EP1789688A1

EP1789688A1 - Anti-friction bearing

Info

Publication number: EP1789688A1
Application number: EP05751000A
Authority: EP
Inventors: Peter Radden; Rochus Hiekisch; Wolfgang Wieth; Jürgen Reichert
Original assignee: SKF AB
Current assignee: SKF AB
Priority date: 2004-06-21
Filing date: 2005-05-30
Publication date: 2007-05-30
Also published as: WO2005124172A1; DE102004029729A1

Abstract

The invention relates to an anti-friction bearing, consisting of at least one internal race and at least one external race, a number of anti-friction bodies, in particular balls being provided between said races. The anti-friction bodies are guided in a cage, which consists of plastic, said plastic being at least partially composed of a polyarylene sulphide. To obtain improved material characteristics, the plastic of the cage has the following composition: between 5 and 50 wt. % modified polyolefin; between 40 and 95 wt. % polyarylene sulphide; between 0 and 60 wt. % additional additives and/or processing adjuvants.

Description

roller bearing

The invention relates to a rolling bearing consisting of at least one inner ring and at least one outer ring, between which a number of rolling elements, in particular balls, are arranged, the rolling elements being guided in a cage, the cage being made of plastic and the plastic being at least partially polyarylene sulfide is.

The materials polyethersulfone (PES), polyetherimide (PEI), polyamide-imide (PAI) and polyetheretherketone (PEEK) have already been successfully used as material for roller bearing cages, in particular to ensure high temperature resistance of the cage material at operating temperatures of over 150 ° C to reach.

A rolling bearing of the type mentioned is known from US 5,590,225. There, polyarylene sulfide in the form of polyphenylene sulfide (PPS) is used as a plastic material in order to further make the bearing or cage suitable or insensitive to high temperatures and harsh environmental conditions; Another aim is that the toughness of the material is as high as possible. In order to achieve this goal, linear-chain polyphenylene sulfide is used, to which glass fibers are added in a proportion of up to 45 percent by weight. Although this type of plastic or plastic composition can already be used to produce cages for rolling bearings that meet high demands for insensitivity to temperatures and aggressive environmental conditions, there is a desire for a further increase in resistance to harsh environmental conditions, with the functionality of the cage particularly in terms of toughness and hardness should be optimized.

The invention is therefore based on the invention, to propose a plastic cage of the type mentioned, the material of which is characterized by further improved behavior in terms of thermal stability and ductility and the properties of which make it possible to further improve the running behavior of the rolling bearing.

The solution to this problem by the invention is characterized in that the plastic of the cage has the following composition:

5 to 50% by weight of modified polyolefin; 40 to 95% by weight polyarylene sulfide; 0 to 60% by weight of further additives and / or processing aids.

The following ranges are preferably provided for the individual components of the plastic mixture:

7 to 25% by weight of modified polyolefin; 50 to 90% by weight polyarylene sulfide; 0 to 50% by weight of further additives and / or processing aids.

The following composition has proven to be a particularly preferred mixture:

10 to 15% by weight of modified polyolefin; 55 to 80% by weight polyarylene sulfide; 0 to 40% by weight of further additives and / or processing aids.

The proportion of polyarylene sulfide is preferably between 57.5% by weight and 66.5% by weight. The proportion of polyarylene sulfide when used without colorant is particularly preferably between 60.75% by weight and 65.75% by weight and is reduced by the amount of colorant used when colorant is used.

For the purposes of the invention, polyarylene sulfides are linear or branched polymers which contain arylene sulfide units. Preferred polyarylene sulfides are polyarylene thioethers with repeating units of the formula

- [(Ar -X] _m - [(Ar Υ] _r [(-Z] _r Ar -W] _v - (I)

wherein Ar ¹ , Ar ² , Ar ³ , Ar ⁴ or W, X, Y and Z are independently the same or different, the indices n, m, i, j, k, 1, o and p independently of one another zero or whole Numbers 1, 2, 3 or 4 are, their sum being at least 2, Ar ¹ , Ar ² , Ar ³ and Ar ^{4 are} arylene systems with 6 to 18 C atoms and W, X, Y and Z represent divalent linking groups from -S0 ₂ -, -S-, -SO-, -CO-, -O-, -COO- or alkylene or Alkylidene groups with 1 to 6 carbon atoms, and at least one of the linking groups W, X, Y or Z consists of -S-.

The arylene systems Ar ¹ , Ar ² , Ar ³ and Ar ⁴ can be optionally substituted or unsubstituted. Preferred arylene systems are phenylene, biphenylene, naphthylene, anthracene and phenanthrene. A particularly preferred polyarylene sulfide is linear-chain polyphenylene sulfide (PPS), which is known, inter alia, under the name ^® Fortron.

The modified polyolefin provided according to the invention can contain at least one of the following groups: carboxyl, carboxyl anhydride, metal carboxylate, carboxyl ester, imino, amino or epoxy group. Examples of the modified polyolefin plastic include modified polyolefin copolymers or grafted copolymers made by chemically following exemplified compounds such as maleic anhydride, fumaric anhydride, citric anhydride, N-phenyl maleimide, N-cyclohexyl maleimide, glyicidyl acrylate, acrylate glycidyl acrylate, glycidyl acrylate, glycidyl acrylate, glycidyl acrylate, glycidyl acrylate, glycidyl acrylate, glycidyl acrylate, glycidyl acrylate, glycidyl acrylate, glycidyl acrylate, glycidyl acrylate, and glycidyl acrylate - [4- (2,3-epoxpropoxy) -3,5-dimethylbenzyljacrylamide (AX), alkyl methacrylates and / or derivatives thereof in polyolefins such as polypropylene, polyethylene or ethylene / propylene copolymers and in polyamide-grafted polyolefins are introduced , The modified polyolefin is not limited in the degree of polymerization, it can also be an oligomer. Preferred modified polyolefins are

Maleic anhydride-modified polyethylene, maleic anhydride-modified polypropylene,

Maleic anhydride-modified polyethylene / polypropylene copolymer, fumaric anhydride-modified polyethylene, fumaric anhydride-modified polypropylene, Fumaric anhydride-modified polyethylene / polypropylene copolymer, glycidyl methacrylate-modified polyethylene, glycidyl methacrylate-modified polypropylene, AX-modified polyethylene, AX-modified polypropylene and polyamide-grafted polyolefins.

As additives and / or processing aids, the plastic of the cage can contain adhesion promoters, fillers, reinforcing materials, stabilizers, antioxidants, agents against heat decomposition and decomposition by UV radiation, lubricants and mold release agents, colorants such as dyes and pigments, nucleating agents, plasticizers, etc.

Compounds based on organosilane are preferably used as adhesion promoters, which the plastic of the cage in amounts between 0 and 2 wt .-%, preferably between 0.1 and 0.5 wt .-%, particularly preferably between 0.2 and 0 , 3 wt .-%, are added. Hydroxyalkoxysilanes, epoxyalkoxysilanes, aminoalkoxysilanes and vinylalkoxysilanes of the general formula R _n Si (OR ') ₍₄ _ _n) are particularly preferred, where R is a hydrocarbon radical which contains an epoxy, amine or vinyl group as a functional unit, n one is an integer from 1 to 3 (in mixtures of different organosilanes, n is on average between 1 and 3) and R 'is an alkyl group with 1 to 4 carbon atoms. Examples of the organosilanes according to the invention are disclosed in US Pat. No. 5,731,397 (columns 6-8), to which reference is made.

Examples of lubricants are esters or amides of saturated or unsaturated aliphatic carboxylic acids with 10 to 40 C atoms with aliphatic saturated alcohols or amines with 2 to 40 C atoms. The Carboxylic acids can be 1- or 2-valent. Examples include pelargonic acid, palmitic acid, lauric acid and particularly preferably stearic acid, capric acid and montanic acid (mixture of fatty acids with 30 to 40 carbon atoms). The aliphatic alcohols can be 1- to 4-valent. Examples of alcohols are glycerol, n-butanol, n-octanol, stearyl alcohol, ethylene glycol, propylene glycol, neopentyl glycol, pentaerythritol, with glycerol and pentaerythritol being preferred. The aliphatic amines can be 1- to 3-valent. Examples of amines are stearylamine, ethylenediamine, propylenediamine, hexamethylenediamine, with ethylenediamine and hexamethylenediamine being preferred. Preferred esters or amides are correspondingly glycerol distearate, glycerol tristearate, ethylenediamine distearate, glycerol monopalmitate, glycerol trilaurate, and pentaerythritol tetrastearate. The esters or amides are added in amounts between 0 and 2% by weight, preferably between 0.1 and 0.5% by weight, particularly preferably between 0.2 and 0.3% by weight. Mixtures of different esters or amides or esters with amides can also be used in combination, the mixing ratio being arbitrary.

Fillers and / or reinforcing materials include fibrous reinforcing materials such as glass fibers, carbon fibers etc. and non-fibrous fillers such as glass powder, graphite, carbon black, metal powder, metal oxides, silicates, carbonates and molybdenum (IV) sulfide. These fillers can be equipped with an adhesion promoter or adhesion promoter system. The total amount of fillers and / or reinforcing materials is usually up to 50% by weight, preferably up to 30% by weight, based on the total mixture. Carbon fibers and / or glass fibers are preferably used. Optionally, the plastic of the cage can contain colorants in the form of any inorganic pigments such as titanium dioxide, ultramarine blue, cobalt blue or organic pigments and colors such as phthalocyanines, anthraquinones or carbon black either individually or as a mixture or together with polymer-soluble dyes in amounts of generally up to 10. 0% by weight, preferably up to 5.0% by weight, particularly preferably up to 4.0% by weight. Colorant concentrates are preferred as colorants. The colorants are usually initially mixed in a high concentration, usually using additional dispersing aids, in polymeric carrier materials, also called carriers. The colorant preparation thus obtained, also called color concentrate or masterbatch, is then added to the plastic to be colored in order to finally achieve the desired color impression. Colorant concentrates are preferably used for coloring the cage according to the invention.

The proposed plastic material has shown particularly good suitability for rolling bearing cages. In particular, there is very good impact strength, which is significantly above the values that have been observed so far in the materials used.

In addition, the hardness of the material surprisingly resulted, which makes it ideally suited for use in rolling bearings. For applications in roller bearings, the lower hardness of the material composition achieved advantageously has the result that an improved scrubbing film structure is possible, which leads to an extension of the operating life of the bearing. This can be explained by an increased elasticity of the material in the micro range, where local surface topography deformations occur. This makes it possible to build a micro-elastohydrodynamic film. Furthermore, this effect is accompanied by less wear, which has a very positive effect in rolling bearing construction.

The lower friction under lubrication, less noise and higher elasticity of the cage are also positive. This can be explained by the very good damping behavior of the material.

Finally, studies have shown that the resistance to aging of the proposed plastic mixture is also very good.

A preferred exemplary embodiment of the invention looks as follows: The plastic mixture has the following composition:

63.25% by weight linear chain polyphenylene sulfide; 11.25% by weight modified polyolefin; 0.25% by weight organosilane-based coupling agent; 0.25 wt% lubricant; 25.00% by weight of reinforcing fibers.

^® Fortron 02141B from Ticona GmbH, Kelsterbach, is used as the polyphenylene sulfide (PPS) (CAS number: 26125-40-6).

Lotader AX8840, a copolymer of ethylene and 8% by weight glycidyl methacrylate (GMA) from Atofina Chemicals, Inc., Philadelphia (USA), is used as the modified polyolefin. As a bonding agent on organosilane base is 3-glycidoxypropyl trimethoxysilane (Silquest ^® A-187) from GE Bayer Silicones BV, Bergen op Zoom, The Netherlands used.

The lubricant used in the exemplary embodiment is pentaerythritol tetrastearate (PETS), which is sold under the brand name ^® Glycolube P by Lonza Ltd. or is available under the trademark ^® Loxiol EP861 from Henkel KGaA (CAS number: 115-83-3).

Fiberglass 165A-11C from Owens-Corning Fiberglass Corp., Toledo, Ohio, USA is used as the reinforcing fiber material.

An alternative solution additionally provides black color concentrate with a proportion of 2.5% by weight, the proportion of the polyphenylene sulfide then being reduced to 60.75% by weight.

A hardness test (according to EN ISO 2039-1, ball pressure hardness; 30 sec value) showed hardness values between 120 and 150 N / mm, which is significantly below the expected hardness, which in any case is higher than 190 for the polyarylene sulfide used as the base material N / mm ² , and already without reinforcing material (glass or carbon fibers); with reinforcement material of, for example, 40% glass fibers, the hardness is even in the range of 322 N / mm ² .

Furthermore, the proposed plastic material is very temperature-stable, so that storage temperatures of approximately 150 ° C. and above can also be endured permanently. This applies in particular to aggressive environmental conditions, for example in oils, fats or acid chemicals.

Claims

May 25, 2005 Claims:

1. Rolling bearing, consisting of at least one inner ring and at least one outer ring, between which a number of rolling bodies, in particular balls, are arranged, the rolling bodies being guided in a cage, the cage being made of plastic and the plastic being at least partially polyarylene sulfide, characterized in that the plastic of the cage has the following composition:

2. Rolling bearing according to claim 1, characterized in that the plastic of the cage has the following composition:

3. Rolling bearing according to claim 1, characterized in that the plastic of the cage has the following composition:

4. Rolling bearing according to one of claims 1 to 3, characterized in that the proportion of polyarylene sulfide is between 57.5 wt .-% and 66.5 wt .-%.

5. Rolling bearing according to one of claims 1 to 4, characterized in that the polyarylene sulfide is linear-chain polyphenylene sulfide.

6. Rolling bearing according to one of claims 1 to 5, characterized in that the modified polyolefin is a copolymer of polyethylene and glycidyl methacrylate.

7. Rolling bearing according to claim 6, characterized in that the copolymer has between 4 and 12 wt .-%, preferably of 8 wt .-%, glycidyl methacrylate.

8. Rolling bearing according to one of claims 1 to 7, characterized in that the filler and / or reinforcing material are fiberglass fibers.

9. Rolling bearing according to one of claims 1 to 7, characterized in that the filler and / or reinforcing material are carbon fibers.