JP6926057B2 - Water-soluble packaging film - Google Patents

Description

The present invention relates to a water-soluble packaging film made of a polyvinyl alcohol-based film.

The polyvinyl alcohol-based film has water solubility and is widely used as a packaging material for containing various chemicals such as pesticides, chemicals, dyes, detergents, fertilizers, cosmetics, and sanitary products. Such a packaging material can be used for obtaining a solution by directly putting it into an aqueous medium by utilizing the water solubility of the film to decompose or dissolve the packaging material, or by pouring the packaging material opened at the time of use into water as it is. It is used for throwing away.

Conventionally, polyvinyl alcohol-based films used for packaging materials have been subjected to satin finish to give a satin pattern on the surface or embossed to give an uneven shape to the film in order to prevent matting and blocking. .. For example, in Patent Documents 1 to 3, in order to prevent blocking, a satin pattern having a surface roughness (Ra) of 0.1 to 8 μm and an uneven pattern having a depth of 50 to 300 μm with 100 mesh or less are formed on the film surface. It is disclosed that it is formed.
Here, in order to add an uneven pattern having a depth of 50 to 300 μm with a depth of 100 mesh or less, it is necessary to perform embossing with a coarse mesh. In Patent Documents 1 to 3, the embossing roll has a depth of 100 mesh or less. An uneven shape of 100 to 400 μm is engraved.

JP-A-2002-347112 JP-A-2002-361379 JP-A-2002-361378

However, when unevenness is engraved on the embossed roll with a coarse mesh as in Patent Documents 1 to 3, the roll durability becomes low, and for example, if dust or foreign matter adheres to the film during embossing, the embossed roll The unevenness of the film may be chipped.
Further, the polyvinyl alcohol-based film is generally stored in a wound state, but if it is stored for a long period of time at a high temperature in a warehouse in summer, for example, blocking is likely to occur. Therefore, the polyvinyl alcohol-based film having irregularities is required to have excellent blocking resistance even when stored at a high temperature for a long period of time.

The present invention has been made in view of the above circumstances, and an object of the present invention is to emboss a polyvinyl alcohol-based water-soluble packaging film while improving the blocking resistance during long-term high-temperature storage. The durability of the roll is to be excellent.

As a result of diligent studies, the present inventor set the surface roughness (Ra) and the maximum height (Rz) of the water-soluble film within a predetermined range to improve the blocking resistance during long-term high-temperature storage, and roll the film. We have found that the durability can be made excellent, and completed the following invention. That is, the present invention provides the following [1] to [7].
[1] A water-soluble packaging film containing a polyvinyl alcohol resin.
A water-soluble packaging film having irregularities on the film surface having a surface roughness (Ra) of 0.3 to 1 μm and a maximum height (Rz) of 3 to 9 μm.
[2] The water-soluble packaging film according to the above [1], which further contains a plasticizer.
[3] The water-soluble packaging film according to the above [1] or [2], wherein the content of the plasticizer is 3 to 25% by mass.
[4] The water-soluble packaging film according to any one of the above [1] to [3], wherein the degree of saponification of the polyvinyl alcohol resin is 80 to 99.9 mol%.
[5] The water-soluble packaging film according to any one of [1] to [4] above, wherein the polyvinyl alcohol resin contains unmodified polyvinyl alcohol.
[6] A method for producing a water-soluble packaging film, in which a film containing a polyvinyl alcohol resin is passed between a matte embossing roll and a backup roll to perform matte embossing processing to form irregularities on the film surface.
The matte embossing roll is a method for producing a water-soluble packaging film, in which the first unevenness is engraved with 300 to 400 mesh and the second unevenness is formed by sandblasting with 250 mesh or less.
[7] The water-soluble packaging film according to the above [6], wherein the first unevenness is formed so that the engraving depth is less than 150 μm.

The present invention provides a polyvinyl alcohol-based water-soluble packaging film having good blocking resistance during long-term high-temperature storage, and also has excellent roll durability for embossing the film. ..

Hereinafter, the present invention will be described in more detail.
[Water-soluble packaging film]
The water-soluble packaging film of the present invention is a water-soluble packaging film containing a polyvinyl alcohol (hereinafter, also simply referred to as “PVA”) resin, and has a surface roughness (Ra) of 0.3 to 1 μm. , It has irregularities with a maximum height (Rz) of 3 to 9 μm.
In the present invention, when either the surface roughness (Ra) or the maximum height (Rz) is less than the above lower limit value, the blocking resistance deteriorates when stored in a high temperature environment for a long period of time. Further, when any of the above upper limit values is exceeded, the unevenness of the embossed roll for forming the unevenness on the film surface becomes rougher than necessary, the durability of the embossed roll is lowered, and the unevenness of the embossed roll is chipped or worn. It is easy to occur.

The surface roughness (Ra) is preferably 0.33 to 0.9 μm, more preferably 0.34 to 0.7 μm, from the viewpoint of improving both roll durability and blocking resistance. The maximum height (Rz) is preferably 3.3 to 8.3 μm, more preferably 3.4 to 7.0 μm. The water-soluble packaging film may have any one surface having the above-mentioned surface roughness (Ra) and maximum height (Rz).
The shape of the unevenness on the film surface is not particularly limited, but for example, an unevenness formed by arranging a large number of convex portions such as a relatively coarse pyramid type, a trapezoidal type, a hexagonal shape, and a diagonal line type, and a finer random unevenness can be obtained. Examples include combinations. The coarse unevenness is formed by the first unevenness of the embossing roll described later, and the fine unevenness is formed by the second unevenness by the sandplast method.

(Polyvinyl alcohol resin)
The water-soluble packaging film of the present invention contains a polyvinyl alcohol resin (PVA resin). The PVA resin is obtained by polymerizing a vinyl ester to obtain a polymer according to a conventionally known method, and then saponifying, that is, hydrolyzing the polymer. Alkali or acid is generally used for saponification, but it is preferable to use alkali. As the PVA resin, only one type may be used, or two or more types may be used in combination.

Examples of the vinyl ester include vinyl acetate, vinyl formate, vinyl propionate, vinyl butyrate, vinyl pivalate, vinyl versatic acid, vinyl laurate, vinyl stearate, vinyl benzoate and the like. The method for polymerizing the vinyl ester is not particularly limited, and examples thereof include a solution polymerization method, a massive polymerization method, and a suspension polymerization method.

The PVA resin may be unmodified PVA or modified PVA. Examples of the unmodified PVA include saponified polyvinyl esters. Examples of the modified PVA include saponified polymers of vinyl ester and other unsaturated monomers.
Examples of other unsaturated monomers include monomers other than vinyl esters and having a carbon-carbon double bond such as a vinyl group, for example, olefins, (meth) acrylic acid and salts thereof, (meth). ) Acrylic acid esters, unsaturated acids other than (meth) acrylic acid, salts and esters thereof, (meth) acrylamides, N-vinylamides, vinyl ethers, nitriles, vinyl halides, allyl compounds, vinylsilyl compounds, Examples thereof include isopropenyl acetate, a sulfonic acid group-containing compound, and an amino group-containing compound.

Examples of olefins include ethylene, propylene, 1-butene and isobutene. Examples of (meth) acrylic acid esters include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, i-propyl (meth) acrylate, and n-butyl (meth) acrylate. , And 2-ethylhexyl (meth) acrylate and the like.
Unsaturated acids other than (meth) acrylic acid, salts and esters thereof include maleic acid and its salts, maleic acid esters, itaconic acid and its salts, itaconic acid esters, methylenemalonic acid and its salts, methylenemalonic acid esters, etc. Can be mentioned.
Examples of (meth) acrylamides include acrylamide, n-methylacrylamide, N-ethylacrylamide, N, N-dimethylacrylamide and the like. Examples of N-vinylamides include N-vinylpyrrolidone and the like. Examples of vinyl ethers include methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether and n-butyl vinyl ether.

Examples of nitriles include (meth) acrylonitrile. Examples of vinyl halides include vinyl chloride and vinylidene chloride. Examples of the allyl compound include allyl acetate and allyl chloride. Examples of the vinylsilyl compound include vinyltrimethoxysilane.
Examples of the sulfonic acid group-containing compound include (meth) acrylamide alkane sulfonic acid such as (meth) acrylamide propane sulfonic acid and a salt thereof, olefin sulfonic acid such as ethylene sulfonic acid, allyl sulfonic acid and methallyl sulfonic acid, or a salt thereof. Can be mentioned.
Examples of the amino group-containing compound include allylamine, polyoxyethylene allylamine, polyoxypropylene allylamine, polyoxyethylene vinylamine, polyoxypropylene vinylamine and the like.

Further, the modified PVA may be PVA to which a carboxyl group, a sulfonic acid group, an amino group, a pyrrolidone group or the like is added by graft polymerization or the like.

The modified PVA is particularly preferably modified with at least one hydrophilic group selected from a sulfonic acid group, a pyrrolidone ring group, an amino group, and a carboxyl group. That is, specific suitable modified PVAs include sulfonic acid group-modified PVA, pyrrolidone ring group-modified PVA, amino group-modified PVA, and carboxyl group-modified PVA. In addition to these functional groups, these hydrophilic groups also include salts of these functional groups such as sodium and potassium. Further, the hydrophilic group is more preferably a sulfonic acid group or a pyrrolidone ring group, that is, the modified PVA is more preferably a sulfonic acid group-modified PVA or a pyrrolidone ring group-modified PVA.

The sulfonic acid group-modified PVA is not particularly limited as long as it has a sulfonic acid group introduced by modification, but it is preferable that the sulfonic acid group is bonded to the polymer main chain via a linking group. Examples of the linking group include an amide group, an alkylene group, an ester group, an ether group and the like. Of these, a combination of an amide group and an alkylene group is preferable. In order to form the linking group as a combination of an amide group and an alkylene group in this way, the above-mentioned (meth) acrylamide alkane sulfonic acid or a salt thereof may be used as the unsaturated monomer.
Further, the sulfonic acid group is preferably composed of a sulfonate, and particularly preferably a sodium sulfonate group. When the modified PVA is a sodium sulfonate-modified PVA, the modified sodium sulfonate-modified PVA preferably has a structural unit represented by the following formula (1).

（式（１）において、Ｒ¹は炭素数１〜４のアルキレン基を表す。）

(In the formula (1), R ¹ represents an alkylene group having 1 to 4 carbon atoms.)

The pyrrolidone ring group-modified PVA is not particularly limited as long as it has a pyrrolidone ring introduced by modification, but preferably has a structural unit represented by the following formula (2). In order to obtain a pyrrolidone ring group-modified PVA having such a structural unit, for example, N-vinylpyrrolidone may be used as another unsaturated monomer.

（上記式（３）中、Ｒ²は単結合又は炭素数１〜１０のアルキレン基を表す。） The amino group-modified PVA is not particularly limited as long as it has an amino group introduced by modification, but preferably has a structural unit represented by the following formula (3).

(In the above formula (3), R ² represents a single bond or an alkylene group having 1 to 10 carbon atoms.)

The carboxyl group-modified PVA is not particularly limited as long as it has a carboxyl group introduced by modification, but is represented by the following formulas (4-1), (4-2) or (4-3). It is preferable to have a unit.

（上記式（４−１）、（４−２）及び（４−３）中、Ｘ^１、Ｘ^２、Ｘ^３、Ｘ^４及びＸ^５は、それぞれ独立に、水素原子、金属原子又はメチル基を表す。すなわち、本明細書におけるカルボキシル基には、カルボキシル基の塩及びメチルエステルも含まれる。金属原子として、例えば、ナトリウム原子等が挙げられる。上記式（４−２）中、Ｒ^３は炭素数１〜１０のアルキレン基を表す。）

(In the above formulas (4-1), (4-2) and (4-3), X ¹ , X ² , X ³ , X ⁴ and X ⁵ are independently hydrogen atoms, metal atoms or methyl groups, respectively. That is, the carboxyl group in the present specification also includes a salt of the carboxyl group and a methyl ester. Examples of the metal atom include a sodium atom and the like. In the above formula (4-2), R ³ is used. Represents an alkylene group having 1 to 10 carbon atoms.)

The modified PVA modified with at least one hydrophilic group selected from a sulfonic acid group, a pyrrolidone ring group, an amino group, and a carboxyl group has a hydrophilic group modification amount of, for example, 0.1 to 20 mol%. be.
More specifically, the sulfonic acid group-modified amount of the sulfonic acid group-modified PVA is preferably 0.1 to 6 mol%, more preferably 1 to 5 mol% from the viewpoint of improving chemical resistance and water solubility. be. From the same viewpoint, the amount of pyrrolidone ring group modified PVA of pyrrolidone ring group modified PVA is preferably 0.1 to 20 mol%, more preferably 0.5 to 10 mol%, and further preferably 1 to 5 mol%. be.
The hydrophilic group modification amount, sulfonic acid group modification amount, or pyrrolidone ring group modification amount is the ratio of the number of moles of each hydrophilic group, sulfonic acid group, or pyrrolidone ring group to the total number of moles of the constituent units of the modified PVA, respectively. means.

The saponification degree of the PVA resin is preferably 80 to 99.9 mol%. When the degree of saponification is within such a range, it becomes easy to secure the water solubility required for the water-soluble packaging film.
Further, the preferable range of the saponification degree of the PVA resin differs depending on the presence or absence of modification and the type of modifying group. For example, the unmodified PVA is preferably 80 to 99.9 mol% as described above, but from the viewpoint of further improving the water solubility, 80 to 95 mol% is more preferable, and 85 to 92 mol% is further preferable.
On the other hand, for example, the saponification degree of modified PVA such as pyrrolidone ring-modified PVA and sulfonic acid group-modified PVA is preferably 80 to 99.9 mol% as described above, but the chemical resistance and water solubility are well balanced. From the viewpoint of improvement, 85 to 99 mol% is more preferable, and 90 to 98 mol% is further preferable.
The saponification degree is measured according to JIS K6726. The degree of saponification indicates the ratio of the units that are actually saponified to vinyl alcohol units among the units that are converted into vinyl alcohol units by saponification.
The method of adjusting the saponification degree is not particularly limited. The degree of saponification can be appropriately adjusted depending on the saponification conditions, that is, the hydrolysis conditions.

The degree of polymerization of PVA is not particularly limited, but is preferably 400 or more, more preferably 700 or more, and even more preferably 900 or more. Further, it is preferably 2000 or less, more preferably 1800 or less, and further preferably 1500 or less. When the degree of polymerization is at least the above lower limit value and at least the upper limit value, the viscosity of the PVA aqueous solution can be made appropriate when the water-soluble packaging film is formed, and the water solubility of the PVA resin can be easily improved. Become. In addition, the strength of the water-soluble packaging film can be easily improved. The degree of polymerization is measured according to JIS K6726.

The viscosity of PVA as a 4% by mass aqueous solution measured at 20 ° C. is preferably 3 mPa · s or more, more preferably 8 mPa · s or more. The viscosity is preferably 30 mPa · s or less, more preferably 20 mPa · s or less. Such viscosity can be measured according to JIS K 6726.

The PVA resin of the present invention preferably contains unmodified PVA. In the present invention, it is possible to improve the blocking resistance by using the unmodified PVA. When unmodified PVA is used, the unmodified PVA may be used alone as the PVA, or the unmodified PVA and the modified PVA may be used in combination.
From the viewpoint of improving block resistance, the content of unmodified PVA in the PVA resin is preferably 50 to 100% by mass, more preferably 70 to 100% by mass, and 90 to 100% by mass with respect to the total amount of the PVA resin. More preferably, it is particularly preferable to use unmodified PVA alone as the PVA resin.

Further, the water-soluble packaging film is mainly composed of PVA resin. Specifically, the content of the PVA resin is preferably 70% by mass or more, more preferably 75% by mass or more, and further preferably 80% by mass or more based on the total amount of the water-soluble packaging film. The content of the PVA resin is preferably 97% by mass or less, more preferably 95% by mass or less, and further preferably 93% by mass or less. When the content of the PVA resin is at least the above lower limit, the water-soluble packaging film tends to have good water solubility. Further, when the value is not more than the above upper limit value, an additive such as a plasticizer can be appropriately blended in the water-soluble packaging film.

(Plasticizer)
The water-soluble packaging film of the present invention preferably further contains a plasticizer. By containing the plasticizer, the water-soluble packaging film can, for example, lower the glass transition point and improve the durability at a low temperature. It is also possible to improve the water solubility of the water-soluble packaging film.
The plasticizer is not particularly limited, and for example, polyhydric alcohols such as glycerin, diglycerin, diethylene glycol, trimethylpropane, triethylene glycol, dipropylene glycol and propylene glycol, and polyethers such as polyethylene glycol and polypropylene glycol. , Phenol derivatives such as bisphenol A and bisphenol S, amide compounds such as N-methylpyrrolidone, compounds in which ethylene oxide is added to polyhydric alcohols such as glycerin, pentaerythritol and sorbitol, water and the like can be mentioned. These may be used alone or in combination of two or more, but it is preferable to use two or more.
Among the above plasticizers, glycerin, trimethylolpropane, polyethylene glycol, polypropylene glycol, triethylene glycol, dipropylene glycol, and propylene glycol are preferable because they can improve water solubility, and the effect of improving water solubility is particularly large. Therefore, glycerin and trimethylol propane are particularly preferable.
The molecular weight of the plasticizer is preferably 90 or more, more preferably 92 or more, preferably 1200 or less, and more preferably 1000 or less.

The content of the plasticizer is preferably 3 to 25% by mass based on the total amount of the water-soluble packaging film. By setting the content of the plasticizer to 3% by mass or more, it becomes easy to obtain the effect of blending the plasticizer. Further, when the content is 25% by mass or less, the bleed-out of the plasticizer is reduced and the blocking resistance is improved. The content of the plasticizer is more preferably 5% by mass or more, still more preferably 7% by mass or more. Further, it is more preferably 22% by mass or less, still more preferably 17% by mass or less.

(Inorganic particles)
The water-soluble packaging film of the present invention does not have to contain inorganic particles, but may contain inorganic particles. The inorganic particles are not particularly limited, and examples thereof include silica, clay, kaolin, aluminum hydroxide, calcium carbonate, titanium dioxide, barium sulfate, satin white, talc, aluminum oxide, and zirconia. Of these, silica is preferred. By containing inorganic particles, the water-soluble packaging film can further improve the blocking resistance.

As the inorganic particles, those having an average particle size of 1 to 10 μm and an oil absorption amount of 230 to 400 ml / 100 g are preferably used. By using such inorganic particles, it becomes easy to improve the blocking resistance by the inorganic particles. In particular, when an oil absorbing amount of 230 ml / 100 g or more is used, inorganic particles are prevented from settling during long-term high-temperature storage, and blocking resistance during long-term high-temperature storage tends to be good.
Further, when the average particle size of the inorganic particles is 10 μm or less, the embossed rolls are prevented from being scratched or chipped by the inorganic particles, and the roll durability is improved. Further, by setting the average particle size to 10 μm or less, clogging is less likely to occur even if the filter used for film forming or the like is made dense. Therefore, since fine foreign matter in the PVA aqueous solution can be captured by the filter, the foreign matter is less likely to be mixed into the water-soluble packaging film.

From the viewpoint of improving the blocking resistance during long-term high-temperature storage, the oil absorption amount is more preferably 240 ml / 100 g or more, further preferably 250 ml / 100 g or more. The oil absorption of the inorganic particles is more preferably 380 ml / 100 g or less, and further preferably 350 ml / 100 g or less.
The average particle size of the inorganic particles is more preferably 2 μm or more, further preferably 3 μm or more, further preferably 9 μm or less, still more preferably 8 μm or less.
In this specification, the average particle size of the inorganic particles is measured by a laser diffraction type particle size distribution measuring device.
The oil absorption was measured by a method based on JIS K5101-13-1 "Pigment Test Method Part 13 Oil Absorption".

The content of the inorganic particles in the water-soluble packaging film is preferably 6% by mass or less based on the total amount of the water-soluble packaging film. By setting the content to 6% by mass or less, it is possible to obtain an effect commensurate with the blending amount without causing sedimentation of inorganic particles and the like. The content of the inorganic particles is more preferably 5% by mass or less, further preferably 4% by mass or less.
The content of the inorganic particles is preferably 0.3% by mass or more. When it is 0.3% by mass or more, the blocking resistance can be effectively improved by the inorganic particles. The content of the inorganic particles is more preferably 0.4% by mass or more, further preferably 0.5% by mass or more, in order to improve the blocking resistance.

(Other additives)
If necessary, the water-soluble packaging film of the present invention may appropriately contain additives usually used for PVA films, such as colorants, fragrances, defoamers, release agents, and ultraviolet absorbers.

The thickness of the water-soluble packaging film of the present invention is not particularly limited, but is, for example, 5 to 150 μm. When the thickness is at least the above lower limit, the strength of the film can be increased. Further, when the content is not more than the above upper limit, the packaging property and heat-sealing property as a packaging film are improved, and the productivity is improved. From these viewpoints, the thickness of the water-soluble packaging film is preferably 10 μm, more preferably 15 μm or more. Further, it is preferably 100 μm or less, more preferably 80 μm or less.

The water-soluble packaging film of the present invention is used for packaging various substances, for example, an agent for containing various chemicals such as pesticides, industrial chemicals, dyes, detergents, fertilizers, cosmetics, sanitary products, and pharmaceuticals. Suitable for packaging films.

[Manufacturing method of water-soluble packaging film]
Examples of the method for producing the water-soluble packaging film of the present invention include a method of first forming a PVA film containing a PVA resin and then performing matte embossing on the PVA film to form irregularities on the surface of the PVA film.

(Formation of PVA film)
The method for forming the PVA film is not particularly limited, but for example, an aqueous PVA solution obtained by diluting an additive such as PVA and a plasticizer added as needed with water is cast on a support member and dried. Then, a method of forming a film and the like can be mentioned. Further, the PVA aqueous solution may be cast after being appropriately filtered.
Examples of the method of casting the PVA aqueous solution on the support member include a casting method, a roll coating method, a lip coating method, a spin coating method, a screen coating method, a fountain coating method, a dipping method, and a spray method.

In the PVA aqueous solution, components other than water are diluted with water at a concentration of preferably 35% by mass or less, more preferably 25% by mass or less, still more preferably 20% by mass or less based on the total amount of the aqueous solution. The components other than water are preferably diluted with water at a concentration of 8% by mass or more, more preferably 10% by mass or more, and further preferably 12% by mass or more.
When the concentration is within the above range, the viscosity of the PVA aqueous solution becomes appropriate, and the flow of the PVA aqueous solution becomes easy. Further, when the concentration is set to the lower limit value or more, the drying time is shortened, and it becomes easy to obtain a water-soluble packaging film of good quality.

The support member may be any as long as it can maintain the PVA aqueous solution on the surface and support the obtained PVA film when the PVA aqueous solution is poured. Examples of the material of the support member include polyolefin, polyester, acrylic resin and the like, but a support member made of a material other than these may be used. Further, the support member may be in the form of a sheet or a film, but may have other shapes. The PVA film formed on the support member is peeled off from the support member by the time the matte embossing process described later is performed.
The drying after casting the PVA aqueous solution may be carried out by any method, and examples thereof include a method of natural drying and a method of heating and drying at a temperature equal to or lower than the glass transition temperature of the PVA resin.

(Matte embossing)
The matte embossing in this manufacturing method is performed by passing a PVA film between the matte embossing roll and the backup roll. As the matte embossing roll, one in which the first unevenness is engraved with 300 to 400 mesh and the second unevenness is formed by sandblasting with 250 mesh or less is used.
In the present manufacturing method, if the marking for forming the first unevenness is performed with less than 300 mesh, the unevenness of the embossed roll becomes rough, so that the roll durability is lowered and the roll is liable to be chipped. In addition, the maximum height (Rz) and surface roughness (Ra) of the water-soluble packaging film described above may become too large. On the other hand, if it is larger than 400 mesh, the maximum height (Rz) and surface roughness (Ra) of the water-soluble packaging film tend to be less than the above-mentioned lower limit values.
Further, when the mesh for sandblasting is made larger than 250, the surface roughness (Ra) or the maximum height (Rz) of the water-soluble packaging film becomes small, and it becomes difficult to adjust within the above range. Further, in the present manufacturing method, by forming two kinds of irregularities, that is, the first and second irregularities on the embossed roll, the roll is less likely to be chipped and worn, and the roll durability is improved.
Further, when the unevenness is formed on the film surface by the above-mentioned matte embossing, it becomes easy to maintain the shape of the unevenness on the film surface even if it is stored for a long time in a high temperature environment.

For forming the first unevenness from the viewpoint of adjusting the surface roughness (Ra) and the maximum height (Rz) of the water-soluble packaging film within a desired range and improving the roll durability. The engraving is preferably performed with 350 mesh or more. Further, the marking for forming the first unevenness is 390 mesh or less from the viewpoint of making it easy to adjust the maximum height (Rz) and surface roughness (Ra) of the water-soluble packaging film to a desired range. It is preferable to do so.
Further, the mesh for sandblasting is preferably 200 mesh or less, preferably 100 mesh, from the viewpoint of making it easy to adjust the maximum height (Rz) and surface roughness (Ra) of the water-soluble packaging film to a desired range. The following is more preferable. Further, the mesh for sandblasting is preferably 20 mesh or more, and more preferably 40 mesh or more.

In the present manufacturing method, the depth of marking for forming the first unevenness is preferably less than 150 μm. When the thickness is less than 150 μm, the roll durability is improved and the roll chipping is less likely to occur. In addition, the maximum height (Rz) and surface roughness (Ra) of the water-soluble packaging film can be easily adjusted to be equal to or less than the above-mentioned upper limit values. From these viewpoints, the marking depth is more preferably 120 μm or less, and further preferably 80 μm or less.
The marking depth is preferably 10 μm or more, more preferably 20 μm or more, and even more preferably 50 μm or more. By setting the marking depth to these lower limit values or more, it becomes easy to adjust the maximum height (Rz) and surface roughness (Ra) of the water-soluble packaging film to the above lower limit values or more.

The engraving for forming the first unevenness is not particularly limited, and may be performed by engraving or the like by a known method such as a meal engraving method, a photographic engraving, or a mechanical engraving. Among these, the meal engraving method is preferable. .. The shape of the engraving is not particularly limited, and examples thereof include a villamit shape, a trapezoidal cross section, a hexagonal shape, and a diagonal line.
Further, the sandplast method for forming the second unevenness may be performed, for example, by spraying sand or an abrasive on the roll.
The formation of the first and second irregularities is usually preferable to be performed uniformly on the roll surface. On the matte embossed roll, the first unevenness may be formed after the second unevenness is formed, but it is preferable to form the second unevenness after the first unevenness is formed. By forming the second unevenness after the first unevenness, the roll durability is further improved, and a uniform uneven pattern can be formed.

A plating layer may be formed on the surface of the matte embossed roll by chrome plating, nickel chrome plating, or the like. By forming the plating layer, the roll durability is further improved. The thickness of the plating layer is not particularly limited, but is, for example, 1 to 1000 μm, preferably 3 to 250 μm, and more preferably 5 to 30 μm.
The plating layer may be formed, for example, after marking for forming the first unevenness. Further, it is preferable to perform the process after the formation of the first unevenness and before the formation of the second unevenness, and when the plating layer is formed at such a timing, the second unevenness is formed on the plating layer.

The backup roll used in the mat embossing may be any roll used for general mat embossing, and for example, a rubber roll having a rubber roll surface may be used. The hardness of the roll surface of the rubber roll is not particularly limited, but for example, the hardness A is 60 to 95 °, preferably 70 to 95 °. The hardness A is a durometer hardness defined in JIS K 6253-3.

At the time of mat embossing, the mat embossing may be heated at, for example, 50 to 150 ° C., preferably 80 to 120 ° C. On the other hand, the backup roll may be heated, but may be kept at room temperature (23 ° C.) without being heated. Specifically, the temperature of the backup roll may be, for example, about 5 to 50 ° C. Further, the mat embossing may be pressed against the backup roll so that the pressing pressure (linear pressure) is, for example, 40 to 250 kg / cm, preferably 50 to 200 kg / cm.
Further, the PVA film may be passed between the matte embossing and the backup roll at a speed of, for example, 1 to 50 m / min, preferably 5 to 20 m / min.

The matte embossing may be performed inline or offline. In the case of in-line, after forming a PVA film from the PVA solution, mat embossing is performed on the production line without winding.
On the other hand, in the case of offline, a PVA film is formed from the PVA solution, wound once to form a roll, and then unwound again for matte embossing. In the offline, the PVA film wound in a roll shape may be wound with the above-mentioned support members stacked on top of each other. It is good to peel off from the support member.
Regardless of whether the film is in-line or offline, after mat embossing, the film is, for example, wound into a roll and stored in a warehouse or the like in the roll.

In this production method, the PVA film may be stretched. The stretching may be performed before the mat embossing or after the mat embossing. When it is performed before the mat embossing, it may be performed during drying after casting or after drying. Examples of the stretching include stretching using a roll, stretching using a tenter, stretching using a winding device, stretching using a drying shrinkage, and stretching combining these. Stretching may be performed at a stretching ratio of, for example, about 1.05 to 3 times. Further, a known treatment such as an annealing treatment may be appropriately performed on the film.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these examples.

The evaluation method of the water-soluble packaging film is as follows.
[Surface roughness, maximum height]
The obtained water-soluble packaging film was left to stand in an environment of 23 ° C. and 50% RH for 4 hours, and then measured in the TD direction of the film at a measurement speed of 0.060 mm / sec, a measurement length of 4 mm, and a measurement range ±. The thickness was 64 μm, and the surface roughness (Ra) and the maximum height (Rz) were measured three times based on JIS B0601-2001, and the average values were taken as the surface roughness (Ra) and the maximum height (Rz), respectively.
[Changes in surface condition over time]
The obtained water-soluble packaging film was placed in an aluminum bag and left at 50 ° C. for 2 weeks. After that, the film is taken out from the aluminum bag, the surface roughness (Ra) and the maximum height (Rz) are measured three times in the same manner as above in the TD direction of the film, and the average values are measured on the surface after aging. Roughness (Ra) and maximum height (Rz) were used. Further, the values of the surface roughness before aging and the surface roughness (Ra) and the maximum height (Rz) after aging with respect to the maximum height (Rz) were calculated as the Ra ratio and the Rz ratio.

[Blocking resistance]
The obtained water-soluble packaging film was made into A4 size, two sheets were bonded together with a 2 kgf roller, placed in an aluminum bag, and vacuum-sealed. The obtained aluminum bag was sandwiched between aluminum plates having a thickness of 2 mm (A size) ^{, weights were evenly placed so as to be 250 kgf / m 2} , and the mixture was left at 50 ° C. for 68 hours. Then, after further leaving it at 23 ° C. and 50% RH for 3 hours, the two water-soluble packaging films bonded together were cut into a size of 15 cm × 20 cm, and peeled off at a temperature of 23 ° C. and 50% RH. The 180-degree peeling force of the water-soluble packaging film was measured under the condition of a speed of 100 mm / min, and the blocking resistance was evaluated as follows.
A: 0.3N / 15mm or less
B: Exceeds 0.3N / 15mm

[Fast solubility]
The obtained water-soluble packaging film was exposed to an environment at a temperature of 23 ° C. and 50% RH for 24 hours. Then, the water-soluble packaging film was cut into a size of 35 mm × 40 mm and fixed to a jig. Then, 500 ml of water was placed in a 500 ml beaker, and the film fixed to the jig was immersed in water while maintaining the water temperature at 20 ° C. while stirring with a stirrer so that the bottom of the spiral reached the mark of 400 ml. The time when the film penetrated from the jig and was torn (tear time) and the time when the residual film was not visible (melting time) were measured and evaluated according to the following criteria.
<Tearing time>
Less than 1:11 seconds 2:11 seconds or more and less than 16 seconds 3:16 seconds or more <Dissolution time>
Less than 1:30 seconds 2:30 seconds or more and less than 40 seconds 3:40 seconds or more

[Roll durability]
Under the conditions of each Example and Comparative Example, the mat embossing process in which the PVA film was passed between the mat embossing roll and the backup roll was carried out for a total of 100 hours, and the durability of the mat embossing roll was evaluated according to the following criteria.
A: No abnormality on the surface of the matte embossed roll B: Chips and scratches are visually visible on the surface of the matte embossed roll

The components used in each Example and Comparative Example are as follows.
PVA (1): Unmodified PVA, degree of polymerization 1300, degree of saponification 88.0 mol%, 4% by mass aqueous solution viscosity (20 ° C.) 14 mPa · s
PVA (2): Sulfonic acid group-modified PVA, degree of polymerization 1200, saponification degree 95.4 mol%, sulfonic acid group modified amount 4 mol%, 4 mass% aqueous solution viscosity (20 ° C.) 12.1 mPa · s
GL: Glycerin, reagent, manufactured by Wako Pure Chemical Industries, Ltd., molecular weight 92
TMP: Trimethylolpropane: Reagent, manufactured by Wako Pure Chemical Industries, Ltd., molecular weight 134
Inorganic particles: silica, silicia 358 (trade name, manufactured by Fuji Silysia Chemical Ltd.), average particle size 3.9 μm, oil absorption 320 ml / 100 g

(Example 1)
[Making mat embossed roll]
As shown in Table 1, a diagonal line-shaped stamp was applied to a roll whose surface material was iron by a meal engraving method using mesh # 380 to a depth of 60 μm to form the first unevenness. .. Then, a chrome-plated layer of about 5 μm was formed. Next, a second unevenness was formed on the surface of the chrome-plated layer by a # 60 mesh by a sandblasting method to obtain a matte embossed roll.

[Preparation of PVA film]
As shown in Table 1, PVA resin is 84.5% by mass, glycerin as a plasticizer is 13% by mass, and trimethylolpropane is 2.5% by mass based on the water-soluble packaging film standard. A PVA aqueous solution having a concentration of 15% by mass was prepared by dissolving and dispersing in water.
The obtained PVA aqueous solution was passed through a filter having a mesh size of 20 μm, and then applied on a polyethylene terephthalate (PET) film (thickness 50 μm) as a support member by a lip coater method. Then, it was dried at 70 ° C. for 10 minutes and then at 110 ° C. for 10 minutes to form a PVA film (thickness 50 μm) on the support member. The laminate consisting of the support member and the PVA film was wound around a paper core having an inner diameter of 3 inches.

[Matte embossing]
After the wound laminate is unwound and the support member is peeled off, a matte embossing roll and a backup roll (a rubber roll manufactured by Yuri Roll Co., Ltd. (the surface is coated with synthetic rubber, hardness A90 °)) are used for the PVA film. The mat was embossed to obtain a water-soluble packaging film having a thickness of 50 μm. The matte embossing was performed by passing the PVA film between the matte embossing roll heated to 100 ° C. and the backup roll at room temperature at a pressing pressure of 100 kg / cm and at a speed of 10 m / min. Table 2 shows the evaluation results of the obtained water-soluble packaging film.

(Example 2)
The procedure was carried out in the same manner as in Example 1 except that the formulation of the PVA aqueous solution was changed as shown in Table 1.

(Example 3)
In the production of the matte embossed roll, the first unevenness is formed by engraving a diagonal line shape to a depth of 120 μm by the mesh # 300 by the meal engraving method, and the surface of the chrome plating layer is # by the sandblasting method. The procedure was carried out in the same manner as in Example 1 except that the second unevenness was formed by the 80 mesh.

(Example 4)
In the production of the matte embossed roll, the first unevenness is formed by engraving a diagonal line shape to a depth of 120 μm by the mesh # 300 by the meal engraving method, and the surface of the chrome plating layer is # by the sandblasting method. This was carried out in the same manner as in Example 1 except that the second unevenness was formed by the 200 mesh.

(Example 5)
The procedure was carried out in the same manner as in Example 1 except that the formulation of the PVA aqueous solution was changed as shown in Table 1.

(Comparative Example 1)
The composition of the PVA aqueous solution was changed as shown in Table 1, and the same procedure as in Example 1 was carried out except that the matte embossing process was not performed.

(Comparative Example 2)
In the production of the matte embossed roll, the first unevenness is formed by engraving a diagonal line shape to a depth of 40 μm by the mesh # 600 by the meal engraving method, and the surface of the chrome plating layer is # by the sandblasting method. This was carried out in the same manner as in Example 1 except that the second unevenness was formed by the 60 mesh.

(Comparative Example 3)
In the production of the matte embossed roll, the first unevenness is formed by engraving a diagonal line shape to a depth of 60 μm by the mesh # 380 by the meal engraving method, and the surface of the chrome plating layer is # by the sandblasting method. This was carried out in the same manner as in Example 1 except that the second unevenness was formed by the 280 mesh.

(Comparative Example 4)
The production of the mat embossed roll was carried out by the following method, and was carried out in the same manner as in Example 1 except that the mat embossed roll in which the second unevenness was not formed was used.
[Making mat embossed roll]
As shown in Table 1, the roll surface is stamped with mesh # 200 by the meal engraving method to a depth of 190 μm to form the first unevenness on the roll made of iron. Then, a chrome-plated layer of about 5 μm was formed to obtain a matte embossed roll.

※表１における質量％は、水溶性包装用フィルム基準の質量％を示す。

* The mass% in Table 1 indicates the mass% based on the water-soluble packaging film.

In Examples 1 to 5, when the PVA film is embossed using an embossing roll in which the first unevenness is engraved with 300 to 400 mesh and the second unevenness is formed by sandblasting with 250 mesh or less. Unevenness with a surface roughness (Ra) of 0.3 to 1 μm and a maximum height (Rz) of 3 to 9 μm was formed on the film surface. Then, blocking resistance, quick dissolution, and roll durability could all be improved. Further, in Examples 1 to 5, the Ra ratio and the Rz ratio were close to 1, and the uneven shape of the film surface could be maintained even if the film was left for a long time in a high temperature environment.
On the other hand, in Comparative Examples 1 to 4, the embossing was not performed, and even when the embossing was performed, the predetermined first and second irregularities were not formed on the embossed roll when the embossing was performed. .. Therefore, unevenness with a surface roughness (Ra) of 0.3 to 1 μm and a maximum height (Rz) of 3 to 9 μm is not formed on the film surface, and the blocking resistance or roll durability during long-term high-temperature storage is not formed. One did not improve.

Claims (8)

A water-soluble packaging film containing a polyvinyl alcohol resin (excluding a water-soluble film containing liquid paraffin) .
A water-soluble packaging film having irregularities on the film surface having a surface roughness (Ra) of 0.3 to 1 μm and a maximum height (Rz) of 3 to 9 μm. The water-soluble packaging film according to claim 1, wherein the maximum height (Rz) is 5.1 to 9 μm. The water-soluble packaging film according to claim 1 or 2 , further containing a plasticizer. The water-soluble packaging film according to claim 3 , wherein the content of the plasticizer is 3 to 25% by mass. The water-soluble packaging film according to any one of claims 1 to 4 , wherein the polyvinyl alcohol resin has a saponification degree of 80 to 99.9 mol%. The water-soluble packaging film according to any one of claims 1 to 5 , wherein the polyvinyl alcohol resin contains unmodified polyvinyl alcohol. The water-soluble packaging film according to any one of claims 1 to 6 , wherein the polyvinyl alcohol resin contains a modified polyvinyl alcohol. The water-soluble packaging film according to any one of claims 1 to 7 , wherein the film has a thickness of 50 μm and a dissolution time in water at 20 ° C. of less than 40 seconds when the size is 35 mm × 40 mm. ..