GB2247031A

GB2247031A - Reinforcement of tissue

Info

Publication number: GB2247031A
Application number: GB8913479A
Authority: GB
Inventors: Roger Louis Bonafont; David Antony Ballard
Original assignee: RUBEROID BUILDING PRODUCTS LIM; MOY INSULATION Ltd
Current assignee: RUBEROID BUILDING PRODUCTS LIM; MOY INSULATION Ltd
Priority date: 1988-06-13
Filing date: 1989-06-12
Publication date: 1992-02-19
Anticipated expiration: 2009-06-12
Also published as: GB8913479D0; GB2247031B; GB8813972D0

Abstract

A method of reinforcing a tissue product such as glass fibre, by applying discrete curable polymer to fill interstices of the tissue to increase tear resistance of the product.

Description

REINFORCEMENT OF TISSUE The invention relates to a method of reinforcing a tissue, for example of glass fibre, and a tissue reinforced by the method.

Tissues made from a random arrangement of fibres, e.g. glass fibres, polyester fibres, cellulose fibres, often have a tendency to tear, particularly at the edges, reducing the strength of the tissue at the edge and making the tissue vulnerable to tearing across its full width. This can lead to difficulties when the tissue is used in continuous or semi-continuous processes such as coating, printing or laminating because the tissue may tear into two pieces and distrupt the operation. In addition the effectiveness of the tissue as a reinforcement for other materials or components is impaired.

A common method of reinforcing such tissues involves placing or bonding continuous strands or length of fibres on or in the tissue. However, these reinforcing strands can become loose or separated from the tissue they are meant to reinforce, and moreover increase the thickness of the tissue which can of itself be a disadvantage where several layers of tissue are required to be laid up in a confined space.

It is accordingly an object of the invention to seek to mitigate these disadvantages.

According to one aspect of the invention there is provided a method of reinforcing a product comprising a plurality of interwoven fibres, the method comprising providing a flowable curable polymer, and applying the polymer to fill interstices between the fibres.

Using the invention, the tear strength of the product may be enhanced.

The method may comprise applying the curable polymer in one or more strips, strands or bands which may be spaced apart over the product, for example at the longitudinal edges.

Using the method of the invention, the polymer becomes embedded in the product, which may be a glass fibre or similar tissue.

The polymer may be a liquid polymer composition which can be applied to the tissue product for example by extrusion, roller coating or spraying, in a controlled manner to form one or more substantially parallel bands of polymer within the intertices of the tissue.

The band(s) may be applied to the tissue as an integral part of the tissue manufacturing process. Thus when manufacturing glass fibre tissue, the liquid polymer may be applied to the tissue soon after the tissue itself has been initially formed from its constituent fibres by interweaving of same, and after, preferably immediately after, a process step of extraction of excess water from the tissue at a vacuum station of a machine for forming the tissue. Alternatively, the polymer may be supplied to the finished tissue as a separate operation.

The tissue with the applied polymer at its edges may then pass to (or through in a continuous process) a curing oven or ovens, where both tissue and applied, embedded, polymer bands may be simultaneously cured. The cured polymer, effectively encapsulated within the tissue hardens on curing and so reinforces the tissue, particularly at the edges, so increasing edge tear resistance of the formed tissue.

The polymer may be applied as a continuous strip or band near the edge of the tissue. The band may be substantially straight or deliberately wavy.

Alternatively, several bands may be applied close together near the edge of the tissue to improve further the edge tear resistance.

Again, the polymer may be applied as a series of continuous bands applied at intervals, possibly regular intervals, across the full width of the tissue to provide general reinforcement across the whole surface area of the tissue.

The bands can be substantially straight and parallel, or wavy.

In another embodiment, the polymer may be applied as extremely wavy bands across the full width of the tissue, effectively providing random reinforcement, the bands overlapping to provide reinforcement.

In yet another embodiment, the polymer may be applied as discrete spots or blobs to fill the interstices on a matrix, rather than as strips, bands, strands or ribbons.

A wide variety of cured polymers may be used to form the reinforcing bands.

It will be understood that the term 'cured' may be taken to mean a) cooling and hardening of the polymer applied as a hot melt; b) drying and coalescing of the polymer if it is applied as a solution; c) drying and coalescing of the polymer if it is applied as an emulsion or latex; d) drying and effecting a chemical change in the polymer (cross linking).

A variety of kinds of polymer may be suitable for use as reinforcement of the tissue, depending on the type of tissue, method of application, curing conditions and end uses for the tissue. Essential requirements are that the polymer system can penetrate into the interstices of the tissue but not run out of the bottom of the tissue and that the cured polymer has a balance of strength and flexibility and adhesion to the fibres in the tissue which will enable it to improve the tear resistance of the tissue. Also the cured polymer must not be sticky.

Suitable polymers may include: a) acrylic polymer latices, including self cross linking and cross linkable types; b) vinyl acetate-ethylene copolymers either as hot melts or emulsions; c) polyvinyl acetate homo and copolymers, especially in form of emulsions, including non cross linking and cross linking types; d) natural and synthetic rubber latices; e) cross linkable polyurethanes, especially in the form of emulsions; f) polyester polymer emulsions.

These polymers may be used alone or in combinations and in conjunction with other polymers such as urea formaldehyde, melamine formaldehyde, or phenol formaldehyde polymers.

Tissues reinforced by a method embodying the invention are diagramnatically illustrated, by way of example, with reference to the accompanying drawings.

Fig. 1 is a schematic plan view of part of a tissue according to the invention showing a reinforcing strip of polymer applied straight (left as viewed) and wavy (right as viewed) adjacent an edge of the tissue; Fig. 2 is a schematic plan view of part of another tissue according to the invention, there being a plurality of reinforcing strips of tissue adjacent a respective edge, there being three substantially straight strips adjacent the left hand edge (as viewed) and three wavy strips adjacent the right hand edge (as viewed); Fig. 3 shows a schematic plan view of part of another tissue according to the invention, there being a plurality of reinforcing strips of polymer applied on substantially straight or parallel lines across the full width of the tissue; Fig. 4 shows a tissue similar to Fig. 3, with the liner being wavy;; Fig. 5 shows a schematic plan view of a part of a tissue according to the invention with a reinforcement of strips of polymer applied in very wavy lines so separate strips overlap one or more other strips to provide random reinforcement across the whole width of the tissue; Fig. 6 shows a schematic plan view of a part of a tissue having a reinforcement of polymer applied thereto as discrete spots distributed according to a predetermined pattern; and Fig. 7 shows a plan view of a tissue like that of Fig. 3, with a knife cut thereon for use as a tear test.

Referring to the drawings, all show a tissue 1 to which is applied a reinforcement of polymer 2 which is largely held in the interstices in the tissue. This reinforces the tissue and improves its tear strength. In the case of Fig. 7, the tissue is a rectangle of 50 mm X 60 mm, with three substantially parallel strips of polymer adjacent and parallel to one edge. Extending towards them from the mid-point of the opposite edge is a knife cut 3, 35 mm long. The tissue is for use in a tear test. In Figs.

3 and 4 respectively, there is closer spacing of the reinforcement strips adjacent the edges 4, 5 (Fig. 3) or the waves and of a lower amplitude at the edge 5 (Fig. 4).

The invention is shown by the following Examples.

E.LUELE 1 Reinforcing polymer type : Self cross linking acrylic Reinforcement : 2 bands close to each other and near the edge of the tissue Test method : Trapezoidal tear test.

Ten test specimens were cut with the parallel edges in line with the longitudinal reinforcement of the tissue. The test specimens were 7.62 cms wide between the parallel edges and 15.24 cms long on its long edge and 13.97 cms long on its short edge.

The specimen was clamped in the tensometer so that the shorter parallel side was straight and the longer side curved.

Jaw separation rate : 50 mm/min Test temperature : 220C.

Reinforced tissue Unreinforced tissue (1) Maximum tearing 143 92 load (N) (1) (2) (2) Tissue weight 65 55 g/m2 Note: (1) average of 10 individual results.

(2) the difference in weight is due to the reinforcing polymer bands.

The reinforcing resin system consisted of a mixture of PRIMAL E358 self cross linking acrylic emulsion and RHEOVIS CR thickening agent. The PRIMAL E358 is supplied by Rohn & Haas and the RHEOVIS CR by Allied Colloids.

The RHEOVIS CR was diluted with twice its weight of water and the diluted solution added to the PRIMAL E358 in the ratio: PRIMAL E358 : 300 g Diluted RHEOVIS CR : 15 g The ph of the blend was adjusted to 8 by adding ammonia.

E.LMIPLE 2 Reinforcing polymer type : Blend of self cross linking acrylic emulsion, cross linking polyurethane emulsion, cross linking agent and viscosity modifier Reinforcement : 3 bands close to each other and near the edge of the tissue Test method : Trouser tear test.

Eight test samples were cut to the dimensions shown in Fig. 7.

Samples were clamped in a tensometer so that the tissue was torn from the end of the knife cut to the bands of reinforcement and then to the edge of the tissue Cross head speed : 1000 nrn/min.

Test temperature Property Unreinforced Reinforced C tissue tissue (1) (1) Maximum tearing 1.8 4.4 22.5 load (N) Weight (g/m) 66 70 (1) (1) Maximum tearing 1.9 45 140 load (N) Weight (g/m2) 66 70

Note (1) : Mean of eight results.

The reinforcing resin consisted of PRIMAL E358 : 2000 g RHEOVIS CR : 95 g WITtOBOND 740 : 2000 g WITCOBOND 410X : 120 g o. 50 5G A-NNONIA SOLUTION : about 9 ml The hITCOBOND 740 is a cross linking polyurethane resin emulsion.

The WITCOBOND 410X is a cross linking agent for WITCOBOND 740.

Both are supplied by Baxenden Chemical Co. The ammonia is added until the ph is 7.9 to 8.o.

With both resin systems (of Examples 1 and 2) it is important that: a) The viscosity is adjusted until the resin penetrated into the interstices of the tissue but does not 'leak out' of the bottom of the tissue onto the supporting belt nor does it stand above the tissue to any significant amount; b) The resin system is capable of curing under practical conditions to a flexible, tough material which can effect the required improvement in tear strength; c) The resin system cures to a 'dry' non tacky material so that the tissue does not stick together when reeled up; d) The viscosity and cure conditions must be adjusted to achieve the above.

The resin systems were applied to the tissues in the form of narrow bands by extrusion through an appropriate nozzle via air pressure of about 60 psi.

The preferred polyers are self cross linking acrylics and cross linkable polyurethanes capable of forming tough, flexible cured polymers.

It will be understood that the product may be paper, fabric or the like, rather than glass fibre. The polymer may be of a different colour than the fibres, to provide a desired pattern or ornament, and to indicate that reinfrocement is present.

The invention extends, it will be understood, to a product comprising interwoven fibres, whenever made by a process as hereinbefore defined. The reinforced product of the invention may be of a substantially uniform thickness.

Claims

CLAIE

1. A method of reinforcing a product comprising a plurality of interwoven fibres, comprising providing a flowable curable polymer, and applying the polymer to fill interstices between the fibres.

2. A method according to Claim 1, comprising applying the curable polymer in one or more strips, strands or bands.

3. A method according to Claim 2, there being a single strip, strand or band at or adjacent a or each longitudinal edge.

4. A method according to Claim 2, there being a plurality of strips, strands or bands spaced apart on the product.

5. A method according to Claim 4, the strips, strands or bands being at or adjacent a or each longitudinal edge.

6. A method according to any preceding claim, the polymer comprising a liquid polymer which can be applied to the tissue product in a controlled manner to provide the polymer within the intertices of the tissue.

7. A method according to Claim 6, the polymer being applied by extrusion roller coating or spraying.

8. A method according to Claim 6 or Claim 7, the polymer being applied to the tissue as an integral part of the tissue manufacturing process.

9. A method according to Claim 6 or Claim 7 the polymer being supplied to the finished tissue as a separate operation.

10. A method according to Claim 7 or Claim 8, the tissue with the applied polymer passing to (or through in a continuous process) a curing oven or ovens, where both tissue and applied, embedded, polymer can be simultaneously cured.

11. A method according to any of Claims 2 to 10, the polymer being applied as a continuous strip or band which is substantially straight or deliberately wavy.

12. A method according to any of Claims 2 to 11, in which a plurality of bands are applied close together near an edge of the issue.

13. A method according to any of Claims 2 to 11, in which the polymer is applied as a series of continuous bands applied at intervals across the full width of the tissue to provide general reinforcement across the whole surface area of the tissue.

14. A method according to Claim 13, the bands being applied at regular intervals.

15. A method according to Claim 11, the polymer being applied as extremely wavy bands across the full width of the tissue and overlapping to provide reinforcement.

16. A method according to Claim 1, the polymer being applied as discrete spots or blobs to fill the interstices on a matrix.

17. A method according to any preceding claim, the polymer comprising acrylic polymer latices, including self cross linking and cross linkable types.

18. A method according to any of Claims 1 to 16, the polymer comprising vinyl acetate-ethylene copolymers either as hot melts or emulsions.

19. A method according to any of Claims 1 to 16, the polymer comprising polyvinyl acetate homo and copolymers, especially in form of emulsions, including non cross linking and cross linking types.

20. A method according to Claim 19, the polymer comprising natural and synthetic rubber latices.

21. A method according to Claim 19, the polymer comprising cross 1 inkable polyurethanes, especially in the form of emulsions.

22. A method according to Claim 19, the polymer comprising polyester polymer emulsions.

23. A method according to any of Claims 17 to 22, the polymers being used in conjunction zith other polymers such as urea formaldehyde, melamine formaldehyde, or phenol formaldehyde polymers.

24. A method according to Claim 1, substantially as hereinbefore described.

25. A method as shown in Example 1 or Example 2.

26. A method substantially as hereinbefore described with reference to the accompanying drawings.

27. A tissue reinforced by a method according to any preceding claim.

28. A tissue according to Claim 27 comprising glass fibre tissues.

29. A product comprising a plurality of interwoven fibres, with a flowable curable polymer filling interstices between the fibres.

30. A tissue, reinforced as disclosed in Examples 1 and 2.

31. A tissue or product substantially as hereinbefore described with reference to Figs. 1 to 6 of the accompanying drawings.