Polyacetal compositions with improved tribological properties

• US 7,851,585 B2
• Filed: 10/16/2008
• Issued: 12/14/2010
• Est. Priority Date: 10/19/2007
• Status: Active Grant

• Current Assignee: Dupont Polymers Inc. (DuPont de Nemours, Inc.)
• Original Assignee: E. I. du Pont de Nemours and Company (Corteva, Inc.)
• Inventors: Brison, Anne-Laure, Renken, Andreas
• Primary Examiner(s): Boykin; Terressa M
• Application Number:
  US12/288,036
• Publication Number:
  US 20090105426A1
• Time in Patent Office: 789 Days
• Field of Search: 264/176.1, 264/219, 264/483, 384/276, 384/279, 384/448, 384/454, 524/100, 524/189, 524/261, 525/400, 525/402, 525/405, 528/250, 528/271, 528/272, 528/472, 528/480, 528/481
• US Class Current: 528/502.00R
• CPC Class Codes: C08L 2666/14 Macromolecular compounds according to C08L59/00 - C08L87/00; Derivatives thereof
• CPC Class Codes: C08L 2666/20 Macromolecular compounds having nitrogen in the main chain according to C08L75/00 - C08L79/00; Derivatives thereof
• CPC Class Codes: C08L 59/00 Compositions of polyacetals; Compositions of derivatives of polyacetals of polyvinyl acetals C08L29/14
• CPC Class Codes: C08L 77/10 Polyamides derived from aromatically bound amino and carboxyl groups of amino-carboxylic acids or of polyamines and polycarboxylic acids
• CPC Class Codes: C08L 83/00 Compositions of macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon only; Compositions of derivatives of such polymers
• CPC Class Codes: F16C 33/201 Composition of the plastic

Abstract

The invention relates to polyacetal compositions comprising a mixture of (i) a polyacetal resin, (ii) p-aramid particles and (III) a vinyl-terminated dimethyl siloxane polymer. These compositions are useful in preparing molded articles exhibiting a good balance between high self-lubricating properties and wear resistance, and especially useful in articles that are in motion with respect to other parts they are in contact with.

Claims

1. A polyacetal composition comprising:

i. 75 wt-% to 98 wt-% of a polyacetal resin;

ii. 1 wt-% to 20 wt-% of p-aramid particles having an average largest dimension that does not exceed 500 μ

m; and

iii. 0.5 wt-% to 5 wt-% of a vinyl-terminated dimethyl siloxane polymer having a viscosity from 150 CST to 10,000 CST at 25°

C.;

with the proviso that the p-aramid particles of (ii) excludes aramids in the form of spun filaments, woven or nonwoven fabrics, or aramid papers.

2. The polyacetal composition of claim 1, wherein the p-aramid particles have an average largest dimension that does not exceed 150 μ

m.

3. The polyacetal composition of claim 1, wherein the p-aramid particles are poly(p-phenylene terephthalamide) particles.

5. A molded article formed from the polyacetal composition described in claims 1, 2, or 3.

6. The molded article according to claim 5, which is a bearing, gear, cam, roller, sliding plats, pulley, lever, guide or a conveyor system component.

7. The molded article according to claim 6, which is a conveyor system component.

4. A method of manufacturing a polyacetal polymer composition, comprising the step of mixing

(i) 75 wt-% to 98 wt-% of a polyacetal resin;

(ii) 1 wt-% to 20 wt-% of p-aramid particles having an average largest dimension that does not exceed 500 μ

m; and

(iii) 0.5 wt-% to 5 wt-% of a vinyl-terminated dimethyl siloxane polymer having a viscosity from 150 CST to 10,000 CST at 25°

C.;

with the proviso that the p-aramid particles of (ii) excludes aramids in the form of spun filaments, woven or nonwoven fabrics, or aramid papers to provide the polyacetal polymer composition.

8. A polyacetal composition comprising:

i. 75 wt-% to 98 wt-% of a polyacetal resin;

ii. 1 wt-% to 20 wt-% of p-aramid particles having an average largest dimension that does not exceed 500 μ

m; and

iii. 0.5 wt-% to 5 wt-% of a vinyl-terminated dimethyl siloxane polymer having a viscosity from 150 CST to 10,000 CST at 25°

C.;

with the proviso that the p-aramid particles of (ii) are in powder form and which have never been spun into filaments or fibers.