JPH0742652B2 - Method for producing flexible leather-like sheet - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a leather-like sheet material, and more specifically, to a base cloth mainly composed of polyester fibers and a porous wet coagulated product of polyurethane elastomer. The present invention relates to a method for producing a leather-like sheet material obtained by filling the sheet material, which has a more improved soft feeling.

[Conventional technology]

It is well known to impregnate a base fabric such as a non-woven fabric with a water-miscible organic solvent solution of a polyurethane elastomer, wet coagulate and dry it into a leather-like sheet, and at that time, to impregnate the polyurethane elastomer solution. It is also known that the flexibility of the obtained sheet-like product is improved by temporarily fixing the base fabric with a water-soluble resin such as polyvinyl alcohol in advance.

This treatment with polyvinyl alcohol forms a sheet between the fibers forming the base cloth and the polyurethane elastomer serving as the binder to allow the fibers to be displaced or deformed to some extent in response to bending or the like. It is intended to improve the flexibility of a product, and in fact, for a base fabric made of fibers such as nylon, acrylic, cotton, and rayon, a sheet-like product having a sufficiently satisfactory flexibility in practical use can be obtained. Has been obtained.

However, regarding a sheet-like material using a base fabric mainly composed of polyester fiber, softening is most desired due to its cost advantage and rigidity due to fiber properties. However, the treatment with polyvinyl alcohol does not show the effective softening effect as seen in other fibers. For this reason, the amount of polyvinyl alcohol used has been made 2 to 4 times that of other fibers (for example, a high ratio of 50 to 60% based on the weight of fiber), but this case is still satisfactory. Not only does the required flexibility not be obtained, but on the contrary, the problem of uneven quality and the problem of wastewater treatment are accompanied by an increase in the amount of polyvinyl alcohol used.

[Problems to be solved by the invention]

In view of the problems of the prior art as described above, the inventors of the present invention have keenly made a method for producing a highly flexible leather-like sheet material using a base fabric mainly composed of polyester fiber, and industrially advantageous. As a result of research, if the alkali metal hydroxide was made to coexist in the system during the treatment with the above-mentioned polyvinyl alcohol, the amount of polyvinyl alcohol used was surprisingly only a fraction of the conventional amount, and more than the conventional amount. Based on such knowledge, the present invention has been completed based on the knowledge that a sheet material having excellent flexibility can be manufactured.

[Means for solving problems]

That is, the present invention, after fixing polyvinyl alcohol to a base fabric mainly composed of polyester fibers, impregnated with a water-miscible organic solvent solution of polyurethane elastomer, and then wet coagulating it in an aqueous medium and washing and drying. A method for producing a leather-like sheet material, characterized in that, when producing a leather-like sheet material, the polyvinyl alcohol is fixed to a base fabric in the presence of an alkali metal hydroxide.

In the present invention, the polyester fiber refers to one having polyethylene terephthalate or polybutylene terephthalate as a main constituent polymer, and these polymers further contain a small amount of a modifier, for example, isophthalic acid, polyethylene glycol, sulfonic acid or phosphonic acid introduced aromatic. It may be modified with a group dicarboxylic acid or the like.

The base fabric mainly composed of polyester fibers generally means a woven fabric, a knitted fabric, a napped product thereof, a non-woven fabric or the like containing about 70% by weight or more of the above polyester fibers. When fibers other than polyester fibers are included as constituent fibers, such other fibers include those that show some resistance to alkali metal hydroxides, such as cotton,
Rayon, polyamide fiber, polyolefin fiber and the like are preferable.

The basis weight of the base fabric, the fineness of the constituent fibers, etc. are not particularly limited from the viewpoint of applicability or effectiveness of the method of the present invention, but the effect of improving flexibility by the method of the present invention, particularly feeling, touch, etc. The effect when considering also the sensory evaluation of, the basis weight is 50 ~ 500 g / m ² , especially 100 ~ 300 g / m ² ,
It is most prominent in the case of a base fabric in which the fineness of the constituent fibers is in the range of 0.1 to 3d, particularly 0.1 to 1.5d.

In the present invention, the base fabric mainly composed of polyester fibers as described above is treated with polyvinyl alcohol before impregnating the polyurethane elastomer, and the polyvinyl alcohol is fixed to the base fabric (more accurately, the surface of the fabric constituting the base fabric). At the time of setting, an alkali metal hydroxide is allowed to coexist in the system.

As the alkali metal hydroxide used here, there are hydroxides such as lithium, sodium and potassium, all of which are effective, but the use of sodium or potassium hydroxide is particularly preferable from an industrial viewpoint. desirable.

There are various methods for fixing polyvinyl alcohol to the base cloth in the presence of these alkali metal hydroxides. First, alkali metal hydroxide is prepared by drying polyvinyl alcohol from a solution state on the base cloth fiber. It is necessary to be in a state of coexistence with polyvinyl alcohol at the time of precipitation and sticking. It is necessary to satisfy the requirements. In a more preferable embodiment, the base fabric (constituent fiber) is present in the presence of an alkali metal hydroxide. Considering that heat treatment may be performed, the following three methods can be exemplified as preferable ones.

First, the first method is a method in which the base cloth is heat-treated in an aqueous solution of an alkali metal hydroxide, and subsequently, a treatment with polyvinyl alcohol is continuously performed on the base cloth without removing the alkali metal hydroxide.

In this case, as the concentration of the alkali metal hydroxide aqueous solution,
0.2-5% by weight (hereinafter, unless otherwise specified, all% means% by weight) is suitable, and the base cloth is soaked in such a solution at 50-98 ° C. for 0.5-30 minutes, If necessary, the solution is squeezed, impregnated with an aqueous solution of polyvinyl alcohol, and dried to fix the polyvinyl alcohol to the base fabric (surface of the constituent fibers). When the concentration of the alkali metal hydroxide aqueous solution exceeds 5% and becomes high, the strength of the polyester fiber itself may decrease due to the strong alkali. Further, if the alkali metal hydroxide adhering to the base cloth is removed by neutralization or washing with water before the impregnation with the aqueous polyvinyl alcohol solution, the flexible sheet material aimed at by the present invention cannot be obtained. (See Comparative Example 5 below).

The second method is a method of impregnating a base cloth with an aqueous alkali metal hydroxide solution, heating and drying, and then performing treatment with polyvinyl alcohol. The heat treatment of the base cloth in the presence of an alkali metal hydroxide is It is carried out in the same manner as the above-mentioned first method except that the heating and drying treatment after impregnation is carried out instead of the immersion heating treatment.

Appropriate heating and drying conditions are 80 to 150 ° C. and 0.5 to 30 minutes. Even in this case, needless to say, if the alkali metal hydroxide is removed by washing with water after the heat drying treatment and before the impregnation with polyvinyl alcohol, the flexibility improving effect becomes insufficient.

The third method is to impregnate a base cloth with a mixed aqueous solution containing an alkali metal hydroxide and polyvinyl alcohol and dry the base cloth, or
Alternatively, it is a method in which the base cloth is immersed and heat-treated in the mixed aqueous solution and then dried.

In this case, the concentration of the alkali metal hydroxide, the impregnation-drying conditions, the immersion heating conditions, etc. are the same as those in the first or second method, and there is no problem.

Among the above methods, as in the impregnation-drying method in the second method or the third method, the heat treatment of the base fabric with the alkali metal hydroxide aqueous solution is performed by the so-called pad-
When the dry method is used, it is desirable to add a small amount of a water-soluble high-boiling-point liquid substance to the aqueous solution. By doing so, the alkali metal hydroxide solution, even when it becomes a highly concentrated state along with the progress of heating and drying, does not cause spotty or granular unevenness on the surface of the hydrophobic polyester fiber, Therefore, after drying, the alkali metal hydroxide will adhere uniformly to the fiber surface. As a result of this uniform adhesion, it becomes possible to obtain a sheet-like material having sufficient flexibility even with the use of a low-concentration aqueous solution of alkali metal hydroxide, and there is no fear of deterioration of the physical properties of the base fabric due to strong alkali.

As the water-soluble high-boiling-point liquid substance used here, glycols such as ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol and dipropylene glycol are suitable, and the addition amount thereof is the medium portion of the alkali metal hydroxide solution. The amount is preferably 10 to 30% of (total of water and high boiling point liquid substance).

The treatment with polyvinyl alcohol can be carried out according to the usual polyvinyl alcohol treatment in any of the above-mentioned three methods.

That is, it is desirable that the polyvinyl alcohol used is rich in water-solubility so that it can be easily dissolved and removed finally, and in that sense, the degree of polymerization thereof is about 300 to 1,000, and the degree of saponification is 88. It is preferably about mol% or more. Generally, the concentration in the solution should be in the range of 5 to 20%. Especially, when it is around 10%, the viscosity is low and the permeability to the base fabric is excellent, while the amount of adhesion to the base fabric can be easily adjusted. It is preferable.

Regarding the amount of polyvinyl alcohol adhered to the base cloth, in the case of the method of the present invention, generally about 5% of the weight of the base cloth has already been found to have a considerable softening effect.
Further, the optimum amount of fixing is determined in consideration of the type of base cloth, the use of the sheet-like material, and the like. For example, in the case of a sheet material used for artificial leather for shoes and bags, it is appropriate to set it in the range of 5% or more, particularly 10 to 20%. It is possible to obtain a rich sheet material. In the case of the conventional method, in order to impart flexibility to a base fabric using the same polyester fiber, it is necessary to achieve a high adhesion amount of up to 60%, and the softening effect is still not sufficient. Therefore, in the method of the present invention,
It is quite surprising that an effective softening effect can be obtained with the above-mentioned low sticking amount, and that it is sufficient from the viewpoint of the quality of the sheet-like product obtained, and also the operability and the economical efficiency. Which is extremely advantageous.

This polyvinyl alcohol is fixed to the base cloth after impregnating the base cloth with a polyvinyl alcohol aqueous solution (or a solution containing polyvinyl alcohol and an alkali metal hydroxide in the case of the third method described above) according to a conventional method. , Squeeze the liquid to adjust to the desired impregnation amount (fixed amount),
It is carried out by heating and drying at 150 ° C for 0.5 to 30 minutes.

As described above, the base fabric on which polyvinyl alcohol is fixed in the presence of the alkali metal hydroxide is then impregnated with the water-miscible organic solvent solution of polyurethane elastomer,
A leather-like sheet material is prepared by wet coagulation, washing with water and drying, and this step can also be performed according to a conventional method.

That is, as a water-miscible organic solvent solution of a polyurethane elastomer (hereinafter referred to as a polyurethane elastomer solution), a polyester-type or polyether-type polyurethane elastomer is added in a water-miscible organic solvent such as tetrahydrofuran, dimethylformamide or dimethylacetamide in an amount of 10 to 25%. %, Preferably 15 to 20% dissolved in the solution is used. The polyurethane elastomer is preferably a polyether type from the viewpoint of alkali hydrolysis resistance, but the polyester type is also used in the washing step (removal of polyvinyl alcohol, alkali metal hydroxide, etc.) after wet coagulation described later. Then, it can be used in the same manner by sufficiently neutralizing and washing with water.

The amount of the polyurethane elastomer solution impregnated into the base cloth varies depending on the intended use of the leather-like sheet material, but generally the ratio of the base cloth to the polyurethane elastomer solid component is in the range of 35:65 to 70:30 by weight. Is appropriate.

Wet coagulation of the base fabric impregnated with the polyurethane elastomer solution is preferably carried out using water or water containing up to 20% of a water-miscible organic solvent as the coagulating medium, and
It is carried out by immersing at -50 ° C for 1-20 minutes. In this wet coagulation, it is preferable to use a coagulation regulator, for example, a coagulation promoter such as urea, or a nonionic or anionic surfactant in combination, which can improve the desolvation property.

After the completion of this wet coagulation, the sheet-like material thus formed is successively washed with water while passing through a squeezing roll to sufficiently elute the organic solvent or polyvinyl alcohol, and then dried according to a conventional method. A desired leather-like sheet is obtained.

In this case, particularly when the polyurethane elastomer used is of the polyester type, in order to prevent the hydrolysis deterioration of the elastomer based on the alkali metal hydroxide which tends to remain even after washing with water even after a small amount of time,
It is desirable to perform a treatment for neutralizing alkali before or during the washing step.

Thus, according to the method of the present invention, the softening of the leather-like sheet material made of the base fabric using the polyester fiber, which is difficult by the conventional polyvinyl alcohol treatment, is reduced to a fraction or less of that in the conventional method. It is possible to easily produce a leather-like sheet material which is made of polyvinyl alcohol and has a length which is more effectively achieved, and which uses polyester fibers and which is excellent in softness and feeling. Although it is not clear why such a particular effect can be obtained by the method of the present invention, the alkali metal hydroxide coexisting in the system during the treatment with polyvinyl alcohol improves the wettability of the polyester fiber surface to polyvinyl alcohol. This may be because the polyvinyl alcohol can uniformly coat the surface of the fiber, or the migration of the polyvinyl alcohol during drying is prevented by the alkali metal hydroxide.

In any case, the present invention provides a leather-like sheet material that uses inexpensive polyester fibers and has a process-friendly method in which the amount of polyvinyl alcohol used is reduced, and that is excellent in flexibility and texture. It has been obtained, and its industrial significance is enormous.

The leather-like sheet material of the present invention can be used for various purposes as it is, but further additional steps,
For example, if a silver surface processing step, a buffing step for sueding, a dyeing finishing step, etc. are performed, a leather substitute that is inexpensive and has a good sense of fulfillment and softness that has never been provided can be provided.

Hereinafter, the present invention will be described in more detail with reference to examples.

In each of the examples, the Gurley stiffness measured by the A method (Gurley method) of the JIS L 1096 bending repulsion test method was used as an index of the flexibility of the sheet-like material. Shows that it is more flexible). The strength and elongation was measured according to JIS K 6550.

Example 1. 60 parts by weight of regular polyester short fibers having a fineness of 1.5d, a fiber length of 38mm and a crimp number of 15 threads / inch, and a fineness of 1.5d, a fiber length of 51mm, a crimp number of 20 threads / inch and a boiling water shrinkage ratio of 30%. Shrink polyester short fiber 40 parts by weight of mixed cotton is made into a web by a carding machine and a cross wrapper machine, and then 40
Needle needle processing is performed at a density of 300 punching / cm ² from the top and bottom respectively, and a needling process is performed to obtain a thickness of 2.0 mm.
A polyester fiber non-woven fabric having a basis weight of 240 g / m ² was prepared.

The non-woven fabric obtained here contains a hot water bath at 98 ° C, a hot water bath at 98 ° C containing 2% caustic soda, or 2% caustic potash
Pass it through one of the hot water baths at 98 ℃ for 15 minutes, squeeze it with a mangle, then heat dry at 110 ℃ and treat three types of non-woven fabrics [one kind of hot water treatment (Comparative Example 1), alkali Two types of metal hydroxide treatment (the present Examples 1 and 2) were obtained.

Next, using each of the treated nonwoven fabrics, a leather-like sheet material was prepared as follows.

The treated non-woven fabric was impregnated with a 10% aqueous solution of partially saponified polyvinyl alcohol having a degree of polymerization of 800 and a degree of saponification of 88 mol%, and the solution was squeezed and dried on a net dryer at 110 ° C. The adhesion rate of polyvinyl alcohol to the non-woven fabric is 15.0%,
The total weight of the non-woven fabric after fixing was 288 g / m ² .

Next, a polyurethane elastomer consisting of polybutylene adipate, 4,4 'diphenylmethane diisocyanate and elene glycol (trade name: Crisbon-8616, manufactured by Dainippon Ink and Chemicals, Inc .; 100% elongation modulus 90 kg
/ cm ² ] 20% dimethylformamide solution was prepared and impregnated with a polyvinyl alcohol-treated nonwoven fabric,
Excess polyurethane elastomer solution on the surface of the non-woven fabric is scraped off with a doctor knife, wet-coagulated in a 10% dimethylformamide aqueous solution at 40 ° C, and then washed thoroughly with water to remove polyvinyl alcohol and alkali metal hydroxides. After further neutralization treatment with a 0.1% acetic acid aqueous solution, it was dried in a dryer at 120 ° C.

The three types of leather-like sheet materials obtained here all have a thickness
Almost the same apparent density (0.3 mm) with 1.5 mm and basis weight of 460 g / m ^2.
1) had.

Table 1 shows the physical properties of these three types of sheet materials.

As shown in Table 1, the sheet-like products obtained by the method of the present invention in which the alkali metal hydroxide treatment is carried out (Invention Examples 1 and 2) are the sheet-like products obtained by the conventional method without the treatment (Comparative Example 1). ), The Gurley stiffness, which is an index of flexibility, was extremely low, and the sensory test showed a very soft and soft feeling.

In Comparative Example 1 (conventional method), the sheet-like material (thickness: 1.5 mm, basis weight: 448 g / m ² , Apparent density 0.3
In 0), the Gurley stiffness was 1,780 mg and the flexibility was still insufficient.

For reference, in place of the polyester short fibers, 6-nylon short fibers having a fineness of 1.5d and a fiber length of 38 mm were used according to Comparative Example 1, and a sheet-like product (thickness 1.
Gurley stiffness of 5 mm, basis weight 455 g / m ² , apparent density 0.30) is 1.
080mg, 1.5mm thick natural kip (cowhide)
260 mg, which indicates that the sheet-like material using the polyester fiber according to the present invention (Examples 1 and 2 of the present invention) is more flexible than natural kip and uses the 6-nylon fiber treated with polyvinyl alcohol (softening treatment). It can be seen that it has a texture close to that of the sheet-like product.

Example 2. Water as a solvent, water / dipropylene glycol = 80/20 mixed solution, or water / polyethylene glycol (molecular weight 40
0) = 90/10 mixed solution (both weight ratio) was used to prepare 3 types of 2% caustic soda solutions having different solvents.

Each of the solutions had the same thickness of 2.0 mm as in Example 1,
A non-woven fabric having a basis weight of 240 g / m ² was impregnated at room temperature, squeezed to a squeezing ratio of 150%, then allowed to freely shrink on a net dryer at 120 ° C., heat treated for 10 minutes, and dried.

The three types of treated non-woven fabrics thus obtained were subjected to polyvinyl alcohol treatment, impregnation with polyurethane elastomer and coagulation treatment in the same manner as in Example 1 to obtain leather-like sheet-like materials.

They had a thickness of 1.4 mm and a basis weight of 350 g / m ² , and had almost the same apparent density (0.25).

Table 2 shows the measurement results of the physical property values of these sheet-like products. From these results, it is possible to exhibit an effective softening effect even when the method of the present invention is carried out by a so-called pad-dry method, In the pad-dry method, it is understood that more preferable results can be obtained by adding the high boiling point liquid substance to the alkali metal hydroxide solution.

Example 3. A non-woven fabric similar to that of Example 1 was impregnated with a mixed aqueous solution containing caustic soda and polyvinyl alcohol (polymerization degree 800, saponification degree 88 mol%) at concentrations of 2% and 10%, respectively, and squeezed. After squeezing the solution to a rate of 150%, it was allowed to freely shrink on a net dryer at 120 ° C for 10 minutes for heat treatment and dried.

Next, this treated non-woven fabric was impregnated with a polyurethane elastomer solution in the same manner as in Example 1 and wet-coagulated, washed with water, neutralized and dried to obtain a leather-like sheet.

This sheet material has a thickness of 1.8 mm, a basis weight of 390 g / m ² , and an apparent density of 0.
The strength and the elongation were 22 and substantially the same values as those of Example 3 of the present invention of Example 2. The Gurley stiffness is
It was as flexible as 890 mg and had a feel similar to that of natural leather.

Example 4. A polyester multifilament (50d / 25 filament) is used as a warp, and a 20-count twin yarn composed of polyester / rayon = 80/20 blended yarn is used as a weft, and a driving density is 40 × 48/25 mm. A twill fabric is woven and raised on one side to give a fabric weight of 250 g / m ² [polyester / rayon = 8
8/12 (weight ratio)] was created.

2% of this raised cloth was treated in the same manner as in Example 5 of the present invention of Example 2.
Caustic soda solution (solvent: water / polyethylene glycol =
90/10) and then heat-dried, and then the treated napped cloth obtained is treated with polyvinyl alcohol and impregnated with polyurethane elastomer and coagulated according to Example 1 to form a leather-like sheet material. Got However, as the polyurethane elastomer, a polyether type polyurethane elastomer composed of polytetramethylene glycol (molecular weight 1,500), 4,4 ′ diphenylmethane diisocyanate and ethylene glycol [trade name: Crisbon-
1846, manufactured by Dainippon Ink and Chemicals, Inc.] was used.

The sheet-like material obtained here has a thickness of 1.0 mm and a basis weight of 400 g / m ² ,
The apparent density is 0.40 and the Gurley stiffness is 1,250 m.
It was g and had a sufficiently soft feeling.

For comparison, a leather-like sheet was prepared in the same manner as above except that the treatment with a 2% caustic soda solution was not performed. The sheet had a Gurley stiffness of 2,500 m.
It was a very rough g.

Example 5 As a treatment liquid for a base fabric, an aqueous solution containing these components at the concentrations shown in Table 3 or 4 was used instead of the mixed aqueous solution containing 2% caustic soda and 10% polyvinyl alcohol. A leather-like sheet material was obtained in the same manner as in Example 3.

The physical properties of these sheet-like materials are shown in Tables 3 and 4.

As is clear from the results in Table 3, according to the method of the present invention,
When the fixing ratio of polyvinyl alcohol to the base cloth is around 5%, it is possible to obtain an excellent softening effect which exceeds the 60% fixing in the conventional method.

Further, the results in Table 4 show that the concentration of the treatment liquid of alkali metal hydroxide (caustic soda) is preferably 0.2% or more.

Comparative Example 5 In the present invention example 1 of Example 1, the nonwoven fabric which has been passed through the hot water of 2% caustic soda and dried is immersed in an acetic acid bath having a concentration of 1 g / l before being treated with polyvinyl alcohol. A leather-like sheet having a thickness of 1.5 mm, a weight per unit area of 456 g / m ² , and an apparent density of 0.30 was obtained in the same manner as in Example 1 of the present invention except that the alkali content was neutralized, followed by washing with water and drying.

The Gurley stiffness of this sheet-shaped product was 1,960 mg, which was no different from that of the sheet-shaped product (Comparative Example 1) prepared by the conventional method in which the alkali metal hydroxide treatment was not performed.

Claims (13)

[Claims] 1. A base fabric mainly composed of polyester fibers, to which polyvinyl alcohol is fixed, then impregnated with a water-miscible organic solvent solution of polyurethane elastomer, which is then wet-coagulated in an aqueous medium, washed with water and dried to form leather. A method for producing a leather-like sheet material, characterized in that the polyvinyl alcohol is fixed to the base fabric in the presence of an alkali metal hydroxide when the sheet-like material is produced. 2. Fixing of polyvinyl alcohol in the presence of an alkali metal hydroxide is carried out by heat-treating a base fabric in an alkali metal hydroxide aqueous solution, then impregnating this with a polyvinyl alcohol aqueous solution, and drying. The manufacturing method according to claim 1. 3. Fixing of polyvinyl alcohol in the presence of an alkali metal hydroxide is performed by applying an alkali metal hydroxide aqueous solution to a base fabric, heating and drying, and then impregnating and drying the polyvinyl alcohol aqueous solution. The manufacturing method according to claim 1, which is performed. 4. The production method according to claim 3, wherein a water-soluble high-boiling-point liquid substance is added to the alkali metal hydroxide aqueous solution. 5. A water-soluble high-boiling-point liquid substance having a solution concentration of 10 to 10
The manufacturing method according to claim 4, wherein 30% by weight is added. 6. The production method according to claim 4 or 5, wherein the water-soluble high-boiling-point liquid substance is selected from glycols. 7. The method for fixing polyvinyl alcohol in the presence of an alkali metal hydroxide by applying a polyvinyl alcohol aqueous solution containing an alkali metal hydroxide to a base fabric and heating and drying. The manufacturing method according to item. 8. The method according to claim 7, wherein the water-soluble high-boiling-point liquid substance is added to an aqueous polyvinyl alcohol solution containing an alkali metal hydroxide. 9. A water-soluble high-boiling-point liquid substance having a solution concentration of 10 to 10
The manufacturing method according to claim 8, wherein 30% by weight is added. 10. A water-soluble high-boiling-point liquid substance selected from glycols according to claim 8 or 9.
The manufacturing method according to item. 11. The solution concentration of alkali metal hydroxide is 0.2.
The manufacturing method according to claim 2, 3, or 7, which is ˜5% by weight. 12. The solution concentration of polyvinyl alcohol is 5 to 5.
The manufacturing method according to claim 2, 3, or 7, which is 20% by weight. 13. A base fabric mainly composed of polyester fiber,
The production method according to claim 1, which comprises 70% by weight or more of polyester fiber.