GB2357091A

GB2357091A - Yarn reinforced product

Info

Publication number: GB2357091A
Application number: GB9928838A
Authority: GB
Inventors: Lieven Vangheluwe; Meyer Willy De
Original assignee: Milliken Europe NV
Current assignee: Milliken Europe NV
Priority date: 1999-12-07
Filing date: 1999-12-07
Publication date: 2001-06-13
Anticipated expiration: 2019-12-07
Also published as: GB2357091A8; GB9928838D0; GB2357091B

Abstract

A yarn reinforced product comprising a body of matrix material (such as a thermoplastic or rubber) and a plurality of elongate twisted yarns applied to or embedded within the matrix material as reinforcement is characterized in that the twisted yarns have consecutive alternating regions of S-twist and Z-twist along the length thereof. The consecutive S-twist and Z-twist regions of the reinforcement yarns are typically interconnected by a transition zone at which the twist direction of the yarn changes, and the yarn plies are typically entangled or intermingled in the transition zone. The matrix may also be a woven or nonwoven textile. Polymeric and inorganic reinforcing yarns are disclosed.

Description

2357091 Yarn Reinforced Product

Field of the invention

This invention relates to a new development in yarns.

Furthermore, the invention relates to the application of these new yarns in the reinforcement of a wide range of products.

In particular, the invention is envisaged as having application in mechanical rubber products such as industrial belting, hoses and tyres and it will be convenient to hereinafter describe the invention with respect to these exemplary applications. It should be appreciated, however, that the invention is not limited to these applications, but that it may also be used in the reinforcement of thermoplastics, thermoplastic elastomers, paper, fabrics, felt and similar non-woven textiles.

Background to the invention

Mechanical rubber products of the type mentioned above are typically formed from natural or synthetic rubber, or a like thermoplastic elastomer, and are reinforced with yarns or cord of textile material. The yarns or cords are applied to and embedded in the rubber matrix of the product in individual strands or as a fabric to reinforce the matrix, increasing its tensile strength and durability. In the case of industrial belting (for example conveyor belts) the cord also assists in giving and maintaining the shape or form of the product.

Textile yarns traditionally used in mechanical rubber applications are comprised of a plurality of plies or threads (e.g. 3-ply) which are twisted together with either a clockwise or counter-clockwise twist. These twist directions will be herein referred to as 'IS-twist" and lIZ-twist11 directions.

2 With traditionally twisted yarns, applying tension to the yarn creates a tendency for it to rotate counter to the twist direction (i.e. to "untwist"). The use of traditional yarns as reinforcement in conveyor belting (particularly in the longitudinal direction of the belt) has therefore been known to cause the belt to curl or to shift position (i.e. "run away") leading to vibration, noise, wear and high maintenance.

In relatively light belting (such as is often used in the food industry and in treadmill belting) where the textile reinforcing cords comprise a larger overall proportion of the belt, it is known to use a combination of both S-twist and Z twist yarns with the direction of cord twist alternating in the cords disposed across the width of the belt. This produces a more uniform construction without the same tendency for the belt to curl or shift, but has the disadvantage of a more complicated manufacturing process requiring two different types of reinforcing cord.

In addition, it is ever sought to develop better yarns having higher modulus of elasticity and higher strength to provide superior reinforced products at an equivalent or lower cost.

The present invention aims to provide such products.

Summarv of the invention A technique has been discovered for fabricating a yarn having a new construction; namely, a yarn in which the plies or threads are twisted together in both the S and Z directions. That is, the new yarn includes consecutively alternating regions of S twist and Z-twist along its length. Adjacent S-twist and Z twist regions are typically interconnected at a transition zone. This new yarn is herein also referred to as "dual twist" yarn.

3i The cord or yarn of the invention may be formed from plies/threads of filament yarns (such as polyester, A, TrI.

polyethylene, polyamide, nylon, viscose rayon, aramid4 glass or 3 carbon), spun yarns or a combination of both spun and filament yarns.

Thus, according to one broad aspect the present invention provides a yarn reinforced product comprising a body of matrix material and a plurality of elongate twisted textile yarns applied thereto or embedded therein as reinforcement, characterised in that said yarns have consecutive alternating regions of S-twist and Z-twist along their length.

In one form of the invention the product matrix material comprises paper. Alternatively, the matrix itself could also be a textile material, either woven or non-woven. For example, the matrix may comprise felt. Furthermore, the matrix body may optionally be formed as a sheet or foil.

In a preferred embodiment, however, the invention provides a product having a matrix comprising any one of PVC, a thermoplastic, a rubber (natural or synthetic) or other thermoplastic elastomer. The matrix material may even be a non thermoplastic polymer.

In one form of the invention each of the yarn twist regions extends a certain distance along the length o the yarn, and the length of each S-twist region is the same as the length of each Z-twist region.

In an alternative and preferred form of the invention, each of the twist regions extends for a certain distance along the length of the yarn and the length of each S-twist region is different from the length of each Z-twist region. In a more preferred embodiment, the length of each of the twist regions varies according to a predetermined pattern or function, for example a sinusoidal function. In another alternative and preferred embodiment, that distance varies in a random manner between a predetermined maximum and minimum, for example by means of a random number generator in the control system of the yarn fabricating apparatus.

4 Each of the consecutive S-twist and Z-twist regions of the reinforcement yarns are preferably interconnected by a transition zone at which the oppositely directed portions of yarn twist meet. The yarn plies/fibres are preferably entangled or intermingled in the transition zones to achieve the transition between twist directions. The size or length of the transition zones is preferably kept as small as possible, being only so long as is necessary to effect a smooth and reliable transition between the twist regions. The transition zone length is preferably substantially constant along the yarn and is desirably only a fraction of the length of the twist regions. For example, the transition zones may be with range of 1 to 10 cm long while each of the twist regions extends in the order of 1 to 2 metre.

The yarn construction, such as the number of plies, yarn count and twist level, can be used to design the mechanical properties (both static and dynamic) of the reinforcement. In addition, the new yarn construction of the invention offers the potential for a large range of possible twists and lengths in the S and Z regions. The mechanical properties of this new yarn construction have been found to be very favourable, with the yarn exhibiting a higher modulus of elasticity and a higher strength yield than traditionally twisted yarns for the same yarn count. The transition zones of entangled or intermingled plies also exhibit reasonable strength and superior modulus to the twisted regions.

While the reinforcement yarns may be disposed or embedded in a product according to the invention in individual strands, it is preferred that the reinforcement yarns are provided in a fabric. The fabric may be laid, woven, braided, knitted or stitched or any combination thereof. Furthermore, the reinforcement yarns having consecutively alternating S-twist and Z-twist regions along their length may be provided as warp yarn and/or bias yarn and/or weft yarn in the fabric.

-5 Although the reinforcement yarns can be produced such that the length of the S-twist and Z-twist regions are equal along of the length of the yarn, it is envisaged that this could create problems by the formation of patterns in fabrics formed from this yarn. In particular, the regular spacing of transition zones may produce an undesirable pattern in the fabric. As stated previously, it is therefore preferred that the yarn for the invention be produced with S-twist and Z-twist regions of varying length, either varying randomly or varying according to some predetermined function.

In another form of the invention the reinforcement yarns are disposed in lengths side-by-side one another (possibly within a fabric) across the width of the reinforced product; for example, across the width of a conveyor belt. The yarns may be arranged so that the adjacent yarn twist regions across the width of the product also consecutively alternate between S twist and Z-twist to provide uniformity in the overall properties and performance of the product.

In a very preferred embodiment, the invention provides a reinforced rubber product such as a conveyor belt. The reinforcement yarns are provided in the form of a fabric material comprising yarn having consecutively' alternating S twist and Z-twist regions along its length in both the warp and weft of the fabric. The higher modulus of the yarn compared with traditionally twisted yarns results in a lower belt elongation and lower belt growth from the use of the yarn in the warp direction. Furthermore, the use of this yarn in the warp reduces the tendency of the belt to "run away" or to curl.

This enables smoother running and can increase the operating life of the belt by reducing damage and/or wear at the edges.

In addition, the use of the dual-twisted yarn in the weft direction produces a more stable belt and consequently lower noise in the running of the belt.

Furthermore, eliminating the need to combine two separate yarn types in the reinforement (e.g. in the creel, bobbins 6 alternate: S-twist yarns and Z-twist yarns) streamlines the manufacturing process, also producing savings.

According to another broad aspect, the present invention provides a method for fabricating a yarn reinforced product including the steps of:

- providing a body of matrix material substantially in the form of said product, and applying thereto or embedding therein as reinforcement a plurality of elongate twisted textile yarns, characterised in that said yarns have consecutively alternating regions of S twist and Z-twist along the length thereof.

In a preferred form of the invention the yarn reinforced product is industrial belting, as discussed previously.

Accordingly, the step of providing the body of matrix material may be carried out using any of the known belting fabrication techniques, such as coating, laminating, coating followed by laminating, calendering, frictioning or spreading.

In a preferred form of the invention the method includes the step of pre-coating or impregnating the reinforcement yarns with a substance to promote adhesion of the yarns to the matrix material. For example, in the case of a reinforced rubber product, this substance may be equivalent or compatible to the rubber or thermoplastic elastomer of the matrix. This coating or impregnation step may be carried out by dipping the yarns in a bath of said adhesion promoting substance prior to their application to the matrix. Indeed, this coating or impregnation step may take place as the dual twist yarn is fabricated. For example, a dipping bath and heater system for drying or curing the dipped yarn may be incorporated between the twisting and final winding/spooling of the yarn production.

In an alternative form of the invention, the reinforcement yarns may undergo a plasma or corona treatment to promote or enhance their adhesion to the matrix material.

7 In a preferred form of the invention the method includes the step of forming the reinforcement yarns into a fabric before being applied to or embedded in the matrix material. The fabric may be laid, woven, knitted, braided or stitched or any combination thereof. Furthermore, the dual-twisted yarn may be disposed in the warp, weft, or both warp and weft and/or bias direction of the reinforcement fabric.

Description of a preferred embodiment

For assistance in arriving at an understanding of the present invention, a yarn reinforced rubber product is hereafter described by way of illustrative example. This example may be read with reference to the preceding description but it is in no way intended to supersede the generality of the preceding description.

As mentioned earlier, a particularly preferred example of the present invention is embodied in a conveyor belt suitable for the food industry. The belt comprises a relatively light weight matrix of polymer material, e.g. PVC, having a plurality of polyester reinforcing yarns (also referred to generally as "cord") embedded therein. The polyester yarns comprise elongate twisted polyester yarns having consecutively Alternating regions of S-twist and Z-twist along the length thereof, with each of the adjacent S-twist and Z-twist regions interconnected at a transition zone. In the transition zone the yarn plies for each of the oppositely directed twist portions are intermingled or entangled. Each of the alternating S-twist and Z-twist regions extends a certain distance along the length of the yarn and that distance varies in a substantially random manner between a predetermined maximum and minimum length. The length of each of the transition zones is substantially constant along the yarn (in the range of 1-10 cm) and constitutes only a fraction of the length of each of the Sand Z-twist regions (1-2 metres). The yarn may be 1100 dtex with 60 turns/meter in each of the S and Z directions.

The reinforcing yarns or cord of the invention are provided in a woven fabric having the dual twist yarn in the warp and with the filling being preferably a monofilament. The yarns may be dipped in a substance to promote adhesion to the PVC matrix of the belt before they are woven into the fabric. Alternatively, however, the complete fabric may be dipped or sprayed to coat or impregnate the reinforcing yarns with the adhesion promoting substance. The fabric is then applied to and embedded in the PVC matrix (using the known techniques for belt production) to produce the reinforced conveyor belt of the invention.

The reinforcing yarns with consecutively alternating S-twist and Z-twist regions exhibit superior yield strength and superior modulus of elasticity compared with a PES 1100/2 dtex yarn with 60 turns/meter in only one of the S or Z directions.

Accordingly, by incorporating these yarns in the warp of the reinforcing fabric, the belt exhibits less growth or slackening in use. Furthermore, the balanced twist direction created by the consecutively alternating S-twist and Z-twist regions provides the belt with a more stable running resulting in less noise and less wear, and a consequently longer lifetime.

Similar benefits are also envisaged for other forms of industrial belting such as heavier duty conveyor belts and transmission belts. In such cases the matrix material would more typically be a natural or synthetic rubber and the yarns would preferably be pre-coated/impregnated with a Resorcinol or Res in- Formal dehyde -Latex (RFL) to promote adhesion thereto.

Furthermore, the reinforcing yarns (i.e. cord) would preferably be provided as a woven fabric in both the warp and weft of the fabric.

In addition, the present invention is also applicable to reinforced rubber hoses such as pneumatic and hydraulic hoses.

The higher modulus and higher strength of the reinforcing yarns would produce a hose having better properties (i.e. higher bursting pressure) from equivalent materials.

9 It will be appreciated that various modifications and/or additions may be made to the construction and arrangement of the parts described with reference to the preceding example without departing from the spirit or ambit of the present invention as defined in the following claims.

8824 1. - 10--- j claim s 1. A yarn reinforced product comprising a body of matrix material and a plurality of elongate twisted yarns applied to or embedded within the matrix material as reinforcement, characterised in that said yarns have consecutive alternating regions of S-twist and Z-twist along the length thereof.

2. A yarn reinforced product as claimed in claim 1, wherein the length of each S-twist region is the same as the length of each Z-twist region.

1-5 3. A yarn reinforced product as claimed in claim 1.

wherein the length of each S-twist region is different from the length of each Z-twist region.

4. A yarn reinforced product as claimed in claim 3, wherein the length of each of the twist regions varies according to a predetermined pattern or function, for example a sinusoidal function.

5. A yarn reinforced product as claimed in claim 3, wherein the length of each twist region varies in a substantially random manner between a predetermined maximum and minimum.

6. A yarn reinforced product as claimed in any one of the preceding claims, wherein each of the consecutive S-twist and Z-twist regions of the reinforcement yarns are interconnected by a transition zone at which the twist direction of the yarn changes.

7. A yarn reinforced product as claimed in claim 6, wherein the yarn plies are entangled or intertmingled in the transition zones.

8. A yarn reinforced product as claimed in claim 6 or 7, wherein the size or length of the transition zones is substantially constant along the yarn and is only a fraction of the length of the twist regions.

9. A yarn reinforced product as claimed in any one of the preceding claims, wherein the reinforcement yarns are provided in a fabric, which fabric may be laid, woven, braided, knitted or stitched or any combination thereof.

10. A yarn reinforced product as claimed in claim 9, wherein the reinforcement cords having consecutively alternating S-twist and Z-twist regions along their length are provided as warp yarn and/or bias yarn and/or weft yarn in the fabric.

11. A yarn reinforced product as claimed in any one of the preceding claims, wherein the reinforcement is formed from filament yarns such as polyester, polyethylene, polyamide, nylon, viscose rayon, arami carbon or glass; spun yarns or a combination of both spun and filament yarns.

12. A yarn reinforced product as claimed in any one of the preceding claims wherein said matrix material comprises a thermoplastic, natural or synthetic rubber or a thermoplastic elastomer.

13. A yarn reinforced product as claimed in any one of the preceding claims wherein said matrix material comprises paper or a woven or non-woven textile.

14. A yarn reinforced product as claimed in any one of the 33 preceding claims wherein said body of matrix material is formed as a sheet or foil.

15. A method for fabricating a yarn reinforced product including the steps of:

providing a body of matrix material in the form of said product, and applying thereto or embedding therein as reinforcement a plurality of elongate twisted yarns, said yarns having consecutively alternating regions of S-twist and Z-twist along the length thereof.

16. A method as claimed in claim 15, further including the step of forming the reinforcement yarns into a fabric before they are applied to or embedded in the matrix material.

17. A method as claimed in claim 16, wherein the yarn fabric is laid, woven, knitted, braided or stitched or any combination thereof, and wherein the dual twisted yarn is disposed in the warp, weft, or both warp and weft of the fabric.

18. A method as claimed in any one of claims 15 to 17, further including the step of pre-coating or pre-impregnating the reinforcements yarns or the fabric with a substance to promote adhesion to the matrix material.

19. A method as claimed in claim 18, wherein the coating or impregnation step is carried out prior to the application of the yarn or fabric to the matrix material.

20. A method as claimed in claim 18 or 19, wherein the coating or impregnation step is carried out by dipping the yarns or the fabric in a bath of said adhesion promoting substance.

21. A method as claimed in claim 20, wherein the coating or impregnation step takes place as the yarn is fabricated and includes heating to dry or cure the dipped yarn.

22. A method as claimed in any one of claims 18 to 20, wherein the adhesion promoting substance is Resorcinol or Resin-Formaldehyde Latex (RPL).

23. A method as claimed in claim 15 or 21, wherein the yarns or the fabric undergo a plasma or corona treatment to promote their adhesion to the matrix material.

24. A method as claimed in any one of claims 15 to 23, Ii wherein the product is industrial belting and wherein the step of providing the body of matrix material in the form of said product includes any one or more of coating, laminating, calendering, frictioning and spreading.

25. A yarn reinforced product as claimed in any one of claims 1 to 14 wherein the product includes a plurality of said yarns arranged side-by-side across a width of the product such that adjacent yarn twist regions consecutively alternate between S-twist and Z-twist across the product width.

26. A method as claimed in any one of claims 15 to 24, further including the step of arranging a plurality of the reinforced yarns side-by-side across a width of the product such that adjacent yarn twist regions consecutively alternate between S-twist and Z-twist across the product width.

8824