JP2003277637A - Aqueous gel and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aqueous gel and a method for producing the same, which are suitable for use as a cooling agent, a fragrance, a poultice, etc., are excellent in uniformity, strength, shape retention, and have little water separation.
In addition, the present invention provides an aqueous gel excellent in gel time adjustment, a method for producing the same, and a use thereof. An aqueous gel comprising an aqueous solution of one or more anionic water-soluble polymers (A), a crosslinking agent (B), and microfibrous cellulose (C).

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an aqueous gel and a method for producing the same. More specifically, fresh food products such as seafood, ham and vegetables, and ice packs provided for the purpose of keeping freshness and keeping cold during distribution of juice, wine, blood and the like,
It is suitable for use as a fragrance used in cars, indoors, toilets, etc., and as a poultice that gives a refreshing feeling or a cold feeling to the part when attached to the skin, and has excellent uniformity, strength, and shape retention, TECHNICAL FIELD The present invention relates to an aqueous gel having a small amount of water separation and excellent in gelation time control, a method for producing the same, and its use.

[0002]

2. Description of the Related Art Conventionally, an aqueous gel obtained by crosslinking an anionic water-soluble polymer with a polyvalent metal ion and a method for producing the same have been proposed.
A gel mainly composed of polyacrylic acid and / or a polyacrylic acid salt (JP-A-53-15413) or a gel mainly composed of carboxymethyl cellulose or carboxymethyl cellulose alkali metal salt (hereinafter, abbreviated as CMC) 7-90121) and the like.

[0003]

A gel obtained by cross-linking an anionic water-soluble polymer as described above with a polyvalent metal ion is
The gelation rate is extremely high, and since gelation proceeds at the same time when the polyvalent metal salt is added, there is a problem that a non-uniform gel is likely to occur. In addition, the conventional gel was not completely satisfactory in strength and uniformity obtained when used as a cooling agent.

Therefore, the present invention aims to provide an aqueous gel having excellent gel strength and gel uniformity. More specifically, the addition of microfibrous cellulose to the gel improves the gel strength and makes the gel uniform. The purpose is to expand the range of application of aqueous gels.

[0005]

The present invention provides an aqueous solution of at least one anionic water-soluble polymer (A) and a cross-linking agent (B).
And a microfibrous cellulose (C).

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The aqueous gel of the present invention and the method for producing the same will be described below in detail. Method for Producing Aqueous Gel Since the aqueous gel of the present invention can be produced by various methods, the method for producing the same is not particularly limited. Hereinafter, the typical manufacturing method will be described and mainly explained.

(I) Raw Material Components In order to produce the aqueous gel of the present invention, the following anionic water-soluble polymer (A), cross-linking agent (B) and microfibrous cellulose (C) are essential components, The polyvalent metal compound (B1) is preferably used as (B), and the acidic compound (D) is used as a preferable component.

(1) Anionic Water-Soluble Polymer (A) The anionic water-soluble polymer (A) contained in the aqueous gel of the present invention (hereinafter simply referred to as “component (A)”) is a gelling group. It is a component that becomes a material. Examples of the component (A) include polyacrylic acid or an alkali metal salt thereof, polymethacrylic acid or an alkali metal salt thereof, an aliphatic carboxylic acid such as a hydrolyzate of a methyl vinyl ether / maleic anhydride copolymer, or a metal thereof. One or more selected from water-soluble polymers of salts, carboxymethyl cellulose or alkali metal salts thereof (hereinafter abbreviated as CMC), and the like can be given. Among these, CMC is particularly preferable.

The CMC preferably has a specific degree of substitution (also referred to as etherification degree or DS) and a molecular weight. The degree of substitution is generally the degree of etherification (carboxymethylation) of the hydroxyl groups of cellulose.
Since there is a numerical value of 0 to 3, there is a numerical value of 0 to 3, but the CMC used in the present invention is 0.5.
Those having a substitution degree of up to 2.5 are suitable, preferably 0.5 to 1.5, and more preferably 0.7 to 1.0. At that time, if the substitution degree is lower than 0.5,
Water solubility is insufficient and a uniform gel cannot be obtained. On the other hand, when the substitution degree is higher than 2.5, the polyvalent metal compound (B
1) Crosslinking by ions may proceed in the molecule and settle without forming a uniform gel.

Further, the molecular weight of CMC is 60 r.m. with a B-type viscometer (rotary viscometer) in a 1 wt% aqueous solution of CMC.
p. The viscosity at 25 ° C. measured by m is 5 to 3000
Those of mPa · s are suitable. Preferably 10
500 mPa · s, more preferably 10 to 200 mP
Those of as are desirable. At that time, the viscosity is 5 mPa · s
If it is smaller, the three-dimensional crosslinking does not proceed effectively and the strength of the gel decreases. On the other hand, when the viscosity is higher than 3000 mPa · s, the viscosity before gelation becomes very high, which causes problems such as poor injection into a container and workability.

When preparing an aqueous gel, since CMC is water-soluble, it is dissolved in water and used as an aqueous solution. At that time, the content of CMC is usually 1 to 5% by weight based on the concentration of the aqueous solution, preferably 1.5 to
It is desirable to set it to 4.5% by weight, more preferably 1.5 to 3.5% by weight. When the concentration of the aqueous solution is lower than 1% by weight, sufficient gel strength cannot be obtained, while the concentration of the aqueous solution is 5%.
If it is higher than wt%, the viscosity before gelation becomes very high,
This causes problems such as poor injection into a container and poor workability.
Further, when preparing an aqueous solution of CMC, it is easy to disperse and dissolve it by once dispersing it in glycerin or the like and then adding the dispersion to water.

(2) Cross-linking agent (B) The cross-linking agent (B) of the present invention is not particularly limited as long as it reacts with the anionic water-soluble polymer (A) to form a cross-linking structure. A metal compound (B1) (hereinafter, simply abbreviated as component (B1)) is preferably used. The (B1) ion contained in the aqueous gel of the present invention is a component that three-dimensionally crosslinks the component (A) in the aqueous gel.
Examples of the component (B1) include the following (b1) compound and (b2) compound. The content of the component (B1) in the aqueous gel, as a metal element, is preferably 0.01 to 5% by weight, and more preferably 0.0.
It is 2-3% by weight.

The amount of the component (B1) used in the present invention is important because it affects the physical properties of the resulting aqueous gel. Therefore, the component (B1) used as the gelling agent is such that, when CMC is used as the component (A), the ion equivalent ratio is usually 0.1 to 1.0 in the aqueous gel. . It is preferably 0.2 to 0.8, and more preferably 0.2 to 0.5. Here, the above-mentioned ion equivalent ratio means, when CMC is used, ((B per unit weight of carboxymethylcellulose sodium salt
1) means the ratio of the number of moles of the component × 3) / (the number of moles of the substitution degree per unit weight of carboxymethyl cellulose sodium salt), the amount of CMC to be used and the substitution degree, and (B1)
It can be easily obtained from the amounts of the components. At this time, if the ion equivalent ratio is less than 0.1, there is a problem that sufficient gel strength cannot be obtained. On the other hand, if the ion equivalent ratio is greater than 1.0, there is a problem that the amount of water separation increases.

In the present invention, as the component (B1),
Poorly soluble polyvalent metal compound (b1) that is difficult to dissolve in water
(Hereinafter, simply abbreviated as (b1) compound) and one or more kinds of easily soluble polyvalent metal compounds (b2) (hereinafter simply abbreviated as (b2) compound), which are easily soluble in water, It is preferable in improving gel strength and uniformity.

In the present invention, the compound (b1) and the compound (b2) can be used in combination, and usually, in a weight ratio,
(B1) compound: (b2) compound = 20: 80 to 80:
Use at 20.

Here, the compound (b1) may be any polyvalent metal compound having a low solubility in water, and a high solubility in water.
A polyvalent metal compound that is easily soluble in water is used for surface coating and p
It may be one that is made insoluble in water by a method such as making it insoluble by adjusting H. The rule of thumb for low solubility in water is that when a polyvalent metal compound or the like is added to water and stirred, it does not dissolve completely in about 1 hour, and some remain undissolved in water. If yes, it applies.
As the polyvalent metal compound used in this way, an aluminum compound is particularly preferable. Examples of aluminum compounds include hydroxides such as aluminum hydroxide, or normal or basic salts of inorganic or organic acids such as aluminum chloride, aluminum sulfate and aluminum stearate, double salts such as potassium alum, There are aluminates such as sodium aluminate, inorganic aluminum complex salts, and organic aluminum chelates.

The polyvalent metal compound (b1) itself has low solubility in water, and examples of the polyvalent metal compound having a low solubility in water include basic aluminum acetate, dihydroxyaluminum aminoacetate (also known as glycinal), magnesium potassium aspartate, and hydroxide. Examples include aluminum and calcium hydroxide.

The compound (b2) may be any polyvalent metal compound having a high solubility in water and having a high solubility in water, but an aluminum compound is particularly preferable. Examples of the aluminum compound corresponding to the compound (b2) include aluminum chloride, potassium alum, aluminum sulfate and aluminum lactate.

As the compound (b1), basic aluminum acetate is particularly preferable, and as the compound (b2),
Particularly, potassium alum is preferable. Further, the poorly water-soluble (b1) compound is easily dispersed and dissolved easily when it is once dispersed in glycerin or the like and then added to an aqueous solution of the anionic water-soluble polymer (A).

(3) Microfibrous Cellulose (C) The microfibrous cellulose (C) of the present invention (hereinafter simply abbreviated as (C) component) is obtained by cleaving a purified cellulose raw material without cutting the fibers. It is microfibrillated and has extremely large water retention. As one method for obtaining this fine fibrous cellulose (C), a method described in JP-A-56-100801 is disclosed.
There is a method in which the purified cellulose raw material is beaten in water at a high pressure to cleave the fibers without breaking them to form microfibrils. Further, as an example of the microfibrous cellulose (C), "Celish" manufactured by Daicel Chemical Industries, Ltd. is commercially available.

The content of the component (C) in the aqueous gel is preferably 0.1 to 10.0% by weight, preferably 0.2 to 5.0% by weight, and more preferably 0.5 to 5.0% by weight.
It is 3.0% by weight. If it is less than 0.1% by weight, sufficient gel strength cannot be obtained, and if it exceeds 10.0% by weight, the apparent viscosity of the pre-gel preparation liquid becomes high, which hinders the gel preparation work.

(4) Acidic Compound (D) The acidic compound (D) contained in the aqueous gel of the present invention (hereinafter, simply referred to as “component (D)”) adjusts the pH of the aqueous solution before gel formation to an acidic range. It is a preferable component for holding and generating the ion of the component (B1) and causing cross-linking by electrostatic interaction to cause gelation. Also, (D)
The addition of the components is preferable from the viewpoint of adjusting the gelation reaction pot life (pot life).

As the component (D), inorganic acids such as hydrochloric acid, sulfuric acid and nitric acid; organic acids such as acetic acid, succinic anhydride, maleic anhydride, fumaric acid, maleic acid, phthalic acid, phthalic anhydride and aspartic acid; And oxyacids such as lactic acid, tartaric acid, malic acid, citric acid, and glucoronic acid, which are one type of organic acids, and at least one component (D) selected from these is used.

In the present invention, succinic anhydride or oxyacid is preferably used, and lactic acid is particularly preferably used as the oxyacid, from the viewpoint of gelation reaction pot life. By adding the oxyacid, the compound (b1) which is hardly soluble in water can be gradually dissolved in the system, and the anionic water-soluble compound (b2) which is easily soluble in water is highly soluble in water. It is possible to slow the reaction with the molecule (A) and prolong the pot life until gelation.

The content of the component (D) in the aqueous gel is preferably 0.1 to 3.0% by weight, particularly preferably 0.2 to 0.5% by weight. If it is less than 0.1% by weight, the effect of adding the component (D) cannot be obtained, and if it exceeds 3.0% by weight, gelation does not sufficiently occur.

The content of water in the aqueous gel is preferably 80 to 97% by weight, particularly preferably 85 to 9%.
It is 7% by weight.

(5) Other optional components In the aqueous gel of the present invention, in addition to the above components, other components, for example, a colorant, within a range not impairing the object of the present invention.
Fragrances, antibacterial agents, antifungal agents, etc. can be added.

The aqueous gel of the present invention preferably has an aqueous solution pH of 1.0 to 6.0, particularly 3.0 to 6.0.
It is preferably 6.0.

(Ii) Method for Producing Aqueous Gel In the present invention, the above-mentioned components (A) to (D) and optionally other optional components are used to carry out the following steps (1) to (6). An aqueous gel is produced.

(1) Preparation of anionic water-soluble polymer (component (A)) solution At room temperature, water is added to component (A) to prepare a solution having a concentration of 1 to 5% by weight.
An aqueous solution in which the component (A) is completely dissolved is prepared. At this time, if the component (A) is once dispersed in glycerin or the like and then the dispersion liquid is added to water, it is easily dispersed and dissolved.

(2) Water-insoluble polyvalent metal compound ((b
1) Addition of compound) To the aqueous solution of the component (A) obtained above, the compound (b1) is added at room temperature with stirring. At this time, if the compound (b1) is dispersed in glycerin or the like and then added to the above aqueous solution, the compound (b1) is easily dispersed and dissolved.
Also, as described in Example 1 below, (b1)
The component (A) may be added to the aqueous solution of the compound.

(3) Water-soluble polyvalent metal compound ((b
2) Addition of compound) A 0.2-5 wt% aqueous solution of the compound (b2) is added to the mixed aqueous solution of the component (A) and the compound (b1) at room temperature with stirring. At this time, it is preferable to add the compound (b1) and the compound (b2) such that the total amount of the compound is 0.01 to 5% by weight as a metal element in the aqueous gel.

Here, it is preferable to add the aqueous solution of the compound (b2) before the compound (b1) is completely dissolved in the aqueous solution of the component (A). That is,
Since gelation gradually progresses after the addition of the compound (b1), it is desirable to add the compound (b2) as soon as possible, preferably within 1 hour. When the compound (B2) is added after the compound (b1) is dissolved, gelation occurs rapidly and the pot life is shortened, which is not preferable.

In the production method of the present invention, the gelation rate can be adjusted. That is, the addition ratio of the compound (b2) to the compound (b1) is increased, or
The gelation rate increases by increasing the addition amount of the compound (b2) used, and conversely, the gelation rate decreases.

(4) Addition of Microfibrous Cellulose (Component (C)) In the present invention, the component (C) is added in order to improve gel strength and uniformity. The component (C) is preferably added after the above step (1) or (2).

(5) Addition of acidic compound (component (D)) In the present invention, it is preferable to add component (D) for the purpose of adjusting the gelation reaction pot life. The component (D) may be added at the same time as, before, or after the above steps (1) to (4). However, when the compound (b2) is added, the component (D) is preferably added at the same time as or before the step (3).

(6) Gelation After completion of the above steps (1) to (5), the solution obtained above is put into a container with stirring as quickly as possible, preferably within 1 hour, for gelation. Make progress. A uniform aqueous gel is obtained by leaving it at room temperature for one day.

[0038]

The present invention will be described in more detail based on the following examples, but the invention is not intended to be limited by these examples.

The aqueous gels obtained in Examples and Comparative Examples were evaluated as follows. (Gelization time) A sparingly soluble polyvalent metal salt (or a glycerin dispersion thereof) was added to an aqueous solution of an anionic water-soluble polymer that had been completely dissolved, and the mixture was stirred and dispersed. An acidic compound (or an aqueous solution thereof) is added and stirred to dissolve (react). (Use about 1000 g of gel. Stir well for 3 minutes with a stir bar.) After stirring, put 200 g in a 500 ml container, mix with a stir bar as appropriate, observe, and determine when the fluidity disappears. The gelation time was defined as the gelation time, and the time from the end of stirring to the gelation point was defined as the gelation time.

(Water separation amount (R)) Diameter 50 mm, height 50
A columnar gel of mm was put in a container, the upper part of the gel composition was visually observed at 25 ° C. for 1 month, and it was confirmed whether water was floating on the surface of the gel composition. To measure. At this time, it is considered that the smaller the amount of water separation, the better the water retention and the better the gel properties.

(Gel Strength (G) (Shape-Retaining Strength)) The gel strength is evaluated using a hood rheometer (manufactured by Sun Kagaku Co., Ltd.). A cylindrical gel having a diameter of 50 mm and a height of 30 mm is put in a container and left standing for 24 hours or longer for evaluation. Using a rod-shaped adapter with a diameter of 11 mm, measurement was performed at 10 points located inside the middle distance from the center to the end of the gel, and it was calculated as the weight per surface area, and the average was calculated as the gel strength (Pa or g / cm ² ).

(Gel Uniformity) The gel uniformity was evaluated by visually observing the presence or absence of irregularities in the appearance, and further, was measured as described above.
Evaluation was made as follows based on the variation of the gel strength (G) at 0 points. ⊚: No unevenness in appearance, variation in gel strength of ± 3% or less ○: No unevenness in appearance, variation in gel strength ± 10%
Less than

[0043]

[Example] [Example 1] Sodium aluminate 0.29
g into an aqueous solution of 47.38 g of water, CMC (D
S0.70, 1% aqueous solution viscosity 75 mPa · s) is 2.9
g, melted, and then Serish (manufactured by Daicel Chemical Industries,
50 g of a 2% aqueous solution of FD-100G (hereinafter, abbreviated as "Cerish") was added and stirred. To this solution, 0.5 g of succinic anhydride dispersed in 1.2 g of glycerin was added,
An aqueous gel was prepared. The properties of the resulting aqueous gel are shown in Table 1.

Example 2 An aqueous solution prepared by dissolving 4.9 g of sodium polyacrylate (hereinafter abbreviated as PANa) (manufactured by Nacalai Tesque, Inc.) in 44.1 g of water was added 50 g of a 2% aqueous solution of Serish. Add and stir. Furthermore, 1.3 g of sodium aluminate was added to the aqueous solution and stirred. 0.5 g of succinic anhydride was dispersed in 1.2 g of glycerin and added to this solution to prepare an aqueous gel. The properties of the resulting aqueous gel are shown in Table 1.

Example 3 In 360 g of water, CMC (DS
25 g of 0.90, 1% aqueous solution viscosity 35 mPa · s) was dispersed in 60 g of glycerin and added, and stirred to dissolve. Furthermore, add 500 g of 2% aqueous solution of Serish,
It was stirred. Next, 1.5 g of basic aluminum acetate was dispersed in 20 g of glycerin and added, and stirring was continued.
Furthermore, an aqueous solution prepared by dissolving 1.5 g of potassium alum and 2.0 g of lactic acid in 40 g of water was immediately added to the aqueous solution obtained above to prepare an aqueous gel. The properties of the resulting aqueous gel are shown in Table 1.

[Examples 4 and 5] An aqueous gel was prepared in the same manner as in Example 3 except that the types and amounts of gel components were changed as shown in Table 1. The properties of the resulting aqueous gel are shown in Table 1.

[Example 6] CMC was added to 41.43 g of water.
(DS 0.90, 1% aqueous solution viscosity 35 mPa · s) 3.
0 g was added and dissolved by stirring. Further, 50 g of a 2% aqueous solution of Celish was added and stirred. Next, 0.57 g of basic aluminum acetate was dispersed in 5 g of glycerin and added, and the mixture was stirred to prepare an aqueous gel. The properties of the resulting aqueous gel are shown in Table 1.

[Comparative Example 1] An aqueous gel was prepared in the same manner as in Example 1 except that the amount of water in the gel component was set to the amount shown in Table 1 and Celish was not added. The properties of the resulting aqueous gel are shown in Table 1.

[Comparative Example 2] An aqueous gel was prepared in the same manner as in Example 2 except that the amount of water in the gel component was set to the amount shown in Table 1 and no Celish was added. The properties of the resulting aqueous gel are shown in Table 1.

[Comparative Examples 3 to 5] An aqueous gel was prepared in the same manner as in Example 3 except that the type and amount of the gel component were changed as shown in Table 1 and no Celish was added. The properties of the resulting aqueous gel are shown in Table 1.

[Comparative Example 6] An aqueous gel was prepared in the same manner as in Example 6 except that the amount of water in the gel component was changed to the amount shown in Table 1 and no Celish was added. The properties of the resulting aqueous gel are shown in Table 1.

[0052]

As is apparent from Table 1, the aqueous gel of the present invention is excellent in gel strength and gel uniformity and is used as a cooling agent, an aromatic agent or a poultice.

[Table 1]

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) A61K 47/38 A61K 47/38 A61L 9/04 A61L 9/04 C08K 3/00 C08K 3/00 C08L 1 / 02 C08L 1/02 C09K 3/00 103 C09K 3/00 103K 103L 5/00 101 5/00 101 F Term (Reference) 4C076 AA74 AA75 BB31 DD21 DD41 DD43 EE01 EE33 FF70 4C080 AA03 BB03 HH06 JJ01 KK03 NN01LL06 KK03 NN01 LL0306 NN24 4J002 AB01X AB03W BG01W DD017 DD076 DE086 DE146 DE186 DF027 DG037 DG046 EF037 EF077 EF117 EG046 EN117 FA04X FD146 FD207 GB01 GC00

Claims (11)

[Claims] 1. An aqueous gel comprising an aqueous solution of one or more anionic water-soluble polymers (A), a cross-linking agent (B) and microfibrillar cellulose (C). 2. The aqueous gel according to claim 1, wherein the cross-linking agent (B) is a polyvalent metal compound (B1). 3. The aqueous gel according to claim 2, wherein the polyvalent metal compound (B1) is two or more polyvalent metal compounds having different solubility in water. 4. The polyvalent metal compound (b) which is sparingly soluble in water (b) comprises two or more kinds of polyvalent metal compounds having different solubility in water.
4. The aqueous gel according to claim 3, which is 1) and a polyvalent metal compound (b2) which is easily soluble in water. 5. The aqueous gel according to any one of claims 1 to 4, which contains one or more acidic compounds (D). 6. The at least one kind of the anionic water-soluble polymer (A) is carboxymethyl cellulose or its alkali metal salt (a1).
The aqueous gel according to any one of claims 1 to 5. 7. The method according to claim 1, wherein at least one kind of the anionic water-soluble polymer (A) is a water-soluble polymer (a2) of an aliphatic carboxylic acid or an alkali metal salt thereof. The aqueous gel according to any one of claims. 8. The aqueous gel according to claim 1, wherein at least one kind of the polyvalent metal compound (B1) is an aluminum compound. 9. The method according to claim 5, wherein at least one of the acidic compounds (D) is an oxyacid (D1) and / or a hydroxyl group-containing organic acid (D2). The described aqueous gel. 10. An aqueous solution of the anionic aqueous polymer (A) is mixed with a water-insoluble polyvalent metal compound (b1), and then the polyvalent metal compound (b1) is an anionic aqueous polymer. The water-soluble gel of any one of claims 4 to 9, wherein the polyvalent metal compound (b2) which is easily soluble in water is mixed before completely dissolved in the aqueous solution of (A). Production method. 11. A cooling agent, a fragrance or a poultice, which comprises the aqueous gel according to any one of claims 1 to 10.