JPH08239428A - Binder for nonwoven fabric - Google Patents

Abstract

PURPOSE: To obtain a binder for nonwoven fabrics which exhibits solubility characteristics varing with water quality by using a water-sol. (meth)acrylic acid-(meth)acrylic ester copolymer contg. a specified amt. of (meth)acrylic acid units of a salt type. CONSTITUTION: This binder for nonwoven fabrics is a copolymer which is formed from 10-90wt.% (meth)acrylic acid and 90-10wt.% at least one alkyl (meth)acrylate having a 1-18C alkyl group and of which 2-70mol% of (meth) acrylic acid units are of a salt type. The alkyl (meth)acrylate is pref. selected from among butyl acrylate, 2-ethylhexyl acrylate, butyl methacrylate, and 2- ethylhexyl methacrylate. The binder pref. has an average mol.wt. of 5,000-100.000.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-woven fabric binder whose dissolution behavior changes depending on a minute difference in salt concentration in water. Specifically, for non-woven fabrics that dissolve in ordinary tap water, but are insoluble in water containing 0.5% by weight or more of neutral inorganic salts composed of monovalent ions, such as NaCl, KCl, and NaBr. It concerns a binder.

2. Description of the Related Art It is known that when an inorganic salt as 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, a polymer that is soluble in tap water but insoluble in aqueous solutions containing 0.5% salt has been developed and has leakproof properties against body fluids, but is soluble in flush toilets. It has been used as a leaky film. 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. Further, in the case of nonionic polymers such as hydroxyethylcellulose and polyvinyl alcohol (PVA), the salt is insolubilized only when the salt concentration is further increased, and for insolubilization, a concentration of about 10% is required in the case of saline. However, simply using these polymers cannot be used as the leak-proof film.
Therefore, various studies have been made. For example, Japanese Patent Laid-Open No. Sho 50
No. 52371 discloses alkali cellulose ether sulfate as a method of utilizing the difference in solubility in water containing a salt. However, the difference between the solubility of the sulfate in tap water and 0.5 wt% saline is unclear, and the alkali cellulose ether sulfate is produced by further sulfating a cellulose derivative such as ethyl cellulose. Has the disadvantage that it is relatively expensive.

On the other hand, a combination of an acrylic acid polymer and polyvinyl alcohol (PVA) (Japanese Patent Laid-Open No.
-75647), a carboxyl group-containing vinyl polymer crosslinked with a polyvalent metal salt (JP-A-49-10538).
No. 6), and those using an alkali-soluble resin such as vinyl acetate and unsaturated carboxylic acid copolymer (JP-A-49-1127).
No. 42), those using a vinyl acetate / crotonic acid copolymer or the like (Japanese Patent Application Laid-Open No. 49-117139), in which a copolymer film of an acrylate ester and an unsaturated carboxylic acid is provided on one surface of a water-soluble resin film. (Japanese Patent Application Laid-Open No. 50-73) is disclosed. However, all of these films are dissolved only when treated with alkaline water, and are not dissolved simply by being introduced into tap water.

Therefore, although the present invention is soluble in tap water, it is soluble in an aqueous solution containing 0.5% or more of a neutral inorganic salt consisting of monovalent ions such as NaCl, KCl and NaBr. The purpose is to provide a binder for non-woven fabric.

[0003]

According to the present invention, a water-soluble polymer obtained by copolymerizing at least two specific monomers and neutralizing a specific amount of a carboxyl group of the monomers is used as a nonwoven fabric binder. It was made based on the finding that the problem could be solved. 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 ester having a C 1-18 alkyl group and a methacrylic acid alkyl ester. A copolymer of (A) / (B) with a monomer in a ratio of 1/9 to 9/1 (weight ratio), wherein the constituent acrylic acid or methacrylic acid is 2 to
Provided is a nonwoven fabric binder comprising a water-soluble polymer, wherein 70 mol% is in a salt form.

[0004]

DETAILED DESCRIPTION OF THE INVENTION The monomer of component (A) used in the present invention is acrylic acid and / or methacrylic acid.
The monomer of the component (B) used in the present invention is an alkyl acrylate or alkyl methacrylate having an alkyl group having 1 to 18, preferably 1 to 8 carbon atoms. Here, the alkyl group is a concept including an alkenyl group, and esters of methyl, ethyl, n-butyl, and 2-ethylhexyl are preferable, and n-butyl and 2-ethylhexyl esters are particularly preferable. In the present invention, it is important that the weight ratio with the component (A) / (B) is 1/9 to 9/1, but preferably 2/8 to 7/3,
Particularly preferably, it is 25/75 to 50/50. When the amount of the component (B) is more than 1/9, the polymer obtained is not soluble in tap water, and when the amount is less than 9/1, the obtained polymer is 0.1.
It is not preferable because it dissolves in water containing 5% of salt. In the present invention, it is essential that 2-70 mol% of the constituent acrylic acid or methacrylic acid in the copolymer is neutralized to form a salt, and preferably 5-65 mol%.
Mol%, particularly preferably 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 be used in water containing 0.5% by weight of salt. It is not preferable because it dissolves.
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, inorganic salts such as sodium hydroxide, potassium hydroxide, lithium hydroxide and sodium carbonate, monoethanolamine, diethanolamine, triethanolamine, diethylaminoethanol, ammonia, trimethylamine, triethylamine, Examples thereof include amines such as tripropylamine and morpholine, and it is preferable to use ethanolamines or sodium hydroxide or potassium hydroxide in combination with ethanolamines. The polymer of the present invention needs to satisfy the above requirements, but has an average molecular weight of 5,000 to 1
00,000, preferably 10,000-50,000
The ones are good. The polymer used as the binder for the nonwoven fabric of the present invention can be polymerized by various known methods, but the solution polymerization method is preferred. As the polymerization solvent, methanol,
Ethanol, lower alcohols such as 2-propanol, or a mixed solvent of these lower alcohols and water, and
A mixed solvent of water and a lower ketone such as acetone or methyl ethyl ketone is used. When a mixed solvent containing water is used, the amount of water in the solvent is 10 to 50%, preferably 20 to 35%.
%.

The polymerization initiator is not particularly limited as long as it dissolves in the solvent used, and for example, 2,2 '.
-Azobisisobutyronitrile, 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, the amount of which is 0.02 to monomer.
5%. 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.

[0007]

According to the present invention, there is provided a binder for nonwoven fabric comprising 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. Is done. Therefore, the non-woven fabric prepared using the binder of the present invention can be suitably used as a non-woven fabric for disposable diapers, sanitary products, surgical dressings and the like. still,
The water-soluble polymer used as the binder for the nonwoven fabric of the present invention is suitably used as a member of a product which is formed into a film and comes into contact with various body fluids (urine, blood, etc.). That is, during use, it is possible to prevent such body fluids from oozing to the outside, and after use, it is possible to discard these products in flush toilets or the like. Examples of such applications include 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.

[0008]

【Example】

Example 1 50 equipped with a stirrer, a reflux condenser and a nitrogen inlet tube
Acrylic acid 22.5 in a 0 ml 4-neck separable flask
g, 2-ethylhexyl acrylate (27.5 g), acetone (130 g) and ion-exchanged water (40 g) were dissolved uniformly, and then nitrogen gas was introduced from a nitrogen introduction tube with stirring. After 20 minutes, 2,2'-azobisisobutyronitrile
An initiator solution prepared by dissolving 0.38 g in 30 g of acetone was added and heated in a water bath at 60 ° C. to start the polymerization reaction. After polymerizing at 60 ° C. for 6 hours while introducing nitrogen, the mixture was cooled to room temperature, and 7.1 g of a 20% aqueous solution of monoethanolamine was added for neutralization. The solid content of the obtained polymer solution measured by a ket moisture meter was 19.2% (average molecular weight: 13,0%).
00). 30 g of this polymer solution is taken and acetone 22.1
g and ion-exchanged water 5.5 g were added to prepare a 10% polymer solution. Create a 10cm square enclosure separated by silicone rubber on a polyethylene plate placed on a horizontal table,
About 5 g of the polymer solution was poured into this and left in a constant temperature and humidity chamber at 25 ° C. and a relative humidity of 50% for 2 days to obtain a film. 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.

Table 1 shows the results of a solubility test performed on the obtained film according to the method described below. Solubility test method About 0.1 g of the obtained polymer film was cut into 5 mm square and placed in a 40 ml styrene bottle, then tap water or 20 g of 0.5% saline solution was added, and the mixture was magnetically stirred at room temperature. The mixture was stirred and the time until dissolution was measured. It was judged as insoluble when it did not dissolve after 3 hours. In addition, 60 mg of calcium chloride in ion-exchanged water /
1 and sodium chloride dissolved at a concentration of 120 mg / l were used as tap water (the same applies hereinafter).

[0010]

[Table 1] Table-1 Tap water 0.5% Salt solution Soluble in 15 minutes Insoluble

Example 2 50 equipped with a stirrer, reflux condenser and nitrogen inlet tube
In a 0 ml 4-neck separable flask, add acrylic acid 35
g, 15 g of butyl acrylate, 130 g of acetone and 40 g of ion-exchanged water were added and uniformly dissolved, and then nitrogen gas was introduced from a nitrogen introduction tube with stirring. 20 minutes later,
An initiator solution obtained 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 initiate a polymerization reaction. 60 while introducing nitrogen
After polymerizing at ℃ for 5 hours, it was cooled to room temperature. The polymer solution obtained had a solid content of 20.1 as measured with a Kett moisture meter.
% (Average molecular weight 23,000). Take 30 g of this solution and add 1.8% of 10% aqueous solution of monoethanolamine to it.
g, 25.5 g of acetone and 4.8 g of ion-exchanged water.
A 0% solution was prepared, and a polymer film was obtained in the same manner as in Example 1.

Example 3 Example 2 except that 15 g of acrylic acid, 35 g of butyl acrylate and 0.40 g of azobisisobutyronitrile were used.
Polymerization was carried out in the same manner as in. The solid content of the obtained polymer solution measured by a ket moisture meter was 19.8% (average molecular weight: 18,000). Take 30 g of this solution, add 6.0 g of a 10% aqueous solution of monoethanolamine and acetone 2
7.8 g and 1.6 g of ion-exchanged water were added to prepare a 10% solution. Thereafter, a polymer film was obtained in the same manner as in Example 1. Comparative Example 1 Example 2 except that 47.5 g of acrylic acid, 2.5 g of butyl acrylate, and 0.56 g of azobisisobutyronitrile were used.
Polymerization was carried out in the same manner as in. The solid content of the obtained polymer solution measured by a ket 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 to make a 10% solution. Thereafter, 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
24.2 g of acetone and 6.1 g of ion-exchanged water were added thereto without adding monoethanolamine.
% Solution, and a polymer film was obtained in the same manner as in Example 1. Comparative Example 3 The polymer solution obtained in Example 3 (solid content: 19.8% by weight) 3
Take 0 g, 7.5% 10% monoethanolamine aqueous solution
g, 10% aqueous sodium hydroxide solution (5.0 g) and ion-exchanged water (29.4 g) were added to make a 10% solution.
A polymer film was obtained in the same manner as described above.

Comparative Example 4 50 equipped with a stirrer, a reflux condenser and a nitrogen inlet tube
2.5 g of acrylic acid in a 0 ml four-neck separable flask,
After 47.5 g of butyl acrylate and 170 g of methanol were added and uniformly dissolved, nitrogen gas was introduced from a nitrogen introduction tube with 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, the mixture was polymerized at 60 ° C. for 7 hours and then cooled to room temperature. The polymer solution obtained had a solid content of 19.3% as measured with a Kett moisture meter (average molecular weight 11,
000). Take 30 g of this solution, add 1.23 g of 10% aqueous solution of monoethanolamine, 0.80 g of 10% aqueous solution of sodium hydroxide, and 27.9 g of methanol to make a 10% solution. I got Table 2 shows the results of the same solubility test as in Example 1 for the polymer films obtained in Examples 2 to 3 and Comparative Examples 1 to 4.

[0015]

[Table 2] Table-2 Copolymer composition Acrylic acid Solubility Film AAC / BA ^* Neutralization rate for parts ─────────── (wt) Tap water 0.5% (mol%) Saline Comparative example 195 / 5 0 12 minutes 18 minutes Comparative Example 2 70/30 0 Insoluble Insoluble Example 2 70/30 5 10 minutes Insoluble Example 3 30/70 40 17 minutes Insoluble Comparative Example 3 30/70 100 7 minutes 9 minutes Comparative Example 4 5/95 100 Insoluble Insoluble * AAC: acrylic acid, BA: butyl acrylate

Example 4 50 equipped with a stirrer, a reflux condenser and a nitrogen inlet tube
In a 0 ml 4-neck separable flask, add acrylic acid 35
g, 2-ethylhexyl acrylate (65 g) and methanol (120 g) were added and dissolved uniformly, and nitrogen gas was introduced from a nitrogen introduction tube with stirring. Twenty minutes later, an initiator solution obtained by dissolving 0.69 g of azobisisobutyronitrile in 30 g of methanol was added, and the mixture was heated in a 60 ° C. water bath to start a polymerization reaction. Polymerization was performed 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 it to a 10% monoethanolamine aqueous solution 6.7.
g, 10% aqueous sodium hydroxide solution (2.2 g) and methanol (83.4 g) were added to make a 10% solution.
A polymer film was prepared in the same manner as in (Acrylic acid neutralization rate: 30 mol%). When a solubility test was carried out in the same manner as in Example 1, it was dissolved in tap water in 25 minutes, and was insoluble in 0.5% by weight saline.

Example 5 50 equipped with a stirrer, a reflux condenser and a nitrogen inlet tube
In a 0 ml 4-neck separable flask, add acrylic acid 15
g, 25 g of 2-ethylhexyl acrylate, 10 g of methyl acrylate and 170 g of methanol were added and uniformly dissolved, and then nitrogen gas was introduced from a nitrogen introduction tube while stirring. After 20 minutes, azobisisobutyronitrile 0.38
g was dissolved in 30 g of methanol, and an initiator solution was added.
The mixture was heated in a water bath at 0 ° C. to start a polymerization reaction. Polymerization was performed at 60 ° C. for 8 hours while introducing nitrogen, and then cooled to room temperature. The polymer solution obtained had a solid content of 19.4% as measured by a Kett moisture meter (average molecular weight: 12,000).
0). 30 g of this polymer solution was taken, and 3.7 g of a 10% aqueous solution of monoethanolamine and 28.
2 g was added to make a 10% solution, and a film was prepared in the same manner as in Example 1 (neutralization ratio of acrylic acid: 25 mol%). As a result of a solubility test, it was dissolved in tap water in 12 minutes and was insoluble in 0.5% saline.

Reference Example 1 22.5 g of the polymer solution adjusted to 10% of Example 1 was
It was poured on a polyethylene plate partitioned into a size of 15 cm × 30 cm with silicone rubber and left in a constant temperature / humidity room at 25 ° C. and a relative humidity of 50% for 2 days to prepare a polymer film. The obtained film was cut into a size of 10 cm × 22 cm, and a cotton-like pulp having a basis weight of 20 g / m ² was further placed on the cut piece.
Over a span of 16 cm, set at a height of about 5 mm,
The whole is wrapped in a surface sheet (polyester fiber and heat-fused fiber (Chisso ES) 50%, heat-fused nonwoven fabric of 50%: basis weight 20 g / m ² ), and heat-sealed at the two shorter ends. , A sanitary napkin was assembled. An acrylic plate was put on two stands of the same height at a distance of about 15 cm, and one 11 cm No. 2 filter paper was placed on the acrylic plate, and the above-mentioned sanitary napkin was placed thereon. . 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 thereon. 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, put into a beaker containing 1 liter of tap water (adjusted according to Example 1), and slowly stirred with a magnetic stirrer.
The film began to disperse after 5 minutes and dissolved and disappeared after 30 minutes.

Example 6 50 equipped with a stirrer, a reflux condenser and a nitrogen inlet tube
50 ml of methacrylic acid in a 0 ml four-neck separable flask
g, butyl methacrylate 50 g and methanol 120
After g was added and uniformly dissolved, nitrogen gas was introduced from a nitrogen introduction tube while stirring. Twenty minutes later, an initiator solution obtained by dissolving 0.67 g of azobisisobutyronitrile in 30 g of methanol was added, and the mixture was heated in a 60 ° C. water bath to start a polymerization reaction. Polymerization was performed at 60 ° C. for 8 hours while introducing nitrogen, and then cooled to room temperature. When the polymer solution thus obtained 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 and add 15.8% of 10% aqueous monoethanolamine solution
g and 66.1 g of methanol are added to make a 10% solution,
Thereafter, a polymer film was prepared in the same manner as in Example 1 (neutralization ratio of acrylic acid: 40 mol%). When a solubility test was performed in the same manner as in Example 1, the compound 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 alkyl methacrylate having an alkyl group having 1 to 18 carbon atoms. (A) / (B) is 1/9 to 9/1 (weight ratio), and 2 to 2 of the constituent acrylic acid or methacrylic acid
A non-woven fabric binder comprising a water-soluble polymer, wherein 70 mol% is in a salt form. 2. The binder according to claim 1, wherein the monomer of component (B) is at least one selected from butyl acrylate, 2-ethylhexyl acrylate, butyl methacrylate, and 2-ethylhexyl methacrylate. 3. An average molecular weight of 5,000 to 100,0.
2. The binder of claim 1 in the range of 00.