JPH01167370A - Thermoplastic resin composition - Google Patents

Abstract

PURPOSE:To obtain a thermoplastic resin composition, having excellent strength, rigidity, processability, dimensional stability, appearance of molded products, etc., and suitable as automotive parts, by blending a thermoplastic resin with a specific amount of specified modified cross-section polyester fibers. CONSTITUTION:A thermoplastic resin composition obtained by blending 10-60wt.% polyester fibers having 1-10 denier, preferably 1-5 denier single fiber size and 3-10g/denier strength, 9-40% elongation, 0.5-10% shrinkage in boiling water and modified cross section with a thermoplastic resin (e.g., polyethylene, polypropylene, nylon-6 or polystyrene).

Description

[Detailed description of the invention]

[Industrial Application Field 1] The present invention relates to a thermoplastic resin composition, and more specifically,
The present invention relates to a thermoplastic resin composition for molding that is suitable for use in industrial materials, etc., which is mainly composed of a thermoplastic resin and polyester fibers with irregular cross sections. [Prior Art I] Examples of the resin matrix for resin composite materials include thermoplastic resins such as polyolefins and nylon, thermosetting resins such as epoxy resins, and unsaturated polyester resins. Furthermore, glass fiber has conventionally been mainly used as a resin reinforcing material. However, recently, by using organic synthetic fibers such as polyester fibers and polyamide fibers together with glass fibers, the rigidity of glass fibers and the elasticity of organic synthetic fibers have a synergistic effect, and molded resin products. Improvements in various physical properties were observed, and it was also revealed that the difference in specific gravity between organic synthetic fibers and glass fibers directly leads to weight reduction of resin composite molded products. organic polymers and glass fibers, such as resin matrices;
When combining dissimilar materials such as organic synthetic fibers, the compatibility of the two greatly influences the performance of the resin composite molded product. However, for boat fishing, there is a problem in that the affinity between the organic synthetic fiber and the resin matrix is extremely low, and poor adhesion is likely to occur. Therefore, many studies have been conducted to improve the adhesion between organic synthetic fibers and resin matrices, and it has been proposed to add coating materials to the fibers to change the physical and chemical properties of the interface between the two to increase their affinity. For example, Japanese Patent Application Laid-Open No. 54-55077 discloses a method of applying synthetic rubber latex to polyester fibers, heating them to form a polymer film on the surface of the polyester fibers, and then blending it into a resin matrix. has been done. Also, JP-A-61-19
No. 879 discloses a method for attaching an organofunctional silane to the surface of polyester fibers. However, although these surface treatments certainly improve the affinity between polyester fibers and the resin matrix, the improvement in adhesion between the fibers and resin is still not sufficient, and the Improvements have been desired in terms of physical performance such as bending strength and flexural modulus, and appearance such as surface unevenness and distortion. [Problem to be solved by the invention 1 The present inventors have improved the above-mentioned problems and improved physical performance,
As a result of intensive research to develop a molding material that can withstand practical use in terms of external appearance, we found that by blending polyester fibers with irregular cross sections into a specific thermoplastic resin, we were able to improve the strength, rigidity, processability, dimensional stability, and molded products. The inventors have discovered that a thermoplastic resin composition for molding that is excellent in terms of appearance and the like can be obtained, and have arrived at the present invention. [Means for Solving the Problems] That is, the present invention provides polyester fibers having an irregular cross section in a thermoplastic resin having a softening point lower than the softening point of the polyester by 10 to 60% by weight. This is a thermoplastic resin composition formed by blending the following. [Function] The thermoplastic resin used in the present invention must have a softening point that is 30° C. or more lower than the softening point of the polyester constituting the irregular cross-section fiber. Preferred specific examples of such thermoplastic resins include polyethylene, polypropylene, nylon-6, polystyrene, acrylonitrile-styrene copolymer, polyacetal, and polycarbonate. The temperature difference between the softening point of thermoplastic resin and the softening point of polyester is 30
If the temperature is less than 0.degree. C., phenomena such as shrinkage and embrittlement occur in the polyester fibers when the thermoplastic resin composition is melted, which is not preferable. In addition, the softening point referred to in the present invention refers to the Vicat test (JIS
K 7206). The polyester fiber having an irregular cross section used in the present invention (hereinafter abbreviated as irregular cross section polyester fiber) refers to the cross-sectional contour circumference of a circular cross-sectional fiber made of the same polymer and having the same denier as the cross-sectional contour circumference of the fiber cross section. When calculating the ratio to the length (hereinafter abbreviated as anomaly index),
Refers to polyester fibers whose irregular shape index is 1.2 or more. The resin matrix and polyester fibers have an affinity due to their interfacial substance, that is, they have adhesive properties, so the larger the adhesive area per unit volume of irregular cross-section polyester fibers, the higher the adhesive strength. becomes. Therefore, the larger the irregularity index, the larger the bonding area, and the better the bonding between the fibers and the resin matrix is achieved. When the irregularity index is less than 1.2, the adhesive area increases only slightly, and no significant improvement in adhesiveness can be expected compared to the case of using ordinary polyester fibers having a circular cross section. Further, as for the cross-sectional shape, it is particularly preferable to have a protrusion such as a three-lobed shape or a four-lobed shape, although the cross-sectional shape is not limited thereto. When the irregular cross-section fiber has such protrusions, the irregularity ratio inevitably increases, and at the same time,
When the resin matrix and fibers are mixed, the protrusions become an obstacle, and compared to fibers without protrusions, the fibers are difficult to pull together, so it is possible to improve the dispersibility of the polyester fibers within the resin matrix. A preferred specific example of the polyester substrate of the polyester fiber having an irregular cross section used in the present invention is one in which 80 mol% or more of the repeating units constituting it is composed of ethylene terephthalate, and copolymers are also included. Copolymerization components include isophthalic acid, adipic acid, sebacic acid, p-β-oxyethoxybenzoic acid, diphenyl ether-4,4°-dicarboxylic acid, diphenoxyethane-
Dicarboxylic acid components such as 4,4"-dicarboxylic acid and glycols such as propylene glycol, butanediol, hexamethylene glycol, neopentyl glycol, and cyclohexanedimetatool are used. These polyesters undergo polycondensation through transesterification. A method of carrying out polycondensation through a direct esterification reaction,
Alternatively, polymers obtained by any method of solid phase polymerization of polymers obtained by these methods can be used. The irregular cross-section polyester fibers used in the present invention can be in various forms such as milled fibers, cut fibers, and filaments. The irregular cross-section polyester fiber used in the present invention has a single fiber fineness of 1.0 to 10.0 denier, more preferably 1.0 to 5.0 denier, a strength of 3 to lag/denier, and an elongation of 9 to 40 denier. % and boiling water shrinkage rate from 0.5 to 101
Preferably, it is 0%. In order to provide sufficient physical performance to the molded product, the denier of the irregular cross-section polyester fiber must also have good mixing and dispersibility with the resin matrix during the manufacturing process, and must withstand mechanical tensile stress during the mixing operation. Since there is
It is preferable that the denier is 1.0 denier or more. Furthermore, if the single fiber denier exceeds the IO0θ denier, the adhesion area with the resin matrix per unit volume of the fiber, that is, per weight, will decrease significantly, and the irregular cross-section polyester This is not preferable because the purpose of using the fibers is diminished and it becomes difficult to maintain good adhesion. Regarding strength and elongation, if the strength of the single fiber is less than 3 g/denier or the elongation exceeds 40%, it is difficult to give the molded product sufficient strength, especially impact resistance, so it is preferable. On the other hand, when using irregular cross-section polyester fibers with a strength exceeding 10 g/denier, sufficient physical performance can be given to the molded product, but stability during the spinning process decreases and manufacturing costs increase. This is not desirable because it causes problems. Generally, strength and elongation are two sides of the same coin, and if you try to improve the strength, the elongation will decrease. Therefore, this problem of decreased stability during production also occurs in fibers with an elongation of less than 9%. When the resin was manufactured, used as a resin-reinforced material, and the performance of resin composite molded products was evaluated, it became clear that performance improvements commensurate with the strength improvements could not be expected. Therefore, it is desirable that the upper limit of the strength of the irregular cross-section polyester fiber used in the present invention is 10 g/denier, and the lower limit of the elongation is 9%. The boiling water shrinkage rate is a factor that has a large effect on the appearance of the molded product. When molded with a mold, the shrinkage rate relative to the mold dimensions is 0.7%, but polyester fibers with irregular cross sections having boiling water shrinkage rates of 11.8% and 12.8% were similarly obtained. The shrinkage rate of the molded product increases rapidly to 1.12% and 1.4%, respectively, causing cracks in the molded product. In addition, when polyester fibers with irregular cross sections with a boiling water shrinkage rate of less than 0.5% are used, the bending strength is 1.1 kg/mm", compared to 6.7 kg/mm" for molded products using glass fibers.
It showed a very low value of 6 or less. This is because the fibers are embrittled due to the high heat history during fiber production in order to reduce the boiling water shrinkage rate to less than 0.5%. The blending ratio of the irregular cross-section polyester fibers in the thermoplastic resin composition of the present invention is 1% to the thermoplastic resin composition.
It is 5 to 60% by weight, preferably 20 to 55% by weight. If it is less than 15% by weight, the improvement effect of the addition of splittable composite fibers will be small in terms of stiffness, dimensional stability, heat resistance, paintability, etc. If it exceeds 60% by weight, the fluidity will not improve even if plasticizers etc. are added. This causes problems in terms of moldability, and it also becomes brittle in terms of strength, making it impractical. It is preferable to use glass fiber in combination with the thermoplastic resin composition of the present invention in order to increase rigidity.The amount of glass fiber added is 0 to 50% by weight, more preferably 5 to 40% by weight. Further, as inorganic fillers, calcium carbonate, magnesium silicate, aluminum silicate, barium sulfate, calcium sulfate, etc., and furthermore, plasticizers for resins can be used. When irregular cross-section polyester fibers and inorganic fillers are used together, improvements in physical properties such as flame retardance, rigidity, and heat resistance can be obtained, but by adding a small amount of inorganic fillers, the dispersion of irregular cross-section polyester fibers can be improved. The effect of improving the impact strength is also observed, and as a result, the impact strength is also improved. In order to uniformly mix these various compounds into the thermoplastic resin, a Banbury mixer, roll mixer, or kneader is used.
1 Extruders, high-speed rotation mixers, and other devices and methods that are generally used for mixing resins and fillers can be used as they are. The thermoplastic resin composition of the present invention may further contain various additives such as colorants, light stabilizers, and antioxidants, if necessary.

【Example】

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples. Example 1 40 parts by weight of ethylene-brobylene block polymer with a melt flow index of 30 and an ethylene content of 8% by weight (softening point 165°C), a melt flow index of 2
0 high-density polyethylene (softening point 129°C) 15 parts by weight, trilobal cross-section polyethylene terephthalate fiber (softening point 235°C, fiber length 6 years old) 10 parts by weight, glass fiber (diameter 11μ, fiber length 1 inch) 15 parts by weight and 20 parts by weight of calcium carbonate (average particle size: 3 pa) were mixed in a kneader heated to 170°C to obtain a thermoplastic resin composition of the present invention. Injection molding was carried out under conditions such that the resin temperature of the polypropylene resin was 190° C., and test pieces for measuring tensile strength, flexural modulus, and Izod impact strength were each injection molded. Table 1 shows the evaluation results of the physical properties of the trilobal cross-section polyethylene terephthalate fiber used and the physical properties of the thermoplastic resin composition of the present invention. The tensile strength, flexural modulus, and Izod impact strength were measured in accordance with JIS-6911. As is clear from Table 1, the thermoplastic resin composition of the present invention has extremely high Izod impact strength. Comparative Example 1 A thermoplastic resin composition was obtained in exactly the same manner as in Example 1, except that 20 parts by weight of glass fiber was used instead of polyethylene terephthalate fiber with a trilobal cross section. The evaluation results of the physical properties of the obtained thermoplastic resin composition were evaluated in the first
Shown in the table. Comparative Example 2 Instead of polyethylene terephthalate fiber with trilobal cross section,
A thermoplastic resin composition was obtained in exactly the same manner as in Example 1, except that polyethylene terephthalate fibers with a circular cross section were used. Table 1 shows the evaluation results of the physical properties of the polyethylene terephthalate fibers used and the physical properties of the obtained thermoplastic resin composition. Reference Example 1 A thermoplastic resin composition was obtained in exactly the same manner as in Example 1, except that polyethylene terephthalate fibers with a trilobal cross section having an elongation of 40% or more were used. Table 1 shows the evaluation results of the physical properties of the polyethylene terephthalate fibers used and the physical properties of the obtained thermoplastic resin composition. Reference Example 2 A thermoplastic resin composition was obtained in exactly the same manner as in Example 1, except that polyethylene terephthalate fibers with a trilobal cross section having a boiling water shrinkage rate of 10% or more were used. The evaluation results of physical properties are shown in Table 1. The irregular cross-section polyethylene terephthalate fiber used here has too high a shrinkage rate in boiling water.
Compared to Example 1, the appearance of the molded product obtained, that is, the surface smoothness, was inferior. Table 1 Examples 2 to 4 and Comparative Examples 3 to 5 As a thermoplastic resin, the melt flow index is 20
of polyethylene (softening point 129°C), relative viscosity 2.5 (
Nylon-6 (softening point 200 in 95% sulfuric acid at 25°C)
A thermoplastic resin composition was prepared by blending various components in the proportions shown in Table 2 in the same manner as in Example 1, except that polystyrene (softening point: 95°C) with a melt flow index of 8.5 was used. I got something. Table 2 shows the evaluation results of the physical properties of the obtained thermoplastic resin composition. [Effect of the Invention J The thermoplastic resin composition of the present invention has significantly superior Izot impact strength compared to conventional fiber-reinforced thermoplastic resin compositions. Therefore, it can be used particularly effectively in fields where impact resistance is important. Although it is possible to mold by various molding methods such as extrusion molding and injection molding, it is particularly suitable for producing a sheet first and then secondary processing it by vacuum molding or the like. Therefore, the molded product can be suitably used for automobile parts and the like by taking advantage of its excellent impact resistance, good appearance, and light weight.

[Brief explanation of the drawing]

FIG. 1 and FIG. 2 are schematic diagrams showing the state of fiber filling in the thermoplastic resin composition of the present invention. Figure 3 shows
FIG. 2 is a schematic diagram showing the state of fiber filling in a conventional thermoplastic resin composition filled with ordinary circular cross-section fibers. l: Fiber 2: Thermoplastic resin Figure 1
Figure 2 Figure 3 Procedure 7 IE "F'? (Voluntary) March 1983 220

Claims (3)

[Claims] (1) A thermoplastic resin composition comprising 10 to 60% by weight of polyester fibers having an irregular cross section mixed with a thermoplastic resin having a softening point 30° C. or more lower than that of the polyester. (2) The thermoplastic resin according to claim 1, wherein the thermoplastic resin is one or more selected from the group consisting of polyethylene, polypropylene, nylon-6, polystyrene, acrylonitrile-styrene copolymer, polyacetal, and polycarbonate. Resin composition. (3) Single fiber fineness of polyester fiber is 1.0 to 10
．． 0 denier, strength 3-10g/denier, elongation 9
40% and a boiling water shrinkage rate of 0.5 to 10.0%.