Process for foaming polyolefin compositions using a fluororesin as a nucleating agent

Patent metadata

Field	Value
Publication number	US-2020123356-A1
Application number	US-201916718367-A
Country	US
Kind code	A1
Filing date	Dec 18, 2019
Priority date	Nov 28, 2014
Publication date	Apr 23, 2020
Grant date	—

Abstract

A polyolefin composition is foamed by a process in which a nucleator is used, and the nucleator comprises 80% or more of unagglomerated fluororesin particles and/or agglomerates of fluororesin particles in which both the unagglomerated particles and the agglomerates are less than 1 μm in size.

First claim

What is claimed is:

1 . A process for foaming a polyolefin composition, the process comprising the steps of:
(A) mixing a masterbatch of a first low density polyethylene having a melt index from 0.1 g/10 min to 50 g/10 min, and a fluororesin powder, wherein the fluororesin powder comprises from 10 to 20 weight percent of the masterbatch; (B) mixing the with a polyolefin blend comprising (i) a high density polyethylene having a melt index from 0.1 g/10 min to 10 g/10 min and (ii) a second low density polyethylene that has a melt index that is different than the melt index of the first low density polyethylene, to form a mixture of the fluororesin substantially uniformly dispersed throughout the polyolefin blend, the mixture comprising:
from 60 wt % to 80 wt % of the high density polyethylene;
from 19 wt % to 39 wt % of a combined amount of the first low density polyethylene and the second low density polyethylene; and
from 0.1 wt % to 0.3 wt % fluororesin, based on the total weight of the mixture,
(C) foaming the mixture of (B); and (D) forming a foam composition having a cell size range from 18.8 to 30.4 microns.

2 . The process of claim 1 , wherein the fluororesin is prepared by dispersion polymerization.

3 . The process of claim 2 , wherein the fluororesin comprises polytetrafluoroethylene (PTFE).

4 . The process of claim 3 , wherein the PTFE is present in the composition in an amount of 0.01 to 1 wt % based on the weight of the composition.

5 . The process of claim 1 , further comprising reducing the size of the fluororesin particles or fluororesin agglomerates to a size of 220 nm.

6 . The process of claim 1 , wherein the composition further comprises at least one of an antioxidant and a cell stabilizer.

7 . The process of claim 1 , further comprising forming the foam composition having an average cell size of 23 microns.

8 . The process of claim 1 , wherein the (B) reducing comprises batch mixing the masterbatch of (A) at a temperature of 120° C. and a mixer loading speed of 35 revolutions per minute for a period of 4 minutes.

9 . The process of claim 1 , further comprising extruding the masterbatch after batch mixing.

10 . A foam made by the process of claim 1 .

11 . A cable comprising an insulation layer comprising the foam of claim 10 .

Assignees

• Dow Global Technologies Llc

Inventors

• Sun Gangwei
• Esseghir Mohamed
• Kmiec Chester J
• Ying Lei
• Sun Yabin
• Xu Xianmin

Classifications

• C08J2427/12

  containing fluorine atoms · CPC title

• C08L2203/14

  used for foams · CPC title

• C08J9/0061 Primary

  characterized by the use of several polymeric components · CPC title

• C08J3/226

  using a polymer as a carrier · CPC title

• C08J2203/06

  CO2, N2 or noble gases · CPC title