WO1981001375A1

WO1981001375A1 - Composite material with two or a plurality of layers

Info

Publication number: WO1981001375A1
Application number: PCT/DE1980/000159
Authority: WO
Inventors: D Sternisa; W Schneider; E Hodes
Original assignee: Glyco Metall Werke; D Sternisa; W Schneider; E Hodes
Priority date: 1979-11-22
Filing date: 1980-10-23
Publication date: 1981-05-28
Also published as: GB2075368B; JPS56501641A; GB2075368A; BR8009010A; DE2947025A1

Abstract

Composite material with two or a plurality of layers with a coating layer (5) which is applied directly on the rough surface (2) of a substrate and which comprises a lake base of polyimid and at least one finely spread additive in said base. Upon forming the coating layer (5) as a friction or sliding layer, such layer may contain about 99 to 60% by volume, preferably 90 to 80% by volume of thermo-setting polyimid lake and about 1 to 40% by volume, preferably 10 to 20% by volume of self-lubrication additives, particularly low molecular weight PTFE, with a grain size comprised between 5 and 7 (Alpha). For manufacturing said composite material, the powder additive is intimately mixed with the polyimid lake and homogenized until it becomes slightly viscous or pasty, deposited on the metal substrate and fixed thereto by sintering.

Description

Two or multi-layer composite

The invention relates to a two- or multi-layer composite material with a cover layer which contains thermally highly resilient, thermosetting polyimide lacquer, by means of which the components of the cover layer are held together and at the same time the cover layer is firmly connected to the substrate carrying it. In particular, the invention relates to such a composite material for friction or sliding elements with a metallic substrate, the cover layer forming the friction or sliding layer.

The application of a top layer containing a thermally highly resilient, thermosetting polyimide lacquer is important for creating protected surfaces on layered composite materials of all kinds, in particular for coating metal surfaces and especially those metal surfaces that are subject to friction. The application of such cover layers by brushing or filling is particularly important.

For example, composite plain bearings are known in which a layer of perforations or recesses made of polyimide is attached to a steel support body by means of acrylic epoxy adhesive, the perforations or recesses being filled with a mixture of solid lubricant and a bearing metal, as they are are disclosed in DE-OS 20 00 632.

However, these known composite plain bearings with polyimide plastics have considerable defects, in particular because the adhesives used do not allow the high thermal load capacity of the polyimide plastics to be exhausted.

DE-OS 22 06 400 describes a composite material and a method for its production, the friction or sliding layer contains polyimide resins and / or polyimide lacquer components, which can also consist of polyesterimides and polyamideimides.

A connection to the metallic support body is made essentially by mechanical clamping. in which the supporting side of the support body is also sintered or a support fabric - for example made of tin bronze - is applied. Perforated steel or bronze sheets are also mentioned as supporting bodies. The application of a sintered structure or a supporting fabric as an intermediate layer or the use of a perforated steel or bronze sheet is necessary to ensure a sufficiently high connection between the plastic layer to be applied and the carrier material. It is obvious that the additional requirement for the existence of a rough base, which allows mechanical clinging, requires additional work steps and is therefore complex and cost-intensive. For example, the sintering structure is sprinkled onto the metallic support body, then μm has to go through a sintering process which has to be controlled in such a way that sufficient pore space is created which is impregnated with the polyimide resin and / or paint components. Attention must be paid to the viscosity of the mixtures in order to be able to achieve a complete impregnation of the available pore space. However, there are limits to this by adding self-lubricating additives. First, the size of these additives must be based on the dimensions of the available pore space of the primer and vice versa. Furthermore, the viscosity of the mixture increases with the proportion of self-lubricating additives.

A disadvantage of the described manufacturing process of friction or sliding elements with a very small bending radius is the fact that they can only be cured or hardened to their final thickness and formed after they have been processed. If the hardening or hardening before processing processing or prior to forming into friction or sliding elements with a very small bending radius, detachments, ie, flaking off of the friction or sliding layer must be expected.

Composite layer materials are also known, the sliding layer of which consists of a fluoropolymer mixture and an additive and which can be mixed with another inorganic or organic substance which improves the sliding properties and is present in powder form. The fluorine-containing polymer is in a continuous process

Coating process by adding filler materials, which have a density ≥ 8 g / cm ³ , which increase a surface connection of the fluoropolymers to the substrate, applied to the metallic carrier material. With this filler material, whose density is ≥ 8 g / cm ³ , the anti-adhesive properties of fluorine-containing polymers are suppressed.

The disadvantage is the need to use additives which are intended to improve the poor binding behavior of fluorine-containing polymers.

In contrast, it is an object of the invention to provide a two-layer or multi-layer composite material with an improved top layer containing polyimide lacquer, which is characterized by high temperature resistance, high mechanical strength, corrosion resistance and high wear resistance and is easy and inexpensive to apply to the composite material should be. As far as the composite material is intended for friction or sliding elements and the cover layer takes on the function of a friction or sliding layer, the disadvantages of the known polyimide sliding bearings are to be eliminated and, above all, significantly improved friction and sliding properties are to be achieved. The object of the invention is achieved in that the matrix of the cover layer is formed by the thermosetting polyimide lacquer and absorbs additives in finely dispersed form therein, and that this cover layer is applied directly to the roughened surface of the substrate. In the case of a composite material according to the invention for friction or sliding elements, the cover layer is to be designed as a friction or sliding layer and is applied directly to the roughened surface of a band-shaped, metallic substrate.

Surprisingly, it has been shown that those polyimide coatings, which are used in the electrical industry as electrical coatings or as wire coatings for insulating purposes, have proven particularly useful. A particular advantage of the composite material according to the invention is that a two- or multi-layer composite material is produced without an adhesion-promoting layer or a rough base which serves for mechanical clamping.

The matrix of the friction or sliding layer can advantageously be formed by polyimide which is soluble in solvents, and this matrix, in which a self-lubricating additive or additives is or are finely dispersed therein, is applied directly to the roughened surface of a metallic substrate will. In a particularly advantageous manner, the friction or sliding layer, which is about 99 to

60% by volume, preferably 90 to 80% by volume, of thermosetting polyimi lacquers and about 1 to 40% by volume, preferably 10 to 20% by volume, of self-lubricating additives. In this case, polyimide lacquers or the solvent-soluble polyimides can advantageously be substances from one or more of the following groups of polyimides:

Carboranimide, hydrogen-free polyimides, poly-triazo-pyromellithimides, polyesterimides and polyamideimides. In a particularly advantageous manner, the polyimide lacquer can be a solvent-soluble polyimide or a polyester crosslinked via tris (2-hydroxyethyl) isocyanurate (THEIC). The self-lubricating additive can advantageously be a low molecular weight PTFE in powder form, the average molecular weight of which is between 35,000 and 100,000, the average grain size of the low molecular weight PTFE being between 5 and 7 μm. The thickness of the friction or sliding layer can advantageously be between 0.05 and 0.5 mm, preferably between 0.07 and 0.2 mm. In an advantageous embodiment, the metallic substrate can be formed from steel according to DIN 1624, aluminum, an aluminum alloy, aluminum-plated steel or copper-containing materials, the metallic substrate having a thickness between 0.5 and 2.0 mm.

The production of the composite layer material according to the invention can be carried out in a continuous pass, the following process step being shown in a particularly advantageous manner. The self-lubricating additive, which is in powder form, is intimately mixed with the polyimide lacquer forming the matrix and homogenized to a low viscous to pasty state, the mixture thus prepared being applied in the desired coating thickness in an appropriate amount to the metallic substrate and fritted onto it can be.

In a particularly advantageous process step, in order to improve the processability of the mixture, it can be provided with a latent solvent, preferably diraethylformamide, the addition of dimethylformamide being 2 to 10% by volume, preferably 4 to 6% by volume. In a next advantageous process step, the mixture provided with a latent solvent can be used Spraying, brushing or rolling are applied to the metallic substrate, the metallic substrate advantageously being able to be heated inductively to the temperature in order to frit the friction or sliding layer against the metallic substrate in an MF oven.

In an advantageous method step, the latent solvent contained in the friction or sliding layer that has been fritted can be volatilized in a subsequent heating section. In a subsequent advantageous process step, the mixture of polyimide lacquer and low molecular weight PTFE applied to the metallic substrate can be fully hardened in a continuous furnace which can be regulated in its top and bottom heat, the initial temperature of the substrate being able to be a maximum of 253 ° C. In a particularly advantageous process step, in order to form the maximum crystallization of the friction or sliding layer, the latter can be cooled in a controlled manner following the hardening and then wound up into a roll for further processing.

The process according to the invention has the advantage that the metallic support material can be coated directly with the low-friction, wear-resistant and temperature-resistant material in a continuous process without complex intermediate layers with optimal adhesion. The demand for a fast and economical production process is taken into account in that the processing times are extremely short and sufficient accuracy when applying the friction or sliding layer helps to avoid dimensional reworking. After the strip provided with a friction or sliding layer has cooled in a controlled manner, it is wound up into a roll without additional thermal or mechanical aftertreatment and is suitable for further processing to conventional sliding bearing elements. Conventional two-layer composite materials with the structure of metallic supports / plastic suffer from non-cutting shaping by, for example, rolling, pressing or bending, irreversible damage to the bond between the substrate and the coating.

Reshaping the two-layer or multilayer material according to the invention, for example by rolling, surprisingly does not damage the layer composite.

The absence of a separate aftertreatment, be it thermal or mechanical, allows the plain bearing two-layer material to be produced continuously in a single pass. In the process according to the invention, a two-layer material can preferably be produced with a support material made of steel DIN 1624, quality St3, preferably St4. Alternatively, other metallic support materials, for example aluminum or aluminum alloys and aluminum-plated steel or copper-containing materials, can also be considered. The thickness of the metallic support materials used is arbitrary, but should preferably be in the range from 0.5 mm to 2.0 mm. A polyester crosslinked via tris (2-hydroxyethyl) isocyanurate (THEIC) is preferably used as the polyimide lacquer. This thermally highly resilient, heat shock-resistant, low-friction and insensitive to mechanical stress is mixed homogeneously with low-molecular PTFE, which is available in powder form and reduces friction and wear.

The homogeneous mixture to be applied to the support layer is between 0.05 mm and 0.5 mm thick, preferably between 0.07 mm and 0.2 mm. The addition of the wear-reducing, slip-improving PTFE in powder form with a grain size of 0.005 mm to 0.007 mm and a volume fraction of 1 to 40%, preferably 10 to 20%, is mixed with the polyimide lacquer, for example polyesterimide. Surprisingly, it was found that adding 2 to 10% by volume, preferably 4 to 6% by volume, of a latent solvent, for example dimethylformamide, increases the processability of the mixture considerably simplified during coating by, for example, painting. Furthermore, it was found that the addition of 2 to 10% by volume, preferably between 4 to 6% by volume, of a latent solvent, preferably dimethylformamide, also greatly improves the film formation of the coating mixture comprising, for example, polyesterimide and PTFE, and it contributes to a closed, non-porous and even and even coating over the entire range.

The embodiment of the plant to be used to carry out the method is described below.

The pretreatment of the metallic support layer, which is to be provided with a friction or sliding layer, is preferably carried out by means of blasting, brushing or grinding, that is to say mechanically.

Another way of pretreatment is by etching, that is, by chemical means. This treatment for increasing the specific surface in a mechanical and / or chemical manner is followed by cleaning the surface to be coated by known solvents.

An embodiment of the invention is explained below with reference to the drawing, which is a greatly enlarged section through a

Two-layer composite shows.

As can be seen from the drawing, a polyimide layer forming the matrix 3, which preferably consists of a polyesterimide, is applied to the pretreated surface 2 of the substrate 1 consisting of, for example, steel DIN 1624 of quality St4. In this matrix 3, consisting of polyester imide, there are low molecular weight PTFE particles as a self-lubricating additive 4 finely dispersed. The grain size of these PTFE particles 4 is between 5 and 7 μm. The fat. of the metallic substrate 1 is 0.2 to 2.5 mm in the manufacture of plain bearings, for example for use in pumps, carburetors or shock absorbers. The thickness of the friction or sliding layer 5 is between 0.07 and 0.2 mm.

The following description of the process is intended to show the production of a two-layer composite material.

A carrier material made of steel of quality St3 according to DIN

1624 or St4 is treated continuously by blasting, brushing or grinding and / or etching and subsequent cleaning or degreasing with preferably organic solvents. This is followed immediately by coating with a mixture of polyester imide and low molecular weight PTFE wax, particle size approx. 5 μm to 7 μm, average molecular weight 35,000 to 100,000. The best results were achieved with a statistical wear test (pin / roller test device) with a maximum of 21% by volume PTFE added.

The application of the friction or sliding layer takes place via an application knife (alternative: roller coating), this being set so that a uniform coating takes place over the entire range. This form of strip coating compensates for any differences in thickness of the support layer, so that an additional work step for thickness regulation is not necessary.

After the sliding layer has been applied, the material mixture is fritted onto the substrate in a preheating oven, an MF oven. The solvents contained in the friction or sliding layer are evaporated in a subsequent heating section. Subsequently, the coating composition is cured in a circulating continuous system.

A closed, smooth and pore-free coating is only created by the described sequence of the coating process and the design of the ovens.

The exit temperature of the strip described is 250 C at the end of the continuous furnace. Subsequent to the continuous furnace, there is slow, controlled cooling, which causes a high degree of crystallization of the coating. The two-layer composite material is wound up into a roll without any dimensional checks, such as rolling or milling, and is suitable for further processing of friction and sliding elements.

Comparative wear tests on test platelets, produced after the coating according to the invention polyesterimide and different volume fractions of low molecular weight PTFE compared to a coating without the addition of PTFE are listed below.

Test conditions: sliding speed: 100 min ^-1 = ¹ 0.523 ms ^-1 static load: 700 N specific load:

8, 9 N / mm ² test plate-: 10 mm

Roll ∅ of the counter rotor 100 mm PV value: 4.68 N / mm ² ms ^-1 hardness: 60 HRc R _t : 2.84 R _a : 0.24 R _z : 1.78 The following results were achieved using the test conditions listed:

An embodiment for producing the two-layer material according to the invention is described below.

Example 1:

The surface of the preferably metallic support layer to be coated with the sliding or friction layer according to the invention can be roughened by customary mechanical processes such as blasting, brushing or grinding. Chemical treatment by etching is also possible.

The production of the coating material according to the invention with e.g. a composition of 93 parts by volume of polyester imide and 7 parts by volume of low molecular weight PTFE is described below.

The mixing process takes place in a high-speed stirrer at a speed of ≤ 4000 rpm.

The initial viscosity at 23 ° C according to DIN 53211 for the polyesterimide is 90 s + 5%.

After mixing with a rotary viscometer, 450 + 5% m Pa. s measured. The mixing time should be kept short at 5 minutes.

The coating of the material according to the invention or the production or application is preferably carried out via an adjustable spreading bar or an application doctor. In a second example, the coating of a correspondingly pretreated support layer with a material according to the following composition is described.

Example 2: The composition of the friction or sliding layer consists of 79 parts by volume polyester imide and 21 parts by volume low molecular weight PTFE.

6 parts by volume, based on the mixture of a latent solvent, are added to the composition listed in the high-speed stirrer in order to improve the film formation when applied with a coating bar and to suppress blistering or pore formation in the case of layer thicknesses ≥ 40 μm.

Large areas, in particular metal surfaces to be protected (metal coating), can also be provided with a covering layer in the process according to the invention. The cover layer can also be applied to the strip-shaped substrate in a continuous process. The top layer can be put together in any desired special requirements, for example as a friction or. Sliding layer.

Claims

P a t e n t a n s r u c h e

1) Two- or multi-layer composite material with a cover layer which contains thermally highly resilient, thermosetting polyimide lacquer, by means of which the components of the cover layer are held together and at the same time the cover layer is firmly connected to the substrate carrying it, characterized in that the matrix ( 3) the top layer by the thermosetting. Polyimide lacquer is formed and absorbs additives in finely dispersed form and that this cover layer is applied directly to the roughened surface (2) of the substrate (1).

2) Composite material according to claim 1, in particular for friction or sliding elements, characterized in that the cover layer is designed as a friction or sliding layer (5) and directly on the roughened surface of a band-shaped, metallic substrate (1). is applied.

3) Composite material according to claim 2, characterized by a friction or sliding layer (5), which is about 99 to 60

% By volume, preferably 90 to 80% by volume of thermosetting polyimide lacquer and approximately 1 to 40% by volume, preferably 10 to 20% by volume, of self-lubricating additives (4).

4) Composite material according to one of claims 1 to 3, characterized in that the polyimide paint are substances from one or more of the following groups of polyimides: carboranimide, hydrogen-free polyimides, poly-triazo-pyromellithimides, polyesterimides and polyamideimides. 5) Composite material according to one of claims 1 to 4, characterized in that the polyimide paint is a solvent-soluble polyimide is a tris (2-hy droxyäthyl) isocyanurate (THEIC) crosslinked polyester.

6) Composite material according to one of claims 3 to 5, characterized in that the self-lubricating additive (4) is a powdered low molecular weight PTFE and has an average molecular weight between 35,000 and 100,000.

7) Composite material according to claim 6, characterized in that the average grain size of the low molecular weight PTFE is between 5 to 7 microns.

8) Composite material according to one of claims 1 to 7, characterized in that the thickness of the cover layer is between 0.05 and 0.5 mm, preferably between 0.07 and 0.2 mm.

9) Composite material according to one of claims 1 to 8, characterized in that the substrate (1) is formed from steel according to DIN 1624, aluminum, an aluminum alloy, aluminum-plated steel and copper-containing materials.

10) Composite material according to claim 9, characterized in that the substrate (1) has a thickness between 0.5 to 2.0 mm.

11) Process for the production of composite material according to claim 1, in which a strip forming the substrate is continuously coated with the material forming the cover layer or friction or sliding layer and this material is fritted by the action of heat and then cooled in a controlled manner, characterized in that that the additive present in powder form is intimately mixed with the polyimide lacquer forming the matrix and homogenized to a low viscous to pasty state, and that the mixture thus prepared is applied in the desired coating thickness in an appropriate amount to the metallic substrate and sintered thereon becomes.

12) Method according to claim 11, characterized in that to improve the processability of the mixture, this is provided with a latent solvent, preferably dimethylformamide.

13) Method according to claim 12, characterized in that the addition of dimethylformamide is 2 to 10% by volume, preferably 4 to 6% by volume.

14) Method according to one of claims 11 to 13, characterized in that the mixture provided with a latent solvent is applied to the metallic substrate by means of spraying, brushing or rolling.

15) Method according to one of claims 11 to 14, characterized in that the metallic substrate is inductively heated in an MF furnace to the temperature for fritting the friction or sliding layer on the metallic substrate.

16) Method according to claim 15, characterized in that the latent solvent contained in the fritted friction or sliding layer is volatilized in a subsequent heating section. 17) Method according to one of claims 11 to 16, characterized in that the mixture of polyimide lacquer and low molecular weight PTFE applied to the metallic substrate is cured in a continuous furnace which can be regulated in its top and bottom heat, the starting temperature of the Substrate is a maximum of 250 ° C.

18) Method according to one of claims 11 to 17, characterized in that in order to form the maximum crystallization of the friction or sliding layer

Connection to the Durαhärung is cooled controlled.

19) Method according to one of claims 11 to 18, characterized in that the composite material is wound into a roll after the controlled cooling for the further processing of friction or sliding elements.