JPS63242345A - Acrylic water absorbent and its preparation - Google Patents

Abstract

PURPOSE:To impart an excellent film forming property, by preparing an acrylic water absorbent from a specific acrylic acid polymer, an alcoholic plasticizer and an adduct of an acrylic acid polymer and the alcoholic plasticizer. CONSTITUTION:20-100wt.% of an acrylic acid monomer and 0-80wt.% of an ethylenic unsaturated monomer are compounded to prepare a monomer compound which is, in turn, subjected to solution polymerization at room temp. in the presence of a liquid alcoholic plasticizer to obtain a copolymer. The obtained copolymer is neutralized with an alkali metal base, an ammoniacal compound or amine and crosslinked by a crosslinking agent to prepare an acrylic water absorbent. This water absorbent has excellent film forming capacity and the water absorbing film composed of the water absorbent itself can be also obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an acrylic polymer containing an acrylic acid polymer and an addition compound of an alcohol plasticizer and the polymer, which can be formed into a film. This invention relates to a water absorbing agent and its manufacturing method.

Conventional technologies and problems Polymer-based water absorbing agents are typically used in disposable diapers and feminine hygiene products, but among their various uses, they are most commonly used in the form of films and sheets. In such cases, the various polymer-based water-absorbing agents that have been proposed so far do not have film-forming ability themselves, so they can be used in the form of granules or powder to be used as water-absorbing paper. Generally, methods have been used to make sheets by sandwiching them between fibers or by mixing them between fibers. However, with these methods, the water absorption points become uneven, and the thickness makes it difficult to use. There were problems in that it was not suitable or required a lot of effort to manufacture.

Therefore, attempts have been made to form a film by dispersing a water-absorbing agent in a resin solution with film-forming ability such as ethylene-vinyl acetate copolymer, or to form a film by mixing a plasticizer with a polymer-based water-absorbing agent. Attempt (Unexamined Japanese Patent Publication No. 53-1
No. 41357), but in all cases, water absorption properties such as water absorption amount and water absorption rate deteriorate, and a satisfactory water-absorbing film has not yet been obtained.

Means for Solving the Problems The inventors of the present invention have conducted intensive research to develop a polymer-based water absorbing agent that exhibits excellent film-forming ability by itself. The inventors have discovered that the object can be achieved by using a product obtained by polymerizing lylic acid monomers, and have accomplished the present invention.

That is, the present invention comprises an acrylic acid polymer, an alcohol plasticizer that is liquid at room temperature, and an addition compound of the acrylic acid polymer and the alcohol plasticizer, and the carboxyl of the acrylic acid polymer component An acrylic water absorbing agent characterized in that the group forms an alkali metal salt, an ammonium salt, or an amine salt and is crosslinked, and 20 to 100% by weight of an acrylic acid monomer and an ethylenically unsaturated monomer. A product obtained by solution polymerizing monomers having a blending ratio of 0 to 80% by weight in the presence of a liquid alcohol plasticizer at room temperature is treated with an alkali metal base, an ammonia compound, or an amine. The present invention provides a method for producing an acrylic water absorbing agent, which is characterized by carrying out a neutralization treatment and a crosslinking treatment using a crosslinking agent.

Function: Excellent water absorption ability is imparted due to the alkali metal salt, ammonium salt or amine salt of the acrylic acid polymer component. Furthermore, based on the addition compound of the acrylic acid polymer and the alcohol plasticizer, excellent film-forming ability is imparted due to its own plasticizing action and the action of increasing compatibility 11 with the alcohol plasticizer. .

Examples of Constituent Elements of the Invention The acrylic water absorbing agent of the present invention comprises an acrylic acid polymer;
It consists of a composition of an alcohol plasticizer that is liquid at room temperature and an addition compound of the acrylic acid polymer and alcohol plasticizer.

The composition can be obtained, for example, by solution polymerizing an acrylic acid monomer and, if necessary, an ethylenically unsaturated monomer in the presence of a liquid alcoholic plasticizer at room temperature. In other words, this treatment causes unique polymerization of monomers such as acrylic acid monomers and polymerization of monomers involving alcohol-based plasticizers, resulting in acrylic acid-based monomers in which only the monomers are polymerized. In addition to the polymer, a compound is formed in which an alcohol plasticizer and an acrylic acid polymer are combined, and an unreacted alcohol plasticizer is added to the compound.

The above polymerization treatment must be carried out by a solution polymerization method, and the addition reaction rate of the alcohol plasticizer to the acrylic acid polymer is suitably 5% or more, particularly preferably 10% or more.

Acrylic acid monomers used in the above polymerization treatment include acrylic acid and methacrylic acid.

Typical examples of ethylenically unsaturated monomers that may be used as copolymerization components include methyl groups, ethyl groups, other alkyl groups having 3 to 1!1 carbon atoms, preferably 4 to 9 carbon atoms, and hydroxyalkyl groups. esters of acrylic acid or methacrylic acid having alkoxyalkyl groups, dialkyl esters of dibasic unsaturated acids such as fumaric acid and maleic acid having alkyl groups having 8 or less carbon atoms, acrylonitrile, acrylamide, vinylpyrrolidone , vinyl acetate, etc. The ethylenically unsaturated monomer is used as a modifier for film-forming ability or properties of the obtained film, and as is clear from the above examples, it may be water-soluble or water-insoluble. It may be something. Water-soluble ones have the advantage of improving film-forming ability and functioning as a water-absorbing matrix. on the other hand,
Water-insoluble ones have the advantage of being excellent in modifying the physical properties of the obtained film, such as by lowering the glass transition point of the polymer and making it possible to form a flexible film.

Therefore, the acrylic acid polymer component in the present invention is a homopolymer of acrylic acid or methacrylic acid, a copolymer thereof, or a copolymer of the above monomer and a water-soluble ethylenically unsaturated monomer. or a copolymer of the above monomer and a water-insoluble ethylenically unsaturated monomer, or a copolymer of the above monomer and a water-soluble ethylenically unsaturated monomer and a water-insoluble ethylenically unsaturated monomer. Consists of copolymers with monomers, etc.

The blending ratio of the monomers used in the polymerization treatment varies depending on the polymerization conditions, such as the type of monomers and reaction medium used, or the desired film-forming ability or film properties, but generally acrylic acid monomers are used. 20-1
00% by weight, preferably 30% by weight or more, ethylenically unsaturated monomers 0 to 80% by weight, preferably 70% by weight or less, particularly 0 to 40% by weight for water-insoluble monomers, preferably 30% by weight It is appropriate that the amount is less than % by weight. Outside the above range, the resulting acrylic water-absorbing agent may have poor water-absorbing ability or poor film-forming ability.

The reaction medium used in the polymerization process is water, or water and methanol, ethanol, isopropanol,
Aqueous media such as mixed solvents with easily water-soluble organic solvents such as acetone and methyl ethyl ketone, benzene,
Partial media consisting of organic solvents (including mixed systems) that are sparingly soluble or insoluble in water, such as toluene and ethyl acetate, and mixed media consisting of easily water-soluble organic solvents and partial media, etc. , is appropriately determined depending on the monomer used. The amount used may be the amount used in a conventional solution polymerization process.

Note that a known polymerization initiator is used, and is appropriately determined depending on the polymerization treatment conditions such as the reaction medium, such as an aqueous system, a partial system, or a mixture thereof, and the monomers used. In the case of an aqueous medium, persulfates such as ammonium persulfate, or redox initiators consisting of persulfates or hydrogen peroxide and metal salts, etc. Organic peroxides such as dibenzoyl peroxide are preferably used. In the case of a mixed medium of an aqueous system and a partial system, those used in the case of an aqueous system or a partial system may be used in combination. The amount of polymerization initiator used may be a normal amount.

The alcoholic plasticizer used in the above polymerization process is liquid at room temperature. Preferably the molecular weight is about 2000
Below, it is about 1000 or less and is difficult to volatilize. Examples include polyhydric alcohols such as glycerin, ethylene glycol, and erythritol, polyethylene glycol, polypropylene glycol, and ethylene oxide/propylene oxide copolymers. Examples include polyether polyols represented by derivatives of ethylene oxide or propylene oxide having a primary or secondary hydroxyl group. As with other components, only one type of alcohol plasticizer may be used, or two or more types may be used. The amount used varies depending on the polymerization conditions, but in general, 5 to 200 parts by weight, particularly 10 to 150 parts by weight, per 100 monomers (total amount) is suitable. If the amount used is too small, the resulting product will have poor film-forming ability, while if it is used in excess, breathing may occur, and the resulting acrylic water absorbing agent may have poor water absorbing ability, which is undesirable.

In the acrylic water absorbing agent of the present invention, the acrylic acid polymer component forms a salt. That is, the acrylic acid polymer that exists independently in the composition and the acrylic acid polymer that is added to the alcohol plasticizer are neutralized with an alkali metal base, an ammonia compound, or an amine. , the carboxyl group is neutralized with an alkali metal salt, ammonium salt or amine salt. In the present invention, 30 mol% or more of carboxyl groups, especially 50 to 9
Suitably, 5 mol% of the salt is converted into salt form.

If the degree of neutralization is less than 30 mol%, the resulting acrylic water absorbing agent will have poor water absorbing ability. In addition, the degree of neutralization is 95 mol%
Even if it is more than that, there will be no substantial difference in the water absorption capacity. Examples of alkali metal bases used in the neutralization treatment include alkali metal salt forming substances such as sodium salts and potassium salts represented by sodium hydroxide and potassium hydroxide, and examples of ammonia compounds include ammonia and aqueous ammonia. ammonium salt forming substances,
Examples of amines include monoamines and polyvalent amines such as monoethanolamine, jetanolamine, triethanolamine, hexamethylene diamine, and tetramethylenehexamine.

The acrylic water-absorbing agent of the present invention is not completely soluble in water and has the ability to maintain a water-absorbing state (it has a cross-linked structure formed through cross-linking treatment. The cross-linking treatment is generally performed using a cross-linking agent). It will be done.

The appropriate amount to use is o, oos to 9 parts by weight per 100 parts by weight of the composition (product), preferably 0.0
It is 2 to 6 parts by weight. If the amount used is less than o or oos parts by weight, the crosslinking density will be low and the amount of components dissolved in water will be large, resulting in poor water absorption ability. On the other hand, if it exceeds 9 parts by weight, the crosslinking density becomes too high, making it difficult to swell (and eventually resulting in poor water absorption capacity). Known crosslinking agents are used, such as triglycidyl isocyanurate, terminal 1,
Alicyclic glycidyl ester system having 2-epoxy group,
Epoxy compounds represented by low molecular weight epoxy compounds such as alicyclic glycidyl ethers, bisphenols, and aliphatic epoxy compounds, polymethylols such as melamine, methylolmelamine, and di(tri, tetra, penta, hexa) methylolmelamine. Examples include polyfunctional compounds such as melamine compounds represented by melamine derivatives such as melamine and alkylated medylol melamine such as methylated medylol melamine.

Note that the cross-tA treatment can be sufficiently carried out by heating when drying the solution of the composition.

The acrylic water-absorbing agent of the present invention itself has film-forming ability, so for example, a neutralizing agent and a crosslinking agent are added to the reaction solution from which the above product is obtained, and this is applied onto a liner, conveyor, etc. The film can be obtained by a conventional method, such as by evaporating the solvent. It can also be used as a laminate sheet by coating it on a supporting substrate such as paper, non-woven fabric, synthetic resin, metal, or wood, or it can be applied to the structure of a porous material such as non-woven fabric or resin foam to impregnate it. It can also be made into a sheet. In this case, a water-absorbing sheet with a large surface area and a high water absorption rate can be obtained.

Effects of the Invention The acrylic water-absorbing agent of the present invention has excellent film-forming ability, and can be formed into a good film even by solution coating.

As a result, it is possible to obtain a water-absorbing film made of the water-absorbing agent itself, and it can also be used as a laminating agent, coating agent, impregnating agent, spraying agent, etc., and can be applied to various uses as a water-absorbing treatment agent. Can be done.

Examples Example 1 30 parts (parts by weight, the same applies hereinafter) of a polyether polyol with a molecular weight of 750 made of a propylene oxide derivative having an ether bond in the molecular chain and a secondary hydroxyl group at the end of the molecular chain, and persulfuric acid. Add 100 parts of acrylic acid and 2-acrylic acid to a solution of 0.2 parts of potassium dissolved in 460 parts of water.
5 parts of ethylhexyl was added, and the mixture was polymerized in a 1e capacity flask equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen gas blowing nozzle at 58-62°C under a nitrogen stream for 8 hours. The viscosity of the obtained reaction solution was 11,200 voices (B
type rotational viscometer, 2 rpm, 30°C). In addition, the amount of free polyether polyol obtained by drying a part of the reaction solution was examined by extraction analysis using benzene, and the addition reaction rate of polyether polyol with acrylic acid polymer was determined from the measured value. The result was 92.7% (7.3% free).

Next, 1% by weight of an aqueous solution containing 10.465 parts of potassium hydroxide (0.8 equivalents to carboxyl group) dissolved in 200 parts of water and 0.023 parts of triglycidyl isocyanurate was added to 100 parts of the reaction solution. The resulting solution was applied onto a polyethylene film and dried to obtain a water-absorbing film with a thickness of about 50 mm.

Example 2 The amount of triglycidyl isocyanurate used was 0.009
A water-absorbing film was obtained according to Example 1 except that

Example 3 95 parts of acrylic acid and 5 parts of butyl acrylate were added to a solution in which 50 parts of the same polyether polyol and 0.3 parts of ammonium persulfate were dissolved in 460 parts of water, and polymerization was carried out in the same manner as above. The viscosity of the obtained reaction liquid was 10,500 voids, and the addition reaction rate of the polyether polyol with the acrylic acid polymer was 54% (measured according to the above method).

Next, in 100 parts of the reaction solution, an aqueous solution in which 8.636N of sodium hydroxide (1 equivalent to carboxyl group) was dissolved in 30 parts of water, and a 1% by weight aqueous solution containing 0.017 part of ethylene glycol diglycidyl ether were added. was added to obtain a water absorbent film with a thickness of about 50 um according to Example 1.

Example 4 Water absorption was carried out according to Example I2, except that the reaction solution obtained in Example 3 was used, and 6.909 parts of sodium hydroxide (0.8 equivalents to carboxyl group) was used instead of potassium hydroxide. A sex film was obtained.

Example 5 A water-absorbing film was obtained in accordance with Example 4, except that the amount of sodium hydroxide used was 4.318 parts (0.5 equivalents to carboxyl group).

Example 6 A water-absorbing film was obtained in accordance with Example 4, except that the amount of sodium hydroxide used was 2.591 parts (0.3 equivalent to carboxyl group).

Example 7 Potassium hydroxide was replaced with sodium hydroxide at 9.691
A water-absorbing film was obtained according to Example 3, except that 0.737 parts of triglycidyl isocyanurate was used in place of ethylene glycol diglycidyl ether.

Example 8 The amount of triglycidyl isocyanurate used was 0.123
A water-absorbing film was obtained in accordance with Example 7 except that

Example 9 The amount of triglycidyl isocyanurate used was 0.015
A water-absorbing film of 11 was obtained in the same manner as in Example 7, except that the water absorption film was 11%.

Example IO 80 parts of a polyether polyol with a molecular weight of 620 consisting of an ethylene oxide derivative having an ether bond in the molecular chain and a primary hydroxyl group at the end of the molecular chain, 0.3 part of ammonium persulfate, and 250 parts of water. 50 parts of methacrylic acid, 30 parts of butyl acrylate, and 20 parts of 2-methoxyethyl acrylate were added to a solution dissolved in a waste solvent containing 100 parts of methanol, and the mixture was heated at a temperature of 58 to 63°C according to the above procedure. Polymerized.

Next, 11 parts of triethanolamine (0.8 equivalents to carboxyl group) and 0.029 parts of glycerin polyglycidyl ether were added to 100 parts of the obtained reaction solution, and the obtained solution was used in Example 1. A water absorbent film having a thickness of approximately 50 μm was obtained in the same manner.

Example 11 A solution in which 50 parts of polypropylene glycol having a molecular weight of 300 and 0.5 parts of potassium persulfate were dissolved in 450 parts of water,
Add 90 parts of acrylic acid and 10 parts of vinyl acetate, and add 5 parts of vinyl acetate.
Polymerization was carried out in the same manner as described above at a temperature of 8 to 62°C.

Next, 8.0 parts of potassium hydroxide was added to 100 parts of the obtained reaction solution.
A solution of 16 parts (0.7 equivalents to carboxyl group) dissolved in 30 parts of water and 0 methyl etherified methylolmelamine
．． A water-absorbing film having a thickness of about 50 μm was obtained according to Example 1 using the obtained solution.

Example 12 A water-absorbing film with a thickness of about 50 μm was obtained in accordance with Example 11, except that the amount of acrylic acid used was 100 parts and vinyl acetate was not used.

The water-absorbing films obtained in the above examples were all transparent without defects such as holes, and had excellent flatness without wavy irregularities.

Moreover, the thickness was almost uniform.

Approximately 1 g (dry product) of the water-absorbing film obtained in Evaluation Test Examples 1 to 12
was immersed in 3,000 g of distilled water, left at room temperature for about 12 hours, filtered through a 200-mesh filtration filter, measured the ffl of the gel that remained unfiltered, and calculated its weight per 1 g of water-absorbent film. This value was converted into water absorption capacity.

The results are shown below.

Example water absorption capacity

Claims (1)

[Scope of Claims] 1. Consisting of an acrylic acid polymer, an alcohol plasticizer that is liquid at room temperature, and an addition compound of the acrylic acid polymer and the alcohol plasticizer, the acrylic acid polymer component An acrylic water-absorbing agent characterized in that the carboxyl group of forms an alkali metal salt, ammonium salt, or amine salt, and is crosslinked. 2. The water absorbing agent according to claim 1, wherein the acrylic acid polymer contains acrylic acid and/or methacrylic acid as a component. 3. Claim 1 in which the acrylic acid polymer contains an ethylenically unsaturated monomer as a copolymerization component
Water absorbing agent as described in section. 4. The water absorbing agent according to claim 1, wherein 30 mol% or more of the carboxyl groups are in the form of a salt. 5. The water absorbing agent according to claim 1, which is formed into a film, a laminate film, or an impregnated sheet. 6. Solution polymerization of monomers with a blending ratio of 20 to 100% by weight of acrylic acid monomer and 0 to 80% by weight of ethylenically unsaturated monomer in the presence of a liquid alcoholic plasticizer at room temperature. A method for producing an acrylic water absorbing agent, which comprises neutralizing the product obtained by the treatment with an alkali metal base, an ammonia compound, or an amine, and crosslinking it with a crosslinking agent. 7. Alcohol plasticizer 5 per 100 parts by weight of monomer
7. A method according to claim 6, using up to 200 parts by weight. 8. Crosslinking agent 0.005-9 per 100 parts by weight of product
7. The method of claim 6, using parts by weight.