JP5324504B2 - Laminated body - Google Patents

Description

  The present invention relates to a laminate that has high penetration strength and can be suitably used as a film for plant cultivation, a film for plant cultivation formed from the laminate, and a method for producing the laminate.

  In plant hydroponics, a non-porous hydrophilic film is placed between the nutrient solution and the plant so that the root penetrates the non-porous hydrophilic film as the plant grows. Has been proposed, and the use of hydrophilic materials such as polyvinyl alcohol, cellophane, cellulose acetate, cellulose nitrate, ethyl cellulose, and polyester as the nonporous hydrophilic film material has been proposed. (See Patent Document 1). However, even with such a plant cultivation method, there is a concern that bacteria or the like may move to the nutrient solution through the penetrating portion and the nutrient solution may rot. Therefore, there has been a demand for a film that has high nutrient permeability and is difficult to penetrate even when the roots of plant bodies grow.

JP 2008-61503 A

  An object of the present invention is to provide a laminate having high nutrient permeability and good plant growth, further having high penetration strength and capable of suppressing root penetration, a method for producing the laminate, and plant cultivation formed from the laminate To provide a film.

  The present inventors have intensively studied to achieve the above object. As a result, it has been found that by laminating a plurality of polyvinyl alcohol polymer films having a specific degree of swelling, nutrient permeability is high and penetration strength is increased. The present inventors have further studied based on these findings and completed the present invention.

That is, the present invention
[1] A laminate having a polyvinyl alcohol polymer layer (A layer) and a polyvinyl alcohol polymer layer (B layer), wherein the swelling degree of the A layer is a mass%, and the swelling degree of the B layer is a laminate satisfying the following formula (1) when b mass% is obtained;
ba- ≧ 20 (1)
[2] The laminate according to the above [1], wherein the swelling degree of the A layer is 160% by mass or less,
[3] The laminate according to the above [1] or [2], wherein the swelling degree of the B layer is 180% by mass or more,
[4] The laminate according to any one of [1] to [3], wherein the thickness of the layer A is 10 to 60% of the thickness of the laminate.
[5] The laminate according to any one of the above [1] to [4], wherein the polymerization degree of each polyvinyl alcohol polymer constituting the A layer and the B layer is 1500 or more.
[6] The laminate according to any one of the above [1] to [5], wherein the saponification degree of each polyvinyl alcohol polymer constituting the A layer and the B layer is 98.0 mol% or more.
[7] A plant cultivation film formed from the laminate according to any one of [1] to [6] above,
[8] A method for producing a laminate comprising a step of laminating a polyvinyl alcohol polymer film having a degree of swelling of a mass% and a polyvinyl alcohol polymer film having a degree of swelling of b mass%, comprising the following formula (1 Manufacturing method satisfying
ba- ≧ 20 (1)
About.

  ADVANTAGE OF THE INVENTION According to this invention, nutrient permeability | transmittance is high, the growth of a plant body is favorable, and also the laminated body which has a high penetration strength and can suppress root penetration, its manufacturing method, and the plant cultivation formed from the said laminated body A film is provided.

The present invention is described in detail below.
The laminate of the present invention has a polyvinyl alcohol [hereinafter, “polyvinyl alcohol” may be abbreviated as “PVA”]-based polymer layer (A layer) and a PVA-based polymer layer (B layer). When the swelling degree of the A layer is a mass% and the swelling degree of the B layer is b mass%, the following formula (1) is satisfied.
ba- ≧ 20 (1)

By satisfying the above formula (1), a laminate having excellent penetration strength and nutrient permeability can be obtained. From the viewpoint of improving penetrating strength and nutrient permeability, ba is preferably in the range of 20 to 100, and more preferably in the range of 30 to 70.
In this specification, the degree of swelling is a value obtained by dividing the mass when layer A or layer B is immersed in distilled water at 30 ° C. for 30 minutes by the mass after drying at 105 ° C. for 16 hours. It can be measured by the method described later in the examples.

  The specific value of the degree of swelling of the A layer is preferably 160% by mass or less, more preferably 158% by mass or less, and preferably 155% by mass or less from the viewpoint of improving penetration strength. Further preferred. The swelling degree of the A layer is preferably 140% by mass or more. On the other hand, the specific value of the swelling degree of the B layer is preferably 180% by mass or more, more preferably 183% by mass or more, and 185% by mass or more from the viewpoint of improving nutrient permeability. More preferably it is. Moreover, it is preferable that the swelling degree of B layer is 240 mass% or less.

  There is no restriction | limiting in particular in the adjustment method of the swelling degree of A layer and B layer, For example, when heat-treating the PVA polymer film mentioned later used as these layers, it can adjust by changing heat treatment temperature and heat treatment time. In general, the degree of swelling can be reduced by increasing the heat treatment temperature and lengthening the heat treatment time.

  The layer structure of the laminate of the present invention is not particularly limited, and a laminate having a layer structure of A layer / B layer in which the A layer and the B layer are directly laminated; the A layer and the B layer include Laminate having a three-layer structure having a layer configuration of A layer / adhesive layer / B layer laminated via an adhesive; having two or more A layers and / or two or more B layers (if necessary A laminate having a layer structure of 3 or more layers (which may further have an adhesive layer); A layer, B layer, and layers other than A layer and B layer (additional adhesive layer if necessary) A layered body having a layer structure of three or more layers may be mentioned, but the layer A / B layer in which the A layer and the B layer are directly laminated because of easy production. A layer / adhesive layer / B layer formed by laminating an A layer and a B layer via an adhesive, or a laminate having a two-layer structure having a configuration It is preferably a laminate of three-layer structure having a layer structure.

  The method for producing the laminate of the present invention is not particularly limited as long as the laminate having the structure defined in the present invention is obtained. For example, the PVA-based polymer film is formed on the PVA-based polymer film that becomes the A layer or the B layer. A method of forming a B layer or an A layer by coating a solution containing a polymer and drying; a PVA polymer or a composition containing the same (PVA polymer and a plasticizer, surfactant and other components described later) A composition comprising at least one selected from the components) and extruding it onto a PVA polymer film to be the A layer or B layer; respectively, forming the B layer or A layer; A layer and B A PVA polymer film (a PVA polymer film having a degree of swelling of a mass% and a PVA polymer film having a degree of swelling of b mass%) to be layered in advance using a known method or the like. Prepared advance, lamination methods such as a method of bonding a thereof. Even when an adhesive layer is provided between layers, a laminate having a desired layer configuration is manufactured by appropriately selecting the above-described lamination method or other known lamination methods and repeating the operation as necessary. Can do. Among these, since it is easy to adjust the swelling degree of the A layer and the B layer, it is preferable to prepare a PVA polymer film to be the A layer and the B layer in advance, and bond them together. A method in which a PVA polymer film to be the A layer and the B layer is prepared in advance and these are bonded using an adhesive is more preferable. Although there is no restriction | limiting in particular in the adhesive agent which forms the said contact bonding layer, For example, what melt | dissolved the PVA type polymer in water can be used preferably.

  The total thickness of the laminate of the present invention is preferably in the range of 10 to 200 μm, more preferably in the range of 20 to 180 μm, and more preferably in the range of 20 to 180 μm from the viewpoints of penetration strength, productivity, and handleability. Is more preferably in the range of 40 to 120 μm. In addition, the thickness of a laminated body can measure | require thickness of arbitrary 5 places, and can obtain | require as those average values.

  In addition, the ratio of the thickness of the A layer to the thickness of the laminate (the total thickness when there are two or more A layers) is within a range of 10 to 60% from the viewpoint of improving penetration strength. It is preferable that it is within a range of 15 to 55%. On the other hand, the ratio of the thickness of the B layer to the thickness of the laminate (the total thickness when there are two or more B layers) is in the range of 40 to 90% from the viewpoint of improving nutrient permeability. Preferably, it is within the range of 45 to 85%.

  The width of the laminate of the present invention is not particularly limited and can be appropriately determined depending on the application. For example, when the laminate of the present invention is used as a plant cultivation film, the PVA polymer film If the width is too wide, it will be difficult to take care of the plant body. Therefore, the width of the PVA polymer film is preferably 2 m or less.

Examples of the PVA polymer constituting the A layer and the B layer include vinyl acetate, vinyl formate, vinyl propionate, vinyl butyrate, vinyl pivalate, vinyl versatate, vinyl laurate, vinyl stearate, vinyl benzoate, and acetic acid. What can be obtained by saponifying a polyvinyl ester polymer obtained by polymerizing one or more vinyl esters such as isopropenyl can be used. Among the above-mentioned vinyl esters, compounds having a vinyloxycarbonyl group (H ₂ C═CH—O—CO—) in the molecule are included from the viewpoint of ease of production, availability, and cost of the PVA polymer. Preferably, vinyl acetate is more preferable.

  The above-mentioned polyvinyl ester polymer is preferably obtained using only one or two or more kinds of vinyl esters as a monomer, and obtained using only one kind of vinyl ester as a monomer. Is more preferable, but may be a copolymer of one or more vinyl esters and other monomers copolymerizable therewith, as long as the effects of the present invention are not impaired. .

  Examples of other monomers copolymerizable with the vinyl ester include, for example, α-olefins having 2 to 30 carbon atoms such as ethylene, propylene, 1-butene and isobutene; (meth) acrylic acid or a salt thereof; (Meth) methyl acrylate, (meth) ethyl acrylate, n-propyl (meth) acrylate, i-propyl (meth) acrylate, n-butyl (meth) acrylate, i-butyl (meth) acrylate, ( (Meth) acrylic acid esters such as t-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, dodecyl (meth) acrylate, octadecyl (meth) acrylate; (meth) acrylamide, N-methyl ( (Meth) acrylamide, N-ethyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, diacetone (meth) acryl (Meth) acrylamide derivatives such as amide, (meth) acrylamide propanesulfonic acid or salts thereof, (meth) acrylamidepropyldimethylamine or salts thereof, N-methylol (meth) acrylamide or derivatives thereof; N-vinylformamide, N-vinyl N-vinylamides such as acetamide and N-vinylpyrrolidone; methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether, n-butyl vinyl ether, i-butyl vinyl ether, t-butyl vinyl ether, dodecyl vinyl ether, stearyl vinyl ether, etc. Vinyl ether; vinyl cyanide such as (meth) acrylonitrile; halogenated vinyl such as vinyl chloride, vinylidene chloride, vinyl fluoride, vinylidene fluoride; vinegar Allyl compounds such as allyl acid and allyl chloride; maleic acid or its salt, ester or acid anhydride; itaconic acid or its salt, ester or acid anhydride; vinylsilyl compound such as vinyltrimethoxysilane; unsaturated sulfonic acid be able to. Said polyvinyl ester-type polymer can have a structural unit derived from 1 type, or 2 or more types of an above described other monomer.

The proportion of structural units derived from the other monomers in the polyvinyl ester polymer is 15 mol% or less based on the number of moles of all structural units constituting the polyvinyl ester polymer. Preferably, it is 10 mol% or less, more preferably 5 mol% or less.
In particular, when the other monomer is a monomer that can be a monomer unit that promotes water solubility of the resulting PVA polymer, such as (meth) acrylic acid or unsaturated sulfonic acid. In order to prevent the film from dissolving when the obtained laminate is used as a film for plant cultivation, the proportion of structural units derived from these monomers in the polyvinyl ester polymer is polyvinyl ester Based on the number of moles of all structural units constituting the polymer, it is preferably 5 mol% or less, and more preferably 3 mol% or less.

  The PVA polymer constituting the A layer and the B layer is modified with one or two or more types of graft copolymerizable monomers as long as the effects of the present invention are not impaired. Also good. The graft copolymerization can be performed on at least one of the polyvinyl ester polymer and the PVA polymer obtained by saponifying it. Examples of the graft copolymerizable monomer include unsaturated carboxylic acids or derivatives thereof; unsaturated sulfonic acids or derivatives thereof; α-olefins having 2 to 30 carbon atoms, and the like. The proportion of structural units derived from the graft copolymerizable monomer in the polyvinyl ester polymer or PVA polymer is based on the number of moles of all structural units constituting the polyvinyl ester polymer or PVA polymer. It is preferable that it is 5 mol% or less.

  In the PVA polymer constituting the A layer and the B layer, a part of the hydroxyl groups may be cross-linked or may not be cross-linked. The PVA polymer constituting the A layer and the B layer may have a hydroxyl group partially reacted with an aldehyde compound such as acetaldehyde or butyraldehyde to form an acetal structure, or reacted with these compounds. The acetal structure may not be formed.

  The degree of polymerization of each PVA polymer constituting the A layer and the B layer is preferably 1500 or more from the viewpoint of the strength of the resulting laminate. When the degree of polymerization of the PVA polymer is 1500 or more, the penetration strength of the obtained laminate is increased, and the effect of suppressing root penetration is improved, so that it is suitable for use as a film for plant cultivation. However, if the polymerization degree of the PVA polymer is too high, it tends to lead to an increase in the production cost of the PVA polymer and poor processability during film formation. The degree of polymerization of each PVA polymer is more preferably in the range of 1500 to 10000, more preferably in the range of 2000 to 8000, and particularly preferably in the range of 2200 to 5000. . In addition, the polymerization degree of a PVA polymer as used in this specification means the average degree of polymerization measured according to description of JISK6726-1994.

  Further, the saponification degree of each PVA polymer constituting the A layer and the B layer is preferably 98.0 mol% or more from the viewpoint of water resistance of the obtained laminate, and 98.5 mol%. More preferably, it is more preferably 99.0 mol% or more. In this specification, the saponification degree of the PVA polymer is the total of the structural units (typically vinyl ester units) of the PVA polymer that can be converted to vinyl alcohol units by saponification and vinyl alcohol units. The proportion (mol%) of the number of moles of the vinyl alcohol unit relative to the number of moles. The degree of saponification can be measured according to the description of JIS K6726-1994.

  The A layer and the B layer preferably do not contain a plasticizer in terms of increasing the penetrating strength, but the PVA polymer is improved in productivity and handleability as long as the effects of the present invention are not impaired. In addition, a plasticizer may be included. As the plasticizer, polyhydric alcohol is preferably used, and specific examples include ethylene glycol, glycerin, propylene glycol, diethylene glycol, diglycerin, triethylene glycol, tetraethylene glycol, trimethylolpropane, and the like. The layer and the B layer can contain one or more of these plasticizers. Among these, glycerin is preferable in that the plastic effect of the A layer and the B layer is increased.

  The content of the plasticizer in each of the A layer and the B layer is preferably in the range of 1 to 20 parts by mass with respect to 100 parts by mass of the PVA polymer contained in each layer, and is 2 to 18 parts by mass. More preferably, it is in the range, and further preferably in the range of 3 to 15 parts by mass.

  Moreover, when manufacturing A layer and / or B layer using the undiluted | stock solution for manufacturing them, generation | occurrence | production of the thickness variation of the layer obtained by improving film forming property is suppressed, and film formation is carried out. When the PVA polymer film to be the A layer and / or B layer is produced using a metal roll or belt, the PVA polymer film can be easily peeled off from the metal roll or belt. It is preferable to mix a surfactant in the stock solution. And when A layer and / or B layer are manufactured from the undiluted | stock solution with which surfactant was mix | blended, surfactant may contain in the said A layer and / or B layer. The type of the surfactant contained in the stock solution for producing the A layer and / or the B layer, and thus the surfactant contained in the A layer and / or the B layer is not particularly limited, but from a metal roll or belt From the viewpoint of releasability, an anionic surfactant or a nonionic surfactant is preferable, and a nonionic surfactant is more preferable.

  As the anionic surfactant, for example, a carboxylic acid type such as potassium laurate; a sulfate ester type such as octyl sulfate; a sulfonic acid type such as dodecylbenzene sulfonate and the like are suitable.

Nonionic surfactants include, for example, alkyl ether types such as polyoxyethylene oleyl ether; alkylphenyl ether types such as polyoxyethylene octylphenyl ether; alkyl ester types such as polyoxyethylene laurate; polyoxyethylene laurylamino Alkylamine type such as ether; alkylamide type such as polyoxyethylene lauric acid amide; polypropylene glycol ether type such as polyoxyethylene polyoxypropylene ether; alkanolamide type such as oleic acid diethanolamide; polyoxyalkylene allyl phenyl ether The allyl phenyl ether type is preferred.
These surfactants can be used alone or in combination of two or more.

  When a surfactant is added to the stock solution for producing the A layer and / or the B layer, the content of the surfactant in the stock solution, and thus the content of the surfactant in the A layer and / or the B layer is , Preferably in the range of 0.01 to 0.5 parts by weight, with respect to 100 parts by weight of the PVA polymer contained in the stock solution or the A layer or B layer, More preferably, it is in the range, more preferably in the range of 0.05 to 0.1 parts by mass. When the content of the surfactant is 0.01 parts by mass or more with respect to 100 parts by mass of the PVA polymer, the film forming property and the peelability can be improved. On the other hand, when the PVA polymer film to be the A layer and / or the B layer is produced by the surfactant content being 0.5 parts by mass or less with respect to 100 parts by mass of the PVA polymer, It can be suppressed that the surfactant is bleed out on the surface thereof to cause blocking and the handling property is lowered.

Each of the A layer and the B layer may be composed of only the PVA polymer, or may be composed of only the PVA polymer and the above-described plasticizer and / or surfactant. You may contain other components other than above-described PVA polymer, a plasticizer, and surfactant, such as antioxidant, antifreezing agent, pH adjuster, hiding agent, coloring inhibitor, and oil agent.
The proportion of the total of the PVA polymer, the plasticizer and the surfactant in each of the A layer and the B layer is preferably in the range of 50 to 100% by mass, and in the range of 80 to 100% by mass. It is more preferable that it is in the range of 95 to 100% by mass.

  The PVA polymer film to be the A layer and / or the B layer is composed of the above-described PVA polymer constituting the PVA polymer film and, if necessary, components such as a plasticizer and a surfactant in a solvent. It can manufacture using the stock solution melt | dissolved in. Such a stock solution can also be used to form a B layer or an A layer by coating it on a PVA polymer film to be an A layer or a B layer and drying it.

  Examples of the solvent used for preparing the stock solution include water, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, ethylene glycol, glycerin, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, and trimethylol. Propane, ethylenediamine, diethylenetriamine and the like can be mentioned, and one or more of these can be used. Among these, water is preferable from the viewpoint of environmental load and recoverability.

  Further, the volatile content ratio of the stock solution (content ratio of volatile components such as a solvent removed by volatilization or evaporation during film formation in the stock solution) varies depending on the film forming method, film forming conditions, etc., but is 50 to 95% by mass. Is preferably within the range of 55 to 90% by mass. When the volatile content of the stock solution is 50% by mass or more, the viscosity of the film-forming stock solution does not become too high, and filtration and defoaming during the preparation of the stock solution are performed smoothly, and the A layer and / or less foreign matter and defects The manufacture of the B layer is facilitated. On the other hand, when the volatile fraction of the stock solution is 95% by mass or less, the concentration of the film-forming stock solution does not become too low, and industrial production of the A layer and / or the B layer is facilitated.

  Examples of the film forming method for producing the PVA polymer film that becomes the A layer and / or the B layer using the above-described stock solution include, for example, a wet film forming method, a gel film forming method, and a dry casting film forming method. And an extrusion film forming method. These film forming methods may be employed alone or in combination of two or more. The PVA polymer film can be dried or heat-treated as necessary.

As a specific method for forming a PVA polymer film, for example, a T-type slit die, a hopper plate, an I-die, a lip coater die, or the like, or a cast film forming method is adopted. The stock solution for film formation is uniformly discharged or cast on the peripheral surface of the heated heated first roll (or belt) located on the most upstream side, and on the peripheral surface of the first roll (or belt) The periphery of a heated second roll (or drying roll) that evaporates and dries volatile components from one side of the discharged or cast film and then rotates the other side of the discharged or cast film. After passing over the surface and drying and further drying on the peripheral surface of one or more rotating heated rolls located downstream of it, or after passing through a hot air dryer and further drying Winding device Method for winding can be industrially employed preferably. Drying with a heated roll and drying with a hot air dryer may be performed in an appropriate combination.
In order to adjust the PVA polymer film to an appropriate state, it is desirable to include a heat treatment device; a humidity control device; a motor for driving each roll; a speed adjustment mechanism such as a transmission.

The laminate of the present invention has high penetration strength. Here, the penetration strength of the laminate can be measured by a measurement method of penetration resistance described later in Examples. It can be judged that the penetration strength is better as the penetration resistance is higher. The penetration resistance force tends to increase when the degree of swelling is low or when the thickness is thick. The penetration resistance (60 μm value) of the laminate of the present invention when the thickness of the entire laminate is 60 μm is preferably 16N or more, more preferably 17N or more, and further preferably 18N or more. preferable. When the penetration resistance (60 μm value) is in the above range, the roots hardly penetrate the film when the laminate is used as a plant cultivation film. When the thickness of the entire laminate is other than 60 μm, the penetration resistance (X μm value) obtained by measuring the thickness of the laminate (X μm) is used, and the thickness is 60 μm according to the following formula (2). It can be set as the said penetration resistance force (60 micrometer value) in terms of the time value.
Penetration resistance (60 μm value) = Penetration resistance (X μm value) x 60 / X (2)

  The laminate of the present invention is preferably used as a film for plant cultivation because it has high nutrient permeability, good plant growth, high penetration strength, and can suppress root penetration. There is no restriction | limiting in particular in the method for forming a film for plant cultivation from said laminated body, You may use the obtained laminated body as a film for plant cultivation as it is, and by performing cutting, bonding, etc. suitably You may use it after making it into a desired shape.

  As a specific method of using the film for plant cultivation, for example, the film for plant cultivation is arranged on the ground soil provided with a depression as necessary so that the A layer is on the upper surface, and the plant body is formed thereon. A method of growing the plant body by separating the soil and the plant body with the film for plant cultivation and arranging them so that they are not in direct contact with each other; on an aqueous solution (nutrient solution) containing nutrients of the plant body By arranging the plant cultivation film so that the A layer is on the upper surface and arranging the plant body thereon, the aqueous solution and the plant body are separated by the plant cultivation film so that they do not come into direct contact with each other. And a method for growing the plant body. By doing so, it is possible to suppress the contamination of the plant body by microorganisms, bacteria, viruses, residual agricultural chemicals, etc. in the ground soil, or through the root of the plant body in an aqueous solution containing the nutrients of the plant body. In this way, it is possible to prevent bacteria and the like from entering and the aqueous solution from decaying.

The present invention will be specifically described with reference to the following examples, but the present invention is not limited to these examples.
In addition, each measurement or evaluation method of the swelling degree of a PVA film and the penetration resistance of a laminated body (or PVA film) and nutrient permeability which were employ | adopted in the following manufacture examples, an Example, and a comparative example is shown.

Measurement of swelling degree of PVA film The PVA film was cut to 1.5 g and immersed in 1000 g of distilled water at 30 ° C. After dipping for 30 minutes, the PVA film was taken out, the surface water was blotted with a filter paper, and then the mass “X” was measured. Subsequently, the PVA film was dried with a dryer at 105 ° C. for 16 hours, then the mass “Y” was measured, and the degree of swelling was calculated by the following formula (3).
Swelling degree (mass%) = 100 × X / Y (3)

Measurement of penetration resistance of laminate (or PVA film) The laminate (or PVA film) was cut into a 3 cm square and immersed in 1000 g of distilled water at 20 ° C. After immersing for 1 minute, the laminate (or PVA film) was taken out and sandwiched between two 1 mm thick stainless steel plates having a thickness of 1 mm with a hole having a diameter of 1 cm in the center, and the two opposing sides were fastened with binder clips. Next, the above sample is fixed to the lower grip of the tabletop precision universal testing machine “Autograph AGS-J” manufactured by Shimadzu Corporation, and the nail has a length of 65 mm and a thickness of 4.6 ± 0.2 mm. Was fixed, and the center of the hole was pierced at a speed of 100 mm / min. The load at that time was defined as penetration resistance (unit: N).

Evaluation of nutrient permeability of laminated body (or PVA film) A sieve was placed inside the bowl, and a laminated body (or PVA film) was placed on the sieve. In the case of Example 1, the PVA film-1 was on the upper side. Next, 150 g of 5% glucose aqueous solution is added between the bowl and the film, and 150 g of distilled water is added onto the laminate (or PVA film), so that the glucose aqueous solution and distilled water are laminated (or PVA film). ) To be isolated. Subsequently, the whole was wrapped with a polyvinylidene chloride film to prevent evaporation of moisture. After standing at 23 ° C. for 24 hours, the concentration of glucose was measured for each of the liquid on the bowl side (original glucose aqueous solution) and the liquid on the other side (original distilled water). A case where the difference between the two concentrations was less than 2.0% was evaluated as “good”, and a case where the difference was 2.0% or more was evaluated as “bad”. In the above evaluation, the glucose concentration means the Brix concentration measured using a digital refractometer “AR200” manufactured by Thermo Fisher Scientific Co., Ltd.

[Production example]
Production of PVA Film Sample An aqueous solution containing 10% by mass of PVA having a polymerization degree of 2400 and a saponification degree of 99.9 mol% was dried on a metal roll at 60 ° C. to obtain a PVA film having a predetermined thickness. The obtained PVA film was fixed to a frame and heat-treated so as to have a predetermined degree of swelling.

[Example 1, Comparative Examples 1 and 2]
On one side of the PVA film (PVA film-1) shown in Table 1 obtained in the above production example, an aqueous solution containing 4% by mass of PVA having a polymerization degree of 2400 and a saponification degree of 99.9 mol% was applied by a bar coater, On top of that, the PVA film (PVA film-2) shown in Table 1 obtained in the above production example was placed and air-dried, whereby a laminate having the configuration of PVA film-1 / adhesive layer / PVA film-2 was obtained. Obtained.
Using the obtained laminate, the penetration resistance and nutrient permeability of the laminate were measured or evaluated by the method described above. The results are shown in Table 1.

[Comparative Examples 3 to 5]
Using the PVA film (PVA film-1) shown in Table 1 obtained in the above production example alone, the penetration resistance and nutrient permeability of the PVA film were measured or evaluated by the method described above. The results are shown in Table 1.

  In Example 1, a laminate having high nutrient permeability and high penetration resistance was obtained. On the other hand, in Comparative Examples 1-5, the laminated body (or PVA film) which was compatible with high nutrient permeability and high penetration resistance was not obtained.

  According to the laminate of the present invention, the nutrient permeability is high, the plant growth is good, the penetration strength is high, and the penetration of roots can be suppressed. It can be preferably used as a film for plant cultivation in cultivation.

Claims (8)

A laminate having a polyvinyl alcohol polymer layer (A layer) and a polyvinyl alcohol polymer layer (B layer), wherein the swelling degree of the A layer is a mass% and the swelling degree of the B layer is b mass%. When this is done, the laminate satisfies the following formula (1).
ba- ≧ 20 (1)   The laminate according to claim 1, wherein the swelling degree of the A layer is 160% by mass or less.   The layered product according to claim 1 or 2 whose swelling degree of said B layer is 180 mass% or more.   The laminated body of any one of Claims 1-3 whose thickness of the said A layer is 10 to 60% of the thickness of the said laminated body.   The laminate according to any one of Claims 1 to 4, wherein the polymerization degree of each polyvinyl alcohol polymer constituting the A layer and the B layer is 1500 or more.   The laminate according to any one of claims 1 to 5, wherein the saponification degree of each polyvinyl alcohol-based polymer constituting the A layer and the B layer is 98.0 mol% or more.   The film for plant cultivation formed from the laminated body of any one of Claims 1-6. A method for producing a laminate comprising a step of laminating a polyvinyl alcohol polymer film having a degree of swelling of a mass% and a polyvinyl alcohol polymer film having a degree of swelling of b mass%, which satisfies the following formula (1) Manufacturing method.
ba- ≧ 20 (1)