JPH0468046A - Rubber-modified styrenic resin composition - Google Patents

Abstract

PURPOSE:To prepare the title compsn. giving a molded article excellent in mechanical strengths and vibration characteristics by compounding a rubber- modified styrenic resin with a specified amt. of a mixture of a zinc oxide whisker with mica. CONSTITUTION:A styrenic monomer (e.g. styrene) and a copolymerizable rubber component (e.g. a butadiene rubber or an isoprene rubber) are copolymerized to give a rubber-modified styrenic resin. 50-98wt.% the resin is mixed with 50-2wt.% mixture of a zinc oxide whisker with mica to give the title compsn. Pref. the whisker is of a tetrapod crystalline structure. The compsn. is suitably used in areas where high mechanical strengths and excellent vibration characteristics are required, e.g. as an exterior material for a low-current electric appliance or a business machine.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a thermoplastic resin composition containing zinc oxide whiskers and mica.

In more detail, the inherent easy moldability of styrenic resins,
This relates to a styrenic resin composition with a novel composition that has excellent mechanical strength (especially flexural modulus), heat resistance, and vibration characteristics, and provides materials that can be applied to light electrical appliances, exterior materials for office equipment, etc. .

<Prior art> As a conventional method for improving the properties of thermoplastic resin compositions, powders such as glass fibers, carbon fibers, talc, charcoal, etc.
Alternatively, scale-like substances such as mica, whiskers such as potassium titanate, etc. are used alone or in combination of two or three types.

In particular, it is known that it is effective to use inorganic fibers such as glass fibers with a large aspect ratio to provide a resin composition with excellent mechanical strength.

However, when an inorganic filler such as glass fiber is used, although the mechanical strength is improved, the loss coefficient (η) obtained by viscoelasticity measurement tends to decrease. Therefore, its vibration characteristics were unfavorable for use as housings for light electrical appliances, office equipment, and the like.

Therefore, there has been a demand for the development of a resin composition that provides molded articles with good mechanical strength and vibration characteristics.

<Problems to be Solved by the Invention> In view of the above circumstances, an object of the present invention is to provide a resin composition with good mechanical strength and vibration characteristics of a molded article.

Means for Solving the Problems> The present invention is a composition in which zinc oxide whiskers and mica are blended into a rubber-modified resin composition, and is characterized by having the following requirements.

That is, it is a rubber-modified styrenic resin composition characterized by comprising 50 to 98% by weight of a rubber-modified styrenic resin and 50 to 2% by weight of a mixture of zinc oxide whiskers and mica, in which the zinc oxide whiskers are tetrapod-type. Having a crystalline structure, the mixture of zinc oxide whiskers and mica
It is preferable in the present invention that the composition has a composition consisting of 5 to 95% by weight of zinc oxide and 95 to 5% by weight of mica, and that the zinc oxide whiskers and/or mica are surface-treated with a silane compound. This is an embodiment.

In the present invention, rubber-modified styrene resins include polydiene rubbers such as butadiene rubber, chloroprene rubber, and isoprene rubber that can be copolymerized with styrene monomers, styrene-diene elastomers such as styrene-butadiene rubber, and styrene-butadiene-styrene rubbers. It is a copolymer of a block copolymer elastomer or the like that has a polydiene block in its molecular structure, such as rubber.

In addition, other monomers that can be copolymerized with the styrene monomer, such as acrylonitriles such as acrylonitrile and methacrylonitrile, unsaturated carboxylic acids such as acrylic acid and methacrylic acid, methyl acrylate, methyl methacrylate, etc. unsaturated carboxylic acid esters, dienes such as chloroprene, butadiene, and isoprene; olefins such as 1-butene and 1-pentene; and other α,β-unsaturated carboxylic acids such as maleic anhydride or their anhydrides, etc. can also be copolymerized at the same time.

Furthermore, the rubber-modified styrene-based resin of the present invention includes a resin mixture made mainly of the above-mentioned various rubber-modified styrene-based resins and blended with other resins. Examples include rubber-reinforced polystyrene, styrene-acrylonitrile copolymer, methyl methacrylate-styrene copolymer, and ABS.

These styrenic resins can be produced using bulk polymerization, solution polymerization,
It can be produced by various polymerization methods such as emulsion polymerization, suspension polymerization, or bulk-suspension polymerization, and also contains plasticizers, antioxidants, ultraviolet absorbers, heat stabilizers, blowing agents,
Commonly used additives such as colorants can be appropriately included.

The zinc oxide whisker used in the present invention consists of a core and a needle-like crystal part extending from the core in different axial directions, the diameter of the base of the needle-like crystal part being 0.7 to 14 μm, and the needle The length from the base to the tip of the crystalline portion is 3 to 200 μm, and a tetrapod-shaped one having a needle-like crystalline portion extending in four axial directions is particularly preferable.

Zinc oxide whiskers have a group on one side that binds to the styrene resin as a matrix, and a group on the other side that binds to the zinc oxide whisker as a filler to improve the bonding force between the two. Surface treatment can be performed with a coupling agent for the purpose of improving the mechanical strength, surface condition, etc. of the resin composition. Coupling agents that can be used for this purpose include silane coupling agents, titanate coupling agents, and aluminum coupling agents.

The above-mentioned 7-run coupling agent generally has the following Noshiro% formula (%) [However, in the formula, R1 is an amino-alkylene group, an amino-alkylene-amino-alkylene group, a vinyl group, an acryloxy group, a methacryloxy group, It is a substituent selected from the group consisting of epoxy-cyclohexyl-alkylene group, glindoxyalkylene group, and mercapto-alkylene group, and R2 is an alkyl group or a hydrogen atom. It is a silane compound represented by T.
-Methacryloxypropyltrimethquine silane, T
-Aminopropyltrimethquine silane, N-β-(amineethyl)-T-aminopropyltrimethinesilane, β-(3,4-epoxychlorohexyl)ethyltrimethquinesilane, T-glycidoxypropyl- List alkoxysilanes such as trimethoxysilane, vinyltriethoxysilane, vinyl-tris(2methoxy-ethoxy)silane, T-mercaptopropyl-trimethquine silane, and hydroxysilanes corresponding to these alkoxysilanes. I can do it.

In addition, examples of the titanate-based coupling agent include known ones such as isopropyl-triisostearoyl-titanate and inpropyl-tridedecylbenzenesulfonyl-titanate, and examples of the aluminum-based coupling agent include acetal alcohol. Known materials such as quin-aluminum diisopropylate can be mentioned. These camping agents can be dissolved in water or an organic solvent, immersed zinc oxide whiskers in this solution, then removed the solvent and dried, or mixed with zinc oxide whiskers in a dry state within the range of room temperature to 250°C. It can be used by conventionally known methods such as mixing. Amount used: 0.01 per 100 parts by weight of zinc oxide whisker
~10 parts by weight, preferably 0.1 to 5 parts by weight.

Additionally, a carboxylic acid may be used in conjunction with the surface treatment if necessary.

The mica used in the present invention is widely commercially available, and the particle size and aspect ratio are not limited.

Similar to zinc oxide whiskers, mica surface-treated with a coupling agent can also be used for the purpose of improving the bonding force with the matrix and improving the mechanical strength, surface condition, etc. of the styrenic resin composition.

Coupling agents that can be used for the second purpose include silane camping agents, titanate camping agents, aluminum camping agents, etc., and are treated in the same manner as the coupling agent treatment for zinc oxide.

By using zinc oxide whiskers and mica in combination, within a certain mixing ratio of zinc oxide whiskers and mica, the loss factor of the composition is surprisingly lower than that of the composition using zinc oxide whiskers and mica alone. It is higher than the value simply calculated proportionally from the loss coefficient and mixture ratio, and can alleviate the sudden drop in impact strength and poor appearance that occur when mica is used alone. Furthermore, when injection molding is performed, when mica is used alone, anisotropy often appears in physical properties such as t1 stiffness and impact strength because the mica is oriented in the direction of the molding flow of the resin, but when zinc oxide whiskers are used together, This has the desirable effect of relaxing the anisotropy of physical properties.

The styrenic resin composition containing the styrene resin, zinc oxide whiskers, and mica can be prepared using an appropriate blender, laboplasto mill, or
- Mix uniformly using a conventional method using a shaft kneader or a twin-screw kneader. Further, the styrenic resin composition thus prepared is molded into a desired product by conventional extrusion molding, injection molding, or the like.

When preparing the above styrenic resin composition, flame retardants, pigments, plasticizers, which are usually added to the styrenic resin,
Antioxidants, ultraviolet absorbers, other additives, dispersants used when blending inorganic fibers as reinforcing agents, modifiers that improve the adhesion between inorganic fibers and thermoplastic resins, inorganic fillers. material, other reinforcing fibers, etc. may be added.

Furthermore, in order to improve the impact resistance of the layer, a rubber-like substance can be appropriately included. In addition, adding a rubbery substance to the rubber-modified styrene resin can improve the loss coefficient, but it also reduces the rigidity and heat resistance, so it
If the housing of office equipment, etc. is discontinued, it becomes unusable. Therefore, when using a rubbery substance, zinc oxide whiskers and mica must be blended to the extent that the rigidity and heat resistance required for the molded product are satisfied.

Examples of rubbery substances to be contained here include polydiene rubbers such as butadiene rubber, chloroprene rubber, and isoprene rubber, styrene-diene elastomers such as styrene-butadiene rubber, and polydiene blocks having a polydiene block in the molecular structure such as styrene-butadiene-styrene rubber. Examples include, but are not limited to, block copolymer elastomers and the like.

In the present invention, the ratio of the mixture of zinc oxide whiskers and mica blended into the rubber-modified styrenic resin varies depending on the type of rubber-modified styrenic resin used, but the ratio is based on 50 to 98% by weight of the styrenic resin. The mixture of zinc oxide whiskers and mica is 50-2% by weight.

When the amount of the mixture of zinc oxide and mica exceeds 50% by weight, the resin composition becomes hard and brittle, and the physical property balance as a resin composition deteriorates. Moreover, if it is less than 2% by weight, the reinforcing effect will be insufficient.

The mixture of zinc oxide whiskers and mica preferably contains 5 to 95% by weight of zinc oxide whiskers and 95 to 5% by weight of mica.

When the proportion of zinc oxide whiskers in the mixture of zinc oxide whiskers and mica is less than 5% by weight or more than 95% by weight, the loss factor value is no different from that when mica or zinc oxide whiskers are used alone, respectively.

The present invention will be specifically described below based on Examples and Comparative Examples.

<Example> The physical properties of test pieces created by injection molding using the rubber-modified styrenic resin compositions of this example and comparative examples were measured by the following methods: (1) Tensile strength, LIS K7113 Measured based on.

(2) Tensile elongation rate Measured based on JIS K7113.

(3) Bending strength AST! , l　Measured based on D790.

(4) Flexural modulus Measured based on ASTM0790.

(5) Izotsu impact strength with notch 1/4” Izotsu impact strength according to JIS
Measured based on K7110.

(6) Vicat softening point Measured based on JIS K7206.

(7) Load deflection temperature Measured based on JIS K7207.

(8) Vibration characteristics The rubber-modified styrene composition was press-molded to a length of 3 mm.
00mm, width 25mm, thickness 3mm plate,
Forced vibration using mechanical impedance method (center vibration), frequency 1000112, temperature is room temperature 20℃, loss coefficient (η
) was measured.

The measuring device used was a vibration damping measurement device manufactured by Kobayashi Rigaku Kenkyu.

Examples 1 to 3 As the styrene resin, rubber-reinforced polystyrene (manufactured by Sumitomo Chemical Co., Ltd., trade name: Nisbright@KS2100) was used.
, hereinafter referred to as old PS), as a zinc oxide whisker, a tetrapod in which the diameter of the base of the needle-like crystal part is 0.7 to 14 μm, and the length from the base to the tip of the needle-like crystal part is 3 to 200 μm. Zinc oxide (manufactured by Matsushita Amtec ■, Panatetra ■) having a shape of
) respectively in weight ratio of old PS/zinc oxide whisker/mica = 80/10/10, "90/8/2.60"
A rubber-modified styrenic resin composition was prepared by blending in a ratio of /20/20 and kneading with an extruder, and subjected to physical property measurements.

Examples 4 to 6 In addition to the old PS, zinc oxide whiskers, and mica of Example 1, styrene was used as a rubbery substance to improve impact resistance.
Butadiene-styrene rubber (manufactured by Asahi Kasei ■Toughprene@
AS and below are SBS rubber. ) to old PS, / zinc oxide twine / mica / SBS rubber = 871515 / 3.
80/1/10/9.52/20/20/8 and kneaded in an extruder to prepare a rubber-modified styrenic resin composition, which was subjected to physical property measurements.

Comparative example 1 Old PS without zinc oxide whiskers was used.

Comparative Examples 2 to 5 HIPS/zinc oxide whisker/mica-46/27/
2.1 (IPS/mica/SBS rubber = 54/40/
6, flIPs/glass fiber=85/15, old PS/
A rubber-modified styrenic resin composition was prepared by blending SBS rubber 90/10 and kneading it in an extruder, and the composition was subjected to physical property measurements.

The measurement results of the above Examples 1 to 6 and Comparative Examples 1 to 5 are shown in Table 1.

Examples 7 to 9, Comparative Examples 6 to 9 Example 1-1 (IF567 by weight, 3 parts by weight of SBS rubber was mixed with zinc oxide whisker/mica ratio changed as shown in Table 2, and kneaded with a press machine) A rubber-modified styrenic resin was prepared and subjected to physical property measurements.

The measurement results of Examples 7 to 9 and Comparative Examples 6 to 9 are shown in Table 2.

<Effect of the invention> Zinc oxide whiskers and mica exhibiting a tetrapod shape,
By blending it with rubber-modified styrene resin, mechanical strength (especially flexural modulus) can be improved, which could not be achieved with conventional compositions containing inorganic fillers, which can be obtained by measuring viscoelasticity. The loss factor (η) could be increased.

Such characteristics can improve the vibration characteristics of housings for light electrical and office equipment, and in particular can significantly improve the acoustic characteristics, such as television housings, speaker box materials, etc. can.

Claims (4)

[Claims] (1) A rubber-modified styrenic resin composition comprising 50 to 98% by weight of a rubber-modified styrenic resin and 50 to 2% by weight of a mixture of zinc oxide whiskers and mica. (2) The rubber-modified styrenic resin composition according to claim 1, wherein the zinc oxide whiskers have a tetrapod crystal structure. (3) The rubber-modified styrenic resin composition according to claim 1 or 2, wherein the mixture of zinc oxide whiskers and mica comprises 5 to 95% by weight of zinc oxide whiskers and 95 to 5% by weight of mica. (4) The rubber-modified styrenic resin composition according to claim 1, 2 or 3, wherein the zinc oxide whiskers and/or mica are surface-treated with a silane compound.