WO2001068746A1

WO2001068746A1 - Molding made of polyvinyl alcohol and process for producing the same

Info

Publication number: WO2001068746A1
Application number: PCT/JP2001/001995
Authority: WO
Inventors: Kazuo Yamaura
Original assignee: Ueda Textile Science Foundation
Priority date: 2000-03-15
Filing date: 2001-03-14
Publication date: 2001-09-20
Also published as: AU4112901A

Abstract

A polyvinyl alcohol molding which is excellent in water resistance, heat resistance, stretchability, color, etc., less influences the living body, and has high strength; and a process by which the polyvinyl alcohol molding can be produced easily and inexpensively. The process for producing a polyvinyl alcohol molding is characterized in that the molding is obtained from an aqueous solution containing a polyvinyl alcohol and a salt. In a preferred embodiment, the salt is at least one of sodium chloride, potassium chloride, sodium sulfate, and ammonium chloride. The polyvinyl alcohol molding is characterized by being obtained by the process.

Description

TECHNICAL FIELD The present invention relates to a polyvinyl alcohol molded article having excellent water resistance, heat resistance, stretchability, tint, etc., a low effect on living bodies, and a high strength. Also, the present invention relates to a method for producing a polyvinyl alcohol molded article which can easily and inexpensively produce the polyvinyl alcohol molded article. Polytechnique Polyvinyl alcohol is a synthetic polymer with an affinity for water. Polyvinyl alcohol derived from vinyl acetate (atactic polyvinyl alcohol)

: A— Films and fibers made from PVA) will dissolve after swelling in water unless treated with water resistance.

Conventionally, methods for imparting water resistance to a polymer molded article (film, fiber, etc.) containing polyvinyl alcohol as a main component and increasing the strength of the polyvinyl alcohol include, for example: (1) water resistance by a crosslinking reaction by formalin treatment or the like; (2) Freeze and thaw the aqueous solution (JP-A-57-130543 and JP-A-58-36630, “Polymer Processing” 1983 1982 32 (1 1) 532 P ~) Method, (3) Gel spinning of an aqueous solution using a mixed solvent of water and an organic solvent such as dimethyl sulfoxide, (4) Blending with a water-soluble natural product (Japanese Unexamined Patent Publication No. Hei 6-2556616) Gazette) Methods, etc. have been implemented. In these methods, the main goal is to construct high-strength and high-modulus materials.

However, in order to achieve high strength and high elastic modulus, the inhibition of stretchability due to hydrogen bonds between polyvinyl alcohol molecules is an obstacle to achieving the above goal. In recent years, polymer molded products containing polyvinyl alcohol as a main component have been developed in the medical field, etc., but their physical compatibility and strength are insufficient, and their use has been limited. . In particular, conventional thermal stabilization methods, such as the methods described in ① and ③ above, use organic solvents and cross-linking agents that are not desirable from the viewpoint of hygiene and safety. Had to be completely removed. In the method (1), there are problems that the number of times of freezing and thawing is large, and that the control of the thawing temperature is complicated. In the above method (2), there is a problem that the drawability of the film (2) cannot be enhanced by blending. An object of the present invention is to provide a polyvinyl alcohol molded article which is excellent in water resistance, heat resistance, stretchability, tint, etc., has a low effect on a living body, and has high strength. An object of the present invention is to provide a method for producing a molded article of polyvinyl alcohol which can be produced at low cost. DISCLOSURE OF THE INVENTION In the method for producing a molded article made of polyvinyl alcohol of the present invention for achieving the object of the present invention, molding is performed using an aqueous solution containing polyvinyl alcohol and salts to obtain a molded article made of polyvinyl alcohol. Further, the molded article made of polyvinyl alcohol of the present invention is obtained by the method for producing polyvinyl alcohol of the present invention. BEST MODE FOR CARRYING OUT THE INVENTION

[Production method of polyvinyl alcohol molded article]

In the method for producing a molded body made of polyvinyl alcohol of the present invention, the molded body is molded using an aqueous solution containing polyvinyl alcohol and salts to obtain a molded body made of polyvinyl alcohol. -Polyvinyl alcohol-

The polyvinyl alcohol is not particularly limited, and includes all known polyvinyl alcohols derived from vinyl acetate, which are conventionally used as a raw material for polyvinyl alcohol films and fibers. In addition, homopolymers of vinyl esters other than vinyl acetate such as vinyl trifluoroacetate, vinyl formate, vinyl vivalate, vinyl butyrate, vinyl benzoate, vinyl t-butyl benzoate, and vinyl esters of these vinyl esters and vinyl acetate And polyvinyl alcohol obtained by saponifying at least two kinds of copolymers. These may be used alone or in combination of two or more. Among these, polyvinyl alcohol and the like derived from vinyl acetate are preferable in terms of price.

The average degree of polymerization of the polyvinyl alcohol is not particularly limited, but is preferably in the range of about 300 to 500.

The saponification degree of the polyvinyl alcohol is not particularly limited, but is preferably in the range of 80 to 100 mol%.

One salt

The salts are not particularly limited and include all conventionally known salts, but sodium chloride, potassium chloride, sodium sulfate, ammonium chloride, and the like are preferable in terms of high versatility and easy availability. Of these, sodium sulfate is preferred in terms of heat resistance and high strength if the effects on the living body are not considered, but it is cheaper, easily available, and has the least effect on the living body. In this respect, sodium chloride and the like are more preferable.

As the sodium chloride, generally used ones are all suitably mentioned, and salt, which is a typical example of a commercially available product, can also be suitably used.

One aqueous solution

The aqueous solution contains the polyvinyl alcohol and the salts.

Conventionally, in the production of the polyvinyl alcohol molded article, an aqueous solution in which salts such as sodium chloride are intentionally dissolved has not been used as a solvent for the polyvinyl alcohol. This is because the polyvinyl alcohol is dissolved in a solvent (water, dimethyls This is because it is important to completely dissolve the compound in rufoxide, etc., and it is important to exclude substances that reduce its solubility from the aqueous solution.

On the other hand, in the present invention, by using an aqueous solution containing the above-mentioned salts (such as sodium chloride), water resistance, heat resistance, stretchability, tint, etc. are excellent, the influence on the living body is low, and the strength is high. A high molded product made of polyvinyl alcohol was obtained. This is because, in the aqueous solution, salt molecules or ions are associated with water molecules, the cohesive force between the polyvinyl alcohol molecules is increased, and a more stable horizontal structure (microcrystal) is formed which solidifies from the aqueous solution. It seems to be related.

In the aqueous solution, the content of the salt relative to the polyvinyl alcohol

(Weight) is preferably from 100 to 200 parts by weight, more preferably from 40 to 80 parts by weight, based on 100 parts by weight of polyvinyl alcohol.

When the content is within the above numerical range, it is possible to obtain a polyvinyl alcohol molded article having more excellent stretchability and color tone and high strength.

In the preparation of the aqueous solution, a uniform solution may be prepared by adding polyvinyl alcohol to a previously prepared aqueous solution containing salts so as to have a desired content. An aqueous solution to be prepared and an aqueous solution containing polyvinyl alcohol may be separately prepared, and then mixed to prepare a uniform solution.

In the former case, the content of the salt in the aqueous solution containing the salt is preferably 0.5 to 30% by weight, more preferably 1 to 10% by weight, and further preferably 2 to 10% by weight. .

If the content is more than 30% by weight, handling may be difficult such as long time required for dissolution, formation of holes during film formation, loss of flexibility, and the like.

In the former case, when the salt is sodium chloride, the content of the salt in the aqueous solution may be 2.5 to 3 in terms of water resistance, heat resistance, stretchability, color and strength of the obtained molded article. It is most preferable that the polyvinyl alcohol be added so that the total amount of the aqueous solution is 4.5 to 5.5% by weight. New The amount of polyvinyl alcohol added in the entire aqueous solution is limited to an upper limit.

It is preferably up to 15% by weight, but the combination such as the optimum content varies depending on the molecular weight.

Further, when the content of the salt in the aqueous solution is 5% by weight or less, even when it is not preferable that the salt remains in the obtained polyvinyl alcohol molded article,

During or after molding, the remaining salts can be removed in a short time. The aqueous solution can be used at atmospheric pressure prior to molding for uniform film and fiber production.

It is preferably heated to 0 to 100 ° C, more preferably heated to 100 to 140 ° C under pressurized conditions.

The pressure for the pressurization is not particularly limited, but is preferably about 0.5 to 3 kgf / cm ² .

In one molding, molding is performed using the aqueous solution. The shaping is not particularly limited, but is preferably performed by a process including at least one of gelation, casting, casting, wet spinning, gel spinning, and freezing and thawing.

In the case where a film-shaped polyvinyl alcohol-based molded article is obtained by the molding, for example, it is preferable to cast the uniform solution after the heating at room temperature. In the case of continuous production, it is preferable to cast the uniform solution.

In the molding, in order to expedite the drying of the obtained polyvinyl alcohol molded article, the molded article may be passed through the heating chamber or forced hot air may be applied. Further, in order to further improve the water resistance of the obtained polyvinyl alcohol molded product, freeze-thaw may be repeated several times and then dried. The thawing temperature is most preferably around −2 ° C., but it is preferably around room temperature (about 20 ° C.) because thawing takes a long time. Although the process is complicated, it may be dried once after gelling.

In the molding, the water resistance of the molded body made of polyvinyl alcohol is further improved. For this purpose, it is preferable to perform the heat treatment in a nitrogen atmosphere at 180 to 210 ° C. If the temperature of the heat treatment exceeds 210 ° C., the obtained molded body may turn brown.

In the present invention, even when the heat treatment is performed at the above-described high temperature, the polyvinyl alcohol molded body does not turn brown, and can be heat-treated at a high temperature. It is possible to obtain a (transparent) molded body having a good quality.

In the molding, it is preferable to perform an operation of removing salts from the obtained polyvinyl alcohol molded product. For example, the film-shaped molded product may be washed with water in a temperature range of room temperature to 50 ° C. And the like. When a fibrous polyvinyl alcohol molded article is obtained by the above-mentioned molding, for example, as in the case of obtaining the above-mentioned film-shaped molded article, it is preferable to use a uniform solution after heating and to perform molding by spinning or the like. preferable. In this case, the content of the polyvinyl alcohol in the aqueous solution is preferably 7 to 15% by weight, and it is preferable to select the optimum content of the salts in accordance with the content of the polyvinyl alcohol.

In the spinning, it is preferable to use a solution obtained by removing dust particles from the solution by filtration or the like. As for the temperature at the time of spinning, if spinning at around room temperature is possible, it is economically preferable. However, to prevent gelation at a low temperature, it is preferable to heat to room temperature to about 80 ° C. As a spinning method, for example, a homogeneous solution maintained at a temperature within the above-mentioned temperature range is extruded from a fine hole into a coagulation bath and stretched through a guide in the coagulation bath, or water is passed through the coagulation bath and subsequently through water. A method of drawing while removing salts such as sodium chloride (wet spinning method). A uniform solution maintained at a temperature within the above-mentioned temperature range is spun into methanol at −20 to −40 ° C. to form a filament. A method of forming a gel and subsequently stretching (gel spinning method) is preferred. After the spinning, it is preferable to finally wind the fiber around a winding roller or the like. The draw ratio is preferably in a range where the spun yarns do not fuse and adhere to each other on a roller, and is usually preferably 3 times or more. Conventionally, as a coagulation bath during the wet spinning, An example is a saturated sodium sulfate aqueous solution used for spinning polyvinyl alcohol. A mixed aqueous solution of sodium sulfate and sodium hydroxide or the like can also be used as a coagulant.

According to the method for producing a polyvinyl alcohol molded article of the present invention described above, a polyvinyl alcohol molded article having excellent water resistance, heat resistance, stretchability, tint, etc., a low effect on living organisms, and high strength is obtained. It can be manufactured easily and at low cost.

[Molded body made of polyvinyl alcohol]

The molded article made of polyvinyl alcohol of the present invention is obtained by the method for producing a molded article made of polyvinyl alcohol of the present invention.

One form etc.

The form of the polyvinyl alcohol molded article of the present invention is not particularly limited, but is preferably at least one of a gel, a film, and a fiber. These are the various molding methods (gelation, casting, casting, wet spinning, gel spinning, and freeze-thaw cycles) described in the section “Molding” in the method for producing a molded article made of polyvinyl alcohol of the present invention. Etc.) can be suitably formed.

When the polyvinyl alcohol molded article is in a gel state, it is preferable to form a hydrogel that is stable in water.

One physical property

The molded article made of polyvinyl alcohol of the present invention is preferably insoluble in water at 65 ° C from the viewpoint of water resistance. Further, when the polyvinyl alcohol molded article is the fibrous form, the tensile modulus (GP a) (room temperature: 24 ° C.) is preferably 20 (GP a) or more from the viewpoint of strength. It is more preferably 25 (GPa) or more.

The content (residual amount) of salts in the polyvinyl alcohol molded article of the present invention is not particularly limited, but is preferably less than 5% by weight, more preferably less than 3% by weight. If the content is 5% by weight or more, holes may be formed in the obtained molded article (film).

—Applications—

The polyvinyl alcohol molded article of the present invention has the above constitution and is obtained by the method for producing a polyvinyl alcohol molded article of the present invention, and is excellent in water resistance, heat resistance, stretchability, color, etc. Effect is low and strength is high. Therefore, it can be suitably used as a molded article for various uses.

For example, by adjusting the amount of salts to an appropriate amount, it can be suitably used in the medical field and the like. In the case where a high-purity molded product that does not contain salts such as sodium chloride is required, it can be suitably removed while maintaining its form by immersing it in water for an appropriate period of time. . Therefore, in addition to medical surgical threads that require biocompatibility, water resistance, heat resistance, strength, etc., various artificial biological organs such as artificial blood vessels, artificial lungs, artificial kidneys, artificial hearts, artificial cornea, etc. Used as various medical materials such as wound cover materials, adhesion prevention film materials, etc., contact lenses that also require transparency, lenses for various optical devices, various light transmitting materials, etc. Can also. In addition, since it is highly safe and has excellent strength, it can be used not only for baby feeding equipment for infants, but also for various toys and tableware for infants. When used for these purposes, sodium chloride and chloride rim are most preferred as salts in terms of availability, cost, and biocompatibility.

The polyvinyl alcohol molded article of the present invention may contain components other than polyvinyl alcohol. Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited to these Examples.

(Example 1Comparative Example 1)

Manufacture of molded articles made of polyvinyl alcohol

Aqueous solution of sodium chloride (NaC1 content: 0 to 10% by weight) 0.5 g of polyvinyl alcohol in 10 ml (viscosity average molecular weight: about 75,000 (average degree of polymerization) : About 1700)) is charged into a pressurized container so that the polyvinyl alcohol content in the aqueous solution is 5% by weight (in this case, the content (weight) of sodium chloride with respect to 100 parts by weight of polyvinyl alcohol is 0 to After heating at 120 ° C in a sealed tube to dissolve the solution, the aqueous solution was heated to about 80 ° C and cast into a horizontally held petri dish. It was left at 20 ° C for several days (1-4 days) to evaporate water and cast to obtain a film (thickness: 10-60 / m). The obtained film was washed once in water at 30 ° C (room temperature), and then kept in water at 30 ° C to remove residual sodium chloride from the film. Thereafter, the film dried at room temperature was stretched in air at 200 ° C. and 220 ° C. until breakage in air. FIG. 1 shows the maximum stretching ratio at this time in relation to the NaC 1 content.

In FIG. 1, the case where the NaC 1 content is 0% by weight corresponds to Comparative Example 1.

In the stretching at 200 ° C., when the NaC 1 content was 1% by weight or less, it was observed that the polyvinyl alcohol molded product was slightly discolored. In the stretching at 220 ° C, discoloration was observed regardless of the NaC1 content.

As is clear from FIG. 1, in the film using the aqueous solution having the NaC 1 content of 3% by weight, the highest draw ratio was 2.5 compared with the film obtained using the aqueous solution containing no NaC 1. More than doubled.

(Example 2Comparative Example 2)

In Example 1 and Comparative Example 1, except that `` stretching until break '' was replaced by `` stretching to a draw ratio 10% lower than the highest draw ratio measured at each NaC 1 content in FIG. 1 '' After stretching in the same manner as in Example 1 and Comparative Example 1, heat treatment was performed for 10 minutes in the stretched state, and the tensile modulus of the obtained molded body was measured. The results are shown in FIG. 2 in relation to the NaC1 content.

In FIG. 2, the case where the NaC 1 content is 0% by weight corresponds to Comparative Example 2. As is clear from FIG. 2, the tensile modulus substantially corresponds to the result in FIG. 1 in which the highest stretching ratio was measured. When the NaC 1 content was 3% by weight, the NaC 1 content was 0%. Weight modulus is almost 3 times that of the case of wt% even at the same stretching temperature. It has become.

Furthermore, the films obtained in Comparative Examples 1-2 were swollen in water near room temperature and then dissolved at 50 ° C or less by heating, but the films obtained in Examples 1-2 were salts After removal of swelling, it swelled in water near room temperature, but did not dissolve up to 70 ° C even when heated.

(Example 3)

An aqueous solution of polyvinyl alcohol containing 10% by weight of sodium chloride (polyvinyl alcohol content: 7% by weight or more) was left at 0 ° C for 24 hours to gel. When the melting point of the obtained gel was measured, it was as high as about 90 ° C.

Claims

The scope of the claims

1. A method for producing a molded body made of polyvinyl alcohol, which comprises forming a molded body made of polyvinyl alcohol by molding using an aqueous solution containing polyvinyl alcohol and salts.

2. The method according to claim 1, wherein the salt is at least one of sodium chloride, potassium chloride, sodium sulfate and ammonium chloride.

3. The method for producing a polyvinyl alcohol molded product according to claim 1 or 2, wherein the aqueous solution is heated to 80 or more before molding.

4. The method for producing a polyvinyl alcohol molded article according to claim 1 or 2, wherein the aqueous solution is heated to 100 to 140 and pressurized before molding. '

5. The method according to any one of claims 1 to 4, wherein the forming is performed by a process including at least one of gelling, casting, casting, wet spinning, gel spinning, and freezing-thawing. The method for producing a polyvinyl alcohol molded article according to any one of the above.

6. The method for producing a molded article made of polyvinyl alcohol according to any one of claims 1 to 5, wherein heat treatment is performed after the molding.

7. The method for producing a polyvinyl alcohol molded article according to any one of claims 1 to 6, wherein salts are removed from the polyvinyl alcohol molded article after molding.

8. The aqueous solution according to any one of claims 1 to 7, wherein the content (weight) of the salt with respect to 100 parts by weight of the polyvinyl alcohol is 10 to 200 parts by weight. A method for producing a molded article made of polyvinyl alcohol.

9. An aqueous solution is prepared by adding polyvinyl alcohol to an aqueous solution containing sodium chloride, and an aqueous solution containing sodium chloride is prepared in the aqueous solution containing sodium chloride. The method for producing a polyvinyl alcohol molded article according to any one of claims 1 to 8, wherein the content of lithium is 1 to 10% by weight.

10. An aqueous solution is prepared by adding polyvinyl alcohol to an aqueous solution containing sodium chloride, and the content of sodium chloride in the aqueous solution containing sodium chloride is 2.5 to 3.5% by weight. 10. The method for producing a polyvinyl alcohol-made molded article according to any one of claims 1 to 9, wherein the polyvinyl alcohol is added so as to be 4.5 to 5.5% by weight in the whole aqueous solution.

1 1. A molded article made of polyvinyl alcohol, which is obtained by the method for producing a molded article made of polyvinyl alcohol according to any one of claims 1 to 10.

12. The molded article made of polyvinyl alcohol according to claim 11, which is in at least one of a gel form, a film form, and a fibrous form.

13. The polyvinyl alcohol molded article according to any one of claims 11 and 12, wherein the molded article is insoluble in water.

14. The fibrous material according to any one of claims 11 to 13, wherein the tensile modulus (GPa) (room temperature: 24 ° C) is 20 (GPa) or more. Molded product made of polyvinyl alcohol.

15. The molded article made of polyvinyl alcohol according to any one of claims 11 to 14, wherein the salt content is less than 5% by weight.

1 6. The molded article made of polyvinyl alcohol according to any one of claims 11 to 15 used for a medical material.

1 7. The molded article made of polyvinyl alcohol according to any one of claims 11 to 15, which is used for a material for light transmission. Claims of amendment

[June 8, 2001 (08.06.01) Accepted by the International Bureau: Claims 1, 3, 4, 5 and 13 originally filed have been amended; other claims remain unchanged. (2 pages)]

1. (After Correction) A method for producing a molded body made of polyvinyl alcohol, which is performed by using an aqueous solution containing polyvinyl alcohol and salts and molding at a temperature exceeding o ° c to obtain a molded body made of polyvinyl alcohol which is biosafe.

2. The method according to claim 1, wherein the salts are at least one of sodium chloride, potassium chloride, sodium sulfate, and ammonium chloride.

3. (After correction) The method for producing a polyvinyl alcohol molded article according to claim 1 or 2, wherein the aqueous solution is heated to 80 ° C or more before molding.

4. (After Correction) Production of the polyvinyl alcohol molded article according to claim 1 or 2, wherein the aqueous solution is heated to 100 to 140 ° C. and pressurized before molding. Method.

5. The method according to any one of claims 1 to 4, wherein the shaping is performed by a step including at least one of gelling, casting, casting, wet spinning, and gel spinning. A method for producing a molded article made of polyvinyl alcohol.

6. The method for producing a polyvinyl alcohol molded article according to any one of claims 1 to 5, wherein a heat treatment is performed after the molding.

7. The method for producing a polyvinyl alcohol molded article according to any one of claims 1 to 6, wherein salts are removed from the polyvinyl alcohol molded article after the molding.

8. The polyvinyl alcohol production according to any one of claims 1 to 7, wherein the content (weight) of the salt with respect to 100 parts by weight of the polyvinyl alcohol in the aqueous solution is 10 to 200 parts by weight. Manufacturing method of the shape.

9. The aqueous solution is prepared by adding polyvinyl alcohol to an aqueous solution containing sodium chloride, and the content of sodium chloride in the aqueous solution containing sodium chloride is 1 to 10% by weight. Any of paragraphs 1 to 8

13

Amended paper (Treaty 19 第, A method for producing a polyvinyl alcohol molded article according to any one of the above.

12. The polyvinyl alcohol molded article according to claim 11, wherein the molded article is in at least one of a gel form, a film form, and a fibrous form.

13. The polyvinyl alcohol molded product according to any one of claims 11 and 12, which is insoluble in water at 65 ° C (after correction).

17. The molded article made of polyvinyl alcohol according to any one of claims 11 to 15, which is used for a material for light transmission.

14

Amended paper (Convention No. 19