Abrasive grain

Abstract

To provide an abrasive grain that does not damage the surface or the like of an object, is protected against friction from repeated work and demonstrates durability, and also resists being electrified with the friction during work.SOLUTION: An abrasive grain comprises a pellet that is composed of a resin composition having a thermoplastic resin (A) blended with a thermoplastic water-soluble polyethylene oxide-based resin, the pellet having a diameter of 50 μm-3000 μm and a length of 0.05 mm-10 mm. The thermoplastic resin (A) is, preferably, a polyester resin or polyamide resin.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to an abrasive grain made of a thermoplastic resin. [Background technology]

[0002] Molded products include various types of molded products, such as injection molding, in which a synthetic resin material is filled into a mold, resin molded products made by transfer molding, castings formed by pouring molten metal into a mold, and resin molded products created using a 3D printer, and since these molded products have unwanted burrs attached to them, a process called deburring is carried out to remove the burrs. Abrasive grains are used for the deburring process, and the process is carried out by spraying the grains against the object, flowing the grains in contact with the object, or putting the object and the grains in a container and stirring them together.

[0003] Abrasive grains for deburring are made of various materials such as glass, steel, alumina, and synthetic resins such as thermosetting resins and thermoplastic resins, and are appropriately selected according to the material of the object, but there is a risk of scratching the surface of the object depending on the hardness and shape of the abrasive grains. In addition, if the abrasive grains are damaged by friction during deburring, the efficiency of the deburring work will decrease. In addition, if static electricity is generated by friction, the abrasive grains will stick to the object, making it difficult to deburr effectively. Patent Document 1 proposes to address this problem by including an antistatic agent in the deburring shot material. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2003-220559 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide abrasive grains which do not damage the surface of an object, are durable and resistant to damage caused by friction during repeated work, and are also resistant to charging due to friction during work. [Means for solving the problem]

[0006] The present inventors have conducted research to solve the above problems and have arrived at the present invention. It serves as the base resin for the resin composition. Thermoplastic resin (A), Weight average molecular weight is 50,000 to 9 million The thermoplastic water-soluble polyethylene oxide resin is blended into the resin composition. the thermoplastic water-soluble polyethylene oxide resin is either a polymer consisting of ethylene oxide alone or a polyethylene oxide-propylene oxide random copolymer, The gist of the invention is an abrasive grain characterized by being in the form of a pellet having a diameter of 50 μm to 3000 μm and a length of 0.05 mm to 10 mm.

[0007] The present invention will be described in detail below. The abrasive grains of the present invention are used for removing burrs generated during the production of molded articles made of resin or the like, and for polishing the surfaces of molded articles, and are composed of a resin composition in which a thermoplastic resin (A) is blended with a thermoplastic water-soluble polyethylene oxide-based resin.

[0008] The thermoplastic resin (A) is a main resin constituting the resin composition, and a polyester-based resin or a polyamide-based resin is preferably used.

[0009] The polyester resin is not particularly limited as long as it has an ester bond in the molecule, and examples of the aromatic polyester include polyethylene terephthalate, polybutylene terephthalate, and polypropylene terephthalate, and examples of the aliphatic polyester include polylactic acid, polybutylene succinate, and polycaprolactone. In addition, the above-mentioned polyester may be copolymerized with other dicarboxylic acid components, diol components, or oxycarboxylic acid components, or may be blends of the above-mentioned polyesters, or blends of polyesters copolymerized with the above-mentioned polyesters, as long as the object of the present invention is not hindered. Examples of other copolymerizable components include dicarboxylic acids such as isophthalic acid, naphthalenedicarboxylic acid, 5-sodium sulfoisophthalic acid, phthalic anhydride, sebacic acid, adipic acid, and succinic acid, and examples of diol components include ethanediol, propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, and cyclohexanedimethanol. In consideration of durability, the relative viscosity of the polyester resin is preferably 1.4 or more, and more preferably 1.5 or more.

[0010] The polyamide resin is not particularly limited as long as it has an amide group in the molecule, and examples thereof include nylon 6, nylon 66, nylon 69, nylon 46, nylon 610, nylon 1010, nylon 11, nylon 12, nylon 6T, nylon 9T, polymetaxyleneadipamide, copolymers or blends of these components, etc. The relative viscosity of the polyamide resin is preferably 2.5 or more, more preferably 3.0 or more, in consideration of durability.

[0011] The resin composition constituting the abrasive grain of the present invention is obtained by blending the thermoplastic water-soluble polyethylene oxide resin with the thermoplastic resin (A). The blending amount of the thermoplastic water-soluble polyethylene oxide resin in the resin composition is preferably 1 to 15% by mass. More preferably, it is 1 to 12% by mass. By making the blending amount of the thermoplastic water-soluble polyethylene oxide 1% by mass or more, the triboelectric charging effect can be effectively exhibited. On the other hand, by making the blending amount 15% by mass or less, the abrasive grain has good strength.

[0012] Considering the dispersibility in the thermoplastic resin (A) that is the base resin constituting the resin composition, the weight average molecular weight of the thermoplastic water-soluble polyethylene oxide resin is 50,000 to 9,000,000. Using The thermoplastic water-soluble polyethylene oxide resin having a weight-average molecular weight of 50,000 to 9,000,000 can be mixed well with the thermoplastic resin (A) in the melt extruder used to manufacture the abrasive grains, and disperses well in the thermoplastic resin (A). When mixing a thermoplastic water-soluble polyethylene oxide resin having a weight-average molecular weight of more than 500,000, the resin disperses well in the polyester resin, which is the base material, if the temperature is set to 300°C or higher. When mixing a thermoplastic water-soluble polyethylene oxide resin having a weight-average molecular weight of 500,000 or less, the resin should be set to 300°C or lower, at which the thermoplastic resin (A) melts, and the resin disperses well in the polyester resin, which is the base material, at a temperature of 300°C or lower.

[0013] Thermoplastic water-soluble polyethylene oxide resins include ethylene oxide. Rhino A tree consisting of only Fat, Also teeth Ethylene oxide is a random copolymer of ethylene oxide and propylene oxide. Rhino Dopropylene oxide Rhino Drandum together It is a polymer R .

[0014] The thermoplastic water-soluble polyethylene oxide resin mixed into the thermoplastic resin (A) is a non-ionic polymer that is not easily affected by coexisting substances, and therefore has excellent compatibility with the thermoplastic resin (A) and disperses well, allowing the strength of the abrasive grains to be well maintained. Furthermore, since the thermoplastic water-soluble polyethylene oxide resin is uniformly dispersed in the parent thermoplastic resin (A), it is believed to function as a slip agent on the surface of the abrasive grains, resulting in an excellent balance between triboelectric charging properties and strength.

[0015] In the present invention, various additives such as heat stabilizers, crystallizing agents, pigments, antioxidants, antibacterial agents, fragrances, plasticizers, dyes, surfactants, etc. may be added to the resin composition as necessary, so long as the effects of the present invention are not impaired. In addition, in order to increase strength, fatty acid amides such as metaxylylene bisstearylamide, metaxylylene bisoleylamide, xylene bisstearic acid amide, ethylene bisstearylamide, ethylene bisstearic acid amide, etc. may be added.

[0016] The abrasive grains of the present invention are composed of a resin composition mainly composed of the above-mentioned thermoplastic resin (A) and a specific amount of thermoplastic water-soluble polyethylene oxide-based resin, but may also be composited with a thermoplastic resin that does not contain a thermoplastic water-soluble polyethylene oxide-based resin.

[0017] The abrasive grains of the present invention are pellet-shaped grains made of the resin composition and have a diameter of 50 μm to 3000 μm and a length of 0.05 mm to 10 mm. The diameter is the diameter in a direction perpendicular to the axial direction of the pellet-shaped grains, and the cross-sectional shape in the direction perpendicular to the axial direction may be circular, irregular, or may have a hollow portion. In addition, when the shape of the surface perpendicular to the axial direction is irregular, the average diameter of the major axis and minor axis may be in the range of 50 to 3000 μm. In addition, when the surface perpendicular to the axial direction has a hollow portion, the outer diameter is regarded as the diameter. The length is the length in the axial direction of the pellet-shaped grains. By setting the diameter and length of the abrasive grains in the above ranges, the abrasive grains have good handleability and moderate strength. In addition, the preferable diameter of the abrasive grains is 100 μm to 1500 μm, and the preferable length is 0.1 mm to 10 mm.

[0018] The abrasive grains of the present invention are preferably used for deburring, and since they do not scratch the surface of the object and improve work efficiency, they can also be preferably used for polishing.

[0019] The abrasive grains of the present invention can be obtained, for example, by melt-spinning the above-mentioned resin composition into a monofilament thread and cutting the obtained monofilament to a predetermined length. When obtaining the monofilament, the thermoplastic resin (A) as the main component is oriented and crystallized, thereby obtaining abrasive grains having good strength and durability.

[0020] Specifically, a predetermined amount of thermoplastic water-soluble polyethylene oxide resin is blended with chips made of thermoplastic resin (A), melt-mixed, and then melt-spun. The filament obtained by melt spinning is then cooled, and an oil agent is applied or not applied, and the filament is wound up as an undrawn filament, or the filament is drawn without being wound up. The filament after melt spinning may be cooled at room temperature, by blowing cooling air, or by passing through a water bath. The filament is hot-drawn at a draw ratio of 2 to 8 times. As a heating means for hot drawing, the filament is hot-drawn in a hot water bath or by using a heated roller. After hot drawing, a winding operation is continuously performed to obtain a monofilament, and the abrasive grain of the present invention can be obtained by cutting the obtained monofilament to a predetermined length in the filament axis direction. Effect of the Invention

[0021] According to the present invention, it is possible to provide an abrasive grain which is unlikely to scratch the surface of an object, is resistant to damage from repeated friction and is durable, and is also unlikely to become charged due to friction during operations such as deburring and surface polishing, thereby providing good work efficiency. EXAMPLES

[0022] The present invention will be described based on examples, but the present invention is not limited to the examples.

[0023] Example 1 5% by mass of polyethylene oxide-propylene oxide random copolymer (manufactured by Meisei Chemical Industry Co., Ltd., trade name Alcox, product number EP-10) with a weight average molecular weight of 1,000,000 and 95% by mass of polyethylene terephthalate resin chips were mixed, and melt-spun at a melt spinning temperature of 295°C from a 1.0 mmφ×4H spinneret. The spun thread was cooled in a water bath at 50°C, and then, without being wound up, was stretched in a hot bath at 90°C at a speed of 20 m / min, and then, without being wound up, was stretched in a dry heat atmosphere at 120°C to a total stretch ratio of 5.3 times and wound up. A monofilament with a fineness of 560 dtex (diameter 0.225 mm) was obtained. The obtained monofilament was cut to a length of 0.5 mm to 5 mm to obtain the abrasive grain of Example 1.

[0024] Example 2 2.5% by mass of polyethylene oxide (manufactured by Meisei Chemical Industry Co., Ltd., trade name Alcox, product number R-400) with a weight average molecular weight of 200,000 and 97.5% by mass of polyamide 6 resin chips were mixed, and melt-spun at a melt spinning temperature of 265°C from a 1.9mmφ×14H spinneret. The spun thread was cooled in a water bath at 25°C, and then stretched in a warm bath at 80°C at a speed of 30m / min without winding, and then stretched and wound in an atmosphere at 175°C to a total stretch ratio of 4.8 times without winding. A monofilament with a fineness of 1858dtex (diameter 0.45mm) was obtained. The obtained monofilament was cut to 0.5mm to 5mm to obtain the abrasive grain of Example 2.

[0025] Comparative Example 1 A monofilament having a fineness of 560 dtex (diameter 0.225 mm) was obtained in the same manner as in Example 1, except that only polyethylene terephthalate resin chips were used in Example 1. The obtained monofilament was cut to a length of 0.5 mm to 5 mm to obtain the abrasive grains of Comparative Example 1.

[0026] Comparative Example 2 A monofilament having a fineness of 1879 dtex (diameter 0.453 mm) was obtained in the same manner as in Example 2, except that only polyamide 6 resin chips were used in Example 2. The obtained monofilament was cut to 0.5 mm to 5 mm to obtain the abrasive grains of Comparative Example 2.

[0027] The obtained abrasive grains of Examples 1 and 2 and Comparative Examples 1 and 2 were used to carry out a deburring test and were evaluated.

[0028] <Deburring test> A rod-shaped molded product with a length of 8 cm, width of 1 cm, and thickness of 2 mm was prepared using a 3D printer as the molded product to be deburred. The molded product was made using polylactic acid resin (Terramac 3D printer filament manufactured by Unitika Ltd.).

[0029] Next, the molded product created by the 3D printer was deburred. 20 g of abrasive grains were placed in a plastic container. The molded product was attached to the tip of a mixer (manufactured by Toyo Seiki Seisakusho), and the molded product attached to the mixer was rotated in the abrasive grains in the container at a rotation speed of 382 rpm for 4 hours to deburr the molded product.

[0030] After the burr removal test, the condition of the molded product was checked to see whether the burrs had been successfully removed without scratching the surface of the molded product (burr removal effect).In addition, after the burr removal test, the abrasive grains were checked to see whether static electricity had been generated (frictional charging property) and the surface condition of the abrasive grains was checked to see whether the abrasive grains had been damaged (abrasion resistance), and these were then evaluated.

[0031] The molded products that underwent the deburring test using the abrasive grains of Examples 1 and 2 had all been successfully deburred, and there were no scratches on the surface of the molded products. In addition, the abrasive grains generated only a small amount of static electricity, and it was evaluated that the work efficiency was good. After the deburring test, only a small portion of the surface of the abrasive grains was chipped, and it was evaluated that the abrasive grains could be used repeatedly and had good durability.

[0032] On the other hand, in the case of the abrasives of Comparative Examples 1 and 2, the burrs of the molded products obtained in the deburring test were all well removed, and there were no scratches on the surfaces of the molded products, but the abrasive grains generated static electricity and stuck to some of the surfaces of the molded products. In addition, many chipped areas were observed on the surfaces of the abrasive grains after the deburring test.

Claims

1. A resin composition comprising a thermoplastic resin (A) as a base resin constituting the resin composition and a thermoplastic water-soluble polyethylene oxide resin having a weight average molecular weight of 50,000 to 9,000,000 blended therein, the thermoplastic water-soluble polyethylene oxide-based resin is either a polymer consisting of ethylene oxide alone or a polyethylene oxide-propylene oxide random copolymer, The abrasive grains are characterized in that they are pellet-shaped with a diameter of 50 μm to 3000 μm and a length of 0.05 mm to 10 mm.

2. 2. The abrasive grain according to claim 1, wherein the thermoplastic resin (A) is a polyester-based resin or a polyamide-based resin.

3. 3. The abrasive grain according to claim 1, wherein the thermoplastic water-soluble polyethylene oxide resin is blended in an amount of 1 to 15 mass % in the resin composition.

4. 4. A deburring abrasive, comprising the abrasive according to claim 1, which is used for deburring.