

 



     Thus, other fibrous materials, granular materials, or solid reactants, finely divided (or in solution), which are not able to remain in suspension in liquids for an extended time, can be mixed with these. last, and that the resulting mixture will acquire the power to form and maintain a static, uniform, prolonged or permanent suspension, without any appreciable segregation occurring, for a long period of time. Consequently, various reactions and other modifications can take place throughout the mass of these three-dimensional suspensions and be successively adjusted to defined degrees (1) of initiation of this reaction, (2) of activation or adjustment, at any desired phase, or (3) completion.



   In addition, other operations can accompany, or intervene between these successive phases of physical and (or) chemical reaction in the system, such as, for example, the shaping or the molding of the mass before starting the process. reaction, after initiation or after the reaction has been facilitated, to any desired degree.



   In addition, further treatments can be exerted on the resulting mixture, at any stage of operation chosen, according to the characteristics of the conditions and the properties thus acquired and according to the changes and results desired.



   For example, in the specific examples described above, when a reactive lime and a reactive silica (slightly in excess of the molecular proportions) are used and the reaction is carried out to complete completion, a new hydrated lime silicate composed of CaO, SiO, NH2O which, on X-ray examination, reveals a new structure which distinguishes it from all known lime silicates.

 <Desc / Clms Page number 42>

 



   It is supposed that in the static network, continuous, but with open filaments, suspended spicules which are characteristically capable of sustaining themselves in such arrangement and dispersion, in the whole volume of In the water in which this network is formed, many reactants, both in solution and in the form of small and comparatively large solids, are made capable of exerting an adjustable reaction both chemical and physical.



   Thus, in the fillers described above, the lime is present both in solution and in the form of particles of colloidal dimensions which may go as far as being visible. Silica is also present in small pieces, either as quartz flour or as pulverized diatomaceous earth, although some particles of the latter may be considerably larger than the fibrous spicules. Silica is also able to go into solution. It follows that one can predict the reaction between dissolved heat and dissolved silica.

   In addition, due to the porosity or permeability, as well as the amorphous and active nature of the silica contained in diatomaceous earth, the lime solution and suspension are able to penetrate relatively freely. in large particles of diatomaceous earth. In addition, the dissolved heat is able, under these conditions, to react with a large number of times, for example 35 times, its molecular equivalent of silica and to disperse or dissolve the resulting combination in the surrounding aqueous medium. A combination of can be considered to form a long chain of silicon and oxygen, combined at its ends with a molecule of lime.

 <Desc / Clms Page number 43>

 



   This action will obviously have the effect of rapidly and completely disintegrating and dissolving, at least momentarily, the silica or the diatomaceous earth, the rate out of proportion with the equimolecular quantity of lime present. However, the concentration of such a combination of lime and silica which can be maintained in solution is rather low. It is likely to be reoriented and, in doing so, fibrous crystals of lime silicate, of the formula CaO, SiO2, NH2O, separate and grow, as described above, being distributed over the entire volume of the mass of reaction.

   The chains of silicon and oxygen, or the chains of silica, thus liberated, can in turn react with a greater quantity of lime to form lime silicates of varying composition, or additional crystalline calcium silicate. These chains of silica or lime silicates also tend to form gels which, in turn, can transform gradually - and quickly or slowly, depending on the conditions - to take on the crystalline, fibrous, growing structure, as described above. , and thus feed the latter. However, when this crystal formation stops, the gel remains.

   Under these conditions, if the water medium is removed, the growth of crystal fibers can be stopped, and the heat and dehydration serve to tighten the gel on the previously formed fibrous spicules, nascent fibrous crystals, and in the core of those. here, by thus opening voids between the fibers and thus creating, through the gel, continuous and consequently permeable openings, so as to form the typical structure of the new product obtained.



   Continuing to heat, dry and dehydrate the spicules, fibrous crystals and gel,

 <Desc / Clms Page number 44>

 are accompanied by shrinkage in absolute volume, hardening and strengthening of each of them - and also of the union between them - to constitute the integral structure, capable of retaining its shape, and robust, which characterizes the whole and which the previous insulating methods and materials have not made it possible to obtain.



   It should also be noted that the permanent self-supporting suspension of 0.1% spiculated asbestos (by weight or 0.04% by volume), which has just been described, is present a large mesh network, in which each fiber is surrounded by many times its volume of water, but until this degree of dilution is reached, the water which surrounds each fiber is associated with it in such a way so that fiber and water act as an entity. They will attract and repel a like fiber and associated water, in a manner sufficient to provide and maintain this uniform spacing ratio, in antagonism to the forces of gravity, whether by buoyancy or by deposition.

   However, when such a slurry is suddenly diluted further with water, the slurry breaks up, the fibers float to the surface, leaving clear water below them. , and forming an upper layer which is constituted by a suspension having approximately the original limit concentration degree that it had before this dilution (or a slightly higher concentration degree) and which floats on the lower water layer.



   Therefore, this degree of dilution indicates the limit of the thickness of the water envelope surrounding the fibers, which acts to keep each fiber away from adjacent fibers and also to prevent a fiber from moving freely and protruding beyond a fiber. other fiber or

 <Desc / Clms Page number 45>

   rub against it; association of water with adjacent fibers also prevents water from flowing freely between these adjacent fibers, so as to determine segregation by deposition or float. On the other hand, the water shell is not associated in a sufficiently firm manner with its fibers to prevent this water from easily filtering or draining from the fibrous mass, thus leaving the fibers. fibers come closer to each other.

   In other words, the system constitutes a discontinuous suspension of fibers, which is stable and permanent as long as the water medium is maintained, but which is neither a gel nor a continuous gel, even with chrysotile fibers which swell slightly.



   Therefore, in this open and three-dimensional fibrous network or network or lattice system, the reactants, in the form of finely divided solids or in colloidal or real solution, are liable to disperse without destroying the lattice structure or suspension. Lime and diatomaceous earth, for example, are both able to subdivide in this way to take colloidal dimensions and go into real solution. When, or so far, the reactants are present under the conditions mentioned last, they react rapidly and produce a gelatinous precipitate of hydrated calcium silicate. Due to the dispersion and dilution of this gelatinous precipitate, it is mobile and is attracted to the spiculated asbestos fibers.

   It freely follows the shape of the outer surfaces of the fibers, forming around each of them a sheath of hydrated, gelatinous calcium silicate. This sheath therefore surrounds each of the fibers within the water envelope which was associated with and surrounded each of these fibers and which, nevertheless, still continues to act for main-

 <Desc / Clms Page number 46>

 hold the hydrated calcium silicate gel coated fibers in the dispersed form at wide intervals from each other.



   As a result, the dissolved reagents penetrate the water envelope of these fibers and a gelatinous precipitate forms directly on each fiber, without affecting or destroying the separating water envelopes around each asbestos fiber. The latter are, therefore, continually maintained at the original distance from each other and continue to occupy the same volume and to present the same shapes as in the network or lattice system they formed in the dispersion. of water alone.



   These reactions of dissolving and combining lime and silica, for example in the form of diatomaceous earth, occur at ordinary temperatures. If the temperature rises, the reactions speed up and the formation of hydrated, crystalline calcium silicate also occurs, either by direct crystallization of the solution or by converting the precipitated gelatinous precipitate into a gel, finally taking prominent crystalline forms. .



  However, the crystal formations according to the invention have been described in detail above.



   These dissolution, reactions and precipitation of the reagents, as well as the selective deposition of the gelatinous precipitates can also take place independently of the fibers and form lumps or colonies of gels and crystals throughout the volume of the mass, without however hindering the lump. order of the dispersion of spiculated fibers, as it was originally generated in pure water.



  As a result, the gelatinous sheaths of hydrated calcium silicate surround the continuously dispersed spiculated asbestos fibers and arise from them, and large clumps of gelatinous precipitate of hydrated calcium silicate also form in a similar fashion. simultaneous, in the middle

 <Desc / Clms Page number 47>

 aqueous, independent of the fibers and at a distance from them.



   Hydrated calcium silicate crystals can also form directly from solution and (or) further crystallization can occur upon conversion of the gelatinous precipitate which is then brought into crystalline form. However, the gelatinous precipitates, particularly those which are on the fibers, tend to form, by consolidation, gels endowed with a greater power of cohesion and adhesion, of a smaller volume and of a greater density. than the original gelatinous precipitates.



   In doing so, they group or unite around the fibers, then contract and leave in a commensurable way, spaces of free water, which go on increasing, between one of these fibers and the next, given that the fibers themselves, no more when bare than when coated with the gelatinous or gel-like sheaths, show no tendency to approach and come into immediate contact with each other, so long that a sufficient relative volume of the aqueous medium is maintained around and between them.



   Accordingly, the filler as a whole initially consists of spiculated, dispersed fibers, with which lime and diatomaceous earth are subsequently mixed, in colloidal suspension, in a finely divided state and in solution. The reaction produces separate gelatinous precipitates which accumulate around the spaced fibers, forming an enveloping sheath around each of them, as well as dispersed gelatinous precipitates, as colonies which are independent of the fibers.



  These gelatinous precipitates can consist of silica,

 <Desc / Clms Page number 48>

 lime, or hydrated calcium silicate. They form at ordinary temperatures and grow larger and larger, over time and as temperatures rise. At elevated temperatures, crystals of hydrated calcium silicate are also formed throughout the mass, which are withdrawn both from solution and from gelatinous precipitates.



   They form on the fibers and are also spaced from them. In all of these reactions and cultures, the fibers retain their original spacing from each other and, as a result, as the gelatinous precipitates solidify around their respective fibers, and the crystals also separate from the intervening spaces, these last. are now occupied only by water.



   When these reactions are complete, the water is allowed to evaporate and escape. The residual gelatinous precipitates or gel sheaths which surround the fibers (and which have already been transformed by shrinkage into real gels) then acquire a porous structure, then form sub-microscopic crystals, and therefore exhibit greater cooling power. cohesion and adhesion as well as greater overall strength.



   Independent lumps or colonies of gelatinous precipitates, which form between and independently of the fibers, do not wet the fibers by a spread meniscus. However, they eventually come into contact with them (with loss of the water of dispersion which keeps them separated) to form masses which retain their shape and which in a way become one-dimensional fibers as they adhere. after dehydration, to rigid gels, and continue to shrink.

   The sheaths

 <Desc / Clms Page number 49>

 gelatinous fibers of the spiculated fibers and the precipitated gel fibers thus formed may or may not be crystallized by further processing, but in either case they enhance the crystal formations generated by the separation from it. the solution existing between the spicules which are described during the preceding description, and constitute an integrated network and a solidified structure.



   The whole mass eventually transforms into a fibrous, integral, crumbling mass of light weight, low heat insulating conductivity, high tensile strength, and resists as well. water than high temperatures, making it a molded, self-sustaining, low bulk density, heat insulator suitable for satisfactory use at elevated temperatures in complete thermal insulation systems, in a single composition and in a single piece.



   All modifications and adaptations, both as regards the fundamental principles and the practical applications of the present invention, come within the scope of the latter.


    

Claims (1)

ABSTRACT 1 - Process for carrying out a chemical reaction and a solidification, starting from a saturated solution of the chemical reaction product, the elements of which are spaced from each other, in three dimensions, this process being characterized by the following points, together or separately: a) It consists in dispersing spiculated fibers, the dimensions of which in cross section vary, predominantly, between 1 / 10th of a micron and 3 microns, and the lengths of which are at least three times the respective dimensions in cross section, in a volume of water <Desc / Clms Page number 50> sufficient to space the spiked fibers apart from each other by an amount equal to at least twice the respective dimensions of said fibers, which constitute not less than about 1.25% by volume, so as to form a static suspension, and to effect the dispersion and reaction of the reagents contained therein, the reagents being in substantially equivalent proportions, to form the chemical reaction product and in proportions of at least 3 to 1, by weight, relative to spiculated fibers, to form an integrated structure, having substantially the volume and shape of the dispersion which this structure retains after dehydration b) The chemical reaction may only be initiated, facilitated to a substantial degree, or continued substantially until complete completion , c) The spiculated fibers can be of organic origin, such as cellulose fibers, or of mineral origin, such as asbestos fibers, d) The product of the reaction is crystallized e) The product of the reaction is gelatinous. f) The reactants react to produce a fiber-forming product; g) The reagents consist of lime and finely divided silica; h) The spiculated fibers are formed from asbestos fibers or cellulose fibers, in a proportion starting from 1.25%, but not exceeding 5% by volume of water, and the reactants consist of lime and finely divided silica, the lime being present in an amount of at least 1.5 to 1, by weight, relative to the spiculated fibers, the silica being present in an amount not less than the proportion equi - <Desc / Clms Page number 51> molecular weight with respect to lime, and the reaction taking place under the effect of heat, without substantial loss of water, to form a hydrated, solid lime silicate. (2) A solidified body of a chemical reaction product, with reciprocal spacing, in three dimensions, having an integrated structure, as well as a volume and a predetermined shape, according to any one or more of the modes of operation enumerated above, this solidified body being constituted, in addition, by the following points, taken together or separately: i) It has a fibrous structure, continuous, free, composed of spiculated fibers, spaced apart, dispersed at random, such as asbestos fibers or cellulose fibers and bound or agglutinated by means of a lime silicate, hydrated solid; j) It has a continuous, free fibrous structure, composed of spiculated, spaced fibers, dispersed at random, these fibers being individually surrounded by gelatinous sheaths, formed from the product of the reaction. EMI51.1 - -. - - * 1 1 - -'l - ^ - -4- - k-- 1 ^ A IN