EP0038887B1

EP0038887B1 - Thermally insulating bulky product and method for its manufacture

Info

Publication number: EP0038887B1
Application number: EP80301385A
Authority: EP
Inventors: Tadakazu Endoh; Hirotsugu Suzuki; Masanori Takahashi
Original assignee: Toray Industries Inc
Current assignee: Toray Industries Inc
Priority date: 1980-04-28
Filing date: 1980-04-28
Publication date: 1984-09-26
Also published as: ATE9602T1; DE3069261D1; EP0038887A1

Abstract

A thermally insulating nonwoven bulky product is made up of substantially continuous single filaments of between 0.01 to 2 deniers stabilized in the product by a surface binder on the filaments. The bulky product may be made from multi-filament polyester (2) direct from the spinneret by passing it in a high speed air current through a nozzle (3) and against a surface (4) where it is broken into single filaments (8) which pass through a mist of binder emulsion ejected from a spraying nozzle (5) and so are deposited on a support conveyor (6). The speed of the conveyor (6) is adjusted so that the filaments settle in folds giving a pile of substantial thickness which is then dried and heat set under heated elements (7). The product, which may well have a bulkiness between 50 and 550 ml/g, can be used for filling articles such as duvets, sleeping bags, anoraks, and the like, and has a thermal insulation comparable to that of down.

Description

The present invention relates to fibrous non- woven materials for stuffing and, more particularly, to light weight, resilient and bulky materials suitable for thermal insulation.
Down and feathers have been well known to have good properties as stuffing for articles, such as eiderdowns, sleeping bags, jackets and the like. However, they are very expensive on account of their short supply, and require considerable care so that they may not undergo damage by insects or microbes. They also have inherent drawbacks, e.g. the necessity of quilting to avoid uneven distribution in stuffed articles and of using expensive closely woven or specially finished fabrics to avoid their leakage through the casing fabrics.
Natural or synthetic discontinuous crimped fibres have also been used as stuffing in the form of wadding or a lap. These fibres however, are inferior to down and feathers in their thermal insulation properties, necessitating the use of heavier stuffed articles to assure comparable thermal insulation. They also have an undesirable tendency, after long use, to protrude through the enveloping material, and to agglomerate and lose their original bulkiness or to disassociate because of irreversible movement resulting from their crimp or surface scale.
It has been found that addition of bonding resin to bond the staple fibres at their cross-over points in the wadding or lap produces improved support for the bulk material and prevents the fibres from migrating. Therefore, it is commercial practice today to cross-lap webs and spread resin on the surface of the layered structure. It has also been recognized that too much bonding causes the web to lose softness.
There has been proposed a stuffing material constituted by a highly corrugated web of continuous filaments, directed substantially in the same direction and wherein the undulations are fixed with the aid of an appropriate resin. The typical method for the preparation of such webs consisted in passing a tow of continuous filaments between two rollers driven at different peripheral velocities, taking up the corrugated web thus formed, spraying a bonding agent on the said undulating lap and, finally, curing the bonding agent thus deposited. The stuffing materials thus obtained retain the original alignment of filaments even though effort has been made to bring about a bulky form by the corrugation, and the anisotropy sometimes results in undesirable performance when in use, e.g. contraction in the direction perpendicular to the alignment of the filaments or breakage along the alignment direction, which results in an insufficient thermal insulation property.
Although many proposals have been made to provide stuffing material intended to solve the above-mentioned defects of staple fibres or tow and to simulate the good property of down, the ideal stuffing material which shall be equal or superior to natural down in its property for heat insulation has not been invented up to the time of making the present invention.
The thermally insulating bulky product of the present invention is made up of a multiplicity of substantially continuous fine, single synthetic filaments stabilized in the product by a surface binder on the filaments and is characterized in that the filaments have an average denier of from 0.01 to 2 (0.011 to 2.2 dtex) the surface binder is at least one synthetic thermoplastic resin whose softening temperature is less than that of the filaments and is present in an amount of from 0.5% to 20% by weight of the filaments, and the product has a specific volume of not less than 40 ml/g.
It should be especially noticed that the substantially continuous filament which may be derived from multifilament is incorporated in the bulky product as a single filament to provide as uniform a distribution as possible of minute spaces between the neighbouring single filaments. It is also important to provide bulky accumulation of the single filaments. Compacted bundles of multi-filament and interlaced fibres should be minimized as far as possible.
A preferred process for making a bulky product according to the present invention comprises the successive steps of

(a) melt spinning the filaments of synthetic polymer,
(b) leading the spun filaments together with compressed air through a nozzle,
(c) crimping and separating the filaments by impinging against a plane,
(d) spraying the crimped and separated filaments with the binder,
(e) spreading out and accumulating the separated filaments into a bulky accumulation,
(f) heating the bulky accumulation of filaments to the final product.

Random crimp in each filament helps to avoid the above-mentioned unfavourable bundling in the accumulated product because the crimp makes filaments tend not to stick together.
Regular crimp such as can be induced by false twisting for example, is however, not desirable because the separation of multi-filaments into individual filaments becomes difficult and because there is a possibility of the filaments sticking together in use, resulting in reduction of bulkiness and of ability of heat insulation. Interlacing or twisting in the multi-filament state should also be avoided for the same reason mentioned above. Filaments in the bulky product of the present invention should preferably have random crimp with uneven form and number of crimps between filaments; this contributes to bring about a stable quality in the thermal insulation over long use because unfavourable agglomeration and loss of the bulkiness can be considerably reduced.
The average percentage crimp should not be too large in order that the unfavourable agglomeration of the filaments may not occur, and it should also not be too small in order that sufficient bulkiness may be secured in use. It should be in the range of 1 to 20 percent, and preferably from 2 to 10 percent.
The percentage crimp of the filament is here defined by the equation:
where 1 is a distance between arbitrarily chosen points in the filament measured under a load of 2 mg/d (2.2 mg/dtex), and 1₁ is the distance between the same points measured under a load of 300 mg/d (330 mg/dtex).
The average fineness of the single filament should be in the range of 0.01 to 2 deniers (0.01 to 2.2 dtex), and preferably from 0.1 to 1 dernier (0.11 to 1.1 dtex). Each filament may be either uniform or have varying denier along its length. Mixing of filaments of different deniers can sometimes be desirable. In any case, too great a thickness of the filament beyond the above-mentioned upper limit should not be used because the intended good thermal insulation property cannot be established, and the softness or drapability of the accumulated product becomes insufficient. On the other hand, use of filaments of a fineness below the above-mentioned lower limit should also be avoided because the intended stable resilient bulkiness of the present invention cannot be brought about.
For industrial production, the filament may be derived from multi-filament having a total denier not less than 10 (11 dtex), and preferably in the range of 30 to 3000 (33 to 3300 dtex).
Synthetic polymers to constitute the filament of the present invention may be any known fibre-forming polymers such as polyesters and polyamides, for example poly-(butylene terephthalate), and preferably poly-(ethylene terephthalate) and its copolymers containing not less than 85% repeating units of ethylene terephthalate. The remaining repeating units which can be copolymerised are preferably those of butylene terephthalate, butylene isophthalate and ethylene isophthalate.
The filaments comprising the accumulated product of the present invention have binder on their surface. This contributes to bind filaments at their cross-over points in the accumulated product and to stabilise the bulkiness and to prevent the filaments from migrating. The binder should not be sticky in the final state of the accumulated product even though it it sticky at an intermediate state to bind the filaments at their cross-over points. Thermoplastic polymers with melting or softening points below that of the filaments are suitable for this purpose. Polyvinylalcohol and polyacrylic esters (which can be used in the form of an emulsion) are the best selection. The emulsified binders should be deposited on the filament as minute particles of mist before the accumulation of the filament so that uniform distribution of the binder in the accumulated product may be established.
The amount of the binder in the accumulated product lies in the range of 0.5 to 20 percent, preferably from 2 to 10 percent. Too much binder should not be used because the softness or drapability of the accumulated product is considerably reduced and accordingly the thermal insulation property also decreases. On the other hand, too little binder can fail to bind the necessary amount of cross-over points, resulting in decrease of the stability of the bulkiness in long use.
If the binder is used as an aqueous emulsion, its molecular weight should not be too large so that stable and minute particles of mist can be obtained from the predetermined concentration of the binder in the water.
. In case of polyvinylalcohol, the average molecular weight should be in the range of 100 to 10,000, preferably from 200 to 2000, and its extent of saponification should be greater than 98 percent.
The accumulated product of the present invention has a specific volume of not less than 40 ml/g, and preferably from 50 to 500 ml/g when measured under a load of 0.125 g/cm² (12.3 N/_M ²). Such a high bulkiness can be obtained by the accumulation on a suitable conveyor of filaments which already have the binder on their surface, and heat setting the bulky form by suitable means as exemplified later. The accumulated product of the present invention can thus exhibit stability of bulkiness even under repeated compression and decompression or repeated shearing and relaxing. The specific volume which is used to designate the bulkiness of the accumulated product is defined here by the following equation:
where A is the weight in grams of a sample whose length and width as 20 cm and 20 cm, respectively; and h is the average height in cms of the sample measured under a load of 0.125 g/cm² (12.3 N/m²). The specific volume, as here defined, should be discriminated from the apparent specific volume, later referred to, this being obtained by calculation without the load above-mentioned.
The manner in which the filaments are laid down in order to form the accumulated product can be varied, provided that the bulkiness and drapability of the present invention are manifested. Preferably, the filaments should be repeatedly folded at both surfaces of the accumulation, and remain in overlapping layers in a loose or relaxed state.
The accumulated product of the present invention can additionally be modified later by using a binder which may be the same as or different from the binder already used for the accumulation. Especially, surface treatment of the product with binders is sometimes desirable so that the product does not protrude through casing fabrics.
In the accompanying drawings:

Fig. 1 schematically illustrates a method for the manufacture of a non-woven bulky product according to the invention; and
Fig. 2 illustrates in side view and with exaggeration how the filaments are laid down on the conveyor.

One method of producing the bulky accumulation of single filaments is illustrated, somewhat diagrammatically, in Fig. 1 of the drawings. Multifilament 2 which is ordinarily one bundle of filaments, but which may be more than one, melt-spun by a conventional method, gushes out through the nozzle 3 and impinges against a surface 4 where the filaments are crimped and individually separated. Then the filaments 8 have binder deposited on their surface by going through the mist of binder emulsion ejected from the spraying nozzle 5, accumulate on the moving support conveyor 6 with an apparent specific volume of not less than 80 ml/g, and successively undergo the treatment of drying and heat setting by passing under heated elements 7.
The multi-filament 2 may be produced by any known methods in the art, but the aerodynamic melt spinning method, where the aerodynamic frictional force of high speed air is used to draw the extruded as-spun filament to provide the useful filament as such, is preferred. In case of polyesters, high take-up speed of the as-spun filament can provide a useful filament without the additional drawing operation usually adopted in the art. This is, accordingly, quite suitable for the preparation of the multi-filament of the present invention. On top of that, weak crimp which is desirable in the present invention can easily be put in if the temperature of the filament impinging against the surface 4 is controlled so as to be in a range higher than the glass transition temperature of the polymer concerned, but not more than 50°C above the glass transition temperature. The shape of the nozzle 3 from which the multi-filament 2 gushes out with the high speed gaseous fluid such as air may be of any form such as a circle, square, or slit. The multi-filament 1 fed to the nozzle 3 may be drawn multi-filament prepared beforehand, but the incorporation of the nozzle 3 in the spinning line of the aerodynamic melt spinning is preferable.
The surface 4 against which the multi-filament gushing out from the nozzle 3 with high speed gaseous fluid impinges may usually be a single plane surface, and the angle between the plane and the impinging multi-filament is determined by the required extent of the crimp and the separation of filaments. It usually lies in the range of 45 to 90 degress. The optimum angle may be readily determined by a few preliminary tests if necessary. A curved surface other than a plane can also be used to provide an enhanced control of the multi-filament. The distance between the exit of the nozzle 3 and the point on the surface 4 where the multi-filament impinges may also be selected by the extent desired for the crimp and the separation of the filaments.
The multi-filament 2 after the impingement upon the surface 4 runs on the surface in a relaxed state by the help of the turbulent flow of the accompanying gaseous fluid, and becomes separated into individual single filaments. The separated single filaments 8 undergo the deposition of binder on their surfaces on their way to a supporting conveyor 6, and thereafter they are spread out and accumulated on the moving support to form an accumulation of desired width and weight per unit area. This deposition of the binder before the accumulation is essential for this process because an appropriate amount of binder on the filament gives the filament additional weight which contributes to stabilize accumulation, and because relatively uniform deposition of binder on the filament surface can be attained with an appropriate amount desirable for the embodiment of the present invention. An attempt to deposit the binder after the accumulation of the filament has failed to provide the accumulated product of the present invention because it is almost impossible to deposit the binder at an appropriate amount throughout the inner part of the accumulation without losing the apparent specific volume.
The binder may be used either as such if it is in liquid state with an appropriate viscosity, or as solution or emulsion with solvent or water. The additional incorporation into the solution or emulsion of emulsifiers, surfactants, antistatic agents, antioxidants, and colouring agents can be adopted if desired. The binder may be selected from the following list: polyvinylalcohol, polyvinylpyrrolidone, polyurethane, synthetic latexes, and polyacrylic esters.
After the deposition of the binder on the filament, the single filaments are spread out and accumulated on the moving support so that layered accumulation of the filaments may be established. The extend of the spreading out can be determined by the relationship between the impinging velocity of the filaments and the moving speed of the collecting conveyor surface. Usually the former speed is considerably higher than the latter one so that the folding of the filament at both surfaces of the accumulated product may be attained. This folding of the accumulating filaments on the first part of the conveyor is shown in Fig. 2 of the drawings, where it can be seen that the comparatively slow speed of the conveyor, compared with the rate at which the filaments are ejected from the surface 4, results in the filaments being laid down in successive overlapping layers with folds 9 and 10 at the upper and lower surfaces respectively. These folds are hardly noticeable in the final product.
Especially if the filaments are obliquely laid with the length between the folds at both surfaces more than twice the height of the accumulation, the layered structure of the accumulated filaments thus obtained provides the accumulated product with high drapability together with the stable bulkiness desired.
If the width of the fan of filaments 8 is smaller than the desired width of the accumulated product, periodical alteration of the point where the impinging filament meets the surface of the conveyor can be adopted with good success. The provision of another spinning head is an alternative to bring about the accumulation of the desired width. A second spraying nozzle (not shown in Fig. 1) for spraying the binder on the surface may be added separately for the filaments from the second spinning head to provide a product with surfaces enriched with the binder.
It is important to lay the filaments so as to form a bulky accumulation whose apparent specific volume is not less than 80 ml/g, and to secure the final heat-set bulkiness of more than 40 ml/g. Accordingly, suction by vacuum from the underside of the support conveyor should not be used because such suction can cause a considerable reduction of the apparent specific volume up to undesirable level.
The accumulated product thus obtained is next transferred to a drier to eliminate the solvent or water if they have been used in the previous step. In this case unnecesary strong blowing of hot air cannot be recommended because significant loss of the bulkiness can result. Heating by infrared rays is the most desirable drying method for the present purpose. Next, the dried accumulated product should undergo heat-setting at a sufficiently high temperature to stabilize the bulkiness of the accumulated product. An accumulated product made up of polyethylene terephthalate, for example, can be heat-set at about 160°C for five minutes to stabilize the crimp and the binding of the cross-over points.
Moreover, polyvinylalcohol, when used as a binder becomes insoluble in water by thermal treatment at around 200°C, and this can be a desirable phenomenon for later use.
The above-mentioned two steps, e.g. drying and heat-setting, should be performed soon after the spread accumulation of filaments. Of course, the drying step can be discarded when neither solvent nor water is used beforehand.
The bulky material thus obtained takes the form of a multi-layered structure of spread single filaments whose cross-over points have been partly united by binder and heat set to stabilize the bulky form. The fact that a partial and appropriate number of cross-over points of the single filaments have been united and heat stabilized contributes to provide a bulky material which can easily deform by a minute compressing or shearing force, but at the same time store the elastic energy to recover to its original state. Therefore high bulkiness and high drapability can coexist in the accumulation of the present invention. The weak crimp endowed in the filament also contributes to enrich the above-mentioned effect. Coexistence of lubricant with binder on the surface of filament is also desirable to improve the resilience of the accumulated bulky product. The weight of lubricant used may amount to 0.01 to 0.5 percent of the weight of the filament. The lubricant may contain poly(organosiloxane).
The bulky materials thus obtained according to the present invention can be used in sleeping bags, bed coverings such as comforters and duvets and clothing such as anoraks, jackets and the like. They exhibit superior thermal insulation as good as the conventional downs and feathers.
The invention is further illustrated by the following preferred and comparative examples which are not intended to be delimitative.

Example 1

From a melt spinning spinneret with 80 holes each of 0.20 millimeter in diameter, polyethylene terephthalate having an intrinsic viscosity of 0.65 measured in o-chlorophenol at 30°C was melt spun at 290°C into a chamber in which a pressure of 2.3 Kg/cm² (226 kN/_M ²) was set by feeding compressed air. The extruded multi-filament entered the nozzle 3, whoe inner diameter and length were 4 millimeters and 60 millimeters respectively, at 50 centimeters below the spinneret, and went through the nozzle with air whose velocity finally reached the sonic velocity at the exit of the nozzle 3.
The multi-filament gushed out from the nozzle at about 6000 meters per minute with the help of the aero-frictional force of the coexisting air of sonic velocity. The multi-filament 2 thus obtained comprised 80 filaments, each of about 0.8 denier (0.9 dtex). At seven millimeters below the exit of the nozzle 3, the multi- filament impinged against the plane 4 whoe direction against that of the impinging multi- filament was 60 degrees, and then ran for 30 centimeters along the surface of the plane 4. During the above processes weak crimp and separation of the multi-filament into individual single relaxed filaments had been accomplished. The single filaments 8 then left the plane 4 and underwent the spraying of binder, and thereafter spread out and laid down on the conveyor 6 whose surface velocity was 0.3 metre per minute. The binder consisted of 100 parts by weight of polyvinylalcohol of molecular weight about 500 and whose extent of saponification was greater than 99%, and one part by weight of a lubricant composition of 7 : 3 stearic acid ester and dodecylbenzene sodium sulfonic acid respectively. It was sprayed on to the single filaments in an emulsified state of 4% in water so that the final deposition was about 5% by weight of the filament.
When the single filaments were spead out and laid on the conveyor, the deposition point of the filaments was reciprocated twice per minute so that 1.5 metre width of the accumulated product was achieved. The resultant accumulation had 20 centimetres in thickness, and 400 ml/g in apparent specific volume. It was then carried for 18 minutes through a drier and heat setter in which an infra-red heater powered by 12 kilowatt electricity has been installed. The temperature of the accumulation at the exit of the heat setter was about 160°C.
The final accumulation of the filaments thus obtained had a stable bulkiness (specific volume) of 104 ml/g and 200 grams per square metre, and exhibited an excellent drapability in spite of such a bulk form.
A comforter (i.e. a stuffed bedcover) in which the bulky material of the present invention was used showed a good drapability and an excellent thermal insulation in long use. The apparent specific volume of the comforter was about 190 ml/g.

Comparative Example 1

Example 1 was repeated, except that the amount of the deposition of the binder was reduced to 0.1 % by weight of the filament, the other factors remaining the same. The resultant accumulation of the filaments took at first a desirable bulky form, but the bulkiness swiftly decreased when the product was used in a comforter. This was considered to be caused by a scant number of cross-over points united by the binder, and by a poor resiliency for the same reason.

Comparative Example 2

Example 1 was repeated, except that the amount of deposition of the binder on the filament was increased to 25% by weight of the filament. The resultant accumulation had lost the drapability intended in the invention.

Example II

The accumulation of the filaments obtained in Example I was further treated on its surfaces with additional polyvinylalcohol and an additional five percent by weight of filament was deposited on the surfaces. The resultant accumulation took a more stable shape which made it easy to be cut or sewed for quilting use.

Example III

The potential of the thermal insulation was compared with the conventional material for the same use. As was indicated in the Table I the bulky material according to the present invention had about twice the thermal insulation of cotton, and was almost comparable with down.
The clo-value is a unit to designate the potential of the thermal insulation, and defined as follows:

One clo means such thermal insulation that a man who lies in rest and discharges heat of 50 Kcal/m2. hr (21 104 J/m^lh) feels comfortable with his skin temperature at 33 degrees centigrade under ambient conditions of 21.2°C and less than 50% relative humidity with an air flow of 10 cm/sec.

Claims

1. A thermally insulating nonwoven bulky product made up of a multiplicity of substantially continuous fine, single synthetic filaments stabilized in the product by a surface binder on the filaments characterized in that the filaments have an average denier of from 0.01 to 2 (0.011 to 2.2 dtex), the surface binder is at least one synthetic thermoplastic resin whose softening temperature is less than that of the filaments and is present in an amount of from 0.5% to 20% by weight of the filaments, and the product has a specific volume of not less than 40 ml/g as calculated by the equation:

wherein A is the weight in grams of a sample having a length and width of 20 cm and 20 cm respectively and h is the average height in centimetres of the sample measured under a load of 0.125 g/cm² (12.3 N/m²).

2. A bulky product according to claim 1 wherein the specific volume of the product lies in the range of 50 to 500 ml/g.

3. A bulky product according to any one of the preceding claims wherein the filaments are crimped, and the percentage crimp lies in the range of 1 to 20%.

4. A bulky product according to claim 3, wherein the percentage crimp lies in the range of 2 to 10%.

5. A bulky product according to any one of the preceding claims wherein the single filaments are derived from multi-filament having a total denier in the range of 30 to 3000 (33 to 3300 dtex).

6. A bulky product according to any one of the preceding claims wherein the single filaments have a fineness in the range of 0.1 to 1 denier (0.11 to 1.1 dtex).

7. A bulky product according to any one of the preceding claims wherein the amount of binder deposited on the surface of the filaments lies in the range of 2 to 10% by weight of the filaments.

8. A bulky product according to any one of the preceding claims wherein the filaments are located in overlapping layers.

9. A bulky product according to any one of the preceding claims wherein the binder is selected from polyvinylalcohol, polyvinylpyrrolidone, polyurethane, synthetic latexes and polyacrylic esters.

10. A bulky product according to claim 9 wherein the binder is polyvinylalcohol whose molecular weight is in the range of 100 to 10,000, and whose extent of saponification is not less than 98%.

11. A bulky product according to any on,1 of the preceding claims wherein the filaments comprise polyesters.

12. A bulky product according to claim 11 wherein the filaments are of either poly-(ethylene terephthalate) or poly(butylene terephthalate).

13. A bulky product according to any one of the preceding claims wherein the filaments are treated with a lubricant to an extent of 0.01 to 0.5% by weight of the filaments.

14. A bulky product according to claim 13 wherein the lubricant contains poly(organosiloxane).

15. A bulky product according to any one of the preceding claims wherein the product is additionally finished by a further surface treatment with a binder.

16. A bulky product according to claim 15 wherein the binder used for the said further surface treatment is polyacrylic ester.

17. A process for producing a bulky product according to claim 1 comprising the successive steps of

(a) melt spinning the filaments of synthetic polymer,

(b) leading the spun filaments together with compressed air through a nozzle,

(c) crimping and separating the filaments by impinging against a plane,

(d) spraying the crimped and separated filaments with the binder,

(e) spreading out and accumulating the separated filaments into a bulky accumulation,

(f) heating the bulky accumulation of filaments to the final product.

18. The process of claim 17 in which step (d) is performed by the use of an emulsion of the binder.

19. The process of claim 18 in which step (d) is performed using an aqueous emulsion of polyacrylic ester.

20. The process of claim 19, followed by the further step of

(g) surface treatment of the product with an aqueous emulsion of polyacrylic ester.

_. 21. The process of any one of claims 17 to 20 in which step (e) provides a bulky form with an apparent specific volume of not less than 80 ml/g.

22. The process of any one of claims 17 to 21 including drying of the filaments prior to step (f).

23. The process of any one of claims 17 to 22, including folding the filaments into overlapping layers.