JP3120811B2 - Polyacetal resin composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to bearings, gears, cams, rollers, sliding plates, pulleys, levers for high quality required for electric / electronic equipment, office equipment, automobiles, industrial equipment, etc. The present invention relates to a polyacetal composition having excellent self-lubricating properties and thermal stability suitable as a material for sliding parts such as guides, and particularly to a polyacetal composition having a small mold deposit.

[0002]

2. Description of the Related Art Polyacetal has excellent mechanical properties,
Since it has good wear characteristics and is lightweight, it is extremely useful as a molding material for sliding parts such as gears and bearings. The polyacetal is usually used after being formed into gears, bearings, cams, rollers, sliding plates, pulleys, levers, guides, and the like by an injection molding method. In order to improve the friction and wear characteristics of polyacetal, a method of mixing polytetrafluoroethylene (for example, JP-B-39-7615, JP-B-4
No. 6-30590) has been proposed. However, this method of mixing polytetrafluoroethylene has a serious drawback that a mold deposit is likely to occur during the molding operation of the resin composition.

In order to reduce mold deposit,
A method of coexisting polyethylene with a specific ester compound (Japanese Patent Publication No. 56-34024), a method of adding and melting polycarbonate (Japanese Patent Publication No. 61-36021), or a method of adding and melting polycarbodiimide [Japanese Patent Publication No. 61-36021] No. 31142] has been proposed. Each of these methods has a certain effect in terms of reducing the mold deposit, but the mechanical properties of the molded article are reduced or deteriorated by the ester compound and polyethylene added or blended therein. Therefore, it is not suitable as a method for producing a molding material requiring high precision.

On the other hand, JP-A-59-223755 discloses that
A composite material has been proposed in which a thermoplastic polymer and a crystalline fluoropolymer forming a fiber reinforcing layer are kneaded and blended by shearing or stretching at a temperature lower than the melting temperature of the crystalline fluoropolymer. . Specific examples of the thermoplastic polymers include, as examples, polyphenylene sulfide, polycarbonate, styrene-acrylonitrile copolymer, α-methylstyrene-acrylonitrile copolymer, amorphous polyethylene terephthalate, polystyrene, polysulfone, polyethylene terephthalate, and the like. Polyamides in the description as examples,
Polymethyl methacrylate, polyvinyl chloride,
Polyether, polyacetal, polyurethane and the like are listed. Further, as specific examples of the crystalline fluoropolymers, only polytetrafluoroethylene is used in Examples, and in other examples, perfluorinated poly (ethylene / propylene), perfluoroalkoxy polymer, Vinylidene chloride is listed. However, in the specification, there is no description about the combination of polyacetal and polyvinylidene fluoride, nor is there any indication of its possibility or effect.

Japanese Patent Application Laid-Open No. 60-199046 discloses that
A vinylidene fluoride resin composition comprising 95 to 30% of vinylidene fluoride resin and 5 to 70% of polyether (including polyacetal) has been proposed. The present invention aims at obtaining a film having excellent dielectric properties, and does not describe at all the mechanical properties and injection molding processability of a composition important as a molding material. That is, in the specification examples of the invention, the composition ratio of polyvinylidene fluoride to polyacetal is 50: 50% by weight and 6%.
Only the dielectric constant and dielectric loss tangent of the blown film at 0: 40% by weight are shown.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide excellent friction and wear resistance, excellent mechanical properties and thermal stability.
An object of the present invention is to provide a polyacetal resin composition having less mold deposit during injection molding. Here, the term "mold deposit" means that components resulting from the resin material adhere to a molding die as the injection molding is repeated. Mold deposits have an adverse effect on the smoothness and uniformity of the surface of a molded product, and cause poor appearance and dimensional defects of the molded product in mass production of gears and rollers.

[0007]

The present inventors have made intensive studies to solve the various problems described above, and as a result, a specific polyacetal resin composition can solve these problems at once. With the knowledge obtained, the inventors further improved and studied and completed the present invention. That is, after mixing 90 to 99.9% by weight of polyacetal and 0.1 to 10 % by weight of polyvinylidene fluoride, the present invention provides a mixture of polyacetal and polyvinylidene fluoride having a melting point or higher. A polycetal resin composition obtained by heating and melting at a temperature.

[0008] The polyacetal used in the present invention is a homopolymer mainly composed of an oxymethylene chain obtained by polymerizing formaldehyde or trioxane, or a trioxane and a cyclic ether compound such as ethylene oxide, propylene oxide,
A copolymer with dioxolane or a block polymer, and its melting index (MI) [ASTM-D123
8: 190 ° C. under a 2.16 kg load] is 0.01 to 60.
Means things. Generally, generally commercially available polyacetal, after subjected to stabilization treatment to prevent decomposition from the molecular end, melamine, melamine resin, stabilizers such as cyanoguanidine and polyamide, and, or,
Antioxidants such as hindered phenol and hindered amine are added and blended. In the practice of the present invention, the stabilizers and antioxidants added / blended here do not adversely affect or hinder the effects of the present invention, but rather are effective in improving the thermal stability of the polyacetal composition, It is a good thing. Usually, commercially available polyacetal is formed into a shape such as powder, flakes, and pellets, but in the practice of the present invention, the polyacetal shape is optional, and if appropriately selected from commercially available products, it can be used. good.

In practicing the present invention, the proportion of polyacetal is preferably 90 to 99.9% by weight, more preferably 90% by weight.
９９99.5% by weight. 90 % polyacetal
If the amount is less than the weight percentage, the mechanical performance of the composition is undesirably reduced. On the other hand, if the proportion of polyacetal exceeds 99.9% by weight, sufficient effects of the present invention cannot be obtained.

In the composition of the present invention, polyvinylidene fluoride is a homopolymer of vinylidene fluoride, a copolymer thereof with an ethylenically unsaturated monomer copolymerizable therewith, or a block polymer, and has a melt index (MI).
[ASTM-D1238: 235 ° C., under a load of 5 kg] means from 0.01 to 1,000. Here, examples of the ethylenically unsaturated monomer copolymerizable with vinylidene fluoride include vinyl fluoride, trifluoroethylene, chlorotrifluoroethylene, ethylene tetrafluoride, and propylene hexafluoride. The ratio of vinylidene fluoride in the copolymer or block polymer is desirably 50 mol% or more of the polymer. Polyvinylidene fluoride is usually obtained by suspension polymerization, emulsion polymerization, or the like, and its shape is powder, flake, pellet, or the like.

In practicing the present invention, the amount of polyvinylidene fluoride is 0.1 to 10 % by weight. If the blending amount of polyvinylidene fluoride is less than 0.1% by weight, a sufficient effect of the present invention cannot be obtained. On the other hand, if the blending amount of polyvinylidene fluoride exceeds 10 % by weight, mechanical strength such as elongation, impact strength and flexural modulus, and heat deformation temperature become insufficient, and the heat deformation temperature decreases, and further, coloring occurs.・ Discoloration may occur. Since polyvinylidene fluoride is an expensive substance, if the amount of use and blending amount is large, the composition becomes expensive and lacks versatility. Therefore, the more preferable blending amount of polyvinylidene fluoride,
It is 0.5 to 10% by weight.

In practicing the present invention, the blending of polyacetal and polyvinylidene fluoride can be carried out by a generally known method. After mixing both polymers, the mixture is mixed with the melting points of polyacetal and polyvinylidene fluoride . At the above-mentioned temperature, it is essential that at least one or more heating and melting processes are allowed to elapse. Although the melting point of polyacetal varies depending on the polymer composition, it is usually 130 to 170 ° C. for a copolymer and 180 to 1 ° C. for a homopolymer.
90 ° C. The melting point of polyvinylidene fluoride is
Although it depends on the polymer composition, it is generally 150 to 180 ° C. for a homopolymer. If the heat melting temperature is too high, the polyacetal is thermally decomposed. Therefore, generally, the heating and melting temperature is selected to be about 180 to 260 ° C. You. Therefore, a more preferable blending amount of polyvinylidene fluoride is 0.2 to 10% by weight.

When the present invention is carried out, the composition of the present invention may contain known fillers and inorganic additives [for example, for the purpose of improving the mechanical properties, appearance, and processability, if necessary. , Molybdenum disulfide, tungsten disulfide,
Graphite fluoride, boron nitride, etc.), a thermoplastic polymer (for example, urethane resin, acrylic resin, polyethylene, Teflon, etc.), a slipping inhibitor, a release agent, a nucleating agent, an antistatic agent, and a pigment. Can be mixed. Examples of fillers include glass fibers, carbon fibers, whiskers (eg, potassium titanate, zinc oxide, silicon carbide, calcium sulfate, magnesium sulfate, alumina, etc.), flakes (mica, talc, glass flakes, kaolin flakes, Graphite, etc.), spherical inorganic fillers [eg, glass beads, glass balloons, spherical silica, spherical aluminum, etc.], amorphous inorganic fillers [eg, magnesium hydroxide, calcium carbonate, etc.].

In practicing the present invention, as an embodiment, in other words, as a method of compounding the raw materials, the raw materials are mixed, and then mixed by a single-screw or twin-screw extruder.
Kneading and extruding at ~ 260 ° C to prepare pellets of the target composition A certain amount of a masterbatch containing polyvinylidene fluoride at a high concentration prepared in advance according to a conventional method is mixed and diluted with polyacetal at the time of injection molding. There is a method of manufacturing a molded article of the target composition by directly injection molding the mixture obtained by mixing the respective raw materials at 180 to 260 ° C. to produce a molded article of the target composition. The purpose can be sufficiently achieved by taking into consideration, appropriately selecting, or combining these methods.

Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto. In addition, the evaluation method of a composition is as follows. Other physical properties were tested and evaluated in accordance with the method specified in ASTM. Mold deposit: Using a screw pre-plastic injection molding machine (manufactured by Sumitomo Heavy Industries, mini mat) and a dropping mold, cylinder temperature 2
30 ° C., mold temperature 35 ° C., molding cycle 8 seconds, 150
At the time of 0 shot, the mold deposit attached to the mold was observed. Dynamic friction coefficient: Using a thrust-type friction and wear tester manufactured by Orientec, for a cylindrical thrust test piece,
When the surface pressure was 5 kg / cm ^2, the measurement was performed for a case where the counterpart material was steel (S45C) and a case where the same resin was used. Strength Test: Tensile strength was measured according to ASTM-D638, and Izod impact strength was measured according to ASTM-D256.

[0016]

EXAMPLES Example 1 Polyacetal [Iupital F20-0 manufactured by Mitsubishi Gas Chemical Co., Ltd.]
2, melting point 165 ° C., MI = 9 g / 10 min] 95 parts by weight (9.5 kg), and polyvinylidene fluoride KF polymer # 850 [manufactured by Kureha Chemical Industry, melting point 177 ° C., melt flow rate: 23 g / 10 minutes ( ASTM-D123
8, 235 ° C., 5 kgf / cm ² )] 5 parts by weight [0.5 kg,
After mixing uniformly using a supermixer (manufactured by Kawada Seisakusho), the mixture was kneaded and extruded at 200 ° C. using a twin screw extruder (manufactured by Ikegai Iron Works, PCM-30) to form pellets. did. Subsequently, using an in-line screw injection molding machine [manufactured by Nissei Plastic Industries, Model PS-40], ASTM-D638 and ASTM-D2 were prepared at a cylinder temperature of 200 ° C, a mold temperature of 80 ° C, and a molding cycle of 30 seconds.
Fifty-six strength test pieces and single cylindrical thrust test pieces were molded, and test measurements of dynamic friction coefficient and strength were performed. Furthermore,
The mold deposit was evaluated using a screw pre-plastic injection molding machine (Minimat, manufactured by Sumitomo Heavy Industries, Ltd.).
Table 2 shows the measurement results. Table 2 shows that a resin composition having excellent mechanical properties and low mold depositability was obtained according to the present invention.

Example 2 In Example 1, 99 parts by weight of polyacetal (9.9 parts) was used.
kg) and 1 part by weight (0.1 kg) of polyvinylidene fluoride KF polymer # 850 (see Table 1), all were treated in the same manner as in Example 1 to obtain the results shown in Table 2.

Example 3 In Example 1, 90 parts by weight of polyacetal (9.0 parts by weight) were used.
kg) and 10 parts by weight (1.0 kg) of polyvinylidene fluoride KF polymer # 850 (see Table 1), all were treated in the same manner as in Example 1 to obtain the results shown in Table 2.

Example 4 In Example 1, 90 parts by weight of polyacetal (9.0 parts by weight) were used.
kg) , polyvinylidene fluoride KF polymer # 1300
[Made by Kureha Chemical Industry, melting point 177 ° C, melt flow
G: 1.1 g / 10 minutes (ASTM-D1238, 235
° C, 5 kgf / cm ² )], and the results shown in Table 2 were obtained in the same manner as in Example 1 except that 10 parts by weight (1.0 kg) was used ( see Table 1).

Example 5 In Example 1, 96 parts by weight of polyacetal (9.6 parts by weight) were used.
kg) using polyvinylidene fluoride KF polymer #
KF polymer # 1300 [manufactured by Kureha Chemical Co., Ltd., melting point 177 ° C., melt flow rate: 1.1 g /
10 minutes (ASTM-D1238, 235 ° C, 5 kgf / c
m ² )] was obtained in the same manner as in Example 1 except that 4.0 parts by weight (0.4 kg) was used (see Table 1), and the results shown in Table 2 were obtained.

Example 6 In Example 1, 96 parts by weight of polyacetal (9.6 parts by weight) were used.
kg) using polyvinylidene fluoride KF polymer #
Vinylidene fluoride-hexafluoropropylene copolymer [manufactured by Kureha Chemical Co., melting point 160 ° C, melt flow rate: 3 g / 10 min (ASTM-D123) instead of 850
8, 235 ° C., 5 kgf / cm ² )] to 4.0 parts by weight (0.4
kg) (see Table 1), and the results shown in Table 2 were obtained in the same manner as in Example 1.

Example 7 In Example 1, 95 parts by weight of polyacetal (9.5 parts) was used.
kg), 5 parts by weight (0.5 kg) of polyvinylidene fluoride KF polymer # 850, and carbon chopped fiber (Dainippon Ink & Chemicals, Donacarbo S-24)
1) was used in an amount of 22 parts by weight (2.2 kg) [see Table 1].
Except for the above, the result shown in Table 2 was obtained in the same manner as in Example 1.

Example 8 In Example 1, 95 parts by weight of polyacetal (9.5 parts) was used.
kg), 5 parts by weight (0.5 kg) of polyvinylidene fluoride KF polymer # 850, and 27 parts by weight (2.7 k) of glass beads (GB731B, manufactured by Toshiba Barotini).
g) Except for using [see Table 1], the results shown in Table 2 were obtained in the same manner as in Example 1.

Example 9 In Example 1, 95 parts by weight of polyacetal (9.5 parts) was used.
kg), 5 parts by weight (0.5 kg) of polyvinylidene fluoride KF polymer # 850, and 11 parts by weight (1.1 k) of glass fiber (NEC Glass, ECS-T-621).
g) Except for using [see Table 1], the results shown in Table 2 were obtained in the same manner as in Example 1.

Example 10 In Example 1, 95 parts by weight of polyacetal (9.5 parts) was used.
kg), 5 parts by weight (0.5 kg) of polyvinylidene fluoride KF polymer # 850, and 16 parts by weight (1.6 kg) of talc (Takehara Chemical Industries, M talc) (see Table 1). In the same manner as in Example 1, the results shown in Table 2 were obtained.

Example 11 In Example 1, 95 parts by weight of polyacetal (9.5 parts by weight) were used.
kg), 5 parts by weight (0.5 kg) of polyvinylidene fluoride KF polymer # 850, and 11 parts by weight (1.1 k) of potassium titanate (Tismo-D, manufactured by Otsuka Chemical Co., Ltd.)
g) Except for using [see Table 1], the results shown in Table 2 were obtained in the same manner as in Example 1.

Comparative Example 1 Using 100 parts by weight of polyacetal, the dynamic friction coefficient , mechanical strength and mold deposit were evaluated in the same manner as in Example 1, and the results shown in Table 2 were obtained.

Comparative Example 2 In Example 1, 50 parts by weight of polyacetal (5.0 parts by weight)
kg), and the results shown in Table 2 were obtained in the same manner as in Example 1 except that 50 parts by weight (5.0 kg) of polyvinylidene fluoride KF polymer # 850 was used (see Table 1).

Comparative Example 3 In Example 1, 5 parts by weight (0.5 kg) of polytetrafluoroethylene (Daikin Industries, Lubron L-5) was used in place of polyvinylidene fluoride KF polymer # 850 (see Table 1). Except for the above, the result shown in Table 2 was obtained in the same manner as in Example 1.

[0030]

According to the present invention, the polyacetal resin composition comprises:
A self-lubricating composition containing polyvinylidene fluoride mixed with polyacetal, which has extremely excellent friction and wear properties, mechanical properties, and low mold depositability, and is a material for various molded parts, especially sliding parts. Can be suitably used.

[0031]

[Table 1]

[0032]

[Table 2]

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masaharu Kimura 3-16-22 Meieki Station, Nakamura-ku, Nagoya City, Aichi Prefecture Mitsubishi Gas Chemical Co., Ltd. Nagoya Branch Examiner Shuji Sasaki (56) References JP-A-4-4 264153 (JP, A) JP-A-3-119048 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08L 59/00-59/04 C08L 27/16

Claims (1)

(57) [Claims] 1. A polyacetal resin obtained by heating and melting a mixture of 90 to 99.9% by weight of polyacetal and 0.1 to 10 % by weight of polyvinylidene fluoride to a temperature not lower than the melting point of polyacetal and polyvinylidene fluoride. Composition.