Process for foaming polyolefin compositions using an azodicarbonamide/citrate mixture as a nucleating agent

Patent metadata

Field	Value
Publication number	US-2018105684-A1
Application number	US-201515562028-A
Country	US
Kind code	A1
Filing date	May 8, 2015
Priority date	May 8, 2015
Publication date	Apr 19, 2018
Grant date	—

Abstract

A process of foaming a polyolefin, e.g., polyethylene, composition using as a nucleator a combination of (A) azodicarbonamide, and (B) a mixture of (1) a first component consisting of at least one of citric acid and an alkali metal citrate, and (2) a second component consisting of at least one of an alkali metal citrate, a di-alkali metal hydrogen citrate, an alkali metal dihydrogen citrate and an alkali metal bicarbonate, with the proviso that the mixture is not solely composed of alkali metal citrate.

First claim

1 . A process of foaming a polyolefin using as a nucleator a combination of:
(A) azodicarbonamide (“ADCA”), and (B) a mixture of:
(1) a first component consisting of at least one of citric acid and an alkali metal citrate, and
(2) a second component consisting of at least one of an alkali metal citrate, a di-alkali metal hydrogen citrate, an alkali metal di-hydrogen citrate, and an alkali metal bicarbonate, with the proviso that said mixture is not solely composed of alkali metal citrates,
wherein said polyolefin and said nucleator are present as components in a foamable polyolefin composition, wherein said ADCA and said mixture are present in an ADCA-to-mixture weight ratio ranging from less than 80:20 to greater than 15:85.

2 . The process of claim 1 , wherein said polyolefin comprises a combination of high-density polyethylene (“HDPE”) and low-density polyethylene (“LDPE”).

3 . The process of claim 2 , wherein said polyolefin consists of a combination of HDPE and LDPE.

4 . The process of claim 2 , wherein said HDPE is present in an amount ranging from 45 to 95 weight percent based on the total weight of said foamable polyolefin composition, wherein said LDPE is present in an amount ranging from 4 to 54 weight percent based on the total weight of said foamable polyolefin composition.

5 . The process of claim 1 , wherein the alkali metal in each of the compounds identified in said first and second components is sodium.

6 . The process of claim 1 , wherein said mixture is selected from the group consisting of (a) a combination of sodium bicarbonate, sodium citrate, and disodium hydrogen citrate, wherein said sodium bicarbonate constitutes in the range of from 50 to 80 weight percent of said mixture with said sodium citrate and said disodium hydrogen citrate constituting the remainder, (b) a combination of citric acid and sodium dihydrogen citrate, wherein said citric acid and said sodium dihydrogen citrate are present in a weight ratio of about 60:40, and (c) mixtures thereof.

7 . The process of claim 1 , wherein said ADCA is present in an amount ranging from 0.03 to 0.09 weight percent, based on the total weight of said foamable polyolefin composition, wherein said mixture is present in an amount ranging from 0.06 to 0.12 weight percent, based on the total weight of said foamable polyolefin composition.

8 . The process of claim 1 , wherein said foamable polyolefin composition further comprises an additive selected from the group consisting of antioxidants, cell stabilizers, and combinations thereof.

9 . A foamed polyolefin prepared by the process of claim 1 .

10 . The foamed polyolefin of claim 9 , wherein said foamed polyolefin has an average cell size of less than 0.360 mm.

11 . A cable comprising an insulation layer, wherein said insulation layer comprises said foamed polyolefin of claim 9 .

12 . A foamable polyolefin composition comprising in weight percent based on the total weight of the foamable polyolefin composition:
(A) 45 to 95 weight percent HDPE; (B) 4 to 54 weight percent LDPE; (C) 0.03 to 0.09 weight percent ADCA; and (D) 0.06 to 0.12 weight percent of a mixture of:
(1) a first component consisting of at least one of citric acid and an alkali metal citrate, and
(2) a second component consisting of at least one of an alkali metal citrate, a di-alkali metal hydrogen citrate, an alkali metal di-hydrogen citrate, and an alkali metal bicarbonate, with the proviso that said mixture is not solely composed of alkali metal citrates.

13 . The foamable polyolefin composition of claim 12 , wherein the alkali metal in each of the compounds identified in said first and second components is sodium.

14 . The foamable polyolefin composition of claim 12 , wherein said mixture of component (D) is selected from the group consisting of (a) a combination of sodium bicarbonate, sodium citrate, and disodium hydrogen citrate, wherein said sodium bicarbonate constitutes in the range of from 50 to 80 weight percent of said mixture with said sodium citrate and said disodium hydrogen citrate constituting the remainder, (b) a combination of citric acid and sodium dihydrogen citrate, wherein said citric acid and said sodium dihydrogen citrate are present in a weight ratio of about 60:40, and (c) mixtures thereof.

15 . The foamable polyolefin composition of claim 12 , wherein said ADCA and said mixture are present in an ADCA-to-mixture weight ratio ranging from less than 80:20 to greater than 15:85.

Assignees

• Dow Global Technologies Llc

Inventors

• Sun Gangwei
• Esseghir Mohamed
• Xu Xianmin
• Kmiec Chester J

Classifications

• C08J2323/06

  Polyethene · CPC title

• C08J2423/06

  Polyethene · CPC title

• C08J9/0061

  characterized by the use of several polymeric components · CPC title

• C08J2205/04

  characterised by the foam pores · CPC title

• C08J9/103

  Azodicarbonamide · CPC title