JP2019044197A - Water-soluble film for packaging - Google Patents

Abstract

To improve blocking resistance during long-term high-temperature storage, and also improve durability of a roll for embossing a film.SOLUTION: The water-soluble film for packaging according to the present invention contains a polyvinyl alcohol resin, where a surface of the film has recesses and projections resulting in a surface roughness (Ra) of 0.3-1 μm and a maximum height (Rz) of 3-9 μm.SELECTED DRAWING: None

Description

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

  Polyvinyl alcohol films have water solubility and are widely used as packaging materials for containing various drugs such as pesticides, drugs, dyes, detergents, fertilizers, cosmetics, and catamenial products. Such packaging materials are put directly into an aqueous medium using the water solubility of the film to decompose or dissolve the packaging materials to obtain a solution, or the packaging materials opened at the time of use are poured into water as they are. It is used for the purpose of discarding.

In the past, polyvinyl alcohol films used for packaging materials have been subjected to a satinizing treatment 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, for the prevention of blocking, a textured surface having a surface roughness (Ra) of 0.1 to 8 μm and an uneven pattern having a depth of 50 to 300 μm and 100 mesh or less are formed on the film surface. It is disclosed to be formed.
Here, in order to add a concavo-convex pattern of 100 mesh or less and a depth of 50 to 300 μm, it is necessary to perform embossing with a coarse mesh, and in Patent Documents 1 to 3, the depth is 100 mesh or less on the embossing roll. An uneven shape of 100 to 400 μm is engraved.

Unexamined-Japanese-Patent No. 2002-347112 JP, 2002-361379, A Unexamined-Japanese-Patent No. 2002-361378

However, when unevenness is imprinted on the emboss roll by coarse mesh like patent documents 1-3, roll durability becomes low, for example, when dirt and a foreign material adhere to a film at the time of embossing, an emboss roll In some cases, chipping may occur.
In addition, polyvinyl alcohol films are generally stored in a wound state, but blocking tends to occur, for example, when stored for a long time under high temperature in a warehouse in summer. Therefore, a polyvinyl alcohol-based film with irregularities is required to have excellent blocking resistance even when stored at high temperatures for a long 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 of the film. To make the durability of the roll excellent.

As a result of intensive investigations, the present inventors set the surface roughness (Ra) and the maximum height (Rz) of the water-soluble film in a predetermined range to improve the blocking resistance during long-term high-temperature storage. The inventors have found that the durability can also be excellent, and completed the present invention described below. That is, the present invention provides the following [1] to [7].
[1] A water-soluble packaging film containing a polyvinyl alcohol resin,
The film for water-soluble packaging which has the unevenness | corrugation whose surface roughness (Ra) is 0.3-1 micrometer, and the largest height (Rz) is 3-9 micrometers.
[2] The water-soluble packaging film according to the above [1], further containing 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 saponification degree of the polyvinyl alcohol resin is 80 to 99.9 mol%.
[5] The water-soluble packaging film according to any one of the above [1] to [4], wherein the polyvinyl alcohol resin contains unmodified polyvinyl alcohol.
[6] A method for producing a water-soluble packaging film, wherein a film containing a polyvinyl alcohol resin is passed between a matte embossing roll and a backup roll to perform matte embossing to form irregularities on the film surface,
The method for producing a water-soluble packaging film according to claim 1, wherein the matte embossing roll is formed by imprinting the first unevenness with 300 to 400 mesh and forming the second unevenness with sand blast of 250 mesh or less.
[7] The water-soluble packaging film according to the above-mentioned [6], wherein the first unevenness is formed so that the depth of imprint is less than 150 μm.

  In the present invention, a polyvinyl alcohol-based water-soluble packaging film having good blocking resistance during long-term high-temperature storage can be provided, and the durability of the roll for embossing the film can also be excellent. .

Hereinafter, the present invention will be described in more detail.
[Water-soluble packaging film]
The film for water-soluble packaging of the present invention is a film for water-soluble packaging containing polyvinyl alcohol (hereinafter, also simply referred to as "PVA") resin, and the surface roughness (Ra) of the film surface is 0.3 to 1 μm. And the unevenness having a maximum height (Rz) of 3 to 9 μm.
In the present invention, when any of the surface roughness (Ra) and the maximum height (Rz) is less than the above lower limit value, the blocking resistance becomes worse when stored under a high temperature environment for a long time. In addition, when any of the above exceeds the upper limit value, the unevenness of the embossing roll for forming the unevenness on the film surface becomes rougher than necessary, the durability of the embossing roll is lowered, and the unevenness of the embossing roll is chipped or worn away. It tends 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 making both the roll durability and the blocking resistance more excellent. Also, the maximum height (Rz) is preferably 3.3 to 8.3 μm, more preferably 3.4 to 7.0 μm. In addition, the film for water-soluble packaging should just have the surface roughness (Ra) and maximum height (Rz) which either side mentioned above.
The shape of the unevenness on the film surface is not particularly limited. For example, unevenness formed by arranging a large number of relatively large pyramids, trapezoids, turtles, diagonal lines, etc. with a large number of projections, and finer random unevenness There may be mentioned a combination. In addition, coarse unevenness is formed of the 1st unevenness of an embossing roll mentioned below, and fine unevenness is formed of the 2nd unevenness by 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 saponifying, that is, hydrolyzing the polymer after polymerizing the vinyl ester to obtain the polymer according to a conventionally known method. For saponification, generally, an alkali or an acid is used, but it is preferable to use an alkali. As PVA resin, only 1 type may be used and 2 or more types may be used together.

  Examples of vinyl esters include vinyl acetate, vinyl formate, vinyl propionate, vinyl butyrate, vinyl pivalate, vinyl versatate, vinyl laurate, vinyl stearate and vinyl benzoate. Further, the polymerization method of the vinyl ester is not particularly limited, and examples thereof include a solution polymerization method, a bulk polymerization method and a suspension polymerization method.

The PVA resin may be unmodified PVA or modified PVA. As unmodified | non_denatured PVA, what saponified polyvinyl ester is mentioned. The modified PVA includes those obtained by saponifying a polymer of a vinyl ester and another unsaturated monomer.
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, ) Acrylic acids, 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 include isopropenyl acetate, a compound containing a sulfonic acid group, and a compound containing an amino group.

Examples of olefins include ethylene, propylene, 1-butene and isobutene. As (meth) acrylic acid esters, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, i-propyl (meth) acrylate, n-butyl (meth) acrylate And 2-ethylhexyl (meth) acrylate and the like.
As unsaturated acids other than (meth) acrylic acid, and salts and esters thereof, maleic acid and salts thereof, maleic acid ester, itaconic acid and salts thereof, itaconic acid ester, methylene malonic acid and salts thereof, methylene malonic acid ester and the like Can be mentioned.
As (meth) acrylamides, acrylamide, n-methyl acrylamide, N-ethyl acrylamide, N, N- dimethyl acrylamide etc. are mentioned. 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 and the like. Examples of halogenated vinyls include vinyl chloride and vinylidene chloride. Examples of the allyl compound include allyl acetate and allyl chloride. As a vinyl silyl compound, vinyl trimethoxysilane etc. are mentioned.
Examples of sulfonic acid group-containing compounds include (meth) acrylamidoalkanesulfonic acids such as (meth) acrylamidopropanesulfonic acid and salts thereof, olefin sulfonic acids such as ethylenesulfonic acid, allylsulfonic acid and methallylsulfonic acid, and salts thereof It can be mentioned.
Examples of the amino group-containing compound include allylamine, polyoxyethylene allylamine, polyoxypropylene allylamine, polyoxyethylene vinylamine, polyoxypropylene vinylamine and the like.

  Moreover, as modified PVA, a carboxyl group, a sulfonic acid group, an amino group, a pyrrolidone group etc. may be added to PVA by graft polymerization etc.

  In particular, the modified PVA is 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, as specific suitable modified PVA, sulfonic acid group modified PVA, pyrrolidone ring group modified PVA, amino group modified PVA, carboxyl group modified PVA can be mentioned. In addition to these functional groups, these hydrophilic groups also include salts such as sodium and potassium of these functional groups. Moreover, as a hydrophilic group, a sulfonic acid group and a pyrrolidone ring group are more preferable. That is, as the modified PVA, a sulfonic acid group-modified PVA and a pyrrolidone ring group-modified PVA are more preferable.

The sulfonic acid group-modified PVA is not particularly limited as long as the sulfonic acid group is 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 amido group, an alkylene group, an ester group and an ether group. Among them, a combination of an amido group and an alkylene group is preferred. In order to make the linking group a combination of an amido group and an alkylene group in this manner, the (meth) acrylamidoalkanesulfonic acid or its salt described above may be used as the unsaturated monomer.
The sulfonic acid group is preferably a sulfonic acid salt, and is particularly preferably a sodium sulfonate group. When the said modified PVA is sodium sulfonate modified PVA, as sodium sulfonate modified PVA, it is preferable to have a structural unit represented by following formula (1).

(In 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 the pyrrolidone ring is introduced by modification, but it is preferable to have a structural unit represented by the following formula (2). In order to obtain a pyrrolidone group-modified PVA having such a structural unit, for example, N-vinylpyrrolidone may be used as another unsaturated monomer.

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

(In the above formulas (4-1), (4-2) and (4-3), X ¹ , X ² , X ³ , X ⁴ and X ⁵ are each independently a hydrogen atom, a metal atom or a methyl group That is, the carboxyl group in the present specification also includes a salt and a methyl ester of a carboxyl group, and examples of the metal atom include a sodium atom etc. In the above formula (4-2), R ³ is It represents a C1-C10 alkylene group.)

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% by mole is there.
More specifically, the amount of sulfonic acid group modification 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. is there. From the same point of view, the amount of pyrrolidone ring group modification of pyrrolidone ring group modified PVA is preferably 0.1 to 20 mol%, more preferably 0.5 to 10 mol%, and still more preferably 1 to 5 mol%. is there.
The hydrophilic group modification amount, the sulfonate group modification amount, or the pyrrolidone ring group modification amount is the ratio of the number of moles of each of the hydrophilic group, the sulfonate group or the pyrrolidone ring group to the total number of moles of the constituent unit of modified PVA. means.

The degree of saponification of the PVA resin is preferably 80 to 99.9 mol%. When the degree of saponification is in this range, the water solubility required for the water-soluble packaging film can be easily secured.
Moreover, the suitable range of the saponification degree of PVA resin changes also with the presence or absence of modification | denaturation, and the kind of modification group. For example, as described above, the unmodified PVA is preferably 80 to 99.9 mol%, but from the viewpoint of further improving the water solubility, 80 to 95 mol% is more preferable, and 85 to 92 mol% is more preferable.
On the other hand, for example, as described above, the saponification degree of modified PVA such as pyrrolidone ring group modified PVA, sulfonic acid group modified PVA is preferably 80 to 99.9 mol%, but chemical resistance and water solubility are well balanced. From a viewpoint of improving, 85-99 mol% is more preferable, and 90-98 mol% is further more preferable.
The degree of saponification is measured in accordance with JIS K6726. The degree of saponification indicates the ratio of units actually saponified to vinyl alcohol units among units converted to vinyl alcohol units by saponification.
In addition, the adjustment method of a saponification degree is not specifically limited. The degree of saponification can be appropriately adjusted according to saponification conditions, that is, hydrolysis conditions.

  The polymerization degree of PVA is not particularly limited, but is preferably 400 or more, more preferably 700 or more, and still more preferably 900 or more. Moreover, it is preferably 2000 or less, more preferably 1800 or less, and still more preferably 1500 or less. When the degree of polymerization is at least the lower limit value and the upper limit value, the viscosity of the aqueous PVA solution can be made appropriate when forming the water-soluble packaging film, 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 in accordance with JIS K6726.

  The PVA preferably has a viscosity of 3 mPa · s or more, more preferably 8 mPa · s or more, as a 4% by mass aqueous solution and measured at 20 ° C. Also, 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 make the blocking resistance more excellent by using a non-modified PVA. Moreover, when using non-modified PVA, although you may use as non-modified PVA alone as PVA, you may use together non-modified PVA and modified PVA.
From a viewpoint of making block resistance favorable, 50 to 100 mass% is preferable with respect to PVA resin whole quantity, as for content of unmodified PVA in PVA resin, 70 to 100 mass% is more preferable, and 90 to 100 mass% More preferably, it is particularly preferable to use unmodified PVA alone as the PVA resin.

  In addition, 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 still more preferably 80% by mass or more, based on the total amount of the water-soluble packaging film. Moreover, content of PVA resin becomes like this. Preferably it is 97 mass% or less, More preferably, it is 95 mass% or less, More preferably, it is 93 mass% or less. When the content of the PVA resin is equal to or more than the above lower limit, the water-soluble packaging film tends to have good water solubility. Moreover, when it is below the said upper limit, it becomes possible to mix | blend additives, such as a plasticizer, appropriately with the film for water-soluble packaging.

(Plasticizer)
The water-soluble packaging film of the present invention preferably further contains a plasticizer. By containing a plasticizer, for example, the glass transition temperature of the water-soluble packaging film can be lowered, and the durability at a low temperature can be improved. In addition, the water solubility of the water-soluble packaging film can also be improved.
The plasticizer is not particularly limited, and examples thereof include polyhydric alcohols such as glycerin, diglycerin, diethylene glycol, trimethylolpropane, triethylene glycol, dipropylene glycol and propylene glycol, and polyethers such as polyethylene glycol and polypropylene glycol. Examples thereof include phenol derivatives such as bisphenol A and bisphenol S, amide compounds such as N-methyl pyrrolidone, compounds obtained by adding ethylene oxide to polyhydric alcohols such as glycerin, pentaerythritol, and sorbitol, and water. Although these may be used independently and 2 or more types may be used, it is preferable to use 2 or more types.
Among the above-mentioned plasticizers, glycerin, trimethylolpropane, polyethylene glycol, polypropylene glycol, triethylene glycol, dipropylene glycol and propylene glycol are preferable since water solubility can be improved, and the effect of improving water solubility is particularly large. In particular, glycerin and trimethylolpropane are particularly preferable.
The molecular weight of the plasticizer is preferably 90 or more, more preferably 92 or more, preferably 1200 or less, 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 is easy to obtain the effect of blending the plasticizer. Moreover, by setting it as 25 mass% or less, the bleed-out of a plasticizer becomes small and blocking resistance becomes favorable. The content of the plasticizer is more preferably 5% by mass or more, still more preferably 7% by mass or more. Moreover, More preferably, it is 22 mass% or less, More preferably, it is 17 mass% or less.

(Inorganic particles)
The water-soluble packaging film of the present invention may or may not 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, zirconia and the like. Among these, silica is preferred. The water-soluble packaging film can further improve the blocking resistance by containing the inorganic particles.

It is preferable to use an inorganic particle having an average particle diameter of 1 to 10 μm and an oil absorption of 230 to 400 ml / 100 g. By using such inorganic particles, blocking resistance can be easily improved by the inorganic particles. In particular, when oil absorption is 230 ml / 100 g or more, inorganic particles are prevented from settling during long-term high-temperature storage, and blocking resistance tends to be good during long-term high-temperature storage.
Further, when the average particle diameter of the inorganic particles is 10 μm or less, the inorganic particles prevent the emboss roll from being scratched or chipped, and the roll durability is improved. Furthermore, by setting the average particle diameter to 10 μm or less, clogging does not easily occur even if the eyes of the filter used at the time of film formation or the like are closed. Therefore, since a fine foreign substance in the PVA aqueous solution can be captured by the filter, the foreign substance is less likely to be mixed in the water-soluble packaging film.

The oil absorption amount is preferably 240 ml / 100 g or more, more preferably 250 ml / 100 g or more, from the viewpoint of making the blocking resistance excellent during long-term high-temperature storage. Moreover, as for the oil absorption amount of inorganic substance particle | grains, 380 ml / 100g or less is more preferable, and 350 ml / 100g or less is further more preferable.
The average particle diameter of the inorganic particles is more preferably 2 μm or more, further preferably 3 μm or more, more preferably 9 μm or less, and still more preferably 8 μm or less.
In the present specification, the average particle size of the inorganic particles is measured by a laser diffraction type particle size distribution measuring apparatus.
Moreover, oil absorption amount is measured by the method based on JISK5101-13-1 "pigment test method 13 part oil absorption amount".

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 achieve an effect commensurate with the compounding amount without causing sedimentation or the like of the inorganic particles. 5 mass% or less is more preferable, and, as for content of inorganic substance particle | grains, 4 mass% or less is more preferable.
The content of the inorganic particles is preferably 0.3% by mass or more. When the content is 0.3% by mass or more, the inorganic particles can effectively improve the blocking resistance. The content of the inorganic particles is more preferably 0.4% by mass or more and still more preferably 0.5% by mass or more in order to make the blocking resistance better.

(Other additives)
The water-soluble packaging film of the present invention may further contain, as necessary, additives usually used in PVA films, such as coloring agents, perfumes, antifoaming agents, release agents, UV absorbers and the like.

  The thickness of the water-soluble packaging film of the present invention is not particularly limited, and 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. Moreover, when below the said upper limit, the packaging property as a film for packaging and heat-sealing property become favorable, and productivity improves. From these viewpoints, the thickness of the water-soluble packaging film is preferably 10 μm, more preferably 15 μm or more. Moreover, Preferably it is 100 micrometers or less, More preferably, it is 80 micrometers or less.

  The water-soluble packaging film of the present invention is used to package various substances, and for example, drugs for containing various drugs such as agricultural chemicals, industrial chemicals, dyes, detergents, fertilizers, cosmetics, sanitary products, pharmaceuticals and the like. It is suitably used for a packaging film.

[Method for producing water-soluble packaging film]
As a method for producing a water-soluble packaging film of the present invention, first, a PVA film containing a PVA resin is formed, and the PVA film is matte-embossed to form irregularities on the surface of the PVA film.

(Formation of PVA film)
The method of forming the PVA film is not particularly limited. For example, an aqueous solution of PVA obtained by diluting PVA and an additive such as a plasticizer added as needed with water is cast on a support member and dried. And the like. The PVA aqueous solution may be cast after passing through a filter as appropriate.
Examples of the method of casting an aqueous solution of PVA on the support member include cast method, roll coating method, lip coating method, spin coating method, screen coating method, fountain coating method, dipping method, spray method and the like.

The PVA aqueous solution is 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 may be diluted with water to a concentration of preferably 8% by mass or more, more preferably 10% by mass or more, and still more preferably 12% by mass or more.
When the concentration is in the above range, the viscosity of the PVA aqueous solution becomes appropriate, and casting of the PVA aqueous solution becomes easy. Further, by setting the concentration to the lower limit value or more, the drying time becomes short, and it becomes easy to obtain a water-soluble packaging film of good quality.

The support member may be any member that can maintain the aqueous PVA solution on the surface and support the obtained PVA film when the aqueous PVA solution is cast. Examples of the material of the support member include polyolefins, polyesters, acrylic resins and the like, but support members made of materials other than these may be used. Also, the support member may be in the form of a sheet or a film, but may be in other shapes. In addition, the PVA film formed on the support member is peeled from the support member until the matte embossing described later is performed.
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 below the glass transition temperature of the PVA resin.

(Matte embossing)
Matt embossing in this manufacturing method is performed by passing a PVA film between a matte embossing roll and a backup roll. As a matte embossing roll, what imprinted the 1st unevenness by 300-400 mesh, and formed the 2nd unevenness by sand blast of 250 mesh or less is used.
In the present manufacturing method, when the marking for forming the first unevenness is performed with less than 300 mesh, the unevenness of the emboss roll becomes rough, so that the roll durability is lowered and the roll is easily chipped. In addition, the maximum height (Rz) and surface roughness (Ra) of the water-soluble packaging film described above may be too large. On the other hand, when 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-described lower limit.
In addition, when the mesh for sandblasting is larger than 250, the surface roughness (Ra) or maximum height (Rz) of the water-soluble packaging film becomes small, and it becomes difficult to adjust within the above-mentioned range. Furthermore, in the present manufacturing method, by forming the two types of irregularities, ie, the first and second irregularities, on the embossing roll, it is difficult for the roll to chip and wear, and the roll durability becomes good.
Furthermore, when the unevenness is formed on the film surface by the above-described matte embossing, the shape of the unevenness on the film surface can be easily maintained even when stored for a long time under a high temperature environment.

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 making the roll durability excellent, to form the first unevenness The marking is preferably performed with 350 mesh or more. Moreover, the marking for forming the first unevenness is 390 mesh or less from the viewpoint of facilitating adjustment of the maximum height (Rz) and surface roughness (Ra) of the water-soluble packaging film to a desired range. It is preferred to do.
Furthermore, from the viewpoint of facilitating adjustment of the maximum height (Rz) and surface roughness (Ra) of the water-soluble packaging film in a desired range, the mesh when sandblasting is preferably 200 mesh or less, and 100 mesh. The following are more preferable. Moreover, 20 mesh or more is preferable and, as for the mesh at the time of sandblasting, 40 mesh or more is more preferable.

In the present manufacturing method, the depth of the marking for forming the first unevenness is preferably less than 150 μm. By setting the thickness to less than 150 μm, the roll durability is improved, and roll chipping and the like are 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 the above-described upper limit or less. From these viewpoints, the depth of the marking is more preferably 120 μm or less, and still more preferably 80 μm or less.
Moreover, 10 micrometers or more are preferable, as for the depth of imprint, 20 micrometers or more are more preferable, and 50 micrometers or more are more preferable. By setting the depth of the marking to the lower limit value or more, the maximum height (Rz) and the surface roughness (Ra) of the water-soluble packaging film can be easily adjusted to the above lower limit value.

The engraving for forming the first unevenness is not particularly limited, and may be performed by a known method such as a mir engraving method, a photo engraving, a mechanical engraving, etc. Among these, the mir engraving method is preferable. . Further, the shape of the stamp is not particularly limited, and examples thereof include a shape in which a large number of concave portions such as a pyramid shape, a trapezoidal cross section, a turtle shell type, and a diagonal line type are arranged.
In addition, it is preferable to perform the sandblasting method for forming the second unevenness by, for example, blowing sand or an abrasive on the roll.
The formation of the first and second irregularities may generally be performed uniformly on the roll surface. Although the first embossing may be formed on the matte embossing roll after forming the second asperity, it is preferable to form the second asperity after forming the first asperity. By forming the second unevenness after the first unevenness, roll durability can be further improved, and a uniform uneven pattern can be formed.

The matte embossing roll may form a plated layer on the surface by chromium plating, nickel chromium plating, or the like. Roll durability is further improved by forming the plating layer. 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 plated layer may be formed, for example, after the marking for forming the first unevenness is performed. Moreover, it is preferable to carry out after the formation of the first unevenness and before the formation of the second unevenness. If the plating layer is formed at such timing, the second unevenness will be formed on the plating layer.

  The backup roll used in matte embossing may be a roll used for general matte embossing, and for example, a rubber roll whose surface is rubber may be used. Although the hardness of the roll surface of the rubber roll is not particularly limited, 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 matte embossing, the matte embossing may be heated, for example, at 50 to 150 ° C., preferably 80 to 120 ° C. On the other hand, the backup roll may be heated, but may be at around normal temperature (23 ° C.) without being heated. Specifically, the temperature of the backup roll may be, for example, about 5 to 50 ° C. In addition, the matte embossing may be pressed by the backup roll so that the pressing force (linear pressure) is, for example, 40 to 250 kg / cm, preferably 50 to 200 kg / cm.
Furthermore, the PVA film may be passed between the matte embossing and the backup roll, for example at a speed of 1 to 50 m / min, preferably at a speed of 5 to 20 m / min.

Matte embossing may be performed either in-line or off-line. In the case of in-line, after the PVA film is formed into a film from the PVA solution, matte embossing is performed on the production line without winding.
On the other hand, in the case of an off-line, a PVA film is formed from a PVA solution, wound once to form a roll, and then drawn out again to perform matte embossing. In the off-line, the rolled up PVA film may be rolled up with the above-mentioned supporting member being overlapped, but even in such a case, the PVA film is taken out after being drawn and before being subjected to mat embossing. It may be peeled off from the support member.
The film is matte embossed in either in-line or off-line manner, and then, for example, is wound into a roll and stored in a warehouse or the like as it is in a roll.

  In the present production method, the PVA film may be stretched. The stretching may be performed before matt embossing, or may be performed after matt embossing. When performed before matt embossing, it may be performed during drying after casting, or may be performed after drying. Examples of the stretching include stretching using a roll, stretching using a tenter, stretching using a winding device, stretching using drying shrinkage, or a combination of these. The stretching may be performed, for example, at a stretching ratio of about 1.05 to 3 times. In addition, a known process to be performed on the film, such as an annealing process, may be appropriately performed.

  Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited by these examples.

The evaluation method of the water-soluble packaging film is as follows.
[Surface roughness, maximum height]
The resulting water-soluble packaging film is allowed to stand in an environment of 23 ° C. and 50% RH for 4 hours, and then in the direction of the film TD, measuring speed 0.060 mm / sec, measuring length 4 mm, measuring range ± The surface roughness (Ra) and the maximum height (Rz) were measured three times based on JIS B 0601-2001 at 64 μm, and the average values were made the surface roughness (Ra) and the maximum height (Rz), respectively.
[Temporal change of surface condition]
The obtained water-soluble packaging film was placed in an aluminum bag and left at 50 ° C. for 2 weeks. Thereafter, the film is taken out of the aluminum bag, and the surface roughness (Ra) and the maximum height (Rz) are measured three times in the same manner as above in the direction of the film TD, and the average value is the surface after aging. Roughness (Ra), maximum height (Rz). The surface roughness before aging, the surface roughness (Ra) after aging with respect to the maximum height (Rz), and 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 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 (size A), weights were evenly placed to be 250 kgf / m ^2, and left at 50 ° C. for 68 hours. Then, after leaving it to stand at 23 ° C. and 50% RH for 3 hours, the laminated film of two water-soluble packaging films is cut into a size of 15 cm × 20 cm, temperature 23 ° C., 50% RH, peeling The 180 degree peel force of the water-soluble packaging film was measured at a speed of 100 mm / min, and the blocking resistance was evaluated as follows.
A: 0.3 N / 15 mm or less
B: More than 0.3 N / 15 mm

[Fast dissolution]
The obtained water-soluble packaging film was exposed to an environment of temperature 23 ° C. and 50% RH for 24 hours. Thereafter, 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 put in a 500 ml beaker, and the film fixed to the jig was immersed in water while keeping the water temperature at 20 ° C. while stirring so that the bottom of the swirl reached the mark of 400 ml by a stirrer. The time when the film penetrated from the jig and was broken (breaking time) and the time when the residue of the film was not visible (dissolving time) was measured and evaluated according to the following criteria.
<Break time>
1:11 seconds or less 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 less than 40 seconds 3:40 seconds or more

[Roll durability]
Under the conditions of each example and comparative example, matting for passing a PVA film between the matting embossing roll and the backup roll was carried out for a total of 100 hours, and the durability of the matting embossing roll was evaluated according to the following criteria.
A: There is no abnormality in the surface of the matte embossing roll B: Chips or scratches can be visually observed on the surface of the matte embossing 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 mass% aqueous solution viscosity (20 ° C.) 14 mPa · s
PVA (2): sulfonic acid group modified PVA, polymerization degree 1200, saponification degree 95.4 mol%, sulfonic acid group modification amount 4 mol%, 4 mass% aqueous solution viscosity (20 ° C.) 12.1 mPa · s
GL: Glycerin, reagent, Wako Pure Chemical Industries, Ltd., molecular weight 92
TMP: trimethylolpropane: reagent, Wako Pure Chemical Industries, Ltd., molecular weight 134
Inorganic particles: silica, Phylysia 358 (trade name; manufactured by Fuji Silysia Chemical Ltd.), average particle size 3.9 μm, oil absorption amount 320 ml / 100 g

Example 1
[Production of matte embossing roll]
On the roll whose material of the roll surface is iron, as shown in Table 1, hatching-shaped indentation was performed by a mesh engraving method using mesh # 380 so as to have a depth of 60 μm to form a first unevenness. . Thereafter, a chromium plating layer of about 5 μm was formed. Next, second irregularities were formed on the surface of the chromium plating layer by # 60 mesh by sandblasting to obtain a matte embossed roll.

[Preparation of PVA film]
As shown in Table 1, based on the film for water-soluble packaging, 84.5% by mass of PVA resin, 13% by mass of glycerin as a plasticizer, and 2.5% by mass of trimethylolpropane are used. It was dissolved and dispersed in water to prepare a PVA aqueous solution having a concentration of 15% by mass.
The obtained aqueous solution of PVA was passed through a filter with an aperture of 20 μm, and then applied by a lip coater method on a polyethylene terephthalate (PET) film (50 μm in thickness) as a supporting member. Thereafter, the film 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 composed of the support member and the PVA film was wound around a paper core having an inner diameter of 3 inches.

[Matte embossing]
After unwinding the wound laminate and peeling off the support member, using a matte embossed roll and a backup roll (rubber roll manufactured by Yuri Roll Co., Ltd. (a synthetic rubber is coated on the surface, hardness A 90 °)) for the PVA film Matt embossing was performed to obtain a water-soluble packaging film having a thickness of 50 μm. Matt embossing was performed by passing the PVA film at a speed of 10 m / minute while pressing between a matt embossing roll heated to 100 ° C. and a backup roll at normal temperature with a pressing force of 100 kg / cm. The evaluation results of the obtained water-soluble packaging film are shown in Table 2.

(Example 2)
The procedure of Example 1 was repeated except that the composition of the PVA aqueous solution was changed as shown in Table 1.

(Example 3)
In the preparation of the matte embossing roll, the first concavities and convexities are formed by mesh engraving with a mesh # 300 so that the depth is 120 μm by the milling engraving method, and the surface of the chromium plating layer is sandblasted # It carried out like Example 1 except the point which formed the 2nd unevenness by 80 meshes.

(Example 4)
In the preparation of the matte embossing roll, the first concavities and convexities are formed by mesh engraving with a mesh # 300 so that the depth is 120 μm by the milling engraving method, and the surface of the chromium plating layer is sandblasted # It implemented similarly to Example 1 except the point which formed 2nd unevenness | corrugation with 200 mesh.

(Example 5)
The procedure of Example 1 was repeated except that the composition of the PVA aqueous solution was changed as shown in Table 1.

(Comparative example 1)
The formulation 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 matte embossing was not performed.

(Comparative example 2)
In the production of the matte embossing roll, the first concavities and convexities are formed by means of mesh # 600 by means of mesh engraving so that the depth becomes 40 μm by means of the milling engraving method, and the surface of the chromium plating layer is sandblasted #. It carried out like Example 1 except the point which formed the 2nd unevenness by 60 mesh.

(Comparative example 3)
In the preparation of the matte embossing roll, the first concavities and convexities are formed by mesh-lined engraving with mesh # 380 so as to have a depth of 60 μm by the mire engraving method, and the surface of the chromium plating layer is sandblasted #. It implemented similarly to Example 1 except the point which formed 2nd unevenness | corrugation with 280 mesh.

(Comparative example 4)
The production of the matte embossing roll was carried out by the following method and carried out in the same manner as in Example 1 except that the matte embossing roll in which the second unevenness was not formed was used.
[Production of matte embossing roll]
On the roll whose material of the roll surface is iron, as shown in Table 1, hatching-shaped indentation is performed with a mesh # 200 by a mesh engraving method by mesh engraving method to form a first unevenness. Then, a chromium plating layer of about 5 μm was formed to obtain a matte embossing roll.

※% by mass in Table 1 indicates% by 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 with sand blast of 250 mesh or less, Asperities having a surface roughness (Ra) of 0.3 to 1 μm and a maximum height (Rz) of 3 to 9 μm were formed on the film surface. And, all of the blocking resistance, quick dissolution and roll durability could be made good. Furthermore, in Examples 1 to 5, the Ra ratio and Rz ratio were close to 1, and even if the film was left for a long time in a high temperature environment, the shape of the irregularities on the film surface could be maintained.
On the other hand, in Comparative Examples 1 to 4, the embossing roll was not formed, and even when the embossing was performed, the predetermined first and second irregularities were not formed on the embossing 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 blocking resistance during long-term high-temperature storage or roll durability One did not get better.

Claims (5)

It is a water-soluble packaging film containing polyvinyl alcohol resin,
The film for water-soluble packaging which has the unevenness | corrugation whose surface roughness (Ra) is 0.3-1 micrometer, and the largest height (Rz) is 3-9 micrometers.   The water-soluble packaging film according to claim 1, further comprising a plasticizer.   The water-soluble packaging film according to claim 1 or 2, 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 3, wherein the saponification degree of the polyvinyl alcohol resin is 80 to 99.9 mol%. The water-soluble packaging film according to any one of claims 1 to 4, wherein the polyvinyl alcohol resin contains unmodified polyvinyl alcohol.