GB2247689A

GB2247689A - Use of ethylene copolymers for filling metallic filament interstices in wire-reinforced rubber articles

Info

Publication number: GB2247689A
Application number: GB9009141A
Authority: GB
Inventors: Marcel Amandus Steurs; Loon Achiel Josephus Maria Van
Original assignee: Exxon Chemical Patents Inc
Current assignee: ExxonMobil Chemical Patents Inc
Priority date: 1990-04-24
Filing date: 1990-04-24
Publication date: 1992-03-11
Also published as: GB9009141D0

Abstract

The invention discloses the use of a polymer derived from ethylene and an ethylenically unsaturated carboxylic acid in a process comprising filling of interstices between metallic wire strands of a metal wire with a composition containing at least 75 wt% of the polymer and embedding such wire in an elastomer matrix as reinforcement, said polymer containing from 5 to 20 wt% of the ethylenically unsaturated carboxylic acid and having a melt viscosity (mPa.s at 190 DEG C) of from 4000 to 10000 overall together with any polymer additives.

Description

USE OF POLYMER DERIVED FROM ETHYLENE AND ETHYLENICALLY UNSATURATED ACID IN MAKING WIRE REINFORCED RUBBER ARTICLES.

Field of invention The invention relates to the use of certain polymers in making metal cord reinforced rubber articles and to the articles resulting from such use.

Background It is known that the metal reinforcing cords in certain rubber articles such as heavy tires and belts corrode, reducing the useful life of the article. There is therefore a need to avoid or reduce such corrosion, preferably without complicating manufacture and without detracting from other product characteristics.

The adhesion of EAA polymers to metal is well known.

Idemitsu Kosan KK - JP 1065148 A discloses a ethylenic copolymer for the coating of an electrical wire. The polymer itself contains filler but there is no suggestion that it be used to fill cable interstices, nor that it could be applied by simple submersion or function satisfactorily at the interface of an elastomer matrix and a tensile strength imparting reinforcement cord.

US-A-4035211 Western Electric uses EAA to seal overlapping cable sheath edges with the high molecular weight material also serving to ensures that the filling of spaces is enhanced.

Siemens DE-A-2434646 also uses EAA to fill a space between a conducting sheath and a dielectric layer.

Sumitomo JP-55163708 uses a watertight compound between elementary wires of a stranded conductor wire. The compound is a mixture of EVA copolymer and from 3 to 50 low molecular weight polyethylene. The overall melt index is over 300.

The reference does not disclose the use of a material containing at least 75 wt% of a low molecular weight carboxylic acid group containing copolymer.

Summarv of invention The invention provides use of a polymer derived from ethylene and an ethylenically unsaturated carboxylic acid in a process comprising filling of interstices between metallic filaments of a multifilament metal cord with a composition containing at least 75 wt% of the polymer and embedding such cord in an elastomer matrix as reinforcement, said polymer containing from 5 to 20 wt% of the ethylenically unsaturated carboxylic acid and having a melt viscosity (mPa.s at 190 OC) overall together with any polymer additives of from 4000 to 10000.

The melt viscosity used herein is the Brookfield melt viscosity.

Preferably the filling step is performed by submerging the cord in molten polymer and/or the cord treated with polymer is surrounded by an array of non-treated wires. The elastomer may be a rubber, such as EP, EPDM, Butyl or halobutyl rubber.

Advantageously the unsaturated carboxylic acid is acrylic acid or methacrylic acid; the acid is present in an amount of from 8 to 15 wtt. Optionally less than 5 wt% is present of an ethylenically unsaturated ester such as vinyl acetate or methylacrylate. The viscosity may be from 5000 to 8000 mPa.s at 1900C.

The invention also provides a rubber article containing a cord embedded in the article whose interstices between cord filaments are filled with a polymer derived from ethylene and from 5 to 20 wt% of an ethylenicaly unsaturated carboxylic acid and having a melt viscosity (mPa at 1900C) of from 4000 to 10000.

The composition advantageously consists substantially of the polymer and is substantially free of particulate filling materials. The polymer is wax-like in properties.

Tests have shown that the invention permits a substantial proportion of filament formed voids in the cord to be filled by a simple dipping operation. The resulting dipped wires adhere strongly to the polymer.

Examples The polymer types, characterised in Table 1, were compared and tested as shown in Table 2. The samples tested in Table 2 were prepared according to ASTM D1871 at a temperature of 1500C and a pressure of 500 bar but without curing. The block dimensions were 20 X 5 X 1.2 cm. Five cords were mounted per block to provide an average reading.

The tests were performed as stated in Table 2.

It can be seen that adhesion, filling and coverage varies critically with comonomer content and molecular weight.

Examples 5, 7 and 8 showed superior performance.

TABLE 1 : PRODUCTS INVESTIGATED

Example VA-CONTENT AA-CONTENT VISCOSITY MELT INDEX wt % wt % (mPa.s 190 C) 1 12 10 3050 2 16 7 3050 3 16 4,5 3050 4 17 7 3050 5 0 12,5 6300 6 0 5 * 10 (325 g/ 10 min 125 7 0 11 * 13 (2.16 kg 10 min 125 8 0 10 * 14 (2.16 kg 10 min 125 * The melt index indicated correspond to viscosity levels of over 20000. TABLE 2 :RESULTS

Exemple Hardness Pull out Melting Coverage* Coverage * Void * Coverage * Overall No. Shore A Adhesion point outside between Filled internal Rating DIN53505 (N) U1871 PSC R & B filaments flam.

5 88 1682 87 100 5 5 5 5 5 6 88 822 4 5 3 5 4 4 84 403 72 87 1 1 1 1 1 7 95 1428 1 2 2 2 2 3 84 387 79 5 5 3 5 3 1 72 246 68 85 1 2 2 4 2 1 60 321 66 82 1 1 1 1 1 8 89 967 2 3 3 3 3 * 1 = no coverage comparative visual rating, performed AFTER the cord has been 5 = fall coverage pulled out the polyer block where it was embedded.

Claims

1. Use of a polymer derived from ethylene and an ethylenically unsaturated carboxylic acid in a process comprising filling of interstices between metallic wire strands of a metal wire with a composition containing at least 75 wt% of the polymer and embedding such wire in an elastomer matrix as reinforcement, said polymer containing from 5 to 20 wt% of the ethylenically unsaturated carboxylic acid and having a melt viscosity (mPa.s at 190 C) of from 4000 to 10000 overall together with any polymer additives.

2. Use according to claim 1 in which the filling step is performed by submerging the wire in molten polymer and/or wherein the wire treated with polymer is surrounded by an array of non-treated wires and/or wherein the elastomer is a rubber.

3. Use according to claim 1 or claim 2 in which the unsaturated carboxylic acid is acrylic acid or methacrylic acid; the acid is present in an amount of from 8 to 15 wt%; optionally less than 5 wt% is present of an ethylenically unsaturated ester such as vinyl acetate or methyl acrylate ; and/or the viscosity is from 5000 to 8000 mPa.s at 190 OC.

4. A process comprising filling of interstices between metallic wire strands of a metal wire with a composition containing at least 75 wt% of a polymer derived from ethylene and an ethylenically unsaturated carboxylic acid and embedding such wire in an elastomer matrix as reinforcement, said polymer containing from 5 to 20 wt% of the ethylenically unsaturated carboxylic acid and having a melt viscosity (mPa.s at 1900C) of from 4000 to 10000 overall together with any polymer additives.

5. A rubber, metal wire reinforced article containing a wire embedded in the article whose interstices between wire strands are filled with a polymer derived from ethylene and from 5 to 20 wt% of an ethylenically unsaturated carboxylic acid and having a melt viscosity (mPa.s at 190 OC) of from 4000 to 10000.