JP2002273791A - Method for producing embossed polyvinyl alcohol film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a polyvinyl alcohol film which is excellent in blocking resistance even when wound in the shape of a roll to be preserved and in appearance which gives a high-grade feel to a product. SOLUTION: The rolled polyvinyl alcohol film is embossed so that the crystallinity index of embossment apex parts is 0.50-0.90.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an embossed polyvinyl alcohol-based film.

[0002]

2. Description of the Related Art Conventionally, packaging materials made of polyvinyl alcohol-based films have been used for pesticides, drugs, dyes, detergents, fertilizers,
It is frequently used as a material for housing cosmetics, sanitary products, etc., and such packaging materials are directly poured into an aqueous medium by utilizing the water solubility of polyvinyl alcohol to decompose or dissolve the packaging materials, thereby obtaining a solution. Or used for such purposes as throwing open packaging material into water as it is and discarding it.However, such a polyvinyl alcohol-based film has a hygroscopic property, so that its surface is exposed to high humidity. Are often tacky and tend to block each other.

In order to prevent such blocking,
The film is usually embossed. For example, in Japanese Patent Application Laid-Open No. 7-290567, the thickness of the concave portion is 15 to 25 μm, and the tensile strength of the film is 2.5 to 4.0.
An embossed water-soluble film of 5 kg / mm ² has been proposed.

[0004]

However, in the above-mentioned film, although the dispersibility in water, the solubility, the mechanical strength and the like are improved, the anti-blocking property is further improved and the product is given a sense of quality. The appearance and the like are not sufficiently considered. In particular, regarding the blocking resistance, the conventional evaluation of the blocking resistance is usually performed by simply applying pressure from above the film and measuring the blocking property at that time, but the actual product form, that is, the film is rolled. Thus, the measurement of the blocking property in the state where the film is wound up is an evaluation closer to a practical level, and also a more severe blocking resistance is required than the evaluation using a simple film.

That is, the object of the present invention is to
An object of the present invention is to provide a method for producing a polyvinyl alcohol-based film having improved anti-blocking properties, capable of maintaining anti-blocking properties even when stored in a roll, and having excellent appearance.

[0006]

The inventor of the present invention has conducted intensive studies on a method for producing an embossed polyvinyl alcohol-based film. As a result, the original polyvinyl alcohol-based film was found to have a crystallinity index of 0.
The inventors have found that the above-mentioned object can be achieved by embossing so as to be 50 to 0.90, and have completed the present invention.

Further, when the ratio (T / t) between the apparent thickness (T μm) of the film after embossing and the thickness (t μm) of the raw film before embossing is 3 to 5,
The effect of the present invention can be more remarkably obtained.
In the present invention, such (T / t) may be referred to as an emboss degree.

In the present invention, when producing the polyvinyl alcohol-based film as described above, 4% by weight
An aqueous solution having a viscosity of 10 to 40 mPa · s (20 ° C.) and a degree of saponification of 70 to 99 mol% using a polyvinyl alcohol-based resin, or having a surface hardness (Shore D) of 60 to 90 as a backup roll during embossing. It has also been found that the intended polyvinyl alcohol-based film can be optimally produced by using a cotton roll or by adjusting the water content of the polyvinyl alcohol-based raw film at the time of embossing to 4 to 15% by weight. It is.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The polyvinyl alcohol-based resin which is a raw material of the polyvinyl alcohol-based raw film used in the present invention is not particularly limited, and can be produced by a known method. That is, it is obtained by saponifying a vinyl ester polymer obtained by polymerizing a vinyl ester compound.

[0010] Such vinyl ester compounds include:
Vinyl formate, vinyl acetate, vinyl trifluoroacetate, vinyl propionate, vinyl butyrate, vinyl caprate, vinyl laurate, vinyl versatate, vinyl palmitate, vinyl stearate, etc. are used singly or in combination. Is preferably vinyl acetate.

In the present invention, other monomers can be copolymerized as long as the object of the present invention is not impaired.
Propylene, isobutylene, α-octene, α-dodecene, olefins such as α-octadecene, acrylic acid,
Methacrylic acid, crotonic acid, maleic acid, maleic anhydride, unsaturated acids such as itaconic acid or salts or mono- or dialkyl esters thereof, acrylonitrile, nitriles such as methacrylonitrile, acrylamide,
Amides such as methacrylamide, ethylene sulfonic acid,
Olefinsulfonic acids such as allylsulfonic acid and methallylsulfonic acid or salts thereof, alkyl vinyl ethers, N-acrylamidomethyltrimethylammonium chloride, allyltrimethylammonium chloride, dimethyldiallylammonium chloride, dimethylallylvinylketone, N-vinylpyrrolidone, chloride Polyoxyalkylene (meth) allyl ether such as vinyl, vinylidene chloride, polyoxyethylene (meth) allyl ether, polyoxypropylene (meth) allyl ether, polyoxyethylene (meth) acrylate, polyoxypropylene (meth) acrylate, etc. Such as polyoxyalkylene (meth) acrylate, polyoxyethylene (meth) acrylamide, polyoxypropylene (meth) acrylamide, etc. Polyoxyalkylene (meth)
Acrylamide, polyoxyethylene (1- (meth) acrylamide-1,1-dimethylpropyl) ester,
Examples thereof include polyoxyethylene vinyl ether, polyoxypropylene vinyl ether, polyoxyethylene allylamine, polyoxypropylene allylamine, polyoxyethylene vinylamine, and polyoxypropylene vinylamine.

In carrying out the polymerization (or copolymerization), there is no particular limitation, and any known polymerization method can be used. However, usually, solution polymerization using an alcohol such as methanol, ethanol or isopropyl alcohol as a solvent is carried out. You. Of course, emulsion polymerization and suspension polymerization are also possible.

The polymerization reaction is carried out using a known radical polymerization catalyst such as azobisisobutyronitrile, acetyl peroxide, benzoyl peroxide and lauroyl peroxide, and the reaction temperature ranges from 50 ° C. to about the boiling point. Is selected from

The saponification of the obtained vinyl ester polymer is carried out in the presence of an alkali catalyst by dissolving the polymer in alcohol. Examples of the alcohol include methanol, ethanol, butanol and the like. The concentration of the copolymer in the alcohol is selected from the range of 20 to 50% by weight.

As the saponification catalyst, sodium hydroxide,
Alkali catalysts such as hydroxides of alkali metals such as potassium hydroxide, sodium methylate, sodium ethylate and potassium methylate and alcoholates can be used. The amount of the catalyst to be used may be 1 to 100 mmole equivalent to the vinyl ester. In some cases, saponification can be performed with an acid catalyst.

Thus, a polyvinyl alcohol-based resin is obtained. As the polyvinyl alcohol-based resin used for the polyvinyl alcohol-based raw film, a 4% by weight aqueous solution has a viscosity of 10 to 40 mPa · s (20 ° C.).
And those having a saponification degree of 70 to 99 mol% are preferred.

The viscosity of the 4% by weight aqueous solution is 10 mPa ·
Below s (20 ° C.), the mechanical strength of the obtained polyvinyl alcohol-based film tends to decrease, and the crystallinity index of emboss tends to decrease too much, and conversely, 40 mPa · s.
When the temperature exceeds (20 ° C.), the solubility in water is reduced, and it is difficult to obtain a good aqueous solution of a polyvinyl alcohol-based resin at the time of film formation. The water solubility of the film decreases,
Further, the crystallinity index of emboss tends to be too high, which is not preferable. A more preferable range of the viscosity of the 4% by weight aqueous solution is 10 to 37 mPa · s (20 ° C.), and a particularly preferable range is 11 to 35 mPa · s (20 ° C.).

The saponification degree is less than 70 mol% or 9
If it exceeds 9 mol%, the solubility of the polyvinyl alcohol-based resin in water decreases, which is not preferable for the same reason as described above. Further, if the saponification degree is less than 70 mol%, the crystallinity index of emboss is too low. On the contrary, if it exceeds 99 mol%, the crystallinity index of emboss tends to be too high, which is not preferable. No. A more preferred range of the degree of saponification is 75 to 98 mol%, and a particularly preferred range is 80 to 98 mol%.
~ 97 mol%.

In producing (forming) a polyvinyl alcohol-based raw film from the polyvinyl alcohol-based resin as described above, there is no particular limitation. After the resin is converted to an aqueous solution, a roll, a drum, an endless belt, or the like is used. A plain polyvinyl alcohol-based raw film can be obtained by a method of casting on a smooth metal surface or a method of melt-molding the resin by appropriately adding water or a plasticizer described below by extrusion or the like. it can.

At the time of the above production, if necessary, a plasticizer (glycerin, diglycerin, triethylene glycol, polyethylene glycol, polypropylene glycol, etc.) and a release agent (sorbitan ester ether, etc.) may be added to the resin or the aqueous solution. , Repelling inhibitors (polyoxyethylene alkyl phenyl ether, etc.), antioxidants (phenolic, amine-based, etc.), stabilizers (phosphates, etc.), coloring agents, fragrances, bulking agents, disinfectants, rust prevention Agents, UV absorbers, inorganic powders, surfactants, and other water-soluble polymers (sodium polyacrylate, polyethylene oxide,
Polyvinylpyrrolidone, dextrin, chitosan, chitin, methylcellulose, hydroxyethylcellulose,
Starch or the like may be added. Further, if necessary, two or more polyvinyl alcohol-based resins may be used in combination.

[0021] The thickness of the polyvinyl alcohol-based raw film is not particularly limited.
m (further 7 to 70 μm, particularly 8 to 65 μm, especially 1
0 to 60 μm), and the film thickness is 5
If it is less than μm, the mechanical strength will be insufficient.
If it exceeds μm, the solubility and the efficiency of film formation decrease, which is not preferable.

The most characteristic feature of the present invention is that the above-mentioned polyvinyl alcohol-based raw film is embossed so that the crystallinity index of the embossed top is 0.50 to 0.90. The crystallinity index is 0.
If it is less than 50, a sufficient apparent film thickness cannot be obtained.
If it exceeds 90, pinholes occur in the film and the object of the present invention cannot be achieved. A more preferred lower limit of the crystallinity index is 0.55, particularly 0.60, and a more preferred upper limit is 0.85, particularly 0.80.

The term "crystallinity index" used herein means a micro ATR method (total reflection absorption measurement method) using an infrared spectrophotometer.
In the infrared absorption spectrum measured by the above method, the intensity ratio (a / b) of the absorption band peak intensity around 1142 cm ^-1 (a), which is known as a crystallization band, to the absorption band peak intensity around 1420 cm ^-1 (b) For example, “MAGNA 76” manufactured by Nicolet, Inc.
0 ”(infrared spectrophotometer) and an ATR prism having a 45 ° incident angle of Ge (Spectra-Te
ch Inc.). In reading the intensity of the above-mentioned absorption band from the chart, each base line was drawn in parallel with the horizontal axis (wave number axis) to determine the intensity of the peak value (see FIG. 1). Further, the above-mentioned embossed top measured by the infrared absorption spectrum is the top of the film stamped by the convex portion of the embossing roll.

The control of the crystallinity index is not particularly limited. In addition to the above-mentioned adjustment of the raw material polyvinyl alcohol-based resin, the embossing pressure when embossing the polyvinyl alcohol-based raw film, the surface hardness of the backup roll, It is possible by appropriately adjusting the embossing speed (film speed at the time of embossing) and the like. Hereinafter, the embossing will be specifically described.

In embossing, an embossing roll and a backup roll are used. As the embossing roll, a metal roll or a ceramic roll whose surface is formed to be convex by engraving or lathing is used. Can be Examples of the shape of the convex portion include a lattice shape, a silk shape, a turtle shell shape, a rhombus shape, and the like.
A roll having a convex portion of 00 mesh, preferably 20 to 100 mesh is used.

If the mesh of the projections is less than 10 meshes, a film having a fine unevenness cannot be obtained.
If it exceeds 00 mesh, it is not preferable because embossing with a three-dimensional effect cannot be obtained.

On the other hand, it is preferable to use a backup roll having a surface hardness (Shore D) of 60 to 90. If the hardness is less than 60, a sharp embossed pattern may not be obtained. If it exceeds 90, pinholes are likely to occur in the film, and the film may be broken, which is not preferable. A more preferred lower limit of the hardness is 65, particularly 70, and a more preferred upper limit is 88, particularly 85.

The surface hardness (Shore D) mentioned here
Is a hardness determined by a measuring method according to JIS K6253, and is measured using a D-type hardness tester.

The backup roll is not particularly limited as long as it has a surface hardness in the above range.
For example, a metal roll, a resin roll, a paper roll, a cotton roll and the like can be mentioned, but it is preferable to use a cotton roll in that a sharp embossed pattern can be easily obtained.

In the present invention, embossing is performed by passing the above-mentioned raw polyvinyl alcohol film into the space between the embossing roll and the backup roll as described above. The pressing force on the raw film can be appropriately selected depending on the surface hardness of the backup roll to be used and the uneven shape of the embossing roll,
Usually, it is preferably 10 to 100 kg / cm, more preferably 30 to 80 kg / cm.

If the pressing force is less than 10 kg / cm, embossing having a sufficient depth cannot be obtained,
If it exceeds / cm, the thickness of the embossed film is partially reduced, mechanical strength is liable to decrease, and pinholes tend to occur, which is not preferable.

Further, in the present invention, the surface temperature of the embossing roll during embossing is set to 100 to 180 ° C. (furthermore, 10 to 180 ° C.).
5 to 170C, in particular 110 to 160C, especially 115 to 170C
150 ° C.), and the surface temperature of the backup roll is 50 ° C. or more (further 55-110 ° C., particularly 60-110 ° C.).
100 ° C., especially 65-95 ° C.).

The surface temperature of the embossing roll is 100
If the temperature is lower than ℃, embossing with a sufficient depth cannot be obtained, while if it is higher than 180 ° C, the solubility of the film decreases, which is not preferable. On the other hand, if the surface temperature of the backup roll is less than 50 ° C., it is not preferable because embossing having a sufficient depth cannot be obtained.

The speed of the film at the time of embossing roll processing cannot be unconditionally determined due to the thickness of the raw film or the like, but is usually 1 to 40 m / min (further 3 to 30 m / min,
In particular, it is preferably in the range of 5 to 20 m / min).

The desired polyvinyl alcohol-based film can be obtained by the embossing as described above. The embossed concave and convex shape is not particularly limited and may be appropriately selected, but is preferably 10 to 200 mesh, preferably 2 mesh.
It is preferably an uneven shape having a pattern such as a lattice shape, a silk shape, a turtle shape, a rhombus shape, or the like of 0 to 100 mesh.

Thus, a polyvinyl alcohol-based film in which the crystallinity index at the embossed top is adjusted can be obtained. In the present invention, the embossing degree of the film is further 3 to 5 (further 3 to 4.5). , Especially 3 ~
4), and the degree of embossing is 3
If it is less than 5, no further improvement effect of the blocking resistance and appearance can be recognized, and if it exceeds 5, the pinhole resistance is undesirably reduced.

The degree of embossing is not particularly limited, but can be adjusted by selecting the thickness of the raw film before embossing or adjusting the water content of the raw film before embossing. .

With respect to the water content of the raw film, the water content is preferably 4 to 15% by weight (more preferably 5 to 12% by weight, particularly 6 to 10% by weight), and the water content is 4% by weight. If it is less than 15% by weight or more than 15% by weight, it may be difficult to increase the degree of emboss of the obtained film, which is not preferable.

As a method for adjusting the water content of the polyvinyl alcohol-based raw film to the above range, the polyvinyl alcohol-based raw film before film formation and after drying is continuously dried to adjust the water content. A method of adjusting the water content by dipping or adjusting the humidity or the like of a polyvinyl alcohol-based raw film having less than% by weight is exemplified.

The film thus obtained has excellent blocking resistance even when stored in a roll form, and furthermore has excellent appearance (there is no shine on the film surface and it has a high-grade feel). Film is made of pesticides, drugs,
It is useful as a packaging material for dyes, detergents, fertilizers, cosmetics, sanitary products, etc., and particularly very useful for unit packaging of various chemicals and the like.

[0041]

The present invention will be specifically described below with reference to examples. In the examples, “%” means on a weight basis unless otherwise specified.

Example 1 Polyvinyl alcohol resin [4% aqueous solution having a viscosity of 30 m
A 25% aqueous solution of Pa · s (20 ° C., degree of saponification: 88 mol%) was cast on a hot roll at 93 ° C. to form a film, and the moisture content was adjusted to 8% to give a thickness of 40 μm. Was produced.

Next, the film was embossed with a embossing roll [40 mesh silk] heated to 130 ° C.
Backup roll [Cotton roll,
A roll having a surface hardness (Shore D) of 85] with a pressing force of 50 kg / cm and a speed of 15 m / min is embossed to form a 40-mesh silk-like (irregular) pattern. Thus, an embossed polyvinyl alcohol-based film having an apparent film thickness of 140 μm (an embossing degree of 3.5) was obtained.

The crystallinity index of the embossed top of the obtained film was measured by the method described in the text to find that it was 0.75.
Met. The following evaluation was performed about the obtained film.

(Blocking resistance) 100 m of the obtained polyvinyl alcohol-based film was rolled (with a branch pipe diameter of about 3 inc.) At a tension of 3 kg / m and a winding speed of 5 m / min.
h), the roll was unwound after leaving it at room temperature for 2 weeks, and evaluated as follows.・ ・ ・: No blocking was observed, and the core could be unwound smoothly up to the core. ×: Blocking was observed at the core, and a part of the film was damaged when unwound.

(Appearance; surface texture) The surface of the obtained polyvinyl alcohol-based film was illuminated with an incandescent lamp at an oblique angle of 45 °, and visually observed from the opposite 45 ° direction. evaluated. ○ ・ ・ ・ No shine is observed × ・ ・ ・ Shiny is observed

Example 2 In Example 1, the surface temperature of the embossing roll and the surface temperature of the cotton roll were changed to 130 ° C. and 10 ° C., respectively.
The same procedure was repeated except that the temperature was changed to 0 ° C.
A polyvinyl alcohol-based film having a thickness of 0 μm (degree of embossing 3.5) and a crystallinity index of 0.67 at the top of the embossing was obtained and evaluated in the same manner.

Example 3 In Example 1, the surface temperature of the embossing roll and the surface temperature of the cotton roll were changed to 100 ° C. and 85 ° C., respectively.
° C and the passing speed of the film is 5 m / min.
Except that the apparent film thickness was 125 μm.
(Embossing degree: 3.1) A polyvinyl alcohol-based film having a crystallinity index of 0.59 at the embossed top was obtained and evaluated in the same manner.

Example 4 In Example 1, the roll surface hardness (Shore D) was 7
A polyvinyl alcohol-based film having an apparent film thickness of 135 μm (an embossing degree of 3.4) and a crystallinity index of 0.72 at the top of the emboss was obtained in the same manner except that a cotton roll of No. 5 was used. Was done.

Example 5 In Example 1, the roll surface hardness (Shore D) was 6
A polyvinyl alcohol-based film having an apparent film thickness of 130 μm (an embossing degree of 3.3) and a crystallinity index of 0.71 at the embossed top was obtained in the same manner except that a cotton roll of No. 5 was used. Was done.

Example 6 In Example 1, the pressing force between the rolls was 70 kg / cm.
Except that the apparent film thickness was 150 μm.
(Emboss degree: 3.8) A polyvinyl alcohol-based film having a crystallinity index of 0.78 at the top of the emboss was obtained, and was similarly evaluated.

Example 7 The same procedure as in Example 1 was carried out except that the moisture content of the polyvinyl alcohol-based raw film to be embossed was changed to 4%, and the apparent film thickness was 130 μm (the degree of embossing 3.3). A polyvinyl alcohol-based film having a crystallinity index of 0.68 at the top of the emboss was obtained and similarly evaluated.

Example 8 In Example 1, the viscosity of a 4% aqueous solution was 15 mPa · s.
(20 ° C.), and the same procedure was performed except that a polyvinyl alcohol-based resin having a saponification degree of 95 mol% was used.
A polyvinyl alcohol-based film having an embossed top having a crystallinity index of 0.80 at 40 μm (degree of embossing 3.5) was evaluated in the same manner.

Example 9 In Example 1, the viscosity of a 4% aqueous solution was 15 mPa · s.
(20 ° C.), using a polyvinyl alcohol-based resin having a degree of saponification of 95 mol%, and setting the water content of the polyvinyl alcohol-based raw film to be embossed to 12%, to obtain an apparent film thickness of 140 μm. (Embossing degree: 3.5) A polyvinyl alcohol-based film having a crystallinity index of 0.85 at the top of the emboss was obtained and similarly evaluated.

Comparative Example 1 In Example 1, the water content of the polyvinyl alcohol-based raw film to be embossed was set to 3%, and the surface temperature of the embossing roll and the surface temperature of the cotton roll were set to 100 ° C. and 70 ° C., respectively. Except that the apparent film thickness was 140 μm (the degree of embossing was 3.
In 5), a polyvinyl alcohol-based film having a crystallinity index of 0.40 at the top of the emboss was obtained, and was similarly evaluated.

Comparative Example 2 In Example 1, the moisture content of the polyvinyl alcohol-based raw film to be embossed was changed to 3%, and the surface temperature of the embossing roll and the surface temperature of the cotton roll were changed to 200 ° C. and 150 ° C., respectively. A polyvinyl alcohol-based film having an apparent film thickness of 140 μm (degree of embossing 3.5) and a crystallinity index of the embossed top of 1.00 was obtained in the same manner as above, and the evaluation was performed in the same manner. Table 1 shows the results of Examples and Comparative Examples.

[Table 1] Blocking resistance Appearance Example 1 ○ ○ 〃 2 ○ ○ 〃 3 ○ ○ 〃 4 ○ ○ ５ 5 ○ ○ ６ 6 ○ ○ ７ 7 ○ ○ ８ 8 ○ ○ ９ 9 ○ ○ Comparison Example 1 × ○ 〃 2 ○ ×

[0058]

According to the present invention, since the embossing process is performed so that the crystallinity index of the embossed top shows a specific value, the obtained polyvinyl alcohol-based film is resistant even when stored in a roll. It has excellent blocking properties and excellent appearance (there is no shine on the film surface and has a high-grade feel). Such films are used for pesticides, drugs,
It is useful as a packaging material for dyes, detergents, fertilizers, cosmetics, sanitary products, etc., and particularly very useful for unit packaging of various chemicals and the like.

[Brief description of the drawings]

FIG. 1 is a chart of an infrared absorption spectrum of a polyvinyl alcohol-based film obtained by the method of the present invention.

Claims (5)

[Claims] 1. A method for producing an embossed polyvinyl alcohol film, comprising: embossing a raw polyvinyl alcohol film so that the crystallinity index at the top of the emboss is 0.50 to 0.90. 2. The ratio (T / t) of the apparent thickness (T μm) of the embossed film to the thickness (t μm) of the raw film before embossing is 3 to 5. Item 4. A method for producing an embossed polyvinyl alcohol film according to Item 1. 3. The raw polyvinyl alcohol film has a 4% by weight aqueous solution viscosity of 10 to 40 mPa · s (20
The method for producing an embossed polyvinyl alcohol-based film according to claim 1 or 2, comprising a polyvinyl alcohol-based resin having a degree of saponification of 70 to 99 mol% at (C). 4. The embossed polyvinyl alcohol film according to claim 1, wherein a cotton roll having a surface hardness (Shore D) of 60 to 90 is used as a backup roll at the time of embossing. Manufacturing method. 5. The production of an embossed polyvinyl alcohol-based film according to claim 1, wherein the water content of the polyvinyl alcohol-based raw film at the time of embossing is 4 to 15% by weight. Method.