JPH05317689A - Highly elastic water-containing gel and its production - Google Patents

Abstract

PURPOSE:To efficiently produce a highly elastic tough water-contg. gel having desired shape and size which are not deformed before and after gelation with simple method and device without applying an intricate and expensive process such as freezing, high-pressure treatment and vacuum treatment. CONSTITUTION:A PVA having >=35 polymerization degree and >=90% saponification degree is dissolved in a polar org. solvent or a mixture of the polar org. solvent and water. A hydrophilic high molecular compd. insoluble or sparingly soluble in water is dispersed in obtained soln., the dispersion is allowed to stand or dipped in a polar poor solvent or a polar nonsolvent to form a gel, and a highly elastic water-contg. gel or its precursor gel is produced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a highly elastic hydrous gel containing a polyvinyl alcohol polymer as a main component, a precursor gel thereof, and a method for producing them.

[0002]

2. Description of the Related Art As a method for obtaining a tough, highly hydrous gel from a polyvinyl alcohol-based polymer, a method in which a highly concentrated aqueous solution of polyvinyl alcohol is frozen and then vacuum dried (Japanese Patent Laid-Open No. 57-159826) is known. There is. However, this method requires repeated freezing and thawing, and requires vacuum drying, which complicates the process and apparatus and is inferior in thermal efficiency. Moreover, this method has a drawback that the molding process is difficult and it is difficult to prepare a gel having a complicated shape.

[0003]

From the above point of view, the present inventors have made it possible to obtain a highly elastic hydrous gel of a polyvinyl alcohol polymer, which is tough and has excellent properties, without performing freeze treatment, high pressure treatment, vacuum treatment or the like. However, as a result of continuous research aimed at developing a method for efficiently producing a polyalcohol-based polymer and other water-soluble polymer compounds with a polar organic solvent or a polar organic solvent and water, It was found that the above object can be achieved by producing a water-containing gel using a solution dissolved in a mixed solvent of (1) and (2) Japanese Patent Application No. 3-274947.

When the present inventors further conducted research on hydrogels, they were highly water-soluble as another polymer compound used in combination with the polyvinyl alcohol polymer in the above-mentioned prior invention of the present inventors. Instead of molecular compounds,
When a water-insoluble or sparingly water-soluble hydrophilic polymer compound is used, the elasticity of the resulting highly hydrous gel is further improved,
Moreover, the inventors have completed the present invention by finding that the highly hydrous gel can be formed into a desired size and shape with almost no dimensional change before and after gelation.

Therefore, according to the present invention, a polyvinyl alcohol polymer having a degree of polymerization of 35 or more and a degree of saponification of 90% or more is dissolved in a solution of a polar organic solvent or a mixed solvent of a polar organic solvent and water insoluble in water. Alternatively, a highly elastic hydrogel or a mixture thereof, which is prepared by dispersing a poorly water-soluble hydrophilic polymer compound and leaving it as it is, or by immersing it in a polar poor solvent or a polar nonsolvent to form a gel. It is a method for producing a precursor gel. And the present invention is
It includes a highly elastic hydrous gel produced by the above method or a precursor thereof.

The polyvinyl alcohol-based polymer used in the present invention means a homopolymer of polyvinyl alcohol containing vinyl alcohol as a main repeating unit or a copolymer of vinyl alcohol and another vinyl monomer. When the polyvinyl alcohol-based polymer is a vinyl alcohol copolymer, the ratio of other vinyl monomers is about 3
It is preferably 5 mol% or less. Other vinyl monomers are, for example, ethylene; styrene, styrene sulfonic acid;
(Meth) acrylic acid esters such as methyl (meth) acrylate and ethyl (meth) acrylate; (meth) acrylic acid; (meth) acrylamide, N-methyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide , N, N-diethyl (meth) acrylamide and the like (N
(Substituted) (meth) acrylamides; (meth) acrylonitrile; N-vinylpyrrolidone; vinylpyridine; vinylsulfonic acid; vinylacetamide such as vinylacetamide and N-methylvinylacetamide. Not done. In the vinyl alcohol copolymer, one kind or two or more kinds of other vinyl monomers may be copolymerized with vinyl alcohol.

In the present invention, it is necessary that the polyvinyl alcohol polymer has a degree of polymerization of 35 or more.
The degree of polymerization is preferably about 500 or more, about 1000
~ 5000 is particularly preferred. When the degree of polymerization of the polyvinyl alcohol-based polymer is less than 35, the strength of the highly elastic hydrogel produced will be poor. The polyvinyl alcohol-based polymer needs to have a saponification degree of 90% or more, and particularly preferably a saponification degree of 95% or more. 90% saponification degree of polyvinyl alcohol polymer
When it is less than 1, the strength of the highly elastic hydrogel obtained is also low.

Examples of the water-insoluble or sparingly water-soluble hydrophilic polymer compound to be dispersed in an organic solvent solution of a polyvinyl alcohol polymer or a mixed solvent solution of an organic solvent and water include, for example, cellulose, dextran, chitin, chitosan, alginic acid, Polysaccharides such as pectic acid; albumin,
Examples thereof include proteins such as elastin and modified products thereof. Among them, cellulose, chitin, chitosan, alginic acid and albumin are preferable. The water-insoluble or sparingly water-soluble hydrophilic polymer compounds may be used alone or in combination of two or more.
Further, the water-insoluble or sparingly water-soluble hydrophilic polymer compound is preferably as fine as possible in order to uniformly disperse it in the solution of the polyvinyl alcohol polymer, and is generally preferably about 100 μm or less.

The polyvinyl alcohol polymer and the water-insoluble or sparingly water-soluble hydrophilic polymer compound are used in a weight ratio of polyvinyl alcohol polymer: water-insoluble or sparingly water-soluble hydrophilic polymer compound = about 90:10. ~ About 3
The ratio may be 0:70, preferably about 90:10 to about 60:40, and particularly at a ratio of 70:30 or thereabout, a highly elastic and tough hydrogel can be obtained.

The "polar organic solvent" used to dissolve the polyvinyl alcohol polymer in the present invention means that the polar organic solvent or a mixed solvent of the polar organic solvent and water causes the polyvinyl alcohol polymer to come to room temperature. Alternatively, it means an organic compound having polarity capable of being dissolved at a temperature of room temperature or higher to form a solution.

In the present invention, as the polar organic solvent, urea compounds such as dimitylimidazolidinone, tetrahydro-2-pyrimidinone, urea, tetramethylurea, dimethylurea and dimethylimidazolone; imidazole, N-methylimidazole, N , Imidazole compounds such as N-dimethylimidazole; amide solvents such as formamide, N, N-dimethylformamide, acetamide, N, N-dimethylacetamide, 2-pyrrolidone, N-methyl-2-pyrrolidone; dimethyl sulfoxide , Tetrahydrothiophene-1,1-dioxide, and other sulfoxide solvents; glycerin, ethylene glycol, and other polyhydric alcohol solvents; hexamethylphosphoric triamide, and other phosphoric acid amide solvents; ethyleneamine, diethylenetriamine, and other amines When using a solvent, the solution of polyvinyl alcohol polymer can be smoothly prepared.

In preparing the polyvinyl alcohol polymer solution, only a polar organic solvent may be used, or a mixed solvent of a polar organic solvent and water may be used, but a mixed solvent of a polar organic solvent and water may be used. It is preferable to use a polar organic solvent: water in a weight ratio of about 95: 5.
It is preferably about 5:95, particularly about 90:10 to about 50:10. When the concentration of the polar organic solvent in the mixed solvent is less than 5% by weight, it becomes difficult to obtain a tough hydrogel.

The polyvinyl alcohol polymer is dissolved in a polar organic solvent or a mixed solvent of a polar organic solvent and water at room temperature or higher, particularly at 50 ° C. or higher. It is desirable in terms of dissolution rate and solution viscosity. Further, the dissolution of the polyvinyl alcohol-based polymer can usually be sufficiently achieved under atmospheric pressure. And the concentration of the polyvinyl alcohol-based polymer in the solution,
It is preferable that about 3 to 60% by weight, particularly 5 to 40% by weight, and the water-insoluble or sparingly water-soluble hydrophilic polymer compound be dispersed in the polyvinyl alcohol-based polymer solution in the above-mentioned proportion.

At this time, the water-insoluble or sparingly water-soluble hydrophilic polymer compound is a polyvinyl alcohol-based polymer produced after the polyvinyl alcohol-based polymer is completely dissolved in an organic solvent or a mixed solvent of an organic solvent and water. In the state in which the hydrophilic polymer compound is dispersed even when added and dispersed in the combined solution or before the polyvinyl alcohol-based polymer is completely dissolved in the organic solvent or the mixed solvent of the organic solvent and water. The polyvinyl alcohol polymer may be completely dissolved in the organic solvent or the mixed solvent of the organic solvent and water.

Then, a mixed solution in which the polyvinyl alcohol polymer prepared as described above is dissolved and a water-insoluble or sparingly water-soluble hydrophilic polymer compound is dispersed is contained at room temperature or lower (usually about 40 ° C. or lower). ) And solidify into a gel. This gel itself is a self-supporting, tough solid that can be handled without crushing, and can be stored, distributed, sold, etc. as the final precursor gel for the highly elastic hydrous gel. .. For example, when the above-mentioned mixed solution is cast on a glass plate or the like to precipitate a precursor gel, a sheet or film-shaped precursor gel is formed, and the above-mentioned mixed solution is injected into a specific container or mold to form a gel. By precipitating, it is possible to form a precursor gel compact having a shape that matches the internal shape of the container or mold.

The precursor gel formed as described above is dipped in an aqueous solvent or in a polar poor solvent or a polar non-solvent for 1 to 14 days, and then in water for 1 to 14 days. A high water content gel can be obtained by immersion. The immersion time is greatly affected by the shape, thickness, surface area, etc. of the sample.For thin materials such as threads and membranes and those with a large surface area, the immersion time is shorter than the above, for example, several minutes to several hours. High water content gel can be obtained by immersion.

Further, in the present invention, a polar poor solvent is used instead of leaving the above mixed solution containing a polyvinyl alcohol polymer and a water-insoluble or sparingly water-soluble hydrophilic polymer compound as it is to form a precursor gel. Alternatively, it can be immersed in a polar non-solvent to form a gel. As the polar poor solvent or polar non-solvent, alcohols such as methanol, ethanol and propanol; ketones such as acetone and methyl ethyl ketone; ethers such as dioxane, tetrahydrofuran and dimethoxyethane; acetonitrile and the like can be used. .. The polar poor solvent or polar non-solvent may be used alone or in combination of two or more. When two or more kinds are used in combination, the gel may be immersed in a mixture of two or more polar poor solvents or polar non-solvents, or after first immersing in the first polar poor solvent or polar non-solvent. The second, third polar poor solvent or polar non-solvent may be sequentially dipped. At that time, a small amount of a polar solvent capable of dissolving the polyvinyl alcohol-based polymer may be added to the polar poor solvent or polar non-solvent, if necessary.

When the above mixture is first immersed in a polar poor solvent such as alcohol or a polar non-solvent,
The first immersion forms a precursor gel, which can be further immersed in water to form a highly elastic hydrous gel.

The temperature and the immersion time for immersing the above mixed solution in which a polyvinyl alcohol polymer is dissolved and a water-insoluble or sparingly water-soluble hydrophilic polymer compound is dispersed in a polar poor solvent or a polar non-solvent are Can be appropriately selected depending on the type of the water-insoluble or sparingly water-soluble hydrophilic polymer compound used, the ratio of the polyvinyl alcohol-based polymer and the hydrophilic polymer compound, the shape of the gel to be produced, etc. However, it is usually good to immerse in a polar poor solvent or polar non-solvent at about 0 to 50 ° C. for several minutes to 14 days.

Further, as described above, the above-mentioned mixed solution containing the polyvinyl alcohol polymer and the water-insoluble or sparingly water-soluble hydrophilic polymer compound is left as it is to form a precursor gel, and then, a polar gel is formed. The highly elastic hydrogel may be produced by immersing in a solvent or a polar non-solvent and further immersing in water. Also in this case, the same temperature and immersion time as described above can be adopted to form a highly elastic heterogeneous hydrogel from the precursor gel.

The reason why a highly elastic hydrogel can be obtained by the present invention using a mixture of a polyvinyl alcohol polymer solution and a water-insoluble or sparingly water-soluble hydrophilic polymer compound has not been sufficiently clarified. In the water-containing gel of the present invention, the particle surface of the water-insoluble or sparingly water-soluble hydrophilic polymer compound and the polyvinyl alcohol-based polymer interact to cause the particles to function as a filler, resulting in a highly elastic water-containing compound. It is presumed that a gel is formed.

The highly elastic hydrogel of the present invention formed as described above is usually white opaque to pale brown opaque,
It is a rubber-like substance with excellent mechanical strength and especially high elastic modulus, and does not release its contained water to the outside even when pressed. This high-elasticity hydrous gel is insoluble in cold to warm water, and usually has a large amount of water of about 60 to 95% based on the weight when it is hydrated, and is cut into any shape and size. be able to.

Further, at the time of producing the highly elastic hydrous gel of the present invention, dyes and pigments, various chemicals, and other additives can be added depending on the intended use and the like, as long as they do not hinder the gel formation. The present invention also includes a heterogeneous gel in which the gel is chemically crosslinked with diisocyanate, dialdehyde, borax, etc., and a heterogeneous gel in which the gel is crosslinked with radiation such as electron beams and γ rays.

The highly elastic heterogeneous hydrogel obtained in the present invention has an extremely high elastic modulus and water retention,
It can be used for various purposes such as artificial joints and artificial skin.
In addition, when this high-elasticity hydrous gel is left in the air, it gradually releases water into the atmosphere for a long period of time, so volatile fragrances, deodorants, bactericides, insecticides, etc. are previously prepared during the production of the high-elasticity hydrous gel. It is also possible to use as a sustained-release perfume gel, deodorant gel, bactericidal / insecticidal gel, etc.

[0025]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. In addition, in the following examples and the like, the water content of the hydrous gel was calculated by the following mathematical formula 1.

[0026]

## EQU1 ## Moisture content (%) = {(AB) / A} × 100 where A: weight of hydrogel (g) B: weight of gel after drying (g)

Further, the magnitude of the difference in shape and size between before and after gel formation in producing a hydrogel was determined by the volume error of the hydrogel expressed by the following mathematical formula 2.

[0028]

[Number 2] vol error _{(%) = (V 1 /} V 0) × 100-100 where V _1: volume of the actually obtained water-containing gel (mm ³⁾ V _0: the liquid injected into the mold (dish) Volume of (mixed liquid) (mm
³ )

Further, the strength, elongation and elastic modulus of the hydrous gel are 20 m using Strograph-T manufactured by Toyo Seiki.
The sample was pulled at a rate of m / min and determined from the initial slope of the strain / strength curve.

Examples 1 to 4 Polyvinyl alcohol (hereinafter referred to as "PVA") (polymerization degree 2000, to 120 g of 50% by weight dimethylsulfoxide aqueous solution with stirring).
Saponification degree 99-100%; Nacalai Tesque, Inc.) 20 g
Then, 6.7 g of a water-insoluble or sparingly water-soluble hydrophilic polymer compound shown in Table 1 below was added, and the mixture was heated to 100 ° C.
It was kept for 1 hour to completely dissolve PVA, and at the same time, a white translucent mixed liquid was prepared in which a water-insoluble or sparingly water-soluble hydrophilic polymer compound was uniformly dispersed. This mixed solution was cast into a glass dish having a diameter of 20 cm to a thickness (depth) of 5 mm [V ₀ = 3.14 × (10 cm) ² × 0.5].
cm = 157 cm ³ ] and left at room temperature (25 ° C.) to obtain a sheet-shaped precursor gel. 24 hours after casting, the precursor gel was taken out from the petri dish, immersed in methanol at 25 ° C., and left as it was for 1 week. afterwards,
When the gel was taken out from methanol and allowed to stand in water at 25 ° C. for 1 week or longer, a tough, rubber-like hydrogel was obtained in each example. The diameter and thickness of the hydrous gel obtained in each example were measured to calculate its volume (V ₁ ), and the volume error was obtained from the above V ₀ and the value of V _{1 by} the above-mentioned mathematical formula 2. Further, other physical properties of the hydrous gels were measured by the above-mentioned methods. The results are shown in Table 1 below.

Reference Examples 1 and 2 To 120 g of 50% by weight dimethylsulfoxide aqueous solution, 20 g of the same PVA used in Example 1 was added with stirring, and then Table 1 below.
6.7 g of the water-soluble polymer compound shown in
The solution was prepared by completely keeping PVA and the water-soluble polymer compound at 1 ° C. for 1 hour. This solution was a transparent to slightly cloudy translucent liquid. 5 parts of this solution in a glass dish with a diameter of 20 cm as in Example 1.
It was cast to a thickness of mm and left at room temperature (25 ° C.) to obtain a sheet-shaped precursor gel. 24 hours after casting, the precursor gel was taken out from the petri dish, immersed in methanol at 25 ° C., and left as it was for 1 week. After that, the gel was taken out from methanol and left in water at 25 ° C. for 1 week or longer to obtain a rubber-like hydrous gel. The diameter and thickness of the hydrous gels obtained in Reference Examples 1 and 2 were measured to calculate the volume (V ₁ ), the volume error was calculated by the above mathematical formula 2, and other physical properties were measured. The results are shown in Table 1.

Comparative Example 1 20 g of the same PVA used in Example 1 was added to 120 g of 80% by weight dimethylsulfoxide aqueous solution with stirring, and the mixture was kept at 100 ° C. for 1 hour to completely dissolve PVA. This solution is 20c in diameter
cast on a glass dish with a thickness of 5 mm,
It left for 16 hours in a -20 degreeC freezer, and the sheet-shaped precursor gel was obtained. When this gel was taken out from the petri dish and allowed to stand in water at 25 ° C. for 1 week or longer, a transparent rubbery hydrous gel was obtained. The diameter and thickness of this hydrogel were measured to calculate the volume (V ₁ ), the volume error was determined by the above formula, and other physical properties were measured. The results are shown in Table 1.

[0033]

[Table 1] Example of physical properties of gel Polymer compound Strength Elongation Elastic modulus Water content Volume error (g / mm ² ) (%) (g / mm ² ) (%) (%) Example 1 PVA / chitosan ^a) 51 340 30 81.4 0 Example 2 PVA / chitin ^b) 41 258 42 84.7 0 Example 3 PVA / cellulose ^c) 43 312 32 78.2 2 Example 4 PVA / albumin ^d) 38 230 37 80.0 1 Reference Example 1 PVA / PDMAAm ^e) 26 388 5 86.1 11 Reference example 2 PVA / PEO ^f) 19 177 13 84.3 6 Comparative example 1 PVA (freeze-thaw) 28 196 10 84.2 8 a) Funakoshi: Chitosan 7B b) Funakoshi: Chitin EX c) Funakoshi: Avicel SF d) Sigma e) Polydimethylacrylamide f) Polyethylene oxide (Aldrich; average molecular weight = 100000)

From the results shown in Table 1, in Examples 1 to 3 of the present invention in which a water-insoluble or sparingly water-soluble hydrophilic polymer compound is used together with the polyvinyl alcohol-based polymer, the polyvinyl alcohol-based polymer and the water-soluble polymer are highly soluble. The elastic modulus of the obtained hydrous gel is higher than those of Reference Examples 1 and 2 using a molecular compound and Comparative Example 1 in which a hydrous gel is produced by freeze-thawing using only a polyvinyl alcohol polymer. I understand. Furthermore, from the results of Table 1, in the case of Examples 1 to 3 of the present invention, the volume error during the production of hydrous gel was 0 to 2% as compared with Reference Examples 1 and 2, and the dimensions before and after gelation were measured. There is no or very little change,
It will be appreciated that hydrous gels of desired size and shape can be obtained.

[0035]

According to the present invention, a tough hydrogel having a high elastic modulus can be efficiently treated by a simple method and apparatus without performing complicated and costly steps such as freezing treatment, high pressure treatment and vacuum treatment. Can be manufactured well. Further, in the case of the present invention, the dimensional change of the gel does not occur before or after the gelation, so that the hydrogel having the intended shape and size can be smoothly produced.

Claims (3)

[Claims] 1. A water-insoluble or poorly water-soluble solution of a polyvinyl alcohol polymer having a degree of polymerization of 35 or more and a degree of saponification of 90% or more in a polar organic solvent or a mixed solvent of a polar organic solvent and water. A highly elastic hydrous gel or a precursor gel thereof, which is characterized in that a mixed solution obtained by dispersing a hydrophilic polymer compound is left as it is or immersed in a polar poor solvent or a polar non-solvent to form a gel. Production method. 2. The method according to claim 1, wherein the water-insoluble or sparingly water-soluble hydrophilic polymer compound is at least one selected from the group consisting of polysaccharides, proteins and derivatives thereof. 3. A highly elastic hydrogel or a precursor thereof produced by the method according to claim 1.