JPS6038579B2 - polyester gear - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a gear made of a special polyester material.

In recent years, thermoplastic resins have come to be used instead of metals as materials for gears due to their advantages such as workability, light weight, and timelessness. Although various thermoplastic resins have been proposed and used as materials, they all have advantages and disadvantages and are not necessarily suitable for this purpose.

For example, polyacetal, which is the most commonly used resin, is easily flammable, but it is difficult to impart the flame retardancy required for electrical and mechanical applications, which is a fatal drawback for such applications. It is. Other resins, such as nylon resin, do not have the drawbacks of polyacetal, but polyurethane resins, which are resins that are susceptible to changes in dimensional stability and physical properties due to moisture absorption, are excellent as silent gears. As is well known, it has very poor injection moldability and poor molding yield, and the quality of the molded products is not consistent, such as some molded products being transparent but others devitrified. This has significantly reduced the product value. Rubber compositions have been improved and hard materials are used in some gears, but as is well known, the processing process is extremely long and burrs are likely to occur during molding.

The present inventor has discovered that the gears possessed by such various thermoplastic resins are
As a result of various studies on materials that do not have any drawbacks, it was discovered that a specific polyacetal is suitable as the material, and the present invention was achieved.

That is, the present invention is a polyester gear made of a thermoplastic resin, characterized in that the material is polyhexamethylene terephthalate having an intrinsic viscosity of 0.4 or more.

The polyhexamethylene terephthalate used in the present invention is obtained by condensing terephthalic acid (or its lower alkyl ester or aryl ester acid halide) as a brewing component and hexamethylene glycol using a known method. be. Such polyhexamethylene terephthalate contains 30 mol% or less of a third component other than the above (o).
(preferably 20 mol% or less) may be copolymerized. Examples of the third component include isophthalic acid, naphthalene dicarboxylic acid (2,6-, 2,7-, 1,6-,
aromatic dicarboxylic acids such as 4,4'-tadiphenylsulpondyllevonic acid; such as adipic acid, azelaic acid, sebacic acid, decane-1,10-dicarboxylic acid Aliphatic dicarboxylic acids; glycols such as ethylene glycol, trimethylene glycol, and neobenzene glycol; and polyglycols such as polyoxyethylene glycol and polyoxytetramethylene glycol. In addition, trimethylolpropane,
Trifunctional or higher functional compounds such as bentaerythritol and pyromellitic acid may also be used in amounts within a range where the polyhexamethylene terephthalate is substantially rim-like.
The polyhexamethylene terephthalate used in the present invention has a small proportion (less than 4% by weight of the total composition) of other polymers such as polyethylene, polypropylene, polyethylene terephthalate, polytetramethylene terephthalate,
It may also be used in combination with nylon).

The polyhexamethylene terephthalate used in the present invention must have an intrinsic viscosity of 0.4 or more.

If the value is less than 0.4, the teeth of the gear may be chipped, making it impossible to obtain a gear that is not strong enough to be practical. On the other hand, those with an intrinsic viscosity of 2.5 or more, particularly 3.0 or more, are too high to be processed, whereas those with an intrinsic viscosity of 2.0 or less and 0.8 or more are preferably used. Such polyhexamethylene terephthalate may contain various additives such as heat and light stabilizers, pigments, dyes, light brighteners, flame retardants, and reinforcing agents.

The gear of the present invention can be molded by a conventionally known molding method, mainly an injection molding method.

Examples are given below. In addition, parts in the examples are "parts by weight", and the intrinsic viscosity is 1.2 in ○-chlorophenol.
The value was measured at a concentration of 35 oo in the evening/100 sails.
Example 1 194 parts of dimethyl tyrephthalate, 236 parts of hexamethylene glycol, 0.17 parts of titanium tetrabutoxide
The mixture was placed in an autoclave equipped with a stirrer and gradually heated in a nitrogen atmosphere.

Methanol produced as a result of the reaction was distilled out of the system via a katani tower.

When the amount of methanol distilled out of the system reached about 95% of the theoretical amount, the temperature inside the system was set to 24,000, and the rice cake column was removed and connected directly to a condenser.

The pressure inside the system was gradually reduced to 30 minutes later, and after another 30 minutes, the pressure was reduced to less than 0.5 days. After about 3.5 hours under the same pressure conditions, the resulting polymer had a weight of 1.
13, the softening point was 148.5 qo.

After drying this polymer in a hot air dryer at 110qC for 3 hours, it was molded into a single piece with a gear of 4 diameters and 2 ribs (a gear of 12 diameters of the same size and 4 ribs in the center). product) was molded using an injection molding machine.

The weight of this molded polymer was 109. 120
The shrinkage rate of the q001 day treatment was 0.3% in the diameter direction of the circle.

When this gear was attached to a test drive device and a rotation test was performed, almost no sound was generated. Comparative Example 1 When a commercially available gear made of polyacetal resin was molded into the same mold as in Example 1 and the same machine was tested, considerable noise was generated.

Example 2 0 [ri] obtained in almost the same manner as in Example 1 was 1
．． 20 polyhexame, ethylene terephthalate 110
It was dried with hot air for 3 hours in the afternoon and molded using the same mold as in Example 1.

The resulting gear had a weight of 1.16. This gear was test-driven at 6 m/m, and no noise was generated even after one week of continuous use.

Comparative Example 2 A composition prepared by blending 5 weights of molybdenum sulfide with nylon 6 was molded into the same mold as in Example 1.

This product produced less noise than gears made of polyacetal, but louder than gears made of polyhexamethylene terephthalate. Example 3 Instead of the polyhexamethylene terephthalate used in Example 1, the acid component was 85 mol% dimethyl terephthalate,
Dimethyldecane-1,10-dicatylboxylate 15
A mol % copolymer ([ri] of 0.98) was used.

This copolymer was vacuum dried at 70 pm for 1 hour to form a gear ([R] = 0.95) similar to that of Example 1.

Claims (1)

[Claims] 1. A gear made of thermoplastic resin, characterized in that the material is polyhexamethylene terephthalate having an intrinsic viscosity of 0.4 or more.