JPH058921B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a method for producing an aqueous gel. More specifically, the present invention relates to a method for producing an aqueous gel that can be produced at room temperature, has good transparency, and has extremely low water repellency at both low and high temperatures. [Prior art and its problems] When several percent of agar is placed in water, heated and dissolved to form an aqueous solution, and then cooled, it gels into a pudding-like form to obtain an aqueous gel. In addition, an aqueous gel can be obtained by gelatin, alginic acid, carrageenan, etc., in the same manner. Gels of these natural products require a step of heating and dissolving, and the gels obtained are brittle, weak, and have extremely poor transparency. Gelatin also has the disadvantage of producing a glue odor. Also, when boric acid or borax is added to an aqueous polyvinyl alcohol solution, an aqueous gel is obtained, but it is extremely weak and may freeze and thaw.
It has the disadvantage that syneresis occurs when it is kept at high temperatures for a long time or when it is repeatedly frozen and heated to high temperatures. Furthermore, there is a manufacturing disadvantage in that gelation tends to occur locally and it is difficult to obtain a uniform aqueous gel. [Means for Solving the Problems] As a result of intensive research on aqueous gels to solve the above problems, the present inventors found that aqueous solutions of acetoacetylated various water-soluble polymer compounds have specific properties. The inventors have discovered that the crosslinking agent quickly gels at room temperature to generate a transparent aqueous gel, leading to the completion of the present invention. That is, the present invention involves mixing an acetoacetylated water-soluble polymer compound, one or more crosslinking agents selected from polyethyleneimine, an aminosilane compound, and a compound having a hydrazide group, and water to form a crosslinked gel. The present invention relates to a method for producing an aqueous gel characterized by the following. The acetoacetylated water-soluble polymer compounds used in the present invention include acetoacetylated water-soluble polymer compounds such as polyvinyl alcohol, hydroxyethyl cellulose, hydroxypropyl cellulose, methyl cellulose, carboxymethyl cellulose, and starch. These can be used alone or in combination. As a method for acetoacetylating a water-soluble polymer compound, using polyvinyl alcohol as an example, polyvinyl alcohol is dispersed in an acetic acid solvent, and then the formula: There is a method of adding diketene as shown in the figure below, a method of dissolving polyvinyl alcohol in a solvent such as dimethyl formaldehyde or dioxane in advance, and adding diketene thereto, and a method of bringing diketene gas or liquid diketene into direct contact with polyvinyl alcohol. The degree of acetoacetylation of the acetoacetylated water-soluble polymer compound is 1 to 15 mol%, preferably 2 to 12
A range of mole % is suitable. If the degree of acetoacetylation is less than 1 mol %, the crosslinking reaction will be difficult to proceed and it will be difficult to obtain an aqueous gel, and if it exceeds 15 mol %, some types of water-soluble polymer compounds will be difficult to dissolve in water. Examples of the crosslinking agent used in the present invention include polyethyleneimine, aminosilane compounds, and compounds having hydrazide groups. These may be used alone or in combination. The polyethyleneimine used in the present invention has the general formula: (In the formula, R ₁ , R ₂ and R ₃ are each a hydrogen atom or CH ₂ CH ₂ NH ₂ , X and Y are integers)
Polyethyleneimine, which is represented by
Aminosilane compounds such as -β(aminoethyl)γ-aminopropyltrimethoxysilane and γ-aminopropyltrimethoxysilane are preferred. As the compound having a hydrazide group used in the present invention, dihydrazide compounds or polyhydrazide compounds are suitable, such as hydrazide compounds, formic acid of dihydrazide compounds,
Organic salts such as oxalic acid, monosubstituted dihydrazide compounds such as methyl, ethyl, propyl, butyl, allyl, etc., and asymmetric disubstituted compounds such as 1,1-dimethyl, 1,1-diethyl, 4-n-butyl-methyl. and symmetrically disubstituted compounds such as 1,2-dimethyl, 1,2-diethyl, and 1,2-diisopropyl. Particularly suitable hydrazide group-containing compounds are carbodihydrazide, oxalic acid dihydrazide, malonic acid dihydrazide, succinic acid dihydrazide, adipic acid dihydrazide, sebacic acid dihydrazide, dodecanedioic acid dihydrazide, isophthalic acid dihydrazide, terephthalic acid dihydrazide, glycolic acid dihydrazide, Polyacrylic acid hydrazide, etc. A water-soluble polymer compound having an acetoacetyl group in its molecule and polyethyleneimine form a crosslinked structure through a reaction mechanism as shown in the following formula, which is a guess, and gels by incorporating water to produce an aqueous gel. . A water-soluble polymer compound having an acetoacetyl group in its molecule and a hydrazide group-containing compound form a crosslinked structure by a reaction mechanism as shown in the following formula, although it is a guess, and an aqueous gel is produced in the same manner as described above. All of the above reactions do not require heating and proceed rapidly at room temperature to produce a transparent aqueous gel. The aqueous gel produced by the production method of the present invention can contain colorants, ultraviolet absorbers, antioxidants, PH adjusters, etc. depending on the purpose. These reactions are carried out at room temperature, in the early case of 2 to 3
The process takes place within seconds, and an aqueous gel is formed. Of course, the gelation time can be freely adjusted by adjusting the degree of acetoacetylation of the type of acetoacetylated polymer compound, the type and ratio of crosslinking agent used, the solution concentration of both, pH, etc. In addition, an aqueous gel can be produced by mixing a powdered acetoacetylated polymer compound and a powdered crosslinking agent, and adding an appropriate amount of water when necessary and stirring and dissolving the mixture. Furthermore, even if either one of them is an aqueous solution, an aqueous gel can be produced simply by mixing and stirring the two. According to the production method of the present invention, unlike agar and carrageenan, there is no need for the process of heating and dissolving and then cooling and gelling, and by simply stirring and mixing at room temperature, it becomes odorless, tough, elastic and transparent. An excellent aqueous gel can be obtained that does not cause syneresis even when frozen and thawed, stored at high temperatures, or repeatedly subjected to high temperatures and freezing. The hardness of the resulting aqueous gel can be varied from fluid and soft to fluid and soft by adjusting the type and ratio of crosslinking agent used, the solution concentration of both, and pH.
It can be controlled over a wide range, including tough, elastic, and hard objects. Therefore, the aqueous gel obtained by the production method of the present invention can be used in a wide range of applications such as buffering agents, excipients, poultices, soundproofing materials, heat insulating materials, bacterial culture media, and product window samples. I can do it. The present invention will be explained by giving Examples and Comparative Examples. Example 1 N-
When 10 parts by weight of a 10% aqueous solution of β(aminoethyl)γ-aminopropyltrimethoxysilane was added, the mixture was stirred and mixed at room temperature, and poured into a 100 mm x 100 mm x 25 mm container, an aqueous gel with excellent transparency was obtained. I got it. At this time, the pH of the solution before gelation was 9.3, and the gelation time was 2 minutes. Also, keep this gel at room temperature for 1
The penetration depth into the gel after leaving it for a week is 3mm.
(static load of 200 g/cm ² ). Furthermore, when this gel was left in a -20°C freezer for 24 hours to freeze and then thawed to room temperature, no syneresis occurred.
Furthermore, when this gel was left in a thermostatic oven at 70°C for 24 hours, syneresis did not occur. [Test method] (a) Gelation time The time it takes for the viscosity of the mixed solution to reach 500 to 1000 cp (area where stirring is not possible) using a BL viscometer after adding and mixing the crosslinking agent at room temperature (25°C). (B) Transparency Visual judgment ○: Transparent △: Transparent ×: Opaque (C) Penetration depth Penetration of the probe into the gel when a static load of 200 g/cm ² is applied to a probe with a diameter of 4 mm Depth (1 week after addition and mixing of crosslinking agent) (d) Syneresis After 100 g of gel is left in a sealed state under the specified conditions, the weight of the separated water is measured and expressed as a percentage of the initial gel weight. (i) Freeze-thaw syneresis Water syneresis rate after freezing after being left in a -20°C freezer for 24 hours and thawing at room temperature (%) (ii) High-temperature syneresis Water syneresis rate after being left in a thermostat at 70°C for 24 hours (%) Examples 2 to 4 and Comparative Examples 1 to 6 Example 1 except that the following aqueous solution of acetoacetylated water-soluble polymer compound and the following crosslinking agent aqueous solution were used in combination as shown in Table 1. An aqueous gel was obtained in the same manner. The physical properties of the aqueous gel obtained were as shown in Table 1. (Aqueous solution of acetoacetylated water-soluble polymer compound) AA-PVA (degree of acetoacetylation 5.5 mol%,
10% aqueous solution of acetoacetylated polyvinyl alcohol with a degree of saponification of 99 mol% and a degree of polymerization of 1100) AA HEC (degree of acetoacetylation 4.1 mol%)
(2% aqueous solution of acetoacetylated hydroxyethyl cellulose) AA MC (2% aqueous solution of acetoacetylated methyl cellulose with acetoacetylation degree of 5.2 mol%) AA CMC (acetoacetylation degree 3.8 mol%)
(2% aqueous solution of acetoacetylated carboxymethyl cellulose) AA starch (degree of acetoacetylation 4.3 mol%)
(5% aqueous solution of solubilized starch) [Aqueous crosslinking agent solution] AEAPTMS [10% aqueous solution of N-β(aminoethyl)γ-aminopropyltrimethoxysilane] GX (10% aqueous solution of glyoxal) COHD (carboxyhydrazide (5% aqueous solution of polypropylene glycol glycidyl ether) PPGGE (10% aqueous solution of polypropylene glycol glycidyl ether) Bt-ME (10% aqueous solution of butylated melamine resin) TAT [10% aqueous solution of di-n-butoxybis(triethanolamine) titanate] TLA (titanium 10% aqueous solution of lactate)

【table】

[Table] [Effects of the Invention] According to the production method of the present invention, unlike agar and carrageenan, there is no need for the complicated process of heating and then cooling to gel, and by simply stirring and mixing at room temperature, An odorless, tough, elastic, and transparent aqueous gel can be obtained quickly, and an excellent aqueous gel that does not release water even after repeated freezing and thawing can be obtained.

Claims (1)

[Scope of Claims] 1 (A) an acetoacetylated water-soluble polymer compound, (B) one or more crosslinking agents selected from polyethyleneimine, an aminosilane compound, and a compound having a hydrazide group, and ( C) A method for producing an aqueous gel characterized by mixing water and forming a crosslinked gel. 2. The method for producing an aqueous gel according to claim 1, wherein the water-soluble polymer compound is one or more selected from polyvinyl alcohol, hydroxyethylcellulose, hydroxypropylcellulose, methylcellulose, carboxymethylcellulose, and starch.