GB2121847A

GB2121847A - Adhesive webs and their production

Info

Publication number: GB2121847A
Application number: GB08316189A
Authority: GB
Inventors: Eric Mcpherson Grant; John Edward Walker
Original assignee: Bondina Ltd
Current assignee: Freudenberg Nonwovens Ltd
Priority date: 1982-06-14
Filing date: 1983-06-14
Publication date: 1984-01-04
Also published as: GB8316189D0; GB2121847B

Abstract

A thermally adhesive web comprises substantially parallel fusible filaments thermally bonded to and interconnected by fusible fibres. The filaments generally have a greater diameter than the interconnecting fibres. Preferably the web is formed by extending matter polymer to form the filaments and the fibres and collecting them on a carrier.

Description

SPECIFICATION Adhesive webs and their production There is described in British Patent Specification No. 1,117,751 the production of thermally adhesive webs comprising a tissue of randomly arranged fusible filaments. The webs are useful as thermal adhesives in various textile and interlining applications. They are lightweight webs, typically weighing from 20 to 50 g/m2.

Because the webs are so thin and light they have rather low tensile strength. It is often desired to use the web in the form of a tape but because of the low tensile strength and because of difficulties in handling the tape, especially using high speed mechanical handling apparatus, it is necessary to ensure that the tape is not too narrow, as otherwise it will break during handling. Typicaliy the minimum width is 13 mm or more.

Despite these difficulties the thermally adhesive webs have been widely used and have come to be recognised as important materials.

A thermally adhesive web according to the invention comprises substantially parallel fusible filaments thermally bonded to and interconnected by fusible fibres.

The interconnecting fusible fibres are preferably provided in the form of a tissue of randomly arranged fusible fibres that are fused to each other. The interconnecting fibres preferably are filaments, i.e. substantially endless fibres. The diameter of the fibres may be within the ranges that are generally encountered in products of the type described in British Patent Specification No.

1,117,751 'for instance 0.005 to 0.02 mm.

The substantially parallel filaments that are interconnected by the randomly arranged filaments or other interconnecting fibres are preferably arranged in substantially rectilinear fashion. As a result it is possible to cut the web in the form of a tape with the parallel filaments extending along the length of the tape. Although the tape can be of conventional width (13 to 50 mum or more) an advantage of the invention is that the tape can be narrower than has previously been satisfactory, without increase in fibre weight Thus the tape can easily be less than 13 mm in width, for instance 4 to 1 3 cm and preferably is 5 or 6 mm in width.

The total weight of the web can be similar to the total weight of conventional thermally adhesive webs, generally about 10 g/m2 but below 80 g/m2, preferably 20 to 50 g/m2. The web is generally a highly porous net work consisting only of the fusible parallel filaments and the fusible interconnecting filaments or other fibres.

The parallel filaments generally provide from 20 to 80% of the web weight, with the interconnecting filaments or other fibres providing the remaining 80 to 20% by weight. For most purposes the parallel filaments provide 30 to 70% by weight. Webs formed of from 30 to 50% by weight parallel filaments and 70 to 50% by weight interconnecting filaments or other fibres are generally preferred for most textile and interlining applications but for uses where maximum permeability and/or maximum longitudinal strength are required webs containing from 70 to 80% by weight of the parallel filaments may be preferred.

The parallel filaments generally have a diameter that is substantially greater than the diameter of the interconnecting filaments or other fibres, for example being 5 to 15 times and generally about 10 times the diameter of those filaments. Typically the diameter of the parallel filaments is between 0.05 and 0.2 mm. The parallel filaments may be provided by individual monofilaments or by groups of filaments in contact with one another. The spacing between adjacent parallel filaments is generally from 0.5 to 5 mm with best results generally being obtained with spacings of 1 to 3 mm, preferably about 2 mm. It is generally desired that the spacing between filaments should be substantially uniform and constant but some variations may occur during manufacture and are tolerable.If the web is to be cut into a tape it is necessary that the tape shouid contain a plurality of the parallel filaments. For instance if the tape is 6 mm wide the filaments must not be more than 2 or 3 mm apart, so as to ensure that the tape contains at least 2 or 3 of the filaments.

The filaments and the interconnecting fibres may be of the same or different polymeric materials. The polymeric materials will generally have a melting point below 1500 C, generally 80 to 1200 C. Any convenient, low melting, fibre forming polymeric material may be used, including especially those that are widely used for forming fusible fibre webs. Examples are various polyolefins, polyurethanes, polyesters and polyamides, including especially co-, ter- or higher-polymers of polyamides, for instance a terpolymer of nylon 6, 66 and 12.

The web is generally suppiied to the user unsupported, for instance as a reel, but if desired may be supplied to the user while supported on a release paper.

The web may be made by depositing parallel filaments onto a preformed tissue, for example supported on a carrier, and fusing the filaments to the tissue. Preferably however the web is made in a single process by collecting onto a carrier parallel filaments and a tissue or other interconnecting filaments and fusing the parallel filaments and interconnecting fibres. Preferably the fusion occurs during collection as a result of the parallel filaments or the interconnecting fibres being in the fully molten or partially molten state at the time of contact.The tissue may be made by extruding filaments from first orifices, stretching them while molten and collecting them in random arrangement on a carrier while partially or fully molten, and, before cr after forming the tissue on the carrier, the parallel filaments are deposited on the carrier by extruding molten polymeric material from second orifices and collecting this as parallel filaments on the carrier. The stretching of the polymeric material from the first orifices is preferably effected by the reaction of gas streams emerging from apertures close to the first orifices.

These orifices are preferably arranged in a straight row, as described in British Patent Specification No. 1,117,751. The row of orifices can be reciprocated during extrusion but this is generally unnecessary. The carrier onto which the tissue is collected is normally 8 to 25, most usually around 15, cm below the extrusion orifices. The filaments are deposited on the carrier in a substantially random manner, generally while they are still partially fused but after they have been drawn substantially while as individual filaments by the gas streams.

The parallel filaments are laid on the carrier or the tissue and preferably this is achieved by extruding the filaments direct onto the carrier or tissue. Preferably the filaments or the tissue are still partially fused when they contact one another but if necessary the web may be heated in order to improve thermal bonding of the parallel filaments to the tissue.

The extrusion of the parallel filaments onto the carrier or tissue is preferably conducted by extrusion through a straight row of orifices positioned close to the carrier, the orifices typically being from 0.5 to 3, and preferably about 1, cm above the carrier. The orifices can be single orifices or they can be provided in the form of groups, for instance as described in British Patent Specification No. 1,178,438. Preferably the carrier is drawn away from the orifices at a speed faster than the speed of the filaments as they approach the carrier, with the result that the filaments are stretched upon contact with the carrier and they maintain their parallel configuration.If desired the filaments may additionally be stretched by gas streams emerging close to the extrusion orifices, but these gas streams must not be such as to create so much turbulence adjacent the carrier that the parallel configuration of the filaments is destroyed.

The thermally adhesive webs of the invention have improved tensile strength compared to the conventional webs, free of the parallel fusible filaments. It is therefore possible to produce a web of the same fibre weight but having improved tensile strength or it is possible to reduce the fibre weight and maintain the tensile strength, compared to known webs. The webs can be cut as narrower tapes and can be unwound from reels at faster speeds than has previously been permissible.

Air permeability is improved and so either the same degree of permeability can be achieved with a higher fibre weight or the fibre weight can be maintained constant and the air permeability improved.

The foliowing are examples of the invention.

EXAMPLE 1 A thermally adhesive web is formed weighing 40 g/m2 and formed of 20 g/m2 parallel filaments and 20 g/m2 interconnecting filaments, all the filaments being formed of a terpolymer of nylon 6, 66 and 12. The parallel filaments are spaced 2 mm apart.

The web is made using apparatus similar to that described in British Patent Specification No.

1,117,751 except that 2 linear spinnerets are used and the web is not heated sufficiently to destroy the filamentary structure.

In particular, the terpolymer is extruded through a row of orifices 2 mm apart onto a carrier positioned about 1 cm below the orifices and is stretched by being drawn away by the carrier upon impact.

The tissue is formed over the parallel filaments by extrusion through a second linear spinneret positioned about 1 5 cm above the carrier, the filaments being stretched by air streams emerging from slots close to and parallel to the row of orifices. The filaments are still partially fused upon impact with the carrier and the continuous filaments and are collected randomly on the carrier. The web may then be heated and pressed sufficient to improve the thermal bonding of the parallel filaments to the tissue.

The resultant web may then be stripped from the carrier and wound onto reels, and may be split into tape 6 mm wide either before or after the winding.

EXAMPLE 2 The process of Example 1 is repeated except that the order of extrusion is reversed. Thus the tissue is formed on the carrier and the parallel filaments are extruded onto that.

The described method of depositing the tissue and the reinforcing filaments by extrusion through first and second orifices may also be applied to the production of other non-woven products by appropriate choice of polymeric materials.

Claims

1. A thermally adhesive web comprising substantially parallel fusible filaments bonded to and interconnected by fusible fibres.

2. A web according to claim 1 in which the interconnecting fibres are randomly arranged.

3. A web according to claim 1 or claim 2 in which the parallel filaments are spaced apart and are arranged substantially rectilinearly in the web.

4. A web according to claim 3 in which the parallel filaments are 1 to 3 mm apart.

5. A web according to claim 3 or claim 4 in the form of a tape having the parallel filaments arranged substantially in the length direction and containing at least 2 of the parallel filaments across its width.

6. A web according to claim 5 in which the tape is from 4 to 13 mm wide.

7. A web according to any preceding claim having a fibre weight of 20 to 50 g/m2.

8. A web according to any preceding claim in which the parallel filaments provide from 30 to 50% by weight of the web.

9. A web according to any preceding claim in which the parallel filaments have a diameter at least 5 times the diameter of the interconnecting fibres.

10. A web according to any preceding claim substantially as herein described with reference to the examples.

11. A method of making a product according to any preceding claim comprising forming a tissue of the interconnecting fusible fibres on a carrier by extruding molten polymeric material through first orifices, stretching the material while molten and collecting the resultant filaments in a random arrangement on the carrier while partially or fully molten and, before or after forming the tissue on the carrier, depositing the parallel filaments on the carrier by extruding molten polymeric material from second orifices and collecting this material as parallel filaments on the carrier.

12. A method of making a non-woven product comprising a tissue of interconnected fibres fused to one another and to substantially parallel reinforcing filaments, the method comprising forming a tissue of the interconnecting fusible fibres on a carrier by extruding molten polymeric material through first orifices, stretching the material while molten and collecting the resultant filaments in a random arrangement on the carrier while partially or fully molten and, before or after forming the tissue on the carrier, depositing the parallel filaments on the carrier by extruding molten polymeric material from second orifices and collecting this material as parallel filaments on the carrier.

13. A method according to claim 11 or claim 1 2 in which the polymeric material from the second orifices is stretched and laid as parallel filaments by drawing the carrier away from the second orifices at a speed greater than the speed at which the filaments approach the carrier.

14. A method according to any claims 11 to 13 in which the polymeric material from the first orifices is stretched by gas streams emerging from apertures close to the orifices.

1 5. A method according to any of claims 11 to 1 4 in which the first and second orifices are arranged in rows extending across the carrier.

16. A method according to any of claims 11 to 1 5 in which the first orifices are positioned 8 to 25 cm above the carrier and the second orifices are positioned 0.5 to 3 cm above the carrier.

17. A method according to claim 11 or claim 1 2 substantially as herein described with reference to either of the examples.