EP0118620A2

EP0118620A2 - Method and apparatus for heat-treating pile fabrics

Info

Publication number: EP0118620A2
Application number: EP83112923A
Authority: EP
Inventors: Kenji Sato; Seiichi Yamagata
Original assignee: Toray Industries Inc
Current assignee: Toray Industries Inc
Priority date: 1983-01-14
Filing date: 1983-12-21
Publication date: 1984-09-19
Also published as: EP0118620A3; JPS59130366A

Abstract

A process is disclosed for heat-treating a pile fabric, which comprises adding a dielectric material to the pile of the fabric and then dielectrically heating the fabric under a condition such that the movement of individual pile fibers is subtantially constrained by the presence of the dielectric material. Also, apparatus for carrying out the process is disclosed, which comprises means for dressing dielectric-soaked fibers of a pile fabric, means for conveying the fabric while keeping the dressed pile fibers substantially intact, and a chamber in which the conveyed pile fabric is subjected to electromagnetic irradiation.

Description

This invention relates to a process for ₇ effectively heat-treating the fibers forming pile of a pile fabric and an effective heat-treating apparatus which operates on the basis of the process.
More specifically, the invention concerns a technique of effectively heat-treating pile fibers by taking the advantage of electromagnetic wave-induced dielectric heating so as to improve the straightness and other physical properties of the fibers, the technique being particularly useful in improving the straightness and other pile properties of fabrics intended for use as artificial furs.
Pile fabrics and their pile fibers have been upgraded in recent years to meet growing demand for furry products. A consequent tendency is toward longer and much denser piles. Many attempts and proposals have been made to make pile fabrics resembling natural furs of a high quality, such as mink.
If an artificial product similar in the fur or pelt structure to mink or other high-grade natural fur is to be made, it must have a combination of at least two pile layers, or guard-hair and wool-hair layers. The requirement is commonly met by forming a double-layer pile structure which consists of a shaggy guard-hair layer of rather coarse, long pile fibers and a fluffy wool-hair layer of fine, short fibers by far greater in :. number than the guard-hair fibers.
For instance, we previously proposed in our Japanese Published Unexamined Patent Application No. 57-61739 to provide a furry pile fabric comprising long and short pile fibers, the long fibers being pointed at the tips for even greater resemblance to the natural fur.
As regards the lengths and numbers of the fibers constituting such a pile, for example, of an artificial fur imitating mink, it is customary to use guard- and wool-hair fibers having maximum lengths, respectively, in the range of about 20 to 30 mm and about 5 to 20 mm, and combine them so that, when the fabric is seen along its edge, the guard- and wool-hair layers are distinctly distinguishable. The fluffy wool-hair layer consists of fine fibers of several deniers or finer and the shaggy guard-hair layer consists of much coarser fibers of tens of deniers up to about 100d. Usually, the guard-hair fibers number about 100 to 500 per square centimeter, whereas the wool-hair layer is far denser with about 5000 to 25000 fibers per the same unit area.
Artificial furs made of such two pile layers, one very long and the other very dense, have often had shortcomings, typically lack of straightness or - undesirable bunching or entanglement of the pile fibers.
Especially where an artificial mink or other imitation of high-quality natural fur is to be produced, inadequate straightness of the guard-hair fibers will have a direct unfavorable bearing on the appearance and feeling of the product. Irregular bunching or entanglement of the fibers, especially of the fluffy wool-hair layer, will mar the lie, softness, and waviness of the pile. Elimination of these shortcomings has been called for because they make the product look unlike the . objective mink or other natural fur.
In our effort for overcoming these difficulties, we have found a way of remarkably improving the appearance and quality of the pile fabric material whose pile fibers, especially of the guard-hair layer, are curled or otherwise non-straight or directed randomly and unevenly, forming an irregular lie or poor appearance. The improvements are realized by keeping those fibers straightly, arranging them all in one direction, and then heat-setting them altogether.
The fluffy wool-hair pile layer is in many cases formed of crimped fibers. Where the crimping is responsible for unusually frequent fiber entanglement, straightening the crimps to some extent will be beneficial. Heat-setting of the more or less uncrimped fluffy pile fibers will prove particularly helpful in improving the pile properties of the product.
In heat-treating the fibers of those pile fabrics which have a very long (thick) and dense pile for some processing, it has been routine to use jets of steam or hot air or pass the fabric through heater means, or between hot rollers or plates. However, the pile is usually so thick, a few to about five millimeters thick even when compressed from above, that heat can scarcely reach the innermost portion of the pile to treat the individual fibers thoroughly. The result is the heat treatment of only the surface portion. If severe treating conditions of higher temperature and longer time are.used to assure a thorough heat treatment, the conditions will be over-specified or too rigorous for the surface portion of the pile and the shaggy guard-hair fibers will readily curl, lie flat, or otherwise deteriorate in quality. Even the guard-hair layer alone consists of a thick, dense mass of fibers, and the ordinary heat treatment, of whatever type, can hardly process both guard and wool layers alike and uniformly throughout the fabric as desired. Unless fibers are heat-set to some degree at their roots or in the wool-hair layer, no.. improvement will be attained in the lie or appearance of the resultant artificial fur. The inner heat-setting should not cause excessive heat-treating of the surface portion, and yet this is undeniably a drawback common to conventional heat-treating methods.
Generally the same applies to the heat treatment of fibers of the fluffy wool-hair pile layer. Under the covering of the coarser and longer guard-hair fibers, the wool-hair fibers again are not fully heat-treated. Even adequate heat transmission to the fluffy layer is difficult. Attempts to use higher temperatures or longer periods for the treatment have often failed as they invite undesired curling, flattening, or other defect of the guard-hair fibers.
In any case, adequate heat treatment for certain processing effects of pile fabrics has been next to impossible where the fabrics have piles long and dense enough or multilayered for furry effects.
In view of the above, the present invention has for its object to provide a process and an apparatus for heat-treating pile fabrics efficiently and reasonably as desired.
The object of the invention is realized by a process for heat-treating a pile fabric which comprises adding a dielectric material to the pile of the fabric and then dielectrically heating the same under conditions such that the movement of the individual pile fibers is substantially constrained by the presence of the dielectric material.
Also, the apparatus according to the invention for heat-treating a pile fabric comprises means for dressing dielectric-soaked fibers of the pile fabric, means for conveying the fabric while keeping the dressed pile fibers substantially intact, and a chamber in which the conveyed pile fabric is subjected to electromagnetic irradiation.

FIG. 1 is a diagrammatic side view of a furry pile fabric, made on a ground with a pile consisting of shaggy guard-hair fibers and shorter, fluffy wool-hair fibers, both of synthetic resins;
FIG. 2 is a diagrammatic side view of the furry pile fabric of FIG. 1 about to be dielectrically heated by the process of the invention;
FIG. 3 is a diagrammatic side view of a furry product obtained by heat-treating the pile fabric material of FIG. 1 in accordance with the invention; and
FIG. 4 is a schematic side view of apparatus embodying the invention for the heat treatment of a pile fabric.

For purposes of the invention, the term "pile fabric" is intended to embrace any of tufted and ordinary pile fabrics, double-raschel fabrics, moquettes and velvets, suedes, raised fabrics prepared by ordinary raising machines, electrically flocked fabrics, water- punched fabrics, artificial furs, carpets, chenilles, and other textile materials having piles or pile-like coverings.
The heating mechanism for the process of the invention applies electromagnetic waves to the pile of a pile fabric soaked beforehand with a dielectric material; so as to heat the dielectric and heat-treat the individual pile fibers of the fabric as desired through the medium of the heated dielectric. The dielectric may be any material which exhibits a dielectric effect, such as water, alcohol, or other organic solvent, or an aqueous urea solution. Water is preferred because of the ease and safety of handling. Where a high temperature above the boiling point of water is required, a suitable material of a higher boiling point may be employed instead of or together with water.
The dielectric heating may be performed by any method provided it involves electromagnetic irradiation. For example, it may be effected by irradiation with microwaves ranging in frequency from 300 to 10000 MHz, high-frequency waves of 3 to 50 MHz, or electromagnetic waves of 3 to 10000 MHz in use with industrial or home electronic ranges.
By the expression "pile fibers constrained by a dielectric" is meant fixing the fibers to some extent with water where the latter is adopted as a dielectric. Thus, the expression does not apply to the state in which the pile fibers are well movable as in ordinary dyeing where a high bath ratio is used; but the expression applies to the state wherein the fibers apparently are unable to move fairly freely. A desirable method comprises soaking all or part of a pile fabric with water, taking out the fabric from the water bath, draining or not draining water naturally by gravity, dressing the wet fibers with a comb or the like, and then subjecting them to electromagnetic irradiation.
The process of the invention permits uniform heating of a pile fabric, from the top to the innermost part, within a very short period of time. This is ascribable to the instantaneous, simultaneous heating to the same degree, that characterizes dielectric heating, of the dielectric material portion permeating deepest in the fabric as well as the remainder of the dielectric. Much elevated temperatures may also be employed for this purpose.
For a more uniform treatment, it is effective to adopt means to combine the dielectric heating with steam heating or cover the pile with dielectric-soaked cloth or the like to prevent suspension of the heat treatment due to evaporation of the dielectric from the outermost part of the fabric.
In the practice of the invention the pile can be easily treated locally and selectively. For example, the surface portion of the fibers in the pile can be primarily heat-treated by applying the dielectric only to that portion. Conversely, the roots of the pile fibers can be primarily heat-treated by applying the dielectric only to the deepest portion of the pile. Further, selective heat-forming and setting of the pile fibers can be done to change the lie or direction of the pile fibers at certain intervals of divided sections.
Moreover, the pile fibers can be heat-set to a desired shape by using a rather viscous substance as the dielectric and then dielectrically heating the fibers while maintaining them in the desired form.
The fibers to form the piles to be handled by the present invention usually are, but not limited to, synthetic or chemical fibers with high moisture percentages. Natural fibers are usable as well. Above all, the fibers sharply pointed at the tips, which are readily bendable, are effectively used in the present process. The dielectric material may contain a dye or dyes to effect dyeing concurrently with the heat treatment. Proper partial or selective heating will impart a desirable dyeing pattern to the pile. Where a minklike product is to be obtained, either the guard-hair or wool-hair pile layer alone can be dyed to provide a natural furry appearance.
Where necessary, the fabric ground, too, can be heat-treated. In the case of chenilles, for example, not only the heat treatment of the pile fibers but also heat setting of the yarns bonded to the ground can be simply performed.
Now the apparatus according to the invention for effectively heat-treating pile fabrics on the basis of the afore-described process will be explained.
FIG. 4 illustrates an embodiment of the pile-fabric heat-treating apparatus of the invention. A length of pile fabric 1 appropriately soaked with a dielectric material is fed forward by a conveyor 6, such as an endless conveyor belt, so that it is handled, while being conveyed, by a pile dresser 7, such as a brushing unit comprising a carding roller. The pile dresser 7 disentangles and arranges the pile fibers in a given direction or in a predetermined pattern, depending on the type of intended subsequent processing. It may be a simple bar guide or the like where it has merely to lay upstanding fibers to a slight angle to the vertical. Where the general lie or pattern of the pile is to be rather deep-rooted or should start from the inner portion of the pile or from the roots of the innermost fibers, while improving their straightness, a more complex unit may be employed, such as a brushing unit using a comb or rotary or stationary carding roller.
With the pile fibers thus dressed in a given direction or pattern, the pile fabric 1' is carried by the conveyor 6 and another unit 6' into an electromagnetic irradiation chamber 8. The conveyors 6, 6' must transport the fabric and allow it to be irradiated while substantially maintaining the lie or pattern of the pile fibers as arranged by the pile dresser. They should not include any mechanism which might seriously disturb the given lie or direction of fiber arrangement. It is essential that they be free of any mechanism which would convey the fabric zigzag or meanderingly within the chamber 8.
The pile fabric l' brought into the chamber 8 is then irradiated with electromagnetic waves from an electromagnetic wave generator 9. The dielectric material attached to the fabric then develops sufficient heat to treat the pile fibers.
The process and apparatus of the invention are applicable to the heat treatment of any pile fabric whose pile fibers have a maximum length of at least 3 mm. More particularly, as already described, they are applicable to the heat treatment of pile fabrics having a pile of multilayer or combination-pile structure of at least two pile layers, one consisting of relatively long, coarse fibers and the other consisting of relatively short, fine fibers to resemble, respectively, the guard-hair and wool-hair of natural furs. In manufacturing artificial mink or fox, generally good result is obtained with a pile fabric of double-layer structure, in which the long guard-hair layer consists of fibers about 10 to 70 mm long and the short wool-hair layer consists of fibers about 5 to 40 mm long. Even such a long, dense pile can be effectively heat-treated within a very short period of time by the process and apparatus of the invention.
The advantageous effects of the present invention may be summarized as follows: The pile fabric treated in conformity with the invention has pile fibers with improved straightness. Especially the fibers located deep in the pile are markedly improved in that property. The improved straightness adds to the gloss of the pile. Furthermore, the straightness-retaining durability of the fabric increases, bringing an outstanding advantage of no entanglement nor objectionable gathering of the fibers after prolonged use of the product.
Although the present invention has so far been described as applied principally to the pile fabrics to be processed into artificial furs, it should be obvious to those skilled in the art that the process and apparatus of the invention are not limited to the manufacture of man-made furs but are also extensively applicable in the field of pile fabrics for the heat treatment of their piles.
The process and apparatus of the invention for heat-treating pile fabrics will be described in more detail below in connection with examples thereof.

Example 1

A furry pile fabric of the structure, diagrammatically shown in FIG. 1, was made in conformity with the procedure described in the specification of Published Unexamined Patent Application No. 57-61739. In FIG. 1, the numeral 1 generally indicates the pile fabric, and 2 is a pile layer of shaggy guard-hair fibers, 3 is a pile layer of fluffy wool-hair fibers, and 4 is a ground weave. The guard- and wool-hair fibers are formed as below:

Guard-hair fibers:- Fineness = 40d; max. length = 26 mm; material = polybutylene terephthalate (PBT)
Wool-hair fibers:- Fineness = 1.2d; max. length = 12 mm; material = polyethylene terephthalate (PET)

The pile fabric was soaked with water throughout its piled side. The bedraggled pile fibers were dressed and freed of excess water by a fine-tooth comb. In this state they were laid aslant in one direction, as FIG. 2 shows diagrammatically. Here, both the wool- and guard-hair fibers were in a state constrained by water 5 while being set almost straight. The fabric was then placed in a home electronic range (600 W) and subjected to microwave heating at an : oscillation frequency of 2450 MHz for 60 seconds. It was taken out of the range, the remaining water was allowed to dry up at ordinary temperature, and the fabric was brushed for a finish. The furry pile fabric thus obtained, as shown in FIG. 3, had a good lie of all the pile fibers in one direction. The loose curls the guard-hair fibers had originally possessed before the heat treatment were gone. More noteworthy was the fact that the crimps of the wool-hair fibers were also straightened well by the heat treatment. The uncrimped fibers scarcely entangled and gave a glossier appearance to the pile. Thus, a furry pile fabric with attractive appearance, feeling, and pile properties was obtained. This fabric was tested by actual wearing for three months. After the test it showed no change in its desirable properties.

Example 2

The furry pile fabric obtained in Example 1 was sampled, and the test specimen was again watered, and dressed and freed of excess water by a fine-tooth comb.
The pile fabric was partly dewatered with blotting paper and then was dried with hot air. The specimen thus prepared contained residual water mostly deep in the pile. In the same manner as in Example 1, this specimen was placed in a home electronic range for microwave heating at an oscillation frequency of 2450 MHz, and was finished.
The furry pile fabric obtained in this way showed almost no fiber entanglement, with the originally crimped wool-hair fibers more uncrimped than those in Example 1. The moderately low crimp of the wool-hair fibers combined with the straightness of the guard-hair fibers to make the fabric superior in quality and usefulness to the product of Example 1.

Example 3

A furry pile fabric was made substantially in the same way as described in Example 1 except that the material for the fluffy wool-hair fibers were replaced by slightly crimped staples.
Water was sprayed over the entire pile of the fabric, and then the pile was combed. The total amount of water thus applied was about one-fifth the volume used in Example 1. Accordingly, water did not permeate into the depth of the pile, but it mostly wetted the surface layer formed of the guard-hair filaments.
This specimen was subjected to microwave heating in a home electronic range at an oscillation frequency of 2450 MHz for 30 seconds. A furry product was obtained with the guard-hair fairly uncurled and straightened.

Example 4

A furry pile fabric of the same materials as used in Example 1 was thoroughly watered and combed so that the pile fibers were arranged in different directions, 90 degrees apart from each other, with respect to the centerline of the specimen (that is, obliquely at an angle of 45 degrees each from the centerline). The specimen in this state was placed in a home electronic range and heated with microwaves at an oscillation frequency of 2450 MHz for 90 seconds. The fabric was taken out and finished. The product was a fashionable one, with the lie of the pile severed into two directions relative to the centerline.

Example 5

The procedure of Example 1 was repeated to make a furry pile fabric of the structure diagrammatically shown in FIG. 1.
The shaggy guard-hair fibers and fluffy wool-hair fibers were as follows:

Guard-hair fibers:- Fineness = 50d; max. length = 40 mm; material = PBT
Wool-hair fibers:- Fineness = 1.7d; max. length = 25 mm; material = PET

Water was sprayed over the entire piled side of the fabric and allowed to permeate into the pile. The pile was thoroughly soaked and evenly laid in one direction. A test specimen of the fabric, 50 cm wide and 2.5 m long, was heat-treated in accordance with the invention in a high-frequency heater (at an oscillation frequency of 13.56 MHz) for 10 minutes.
The furry pile fabric so. treated had a good lie of the pile in one direction. The shaggy guard-hair . fibers that had been slightly curled before the heat treatment were straight and added to the fine appearance and gloss of the fabric. Also, the originally crimped wool-hair fibers were fairly uncurled and accordingly showed much less entanglement, with increased gloss. The furry product was satisfactory in all respects, including the appearance, feeling, and pile properties.

Example 6

A furry pile fabric of the same structure as used in Example 1, 40 cm wide and 3 meters long, with its pile watered, was moved through a heat-treating apparatus of the construction shown in FIG. 4. The pile dresser 7 was a carding roller, and the electromagnetic wave generator 9 had a power output of 5 kW and generated microwaves at an oscillation frequency of 2450 MHz. The conveying speed of the conveyors 6, 6' was set so that a microwave-treating time of 4 minutes was obtained.
The treated furry pile fabric upon finishing was as satisfactory in pile appearance, gloss, and other properties as the product of Example 1.

Claims

1. A process for heat-treating a pile fabric which comprises adding a dielectric material to the pile of the fabric and then dielectrically heating the same under a condition such that the movement of the individual pile fibers is substantially constrained by the presence of said dielectric.

2. A process as defined in claim 1, wherein said pile is of a multilayer structure having at least two layers, one consisting of relatively long, coarse pile fibers and the other consisting of relatively short, fine pile fibers.

3. A process as defined in claim 1, wherein the longest pile fibers are at least 3 mm long.

4. A process as defined in claim 2, wherein said relatively long, coarse pile fibers are 10 to 70 mm long and said relatively short, fine pile fibers are 5 to 40 mm long.

5. A process as defined in claim 2, wherein said relatively long, coarse pile fibers are sharply pointed at the tips.

6. A process as defined in claim 1, wherein the dielectric heating is performed with electromagnetic waves which are microwaves.

7. Apparatus for heat-treating a pile fabric which comprises means for dressing dielectric-soaked fibers of the pile fabric, means for conveying the fabric while keeping the dressed pile fibers substantially intact, and a chamber in which the conveyed pile fabric is subjected to electromagnetic irradiation.

8. Apparatus as defined in claim 7, wherein said dresser means takes the form of a guide which forces the pile fibers to lie obliquely in one direction.

9. Apparatus as defined in claim 7, wherein said dresser means is a comb or comblike implement.

10. Apparatus as defined in claim 7, wherein said dresser means is a brushing unit.