GB2087446A

GB2087446A - Improvements in or Relating to Pressed Felts

Info

Publication number: GB2087446A
Application number: GB8036656A
Authority: GB
Original assignee: BURY COOPER WHITEHEAD Ltd
Current assignee: BURY COOPER WHITEHEAD Ltd
Priority date: 1980-11-14
Filing date: 1980-11-14
Publication date: 1982-05-26
Also published as: GB2087446B

Abstract

A method of making a pressed felt is disclosed wherein a batt including animal and heterofibres is formed and the animal fibres felted together mechanically to interlock to form a matrix supporting the heterofibres. The batt can be subsequently heated to cause the heterofibres to interlock to form a second cohesive matrix adding further strength to the felt. The matrices can be intimately interlaced or arranged in discrete layers.

Description

SPECIFICATION Improvements in or Relating to Pressed Felts The invention concerns pressed felts, and has reference to a method of producing a pressed felt and a felt produced by such method.

According to one aspect of the present invention a method producing a pressed felt comprises the steps of forming a batt including animal fibres and heterofibres in adjacent disposition and effecting a mechanical interlocking, by felting, of the animal fibres of the batt to form an animal fibre matrix supporting the heterofibres.

The animal fibres and heterofibres may be provided as an homogeneous blend thereof or may each define a respective web layer or layers within the batt.

Usually the heterofibre will be present in staple form, but continuous heterofilaments may be used in coherent woven or knitted form of in laidin form, if preferred.

According to another feature of the invention the method includes the step of heating the batt to a temperature and for a time sufficient to effect bonding of the heerofibres of the blend to form a matrix defined by the bonded fibres.

The mechanical interlocking of the animal fibres and the bonding of the heterofibres will usually occur sequentially, in the sense of being separate process steps, the felting ordinarily preceding the bonding step. However, it may be found convenient in some circumstances, particularly in the context of a continuous pressed felt production process, for the mechanical interlocking of the animal fibres and the bonding of the heterofibres to take piace simultaneously as separate parts of that continuous process.

By subjecting the pressed felt to pressure during the bonding step, particularly in the case of batts including heterofibres as distinct from continuous heterofilaments, when the bonding step follows the felting, the characteristics of the end product may be varied, an increase in the pressure applied increasing the density of the end product According to a still further feature of the invention, if it is required to produce a pressed felt or pressed felt article or profiled form, the method aforesaid includes the still further step of causing the batt to assume a requisite profile after mechanical interlocking of the animal fibres but before the heating step.

The invention also includes a pressed felt produced by the method aforesaid and including a matrix of mechanically interlocked fibres and/or a matrix of bonded heterofibres.

According to a preferred feature the pressed felt aforesaid comprises a first matrix of felted animal fibres and a second matrix of bonded heterofibres or heterofilamentary material, the first and second matrices being mutually interlaced. The respective matrices may exist in interlaced disposition at one or both surfaces of the fabric, at a position or positions inwardly of the fabric, or throughout the full extent of the fabric in the thickness direction thereof.

It is to be understood, however, that localised heterofibre matrices arranged at spaced locations throughout the felt may be preferred in some instances.

The support given to the heterofibres by either of the matrices during handling is such that the felting and bonding steps can be carried out at widely different locations, and indeed the felt manufacturer can provide an article of commerce by creating one oniy of the matrices, the second matrix being created by the converter.

The invention will now be described further, with reference to several examples, as follows:- Example 1 An engineering felt was produced from a layered batt of wool and heterofibres, the heterofibres comprising a polyethylene sheath and an offset polypropylene core. The face and the back of the batt each comprised 56 to 60's quality wool, whilst the core comprises a blend of 85% and 15% 3-denier heterofibres having a melting point of 1 300C. The batt initially had a weight of 1400 grams/metre2, the face and back layers each contributing one-eighth of the total weight of the batt the batt was hardened in conventional manner and after hardening the pressed felt had a density of 0.1 8 grams/cm3.

After milling to a density of 0.26 grams/cm3 the felt was heat pressed for six minutes at 1 500C to give a thickness of 6mm and a density of 0.30 grams/cm3. The stiffness of the resultant product was in excess of that of a felt of that thickness and density. An increase in the temperature and/or time of the heat pressing step will further increase the stiffness.

The engineering felt produced as aforesaid is of application as a lubrication washer, the wool faces providing a conventional friction surface to moving parts and the core or inside layer receiving and retaining oil for lubrication purposes.

Example 2 A pressed felt capable of receiving a transfer print was produced by bringing together back and facing laps respectively comprising a blend of 50% wool and 50% viscose and a blend of 75% polyester, 15% wool and 10% heterofibres, the heterofibre having a polyester core and a concentric copolymer sheath and a fusing temperature of 1 90at. The wool was of 5660's quality, whilst the viscose, polyester and heterofibres were of 3, 5, and 3 denier, respectively. After hardening the layered structure in a Garside plate in the pressure of steam for one minute, the transfer print paper was applied to the facing and a treatment time of 30 seconds at 1 900C effected bonding of the heterofibres and transfer of the print.

Example 3 A felt was produced having three layers of substantially equal weight, the face being a cross iaid batt and the back being straight-laid. The face comprised a blend of 35% wool and 65% viscose, whilst the back was a blend of 40% wool and 60% synthetic fibres The middle layer consisted of a blend of 40% heterofibres, 40% wool and 20% synthetic fibres.

The multilayered structure was hardened, milled and dyed, and the heterofibres were bonded during drying in a tenter at 1 600C using a positive down draft system. The felt emerging from the tenter was slightly stiffened. The finished weight of the felt was 233 grams/metre2 and its thickness was 1.48mm. The wet shrinkage was 1% when tested in accordance with BS 4060, whilst the steam shrinkage of the felt was found to be 1.4%. Corresponding wet shrinkage and steam shrinkage figures for a conventional equivalent felt of this weight and made from 35% wool/65% synthetic are 10 to 20% and 12 to 22% respectively, the high stability being thought to arise, at least in part, from the combination of cross-laid and straight-laid batts at the respective faces.

Example 4 In producing a hat felt in accordance with the invention a multilayered batt having three layers of equal weight was hardened, milled and dyed, and was then dried at a temperature less than the fusing temperature of the heterofibres. The heterofibres comprised a polyethylene sheath and an offset polypropylene sheath and an offset polypropylene core, the fusing temperature being 1300 C. The face and back layers each comprised a blend of 35% wool/65% synthetic fibres, whilst the middle layer was a blend of 40% heterofibres, 40% wool and 20% synthetic fibres.

In processing the resultant felt, the felt, in sheet form, was steam-heated prior to blocking, and was then blocked for two minutes in a male/female mould set at 1 500C, the stiffened article being removed from the cool mould.

The invention is not restricted to the exact detail of the Examples hereinbefore set forth, since blends, combinations of blends and process parameters appropriate to the intended end product will be selected according to the end product concerned.

Thus, the denier of the various synthetic fibres involved may differ from the denier hereinbefore mentioned in relation to the specific examples, the likely range of denier being from 1 to 1 5 although fibres having a denier outside this range may be of application in specific circumstances.

The wool will ordinarily be of 56's to 70's quality, but again specific applications may require a wool quality outside this range.

Furthermore, this method is believed to be of application to the production of pressed felts, for use in contexts other than those mentioned.

Typically, a fabric produced in accordance with example 1 can be used in the manufacture of wiper blades, the stiffness arising from the heterofibre component providing as adequate rigidity and the soft surface of the wool constituting a suitable wiping surface.

By means of our invention we are able more readily to produce, and indeed reproduce, a psssex 9 ppetim especially as regards stiffness and stability, than has hitherto been possible, and, more importantly, to reduce the proportion of animal fibres necessary in producing that felt. Furthermore, we are able to achieve a requisite level of stiffness in the felt without the extensive milling required in conventional methods.

Claims

1. A method of producing a pressed felt comprising the steps of forming a batt including animal fibres and heterofibres in adjacent disposition and effecting a mechanical interlocking, by felting, of the animal fibres of the batt to form an animal fibre matrix supporting the heterofibres.

2. A method as claimed in claim 1 wherein the animal fibres and heterofibres are provided as an homogeneous blend thereof.

3. A method as claimed in claim 1 wherein the animal fibres and heterofibres each define a respective web layer or layers within the batt.

4. A method as claimed in claim 1,2 or 3 wherein the heterofibres are present in staple form.

5. A method as claimed in claim 1,2 or 3, wherein the heterofibres are in the form of continuous heterofilaments.

6. A method as claimed in claim 5 wherein the heterofilaments are in coherent woven form.

7. A method as claimed in claim 5 wherein the heterofilaments are in coherent knitted form.

8. A method as claimed in claim 5 wherein the heterofilaments are laid-in.

9. A method as claimed in any preceding claim, wherein the method includes the step of heating the batt to a temperature and for a time sufficient to effect bonding of the heterofibres of the blend to form a matrix defined by the bonded fibres.

10. A method as claimed in claim 9, wherein the mechanical interlocking of the animal fibres, and the bonding of the heterofibres occurs sequentially, in the sense of being separate process steps.

11. A method as claimed in claim 10, wherein the felting precedes the bonding step.

12. A method as claimed in claim 9, wherein the mechanical interlocking of the animal fibres and the bonding of the heterofibres takes place - simultaneously.

13. A method as claimed in any preceding claim, wherein the pressed felt is subjected to pressure during the bonding step to vary the characteristics of the end product.

14. A method as claimed in any of claims 1 to 10, wherein to produce a pressed felt or pressed felt articles of profiled form, the batt is caused to assume a requisite profile after mechanical interlocking of the animal fibres but before the heating step.

1 5. A method of producing a pressed felt substantially as hereinbefore described with reference to any one of the examples.

1 6. A pressed felt produced by the method of any preceding claim.

1 7. A pressed felt made by forming a batt including animal fibres and heterofibres in adjacent disposition and effecting a mechanical interlocking, by felting, of the animal fibres of the batt to form an animal fibre matrix supporting the heterofibres.

18. A felt as claimed in claim 17 and comprising a first matrix of felted animal fibres and a second matrix of bonded heterofibres or heterofilamentary material, the first and second matrices being mutually interlaced.

1 9. A felt as claimed in claim 18, wherein the respective matrices exist in interlaced disposition at one or both surfaces of the fabric, at a position or positions inwardly of the fabric, or throughout the full extent of the fabric in the thickness direction thereof.

20. A felt as claimed in claim 18, wherein localised heterofibre matrices are arranged at spaced locations throughout the felt.

21. A felt as claimed in any of claims 17 to 20, wherein the support given to the heterofibres by either of the matrices during handling is such that the felting and bonding steps can be carried out at widely different locations.

22. A pressed felt substantially as hereinbefore described with reference to any of the examples.