JPH0673287A - Polyamide composition - Google Patents

Abstract

PURPOSE:To obtain a polyamide composition which exhibits abrasion resistance sufficient to withstand even a high speed and a high load and is excellent in self-lubricating properties by dispersing a polyethylene wax and a specified modified polyethylene wax each in a specified amount in a poly-epsilon-caprolactam. CONSTITUTION:1-9 pts.wt. polyethylene wax and 0.1-1.5 pts.wt. polyethylene wax having preferably about one to three carboxyl groups at the end or in the side chain are dispersed in 100 pts.wt. poly-epsilon-caprolactam to form the objective composition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyamide composition, particularly a monomer cast nylon composition which is excellent in self-lubricating property and wear resistance and is suitable for obtaining mechanical parts such as bearings and gears. .

[0002]

2. Description of the Related Art Polyamides, especially monomer cast nylons, have self-lubricating properties and resist wear, and are therefore used as materials for bearings and the like used without lubrication. However, under a use condition in which high-speed and high-load wear is applied, the bearing and the like are worn out or seized due to frictional heat, and the lubricity of the polyamide itself is not practically sufficient. In order to solve these problems, it has been conventionally proposed to add a lubricant (for example, molybdenum disulfide, graphite, polytetrafluoroethylene, mineral oil, silicon oil, petroleum wax) during the polymerization of ε-caprolactam.

However, although such a material has some effects of wear resistance and lubricity, the dispersion of the lubricant may become uneven. If the dispersion of the lubricant becomes non-uniform, the degree of wear resistance and lubricity may be partially non-uniform in the product itself, or a part having a different appearance may occur. In addition, even among products of the same type, the degree of wear resistance and lubricity may vary, or products with different appearances may occur, and the wear resistance and lubricity of the product itself may not be effective. It drops. Further, since the lubricant is easily separated, the molding conditions are restricted.

[0004]

DISCLOSURE OF THE INVENTION The present inventors have solved the above-mentioned problems of the prior art, and obtained a polyamide composition which sufficiently withstands a high-speed, high-load wear load and exhibits an improved self-lubricating property. With the aim of achieving the object, the inventors have arrived at the present invention which achieves this object.

The gist of the present invention is to add 100 parts by weight of poly-ε-caprolactam to 1 to 9 parts by weight of polyethylene wax and 0.1 to 1.5 parts of polyethylene wax having a carboxyl group at the terminal or side chain. It exists in a polyamide composition obtained by dispersing and blending in a proportion of parts by weight.

The polyethylene wax used in the present invention (hereinafter abbreviated as PE wax) has a molecular weight of 80.
It has a relatively low molecular weight, such as 0 to 5000, and the melting point is usually 90 to 140 ° C., for example, as a by-product when ethylene is polymerized to produce polyethylene, or the decomposition or direct polymerization of polyethylene, etc. Obtained by

The polyethylene wax having a carboxyl group at the terminal or side chain used in the present invention has a molecular weight of 800.
˜5,000, melting point is usually 90 to 140 ° C., obtained by a known method, and one having 1 to 3 carboxyl groups at the end or side chain of one molecule of PE wax.

In the present invention, the blending ratio of PE wax is 1 to 100 parts by weight of poly-ε-caprolactam.
It is 9 parts by weight, preferably 2 to 6 parts by weight. If this proportion is less than 1 part by weight, the lubricating effect will be poor, and if it exceeds 9 parts by weight, the mechanical strength of the composition will decrease.

In the present invention, the PE wax having a carboxyl group at the terminal or side chain (hereinafter, may be abbreviated as modified PE wax) is blended in a poly-ε-type.
The amount is 0.1 to 1.5 parts by weight, preferably 0.3 to 1 part by weight, based on 100 parts by weight of caprolactam. If this proportion is less than 0.1 parts by weight, the dispersing effect of the lubricant will be poor, while if it exceeds 1.5 parts by weight, the polymerization of ε-caprolactam will be hindered and the mechanical strength of the composition will decrease.

The composition of the present invention can be produced by a conventionally known anionic polymerization method. That is, PE wax and modified PE wax are added to anhydrous ε-caprolactam, and the melting point of ε-caprolactam is higher than the melting point of poly-ε-caprolactam (usually 130 to 180 ° C.) in the presence of an anionic polymerization catalyst and a polymerization promoter. Then, the ε-caprolactam is anionically polymerized by heating.

The polymerization catalyst and the polymerization cocatalyst may be those usually used, and examples of the polymerization catalyst include alkali metals, alkaline earth metals and hydrides, hydroxides and oxides of these metals, and polymerization promoters. As the catalyst, for example, isocyanates, triazines and substituted ureas are usually used.
It is used within the range of 05 to 2 mol%. INDUSTRIAL APPLICABILITY The polyamide composition of the present invention is used as a material for mechanical parts such as bearings, gears, and slide plates used without lubrication, and a product having excellent mechanical strength and lubricity can be obtained.

[0012]

EXAMPLES In the following examples and comparative examples, for each composition, the limit PV value (unit: kg / cm ² · m /
Min) and tensile strength (unit: kg / cm ² ) were measured.
The limit PV value indicates the evaluation of lubricity and wear resistance, and this value was measured by a Suzuki type friction and wear tester manufactured by Toyo Baldwin Co., Ltd. for various surface pressures P of polyamide molded products and S-45C steel. (Kg / cm ² ) and friction velocity V (m / min)
And shows the maximum value of PV that does not cause abnormal wear for 3 minutes. The tensile strength is a value obtained by performing the ASTM standard D-638 method at room temperature.

Examples 1-8 and Comparative Examples 1-9 Anhydrous ε-caprolactam 5 was added to a stainless steel beaker.
0 weight part is taken and it adjusts at 160 degreeC. 0.5 parts by weight of tolylene diisocyanate as a polymerization co-catalyst was added to this, and PE wax (molecular weight 4000,
Melting point 132 ° C) and 1 at the end of the PE wax molecule
Modified P in which 1 to 2 carboxyl groups are introduced into the side chain
E-wax is added at a ratio of various parts by weight shown in Table 1 below and stirred uniformly.

In another stainless steel beaker, anhydrous ε-
Take 50 parts by weight of caprolactam, add 0.2 parts by weight of sodium hydride (oil-based 63%) as a polymerization catalyst to 1 part, and add
Adjust to 50 ° C. This is mixed with a mixture containing the above PE wax and the like, and the system is homogenized.
Was injected into the mold to obtain a poly-ε-caprolatacum composition in which a lubricant and the like were dispersed.

The amount of PE wax and modified PE wax used in the obtained poly-ε-caprolactam composition (unit: parts by weight), the limit PV value of each composition (unit: k
g / cm ² · m / min) and tensile strength (unit is kg / cm)
² ) is shown in Table 1. In the table, the asterisk * in the remarks indicates that the added wax was separated and floated above the polymer. Further, the ratio 1 in Table 1 represents Comparative Example 1, the actual 1 represents Example 1, and
Hereinafter, the same display will be made.

[0016]

[Table 1]

From the results shown in Table 1 above, the following can be understood. If 1 part by weight or more of PE wax is added (the amount per 100 parts by weight of poly-ε-caprolactam, the same applies hereinafter), the limit PV value is improved, but if it exceeds 9 parts by weight, the decrease in the limit PV value is recognized, The tensile strength decreases as the blending amount of the PE wax increases (results of actual 1 to actual 5 and ratio 6, ratio 7).

Further, as in the ratio 2, the ratio 3, and the ratio 7,
When the PE wax is blended alone, or when the PE wax is blended in a large proportion even if the modified PE wax is blended, the PE wax is separated. When the modified PE wax is blended alone as seen in the ratios 4 and 5, the limiting PV value is greatly lowered and the polymerization reaction is inhibited.
According to the blending ratio satisfying the requirements of the present invention, the limiting PV value is 1000 or more and the tensile strength is 500 or more, showing good balance and good physical properties.

[0019]

According to the present invention, it is difficult to disperse P by itself.
E P having a carboxyl group at the end or side chain in the wax
By compounding E wax together, the above composition can be uniformly dispersed in ε-caprolactam without lowering the mechanical strength, and a composition having improved self-lubricating property and abrasion resistance can be obtained. .

Claims (1)

[Claims] 1. Poly-ε-caprolactam is dispersed in 100 parts by weight of polyethylene wax in an amount of 1 to 9 parts by weight, and polyethylene wax having a carboxyl group at a terminal or a side chain is dispersed in an amount of 0.1 to 1.5 parts by weight. , A polyamide composition prepared by blending.