JPH0754241A - Base fabric for forming composite material - Google Patents

Abstract

PURPOSE:To obtain a base fabric for forming composite materials excellent-in mesh slippage and/or handleability. CONSTITUTION:This base fabric for forming composite materials is constituted from the following contents: (1) weft yarn is synthetic fiber made from a thermoplastic polymer; (2) the weft yarn is prepared by combining PBZ fiber having a high strength and elastic modulus with the thermoplastic synthetic fiber and (3) the size ratio of warp to weft yarns is >=5.0.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a base fabric for molding a composite material which has a small misalignment and is easy to handle. More specifically, the present invention relates to a base cloth which has excellent handleability and high physical properties of a composite material molded article which have not been heretofore obtained by weaving a thread having a specified ratio of components and thread diameters into a warp and a weft.

[0002]

2. Description of the Related Art Composite molded articles have excellent mechanical performance and are expected as important industrial materials. Normal,
The composite material molded body is formed by integrating a fiber material, which is a reinforcing material, with a thermosetting resin having good fluidity at room temperature as a matrix. However, since this molding method requires a long molding time, mainly a thermosetting time, productivity is a problem, and in recent years, in order to improve this defect, development of a composite material molded body using a thermoplastic polymer as a matrix has been advanced. . For example, JP-A-60-
Japanese Patent No. 56545 discloses a technique in which reinforcing fibers and fibers made of a thermoplastic polymer are combined to form a yarn, and a fabric obtained by weaving the yarn is heat-treated to form a composite material molded body. .
In this case, since the yarns are not in a mixed fiber state, there is no guarantee that the matrix material will be uniformly melted and penetrated into the reinforcing fibers when the cloth is melted by heating. JP-A-60-209033 proposes a method of uniformly mixing fibers made of a thermoplastic polymer and reinforcing fibers with a single fiber in order to improve the melt penetration of the matrix material into the reinforcing fibers. However, in order to improve the handleability when the composite material is formed, the cloth is first knitted and woven. This composite yarn is susceptible to damage in the rewinding process and the weaving and weaving process, and because it is used for the weft yarn and the warp yarn, the amount of fibers made of a thermoplastic polymer is increased and the physical properties of the composite material molded product are deteriorated. have. According to Japanese Patent Laid-Open No. 63-66362, warp yarns containing reinforcing fibers wound with heat-fusible yarns are arranged in one direction, and then wefts wound with the heat-fusible yarns are superposed and then heat-bonded to both yarns. There is disclosed a technique for fixing a fabric to form a fabric. In this technique, if weaving and heat-bonding treatment are not performed simultaneously or continuously, misalignment of the fabric is likely to occur, making it difficult to handle, and the use of heat-sealing yarns impairs the physical properties of the molded composite material. There is a problem.

A base fabric in which warp yarns containing reinforcing fibers are arranged in one direction and fixed at mutual positions by tricot knitting or the like is also known, but the base fabric obtained by knitting needles is damaged by friction of the reinforcing fibers during knitting. Strength tends to decrease. A biaxial or more multiaxial woven fabric is also known. Since this woven fabric generally has no great difference in the yarn diameter of the warp and the weft and the physical properties of both yarns, the intersection between the warp and the weft is stable, and the misalignment is prevented. It does not easily occur and has good workability. However, the woven crimp causes the reinforcing fiber to bend, so that there is a problem in that the strength utilization factor decreases. Japanese Unexamined Patent Publication (Kokai) No. 3-69628 attempts to prevent the reinforcing fibers from being bent and deformed due to weaving crimps to reduce the strength utilization ratio by setting the yarn diameter ratio of the weft yarns to the warp yarns to 10 times or more. However, since the yarn diameter ratio of the weft yarn and the warp yarn is as large as 10 times or more, the intersection between the warp yarn and the weft yarn is unstable and misalignment is likely to occur. In order to prevent misalignment, it is necessary to use a large amount of yarn made of a thermoplastic polymer having high thermal adhesiveness, and the physical properties of the composite material are likely to be impaired. Therefore, it does not lead to an essential solution.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a base fabric for molding a composite material, which solves the above-mentioned drawbacks of the prior art and provides a composite material having a small misalignment and excellent physical properties. The present inventors have detailed the combination of reinforcing fibers and thermoplastic synthetic fibers that have been conventionally used as a material for forming a base fabric for molding composite materials, the fabric structure and shape retention, and the physical properties of the composite material molded body. As a result of study, they have found that the use of synthetic fibers having high physical properties and heat resistance, which were not available in the past, as the reinforcing fibers can remarkably improve the above-mentioned drawbacks, and thus arrived at the present invention.

[0005]

That is, according to the present invention, a thermoplastic synthetic fiber having a melting point of 300 ° C. or less is used for a warp and a polybenzazole fiber and the thermoplastic synthetic fiber are used for a weft in a weight ratio (%) of 20. : 80 to 80:20, which is a composite yarn mixed with a yarn having a fineness of 5 times or more that of the warp yarn.

The present invention will be described in more detail below. First, synthetic fibers made of a thermoplastic polymer having thermal adhesiveness are used as fibers constituting all components of the warp and one component of the weft. Here, when weaving using synthetic fibers of different thermoplastic polymers as all components of the warp and one component of the weft, phase separation tends to occur during the heat-bonding treatment of the obtained fabric, so use the same type of synthetic fibers. Is preferred. For example, synthetic fibers of polyesters such as polyethylene terephthalate and polybutylene terephthalate, synthetic fibers of polyamides such as nylon 6, nylon 66 and nylon 46, synthetic fibers of polyolefins such as polyethylene and polypropylene,
Meltable thermoplastic synthetic fibers having a melting point of 300 ° C. or less can be targeted. Here, polyethylene terephthalate fibers are most preferable in consideration of thermal deterioration of the thermoplastic synthetic fibers when heat treatment is carried out for eye contact, adhesiveness with the matrix resin after forming the composite material molded body, and the like. Further, the physical properties of the thermoplastic synthetic fiber are important in terms of woven crimps generated in the weft during weaving, shape retention when heat-treating the base fabric, and the like, with an elongation (DE) of 25% or more and a dry heat shrinkage rate. It is preferably 10% or less and the maximum thermal stress is 0.5 g / d or less. If the elongation of the warp containing thermoplastic synthetic fibers as the whole component is less than 30%, it is difficult to absorb the tension during weaving, and the weft tends to be woven crimped. Similarly, the dry heat shrinkage of the warp containing thermoplastic synthetic fibers as all components is greater than 10% and the shrinkage stress is 0.5 g /
When it exceeds d, it depends on the physical properties and fineness of the polybenzazole fiber (PBZ fiber), but it is not preferable because the weft yarn is likely to be woven crimp due to the shrinkage force in the process of melting the warp yarn by subjecting the fabric to heat treatment.

When the PBZ fiber is used as a reinforcing material, if the matrix component breaks before the fiber exhibits its maximum strength, it does not lead to the reinforcement of the composite molded body. Therefore, the elongation of the PBZ fiber is preferably low although it depends on the characteristics of the fiber (matrix material) made of the thermoplastic polymer to be used, and more preferably 4% or less. The P
When the elongation of the BZ fiber exceeds 4%, the maximum strength of the PBZ fiber cannot be effectively used. As a matter of course, the strength of the PBZ fiber is also reflected in the strength of the composite material molded body, so that the strength of the fiber is preferably high, and the PBZ fiber satisfying this requirement is suitable in that it has a tensile strength of 4.0 GPa or more. It is a material.

Further, in the present invention, since the synthetic fibers made of a thermoplastic polymer are melted and solidified to form a matrix component, the reinforcing fibers have a melting point or decomposition temperature higher than the melting point of the synthetic fibers of the thermoplastic polymer by 10 ° C. or more. If it does not last and is not thermally stable, the function as a reinforcing fiber will deteriorate when it is made into a composite material molded body. From this point of view, the thermal decomposition temperature of the PBZ fiber is extremely high at 670 ° C. or higher, so that the range of the thermoplastic synthetic fiber applicable to the present invention is extremely wide and the problem of thermal deterioration hardly occurs.

It is preferable that the yarn used as the weft yarn contains thermoplastic synthetic fibers mixed with the PBZ fibers in order to enhance the impregnation property of the matrix. There is no particular limitation on the method for mixing the yarns used as the weft, and a generally known method can be used. Of these, a method of mixing fibers in an opened state using electricity or fluid is particularly preferable. Since the fiber component mixed here has a great influence on the characteristics of the composite material molded body, the weight ratio defined by the following formula is from 20:80 to 8:
It is important to set the range to 0:20.

W = (DA × FA) / [(DA × FA) +
(DB x FB)] x 100 DA: Fineness of thermoplastic synthetic fiber FA: Number of yarns of thermoplastic synthetic fiber DB: Fineness of PBZ fiber FB: Number of yarns of PBZ fiber

If the weight ratio of the thermoplastic fibers is less than 20%, it is difficult to uniformly melt and penetrate the cloth when the cloth is heat-treated. On the other hand, if the weight ratio of the thermoplastic fibers exceeds 80%, the amount of the supplementary fibers will decrease and the characteristics of the composite material molded body will deteriorate. Further, the dispersion state of the component fibers in the composite yarn is an important factor in terms of misalignment and reinforcing effect, and the higher the degree of dispersion is, the more preferable is at least 25%. When the degree of dispersion of the composite yarn is less than 25%, when the thermoplastic synthetic fiber is melted and solidified to form a composite material molded body, the penetration of the matrix component into the PBZ fiber becomes non-uniform, and when a load is applied, the interphase changes. Are easily peeled off and the effect of the reinforcing material is reduced. The dry heat shrinkage of the thermoplastic synthetic fiber used for the weft is also an important factor for preventing misalignment.
% Or less is preferable. When a yarn having a dry heat shrinkage ratio of more than 10% is used for the weft, the fixing of the reinforcing fiber is insufficient at the time of melting, and a part of the reinforcing fiber spreads or sags. As another means to prevent this, the length of the thermoplastic synthetic fiber relative to the length per unit length of the composite yarn is set to be shorter (giving a difference in yarn length) in advance in the mixed fiber stage in proportion to the dry heat shrinkage ratio. Good. From the viewpoint of suppressing the occurrence of woven crimp, PBZ fiber having an initial elastic modulus of at least 140 GPa is suitable.

Next, the thickness (fineness) of the warp and the weft constituting the base fabric of the present invention will be described. The fineness ratio is an important factor related to weaving crimps, and the weft yarn must have a fineness of at least 5 times that of the warp. When it is less than 5 times, the fixing of the crossing point is surely achieved, but the tension of the warp yarn is apt to be crimped in the weft yarn during weaving. The cloth containing the woven crimp in the weft is fixed by the matrix material while maintaining its shape when heated and melted, and the reinforcing effect in the composite molded body is reduced.

Although weaving is performed using the weft and warp whose composition and constitution are specified in this way, it is essential that the weft is not damaged when the weft containing the reinforcing fiber is inserted. Is preferably used.

The fabric woven and knitted from the yarn according to the present invention is cut into a predetermined size and stacked in a number equal to the weight of the composite molded product so as to be supplied to the secondary processing process. Next, the laminate is filled in a mold heated to a temperature sufficient to melt the thermoplastic synthetic fibers constituting the warp, and the mold is pressed to form a desired shape. Generally, the pressing pressure is required to be 10 to 120 Kg / cm ² with respect to the projected area, and the higher the pressing speed is, the better, and 1 to 3 seconds is preferable. After this pressure compression molding, the surface temperature under pressure is 100 ° C. or less,
It is preferably cooled to a temperature of 80 ° C. or lower and the molded product is taken out of the mold. The mold may be removed after the pressure compression molding and then cooled. In any case, the required cooling time of the molded product is preferably determined in consideration of the thickness of the thickest part of the molded product.

[0015]

EXAMPLES The present invention will be described below with reference to examples, but of course the present invention is not limited thereto. Each scale used in the evaluation of the present invention was obtained by the following procedure.

<Fiber Strength and Elongation> JIS L-1
In accordance with 013, with a tensilon manufactured by Orientec Co., Ltd., a gripping interval of 20 cm, a pulling speed of 100% / mi
The measurement of n and n = 10 was performed to obtain the arithmetic mean value.

<Fiber Dispersion> (a) A cross-sectional photograph of the composite yarn (weft) is taken. (B) Count the number of filaments in the PBZ fiber that are in contact with the thermoplastic synthetic fiber (or that would be in contact with a slight movement of the fiber). (C) The dispersion degree is calculated according to the following formula.

Dispersion = (B / A) × 100 (%) A: Number of PBZ fiber filaments in contact with thermoplastic synthetic fibers B: Total number of PBZ fiber filaments

<Dry Heat Shrinkage of Fiber> JIS L-101
According to 3, the measured values of n = 5 were averaged.

<Flexural Strength and Flexural Modulus of Prepreg> In accordance with JIS K-7055, the fulcrum distance is 48.0 m.
A 3-point bending test was performed at a bending speed of 3.0 mm / min.

<Example 1, Comparative Examples 1 to 3> As the thermoplastic synthetic fiber, polyethylene terephthalate fiber having an elongation of 32.5%, a dry heat shrinkage of 7.6% and a melting point of 265 ° C. was used.
On the other hand, polybenzoxazole fiber (PBO fiber) having a strength of 6.0 GPa, an initial elastic modulus of 299 GPa and an elongation of 3.1% was used as a reinforcing fiber, and both were electrically opened and mixed to prepare a composite yarn. . The fineness and weight ratio of both fibers mixed at this time were changed. Next, using the obtained composite yarn as a weft yarn and using the polyethylene terephthalate fiber (PET fiber) as a warp yarn, using a single rapier loom, a weaving density of 10 yarns /
Weaved in cm. After cutting the obtained cloth into a certain size, a plurality of the cut cloths are stacked so that the PBO fiber directions are orthogonal to each other to form a laminated body having a thickness of 5.0 mm. A heat treatment for 5 minutes was carried out by applying a pressure of 17 kg / cm ² at a temperature of ° C. After that, remove the mold and air cool until the surface temperature drops to 80 ℃, width 15.0mm
A PBO fiber reinforced prepreg sheet having a length of 70.0 mm and a thickness of 3.0 mm was obtained. The bending properties of the obtained prepreg are shown in Table 1.

[0022]

[Table 1]

As shown in Table 1, the strength of the prepreg sheet in Comparative Example 1 is low, because the weft and warp yarns have a fineness ratio of less than 5, the weaving weaving is prominently woven and the prepreg sheet has such a form. It is presumed that the function of the PBO fiber was not fully exhibited in the prepreg sheet brought in. In Comparative Example 2, the weight ratio of the PBO fiber in the composite yarn C used for the weft is less than 20%, and the bending strength of the prepreg sheet is weak. From Comparative Example 3, it can be seen that if the proportion of PBO fibers exceeds 80% by weight, the amount of synthetic fibers composed of the thermoplastic polymer in the prepreg sheet becomes unnecessarily large and the bending properties of the prepreg deteriorate. As described above, the performance of the prepreg sheets of Comparative Examples 1 to 3 as a composite material molded body was insufficient. On the other hand, the prepreg sheet of Example 1 belonging to the present invention has good performance as a composite material molded body.

<Examples 2 to 4> The weight ratio of PBO fibers in the weft yarn was fixed at 63.9%, the fineness ratio of the weft yarn and the warp yarn was fixed at 8.5, and the polyethylene terephthalate fiber and the PBO fiber were dispersed in the weft yarn. I changed the degree. Except for this, prepreg sheets were prepared according to the same molding procedure and method as those shown in Example 1 and Comparative Examples 1 to 3. The results are shown in Table 2.
Shown in.

[0025]

[Table 2]

As can be seen from Table 2, if the dispersity of the composite yarn used for the weft yarn is low, the bending property of the prepreg using the obtained cloth as a base fabric tends to be deteriorated. Especially the degree of dispersion is 2
Those less than 5% (Example 4) were not sufficiently satisfactory in practical use.

<Examples 5 to 7> The weight ratio of PBO fiber in the weft yarn was fixed at 63.9%, the fineness ratio of the weft yarn and the warp yarn was fixed at 8.5, and the elongation and dry heat shrinkage of the thermoplastic synthetic fiber were fixed. Each rate was changed. Except for this, a prepreg sheet was prepared according to the molding procedure and method described in Example 1 and Comparative Examples 1 to 3. The results are shown in Table 3.

[0028]

[Table 3]

As is apparent from Table 3, it is clear that the bending property of the prepreg sheet obtained when the yarn having the elongation of less than 30% or the dry heat shrinkage of more than 10% is used as the warp is deteriorated. became.

<Example 8 and Comparative Examples 4 to 5> By using fibers having different physical properties (strength, elongation, elastic modulus) as reinforcing fibers, the molding procedure according to Example 1 and Comparative Examples 1 to 3 and A prepreg sheet was prepared according to the method. The results are shown in Table 4.

[0031]

[Table 4]

As is clear from Table 4, the bending characteristics of the prepreg sheet using the reinforcing fiber whose strength, elongation and initial elastic modulus do not belong to the present invention are insufficient.

<Comparative Examples 6 to 7> PET in Example 1
When PBO fiber is used instead of the fiber (Comparative Example 6),
Molding according to Example 1 in the case of using polyarylate fiber having a melting point of 320 ° C. (Comparative Example 7), the case of using polyimide fiber (PID fiber) having a decomposition initiation temperature of 500 ° C. (Comparative Example 8), etc. A prepreg sheet was prepared according to the procedure and method. The results are shown in Table 5.

[0034]

[Table 5]

As is clear from Table 5, PBO fiber (melting point:
None, when using decomposition start temperature: 670 ° C. for the weft and the warp (Comparative Example 6), a good sheet-like prepreg could not be obtained. When a reinforcing fiber having a melting point not belonging to the present invention was used (Comparative Example 7), temperature control during pressure compression molding was difficult, and the obtained prepreg sheet had large weave crimps and misalignment. . Reinforcing fibers not belonging to the present invention (PID fiber: glass transition temperature 31
When 5 ° C., no melting point, and decomposition initiation temperature of 500 ° C.) was used (Comparative Example 8), the obtained prepreg sheet had large weave crimps and large misalignment as in Comparative Example 7, and was not practical.

[0036]

EFFECTS OF THE INVENTION According to the present invention, it is possible to form a prepreg sheet excellent in bending property with less generation of weave crimp, which has never been seen before, and a base suitable for forming a composite material with less misalignment and excellent handleability. Cloth can be provided. A composite material molded body obtained by using this base cloth is useful as a material for various mechanical structural parts, pressure vessels or tubular objects, and greatly contributes to the industry.

Claims (1)

[Claims] 1. A thermoplastic synthetic fiber having a melting point of 300 ° C. or less is used for the warp, and a polybenzazole fiber and the thermoplastic synthetic fiber are used for the weft in a weight ratio (%) of 20:80 to 80:20.
The base fabric for forming a composite material, which is formed by arranging a yarn having a fineness of 5 times or more that of the warp yarn, which is a composite yarn mixed in the ratio of.