Thermoplastic elastomer composition

Patent metadata

Field	Value
Publication number	US-9976019-B2
Application number	US-201514666930-A
Country	US
Kind code	B2
Filing date	Mar 24, 2015
Priority date	Mar 31, 2014
Publication date	May 22, 2018
Grant date	May 22, 2018

Abstract

Provided is a thermoplastic elastomer composition from which an air bag cover having an appearance suitable for painting-free applications can be produced, specifically, a thermoplastic elastomer composition obtained by dynamically heat-treating 25% by weight to 50% by weight of a prescribed heterophasic polymeric material (A), 15% by weight to 40% by weight of a prescribed propylene-ethylene copolymer (B), 15% by weight to 35% by weight of a prescribed ethylene-α-olefin copolymer (C), and 15% by weight to 35% by weight of a prescribed ethylene-α-olefin copolymer (D) in the presence of a crosslinking agent, provided that the combined amount of the above-mentioned (A), (B), (C) and (D) is taken as 100% by weight.

First claim

What is claimed is:

1. A method for producing a thermoplastic elastomer composition, comprising:
dynamically heat-treating 25% by weight to 40% by weight of a heterophasic polymeric material (A) defined below, 15% by weight to 30% by weight of a propylene-ethylene copolymer (B) defined below, 15% by weight to 35% by weight of an ethylene-α-olefin copolymer (C) having a density of not lower than 0.850 g/cm 3 but lower than 0.860 g/cm 3 and a melt flow rate, measured at 190° C. under a load of 21.18 N, of 0.9 g/10 min to 5 g/10 min, and 15% by weight to 35% by weight of an ethylene-α-olefin copolymer (D) having a density of not lower than 0.850 g/cm 3 but lower than 0.865 g/cm 3 and a melt flow rate, measured at 190° C. under a load of 21.18 N, of not less than 0.01 g/10 min but less than 0.6 g/10 min, in the presence of a crosslinking agent (E), wherein the total amount of the ethylene-α-olefin copolymer (C) and the ethylene-α-olefin copolymer (D) is 33% by weight to 55% by weight, provided that the combined amount of (A), (B), (C) and (D) is taken as 100% by weight; wherein
the heterophasic polymeric material (A) is a polymeric material obtained through multistage polymerization and composed of 70% by weight to 90% by weight of a propylene homopolymer (I) and 10% by weight to 30% by weight of a copolymer (II) obtained by polymerizing at least any one monomer selected from the group consisting of propylene and α-olefins having 4 or more carbon atoms with ethylene, provided that the weight of the entire heterophasic polymeric material (A) is taken as 100% by weight, wherein the content of monomer units derived from ethylene is 22% by weight to 60% by weight, where the weight of the copolymer (II) is taken as 100% by weight,
the propylene-ethylene copolymer (B) is a propylene-ethylene copolymer having a content of monomer units derived from propylene of 80% by weight to 98% by weight and a content of monomer units derived from ethylene of 2% by weight to 20% by weight, provided that the weight of the entire propylene-ethylene copolymer (B) is taken as 100% by weight,
the thermoplastic elastomer composition has a melt flow rate, measured at 230° C. under a load of 21.18 N, of 1 g/10 min to 100 g/10 min, and
the crosslinking agent (E) is used in an amount of 0.01 parts by weight to 1.0 part by weight relative to 100 parts by weight of the combined amount of (A), (B), (C) and (D).

2. The method according to claim 1 , wherein the propylene-ethylene copolymer (B) is a random copolymer.

3. The method according to claim 1 , wherein the crystallization time of the thermoplastic elastomer composition is 85 seconds or more.

4. The method according to claim 1 , wherein the number of the carbon atoms in the α-olefin constituting the ethylene-α-olefin copolymer in the ethylene-α-olefin copolymer (C) is 6 to 12.

5. The method according to claim 1 , wherein the number of the carbon atoms in the α-olefin constituting the ethylene-α-olefin copolymer in the ethylene-α-olefin copolymer (D) is 4.

6. The method according to claim 1 , wherein the amount of the heterophasic polymeric material (A) is 25% by weight to 35% by weight.

Assignees

• Sumitomo Chemical Co

Inventors

• Matsunaga Kazuyuki

Classifications

• C08L2205/025

  containing two or more polymers of the same hierarchy C08L, and differing only in parameters such as density, comonomer content, molecular weight, structure · CPC title

• C08L2205/035

  containing four or more polymers in a blend · CPC title

• C08L2207/02

  Heterophasic composition · CPC title

• C08L2312/00

  Crosslinking · CPC title

• C08L2205/03

  containing three or more polymers in a blend · CPC title