JPH0525764A - Water-dispersible nonwoven fabric - Google Patents

Abstract

PURPOSE:To provide water-dispersible nonwoven fabric comprising specific nonwoven fabric and a specified water-soluble binder in a specific ratio, having excellent mechanical strength and disaggregation dispersibility and useful for sanitary articles, etc. CONSTITUTION:In the objective water-dispersible nonwoven fabric comprising a water-dispersible fiber layer bound with a water-soluble binder consisting mainly of an unsaturated carboxylic acid (e.g. acrylic acid)/an unsaturated carboxylic acid ester (e.g. cyclohexyl acrylate), preferably 5-50mol.% of the unsaturated carboxylic acid having been converted into a neutral salt, the fiber layer comprises a mixture of <=30mm long crimped fibers, in the mixture the content of crimped fibers having a crimping number of <=19 crimps/inch being 40-90wt.%, the content of the crimped fibers having a crimp number of 20-25 crimps/inch being 0-60wt.%, and the content of the crimped fibers having a crimp number of 26-30crimps/inch being 5<=10wt.%, and the content of the binder in the nonwoven fabric being 0.1-10wt.%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water-decomposable non-woven fabric which can be easily dissociated and dispersed by being put into water.

[0002]

BACKGROUND OF THE INVENTION Nonwoven fabrics are widely used as a constituent material for disposable absorbent articles such as sanitary napkins and disposable diapers. The nonwoven fabric used for such an absorbent article is required to have sufficient strength so as not to be broken even when it is wet with a body fluid such as menstrual blood or urine in view of its use characteristics. Therefore, a water-insoluble resin is generally used as a so-called non-woven fabric binder that binds fibers together.

On the other hand, non-woven fabrics used for absorbent articles such as sanitary napkins and disposable diapers are provided with the property of being finely disentangled and dispersed in water, that is, water disintegration so that they can be disposed of after use by flush toilets. Is required. From this point of view, the non-woven fabric product using the water-insoluble resin as a binder is unsatisfactory.

Several proposals have been made so far for water-decomposable nonwoven fabrics. For example, JP-A-1-306
In Japanese Patent No. 661, an aqueous dispersion in which a part of an unsaturated carboxylic acid component is bonded with a water-soluble binder containing an unsaturated carboxylic acid / unsaturated carboxylic acid ester copolymer as a main component, which is formed in a neutralized salt. A water-decomposable non-woven fabric comprising a hydrophilic fiber layer is disclosed.

In this water-decomposable non-woven fabric, a fibrous web formed by air laying is used as the fiber layer, using viscose rayon fiber having a length of 26 mm and a thickness of 2 denier. However, in the case of this water-decomposable non-woven fabric,
When the binder content was set to 10% by weight or less in order to obtain a nonwoven fabric which was satisfactory in terms of water decomposability, its mechanical strength was weakened and it was still unsatisfactory in terms of practicality.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems found in the prior art and to provide a nonwoven fabric excellent in mechanical strength and water decomposability.

[0007]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have solved the problems by using a mixture of specific crimped fibers as a fiber layer constituting a nonwoven fabric. They have found that they can be solved and have completed the present invention.

That is, according to the present invention, a water-soluble binder containing an unsaturated carboxylic acid / unsaturated carboxylic acid ester copolymer as a main component in which a part of the unsaturated carboxylic acid component is formed in a neutralized salt is used. In a water-decomposable non-woven fabric comprising bonded water-dispersible fiber layers, the fiber layers have a fiber length of 30 mm.
A mixture of the following crimped fibers, wherein the content of the crimped fibers having a crimping number of 19 or less is 40 to 90% by weight and the crimping fiber having a crimping number of 20 to 25 / inch is contained in the mixture. The content is 10 to 60% by weight, the content of crimped fibers having a number of crimps of 26 or more is 10% by weight or less, and the content of the binder in the nonwoven fabric is 0.1 to 10% by weight. A water-decomposable nonwoven fabric is provided.

The types of fibers constituting the fiber layer (hereinafter, also referred to as a web) are conventionally known, such as cotton,
Examples include natural fibers such as hemp, jute, cotton linter, and wood pulp, regenerated cellulose fibers such as rayon and cupola, modified cellulose fibers such as cellulose acetate, polyvinyl alcohol, polyester, polyamide, and polyolefin-based synthetic fibers. These fibers can be used alone or as a mixture, but the use of natural fibers or cellulose fibers is advantageous in terms of biodegradability.

The web used in the present invention has a fiber length of 30 mm.
It consists of the following crimped fiber mixture. In this crimped fiber mixture, the content of crimped fibers having the number of crimps of 19 or less is 40 to 90% by weight, preferably 50 to 60% by weight, and the number of crimps of 20 to 25 per inch is obtained. The content of crimped fibers is 10 to 60% by weight, preferably 40 to 50% by weight, and the content of crimped fibers having a crimp number of 26 / inch or more is 1
It is 0% by weight or less, preferably 5% by weight or less.

When the fiber length of the crimped fiber (fiber length when the crimped fiber is extended) exceeds 30 mm, when the nonwoven fabric is hydrolyzed in water, a phenomenon of forming a "naw" in which the fibers are entangled with each other is caused. Occurs. Such a fiber “narrow” has poor fluidity and is difficult to flow out through a flush toilet.
Therefore, the fiber length is preferably 30 mm or less, and more preferably 20 mm or less in order to avoid the formation of such a "hook" of the fiber. Further, the fiber length of 5 mm or more is advantageous in producing the web.

With respect to the crimped fibers contained in the web, it is preferable that the maximum number of crimps is specified to be 30 pieces / inch or less. If the number of crimps is too large, it becomes easier to make a "nose" of the fiber. The minimum number of crimps is preferably specified to be 5 or more. If the number of crimps is too small, the mechanical strength of the nonwoven fabric will be impaired. In the present invention, as the web, a mixture of 40 to 90% by weight of crimped fibers having 5 to 19 crimps / inch and 10 to 60% by weight of crimped fibers having 20 to 25 crimps / inch is used. Is preferred.

As a method for producing the web, either a wet method or a dry method can be used, but the dry method is preferable from the viewpoint of the texture of the obtained product. In the present invention, since the crimped fiber mixture containing crimped fibers having the number of crimps of 25 or less as the main component is used, the web can be easily produced by the dry method. In general,
With short fibers having a fiber length of 30 mm or less, it is difficult to produce a web by a carding method (dry method), but since the crimped fibers used in the present invention are excellent in a card, it is easy to use a carding method. A web can be made.

The web used as the raw material for the nonwoven fabric in the present invention is preferably subjected to a water needling treatment. In this case, the water pressure in the water needling process is preferably 40 kg / cm ² or less.

The binder used for binding the web in the present invention is a water-soluble binder containing a copolymer of an unsaturated carboxylic acid and an unsaturated carboxylic acid ester in which a part of the unsaturated carboxylic acid component is formed as a neutralized salt. It is a binder. in this case,
As the unsaturated carboxylic acid, conventionally known ones, for example,
Acrylic acid, methacrylic acid, maleic acid, fumaric acid and the like can be mentioned, with acrylic acid and / or methacrylic acid being particularly preferred. As the unsaturated carboxylic acid ester,
Examples thereof include alkyl esters of unsaturated carboxylic acids and cyclohexyl esters.

The average molecular weight of the copolymer used in the present invention is 5,000 to 100,000. The weight ratio A / B of the unsaturated carboxylic acid component A and the unsaturated carboxylic acid ester component B is 1/9 to 9/1, preferably 3/7 to 8/2. Of the component A, 2 to 60 mol%, preferably 5 to 50 mol% thereof is formed as a neutralized salt. If the neutralization ratio of the unsaturated carboxylic acid component A is smaller than the above range, the water solubility becomes poor, which is not preferable. On the other hand, if the neutralization ratio of the unsaturated carboxylic acid component A is larger than the above range, the strength against body fluid is decreased. . When the proportion of the unsaturated carboxylic acid ester component B in the copolymer increases, the neutralization rate of the unsaturated carboxylic acid component A should be increased to increase the water solubility. For example, when the ratio of the unsaturated carboxylic acid ester component B is 50% by weight or more, the unsaturated carboxylic acid ester component A is
A non-woven fabric having excellent water-decomposability can be obtained by setting the neutralization rate of 20 mol% or more.

As the neutralizing agent used for neutralizing the unsaturated carboxylic acid component A, an inorganic base and an organic base are optionally used. Examples of such substances include inorganic bases such as sodium hydroxide, potassium hydroxide, lithium hydroxide and sodium carbonate, as well as monoethanolamine, diethanolamine, diethylaminoethanol, ammonia, trimethylamine, triethylamine, tripropylamine and morpholine. Examples of such amines include ethanolamines, sodium hydroxide, or potassium hydroxide in combination with ethanolamines.

The water-soluble binder used in the present invention is a water-soluble binder containing the above-mentioned copolymer as a main component, and the above-mentioned copolymer can be used alone, or other water-soluble polymer such as polyvinyl alcohol or Acrylic acid, methacrylic acid or a polymer of a salt thereof, carboxymethyl cellulose, and the like can be used together in an appropriate amount (20% by weight or less in the total polymer binder).

The content of the water-soluble binder contained in the nonwoven fabric is 0.1 to 10% by weight, preferably 0.2 to 5% by weight. When the content of the binder is less than the above range, the resulting nonwoven fabric is insufficient in practical use in terms of mechanical strength. On the other hand, when the content is more than the above range, the resulting nonwoven fabric has poor texture (flexibility). Become.

As a method of applying the water-soluble binder to the web, a spray method, a dipping method, a printing method and the like are adopted. When the water-soluble binder is dispersed in the web, the binder can be distributed throughout the web, or it can be distributed in a number of closely spaced dots. When the binder is dispersed in the web to bond the fibers, it is preferable to leave an unbonded portion in the web. This unbonded fiber portion plays a role of easily absorbing water that has penetrated into the binder existing portion and dispersing the nonwoven fabric in water in a short time.

[0021]

The non-woven fabric of the present invention does not dissolve the binder even when it is contacted with various body fluids such as blood, menstrual blood, urine, etc. and wetted, and the binder does not dissolve due to the high salt concentration of the body fluid. It retains structural integrity and has satisfactory mechanical strength in use. On the other hand, when it comes into contact with water, the salt concentration of the body fluid becomes extremely low, so that the binder dissolves and is easily dissociated and dispersed in water. Therefore, the nonwoven fabric of the present invention can be discarded by a flush toilet. The nonwoven fabric of the present invention,
It is suitable for use as a member of an absorbent article that comes into contact with various body fluids such as blood, menstrual blood, and urine. For example, it can be advantageously used as an exterior material or surface member in absorbent articles such as sanitary napkins and disposable diapers. Then, such an article can be thrown into a flush toilet after use and discarded. Furthermore, the nonwoven fabric of the present invention can be advantageously used as various disposable nonwoven products such as disposable wipes, disposable bed sheets, and defecation sheets for pets.

[0022]

EXAMPLES Next, the present invention will be described in more detail by way of examples. Example 1 As the fiber, a cellulose acetate crimped fiber having a thickness of 2 denier and the fiber length and the crimp number shown in Table 1 was used. The fibers were mixed by a carding method to form a web, which was then water-needed at a water pressure of 30 kg / cm ² and dried to obtain a web having a basis weight of 30 g / m ² .

Next, 3% by weight of an acrylic acid / cyclohexyl acrylate copolymer having the following properties was added to this web:
The aqueous solution was applied and dried by a printing method to obtain a nonwoven fabric having a binder content of 3% by weight. (Properties of copolymer) Acrylic acid component: 65 mol% Cyclohexyl acrylate component: 35 mol% Neutralization rate of acrylic acid component (sodium salt): 45 mol% Molecular weight: 32,000 About the non-woven fabric thus obtained The performance was evaluated as follows, and the results are shown in Table 1.

(1) Texture (flexibility) The feel of the non-woven fabric was sensory evaluated in four levels. ◎ ・ ・ ・ Very good ○ ... good △ ・ ・ ・ Slightly bad × ... bad

(2) Dry strength nonwoven fabric is cut into 2.5 cm × 9 cm to prepare a sample, and this sample is subjected to a tensile strength tester (Toyo Boldline Co., Ltd.).
Manufactured by MODEL GAC-100), the strength was measured under the conditions of a chuck interval of 5 cm and a pulling speed of 100 mm / min.

(3) Wet strength A non-woven fabric was cut into 2.5 cm × 9 cm to prepare a sample, which was immersed in the following artificial urine for 1 minute and then taken out so that the liquid content was 150% by weight. The water was removed with filter paper, and the strength was measured in the same manner as in the dry strength measurement. (Artificial urine) Urea: 2.0 wt%, NaCl: 1.0 wt%, CaC
l ₂ : 0.1 wt%, MgCl ₂ : 0.07 wt%, water:
balance

(3) Water dispersibility In a cylindrical container with a lid of 1000 ml, 500 ml of a solution prepared by diluting the artificial urine 200 times with water-conducting water is put, and a non-woven fabric having a size of 6 cm × 6 cm is put into this solution. Next, this cylindrical container was placed on a shaker and shaken at a shaking frequency of 300 reciprocations / minute for 5 minutes, and then the water dispersion state of the nonwoven fabric was evaluated. 3 ... Almost completely dispersed 2 ... Some poorly dispersed 1 ... Not dispersed

No. 1 shown in Table 1 3 to No. In the nonwoven fabric of No. 5, No. 5 3 and No. No. 4 is insufficient in dispersibility because the fiber length of the crimped fibers used is too long. In the case of No. 5, the content of crimped fibers having 30 crimps / inch is too high, so that the dispersibility is poor.

[0029]

[Table 1]

Example 2 A grammage of 30 g / m ² was obtained in the same manner as in Example 1 except that rayon fiber having a thickness of 2 denier was used as the crimped fiber.
Was prepared, and the aqueous binder solution shown in Example 1 was applied and dried to obtain a nonwoven fabric having a basis weight of 30 g / m ² .
In this case, as a coating method, a printing method (P), a spray method (S) or a dipping method (D) was used.

The performance of the non-woven fabric obtained as described above was evaluated in the same manner as in Example 1, and the results are shown in Table 2. Table 2
In the non-woven fabric shown in No. 2, since the content of crimped fibers having a crimp number of 19 or less exceeds 90% by weight,
It was impossible to make a web by the dry method. No5 and N
No. o6 is inferior in texture because the binder content is too high.

[0032]

[Table 2]

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[Procedure amendment]

[Submission date] February 21, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0010

[Correction method] Change

[Correction content]

The web used in the present invention has a fiber length of 30 mm.
It consists of the following crimped fiber mixture. In this crimped fiber mixture, the content of crimped fibers having a number of crimps of 19 or less is 40 to 90% by weight, preferably 60 to 70% by weight, and the number of crimps is 20 to 25 per inch. The content of crimped fibers is 10 to 60% by weight, preferably 30 to 40% by weight, and the content of crimped fibers having a crimp number of 26 / inch or more is 1
It is 0% by weight or less, preferably 5% by weight or less.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0014

[Correction method] Change

[Correction content]

The web used as the raw material for the nonwoven fabric in the present invention is preferably subjected to a water needling treatment. In this case, the water pressure in the water needling treatment is preferably 60 kg / cm ² or less.

[Procedure 3]

[Document name to be amended] Statement

[Name of item to be corrected] 0027

[Correction method] Change

[Correction content]

(3) Water dispersibility In a cylindrical container with a lid of 1000 ml, 500 ml of a solution prepared by diluting the artificial urine 200 times with tap water is put, and a non-woven fabric having a size of 6 cm × 6 cm is put into this solution. Next, this cylindrical container was placed on a shaker and shaken at a shaking frequency of 300 reciprocations / minute for 5 minutes, and then the water dispersion state of the nonwoven fabric was evaluated. 3 ... Almost completely dispersed 2 ... Some poorly dispersed 1 ... Not dispersed

[Procedure amendment 4]

[Document name to be amended] Statement

[Name of item to be corrected] 0029

[Correction method] Change

[Correction content]

[0029]

[Table 1]

[Procedure Amendment 5]

[Document name to be amended] Statement

[Name of item to be corrected] 0032

[Correction method] Change

[Correction content]

[0032]

[Table 2]

Claims (3)

[Claims] 1. A water dispersibility in which a part of an unsaturated carboxylic acid component is bound with a water-soluble binder containing an unsaturated carboxylic acid / unsaturated carboxylic acid ester copolymer as a main component, which is formed in a neutralized salt. In a water-decomposable non-woven fabric consisting of a fiber layer,
The fiber layer is composed of a mixture of crimped fibers having a fiber length of 30 mm or less, and the content of the crimped fibers having a crimp number of 19 / inch or less is 40 to 90% by weight and the crimp number is 20 to 25 in the mixture. The content of the crimped fibers of 10 pieces / inch is 10 to 60% by weight, the content of the crimped fibers having the number of crimps of 26 to 30 is 10% by weight or less, and the content of the binder in the nonwoven fabric is 0. 1 to
A water-decomposable non-woven fabric, which is 10% by weight. 2. The fiber layer is made of a mixture of 40 to 90% by weight of crimped fibers having a crimp number of 5 to 19 / inch and 10 to 60% by weight of crimped fibers having a crimp number of 20 to 25 pieces / inch. The water-decomposable non-woven fabric according to claim 1. 3. The water-decomposable nonwoven fabric according to claim 1, wherein the fiber layer is subjected to water needling treatment.