BE596181A - - Google Patents

Description

       

   <Desc / Clms Page number 1>
 



  : NON-POROUS PLASTIC PIPES ADDED WITH ASBESTOS FIBERS ".

 <Desc / Clms Page number 2>

 



   The present invention relates to molded plastic articles reinforced by means of fibers, to molding materials by which these plastic articles can be produced, to processes for the preparation of such molding materials, as well as to than to methods for forming the new fiber reinforced plastic molded articles. The term "articles" as used herein, and in the claims which terminate it, embraces pipes, pipe fittings, pipe fittings and all other items normally associated with the general use of pipe fittings. convey fluids.

   More particularly, the invention relates to molded plastic articles, which are reinforced with asbestos fibers and which are obtained from molding materials allowing the production of plastic articles having a structure. homogeneous, excellent mechanical strength and other good physical properties.

   The invention especially relates to the formation of fiber reinforced plastic pipes, such pipes having a homogeneous structure, having walls with relatively smooth inner and outer surfaces, being free of any liquid seepage through their walls, when the pipes contain liquids under hydrostatic pressure, and being capable of being mechanically threaded using ordinary pipe tapping machines.

 <Desc / Clms Page number 3>

 



   Field of the invention.



   It is common practice to incorporate various fillers into molding compositions made from thermosetting resins, so that the mechanical strength and other physical features of articles molded using the resinous compositions can be controlled or altered to suit. appropriate way. It is also well known to incorporate in molded plastic articles, glass fibers, asbestos fibers, synthetic filaments or similar filaments, ae so as to reinforce the articles obtained and to give them greater strengths. to tension, traction, flexion and the like, than those obtainable by using the unreinforced plastic.



   Due to the low density and high degree of corrosion resistance possessed by many plastics, both thermoplastic resins and thermosetting resins have been used on a large scale for the production of plastic pipes and tubes. . As a result, it has become possible to manufacture pipes and tubes of much less weight and of considerably better resistance to corrosion by many fluids than was possible with metal pipes or tubes.

   On the other hand, the plastics available for the commercial manufacture of pipes impose serious limitations on the structural strength of pipes or tubes made from such plastics. Therefore, in order to increase the structural resistance of plastic pipes and to make them, in this respect, competitive with metal pipes or tubes, it has been necessary to develop processes and materials.

 <Desc / Clms Page number 4>

 with the help of which reinforcing fibers or other elements can be incorporated into the plastic pipe.



   The incorporation of reinforcing fibers into tubular plastic sections has heretofore been effected in a number of ways. Thus, it is possible to form a tubular section of reinforcing fibers using a fabric of woven fibers or using strands of fibers, place the resulting fibrous tube in a centrifugal molding form, introducing a suitable plastic molding material into the mold, and then subjecting the mold and its contents to suitable conditions to form a plastic pipe reinforced with fibers and obtained by centrifugal casting.



  Such methods of obtaining pipes are described, for example, in US Patents Nos. 02,785,442 and 2,790,997.



   Another method of obtaining plastic pipes reinforced with fibers is to wind a woven fabric or non-woven fibers on a mandrel, to impregnate the wound fibers with plastic material, for example by spraying, brush coating or other similar manner, then subjecting the mandrel and the plastic-impregnated fiber shell to the appropriate curing conditions to form the final pipe. The method of winding on a mandrel for obtaining plastic pipes is described, for example, in the patents of the United States of America. not
 EMI4.1
 2,467,999, 2,614,056 and 2.'135.1 + i + 2.



   Yet another basic process is known for forming tubes or pipes using plastics comprising reinforcing fibers. This process involves forming a woven or non-woven web using

 <Desc / Clms Page number 5>

 suitable reinforcing filaments, impregnating the self-supporting web with a resinous material, mounting the impregnated fibrous web on a mandrel or other suitable form, and applying to the resulting structure the conditions temperature and pressure necessary for the resinous impregnation material of the various layers of the fibrous web formed to melt and harden, until forming a solid mass in one piece comprising the reinforcing fibers.

   This third basic process for the production of plastic tubes is used in the procedures described in United States Patents Nos. 2,803,576 and 2,854,031.



   Although methods of obtaining plastic pipes, such as those described above and others, have been known for some time, the potential market for the sale of plastic pipes using strong fibers is. far from being supplied in an adequate manner, because of the difficulties and the cost of the methods known at present for the production of plastic pipes. Thus, although the various methods of manufacture described above are theoretically sound, their application for the formation of plastic pipes involves some serious complications.

   Thus, the incorporation of reinforcing fibers into the pipe structure tends to create tiny needle holes, through which the liquid contained under pressure in the pipe will slowly seep out. This defect of plastic pipes makes them unusable in a large number of applications envisaged.



   Various attempts have been made to suppress the problem of seepage in plastic pipes reinforced with fibers. Thus, it is known. To incorporate the non-fibrous layers or fillings into the in-

 <Desc / Clms Page number 6>

 inside the pipes, to create a barrier to prevent possible seepage of liquids into the needle holes which may present in the outer layers of the plastic pipe. In the centrifugal casting pipe forming process, as described above, this can be done by introducing an excess of the resinous material into the mold, so that an unfilled plastic layer accumulates in the central part of the mold. pipe, during its formation, so as to form an inner layer free of fibers.

   On the other hand, non-fibrous linings or inner layers can be formed in the other above-described pipe-forming methods, by first winding on the mandrel a non-fibrous sheet or web of suitable plastic material and then winding on this sheet or web. the desired number of fiber turns, so as to constitute the reinforced outer layers of the pipe. These methods for solving the problem of seepage are not, however, entirely satisfactory, because they impart an inhomogeneous structure to the pipes, so that the mechanical strength characteristics thereof may be reduced or may occur. delamination or stratification in the pipe during use.



   Another problem associated with the sale and use of fiber reinforced plastic pipes is the coupling elements, such as elbows, fittings and the like, which are required with such pipes. The fibers which are incorporated in some plastic pipes make it impossible to form suitable threads or threads at the ends of the pipes, so that threaded or tapped fittings cannot be fitted to the pipes. This drawback has been solved, in the case of some plastic pipes, by using cements and fittings of the type to be welded with the plastic pipes.

 <Desc / Clms Page number 7>

 



   However, this method of making connections is not possible with other known plastic pipes, because the surface of the pipes is so rough, due to the presence in them of reinforcing fibers, that it It is not possible to establish a satisfactory joint with cement between the pipe and a fitting.



   It is certain that plastic pipes would be accepted and used on a larger scale in commerce, if it was not necessary to use special fittings and special processes to connect pipe sections together, for example. example if it was possible to connect. aes plastic pipes using commonly used pipe-tapping processes and machines.



   Objects of the invention.



   The main object of the present invention is new forms of molded plastic articles reinforced with fibers. The objects of the invention are also:
1. New types of molding materials for use in forming plastic molded articles reinforced with fibers;
2. New processes for the production of molding materials for use in molding plastic articles reinforced with fibers;
3. New processes for forming plastic articles reinforced with fibers;
4.

   Fiber-reinforced plastic molded pipes, these pipes having a homogeneous structure and capable of being threaded or tapped mechanically by threading or using the usual pipe tapping machines;
5. Molded plastic pipes, without lining, reinforced with fibers, such pipes being able to contain water or comparable fluids under pressure.

 <Desc / Clms Page number 8>

 hydrastatic continues up to the tension or burst pressure of these pipes, without appreciable seepage of liquid through their walls; o.

   New molding materials comprising thermosetting resins and asbestos fibers, which can be used commercially, for the formation of pipes or other molded plastic articles, without appreciable tendency of the molded articles present. - make small needle holes or other uneven areas which may weaken the pipes or cause leaks;
7.

   New methods whereby molded plastic articles can be formed using the appropriate proportions of plastic and reinforcing fibers, to provide the desired structural and physical properties in the final molded article, without being necessary at the same time to use an unusual molding or handling machine or to apply special molding or tensile operations, which may increase the cost of plastic pipes to a level such that they become non competitive with metal pipes having comparable structural and physical properties.



   Other objects and advantages of the present invention will emerge from the following detailed description.



   It should be noted, however, that this detailed description, while indicating preferred embodiments of the invention, is given for illustrative purposes only, various changes and modifications may be made to the details of this invention. description, without departing from the scope and scope of the invention, as will be understood by those skilled in the art.

 <Desc / Clms Page number 9>

 



   GENERAL DESCRIPTION. according to the invention, a molding material is formed using an asbestos-based paper of a high mass, impregnated with about 40 to 65% by weight of a thermosetting resin, the impregnated paper is heated in controlled temperature conditions, to drive off any volatile solvent which may be contained in the paper, and the thermosetting resin is partially cured to a thermoplastic state commonly referred to as stage B. The paper impregnated with The resin obtained is a substantially dry self-supporting paper, which can be handled in sheet form or can be macerated so as to form fragments, which can be used as a molding material.



   Fiber-reinforced plastic pipes having a substantially homogeneous structure and having smooth inner and outer surfaces can be obtained by winding the B-stage resin-impregnated paper on a mandrel, at room temperature or at elevated temperature, and preferably using slight pressure or tension in the paper, to properly apply this paper to the core. The coiled paper and the core wrapped by the paper are then subjected to an elevated temperature and other conditions sufficient to melt the resin so as to transform it into a unit mass and to cure the resin to the commonly qualified stage. stage C.

   The operation of melting and curing the resin can be carried out in heated ovens or in other suitable devices.



  Curing in an oven is done by wrapping the paper wound on the mandrel in a non-fibrous plastic material, such as cellophane or polyethylene terephthalate, and placing it in a heated oven.

 <Desc / Clms Page number 10>

 



   The plastic wrap contracts slightly, exerting some pressure on the resin impregnated paper during curing.



   Other fiber reinforced plastics articles of a different shape can be obtained by placing sections of asbestos-based paper impregnated with stage B resin on a suitable form having the general shape as desired. desired to impart to the final plastic article, then subjecting the assembled sections to heat and pressure sufficient to mold the assembly to the desired final shape, to melt the resin and to cure it to the infusible state. In such operations, sheets of paper can be used or pieces of paper obtained by maceration of the sheets of paper can be used.



   The use of shredded paper as a molding material is preferred when it comes to forming articles with special contours or complicated shapes. The macerated resin impregnated paper can be used as a molding material in ordinary compression molding apparatus, especially for the manufacture of plastic articles of small dimensions.



   The molded plastic pipe free of interior liner or liner formed by the method of the invention has a homogeneous structure and has smooth interior and exterior surfaces. This pipe can be threaded or threaded using common pipe tapping machines, so that it can be connected to suitable fittings or coupling elements. On the other hand, since the surfaces of the pipe are smooth, connections using weld-type coupling members can easily be made using a suitable adhesive material.

   Application of molding operations using sheets or pieces of paper, as described

 <Desc / Clms Page number 11>

 above, provides elbow pipes, T-fittings, nipples and the like for use with new fiber-reinforced plastic pipes, without holes in the fittings or in the pipes needle or other small holes or cracks, through which could. flow of the fluid contained, under pressure, in the pipes or fittings.



   EXAMPLES.



   The invention will be further understood by reference to the following illustrative examples, in which all parts and percentages are by weight, unless otherwise indicated.



   Example 1
Various asbestos-based papers, obtained using certain particular asbestos fibers and having a mass of at least 0.3, are each impregnated with a solution of thermosetting resin. The impregnation of each asbestos-based paper is carried out by unwinding the paper from a roll at a controlled speed, passing it over an idle roller in a tank containing the resin solution, removing the paper from the tank, by passing it between squeeze rolls, so as to control the amount of liquid saturation material remaining in the paper, by passing the solution impregnated paper through an oven maintained under controlled conditions so as to heat the sheet impregnated up to a controlled temperature and for a controlled time,

   to evaporate the volatile components from the sheet and to partially cure the impregnated resin to stage B, the paper being finally wound onto a spool or a take-up roll. Details concerning the various operating conditions and characteristics of the materials used in these paper impregnation operations are as follows:

   

 <Desc / Clms Page number 12>

 TABLE 1
 EMI12.1
 
<tb>
<tb> Paper <SEP> asbestos <SEP> Test <SEP> n 1 <SEP> Test <SEP> n <SEP> 2 <SEP> Test <SEP> n 3
<tb> Identity <SEP> of the <SEP> fibers
Asbestos <tb> <SEP> 4X <SEP> Munro <SEP> 4X <SEP> Munro <SEP> 4XMunro
<tb> <SEP> content in <SEP> fibers
<tb> asbestos <SEP> 99% <SEP> 97%
<tb> dobby <SEP> binding
<tb> no <SEP> fibrous <SEP> WC-9 <SEP> WC-9 <SEP> WC-9
<tb> Content <SEP> in <SEP> binding <SEP> 1% <SEP> 3 <SEP> 3%
<tb> Caliber <SEP> (inches) <SEP> 0.010 <SEP> 0.0105 <SEP> 0.0105
<tb> Weight <SEP> (pounds / 100
<tb> <SEP> square feet) <SEP> 3.0 <SEP> 3.0 <SEP> 3.0
<tb> Mass <SEP> (100 <SEP> x
<tb> size / weight) <SEP> 0.33 <SEP> 0.35 <SEP> 0.35
<tb> <SEP> impregnation solution
<tb> Identity <SEP> of <SEP> the <SEP> resin <SEP> A <SEP> B <SEP> c <SEP>
<tb> Viscosity <SEP> 50 <SEP> c.p. <SEP> 50 <SEP> c.p.

   <SEP> 100 <SEP> c.p.
<tb>



  Solvent <SEP> nil <SEP> MEK <SEP> ethanol
<tb> Content <SEP> in <SEP> resin <SEP> 99% <SEP> 59.5% <SEP> 60%
<tb> Content <SEP> in <SEP> solvent <SEP> none <SEP> 27% <SEP> 39%
<tb> identity <SEP> of the <SEP> catalyst <SEP> X <SEP> Y
<tb> <SEP> content of <SEP> catalyst <SEP> 1% <SEP> 10.5% <SEP> - <SEP> - <SEP>
<tb> Identity <SEP> of <SEP> the
<tb> material <SEP> auxiliary <SEP> none <SEP> black <SEP> of <SEP> colorant
<tb> <SEP> content in <SEP> material <SEP> carbon
<tb> auxiliary- <SEP> - <SEP> 3%
<tb> Conditions <SEP> of <SEP> saturation.
<tb>



  Paper <SEP> speed <SEP>
<tb> (feet / min.) <SEP> 1.0 <SEP> 1.5 <SEP> 1.0
<tb> Temperature <SEP> (F) <SEP> 130 <SEP> 200 <SEP> 260
<tb> Heating <SEP> time <SEP>
<tb> (min) <SEP> 15 <SEP> 10 <SEP> 10
<tb> <SEP> content in <SEP> resin
<tb> final <SEP> of the <SEP> paper <SEP> 56% <SEP> 53% <SEP> 52%
<tb>
 
In the preceding Table 1, the following expressions and terms have the following meanings:
4XMunro refers to a chrysotile asbestos fiber, which has been refined to have a low fine fiber content, so that less than 30% of the fibers have a gauge of less than 200 mesh, while in the rest of the fibers, at at least 50% of these have a gauge between 28 and 100 meshes.

   The fibers also have a 3chopper-Riegler degree of independence of between

 <Desc / Clms Page number 13>

 500 and 560 and a Tappi standard minimum gloss (when wet) of 80.



   WC-9 denotes an emulsion of a polyalkyl acrylate sold by Rohm and Haas Co. under the name "Rhoplex WC-9".



   Resin A is a thermosetting unsaturated polyester resin comprising diallyl phthalate and styrene in a ratio of about 80:20.



   Resin B is a thermosetting epoxy resin consisting predominantly of polyglycidyl ether of 4,4'-dihydroxy diphenyl dimethylmethane.



   Resin C is a thermosetting phenolic resin consisting predominantly of the condensation product of phenol and formaldehyde and comprising a suitable catalyst, such as hexamethylenetetramine; for hardening.



   MEK denotes methyl ethyl ketone.



   Catalyst X is a mixture of equal parts of benzoyl peroxide and of methyl ethyl ketone peroxide.



   Catalyst Y is divine N-phenylene.



   The impregnated and dried paper rolls obtained in tests 1 to 3 are fed to a machine, in which sheets of paper from each test are wound on heated chroma polished mandrels with a diameter of 2 1/8 inches. Papers are wound on the mandrels in a direction such that the direction of the paper machine extends circoferentially and these sets are referred to as "Tests 1a, 2A, and 3A". A second set of polished chrome mandrels are wrapped in paper, winding the paper onto the mandrels so that the direction of the paper machine extends longitudinally, these sets being referred to as "Runs 1B, 2B, and 3B".

 <Desc / Clms Page number 14>

 



   The winding machine comprises two driven horizontal rollers, which are heated, the mandrel resting in the gap between these two rollers. Above the gap between the rolls is a third idle roller carried by a pneumatic cylinder and piston device, which allows the idle roller to be pushed down against the mandrel and to duplicate the paper pressure, while 'it is wound on the mandrel.



   A sufficient amount of paper is wound on each core, to achieve the desired thickness, after which the core carrying the paper layers is removed from the machine, wrapped in cellophane sheets and placed in an oven, where it is heated, for a time sufficient to melt and harden the resin with which the papaya tree is impregnated. The resulting pipes are then removed from the mandrels and trimmed to form finished pipes. Finally, the finished pipes are subjected to various tests, to determine their mechanical strength and other physical properties.



  The data relating to the manufacturing operations of the pipes and to the tests carried out on them are shown in Table 2 below:

 <Desc / Clms Page number 15>

   TABLE 2
 EMI15.1
 
<tb> Paper <SEP> Temp- <SEP> Tempe- <SEP> Pressure <SEP> Temper. <SEP> Temp. <SEP> Pressure <SEP> Thick- <SEP> Tension <SEP> Oozing
<tb> assault <SEP> erasing <SEP> erasing <SEP> rollers <SEP> of <SEP> hard- <SEP> of <SEP> hard- <SEP> atecla- <SEP> seur <SEP> at burst < SEP> raaial
<tb> rollers <SEP> mandrel <SEP> cisse- <SEP> cisse- <SEP> tement <SEP> of the <SEP> pounds / inch <SEP> checked
<tb> ment <SEP> ment <SEP> pounds / <SEP> walls
<tb> inch <SEP> square
<tb> lA <SEP> 175 F <SEP> 325 F <SEP> 100 <SEP> live. <SEP> 1 <SEP> hre <SEP> 300 F <SEP> 1500 <SEP> delivered / <SEP> 0.146 <SEP> pce <SEP> 12.800 <SEP> none
<tb> Engl.

   <SEP> Engl.
<tb> inch <SEP> inch
<tb> square <SEP> square
<tb> 2A <SEP> 160 <SEP> 300 <SEP> 100 <SEP> 1 <SEP> 300 <SEP> 1350 <SEP> 0.130 <SEP> 11.800 <SEP> "
<tb> 3A <SEP> 125 <SEP> 260 <SEP> 100 <SEP> (2 <SEP> (300 <SEP> 1175 <SEP> 0.116 <SEP> 12.700 <SEP> "
<tb> (3 <SEP> (350
<tb> 1B <SEP> 175 <SEP> 325 <SEP> 100.1 <SEP> 300 <SEP> 800 <SEP> 0.117 <SEP> 7.500 <SEP> "
<tb> 2B <SEP> 150 <SEP> 250 <SEP> 100 <SEP> 1 <SEP> 250 <SEP> 1350 <SEP> 0.143 <SEP> 7. <SEP> 200 <SEP> "
<tb> 3B <SEP> 125 <SEP> 260 <SEP> 100 <SEP> 2 <SEP> 260 <SEP> 700 <SEP> 0.125 <SEP> 6.

   <SEP> 900 <SEP> "
<tb> lA <SEP> 80 <SEP> 150 <SEP> 80 <SEP> 1 <SEP> 300 <SEP> 1450 <SEP> 0.132 <SEP> 13.700 <SEP> "
<tb> 2A <SEP> 155 <SEP> 300 <SEP> 100 <SEP> 1 <SEP> 300 <SEP> 1400 <SEP> 09128 <SEP> 11.900 <SEP> "
<tb> 3A <SEP> 125 <SEP> 225 <SEP> 100 <SEP> (2 <SEP> (260 <SEP> 1800 <SEP> 0.121 <SEP> 16.700 <SEP> "
<tb> (16 <SEP> (300
<tb> 1B <SEP> 150 <SEP> 300 <SEP> 100 <SEP> 1 <SEP> 300 <SEP> 800 <SEP> 0.148 <SEP> 7. <SEP> 700 <SEP> "
<tb> 2B <SEP> 150 <SEP> 250 <SEP> 100 <SEP> 1 <SEP> 250 <SEP> 1350 <SEP> 0.167 <SEP> 6.500 <SEP> "
<tb> 3B <SEP> 110 <SEP> 200 <SEP> 50 <SEP> (1 <SEP> (260 <SEP> 800 <SEP> 0.121 <SEP> 7.

   <SEP> 700 <SEP> "
<tb> (16 <SEP> (300
<tb>
 

 <Desc / Clms Page number 16>

 
The burst pressures shown in Table 2 are obtained by the ASTM D1180-51T process, by subjecting sections of pipe to increasing hydrostatic pressure, until the pipe breaks, the hydrostatic pressure at the time of the tension being determined in pounds per square inch, using a suitable pressure gauge mounted in the pressurized fluid line.



   The hydrostatic burst stress, at the time of pipe failure, is calculated for each pipe from the burst pressure, using the formula S = Pd / 2t, where 3 is the voltage, P is the internal pressure, t is the thickness of the pipe wall and d is its outside diameter.



   The seepage tests are carried out, using the hydrostatic burst apparatus, the pipe being held at a pressure of 300 pounds per square inch, for 2 hours, at room temperature. Visual observation of water droplets indicates radial seepage.



   Example II
An asbestos paper having a specific fiber content and exhibiting specific properties is impregnated with the aid of a phenolic resin, by applying the general impregnation process described in Example I.



  Asbestos paper is made of 4X Munro fibers and contains 97% of these fibers and 3% acrylic resin (Rhoplex WC-9 :) as a binder. The paper has a mass of 0.3.



   The phenolic resin used is a high temperature phenol-formaldehyde resin sold by the American Reinforced Plactics, Inc., under the name "Resin CTL 91-LD" dissolved in methyl isobutyl ketone (70% resin for 30% of solvent). After passing through the resin solution tank, the paper is made to pass through

 <Desc / Clms Page number 17>

 vertical drying towers, in which the impregnated sheet is subjected to the action of a current of air heated to 200 F, for 20 minutes.



   The resulting resin-impregnated paper contained 55% stage B phenolic resin. Sheets of this paper were wound on aluminum mandrels with an outside diameter of 2 inches, applying a tension of 10 pounds per square inch to the sheets. , during their winding. The winding machine operates with a roll pressure of 45 English pounds per square inch, with a mandrel speed of 6 revolutions per minute, the rolls and mandrels being heated to 240 F. The tubes obtained are heated, with a view to their hardening, for 1 hour at 300 F in an oven.



   The resulting pipes are machined to a wall thickness of 0.060 to 0.065 inch and are intended for use in a thermal battery as a replacement. of mica tubes. The tubes perform satisfactorily in the thermal coil, being exposed to temperatures of up to 1000 F for times of up to 5 minutes, without peeling or delamination of the paper layers.

   example III
Asbestos paper having a mass of 0.3 and containing 99% 4X Munro asbestos fibers and 1% Il Rhoplex WC-9 "binder is impregnated with an unsaturated polyester resin, consisting of 'a mixture of 80 parts of "Laminac 411111 and 20 parts of" Laminac 4119 "containing 0.5 part of benzoyl peroxide and 0.5 part of methyl ethyl ketone peroxide. The paper is passed through the saturation liquid at a speed of 1 revolution per minute, then dried and subjected to pre-curing in a vertical tunnel oven, for 20 minutes, at 200 F.

 <Desc / Clms Page number 18>

 



   Pipe sections are made by winding the resin-impregnated paper on 2-inch diameter chrome mandrels rotating at a speed of 6 revolutions per minute, the support rollers being heated to 200 F and a pressure of 60 English pounds. per square inch being applied through the rubber lined roller carried by cylinders directly above the manain.



  As soon as the desired thickness of the pipe wall has been obtained, the asbestos paper is cut and a sheet of cellophane is rolled up, so as to cover the tube with asbestos paper. The cellophane-covered tube is then rolled, for an additional 10 minutes, maintaining the temperature of the support rolls at 240 F. The pressure is then removed and the tubes are then placed in an oven, where they are subjected to final hardening by heating. at a temperature of 350 F for 30 minutes.



   The tubes obtained are subjected to various tests.



   They have the following properties:
 EMI18.1
 
<tb>
<tb> Specific <SEP> weight <SEP> 1.35
<tb> Percentage <SEP> of absorption <SEP> of water <SEP> 0.80
<tb> Average <SEP> burst voltage <SEP>
<tb> (pounds <SEP> inch <SEP> square) <SEP> 11,000
<tb> Seep <SEP> none
<tb> Modulus <SEP> of <SEP> rupture <SEP> (pounds / inch <SEP> squared) <SEP> 21,500
<tb> Resistance <SEP> at <SEP> the <SEP> bending
<tb> (pounds / square inch <SEP>) <SEP> 17,400
<tb>
 
In the tests referred to in the table above the water absorption is obtained by immersing a weighed sample of pipe in water at 190 F for 7 days. The sample is then removed from the water, dried and immediately re-weighed. The percentage of water absorbed is calculated from the difference between the original weight and the final weight.

   Flex @ ion strength is determined by centrally loading a pipe placed on supports 24 inches apart.

 <Desc / Clms Page number 19>

 



   In another case, the asbestos paper is impregnated in an apparatus, which allows the paper to be subjected to a vacuum, before passing it through the impregnation solution. It can be seen that a pipe formed using this paper has substantially the same properties as the pipe referred to above.



   In another case, the asbestos paper is preheated to 400 F for 5 hours, before impregnation.



    @n see that a pipe made using this paper has substantially the same properties as the pipe of the first case.



   Example IV.



   Other papers have been made using asbestos fibers different from those mentioned in the previous examples. Jeffrey 5K04 and Munro 4Y fibers were used. Several different asbestos papers having a mass of at least 0.30 have been made, using these fibers in combination with cellulosic fibers, the total of cellulosic fibers reaching 20% of the weight of the total fibers. The papers were impregnated with various thermosetting resin solutions, substantially as described above. The data relating to the various operating conditions and to the characteristics of the materials used in the impregnation processes are given in the following table:
TABLE 3.
 EMI19.1
 
<tb>
<tb>



  Paper <SEP> asbestos <SEP> Test <SEP> n <SEP> 4 <SEP> Test <SEP> n <SEP> 5
<tb> Identity <SEP> of the <SEP> fibers
<tb> asbestos <SEP> 5KO4 <SEP> Jeffrey <SEP> rY <SEP> Munro
<tb> <SEP> content in <SEP> fibers
<tb> asbestos <SEP> 78% <SEP> 78%
<tb> Identity <SEP> of the <SEP> fibers
<tb> cellulosic <SEP> Kraft <SEP> (bleached) <SEP> Kraft <SEP> (bleached)
<tb> <SEP> content in <SEP> fibers
<tb> cellulosics <SEP> 19% <SEP> 19%
<tb> Binding material <SEP> <SEP> non <SEP> fibrous <SEP> WC-9 <SEP> WC-9
<tb>
 

 <Desc / Clms Page number 20>

 
 EMI20.1
 
<tb>
<tb> <SEP> content in <SEP> binding <SEP> 3% <SEP> 3%
<tb> Caliber <SEP> (inches) <SEP> 0.03 <SEP> 0.03
<tb> Weight <SEP> (pounds / 100
<tb> <SEP> square feet) <SEP> 3.0 <SEP> 3.0
<tb> Mass <SEP> (100 <SEP> x <SEP> caliber / weight) <SEP> 0.35 <SEP> 0,

  35
<tb> <SEP> impregnation solution
<tb> Identity <SEP> of <SEP> the <SEP> resin <SEP> C <SEP> B
<tb> Viscosity <SEP> 100 <SEP> c.p. <SEP> 50 <SEP> c.p.
<tb>



  Solvent <SEP> ethanol <SEP> MEK
<tb> <SEP> content in <SEP> Resin <SEP> 60% <SEP> 59.5%
<tb> <SEP> content in <SEP> solvent <SEP> 39% <SEP> 27%
<tb> Identity <SEP> of the <SEP> catalyst <SEP> - <SEP> y
<tb> <SEP> content of <SEP> catalyst <SEP> - <SEP> 10.5%
<tb> Identity <SEP> of <SEP> the <SEP> material
<tb> auxiliary <SEP> coloring <SEP> black <SEP> of
<tb> carbon
<tb> Content <SEP> in <SEP> material
<tb> auxiliary <SEP> 1% <SEP> 3%
<tb> Conditions <SEP> of <SEP> saturation
<tb> <SEP> speed <SEP> paper <SEP> (feet / min) <SEP> 1.0 <SEP> 1.5
<tb> Temperature <SEP> (F) <SEP> 260 <SEP> 2000
<tb> Heating <SEP> time <SEP> <SEP> (min) <SEP> 10 <SEP> 10
<tb> <SEP> content <SEP> resin <SEP> of the
<tb> final <SEP> paper <SEP> 52% <SEP> 53%
<tb>
 
Example V
Other asbestos papers have been made using still other types of asbestos fibers,

   namely the Cape Blue type. A molded pipe was made using this fiber with epoxy resin and phenolic resin;
The data concerning the operating conditions and the characteristics of the materials correspond substantially to those of tests n 2 and n 3 of Example I, except that the asbestos fiber used was different. The results of tests No. 6 and No. 7 carried out with these articles are given in Table IV.



   This table 4 represents the best results obtained with the papers produced during tests 4 to @ described above. In all cases, the papers were wound on the mandrels, which spread out; formed by chrome cylinders having a diameter of 2.035 inches, the machine direction of the paper extending circumferentially.

 <Desc / Clms Page number 21>

 



    TABLE 4
 EMI21.1
 
<tb> Paper <SEP> Tempera- <SEP> Temp- <SEP> Pressure <SEP> Temp. <SEP> Temp. <SEP> Pressure <SEP> Thickness <SEP> Tension <SEP> Oozing
<tb> ture <SEP> erasing <SEP> rollers <SEP> of <SEP> hard- <SEP> of <SEP> hard- <SEP> of burst- <SEP> of <SEP> pa- <SEP> d 'radical <SEP> burst
<tb> rollers <SEP> mandrel <SEP> liv / Ang / <SEP> cisse- <SEP> cisse- <SEP> ment <SEP> kings <SEP> pounds / inch
<tb> pce <SEP> square <SEP> ment <SEP> ment <SEP> liv / pce <SEP> square
<tb>
 
 EMI21.2
 .25 F. 260 OF 100:

   . , h.hre 3 25 F - 0.170 None
 EMI21.3
 
<tb> 5 <SEP> 160 <SEP> 300 <SEP> (100 <SEP> (2 <SEP> (325 <SEP> 1870 <SEP> 0.187 <SEP> 11.500 <SEP> "
<tb> (0 <SEP> (4 <SEP> (400
<tb> 6 <SEP> 160 <SEP> 300 <SEP> 100 <SEP> 4 <SEP> 300 <SEP> 2100 <SEP> 0.171 <SEP> 14. <SEP> 700 <SEP> "
<tb> 7 <SEP> 125 <SEP> 260 <SEP> 100 <SEP> (2 <SEP> (300 <SEP> 2100 <SEP> 0.171 <SEP> 14.700 <SEP> "
<tb> (3 <SEP> (350
<tb>
 

 <Desc / Clms Page number 22>

 
DETAILED DESCRIPTION.



   The success of the present invention is due in large measure to the discovery of a critical difference in the behavior of certain specific asbestos papers, when used for the formation of fiber reinforced plastic articles. In general, reinforced thermosetting plastics articles tend to be somewhat porous, regardless of the reinforcing fibers or filaments contained therein, unless such reinforcing materials are present in low proportions. Consequently, it was the rule that pipes made of thermosetting plastic material, devoid of interior lining and reinforced with the aid of asbestos fibers, glass fibers or cellulosic fibers, revealed an oozing of liquid through their wall, when subjected to hydrostatic pressure.

   However, it has now been found that if the asbestos fibers to be used as reinforcing elements are first incorporated into paper having certain defined high mass characteristics, which will be elucidated further in the remainder of this specification, and if the paper is then impregnated with a determined amount of chermosetting resin, after which the impregnated paper is pressure and hot molded, so as to form a molded article, the problem of liquid seeping through the walls of the article, when the liquid contained therein is subjected to hydrostatic pressure, is substantially emitted.



   The paper to be used for carrying out the new plastic forming operations according to the present invention is characterized by the fact that it consists essentially of asbestos fibers with a minimum amount of added binding materials or other auxiliary agents added. This paper is referred to as "asbestos paper".

 <Desc / Clms Page number 23>

 



  Other fibrous materials, such as cellulosic fibers, may be incorporated into the asbestos paper in amounts which do not significantly affect the basic characteristics of the paper used in accordance with the present invention. Thus, as the examples which have been given above reveal, cellulosic fibers, such as Kraft fibers, can be incorporated, in high proportions, in the asbestos paper, while providing a paper which is perfectly suitable for use in producing molded articles free from seepage. Therefore, as long as the asbestos paper retains its high mass characteristic and its ability to form seep-free molded articles, it can be modified in this way.

   The expression "asbestos paper", as used herein, has a meaning encompassing the variations just discussed. Specifically, the paper should have substantially 90-99% fiber and 1-10% binder or other auxiliary materials.



   The asbestos fibers preferably used in paper are those which are referred to in the trade as "coarse". Coarse asbestos fibers are those obtained from asbestos of the group consisting of chrysotile, crocidolite and amosite. Examples of satisfactory commercial asbestos fibers include 4X Munro and 6D Jeffrey fibers. Preferably, the asbestos fibers to be used for preparing the paper employed in the process according to the present invention should be refined, so as to have a low content of fine fibers.

   Thus, the asbestos fibers should preferably be refined so that at most 30% of these fibers have a gauge of less than 200 mesh, that is to say that no more than 30 by weight of fibers pass through a standard 200 mesh screen. The ... remaining fibers may have a caliber

 <Desc / Clms Page number 24>

 any over gauge 200 mesh, but at least about 50% of that remaining. of. The fibers shall be of such a size that it will pass through a standard 28 mesh screen and be retained by a standard 100 mesh screen.



   In addition to the type and size of the asbestos fibers to be used in preparing the paper employed in the process according to the present invention, it has also been found that the asbestos fibers should preferably be well open, so that only a relatively small amount of bundles is found among the fibers. The term "bundle" denotes an assembly of asbestos fibers 1/32 to an inch or more in diameter. The suitability of the asbestos fibers can, 4 (in this regard, be determined by the Schopper-Riegler independence test. In this test, the asbestos fibers to be used in the process according to the invention must have an independence value of between approximately 500 and 560.

   In addition, the fibers must be relatively clean, so that when subjected to the standard Tappi gloss test (wet), the gloss of these fibers is not less than 70.



   The most desirable results, with respect to the strength of the molded pipe and the absence of any weeping therein, are obtained when using a paper formed from asbestos fibers as indicated, with a minimum quantity. binder or other added material.



  Thus, although it is possible to use from 1 to 10% of added binder, it is preferred that the percentage of added binder is between 3 and 5% by weight, relative to the total weight of the paper. The non-fibrous binder material, which is used in asbestos paper, serves to impart sufficient wet strength to this paper to enable it to be handled and subjected to subsequent stages of impregnation using of resin. Various binding materials of this type are known in the art of making asbestos paper.

 <Desc / Clms Page number 25>

 



  Among these binding materials, mention may be made of vinyl resins, such as polyvinyl chloride resins, preferably employed in the form of aqueous emulsions, acrylic resins, such as methyl, ethyl, butyl and hexyl esters of acrylic acids and methacrylic, copolymers or mixtures of this? resins, cellulose ethers or esters, and comparable non-fibrous resinous materials, which can be used in asbestos paper, to impart the required cohesive qualities thereto.



   In addition to a non-fibrous binder material, the asbestos paper may contain, within the limits indicated, fillers or pigments, for example for the purpose of modifying the appearance or color of the paper. Among these fillers or pigments, mention may be made of titanium dioxide, carbon black, silica, red pigments, heavy metal pigments, etc. In some cases, it / may be desirable to laminate or assemble the asbestos paper with woven or non-woven webs of other fibers, for example with glass fiber cloth, with nylon felt, or with woven or non-woven webs of other fibers. analogous materials.



   The paper to be used in accordance with the present invention should not only consist of the fibers specified above, but should also have a relatively high mass. The mass is the caliber divided by the weight multiplied by 100. The caliber is the thickness measured in inches and the weight is measured in pounds an-
 EMI25.1
 , -, ¯-¯ 'AA -in- --- d- A- ¯4o Too oo x'> m; nlr, p -y'1d1'7cJ by # ïôu..W.crrc.; A w. .1 -'......, ..., .............--- # Y-. - ni3.?i*'ç to be used in the process according to the present invention must have a mass of at least 0.3 and this mass should preferably be between 0.3 and 0.6.

   It cannot be categorically stated that satisfactory results cannot be obtained with paper of mass less than

 <Desc / Clms Page number 26>

 
0.20, but it is known that commercial 10 pound asbestos papers with a mass of 0.22 certainly do not produce satisfactory results, and therefore a mass less than about 0.28 does not. may not be commercially recommended.



   The exact reason why the specified types of paper are suitable in the processes of forming plastic articles, for the production of pipes and other articles free from seepage has not been determined. There appears to be a kind of unique cooperation between the fibers of this class of paper and the thermosetting resins used to impregnate it, such cooperation being such that molded articles are obtained which possess strength characteristics. high to breakage and, at the same time, free from pinholes or other cracks or openings of small dimensions, which could give rise to seepage or flow of the fluid through the walls of the molded articles.

   In any case, the use of the specified type of asbestos paper in combination with thermosetting resins makes it possible, in accordance with the present invention, to produce fiber-reinforced plastic pipes, which possess physical and structural properties. remarkable, without any tendency to ooze or seep and without the need to use interior linings or linings of plastics, non-fibrous layers of plastics or the like inside the pipes , to prevent seepage;

   Otherwise . the use of asbestos paper in the manner specified permits the production of pipes and other molded articles, which have a substantially homogeneous structure, the fibers being distributed throughout the resinous backing so that the reinforcing material does not. does not affect the possibilities of tapping or mechanical threading of pipes, using the usual threading or tapping machines.

 <Desc / Clms Page number 27>

 



   There are a wide variety of thermosetting resins which can be used for the production of the novel molding materials of the present invention and for the manufacture of such fiber reinforced articles by the methods described herein. Furthermore, it is probable that as the technology of synthetic resins develops, new thermosetting resins will be developed which can be used in the process according to the present invention.



   The thermosetting resins which have proved to be the most satisfactory in the process according to the present invention are those which are called, in the trade, phenolic resins, unsaturated polyester resins and epoxy resins.



   Phenolic resins are condensation products of a phenol and an aldehyde, for example phenol, cresol, p-hydroxy diphenyl or other phenols, with formaldehyde, furfural and other aldehydes. Any type of phenolic resins capable of being brought to a final condensation stage can be used. The preparation and chemical structure of the phenolic resins which can be used of Ç are given in the work entitled "Encyclopedia Chemical
Technology ", published in 1953 by The Interscience Encyclopedia Inc., volume 10, pages 335 to 369. Suitable phenolic resins are also described in numerous patents, notably in United States Patents Nos.
1,126,926, 2,272,155 and 2,736,718.



   Unsaturated polyester resins are the esterification products of unsaturated alcohols with polybasic acids or of unsaturated acids with monohydric or polyhydric alcohols. These resins are those which are described in the synthetic resin industry as "Contact resins"; see, for example the work "Encyclopedia of Chenical Technology", supra, volume 1, pages 590 and 591 and

 <Desc / Clms Page number 28>

 volume 10, pages 807 and 808. Specific examples of such preferred resins include polymers of diallyl phthalate, diallyl maleate, glycol diacrylate, glycol dimethacrylate and similar unsaturated polyesters, such as those described in U.S. Patents 2,501,610, 2,596,162, 2,806,014 and 2,810,712.

   Commercial products of this type are usually blends of the unsaturated polyesters, which often contain small amounts of other polymerizable materials, such as styrene, divinylbenzene, vinyl acetate, l. methyl acrylate and the like.



   Commercial polyester resins sold by the American
Cyanamid Company under the trade names "Laminac
4111, "" Laminac 4116 "and" Laminac 4134 "give good results.



   Epoxy resins are thermosetting ethoxylin resins of polyglycidyl ethers of polyhydroxy compounds with polybasic carboxylic acid anhydrides or with equivalent polyfunctional compounds.



   The production and chemical structure of usable epoxy resins are described in volume 45, pages 2715 to
2721 of the work "Industrial and Engineering Chemistry", and in the first supplement (1957) of the work "Encyclopedia
Of Chemical Technology, "supra, pages 312-329. Specific examples of usable epoxy resins are described in U.S. Patents 2,824,851, 2,863,853,
2,890,196 and 2,890,204. As commercial epoxy resins which can be used, mention may be made of "Epon
828 "and" Epon 892 "sold by Shell Chemical Co.



   In order to achieve the proper combination of structural strength and non-seepage of the molded plastic articles according to the invention, the ratio of resin to asbestos paper must be adjusted, from

 <Desc / Clms Page number 29>

 such that the resin-impregnated, solvent-free paper which serves as the molding material according to the invention contains about 40 to 65% by weight of resin, based on the total weight of the resin-impregnated paper. It has been found that a resin content of less than 40% produces molded articles showing a tendency to weep. On the other hand, the use of more than about 65% resin produces molded articles, which tend to have insufficient tensile strength and other mechanical properties.



   A small amount of catalyst must generally be contained in the resin-based liquid impregnation mass used to saturate the asbestos paper. however, some commercially available resins contain a catalyst and therefore do not require the addition of a catalyst material. The exact amount of catalyst used can vary and depends, to some extent, on the particular catalyst used, as well as the particular thermosetting resin used. Preferred resinous impregnation solutions will, however, contain from about 0.1 to 10% by weight of catalyst, based on the weight of the thermosetting resin, with a quantity of catalyst of between 0.5 and 5% by weight being especially effective.



   Many different types of catalyst are known and are useful in the process according to the present invention, along with the various types of thermosetting resins which can be used. As catalysts which can be used for phenolic resins, mention may be made of the oxides and hydroxides of sodium and other alkali metals and ammonia, calcium and other alkaline earth metals, zinc, aluminum, amines, such as ethylene diamine, aniline and cyclohexylamine, quaternary ammonium bases, such as tetramethyl ammonium hydroxide, methylpyridinium chloride or the like, as well as mixtures of these compounds.

 <Desc / Clms Page number 30>

 



   As catalysts which can be used for unsaturated polyester resins, mention may be made of organic peroxides, such as benzoyl peroxide, acetyl peroxide, butoyl peroxide, methyl ethyl ketone peroxide, tert.-butyl hydroperoxide, peroxide. stearyl, cumene hydroperoxide, caprylyl peroxide, salts of heavy metals, such as copper or cobalt linoleates and naphthenates, azo compounds, such as azobisisobutyronitrile, methyl azoisobutyrate, and mixtures of these materials.



   As suitable catalysts for epoxy resins, mention may be made of amines, such as m-phenylenediamine, ethanoldiamine, dialkoylaminopropylamines, triethylanine, piperidine, etc., amides, such as formamide, phthalimide, succinl diamide, acid anhydrides, such as phthalic anhydride, pyromellitic dianhydride, maleic anhydride, sulfones, such as diaminodiphenyl sulfone, as well as mixtures of these and equivalent materials.



   The new molding materials according to the invention composed of asbestos paper impregnated with a thermosetting resin in stage B do not have an unlimited shelf life, that is to say if these materials are kept at room temperature for several days or more, the resin contained therein may undergo some transformation towards stage C, which may tend to make the subsequent molding unsatisfactory. Molding materials made from unsaturated polyester resins or from epoxy resins have, as has been observed, a shorter shelf life than molding materials obtained using resins. phenolic. The shelf life of molding materials can be extended by storing these materials under refrigeration.

   However, another method to prolong

 <Desc / Clms Page number 31>

 The shelf life of molding materials has also been developed. This process consists in using special catalyst mixtures in the preparation of the resin-impregnated asbestos papers according to the invention. These catalyst mixtures consist of a catalyst material capable of producing only a partial cure of the thermosetting resin at a temperature below about 200 F, this catalyst material being added with another catalyst which is not. not active enough to cure the resin at temperatures below 200 ° F, but which acts at temperatures above about 200 ° F to completely cure the resin to its final state.

   The first component of the catalytic mixture allows the resin with which the asbestos paper is impregnated to harden up to stage 3, without the resin tending to polymerize or to condense, to an undesirable extent, until the final stage, before the final molding operation. An example of this type of catalytic system is a cast made of equal parts benzoyl peroxide and peroxide (methyl ethyl ketone, for use with unsaturated polyester resins.) Asbestos paper sheets impregnated with the aid of a solution of an unsaturated polyester resin, such as diallyl phthalate polymer, can be subjected to pre-curing, using 1% of said catalyst mixture, resulting in 15 to 30 minutes at 130 F, so as to form dry sheets impregnated with resin and free from solvent.

   Under such pre-curing conditions, the methyl ethyl ketone peroxide in the catalyst apparently polymerizes the resin to stage B. The molding material can then undergo final curing at a temperature of 300 F for a period of time. half to one hour, during which the resin melts and is activated until the final stage of hardening, by the action of benzoyl peroxide.

 <Desc / Clms Page number 32>

 



  As other examples of catalytic mixtures with delayed action, there may be mentioned mixtures of sodium hydroxide and sodium phenol or mixtures of calcium oxalate and p-phenylenediamine for phenolic resins; Mixtures of be.:zoyl peroxide and tert-butyl hydroperoxide for unsaturated polyester resins; mixtures of maleic anhydride and adipic acid or mixtures of phthalic anhydride and phthalimide for epoxy resins.



   In order to form the resinous impregnation solutions serving to saturate the asbestos paper, volatile solvents can be used to obtain the desired viscosity of the impregnation solution, if the thermosetting resin itself does not have the properties. desired viscosity. Furthermore, it is also possible to adjust the viscosity of the impregnation solution by mixing together two or more fractions of thermosetting resins which have different viscosities, so that the final mixture of resins has an adequate viscosity to impregnate the asbestos paper to such an extent that, when the impregnated paper has been subjected to pre-curing to bring the resin to stage B,

   this paper contains the above-mentioned desired proportion of 40 to 65% by weight of resin. It goes without saying that, if the impregnation solution is too fluid, the paper will not be able to retain sufficient impregnation liquor during its subsequent handling, to make it possible to obtain the desired resin content. Conversely, if the impregnation solution is too viscous, it is not possible to properly impregnate the paper with the desired amount of resin. It has been found that impregnation solutions with viscosities between about 50 and 100 centipoise produce the best results, these viscosities being measured using the Gardner-Holt viscometer.

 <Desc / Clms Page number 33>

 



   When a volatile solvent is used to form impregnation solutions of desired viscosity with the
 EMI33.1
 heat-setting resins, it is preferable to use solvents which dissolve thermosetting resins, have a boiling point of less than 250 F and, in particular, a boiling point of between 80 and 200 F approximately.



  As examples of solvents which can be used, there may be mentioned methanol, ethanol, butanol, benzene, toluene, acel.
 EMI33.2
 tone, methyl ethyl ketone, / methyl isobutyl ketone, ethylene dichloride, carbon tetrachloride, ethyl acetate and other volatile organic solvents of comparable dissolving power and comparable volatility. The amount of solvent used to form the impregnation solutions depends primarily on the viscosity of the heat-setting resin used, as well as on the solvent used to form the impregnation mass. With very viscous thermosetting resins, up to 50% by weight of solvent can be used, relative to the total weight of the impregnation solution.

   In general, the amount of volatile solvent used varies between about 5 and 20% of the weight of the impregnation solution.



   The impregnation of the asbestos paper with the aid of the thermosetting resin can be carried out in any suitable type of apparatus. Impregnation tanks, padding devices, squeegee devices, roller coating devices, spray devices or the like can be used. Whatever the device used, the operation of
 EMI33.3
 turing v4d'impgnatiûn must be done in conditiûfi5 tülGVlVi1 VIfU l1111G11cttiiVll '-tOit j-airë t10.11.y.tGv7 .Vlll, tltn1V11J such that a sufficient quantity of the resin is incorporated into the asbestos paper, so that the latter exhibits, after removal of all the volatile solvents, a solid resin content of between approximately 40 and 65% by weight.

 <Desc / Clms Page number 34>

 



   After impregnation of the paper with the thermosetting resin, the impregnated sheets are subjected to conditions suitable for removing all of the volatile organic solvents and the like and for partially converting the thermosetting resin, so that that - this is at stage B of its transformation. To this end, it is possible to use, in a satisfactory manner, tunnel ovens or dryers heated by steam, infrared rays or by induction.



   The conditions applied for the treatment of impregnated asbestos papers, to obtain the new molding materials according to the present invention, may vary and will depend, in part, on the thermosetting resin used to impregnate the paper. Phenolic resins, in general, require more severe temperature and time conditions than epoxy resins or polyester resins. Furthermore, the treatment time at a given temperature will depend to some extent on the amount of solvent contained in the resinous impregnation solution.

   However, for the preferred resinous impregnation masses described above, temperatures between
100 and 200 F, applied for 5 to 60 minutes, are generally the most suitable for obtaining new molding materials from asbestos papers impregnated with thermosetting resins.



   At the end of the pre-curing operations which have just been described, one can obtain papers impregnated with resin, which are self-supporting, substantially: 5 secs and can be wound up, so as to form rolls, for their use. subsequent. Such resin impregnated papers can be wound on mandrels, so as to form stubs or tubular sections of suitable thickness, from which fiber-reinforced plastic pipes can be obtained by operations.

 <Desc / Clms Page number 35>

 appropriate molding.

   Similarly, sections of the sheets of paper can be assembled into suitable shapes and then subjected to molding conditions such as to form molded articles of various shapes, such as elbows, tees, nipples or parts. Similar tubulars intended to serve as a connection with the long sections of plastic pipes, which can be cast on cylindrical mandrels from the resin-impregnated sheets.

   Molds or forms made of low melting point metal alloys can be used to advantage for these molding operations, because after converting the resin-impregnated paper into a molded article, by applying suitable curing conditions, the term metallic can be removed by heating the assembly to a temperature above the melting point of this metallic form, which allows the metal to be poured out of the plastic article.

   On the other hand, in the special case of molding small plastic articles or objects or articles having special shapes or contours, the sheets of paper may be macerated or shredded, so as to form fragments. , which can then be sent under pressure into suitable molding cavities, so as to form articles of desired shape by well known compression molding operations.



   It is. It is possible to perform molding and final curing of the resin impregnated asbestos paper without the application of pressure. However, the most satisfactory results are obtained when high pressures are applied to the molding material during the curing operation. In cases where it is a question of molding sections or sections of pipe, a satisfactory pressure can be obtained by wrapping the mandrel and the asbestos paper wound on it in a wrap of cellophane, polyethylene terephthalate or 'a similar material,

 <Desc / Clms Page number 36>

 which will contract slightly under curing conditions, so as to apply slight pressure to the paper wound on the core.

   Similarly, any other suitable mode of applying pressure and heat to the sections of resin impregnated paper can be used.



  Ordinarily, a temperature of at least 300 F applied for at least 1 hour will be used for curing the molding material. More particularly, temperatures of 300 to 500 F, applied for 1 to 24 hours, can be employed at pressures of 1 to 500 pounds per square inch, for example. The hardening of the molding materials can take place in several different stages. Thus, the initial curing can be performed at pressures above atmospheric pressure, while a longer curing can subsequently be performed at atmospheric pressure.

   This is of particular interest in the case of molding materials made from phenolic resins, which generally require longer cure times for full cure. If difficulties are encountered in removing mandrels or other shapers from molded articles, special agents can be used to overcome these difficulties. As is known, release or detachment agents may be incorporated into the molding material or may be applied, as a film, to the mandrel or other shaping device.



  As such agents, heavy metal salts of fatty acids, graphite, silicone resins, high molecular weight fluorocarbons or the like can be used.



   CONCLUSIONS.



   In the foregoing description, new methods have been described for the manufacture of plastic pipes reinforced with fibers and other articles.

 <Desc / Clms Page number 37>

 fiber-reinforced plastics, while methods have also been described which can be used to obtain molding materials for use in the manufacture of the pipes and molded articles in question.



  The new molding processes are characterized in that they produce fiber reinforced plastic structures which are substantially homogeneous and yet contain at least 35 to 60% by weight of reinforcing fibers. Furthermore, the new plastic articles are substantially free from any tendency to ooze, i.e. they do not allow liquid to pass through their wall, when the liquid is contained in these articles under pressure. substantial hydrostatic.

   The pipes, fittings or other articles obtained by the process according to the invention can be subjected to hydrostatic pressures of at least 600 English pounds per square inch at room temperature for an indefinite time, without showing any sign of ooze or oozing. , while they can also withstand pressures of 300 English pounds per square inch for at least 24 hours at 200 F. In addition, the new plastic articles withstand high temperatures, for example temperatures of about 1000 F for at least 5 minutes, without undergoing disintegration or delamination.

   Another feature of the molding process according to the invention is that the articles, such as molded pipes, can be tapped or threaded using the usual apparatus and methods for threading or tapping pipes, while 'They do not require the use of special fittings or special molding operations to create a fluid-tight seal between a pipe and a fitting.


    

Claims (1)

CLAIMS. 1.- Material intended for use in forming molded plastic articles reinforced with fibers and impermeable to fluids, characterized in that it consists of asbestos paper impregnated with 40 to 65% by weight approximately of a thermosetting resin, this paper having, before impregnation, a mass greater than 0.3 and consisting essentially of 90 to 99% by weight of reinforcing fibers consisting essentially of asbestos fibers and 1 at 10% of a non-fibrous binder. 2.-. Material according to claim 1, characterized in that the paper is macerated so as to form a mass of dry and free fragment'3 of asbestos paper impregnated with resin. 3.- 1-side according to claim 1, characterized in that it contains two curing catalysts, one of these catalysts being capable of producing only a partial curing of the resin at a temperature below 200 F, while the other catalyst is relatively inefficient at temperatures below 200 F, but is effective at temperatures above about 200 F. to completely harden the resin to its final stage. 4.- Process for obtaining a molding material intended to be used for the manufacture of molded plastic articles reinforced by means of fibers, these articles being impermeable to fluids, characterized in that a paper of 'asbestos having a mass greater than 0.28 and consisting essentially of 90 to 99% by weight of fibers and from 1 to 10% of non-fibrous binder, the fibers consisting essentially of asbestos, this paper is impregnated using of a liquid mass comprising a thermosetting resin, the proportion of liquid mass relative to the paper being such that the final impregnated paper contains .. 40 to 65% <Desc / Clms Page number 39> by weight of resin, and the impregnated paper is heated so as to remove volatiles therefrom and to polymerize the resin to a stage 3 at which a dry asbestos paper impregnated with resin and containing about 40 to 65% by weight of thermosetting resin is obtained. 5. A method according to claim 4, characterized in that the heat-setting resin is an epoxy resin. 6. A method according to claim 4, characterized in that the thermosetting resin is an unsaturated polyester resin. 7.- Method according to claim 4, characterized in that the asbestos fibers have a Schopper-Riegler independence of between 500 and 560 approximately and a Tappi gloss of at least 80. c.- Method according to claim 4, characterized in that the non-flowering binder is a water-insoluble acrylic ester polymer. 9. A method according to claim 4, characterized in that the impregnated paper shreds, so as to form dry and diatincts fragments. 10.- Material intended to be used for the manufacture of molded plastic articles reinforced with fibers and impermeable to fluids, this material is characterized in that it consists essentially of a paper based on asbestos fibers, free from volatile solvents and impregnated with 40 to 65% of a thermosetting phenol-formaldehyde resin partially cured up to stage 2, the paper having, before its impregnation, a mass greater than 0.3 and consisting essentially of 90 to 99 % by weight of fibers and from 1 to 10% of a non-fibrous polymeric binder insoluble in water, the fibers consisting essentially of coarse asbestos fibers of a size such that at least about 50% by weight of these fibers pass through a screen <Desc / Clms Page number 40> 28 mesh standard and are retained by a standard 100 mesh screen with at least 70% by weight of the fibers being retained by a 200 mesh screen. 11.- Material intended to be used for the manufacture of molded plastic articles, reinforced with fibers and impermeable to fluids, characterized in that it consists essentially of a paper based on asbestos fibers, free from volatile solvents and impregnated with approximately 40 to 65% of a thermosetting phenol-formaldehyde resin partially cured to stage B, the paper having, before its impregnation, a mass greater than 0.3 and consisting essentially of 90 to 99 ;: by weight of fibers and the% of a non-fibrous, water-insoluble polymeric binder, the fibers consisting of 80% by weight of asbestos fibers and 20% by weight of cellulosic fibers . 12.- Material according to claim 11, characterized in that the asbestos fiber is a rough fiber of a size such that at least 50% by weight of the fibers pass through a standard 28 mesh screen and are retained by a standard 100 mesh screen, at least 70% by weight of the fibers being retained by a standard 200 mesh screen. 13. - Molded article of fiber-reinforced plastic material and fluid-tight, characterized in that it is formed of sections of paper based on asbestos fibers fixed in a support formed of a thermoset synthetic resin, the resin. constituting from about 40 to 65% by weight of the article, the remainder of the latter being constituted by the asbestos paper which comprises at least 90% by weight of reinforcing fibers consisting essentially of asbestos fibers. 14. A molded article according to claim 13, characterized in that the asbestos fibers have a size such that at least about 50% by weight of these fibers pass <Desc / Clms Page number 41> through a standard 28 mesh screen and be retained by a standard 100 mesh screen, at least 70% by weight of the fibers being retained by a standard 200 mesh screen. 15. - Molded plastic pipe reinforced with fiber medium and capable of containing water under continuous hydrostatic pressure up to the burst pressure of the pipe, without any appreciable seepage of liquid through the walls of this pipe , characterized in that it consists of turns of a paper based on asbestos fibers fixed in a support made of a thermoset synthetic resin, the resin constituting from 40 to 65% by weight of the article, the remainder thereof being constituted by asbestos fibers of which at least 78% by weight are coarse asbestos fibers. 16.- Molded plastic pipe, characterized in that it consists of a mass of reinforcing fibers distributed homogeneously in a support made of a thermoset plastic material, the reinforcing fibers consisting essentially of asbestos fibers, while the plastic constitutes about 40-65% by weight of the pipe, the inner and outer surfaces of this pipe being substantially smooth and this pipe being capable of containing water under continuous hydrostatic pressure up to 'at burst pressure, without appreciable water seepage through these walls, this pipe being capable of being threaded or threaded mechanically using ordinary pipe threading or tapping machines. 17.- Molded plastic pipe, characterized in that it consists of a mass of reinforcing fibers distributed / homogeneously, in a thermoset plastic support, these reinforcing fibers consisting of 80% by weight of asbestos fibers and 20% by weight of cellulosic fibers, the plastic <Desc / Clms Page number 42> constituting about 40 to 65% by weight of the pipe, the inner and outer surfaces of such pipe being substantially smooth, but capable of containing water under continuous hydrostatic pressure up to the pressure of bursting, without appreciable water seepage through its walls, this pipe being capable of being tapped or threaded mechanically using ordinary pipe threading or tapping devices. 18. Process for obtaining articles of plastic material reinforced with fibers, characterized in that a paper based on asbestos fibers having a mass greater than 0.3 and consisting essentially of 90 to 99% (by weight of coarse asbestos fibers and in. 1 to 10% by weight of a non-fibrous binder, these coarse asbestos fibers. having a size such that at least about 50% by weight of such fibers pass through a standard 28 mesh screen and are retained by a standard 100 mesh screen, at least 70% by weight of the fibers being retained by a tarnish 200 meshes, the said paper is impregnated with a solution, in a volatile solvent, of a thermosetting resin, the proportion of solution relative to the paper being such that the resin content of the impregnated paper is between 40 and 65% by weight, and the impregnated paper is heated to evaporate all the solvent and to polymerize the resin to a stage B, the dry resin-impregnated asbestos paper is placed in the general shape desired for the final article and the paper is then subjected to a temperature and pressure EMI42.1 SuW 2saraLf .- 'S for lfl () Ulcr l! t: 116ê: illble d 1cL final fOïüe and to harden the resin to the final stage, the plastic articles obtained being liable to contain water under continuous hydrostatic pressure up to the bursting pressure, without any appreciable seepage of water through their walls. <Desc / Clms Page number 43> 19. A method according to claim 18, characterized in that after drying the paper is macerated, so as to form distinct fragments impregnated with resin, which are then subjected to the assembly and molding operations. 29.- A process for obtaining a fiber-reinforced plastic pipe having smooth inner and outer surfaces and capable of being threaded and tapped using the usual pipe threading or tapping machines, characterized in that that an asbestos paper having a mass greater than 0.3 and consisting essentially of 95 to 97% by weight of coarse asbestos fibers and of 3 to 5% of a non-fibrous binder, the fibers of at- EMI43.1 ..: 1 "& nte coarse being of a caliber such as at least 50; i, approximately in weight of these fibers pass through a standard 28 mesh screen and are retained by a standard 100 mesh screen, at least 70% of the fibers being retained by a standard 20 mesh screen, said paper is impregnated using a solution, in a volatile solvent, of a thermal resin EMI43.2 : ..ourecissable, the proportion of solution relative to the paper being such that the resin content of the impregnated paper is between 40 and 65% by weight and the impregnated paper is heated so as to evaporate all the solvent and to polymerize the resin until 'In step B, an elongated section of dry resin impregnated asbestos paper is wound onto a mandrel, and the mandrel and / the wrapped paper are subjected to sufficient temperature and pressure to mold the paper into a smooth-surfaced pipe. and to harden the resin EMI43.3 1Jc: tpa1.CJ. C.1 \ .41. "\" & '. 1 "" "" \. 4 .............-- ----- ... :: ¯- - = "" --- ¯: J .. v ..... + .... 7 .. .f ".;, ...., .. 1 a, i îiu cmi ..muu.. Imu .. 21.- Process of obtaining plastic pipes reinforced with fibers, characterized in that a fibrous paper consisting essentially of asbestos is used, this paper is impregnated with a solution, in a solvent, of a thermosetting resin, the proportion of solution <Desc / Clms Page number 44> relative to the paper being such that the resin content of the impregnated paper is between 40 and 65% by weight, and the impregnated paper is heated so as to evaporate all the solvent and to polymerize the resin up to stage B, the paper is formed into a hollow cylinder and the impregnated paper in the cylindrical form is subjected to a temperature and pressure sufficient to bring the resin to the final curing stage. 22. - Methods and materials for the manufacture of pipes and other molded plastic articles reinforced with fibers, in substance, as described above.