JPH02308840A - Styrene-based resin composition - Google Patents

Abstract

PURPOSE:To obtain the subject composition, capable of improving dimensional accuracy of molded products while maintaining impact resistance and high rigidity and having stable antistatic performance at a high level by blending specific carbon fiber with a filler composed of scaly glass flakes. CONSTITUTION:A composition obtained by blending (A) 60-90wt.% styrene-based resin with (B) 10-40wt.% inorganic filler composed of carbon fiber containing 20-80wt.% thereof having >=20 L/D and 5-20muphi fiber diameter and scaly glass flakes containing 20-80wt.% thereof having 1-10mum thickness and 20-500mum size.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a styrenic resin composition containing an inorganic filler, and more specifically to an antistatic resin composition with excellent rigidity and dimensional accuracy. It is related to.

(Prior art) Generally, it is widely known that a highly rigid composition can be obtained by mixing and filling an inorganic filler into a resin 7trix, but alternatives to metal die casting and sheet metal products are being considered. For example, when a molded product made of a resin composition filled with an inorganic material is used for paper feeding mechanisms of office automation equipment, office equipment, internal chassis, frames, etc., the rigidity is high, but the mechanical strength is low. In particular, it is difficult to use practically because the impact resistance is low and the precision of the molded product is poor.Moreover, since plastic is an insulator, paper feeding problems occur in the paper feeding mechanism. Therefore, anti-static equipment is required, and therefore,
There were limits to the miniaturization of OA equipment and office equipment.

In an attempt to obtain a highly rigid composition, glass peas were used as a filling shrine.
Although studies have been conducted using glass flakes, glass balloons, mica, talc, kaolin, phosphoric acid, potassium titanate, lucium carbonate, etc., they have low impact resistance.
On the other hand, although fibrous glass fibers, asbestos fibers, rock wool, carbon fibers, etc. have been considered as fillers, they have been put into practical use in some molded products. The reality is that it is not used in molded products that require strict dimensional accuracy.Also, there have been attempts to blend carbon rack into glass fibers to provide antistatic performance, but it has not been used in terms of performance. Since the stability and antistatic level have not yet been satisfied, there is a need for a resin composition that has high rigidity, maintains practical impact resistance, has excellent dimensional accuracy, and has antistatic performance. It was strongly requested.

(Problems to be Solved by the Invention) The purpose of the present invention is to solve the problem of decrease in impact resistance and dimensional accuracy that occur when an inorganic filler is blended with styrene resin.
Solved the unstable anti-static performance, etc., to styrene resin,
A resin that maintains high rigidity without reducing the impact resistance of molded products obtained by blending inorganic fillers, improves the dimensional accuracy of molded products, is stable, and has a high level of antistatic performance. An object of the present invention is to provide a composition.

(Means for Solving the Problem) That is, the present invention provides a composition in which 10 to 40 weight percent of an inorganic filler is blended to 60 to 90 weight percent of a styrene resin. 2 of them
0 to 80% have an L/D of 20 or more and a fiber diameter of 5
Consisting of carbon fibers of ~20 μφ, 20 to 80% have a thickness of 1 to 10 μm and a size of 20 to 500 μm.
A styrenic resin composition characterized by comprising scaly glass flakes. The present invention will be explained in detail below.

The styrenic resins used in the present invention include polystyrene, rubber-reinforced polystyrene, acrylonitrile-styrene copolymer, acrylonitrile-α-methylated styrene copolymer, acrylonitrile-butadiene-styrene ternary copolymer, and acrylonitrile-butadiene copolymer. The -α-methylated styrene terpolymer and the like may be used alone, or in the case of polymers with good compatibility, two or more types may be used as a mixture, if necessary.

Among the inorganic fillers in the present invention, carbon fiber is L
/D is 20 or more, the fiber diameter is 5 to 20 μφ, and the carbon fiber is treated with a surface treatment agent during the manufacturing process.
Alternatively, an untreated product may be used, and as a binding agent, aracrylic,
A urethane-based or epoxy-based treatment agent may be used. Further, the carbon fiber used in the present invention is a high elastic modulus carbon fiber made from polyacrylonitrile fiber,
or low elastic modulus carbon fiber made from pitch.

On the other hand, the glass flakes used in the present invention have a thickness of 1 to 1
It is a flaky thin film glass with a size of 0 μm and a size of 20 to 500 μm, and may be surface-treated or untreated during the manufacturing process.

In the present invention, 10 to 40 weight percent of the inorganic filler is blended to 60 to 90 weight percent of the styrene resin. That is, if the amount of inorganic filler added is less than 10% by weight, the rigidity aimed at by the present invention will be insufficient, and if it exceeds 40% by weight, the molded product will become brittle and the surface smoothness will be significantly impaired. .

20-80% of this mineral filler must consist of carbon fibers and 20-80% of glass flakes, which means that less than 20% of the mineral fillers are carbon fibers and glass flakes are less than 20% of the mineral filler. When it exceeds 80%, the difference in molding shrinkage rate decreases, but on the other hand, the absolute value of molding shrinkage rate increases, and the mechanical properties, especially impact resistance, decrease significantly, and moreover, it is not the original purpose. This is undesirable because a decrease in rigidity and a decrease in antistatic properties are observed. On the other hand, if the carbon fiber content exceeds 80%, the effect of using glass flakes in combination will be halved, and the difference in molding shrinkage will increase, making it easier for the molded product to warp or twist.

In addition, among the above inorganic fillers, carbon fiber has a diameter of 5 to 2
It must be a short fiber with a diameter of 0μφ and L/D of 20 or more, but fibers with an L/D smaller than 20 are not very effective for reinforcing styrene resin, and fibers with a fiber diameter larger than 20μφ will not be suitable for molded products. The appearance of the fiber is impaired, the strength decreases at a large rate at the weld line, and the mechanical strength of fibers with a fiber diameter smaller than 5 μφ tends to decrease, resulting in poor economic effects.

On the other hand, if the size of the scaly glass flakes exceeds 500 μm, the appearance of the molded product will be impaired, and the rate of decrease in strength at the weld line portion will increase, which is not preferable.

The resin composition is prepared by taking styrene resin and inorganic fillers such as carbon fiber and glass flakes within the above-mentioned range and using a V-shaped tumbler or the like in a known manner. This is done by uniformly mixing.

The prepared composition is subjected to conventional extrusion or injection molding.

In addition, when preparing the resin composition, it is filled with pigments, plasticizers, stabilizers, antioxidants, ultraviolet absorbers, lubricants, and other additives and inorganic fillers that are usually added to styrene resins. Of course, it may also contain a dispersion aid, etc. used when doing so. Examples of the present invention are shown below.

(Example) Examples 1 to 4 Acrylonitrile-styrene copolymer (bonded acrylonitrile 26 wt%, solution viscosity 0.9ηSl)/C)
(AS resin) and acrylonitrile-butadiene-styrene terpolymer (rubber content 27 wt%) (ABS
Resin), commercially available carbon fiber-A (diameter 10 μΦ, fiber length 6 mm, carbon fiber surface-treated and treated with epoxy binder during the manufacturing process) and commercially available glass flake-A (average viscosity 150 mesh, average thickness 3 μm 1 During the manufacturing process, the four components of the aminosilane-treated product were thoroughly mixed using a V-type blender so that the compositions shown in Table 1 were obtained.

The obtained mixture was extruded at 230°C using a vent-type extruder with a diameter of 40 mm and formed into pellets with a diameter of 3 to 5 mm and a length of 4 to 7 mm, and then heated at 80 °C for at least 3 hours. After drying, a test piece for measuring physical properties and a flat plate (120 x 120 x 2 mmt, film gate) for measuring mold shrinkage were produced using a screw in-line injection molding machine at a molding temperature of 230°C.

As for its physical properties, as shown in Table 1, the rigidity tends to increase as the filler content increases, and it also maintains an Izot impact strength that can be used practically, and has good appearance and surface smoothness. Furthermore, the difference in molding shrinkage between the flow direction of the resin and the direction perpendicular to it, which is an index of dimensional accuracy which is the main objective of the present invention, is 0.2% or less, making it ideal for applications that require high dimensional accuracy. It was confirmed that the resin composition was usable, and that the surface resistivity, which is an indicator of antistatic performance, was 1013Ω or less.

For comparison with the above examples, a polymer paste containing no inorganic filler has a rigidity of 2 as shown in Comparative Example 1.
It is extremely low at 500kg/c♂, and can be used alone with inorganic filler or glass fiber (diameter 11μφ, fiber length 6mrns, glass fiber treated with aminosilane surface treatment and epoxy binding treatment during the manufacturing process), glass frame alone, or carbon fiber alone. If the amount of inorganic filler exceeds 40% by weight, the difference in molding shrinkage rate is large, the appearance and surface smoothness of the molded product are reduced, the impact strength is low, or the surface resistivity is similar to that of general plastics. level of 10]6
Only Ω was reached, or some drawback was maintained.

Examples 5-7 The same A used in Examples 1-4 as the polymer paste
The same commercially available carbon as used in Examples 1 to 4 was used for each of the S resin, ABS resin, and acryloni i/true butadiene-α methylstyrene-styrene copolymer (rubber content 14 wt%) (heat-resistant ABS) resin. Fiber-A, commercially available carbon fiber-B (diameter: 8 μΦ, fiber length: 3 cm, carbon fiber surface-treated and treated with epoxy binding agent during the manufacturing process), commercially available glass flakes used in Examples 1 to 4. The 3 to 4 components were mixed well in a ■-type blender so as to have the composition shown in Table 1, and the same method as in Examples 1 to 4 was used to prepare a test piece for measuring physical properties and a flat plate for measuring mold shrinkage rate (120X120X
2n+n+t, film gate] was produced.

As for its physical properties, as shown in Table 2, it has a high rigidity, maintains an Izot impact strength that is suitable for practical use, and has an excellent appearance.
The surface smoothness is also good, and the difference in molding shrinkage between the flow direction of the resin and the direction perpendicular to it, which is the main objective of the present invention, is 0.
It was confirmed that the resin composition was 2% or less and could be used in applications requiring high dimensional accuracy, and that the surface resistivity, which is an indicator of antistatic performance, was 1013Ω or less.

Furthermore, it was confirmed that the difference in carbon fiber diameter (18 μφ, 1° μφ) did not significantly affect the mechanical properties, appearance, surface smoothness, and dimensional accuracy of the molded product.

In addition, in order to compare with the above example, commercially available carbon fiber-〇 (diameter 20 μφ, average fiber length 350 μm, untreated carbon fiber during the manufacturing process, L/D 20), commercially available glass flake B (glass flake particle size 500 to 2000 μm 1 Average thickness: 5 μm 1 (untreated product during the manufacturing process) was added for comparison, but as shown in Comparative Examples 6 to 9, the difference in molding shrinkage rate was large, or only molded products with deteriorated appearance and surface smoothness were obtained. , rigidity and impact strength were low, or had some other drawback. That is, Comparative Examples 6 and 7 had a large difference in molding shrinkage rates, and Comparative Example 8 only produced molded products with reduced rigidity and practical impact resistance. Although Comparative Example 9 was effective against differences in mechanical properties and molding shrinkage, the appearance and surface smoothness were significantly impaired, and the adhesion strength at the welt line portion was significantly reduced.

(Effects of the Invention) As shown above, the composition of the present invention can be subjected to extrusion molding or injection molding to obtain a molded product extremely easily, and the molded product has a physical property that is higher than that of conventional filler-reinforced styrene resins. Balanced properties, appearance, and surface smoothness,
In addition, the dimensional accuracy was improved by 1], and the antistatic performance was excellent, making it a successor to metal die casting.

Therefore, there is a diversity of designs unique to thermoplastic resins,
Since a number of parts can be molded at once, the number of assembly steps can be significantly reduced, and together with ease of processing, it is expected to have a significant practical effect as an industrial material.

Claims (1)

[Claims] In a composition in which 10 to 40 percent by weight of an inorganic filler is blended with 60 to 90 percent by weight of a styrene resin, 20 to 80 percent of the inorganic filler has an L/D of 20 or more and is a fiber. It is made of carbon fiber with a diameter of 5 to 20μφ, and 20 to 80% of the carbon fibers have a thickness of 1 to 1
1. A styrenic resin composition comprising scaly glass flakes with a diameter of 0 μm and a size of 20 to 500 μm.