DD258641A1 - METHOD FOR PRODUCING LAYER LAYERS HAVING A HIGH LONG-TERM EFFECT - Google Patents

Abstract

A process is to be developed for the production of self-lubricating sliding layers based on polycaproamide, which are distinguished by good tribological properties and in particular by a high long-term effect. The object has been achieved according to the invention by mixing in a polycaproamide solution additives which act as internal lubricants, in powder form, so that a viscous resin composition is formed, which is applied to a Traegerschicht and is then cured at temperatures above the boiling point of the solvent , The resulting fine-capillary structure with an open-pore surface is enriched by tempering in hot oil with additional lubricant. The invention is used in mechanical engineering for producing sliding layers of high service life and in the field of maintenance for the regeneration of running surfaces.

Description

Surprisingly, larger amounts of additives in polycaproamide can be introduced by the process according to the invention than by known processes. Compared to the extrusion process, the inventive method works with a lower basic agent and energy expenditure. The production of the sliding layers takes place in particular for maintenance and repairs, whereby individual productions and individual adaptation to concrete problems are possible without much effort. Due to the high content of "internal lubricants", the sliding layers have excellent tribological properties.

These slip layers produced according to the invention have excellent tribological properties with a pronounced long-term effect.

embodiments example 1

In 90% formic acid as solvent 40Ma .-% PA 6 are dissolved and 40Ma .-% PTFE powder and 20Ma .-% lead powder mixed homogeneously. This viscous resin composition is rolled onto sheets. The coated sheets are cured at a temperature of 12O ⁰ C and then annealed in hot gear oil at 80 ⁰ C 4h. The coated sheets are cut to size and rolled into bushings, which are installed and locked in place as inserts in plain bearings. These layers are characterized by a very low coefficient of friction, by a much smaller wear volume and by eliminating the disturbing stick-slip friction. The following results were achieved (Table 1)

Table 1

Tribological behavior of sliding layers Testing principle: Shaft / dry run Sliding speed: 0.1 m / s Load force: 150N

Sliding friction linear wear running time of the specimens Remarks

coefficient of intensity up to permissible

Wear depth of O, 5mm [h]

Sliding layer of 0.8 5-10 " ⁸ 40 distinct

Polycaproamide stick-slip friction

according to the invention 0.12 2-10 " ¹⁰ 9200 no stick-slip

Sliding friction

Example 2

A glass fleece is dipped in a solution of 90% formic acid with 40 wt .-% PA 6 and impregnated. Thereafter, the impregnated nonwoven fabric is coated with the viscous resin composition of the composition according to Example 1, cured at 120 ° C and then annealed at 80 ⁰ C for 2 h in hot gear oil. Stripes are cut from these impregnated and coated glass fleeces and glued as a sliding layer on a sliding plane. In the case of an oscillating movement of a sliding partner made of steel on a sliding plane in dry running at a sliding speed of 0.3 m / s and a contact pressure of 150 N, the following lifetimes result:

Lifetime sliding surface temperature

Sliding layer of PA6 with 4600h 275K

one-time grease lubrication

Inventive slip layer 37 000 h 314 K.

Example 3

A shaft stump made of steal is coated with the viscous resin composition according to Example 1, cured and tempered in oil (according to Example 1). Depending on the required dimensional accuracy, a mechanical post-processing, e.g. to perform by overspeeding. The installation of the coated shaft in the plain bearing takes into account the thickness of the sliding layer.

The following results were achieved:

Parameter: dry run, V = 0.2 m / s, glide travel = 300km

Load: 120N

Bearing Type Linear Wear - Sliding Surface Friction

intensity temperature coefficient ^ _R

Metal shaft against 5-10 " ⁸ 380K 0.75

PA6 jack

inventively

coated shaft 2-10 " ¹⁰ 320K 0.15

against metal bush

Claims (1)

A process for the production of overlays with high long-term effect by incorporating additives in polycaproamide by extrusion, characterized in that a Polycaproamidlösung powdery additives are mixed, the viscous Polycaproamidmasse applied to a carrier layer and cured at temperatures above the boiling temperature of the solvent and in oil at temperatures of 60 ° C to 100 ⁰ C is annealed. Field of application of the invention The invention relates to a process for the preparation of dry sliding layers based on polycaproamide, which are characterized by a high lubricating effect with high long-term effect. Their application as an intermediate layer of moving machine elements leads to a reduction in the wear of both friction partners and to increase the service life of these machine elements. Characteristic of the known technical solutions Polycaproamide is an excellent plain bearing material, which has been proven for many years in various industries. Nevertheless, the literature has described numerous attempts to further improve the tribological behavior. In the dissertation grid, TU Dresden, 1975, "Investigations of self-lubricating sliding bearing materials" and in plastics 67 (1977) 6 p 345 "self-lubricating thermoplastics" Kerenleber possibilities of modifying plastic materials by incorporation of special additives to achieve a self-lubricating effect in dry running described. Polytetrafluoroethylene, polyethylene, lead, graphite, molybdenum disulphide are referred to as "internal lubricants." These "internal lubricants" are homogeneously incorporated in powder form through the extrusion process in a specific technological step. In the case of a thermoplastic matrix, this gives a sprayable granulate for the production of gears, bushings or other sliding elements. According to DD-PS 202885 and PolymeryTworzywa Wielkoszasteczkowe Warsaw 30, 19835 pp. 110-112, "Modification of PA 6 with Paraffin Oil" is specifically incorporated in the anionic polymerization of caprolactam oil as an internal lubricant The lubricating effect and, in particular, the duration of the action depend on plastic processor 36 (1985) 8 p.42 "Oil-soaked PA bearings" from the supply of these "internal lubricants" in the matrix material. However, there are limits to the amount of these additives which can be incorporated into the polycaproamide matrix via the extrusion process since these "internal lubricants" have a certain incompatibility with the matrix material and therefore migration occurs According to DD-PS 215560 it is known to slow down the diffusion process by incorporating special binders and thus to increase the duration of action The incorporation of the special binders takes place via the extrusion process However, the duration of action is not sufficient for many applications, especially in mechanical engineering. Object of the invention The aim of the invention is to improve the tribological properties and in particular the long-term effect of self-lubricating sliding layers based on polycaproamide. Explanation of the essence of the invention The invention has for its object to develop a method that makes it possible to incorporate larger amounts of additives in self-lubricating sliding layers based on modified polycaproamide resin compositions. This object is achieved by a process for the production of overlays with high long-term effect by incorporating additives in polycaproamide by extrusion, wherein according to the invention a Polycaproamidlösung powdery additives are mixed, applied the viscous Polycaproamidmasse on a support layer and cured at temperatures above the boiling temperature of the solvent and in Oil is tempered at temperatures of 60 ° C to 100 ⁰ C. The polyamide resin composition is dissolved in a suitable solvent, e.g. B. formic acid. In this solution, additives in powder form of polytetrafluoroethylene, polyethylene, lead, graphite are mixed as "internal lubricant" acting composite components, so that depending on the solvent content and depending on the proportion of additives a viscous resin composition is formed, which can be adjusted spreadable or spatula The proportion by mass of the additives can be up to 100% .This resin composition is conventionally applied to a carrier material, eg textile flat fabrics, glass mats, roving fabrics or metal sheets, and cured at temperatures above the boiling point of the solvent Rapid evaporation of the solvent A subsequent tempering in hot oil causes a rapid diffusion of the oil into the structure, so that an additional high supply of lubricant is formed e sliding surface as required.