JPS6132345B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a thermoplastic resin composition containing inorganic fibers as a reinforcing material, and particularly to a styrenic resin composition that has excellent properties such as a good surface condition for molded products and a small coefficient of linear expansion. In recent years, plastics have made significant inroads into engineering fields such as various mechanical elements and electronic parts, and are known not only for their excellent mechanical strength, heat resistance, and chemical resistance, but also for the surface properties of molded products. There is a need for a plastic material that is in good condition, has an excellent appearance, is easy to paint, has a small coefficient of linear expansion, is less affected by temperature changes such as air temperature, and has good dimensional stability. To meet these demands, glass fibers, carbon fibers, powders or scale-like substances such as talc and charcoal, whiskers such as potassium titanate, etc., are added to thermoplastic resins either singly or in combination. Blending is being done. In particular, to provide a resin composition with excellent mechanical strength, it is recommended to use glass fibers in combination with other carbon fibers, powders or scale-like substances such as talc and charcoal, or whiskers such as potassium titanate. Are known. However, whiskers such as carbon fiber and potassium titanate are expensive materials, and using them in combination with glass fiber is disadvantageous in terms of the cost of the resin composition. Alternatively, when a scaly substance is used in combination with glass fiber, the improvement in strength by glass fiber tends to be inhibited.Furthermore, when a large amount of glass fiber is used, the linear expansion coefficient decreases and dimensional stability improves, but The surface condition of the molded product deteriorates, and conversely, if the amount of glass fiber used is small, the surface condition of the molded product is good, but the coefficient of linear expansion increases and the dimensional stability tends to decrease. There has been a demand for the development of a resin composition that satisfies both of the following. In view of this point of view, the present inventors have created a molded product that not only has excellent mechanical retraction strength, etc., but also has a good surface condition, a small coefficient of linear expansion, and excellent dimensional stability. As a result of extensive research on inexpensive resin compositions, we have developed a new resin composition by using styrene resin as the matrix resin and blending glass fiber and ground rock wool with an aspect ratio of 10 to 60 as fillers in a predetermined ratio. , there is no significant decrease in mechanical strength compared to using only glass fiber,
Furthermore, the inventors have discovered that it is possible to obtain a resin composition that satisfies both the surface condition and linear expansion coefficient of a molded article, and has completed the present invention. That is, the present invention is a composition mainly containing 20 to 90% by weight of a styrene resin and 10 to 80% by weight of inorganic fibers, of which 85 to 15% by weight has an aspect ratio of 65 or more. The styrenic resin composition is glass fiber and the remaining 15 to 85% by weight is ground rock wool with an aspect ratio of 10 to 60. In the present invention, styrenic resins include polymers obtained by individually polymerizing styrene monomers such as styrene, methylstyrene, and chlorostyrene, such as polystyrene, polymethylstyrene, and polychlorostyrene. In addition to coalescence, copolymers of these styrenic monomers and other monomers, elastomers, etc. that can be copolymerized with them are included. Other monomers that can be copolymerized with the styrenic monomer include, for example, acrylonitrile,
Acrylonitrile such as methacrylonitrile, unsaturated carboxylic acids such as acrylic acid and methacrylic acid, unsaturated carboxylic acid esters such as methyl acrylate and methyl methacrylate, dienes such as chloroprene, butadiene and isoprene, 1-butene, Examples include olefins such as 1-pentene, and other α/β-unsaturated carboxylic acids such as maleic anhydride or anhydrides thereof. Elastomers that can be copolymerized with styrene monomers include polydiene rubbers such as butadiene rubber, chloroprene rubber, and isoprene rubber, styrene-diene elastomers such as styrene-butadiene rubber, and molecules such as styrene-butadiene-styrene rubber. Examples include block copolymer elastomers having a polydiene block in their structure. Furthermore, the styrenic resin also includes a resin mixture formed mainly of the above-mentioned various styrene resins and blended with other resins. Specific examples of such styrene resins include general-purpose polystyrene, rubber-reinforced polystyrene, styrene-acrylonitrile copolymer, and methyl methacrylate.
Examples include styrene copolymer and ABS. These styrenic resins can be produced by various polymerization methods such as bulk polymerization, solution polymerization, emulsion polymerization, suspension polymerization, or bulk-suspension polymerization. , antioxidants, ultraviolet absorbers, heat stabilizers, colorants, and other commonly used additives may be appropriately contained. In addition, the glass fibers used in the present invention include CaO,
The main components are SiO ₂ and Al ₂ O ₃ , usually
CaO 10-20% by weight, SiO ₂ 50-70% by weight and
Preferably, it contains 2 to 15% by weight of Al ₂ O ₃ . This glass fiber is not limited as long as it can be used as a reinforcing material for resin, and may be either roving or chopped strand.
Further, although the fiber surface may be untreated or the surface of the fiber may be treated with a borane or silane compound, short fiber glass wool is not preferable. This glass fiber usually has an average fiber length (L) of 1 to 10 mm and an average fiber diameter (D) of 10 mm.
~15μ and an aspect ratio (L/D) of 65 or more is used. Since the glass fibers may be cut when mixed with the thermoplastic resin, the average fiber length in the resin composition varies depending on the length of the glass fibers used and the mixing conditions, but is 0.2~ 2
mm, preferably 0.3 to 1 mm. Rock wool, which is blended into styrene resin together with the glass fibers mentioned above, is also called rock wool, slag wool, mineral wool, etc., and usually contains 20 to 45% CaO by weight.
The main components are 30 to 50% by weight of SiO ₂ and 5 to 20% by weight of Al ₂ O ₃ , and also contains components such as MgO. Rotsk wool is usually basalt, andesite,
Fibers are made by melting natural stones such as diabase and blast furnace slag, which is a by-product during iron manufacturing, and the fiber length is several mm.
The particle size is from several centimeters to several centimeters, and the particle content is about 30 to 40%. Such rock wool is used by grinding it to an aspect ratio of 5 to 100. Milling of rock wool means cutting or crushing rock wool, and can be crushed using a rotating disk type mill, a compression mill, an opposed roll type mill, or the like. As the ground rock wool used in the present invention, it is particularly preferable to use one that has been ground with the above-mentioned grinder and then classified into fibers and particles using an air classifier or the like. Such ground rock wool has an average fiber length of 20~
500μ, preferably 70% or more of 100~200μ,
The average fiber diameter is 2 to 10 microns, preferably 70% or more thereof is 3 to 5 microns, and the aspect ratio is 5 to 100. As with glass fibers, this ground rock wool may be cut when mixed with the thermoplastic resin, but because it has been previously ground, the degree of cutting is relatively small. In short, the length and aspect ratio of the ground rock wool contained in the resin composition are important, and it is desirable that the average fiber length is 20 to 500μ, preferably 50 to 200μ, and that the variation in length is relatively small. Something is good. Further, the average aspect ratio is adjusted to be in the range of 10 to 60. The above-mentioned ground rock wool has a group that binds to the styrene resin as a matrix on one side, and a group that bonds to the ground rock wool as a filler on the other side to increase the bonding force between the two. In order to improve the mechanical strength, surface condition, etc. of the styrenic resin composition, surface treatment can be performed with a coupling agent. Coupling agents that can be used for this purpose include silane coupling agents, titanate coupling agents, and aluminum coupling agents. The above-mentioned silane coupling agent generally has the following general formula R ₁ -Si(OR ₂ ) ³ [wherein R ₁ is an amino-alkylene group, an amino-alkylene-amino-alkylene group, a vinyl group, an acryloxy group, methacryloxy group,
It is a substituent selected from the group consisting of epoxy-cyclohexyl-alkylene group, glycidoxy-alkylene group and mercapto-alkylene group, and _R2 is an alkyl group or a hydrogen atom. ]
It is a silane compound represented by γ-
methacryloxypropyl-trimethoxysilane, γ-aminopropyl-trimethoxysilane,
N-β-(aminoethyl)-γ-amino-propyl-trimethoxysilane, β-(3,4-epoxycyclohexyl)ethyl-trimethoxysilane,
Compatible with alkoxysilanes such as γ-glycidoxypropyl-trimethoxysilane, vinyl-triethoxysilane, vinyl-tris(2-methoxy-ethoxy)silane, γ-mercaptopropyl-trimethoxysilane, and these alkoxysilanes. Mention may be made of hydroxysilanes.
Further, examples of the titanate-based coupling agent include known ones such as isopropyl-triisostearoyl-titanate and isopropyl-tridedecylbenzenesulfonyl-titanate, and examples of the aluminum-based coupling agent include acetalkoxy-aluminum-titanate.
Known ones such as diisopropylate can be mentioned. Regarding these coupling agents,
Conventionally known methods include dissolving ground rock wool in water or an organic solvent, immersing the ground rock wool in this solution, removing the solvent and drying it, or mixing it with ground rock wool in a dry state at a temperature ranging from room temperature to 250°C. The amount used is 0.01 to 10 parts by weight, preferably 0.1 to 5 parts by weight, based on 100 parts by weight of ground rock wool. In the present invention, the proportion of inorganic fibers blended into the styrene resin varies depending on the type of styrene resin used, but
20 to 90% by weight of inorganic fibers, preferably 40 to 90% of styrene resin and 10 to 60% of inorganic fibers, more preferably 55 to 85% of styrene resins and inorganic fibers. The fiber content is 45-150% by weight. If the amount of inorganic fiber blended exceeds 80% by weight, the strength will decrease and the surface condition of the molded product will deteriorate, while if it is less than 10% by weight, the reinforcing effect will be insufficient and the linear expansion coefficient will not improve. It is enough. The inorganic fibers used are a combination of glass fiber and ground rock wool. Although glass fiber alone can achieve the objective of high strength, it is unfavorable in terms of the surface condition of the molded product, and ground rock wool alone is insufficient in terms of strength. The proportion between glass fibers and ground rock wool is 85-15% by weight, preferably 70-30% by weight of glass fibers and 15-85% by weight, preferably 30-70% by weight of ground rock wool. be. Or, in terms of the content of glass fiber and ground rock wool in the resin composition, the former is 5 to 40% by weight, and the latter is 5 to 40% by weight.
The total amount is preferably 10 to 60% by weight. The styrenic resin composition containing the styrene resin, glass fiber, and ground rock wool is prepared by uniformly mixing the styrene resin, glass fiber, and ground rock wool using a suitable blender or the like in a conventional manner within the above-mentioned blending ratio range. Ru. Further, the styrenic resin composition thus prepared is molded into a desired product by conventional extrusion molding, injection molding, or the like. In addition, when preparing the above styrenic resin composition, inorganic fibers are added as flame retardants, pigments, plasticizers, antioxidants, ultraviolet absorbers, other additives, and reinforcing agents that are usually added to styrenic resins. A dispersant used in blending, a modifier that improves the adhesion between the inorganic fiber and the thermoplastic resin, an inorganic filler, and other reinforcing fibers may be added. According to the present invention, by blending glass fiber and ground rock wool in a styrene resin at a predetermined ratio, the molded product can be displayed while maintaining almost the same mechanical strength as when only glass fiber is used. At the same time, it is possible to suppress the coefficient of linear expansion to a small value and improve dimensional stability. In other words, by replacing part of the glass fiber with ground rock wool, the surface condition of the molded product can be improved, and by adding ground rock wool to the glass fiber, the coefficient of linear expansion can be improved without reducing physical properties such as strength. can be made smaller.
As a result, the amount of expensive glass fiber used is reduced,
Furthermore, since a resin composition with satisfactory physical properties can be provided without using carbon fibers or the like, costs can be reduced. Hereinafter, the present invention will be specifically explained based on Examples and Comparative Examples. Examples 1 to 6 and Comparative Examples 1 and 2 Acrylonitrile-styrene copolymer (trade name: Estyrene AS30, manufactured by Nippon Steel Chemical Co., Ltd.) was used as the styrene resin, and glass fiber was added to it in the proportions shown in Table 1. (average fiber length 3mm, average fiber diameter 9μ, aspect ratio 333) and ground rock wool (average fiber length 120μ, average fiber diameter 4μ, aspect ratio 30, particle (10μ or less) content 1% by weight or less, Nippon Steel Chemical A styrene-based resin composition was prepared by blending with Kogyo Co., Ltd. (trade name: S-Fiber FF) and kneading in an extruder. Test pieces were molded by injection molding using the styrene resin compositions of Examples 1 to 6, and the tensile strength (JIS K 6871), tensile elongation rate (JIS K 6871), and bending strength (ASTM) were determined for each test piece. D-790),
The flexural modulus, notched 1/4″ isot impact strength (ASTM D-256), and melt flow index (JIS K 6870) were measured to evaluate the mechanical strength of each test piece and to evaluate the surface condition of the molded product. 4
Evaluation was performed using a graded evaluation system (◎: excellent, ◯: good, △: fair, ×: poor), and the linear expansion coefficient was determined. The results are shown in Table 1.

【table】

[Table] Also, the above Examples 1, 4 and 6 and Comparative Example 1
The surface condition of each test piece was measured at a magnification of 4×10
It was filmed in The results are shown in Figures 1 to 4. The length of one memory shown in the figures is 25μ. Examples 7 to 11 and Comparative Examples 3 to 7 The above acrylonitrile as the styrene resin
Styrene copolymer, general-purpose polystyrene (product name: Estyrene G20, manufactured by Nippon Steel Chemical Industry Co., Ltd.),
Rubber-reinforced polystyrene (product name: Estyrene H65, manufactured by Nippon Steel Chemical Industry Co., Ltd.) and ABS resin (product name: Estyrene, manufactured by Nippon Steel Chemical Industry Co., Ltd.)
Test pieces were prepared in the same manner as in Examples 1 to 6 above using 70 parts by weight of ABS200), 20 parts by weight of glass fibers having the diameter shown in Table 2, and 10 parts by weight of the above-mentioned ground rock wool. The mechanical strength, surface condition evaluation, and linear expansion coefficient of each test piece were determined. The results are shown in Table 2. Comparative examples were also prepared with resin compositions containing 80 parts by weight of each styrene resin and 20 parts by weight of glass fiber.

[Table] Comparative Examples 8 to 10 In place of the ground rock wool used in Example 1, ground glass fibers shown in Table 3 or ground rock wool with different aspect ratios were used, and the same styrene resin composition as in Example 1 was used. The surface conditions and linear expansion coefficients of test pieces molded using these styrenic resin compositions were examined in the same manner as in Example 1. The results are shown in Table 3.

【table】 [Brief explanation of the drawing]

Figures 1 to 4 are microscopic photographs taken of the shapes of fibers appearing on the surfaces of the test pieces of Example 1, Example 4, Example 6, and Comparative Example 1, respectively, in order to examine their surface conditions. .

Claims (1)

[Claims] 1 Styrenic resin 20-90% by weight and inorganic fiber 80%
-10% by weight, 85-15% by weight of the above inorganic fibers are glass fibers with an aspect ratio of 65 or more, and the remaining 15-85% by weight are glass fibers with an aspect ratio of 10-60. A styrenic resin composition characterized by being ground rock wool.