Production of TPO roofing membrane via counter-rotating extrusion

Patent metadata

Field	Value
Publication number	US-9987786-B2
Application number	US-201314649749-A
Country	US
Kind code	B2
Filing date	Dec 23, 2013
Priority date	Dec 27, 2012
Publication date	Jun 5, 2018
Grant date	Jun 5, 2018

Abstract

The present disclosure is directed to a process for producing thermoplastic polyolefin roofing membrane. The process includes directly adding components of a high-load flame retardant TPO formulation to a counter-rotating twin screw extruder. The process includes extruding the formulation with counter-rotation of the twin screws and forming a TPO roofing membrane having a tensile strength of greater than 10 MPa and a flame retardance of rating of classification D as measured in accordance with EN ISO 1 1925-2, surface exposure test.

First claim

The invention claimed is:

1. A process comprising:
directly adding, to the exclusion of a prior compounding step, components of a high-load flame retardant thermoplastic polyolefin (TPO) formulation to a counter-rotating twin screw extruder, the high-load flame retardant TPO formulation comprising
an ethylene/α-olefin multi-block copolymer;
a polyolefin;
greater than 30 wt % of a granular flame retardant;

extruding, with counter-rotation of the twin screws at a rotation rate from 15 rpm to 40 rpm, the components of the high-load flame retardant TPO formulation; and
forming a TPO roofing membrane having
a tensile strength (CD) greater than 10 MPa, and
a flame retardance rating of classification D as measured in accordance with EN ISO 11925-2, surface exposure test.

2. The process of claim 1 comprising forming a TPO roofing membrane having a flame retardance rating of classification D as measured in accordance with EN ISO 11925-2, edge exposure test.

3. The process of claim 1 comprising performing the counter-rotating extrusion at a temperature less than 185° C.

4. The process of claim 1 comprising directly adding components of a high-load TPO formulation comprising
20 wt % to 50 wt ethylene/α-olefin multi-block copolymer;
10 wt % to 30 wt % ethylene/α-olefin copolymer;
35 wt % to 75 wt % of a flame retardant; and
forming a TPO roofing membrane having
a tensile strength (CD) greater than 10 MPa;
an elongation at break greater than 500%; and
an E-modulus less than 100 MPa.

5. The process of claim 1 comprising directly adding components of a high-load flame retardant TPO formulation comprising
20 wt % to 40 wt % ethylene/α-olefin multi-block copolymer;
15 wt % to 30 wt % ethylene/α-olefin copolymer having a density from 0.90 g/cc to 0.91 g/cc;
35 wt % to 60 wt % of a flame retardant;
1 wt % to 5 wt % additive; and
forming a TPO roofing membrane having
a tensile strength from greater than 10 MPa to 25 MPa;
an elongation at break from greater than 500% to 1100%; and
an E-modulus less than 100 MPa.

6. The process of claim 1 wherein the ethylene/α-olefin multi-block copolymer has a density from 0.860 g/cc to 0.880 g/cc.

7. The process of claim 1 wherein the ethylene/α-olefin multi-block copolymer comprises from 60 mole percent to 85 mole percent ethylene.

8. The process of claim 1 wherein the ethylene/α-olefin multi-block copolymer consists of ethylene and an α-olefin comonomer.

9. The process of claim 1 wherein the ethylene/α-olefin multi-block copolymer is an ethylene/octene multi-block copolymer.

Assignees

• Dow Global Technologies Llc

Inventors

• Stoiljkovic Aleksandar
• Ultsch Stefan
• Wu Xiaosong

Classifications

• B29C48/288

  in solid form, e.g. powder or granules · CPC title

• B29C48/07

  Flat, e.g. panels · CPC title

• B29K2023/08

  Copolymers of ethylene (B29K2023/16 takes precedence) · CPC title

• B29K2105/0026

  Flame proofing or flame retarding agents · CPC title

• B29C48/022

  characterised by the choice of material · CPC title