POLYVINYL-ALCOHOL-BASED FIBER, FIBER STRUCTURE, AND METHOD FOR MANUFACTURING SAME

Abstract

A polyvinyl alcohol fiber that is excellent in water absorption properties, water solubility and mechanical strength; a fiber structure including the polyvinyl alcohol fiber; and a method for producing the polyvinyl alcohol fiber are provided. The polyvinyl alcohol fiber includes 1 mol % or more of at least one functional group selected from a sulfonic acid group, a sulfonate group, a maleic acid group, an itaconic acid group, an acrylic acid group, and a methacrylic acid group. The polyvinyl alcohol fiber has a degree of cross-linking of 0% and a tensile strength of 3 cN/dtex or more.

Claims

1: A polyvinyl alcohol fiber, comprising: 1 mol % or more of at least one functional group selected from the group consisting of a sulfonic acid group, a sulfonate group, a maleic acid group, an itaconic acid group, an acrylic acid group, and a methacrylic acid group, wherein the polyvinyl alcohol fiber has a degree of cross-linking of 0% and a tensile strength of 3 cN/dtex or more.

2: The polyvinyl alcohol fiber as claimed in claim 1, wherein the polyvinyl alcohol fiber has a water absorption ratio of 5 times or more after being immersed in physiological saline at 30? C. for 1 hour.

3: The polyvinyl alcohol fiber as claimed in claim 1, wherein the polyvinyl alcohol fiber has a dissolution temperature in physiological saline or water of 80? C. or less.

4: The polyvinyl alcohol fiber as claimed in claim 1, wherein the polyvinyl alcohol fiber has a degree of saponification of 95 mol % or more.

5: The polyvinyl alcohol fiber as claimed in claim 1, wherein the polyvinyl alcohol fiber has a crystallinity of 20 to 50%.

6: A fiber structure, comprising the polyvinyl alcohol fiber as claimed in claim 1 at least in part.

7: A method for producing the polyvinyl alcohol fiber as claimed in claim 1, the method comprising: wet or dry-wet spinning a spinning stock solution containing polyvinyl alcohol in a solidifying bath mainly composed of an organic solvent capable of solidifying the polyvinyl alcohol to obtain a fiber, the polyvinyl alcohol comprising 1 mol % or more of at least one functional group selected from the group consisting of a sulfonic acid group, a sulfonate group, a maleic acid group, an itaconic acid group, an acrylic acid group, and a methacrylic acid group, wherein in any drying, stretching, or heating the fiber, a total stretching ratio of the fiber in all processes is 3 times or more.

Description

EXAMPLES

[0094] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[Degree of Polymerization]

[0095] Based on JIS K 6726, the degree of polymerization was calculated by the following formula (1) from the measured value of the intrinsic viscosity [n] of an aqueous solution at 30? C. In this regard, P is an average degree of polymerization of the polyvinyl alcohol.

[00001]$\begin{array}{cc}\log P=1.613.Math.\log \left(\left[?\right]?{10}^4/8.29\right)& \left(1\right)\end{array}$

[Degree of Saponification (Mol %)]

[0096] Measured according to JIS K 6726.

[Tensile Strength (cN/Dtex)]

[0097] Measured according to JIS L 1013.

[Crystallinity of Polyvinyl Alcohol Fiber]

[0098] Using a Mettler differential scanning calorimeter (DSC-20), an endothermic amount ?H (J/g) at an endothermic peak was measured when 10 mg of the fiber sample was heated at a rate of 20? C./min under nitrogen. Next, the degree of crystallinity was calculated by the following formula (2) from a ratio to 174.5 J/g, which is the heat of fusion of complete crystals of the polyvinyl alcohol.

[00002]$\begin{array}{cc}\mathrm{Crystallinity}\left(\%\right)=?H\left(J/g\right)/174.5\left(J/g\right)?100& \left(2\right)\end{array}$

[Dissolution Temperature of Fiber in Water (? C.)]

[0099] 0.02 g of the fiber cut into a length of 2 mm was held in water, the water temperature was raised at a rate of 2? C./min, and the temperature at which the fiber dissolved was taken as the dissolution temperature in water.

[Water Absorption Ratio of Fiber]

[0100] The fibers were precisely weighed and immersed in physiological saline (0.01 mol/L phosphate buffered saline) at 30? C. for 1 hour. After that, the liquid was drained by leaving it for 10 minutes, and the mass was measured. When the mass of the fiber before immersion in physiological saline is A (g) and the mass after immersion is B (g), the water absorption ratio was calculated by the following formula.

[0101] Water absorption ratio (times)=(B)/(A) (3)

[Fiber Processability]

[0102] According to a known manufacturing method, the fibers were opened with a roller card machine to form a web, and those that could be processed into non-woven fabrics were marked with OK, and those that could not be processed were marked with NG.

[Degree of Cross-Linking (Mol %)]

[0103] In the polyvinyl alcohol fiber into which a cross-linking component that forms an ether bond has been introduced, a measurement sample and a 1N hydroxylammonium chloride aqueous solution of 100 times the mass of the sample are placed in a test tube, sealed, and dissolved at 121? C. for 2 hours. The resulting solution was titrated with 0.1 N NaOH aqueous solution until the pH reached that of 1N hydroxylammonium chloride aqueous solution, and the degree of cross-linking was calculated from the titration amount by the following formula.

Degree of cross-linking (mol %)=[neutralized alkali amount (mol %)/(PVA mass (g)/44)]??(4)

Example 1

[0104] A polyvinyl alcohol copolymer (Elvanol 30-18 manufactured by Kuraray Co., Ltd.), which is a copolymer with methyl acrylate containing 5.2 mol& of an acrylic acid group, was dissolved in DMSO with stirring at 90? C. for 5 hours, and a spinning stock having a polyvinyl alcohol concentration of 22% by mass was obtained. This spinning stock solution was wet spun in a methanol/DMSO=80/20 solidifying bath at 10? C. through a nozzle with 40,000 holes and a hole diameter of 0.08 mm?, and subjected to wet heat stretching of 3.0 times in a methanol bath at 20? C. Next, after extracting DMSO in the fiber with methanol, a spinning oil was applied and dried at 140? C. Next, the dry raw yarn obtained was subjected to dry heat stretching at 160? C. under the conditions of a dry heat stretching ratio of 2.0 times (total stretching ratio TD=6.0 times). Then, dry heat shrinkage was performed at 160? C. with a dry heat shrinkage rate of 1% to produce a polyvinyl alcohol water-retaining fiber. Table 1 shows the results of measuring the water absorption properties, tensile strength and water solubility temperature of the obtained fiber.

Example 2

[0105] A polyvinyl alcohol copolymer (Elvanol T-25 manufactured by Kuraray Co., Ltd.), which is a copolymer with methyl methacrylate containing 2.5 mol % of methacrylic acid group, was dissolved in DMSO with stirring at 90? C. for 5 hours, and a spinning stock solution having a polyvinyl alcohol concentration of 20% by mass was obtained. This spinning stock solution was dry-wet spun in a methanol/DMSO 80/20 solidifying bath at 5? C. through a nozzle with 20 holes and a hole diameter of 0.15 mm?, and subjected to wet heat stretching of 3.0 times in a methanol bath at 20? C. Next, after extracting DMSO in the fiber with methanol, a spinning oil was applied and dried at 120? C. Next, the dry raw yarn obtained was subjected to dry heat stretching at 180? C. under the conditions of a dry heat stretching ratio of 2.0 times (total stretching ratio TD=6.0 times). Then, dry heat shrinkage was performed at 180? C. with a dry heat shrinkage rate of 18 to produce a polyvinyl alcohol water-retaining fiber. Table 1 shows the results of measuring the water absorption properties, tensile strength and water solubility temperature of the obtained fiber.

Example 3

[0106] A polyvinyl alcohol copolymer (K-5112 manufactured by Kuraray Co., Ltd.), which is a copolymer of monomethyl maleate containing 4.0 mol % of maleic acid group, was dissolved in DMSO with stirring at 90? C. for 5 hours, and a spinning stock solution having a polyvinyl alcohol concentration of 25% by mass was obtained. This spinning stock solution was dry-wet spun in a methanol/DMSO=80/20 solidifying bath at 5? C. through a nozzle with 80 holes and a hole diameter of 0.12 mm?, and subjected to dry heat stretching of 3.0 times in a methanol bath at 20? C. Next, after extracting DMSO in the fiber with methanol, a spinning oil was applied and dried at 120? C. Next, the dry raw yarn obtained was subjected to dry heat stretching at 180? C. under the conditions of a dry heat stretching ratio of 2.0 times (total stretching ratio TD=6.0 times). Then, dry heat shrinkage was performed at 180? C. with a dry heat shrinkage rate of 1% to produce a polyvinyl alcohol water-retaining fiber. Table 1 shows the results of measuring the water absorption properties, tensile strength and water solubility temperature of the obtained fiber.

Example 4

[0107] A polyvinyl alcohol copolymer, which is a copolymer of 2-acrylamido-2-methylpropanesulfonic acid containing 2.0 mol % of sulfonic acid group, was dissolved in DMSO with stirring at 90? C. for 5 hours, and a spinning stock solution having a polyvinyl alcohol concentration of 21% by mass was obtained. This spinning stock solution was dry-wet spun in a methanol/DMSO=85/15 solidifying bath at 5? C. through a nozzle with 30000 holes and a hole diameter of 0.07 mm?, and subjected to wet heat stretching of 3.0 times in a methanol bath at 20? C. Next, after extracting DMSO in the fiber with methanol, a spinning oil was applied and dried at 165? C. Next, the dry raw yarn obtained was subjected to dry heat stretching at 180? C. under the conditions of a dry heat stretching ratio of 2.67 times (total stretching ratio TD=8.0 times). Then, dry heat shrinkage was performed at 180? C. with a dry heat shrinkage rate of 18 to produce a polyvinyl alcohol water-retaining fiber. Table 1 shows the results of measuring the water absorption properties, tensile strength and water solubility temperature of the obtained fiber.

Example 5

[0108] A polyvinyl alcohol copolymer (KL-118 manufactured by Kuraray Co., Ltd.), which is a copolymer with itaconic acid containing 1.5 mol % of itaconic acid group, was dissolved in DMSO with stirring at 90? C. for 5 hours, and a spinning stock solution having polyvinyl alcohol a concentration of 25% by mass was obtained. This spinning stock solution was dry-wet spun in a methanol/DMSO=80/20 solidifying bath at 5? C. through a nozzle with 80 holes and a hole diameter of 0.12 mm?, and subjected to wet heat stretching of 3.0 times in a methanol bath at 20? C. Next, after extracting DMSO in the fiber with methanol, a spinning oil was applied and dried at 120? C. Next, the dry raw yarn obtained was subjected to dry heat stretching at 160? C. under the conditions of a dry heat stretching ratio of 2.0 times (total stretching ratio TD=6.0 times). Then, dry heat shrinkage was performed at 160? C. with a dry heat shrinkage rate of 18 to produce a polyvinyl alcohol water-retaining fiber. Table 1 shows the results of measuring the water absorption properties, tensile strength and water solubility temperature of the obtained fiber.

Comparative Example 1

[0109] A Polyvinyl alcohol (22-88 manufactured by Kuraray Co., Ltd.) having no functional groups of sulfonic acid group, sulfonate group, maleic acid group, itaconic acid group, acrylic acid group and methacrylic acid group was dissolved in DMSO with stirring at 90? C. for 5 hours, and a spinning stock having solution a polyvinyl alcohol concentration of 22% by mass was obtained. This spinning stock solution was wet spun in a methanol/DMSO=80/20 solidifying bath at 10? C. through a nozzle with 40,000 holes and a hole diameter of 0.08 mm?, and subjected to wet heat stretching of 3.0 times in a methanol bath at 20? C. Next, after extracting DMSO in the fiber with methanol, a spinning oil was applied and dried at 165? C. Next, the dry raw yarn obtained was subjected to dry heat stretching at 160? C. under the conditions of a dry heat stretching ratio of 2.0 times (total stretching ratio TD=6.0 times). Then, dry heat shrinkage was performed at 160? C. with a dry heat shrinkage rate of 1% to produce a polyvinyl alcohol water-retaining fiber. Table 1 shows the results of measuring the water absorption properties, tensile strength and water solubility temperature of the obtained fiber.

Comparative Example 2

[0110] A Polyvinyl alcohol copolymer, which is a copolymer with methyl acrylate containing 0.5 mol % of an acrylic acid group, was dissolved in DMSO with stirring at 90? C. for 5 hours, and a spinning stock solution having a polyvinyl, alcohol concentration of 19% by mass was obtained. This spinning stock solution was wet spun in a methanol/DMSO=80/20 solidifying bath at 10? C. through a nozzle with 40,000 holes and a hole diameter of 0.08 mm?, and subjected to wet heat stretching of 3.0 times in a methanol bath at 20? C. Next, after extracting DMSO in the fiber with methanol, a spinning oil was applied and dried at 165? C. Next, the dry raw yarn obtained was subjected to dry heat stretching at 160? C. under the conditions of a dry heat stretching ratio of 2.0 times (total stretching ratio TD=6.0 times). Then, dry heat shrinkage was performed at 160? C. with a dry heat shrinkage rate of 18 to produce a polyvinyl alcohol water-retaining fiber. Table 1 shows the results of measuring the water absorption properties, tensile strength and water solubility temperature of the obtained fiber.

Comparative Example 3

[0111] A Polyvinyl alcohol copolymer, which is a copolymer with itaconic acid containing 0.5 mol % of itaconic acid group, was dissolved in DMSO with stirring at 90? C. for 5 hours, and a spinning stock solution having a polyvinyl alcohol concentration of 198 by mass was obtained. This spinning stock solution was wet spun in a solidifying bath of saturated sodium sulfate at 40? C. through a nozzle with 1,000 holes and a hole diameter of 0.08 mm?, and the fiber thus formed were subjected to a wet heat stretching of 2.0 times and then applied with a spinning oil. Then, water in the fiber was dried at 130? C. to produce a polyvinyl alcohol fiber. Table 1 shows the results of measuring the water absorption properties, tensile strength and water solubility temperature of the obtained fiber.

Comparative Example 4

[0112] A Polyvinyl alcohol copolymer, which is a copolymer with itaconic acid containing 1.0 mol % of itaconic acid group, was dissolved in which water to 2 g/L of glutaraldehyde as a cross-linking agent had been added with stirring at 90? C. for 5 hours, and a spinning stock solution having a polyvinyl alcohol concentration of 15% by mass was obtained. This spinning stock solution was spun in an acidic coagulation bath containing a saturated mirabilite solution through a nozzle with 15,000 holes and a hole diameter of 0.16 mm? for coagulation and cross-linking. Further, the fiber obtained was subjected to wet heat stretching at a roller draft of 3.0 times, washed with water, further dried at 130? C., and then subjected to dry heat stretching at a stretching ratio of 2.0 times at 170? C. Then, the fiber was subjected to dry heat shrinkage at 170? C. under the conditions of a dry heat shrinkage rate of 1% to produce a polyvinyl alcohol fiber having a degree of cross-linking of 0.07 mol %. Table 1 shows the results of measuring the water absorption properties, tensile strength and water solubility temperature of the obtained fiber.

Comparative Example 5

[0113] An ethylene-vinyl alcohol copolymer containing 5.0 mol % of ethylene group was dissolved in DMSO with stirring at 90? C. for 5 hours, and a spinning stock solution having a polyvinyl alcohol concentration of 19% by mass was obtained. This spinning stock solution was wet spun in a solidifying bath of saturated sodium sulfate at 40? C. through a nozzle with 1,000 holes and a hole diameter of 0.08 mm?, and the fiber thus formed were subjected to a wet heat stretching of 2.0 times and then applied with a spinning oil. Then, water in the fiber was dried at 130? C. to produce a polyvinyl alcohol fiber. Table 1 shows the results of measuring the water absorption properties, tensile strength and water solubility temperature of the obtained fiber.

TABLE-US-00001 TABLE 1 Amount of Water functional Degree of Cross- absorption Tensile Dissolution Functional group Saponification linking ratio strength Crystallinity temperature in group type (mol %) (mol %) agent (times) (cN/dtex) (%) Processability water (? C.) Example 1 Acrylic acid 5.2 99.5 None 8.1 5.3 39.3 OK 40.2 group Example 2 Methacrylic 2.5 99.5 None 6.8 5.9 45.5 OK 53.2 acid group Example 3 Maleic acid 4.0 98.0 None 20.3 3.5 26.1 OK 60.5 group Example 4 Sulfonic 2.0 98.0 None 10.0 4.6 29.2 OK 24.5 acid group Example 5 Itaconic 1.5 97.0 None 5.7 6.2 49.0 OK 70.3 acid group Comparative None 88.0 None Dissolved 4.5 29.5 OK 15.2 Example 1 Comparative Acrylic acid 0.5 99.5 None 2.5 5.3 46.1 OK 75.1 Example 2 group Comparative Itaconic 0.5 97.0 None 2.0 1.5 43.1 NG 85.0 Example 3 acid group Comparative Itaconic 1.0 97.0 Contained 19.6 3.1 39.2 OK 95 or more Example 4 acid group Comparative Ethylene 5.0 98.0 None 2.8 1.3 35.7 NG 65.3 Example 5 group

[0114] As is clear from Table 1 above, the polyvinyl alcohol fiber of the present invention is excellent in water absorption properties, water solubility and mechanical strength.

[0115] The fiber structure containing the vinyl alcohol fiber of the present invention at least in part can be suitably used as a wound dressing material, a packaging material for soaps, detergents, bleaches and the like, a binder with glass non-woven fabric, and a disposable diaper.