HK1079557A - Lofty, stretchable thermal insulator - Google Patents

Description

Fluffy and stretchable thermal insulator

Technical Field

The present invention is directed to insulating materials, and particularly to materials that have not only insulating properties but also are stretchable.

Background

A great deal of effort has been tried to produceSynthetic insulating material which is a substitute for natural material. For example, down has long been a precious natural insulating material. There are numerous alternatives. Particularly effective materials as a down alternative are those described in U.S. Pat. No. 4,992,327 entitled "synthetic Down", the disclosure of which is incorporated herein by reference. In this patent document, synthetic fiber insulation material in the form of fiber strands has been disclosed. The bonded fibrous structure comprises a mixture of microfibers and macrofibers of different sizes and different weight percentages. The resulting material has excellent thermal insulation properties and has achieved widespread commercial success. Currently marketed under the trademark Primaloft by Albany International Corp^*The product for sale.

It is desirable that such insulation have additional properties for particular applications. For example, such materials are stretchable, which is desirable for use in, for example, stretchable athletic garments and gloves.

Stretchable fibers are well known and include the Dupont company under the trademark Lycra^*Elastane fibers are sold. Elastic fibers generally provide elasticity in most stretch coats.

Thus, while it is desirable to have a thermal insulation material having the characteristics described in the above-mentioned patent documents, it is desirable that such a material not only be stretchable but also have a bulky nature.

Summary of The Invention

It is therefore a principal object of the present invention to provide a thermal insulation material in the form of a stretchable strip or fabric of fibers.

It is another object of the present invention to provide a bonded insulation material that can utilize existing fiber chemistry to provide stretchability.

It is a further object of the present invention to provide such a material which has excellent insulating properties while being obtainable from synthetic fibres.

It is another object of the present invention to provide a material containing desired microfibers and macrofibers, in addition to fibers that impart stretchability to the batt or web.

It is another object of the present invention to provide a bonded insulation in which the degree of loft is adjustable by the ratio of micro fibers to long fibers.

These and other objects and advantages are achieved by the present invention. In this respect, the invention is directed to insulation having a desired percentage of micro fibers and long fibers. Such fibers are preferably synthetic fibers, but may also be a mixture of synthetic fibers and natural fibers such as cotton or wool. In order to provide stretchability of the material, fibers of the elastane type are blended in the mixture. Spandex fibers include fibers having a spandex core and a binder sheath, and may be used in place of or in conjunction with conventional binder fibers disclosed in the aforementioned patents. The spandex core has a significantly higher melting temperature than the binder sheath. The binder/spandex sheath/core fiber will impart the desired in-plane (in-plane) elastic stretch to the batt or web of insulation material.

The fibers will provide a mechanical bond between the majority of the fibers in the sliver or fabric. The additional bonding required can be achieved by the binder fibers themselves to the extent that the desired stretchability is not compromised.

In addition, if increased loft and maintenance of a high degree of in-plane elastic stretch is desired, this can be achieved by adjusting the amount and properties of the filaments relative to the microfibers.

Drawings

The objects and advantages of the invention will be understood by the description of the invention taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a side cross-sectional view of a stretchable insulation material in the form of a fiber strip that embodies teachings of the present invention;

FIGS. 2A-2E are side cross-sectional views of a fiber having a stretchable core and a coating or sheath formed of a binder material that embodies teachings of the present invention; and

FIG. 3 is a flow chart for making bicomponent fibers that embodies teachings of the present invention.

Detailed description of the preferred embodiments

Referring now to the drawings in particular, FIG. 1 generally shows the insulation of the present invention in the form of a fiber strip or fabric 10. The batt 10 is made of micro and macro fibers, which may be of a form to some extent as described in the aforementioned U.S. patent No. 4,992,327. In this patent, suggestions and examples of fiber diameter/weight percent have been made that can provide products with excellent insulation properties. For example, the insulation material may be 70 to 95 weight percent of spun and drawn synthetic polymeric microfibers having a diameter of 3 to 12 micrometers mixed with 5 to 30 weight percent of synthetic long fibers having a diameter of 12 to 50 micrometers. As discussed in the specification of the present application, the present invention makes adjustments or improvements to such parameters. Furthermore, the insulation material of the present invention can be mixed with the insulation material as disclosed in said patent to obtain a product having stretchability while also providing thermal insulation.

In this regard, as described in the above-mentioned patents, the use of too high a proportion of long fibers will tend to reduce the overall insulation characteristics. However, a problem with a high percentage of microfibers is the mechanical stability of the sliver, especially when wet. Thus, there is a balance; that is, although it is necessary to have a higher percentage of microfibers in order to increase the insulation property, the mechanical stability and recovery property are reduced. Larger diameter fibers increase stability and recovery, but reduce the insulating effect.

Thus, in the present invention, it may be desirable to increase the percentage of long fibers to increase the loft of the batt while increasing the degree of in-plane elastic stretchability. The reason for this is that the long fibres provide the stretchability of the material. The larger the amount of long fibers used, the greater the bulk and the higher the stretchability. This will be a balance of the insulating properties of the material. However, this ratio can be adjusted to achieve the desired effect on loft, insulation and stretchability.

The composition of the bicomponent stretchable binder fiber is described next, in which connection it is convenient to first make some of the description. In general, it is noted that while composite filaments are known (see, for example, U.S. Pat. No. 4,159,618), the fibers of the present invention are intended to have an elastic fiber core. Generally, the minimum denier produced by the spandex manufacturer is about 10 denier. The production of low denier products (less than 20 denier) is not economically attractive using current dry spinning technology.

Traditionally, dry spun spandex is covered with polyester or nylon fibers by mechanically wrapping another fiber around the elongated spandex, or by air wrapping staple fibers around the elongated spandex. Thermoplastic Polyurethane (TPU) has been demonstrated to be melt spun into bicomponent fibers as a core material with a nylon sheath. Commercially available elastic fibers are combined polyurethane-polyureas, and commercial TPUs are nearly 100% polyurethane compositions.

Of the commercially available elastane and TPU melt spun elastane, commercially elastane materials have shown to be the preferred elastomers. The mechanical properties of elastic fibers, elongation, tenacity, hysteresis and set (fiber recovery) are significantly better than TPU. The improved elasticity is due to the addition of a polyurea component which allows better phase separation of the hard and soft segments of the polyurethane molecule, resulting in better recovery and toughness characteristics. During melt spinning, the TPU may be compositionally modified to produce physical property modification effects, such as adding a crosslinking agent to the TPU during melt extrusion. This process technology significantly improves the properties of TPU for use in selected fabric markets.

People are openingSignificant melt spinning operations for fine denier TPU products are disclosed. Albeit with a Lycra of e.g. dupont^*The melt spinning technique of the elastic fiber is not yet mature compared to the conventional dry spinning, but it is desirable because the melt spinning of TPU results in lower investment costs compared to dry spinning.

Commercial sources of elastic fibers in the higher denier range are composed of polyether based materials rather than polyester based materials. The latter has a high compatibility with polyethylene terephthalate (PET). Furthermore, commercial spandex fibers contain a topical silicone finish to facilitate package stability and subsequent fiber processing. This finish is typically removed after the fibers are constructed. Thus, no very good adhesion can be expected without a washing procedure and with the use of tackifiers.

As required for predictable incorporation into insulation forms, very fine spandex can be covered using conventional spandex covering operations as described above, although this approach is not compatible with staple yarn manufacture and processing.

However, one method of achieving the above is bicomponent melt spinning. This process is possible because the melt extruded TPU core meets the elasticity requirements for use in stretchable insulation products. While TPU currently used in commercially melt spun fibers, or TPU modified to optimize mechanical properties, may be used for the elastic core.

Another method of making bicomponent fibers is cable coating. Cable coating is a technique applied in the electronics industry for manufacturing electrical conductors, which involves coating electrical conductors (copper wires) with an insulator (polyethylene). The processing technology is roughly as follows: a) drawing a commercial source of elastic fiber through a cable coating die, b) applying a low melting PET binder to the surface of the elastic fiber as it exits the die, and c) cooling and winding the resulting bicomponent fiber on a spool in a bath.

A similar process is described in U.S. patent No. 4,159,618 to Sokatis, the disclosure of which is incorporated herein by reference. While this patent document relates to high temperature resistant composite filaments that can be used to make woven (woven) and knitted (knit) fabrics for high temperature applications, this technology can be modified and adapted to produce the useful inventive fibers/filaments for thermal insulation materials.

Another method of producing bicomponent fibers is illustrated in fig. 2 a-2E. Bicomponent fibers can be made from a core of spandex embedded into a U-shaped low melting thermoplastic Polyester (PET) filament. In this aspect, a PET filament 20 is extruded with one or more U-shaped channels 22. The PET filaments may have different shapes and sizes, including square, rectangular, oval, or other shapes suitable for the desired purpose. Physically inserted into the U-shaped channel 22 is an elastic fiber core fiber 24. If desired, the bicomponent fibers 26 may then be heat-set (heatset) together to the necessary degree before the bicomponent fibers 26 are blended into the batt from which the insulation is made. This is possible because the melting point of the elastic fiber core 24 is about 450 ° F, while the banyan point of the PET fiber filament 22 is about 230 ° F.

The method described above is described in fig. 3. In this method, block 32 illustrates the step of extruding a low melt polyester (e.g., PET) filament having one or more U-shaped grooves. The next step 34 is to ensure that the filaments are properly positioned (drawn), if necessary. If more than one U-shaped channel is used, the spandex core is inserted (38) into the channel. If there is insufficient load bearing or frictional force to maintain the core in the channel, then, if desired, the bicomponent fibers may be partially heated (40) to create a bond between the spandex and the sheath. The formed fibers can now be collected (42) and, after cutting and rolling etc. (43), finally incorporated into the batt 10 by carding and heat setting, thereby producing a coherent stretchable insulation product.

Despite the mismatch in flexibility between the core and the sheath, a relatively thin sheath may minimize difficulties, which may allow for breaks in the sheath to conform to the greater elongation of the core. Sheath breakage should not affect the quality of the sliver to a detrimental extent.

It is noted that while bicomponent fibers having a spandex core and a binder sheath are effective as components of improved lofty and stretchable insulation, a variety of variations are envisioned. For example, microfibers, macroelastic fibers, binder fibers, and/or blends of fibers in the appropriate proportions as described in U.S. Pat. No. 4,992,327, provide products with desirable properties. Further, while reference is generally made to an elastomeric fiber core in this specification, a TPU core may be used in place of an elastomeric fiber core, or a core of other elastomeric material suitable for the purpose may be used. Furthermore, while the present invention focuses on long fibers having an elastomeric fiber or TPU core, it is envisioned that they may also be applied to microfibers in some respects.

Thus, the objects and advantages of the invention will be realized and attained by the structure particularly pointed out in the written description. Although preferred embodiments have been disclosed and described in the specification, the scope and purpose of the present invention should not be limited by these examples, which should be determined by the claims appended hereto.

Claims (18)

1. A fibrous insulation in the form of a bonded structure comprising in combination:

a fiber having a first composition;

a fiber having a second composition;

at least one of the compositions is elastic; and

means for bonding the fibres together to form a bonded structure which acts as a thermally insulating material and which is simultaneously stretchable.

2. The insulation of claim 1, wherein the material comprises micro fibers and long fibers.

3. The insulation of claim 2, wherein the long fibers are comprised of elastic fibers or TPU.

4. The insulation of claim 3, wherein the long fiber is a bicomponent fiber having a core and a sheath, wherein the core is comprised of spandex or TPU, and the sheath is comprised of a binder.

5. The insulation of claim 1, wherein at least one of the fibers is a long fiber having a core and a sheath, wherein the core is comprised of spandex or TPU, and the sheath is comprised of a binder, wherein the stretchability is provided by the spandex or TPU and the fibers are bonded together by the binder.

6. The insulating material of claim 4, wherein the core is mechanically inserted into and bonded to the sheath.

7. The insulating material of claim 5, wherein the core is mechanically inserted into and bonded to the sheath.

8. A synthetic fiber insulation material in the form of a bonded structure comprising, in combination:

about 70 to 95 weight percent of spun and drawn synthetic polymeric microfibers having a diameter of 3 to 12 microns; and

about 5 to 30 weight percent of synthetic polymeric long fibers having a diameter of 12 to 50 microns in admixture with:

bicomponent fibers having a core and a sheath, wherein the core is comprised of spandex or TPU and the sheath is comprised of an adhesive.

9. The insulation of claim 8, wherein the elastic fibers or TPU provide stretch and the binder binds the fibers together.

10. The insulating material of claim 9, wherein the core is mechanically inserted into and bonded to the sheath.

11. A method of making a bicomponent fiber having stretchability, the method comprising the steps of:

providing a cable coating die device;

providing a material made of spandex or TPU;

drawing the elastic fiber or TPU through a cable coating die;

applying a PET adhesive to the surface of the elastic fiber or TPU as the elastic fiber or TPU exits the die; and coating the resulting bicomponent fiber.

12. A method of manufacturing an insulating material in the form of a bonded structure, the method comprising the steps of:

combining the bicomponent fiber of claim 11 with other fibers to form a fiber strand material.

13. The method of claim 12, including the step of providing said other fibers, wherein said other fibers comprise about 70 to 95 weight percent spun and drawn synthetic polymeric microfibers having a diameter of 3 to 12 microns; and about 5 to 30 weight percent of synthetic polymeric long fibers having a diameter of 12 to 50 microns.

14. A method of making a stretchable bicomponent fiber comprising the steps of:

extruding a low melt polyester filament with a "U" shaped channel extending along the length of the filament;

optionally positioning the extruded filaments;

inserting an elastomeric fiber or TPU core into the "U" shaped channel to produce a bicomponent fiber; and

heating the bicomponent fiber to bond the elastic fiber or TPU core to the filament.

15. A method of making an insulation material in the form of a bonded fibrous structure, the method comprising the steps of:

bicomponent fibers according to claim 14 are combined with other fibers to form a fiber strand material.

16. The method of claim 15, including the step of providing said other fibers, wherein said other fibers comprise about 70 to 95 weight percent spun and drawn synthetic polymeric microfibers having a diameter of 3 to 12 microns; and about 5 to 30 weight percent of synthetic polymeric long fibers having a diameter of 12 to 50 microns.

17. The method of claim 14, comprising the steps of: the TPU core is formed by melt spinning.

18. A method of making a stretchable bicomponent fiber comprising the steps of:

providing a polyester material;

providing a TPU; and

melt spinning the polyester material and the TPU to form the bicomponent fiber.