JPH0420007B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an amphoteric type liquid-absorbing resin. Conventionally, pulp products have often been used to absorb and retain water. However, the amount of water absorbed by pulp is about 10 times its own weight, and in order to absorb and retain a large amount of water, a large amount of pulp is required and the product becomes very bulky.
It has the disadvantage that water easily separates when pressure is applied to something that has absorbed water. Therefore, various efforts have been made to develop super absorbent resins that absorb and retain large amounts of water with a small weight. These resins include starch graft polymers (Japanese Patent Publication No. 53-46199) and cross-linked polyacrylates (Japanese Patent Publication No. 54-30710), but most of these industrialized resins are anionic super absorbent resins. It is. The biggest drawback of this resin is that it exhibits high water absorption capacity in distilled water, but a significant drop in water absorption capacity is observed in electrolyte solutions. Super absorbent resins are used in disposable diapers, sanitary napkins, soil water retention agents, and other applications that rarely involve pure water, but mostly liquids containing salt. As a result of intensive research to overcome this drawback, the present inventors found that amphoteric type liquid-absorbing resins have higher liquid-absorbing ability for electrolyte solutions and alcohol than anionic type resins, and arrived at the present invention. . That is, the present invention uses a cationic acrylic monomer represented by the following formula and (meth)acrylic acid in a ratio of 10:90 to
0.005 to 0.5 part by weight per 100 parts by weight of a water-soluble monovinyl monomer containing 10 parts by mole or less of (meth)acrylamide per 1 part by mole of the ionic monomer in a molar ratio of 90:10. It is a liquid-absorbing resin that is made of a swellable polymer crosslinked product produced by polymerization in the coexistence of a water-miscible and/or water-soluble divinyl compound, and is characterized by absorbing water and/or alcohol. However, R ¹ is H or CH ₃ , R ² and R ³ are CH ₃ ,
_{C2H5 ,} A represents O or NH, _B represents _{C2H4 , C3H6} . Examples of vinyl monomers having a tertiary amino group used in the present invention include dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, dimethylaminopropyl (meth)acrylamide, diethylaminopropyl (meth)acrylamide, and dimethylaminomethyl ( Examples of the vinyl monomer having a carboxyl group include (meth)acrylic acid; however, in the present invention, the type of monomer is not limited; A combination of three or more types may be used. Acrylamide is a typical nonionic water-soluble vinyl monomer that may be used as needed, but is not particularly limited. The molar ratio of the monomer having a tertiary amino group and a carboxyl group can be selected from the range of 90:10 to 10:90 depending on the pH of the liquid to be absorbed, but preferably 30:70 to 70:30. This range is preferable from the viewpoint of water absorption capacity. Examples of the water-miscible or water-soluble divinyl compound used as a crosslinking agent include N,N-methylenebis(meth)acrylamide, tetraethylene glycol di(meth)acrylate, decaethylene glycol di(meth)acrylate, etc. , N,N-methylenebisacrylamide is industrially preferred. The amount of the divinyl compound is preferably 0.005 to 0.5 parts by weight, based on 100 parts by weight of the total weight of the monomer having a tertiary amino group and a carboxyl group or the nonionic water-soluble monomer, and if it is less than this range. The water-containing gel is in a semi-dissolved state, and if it is too large, the degree of crosslinking will increase, and in both cases the water absorption capacity will decrease. The polymerization of the product of the present invention is usually carried out in an aqueous solution, and any commonly used initiator, such as redox type or azo type, may be used. Further, the polymerization concentration is not particularly limited and can be selected within any concentration range, but in consideration of the drying process, it is advantageous to carry out the polymerization at a concentration as high as possible. For example, it is also possible to perform polymerization with a highly concentrated aqueous solution of about 70%, evaporate water by the heat of polymerization generated, and then directly carry it to the pulverization process without going through the drying process. Furthermore, the initiation temperature is not particularly limited, as the temperature at which polymerization is initiated differs depending on the type of initiator, as long as the polymerization is initiated at a temperature higher than the temperature at which the initiator functions. Next, the present invention will be described in more detail based on Examples, but the present invention is not limited to the following Examples unless the gist thereof is exceeded. Example 1 Dimethylaminoethyl methacrylate 44.3
g, acrylic acid 12.2g acrylamide 3.5g 140
g of distilled water, and the pH was adjusted to 4 with 11 g of 35% hydrochloric acid. Furthermore, 0.09 g of N,N-methylenebisacrylamide was added. 0.024 g of ammonium persulfate and 0.024 g of sodium bisulfite were added as an initiator, and polymerization was initiated at 40°C. Example 2 Dimethylaminoethyl methacrylate 39.5g
21.6 g of methacrylic acid and 8.9 g of acrylamide were dissolved in 25 g of distilled water, and 0.07 g of N,N-methylenebisacrylamide was added. Next, 10 c.c. of an acetone solution containing 0.7 g of 2,2'-azobisisobutyronitrile as an initiator was added. This solution
They were placed in a box-shaped container (Teflon-treated glass fiber material) heated in a constant-temperature water bath at 85°C. As the temperature of the solution rose, a polymerization reaction started, and water was evaporated by the generated heat of polymerization, yielding a liquid-absorbing resin as a porous solid with a low water content. Example 3 Dimethylaminoethyl methacrylate 54.9g
15.1 g of acrylic acid was dissolved in 10 g of distilled water, and 14 g of 35% hydrochloric acid was added to adjust the pH to 4. Added 0.21 g of N,N methylenebisacrylamide, and further added 2,2'-azobis(2-amidinopropane) as an initiator.
0.7 g of hydrochloride was added and mixed. This solution was placed in the box-shaped container described above and heated. As soon as polymerization started, water evaporated due to the heat of polymerization, yielding a liquid-absorbing resin as a porous solid with a low water content. Example 4 The polymer obtained in Example 1 was dehydrated with acetone, dried, and then ground. Moreover, the polymers obtained in Examples 2 and 3 were directly pulverized without going through a drying process to obtain powdery liquid-absorbing resins. A water absorption test was conducted comparing the powdered ampholytic liquid-absorbent resins of Examples 1 to 3 with a commercially available product (super absorbent resin made of a cross-linked product of sodium polyacrylate). Add with stirring and leave for 1 hour, then 100mesh
The amount of water absorbed was measured from the amount of liquid. Further, 5 g of powder was added to 5% saline solution and 1 part of methanol, and the same test was conducted. The result is the liquid absorption capacity (liquid absorption amount ÷ weight of added super absorbent resin)
The results are shown in Table 1. 【table】

Claims (1)

[Claims] 1. 10 to 1 mole part of an ionic monomer containing a cationic acrylic monomer represented by the following formula and (meth)acrylic acid in a molar ratio of 10:90 to 90:10. 0.005 to 100 parts by weight of water-soluble monovinyl monomer containing molar parts or less of (meth)acrylamide
A liquid-absorbing resin comprising a swellable crosslinked polymer produced by polymerization in the coexistence of 0.5 parts by weight of a water-miscible and/or water-soluble divinyl compound, and characterized in that it absorbs water and/or alcohol. [However, R ¹ is H or CH ₃ , R ² and R ³ are CH ₃ ,
_{C2H5 ,} A represents O or NH, _B represents _{C2H4 , C3H6} . 2. Claim 1, wherein the molar ratio of the cationic acrylic monomer represented by the formula according to Claim 1 and (meth)acrylic acid is in the range of 30:70 to 70:30. The liquid-absorbing resin described. 3 (Meta) in water-soluble monovinyl monomer mixture
The liquid-absorbing resin according to claim 1, wherein the content ratio of acrylamide is 20 mol% or less.