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

Patent metadata

Field	Value
Publication number	US-10550249-B2
Application number	US-201415528850-A
Country	US
Kind code	B2
Filing date	Nov 28, 2014
Priority date	Nov 28, 2014
Publication date	Feb 4, 2020
Grant date	Feb 4, 2020

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) preparing with batch 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 composed of agglomerates and particles in which (1) the fluororesin powder comprises from 10 to 20 weight percent of the masterbatch, and (2) at least 80% of the fluororesin powder comprises agglomerates of submicron fluororesin particles, the agglomerates having a size from 5 microns to 20 microns, based on the total number of agglomerates and particles in the fluororesin powder,
(B) reducing the size of the fluororesin agglomerates such that 80% or more of the fluroresin powder in the masterbatch comprises fluororesin agglomerates or fluororesin particles of a size less than 0.3 μm, based on the total number of agglomerates and particles in the fluororesin powder,
(C) mixing the masterbatch of (B) 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 fluroresin powder 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 powder, based on the total weight of the mixture,

(D) foaming the mixture of (C) to form a foam composition having a cell size range from 18.8 to 30.4 microns.

2. The process of claim 1 in which the fluororesin powder is prepared by dispersion polymerization.

3. The process of claim 2 in which the fluororesin powder comprises polytetrafluoroethylene (PTFE).

4. The process of claim 3 in which the masterbatch of (B) further comprises at least one of an antioxidant and a cell stabilizer.

5. The process of claim 1 comprising forming the foam composition to have an average cell size of 23 microns.

6. 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 about 4 minutes.

7. The process of claim 6 wherein the (B) reducing further comprises extruding the masterbatch after batch mixing.

8. The process of claim 1 comprising (B) reducing the size of the fluororesin particles or fluororesin agglomerates to a size of 220 nm.

Assignees

• Dow Global Technologies Llc

Inventors

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

Classifications

• C08J2201/024

  Preparation or use of a blowing agent concentrate, i.e. masterbatch in a foamable composition · CPC title

• H01B3/445

  from vinylfluorides or other fluoroethylenic compounds · CPC title

• C08J9/0061 Primary

  characterized by the use of several polymeric components · CPC title

• C08J2427/12

  containing fluorine atoms · CPC title

• C08L23/04 Primary

  Homopolymers or copolymers of ethene · CPC title