JPH032246A - Styrene-based resin composition - Google Patents

Abstract

PURPOSE:To obtain the subject antistatic composition, excellent in rigidity, dimensional accuracy, appearance, surface smoothness and processability by blending a styrene-based resin with a specific inorganic filler. CONSTITUTION:The objective composition obtained by blending 60-90wt.% styrene-based resin with 10-40wt.% inorganic filler. In the above-mentioned composition, 20-80wt.% aforementioned inorganic filler is composed of carbon fiber having >=20 ratio (L/D) and 5-20muphi fiber diameter and 20-80wt.% thereof is composed of potassium titanate having 0.1-0.6mum diameter and 5-50mum length.

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 matrix, but it seems that 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 applications such as 0AJII machines, paper feed mechanisms of office equipment, and internal chassis frames, the rigidity is high, but the mechanical strength, particularly the durability, is high. It is difficult to use in practice due to the low impact resistance and poor precision of the molded product.Furthermore, since plastic is an insulating material, paper feeding problems may occur in the paper feeding mechanism, so anti-static accessories are required. Therefore, there was a limit to the miniaturization of OA equipment and office equipment.

Attempts to obtain a highly rigid composition include glass peas as a filler,
Although studies have been conducted using glass flakes, glass balloons, mica, talc, kaolin, silica, potassium titanate, lucium carbonate, etc., they have low impact resistance.
It cannot be used practically, and on the other hand, fibrous glass fibers, asbestos fibers, rock wool, carbon fibers, etc., have been considered as fillers and 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% has an L/D of 20 or more and a fiber diameter of 5 to 80%.
The styrenic resin composition is composed of carbon fibers having a diameter of 20 μΦ, and 20 to 80% of the composition is composed of fibrous potassium titanate having a diameter of 0°1 to 0.6 μm and a length of 5 to 50 μm. The present invention will be explained in detail below.

Examples of the styrenic resin used in the present invention include polystyrene, rubber-reinforced polystyrene, acrylonitrile-styrene copolymer, acrylonitrile-α methylated styrene copolymer, acrylonitrile-butadiene-styrene ternary copolymer, acrylonitrile-butadiene-α The methylated styrene terpolymer and the like may be used individually, 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 20μφ3, and is treated with a surface treatment agent during the carbon fiber 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.

The fibrous potassium titanate used in the present invention is, for example, 6
Potassium titanate (K20@6TiO2), potassium hexatitanate hydrate (K2O・6Tio 2-1/2
H2O), average fiber length 5-50μm fiber diameter 0.1
~0.6 μm. The potassium titanate fibers may be treated with a surface treatment agent during the production process or may be untreated.

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. .

Of this mineral filler, 20 to 80 percent must consist of carbon fibers and 20 to 80 percent must consist of fibrous potassium titanate; When the potassium titanate content 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 deteriorate, especially.
This is not preferable because the impact resistance is greatly reduced, and the originally intended rigidity and antistatic properties are also reduced. On the other hand, if the carbon fiber content exceeds 80%, the effect of using fibrous potassium titanate in combination is halved, and the difference in molding shrinkage rate increases, 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
The short fibers must be 0 μφ and L/D of 20 or more, but fibers with L/D smaller than 20 are not very effective for reinforcing styrene resin, and fibers with a fiber diameter larger than 20 μφ 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 fibers with a fiber diameter smaller than 5 μΦ tend to have lower mechanical strength, resulting in poor economic effects.

The resin composition of the present invention can be prepared by taking styrene resin and inorganic fillers such as carbon fiber and glass flakes within the above-mentioned range, and using a known method such as a V-shaped tumbler to make the composition more uniform. It is made by 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 5 Acrylonitrile-styrene copolymer (bound acrylonitrile 26 W t%, solution viscosity 0.9ηsp/c) (
Commercially available carbon fiber-A (diameter 10 μφ, fiber length 6
Regarding carbon fiber, which was surface-treated and treated with an epoxy binder during the manufacturing process, and commercially available carbon fiber-B (diameter 18μ
φ, fiber length 3 R11, carbon fiber treated with surface treatment and epoxy binding agent during the manufacturing process) and commercially available potassium titanate fiber-A (average fiber length 15 μm, average diameter 0.3
μm 1 aminosilane treated product during the manufacturing process), commercially available potassium titanate fiber-B (average fiber length 18 μm 1 average diameter 0
．． The four components of the epoxy silane-treated product were thoroughly mixed in a V-type blender to obtain the composition shown in Table 1.

The obtained mixture was extruded at 230°C using a 40++sφ vent type extruder, formed into pellets with a diameter of 3 to 5IIllφ and a length of 4 to 7 mm, and then sufficiently dried at 80°C for 3 hours or more. Later, using a screw in-line injection molding machine, a test piece for physical property n1 and a flat plate for measuring molding shrinkage rate (120 x 120 x 2
mm t , film gate) was prepared.

As for its physical properties, as shown in Table 1, the rigidity tends to increase as the blending ratio of filler 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.

Also, the difference in carbon fiber diameter (18μφ, 10μφ) is due to the mechanical properties of the molded product. It was confirmed that the appearance, surface smoothness, and dimensional accuracy were not significantly affected.

For comparison with the above examples, a polymer base containing no inorganic filler has a rigidity of 2 as shown in Comparative Example 1.
It is extremely low at 500 kg/c-, and the inorganic filler is glass fiber (diameter 11μφ, fiber length 6, glass fiber treated with aminosilane surface treatment and epoxy binding treatment during the manufacturing process).
If the amount of the inorganic filler exceeds 40% by weight, whether it is inorganic filler alone, fibrous potassium titanate alone, or carbon fiber alone, molded products with a large difference in molding shrinkage rate or poor appearance and surface smoothness may be obtained. The impact strength is low, or the surface resistivity is on the same level as general plastics1.
Although it reached only 0.016Ω to ■, it still had some defects.

In addition, commercially available carbon fiber-C (diameter 20μφ, fiber length 3
50μm1 Carbon fiber with no surface treatment during the manufacturing process)
and commercially available fibrous potassium titanate-A were used in combination for comparison.

As shown in Comparative Example 6, the rigidity and impact strength were so low that it was not practical.

(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,
Moreover, it was greatly improved in terms of dimensional accuracy and had excellent antistatic performance, succeeding metal die casting. Therefore, there is a diversity of designs unique to thermoplastic resins, and since a number of parts can be molded together, it is expected to have a significant practical effect as an industrial material due to a significant reduction in assembly man-hours and ease of processing. .

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% have a diameter of 0.1 to 20%.
A styrenic resin composition comprising fibrous potassium titanate having a length of 0.6 μm and a length of 5 to 50 μm.