JPS629539B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a drawing method for producing glassy oxide fibers with high values of elastic modulus, and more particularly to a defined narrow temperature range and a drawing process for controlling the crystallization of the glassy fibers. The present invention relates to an improved method for drawing glass fibers in which drawing is carried out by extremely limiting the exposure time of the fibers. A non-viscous melt of metals, metal oxides, and mixtures of metal oxides is extruded through the pores into the atmosphere and acts on the fiber surface to stabilize the fibers so that they do not disperse into droplets before solidification. A method for continuously manufacturing fibers by forming sheath-like coatings is disclosed in U.S. Pat. No. 3,658,979 and Reissue Patent No. 27,123. Fibers produced by this method are called inviscid melt spun fibers.
In the following description, it will be abbreviated as "IMS fiber". Some of these fibers have properties that are particularly desirable for some applications.
Fibers that are currently considered particularly desirable are spun from melts consisting primarily of one or more refractory vitreous metal oxides or mixtures of metal oxides whose melt temperatures are typically above 1300°C. This is the fiber produced. 〓〓〓〓
Such IMS fibers, ie, IMS fibers produced from such melts, have certain desirable attributes. First of all, this fiber has a relatively high modulus of elasticity, which makes it
Particularly suitable for use as a reinforcing material in combination with various synthetic resin systems to manufacture not only aircraft parts such as wings, lower wings, engine covers, etc., but also all kinds of products such as bathtubs, boats, fishing rods, etc. ing. However, while the prior art IMS fibers are suitable for some applications, their elastic modulus is still considered insufficient for many applications, and it is therefore a primary object of the present invention to The object of the present invention is to provide a method for significantly increasing the elastic modulus of. The above fibers have a melting temperature of 130℃
Rayleigh medium ranging from 1 to 50, preferably from 2 to 25, as described in U.S. Pat. No. 3,658,979; It is an IMS fiber with a variable (Rayleigh parameter), and the Rayleigh parameter is

It is a dimensionless number expressed by the formula, whose value is the square root of the well-known Weber number. (Symbols are respectively for the melt, V = flow velocity, D = flow diameter, ρ
= density, γ = surface tension). Furthermore, the fibers to which the present invention can be applied are extremely glassy fibers, and furthermore, they contain almost no silica for reasons described below. Although the above-mentioned patent describes that the method disclosed therein is applicable to fibers of various metals and many metal alloys, the present invention is independent of fibers of such metals and metal alloys; It has nothing to do with the silica-containing melt that is given. That is, the presence of silica tends to make the mixture viscous in approximately direct proportion to the amount of silica present, and this book aims to provide a method for drawing fibers from non-viscous melts. The invention eliminates the need to utilize the method of the above patent using conventional stretching methods with viscous mixtures. It is generally formed from a melt of one or more glassy metal oxides, as defined above, which melts at temperatures above 1300°C and does not contain oxides such as silicon or boron. The so-called IMS fibers to which the method of the invention is applicable are generally produced at temperatures well below the melting point characteristic of their mixtures (i.e. below the generally determined solidus temperature for those mixtures). (which can be determined empirically) and within an extremely limited temperature range, it is stretched as if it were viscous. At this temperature, the drawing of IMS fibers takes an absolute minimum time, i.e. from 0.01 seconds to 0.2~
This can be achieved by exposing the above-mentioned low temperature for a time of 0.3 seconds or less, and at this temperature, the time during which the fiber is exposed to the above-mentioned temperature at the part where it is thinly drawn is preferably about 1/1000 second. It is also possible to shorten it. The stretching ratio and degree of stretching can vary widely. Drawability is the ratio of the starting and ending diameters of the fibers treated according to the invention. On the other hand, the draw ratio can be defined as the ratio of the length of a selected segment of untreated IMS fiber to the length of the same segment after being treated according to the present invention. In the present invention, the stretch ratio can range from 2 to perhaps 200. The stretching rate can of course be varied as required or as energy is supplied in the form of heat to the stretched section. A 2-fold increase in the elastic modulus has already been obtained, and a 4-fold increase in modulus can be expected. In particular, 10×
Factor increases ranging from 10 ⁶ psi to as high as 24×10 ⁶ psi have been obtained in some instances, with 10×10 ⁶
A modulus increase of 40×10 ⁶ psi is expected. The present invention provides a method by which such fairly high modulus increases can be obtained with any of a number of fibers of widely varying composition.
Note that 1×10 ⁶ psi is approximately 0.07×10 ⁶ Kg/cm ² . A first object of the present invention is to provide a drawing process that increases the modulus of inviscid melt spun fibers (IMS fibers). A second object of the present invention is to obtain glass fibers having an elastic modulus 2 to 4 times higher than conventional ones, in order to improve the usefulness of composite structures with polymerized synthetic resin materials by this treatment method. An object of the present invention is to provide a stretching method. Glass fiber reinforced plastics are widely used where high strength to weight is important. Glass that has not been devitrified (crystallized) beyond a certain limit generally has ceramic properties.
It is widely used due to its thermal shock resistance and strength. Glass, or in other words, usually transparent glassy ceramics, is a strong, rock-like material that can be fabricated into a variety of shapes. One drawback, brittleness, is overcome by spinning the glass into fibers and using the glass fibers as reinforcement in a low modulus matrix. The role of the low modulus matrix in most composites is to spread out the stress concentrations, thereby evenly distributing the load on each fiber and preventing overloading on each single fiber. The strength of glass is very high in fibrous form, especially when combined into composites. The modulus of glass is high enough to serve most purposes, but too low to take full advantage of its strength. The practicality of composite building components is
Even if it does not break, it will be lost depending on the degree of bending and deformation. The elastic modulus of conventional glasses is determined primarily by the viscosity requirements of conventional manufacturing methods, ie, continuous drawing from a viscous melt. Such stretching methods require a melt viscosity of approximately 10 ³ poise. The prerequisite for molten threads is, of course, that they do not crystallize at the temperatures necessary to obtain drawing viscosity. In order to satisfy the latter condition, a method has conventionally been adopted in which a considerable amount of silica (SiO ₂ ) is included in the oxide mixture constituting the glass. Other network formers, such as volium and germanium, have also been used in special cases. The partially covalent nature of the Si--O bonds in silica commonly serves to increase the viscosity of most metal oxides and mixtures thereof by 10 to 100 centipoise when heated above their melting points. Among the refractory oxides that make up glass, silica has the lowest elastic modulus of 10.5×10 ⁶ psi. Therefore,
Considering the large proportion of silica in the glass composition, the elastic modulus of glass is naturally limited. According to the official designation of a few glasses, their modulus of elasticity is 15×
¹⁰⁶ psi. For silica-based glasses, the highest modulus obtainable is 18 x 10 ⁶ psi. Crystal glass with superior fire resistance is
It has an elastic modulus of 40×10 ⁶ to 60 to 10 ⁶ psi, and if silica can be removed from the glass components.
This shows that it is possible to have an elastic modulus significantly greater than 18×10 ⁶ psi. However, if silica is removed, the viscosity at the melting point is significantly reduced. When the viscosity decreases, it becomes very difficult to form glass fibers by conventional drawing methods. Rapid cooling is required to pass the melting point without crystallization or devitrification phenomena. Extrusion or spinning processes, such as the non-viscous melt spinning process disclosed in U.S. Pat. It is shown. This method also avoids another problem deriving from the low viscosity of the flow, the so-called Rayleigh dispersion. That is, the rapid formation of a hard sheath stabilizes the cylindrical shape of the initial stream until the melt solidifies. This pod is
For example, it is formed from carbon obtained by thermally decomposing hydrocarbons. Ceramic fibers formed by the above technique exhibit glassy properties even without containing silica. This glassy property is evident both in visual observation and in the diffusive properties of the X-ray diffraction pattern. Its density is also much lower than what would be expected from the crystal density of its constituent oxides. As a result of the above, in the conventional glass drawing technology,
It has been demonstrated that it is possible to rework or draw IMS fibers into finer fibers by greatly reducing the time that the fibers are exposed to the required temperature when the fibers are reduced in their diameter. Ta. Most glasses are thermodynamically unstable.
The glass eventually hardens and rearranges itself into a denser, harder, and possibly stronger crystalline structure. This phenomenon occurs rapidly at temperatures just below the melting point;
Occurs more slowly. The strength of glass fibers can be increased or decreased upon crystallization or devitrification. Whether and to what extent the intensity increases or decreases is determined by the devitrification properties. If devitrification is intense and intensive, the glass may lose virtually all of its strength. On the contrary, the devitrification is uniform and the crystal content is
If dispersion takes place, the intensity increases. As is known, in order to uniformly distribute the crystallites in the glass, which determines its strength, the concentration of nuclei, the degree of supersaturation, fluidity, the time for maintaining supersaturation and fluidity, and the concentration of the substance to be crystallized are required. It is necessary to mutually balance several parameters such as. It goes without saying that the distribution and general composition of the nuclei must be uniform initially. In drawing IMS fibers or other glass fibers, the ratio of tensile stress to drawing rate is determined by the viscosity, which in turn is determined by the temperature at which the drawing is carried out. The ultimate tensile strength of the drawn fiber is thus one factor determining the lower limit of the fiber diameter, while temperature constitutes an additional parameter controlling the degree of drawing. The final variable that controls the degree of drawing is the residence time in the hot zone, which is usually determined by the glass feed rate, i.e., the IMS fiber, into the furnace or hot zone where it is drawn, and the temperature of the hot zone in the furnace. controlled by the length of The range of viscosities useful in drawing from IMS fibers or other glass fibers is only about 10 ³ poise. Since viscosity is an exponential function of temperature, this is only equivalent to several tens of degrees Celsius.
Therefore, a certain limit of crystallization that occurs simultaneously with the drawing of IMS fibers must be controlled in relation to these temperature limits. That is, the degree of supersaturation and fluidity are also controlled accordingly. Thus, nucleation and synthesis should be carried out with sufficient time to obtain uniform crystallization during drawing of the IMS fiber, adapting the above limitations to flowability and supersaturation. It is doubtful whether it can be done. However, the inventor of the present application has developed a method that allows ISM fibers to be drawn to a smaller diameter, and at the same time, to achieve uniformly dispersed crystallization within a predetermined limit (usually about 10 ± 5% crystallinity), and to achieve elasticity. We have discovered conditions that can also increase the rate. The equipment for carrying out this method has a very simple configuration;
An automatic feeding mechanism is placed at the top to extrude the IMS fibers in a vertical direction, a mechanism is placed at the bottom to wind up the stretched fibers while maintaining tension, and a mechanism is placed in between these to apply heat to the fibers passing through them, thereby increasing the strength of the fibers. It consists of a heating furnace that stretches it even thinner. Example 1 A platinum wire coil (length 0.59 cm) with a diameter of 0.0081 cm was used as a heating means. This coil has a diameter of
It was 0.159 cm in diameter, and was surrounded by heat insulating material, with holes provided in the center of the top and bottom to allow the fibers to pass through. The temperature was measured by an optical pyrometer at the platinum wire and the inner wall of the furnace. As the winding mechanism, a roller similar to the conventional one was used. The IMS fiber was fed vertically through the furnace from the feeding device and its ends were attached to the winding means. The feeder was then started and the furnace temperature was rapidly raised to the desired voltage and amperage to effectuate the drawing. In the case of drawing, the IMS fibers were fed vertically, but they may also be fed horizontally or at an appropriate angle. Several lengths of fiber were drawn from the IMS fiber, which was spun from a melt made from a reagent grade product consisting of 53.5% alumina and 46.5% calcia by weight. IMS fibers per second
It was fed into the furnace at a speed of 0.25 cm. By measuring the temperature of the inner wall of the furnace and the coil, it was found to be between 1200 and 1300 degrees Celsius, which is considerably lower than the melting point of the ceramic from which the IMS fibers were made.
The drawing temperature of the IMS fiber was controlled so that The results were as shown in Table 1 below.

[Table] 〓〓〓〓

[Table] The elastic modulus was determined using the Reed vibration method using its fundamental (lowest frequency) and first to third harmonics. As seen in Table 1, the elastic modulus of the drawn fibers increased significantly. X-ray diffraction was performed on another fiber drawn from the same IMS fiber stock. The X-ray diagram showed that the crystallinity was 10±5%, and the microcrystals had a diameter of 10 ^-3 to ^{10 -5} cm. There were no crystals in the X-ray diagram of the parent IMS fiber. Another drawn fiber sample was hung vertically, and an aluminum tip was suspended from the lower end of the fiber. Water was slowly and carefully added to the tip with a hyperdermic needle until the fibers broke. The weight of the tip, water and cut fiber ends was 3.957 g. The cut fiber diameter was 0.00081 cm (8.1 microns) and the final tensile strength was 109 x ¹⁰³ psi (7.66 x ¹⁰³ Kg/ ^cm2 ). The fibers did not break at the points where they were connected to the tips and support means. Aluminum oxide 64.5%, calcium oxide 35.5%
% IMS fibers are fiberized using the same equipment, compositional effects can be seen. Failure occurred due to high devitrification due to limitations in equipment performance. Even at the maximum feed speed, all but the very short fibers were stretched and the fibers broke. 53.5% aluminum oxide (Al ₂ O ₃ )
The mixture containing 64.5% aluminum oxide had the lowest melting point, corresponding to a compound of aluminum oxide and calcium oxide. Because the composition of the crystal lattice is unmixed with other species, the lattice crystallizes faster. The fibers can be drawn in a furnace whose length is 1/3 that of the above furnace and whose heating zone is 0.20 cm. In other words, 3 of the above devices
The same effect can be obtained with an improved device having twice the feed rate of 0.75 cm per second. For this and other reasons, shorter furnace lengths and/or faster feed rates are recommended for aluminum oxide 80.7%, calcium oxide
It is necessary to draw fibers from IMS fibers consisting of 19.3%. This is especially true for IMS fibers made entirely of aluminum oxide. Consists of aluminum oxide and calcium oxide
The elastic modulus of IMS fibers increases approximately linearly with increasing aluminum oxide content. The elastic modulus is expressed by the following formula. Modulus of Elasticity (psi) = (0.396 x -10.0) x ¹⁰⁶ (X is % aluminum oxide content) The elastic modulus of the drawn fibers is significantly greater than that of each parent IMS fiber. No nucleating agent was added to the melt, but fibers were sequentially spun and drawn from the melt. Some nucleation took place due to the generation of platinum vapor from the heating coils of the furnace. However, this nucleation will only occur at the surface and will probably not provide any appreciable strength increase. A more uniform dispersion, i.e. a dispersion more consistent with the measured strength,
The drawing step, or fiber thinning step, was carried out either in conjunction with the native shearing action or with dispersed tungsten from the tungsten crucible from which the IMS fibers were drawn. Vitreous IMS ceramic fiber can be made. And from this, by controlling the stretching, from a metal oxide containing almost no oxides forming a network (crystalline structure) such as silica or other oxides such as boria, germania, or a mixture of two or more of these metal oxides. Degree of devitrification (crystalization)
can be made into controlled fibers within certain predetermined limits. Small amounts of silica or other network formers are difficult to remove, and only about 1% can remain without causing harm. Table 2 is a list of metal oxides with high melting points to which the method of the present invention can be applied, and since these metal oxides have a high modulus of elasticity, they can be easily made into fibers. In many cases, the elastic modulus of crystalline metal oxides varies with their melting point. The method of the invention, applied to eutectic mixtures and other mixtures, shows how some stiff fibers can be made from high melting point metal oxides by operating at relatively low temperatures.
Table 3 shows a number of eutectic mixtures, which have a low melting point and have the effect of somewhat inhibiting crystallization, resulting in a shorter duration in the heating zone during drawing. The need to do so is alleviated. However, compositions in which the oxide is not entirely eutectic, but are partially eutectic, are optimal for the process of the invention. While single compositions and eutectic mixtures have precise melting points, other compositions according to the invention have melting points that vary somewhat. That is, the upper limit of each melting range is the liquefaction point, and the lower limit of each melting range is the solidification point. When the liquefaction point and solidification point match, the melting point of the composition can be determined accurately. In order to limit the stretching conditions of the present invention,
Melting point and solidification point may be regarded as the same thing.

【table】

【table】

[Table] 〓〓〓〓

It will be clear to those skilled in the art that equivalents thereof may be used in place of the substances mentioned above. Thus, in the method of the present invention, regardless of the raw material, the IMS fibers are drawn as if they were viscous under the above processing conditions, and the elastic modulus of the drawn fibers is lower than the average value of conventional products. 2~
A four-fold increase has been demonstrated. On the other hand, the strength of the drawn fibers depends on whether or not the glassy crystallization is uniformly dispersed at the time of completion of the drawing.
The permissible range at temperatures close to °C is several tens of degrees, and the residence time is preferably 0.01 to 0.3 seconds. The residence time can be controlled by the length of the predetermined high temperature zone through which the fibers are passed for drawing, and by the running speed. Therefore, the drawing method of the present invention can be carried out using relatively simple equipment, and the glass fibers obtained thereby have sufficient strength and a higher elastic modulus than conventional products, and can be widely used in various applications. It became possible. 〓〓〓〓

Claims (1)

[Scope of Claims] 1 Consisting of at least one refractory metal oxide substantially free of about 1% or more of silicon, boron, germanium, and neighboring oxides, and having a solidus point or melting point of 1300°C or more A method for drawing non-viscous melt-spun fibers having a composition, wherein all temperatures in the heating zone where the glassy fibers, which are continuously fed out in a fixed quantity, are heated and drawn, are below the solidus point of the composition. or glassy crystallization to maintain the drawing viscosity of the fiber at a temperature substantially below the melting point, less than 100°C below the temperature at which the composition melts, and to obtain sufficient strength and high modulus. In order to control the temperature within a predetermined limit, the time during which the fiber is exposed to a temperature lower than the melting point is limited to 0.01 to 0.3 seconds, and the fiber is drawn. Method. 2. The method for drawing glass fibers according to claim 1, wherein the composition is a eutectic mixture of the metal oxides. 3. The method of drawing glass fibers according to claim 2, wherein the eutectic mixture is 53.5 weight percent aluminum oxide and 46.5 weight percent calcium oxide.