JPS60206435A - Preparation of water-containing gel - Google Patents

Abstract

PURPOSE:To obtain a uniform gel body, by dissolving a reducible metal ion in a solution of a hydrophilic high-molecular substance having a carboxy group before changing the same to an oxide form. CONSTITUTION:A synthetic high-molecular substance such as a polyacrylic acid, a polymethacrylic acid, a hydrolysate of an acrylic acid copolymer or monovalent alkali metal salts thereof is dissolved in a solvent based on water. A reducible metal ion such as Fe, Co, Ni, Cu or Ag is added to the resulting solution in an amount of 0.001-0.1pts.wt.-100pts.wt. of the high-molecular substance. Subsequently, an oxidizing agent such as hydrogen peroxide or potassium permanganate is dissolved in said solution and the metal ion is changed to an oxide form to apply the crosslinking of the metal ion as a crosslinking active type.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a water-containing gel cross-linked with metal ions, and more specifically, a reduced form inert to a cross-linking reaction is added to a solution of a hydrophilic polymer substance having carboxyl groups. A method for producing a hydrogel having a uniform degree of crosslinking obtained by dissolving metal ions and then changing the metal ions into an oxidized form having crosslinking activity using an oxidizing means such as an oxidizing agent to cause a crosslinking reaction. It is.

In recent years, water-containing gels made by crosslinking hydrophilic polymer substances in a water-containing state to make them water-insoluble have been used for medical hygiene applications such as poultices, and cosmetic applications such as facial packs. In order to produce a hydrophilic gel like lin, there is cross-linking of the base polymer material with various cross-linking agents as a means of making it into a gel state. There is a method of crosslinking with a crosslinkable metal salt. In the case of this method, the reaction system is aqueous, and the metal ions that are easily dissociated and ionized quickly come into contact with carboxyl groups, which are reaction sites, and the crosslinking reaction occurs quickly. On the other hand, however, the reaction proceeds too quickly, and before the ionized metal ions are evenly dissolved in the reaction system, the reaction proceeds immediately after the metal salt is mixed, causing local cross-linking and In many cases, it was difficult to obtain a gel body. As a method for solving the above problems, there is a method of adding a crosslinking reaction retarder to the reaction system in advance. For example, when polyacrylate is crosslinked with a polyvalent metal salt, the progress of the crosslinking reaction can be delayed by adding 15% by weight or more of a polyhydric alcohol such as glycerin or propylene glycol. 15413, and it is also known that addition of sucrose retards the crosslinking reaction in the case of hydrophilic polymeric substances such as pectin and alginic acid.

When added to the reaction system, the crosslinking reaction retarder has the property of delaying the reaction between the crosslinking agent and the substance to be crosslinked, but in order to achieve this effect, it is necessary to add a relatively large amount of the retarder. However, it has the disadvantage that the properties of the resulting hydrogel are significantly deteriorated.

In view of these circumstances, the present inventors have repeatedly investigated methods that can control the crosslinking reaction without using crosslinking reaction retarders. When a metal ion having an ionic valence of
discovered that a hydrogel with desired properties could be obtained,
This led to the present invention.

That is, in the present invention, reduced metal ions are dissolved in a solution of a hydrophilic polymer substance having a carboxyl group in the molecule, and then the metal ions are changed into oxidized forms to perform metal ion crosslinking and a gelation reaction. The present invention relates to a method for producing a hydrogel, which is characterized by causing the following.

The hydrophilic polymer substance used in the present invention is not particularly limited as long as it has a carboxyl group as a crosslinking reaction site in the molecule, and examples thereof include acrylic acid polymers, methacrylic acid polymers, and acrylic acid copolymers.

Synthetic polymer substances such as methacrylic acid copolymers, hydrolysates of maleic anhydride copolymers, and their -valent alkali metal salts, and semi-synthetic substances such as carboxy-modified cellulose ethers such as carboxymethyl cellulose and carboxyethyl cellulose. Examples include polymeric substances, natural polymeric substances such as alginic acid and pectin. These hydrophilic polymer substances have the property of being soluble in water or a mixture of water and a hydrophilic solvent such as alcohol. Those that dissolve are used.

The metal ions used as crosslinking agents in the present invention are 2
Any material having an ionic valence of more than one type may be used, such as Fe (bivalent, trivalent), Co (divalent, trivalent), N1 (divalent, trivalent), Cu (monovalent, divalent), Ay (monovalent, 2
valence), Sn (bivalent, tetravalent), Au (monovalent.

Examples include metal ions such as Ti (trivalent and tetravalent), and these are in the form of salts or oxides with bound anions in an amount of 0.001 parts by weight per 100 parts by weight of the above hydrophilic polymeric substance. ~
It is desirable to add within the range of 0.1 part by weight. The amount of these additives can be set appropriately depending on the type of hydrophilic polymer substance, solution viscosity, etc., but if it is less than 0.001 part by weight, the crosslinking of the resulting hydrogel will be insufficient, and 0.1 part by weight If it exceeds 100%, the crosslinking reaction will proceed excessively, resulting in poor water retention and flexibility, which is undesirable.

The metal ions mentioned above are added to the solution of the hydrophilic polymer substance in a reduced state, but the metal ions in this state have poor crosslinking reactivity with carboxyl groups, and can be mixed and homogenized before the crosslinking reaction progresses. It is.

After homogeneous mixing of the reduced metal ions is completed, the reduced metal ions are oxidized to oxidized metal ions, for example from Fe2+ to Fe, using an oxidizing means such as an oxidizing agent to be described later, and the metal ions are crosslinked into a crosslinking active type. Rub. When carrying out such a crosslinking reaction, it is preferable to use Fe compounds from the viewpoint of the oxidizability of metal ions, versatility, safety, etc., and ferrous chloride, ferrous sulfate, etc. are preferable. Yes.

Examples of oxidation means include the use of oxidizing agents such as hydrogen peroxide, potassium permanganate, and water-soluble organic peroxides. Hydrogen peroxide has moderate reactivity and the reaction product is harmless. It is recommended to use In addition, even without using an oxidizing agent, reduced metal ions can be gradually changed into oxidized forms by oxygen dissolved in a solution of a hydrophilic polymer substance or oxygen in the air, so it is possible to gradually change reduced metal ions to oxidized forms by leaving them for a long time. Crosslinking is also possible. The above-mentioned oxidizing agent can be used by mixing a hydrophilic polymeric substance containing reduced metal ions with a solution containing an oxidizing agent in a solution state, or by shaping the polymeric substance into a desired shape (
Examples include a method in which the molded product is molded into a sheet shape and then immersed in a solution containing an oxidizing agent, and a method in which the surface of the molded product is coated or sprayed with a solution containing an oxidizing agent.

The hydrogel obtained by the production method of the present invention can contain 95% by weight or more of water by changing the degree of crosslinking, but from the viewpoint of shape retention and practicality, the content is about 5 to 70% by weight. equipment is preferred.

In addition, fillers such as crystalline cellulose, colloidal silica gel, and hydroxypropyl cellulose are used to improve the flexibility properties of the obtained hydrogel and to impart new properties for cosmetic applications.

Hydrophilic polymer substances that do not have carboxyl groups in their molecules, such as methylcellulose, polyvinyl alcohol, and polyvinylpyrrolidone, ethanol, etc. -Alcohols such as butanol and propylene glycol, cosmetics, pharmaceuticals,
Surfactant 2 Colorant.

Various substances such as fragrances can be added.

As described above, according to the production method of the present invention, after a reduced metal ion with poor crosslinking reactivity is uniformly contained in a solution of a hydrophilic polymer substance having a hydrophoxyl group in the molecule, an appropriate In order to cause a gelation reaction by changing it into an oxidized metal ion with excellent crosslinking reactivity by oxidation means,
Since it has the characteristic of being able to freely control the timing of the start of gelation, it is possible to carry out the oxidation reaction after defoaming even when the solution of hydrophilic polymer substance is in a highly viscous state, thereby preventing appearance defects caused by air bubbles. You can.

Examples of the present invention will be shown and specifically explained below, but the present invention is not particularly limited thereto.

In the text, parts mean parts by weight.

Example 1 10 parts of a 1% by weight aqueous solution of ferrous chloride was added to 90 parts of a 20% by weight aqueous solution of polyacrylic brew, and the mixture was thoroughly mixed until uniform.

Next, this liquid was cast onto a glass plate to a thickness of 1 m, and then immersed in a 1% by weight hydrogen peroxide aqueous solution for 3 minutes.
A sheet-like hydrogel was obtained.

The properties of the obtained hydrogel were observed after it was stored in a sealed container at room temperature for one month, and it was found that there was almost no syneresis from the gel.
Shape retention was also good. In addition, the texture was unchanged from immediately after manufacture, and it had the same elasticity as human skin.

Example 2 Methyl vinyl ether/maleic anhydride copolymer (trade name: GANTREZ AN169, manufactured by GAF)
To 95 parts of a 5% by weight aqueous solution of ferrous chloride, 5 parts of a 1% by weight aqueous solution were added and thoroughly mixed until uniform.

Next, this liquid was cast into a polyethylene container to a thickness of IOW, and then a 3% by weight aqueous hydrogen peroxide solution was uniformly sprayed from the top, and the mixture was left to stand day and night to obtain a hydrogel.

The properties of the obtained hydrogel were observed after it was stored in a sealed container at room temperature for one month. As a result, there was almost no water separation from the gel.
Shape retention was also good. In addition, the texture was unchanged from immediately after manufacture, and it had agar-like elasticity.

Example 3 20 parts of a 0.1% by weight aqueous solution of ferrous sulfate was added to 80 parts of a triple ffi% aqueous solution of carboxymethylcell 4-SuNcL, and the mixture was sufficiently mixed until the mixture became homogeneous.

Next, this liquid was cast onto a glass plate to a thickness of 2 mw, and then left to stand day and night to obtain a sheet-like hydrous gel.

The properties of the resulting hydrogel were observed after it was stored in a sealed container at room temperature for one month. As a result, there was almost no syneresis from the gel.
Shape retention was also good. Furthermore, the texture was unchanged from immediately after manufacture, and it had agar-like elasticity.

Comparative Examples 1 to 3 Comparative Examples 1 to 3 correspond to Examples 1 to 3, except that the ferrous compound in each example was replaced with a ferric compound, and the oxidation treatment with an aqueous hydrogen peroxide solution was excluded. I did a similar trick. In the manufacturing method of each comparative example, the crosslinking reaction proceeded locally and the crosslinking reaction occurred immediately after the addition of the ferric compound, so that precipitation occurred and a hydrogel could not be obtained.

As described above, it can be seen that according to the method for producing a hydrogel of the present invention, a hydrogel having excellent properties such as water retention, shape retention, and flexibility can be obtained.

patent applicant Nitto Electric Industry Co., Ltd. Representative Sanbe Hijikata

Claims (2)

[Claims] (1) After dissolving reduced metal ions in a solution of a hydrophilic polymer substance having carboxyl groups in the molecule,
A method for producing a hydrogel, which comprises changing the metal ion into an oxidized form, crosslinking the metal ion, and causing a gelation reaction. (2) The method for producing a hydrogel according to claim 1, wherein the reduced metal ion is Fe 2 and the oxidized metal ion is Fe 2 .