JP2015196675A - Water-absorbing resin crosslinking agent and absorbent - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water-absorbing resin crosslinking agent that has an excellent safety property, can efficiently crosslink water-absorbing resin at a low-temperature and produce an absorbent having high water-absorption capability, and to provide the absorbent obtained by crosslinking a water-absorbing resin with the water-absorbing resin crosslinking agent.SOLUTION: There is provided a water-absorbing resin crosslinking agent containing halohydrin compound having [A] and [B] in the molecule. [A] a halohydrin group represented by formula (1), [B] an amide bond and/or an ester bond. (A is a single bond or an alkylene group; Ris H or an alkyl group; X is Cl or Br.)

Description

  The present invention provides a novel water-absorbent resin cross-linking agent that is excellent in safety, can efficiently cross-link water-absorbing resins at low temperatures, and can produce a water-absorbing agent having a high water-absorbing capacity, a method for producing the same, and the cross-linking agent It relates to a water-absorbing agent obtained by crosslinking a water-absorbent resin.

Water-absorbing resins are widely used in various fields such as sanitary goods, foods, agriculture and forestry, and civil engineering. In particular, the water-absorbing resins are widely used in sanitary goods such as paper diapers and sanitary napkins, taking advantage of their water absorption. As the water-absorbent resin used in such sanitary goods, generally partially neutralized salts of polyacrylic acid and polymethacrylic acid are exemplified.
A water-absorbing resin used in sanitary goods such as paper diapers is required to have a high water-absorbing capacity not only under normal pressure but also under body pressure (under pressure).

As one of the technical means that can solve the above problems, a method of crosslinking the surface of water-absorbent resin particles with a crosslinking agent is known. Such a surface cross-linking method uses a cross-linking agent to cross-link the surface layer of water-absorbing resin particles having a carboxylic acid group and / or a carboxylic acid group, while suppressing the internal cross-linking of the water-absorbing resin particles to maintain the water absorbing ability. Thus, a water-absorbing agent having a high water absorption rate is obtained.
Conventionally, a compound having an epoxy group has been used as the crosslinking agent. However, the crosslinking agent containing a compound having an epoxy group has a concern about problems with skin irritation. Therefore, a crosslinking agent that does not contain a compound having an epoxy group has been proposed. Examples of such a cross-linking agent include a compound having at least two halohydrin groups in the molecule and a cross-linking agent containing a compound having a halohydrin group and a quaternary ammonium group in the molecule (see Patent Document 1). ). Moreover, the crosslinking agent containing the polyhydric alcohol which has a some amide skeleton or oxazole skeleton in a molecule | numerator can also be mentioned (refer patent document 2). These cross-linking agents also provide the water-absorbing resin particles with a water absorption capacity equivalent to that of an epoxy group-containing cross-linking agent.

  As described above, various cross-linking agents for cross-linking the water-absorbing resin particles have been developed. However, in recent years, the water-absorbing resin particles cross-linked with the conventional cross-linking agent are higher with the thinning of sanitary goods such as paper diapers. Development of a technique capable of producing a water-absorbing agent having a water-absorbing ability is desired.

JP 2002-060544 A JP 2003-020363 A

  The main subject of this invention is providing the novel water absorbing resin crosslinking agent used in order to obtain a water absorbing agent with high water absorption capability. Another object of the present invention is to provide a novel water absorbent obtained by using such a water absorbent resin crosslinking agent.

  As a result of intensive studies, the present inventors have used a water-absorbing resin crosslinking agent containing a compound having at least one halohydrin group and an amide bond and / or an ester bond in the molecule in the production of a water-absorbing agent. The present invention was completed by discovering that a water-absorbing agent having high water absorption can be obtained.

Examples of the present invention include the following [1] to [7].
[1] A water-absorbent resin cross-linking agent containing a halohydrin compound having the following [A] and [B] in the molecule:
[A] A halohydrin group represented by the following general formula (1);

(In the formula, A represents a single bond or an alkylene group, R ¹ represents a hydrogen atom or an alkyl group, and X represents a chlorine atom or a bromine atom.)
[B] Amide bond and / or ester bond.

[2] The water-absorbent resin cross-linking agent according to the above [1], wherein the alkylene group is a methylene group.

[3] Group represented by the following general formula (2):

(In the formula, E represents a single bond or a hydrogen atom, R ¹ represents a hydrogen atom or an alkyl group, X represents a chlorine atom or a bromine atom, and Y represents an oxygen atom or a sulfur atom.)
Or a group represented by the following general formula (3):

(In the formula, R ¹ represents a hydrogen atom or an alkyl group, and X represents a chlorine atom or a bromine atom.)
The water-absorbent resin cross-linking agent according to the above [1] or [2], comprising a halohydrin compound having at least one in the molecule.

[4] A compound obtained by reacting an epihalohydrin with at least one compound selected from the group consisting of aliphatic polyvalent carboxylic acids, aromatic polyvalent carboxylic acids, oxycarboxylic acids and urea, and derivatives thereof. The water-absorbent resin cross-linking agent according to any one of [1] to [3] above.

[5] A compound in which the halohydrin compound is represented by the following general formula (4) (hereinafter referred to as “halohydrin compound (4)”):

(Wherein R ¹ represents a hydrogen atom or an alkyl group, and R ² and R ³ are the same or different and each represents an alkyl group optionally substituted with a hydrogen atom or a hydroxyl group, or R ² and R 3 ³ forms a cyclic structure having 3 to 5 carbon atoms together with the adjacent nitrogen atom, G represents a hydrogen atom or a group represented by the following general formula (5), and X represents a chlorine atom or a bromine atom Y represents an oxygen atom or a sulfur atom.)

(Wherein R ¹ represents a hydrogen atom or an alkyl group, and X represents a chlorine atom or a bromine atom),
Compound represented by the following general formula (6) (hereinafter referred to as “halohydrin compound (6)”):

(In the formula, R ¹ represents a hydrogen atom or an alkyl group, and J represents a single bond, an alkylene group or alkenylene group which may be substituted with a hydroxyl group, a phenylene group, or the following general formula (7). Represents a group, G represents a hydrogen atom or a group represented by the general formula (5), and X represents a chlorine atom or a bromine atom.)

(In the formula, G represents a hydrogen atom or a group represented by the general formula (5)).

Compound represented by the following general formula (8) (hereinafter referred to as “halohydrin compound (8)”):

(Wherein R ¹ represents a hydrogen atom or an alkyl group, and J represents a single bond, an alkylene or alkenylene group optionally substituted with a hydroxyl group, a phenylene group, or the following general formula (9): Represents a group, G represents a hydrogen atom or a group represented by the general formula (5), and X represents a chlorine atom or a bromine atom.)

(Wherein G represents a hydrogen atom or a group represented by the general formula (5)), and

Compound represented by the following general formula (10) (hereinafter referred to as “halohydrin compound (10)”):

(In the formula, R ¹ represents a hydrogen atom or an alkyl group, L represents a single bond or an alkylene group or alkenylene group optionally substituted with a hydroxyl group, and M represents phenyl optionally substituted with a hydroxyl group. And X represents a chlorine atom or a bromine atom, provided that at least one hydroxyl group is present on L or M.)

The water absorbent resin crosslinking agent according to any one of the above [1] to [4], which is at least one compound selected from the group consisting of:

[6] To the water-absorbent resin having a carboxylic acid group and / or a carboxylate group, the water-absorbent resin cross-linking agent according to any one of the above [1] to [5] is added, heated and cross-linked. Water absorbent.

[7] The water-absorbent resin crosslinking agent according to any one of [1] to [5] above is added to a water-absorbent resin having a carboxylic acid group and / or a carboxylate group, and the mixture is heated and crosslinked. A method for producing a water-absorbing agent.

  The water-absorbent resin cross-linking agent of the present invention does not have a functional group having skin irritation such as an epoxy group, so that the water-absorbent resin is efficiently cross-linked at low temperature as well as being excellent in safety, A water-absorbing agent having a high water-absorbing ability can be produced.

I. First, the water absorbent resin crosslinking agent of the present invention (hereinafter referred to as “the present invention crosslinking agent”) will be described in detail.

I-1. Halohydrin Compound According to the Present Invention The crosslinking agent of the present invention includes a halohydrin compound having the following [A] and [B] in the molecule.
[A] A halohydrin group represented by the following general formula (1);

(In the formula, A represents a single bond or an alkylene group, R ¹ represents a hydrogen atom or an alkyl group, and X represents a chlorine atom or a bromine atom.)
[B] Amide bond and / or ester bond.

In the present invention, examples of the “alkyl group” according to R ¹ include linear or branched ones having 1 to 3 carbon atoms, specifically, for example, methyl group, ethyl Group and n-propyl group. Of these, a methyl group is preferable.

  Examples of the “alkylene group” according to A include linear or branched ones having 1 to 4 carbon atoms, and specific examples include a methylene group, an ethylene group, an n-propylene group, An n-butylene group can be mentioned. Of these, a methylene group is preferable.

  The halohydrin compound according to the present invention is not particularly limited as long as it is a compound having the halohydrin group and an amide bond and / or an ester bond in one molecule, but is represented by the following general formula (2). Group:

(In the formula, E represents a single bond or a hydrogen atom, R ¹ and X are as defined above, and Y represents an oxygen atom or a sulfur atom.)
Or a group represented by the following general formula (3):

(In the formula, R ¹ and X are as defined above.)
Is preferably a halohydrin compound having at least one in the molecule.

I-2. Specific examples of the halohydrin compound according to the present invention and a method for producing the same As the halohydrin compound according to the present invention, for example, an aliphatic polyvalent carboxylic acid, an aromatic polyvalent carboxylic acid, an oxycarboxylic acid and urea, and a group consisting of derivatives thereof Mention may be made of compounds obtained by reacting at least one selected compound with epihalohydrin.

  The halohydrin compound according to the present invention can be specified, for example, as a compound obtained by the above reaction, but is not limited to such a compound. A halohydrin compound produced by another production method is also included in the halohydrin compound according to the present invention as long as it is a halohydrin compound having [A] and [B] in the molecule.

  The aliphatic polycarboxylic acid is not particularly limited as long as it can react with epihalohydrin. Specifically, for example, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, and pimelic acid are used. Divalent carboxylic acids such as suberic acid, azelaic acid, sebacic acid, fumaric acid and maleic acid; hydroxy acids such as malic acid, tartaric acid and tartronic acid; and trivalent carboxylic acids such as citric acid and isocitric acid. Can do. Of these, citric acid and isocitric acid are preferred.

  The aromatic polyvalent carboxylic acid is not particularly limited as long as it can react with epihalohydrin. For example, terephthalic acid, isophthalic acid, phthalic acid, diphenylmethane-4,4′-dicarboxylic acid, diphenyl ether-4 4,4'-dicarboxylic acid, diphenylsulfone-4,4'-dicarboxylic acid, pyridine-2,6-dicarboxylic acid, trimellitic acid, trimesic acid, pyromellitic acid and the like.

  The oxycarboxylic acid is not particularly limited as long as it can react with epihalohydrin, and examples thereof include hydroxycinnamic acid such as salicylic acid, mandelic acid, gallic acid, and caffeic acid.

  Examples of the derivatives of the aliphatic polyvalent carboxylic acid and aromatic polyvalent carboxylic acid include primary polyamides derived from aliphatic polyvalent carboxylic acids or aromatic polyvalent carboxylic acids.

  The urea derivative is not particularly limited as long as it can react with epihalohydrin. For example, cyclic urea derivatives such as ethylene urea and trimethylene urea; chain urea derivatives such as monomethylol urea and dimethylol urea; thiourea And thiocarbonylurea derivatives such as ethylenethiourea.

  Examples of epihalohydrin include epichlorohydrin and epibromohydrin. Of these, epichlorohydrin is preferable because it is easily available.

  In the halohydrin compound according to the present invention, at least one of a carboxy group or an amide group of an aliphatic polyvalent carboxylic acid, an aromatic polyvalent carboxylic acid, an oxycarboxylic acid and urea, and a derivative thereof reacts with an epihalohydrin. It may be a compound obtained by this, and may have an unreacted carboxy group or amide group in the molecule.

  More specifically, examples of the halohydrin compound according to the present invention include the halohydrin compound (4).

Here, in the present invention, examples of the “alkyl group” according to R ² and R ³ include linear or branched ones having 1 to 4 carbon atoms, specifically, For example, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, and a sec-butyl group can be exemplified.
The “alkyl group” according to R ² and R ³ may have 1 to 3, preferably 2 hydroxyl groups at any substitutable position.

  The halohydrin compound (4) can be usually obtained by reacting urea or a derivative thereof with epihalohydrin. Examples of the halohydrin compound (4) in which G is a hydrogen atom include compounds obtained by reacting only one nitrogen atom on urea or a derivative thereof with epihalohydrin, and G represents the general formula (5). As the halohydrin compound (4) which is a group represented by the formula (hereinafter referred to as “substituent (5)”), for example, a compound obtained by reacting two nitrogen atoms on urea or a derivative thereof with epihalohydrin is exemplified. be able to.

Examples of the halohydrin compound (4) in which at least one of R ² and R ³ is a hydrogen atom include compounds obtained by reacting urea, monomethylolurea and the like with epihalohydrin.

Examples of the halohydrin compound (4) in which R ² and R ³ are not hydrogen atoms include compounds obtained by reacting dimethylolurea with epihalohydrin.

Examples of the halohydrin compound (4) in which R ² and R ³ together with the adjacent nitrogen atom form a cyclic structure having 3 to 5 carbon atoms include reacting ethylene urea or triethylene urea with epihalohydrin. The compound obtained by this can be mentioned.

  Examples of the halohydrin compound (4) in which Y is a sulfur atom include compounds obtained by reacting thiourea, ethylenethiourea and the like with epihalohydrin.

  The amount of epihalohydrin used in the reaction of urea or its derivative with epihalohydrin is suitably 0.5 to 4 equivalents of epihalohydrin, preferably 1 to 3 with respect to 1 equivalent of urea group of one molecule of urea or its derivative. Is equivalent.

  The reaction of urea or a derivative thereof and epihalohydrin is usually performed in a suitable solvent. Such a solvent is not particularly limited as long as it is inactive in the reaction of urea or a derivative thereof with epihalohydrin. For example, aromatic hydrocarbons such as toluene and xylene; aliphatic hydrocarbons such as hexane and heptane; diethyl Examples include ethers such as ether, diisopropyl ether, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, and dioxane; and highly polar solvents such as water, dimethylformamide, dimethylacetamide, and dimethyl sulfoxide. These may be used alone or in combination of two or more. Although the quantity of a solvent is not specifically limited, Usually, it is 10-1000 weight part with respect to 100 weight part of urea or its derivative (s), Preferably it is 50-500 weight part.

  Moreover, it is preferable to perform reaction of urea or its derivative (s), and epihalohydrin in presence of a suitable base. Examples of such a base include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, and alkali metal carbonates such as sodium carbonate and potassium carbonate. The amount of the base to be added is not particularly limited, but is usually 0.005 to 0.2 equivalent, preferably 0.01 to 0.1 equivalent, with respect to 1 equivalent of urea or a derivative thereof.

  The reaction temperature varies depending on the type and amount of urea or its derivative or epihalohydrin as a raw material, but 60 ° C to 100 ° C is suitable. The reaction time varies depending on the type and amount of urea or its derivative or epihalohydrin as a raw material, but 1 to 8 hours is appropriate.

Other specific halohydrin compounds according to the present invention include the halohydrin compound (6).
Here, in the present invention, examples of the “alkylene group” according to J include linear or branched ones having 1 to 8 carbon atoms (preferably 1 to 4 carbon atoms), Specific examples include a methylene group, an ethylene group, an n-propylene group, and an n-butylene group.
As the “alkenylene group” according to J, for example, linear or branched ones having 2 to 8 carbon atoms (preferably 2 to 4 carbon atoms) can be mentioned. A vinylene group, a propenylene group, 1-butene-1,4-diyl, 2-butene-1,4-diyl can be mentioned.
The “alkylene group” and “alkenylene group” according to J may have 1 to 3 hydroxyl groups at any substitutable positions.
Examples of the “phenylene group” according to J include 1,2-phenylene, 1,3-phenylene, and 1,4-phenylene.

  The halohydrin compound (6) can be usually obtained by reacting a polyvalent carboxylic acid with an epihalohydrin. Examples of the halohydrin compound (6) in which G is a hydrogen atom include compounds obtained by reacting only one carboxy group on the polyvalent carboxylic acid with epihalohydrin, and G is a substituent (5). An example of the halohydrin compound (6) is a compound obtained by reacting two carboxy groups on a polyvalent carboxylic acid with epihalohydrin.

  As the halohydrin compound (6), wherein J is a single bond or an alkylene group or alkenylene group optionally substituted with a hydroxyl group, for example, a compound obtained by reacting a divalent aliphatic carboxylic acid with an epihalohydrin Examples of the halohydrin compound (6) in which J is a phenylene group include a compound obtained by reacting a divalent aromatic carboxylic acid with an epihalohydrin. Examples of the halohydrin compound (6) in which J is a group represented by the general formula (7) (hereinafter referred to as “substituent (7)”) include compounds obtained by reacting citric acid with epihalohydrin. Can be mentioned.

  More specifically, examples of the halohydrin compound (6) in which J is a single bond include compounds obtained by reacting oxalic acid and epihalohydrin. As the halohydrin compound (6) in which J is an alkylene group, for example, a saturated dicarboxylic acid such as malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid or sebacic acid is reacted with epihalohydrin. The compound obtained by this can be mentioned. Examples of the halohydrin compound (6) in which J is an alkylene group substituted with a hydroxyl group include compounds obtained by reacting a hydroxy acid such as malic acid or tartaric acid with an epihalohydrin. Examples of the halohydrin compound (6) in which J is an alkenylene group optionally substituted with a hydroxyl group include compounds obtained by reacting an unsaturated dicarboxylic acid such as fumaric acid and maleic acid with epihalohydrin. Can do.

  Examples of the halohydrin compound (6) in which J is a phenylene group include compounds obtained by reacting an aromatic dicarboxylic acid such as terephthalic acid, isophthalic acid or phthalic acid with epihalohydrin.

  Examples of the halohydrin compound (6) in which J is a substituent (7) include compounds obtained by reacting citric acid with epihalohydrin. Among them, the halohydrin compound (6) in which G is a substituent (5) is usually obtained by reacting all carboxy groups on citric acid with epihalohydrin.

  The amount of epihalohydrin used in the reaction between the polyvalent carboxylic acid and epihalohydrin is suitably 0.8 to 5 equivalents of epihalohydrin, preferably 1 to 1 with respect to 1 equivalent of carboxy group of one molecule of polyvalent carboxylic acid. .5 equivalents.

  The reaction between the polyvalent carboxylic acid and the epihalohydrin may be appropriately adjusted depending on the type and amount of the polyvalent carboxylic acid or epihalohydrin used as the raw material, but is usually the same as the above-described reaction between urea or a derivative thereof and the epihalohydrin. Can be done under conditions.

Other specific halohydrin compounds according to the present invention may also include the halohydrin compound (8).
The halohydrin compound (8) can be usually obtained by reacting a primary amide with an epihalohydrin. Examples of the halohydrin compound (8) in which G is a hydrogen atom include compounds obtained by reacting only one amide group on the primary amide with epihalohydrin, and the halohydrin in which G is a substituent (5). Examples of the compound (8) include a compound obtained by reacting two amide groups on a primary amide with epihalohydrin.

  Examples of the halohydrin compound (8) in which J is a single bond include compounds obtained by reacting oxamide with epihalohydrin. Examples of the halohydrin compound (8) in which J is an alkylene group include saturated dicarboxylic acids such as malonic acid such as malonamide and succinic acid amide, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, and sebacic acid. The compound obtained by making the amide derivative of an acid and epihalohydrin react can be mentioned.

  Examples of the halohydrin compound (8) in which J is an alkylene group substituted with a hydroxyl group include a compound obtained by reacting an amide derivative of a hydroxy acid such as malic acid or tartaric acid with an epihalohydrin. . As the halohydrin compound (8) in which J is an alkenylene group optionally substituted with a hydroxyl group, for example, a compound obtained by reacting an amide derivative of an unsaturated dicarboxylic acid such as fumaric acid or maleic acid with an epihalohydrin Can be mentioned.

  Examples of the halohydrin compound (8) in which J is a phenylene group include terephthalic acid amide, isophthalic acid amide, and a compound obtained by reacting phthalic acid amide with epihalohydrin.

  Examples of the halohydrin compound (8) in which J is a substituent (7) include a compound obtained by reacting an amide derivative of citric acid with an epihalohydrin. Among them, the halohydrin compound (8) in which G is a substituent (5) is usually obtained by reacting all amide groups on the amide derivative of citric acid with epihalohydrin.

  The amount of epihalohydrin used in the reaction between the primary amide and epihalohydrin is suitably 0.8 to 5 equivalents of epihalohydrin, preferably 1 to 1.5 equivalents, relative to 1 equivalent of the amide group of one primary amide molecule. is there.

  The reaction between the primary amide and the epihalohydrin may be appropriately adjusted depending on the type and amount of the primary amide or epihalohydrin used as a raw material, but it is usually performed under the same conditions as the reaction between urea and its derivative and epihalohydrin. Can do.

  Other specific halohydrin compounds according to the present invention may also include the halohydrin compound (10).

Here, in the present invention, examples of the “alkylene group” according to L include linear or branched ones having 1 to 8 carbon atoms (preferably 1 to 4 carbon atoms), Specific examples include a methylene group, an ethylene group, an n-propylene group, and an n-butylene group.
Examples of the “alkenylene group” related to L include linear or branched ones having 2 to 8 carbon atoms (preferably 2 to 4 carbon atoms). A vinylene group, a propenylene group, 1-butene-1,4-diyl, 2-butene-1,4-diyl can be mentioned.
The “alkylene group” and “alkenylene group” according to L may have 1 to 3 hydroxyl groups at any substitutable positions.

  The “phenyl group” according to M may have 1 to 5, preferably 1 to 3 hydroxyl groups at any substitutable position.

The halohydrin compound (10) has at least one hydroxyl group on L or M. The substitution position of the hydroxyl group is not particularly limited as long as it can be substituted, and may have a hydroxyl group only on L, may have a hydroxyl group only on M, and may be on L and It may have a hydroxyl group on both of M.
The number of hydroxyl groups is not particularly limited, but is preferably 1 to 5 and more preferably 1 to 3 in one molecule.

  The halohydrin compound (10) can be usually obtained by reacting an oxycarboxylic acid with an epihalohydrin.

  Examples of the halohydrin compound (10) in which L is a single bond include compounds obtained by reacting salicylic acid or gallic acid with epihalohydrin. Examples of the halohydrin compound (10) in which L is an alkylene group which may be substituted with a hydroxyl group include compounds obtained by reacting mandelic acid with epihalohydrin. Examples of the halohydrin compound (10) in which L is an alkenylene group optionally substituted with a hydroxyl group include compounds obtained by reacting hydroxycinnamic acid such as caffeic acid with epihalohydrin.

  The amount of epihalohydrin used in the reaction of oxycarboxylic acid and epihalohydrin is suitably 0.8 to 5 equivalents of epihalohydrin, preferably 1 to 1.5, per 1 equivalent of carboxy group of one molecule of oxycarboxylic acid. Is equivalent.

  The reaction between the oxycarboxylic acid and the epihalohydrin may be appropriately adjusted depending on the type and amount of the oxycarboxylic acid or epihalohydrin used as a raw material, but usually under the same conditions as described above for the reaction between urea and its derivatives and epihalohydrin. It can be carried out.

  By the crosslinking agent of the present invention containing the halohydrin compound according to the present invention, the surface of a water-absorbing resin (described later) having a carboxylic acid group and / or a carboxylic acid group is efficiently crosslinked to produce a water-absorbing agent having a high water-absorbing ability. be able to. For this reason, it can be conveniently used as a surface cross-linking agent for a water-absorbent resin. Moreover, the inside of a water absorbing resin can also be bridge | crosslinked with this invention crosslinking agent as needed.

II. Next, the water-absorbing agent of the present invention will be described in detail with respect to the water-absorbing agent (hereinafter referred to as “the water-absorbing agent of the present invention”) obtained by crosslinking the water-absorbing resin with the present crosslinking agent.

  The water-absorbing agent of the present invention is obtained by adding the cross-linking agent of the present invention to a water-absorbing resin having a carboxylic acid group and / or a carboxylic acid group, heating and crosslinking.

  The water-absorbing agent of the present invention is obtained by cross-linking the surface of a water-absorbing resin having a carboxylic acid group and / or a carboxylic acid group using the cross-linking agent of the present invention. . A water absorbing agent that is internally cross-linked by the water absorbing agent of the present invention is also included in the present invention.

II-1. Surface Crosslinking A case where the surface of a water-absorbing resin having a carboxylic acid group and / or a carboxylic acid group is cross-linked by the cross-linking agent of the present invention will be described.

  The water-absorbing resin having a carboxylic acid group and / or a carboxylic acid group is not particularly limited as long as it has a carboxylic acid group and / or a carboxylic acid group and absorbs water and swells to form a hydrogel. For example, a well-known water-absorbing resin can be mentioned. Specific examples include a crosslinked polyacrylic acid partial neutralized product, a self-crosslinked polyacrylic acid partially neutralized product, a starch-acrylate graft copolymer crosslinked product, and a starch-acrylonitrile graft copolymer crosslinked product. , Cross-linked vinyl alcohol-acrylate copolymer, cross-linked acrylate-acrylamide copolymer, hydrolyzate of cross-linked acrylate-acrylonitrile copolymer, acrylate and 2-acrylamide-2- Mention may be made, for example, of a crosslinked copolymer of methylpropanesulfonate. These may be used alone or in combination of two or more.

  Among the water-absorbing resins exemplified above, a water-absorbing resin having a high density of carboxylic acid groups and / or carboxylic acid bases is preferable because of its high water absorption capability. Specific examples of such a water-absorbing resin include a crosslinked product of a partially neutralized acrylic acid and a self-crosslinked polyacrylic acid partially neutralized product. Here, examples of the carboxylate include a sodium salt, a potassium salt, and an ammonium salt, and a sodium salt is particularly preferable.

  The production method and shape of the water-absorbing resin having a carboxylic acid group and / or a carboxylate group are not particularly limited. For example, the reverse-phase suspension polymerization method, the pearl-like water-absorbing resin particles obtained thereby, and the aqueous solution polymerization method Examples of the water-absorbent resin include scaly, lump, rock, granule, and amorphous shapes obtained by pulverizing the dried product after polymerization. Moreover, what granulated these water absorbing resin particles can be mentioned.

  When surface crosslinking is performed with the crosslinking agent of the present invention, the crosslinking agent of the present invention is used for 100 parts by weight of the water-absorbent resin, depending on the type and degree of crosslinking of the water-absorbent resin and the degree of surface crosslinking desired. The amount of the halohydrin compound in the inventive cross-linking agent to be usually 0.01 to 20 parts by weight, preferably 0.05 to 10 parts by weight can be used. When the content of the halohydrin compound in the crosslinking agent of the present invention to be used is within the above range relative to 100 parts by weight of the water absorbent resin, not only can the water absorbent resin be effectively crosslinked, but the crosslinking density becomes too high. It is possible to prevent a decrease in water absorption capacity and water absorption speed of the water absorbing agent obtained.

  When the water-absorbent resin is surface-crosslinked with the crosslinking agent of the present invention, the crosslinking agent of the present invention is dissolved in water, a hydrophilic organic solvent or a solvent composed of a mixture thereof, and then the resulting crosslinking agent-containing solution of the present invention is obtained. It is preferable to mix a water absorbent resin. Examples of the hydrophilic organic solvent include lower aliphatic alcohols such as methanol, ethanol, n-propyl alcohol, and isopropyl alcohol; ketones such as acetone; ethers such as dioxane, tetrahydrofuran, and methoxy (poly) ethylene glycol; Amides such as ε-caprolactam and N, N-dimethylformamide; sulfoxides such as dimethyl sulfoxide; ethylene glycol, diethylene glycol, propylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, 1,3-propanediol, Examples thereof include polyhydric alcohols such as dipropylene glycol, polypropylene glycol, glycerin, and polyglycerin. These hydrophilic organic solvents may be one kind or a mixed solvent of two or more kinds.

  The amount of the solvent used may be appropriately adjusted depending on the type, particle size, water content, etc. of the water-absorbent resin, but is usually 0.1 to 20 parts by weight, preferably 100 parts by weight, based on the solid content of the water-absorbent resin. 0.5 to 10 parts by weight.

  The mixing of the crosslinking agent of the present invention and the water-absorbing resin can be performed, for example, by spraying a solution containing the crosslinking agent of the present invention onto the water-absorbing resin, and then mixing a cylindrical mixer, a V-shaped mixer, a ribbon-type mixer, Can be carried out by a known method using a machine, a double-arm mixer, a pulverizing kneader or the like. At this time, a surfactant can be added as necessary.

  In addition, a well-known surface crosslinking agent can also be used together in the range which does not prevent the effect of the surface crosslinking by this invention crosslinking agent. Examples of such known surface crosslinking agents include polyhydric alcohol compounds, polyvalent amine compounds, polyisocyanate compounds, polyvalent oxazoline compounds, alkylene carbonate compounds, silane coupling agents, and polyvalent metal compounds. Furthermore, an epoxy compound or a haloepoxy compound can be used in combination.

  Examples of the polyhydric alcohol compound include ethylene glycol, diethylene glycol, propylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, 1,3-propanediol, dipropylene glycol, 2,2,4-trimethyl-1, 3-pentanediol, polypropylene glycol, glycerin, polyglycerin, 2-butene-1,4-diol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol 1,2-cyclohexanedimethanol, 1,2-cyclohexanediol, trimethylolpropane, diethanolamine, triethanolamine, polyoxypropylene, oxyethylene-oxypropylene block copolymer , Mention may be made of pentaerythritol, sorbitol.

  Examples of the epoxy compound include ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerol polyglycidyl ether, diglycerol polyglycidyl ether, polyglycerol polyglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, and glycidol. Can be mentioned.

  Examples of the polyvalent amine compound include ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, polyethyleneimine, and inorganic salts or organic salts (such as aditinium salts) of these polyvalent amine compounds. it can.

  Examples of the polyisocyanate compound include 2,4-tolylene diisocyanate and hexamethylene diisocyanate, and examples of the polyvalent oxazoline compound include 1,2-ethylenebisoxazoline.

  Examples of the alkylene carbonate include 1,3-dioxolan-2-one, 4-methyl-1,3-dioxolan-2-one, 4,5-dimethyl-1,3-dioxolan-2-one, 4, 4-dimethyl-1,3-dioxolan-2-one, 4-ethyl-1,3-dioxolan-2-one, 4-hydroxymethyl-1,3-dioxolan-2-one, 1,3-dioxane-2 -One, 4-methyl-1,3-dioxan-2-one, 4,6-dimethyl-1,3-dioxan-2-one.

  Examples of the haloepoxy compound include epichlorohydrin, epibromohydrin, α-methylepichlorohydrin and polyvalent amine adducts thereof (eg, Kaimen (registered trademark) manufactured by Hercules).

Other known crosslinking agents include, for example, silane coupling agents such as γ-glycidoxypropyltrimethoxysilane and γ-aminopropyltriethoxysilane, and hydroxides such as zinc, calcium, magnesium, aluminum, iron, and zirconium. And polyvalent metal compounds such as chlorides.
These known crosslinking agents may be used alone or in combination of two or more.

  Although the heating temperature at the time of surface cross-linking may be appropriately changed according to the type of the cross-linking agent of the present invention and the water-absorbent resin, it is usually 40 ° C to 250 ° C. When the heating temperature is within the above range, the surface of the water-absorbent resin particles is uniformly cross-linked without deterioration of the water-absorbent resin particles, and has an excellent balance between the water absorption capacity under normal pressure and the water absorption capacity under pressure. A water-absorbing agent with high ability can be obtained.

  However, since the crosslinking agent of the present invention has high reactivity, the surface crosslinking reaction can be carried out quickly and uniformly even at a relatively low heating temperature. Therefore, the heating temperature is preferably 60 ° C to 200 ° C, more preferably 70 ° C to 200 ° C.

  The heating time may be appropriately adjusted according to the type of the crosslinking agent of the present invention and the water-absorbent resin, but is usually 0.2 hours to 3 hours.

  The water-absorbing agent of the present invention is a disinfectant, a deodorant, an antibacterial agent, a fragrance, various inorganic powders, a foaming agent, a pigment, a dye, a hydrophilic short fiber, a fertilizer, an oxidizing agent, a reducing agent for the purpose of imparting various functions. Other additives such as agents, water, and salts can be included. The addition amount and timing of addition of these other additives are appropriately selected by those skilled in the art.

  The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. In the following, “%” represents “% by weight”.

(Water absorption ratio under pressure of water absorbent)
The water absorption performance under pressure of the water absorbent produced by crosslinking the water absorbent resin with the crosslinking agent according to the present invention was evaluated as follows.
A crucible type glass filter (inner diameter 40 mm, height 70 mm) was set up vertically, and 1 g of the water-absorbing agent was uniformly put therein. A PET film (thickness: 100 μm) was placed on the water absorbing agent, and the initial weight was measured. Further, a weight with an outer diameter of 38 mm was placed thereon so as to obtain a load of 50 g / cm ² . Next, immerse the crucible glass filter containing the above water-absorbing agent into a vat (210 mm long, 170 mm wide) containing approximately 630 g of physiological saline (concentration 0.9%) for 30 minutes with the bottom facing down. Then, it was pulled up and the weight increase was measured to obtain the water absorption capacity under pressure.

(Examples of the present crosslinking agent)
Example 1
A 300 mL separable flask is charged with 20.0 g (0.33 mol) of urea, 20 g of ion exchange water, and 2.7 g of 48.7% sodium hydroxide aqueous solution, and the internal temperature is heated to 80 to 85 ° C. to dissolve. It was. While maintaining the internal temperature at 80 ° C. to 90 ° C., 33.9 g (0.37 mol) of epichlorohydrin was added dropwise thereto. After completion of the dropwise addition, the external temperature was heated to 100 ° C., and the reaction was terminated based on the determination of hydrolyzable chlorine (the amount of chlorine in the chlorohydrin group) by titration to obtain the present crosslinking agent (A1).

Example 2
A 300 mL separable flask was charged with 30.0 g (0.16 mol) of citric acid, 30 g of ion exchange water, and 1.3 g of 48.7% aqueous sodium hydroxide solution, and the internal temperature was heated to 80 ° C. to 85 ° C. to dissolve. I let you. While maintaining the internal temperature at 80 ° C. to 90 ° C., 36.1 g (0.39 mol) of epichlorohydrin was added dropwise thereto. After completion of the dropwise addition, the external temperature was heated to 100 ° C., and disappearance of epichlorohydrin was confirmed based on the quantification of the epoxy group by titration, and the reaction was terminated to obtain the present crosslinking agent (A2).

Synthesis example 1
A 500 mL separable flask was charged with 100 g (0.55 mol) of sorbitol and dissolved at an internal temperature of 110 ° C. to 115 ° C., and then 0.4 g of tin tetrachloride was charged as a catalyst. While maintaining the internal temperature at 95 ° C. to 100 ° C., 124 g (1.3 mol) of epichlorohydrin was added dropwise thereto. At the end of the addition, the reaction system was a homogeneous solution. After completion of the dropwise addition, stirring was continued in the same temperature range, and the disappearance of epichlorohydrin was confirmed based on the quantification of the epoxy group by titration to complete the reaction. After completion of the reaction, 125 g of ion exchange water and 1.6 g of 48.5% aqueous sodium hydroxide solution were added within the same temperature range, and the solvent was distilled off by concentration under reduced pressure to obtain a sorbitol chlorohydrin compound.

(Example of the water-absorbing agent of the present invention (surface-crosslinking of water-absorbent resin particles))
Example 3
An aqueous solution was prepared by diluting 0.1 g of the present crosslinking agent (A1) with 0.5 g of water (1% / water-absorbing resin particles). An aqueous solution was prepared by diluting 0.2 g of the present crosslinking agent (A1) with 1.0 g of water (2% / water-absorbent resin particles).
The aqueous crosslinking agent solution was sprayed on 10 g of polyacrylic acid water-absorbing resin particles, and mixed well. The water-absorbing resin thus treated was heated at 150 ° C. for 60 minutes to obtain the water-absorbing agent of the present invention that was surface-crosslinked with the crosslinking agent of the present invention. The performance of this water-absorbing agent is shown in Table 1.

Example 4
In Example 3, this invention water absorbing agent was obtained like Example 3 except having used 0.1 g and 0.2 g of this invention crosslinking agent (A2), respectively. The performance is shown in Table 1.

Comparative Example 1
In Example 3, a comparative water-absorbing agent was obtained in the same manner as in Example 3 except that 0.1 g and 0.2 g of the sorbitol chlorohydrin compound obtained in Synthesis Example 1 were used as the crosslinking agent. The performance is shown in Table 1.

  As shown in Table 1, it is clear that the water-absorbing agent of the present invention obtained using the cross-linking agent of the present invention exhibits a high water absorption capacity.

  The crosslinking agent of the present invention is excellent in safety and can efficiently crosslink the water absorbent resin at a low temperature. Therefore, the water-absorbing agent obtained by using the cross-linking agent of the present invention (the water-absorbing agent of the present invention) has a high water-absorbing ability and is useful in the field of sanitary products such as paper diapers.

Claims (7)

Water-absorbent resin cross-linking agent containing a halohydrin compound having [A] and [B] below in the molecule:
[A] A halohydrin group represented by the following general formula (1);

(In the formula, A represents a single bond or an alkylene group, R ¹ represents a hydrogen atom or an alkyl group, and X represents a chlorine atom or a bromine atom.)
[B] Amide bond and / or ester bond. The water absorbent resin crosslinking agent according to claim 1, wherein the alkylene group is a methylene group. Group represented by the following general formula (2):

(In the formula, E represents a single bond or a hydrogen atom, R ¹ represents a hydrogen atom or an alkyl group, X represents a chlorine atom or a bromine atom, and Y represents an oxygen atom or a sulfur atom.)
Or a group represented by the following general formula (3):

(In the formula, R ¹ represents a hydrogen atom or an alkyl group, and X represents a chlorine atom or a bromine atom.)
The water-absorbent resin crosslinking agent according to claim 1, comprising a halohydrin compound having at least one in the molecule. The halohydrin compound is obtained by reacting an epihalohydrin with at least one compound selected from the group consisting of aliphatic polyvalent carboxylic acids, aromatic polyvalent carboxylic acids, oxycarboxylic acids and urea, and derivatives thereof. The water absorbent resin crosslinking agent according to any one of claims 1 to 3. A compound in which the halohydrin compound is represented by the following general formula (4):

(Wherein R ¹ represents a hydrogen atom or an alkyl group, and R ² and R ³ are the same or different and each represents an alkyl group optionally substituted with a hydrogen atom or a hydroxyl group, or R ² and R 3 ³ forms a cyclic structure having 3 to 5 carbon atoms together with the adjacent nitrogen atom, G represents a hydrogen atom or a group represented by the following general formula (5), and X represents a chlorine atom or a bromine atom Y represents an oxygen atom or a sulfur atom.)

(Wherein R ¹ represents a hydrogen atom or an alkyl group, and X represents a chlorine atom or a bromine atom),
Compound represented by the following general formula (6):

(In the formula, R ¹ represents a hydrogen atom or an alkyl group, and J represents a single bond, an alkylene group or alkenylene group which may be substituted with a hydroxyl group, a phenylene group, or the following general formula (7). Represents a group, G represents a hydrogen atom or a group represented by the general formula (5), and X represents a chlorine atom or a bromine atom.)

(In the formula, G represents a hydrogen atom or a group represented by the general formula (5)).
Compound represented by the following general formula (8):

(Wherein R ¹ represents a hydrogen atom or an alkyl group, and J represents a single bond, an alkylene or alkenylene group optionally substituted with a hydroxyl group, a phenylene group, or the following general formula (9): Represents a group, G represents a hydrogen atom or a group represented by the general formula (5), and X represents a chlorine atom or a bromine atom.)

(Wherein G represents a hydrogen atom or the general formula (5)), and a compound represented by the following general formula (10):

(In the formula, R ¹ represents a hydrogen atom or an alkyl group, L represents a single bond or an alkylene group or alkenylene group optionally substituted with a hydroxyl group, and M represents phenyl optionally substituted with a hydroxyl group. And X represents a chlorine atom or a bromine atom, provided that at least one hydroxyl group is present on L or M.)
The water-absorbent resin crosslinking agent according to any one of claims 1 to 4, which is at least one compound selected from the group consisting of: A water-absorbing agent obtained by adding the water-absorbing resin cross-linking agent according to any one of claims 1 to 5 to a water-absorbing resin having a carboxylic acid group and / or a carboxylic acid group, followed by heating and crosslinking. A water absorbent resin having a carboxylic acid group and / or a carboxylate group, the water absorbent resin cross-linking agent according to any one of claims 1 to 5 is added, heated and cross-linked. Production method.