JPH06340035A - Formation of membrane of polyvinyl alcohol type polymer and polyvinyl alcohol type polymer coated sheet - Google Patents

Abstract

PURPOSE:To provide a polyvinyl alcohol type polymer coated sheet excellent in printability and gas barrier properties. CONSTITUTION:A polyvinyl alcohol type polymer containing 0.05-15mol% of an ethylene group having a 2-18C alkyl group on its side chain is dissolved in a mixed solvent of a water and an org. solvent easily soluble in water to prepare a mixed soln. which is, in turn, applied to support paper soluble or easily dispersible in water to form the membrane of the polyvinyl alcohol type polymer. By this method, a polyvinyl alcohol type polymer coated sheet is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a thin film of a polyvinyl alcohol polymer, and a polyvinyl alcohol polymer coated sheet obtained by the method.

[0002]

2. Description of the Related Art In recent years, water-soluble or water-dispersible paper has been widely used in the fields of agriculture and toiletries. Above all, packaging bags and sheets for seeding and raising seedlings are
In order to improve mechanical strength and printability and to impart a barrier property, a water-soluble polymer is coated on the surface of a support paper which is water-soluble or easily dispersible in water. Polyvinyl alcohol (hereinafter sometimes referred to as PVA) is generally used as the water-soluble polymer. When forming a water-soluble polymer film on the surface of water-soluble or water-dispersible paper,
Since the paper as the support is water-soluble or easily dispersible in water, it is not preferable to directly apply the aqueous solution of the polymer since the structure and shape of the paper will be impaired. Therefore,
Currently, water-soluble or water-dispersible paper and PV
A method of sticking the A film is used.

However, in this method, the film thickness is 30 μm.
It is technically difficult and costly to make the following. Therefore, as an improved method of directly applying the aqueous polymer solution, PVA is dissolved in a mixed solvent of water and an organic solvent easily soluble in water, and then the obtained mixed solution is applied to the surface of the support paper. The method of forming a thin film of PVA on the surface of a water-soluble or water-soluble support paper at low cost without damaging the structure and shape of the paper (JP-A-4-3)
No. 51545) has been proposed.

In this method, the proportion of the organic solvent can be increased by lowering the saponification degree of PVA. However, if the saponification degree is too low, the PVA itself becomes soft and the winding step after coating and drying is performed. In, the fusion between the thin film occurs,
There is a problem in that the water-solubility of PVA is impaired and the printability is lowered, so that the application purpose of PVA cannot be achieved. Furthermore, if the proportion of the organic solvent is too large, PV
There is a problem that the solubility in the mixed solution of A is lowered and the PVA polymer is insolubilized to be precipitated and a uniform thin film cannot be obtained. In fact, since the proportion of the organic solvent cannot be increased, the paper structure and It is difficult to form a uniform thin film of a water-soluble polymer without losing its shape.

[0005]

The conventional method as described above has a problem that a water-soluble polymer thin film cannot be formed on a paper surface which is water-soluble or easily dispersible in water. It is an object of the present invention to form a thin film of a water-soluble polymer on the surface of a support paper without impairing the structure and shape of the water-soluble or water-dispersible support paper.

[0006]

Means for Solving the Problems As a result of intensive studies for solving the above problems, the present inventors have surprisingly found that a specific PVA-based polymer is mixed with water and an organic solvent easily soluble in water. It has been found that the above object can be achieved by applying a mixed solution dissolved in a solvent, and the present invention has been completed.

That is, according to the present invention, a polyvinyl alcohol polymer containing 0.05 to 15 mol% of an ethylene group having a side chain of an alkyl group having 2 to 18 carbon atoms as a structural unit is easily soluble in water and water. A method for forming a thin film of a polyvinyl alcohol-based polymer, characterized in that a mixed solution dissolved in a mixed solvent with an organic solvent is applied onto a water-soluble or water-dispersible support paper. .

Further, the present invention is directed to a polyvinyl alcohol polymer-coated sheet obtained by the above method.

A polyvinyl alcohol polymer containing 0.05 to 15 mol% of an ethylene group having a side chain of an alkyl group having 2 to 18 carbon atoms as a structural unit is an organic solvent in a mixed solvent system of water and an organic solvent. It can be uniformly dissolved in a mixed solvent having an increased ratio. By coating the polyvinyl alcohol-based polymer solution having a high organic solvent ratio on the support paper, a uniform thin film can be formed without impairing the structure and shape of the support paper.

The paper as the support in the present invention is water-soluble or water-dispersible paper, and commercially available ones can be used.

The PVA polymer used in the present invention is
PVA containing an ethylene group having a C2-18 alkyl group in its side chain as a structural unit in an amount of 0.05 to 15 mol%
It is a polymer and is produced by a known method. For example, these are alkyl vinyl ethers such as butyl vinyl ether, lauryl vinyl ether, stearyl vinyl ether, butyl acrylate,
One or more monomers selected from acrylic acid esters such as octyl acrylate and long chain branched aliphatic vinyl esters such as vinyl pivalate and vinyl versatate, and fats such as vinyl formate and vinyl acetate It is obtained by saponifying a copolymer with a group vinyl ester. At this time, other monomers copolymerizable with these monomers may be copolymerized within a range not impairing the effects of the present invention.

As other copolymerizable monomers, unsaturated acids such as ethylene, (meth) acrylic acid, crotonic acid, maleic acid and itaconic acid or salts thereof or methyl esters thereof, acrylonitrile, (meth) acrylamide, Unsaturated sulfonic acids such as methyl vinyl ether, vinylpyrrolidone, vinylamine, allyl alcohol, allyl acetate, allylsulfonic acid, vinylsulfonic acid, acrylamidopropanesulfonic acid or salts thereof, acrylamidopropylmethylammonium chloride and the like, but not limited to these It does not make one.

It can also be obtained by a reaction (acetalization reaction) between a PVA polymer and aldehydes,
The PVA polymer used at this time is unmodified PVA.
Not only a system polymer but also a saponified product of a copolymer of an aliphatic vinyl ester and another monomer may be used as long as the effects of the present invention are not impaired. The method for producing the PVA polymer used in the present invention is not limited to the above method.

The PVA-based polymer contains water and an organic solvent easily soluble in water when the ethylene group as a structural unit having an alkyl group having 2 to 18 carbon atoms in its side chain is less than 0.05 mol%. It is not possible to increase the mixing ratio of the organic solvent in the mixed solvent. On the other hand, if it exceeds 15 mol%, P
The water solubility of the VA resin is impaired.

The degree of saponification of the PVA-based polymer is not particularly limited, but in consideration of the water-soluble retention of the PVA-based polymer, printability of the thin film formed on the paper surface, gas barrier property, etc.
It is preferably 0 mol% or more.

The degree of polymerization of the PVA polymer is not particularly limited, but is 300 to 5 in consideration of the strength of the coating film and the viscosity of the solution.
000 is preferable.

In the present invention, a mixed solvent of water and an organic solvent easily soluble in water, which dissolves the PVA polymer, is
It is desirable that the mixing ratio of the organic solvent is as high as possible.
Examples of the organic solvent include alcohols, ketones,
Esters and the like can be used, but alcohols such as methanol, ethanol, n-propanol, isopropanol and butanol are preferable.

The method for preparing the mixed solution is not particularly limited. For example, a predetermined amount of an organic solvent may be added to a solution prepared by previously dissolving the PVA polymer in water with stirring, or may be mixed with water. It may be prepared by adding a PVA polymer to a mixed solvent of organic solvents. In the mixed solvent, it is desirable that the mixing ratio of the organic solvent is as large as possible.

Next, the solution of the PVA-based polymer thus obtained is applied to water-soluble or water-dispersible paper which is a support. The coating method is not particularly limited,
It can be applied by a known printing application method, spray application method or the like. At this time, one side or both sides can be applied.

[0020]

EXAMPLES Next, the present invention will be described in more detail with reference to Examples and Comparative Examples. Example 1 Containing 0.8 mol% of lauryl vinyl ether unit,
100 g of a PVA-based polymer having a degree of saponification of 92 mol% and a degree of polymerization of 1500 was added to 900 g of a mixed solvent of water and methanol at a mixing ratio of 5: 5 and stirred to obtain a solution. This is applied to one side of commercially available water-soluble paper with a bar coater (application amount: 1
g / m ² ), immediately dry in a 105 ° C drum dryer,
A PVA polymer coated sheet without damage was obtained.

Example 2 100 g of a water-soluble PVA polymer having a butyralization degree of 12 mol% by a butyral reaction of PVA having a saponification degree of 97 mol% and a polymerization degree of 1700 was mixed with water and methanol at a mixing ratio of 6: 4. The mixed solvent was added to 900 g and stirred to obtain a solution. This was coated on water-soluble paper and dried in the same manner as in Example 1 to obtain a PVA-based polymer-coated sheet without damage.

Comparative Example 1 100 g of a water-soluble PVA polymer having a degree of saponification of 80 mol% and a degree of polymerization of 1000 was added to 900 g of a mixed solvent of water and methanol at a mixing ratio of 7: 3, and the mixture was stirred. It did not dissolve and no uniform solution was obtained. In addition, the water-soluble PV
The A-type polymer was added to a mixed solvent of water and methanol at a mixing ratio of 8: 2 and stirred to obtain a solution. This was coated on water-soluble paper and dried in the same manner as in Example 1 to obtain a sheet. This sheet had a large number of holes.

[0023]

As described above, according to the present invention, a thin film of the PVA polymer is formed on the surface of the support paper without impairing the structure and shape of the water-soluble or water-dispersible support paper. Can be uniformly formed, whereby a PVA polymer-coated sheet excellent in printability and gas barrier property can be obtained.

Claims (2)

[Claims] 1. An ethylene group having a side chain of an alkyl group having 2 to 18 carbon atoms as a structural unit is 0.05 to 15 mol%.
A polyvinyl alcohol-based polymer containing a mixed solution prepared by dissolving a mixed solvent of water and an organic solvent which is easily soluble in water, a polyvinyl alcohol characterized by being applied on a support paper which is water-soluble or easily dispersible in water. Method for forming thin film of polymer. 2. A polyvinyl alcohol polymer-coated sheet obtained by the method according to claim 1.