GB2239215A

GB2239215A - Fibre insulating pads

Info

Publication number: GB2239215A
Application number: GB9018743A
Authority: GB
Inventors: Michael Frederick Unwin
Original assignee: VITA FIBRES Ltd
Current assignee: VITA FIBRES Ltd
Priority date: 1988-06-11
Filing date: 1990-08-28
Publication date: 1991-06-26
Also published as: GB9018743D0

Abstract

"An insulating pad comprising a relatively thin base layer of synthetic staple fibres and a relatively thick surface layer of synthetic staple fibres, the fibres including a first component having a first relatively lower "softening point" and a second component having a second relatively higher "softening point" and the fibres being bonded together by the first fibre component."

Description

Title; "Fibre Insulating Pads for Upholstery Units" Description of Invention This invention relates to insulating pads for upholstery units for items of furniture or bedding and particularly, but not exclusively, interior spring upholstery units.

Conventionally, in interior spring upholstery units, an insulating pad of natural fibre, such as coir, has been placed between the springs and the remainder of the upholstery. Insulating pads of natural fibre have a number of disadvantages which include the following.

After a period of use, they wear unevenly and so that fibres become displaced and tend to agglomerate and descend through into the spring unit, this giving an uneven surface and eventually the insulating pad may disintegrate completely. In addition, a natural fibre, e.g. coir, can contain dirt and micro-organisms which are difficult to remove completely and being a natural fibre it can rot due to fungi, mildew and bacterial action and can be eaten by insect life in use.

Further, the price and availability of natural fibres can vary from timeto-time according to the climatic and political conditions prevailing in the country from which the natural fibre is obtained.

In upholstery units not employing interior spring, there is usually a wooden supporting frame and resilient padding material, e.g. foam plastics material provided between the frame and covering materials for the unit.

Over a period of time, the appearance and performance of the unit is liable to deteriorote since, in use, the padding material tends to rub against the wooden frame with consequent degradation of the padding material, particularly when the wooden frame is not provided with a smooth finish as can occur in the manufacture of such units.

There is today a demand for an insulating pad which has good fire resistance properties and in particular which will meet proposed United Kingdom Government legislation on flammability fillings for upholstered furniture.

An object of the invention is to provide an insulating pad for upholstery units for furniture and bedding whereby the above mentioned disadvantages may be reduced or avoided, and which hos good fire resistance properties.

According to one aspect of the invention, we provide an insulating pad comprising a relatively thin base layer of synthetic staple fibres and a relatively thick surface layer of synthetic staple fibres, the fibres including a first component having a first relatively lower "softening point" and a second component having a second relatively higher "softening point" and the fibres being bonded together by the first fibre component.

The first component may comprise one part of each fibre of a first set of fibres, another part of each fibre comprising the second component together with fibres of the second set.

The one part may be an outer sheath which surrounds said other part of the fibres of the first set.

Alternatively, the one part may provide one external surface portion and said other part provide another external surface portion of each fibre of the first set of fibres.

Alternatively, the first component may comprise the whole of each fibre of the first set of fibres and the fibres of the second set of fibres comprising the whole of the second component.

The first set of fibres may comprise 15-50% by weight of the total weight of fibres.

The second set of fibres may comprise fibres of uniform composition.

The fibres of the first set may be of 1-17 decitex and/or 5-120mm long.

The fibres of the second set may be of 10-24 decitex and/or 15-120mm long.

The fibres of the first set may be polyester fibres or polyolefin fibres, such as polypropylene or polyamide fibres such as Nylon, or Chlorofibre such as vinylchloride fibres.

In each case the fibres may be made wholly of such material having said relatively low "softening point" or the fibres may be made partly of said material having said relatively low "softening point" and partly of said material having said relatively high "softening point".

For polyester fibres, the relatively low softening point may be in the range 1000C to 2000C and the relatively high softening point may be in the range 2550C to 2950C.

For polyolefin fibres, the relatively low softening point may be in the range 100 C to 1400C and the relatively high softening point may be in the range 1600C to 1700C.

For polyamide fibres, the relatively low softening point may be in the range 2000C to 2200C and the relatively high softening point may be in the range 240 C to 2600C.

For chlorofibres, the relatively low softening point may be in the range 0 0 52 C to 215 C and the relatively high softening point may be in the range 0 0 245 C to 255 C.

The fibres of the second set may comprise polyester fibres or polyamide fibres such as Nylon. If desired, the fibres of the first set and/or the fibres of the second set may be made of other materials than described hereinbefore so long as the first component of the fibres of the first set has a "softening point" which is sufficiently below the "softening point" of the second component, i.e. the fibres of the second set and the other part of the fibres of the first set where the fibres of the first set are composites.

The bonded pad may have a total weight lying in the range 300-550 g/m2 and a total loft (thickness) lying in the range 8-50mm.

The base layer may have a loft lying in the range 2-9mm and the surface layer may have a loft lying in the range 6-41mm.

The base layer may have a weight lying in the range 40-5% of the total weight of the pad whilst the surface layer may, correspondingly, have a weight lying in the range 35-60SYo of the total weight of the pad.

Where the insulating pad is for an interior spring upholstery unit for furniture or bedding, the base layer is for engagement with the ends of the springs of the unit. When the insulating pad is for an upholstery unit having a supporting frame, the resilient padding and covering material, the base layer is for engagement with the supporting frame between the frame and the resilient padding.

According to another aspect of the invention, we provide a method of making an insulating pad comprising forming a pad having a relatively thin base layer of synthetic staple fibres and a relatively thick surface layer of synthetic staple fibres, the fibres including a first component having a first relatively lower "softening point" and a second component having a second, relatively higher, "softening point", applying heat thereto at a temperature above the first "softening point" and below the second "softening point" to cause the first component to soften and bond together the fibres of the second component.

The method may comprise the step of needling a web of said synthetic staple fibres through only a part of the thickness thereof to form said base layer in the needled portion.

Alternatively, the method may comprise the step of needling a first web of said synthetic staple fibres to form a consolidated base layer and needling a second web of said synthetic staple fibres to form said surface layer and joining together the resultant base layer and surface layer by needling.

The references made above to weight per unit area is the commonly adopted manner in the art of expressing the weight of a piece of insulation pad. It is the weight of a unit area of a layer so that variation in thickness of the layer will only affect the density and not the weight per unit area of the layer. Thus, whilst weight per unit area will not alter when a layer undergoes treatment to alter its thickness it will be apparent that the density will alter.

If desired, the surface layer may be needled as well as the base layer but less heavily.

There will now be described by way of example an embodiment of insulating pad according to the invention and the method for the manufacture thereof.

In this example, the insulating pad is made from synthetic material in the form of staple fibres which if desired may be crimped, and comprises a base layer which, where the insulating pad is used with a spring upholstery unit, is placed on the springs and a surface layer of synthetic staple fibres arranged in a less dense layer to provide a soft finish which will, in use, be below the covering material of the spring upholstery unit. Again, the fibres of the surface layer may be crimped if desired.

In this example, the pad is made from standard polyester fibres, a first set of which comprises 25% of the total fibres by weight and are 4.4 decitex 51 mum long having a standard polyester core of generally cylindrical configuration with a "softening point" of 2400 C surrounded by a low "softening point" polyester sheath having a "softening point" of 11 00C. The sheath has a wall thickness of 0.003mm and the core is of 0.014mm diameter.

The material of the sheath comprises a first component of the web and the material of the core comprises part of a second component of the web.

The remainder of the second component of the web is provided by the fibres of a second set of fibres which comprise 75% of the fibres, by weight, and comprise, in the present example, polyester fibres of 17 decitex and 76mm long having a "softening point" of 2400C.

If desired, the fibres of the first set may comprise 15-50 S by weight of the total fibres and, of course, the fibres of the second set may comprise 8550% by weight of the total fibres respectively.

If desired, the fibres of the second set may alternatively comprise polyamide fibres, such as Nylon fibres and the fibres of the first set may alternatively comprise polyolefine fibres such as polypropylene or polyomide fibres such as Nylon, or chlorofibres.

The fibres of the first set may be of uniform composition or they may be of composite composition, for example the above mentioned cylindrical core and hollow sheath made of materials of the same type but of different "softening point", for example by virtue of being of different molecular weight, or they may comprise components of different geometrical distribution, for example a semi-cylindrical part of one component and a semi-cylindrical part of the second component, or any other desired configuration to provide an external surface portion of said one component and another external surface portion of said second component.

Further alternatively, the fibres of the first set when of composite construction may comprise a first component of one type such as polyester and a second component of another type such as polyolefin.

The fibres of the first set may be of 1-17 decitex and 5-120mm long, whilst the fibres of the second set may be in the range 10-24 decitex and again 15-120mm long.

Staple fibres as described above are formed into a homogeneous blend which is processed through a card in conventional manner to produce a web of 21 g/m2 weight. The web is layered up to form a multi-layered high loft batt approximately 150mm thick and 500 g/m2 weight.

A base layer is then formed by needling the pad from the upper surface at 40 needles per square centimetre to such a depth that the resultant web is 20mm thick. The resultant consolidated base layer is 220 g/m2 and the high loft surface layer is 180 g/m2 weight.

The web is then passed through a gas fired oven heated to a temperature of 1400C. The first component then softens and flows, under its own weight, along the core around which it was disposed as a sheath, to the fibre cross-over points where it accumulates due to surface tension effects and, when the web passes out of the oven and cools down, forms a bond, at a tempetoture lower than about 1 100C at the fibre cross-over points to bond together the fibres of the second component which comprises the cores of the first set of fibres and the fibres of the second set of fibres.

The resultant pad has a weight of 400 g/m2, a total loft of 17mm with a base layer loft of 6mm and an upper layer loft of I Imm. The base layer weight is 55% of the total weight and the surface layer weight is 45% of the total.

If desired, the total weight may lie in the range 300-550 g/m2, the total loft 8-50mm, the base layer loft 2-9mm, the upper layer loft 6-41mm, the base layer weight 40-5% of the total and the surface layer weight correspondingly 35-60% of the total.

Although in this example the pad is made from a single homogeneous batt which is needled through only a part of its thickness, if desired the pad may be made from two separate initial batts. In this case, a first initial web batt is made of the above mentioned homogeneous blend then processed 2 through a card to produce a web 22 9/m2 weight. The web is layered up to form a multi-layered high loft batt approximately 90mm thick and 305 g/m2.

This first web is then needled throughovt its thickness with 40 needles per square centimetre to produce a resultant web 6mm thick and 220 g/m2 weight.

A second web batt is similarly processed through a card from the same homogeneous fibres to produce a web 22 g/m2 weight. The second web is layered up to form a multi-layered high loft batt approximately 70mm thick and 220 g/m2 weight.

The web is lightly needled with 6 needles per square centimetre to 2 produce a relatively high loft surface layer 15mm thick and 180 g/m2 weight.

The needling in all cases intermingles the fibres with some of the fibres being drawn in directions transverse to the general plane of the web by the needles.

To join the two webs together, the consolidated base web is placed on the surface web and is subjected to needling at a penetration of the needles sufficient to pass through the base web and the interface between the webs and into the surface web. This serves to attach the layers together by intermingling of the fibres thereof and, by passing the needles completely through the base web, but only partly into the surface web, the surface web is consolidated further to only a small extent and so retains its "high loft" suitable to form a resilient layer in an upholstery unit.

The base layer, which is of "low loft" is further consolidated, but only to a small extent by the needling to join to two layers together. Thereafter, the needled together webs are passed through an oven to form a bond as described hereinbefore.

If desired, in both embodiments the web may be heated by means other than a gas fired oven, such as infra-red heaters. The time and temperature of heating is such as to ensure that the fibres of the first component are heated to a temperature above their "softening temperature" throughout the thickness of the web.

The insulating pad may be used in interior spring upholstery units such as mattresses and seat bases. However, the insulating pad may also be employed in upholstery units not having interior springs, such units usually having a supporting frame generally of wood, resiliently padded, e.g. foam plastics engaging the frame, and covering material overlying the padding. In such units, the insulating pad may be arranged between the frame and the padding with its base layer engaging the frame in order to protect the padding from deterioration by rubbing contact with the frame during use.

When the insulating pad is employed in an interior spring upholstery unit, the base layer is arranged in engagement with the springs, and the surface layer is located outermost to provide a relatively soft finish. The base layer has superior wearing properties weight for weight as compared with the known insulators employing natural fibres such as coir, copra, jute and sisal.

Further, the base layer, in use, resists the tendency for the springs to tear the layer and resist the effects of rubbing friction between the springs and the layer and also shields the effect of the springs, whereas the surface layer, which is less dense and of higher loft, provides satisfactory finish to the upholstery unit by giving a soft "feel" to the covering surrounding the upholstery unit.

In both embodiments the needles are 4" die-pressed, closed barb guage 38 type needles.

In this specification, the term "softening point" is used to refer to the temperature at which the first component attains sufficient bonding copacity for the fibres of the second component to be bonded together thereby. The temperature at which this occurs varies depending upon the type of fibre and the molecular weight of the polymer and on additions made to the polymer to adjust this temperature. The temperature is sometimes referred to as ti"e "melting point" and sometimes as the "glass transition temperature" and sometimes as the "tack point". When fibres are "crystalline" there is a definite melting point and thus this temperature constitutes the "softening point" as herein defined.Other fibres are amorphous and in this case the molecular orientation produced during manufacture of the fibre is maintained at normal temperatures. When such fibres are heated the molecular orientation is cancelled and the molecules can fake up preferred statistic random positions on reaching a temperature which is referred to as the "glass transition temperature". This is evidenced by shrinkage of the fibres, a tendency to become tacky and the ease of deformation of the fibres.

Generally, the "glass transition temperature", "tack point" and "softening point" are substantially the same.

Generally, the "softening point" is the temperature at which the fibre becomes sufficiently liquid as to flow under its own weight.

The features disclosed in the foregoing description, or the following claims, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, or a class or group of substances or compositions, as appropriate, may, separately or any combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims

CLAIMS:

I. An insulating pad comprising a relatively thin base layer of synthetic staple fibres and a relatively thick surface layer of synthetic staple fibres, the fibres including a first component having a first relatively lower "softening point" and a second component having a second relatively higher "softening point" and the fibres being bonded together by the first fibre component.
2. A pad according to Claim I wherein the first component comprises one part of each fibre of a first set of fibres, another part of each fibre comprising the second component together with fibres of the second set.
3. A pad according to Claim 2 wherein the one part is an outer sheath which surrounds said other part of the fibres of the first set.
4. A pad according to Claim 2 wherein the one part provides one external surface portion and said other part provides another external surface portion of each fibre of the first set of fibres.
5. A pad according to Claim 2 wherein the first component comprises the whole of each fibre of the first set of fibres and the fibres of the second set of fibres comprising the whole of the second component.
6. A pad according to any one of Claims 2 to 5 wherein the first set of fibres comprise 15-50% by weight of the total weight of fibres.
7. A pad according to any one of Claims 2 to 6 wherein the second set of fibres comprise fibres of uniform composition.
8. A pad according to any one of Claims 2 to 7 wherein the fibres of the first set are of 1-17 decitex and/or 5-120mm long.
9. A pad according to any one of Claims 2. to 8 wherein the fibres of the second set are of 10-24 decitex and/or 15-X20mm long.
10, A pad according to any one of Claims 2 to 9 wherein the fibres of the first set are polyester fibres or polyolefin fibres, or polyamide fibres or chlorofibres.
II. A pad according to Claim 10 wherein the fibres are polyester fibres and the relatively low softening point is in the range 1000C to 2000C and the relatively high softening point is in the range 2550C to 295 C.
12. A pad according to Claim 10 wherein the fibres are polyolefin fibres and the relatively low softening point is in the range 1000C to 1400C and the relatively high softening point is in the range 1600C to 1700C.
13. A pad according to Claim 10 wherein the fibres are polyamide fibres and the relatively low softening point is in the range 2000C to 220 0C and the relatively high softening point is in the range 2400C to 260or.
14. A pad according to Claim 10 wherein the fibres are chlorofibres and the relatively low softening point is in the range 520C to 2150C and the relatively high softening point is in the range 2450C to 255 C.
A A pad according to any one of Claims 2 to 14 wherein the fibres of the second set comprise polyester fibres or polyamide fibres.
16. A pad according to any one of the preceding claims wherein the bonded pad has a total weight lying in the range 300-550 g/m2 and a total loft (thickness) lying in the range 8-50mm.
17. A pad according to any one of the preceding claims wherein the base layer has a loft lying in the range 2-9mm and the surface layer has a loft lying in the range 6-41mm.
18. A pad according to any one of the preceding claims wherein the base layer has a weight lying in the range 40-65% of the total weight of the pad whilst the surface layer has a weight lying in the range 35-606 of the total weight of the pad.
19. A pad according to any one of the preceding claims wherein the insulating pad is in an interior spring upholstery unit for furniture or bedding and the base layer is in engagement with the ends of the springs of the unit.
20. A pad according to any one of Claims I to 18 wherein the insulating pad is in an upholstery unit having a supporting frame, resilient padding and covering material and the base layer is in engagement with the supporting frame between the frame and the resilient padding.
21. An insulating pad substantially as hereinbefore described.
22. A method of making an insulating pad comprising forming a pad having a relatively thin base layer of synthetic staple fibres and a relatively thick surface layer of synthetic staple fibres, the fibres including a first component having a first relatively lower "softening point" and a second component having a second, relatively higher, "softening point", applying heat thereto at a temperature above the first "softening point" and below the second "softening point" to cause the first component to soften and bond together the fibres of the second component.
23. A method according to Claim 22 wherein the method comprises the step of needling a web of said synthetic staple fibres through only a part of the thickness thereof to form said base layer in the needled portion.
24. A method according to Claim 22 wherein the method comprises the step of needling a first web of said synthetic staple fibres to form a consolidated base layer and needling a second web of said synthetic staple fibres to form said surface layer and joining together the resultant base layer and surface layer by needling.
25. A method according to any one of Claims 22 to 24 wherein the insulating pad is in accordance with any one of Claims I to 2 1.
26. A method of making an insulating pad substantially as hereinbefore described.
27. Any novel feature or novel combination of features disclosed herein.