JPH0713115B2 - Water-soluble polymer - Google Patents

Description

[Detailed Description of the Invention] [Industrial field of application] The present invention relates to a polymer whose dissolution behavior is changed by a minute difference in salt concentration in water. More specifically, the present invention relates to a water-soluble polymer which is soluble in ordinary tap water but insoluble in water containing neutral inorganic salts composed of monovalent ions, such as NaCl, KCl, and NaBr in an amount of 0.5% by weight or more. It is a thing.

[Conventional technology]

It is known that when an inorganic salt that is an electrolyte is added to an aqueous solution of a water-soluble polymer, the polymer is precipitated by salting out. On the other hand, it is known that body fluid such as human urine contains about 0.5% by weight (hereinafter, abbreviated as%) or more of salt. Therefore, we developed a polymer that is soluble in tap water, but insoluble in an aqueous solution containing 0.5% salt, and exhibits leakproofness against body fluids, but dissolves in flush toilets. Is used as. However, anionic polymers such as polyacrylic acid and carboxymethylcellulose sodium salt have a slow change in solubility in an electrolyte aqueous solution, and, for example, in the case of saline, the anionic polymer is not insolubilized unless the concentration thereof becomes 4 to 5% or more. Also, in the case of nonionic polymers such as hydroxyethyl cellulose and polyvinyl alcohol (PVA), insolubilization is required only when the salt concentration becomes higher, and in order to insolubilize it, a concentration of about 10% is required for saline solution. However, if these polymers are simply used, they cannot be used as the leak-proof film. Therefore, various studies have been conducted. For example, JP-A-50-52371 discloses alkali cellulose ether sulfate as a method of utilizing the difference in solubility in water containing a salt. However, the sulfate tap water and 0.5 wt%
The difference in solubility in saline is unclear, and alkali cellulose ether sulphate is produced by further sulphating a cellulose derivative such as ethyl cellulose, and the price of the polymer becomes relatively expensive. There is a drawback that it ends up.

On the other hand, a combination of an acrylic acid-based polymer and polyvinyl alcohol (PVA) (JP-A-48-75647), a carboxyl group-containing vinyl polymer cross-linked with a polyvalent metal salt (JP-A-49-75). 105396), those using an alkali-soluble resin such as vinyl acetate and an unsaturated carboxylic acid copolymer (JP-A-49-112742), those using a vinyl acetate / crotonic acid copolymer (JP-A-49-112742). No. 117139), a water-soluble resin film provided with a copolymer film of an acrylic ester and an unsaturated carboxylic acid on one surface (JP-A No. 50-73). However, each of these films dissolves only when treated with alkaline water, and does not dissolve when simply put into tap water.

[Problems to be solved by the invention]

Therefore, although the present invention is soluble in tap water, NaCl, KCl, NaB
It is an object of the present invention to provide a polymer that does not dissolve in an aqueous solution containing 0.5% or more of a neutral inorganic salt composed of a monovalent ion such as r.

[Means for solving problems]

The present invention is based on the finding that when at least two specific types of monomers are copolymerized and a specific amount of the carboxyl groups of the monomers is neutralized, they are sensitive to salt concentration and become water-insoluble. Was done.

That is, the present invention comprises at least one selected from the group consisting of (A) acrylic acid and / or methacrylic acid, and (B) an alkyl acrylate and methacrylic acid alkyl ester having an alkyl group having 1 to 18 carbon atoms. A copolymer of (A) / (B) with a monomer of 1/9 to 9/1 (weight ratio), wherein the constituent acrylic acid or methacrylic acid is 2 to 70%.
Provided is a water-soluble polymer characterized in that mol% is in the form of a salt.

The monomer of the component (A) used in the present invention is acrylic acid and / or methacrylic acid. The monomer of component (B) used in the present invention is an alkyl acrylate or methacrylic acid alkyl ester having an alkyl group having 1 to 18 carbon atoms, preferably 1 to 8 carbon atoms. Here, the alkyl group is a concept including an alkenyl group, and methyl, ethyl, n-butyl, and 2-ethylhexyl esters are preferable, and n-butyl and 2-ethylhexyl esters are particularly preferable.

In the present invention, the weight ratio of the components (A) / (B) is 1 /
It is important to set 9 to 9/1, but preferably 2/8 to 7 /
3, particularly preferably 25/75 to 50/50. If the amount of component (B) is larger than 1/9, the polymer obtained will not dissolve in tap water, and if it is smaller than 9/1, it will dissolve in water containing 0.5% salt. Because there is no.

Further, in the present invention, it is essential to neutralize 2 to 70 mol% of the constituent acrylic acid or methacrylic acid in the copolymer to form a salt, preferably 5 to 65 mol%, particularly preferably, It is 10 to 60 mol%. If the neutralization rate is less than 2 mol%, it will not dissolve in tap water, and if the neutralization rate exceeds 70 mol%, it will also dissolve in water containing 0.5 wt% salt. It is not preferable. The method of neutralization is not particularly limited and may be neutralized after polymerization or may be polymerized after neutralizing the monomer, but in the case of polymerizing after neutralizing the monomer, the selection range of the polymerization solvent is Since it is limited, it is preferable to neutralize after polymerization.

As the alkali used for neutralization, sodium hydroxide,
Inorganic salts such as potassium hydroxide, lithium hydroxide, sodium carbonate, monoethanolamine, diethanolamine,
Examples include amines such as triethanolamine, diethylaminoethanol, ammonia, trimethylamine, triethylamine, tripropylamine, and morpholine, and ethanolamines or sodium hydroxide or potassium hydroxide in combination with ethanolamines are preferable.

The polymer of the present invention is required to satisfy the above requirements, but the average molecular weight is 5,000 to 100,000, preferably 10,000 to
50,000 is good.

The polymer of the present invention can be polymerized by various known methods,
The solution polymerization method is preferred. As the polymerization solvent, lower alcohols such as methanol, ethanol and 2-propanol, or a mixed solvent of these lower alcohols and water,
Further, a mixed solvent of a lower ketone such as acetone and methyl ethyl ketone and water is used. When using a mixed solvent containing water, the amount of water in the solvent is 10 to 50%, preferably 20 to 35%.
Is.

The polymerization initiator is not particularly limited as long as it is soluble in the solvent used, and examples thereof include 2,2′-azobisisobutyronitrile and 2,2′-azobis (2-methylbutyronitrile). , 2,2'-azobis (2,4-dimethylvaleronitrile), 2,2'-azobis (2-amidinopropane)
Dihydrochloride, 2,2′-azobis (N, N′-dimethyleneisobutylamidine) and the like can be mentioned, and the amount thereof is 0.02 to 5% based on the monomer.

The polymerization temperature varies depending on the polymerization solvent used, but is 50 to 80 ° C.
And the polymerization time is 3 to 8 hours.

〔The invention's effect〕

According to the present invention, there is provided a polymer which is soluble in tap water and insoluble in water containing 0.5% or more of a neutral inorganic salt composed of monovalent ions.

Therefore, it can be molded into a film and used for various body fluids (urine, blood, etc.)
It is preferably used as a member of a product that comes into contact with. That is, it is possible to prevent these body fluids from oozing out to the outside during use, and to dispose of these products in a flush toilet after use. Examples of such applications include non-woven fabric binders such as paper diapers and sanitary products or surgical bandages, and leak-proof films for paper diapers and sanitary products.

It can also be used in the form of a solution and used to detect salt-containing aqueous solutions.

Next, the present invention will be described with reference to examples, but the present invention is not limited thereto.

〔Example〕

Example 1 500 m equipped with a stirrer, reflux condenser and nitrogen inlet tube
Into a 4-necked separable flask of l, 22.5 g of acrylic acid, 27.5 g of 2-ethylhexyl acrylate, 130 g of acetone and 40 g of ion-exchanged water were put and uniformly dissolved, and then nitrogen gas was introduced from a nitrogen introduction tube while stirring. . 20 minutes later, 2,
2'-azobisisobutyronitrile 0.38 g acetone 30 g
The initiator solution dissolved in was added and heated in a water bath at 60 ° C. to start the polymerization reaction. Polymerize at 60 ° C for 6 hours while introducing nitrogen, then cool to room temperature to obtain 20% monoethanolamine.
% Aqueous solution 7.1 g was added to neutralize. The solid content of the obtained polymer solution measured by a Kett moisture meter was 19.2% (average molecular weight: 13,000).

30 g of this polymer solution was taken, and 22.1 g of acetone and 5.5 g of ion-exchanged water were added to prepare a 10% polymer solution. On a polyethylene plate placed on a horizontal table, make a 10 cm square enclosure partitioned by silicone rubber, pour about 5 g of polymer solution into it, and put it in a constant temperature room at 25 ° C and a relative humidity of 50%. The film was left standing for a day. The film thickness of the obtained film was in the range of 35 μm to 50 μm, though it varied depending on the measurement location.

The results of a solubility test conducted on the obtained film according to the method shown below are shown in Table 1.

Solubility test method About 0.1 g of the obtained polymer film was cut into 5 mm square and 40 m
l Put in a styrene bottle, then tap water, or
20 g of 0.5% saline was added, and the mixture was stirred with a magnetic stirrer at room temperature, and the time until dissolution was measured. It was judged as insoluble when it did not dissolve after 3 hours. It should be noted that tap water was prepared by dissolving calcium chloride in ion-exchanged water to a concentration of 60 mg / sodium chloride to a concentration of 120 mg / (hereinafter the same).

Example 2 500 m equipped with a stirrer, reflux condenser and nitrogen introducing tube
35 g of acrylic acid, 15 g of butyl acrylate, 130 g of acetone and 40 g of deionized water are placed in a 4-neck separable flask.
After the mixture was charged and uniformly dissolved, nitrogen gas was introduced from a nitrogen introduction tube while stirring. After 20 minutes, an initiator solution prepared by dissolving 0.49 g of 2,2'-azobisisobutyronitrile in 30 g of acetone was added, and the mixture was heated in a water bath at 60 ° C to start the polymerization reaction. Polymerization was carried out at 60 ° C. for 5 hours while introducing nitrogen, and then cooled to room temperature. The solid content of the obtained polymer solution measured by a Kett moisture meter was 20.1% (average molecular weight: 23,000). Take 30 g of this solution, and add 1.8 g of a 10% aqueous solution of monoethanolamine, 25.5 g of acetone, and 4.8 g of ion-exchanged water to add 1
A 0% solution was prepared, and then a polymer film was obtained in the same manner as in Example 1.

Example 3 Polymerization was carried out in the same manner as in Example 2 except that 15 g of acrylic acid, 35 g of butyl acrylate and 0.40 g of azobisisobutyronitrile were used. The solid content of the obtained polymer solution measured by a Ket moisture meter was 19.8% (average molecular weight 1
8,000). Take 30 g of this solution, and add 6.0 g of a 10% aqueous solution of monoethanolamine, 27.8 g of acetone, 1.6 parts of deionized water.
g was added to prepare a 10% solution, and then a polymer film was obtained in the same manner as in Example 1.

Comparative Example 1 Polymerization was carried out in the same manner as in Example 2 except that 47.5 g of acrylic acid, 2.5 g of butyl acrylate and 0.56 g of azobisisobutyronitrile were used. The solid content of the obtained polymer solution measured by a Kett moisture meter was 20.2% (average molecular weight
38,000). 30 g of this solution was taken, and 24.5 g of acetone and 6.1 g of ion-exchanged water were added thereto to form a 10% solution. Then, a polymer film was obtained in the same manner as in Example 1.

Comparative Example 2 30 g of the polymer solution (solid content 20.1%) obtained in Example 2 was taken, and 24.2 g of acetone and 6.1 g of ion-exchanged water were added thereto without adding monoethanolamine to obtain a 10% solution. A polymer film was obtained in the same manner as in Example 1.

Comparative Example 3 30 g of the polymer solution obtained in Example 3 (solid content: 19.8% by weight)
Then, 7.5 g of a 10% aqueous monoethanolamine solution, 5.0 g of a 10% aqueous sodium hydroxide solution and 29.4 g of ion-exchanged water were added to make a 10% solution, and then a polymer film was obtained in the same manner as in Example 1.

Comparative Example 4 500 m equipped with a stirrer, reflux condenser and nitrogen inlet
2.5 g of acrylic acid, 47.5 g of butyl acrylate and 170 g of methanol were placed in a 4-necked separable flask (1) and uniformly dissolved, and then nitrogen gas was introduced from a nitrogen introduction tube while stirring. After 20 minutes, an initiator solution prepared by dissolving 0.33 g of azobisisobutyronitrile in 30 g of methanol was added, and the mixture was heated in a water bath at 60 ° C to start the polymerization reaction. While introducing nitrogen, polymerization was carried out at 60 ° C. for 7 hours and then cooled to room temperature. The solid content of the obtained polymer solution measured with a ket moisture meter is
It was 19.3% (average molecular weight 11,000).

30 g of this solution was taken, 1.23 g of 10% aqueous monoethanolamine solution, 0.80 g of 10% aqueous sodium hydroxide solution and 27.9 g of methanol were added to make 10% solution, and a polymer film was obtained in the same manner as in Example 1 below. .

The results of the same solubility test as in Example 1 on the polymer films obtained in Examples 2 to 3 and Comparative Examples 1 to 4 are shown in Table-.
2 shows.

Example 4 500 m equipped with a stirrer, reflux condenser and nitrogen inlet
35 g of acrylic acid, 65 g of 2-ethylhexyl acrylate and 120 g of methanol were placed in a 4-necked separable flask of l, and after uniformly dissolving, nitrogen gas was introduced from a nitrogen introducing tube while stirring. After 20 minutes, an initiator solution prepared by dissolving 0.69 g of azobisisobutyronitrile in 30 g of methanol was added,
The mixture was heated in a water bath at 60 ° C to start the polymerization reaction. Polymerization was carried out at 60 ° C. for 8 hours while introducing nitrogen, and then cooled to room temperature. The solid content of the obtained polymer solution measured by a Kett moisture meter was 37.8% (average molecular weight 14,000).

Take 30 g of this polymer solution, and add 6.7 g of 10% monoethanolamine aqueous solution and 2.2 g of 10% sodium hydroxide aqueous solution.
And 83.4 g of methanol were added to make a 10% solution.
A polymer film was prepared in the same manner as in Example 1 (acrylic acid neutralization rate: 30 mol%). When the same solubility test as in Example 1 was conducted, it was dissolved in tap water in 25 minutes, and
It was insoluble in 5 wt% saline.

Example 5 500 m equipped with a stirrer, reflux condenser and nitrogen introducing pipe
Into a 4-necked separable flask (1), 15 g of acrylic acid, 25 g of 2-ethylhexyl acrylate, 10 g of methyl acrylate and 170 g of methanol were put and uniformly dissolved, and then nitrogen gas was introduced from a nitrogen introduction tube while stirring. After 20 minutes, an initiator solution prepared by dissolving 0.38 g of azobisisobutyronitrile in 30 g of methanol was added, and the mixture was heated in a water bath at 60 ° C to start the polymerization reaction. Polymerization was carried out at 60 ° C. for 8 hours while introducing nitrogen, and then cooled to room temperature. The solid content of the obtained polymer solution measured by a Kett moisture meter was 19.4% (average molecular weight 12,000).

Take 30 g of this polymer solution, add 3.7 g of 10% monoethanolamine aqueous solution and 28.2 g of methanol to this,
% Solution, and a film was prepared in the same manner as in Example 1 (neutralization rate of acrylic acid: 25 mol%). When a solubility test was conducted, it was dissolved in tap water in 12 minutes and was insoluble in 0.5% saline.

Example 6 22.5 g of the polymer solution adjusted to 10% of Example 1 was poured onto a polyethylene plate partitioned by silicon rubber into a size of 15 cm × 30 cm, and placed in a constant temperature and humidity chamber at 25 ° C. and a relative humidity of 50%. A polymer film was prepared by standing for 2 days. The obtained film is cut into a size of 10 cm × 22 cm, on which a cotton-like pulp having a basis weight of 20 g / m ² is spread over a width of 7 cm × 16 cm,
It is installed at a height of about 5 mm, and the entire surface sheet (polyester fiber and heat fusion fiber (Chisso ES) 50
%, 50% of heat-bonded non-woven fabric: 20 g / m ^{2 of} basis weight, and the two short ends were heat-sealed to assemble a sanitary napkin.

Place the acrylic plate on two tables of the same height at a distance of about 15 cm, put an 11 cm No. 2 filter paper on it, and put the above sanitary napkin on it. . 5 ml of simulated menstrual blood in which a water-soluble dye (Red No. 504) was dissolved was added to the center of the napkin, and an acrylic plate and a weight of 5 kg were placed on it. A mirror was placed between the two stands and the condition of the filter paper was observed, but no leakage of simulated menstrual blood into the filter paper was observed even after 4 hours. The napkin after the leak test was disassembled, the film was taken out, and the film was put into a beaker containing tap water (adjusted according to Example 1) 1 and slowly stirred with a magnetic stirrer.
The film started to disperse after minutes, and dissolved and disappeared after 30 minutes.

Example 7 500 m equipped with a stirrer, reflux condenser and nitrogen inlet tube
50 g of methacrylic acid, 50 g of butyl methacrylate and 120 g of methanol were put into a 4-necked separable flask of 1 l and uniformly dissolved, and then nitrogen gas was introduced from a nitrogen introducing tube while stirring. After 20 minutes, an initiator solution prepared by dissolving 0.67 g of azobisisobutyronitrile in 30 g of methanol was added, and the mixture was heated in a water bath at 60 ° C to start the polymerization reaction. Polymerization was carried out at 60 ° C. for 8 hours while introducing nitrogen, and then cooled to room temperature. When the obtained polymer solution was measured with a Kett moisture meter, the solid content was 37.3% (average molecular weight 9,000).

Take 30 g of this polymer solution, add 15.8 g of 10% aqueous monoethanolamine solution and 66.1 g of methanol to it,
A 10% solution was prepared, and a polymer film was prepared in the same manner as in Example 1 (neutralization rate of acrylic acid: 40 mol%). When the same solubility test as in Example 1 was conducted, it was dissolved in tap water in 20 minutes and was insoluble in 0.5% saline.

Claims (3)

[Claims] 1. At least one monomer selected from the group consisting of (A) acrylic acid and / or methacrylic acid, and (B) alkyl acrylate and methacrylic acid alkyl ester having an alkyl group having 1 to 18 carbon atoms. And (A) / (B) is a copolymer of 1/9 to 9/1 (weight ratio), wherein 2 to 70 mol% of the constituent acrylic acid or methacrylic acid is in the form of a salt. And water-soluble polymer. 2. The polymer according to claim 1, wherein the monomer of the component (B) is at least one selected from butyl acrylate, 2-ethylhexyl acrylate, butyl methacrylate and 2-ethylhexyl methacrylate. . 3. The polymer according to claim 1, having an average molecular weight in the range of 5,000 to 100,000.