JPS6264803A - Highly water-absorptive chitosan derivative and absorbent containing the same - Google Patents

Abstract

PURPOSE:To facilitate the production of the titled insoluble derivative excellent in water absorptivity, biodegradability and salt resistance, by converting an (alkylated) chitosan into the corresponding hydroxyalkyl ether of a specified degree of substitution and crosslinking it. CONSTITUTION:Chitosan is obtained by deacetylating white to slightly red chitin having a degree of polymerization of a glucosamine structural unit >=1,000, a MW >=150,000 and a nitrogen content of about 7% (obtained from shells of crabs, lobsters and planktons of crustacea or arthropods) by heating it with an concentrated alkali. If necessary, the free amino groups of this chitosan are alkylated with an alkylating agent to obtain an alkylated chitosan. A hydroxyl ether product obtained by reacting this (alkylated) chitosan with a neutral water-soluble agent for introducing hydroxyalkyl ether groups (e.g., ethylene oxide) to a degree of substitution of 0.7-2.0 is crosslinked with 0.0001-2pts.wt., per pt.wt. hydroxyalkyl ether, crosslinking agent (e.g., aldehyde) to obtain the titled water-soluble derivative having a nitrogen content of 4-7%, an average MW of 20,000-2,000,000 and a water absorption of 30-100pts.wt., per pt.wt. its weight.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to highly water-absorbent chitosan derivatives and absorbents containing the same. The present invention relates to a chitosan derivative exhibiting high water absorption properties suitable as an absorbent for products used to absorb water, and an absorbent containing the same.

Conventionally, non-woven fabric, paper, pulp, sponge-like urethane resin, sponge, etc. have been used as absorbents in these liquid-absorbing products, but these absorbents are rarely fully satisfactory in terms of performance, and in recent years , cross-linked polyethylene oxide, cross-linked poval, and starch-acrylonitrile graft polymer hydrolysates have been developed, and absorbents using these materials alone or in combination with other components have been developed. It has become.

However, such water-absorbing materials also have a significant decrease in water-absorbing properties for liquids containing salt, have some manufacturing difficulties, and make products expensive. Since they lack biodegradability, there are problems with disposal.

Still not fully satisfied.

In view of these circumstances, the present inventor has conducted intensive research to obtain a water-absorbing substance that is relatively easy to produce, has high water absorption and biodegradability, and has excellent salt resistance.
We have found that certain chitosan derivatives are suitable for that purpose.

In other words, chitosan is a polymeric substance obtained by deacetylating the N-acetyl group at the 2-position of chitin, which is widely found in crustaceans and insects. At present, it is a resource that is hardly used, and its deacetylated product, chitosan, is also hardly used. This chitosan or the free hydroxyl group of the alkylated chitosan, which is made into a quaternary ammonium salt by alkylating the amino group at the 2-position, is converted into a hydroxyalkyl ether with a specific degree of substitution and crosslinked, resulting in a water-absorbing material. It was found that it has extremely excellent properties.

Therefore, the present invention provides hydroxyalkyl etherification with a degree of substitution of 0.7 to 2.0, and 0.0
The present invention provides a highly water-absorbing chitosan derivative selected from chitosan cross-linked with 0.001 to 2 parts of a cross-linking agent or alkylated chitosan, and the chitosan derivative can be easily produced and has high water absorption compared to conventional water-absorbing substances. biodegradable,
It has excellent properties such as salt resistance, and has the advantage of being able to use abundant unused resources as a raw material.
Alternatively, it can be combined with other components such as cellulose to form an absorbent, and such absorbents are also within the scope of the present invention.

The highly water-absorbing chitosan derivative of the present invention is obtained by deacetylating chitin to obtain chitosan, which is then reacted with an appropriate hydroxyalkyl etherification agent to replace the free hydroxyl group with hydroxyl at a degree of substitution of 0.7 to 2.0. After the alkyl etherification, 0.0001 to 2 parts of a suitable crosslinking agent is further applied to 1 part of the hydroxyalkyl etherified product, and if desired, the free amino 7 of chitosan is released before or after the hydroxyalkyl etherification or after the crosslinking. Obtained by alkylating the group.

Alternatively, hydroxyalkyl etherification of chitin may be followed by deacetylation and, if desired, alkylation, and crosslinking can also be performed before or simultaneously with hydroxyalkyl etherification. .

The term "degree of substitution" as used herein refers to the average number of hydroxyalkyl etherified free hydroxy groups per glucosamine unit constituting chitosan,
If all the free hydroxy groups are hydroxyalkyl etherified, the degree of substitution will be 2. Note that hydroxyalkyl etherification occurs not only on the free hydroxyl groups of chitosan but also on the free hydroxyl groups present in the hydroxyalkyl etherified chain side, so the actual addition mole of hydroxyalkyl etherification agent Class and degree of substitution do not necessarily correspond.

Chitin used as a raw material is not particularly limited, and is usually obtained from crab, shrimp, crustacean plankton shells, or arthropods by known methods. For example, a crab shell is washed under running water, scraped off the muscles and other foreign substances that have adhered to it, and then air-dried.
The carbonate is decomposed and eluted by immersion in a sufficient amount of 2N hydrochloric acid.

After the carbonate has been decomposed and eluted, it is thoroughly washed with water, air-dried, finely ground using a ball mill or other grinder, and then added to 2N hydrochloric acid again for 4 hours.
Soak for 8 hours. This is washed with water, centrifuged, and air-dried to obtain chitin. These chitins are generally white to pale pink powders with a degree of polymerization of glucosamine structural units of 1,000 or more, a molecular weight of about 150,000 or more, and a nitrogen content of about 7%.

The chitin can be deacetylated to chitosan by conventional methods such as heating with a concentrated alkali, such as a 5-50% aqueous solution of sodium hydroxide.

Alkylation of the free amine groups of chitosan can be carried out using alkylating agents such as alkyl halides such as methyl iodide, methyl bromide, methyl chloride, ethyl iodide, ethyl bromide, ethyl chloride, etc. :x, (R,
5enju, Bull, Chem, Soc.

Japan, Vol. 26, p. 143 (1953)].

Hydroxyalkyl etherification is carried out using neutral water-soluble hydroxyalkyl etherification agents such as ethylene oxide, propylene oxide, butylene oxide in the presence of an alkali or acid catalyst.

This is done by using ethylene chlorohydrin, propylene chlorohydrin, etc. As mentioned above, the degree of substitution is 0.7
~2.0. In general, the water-absorbing substance used in the absorbent needs to be water-insoluble itself; on the other hand, the higher the degree of substitution, the more hydroxyalkyl etherified t;
Shows water solubility. However, in the present invention, the degree of substitution may be high because the crosslinking makes the polymer insoluble in water.

Crosslinking can be carried out according to a conventional method using a conventional crosslinking agent having two or more functional groups that react with hydroxyl groups. Such crosslinking agents include glutaraldehyde, glyoxal, adipaldehyde, formaldehyde,
Aldehydes such as rose formaldehyde, epichlorohydrin, ethylene glycol diglycidyl ether,
Epoxy compounds such as polyethylene glycol diglycidyl ether, trimethylolpropane triglycidyl ether, glycerin diglycidyl ether, 1,6-hexanediol diglycidyl ether, 2,4-tolylene diisocyanate, hexamethylene diisocyanate/a' etc. Isocyanates , polyols such as ethylene glycol, trimethylolpropane, glycerin, and polyoxyethylene glycol, bisacrylamides such as N,N-methylenebisacrylamide, and di- or triacrylic acid obtained by reacting polyepoxide with acrylic acid or methacrylic acid. Examples include acids or methacrylic esters. As mentioned above, these crosslinking agents are used in an amount of 0.0001 to 2 parts, preferably 0.0005 parts, per 1 part of the hydroxyalkyl ether compound.
Act at a rate of ~1 part.

If the crosslinking density is too high, the water absorption capacity will be reduced, so this range is preferable.

The chitosan derivative of the present invention is usually obtained in the form of a white to light brown powder, and the hydroxyalkyl etherification agent used,
Depending on the crosslinking agent or alkylating agent, it is water-insoluble, has a nitrogen content of about 4-7%, and has a nitrogen content of about 20,000-200%.
It has an average molecular weight of 1,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,00,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000 type type type type type type type type type type type type type type type form type.

The obtained chitosan derivative can be used alone or in combination with other ingredients to make sanitary products, paper diapers, and gauze.

Absorption of paper towels, soil water retention improvers, interior building materials, etc.
used as an agent.

Other ingredients used in the absorbent may be any commonly used ones, such as other water-absorbing substances, fillers, pigments, deodorants, preservatives, fertilizers, etc. The amounts of these ingredients also depend on the purpose. Although it can be selected as appropriate depending on the situation, it is preferable that the amount of the chitosan derivative in the absorbent is at least 5% (wt%, the same applies hereinafter). Further, the dosage form of the absorbent is not particularly limited, and it can be made into various dosage forms such as powder, granules, and film according to conventional methods.

As a particularly preferred absorbent, the chitosan derivative and 10
Examples include those containing ~95% unmodified cellulose such as wood pulp, cotton, regenerated cellulose, etc. In such absorbents, the water absorption properties of chitosan derivatives and unmodified cellulose are mutually exclusive. shows higher water absorption.

Next, the present invention will be explained in more detail with reference to Examples.

Example 1 5 parts of chitin powder is immersed in a 42% aqueous sodium hydroxide solution for 2 hours at room temperature. Then, remove excess sodium hydroxide solution by centrifugation and reduce to about 1/4 volume.
00 parts of crushed ice to obtain a viscous chitin dispersion.

After adding new sodium hydroxide to adjust the concentration of sodium hydroxide to 12-13%, ethylene oxide 3
1 part and reacted in an autoclave at 30°C for 2 hours. Then, the mixture is gradually heated and held at 60° C. for 18 hours for deacetylation to obtain glycol chitosan. The obtained glycol chitosan is precipitated with methanol, washed and dried at %60°C to obtain glycol chitosan with a degree of substitution of 1.0. While stirring, 5 parts of 34% formaldehyde was added to a mixed solution of 20 parts of glycol chitosan, 10 parts of water, 250 parts of methanol, and 10 parts of 0.01N hydrochloric acid.
Glycol chitosan crosslinked with formaldehyde is obtained by standing at room temperature for 10 hours. The obtained crosslinked glycol chitosan is thoroughly washed with methanol and then dried at 60°C.

The water absorption amount of the obtained crosslinked glycol chitosan is 78% of its own weight.
The average molecular weight was approximately 1.6 million.

Example 2 4 parts of crosslinked glycol chitosan obtained in Example 1 was dispersed in 40 parts of water, 3.5 parts of sodium carbonate and 15 parts of methyl iodide were added, and 1
The reaction is carried out at 00° C. for 2 hours to obtain a methylated product of crosslinked glycol chitosan. The obtained methylated crosslinked glycol chitosan is washed with methanol and dried at 60°C.

The water absorption amount of this methylated crosslinked glycol chitosan was 72 times its own weight, and the average molecular weight was about 1.7 million.

Example 3 The crosslinked glycol chitosan obtained in Example 1 was ground in a ball mill and passed through a 34 mesh sieve. The resulting powder is thoroughly bleached beforehand.

Mix well with Southern Pine Kraft wood pulp powder passed through a 60 mesh sieve in a weight ratio of 1:1 to obtain a powdered absorbent.

0.5 g of each powder obtained by varying the proportions of the crosslinked glycol chitosan and wood pulp was compressed for 2 minutes under a pressure of 14 Q Ky / Cm2 using a KBr pellet press to obtain a pellet-like absorbent. The absorbency of each pellet was tested by placing the pellets in a certain amount of 1% saline solution for a certain period of time, and then removing the unabsorbed saline solution. The results are shown in the table below.

As is clear from these results, the absorption amount is extremely low when using wood pulp alone, and the absorption amount is low when using crosslinked glycol chitosan alone, but when both are used together, the absorption amount increases significantly.

Special plan applicant: Day 8 Chemical Co., Ltd.

Claims (7)

[Claims] (1) Chitosan or alkylated chitosan that has been hydroxyalkyl etherified with a degree of substitution of 0.7 to 2.0 and crosslinked with 0.0001 to 2 parts by weight of a crosslinking agent per 1 part by weight of the hydroxyalkyl etherified product. Water-insoluble, nitrogen content 4-7%, average molecular weight 20,000-200
A highly water-absorbing chitosan derivative having a water absorption capacity of 30 to 100 times its own weight. (2) The derivative according to item (1) above, wherein the hydroxyalkyl etherified product is a hydroxyalkyl etherified product with ethylene oxide, propylene oxide, butylene oxide, ethylene chlorohydrin or propylene chlorohydrin. (3) The crosslinking agent is aldehydes, epoxy compounds, isocyanates, polyols, bisacrylamides,
Diacrylic esters, triacrylic esters,
The derivative of item (1) or (2) above selected from dimethacrylic esters and trimethacrylic esters. (4) The derivative according to any one of items (1) to (3) above, wherein the alkylated chitosan is methylated chitosan. (5) Chitosan or alkylated chitosan that has been hydroxyalkyl etherified with a degree of substitution of 0.7 to 2.0 and crosslinked with 0.0001 to 2 parts by weight of a crosslinking agent per 1 part by weight of the hydroxyalkyl etherified product. Water-insoluble, nitrogen content 4-7%, average molecular weight 20,000-200
An absorbent characterized by containing a highly water-absorbing chitosan derivative having a water-absorbing capacity of 30 to 100 times its own weight. (6) The absorbent according to item (5) above, which contains the chitosan derivative and unmodified cellulose. (7) The absorbent according to item (6) above, containing at least 5% by weight of the chitosan derivative.