JPH0777521B2 - Method for forming water-soluble polymer thin film on the surface of water-soluble or water-dispersible paper - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to sowing of vegetables, flowers, etc.,
The present invention relates to a method for producing a seedling-raising sheet used for raising seedlings, and particularly to a seedling-raising seedling capable of efficiently mounting small-diameter seeds.
The present invention relates to a method for manufacturing a sheet for use .

[0002]

2. Description of the Related Art In recent years, in the field of hydroponics, a seeding and raising seedling sheet has been used in which a small dot adhesive is applied on water-soluble paper so that seeds can be mounted. When seeds are mounted on the adhesive dots one by one, if the seed size becomes smaller, the adhesive dots must be made smaller accordingly, but when the water-soluble paper surface is rough, Difficult to form. Due to such technical difficulty, a seeding and raising seedling sheet capable of easily and effectively mounting extremely small seeds has not been produced yet. Therefore, as a sheet base material for ultra-small dots, water-soluble paper whose surface is smoothed with a water-soluble polymer is desirable.

Paper obtained by laminating water-soluble paper and water-soluble polyvinyl alcohol is already on the market (for example, Dissolvo WAL manufactured by Mishima Paper Co., Ltd.). When a water-soluble polymer film is to be formed on the surface of a water-soluble paper, the method of directly coating an aqueous solution of the polymer cannot be adopted because the water-soluble paper as the base material is water-soluble. Therefore, in general, a method in which the separately prepared paper and the polymer film are bonded together
(Lamination method) is used. However, in the case of using the laminating method, if the polymer film is thick, the bonded product will be curved by a slight change in conditions. Therefore, when adopting a method of preliminarily forming and bonding a polymer film rich in water solubility, it is necessary to make the film thickness as thin as possible, but it is difficult to reduce the thickness to 30 μm or less with the current technology. In addition, the finished product becomes extremely expensive.

[0004]

As described above, in the prior art, a satisfactory method for forming a water-soluble polymer thin film on a water-soluble or water-dispersible substrate has not been established. Also, for this reason, a seeding and raising seedling sheet capable of efficiently mounting small diameter seeds has not been obtained.

The object of the present invention is to solve the problems of the above-mentioned prior art and to provide a structure of a water-soluble or water-dispersible substrate (hereinafter simply referred to as a water-soluble substrate), An object of the present invention is to provide a method for forming a thin film of a water-soluble polymer on a water-soluble substrate at a low cost without damaging the shape.

[0006]

The above object is to provide a method of forming a thin film of a water-soluble polymer on the surface of water-soluble or water-dispersible paper, wherein the water-soluble polymer is an organic solvent easily soluble in water and water. Is dissolved in a mixed solvent of, and the solution is applied to the surface of a support, and before or after partially removing the mixed solvent, water-soluble or water-dispersible paper is stuck, and then the mixed solvent. It can be achieved by forming a water-soluble polymer thin film on the surface of a water-soluble or water-dispersible paper, which is characterized in that the support is peeled off after removing.

At this time, in the above-mentioned procedure, the water-soluble polymer solution is applied to the surface of the support and is bonded to the water-soluble substrate before the solvent is completely removed. It is necessary to spread evenly without being repelled by the surface. On the other hand, regarding the support, it is necessary that the support is hard to repel even when it is coated with the water-soluble polymer solution, and that it can be easily peeled off from the water-soluble polymer thin film after drying.

By forming a uniform water-soluble polymer thin film on the surface of the water-soluble base material, it becomes possible to coat the small adhesive dots at a desired interval and in a desired pattern, so that the seedling raising seedling has excellent characteristics. The sheet for use can be easily and inexpensively produced.

[0009]

It is extremely difficult to apply a polymer using water as a solvent on a water-soluble substrate without changing its internal structure or surface state. Therefore, in order to form a thin film of a water-soluble polymer on a water-soluble substrate without significantly impairing its properties, it is necessary to improve the coating method and the water-soluble polymer solution.

Regarding the coating method, it is difficult to directly coat the surface of the water-soluble base material with the water-soluble polymer solution because the water-soluble base material is dissolved and the shape is destroyed. For this, the water-soluble polymer solution is coated on a support that has a flat surface and does not penetrate the water-soluble polymer solution, and the water-soluble substrate is attached to A polymer thin film can be formed. At this time, the water-soluble polymer solution is applied on the support, and the water-soluble substrate is attached after the solvent is completely removed, because the water-soluble polymer thin film itself does not have tackiness. It is impossible. Therefore, it is necessary to bond the water-soluble base material before or after removing the solvent to some extent.

Here, examples of the water-soluble polymer include polyvinyl alcohol, carboxymethylcellulose sodium salt, methylcellulose, hydroxypropylcellulose, hydroxyethylcellulose, starch, dextrin, casein sodium, pullulan, polyvinylpyrrolidone, sodium acrylate and the like. . Of these, partially saponified polyvinyl alcohol having a saponification degree of 90% or less is particularly effective in view of solubility in water, economy and the like.

With respect to the above water-soluble polymer solution, when the polymer solution is coated on the support, the uniform water-soluble polymer thin film cannot be formed if the polymer solution is repelled by the support. Therefore, it is desirable that the support does not or does not easily repel.

Here, the case where polyvinyl alcohol (hereinafter abbreviated as PVA) is taken as the water-soluble polymer will be described. PVA has different solubility in water depending on its saponification degree and polymerization degree. Fully saponified PVA dissolves easily in hot water, but not in room temperature water. On the other hand, low saponification degree (for example, saponification degree 90% or less)
Things easily dissolve in water at room temperature. Regarding the degree of polymerization, the higher the degree of polymerization, the lower the solubility in water, but the degree of polymerization is not so affected. Further, once dissolved in water, the dissolved state is maintained even if the temperature is lowered. Therefore, when a highly water-soluble one is required at room temperature, a saponification degree of 90% or less is used.

As described above, PVA has a certain solubility in water, but it is hardly soluble in a solvent other than water except for a special solvent such as dimethyl sulfoxide.
Here, when an organic solvent that dissolves well in water is added to the aqueous solution of PVA, the solubility of PVA gradually decreases, the solution gels in the region of a certain mixing ratio of both solvents, and the amount of organic solvent further increases. As the value increases, PVA begins to precipitate. Therefore, P
Repulsion by the support can be controlled by using a mixed solvent in which VA does not precipitate. Also, thickeners (eg, carboxymethyl cellulose sodium salt)
The same effect can be obtained by adding the surfactant, and the addition of the surfactant improves the wettability with respect to the support, whereby a uniform PVA thin film can be formed on the surface of the water-soluble substrate.

As the organic solvent to be mixed with water, many kinds such as alcohols, ketones, esters and ethers can be used, but in view of compatibility with water, economical efficiency, etc., methanol, Monohydric alcohols such as propanol are suitable.

The water-soluble polymer thin film may be formed on only one side of the water-soluble substrate or on both sides.

Looking at the printing of adhesives, generally, when the surface to be printed is flat and the wettability of printing ink is good, it is 0.
Printing with a width of about 1 mm is extremely easy, but it is difficult to print finely on paper that has a rough surface to be printed, is rich in irregularities, and has large bleeding of printing ink. The water-soluble base material coated with the PVA film has a significantly improved surface condition and becomes uniform and flat, and since the penetration of printing ink is prevented, it is possible to print a fine pattern on the surface. It is exactly the same when the adhesive solution is used as the printing ink. Therefore, it becomes possible to directly form the small dots of the adhesive on the surface of the water-soluble substrate coated with the PVA thin film, and the small dots of the adhesive are mounted. A sheet for seeding and raising seedlings can be obtained.

[0018]

EXAMPLES Hereinafter, the constitution of the present invention will be described more specifically by way of examples.

[0019]

Example 1 First, P having a saponification degree of 88% and an average polymerization degree of 1700 was used.
Mixing ratio of 120 g VA to water and isopropyl alcohol 1:
880 g of a mixed solvent of 0.5 was added and well stirred to obtain a clear solution of PVA. Then, as shown in FIG. 1, this solution 2 is coated on a commercially available polyester film 1 using a comma coater, and a water-soluble paper 3 made of a commercially available nonwoven fabric is attached to the coated surface (FIG. 1 (c)). Immediately after drying, the polyester film used as the support was peeled off to obtain a water-soluble paper having a PVA thin film on one side (FIG. 1 (d)).
At this time, almost no damage to the water-soluble paper due to the solvent containing water was observed.

Also, in the same manner as above, P on both sides of the water-soluble paper
A VA thin film was formed. Also in this case, almost no damage to the water-soluble paper was observed.

[0021]

[Example 2] PVA 100 having a saponification degree of 88% and an average degree of polymerization of 1700
g was added to 900 g of a mixed solvent of water and methanol at a mixing ratio of 1: 1 and stirred well to obtain a clear solution of PVA. This solution is coated on a commercially available polyester film using a doctor blade, a water-soluble paper made of a commercially available non-woven fabric is attached to the coated surface, and immediately after drying, the polyester film used as a support is peeled off to give one side. To PVA
A water-soluble paper on which a thin film was formed was obtained. At this time, almost no damage to the water-soluble paper due to the mixed solvent containing water was observed. In addition, in the same manner as in Example 1, both sides of the water soluble paper
Although a PVA thin film was formed, damage to the water-soluble paper was hardly observed in this case as well.

[0022]

[Example 3] A dot-shaped adhesive 5 was prepared by applying an adhesive solution having a viscosity of 4 Pa · s dissolved in a high-boiling-point solvent on the PVA thin film-coated water-soluble paper 3 prepared by the method described in Example 1 in dots. A seeding sheet was prepared having FIG. 2 (a) is a sectional view of the seeding sheet, and FIG. 2 (b) is a plan view of the seeding sheet. Here, the size of the adhesive dot is from 0.2mmφ to 0.1mm
Although every 1 mmφ was set, good adhesive dots could be formed in any case.

[0023]

As described above, the method of the present invention is applied to the method of forming a thin film of a water-soluble polymer on the surface of a water-soluble substrate to solve the problems of the prior art. It has been possible to provide a method capable of forming a thin film of a water-soluble polymer on a water-soluble substrate at low cost without impairing the structure and shape of the water-soluble substrate.

Further, by applying this method,
It is possible to obtain a water-soluble base material having a water-soluble polymer thin film surface that is excellent in smoothness and does not penetrate ink or the like, and as a result, a water-soluble group in which small dots of adhesive are provided at desired intervals and in desired patterns. It was possible to obtain a sheet for seeding and raising seedlings made of wood.

[Brief description of drawings]

FIG. 1 is a diagram showing a procedure of a method of the present invention.

FIG. 2 is an explanatory view of a method for producing a seedling raising seedling sheet of the present invention,
(a) is a sectional view and (b) is a plan view.

[Explanation of Codes] 1 ... Polyester film, 2 ... PVA solution, 3 ... Water-soluble base material, 4 ... PVA thin film, 5 ... Adhesive.

Claims (4)

[Claims] 1. A method of forming a thin film of a water-soluble polymer on the surface of water-soluble or water-dispersible paper, wherein the water-soluble polymer is dissolved in a mixed solvent of water and an organic solvent which is easily water-soluble, The solution is coated on the surface of the support, and water-soluble or water-dispersible paper is attached before or after partially removing the mixed solvent, and then the support is peeled off after removing the mixed solvent. A method of forming a water-soluble polymer thin film on the surface of water-soluble or water-dispersible paper. 2. The surface of a water-soluble or water-dispersible paper according to claim 1, wherein the water-soluble polymer is polyvinyl alcohol, preferably polyvinyl alcohol having a saponification degree of 90% or less. Method for forming water-soluble polymer thin film. 3. The water-soluble polymer thin film is formed on the surface of the water-soluble or water-dispersible paper according to claim 1, wherein the water-soluble organic solvent is a monohydric alcohol. how to. 4. The support to which the water-soluble polymer is applied is one in which the water-soluble polymer solution does not penetrate and is applied uniformly, and is water-soluble or The water-soluble polymer on the surface of a water-soluble or water-dispersible paper according to claim 1, which is easily peeled from a water-soluble polymer thin film formed on the surface of a water-dispersible paper. Method for forming thin film.