JP4288618B2 - Method for producing carboxymethylcellulose gel - Google Patents

Description

  The present invention stabilizes foods, pharmaceuticals, and the like by causing molecular bonds (crosslinking) to occur in an carboxymethylcellulose alkali metal salt (hereinafter simply referred to as CMC), which is an anionic cellulose derivative, using an acid or an aqueous acid solution. The present invention relates to a method for producing a gel used for improving property and shape retention.

  CMC is the most commonly used water-soluble polymer at present. CMC is a white or similar white powder that dissolves in water and becomes a clear, odorless viscous liquid. Since CMC uses natural pulp as a raw material, it is highly safe. By cross-linking the CMC molecules, a cellulose molecule has a three-dimensional network structure, and a gel in which water is firmly captured inside the network structure is obtained. The gel thus obtained is widely used in foods, pharmaceuticals, daily necessities, cold insulation materials, building materials and the like.

  As a method for producing such a gel, conventionally, a method of preparing a gel by crosslinking an anionic water-soluble polymer with a polyvalent metal ion (for example, Patent Documents 1, 2, 3, and 4), an anionic water-soluble polymer, and the like. A gel is prepared by adding a crosslinking agent to a polymer to prepare a gel (for example, Patent Documents 5, 6 and 7), and adding water to an anionic water-soluble polymer and kneading it into a paste to irradiate the gel. There are known methods (for example, Patent Documents 8 and 9 and Non-Patent Documents 1, 2 and 3).

JP-A-7-90121 JP-A-11-106561 JP2000-191802A JP-A-2005-263858 JP2003-190991A JP-A-9-277421 JP 10-251447 A JP 2005-82800 A JP2001-2703 Bin Fel, Radoslaw A. Wach, Hiroshi Motomo, Fumio Yoshii, and Tamikazu Kume, Journal of Applied Polymer Science, 78, 278-283 (2000) Fumio Yoshii, Long Zhao, Radoslaw A. Wach, Naotsugu Nagasawa, Hiroshi Mitomo, and Tamikazu Kume, Nuclear Instruments and Methods in Physics Research B, 208 (2003), 320-324 Radoslaw A. Wach, Hiroshi Mitomo, Naotsugu Nagasawa and Fumio Yoshii, Radiation Physics and Chemistry, 68 (2003), 771-779

  However, in the method of preparing a gel by cross-linking an anionic water-soluble polymer with polyvalent metal ions, there is a possibility that the polyvalent metal ion may remain in the gel. Most of them are toxic, and there are limitations such as the limited use of the generated gel and the production method using radiation requires special equipment because it uses radiation.

  The object of the present invention is to provide a method for producing a gel using a carboxymethyl cellulose alkali metal salt as a raw material, which is highly safe for the environment and the human body, can be produced at low cost with simple equipment, and can be used with peace of mind in foods and pharmaceuticals. It is to provide.

  The basic principle of the present invention is that an anionic cellulose derivative carboxymethylcellulose alkali metal salt (CMC) can be made to form a molecular bond (cross-linking) using an acid or an acid aqueous solution, thereby obtaining a CMC gel. , Based on the inventor's new knowledge.

  In the more specific and preferred gel production method of the present invention, carboxymethyl cellulose alkali metal salt (CMC), which is a highly safe anionic water-soluble polymer made from natural pulp, is employed as a starting material, and the starting material is used. A gel using CMC as a raw material is produced by adding an acid or an aqueous acid solution to CMC and kneading.

  Further, in the method for producing a gel using CMC as a raw material according to another aspect of the present invention, CMC is kneaded with water to make a paste, and then the paste CMC is immersed in an acid or an acid aqueous solution. A gel made from CMC is produced.

In addition, the mechanism of the gel production | generation by kneading | mixing CMC and an acid is considered as follows.
As a result of measuring the infrared absorption spectrum of the gel produced by the acid treatment, it was found that the gel was almost the same regardless of the type of acid. From the measurement results of the elemental analysis, thermogravimetric analysis, and differential thermal analysis of the gel, it is presumed that the gel is not a newly introduced covalent bond but a gel formed by aggregation of CMC molecular chains. Since CMC used is a sodium salt, it is water-soluble, but when an acid enters, the carboxyl group of CMC becomes -COOH having a low dissociation degree. Therefore, the spread of the CMC molecular chain is suppressed, aggregates, and forms a hydrogen bond. As a result, a gel is formed. If some of the carboxyl groups remain in the form of -COONa, it is considered that there are few crosslinking points and a softer gel is formed.

Furthermore, in the method for producing a gel using CMC as a raw material according to another aspect of the present invention, an acid or an aqueous acid solution is added to the starting material CMC, kneaded, and then irradiated with ionizing radiation.
By irradiating with ionizing radiation, chemical bonds can be introduced into the CMC, and the gel fraction can be increased. That is, by irradiating with ionizing radiation, molecular bonding (crosslinking) of CMC increases and gel modification is performed.

Furthermore, in the method for producing a gel using CMC as a raw material according to another aspect of the present invention, after the CMC is kneaded with water to make a paste, the paste-like CMC is immersed in an acid or an aqueous acid solution, Further, ionizing radiation is irradiated.
Also in this case, chemical bonds can be introduced into the CMC by irradiating with ionizing radiation, and the gel fraction can be increased. That is, by irradiating with ionizing radiation, molecular bonding (crosslinking) of CMC increases and gel modification is performed.

  Furthermore, in the method for producing a gel using CMC as a raw material according to another aspect of the present invention, CMC is dissolved in water to make a paste, and the paste-like CMC is irradiated with ionizing radiation, and then the acid or acid aqueous solution is added. I am trying to immerse. In this case as well, the same effect as the above-mentioned irradiation with ionizing radiation can be obtained.

According to the present invention, since a gel can be generated simply by kneading an acid or an acid aqueous solution into CMC, it is not necessary to use a toxic reagent as in the prior art. Further, in the method for producing a gel without irradiating with ionizing radiation, it is not necessary to use a special device such as a radiation irradiation device. In particular, since the gel produced according to the present invention has an excellent compressive elastic modulus not found in conventional gels and has high heat resistance and acid resistance, it can be expected to be applied to a wider range of applications than ever before.

Hereinafter, the manufacturing method of the CMC gel of this invention is demonstrated in detail based on an Example, referring drawings.
Example 1 (Gel A)

Various CMCs (manufactured by Daicel Chemical Industries, Ltd.) (see FIG. 2) having different degrees of substitution (degree of etherification) and viscosity (higher molecular weight is higher) and 3 mole / l phosphoric acid aqueous solution were kneaded well. However, gelation occurred in all the CMCs used. The gelation flow is shown in FIG. The gel thus prepared (hereinafter referred to as gel A) has a relatively large compression modulus. The produced gel A was poured into water to remove uncrosslinked CMC and phosphoric acid, and the proportion of the insoluble portion in water was determined as the gel fraction. The results are shown in FIGS. FIG. 3 (A) is a graph expressed by paying attention to the gel fraction of FIG. 2, and FIG. 3 (B) is a graph expressed by paying attention to the water absorption amount of FIG. From FIG. 3 (A), it can be seen that the higher the viscosity of the CMC, the higher the gel fraction. Similarly, it can be seen from FIG. 3B that CMC with a higher degree of substitution (etherification degree) tends to have a higher water absorption. As a result of quantifying phosphorus in the gel using EDX (energy dispersive X-ray fluorescence spectrometer) and ICP (inductively coupled plasma mass spectrometer), it was confirmed that no phosphorus remained in the gel.

  The above examples relate to the formation of gel A by kneading CMC and phosphoric acid, but similar experiments were performed for other acids. The results are shown in FIG. 4 (A), (B) and (C). FIG. 4C is a graph of the data of FIGS. 4A and 4B. From FIG. 4, even when kneading CMC1380, which is a general CMC, and an aqueous solution of any of formic acid, citric acid, acetic acid, lactic acid, phosphoric acid, maleic acid, oxalic acid and hydrochloric acid, a firm hardness (N) is obtained. It can be seen that the CMC gel A is produced. In addition, about ascorbic acid, it turned out that a soft gel is produced | generated. Moreover, it is clear that no matter what acid is used, the lower the pH of the acid, the higher the gel fraction and the harder the gel, so that it is not necessary to specify the type of acid in the present invention. Furthermore, the hardness of the gel can be adjusted by changing the type and concentration of the acid.

  From the experimental results shown in FIG. 2, it can be said that all commercially available CMCs can be used as the CMC. That is, it can be said that all CMCs are gelled by being kneaded with an acid or an acid aqueous solution. Regardless of the degree of substitution (etherification degree) and viscosity, gel A having different characteristics can be obtained by using CMC having different degree of substitution (etherification degree) and molecular weight. Regarding the concentration of CMC, gelation is fast at a high concentration and slow at a low concentration. The concentration of CMC is within a range where it can be kneaded with an acid or an aqueous acid solution, and is preferably 2.5 wt% or more and 40 wt% or less.

  Depending on the combination of CMC and acid, it is possible to produce gels with different properties. Although the acid concentration varies depending on the type of acid, it is generally preferably at least 0.1 mole / l. When an acid having a high concentration is used, gelation is fast, gel fraction is high, and a hard gel is formed. As an example for explaining this, FIG. 5 shows the relationship between phosphoric acid concentration (%) and gel fraction (%). In the case of phosphoric acid, the gel fraction (72.35%) increases rapidly until the concentration is around 7.75%, but thereafter, the gel fraction gradually increases even if the concentration is increased. The gel fraction can also be increased by increasing the concentration of CMC. According to an experiment by the present inventors, when 3 mole / l phosphoric acid was kneaded, when the CMC concentration (%) was 5, 10 and 20, the gel fraction (%) was 21.5 and 85.8, respectively. And a value of 86.1.

  The temperature at which CMC and acid or acid aqueous solution are kneaded is not limited. In general, the higher the temperature at the time of kneading, the faster the gelation proceeds. However, kneading at a temperature at which CMC is hydrolyzed, for example, 70 ° C. or higher should be avoided. Moreover, the time to leave after kneading | mixing CMC and an acid or an acid aqueous solution does not ask | require. When the concentration of CMC and acid is high, gelation proceeds instantaneously and gelation occurs simultaneously with kneading. When the concentration is low, gelation proceeds relatively slowly. In general, the longer the standing time after kneading, the higher the gel fraction, but the reaction is completed within 24 hours.

Example 2 (Gel C)
One is 20 parts by weight of CMC, and the other is CMC gel A (produced according to the flow shown in FIG. 1A) in which 20 parts by weight of CMC and 1 mol of phosphoric acid are kneaded. These CMC and CMC gel A were each irradiated with γ rays. As a result, a new modified gel (hereinafter referred to as gel C) was obtained. The procedure for producing this modified gel is shown briefly in FIG. As a result of measuring each gel fraction (%) and water absorption (g water / g gel) of CMC and CMC gel C having absorbed doses of 5 kGy, 10 kGy, 20 kGy, 30 kGy, 40 kGy and 50 kGy, FIG. The numerical data shown are obtained. 6B and 6C are graphs showing the gel fraction (%) and water absorption (g water / g gel), respectively, based on the numerical value w data shown in FIG. 6A. FIG.

From these graphs, it is easily understood that, in the case of only 20 parts by weight of CMC not gelled with acid, the gel fraction increases and the water absorption decreases as the absorbed dose of radiation increases. That is, a stronger gel can be obtained by irradiation with radiation. In addition, in the case of a gel obtained by kneading CMC and acid or an aqueous acid solution, gelation is performed at a lower dose as compared with the case where the paste-like CMC obtained by kneading CMC and water is irradiated with radiation. Progresses. Furthermore, a gel gelled using a high concentration acid has a small amount of water absorption and is hardly affected by radiation irradiation.
Example 3 (Gel B)

When paste-like CMC produced by kneading 20 parts by weight of CMC and 80 parts by weight of water was poured into a 0.1 mole / l aqueous hydrochloric acid solution, a gel (hereinafter referred to as gel B) was produced. The gel fraction of the produced gel was 35%, and the water absorption per gram of the dried gel was 340 g.
FIG. 1B briefly shows the procedure for producing gel B. The conditions for preparing gel B are the same as those for preparing gel A. When CMC kneaded in paste form was immersed in an acid or an acid aqueous solution, gelation occurred with a lower concentration of acid or acid aqueous solution than kneading and gelling CMC and acid or acid aqueous solution.
Example 4 (Gel D)

  As described above, the CMC gel (hereinafter referred to as gel B) obtained by immersing CMC kneaded in paste form by adding water into an acid or an acid aqueous solution was further irradiated with γ-rays. The produced gel (hereinafter referred to as gel D) was produced.

The formation process of this gel D is shown in FIG. Moreover, the numerical data of the gel fraction (%) of the gel B before γ-ray irradiation and the modified gel D after γ-ray irradiation are shown in FIG. FIG. 8B is a graph of the numerical data shown in FIG. The following is recognized from FIGS. 8A and 8B. When the acid concentration is sufficiently low, the gel fraction is remarkably increased by irradiation with γ rays. However, when the absorbed dose of γ-rays exceeds 10 kGy, the gel fraction shows almost flat characteristics. Conversely, when the acid concentration is sufficiently high, a sufficiently high gel fraction is obtained at the stage of gel B, and the gel fraction does not increase even when γ rays are irradiated.
Example 5 (Gel E)

  100 parts by weight of radiation-crosslinked CMC gel produced by irradiating 5 kGy of γ rays to paste-like CMC produced by kneading 20 parts by weight of CMC and 80 parts by weight of water was added to 1000 parts by weight of 0.1 mole. When placed in an aqueous hydrochloric acid solution of / l and allowed to stand at room temperature for 16 hours, the gel fraction increased from 33% to 73%. The water absorption per gram of the dried gel decreased from 887 g to 90 g. This indicates that by immersing the gel in an aqueous hydrochloric acid solution, physical cross-linking progressed and a new modified gel (hereinafter referred to as gel E) was produced. The gel thus produced corresponds to the gel fraction and water absorption of the radiation cross-linked gel prepared at an absorbed dose of 20 kGy, and the treatment in acid means that the absorbed dose is reduced. A gel with higher strength can be obtained by placing the gel crosslinked with radiation in an acid or an aqueous acid solution. This is a technique that contributes to a reduction in absorbed dose.

  The process until the above gel E is produced is shown in FIG. Moreover, the gel fraction of the gel E produced | generated according to the flow of FIG. 9 is shown by numerical data in FIG. 10 (A). FIG. 10B is a graph of the numerical data shown in FIG. As can be easily understood from the graph of FIG. 10B, it can be seen that the gelation rate with respect to the gel E hardly changes even when the value of the absorbed dose of radiation is high or low.

  In the above embodiment, for example, γ rays are further irradiated to a gel formed by kneading CMC with an acid or an acid aqueous solution. However, as is apparent from the principle of the present invention, the gel is not limited to γ rays. For example, it may be an electron beam used in a conventional radiation crosslinking technique.

Furthermore, although only one type of acid is used in the above description, it can be seen that a similar gel can be formed by combining two or more types of acids in view of the principle of the present invention.
In the above description, the terms gel A, gel B, gel C, gel D and gel E are used, but these do not indicate the molecular bond structure of the gel itself, but merely an understanding of the production method. It is only used to make it easier.

The gel produced as described above can be used in a wide range of fields such as industry, agriculture, medicine and food. Examples thereof are given below, but are not limited thereto.
(1) Sustained drug release capsules (especially capsules that can release drugs in the large intestine): By kneading carboxymethylcellulose or carboxymethylcellulose alkali metal salt (hereinafter abbreviated as CMC) and an acid, it has excellent acid resistance and alkali resistance. Since a low gel is formed, it is expected that the drug reaches the intestine without being decomposed in the stomach and is released in the intestine.
(2) Food additive: A gel usable for food can be produced by kneading an acid approved as a food additive with CMC.
(3) Coolant: A gel can be easily formed by kneading CMC with an acid. If it is used without removing the acid, it can be used at lower temperatures because of the freezing point depression.
(4) Metal adsorbent, wastewater treatment agent: has metal adsorbing ability for certain metals.
(5) Poultice, peeling agent: A gel is formed by kneading CMC with a non-toxic acid. A soft gel can be prepared depending on the concentration and type of acid.

(A) is a figure which shows the flow until it obtains a gel by kneading | mixing CMC and an acid, (B) is the flow until a paste obtained by adding water to CMC is immersed in an acid to obtain a gel. FIG. It is a figure which shows the characteristic of the gel formed by kneading | mixing various CMC and phosphoric acid. (A) is a graph showing the relationship between the viscosity and gel fraction shown in FIG. 2, and (B) shows the relationship between the degree of substitution (degree of etherification) shown in FIG. 2 and the water absorption of the gel. It is a graph to show. It is a figure which shows the characteristic of each CMC gel obtained by kneading | mixing CMC1380 and various acid aqueous solution. FIG. 5 is a view similar to FIG. It is the figure which graphed the data shown by (A) and (B). It is a graph which shows the density | concentration of the phosphoric acid kneaded with CMC, and the relationship of a gel fraction. (A) (B) and (C) are the production flow of the modified gel produced by irradiating the gel formed by kneading CMC and acid, and the gel fraction and water absorption of the obtained modified gel. (D) is a figure which shows the flow until it irradiates with radiation to the gel obtained by kneading | mixing CMC and an acid, and obtains a modified gel. It is a figure which shows the flow until it irradiates to the gel obtained by immersing the paste obtained by adding water to CMC in an acid, and obtains a modified gel. It is a figure which shows the gel fraction and water absorption of the modification | reformation gel produced | generated by irradiating the gel obtained by immersing the paste obtained by adding water to CMC in an acid. It is a figure which shows the flow until it immerses in the acid after irradiating the paste obtained by adding water to CMC, and is immersed in an acid. It is a figure which shows the characteristic of the modification | reformation gel produced | generated by irradiating the acid obtained after irradiating the paste obtained by adding water to CMC, and gamma rays.

Explanation of symbols

CMC Carboxymethylcellulose HCL Hydrochloric acid PA Phosphoric acid CA Citric acid

Claims (4)

A carboxymethyl cellulose alkali metal salt that is an anionic cellulose derivative is simply added with an acid or an aqueous acid solution to form a molecular bond (crosslinking) to obtain a gel using the carboxymethyl cellulose alkali metal salt as a raw material. The manufacturing method of the gel which uses methylcellulose alkali metal salt as a raw material.   In the manufacturing method of the gel which uses the carboxymethylcellulose alkali metal salt of Claim 1 as a raw material, ionizing radiation is irradiated to the said gel which uses the obtained carboxymethylcellulose alkali metal salt as a raw material, The carboxymethylcellulose alkali metal characterized by the above-mentioned. A method for producing a gel using salt as a raw material. Production of a gel using a carboxymethyl cellulose alkali metal salt as a raw material, by simply adding an acid or an acid aqueous solution to a carboxymethyl cellulose alkali metal salt and kneading to obtain a physical gel made from the carboxymethyl cellulose alkali metal salt as a raw material Method.   In the manufacturing method of the gel which uses the carboxymethylcellulose alkali metal salt of Claim 3 as a raw material, after the said kneading | mixing, it further irradiates with ionizing radiation, The carboxymethylcellulose alkali metal salt characterized by the above-mentioned is obtained. A method for producing a gel as a raw material.

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