DD215560A1 - SELF-POLISHING POLYAMIDE RESINS - Google Patents

Abstract

The invention relates to self-lubricating polyamide resin compositions which can be economically produced and processed. Molded parts made of it are ideal for heavy duty self-lubricating sliding elements in continuous use. According to the invention, the resin compositions consist of a polyamide base resin, a lubricating oil, an oil binder of a combination of low density polyethylene and ethylene-norbornene copolymers, an intensifying binder from the group talc, active silicic acid, graphite and a dispersant based on an anoxidized low molecular weight polyolefin or Metal salt of a fatty acid.

Description

VEB Leuna-Werke Leuna, May 12, 1983

"Walter Ulbricht"

, . ^'.':;, .. ', -LP 82 142'"...'' ^- / Title of the Invention A self-lubricating polyamide resin compositions field of application of the invention..

The invention relates to self-lubricating polyamide resin compositions which can be produced and processed economically. The moldings produced therefrom are outstandingly suitable for highly loadable and self-lubricating sliding elements in continuous use, both at low and at high sliding speeds.

Characteristic of the known technical solutions

The production of self-lubricating bearing masses conventionally uses such materials as polyamide, polycarbonate, polyacetal. Slip elements made of these have good properties in terms of low friction and high design characteristics, but have the great disadvantage of being usable only at low loads and sliding speeds since they otherwise due to frictional heat due to flow and melting and / or stick-slip

, λ r \ r \

Friction become unusable ·

By incorporation of inorganic solid lubricants (molybdenum disulfide, graphite), although a certain improvement in the mechanical strength, but no significant increase in the resilience is achieved, stick-slip friction occurs unabated. An improvement of the wear resistance and reduction of the stick-slip susceptibility is achieved by incorporation of high-density polyethylene and / or polytetrafluoroethylene (DB-OS 2 60i 042). However, these additives cause a deterioration of the Pließverhaltens and the Forrateilqualität inadequate improvement of GIeiteigenschaften and a drop in the structural properties (dimensional stability, strength). ':. ^: . ^: "- '.' """"""''.' It is also known to incorporate lubricating oils, optionally mixed with O1 binders, into polyamides, for example lubricating oil, lubricating oil and high density polyethylene (US Pat Copolymer (WP008 L / 233 O42 / O). It has also been proposed to polymerise epsilon-caprolactan in admixture with cut oil (WP C 08 G / 234 δδβ / 3). However, since polyamides are incompatible with lubricating oils and polyolefins, this leads to Uachteilen

- Complicated incorporation into the molding compound

poor transport of the molding compound, in the extruder and in the injection molding machine

- poor surface quality (delamination, sticky surface) '-' .., ·

- time-limited self-lubricating effect by complete emigration of the lubricant.

It is known to avoid these disadvantages by homogeneously mixing lubricating oil and optionally further additives such as dispersing agents or agents for improving the surface properties in the oil-bearing binder and dispersing this mixture in a base resin. DE-OS 2,526,194, for example, US Pat Lube naphthenic, paraffinic. or aromatic hydrocarbons, as

Oil binder high density polyethylene and used as a surface improver graphite, carbon black or molybdenum disulfide. Polynorbornene resin and / or expanded graphite as oil binder are described in DE-OS 3 030 870. The disadvantage of this solution is:

Good self-shearing properties are achieved only for relatively low load and sliding speed ranges or the service life is too short

The processability of the molding compounds and the surface condition of the sliding elements produced therefrom are unfree

. '"exhausting.""'".'. · - ^; · .-, ' ^: ''' -.

- Mechanic solidity-,. Stiffness, dimensional stability and dimensional stability are reduced too much.

Object of the invention

The aim of the invention are self-lubricating polyamide resin compositions with improved properties.

Presentation of the 'being of the invention'

It is an object of the present invention to provide self-lubricating polyamide resin compositions of polyamide base resin, organic oil binders, such as polyethylene, ethylene copolymers, inorganic additives, as sliding members in a wide compressive load sliding speed range and sliding life and optionally further additives, wherein the resin compositions according to the invention 95 to 55% by mass of a Polyamidgrundharzese, 2 to 10% by mass of a lubricating oil which is liquid at room temperature or below the flow temperature of the organic ölbindemitteis liquid, 0.5 to 10 mass ^ 5 a combination of low density polyethylene and ethylene-IJorbornen copolymers, 2 to 20 mass of a strength-increasing, optionally nucleating inorganic binder from the group talc, active

Silica, graphite, 0.5 to 5 mass% of a dispersant based on an anoxidized low molecular weight polyolefin and / or a metal salt of a fatty acid.

Suitable lubricating oil is a paraffin or naphthene-based raffinate, V,

Advantageously, the molding composition should contain heat stabilizers. Furthermore, flame retardants, glass fibers and other known additives can be added. The polyamide resin composition can be prepared by known processes by metering all additives into the polyamide resin melt and homogenizing them in the lubricant components and dispersant but form a uniform phase, it is more advantageous to mix them in a separate processing step at a temperature where the lubricating oil is completely adsorbed by the binder and then to disperse it finely in the polyamide resin.

The combination of low-density polyethylene and ethylene-Iorbornene copolymers as binders for the lubricating oil, the dispersant to ensure excellent processing and bonding properties and the inorganic reinforcing binders to ensure the necessary preservative properties (ring shrinkage and distortion tendency ,, high strength) and additional improvement in compressive strength, it was possible to obtain a polyamide resin composition having the following excellent slip properties: - Consistent excellent self-lubricating properties over a long service life

-. very low frictional resistance, extremely low wear and no stick-slip tendency at different loads or sliding speeds ₀

Exemplary embodiments Example 1

In a twin-screw extruder, at a speed of 15 ° C. and a cylinder temperature of 510 K, 75 parts by weight of polyepsiloncaprolactam,

2 parts by weight of low-density polyethylene (density 0.919 to 0.925 g / cm, melt index 0.2 to 0.4 g / 10 min)

1 part by weight of ethylene-horbornene copolymer 5 parts by weight of naphthenic raffinate 15 parts by weight of talc

2 parts by weight zinc stearate

homogeneously mixed with each other, whereby the solid components are added by means of dosing belt weigher and the lubricating oil by means of metering pump. The mixture is extruded into strands and granulated after cooling in a water bath.

Example 2 to "4

The molding compositions were prepared analogously to Example 1. The composition and the properties are shown in Table 1.

Comparative Example 1 Polyepsiloncaprolactam Comparative Examples 2 and 3

A molding composition consisting of 90 parts by weight of polyepsiloncaprolactam, G parts by weight of paraffin-based lubricating oil and 4 parts by mass of low-density polyethylene or ethylene-horbomene copolymers was prepared by the method of Example 1. The properties can be seen from Table 2. , '' ·· ..; The molding compositions of Examples 1 to 4 and Comparative Examples 1 to 3 were injection-molded into test specimens according to TGL 20 055 using a screw injection molding machine.

The surface condition of the specimens sprayed therefrom was assessed visually.

The flexural modulus and shrinkage were extracted to evaluate the design properties. The friction and wear behavior was tested on a model test bench according to the principle that a hardened steel ring is moved on an injection molded panel at a defined selectable contact pressure and speed Tables 1 and 2 summarize the results. It is clearly evident that the molding compositions of the invention correspond to Examples 1 to 4 in contrast to Comparative Examples 1 to 3 outstanding properties; with regard to frictional and wear behavior while at the same time ensuring excellent matching parameters''... -V λ '';'':' , [ - '-'' ^:

Table 1 measures 1 Examples 2 3 4 recipe Ness Dimensions 75 81 70 72 ,: 2, 1 1 2 Polyepsilöncaprolactam 1 2 'S 2 ·. >'.'' Polyethylene, low density "     5 .: ' 4 5 6 Ethylene basket-type copolymer - 10 naphthenbasiscb.es Raf finat 15 10 10 ¹⁵ ' . ' colloidal graphite - 2 1 • Μ " talc 2 , - 1 ² : ' Dispersing agent. ; zinc stearate 1 1 1 1 properties 38 48 30 55 Surface BehaviorO cm 3300 3000 3200 3500 spiral length N / cm ² 0.9 0.75 0.8 0.63 Bending modulus of elasticity (according to TGL 14067) /O 95 78 130 108 shrinkage ^Έ 73 65 " 70 76 maximum load capacity at 300 min * " ¹ H 0.03 0.03 0,025 0.03 at 600 min " ¹ 13 13 16 14 Friction coefficient κ Temperature rise '

Table 2

recipe

Unit of measurement 100 Comparative Examples 2 .3 90 Mass' % - ··. - , - - ·. 90 4 4 6 - 6

polyepsiloncaprolactam

Polyethylene, low density

Ethylene lTorbornen-copoly

mer · '\ /'']''':. · naphthenic raffinate Kollo ifidgraphit talc

dispersant

zinc stearate

properties

Surface texture Spiral length

Bend modulus (according to TGL 14067) Shrinkage

maximum load capacity at 300 min ~ 1

at 600 min "*

"2 V

Friction coefficient ^J

2)

Temperature rise ^J

cm

H / cm '

Έ Έ

1 4 4 19 40 45 2400 1800 1900 1.05 1.48 1.41 20 60 32 0 32 36 0.35 0.04 0.05 31 19 21

1) Quality rating

1 9 very good 4 «bad

2 s good 5 "very bad

3 »satisfactory

2) Condition: 8 II Speed: 300 min Time: 2h

Claims (1)

invention claim Self-lubricating polyamide resin compositions of polyamide base resin, lubricating oil, organic oil binders, such as polyethylene, ethylene Copolyraeren, inorganic additives and optionally other additives, characterized in that the resin compositions 95 to 55 Mäss- ^ a polyamide base resin, 2 to 10% by mass of a lubricating oil, at Room temperature is liquid or becomes liquid below the flow temperature of the organic oil binder, 0.5 to 10% by mass of a combination of low density polyethylene and ethylene-norbornene copolymers, 2 to 20 mass- $ of a strength-increasing optionally ntikleierend acting inorganic binder from the group of talc, active silicic acid, graphite, 0.5 to 5% by mass of a dispersant based on an anoxidized low molecular weight polyolefin and / or a metal salt of a fatty acid ·