JP2002284954A - Water-soluble film and laminated film and method for producing them - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water-soluble film having high solubility to water and also high water resistance and mechanical strength. SOLUTION: This water-soluble film is such that the resin component thereof comprises 50-91 wt.% of a polyvinyl alcohol-based resin <=600 in polymerization degree and 9-50 wt.% of a 2nd polyvinyl alcohol-based resin >600 in polymerization degree.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water-soluble film and a laminated film suitably used as a back sheet of a sanitary article and a method for producing the same.

[0002]

2. Description of the Related Art Films having both water solubility, water resistance and strength include sanitary articles, cleaning sheets, agricultural films,
It is useful in various fields such as food packaging films and general packaging films, and the appearance of such films is desired. In particular, for sanitary articles such as sanitary napkins and orimono absorbent sheets, there is a demand for a film which does not cause clogging of pipes even when flushed into a toilet after use and has a small load on a septic tank. Hygiene articles generally have a body fluid-absorbing member sandwiched and surrounded by a body fluid-permeable top sheet and a body fluid-impermeable back sheet, and to fix the sanitary article to underwear on the outer surface of the back sheet. Is formed. FIG. 1 is a partially cutaway perspective view schematically showing a conventional sanitary article, and FIG. 2 is a cross-sectional view taken along line AA of FIG. Numeral 1 is a sanitary article, in which a body fluid-permeable top sheet 11, a body fluid-absorbing member 12, a body fluid-impermeable back sheet 13 and an adhesive layer 14 are laminated in this order.
Release paper 15 is temporarily fixed to the adhesive layer 14.

[0003] The above sanitary articles are discarded after use. Conventionally, however, they often include a non-water-disintegrable member as a whole. In particular, a non-water-disintegrable member is used for a back sheet that requires leakproofness. There is a problem that pipes are clogged when flushed to the toilet.

As a method of solving the above problem, for example,
JP-A-9-272719 discloses a film made of a polyvinyl alcohol-based resin and having excellent water solubility. However, although the film is excellent in water solubility, for example, when used as a back sheet for sanitary goods as described above, there is a problem that water resistance is insufficient, and the strength is reduced due to swelling due to sweat, body fluids, and the like. was there.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a water-soluble film which is excellent in water-solubility and excellent in water resistance and strength. Another object of the present invention is to
In addition to the above, an object of the present invention is to provide a laminated film that rapidly disintegrates in water. Still another object of the present invention is to provide
An object of the present invention is to provide a method for easily producing the water-soluble film or the laminated film with high productivity.

[0006]

The water-soluble film of the present invention has a resin component of a polyvinyl alcohol resin having a polymerization degree of 600 or less (hereinafter referred to as "low polymerization degree PVA") 50.
Polyvinyl alcohol-based resin having a polymerization degree of ９１91% by weight and a polymerization degree exceeding 600 (hereinafter referred to as “high polymerization degree PVA”) 9
-50% by weight.

The low polymerization degree PVA used in the present invention includes polyvinyl alcohol or a modified product thereof.
These may be used alone or in combination of two or more. Examples of the modified polyvinyl alcohol include those obtained by oxyalkylating polyvinyl alcohol, those obtained by adding ethylene oxide to polyvinyl alcohol, and ethylene-vinyl alcohol copolymers having an ethylene content of less than 50 mol%. The ethylene content of the ethylene-vinyl alcohol copolymer is preferably from 3 to 40 mol% since the water resistance of the obtained water-soluble film decreases as the amount decreases, and the water solubility of the obtained water-soluble film decreases as the amount increases.

The higher the degree of polymerization of the low-polymerization degree PVA, the lower the degree of polymerization of PVA in the resulting water-soluble film.
Is reduced, the water solubility of the water-soluble film is reduced, and the extrusion process becomes difficult in the production process, and when the water-soluble film is reduced, the water-soluble film obtained has a large proportion of the low-polymerization degree PVA. In addition, the water resistance or strength of the water-soluble film may be reduced, and the extrusion molding becomes difficult in the production process. Therefore, the water-soluble film is limited to 600 or less, and preferably 300 to 600. Also,
As the low polymerization degree PVA, one kind of low polymerization degree PVA may be used alone, or a mixture of low polymerization degree PVAs having different polymerization degrees may be used. The degree of polymerization referred to in the present invention is JIS
It is a value measured according to K 6726.

The lower the degree of saponification of the low polymerization degree PVA, the lower the water resistance of the resulting water-soluble film, the lower the strength due to moisture, and the lower the degree of saponification.
90 or more is preferable. In the present invention, the degree of saponification is J
It is a value measured according to IS K 6726.

The high polymerization degree PVA used in the present invention includes polyvinyl alcohol or a modified product thereof.
These may be used alone or in combination of two or more. Examples of the modified polyvinyl alcohol include those obtained by oxyalkylating polyvinyl alcohol, those obtained by adding ethylene oxide to polyvinyl alcohol, and ethylene-vinyl alcohol copolymers having an ethylene content of less than 50 mol%. As the ethylene content of the ethylene-vinyl alcohol copolymer decreases, the water resistance of the obtained water-soluble film decreases, and as the water content or hydrophilicity of the obtained water-soluble film decreases, the ethylene content decreases.
3-40 mol% is preferred.

When the degree of polymerization of the above-mentioned high polymerization degree PVA decreases, the high polymerization degree PVA
Because the amount of the water-soluble film decreases, the water resistance or strength of the water-soluble film is reduced, and when the water-soluble film is large, the mixing ratio of the high polymerization degree PVA in the obtained water-soluble film is large, the water solubility of the water-soluble film is reduced In addition, since extrusion molding may be difficult in the production process, it is limited to more than 600, preferably 600 to 5000, more preferably 700 to 2000. In addition, high polymerization degree PV
As A, one kind of high polymerization degree PVA may be used alone, or a mixture of high polymerization degree PVAs having different polymerization degrees may be used.

The saponification degree of the high polymerization degree PVA is preferably 90 or more, since the water resistance of the obtained water-soluble film decreases as the degree of saponification decreases.

The resin component constituting the water-soluble film of the present invention comprises the above-mentioned low polymerization degree PVA and high polymerization degree PVA. In the above resin component, the blending amount of the low-polymerization degree PVA decreases the water solubility of the obtained water-soluble film, and the extrusion molding becomes difficult in the production process, and increases the water resistance of the obtained water-soluble film. The content or strength is reduced, so it is limited to 50 to 91% by weight, preferably
5 to 87% by weight, and the blending amount of the high polymerization degree PVA decreases as the water resistance or strength of the obtained water-soluble film decreases, and as the amount increases, the water solubility of the obtained water-soluble film decreases. Extrusion molding becomes difficult in the manufacturing process, so it is limited to 9 to 60% by weight, preferably 13% by weight.
~ 45% by weight.

The water-soluble film referred to in the present invention is a water-soluble film that is dissolved in water by a large amount of water flow.

It is preferable that a polyhydric alcohol is added to the resin component as required. The polyhydric alcohol improves the flexibility of the obtained water-soluble film, and includes, for example, dihydric alcohols such as ethylene glycol, diethylene glycol, triethylene glycol and polyethylene glycol, trihydric alcohols such as glycerin, and dihydric alcohols. In addition to tetrahydric alcohols such as glycerin, polyglycerin and the like may be mentioned, and these may be used alone or in combination of two or more. Among them, glycerin or diglycerin has good compatibility with the polyvinyl alcohol-based resin, excellent flexibility of the obtained water-soluble film, and a small amount of smoke when the polyvinyl alcohol-based resin is melt-extruded, and has a low moldability. It is preferable because it is excellent.

The amount of the polyhydric alcohol to be added may be appropriately determined according to the intended use and the required flexibility. However, when the amount is small, the flexibility of the obtained water-soluble film is reduced, and when the amount is large, the water-soluble film is obtained. The water resistance of the film is reduced, and the polyhydric alcohol bleeds out to the surface of the water-soluble film to be obtained, so that it easily migrates to the contact material. Preferably, it is more preferably 2 to 15 parts by weight.

The method for obtaining the water-soluble film of the present invention is not particularly limited, but additives such as polyhydric alcohol may be added to the above-mentioned resin component, if necessary, and a conventionally known kneading method such as a kneader mixer or a roll may be used. After melt-kneading with an apparatus, it is preferable to introduce the resin component into an extruder and extrude the film into a film of a desired thickness from a die such as a T die attached to the extruder tip. The above-mentioned melt-kneading may be performed in an extruder. In the method by extrusion, a drying step necessary for a casting method usually applied to a polyvinyl alcohol-based resin is not required, the production efficiency is good, and the thickness and the tensile strength are easily adjusted, for example, 30 μm or less. Even a thin water-soluble film can be easily produced.

The obtained water-soluble film is wound up by a roll while being cooled. When winding, the tension is applied by adjusting the speed of the roll, so that the water-soluble film is orthogonal to the extrusion direction (MD) of the water-soluble film and the MD. Direction (TD)
It is preferable to adjust the tensile strength. The tensile strength in each direction may be appropriately determined according to the application.

The basis weight of the water-soluble film may be appropriately adjusted depending on the application. However, when the water-soluble film is small, it is difficult to obtain a film, and when it is large, the obtained water-soluble film becomes too strong. When the water-soluble film is used as a back sheet of a sanitary article, the usability is reduced, so that the amount is preferably 5 to 100 g / m ² , more preferably 10 to 40 g / m ² .

When the above-mentioned water-soluble film is used for applications such as a back sheet of a sanitary article, a cleaning sheet, etc., a water-disintegrable base material is integrally laminated on one surface to form a laminated film. preferable.

The water-decomposable substrate is not particularly limited as long as it is a sheet having water-decomposability. For example, water-decomposable fibers in which fibers are entangled in water and fibers are separated from each other And a non-woven fabric is preferred. Examples of the water-disintegrable fiber include pulp, rayon, cupra, cotton,
Hemp, wool, silk and the like can be mentioned, among which pulp is preferable.
The water-decomposable fibers may be bound together by a water-soluble binder. Examples of the water-soluble binder include polyvinyl alcohol, cellulose resins such as methylcellulose and hydroxyethylcellulose, starch, sodium alginate, sodium polyacrylate, and polyacrylate.

In addition to the above nonwoven fabric, a sheet or the like in which short fibers made of a synthetic resin are bound to each other by a water-soluble binder can be used as long as they have water dissolvability.
Examples of the synthetic resin include a polyethylene-based resin, a polypropylene-based resin, a polyester-based resin, and a polyamide-based resin. Examples of the water-soluble binder include those similar to those used for the nonwoven fabric.

When the basis weight of the water-disintegrable base material is reduced, the strength is reduced, processing into a laminated film becomes difficult, and when the basis weight is increased, the water-disintegrability of the obtained laminated film is reduced.
10 to 100 g / m ² is preferred.

The method for obtaining the laminated film is not particularly limited, but an additive such as a polyhydric alcohol may be added to the resin component, if necessary, to form a kneader mixer.
After melt-kneading with a conventionally known kneading device such as a roll, the resin component is introduced into an extruder, and extruded from a die such as a T die attached to the tip of the extruder into a film of a desired thickness to form a water-decomposable base material. Extrusion lamination on one side is preferred. The above-mentioned melt-kneading may be performed in an extruder.

In the above-mentioned extrusion lamination method, since water is not required unlike the casting method usually applied to polyvinyl alcohol-based resins, the water-soluble base material is integrated when the water-soluble film and the water-decomposable base material are integrated. The material can be easily and reliably laminated and integrated without being hydrolyzed by moisture. In addition, the extrusion laminating method does not require a drying step required for a casting method or the like, and has good production efficiency. Further, it is easy to adjust the thickness and tensile strength. For example, a water-soluble film having a thickness of 30 μm or less is used. Can be easily laminated on a water-disintegrable substrate. Further, in the method by extrusion lamination, since the water-soluble film and the water-disintegrable substrate are integrated over the entire surface, the dispersing power of the water-disintegrable substrate that is easily dispersed in water in the obtained laminated film is reduced by the hydrolysis of the water-soluble film. This promotes the properties and makes the laminated film easily hydrolyzed.

In addition to the above-described extrusion laminating method, a method in which a water-soluble film is partially adhered to one surface of a water-disintegrable substrate with an adhesive may be used.

The above water-soluble film and laminated film are
For example, it can be suitably used as the back sheet 13 of the sanitary article 1 shown in FIG. That is, the body fluid-absorbing member is sandwiched and surrounded by the water-soluble film or the laminated film and the topsheet, and the pressure-sensitive adhesive layer is formed on the surface of the water-soluble film or the laminated film opposite to the body fluid-absorbing member side. Is formed, and is regarded as a sanitary article.

The water-soluble film constituting the water-soluble film or the laminated film has water-solubility but also has excellent water resistance, so that it is impermeable to a small amount of water such as body fluids and sweat. .

The topsheet is a sheet having water-dissolving properties and body fluid permeability. For example, a fibrous body composed of water-dissolving fibers in which fibers become entangled in water and become separated from each other is formed. Among them,
Non-woven fabrics are preferred. Examples of the water-decomposable fiber include pulp, rayon, cupra, cotton, hemp, wool, silk, and the like. Among them, pulp is preferable. Water degradable fiber
They may be bound to each other by a water-soluble binder.
Examples of the water-soluble binder include polyvinyl alcohol, cellulose resins such as methylcellulose and hydroxyethylcellulose, starch, sodium alginate, sodium polyacrylate, and polyacrylate.

When the basis weight of the topsheet is small, the strength is reduced, and when the sanitary goods are used, the basis sheet is easily torn. When the basis weight is large, the feeling of wearing the sanitary goods is reduced.
0-100 g / m < ² > is preferable.

The body fluid-absorbing member has a water-dissolving property and a body-fluid-absorbing property. For example, a fibrous body composed of water-disintegrable fibers in which fibers are entangled in water and fibers are separated from each other can be mentioned. In particular, a non-woven fabric is preferred. Examples of the water-decomposable fiber include pulp, rayon, cupra, cotton, hemp, wool, silk, and the like. Among them, pulp is preferable. The water-decomposable fibers may be bound together by a water-soluble binder. As the water-soluble binder, for example, polyvinyl alcohol,
Cellulose resins such as methylcellulose and hydroxyethylcellulose, starch, sodium alginate, sodium polyacrylate, polyacrylate and the like can be mentioned.

When the basis weight of the body fluid-absorbing member is small, the body fluid absorbency of the sanitary article decreases, and when the basis weight increases, the stiffness of the sanitary article becomes too strong and the feeling of wearing deteriorates.
00 g / m ² is preferred.

As the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer,
Any conventionally known one may be used, and examples thereof include an acrylic pressure-sensitive adhesive.

Although the shape of the sanitary article is not particularly limited, it is generally formed so as to become gradually narrower toward the center as shown in the conventional sanitary article in FIG. A top sheet having a substantially vertically elongated rectangular shape and a back sheet having substantially the same shape as the top sheet are disposed so as to sandwich the body fluid absorbing member made smaller than the top sheet and the back sheet from the front and back. Opposite peripheral portions of the back sheet are integrated by heat fusion or a polyvinyl alcohol-based adhesive, and an adhesive layer is formed outside the back sheet.

[0035]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

(Example 1, Comparative Examples 1 to 3) Polyvinyl alcohol having a degree of polymerization of 500 (99% saponification degree) and polyvinyl alcohol having a degree of polymerization of 1000 (99% saponification degree) in the prescribed amounts shown in Table 1. Is extruded into an extruder, melt-kneaded at 220 ° C., extruded at 30 m / min from a T-die (lip width 500 mm × clearance 0.5 mm) attached to the extruder tip, and has a basis weight of 35 g / m 2.
² (thickness: 30 μm) was obtained.

Example 2 The procedure of Example 1 was repeated, except that polyvinyl alcohol having a polymerization degree of 400 (99% saponification degree) was used instead of polyvinyl alcohol having a polymerization degree of 500 (99% saponification degree). Basis weight 35g / m ² (thickness 30μ
m) was obtained.

Example 3 The same resin component as in Example 1 was charged into an extruder, melt-kneaded at 220 ° C., and then a T-die (lip width 500 mm × clearance 0.5 mm) attached to the extruder tip. Extruded at 30 m / min, basis weight 3
5 g / m ² non-woven fabric made of pulp (basis weight 1
Extrusion lamination was performed on one side of 5 g / m ² ) to obtain a laminated film.

Example 4 The same resin component as in Example 2 was charged into an extruder, melt-kneaded at 220 ° C., and then a T-die (lip width 500 mm × clearance 0.5 mm) attached to the extruder tip. Extruded at 30 m / min, basis weight 3
5 g / m ² non-woven fabric made of pulp (basis weight 1
Extrusion lamination was performed on one side of 5 g / m ² ) to obtain a laminated film.

The films or laminated films obtained in the examples and comparative examples were evaluated as follows, and the results are shown in Table 1.

(Water-soluble, water-disintegrable) JIS P 4501
According to the test.

(Water resistance) A cylinder having a diameter of 92 mm is prepared.
It was arranged on a horizontal desk so that the upper part became an opening. Next, a film or laminated film in the upper opening of the cylinder,
It was spread so as to cover all the openings and not to apply tension. In the case of a laminated film, the nonwoven fabric was directed to the inside of the cylinder. 0.1 cm ³ of water is dropped on the substantially central portion of the stretched film or the laminated film,
A 5.5 g weight was placed on the dropped portion from above and left as it was, and the time required for the weight to break through the film or the laminated film and fall down was measured.

(Film forming property / thickness unevenness) The width direction of the film immediately after being extruded from the T-die (the direction perpendicular to the extrusion direction)
At approximately the center, the thickness at 30 points was randomly measured along the extrusion direction, and the thickness variation rate was calculated according to the following equation. Thickness variation (%) = ｛(maximum thickness-minimum thickness) (mm)
/ Average thickness (mm)｝ × 100 ○: Thickness variation is not more than 20% Δ: Thickness variation is more than 20 to 40% ×: Thickness variation is more than 40%

(Film-forming property / Neck-in presence / absence) The lip width of the T-die and the width of the film immediately after being extruded from the T-die (a direction perpendicular to the extrusion direction) were compared and evaluated as follows. ：: The width of the film exceeds 85% of the lip width Δ: The width of the film exceeds 70 to 85% of the lip width ×: The width of the film is 70% or less of the lip width

[0045]

[Table 1]

[0046]

The water-soluble film of the present invention has excellent strength, exhibits excellent water solubility in a large amount of water flow, exhibits excellent water resistance to a small amount of water, and has excellent water resistance. Is not absorbed to reduce the strength. Also,
Since the laminated film of the present invention is formed by laminating and integrating a water-disintegrable base material having excellent water-disintegrability on the water-soluble film, the dispersing power of the water-disintegrable substrate in water promotes the water-disintegration of the water-soluble film, Is quickly hydrolyzed. Therefore, the water-soluble film and the laminated film are, for example, required to have water resistance and strength at the time of use, and are suitably used for applications that may be flushed after use, and particularly suitably used as a back sheet for sanitary goods. Is done. Furthermore, the production method of the present invention can easily produce the water-soluble film or the laminated film with good productivity and does not require moisture as in a casting method usually applied to a polyvinyl alcohol-based resin. Not required. In particular, in the production of laminated films, the water-disintegrable substrate is not easily hydrolyzed by moisture during lamination and integration of the water-soluble film and the water-disintegrable substrate, and is easily and reliably laminated. As it can be integrated, the water-soluble film and the water-disintegrable substrate are integrated over the entire surface, so that the dispersing power of the water-disintegrable substrate that is easily dispersed in water further promotes the water-disintegrability of the water-soluble film, A laminated film excellent in water disintegration is obtained.

[Brief description of the drawings]

FIG. 1 is a partially cutaway perspective view schematically showing a conventional sanitary article.

FIG. 2 is a sectional view taken along line AA of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Sanitary article 11 Top sheet 12 Body fluid absorbing member 13 Back sheet 14 Adhesive layer 15 Release paper

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4F071 AA29 AA81 AC05 AH19 BA01 BB06 BC01 4F100 AK21A AT00B BA02 BA07 DG15 EH23 GB72 JA07A JB07 JB09 JB09B JK01 YY00A 4J002 BE031 BE032 EC046 EC056 FD206 GA01

Claims (5)

[Claims] 1. A water-soluble film comprising a resin component comprising 50 to 91% by weight of a polyvinyl alcohol resin having a degree of polymerization of 600 or less and 9 to 50% by weight of a polyvinyl alcohol resin having a degree of polymerization exceeding 600. 2. The water-soluble film according to claim 1, wherein 1 to 20 parts by weight of a polyhydric alcohol is added to 100 parts by weight of the resin component. 3. A laminated film, wherein a water-disintegrable substrate is laminated and integrated on one surface of the water-soluble film according to claim 1. 4. A resin component comprising 50 to 91% by weight of a polyvinyl alcohol resin having a polymerization degree of 600 or less and 9 to 50% by weight of a polyvinyl alcohol resin having a polymerization degree of more than 600 is extruded into a film. The method for producing a water-soluble film according to claim 1, wherein: 5. Melting and kneading 50 to 91% by weight of a polyvinyl alcohol-based resin having a degree of polymerization of 600 or less and 9 to 50% by weight of a polyvinyl alcohol-based resin having a degree of polymerization exceeding 600, and then extruding one surface of the water-disintegrable base material. The method for producing a laminated film according to claim 3, wherein lamination is performed.