BRONZE-POLYTETRAFLUOROETHYLENE COMPOUNDS BASED ON AN OXIDATION-RESISTANT BRONZE POWDER

Abstract

The present invention relates to a bronze-polytetrafluoroethylene compound based on an oxidation-resistant bronze powder, and to a method for producing the bronze-polytetrafluoroethylene compound. In another aspect, the present invention relates to an oxidation-resistant bronze powder for use in polytetrafluoroethylene compounds.

Claims

1. A bronze-polytetrafluoroethylene compound, comprising a sintered mixture of bronze particles and polytetrafluoroethylene, wherein the amount of the bronze particles is from 40 to 60 mass %, and the amount of the polytetrafluoroethylene is from 60 to 40 mass %, based on the total mass of the bronze particles and the polytetrafluoroethylene, characterized in that the bronze particles have an elemental composition consisting of: Sn in an amount of from 10 to 30 mass %; Zn in an amount of from 2 to 20 mass %; and one of the following elements: Al in an amount of from 0.1 to 5 mass %; or P in an amount of from 0.01 to 0.4 mass %, with the remainder consisting of Cu and inevitable impurities, wherein the bronze particles have no surface coating

2. The bronze-polytetrafluoroethylene compound according to claim 1, wherein the amount of the bronze particles having a particle size of 100 pm or more is at most 5%, as measured by sieve analysis in accordance with DIN 66165.

3. The bronze-polytetrafluoroethylene compound according to claim 2, wherein the amount of the bronze particles having a particle size of 50 pm or more is at most 5%, as measured by sieve analysis in accordance with DIN 66165.

4. The bronze-polytetrafluoroethylene compound according to any claim 1, wherein the bronze particles are irregularly shaped.

5. The bronze-polytetrafluoroethylene compound according to claim 1, wherein the bronze particles are spherically shaped.

6. The bronze-polytetrafluoroethylene compound according to claim 1, wherein the amount of Sn is from 10 to 20 mass %.

7. The bronze-polytetrafluoroethylene compound according to claim 6, wherein the amount of Sn is from 10 to 15 mass %.

8. The bronze-polytetrafluoroethylene compound according to claim 1, wherein the amount of Zn is from 2 to 10 mass %.

9. The bronze-polytetrafluoroethylene compound according to claim 8, wherein the amount of Zn is from 2 to 5 mass %.

10. The bronze-polytetrafluoroethylene compound according to claim 1, wherein the amount of the bronze particles is from 40 to 50 mass %, and the amount of the polytetrafluoroethylene is from 60 to 50 mass %, based on the total mass of the bronze particles and the polytetrafluoroethylene.

11. The bronze-polytetrafluoroethylene compound according to claim 10, wherein the amount of the bronze particles is from 40 to 45 mass %, and the amount of the polytetrafluoroethylene is from 60 to 55 mass %, based on the total mass of the bronze particles and the polytetrafluoroethylene.

12. A method for producing a bronze-polytetrafluoroethylene compound, comprising the steps of: (a) providing bronze particles and polytetrafluoroethylene, wherein the amount of the bronze particles is from 40 to 60 mass %, and the amount of the polytetrafluoroethylene is from 60 to 40 mass %, based on the total mass of the bronze particles and the polytetrafluoroethylene, characterized in that the bronze particles have an elemental composition consisting of: Sn in an amount of from 10 to 30 mass %; Zn in an amount of from 2 to 20 mass %; and one of the following elements: Al in an amount of from 0.1 to 5 mass %; and P in an amount of from 0.01 to 0.4 mass %, with the remainder consisting of Cu and inevitable impurities, and wherein the bronze particles have no surface coating; (b) mixing the bronze particles and the polytetrafluoroethylene provided in step (a), thereby obtaining a mixture; (c) subjecting the mixture obtained in step (b) to high pressure treatment in the range of from 10 to 100 MPa, thereby obtaining a green body; and (d) sintering the green body obtained in step (c) while optionally maintaining the pressure in the range of from 10 to 100 MPa, thereby obtaining a bronze-polytetrafluoroethylene compound.

13. A bronze powder comprising bronze particles, wherein the bronze particles have an elemental composition consisting of: Sn in an amount of from 10 to 30 mass %; Zn in an amount of from 2 to 20 mass %; and one of the following elements: Al in an amount of from 0.1 to 5 mass %; or P in an amount of from 0.01 to 0.4 mass %, with the remainder consisting of Cu and inevitable impurities, wherein the bronze particles have no surface coating.

14. A bronze-polytetrafluoroethylene compound comprising the bronze powder according to claim 13.

Description

[0063] The FIGURE shows:

[0064] FIG. 1 shows a typical process flow of the production of the bronze particles used herein.

EXAMPLES

[0065] The present invention is further illustrated by the following Examples. However, the present invention is not to be construed as being limited thereto.

[0066] Bronze-polytetrafluoroethylene compounds were prepared based on bronze powders comprising the bronze particles specified in Table A and Table B, below. All the bronze-polytetrafluoroethylene compounds prepared contained 42.5 mass % of the respective bronze particles and 57.5 mass % of polytetrafluoroethylene, based on the total mass of the bronze particles and the polytetrafluoroethylene.

TABLE-US-00001 TABLE A elemental compositions (remainder being Cu and inevitable impurities) Sn Zn P Al bronze particles [mass %] [mass %] [mass %] [mass %] sample 1 10 2 0.2 sample 2 11 4 0.01 sample 3 15 4 0.01 sample 4 20 4 0.01 sample 5 10 2 1

TABLE-US-00002 TABLE B mechanical characteristics particle mean particle apparent bronze size size d.sub.50 particle density particles [m] [m] shape [g/cm.sup.3] sample 1 <32 19 spherical 5.0 sample 2 <32 23 irregular 3.2 sample 3 <32 21 irregular 3.2 sample 4 <32 19 irregular 3.4 sample 5 <32 21 irregular 3.5

[0067] When using the bronze particles specified in Table A and Table B, neither dark streaks inside the compound nor an edge zone oxidation could be observed in the course of sintering the green bodies. The obtained bronze-polytetrafluoroethylene compounds had a uniform appearance, in particular a consistent color, thus being particularly suitable in applications requiring high quality, e.g. in the automobile industry.