JP2003055849A - Composite yarn for forming composite material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a yarn for forming the base fabric that is suitable as a reinforcing material for composite formed products and a yarn that can be directly used as a reinforcing fiber by itself. SOLUTION: The composite yarn for forming composite materials is constituted with polybenzazole fiber that has the half value width of <=0.3 deg./GPa in the X-ray meridian diffraction and the proton T1H relaxation time of >=5.0 sec. and the matrix fiber made of a thermoplastic polymer melting at 200-600 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite yarn suitable for forming a composite material molded body. More specifically, a yarn for manufacturing a fabric used as a reinforcing material for structural parts of various machines, a pressure vessel, a tubular structure, or the like, or the yarn itself is used for reinforcement in a molded composite material or the like. The present invention relates to a composite yarn that can be used as a fiber.

[0002]

2. Description of the Related Art A molded composite material is expected to have a wide range of uses because of its excellent properties such as high strength, high initial elastic modulus, high fatigue resistance and low specific gravity, and has been attracting attention as an important industrial material. In this composite material molded body, reinforcing fibers as a reinforcing material are bonded and integrated with a thermosetting resin having good fluidity at room temperature as a thermoplastic matrix. However, one of the problems of this molding method is that the working efficiency or productivity is low because the time required for molding, mainly the thermosetting of the matrix resin, takes a long time. On the other hand, in order to improve this drawback, development of a composite material molded body in which reinforcing fibers are bonded and integrated with a matrix made of a thermoplastic polymer is underway. For example, JP-A-60-56545 discloses that a reinforcing fiber and a matrix fiber made of a thermoplastic polymer are combined, and the yarn is used as a warp and a weft, and the resulting fabric is heat treated to form a composite material. The body technology is disclosed. Since the composite yarn according to the same publication is not in a mixed fiber state, there is no guarantee that the thermoplastic matrix fibers uniformly permeate the reinforcing fiber gaps when the fabric is heated and melted. Japanese Patent Laid-Open No. 60-20903
Japanese Unexamined Patent Publication No. 3 proposes a method of mixing the thermoplastic matrix fiber and the reinforcing fiber at the single fiber level so that the melted thermoplastic matrix fiber uniformly penetrates into the gap between the reinforcing fibers. However, in general, in order to improve the handleability of the composite material molded body in the processing step, it is first knitted and woven into a cloth form. However, in this case, the composite yarn is likely to be damaged in the rewinding process and the weaving / knitting process, and when the composite yarn is used for the weft yarn and the warp yarn, the amount of the thermoplastic matrix fiber in the fabric is increased, etc. The mechanical properties of the green compact tend to deteriorate. Conventionally, the strength of the high-strength fiber used as a reinforcing fiber has been about 3.0 GPa, but an ultra-high-strength polyethylene fiber has been developed and is disclosed in JP-A-1111034.
The publication proposes a composite yarn formation suitable for forming a composite molded body by using the ultrahigh-strength polyethylene fiber as a reinforcing fiber and combining this with a thermoplastic fiber having a melting point lower than that of the polyethylene fiber by 10 ° C. or more. There is. However, ultra-high-strength polyethylene fibers have low heat resistance, and strict temperature control is required at the time of melt molding in order to prevent thermal deterioration of low-melting-point reinforcing fibers. Further, since these fibers generally have low adhesiveness, they are inevitable. However, there are various manufacturing problems such as a narrow selection range of the types of thermoplastic matrix fibers. Further, JP-A-1-306679 proposes a polybenzazole- and / or polybenzothiazole-coated fiber coated with a thermoplastic resin. However, again, JP-A-1-306679
The publication proposes polybenzazole and / or polybenzothiazole coated fibers coated with a thermoplastic resin.
The coated fiber proposed in the same publication is a polybenzazole and / or polybenzothiazole fiber to which a thermoplastic resin or a molten thermoplastic resin dissolved in a solvent is applied. The method of applying the thermoplastic resin with a solution requires a solvent evaporation step, and the method of applying the molten thermoplastic resin, when the fiber form is multifilament, obtains fibers in which each filament is uniformly coated. It is difficult to do so.

[0003]

DISCLOSURE OF THE INVENTION According to the present invention, when a fabric made of a composite yarn is formed by heating, the permeability of the thermoplastic matrix fiber into the gap between the reinforcing fibers is good, and the obtained composite molded product is a conventional product. In comparison, the composite yarn exhibits high heat resistance and mechanical properties, and it is an object of the present invention to provide a composite yarn that can be used as a reinforcing fiber of a composite molded body.

[0004]

That is, the present invention has the following constitution. 1. Polybenzazole fiber having an X-ray meridional diffraction half-width factor of 0.3 ° / GPa or less and a melting point of 200 to 600 ° C.
7. A composite yarn for molding a composite material, which comprises a matrix fiber made of the thermoplastic polymer. 2. The composite yarn for molding a composite material according to 1, wherein the T1H relaxation time of protons of the polybenzazole fiber is 5.0 seconds or more. 3. The composite yarn for molding a composite material according to 1, wherein the T13 relaxation time of carbon 13 of the polybenzazole fiber is 2000 seconds or more. 4. 2. The composite yarn for molding a composite material according to 1, wherein the thermal conductivity of the polybenzazole fiber is 0.23 W / cmK or more. 5. The composite yarn for molding a composite material according to 1, wherein the void diameter of the polybenzazole fiber is 25.5Å or more.

Hereinafter, the present invention will be described in detail from a method for producing a fiber to a method for producing a composite yarn for forming a composite material. Rigid polymers such as so-called ladder polymers have been considered as a means of achieving the ultimate physical properties of fibers for composite reinforcement, but such rigid polymers are not flexible and have flexibility and processability as organic fibers. In order to achieve this, a linear polymer is an essential condition.

SG Wierschke et al.
iety Symposium Proceedings Vol.134, p.313 (1989)
As shown in Fig. 3, the linear polymer having the highest theoretical elastic modulus is cis-type polyparaphenylene benzobisoxazole. This result was also confirmed by Tashiro et al. (Macromolecules vol. 24, p. 3706 (1991)), and among polybenzazoles, cis-type polyparaphenylenebenzobisoxazole has a crystal elastic modulus of 475 GPa (P . Galen et al. Material Research Society Symposium P
roceedings Vol. 134, p.329 (1989)), considered to have the ultimate primary structure. Therefore, in order to obtain the ultimate elastic modulus, the theoretical conclusion is to use polyparaphenylene benzobisoxazole as the polymer material.

Fiberization of the polymer is described in US Pat. No. 5,2961,
No. 85, US Pat. No. 5,385,702, and the heat treatment method is the method proposed in US Pat. No. 5,296,185, but the sound wave propagation velocity of the yarn obtained by such a method is at most 1.3 × 10. It is about ⁶ cm / sec. Therefore, the inventors have keenly felt the need for research on the improvement of these methods, and as a result of earnest research, they have found that the desired physical properties can be easily achieved industrially by the following methods.

Ohta, Polymer Engineering and Science,
As shown in 23, p697 (1983), so-called defect structures such as voids, disordered crystal orientation, and the presence of molecular ends and amorphous portions are present in the fiber. The presence of these defects hinders the transfer of thermal vibrations and sound waves, resulting in a decrease in thermal conductivity. However, since the polybenzazole fiber is produced by removing the solvent from the polymerization solution, generation of voids is unavoidable. For this reason, many methods have been proposed to prevent the deterioration of the physical properties of the fiber by reducing the void diameter in the fiber to 25 Å or less (for example, JP-A-6-240653 and JP-A-6-245).
675 and JP-A-6-234555,
Etc.), it is not easy to produce such a fiber in view of cost and industrial production. However, in order to increase the thermal conductivity of the polybenzazole fiber, it is essential to reduce the defect structure existing in the fiber structure.

A dope composed of polyparaphenylene benzobisoxazole (PBO) and polyphosphoric acid is spun from a spinneret. Thereafter, it is manufactured through coagulation, neutralization, washing with water, drying, and heat treatment under tension. To increase the thermal conductivity,
It is essential to eliminate as much as possible the defective structure such as amorphous that interferes with the thermal vibration propagation of fibers. For this purpose, we succeeded in changing the internal structure of the polybenzazole fiber to the defect structure free even if the void diameter in the fiber is 25.5Å or more, and the polybenzazole fiber having a high propagation speed of sound waves. Was obtained industrially.

In order to exhibit the above characteristics, it can be realized by the following production examples. That is, a spun yarn obtained by extruding a polymer dope composed of polyparaphenylene benzobisoxazole into a non-coagulating gas from a spinneret was introduced into a coagulating bath to extract phosphoric acid contained in the dope yarn. After that, neutralization, washing with water, drying, and heat treatment are carried out. At that time, it was found that by heating the fiber at a constant tension of 500 ° C. or higher, polybenzazole having a reduced defect structure inside the fiber was obtained.

The method for producing fibers will be described in detail below. The polybenzazole fiber in the present invention means a PBO homopolymer and a random, sequential or block copolymer with a polybenzazole (PBZ) containing substantially 85% or more of PBO components. Here, the polybenzazole (PBZ) polymer is, for example, “Liquid Crystalline Polymer Compositions, Process” by Wolf et al.
and Products ”U.S. Pat. No. 4,703,103 (10 October 1987)
27th), "Liquid Crystalline Polymer Compositio
ns, Process and Products ”US Pat. No. 4,533,692 (1
August 6, 1985), "Liquid Crystalline Poly (2,6-
Benzothiazole) Compositions, Process and Product
s "U.S. Pat. No. 4,533,724 (August 6, 1985)," Li
quid Crystalline Polymer Compositions, Process and
Products "U.S. Pat. No. 4533693 (August 6, 1985)
Sun), Evers'"Thermooxidative-ly Stable Articulat
ed p-Benzobisoxazole and p-Benzobisoxazole Polymer
s "U.S. Pat. No. 4539567 (November 16, 1982),
Tsai et al. `` Method for making Heterocyclic Block Cop
olymer ”US Pat. No. 4,578,432 (March 25, 1986)
Date), etc.

The structural unit contained in the PBZ polymer is preferably selected from lyotropic liquid crystal polymers. The monomer units consist of the monomer units described in structural formulas (a) to (h), and more preferably essentially consist of monomer units selected from structural formulas (a) to (d).

[0013]

[Chemical 1]

[0014]

[Chemical 2]

Suitable solvents for forming the dope of the polymer consisting essentially of PBO include cresol and non-oxidizing acids capable of dissolving the polymer. Examples of suitable acid solvents are polyphosphoric acid, methanesulphonic acid and concentrated sulfuric acid or mixtures thereof. Further suitable solvents are polyphosphoric acid and methanesulfonic acid. The most suitable solvent is polyphosphoric acid.

The concentration of polymer in the solvent is preferably at least about 7% by weight, more preferably at least 10%.
% By weight, most preferably 14% by weight. The maximum concentration is
Limited by practical handling properties such as polymer solubility and dope viscosity. Due to these limiting factors, the polymer concentration does not exceed 20% by weight.

Suitable polymers, copolymers or dopes are synthesized by known methods. For example, Wolfe et al., U.S. Pat. No. 4533693 (August 6, 1985), Sybert et al., U.S. Pat. No. 4,772,678 (September 20, 1988), Har.
synthesized by the method described in US Pat. No. 4,847,350 of ris (July 11, 1989). Polymers consisting essentially of PBO are described by Gregory et al., US Pat. No. 5,089,591 (1992).
(February 18, 2012), it is possible to achieve a high molecular weight at a high reaction rate in a dehydrating acid solvent under relatively high temperature and high shear conditions.

The dope polymerized in this manner is supplied to the spinning section and is usually discharged from the spinneret at a temperature of 100 ° C. or higher. A plurality of die holes are usually arranged in a circumferential shape or a lattice shape, but other arrangements may be used. The number of spinneret pores is not particularly limited, but it is important that the array of spinneret pores on the surface of the spinneret is maintained at a pore density such that fusion between discharge yarns does not occur.

The spun yarn requires a sufficient draw zone length, as described in US Pat. No. 5,296,185, in order to obtain a sufficient draw ratio (SDR), and at a relatively high temperature (dope It is desirable to uniformly cool with a rectified cooling air having a solidification temperature or higher and a spinning temperature or lower). The length (L) of the draw zone is required to be such that the solidification is completed in the non-solidifying gas, and is roughly determined by the single hole discharge amount (Q). In order to obtain good fiber properties, it is desirable that the draw-out stress in the draw zone is 2 g / d or more in terms of polymer (assuming stress is applied only to the polymer).

The yarn drawn in the draw zone is then introduced into the extraction (coagulation) bath. Since the spinning tension is high, it is not necessary to consider disturbance of the extraction bath and any type of extraction bath may be used. For example, a funnel type, an aquarium type, an aspirator type or a waterfall type can be used. The extract is preferably phosphoric acid aqueous solution or water. Finally, in the extraction bath, the phosphoric acid contained in the yarn is extracted by 99.0% or more, preferably 99.5% or more.
The liquid used as the extraction medium in the present invention is not particularly limited, but preferably water, methanol, ethanol, acetone, ethylene glycol or the like which is substantially incompatible with polybenzazole. Also extraction (coagulation)
It is also possible to separate the bath in multiple stages, dilute the concentration of the phosphoric acid aqueous solution sequentially, and finally wash with water. Further, it is desirable to neutralize the fiber bundle with an aqueous solution of sodium hydroxide and wash it with water. Then, it is dried and heat-treated to produce fibers.

In order to reduce the presence of defects infinitely (defect-free) from the fiber structure, the solidification rate should be slowed down.
As a result of diligent study, it was found that it is particularly important to heat-treat the material on which the fiber structure has been carefully formed and then to dry it, and to further heat-treat it. For that purpose, it is important to control the solidification temperature,
The bath temperature is maintained at -20 to 0 degrees Celsius, preferably -15 to -5 degrees Celsius, and more preferably -12 to -8 degrees Celsius. As the coagulant, an aqueous solvent may be used, but an organic solvent compatible with water showed better results. Particularly, a compound having a -OH group having a molecular weight of 400 or less, such as a lower alcohol such as methanol or ethylene glycol, was particularly effective. When the bath temperature is less than -20 ° C, the physical properties of yarn tend to be dramatically reduced, which is not preferable. The drying temperature is a temperature at which the fiber strength is not lowered, specifically, 150 ° C. or higher and 400 ° C. or lower, preferably 200 ° C. or higher and 300 ° C. or lower,
More preferably, the temperature is 220 ° C. or higher and 270 ° C. or lower. Regarding the heat treatment conditions, the temperature is 500 ° C or higher and lower than 700 ° C,
It is preferably carried out at 550 ° C or higher and lower than 650 ° C, more preferably 580 ° C or higher and lower than 630 ° C. The tension applied at this time is 1.5 g / d or more and less than 12 g / d, preferably 3.0 g / d or more 1
It is less than 1 g / d, more preferably 5.0 g / d or more and less than 10.5 g / d. The moisture content of the fiber to be heat treated is 3% or less and 1% or more,
It is preferably adjusted to 2.7% or less and 1.7% or more.

The fiber according to the present invention has an X-ray meridional diffraction half-width factor of 0.3 ° / GPa or less, preferably 0.25 ° / GPa or less, more preferably 0.2 ° / GPa or less, and most preferably 0.15. Degrees below ° / GPa. More preferably, the elastic modulus decrement Er due to molecular orientation change is 30 GPa or less, preferably 25 GPa or less, more preferably 20 GPa or less, T1H relaxation time of proton is 5.0 seconds or more, preferably 6.5 seconds or more, and further preferably 8 T of carbon 13 indicating seconds or more
1C relaxation time is 2000 seconds or more, preferably 2300 seconds or more, more preferably 2700 seconds or more, thermal conductivity is 0.23W / cm K or more, preferably 0.3W / cmK or more, more preferably 0.36W / cmK or more, void diameter is 25 5 Å or more, preferably 30 Å or more, 150 Å
Less, more preferably 35 Å or more and less than 90 Å.

An analysis method for proving the realization of a defect-free structure will be described below. Since polybenzazole fiber has a very rigid structure as an organic fiber,
It is not easy to make ultrathin sections and observe them with an electron microscope. Crystals have structural asymmetry called axial shift and do not form a firm and complete crystal. Therefore, sufficient information cannot be obtained even by analysis using static wide-angle X-ray diffraction or small-angle X-ray scattering method. It was Therefore, measuring the X-ray diffraction while applying stimulation (stress) to the fiber,
Structural analysis was performed by evaluating the relaxation time using MR.

(Measurement method of X-ray full width at half maximum factor) An apparatus for applying tension to a fiber was prepared and a goniometer (Ru-
200 X-ray generator, RAD-rA system), and the stress dependence of the (00 10) diffraction line width was measured. It was operated at an output of 40 kV x 100 mA, and CuKα rays were generated from a copper rotating target. The diffraction intensity was recorded on a Fujifilm Imaging Plate (Fujifilm FDL UR-V). Diffraction intensity is read out by JEOL's digital microluminography (PIX
sysTEM) was used. In order to evaluate the full width at half maximum of the obtained peak profile with high accuracy, curve fitting was performed using the synthesis of Gaussian function and Lorentz function. The results obtained were plotted against the stress applied to the fiber. The data points are arranged in a straight line, and the half-width factor (Hws) was evaluated from the slope.

(Method of measuring orientation change factor) The above-mentioned device for applying stress to the fiber was attached to a small angle X-ray scattering device made by Rigaku, and the spread of the peak in the azimuth direction of the (200) diffraction point was measured, The elastic modulus Er due to the orientation change was measured.

The orientation change <sin ² φ> was calculated from the azimuth angle profile I (φ) of the (200) diffraction intensity using the following formula.

[Formula 1] The origin of the azimuth was φ = 0 on the meridian.

The theory proposed by Nosalt (Polymer 21, p
According to 1199 (1980)), the strain (ε) of the whole fiber can be described as a synthesis of crystal elongation (εc) and rotation contribution (εr). ε = εc + εr εc is the crystal modulus Ec and stress σ, and εr is
Using the result of measuring in ² φ> as a function of σ, ε
Can be rewritten as the following formula to calculate. ε = σ / Ec + (<cosφ> / <cosφ ₀ > -1) Here, φ ₀ represents the orientation angle when the stress is 0, and φ represents the orientation angle when the stress is σ.

The elastic modulus decrement Er caused by the orientation change is defined by the following equation.

[Formula 2] Here, the inside of the bracket in the second term on the right side of the above equation is the slope of the tangent line of ε at σ = 0.

(Measurement Method of Solid State NMR) Solid 13C-N
MR measurement is made by Varian XL-300 spectroscope (1H measurement 300MHZ, 13C measurement 75MHz), TH
AMWAY solid state amplifier A55-8801, A55
-6801MR, using a solid probe made by DOTY. The measurement was carried out by CP-MAS with 1H nucleus and 13
The longitudinal relaxation time of C nucleus was measured. The measurement is performed at room temperature, sample rotation speed 4 KHz, 1H 90 degree pulse 4.5 microseconds,
The rocking magnetic field strength was 55.5 KHz, the decoupler strength was 55.5 KHz, the contact time was 3 milliseconds, and the pulse waiting time was 40 seconds. 1H nuclear relaxation time (T1H) is C
Peak intensity I (t) with retention time (t) of the peak appearing at 128 ppm, measured by P-MAS inversion recovery method
Was determined by curve fitting according to the formula I (t) = A · exp (-t / T1H). Vertical relaxation time of 13C nucleus (T1
C) has a retention time of 0, 0.
001,1.56,3.12,6.24,12.5,2
5.0, 50.0, 100, 150, 200, 300,
It was measured as 400, 500, 600, 700, 800 seconds. The attenuation of the peak intensity I (t) with the retention time (t) of the peak appearing at 128 ppm is I (t) = Ao · e
xp (-t / 0.1) + Aa · exp (-t / T1Ca)
+ Ab ・ exp (-t / T1Cb) + Ac ・ exp (-t
/ T1Cc) was calculated by curve fitting. here,
Let T1Cc (T1Ca≤T1Cb≤T1Cc) be the relaxation time T1C of the 13C carbon nucleus.

(Measurement of Thermal Conductivity) The thermal conductivity was measured by Fu
Method of jishiro et al. (Jpn. J. Appl. Vol. 36 (1997) p563
Measurement was carried out at a temperature of 100 K according to 3).

<Small-angle X-ray scattering measurement method> The void diameter was evaluated by the following method using the small-angle X-ray scattering method. The X-rays used for measurement are rotor flex RU-3 manufactured by Rigaku Corporation.
It was generated using 00. A copper anticathode was used as a target, and the operation was performed at a fine focus of 30 kV x 30 mA. The optical system was a point-focusing camera manufactured by Rigaku Corporation, and the X-rays were monochromatic using a nickel filter. The detector is
Imaging plate (FDL U manufactured by Fuji Photo Film Co., Ltd.)
RV) was used. Distance between sample and detector is 200mm to 350m
Any suitable distance between m is acceptable. A helium gas was filled between the sample and the detector in order to suppress interfering background scattering from air and the like. The exposure time was 2 hours to 24 hours. Digital micrography (FDL5000) manufactured by Fuji Photo Film Co., Ltd. was used to read the scattering intensity signal recorded on the imaging plate. For the obtained data, a Guinier plot (the natural logarithm ln (I) of the scatter intensity after the background correction is squared to the scatter vector to the scatter intensity I in the equatorial direction after the background correction is performed.
plotting against k ² ) was made. Here, the scattering vector k is k = (4π / λ) sin θ, λ is the X-ray wavelength 0.1458 nm, θ
Is half the scattering angle 2θ.

The reinforcing fibers constituting the composite yarn of the present invention are the above-mentioned polybenzazole fibers. Considering that a composite material molded body composed of a fabric obtained by knitting and weaving the composite yarn as warp and / or weft is used for various machine parts and the like requiring high strength, at least 4. It preferably has a tensile strength of 0 GPa or more. The same applies when the composite yarn is used as a reinforcing material as it is. There is no particular limitation on the physical properties required for the thermoplastic matrix fiber, and it is sufficient if the fiber has mechanical properties sufficient to exhibit stable process passability in the rewinding process, the fiber opening process, and the weaving and weaving process. .

The yarn in which the reinforcing fiber and the thermoplastic matrix fiber are composited is used alone as a reinforcing material in a composite molding material, or after the composite yarn is knitted into a fabric as warp and / or weft, Used as a reinforcing material in composite molding materials. In either case, the thermoplastic matrix fibers are melted by thermoforming. Naturally, it is advantageous to use a thermoplastic matrix fiber having a low melting point from the viewpoint of workability at the time of heat molding, but inevitably only a composite molding material having low heat resistance can be obtained. In order to effectively utilize the excellent heat resistance of polybenzazole fibers, it is essential to combine thermoplastic matrix fibers with high heat resistance. For this purpose, the thermal decomposition of polybenzazole fibers at a melting point of at least 200 ° C or higher is required. It is necessary to select the thermoplastic matrix fibers from the thermoplastic polymer fibers that are below the initiation temperature. Examples of the thermoplastic synthetic fiber having a melting point of 200 ° C. or higher include polyester-based thermoplastic polymers such as polyethylene terephthalate and polybutylene terephthalate, and polyamide-based thermoplastic polymers such as nylon 6, nylon 66 and nylon 46. Fibers that have been used. Among the above-mentioned thermoplastic synthetic fibers, polyethylene terephthalate fibers are most preferable in consideration of price, thermal stability, and adhesiveness with the thermoplastic matrix fiber after forming the composite material molded body. In addition, the decomposition initiation temperature of polybenzazole fiber is 600 ° C, which has extremely high heat resistance among organic synthetic polymers. It depends on the type of thermoplastic matrix fiber to be combined, but it is a thermoplastic matrix fiber with a relatively high melting point. Even if there is, it is possible to perform heat molding to a high temperature range. Therefore, if it is a thermoplastic matrix fiber with a relatively high thermal decomposition temperature, the melt viscosity is lowered by hot molding at high temperature to increase the permeability of the matrix and the composite material molding with excellent physical properties and appearance with a low void generation rate. The body is obtained. When a thermoplastic matrix fiber having a melting point of less than 200 ° C. is used, the heat resistance of the composite molding material in which the knitted fabric is molded is naturally lowered, and a composite material molded body utilizing the excellent heat resistance of the polybenzazole fiber is obtained. Can't get On the other hand, the melting point of the thermoplastic matrix fiber must be 600 ° C. or lower in view of the heat resistance of the polybenzazole fiber.

The composite yarn itself or the composite yarn is knitted or woven to form a fabric, and is further subjected to heat molding. As described above, the permeability of the molten thermoplastic matrix fiber at the time of melting is the composite molding. It affects the material, and also the physical properties, morphology and appearance of the product. For that purpose, it is important to preliminarily make a uniform mixed state of the composite yarn composed of the reinforcing fiber and the thermoplastic matrix fiber constituting the composite material. In general, the mixed state is a composite in a non-mixed fiber state, that is, a side-by-side or covering type by covering in which the reinforcing fiber yarn and the thermoplastic matrix fiber yarn are simply aligned. When a fabric composed of composite yarns mixed in such a form is melt-molded, the permeability of the thermoplastic matrix fiber into the reinforcing fiber is low, which is not preferable. The mixed state of the present invention means that the matrix fiber single fibers and the reinforcing fiber single fibers made of a thermoplastic polymer are arranged or arranged substantially randomly with respect to each other in any cross section of the composite yarn. That is, in order to keep the occurrence rate of cavities low by increasing the permeability of the matrix fiber melted at the time of heat molding into the reinforcing fiber gap and keep the strength of the final composite material molded body good, Let A be the number of filaments of the polybenzazole fiber in contact with the single filaments of the matrix fiber made of the thermoplastic polymer in the cross section, and B be the total number of filaments of the polybenzazole fiber, (A / B) × 10
The dispersity of single fibers calculated at 0% is preferably 46% or more and less than 74%. When the degree of dispersion of the filaments of the reinforcing fiber in the composite yarn is less than 46%, when a fabric composed of the composite yarn as a single component or only the composite yarn is heat-molded, the matrix is dispersed in the reinforcing fiber gap. Permeability tends to be non-uniform and voids are likely to occur. On the other hand, a higher dispersity is preferable in terms of quality and quality of the composite material molded body, but it is not easy to obtain a dispersity of 74% or more in a stable state at the current level of mixed fiber technology, and 74% or more. Even if the degree of dispersion of 1 is obtained, the degree of contribution (quality / cost) to the quality / quality improvement of the composite material molded body cannot be expected, so the degree of dispersion may be less than 74%.

The mixing ratio of the reinforcing fiber (polybenzazole fiber) and the fiber made of a thermoplastic polymer (matrix fiber) is important from the viewpoint of the reinforcing effect of the composite material molded body, and in particular, the composite yarn is made into a fabric. This is an extremely important factor when used as a composite material without knitting or weaving. From this viewpoint, the content of the reinforcing fibers and the thermoplastic matrix fibers is preferably 30 to 85% by weight / 70 to 15% by weight, and more preferably 40 to 70% by weight / 60 to 30% by weight. is there. When the content of the reinforcing fiber in the composite yarn is less than 30% by weight, the reinforcing effect of the composite material molded body is relatively low, and when the content of the reinforcing fiber exceeds 99% by weight, the dispersity of the composite yarn is high. Even when the above conditions are satisfied, the melting and penetrating properties of the thermoplastic matrix fiber become low, and the void ratio V% of the final composite material molded product becomes large.

Specific preferred fiber mixing methods include, for example, the so-called Taslan method in which a plurality of multi-thread yarns are supplied to the fluid turbulent zone of an air jet in a relaxed state to form loops or entanglement, and a multi-thread yarn is also used. A so-called electric fiber opening method in which fibers are electrically opened, short fibers are superposed on the front roller, twisted and wound, and further, two or more eddy turbulent flow zones are arranged substantially parallel to the yarn axis. And a so-called interlace method in which a yarn is guided into the zone to form a non-bulky and tight yarn under a tension that does not cause a loop or crimp.
When the reinforcing fiber and the thermoplastic matrix fiber are mixed and depending on the opening means, for example, when the electric opening method is adopted, the opened state is extremely stable in the range of 100 denier to 1500 denier, A composite yarn with high dispersibility can be obtained. Further, the single yarn fineness of the reinforcing fibers and the thermoplastic matrix fibers has a considerable influence on the uniformity of the mixed state of the fibers, and the fineness range of 0.5 to 3.0 denier is preferable for both the reinforcing fibers and the thermoplastic matrix fibers. However, the fineness of the single fiber is not particularly limited to this range and may be appropriately selected according to the opening / mixing means to be used.

The composite yarn of the present invention is formed into a sheet of a composite molded article by itself or through a fabric knitted and woven in combination with a thermoplastic matrix fiber yarn, and further, a sheet having a predetermined size is provided for secondary processing. And a predetermined number of sheets are superposed on each other, placed in a mold preheated to a temperature higher than the melting point of the thermoplastic matrix fiber yarn, and the mold is pressed to form a sheet of the composite molded article. It is molded into a desired shape. The cloth knitted and woven here includes knits, woven fabrics, and non-woven fabrics, and the knitted and woven structure thereof is not particularly limited.

<Fiber Tensile Strength / Elongation and Initial Tensile Elastic Modulus> According to JIS L 1013, a tensilon manufactured by Orientec Co., Ltd. was used to measure a gripping interval of 20 cm, a pulling speed of 100% / min, and n = 10. Then, the arithmetic mean value was calculated from the measured values.

<Fiber dispersity%> (a) A cross-section (a plane perpendicular to the yarn axis) is cut at an arbitrary number of points in the composite yarn with a sharp blade, and the entire cut surface is photographed. . (B)
From the photograph, the number of filaments of the polybenzazole fiber that would come into contact with the filaments of the matrix fiber made of a thermoplastic polymer or the filaments of the matrix fiber that would contact if the filament fiber of the matrix fiber was displaced by 10% of the diameter was measured. A (book). (C) The total number of filaments of the polybenzazole fiber existing in the entire cross section of the composite yarn taken in the photograph is measured, and this is designated as B (book). (D) The dispersion degree% of the polybenzazole fiber is calculated from the measured A and B according to the following formula. Dispersion (%) = (A / B) × 100

<Reinforcement Fiber Content FK%> Weight DK (g) of reinforcement fiber measured after dissolving and removing the test piece of the composite material molded body using a solvent that selectively dissolves only the thermoplastic matrix fiber The content FK% of the reinforcing fiber was calculated from the following formula and the weight DT (g) of the test piece of the composite material molded body before the dissolution treatment. FK (%) = DKx100 / DT

<Tensile Strength, Elongation and Initial Tensile Elastic Modulus of Composite Molded Article> Tensile properties were measured according to JIS K-7054 with the axial direction of the reinforcing fiber as the tensile direction of the test piece.

<Cavity rate V%> (a) JIS K 7112
Specific gravity S of the test piece of the composite material molded body according to the A method specified in
GT, specific gravity SGK of reinforcing fiber, and specific gravity SGM of thermoplastic matrix fiber are determined. (B) After the test piece of the composite material molded body is dissolved and removed using a solvent that selectively dissolves only the thermoplastic matrix fiber, the weight of the reinforcing fiber is measured, and the test of the composite material molded body before the dissolution treatment is performed. The weight of the matrix fiber was determined from the weight difference from the weight of the piece. From these weight data, the reinforcing fiber mass content FK% and the matrix fiber mass content FM% were obtained, and the void content V% of the sample was calculated by JI.
It was calculated by the following formula described in SK 7053-1987. V = 100-SGT [(FK / SGK + FM / SG
M)]

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EXAMPLES (Examples 1 and 2, Comparative Examples 1 and 2) US Patent No.
Polyparaphenylene benzobisoxazole having an intrinsic viscosity of 24.4 dL / g, measured by a methanesulfonic acid solution at 30 ° C., obtained by the method shown in No. 4533693 (14.0% by weight) and phosphorus pentaoxide content of 83.17% A spinning dope consisting of phosphoric acid was used for spinning. The dope was passed through a metal mesh filter material, then kneaded and defoamed with a biaxial kneading device, and then the pressure was raised to maintain the polymer solution temperature at 170 ° C and from a spinneret having 166 holes. After spinning at 170 ° C and cooling the discharged yarn using cooling air at a temperature of 60 ° C, and further cooling the discharged yarn to 40 ° C by natural cooling,
It was introduced into the coagulation bath. Fibers were prepared using a phosphoric acid aqueous solution having a concentration of 25% and a temperature of -15 ° C as a coagulating liquid. Next, the fiber was wound around a gozette roll, the yarn was washed with ion-exchanged water in a second extraction bath at a constant speed, and then the fiber was immersed in a 0.1 N sodium hydroxide solution for neutralization. After further washing with water in a washing bath, it was wound up, dried in a drying oven at 80 ° C., and allowed to stand until the moisture content in the fiber became 2% or less. Further, heat treatment was performed for 2.4 seconds under the condition of tension of 5.0 g / d and temperature of 600 ° C. The fiber thus obtained was used as a raw yarn for producing a composite yarn. The X-ray meridian half-width factor of this fiber was measured and found to be 0.24 ° / GPa. Next, using the interlacer device in which two pairs of opposed roller fluid conduits are opened using the polybenzoxazole fiber prepared as described above as the reinforcing fiber and the polyethylene terephthalate fiber having a melting point of 260 ° C. as the matrix fiber. And the article. The processing conditions were set at a fluid pressure of 3.5 kg / cm ² and a yarn speed of about 500 m / min. The fineness of the composite yarn after mixing was 850 denier, and at this time, the polybenzazole fiber content and the single fiber fineness of the polybenzazole fiber and the polyethylene terephthalate fiber were changed. Next, using this composite yarn as the warp and using only polyethylene terephthalate fiber as the weft, the warp density is 50 yarns / inch and the weft density is 5
A plain weave was woven at 0 yarns / inch. 20 pieces of the obtained cloth
After cutting into a size of cm x 20 cm, the fabric is heated to 80 ° C.
Vacuum drying for 16 hours under 0.1 mmHg or less, and then the fabric is woven for 3 times so that the reinforcing fibers are aligned in the same direction.
Layered on top of each other to form a laminated body, put it in the mold and 290 ℃
At the temperature of 1, the pressure of 17.0 Kg / cm ² was applied and the heat treatment was performed for 5 minutes. Then remove the mold and the surface temperature is 80
Air-cooled until the temperature fell to ℃, to obtain a unidirectionally oriented reinforced laminate. Table 1 shows the tensile properties of the laminate.

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[Table 1]

Comparative Example 3 Except that aramid fiber (Kevlar 29) was used in place of polybenzazole fiber,
A reinforced laminate was prepared in the same manner as in Example 1. Table 1 shows the physical properties of the laminate.

Example 3 For a notebook computer, a reinforced laminated plate having a thickness of 1 mm (fibers oriented in the same direction) was prepared using the same reinforced fibers and conditions as in Example 1 and then die-cut. I made a heat sink. For the connection between the CPU and the heat sink, the dedicated jig attached to the computer was used as it was. Next, the heat sink created in this way is attached to the Macintosh computer PowerBook2400C (notebook type, G3 specification accelerator additional equipment is attached) with screws and then the power is turned on and the OS (operating system) is in a booted state. I left it. I continued to operate the keys as appropriate to prevent the sleep function from working. The computer was operating normally after being left for 24 hours. The warning indicating the CPU temperature was also within the normal range. At this time, the temperature of the bottom of the main body was measured and found to be 45 ° C. It can be understood that the heat sink sufficiently plays the role of discharging the heat generated by the CPU to the outside of the computer main body.

(Comparative Example 4) A reinforced laminated board having a thickness of 1 mm made by using the same reinforcing fibers and conditions as in Comparative Example 1 was used as a Macintosh computer PowerBook2400C (notebook type, G3).
Equipped with additional equipment for specification accelerator. ), The OS was started up under the same conditions as in Example 4 and left unattended, and no key operation was accepted after 35 minutes had elapsed. At this time, the warning display showing the temperature of the CPU was completely on the high temperature side. At this time, the temperature at the bottom of the main body was measured and found to be 33 ° C.

(Comparative Example 5) The same heat dissipation plate as in Example 4 was prepared using polybenzazole fiber having an X-ray meridional diffraction half width width factor of 0.35 ° / GPa, and the same conditions as in Example 4 were used. When the computer was started up and left unattended, no key operation was accepted after 9 hours and 32 minutes had passed. At this time, the warning display showing the temperature of the CPU was completely on the high temperature side. The temperature at the bottom of the body was 37 ° C. In Comparative Examples 4 and 5, it is understood that the heat sink does not play its role.

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The composite yarn of the present invention can be melt-impregnated at high temperature, has good permeability, can reduce voids, and has good workability. The laminated body can provide a yarn that enables production of a base fabric suitable for a composite molded body having excellent tensile strength properties. It was also shown that a composite molded body having better thermal conductivity can be prepared. Therefore, the composite material molded body obtained by further using the base fabric made of this yarn for the composite material molded body is required to have mechanical properties, heat resistance, and thermal conductivity as automobile parts, aerospace members, and computer-related members. It is important to contribute in the fields where

Claims (5)

[Claims] 1. The X-ray meridional diffraction half-width factor is 0.3 ° / G.
Polybenzazole fiber having Pa or less and a melting point of 200 to
A composite yarn for molding a composite material, which comprises a matrix fiber made of a thermoplastic polymer at 600 ° C. 2. The T1H relaxation time of protons of polybenzazole fiber is 5.0 seconds or more.
A composite yarn for molding a composite material as described. 3. T of carbon 13 of polybenzazole fiber
The composite yarn for molding a composite material according to claim 1, wherein the 1C relaxation time is 2000 seconds or more. 4. The thermal conductivity of polybenzazole fiber is 0.23 W /
The composite yarn for forming a composite material according to claim 1, wherein the composite yarn is cmK or more. 5. The void diameter of the polybenzazole fiber is 25.
The composite yarn for molding a composite material according to claim 1, which has a length of 5 Å or more.