JPS5910388B2 - Molding material with excellent self-lubricating properties - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention has extremely low friction coefficient increase, wear resistance,
This invention relates to a self-lubricating composite material composition with excellent heat resistance and mechanical properties.

Compared to nylon or polyethylene terephthalate, polytetramethylene terephthalate has superior hygroscopicity and moldability, has excellent compatibility with various fillers or reinforcing materials, and has a good balance in overall resin properties such as mechanical and thermal properties. Because of its excellent performance, it is expected to be widely used as an engineering plastic in sliding parts, housing materials, electrical parts, etc.

However, polytetramethylene terephthalate resin alone has a high friction coefficient, especially at the initial stage of use, and the product of the maximum pressure and running speed under friction conditions in which a normal friction coefficient can be measured (hereinafter this is the limit). It has a rather low PV value (PV value) and does not exhibit sufficient properties as a self-lubricating material. Sulfides of elements in Group A of the periodic table, especially molybdenum and tungsten disulfides, have a unique layered crystal structure consisting of a metal atomic layer and a sulfur atomic layer, so they have a very small coefficient of friction. It has excellent properties as a solid lubricant.

Therefore, it is expected that by combining this metal sulfide and polytetramethylene terephthalate resin, a self-lubricating material with a low coefficient of friction and excellent wear resistance, heat resistance, and mechanical properties can be obtained. be done. However, the softening temperature of polytetramethylene terephthalate resin is relatively high, and the temperature at which injection molding can be performed is 230°C or higher, and usually about 250°C to 290°C.
Sulfides of the elements of group II a of the periodic table, especially molybdenum,
Tungsten disulfide is 2
M0S2+702→2Mo03+ 4S022WS2+
There is a tendency to form molybdenum or tungsten oxides through oxidation reactions such as 702→2WO3+ 4502.

It is said that the reaction rate of this oxidation reaction increases in air at about 350°C for molybdenum disulfide and at about 400°C for tungsten disulfide, but the oxidation reaction proceeds even at temperatures of 200°C or higher, especially for the above metal sulfides. When the particle size of is small, the reaction rate is quite high. Therefore, the metal sulfide filled in the polytetramethylene terephthalate resin is oxidized during heat molding, and as a result, the resulting oxide has a significantly increased friction coefficient, and the resulting molded product has a significantly increased coefficient of friction during use. Even when the environmental temperature is not so high, the frictional force causes a rapid temperature rise on the friction surface, which causes the oxidation of the metal sulfide, resulting in a significant increase in the friction coefficient, resulting in extremely insufficient friction and wear properties. do not have. It has also been proposed to improve the wear resistance by adding graphite (scaly graphite) to polytetramethylene terephthalate resin. However, when only graphite is added, although a slight improvement in the limit PV value is observed, it is difficult to lower the coefficient of friction, and as a result, there is a drawback that heat generation at the surface is large. Furthermore, in the method of adding sulfide of Group A elements of the periodic table in combination with graphite, although an improvement in the limit PV value is recognized, it is not possible to sufficiently lower the friction coefficient. It is not possible to improve problems such as significant increase.

In view of the above-mentioned current situation, the present inventors have developed polytetramethylene that has a low friction coefficient, excellent frictional friction properties, heat resistance, and mechanical properties by preventing the oxidative deterioration of metal sulfides during heat forming. As a result of intensive studies to obtain a composite material mainly composed of terephthalate resin, we added and mixed molybdenum disulfide and/or tungsten disulfide, antimony trioxide and/or sodium antimonate, and graphite to polytetramethylene terephthalate resin. As a result, a self-lubricating composite material composition with excellent friction and wear characteristics, heat resistance, and mechanical properties, which provides a stable high limit PV value even at high running speeds, has a low coefficient of friction, and is easy to injection mold, can be obtained. The present invention was based on the discovery that polytetramethylene terephthalate resin 30
~80 parts by weight, consisting of (4) molybdenum disulfide and/or tungsten disulfide and 8 antimony trioxide and/or sodium antimonate, and the molar ratio of (4)/(t) is 1/1 to 5/1. 10 to 50 parts by weight of solid lubricant mixture, and 10 to 50 parts by weight of graphite (total 100 parts by weight)
(parts by weight) is a resin composition with excellent self-lubricating properties and moldability.

Here, the term "polytetramethylene terephthalate" refers to, for example, a polytetramethylene terephthalate polymer synthesized from dimethyl terephthalate and 1,4-butanediol, diols such as ethylene glycol and 1,3-propanediol, and isophthalic acid as necessary. Polymers co-condensed by adding a small amount of carboxylic acids such as, etc., polytetramethylene terephthalate polymers obtained in this way, or mixtures of co-condensation polymers and 50% by weight or less of other polymers.

The content of the polytetramethylene terephthalate resin needs to be 30 to 80 parts by weight based on 100 parts by weight of the resin composition.

When the content is less than 30 parts, the moldability of the composition decreases, making ordinary injection molding difficult, and when the content exceeds 80 parts, the composition cannot be molded. The friction and wear properties and heat resistance of the composite material produced by this process become insufficient. In the present invention, it is particularly important to use molybdenum disulfide and/or tungsten disulfide, antimony trioxide and/or sodium antimonate, and graphite in combination in a specific ratio.

When applying only molybdenum disulfide and/or tungsten disulfide and antimony trioxide and/or sodium antimonate to polytetramethylene terephthalate, it is necessary to add a considerably large amount, which improves flow processability and productivity. decreases. Note that when the amount added is small, the speed dependence of the wear characteristics becomes large, and the limit PV value during high-speed running is extremely low. On the other hand, when molybdenum disulfide and/or tungsten disulfide, antimony trioxide and/or sodium antimonate, and graphite are used together in a specific ratio, a product exhibiting excellent friction and wear properties can be obtained. Moreover, there is little deterioration in productivity, flow processability, etc. Generally, when such fillers are added to a resin having flexibility, the mechanical properties are usually greatly reduced, but the composite material composition mainly composed of polytetramethylene terephthalate of the present invention does not cause such a problem. No significant deterioration was observed, showing good resin properties. The ratio of 8 antimony trioxide and/or sodium antimonate to (4) molybdenum disulfide and/or tungsten disulfide in the solid lubricant mixture used in the present invention is such that the molar ratio of CA)/8 is 1/1 to 5. It is necessary that the range is /1.

When the molar ratio of (A)/(B) is less than 1/1, no significant increase in the addition effect is observed, and on the contrary, the characteristics unique to molybdenum disulfide and/or tungsten disulfide are less likely to occur. It is undesirable that the friction and wear characteristics of the composite material obtained using the composition in this range increases, such as an increase in the coefficient of friction. (4) If the molar ratio exceeds 5/1, oxygen or Since the increase in the coefficient of friction increases in the presence of the solid lubricant mixture, it is difficult to obtain a composite material composition with excellent wear resistance, which is not preferable. 50 parts by weight, and the amount of graphite added must also be within the range of 10 to 50 parts by weight.
If the amount is less than 0 parts by weight, the effect of the addition will not be sufficiently exhibited, and the reduction in the limit PV value during high-speed running, which is the object of the present invention, cannot be prevented. Further, if the amount added exceeds 50 parts by weight, fluidity decreases, injection molding becomes difficult, and mechanical properties deteriorate, which is not preferable. (A), (B) and graphite are contained in the range of 20 to 70 parts by weight based on 100 parts by weight of the total resin composition. When obtaining the resin composition of the present invention, it is important to mix it uniformly, and methods using various mixers such as a V-type blender, pen shell mixer, and ball mill are suitable, but are not limited to these methods. isn't it.

The uniformly mixed resin composition is melt extruded at 250 to 270 DEG C. using a single screw extruder to form pellets, which are then injection molded.

The optimum temperature for injection molding varies slightly depending on the mixing ratio of polytetramethylene terephthalate resin and other compounds, but cylinder temperature is 250-290℃, mold temperature is 60-1
20°C is suitable. The molded product thus obtained from the resin composition of the present invention is used for mechanical parts such as bearings, cams, and gears, which have excellent self-lubricating properties, heat resistance, and mechanical properties.

Additives that improve properties and appearance, such as glass fibers,
Reinforcing fillers such as asbestos, colorants, plasticizers, hardening agents, flame retardants, etc. can be incorporated into the resin composition of the present invention.

Example: Molybdenum sulfide (B powder manufactured by Nippon Molybdenum Industries, average particle size 2μ, specific gravity 4.8) and antimony trioxide (manufactured by Nippon Seiko Co., Ltd., 200 mesh pass, specific gravity 5.2) were mixed in a ball mill in the proportions shown in Table 1. A solid lubricant mixture was obtained by mixing for 16 hours.

30 parts by weight of this mixture, 40 parts by weight of polytetramethylene terephthalate (hereinafter referred to as PTMT), and 30 parts by weight of graphite (CPB manufactured by Nippon Graphite) were mixed using a V-type blender, and the resulting composition was mixed into a 40 mmφ Cylinder temperature 200-250℃ using screw extruder
The mixture was melt-extruded and shaped into pellets. After thoroughly drying the pellets, the cylinder temperature was 270℃ and the mold temperature was 100℃ using a 36m71Lφ screw injection molding machine.
, cycle 60 seconds, bending strength, heat distortion temperature (HDT)
Test specimens, rings for wear tests, etc. were molded.

Using the obtained specimen, we tested the bending strength according to ASTM D79O, the HDTl according to ASTM D648, and the mating material S55C steel with a thrust type friction abrasion tester.
Table 1 shows the results of measurement and evaluation of the friction coefficient and specific wear amount at a pressure of 10 kg/h.
CiL. It was measured at a speed of 60c!RL/Sec, and the limit PV value is when the pressure is increased by 5kg/C7/L every 10 minutes at a speed of 60c!RL/SeC, and the friction coefficient increases rapidly or the specimen melts and deforms. As is clear from Table 1, the composition of the present invention exhibits excellent friction and wear properties, and the molar ratio of Group A sulfide to antimony compound is in the range of 1/1 to 5/1. It shows that it is important to have

Sample No. 7 is made only of PTMT and was evaluated in the same manner as in the examples. Example 2 Molybdenum disulfide and antimony trioxide in a molar ratio of 3/1
The solid lubricant mixture prepared in Table 2 was mixed in the same manner as in Example 1, and this mixture was mixed with polytetramethylene terephthalate resin and graphite in the proportions shown in Table 2. Extrusion and injection were carried out in the same manner as in Example 1. Table 2 shows the results of molding and evaluation.

Table 3 shows the results of similar evaluations of resin compositions that do not contain either the solid lubricant mixture or graphite. As is clear from Tables 2 and 3, the composition of the present invention exhibits excellent friction and wear properties only when the three components of polytetramethylene terephthalate resin, solid lubricant mixture, and graphite coexist in specific proportions. and has high mechanical strength.

Example 3 Sample No. 3 of Example 1 had exactly the same composition except that tungsten disulfide powder (manufactured by Kawamura Research Institute, specific gravity 7.8) was used instead of molybdenum disulfide, and this was injected. Table 4 shows the results of molding and evaluation.

Further, in Sample No. 3, a composition of the present invention was obtained in the same manner using sodium antimonate NaSbO3, %H2O (manufactured by Nippon Seiko Co., Ltd., 200 mesh pass) instead of antimony trioxide.

Claims (1)

[Claims] 1 Polytetramethylene terephthalate resin 30-80
parts by weight, consisting of (A) molybdenum disulfide and/or tungsten disulfide and (B) antimony trioxide and/or sodium antimonate, with a molar ratio of (A)/(B) of 1
A resin composition with excellent self-lubricating properties and moldability, characterized by comprising 10 to 50 parts by weight of a solid lubricant mixture having a ratio of /1 to 5/1 and 10 to 50 parts by weight of graphite (total 100 parts by weight). .