CA1083073A - Reinforcement for elastomeric articles - Google Patents

Abstract

ABSTRACT
A reinforcement strip for an elastomeric material article such as belting or hose comprising a multiplicity of mutually parallel substantially untwisted filaments which are impregnated such that substantially every filament is coated by a matrix material providing a peel strength between filaments of at least 3.15 KN/m. The matrix material may be a plastisol e.g. pvc and dry bonding agents are preferably incorporated. Belting and a method of manufacture are included in the invention.

Description

~3~3 This invention relates to reinforcement o~ elastomeric articles and in particular to a strip rein~orcement for use in elongated articles such as belting and hose.
It is known to provide for longitudinal strength in a strip by means of a multiplicity of substantially parallel filaments embedded in elastomer. To provide sufficient strength for the article it has previously been necessary to group the filaments into discrete groups or yarns and to space apart the groups across the sheet.
In the case of belting it is conventional to use reinforcement layers or plies of woven textile fabric the plies being separated by layers of rubber or PVC. The resultant reinforcement structure is of substantial thickness due to the number of plies required but the crimp ln the woven plies allows the absorption of compressive strain in the radially inner reinforcement plies when the belting is passed around end rollers. Thus crimp is essential in such beI~ing but crimp has an unwanted effect on the longitudinal belting modulus as tensile forces cause straightening of the crimped yarns as well as stretching.
The requirements of trànsverse strength and stiffness r are related to the ~ and load support of a belt, these functions are related to the extensibility, weave of the fahrics and number of plies used in the construction of the belt and will vary according to the width of the belt.
Furthermore the transverse stiffness is required to be predictable and consistent to allow satisfactory use of the belting in a troughed configuration.

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~3~73 High modulus belting uses steel cords or cables spaced apart across the width of the belt and extendiny longitudinally of the belt. This construction allows for satisfactory load support and troughing. The cables pro-vide discrete groups of filaments but in belting makedifficulties in the reliable attachmen~ of fasteners.
The applicants have discovered that it is possible to form a useful reinforcement strip without grouping the filaments into discrete groups and one objec~ of the present invention is to provide such a strip.
Another object, specifically relating to belting, is to provide conveyor belting in which the reinforcement strip provides a comparatively thin reinforcement layer which uses the reinforcement material efficiently and allows economic manufacture of belting.
According to one aspect of the present invention a conveyor belt reinforced by a reinforcement strip comprises a multiplicity of closely packed mutually parallel filaments extending in the direction of the length of the conveyor belt, said filaments being arranged in a two-dimensional array and embedded in a matrix of flexible polymeric material which coats and bonds to substantially each individual filament and pro-vides a peel adhesion of at least 3.~5 KN~m when tested according to BS 490: Part 1: 1972, said matrix of flexible polymeric material prior to coating and bonding to said fila-ments having a viscosity less than 20,000 centipoise.
The peel adhesion is tested according to British Standard B.S. 490: Part I: 1972 by means of pulling apart two reinforcement strips. Peeling may occur between the two strips or within either strip and thus is a measure of the peel adhesion of the matrix material.

Preferably the peel adhesion is greater than 5.0 RN/m. ;
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~3~73 PreEerably the matrix material has a tear strenyth greater than 100 N/standard t~st piece when tested accordiny to sxitish Standard B.S. 903 : Part A3: 1972. It should be noted that this tear strength is equivalent to a minimum tensile strength of 10 MN/m2 when tested according to British Standard B.S. 903: Part A2 : 1971 More preferably the tear strength is greater than 130 N/standard test piece which is equivalent to a tensile strength of 12 MN/m2.
Furthermore the matrix material preferably has a modulus greater than 4 MN/m2 when measured at 100% and greater than 8 MN/m2 when measured at 200% the modulus being tested according to British Standard 903: Part A2 : 1971.
More preferably the modulus of the material is greater than 8 MM/m2 at 100% and 12 M~/m2 at 200%.
Preferably the filaments are substantially untwisted filaments.
me ratio between the area of the material and the area of the filaments comprising the reinforcement strip when taken in a transverse cross-sec~ion of the strip is preferably less than 3Ø Furthermore the ratio may in addition be greater than 1Ø
A preferred matrix material is a plastisol having bonding agents incorporated therein. The plastisol may be PVC.
Preferably when ungelled the PVC matrix material has a viscosity before impregnation less than 20,000 centipoise as rk) measured by a Brookfield Viscometer~at 50 r.p.m. with a , No. 7 spindle. A viscosity in the range 3000-6000 centipoise is still more preferable. Such vi~cosities enable e~fective .
:- ' ~ ., . ... , ... .. . . . .. . . .. , -impregnation to be obtainecl. It is known that such viscosities may be achieved in the case of plastisols by increasing the quantity of plasticizer but hitherto such changes have been accompanied by correspondiny reductions in tensile strength and tear strength of the gelled plastisol.
Typical effects are as follows:~
Plasticizer content (pphp) 45 55 65 Viscosity (cP) 52,400 14,100 5600 Tear strength (~/test piece) 205 162 134 Tensile strength (MN/m ) 18.818.1 15.8 Another aspect of the present invention provides a plastisol matrix material for belting having a viscosity suitably reduced by the inclusion of for example between 1 and 5 p.p.h.p. o~ a viscosity depressant and in ad~ition a relatively small proportion of a monomeric plasticizer which can be cross-linked during subsequent heat treatment. Suitable viscosity depressants include alkyl aryl polyethers (such as Triton X 45 Trade Mark o~ Rohm & Haas) and suitable monomeric plasticizers include acrylates or esters of allyl alcohol which may be cross-linked by an included peroxide (such as Dicumyl pero~ide). In preferred plastisols having low viscosity and high ~ensile and tear properties, the total plasticizer level is in the range of 40~70 parts per hundred of polymer, with o-35 parts per hundred of polymer in the form of the monomeric cross-linkable variety.
To provide the bond strength to give the stated peel strengths it is preferred to use bonding agents such as those resin precursors which react to formaldehyde condensation resin.

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Typical precursors are aromatic hydro~y compounds. Preferred bonding agents are resorcinol plus hexamethylene tetramine (E~T). The quantity of resorcinol for nylon filaments is preferably in the range 1.0 - 12.0 pphp though more preferably in the range 3.0 - 9.0 pphp. Suita~le MM~ quantities are 1.0 -8.0 pphp with a preferred range of 1.5 - 5.0 pphp.
Many different filament materials may be used in addition to nylon disclosed above such as for example aliphatic and aromatic polyamides in general including those sold as ~n~ polyesters, polyvinyl derivatives, polyolefin derivatives, rayon, glass and metals and these may be in either ; continuous filament or staple fibre form. The materials are preferably used in the linearly anisotropic form (e.g drawn polyamide filaments). -Since, in accordance with the invention, there are a substantial number of filaments superimposed upon one another in the depth of the reinforcement strip, there is an inherent compliance or cushioning in the strip enabling the filaments to lie ~lat in the impregnated strip. The resultant sub-~ta~tially smooth strip surfaces greatly facilitate belting assembly as it precludes air entrapment.
Yet further aspects of the invention provide belting having covers, i.e. outer surface layers, of extruded spread or calendered PVC belting having PVC/nitrile rubber mix covers and ~elting having rubber and other elastomeric matexial coversO
In the first case the PVC covers are self-bonding to the PVC impregnated reinforcement strip assembly but in the .
~: .. : . . , 33~3 case of rubber covers a priming treatment may i~ nece~sary be used to ensure adequate bonding of the covers.
The invention also includes providing different numbers of reinforcement filaments in the strip reinforcement.
Thus the strip may be of any required longitudinal strength rating. Furthermore, two or more strips may be joined side-by-side either by a butt join or an overlapping edge joint to form different widths of reinforcement for different widths of belting.
More than one reinforcement ply may be utilised and the use of two or more longitudinal reinforcement plies allows belting of high strength to be formed without having to manufacture an excessively thick reinforcement strip. Further- -more, one or more plies of strip reinforcement may be included having the filaments running transversely of the belting to provide for control of the transverse strength and flexibility of the belting. The transverse layers may be perpendicular to the length of the belting or at any angle thereto. Angles in ; the range of 45 to 75 are useiul and in particular 60.
Preferably a ~alanced ~tructure is used with equal numbers of plies biased to either side of the length of the belting.
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Various combinations of layers are included, for example:-(a) one or more layers of longitudinally rein~orced ~ .
~heet having one or more layers of transversely reinforced sheet attached to one side.
tb) two or more layers of longitudinally reinforced sheet are separated from each other by one or more ,.i 7.

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layers of tran~versely reinforced sheet.
(c) one or more longitudinally reinforced ~heets from the centre of the laminate and have one or more transversely reinforced sheets attached to each side.
(d) one or more transversely reinforced sheets form the centre of the laminate and have one or more longitudinally reinforced sheeks attached to each side.
The non-woven thin nature o the textile reinforcement allows for localised addi~ional reinforcement and the placing of reinforcement breakers, stepped plies and reverse stepped plies together with rip stops which were well known in the art when cokton reinforced and mixture bèlting was universally manufactured. Present designs have reduced the need for such constructions bu~ this invention allows, for example, the possibility of the use of stepped plies in a belt construction economically and efficiently to modify the lateral rigidity and hence the flexibility for troughing across the width of a belt.
In order to optimise the belting properties and in ~particular to provide good fastened hold and peel strength the layers may be spaced-apart by means of a thin interlayer.
The interlayer may be of the same material as the covers but is preferably a nitrile rubber compound or more prefera~ly the matrix material. In the latter ca=e the inter- -

2~ layer may be a separate sheet of specially formulated matrix material or may be forme~ integral with the reinforcement strip by means of a high pick-up of makrix material, on one or both ~ ~ side= of the ass=m~led filaments. Conveniently a thickened : :
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matrix layer is formed on one side only such that the strip may be used either way up dependent on the precise require-ments of interlayer or no interlayer between particular layerq of reinforcement strip in a belt.
The invention also provides a method of impregnating or encapsulatiny reinforcement filaments to form a reinforcement strip as described together with a method of assembling belting.
According to another aspect of ~he present invention a method of impregnating a reinforcement strip as described above comprises bringing together the required number of filaments to form a sheet, passing them downwardly through matrix material and the nip of a pair o~ converging coating members and solidifying the strip of material. The solid-i~ication step may be gelling, drying or polymerising dependent on the matrix material shown. The converging coating member is preferably curved and may comprise a pair of cylindrical sections. The impregnated sheet may be taken over a heated roller after ~he converging guides to effect solidificationO
` According to another aspect of the invention an apE~ra~us for impregnating reinforcement strip as described comprises a pair of horizontal, parallel stationery con-verging coating members, end ~eals to form an open-topped trough for matrix material, guide means for guiding the required sheet o~ filaments downwardly between the coating members, means for solidifying the impregnated strip of material and take-up means.

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~ID~3V~3 Further aspects of the invention will ~e made apparent by way of example only f.rom the following description of several embodiments of the invention read in conjunction with the drawings in which:-Figure 1 shows an apparatus for impregnating the reinforcement strip of the present invention;
;~ Figure 2 shows a reinforcement strip having a multiplicity of filaments impregnated with ~ 10 matrix material;
: Figure 3 shows the strip of Figure 2 with an attached layer of elastomer;
Figure 4 is a stepwise section piece of belting comprising outer covers of rubber a central longitudlnally extending reinforcement layer and either side of the longitudinally extending reinforcement layer a layer of transversely extending reinforcement filaments;
Figure 5 shows a transverse reinforcement strip laid.at a bias angle of 60 relative to the longitudinal centre line of the belting.
In a first embodiment of the invention a reinforcement : strip or sheet as shown in Figure 2 was formed by bringing 2S together, at an end spacing of 276 yarns per 100 mm of 94 tex ,~ nylon yarns each comprising 140 filaments. The assembly was ..
encapsulated in the apparatus of Figure 1 with a PVC plastisol ~ . :
formulation 1 of 5600 cP viscosity followed by a gelling stage ~ ::

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at 170C. for 25 seconds which completed penetration through the assembled filamentary structure and hardened the sheet.
(Further details of the encapsulation method and apparatus will be described later).
A second sheet was made in preclsely the same manner using a PVC plastisol formulation 2 without the adhesion promotors.
Peel adhesion of each sheet was then tested according to B.S. 490: Park I: 1972 by measuring the mean force to separate a laminate of two encapsulated filament sheets. The laminate was backed with a rubber cover as shown in Figure 3 and cured for 15 minutes at 160C. to simulate a belt.
The PVC formulations and peel adhesion results are as follows:-Formulation 1 Formulation 2 PVC . 100 100 ., Dioctyl phthalate 65 65 Tribase (T~ofæ ~rk) 5 5 Resorcinol - 5 Hexamethylene tetramine 3 ~ . ~
Peel adhesion (KN/m) 3.4 0-5 The peel adhesion results demonstrate the lmportance of ensuring a high level of fibre/matrix bonding by adding suitabl~ bonding agents to the matrix mix.
A complete conveyor belt of 8 mm thickness was built to standard 315 K~/m strength specification, i.e. required longitudinal strength of 350 K~/m and required transverse , 1 1 .

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~30 73 strength of 130 KN/m. The heltiny is shown i~ Figure 4.
A lonyitudinal reinforcing sheet, 1050 mm wide~ was produced by assembliny 2898 ends of 94 tex nylon tyre yarn (140 filaments per yarn) which therefore provided in total 405~720 filaments of 0.67 tex into a sheet of regular end spaciny and encapsulatiny the assembled filaments with a PVC
plastisol to a level of 300/0 based on yarn weight (i.e. a matrix material to reinforcement ratio of 2.4 based on cross-sectional area.
The following PVC plastisol formulation was used:-Norvinyl P 10 (Trade Mark of the Norsk-Hydro Co.) 100 - Diisoctyl phthalate 45 Diallyl phthalate 10 Dicumyl peroxide Tribasic lead su-lphate ~ 5 Resorcinol 7-5 Hexamethylene tetramine 4 5 ; Triton X 45 (Trade Mark of Rohm & ~aas) 2 The encapsulation treatment was carried out by passing the filaments in a downward direction through the nip of two ~J6(~r;na~h~leno Pro~gy/e~
sta~ionery rollers con~aining ~he plastisol and onto~ coated, internally~heated, rotating rollers for a gelling treatment of 25 seconds at 170 & . (Further details of the encapsulation will be given later).
A transverse reinforcing sheet 1050 mm wide was prepared by assembling 966 ends of 94 tex nylon tyre ya~n (140 filaments per yarn) i.e. a total of 135,240 filaments from 3 yarn beams into a sheet of regular spacing and encapsulating this assembly :~ : ` ,.`
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3~D~73 with the same plastisol formu]ation as above, also to a level o~ 300% o~ yarn weight (i.e. a matrix material to reinforcement ratio in cross-section of 2.~). After sprayiny Chemlo~ 220 (Trade Mar~ of the Hughson chemical Co.) onto the sides with the lower matrix picX up, (i.e. the side in contact with the first heated roller), the transverse sheet was cut into lengths, these were turned through 90, and their Chemlok treated surfaces were rolled against two rubber covers in an abut~ing arrangement to form two layers of transverse reinforcement.
The ~wo rubber covers were 2 mm and 4 mm thick respectively.
In order to optimise interply peel adhesion in the centre of khe belt, two longitudinal reinforcing sheets were assembled with the sides having higher matrix pick-up facing inwards (i.e. the sides furthest from the first gelling roller).
The rubber covers with the transverse reinforcement attached were placed one on either side of the two longitudinal rein-forcing sheets ko form a lamina~e of (cover/l transverse sheet/2 longitudinal sheets/l transverse sheet/cover) assembly which was then cured in a belting press for 15 minutes at 160C.
At the end of the cure cycle, the belt was cooled in the press for 2 minutes and after removal from the press it was trimmed to its final width of 1 metre.
The belt was tested and the results compared with those of conventionally reinforced belting:~

Reinforced Conventional Belt according Fabric ~ ~ - Reinforced Belt Strangth efficiency of helt based on yarn strength (%) 94 78 Peel adhesion according to BS 490 (KN/m) - , . ., , - - . . . - .
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Reinforced Conventional Belt accordiny Fahric to the inventlon ~einforced Belt Ply to Ply 6.25 7.0 cover to ply 12+ 12+

Strength loss after flexing for 50 hours (%) 0 0 Static fastener efficiency based on belt strength (%) (Dunlop Champion fasteners) 64 62 Dynamic fastener performance (hours to fai.lure) 130+ 40-100 ,~, ;rr~u~, h ~ ~fi according to B.S. 490 0.19 0.30 The resultant high strength efficiency of the new belting is due at least in part to the non-woven structure of the fibre-film reinforcement, the high degree of encapsulation, and the high level of fibre matrix bonding.
Furthermore the reinforcement structure or carcase of the belti.ng is thin when compared with conventional textile reinforced belting which allows good longitudinal and trans-verse flexibility and fatigue life by not~subjecting the rein-forcement filaments to any substantial compression. ~-Two further belting examples were made each containing three layers of 1050 mm wide longitudinal rain~orcing sheet, - consisting of 2898 ends of 94 tex nylon tyre yarn (140 filaments per yarn) encapsulated with a PVC plastisol to a level of 250%, and 4 layers of 1050 mm wide transverse reinforcing sheet, each .
; consisting of 1449 ends of 94 tex nylon tyre yarn (140 filaments per yarn) encapsulated with a PVC plastisol to a level of 300%.
Both belts were constructed in the following order: Bottom rubber cover, Chemlok 220 layer, two layers of transverse reinforcing , ' ' ' :, 14.

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shee-t, one layer of longitudinal reinforcing sheet, two layers of trans~erse reinforcing shee-t, two layers o~ longitudinal reinforcing sheat, Chemlok 220 layer, top rubber co~er.
In one belt all -the -transverse layers wexe arranged at 90 to the longitudinal layers, but in -the other belt as shown in Figure 5 the two transverse layers of both sets were arranged at opposite bias angle o~ + 60 to the longitudinal direction~
The test results below show that a biassed weft construction impro~ed the troughing.

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Angle of Transverse O Troughing at Rein~orcement 2L~ C -10C
F/L An~le F~L _ An~le 0O140 40 0.076 26 _ 0.212 52 0O115 36 -The troughing was measured according to BoS D L~go Part I: 1972 and this F/L ratio is a measure o~ the troughing and the angle is the resultant troughing angle wherein L is the width of the belt and F is the distance the centre of the belt sags below the edges, i e the ~all at the centreO (L as tested = 650 mm).
Belting for low temperat~re applications may be made with only slight changes to the P~C matrix material ~ormulationO The changes are to use any of the well-known low temperature plasticizers for example esters of linear acids and linear alcohols eOgO ''PLIA~RACI' 985 (Trade ~lark of Albright & Wilson) which is an ester of saturated C4 - C6 dibasic acids and higher normal alocholsO
Flame resistan-t belting may be made by other modi~ications to the materials used such as for example using a .: .

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phthalate plasticizer or flame resistant additives.
Furthermore the beltiny of the present inven~ion may be of low strength such as is used for food helting and package handling belting. Such light tension applications are met by simple reinforcement structure arrangements (e.g.
one or two longitudinal sheets only) and the PVC matrix material may be used to provide the belt surfaces so that covers need not be used.
Figure 1 shows the apparatus used for impregnating the filaments to form the yarn strip or siheet. A series of beams 1 each carrying a set of yarn ends are moun~ed in a rack so that ~he ends may all be ~aken off in an array 2.
A condensing reed arrangement 3 sets the position of each yarn in the array 2 and the yarns are then formed into two sheets which are passed one over each of a pair of guide rollers 4. The two sheets are brought together, fed through a final spacing reed 5 to assemble the yarns as required in the final strip and are passed into the impregnation head.
The impregnation head comprises a pair of coating members 6 which are ~ rollers~ a pair of side plates 7 and end plates (not shown) to form a trough which is kept full of the matrix material.
The strip or shaet of yarns is drawn downwardly through the trough of matrix material and ~he nip of the coating members 6. On leaving the impregnation head ~he strip is passed over a pair of internally hea~ed gelling rollers 8 which are coated with a non stick surface such as fluorinated ethylene propylene. The strip i5 gelled with the filaments in , 16.

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~L~3~73 the positions set by the spaciny reed 5.
~he strip is taken over a guide xoller 9 throuyh a haul~off unit 10 and to a batch~up 11. ~he haul~off unit draws the yarn strip through the apparatus from the ~eams which are lightly braked to maintain an even filament tension and thus provide uniformity in fibre distribution. The spacing reed 5 and the condenser reed 3 are arranged to space the yarns so ~hat an even filamenk distribution is obtain~d in the strip.
, Uniformity in filament distribution within the impregnated strip is assisted, particularly in the case of reinforcing strip having both a low flbre and a low matrix content, by;the addition of a spreader bar 12 inserted between the coating members 6 and the gelling rollers 8. The spreader bar 12 is held in contact with one side of the strip.
~he free mov~ment of the yarn sheet through the impreynation head causes the matrix material to be forced . into the assembly of filaments thereby excluding air without ; relatively displacing the filaments.
2Q When using higher viscosity matrix materials the level o~ impregnation may be increased by heating the mat~rial in the trough either before putting it in the trough or byO for example, using heated coatlng members. A temperature just below the khreshold set temperature e.g. 45C. is suitable .
for ~VC matrix materials.
The amount of matrix material i5 controlIed by the nip setting of the coating members 6 (i.e. the gap between them).
Typical settings are in the range of 0.1 = 1.0 mm. Such gaps ~ ~ .

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require the use oF knotless yarns or alr spLiced yarns.
~Iowever, knotted yarns may be used if the coatiny members 6 have a resilient surface such as for example nitrile rubber in the region of the nip.
Surface regularity of the impregnated yarn sheet is controlled at the gelling stage. The gelling rollers have a non~stick surface of low porosity such as is obtained by fitting a sleeve of extruded fluorinated ethylene propylene so as not to trap degraded PVC or bonding resin contained in the matrix material. Furthermore the slight ridging caused on the side not in contact with the first gel roller 8 is partly levelled by the second gel roller 8 but may be completely removed by using an additional roller 13 as a levelling roller which contacts the other side of the sheet -immediately after it contacts the first gel roller 8.
As an alterna~ive to the additional levelling roller 13 a saddle may be used which comprises a short non~stick band around two spaced apart end rollers and held in contact with the outer surace of the strip for part of the path around the first gelling roller 8. The s~rlp is thus held between a pair of surfaces, one the roller and the okher end band surface, while initial gelling occurs and th2 resultant strip has very smooth upper and lower surfaces.
Lease bars may be used prior to passing the filaments through the trough to achieve regular distribution of --filaments, when operating from creels at low tension.
Finally the coating members, gelling rollers and filament haul~off tension may be set to form a sheet having , "
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31~3 a thicker layer of matrix material on one side than on the other side.

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Claims (51)

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

1. A conveyor belt reinforced by a reinforcement strip comprising a multiplicity of closely packed mutually parallel filaments extending parallel with the direction of the length of the conveyor belt, said filaments being arranged in a two-dimensional array and embedded in a matrix of flexible polymeric material which coats and bonds to substantially each individual filament and provides a peel adhesion of at least 3.15 KN/m when tested according to BS 490: Part 1: 1972, said matrix of flexible poly-meric material prior to coating and bonding to said filaments having a viscosity less than 20,000 centipoise.

2. A conveyor belt according to Claim 1 wherein the peel adhesion is greater than 5.0 KN/m.

3. A conveyor belt according to Claim 1 wherein the matrix material has a tear strength of at least 100 N/ standard test piece when tested according to British Standard BS 903:
Part A3: 1972.

4. A conveyor belt according to Claim 3 wherein the matrix material has-a tear strength greater than 130 N/ standard test piece.

5. A conveyor belt according to Claim 1 wherein the matrix material has a modulus greater than 4 MN/m2 measured at 100% and greater than 8 MN/m2 measured at 200% when tested according to British Standard BS 903: Part A2: 1971.

6. A conveyor belt according to Claim 5 wherein the matrix material has a modulus greater than 8 MN/m measured at 1005 and greater than 12 MN/m2 measured at 200% when tested.

7. A conveyor belt according to Claim 1 wherein the ratio between the area of the matrix material and the area of the filaments comprising the reinforcement when taken in a trans-verse cross-section of the strip is less than 3Ø

8. A conveyor belt according to Claim 7 wherein the ratio i greater than 1Ø

9. A conveyor belt according to Claim 1 wherein the matrix material is a plastisol having bonding agents incorporated therein.

10. A conveyor belt according to Claim 9 wherein the plastisol is polyvinyl chloride.

11. A conveyor belt according to Claim 10 wherein the matrix material includes nitrile rubber.

12. A conveyor belt according to Claim 9 wherein the bonding agents comprise resin precursors which react to form an aldehyde condensation resin.

13. A conveyor belt according to Claim 12 wherein the resin precursors are an aromatic hydroxy compound and a compound which generates methylene groups in heating.

14. A conveyor belt according to Claim 13 wherein the precursor agents are resorcinol and hexamethylene tetramine.

15. A conveyor belt according to Claim 1 wherein the matrix material immediately prior to impregnating the fila-ments has a viscosity in the range of 3,000 - 6,000 centi-poises.

16. A conveyor belt according to Claim 15 wherein the matrix material is a plastisol having bonding agents incorp-orated therein and viscosity is obtained by including between 1 and 5 parts per hundred parts of a viscosity depressant.

17. A conveyor belt according to Claim 16 wherein the viscosity depressant is an alkyl aryl polyether.

18. A conveyor belt according to Claim 16 wherein a monomeric plasticiser which cross links during heat treatment of the sheet is included.

19. A conveyor belt according to Claim 18 wherein the monomeric cross-linkable plasticiser is an acrylate or ester of allyl alcohol.

20. A conveyor belt according to Claim 9 wherein the total plasticiser content is in the range of 40 70 parts per hundred of polymer and less than 35 parts of the said polymer is in the form of a monomeric cross-linkable variety.

21. A conveyor belt according to Claim 1 wherein the filaments comprise continuous filaments.

22. A conveyor belt according to Claim 1 wherein the filaments comprise staple fibres.

23. A conveyor belt according to Claim 1 wherein the filaments are substantially untwisted.

24. A conveyor belt according to Claim 21 wherein the filament material is drawn.

25. A conveyor belt according to Claim 24 wherein the filaments comprise an aliphatic polyamide.

26. A conveyor belt according to Claim 24 wherein the filaments comprise an aromatic polyamide.

27. A conveyor belt according to Claim 24 wherein the filaments are chosen from the group of reinforcement materials comprising polyesters, polyvinyl derivatives, poly-olefin derivatives, rayon, glass and metals.

28. A conveyor belt according to Claim 27 as dependent on Claim 14 wherein the filaments comprise nylon and the quantities of resorcinol and hexamethylene tetramine are in the ranges 3.0 - 9.0 parts per hundred of polymer and 1.5 -5.0 parts per hundred of polymer respectively.

29. A conveyor belt according to Claim 1 wherein a layer of elastomeric material is attached to one side of the strip.

30. A conveyor belt according to Claim 29 wherein the elastomeric material is rubber.

31. A conveyor belt according to Claim 29 or 30 wherein a primer is used to assist in bonding to the elastomer.

32. A conveyor belt having an embedded reinforcement layer or ply comprising a reinforcement strip according to Claim 1.

33. A conveyor belt according to Claim l wherein the strip is of the same width as the belting.

34. A conveyor belt according to Claim 33 wherein the reinforcement structure comprises two or more strips positioned edge-to-edge and each extending longitudinally of the belting.

35. A conveyor belt according to Claim l comprising two or more longitudinal reinforcing plies.

36. A conveyor belt according to Claim 35 wherein the reinforcing plies are adjacent to one another.

37. A conveyor belt according to Claim 35 wherein the reinforcing plies are separated by an interlayer ply of elastomer.

38. A conveyor belt according to Claim l having in addition to said longitudinally extending ply a transverse ply positioned with the filaments extending transversely of the belt.

39. A conveyor belt according to Claim 38 wherein two or more transverse plies are provided.

40. A conveyor belt according to Claim 39 wherein the transverse plies are spaced apart in the thickness of the belting.

41. A conveyor belt according to Claim 40 wherein the transverse plies are separated by the longitudinal rein-forcement plies.

42. A conveyor belt according to Claim 38 wherein the filaments of a transverse ply are substantially perpendic-ular to the length of the belting.

43. A conveyor belt according to Claim 38 wherein the filaments of a transverse ply subtend angles of between 45 and 75° to the length of the belting.

44. A conveyor belt according to Claim 43 wherein the filaments of a transverse ply are at 60° to the length of the belting.

45. A conveyor belt according to Claim 43 or 44 having two or more transverse plies laid at opposite bias angles to the length of the belting to provide a balanced construction.

46. A conveyor belt according to Claim 1 having an outer cover layer of elastomeric material at one side of the belting.

47. A conveyor belt according to Claim 1 having an outer cover layer at each side of the belting.

48. A conveyor belt according to Claim 46 or 47 wherein the cover material is PVC.

49. A conveyor belt according to Claim 46 or 47 wherein the cover material is natural rubber.

50. A conveyor belt according to Claim 46 or 47 wherein the cover material is polyvinyl chloride and nitrile rubber.

51. A conveyor belt according to Claim 46 or 47 wherein the cover material is nitrile rubber.