DD146716A1 - METHOD FOR THE PRODUCTION OF LAYERED MATERIALS - Google Patents

Abstract

The invention relates to a method for producing maintenance-free sliders or sliding elements in solid or Verbundausfuehrung. The sliding materials should contain such an additive based on PTFE, which has the required properties in terms of incorporability, compatibility of the resin component and homogeneous Feinverteilunh. According to the invention, this is achieved by incorporating a PTFE fine powder with functional groups in the production of the sliding material, the functional groups being incorporated by irradiation of the PTFE powder with high-energy rays.

Description

-A-

Method for the production of sliding materials

Field of application of the invention

The invention relates to a method for the production of sliding materials in solid or composite design, which are used in particular for the production of maintenance-free plain bearings or sliding elements.

Characteristic of the known technical solutions

For the purpose of improving the running properties of bearing materials, a larger number of processes using various lubricants have been proposed.

The best results could be achieved by using polytetrafluoroethylene (PTFE).

By applying compact PTFE coatings (DT-OS 1425 998) by sticking a PTFE film or multiple spraying a PTPE dispersion Although low sliding friction coefficients are achieved, However, this method is technically and finanaiell consuming, and at higher mechanical and thermal loads v / earth the coatings again detached from the substrates.

By incorporating PTFE threads or fibers, preferably in the form of woven or non-woven fabrics, into the surface of plastic bearings (DT-OS 1400 949, DT-OS 1569 057, US Pat.

DT-OS 1575 362, DT-OS 1629 417, DT-OS 1779 844, DT ~ 0S 1922 52Q, DT-OS 1924 505, DT-OS 2140 917, DT-OS 2150 847, DT-OS 2302 641) is the Liability '(anchoring) of the PTi ¹ B significantly improved.

The procedures for applying or incorporating PTFE on or in surfaces are applicable only to formed bearings.

Sliding bearing materials, which are to be sawn or cut to a desired bearing shape after hardening, require a uniform distribution of the PTFE throughout the material. For this purpose, it has been proposed to incorporate the PTFE in granulated, pulverized or, in the interest of better anchoring, in fibrous form incorporate thermosetting resin matrix. The recommended PTFE materials (DT-AS 1295 808, DT-OS 1704 706, DD-PS 114 238, DT-PS 1260 234) have particle diameters of mostly over 350 / um. It has been found that when using these rather coarse particles as well as the fibers, the lubricant effect is not sufficiently homogeneous due to insufficient fine distribution of the PTFE over the bearing surface. Further, at higher load, the anchoring mechanism between PTFE and resin breaks down.

Carrying capacity, wear resistance and homogeneity can be substantially improved by using finely divided polytetrafluoroethylene 3 with particle sizes between 0.1 and 5 / μm (DT-PS 2029 400, DT-OS 2264 132, British Patent 974 629). A disadvantage of these methods is that due to the highly organophobic properties of the PTFE, the fine powders are difficult to incorporate into the resin, the particles tend to agglomerate, the distribution in the resin is not sufficiently homogeneous and only at levels above 20%, preferably 25 %, based on the material mixture, a good effectiveness is achieved. These high amounts are costly and due to the poor thermal conductivity of the PTFE problems in the derivation of frictional heat from the bearing. Therefore, this solution is well suited only for such camps, which is a relatively thin layer of the resin as a coating on a preferably good heat-conducting base material, such as

Steel, own or contain heat-conductive fillers, such as lead, bronze, white metal or graphite powder.

Object of the invention

The object of the invention is a process for producing sliding materials containing such a PTPE-based additive which has the required properties with regard to incorporation, compatibility with the resin component and homogeneous particle distribution.

Essence of the invention

The invention has for its object to develop a process for the production of sliding materials, in which the additive based on PTPE by suitable technological steps is treated so that its sliding properties at lower concentrations come into their own than conventional PTFE fine powders. According to the invention, this is achieved by incorporating a PTFE powder with functional groups in the production of the sliding material, which preferably consists of web-shaped carrier material impregnated with synthetic resins.

It has been found that a PTPE prepared by radiation path in the presence of air, oxygen or additives, such as sulfites, carbonates, nitrites, nitrates, halides, cyanides, ureas, amines, amino alcohols, alcohols, aldehydes or organic acids and optionally after subsequent grinding -Pine powder is well suited. The powder thus produced in the steel field, preferably a gamma source or an electron accelerator of PTPE suspension polymer, emulsion polymer, powder batches, mechanical PTFE machining residues or radiation-polymerized tetrafluoroethylene, is technologically light, accessible and, unlike the starting materials, free-flowing , The average primary particle size is e.g. in the case of the output of PTPE suspension polymer

at 3 / Um and the output of PTFE emulsion polymer under 1, to. Agglomerates of these primary particles are easy to divide. The functional groups provide sufficient compatibility of the otherwise organophobic perfluorocarbone with the resin component. For this reason, the fine powders are well incorporated in homogeneous, fine distribution in the organic resin; Agglomeration in the resin is omitted. ·

The nature of the functional groups is determined by the choice of added in the production of fine powder be-. Right. This makes it possible to modify the adhesive properties of the particles. Possible groups are "-COOH, -SOoH, -GONH ₂ J-COOR, -COX, -OR, -CN, -X (X = halogen, R = alkyl) .The functional groups are located predominantly on the particle surface, where they are also needed for bonding.

The embedded PTFE particles can their. Fully unfold properties even at relatively low concentration. It suffice proportions of 5 to 15 % _t, preferably 10%, based on the cured bearing material. At this low concentration, the thermal conductivity of the bearing material is not significantly affected. The fineness and the good Plafteigenschaften the stored powders ensure good wear behavior of the finished bearing materials.

For the production of phenolic resin laminates, it is advantageous to first of all use the PTFE fine powder having functional groups with a dispersant, a wetting agent and methanol and then to introduce it into the phenol resin solution using a high-speed mixer. In this way any existing agglomerates of the dry PTFE fine powder are divided and a homogeneous, stable dispersion is achieved. Closing the resin mixture with the. impregnated carrier material as usual processed to laminating and thermally cured. ·

The sliding materials produced in this way are suitable for the manufacture of maintenance-free bearings. Their mechanical properties are very good. The sliding friction numbers are below 0.2. By additional lubrication, the slight abrasion can be further reduced.

For economic reasons, it is advantageous to equip the sliding zone with the material according to the invention and the support zone with conventional materials.

embodiments

The invention will be explained in more detail below with reference to Ausführüngsbeispielen.

Example 1:

0.84 kg PTFE fine powder produced by irradiation of PTFE suspension polymer at room temperature and presence of air in the radiation field of a co-gamma source with a dose of 20 billion, with 0.23 kg of a non-ionic dispersant, 0.16 kg an anioactive dispersant and O | 46 kg of methanol. This mixture is homogenized with 5.7 kg of a 65% phenol resin solution in a high-speed mixer and processed with 3 »7 kg cotton fabric or Faderlagennähgewirke to a laminating. The hardened material contains 10% PTFE. The required maintenance-free plain bearings are produced by mechanical processing.

Example 2;

40.5 PTPE-Peinpulver, prepared by irradiation of a 10 mm thick layer of coagulum a PTFE emulsion (Pehlcharge) in a homogeneous mixture with 8 kg Ammomiumsulfit in the radiation field of an electron accelerator (accelerating voltage 1000 kV, beam current 6 mA) up to a dose of 40 Billion at a maximum of 120 ⁰ C, washing the excess salt with an ethanol-water mixture (1: 1) and then grinding with a pin mill, are pasted with 24.5 kg of nonionic dispersant, 16 kg of anionic dispersant and 41 kg of methanol. This mixture is then processed with 609 kg of a 65% phenolic resin solution and 525 kg of cotton fabric as in Example 1 to maintenance-free bearings. The bearing material contains 5 % PTPE.

Claims (3)

Claim for invention 1. A process for the preparation of sliding materials, which are preferably prepared by pressing impregnated with synthetic resins web-like carrier material and an additive based on PTFE, characterized in that in the manufacture of the sliding material, a PTFE fine powder is incorporated with functional groups, wherein functional Groups can be, for example, -COOH, SO ₃ H, -CONH ₂ , -COOR, -COX, -OR, -CN, -X; where X = halogen and R = alkyl. 2. Method according to item 1, characterized in that the functional groups are obtained by irradiating the PTPE powder with high-energy radiation, preferably with a gamma source or an electron accelerator, in the presence of air, oxygen or additives, such as sulfites, carbonates, nitrites, nitrates, Halides, cyanides, ureas, amines, amino alcohols, alcohols, aldehydes or organic acids attached to the PTFE. 3 # Method according to items 1 and 2, characterized in that the sliding material contains up to 20%, preferably 5-15 % PTFE powder with functional groups.