JPH0124814B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] This invention relates to a resin composition for cutting and engraving that has improved machinability, paintability, electrostatic properties, adhesiveness, and texture, and more specifically, has improved machinability, paintability, adhesiveness, etc. The present invention relates to a resin composition for cutting and engraving, which has excellent hardness and has a suitable weight feeling, and is suitable for, for example, toy molded products. [Prior art and its problems] In recent years, toy products, hobby products, etc. have become popular, and the materials of these products are wood, rubber, clay, plastic, etc. Wood as a material has very good machinability, paintability, texture, etc., but there are difficulties in workability and design freedom of the prototype (rough prototype), so the above-mentioned wooden products are difficult to cut into shapes. Many of them are simple. Further, since rubber has rubber elasticity due to its nature and lacks the hardness necessary for cutting, it is difficult to cut a rubber master mold into a complicated shape. The clay is
Shape retention and curing takes time. Plastics are particularly poor in cuttability, paintability, and adhesion, and
Since it is highly electrostatically charged, it is difficult to remove chips when cutting. Therefore, each of the above-mentioned materials has advantages and disadvantages, and cannot be said to be the most suitable material for toys, hobby products, etc. Based on the above-mentioned problems, this invention has been developed to provide excellent machinability, paintability, electrostatic properties, and adhesiveness, as well as suitable weight and texture for toy products, hobby products, etc. The object of the present invention is to provide a resin composition for cutting and engraving that has improved properties, adhesive properties, and texture. [Means for solving the above problems] The outline of this invention for achieving the above objects is as follows:
10 to 60 parts by weight of an ethylene-vinyl acetate copolymer having a vinyl acetate content of 5 to 40% by weight, 20 to 60 parts by weight of polyethylene, and 10 to 30 parts by weight of an inorganic filler and/or an organic filler are kneaded. This is a resin composition for cutting and engraving that has improved machinability, paintability, electrostatic properties, adhesiveness, and texture. The ethylene-vinyl acetate copolymer used in this invention usually has a vinyl acetate content of 5 to 40% by weight, preferably 10 to 30% by weight. If the content of vinyl acetate is less than 5% by weight, the effect of blending polyethylene and ethylene-vinyl acetate copolymer cannot be obtained, and if this content is more than 40% by weight, the combination with polyethylene Compatibility deteriorates, making it difficult to blend polyethylene and ethylene-vinyl acetate copolymer. In this case, the vinyl acetate content is a value measured by a saponification method. In addition, in this invention, the ethylene-vinyl acetate copolymer may be a random copolymer of ethylene and vinyl acetate, a block copolymer, or a copolymer of vinyl acetate in the copolymer. It may also be a partially saponified product. Furthermore, in this invention,
It is preferable that only one type of ethylene-vinyl acetate copolymer is blended as the ethylene-vinyl acetate copolymer, but two or more types of ethylene-vinyl acetate copolymers having different contents of vinyl acetate may be blended. A small amount, for example about 10% by weight of the total polymer, that can be combined or copolymerized with ethylene and vinyl acetate.
Those containing up to a third monomer can also be used. The polyethylene used in this invention preferably has a density of 0.90 to 0.93 and a melt index of 4 to 20, particularly 10 to 15. This is because by blending such polyethylene and the ethylene-vinyl acetate copolymer, good machinability of the resin composition for cutting and engraving is realized. Further, the polyethylene may be either branched polyethylene or linear polyethylene. The inorganic filler used in this invention may be any conventional inorganic material, such as calcium carbonate, magnesium carbonate, calcium sulfite, barium sulfate, aluminum hydroxide, magnesium hydroxide,
Gypsum, kaolin clay, waxite clay, nepheline, wollastonite, quartz powder (flint), feldspar powder, talc, mica, white carbon, etc. can be used, and among these, calcium carbonate,
Talc, barium sulfate, etc. are preferred. Furthermore, the inorganic filler referred to in the present invention can also include metal powder, and examples of the metal powder include zinc powder, aluminum powder, copper powder, etc., and zinc powder is particularly preferred. The inorganic filler preferably has a particle size of 3 to 30 microns, particularly 5 to 15 microns. If the particle size exceeds 30μ, the dispersion of the inorganic filler in the resin composition may become poor, which may cause the surface of the molded product to become rough; if the particle size is smaller than 3μ, the inorganic filler may The agent coagulates, making it difficult to blend, and even if blending is possible, the mechanical strength of the molded product may decrease. The surface of the inorganic filler may be treated with, for example, a titanate coupling agent. Examples of the titanate coupling agent include monoalkoxy organic titanates, such as isopropyl-triisostearoyl-titanate, isopropyl-isostearyl-dimethacryl-titanate, isopropyl-isostearoyl-diallyl-titanate, isopropyl-tri(dioctyl-pyro-phosphate) ) titanate, isopropyl-tri(dioctylphosphate) titanate, etc. Among these, isopropyl-triisostearoyl-titanate has good compatibility with polyethylene and ethylene-vinyl acetate copolymer, and is suitable for inorganic surfaces. It is preferable because of its good dispersibility. Examples of the inorganic filler used in this invention include cork and wood flour, with wood flour being particularly preferred. The diameter of the wood powder used is 60~
325, especially 80 to 200 meshes.
If the diameter of the wood powder is smaller than 325 mesh, it may cause roughness on the surface of the molded product, and if it is larger than 60 mesh, it may cause a decrease in mechanical strength, as in the case of the inorganic filler. . In this invention, either or both of the inorganic filler and organic filler can be blended. What is important in this invention is that the ethylene-vinyl acetate copolymer having a vinyl acetate content of 5 to 40% by weight is used in an amount of 10 to 60 parts by weight, preferably 20 to 50 parts by weight, and the polyethylene is added in an amount of 60 to 60 parts by weight. 20 parts by weight, preferably 60 to 10 parts by weight, of the inorganic filler and/or
Alternatively, the organic filler is blended in an amount of 10 to 30 parts by weight, preferably 15 to 30 parts by weight. The amount of the ethylene-vinyl acetate copolymer is
If the amount of the polyethylene is more than 60 parts by weight or less than 20 parts by weight, the resin composition for cutting and engraving will become soft and have poor texture, and if the amount of the ethylene-vinyl acetate copolymer is Ten
If the amount of polyethylene is less than 60 parts by weight, the cutting and engraving resin composition will have poor cutting properties, coating properties, electrostatic properties, and adhesive properties. If the blending amount of the inorganic filler and/or the organic filler is less than 10 parts by weight, the resin composition for cutting and engraving will have electrostatic properties, making it difficult to remove chips during cutting, and causing paint problems. The drying time of the filler becomes slower and the amount of the filler added is
If the amount exceeds 30 parts by weight, cutting properties and paintability will deteriorate. The resin composition for cutting and engraving according to the present invention contains, in addition to the ethylene-vinyl acetate copolymer, the polyethylene, the inorganic filler and/or the organic filler, an anti-aging agent, a processing aid, a stabilizer, and an oxidizing agent. Additives such as inhibitors, pigments, lubricants, antiblocking agents, and flame retardants may be appropriately blended.
The amount of this additive can be determined as appropriate within a range that does not impede the good properties of the resin composition for cutting and engraving according to the present invention.
About 0.005 to 3 based on the total amount of the vinyl acetate copolymer, the polyethylene, and the inorganic and organic fillers.
Approximately % by weight is sufficient. This resin composition for cutting and engraving is made into a master mold by kneading the above-mentioned components, for example, into pellets, and molding the resulting pellets as a raw material. For the kneading operation, for example, open rolls,
Banbury mixer, single screw extruder, 2
Axial screw extruders, co-kneaders, etc. can be used. In addition, the molding process includes compression molding, injection molding,
Various molding methods such as mold molding, extrusion molding, etc. can be employed. Among these various molding methods, injection molding is preferred. The prototype obtained in the above manner is further cut into a complex shape by cutting, or is glued with other prototypes obtained in the same manner as described above, and painted to produce, for example, toy products, hobby products, etc. be done. [Effects of the Invention] According to the present invention, an ethylene-vinyl acetate copolymer containing vinyl acetate in a specific proportion, polyethylene, and an inorganic filler and/or an organic filler are mixed and kneaded in a predetermined proportion. Molded articles obtained using this resin composition for cutting and engraving can have extremely good machinability, paintability, electrostatic properties, adhesive properties, and texture. Therefore,
By using the molded product as a master mold, it can be easily cut into a finished product with a complex shape by cutting or engraving, and there is no possibility that the cutting blade etc. will slip on the surface of the master mold and make it difficult to cut. . Furthermore, since the resin composition has good adhesive properties, it is possible to construct a finished product with a complex shape by molding various parts using the master mold of the resin composition for cutting and engraving according to the present invention and gluing these together. Moreover, since the paintability is good, not only can the surface of the finished product be beautifully finished, but also the finished product and the original model can be easily modified and repaired. Moreover, since this resin composition for cutting and engraving has extremely low electrostatic chargeability, it is possible to eliminate the inconvenience of chips adhering to the processed surface during cutting. Furthermore, this resin composition for cutting and engraving has a moderate weight feeling without giving the characteristic texture of plastic, and can be suitably used for molded products such as toys and hobby products. [Examples] Next, the present invention will be explained in more detail by showing examples and comparative examples of the present invention. (Examples 1 to 6, Comparative Examples 1 to 6) Ethylene-vinyl acetate copolymer in the amount shown in Table 1, polyethylene in the amount shown in Table 1, and calcium carbonate in the amount shown in Table 1. Combined with
The mixture was kneaded using a Banbury mixer at a heating temperature of 120 to 130°C for 15 minutes, and then pelletized. The pellets obtained in this way are heated to a temperature of
Test pieces were prepared at 200°C and evaluated as shown below.
Further, a rod-shaped molded product having a diameter of 30 mm and a length of 100 mm was produced using the pellet in the same manner as in the production of the test piece, and the adhesive strength was evaluated as follows. The evaluation results are shown in Table 1. The specifications of the raw materials used are as follows. 1 EVA Ethylene-vinyl acetate copolymer manufactured by Mitsui Polychemical Co., Ltd., trade name "Evaflex 550", vinyl acetate content: 14% by weight 2 PE polyethylene manufactured by Toyo Soda Co., Ltd., trade name "Petrocene 342", density: 0.917 Melt index Tux; 8 3 Calcium carbonate (A) Calcium carbonate manufactured by Kinpei Mining Co., Ltd., particle size 5μ, heavy calcium carbonate, each evaluation method is as follows. 1 Specific gravity Based on the underwater displacement method. Unit: g/cm ³ 2 Impact strength Based on ASTM D256. Unit: Kg・cm/cm 3 Cutting property Evaluation was made by lightly cutting a test piece with a normal cutter. 4 Paintability After applying color paint for plastic models with a brush, it was dried at room temperature for 6 hours, and then cellophane tape was adhered to the painted surface, and when the cellophane tape was peeled off, it was confirmed whether the paint peeled off or not. . 5 Electrostatic properties After cutting a test piece with an ordinary cutter, the ease with which the generated cutting powder could be removed was evaluated. 6 Adhesive strength The end faces of two rod-shaped molded products were joined together using epoxy adhesive, and after 6 hours had passed, the joined rod-shaped molded products were allowed to fall naturally from a height of 1 m to check for peeling. Observed. 7 Texture Evaluated visually. (Examples 7 to 11, 13, 14) The same type of ethylene-vinyl acetate copolymer used in Example 1, polyethylene, and the type of filler shown in Table 2 were mixed as shown in Table 2. The procedure was the same as in Example 1 except that the amounts were blended. The evaluation results are shown in Table 2. The specifications of the filler used are as follows. 1 Charcoal Calcium (B) Calcium carbonate manufactured by Kinpei Mining Co., Ltd., particle size 10μ, heavy calcium carbonate, 2 Talc manufactured by Asada Seifun Co., Ltd., particle size 10μ, 3 Wood flour Particle size 100 mesh 4 Barium sulfate manufactured by Barite Industries Co., Ltd., particle size 5μ 5 Zinc dust Manufactured by Sakai Chemical Co., Ltd., particle size 3μ (Example 12) The same procedure as in Example 4 was carried out except that linear polyethylene was used instead of the polyethylene used in the above example. The evaluation results are shown in Table 2. The polyethylene used was Urtozex 20200J manufactured by Mitsui Petrochemicals, and its density was 0.920.
Melt index is 18. (Evaluation) As shown in Table 1, this resin composition for cutting and engraving has an ethylene-vinyl acetate copolymer content of 10 to 60 parts by weight and a polyethylene content of 60 to 20 parts by weight. It has an appropriate specific gravity that is neither too heavy nor too light, has high impact strength, and has excellent cutting properties, paintability, electrostatic properties, adhesive properties, and texture. Also,
When the content of the ethylene-vinyl acetate copolymer is about 10 parts by weight, this resin composition for cutting and engraving becomes
Impact strength, cutting properties, paintability, electrostatic properties, and adhesion properties are slightly reduced, but this is practically negligible for molded toys and hobby products. In addition, the filler is 10
When the blending amount is ~30 parts by weight, a resin composition for cutting and engraving can be obtained that has appropriate specific gravity, high impact strength, and has good machinability, paintability, electrostatic properties, adhesiveness, and texture. I understand. From Table 2, it can be seen that the combination of organic, inorganic, and metallic fillers is also effective in this invention.

【table】

【table】

【table】

Claims (1)

[Claims] 1. 10 to 60 parts by weight of an ethylene-vinyl acetate copolymer having a vinyl acetate content of 5 to 40% by weight, 20 to 60 parts by weight of polyethylene, and an inorganic filler and/or an organic filler 10 A resin composition for cutting and engraving with improved machinability, paintability, electrostatic properties, adhesiveness and texture, characterized by kneading ~30 parts by weight. 2. The polyethylene has a density of 0.90 to 0.93 and a melt index of 4 to 20. The cutting material has improved machinability, paintability, electrostatic property, adhesion, and texture according to claim 1. Resin composition for engraving.