Process for the production of sintered moldings

Patent metadata

Field	Value
Publication number	US-2018185919-A1
Application number	US-201515315594-A
Country	US
Kind code	A1
Filing date	Jun 1, 2015
Priority date	Jun 2, 2014
Publication date	Jul 5, 2018
Grant date	—

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.

First claim

1 .- 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 —CH 2 O— 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.

Assignees

• Basf Se

Inventors

• Hermant Marie-Claire
• Von Bernstorff Bernd-Steffen

Classifications

• B22F1/10 Primary

  Metallic powder containing lubricating or binding agents; Metallic powder containing organic material · CPC title

• B28B1/24

  by injection moulding {(injection moulding of ceramic slips B28B1/265; of tubular articles B28B21/38)} · CPC title

• B22F3/1025 Primary

  not by heating only · CPC title

• B22F3/225

  by injection molding · CPC title

• C08L59/02

  Polyacetals containing polyoxymethylene sequences only · CPC title