CA1249189A - Laminate structures - Google Patents

Abstract

Abstract A PVC-impregnated textile fabric carcase, particularly a solid woven conveyor belting fabric, is coated with a normally PVC-incompatible synthetic rubber facing layer such as polychloroprene by means of a fire resistant nitrile rubber adhesive compound, the rubber facing layer incorporating a minor proportion of a disintegrating agent comprising a material compatible with the synthetic rubber, but which on exposure to heating above 100°C causes breakdown of the rubber matrix.

Description

~2~g~85~

IMPROVEMEN~ IN AND RELATI~ TO LAMIMATE STRUCTURES

This invention relates to laminate structures in which one polymeric material i8 employecl to provide a different polymeric material with a surface or surface laysr of desired physical and/or chemical properties. In particular it relates to providing a polyvinylchloride (PVC) - coated eubstrate with a rubber surface layer.
Our copending Canadian patent application No.
451,727 describes a method of providing a pvc-aoated ubstrate with a surface layer of a normally pvc-incompatible rubber by a proaess aomprising applying to the sub6trate a thin layer of uncured, preferably fire resistant nitrile rubber adhesive compound followed by applying a cover layer of uncured, normally pvc-incompatible rubber and thereafter 6ubjecting the resultant la~inate to a curing treatment.
The process is particularly useful ~or making pvc ~onveyor belting having at lea6t one facing layer of synthetic rubber such a8~ a polychloroprene rubber. The belting may be ~olid woven, or plied.
Whil~t the products of~the proces6 ju t described are extremely sati factory in terms of excsllent bond strength betwee~ the layers, certain applications call for compliance with fire resi;stance tests.
One such test i6 the "drum friction test" designed ~
to asse s the~behaviour of a conveyor belt under stalling conditio~s. The test~ which~is described ~n B.S. 3289, ; comprises sub~ecting a stationary Iength of belt to the action of a simulated driving drum which i8 rotated again~t the belt Rurface. High frictional heating : *

,~

.; , .,.,. .. :
..:
:; .
. ~
~. :, ' ,, :~
" ~, ' ::
: :~

~2491~39 results and the test specifie6 amongst other things that a ~atisfactory belt shall not glow, under the test conditions, before it breaks.
Conveyor belting with PVC covers readily passes this test, but this is not the case with rubber covered belting. A solution to the problem has ]been proposed in the U.K. Patent No. 1,310,291 by Fenner and Co. published March 14, 1973 in which a thermoplastic layer is interpo~ed between a pvc-impregnated belting carcase and a nitrile rubber surface layer. Frictional heating under drum friction test conditions melts the thermoplastic interlayer, causing the belt to de-laminate. The nitrile rubber peels off and leaves the pvc-based carcase to break in the usual way, without glowing.
If an elastomeric adhesive interlayer is employed, giving high interlaminar bond strength even at elevated temperatures, using the method of our copending application, then the above described solution to the problem is inapplicable.
~0 According to the present invention a pvo-impregnated textile fabric carcase coated with a normally-pvc incompatible synthetic rubber facing layer by means of a ~fire resistant nitrile rubber adhesive compound includes in said rubber facing layer a minor proportion of a ~ disintegrating agent comprising a material which is compatible with~ the synthetic rubbe~r but which on synthetic rubber but which on exposure to heating above 100-C causes breakdown o~ the rubber matrix. Breakdown ~ preferably takes place below 200 C, well below~the glow temperature of the facing rubber~ Minor proportion"
~preferably means from 1 to 20 parts per 100 parts by weight of the ynthetic rubber, aB otherwise the ~defiirable prQpertias of the latter may be unduly affected by the presence of the disintegrating agent.
Suitable disintegrating~agents include various ~-.~ :

,," " ' ~ :
~ " , ~' ';` ' ~ ' '' ' ,:.
.

- 3 - ~ 9 thermoplastics resins such as chlorinated polyethylene, high styrene resins, ethylene vinyl a~etate copolymers and aromatic hydrocarbon resins.
In assessing suitability it will usually be necsssary to carry out experiments, since the precise amount of disintegrating agent needed for a particular synthetic rubber is not readily predictable.
Preferred synthetio rubbers are the poly~hloroprenes, such as "NEOPRENE" and chlorosulp~onated polyethylenes, such as "HYPALON"*.
It is normally essential to achievs a proper balance between conflicting test specifications for the end product; for example, the product may pass the drum friction test, only to fail other tests described in British Standrd 3289 or to be deficient in other properties such as abrasio~ resistance or coefficient of friction which are critical for satisfactory service.
In order that the invention be better understood an example of it will now be given by way of illu~tration.
Exam~le A cotton/nylon solid woven belting carcase was - impregnated with pvc plastisol using the process of UK
patent No. 2036818. A Q.3mm layer of an uncured fire-resi tant nitrile rubber adhesive compound was applied to each surface of this carcase, by calendering. A 2mm ~hset of uncured polychloroprene rubber ("NEOPRE~E" GRT) was applied to each nitrile~rubber layer prior to consolidating/curing the assembly in a convention beltlng press at 160~C. The polychloroprene rubber was a aonventional carbon blaak reinforced, abrasion resistant compound,~and included material for conferring fire ~resistance. It also included 10 parts (per 100 parts of polychloroprene) by weight of a disintegrating agent, in * TRADEMARK

~,. .

'' ' ~ ",~ ' , ;
: . ~
, : . ,; ' .::
' ~
... . ..
,, :-:; .

: .

_ 4 - 1~4~

this particular case an ethylene vinyl acetate copolymer, sold under the brand ELVAX 360.
The resulting belting exhibited excellent interlaminar adhesion in excess of 6KN per metre width;
it also passed the drum friction and other fire tests carried out to B.S. 3289. In the drum friction text, the synthetic rubber matrix broke down at about 180-C, as a result of the inclusion of the disintegrating agent.
This was followed rapidly by breaXing of the belt, without flame or even glow. This was especially surprising in view of the fact that ELVAX 360 itself burns ~uite readily. It follows that a good disintegrating agent for present purposes may itself be flammable, even where the end product incorporating it must pass a relatively severe fire test.

: : `
.
-.

:: :
: i TRADEM~RK ~ ~ ~

. . .
.. . ..

.. .
,, . :.
.
.

Claims (4)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A pvc-impregnated textile fabric coated with a normally pvc-incompatible synthetic rubber facing layer by means of a nitrile rubber interlayer, wherein. the synthetic rubber includes a minor proportion of a disintegrating agent comprising a material which is compatible with the synthetic rubber but which on exposure to heating above 100°C causes breakdown of the rubber matrix.

2. A fabric according to claim 1 wherein the synthetic rubber facing layer includes from 1 to 20 parts by weight per 100 parts of the rubber polymer of a disintegrating agent compatible with the rubber, but which an exposure to heating in the range 100 to 200 C causes breakdown of the rubber matrix.

3. A fabric according to claim 1 or 2 wherein the synthetic rubber is a polychloroprene and the disintegrating agent is selected from chlorinated polyethylene, high styrene resins, ethylene vinyl acetate copolymers and aromatic hydrocar-bon resins.

4. A fabric according to claim 1 or claim 2 wherein the synthetic rubber is a chlorosulphonated polyethylene.