PROCESS FOR THE PRODUCTION OF SINTERED MOLDINGS

• US 20180185919A1
• Filed: 06/01/2015
• Published: 07/05/2018
• Est. Priority Date: 06/02/2014
• Status: Active Grant

• Current Assignee: BASF SE
• Original Assignee: BASF SE
• Granted Patent: US 10,456,834 B2
• Time in Patent Office: Days
• CPC Class Codes: B22F 1/10 Metallic powder containing lubricating or binding agents; Metallic powder containing organic material
• CPC Class Codes: B22F 2302/45 Others, including non-metals
• CPC Class Codes: B22F 3/1025 not by heating only
• CPC Class Codes: B22F 3/16 in successive or repeated steps
• CPC Class Codes: B22F 3/225 by injection molding
• CPC Class Codes: C23F 1/12 Gaseous compositions
• CPC Class Codes: C23F 1/16 Acidic compositions C23F1/42 takes precedence

Abstract

The present invention relates to an improved process for the production of sintered moldings by molding a mixture of a sinterable ceramic or metallic powder and polyoxymethylene or a copolymer containing a majority of oxymethylene units as binder to give a compact, removing the binder from the compact by treatment with a gaseous acid, and sintering the resulting molding.

Claims

1-8. -8. (canceled)

9. A process for the production of sintered moldings which comprises:

molding a mixture comprising

A a sinterable metallic powder and

B1 polyoxymethylene or a polyoxymethylene copolymer having at least 50 mol % of —

CH₂O—

repeat units in the main polymer chain as binder to give a compact, removing the binder from the compact by treatment with a gaseous or liquid acid to obtain a molding, and sintering the molding,

wherein the acid is selected from methanesulfonic acid or a solution of methanesulfonic acid, oxalic acid or mixtures thereof in a solvent, selected from water, C_1-4-carboxylic acids and mixtures thereof, wherein as component B1 a thermoplastic composition comprising

from 10 to 90% by weight of a polyoxymethylene homo- or copolymer with a weight-average molar mass (M_W) in the range from above 60 000 to 200 000 g/mol as component B1.1 and

from 10 to 90% by weight of a polyoxymethylene copolymer with a weight average molar mass (M_W) in the range from 10 000 to 60 000 g/mol, as component B1.2, is employed, the molecular weights being determined by way of gel permeation chromatography.

10. The process of claim 9, wherein the amount of methanesulfonic acid, oxalic acid or mixtures thereof in the acid/solvent mixture is in the range of from 1 to 100 wt %.

11. The process of claim 9, wherein the C_1-4-carboxylic acid is selected from formic acid, acetic acid and propionic acid.

12. The process of claim 9, wherein the binder is removed by treatment with a gaseous acid, selected from a solution of methanesulfonic acid, oxalic acid or mixtures thereof in a solvent, selected from water C_1-4-carboxylic acids and mixtures thereof.

13. The process of claim 9, wherein the metallic powder is selected from Cu, Mg, Al and MgAl-alloys.

14. The process of claim 9, wherein a mixture is used, comprising

A.) from 40 to 70% by volume of a sinterable pulverant metal or a sinterable pulverant metal alloy or mixtures thereof;

B.) from 30 to 60% by volume of a binder comprising of the mixture of;

B1.) from 50 to 98% by weight of one or more polyoxymethylene homopolymers or copolymers based on the total amount of the component B;

B2.) from 2 to 35% by weight of one or more polyolefins, based on the total amount of component B;

B3.) from 0 to 40% by weight of poly1-,3-dioxolane, poly-1,3-dioxepane or polytetrahydrofurane or mixtures thereof, based on the total amount of component B, the sum of B1.), B2.) and B3.) adding up to 100% by weight.

15. The process of claim 14, wherein at least 90% by weight of component B1.1, based on the polymer, derived from trioxane and optionally butanediol formal as monomers.

16. The process of claim 14, wherein at least 90% by weight of component B1.1, based on the polymer, derived from trioxane and butanediol formal as monomers, with a proportion of butanediol formal, based on the polymer, in the range from 1 to 5% by weight.

17. The process of claim 14, wherein at least 90% by weight of component B1.1, based on the polymer, derived from trioxane and butanediol formal as monomers, with a proportion of butanediol formal, based on the polymer, in the range from 2 to 3.5% by weight.

18. The process of claim 14, wherein at least 90% by weight of component B1.1, based on the polymer, derived from trioxane and butanediol formal as monomers, with a proportion of butanediol formal, based on the polymer, in the range from 2.5 to 3% by weight.

19. The process of claim 9, wherein the binder is removed at atmospheric pressure or under reduced pressure.