JP5632005B2 - Film and manufacturing method thereof - Google Patents

Description

  The present invention relates to a film suitable as a film for plant cultivation, a production method thereof, and a plant cultivation method using the same. More specifically, the present invention relates to a film formed using polyvinyl alcohol and a polycarboxylic acid whose carboxyl group may be neutralized, a method for producing the film, and a plant cultivation method using the film.

  In plant hydroponics, a plant cultivation method has been proposed that suppresses the decay of the nutrient solution by placing a film between the nutrient solution and the plant body (see Patent Document 1). It is important for the film to transmit nutrients, and hydrophilic materials such as polyvinyl alcohol, cellophane, cellulose acetate, cellulose nitrate, ethyl cellulose, and polyester have been proposed as film materials. However, when such a hydrophilic material is simply used when cultivating a plant by the above cultivation method, there is still a concern that bacteria or the like will move to the nutrient solution through the root penetration and the nutrient solution will rot. Was.

  Although it is conceivable to increase the strength of the film as a method of suppressing root penetration, there is a problem that properties other than strength, such as nutrient permeability, are deteriorated simply by increasing the strength of the film. For example, there is introduction of crosslinking as a technique for increasing the strength of a polyvinyl alcohol film, but as described in Patent Documents 2 and 3, polyacrylic acid or a partially neutralized product thereof is used as a crosslinking agent for a long time at a high temperature. The heat-treated film has high strength, but the nutrient permeability is very poor and is not suitable as a film for plant cultivation. In addition to the methods disclosed in Patent Documents 2 and 3, in addition to Patent Documents 2 and 3, a film made of a composition obtained by polymerizing methacrylic acid in the presence of polyvinyl alcohol (see Patent Document 4) or a specific polyvinyl alcohol. And a film formed from a composition containing a specific carboxyl group-containing polymer (see Patent Document 5), these films have room for further improvement in terms of film strength. Therefore, a film having high film strength and excellent nutrient permeability has been demanded.

JP 2008-61503 A JP-A-6-220221 Japanese Patent Application Laid-Open No. 7-102083 US Pat. No. 2,169,250 JP 2007-199248 A

  An object of the present invention is a film suitable as a film for plant cultivation, which has high film strength and can suppress root penetration, is excellent in nutrient permeability, and has good plant growth, and its production It is in providing a method and a plant cultivation method using the method.

  As a result of intensive studies to achieve the above object, the present inventors have used polyvinyl alcohol and polycarboxylic acid whose carboxyl group may be neutralized at a mass ratio of 65:35 to 95: 5. If the softening point is adjusted to 75-90 ° C. by heat-treating the film under specific conditions, the film strength is high and root penetration can be suppressed, and the nutrient permeability is also excellent. And found that the film grows well. The present inventors have further studied based on these findings and completed the present invention.

That is, the present invention
[1] Polyvinyl alcohol (hereinafter, “polyvinyl alcohol” may be abbreviated as “PVA”) and a polycarboxylic acid whose carboxyl group may be neutralized (hereinafter, “the carboxyl group is neutralized”) A film having a softening point of 75 to 90 ° C., which may be abbreviated as “polycarboxylic acid” in a mass ratio of 65:35 to 95: 5,
[2] The film of [1], wherein the polycarboxylic acid is at least one of a poly (meth) acrylic acid polymer and a neutralized product of a poly (meth) acrylic acid polymer,
[3] When the penetration resistance measured as the maximum load when piercing a thick iron round nail (CN65) specified in JIS A5508: 2009 after being immersed in water at 20 ° C. for 1 minute is 60 μm in thickness The film of [1] or [2], which is 17.0 N or more when converted to the value of
[4] Any one film of the above [1] to [3], which is a film for plant cultivation,
[5] A step of heat-treating a film formed from a stock solution containing PVA and polycarboxylic acid in a mass ratio of 65:35 to 95: 5 at a temperature in the range of 130 to 170 ° C. for 6 to 14 minutes. Including a method for producing a film,
[6] The method according to [5], wherein the polycarboxylic acid is at least one of a poly (meth) acrylic acid polymer and a neutralized product of a poly (meth) acrylic acid polymer,
[7] The method according to [5] or [6] above, which is a method for producing a film for plant cultivation,
[8] A plant cultivation method for cultivating a plant so that the plant and the film of [4] are in direct contact with each other,
About.

  According to the present invention, the film strength is high, the penetration of roots can be suppressed, the nutrient permeability is excellent, and the growth of the plant body is improved, and the film suitable as a film for plant cultivation, its production A method and a plant cultivation method using the method are provided.

The present invention is described in detail below.
Examples of PVA used in the present invention include vinyl acetate, vinyl formate, vinyl propionate, vinyl butyrate, vinyl pivalate, vinyl versatate, vinyl laurate, vinyl stearate, vinyl benzoate, and isopropenyl acetate. What can be obtained by saponifying the polyvinyl ester obtained by superposing | polymerizing 1 type (s) or 2 or more types of ester can be used. Among the above vinyl esters, vinyl acetate is preferable from the viewpoints of ease of production of PVA, availability, cost, and the like.

  The polyvinyl ester is preferably obtained using only one or two or more vinyl esters as monomers, and more preferably obtained using only one vinyl ester as a monomer. However, as long as it does not impair the effects of the present invention, it may be a copolymer of one or more vinyl esters and other monomers copolymerizable therewith.

  Examples of other monomers copolymerizable with the vinyl ester include α-olefins having 2 to 30 carbon atoms such as ethylene, propylene, 1-butene and isobutene; methyl (meth) acrylate, (meth) Ethyl acrylate, n-propyl (meth) acrylate, i-propyl (meth) acrylate, n-butyl (meth) acrylate, i-butyl (meth) acrylate, t-butyl (meth) acrylate, ( (Meth) acrylic acid esters such as 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) acrylamide, (meth) acrylamide Pansulfonic acid or a salt thereof, (meth) acrylamidepropyldimethylamine or a salt thereof, (meth) acrylamide derivatives such as N-methylol (meth) acrylamide or a derivative thereof; N-vinylformamide, N-vinylacetamide, N-vinylpyrrolidone N-vinylamides such as 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, and other vinyl ethers; (meth) acrylonitrile Vinyl halides such as vinyl chloride, vinyl halides such as vinyl chloride, vinylidene chloride, vinyl fluoride and vinylidene fluoride; allylation such as allyl acetate and allyl chloride Compound; Vinylsilyl compound such as vinyltrimethoxysilane; Unsaturated sulfonic acid and the like. Said polyvinyl ester 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 described above in the polyvinyl ester is preferably 15 mol% or less based on the number of moles of all structural units constituting the polyvinyl ester, and is preferably 10 mol%. More preferably, it is more preferably 5 mol% or less.
In particular, when the other monomer described above is a monomer that may promote water solubility of the obtained PVA, such as unsaturated sulfonic acid, the obtained film is used as a plant cultivation film. In order to prevent the film from dissolving when used, the proportion of structural units derived from these monomers in the polyvinyl ester is 5 moles based on the number of moles of all structural units constituting the polyvinyl ester. % Or less, and more preferably 3 mol% or less.

  The PVA may be modified with one or two or more types of graft copolymerizable monomers as long as the effects of the present invention are not impaired. Examples of the graft copolymerizable monomer include unsaturated sulfonic acid or a derivative thereof; α-olefin having 2 to 30 carbon atoms. The proportion of structural units derived from the graft copolymerizable monomer in PVA is preferably 5 mol% or less based on the number of moles of all structural units constituting PVA.

  In the PVA, a part of the hydroxyl groups may be cross-linked or may not be cross-linked. The PVA may have a hydroxyl group partially reacted with an aldehyde compound such as acetaldehyde or butyraldehyde to form an acetal structure, or does not react with these compounds to form an acetal structure. May be.

  The polymerization degree of the PVA is preferably in the range of 1500 to 6000, more preferably in the range of 1800 to 5000, and still more preferably in the range of 2000 to 4000. When the degree of polymerization is less than 1500, the penetration resistance of the resulting film tends to be low. On the other hand, if the degree of polymerization is greater than 6000, the production cost tends to increase and the process passability during film formation tends to be poor. In addition, the polymerization degree of PVA as used in this specification means the average polymerization degree measured according to description of JISK6726-1994.

  The saponification degree of the PVA is preferably 98.0 mol% or more, more preferably 98.5 mol% or more, and 99.0 mol% or more from the viewpoint of water resistance of the obtained film. More preferably it is. When the saponification degree is less than 98.0 mol%, PVA tends to be eluted and the strength tends to decrease. In this specification, the degree of saponification of PVA refers to the total number of moles of structural units (typically vinyl ester units) that can be converted into vinyl alcohol units by saponification and the vinyl alcohol units of PVA. The proportion (mol%) occupied by the number of moles of vinyl alcohol units. The degree of saponification can be measured according to the description of JIS K6726-1994.

  As the polycarboxylic acid used in the present invention, any compound having two or more carboxyl groups in the molecule can be used. Examples of such compounds include polymers having carboxyl groups (carboxyl group-containing polymers); molecular weights of malonic acid, succinic acid, glutaric acid, adipic acid, maleic acid, fumaric acid, itaconic acid, phthalic acid, etc. 500 The following low molecular weight compounds are exemplified, and one of these may be used alone, or two or more may be used in combination.

  Specific examples of the carboxyl group-containing polymer include acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid, 2- (meth) acryloyloxyethylmaleic acid, and 2- (meth) acryloyloxyethyl. Mention may be made of those obtained by polymerizing one or more unsaturated compounds having a carboxyl group such as phthalic acid and 2- (meth) acryloyloxyethyl hexahydrophthalic acid. The carboxyl group-containing polymer may be obtained by copolymerizing one or more of the above unsaturated compounds having a carboxyl group and an unsaturated compound having no carboxyl group. The ratio of the number of moles of structural units derived from the unsaturated compound having a carboxyl group to the number of moles of all structural units constituting the carboxyl group-containing polymer is in the range of 50 to 100 mol%. Is more preferable, it is more preferably in the range of 80 to 100 mol%, further preferably in the range of 95 to 100 mol%, particularly preferably 100 mol%. In the present invention, only one kind of carboxyl group-containing polymer may be used as the carboxyl group-containing polymer, or two or more kinds of carboxyl group-containing polymers may be used in combination.

  The number average molecular weight of the carboxyl group-containing polymer is preferably in the range of 50,000 to 1,000,000, and more preferably in the range of 100,000 to 500,000. When the number average molecular weight is less than 50000, the strength of the resulting film tends to decrease, and when it exceeds 1000000, the viscosity tends to increase when an aqueous solution is prepared, making it difficult to produce the film. is there.

  Some or all of the carboxyl groups of the polycarboxylic acid may be neutralized. When the carboxyl group which polycarboxylic acid has is neutralized, it is preferable that the neutralized carboxyl group is in the form of a metal salt such as sodium, calcium or magnesium.

  When using a neutralized carboxyl group as the polycarboxylic acid, the degree of neutralization in all polycarboxylic acids used (carboxyl neutralized relative to the total number of moles of carboxyl groups that may be neutralized) The ratio of the number of moles of the group) is preferably 20 mol% or less, and more preferably 15 mol% or less.

  The polycarboxylic acid used in the present invention is preferably a carboxyl group-containing polymer from the viewpoint of the film strength of the obtained film. Also, among the carboxyl group-containing polymers, since they are excellent in availability and low in cost, at least one of a poly (meth) acrylic acid polymer and a neutralized product of a poly (meth) acrylic acid polymer is Preferably, at least one of a polyacrylic acid polymer and a neutralized product of a polyacrylic acid polymer is more preferable, a polyacrylic acid polymer is more preferable, and a polyacrylic acid that is a homopolymer of acrylic acid is particularly preferable. .

  The film of the present invention is formed by using PVA and polycarboxylic acid at a mass ratio in the range of PVA: polycarboxylic acid = 65: 35 to 95: 5. When the mass ratio of PVA to polycarboxylic acid is lower than the above range, the film strength of the resulting film is lowered. On the other hand, when the mass ratio of PVA to polycarboxylic acid is higher than the above range, nutrient permeability of the resulting film is deteriorated. The mass ratio of PVA to polycarboxylic acid is preferably in the range of 68:32 to 90:10, and more preferably in the range of 70:30 to 85:15.

  The film of the present invention preferably does not contain a plasticizer in terms of increasing the film strength. However, if it is within the range not impairing the effects of the present invention, the plasticizer is included because productivity and handleability are improved. May be. 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, etc. The inventive film may contain one or more of these plasticizers. Among these, glycerin is preferable in terms of improving the handleability of the film.

  The content of the plasticizer in the film of the present invention is preferably in the range of 0 to 20 parts by mass, and in the range of 0 to 12 parts by mass with respect to 100 parts by mass of the total of PVA and polycarboxylic acid used. It is more preferable that it is in the range of 0 to 8 parts by mass.

  When the film of the present invention is produced using a stock solution described later as a raw material, the occurrence of thickness unevenness in the film obtained by improving the film forming property is suppressed, and a metal roll or belt is used for film formation. Therefore, when the film is produced, it is preferable to blend a surfactant in the stock solution because the film can be easily peeled off from these metal rolls and belts. When the film of the present invention is produced from a stock solution containing a surfactant, the film contains a surfactant. Although the kind of said surfactant is not specifically limited, From a peelable viewpoint from a metal roll or a belt, an anionic surfactant or a nonionic surfactant is preferable and a nonionic surfactant is more preferable.

  Suitable examples of the anionic surfactant include carboxylic acid types such as potassium laurate; sulfate ester types such as polyoxyethylene lauryl ether sulfate and octyl sulfate; and sulfonic acid types such as dodecylbenzene sulfonate.

  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 individually by 1 type or in combination of 2 or more types.

  When the surfactant is blended, the blending amount is preferably in the range of 0.01 to 0.5 parts by mass with respect to 100 parts by mass of the total of PVA and polycarboxylic acid used. It is more preferably in the range of 02 to 0.3 parts by mass, and still more preferably in the range of 0.05 to 0.1 parts by mass. When the blending amount of the surfactant is 0.01 mass or more with respect to a total of 100 mass parts of PVA and polycarboxylic acid to be used, the film forming property and the peelability can be improved. On the other hand, when the compounding amount of the surfactant is 0.5 parts by mass or less with respect to the total of 100 parts by mass of PVA and polycarboxylic acid used, the surfactant bleeds out on the surface of the obtained film. It is possible to suppress the occurrence of blocking.

The film of the present invention may further contain components such as an antioxidant, an antifreezing agent, a pH adjuster, a hiding agent, a coloring inhibitor, and an oil as necessary.
The proportion of the total of components derived from PVA and / or polycarboxylic acid, plasticizer and surfactant in the film of the present invention is preferably in the range of 50 to 100% by mass, and 80 to 100% by mass. % Is more preferable, and a range of 95 to 100% by mass is even more preferable.

  The softening point of the film of the present invention is required to be in the range of 75 to 90 ° C, preferably in the range of 76 to 88 ° C, and more preferably in the range of 77 to 85 ° C. . When the softening point of the film is lower than 75 ° C., the film strength is lowered. On the other hand, when the softening point of the film is higher than 90 ° C., the nutrient permeability deteriorates. In addition, the softening point of a film can be measured by the method mentioned later in an Example.

  In the present invention, a film formed from a stock solution containing the above-described PVA and the above-described polycarboxylic acid in a mass ratio of 65:35 to 95: 5 is heat-treated at a temperature in the range of 130 to 170 ° C. for 6 to 14 minutes. The manufacturing method of the film including the process (heat treatment process) to include is included. By the said manufacturing method, the above-mentioned film of this invention can be manufactured efficiently and smoothly.

  As said undiluted | stock solution, above-mentioned PVA, polycarboxylic acid, and what melt | dissolved components, such as a plasticizer and surfactant further in the solvent as needed, PVA, polycarboxylic acid, and as needed In addition, it is possible to use a material in which PVA is melted, further including components such as a plasticizer and a surfactant. In these stock solutions, each component is preferably mixed uniformly.

  The mass ratio of PVA to polycarboxylic acid in the stock solution is preferably in the range of PVA: polycarboxylic acid = 65: 35 to 95: 5, and preferably in the range of 68:32 to 90:10, More preferably, it is within the range of 70:30 to 85:15.

  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 (the 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 stock solution does not become too high, and filtration and defoaming during the preparation of the stock solution are performed smoothly, making it easy to produce a film with less foreign matter and defects. . On the other hand, when the volatile content of the stock solution is 95% by mass or less, the concentration of the stock solution does not become too low, and the industrial production of the film becomes easy.

  As a method for preparing the stock solution, PVA and polycarboxylic acid are mixed and then dissolved in a solvent; PVA and polycarboxylic acid are separately dissolved in a solvent to form a solution, and then both solutions are mixed at an appropriate ratio. General mixing methods such as a method of mixing; a method of dissolving one of PVA and polycarboxylic acid in a solvent and then dissolving the remaining polymer (for example, a method of dissolving polycarboxylic acid in a PVA solution) Can be adopted. However, when the PVA and the polycarboxylic acid are mixed and then heated to a high temperature, the viscosity tends to increase and film formation tends to be difficult. Therefore, a PVA solution is prepared in advance, and this and the polycarboxylic acid or the solution thereof, A method of mixing at a relatively low temperature, preferably 70 ° C. or lower is preferred.

  Examples of the film forming method for forming a film to be subjected to the heat treatment step from the above stock solution include a wet film forming method, a gel film forming method, a dry cast film forming method, and an extrusion film forming method. . These film forming methods may be employed alone or in combination of two or more.

Among the film forming methods described above, a cast film forming method using a T-shaped slit die, a hopper plate, an I-die, a lip coater die or the like is preferable. As a specific method of the cast film forming method, for example, there is a method in which the above-mentioned stock solution is discharged or cast onto the peripheral surface of a heated roll (or belt) that rotates and dried. In particular, when continuously forming a cast film, the above-described stock solution is uniformly discharged or cast on the peripheral surface of a rotating heated roll (or belt) positioned on the most upstream side, and this roll (or belt) The peripheral surface of one or a plurality of rotating heated rolls disposed on the downstream side thereof by evaporating and drying volatile components from one surface of the film discharged or cast on the peripheral surface It is possible to employ industrially preferably a method of further drying on the above or passing it through a hot-air drying device and further winding it with a winding device. Drying with a heated roll and drying with a hot air dryer may be performed in an appropriate combination.
In order to adjust the film to an appropriate state, it is desirable to provide a humidity control device; a motor for driving each roll; a speed adjustment mechanism such as a transmission.

  When continuously casting as described above, the heat treatment step in the production method of the present invention may be performed after unwinding the film after being wound by the winding device, if necessary. Alternatively, it may be performed during or after drying with a heated roll or hot air drying device and before winding with a winding device. Among these, since it is excellent in productivity of a film, it is preferable to perform a heat treatment process before winding with a winding device.

Since the moisture content of the film subjected to the heat treatment step can improve the effect of the heat treatment step, it is more preferably in the range of 1 to 15% by mass, and in the range of 2 to 13% by mass. Is more preferable. The moisture content of the film can be calculated from the mass before and after the drying of the film. Specifically, the mass (A) of the target film and the mass after vacuum drying the film at 50 ° C. for 4 hours. From (B), it is computable by following formula (1).
Moisture content (mass%) = 100 × [(A−B) / A] (1)

  Examples of the heat treatment method in the heat treatment step include a method of contacting a heated roll and a method of applying hot air, but a method of contacting the heated roll is preferable because the heat treatment can be performed uniformly. These heat treatment methods may be employed alone or in combination of two or more. By the heat treatment step, the crosslinking reaction in the film can be appropriately advanced, whereby a film having a softening point adjusted can be obtained.

  The temperature of the heat treatment step is in the range of 130 to 170 ° C., preferably in the range of 135 to 165 ° C., and in the range of 140 to 160 ° C. in order to cause the crosslinking reaction in the film to proceed appropriately. It is more preferable. When the said temperature is lower than 130 degreeC, film strength will become low. On the other hand, when the said temperature is higher than 170 degreeC, nutrient permeability will deteriorate.

  The heat treatment time in the heat treatment step is in the range of 6 to 14 minutes, preferably in the range of 7 to 13 minutes, and in the range of 8 to 12 minutes, in order to appropriately advance the crosslinking reaction in the film. More preferably. If the heat treatment time is shorter than 6 minutes, it is easy to form heat treatment spots and it is difficult to carry out the crosslinking reaction uniformly. On the other hand, when the heat treatment time is longer than 14 minutes, nutrient permeability deteriorates.

The film of the present invention has a high film strength. Here, the film strength is a thick iron round nail (CN65) defined in JIS A5508: 2009 after the target film is immersed in water at 20 ° C. for 1 minute, as will be specifically described in the examples described later. It can be evaluated by the penetration resistance force measured as the maximum load when stabbed. That is, it can be determined that the higher the penetration resistance, the higher the film strength. The penetration resistance tends to increase when the softening point of the film is high or when the thickness is thick. The film of the present invention has a penetration resistance (60 μm value) when the thickness is 60 μm, preferably 17.0 N or more, more preferably 17.5 N or more, and 18.0 N or more. Is more preferable. When the penetration resistance (60 μm value) is in the above range, the root can penetrate more effectively when the film is used as a plant cultivation film. When the thickness of the film of the present invention is other than 60 μm, the penetration resistance (X μm value) obtained by measuring the film thickness (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 thickness of the film of the present invention is preferably in the range of 10 to 200 μm, more preferably in the range of 20 to 150 μm, more preferably in the range of 30 to 120 μm, from the viewpoints of penetration resistance, productivity, and handleability. It is more preferable that it is within the range, and it is particularly preferable that it is within the range of 40 to 100 μm. In addition, the thickness of a film can measure the thickness of arbitrary 5 places, and can obtain | require it as those average values.

  The shape of the film of the present invention is not particularly limited, and examples thereof include a quadrangle (for example, a rectangle, a square, etc.), a circle, a triangle, and the like, and can be appropriately set according to the use and usage of the film of the present invention. However, since it can be continuously manufactured and storage and transportation become easy, it is preferable that the long film is wound in a roll shape. The width of the long film is not particularly limited, and can be appropriately determined according to the use or usage pattern. For example, when the film of the present invention is used as a plant cultivation film, the width is wide. If it is too high, it is difficult to care for the plant, so it is preferably 2 m or less, and preferably in the range of 10 cm to 1.5 m. When using it for uses other than the film for plant cultivation, the width of the long film is preferably in the range of 10 cm to 4 m, and more preferably in the range of 50 cm to 3 m. Moreover, the length of a long film is not specifically limited, For example, 5-5000 m can be illustrated.

  Although there is no particular limitation on the use of the film of the present invention, the film of the present invention has high film strength and can suppress root penetration, and is excellent in nutrient permeability and has good plant growth. Therefore, it is preferably used as a film for plant cultivation. When the film of the present invention is used as a film for plant cultivation, the film of the present invention may be used as it is, or may be used after making it into a desired shape by appropriately performing cutting, overlapping, etc. Good.

  Examples of the method of using the film of the present invention as a film for plant cultivation include a method of cultivating a plant so that the plant and the film of the present invention are in direct contact, such as cultivating a plant on the film of the present invention. A specific method of using the film of the present invention as a plant cultivation film is, for example, by placing the film of the present invention having a desired shape on the earth soil provided with a depression as necessary, and on the ground soil. A method of growing a plant body by separating the ground soil and the plant body by arranging the plant body so that they are not in direct contact with each other; on an aqueous solution (nutrient solution) containing nutrients of the plant body, By disposing the film of the present invention having a desired shape and disposing the plant body thereon, the aqueous solution and the plant body are separated by the film, and the plant body is grown so that they are not in direct contact with each other. The method etc. are mentioned. 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 softening point of a film, penetration resistance, nutrient permeability, and penetration test with roots employed in the following Examples and Comparative Examples is shown below.

Method for Measuring Softening Point of Film The softening point of the film obtained in the following examples or comparative examples was measured using an automatic softening point measuring device “EX-820” manufactured by Daiichi Rika Co., Ltd. That is, the film was cut into a 3 cm square size, a 1 mm thick 3 cm square stainless steel plate with a 1 cm diameter circular hole in the center, and a 1 mm thick 3 cm square stainless steel plate with a 1 cm × 2 cm rectangular hole in the center. The steel plate with a circular hole is placed on the base with the circular hole in the upper surface, and a steel ball (Nominal: 3/8 (Diameter: JIS B 1501: 2009) is placed on the film located in the center of the circular hole. 9.525 mm), grade: G60, mass: 3.5 g ± 0.05 g). Subsequently, 750 ml of 25 ° C. distilled water was added, the temperature was raised at 5 ° C. per minute, and the temperature when the film was lowered from the pedestal to a position of 25 mm was taken as the softening point of the film. When the softening point of the film exceeded 90 ° C., measurement was impossible and “> 90” was set.

Evaluation method of penetration resistance of film The films obtained in the following Examples or Comparative Examples were cut into a 3 cm square size and immersed in 1000 g of distilled water at 20 ° C. After immersion for 1 minute, the film was taken out and sandwiched between two 3 cm square stainless steel plates having a thickness of 1 mm with a hole having a diameter of 1 cm in the center, and the left and right portions were clipped. Next, the above sample is fixed to the grip under the tabletop precision universal testing machine “Autograph AGS-J” manufactured by Shimadzu Corporation, and the thick iron round nail CN65 as defined in JIS A5508: 2009 is attached to the top grip. Was fixed, and a film located at the center of the hole in the stainless steel plate was pierced at a speed of 100 mm / min. The maximum load at that time was defined as penetration resistance (unit: N). In addition, in order to prevent the film from drying, the work from immersing in water to taking out was performed within 30 seconds. The measurement temperature was 20 ° C. The case where the penetration resistance (60 μm value) was 17.0 N or more was evaluated as “◯” (good), and the case where the penetration resistance (60 μm value) was less than 17.0 N was evaluated as “x” (defect).

Method for evaluating nutrient permeability of film A sieve was placed inside the bowl, and a film obtained in the following Examples or Comparative Examples was placed on the sieve. Next, 150 g of an aqueous glucose solution having a concentration of 5% was placed between the bowl and the film, and 150 g of distilled water was placed on the film so that the aqueous glucose solution and the distilled water were separated from each other by the film. 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). The case where the difference between both concentrations was less than 1.6% was evaluated as “◯” (good), and the case where it was 1.6% or more was evaluated as “x” (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.

200g of nutrient solution ("Hyponex" EC = 2 manufactured by Hyponex Japan Co., Ltd., diluted 200-fold) is put into the penetration test bowl with roots , and obtained in the following examples or comparative examples so that one side is in contact with the nutrient solution. The film was placed. Place 50 g of coconut chip as soil on the film, sow turf seeds (Western turf "Bentgrass Highland" manufactured by Takii Seed Co., Ltd.) Wrapped with film. This was placed in a room at 15 to 25 ° C. and cultivated using an artificial light. After the turf grew and contacted the polyvinylidene chloride film, the polyvinylidene chloride film was removed. The case where the day when the root penetrated the film was cultivated for 150 days or more was evaluated as “◯” (good), and the case of less than 150 days was evaluated as “x” (bad).

[Example 1]
0.1 parts by mass of sodium polyoxyethylene lauryl ether sulfate as a surfactant with respect to 100 parts by mass of PVA (polymerization degree 2400, saponification degree 99.9 mol%) obtained by saponifying a homopolymer of vinyl acetate Distilled water was added so that the PVA concentration was 10% by mass, and the mixture was stirred at 95 ° C. for 3 hours to prepare an aqueous PVA solution. The PVA aqueous solution is cooled to 60 ° C., polyacrylic acid having a number average molecular weight of 150,000 is added at a ratio of 20 parts by mass with respect to 80 parts by mass of PVA, and sufficiently stirred at 60 ° C. until uniform, did. Thereafter, the stock solution was cast on a metal roll at 60 ° C. and dried until the water content became 3% by mass, followed by heat treatment at 150 ° C. for 10 minutes to produce a 60 μm thick film.
Using the obtained film, the softening point, penetration resistance and nutrient permeability of the film were measured or evaluated by the method described above, and a penetration test using roots was performed. The results are shown in Table 1.

[Example 2]
In Example 1, it replaced with having used polyacrylic acid in the ratio of 20 mass parts with respect to 80 mass parts of PVA, and was using it in the ratio of 30 mass parts with respect to 70 mass parts of PVA. A film having a thickness of 60 μm was prepared by the above method.
Using the obtained film, the softening point, penetration resistance and nutrient permeability of the film were measured or evaluated by the method described above, and a penetration test using roots was performed. The results are shown in Table 1.

[Example 3]
In Example 1, it replaced with having used the polyacrylic acid in the ratio of 20 mass parts with respect to 80 mass parts of PVA, and was used in the ratio of 10 mass parts with respect to 90 mass parts of PVA. A film having a thickness of 60 μm was prepared by the above method.
Using the obtained film, the softening point, penetration resistance and nutrient permeability of the film were measured or evaluated by the method described above, and a penetration test using roots was performed. The results are shown in Table 1.

[Examples 4 to 7 and Comparative Examples 1 to 6]
A film having a thickness of 60 μm was produced in the same manner as in Example 1 except that the heat treatment temperature or time was changed to that shown in Table 1 in Example 1.
Using the obtained film, the softening point, penetration resistance and nutrient permeability of the film were measured or evaluated by the method described above, and a penetration test using roots was performed. The results are shown in Table 1.

[Comparative Example 7]
In Example 1, it replaced with having used polyacrylic acid in the ratio of 20 mass parts with respect to 80 mass parts of PVA, and was used similarly to Example 1 except having been used in the ratio of 40 mass parts with respect to 60 mass parts of PVA. A film having a thickness of 60 μm was prepared by the above method.
Using the obtained film, the softening point, penetration resistance and nutrient permeability of the film were measured or evaluated by the method described above, and a penetration test using roots was performed. The results are shown in Table 1.

[Comparative Example 8]
A film having a thickness of 60 μm was prepared in the same manner as in Example 1 except that the polyacrylic acid was not added and the PVA aqueous solution was used as it was as a film-forming stock solution.
Using the obtained film, the softening point, penetration resistance and nutrient permeability of the film were measured or evaluated by the method described above, and a penetration test using roots was performed. The results are shown in Table 1.

[Comparative Examples 9 and 10]
In Comparative Example 8, a film having a thickness of 60 μm was produced in the same manner as in Comparative Example 8 except that the heat treatment temperature was changed to that shown in Table 1.
Using the obtained film, the softening point, penetration resistance and nutrient permeability of the film were measured or evaluated by the method described above, and a penetration test using roots was performed. The results are shown in Table 1.

[Comparative Example 11]
40 parts by mass of an aqueous solution containing 20% by mass of PVA (degree of polymerization 2400, degree of saponification 99.9 mol%) obtained by saponifying a vinyl acetate homopolymer, 4 parts by mass of methacrylic acid, and 10 parts by mass of water are mixed. After heating at 90 ° C. for 16 hours to polymerize methacrylic acid, the resulting composition was cast into a film. The film obtained after drying in cast film formation was heat-treated at 140 ° C. for 5 minutes to produce a film having a thickness of 60 μm.
Using the obtained film, the softening point, penetration resistance and nutrient permeability of the film were measured or evaluated by the method described above, and a penetration test using roots was performed. The results are shown in Table 1.

[Comparative Example 12]
100 mass parts of PVA (polymerization degree 2400, saponification degree 99.9 mol%) obtained by saponifying a homopolymer of vinyl acetate, polyacrylic acid having a weight average molecular weight of 5000 (manufactured by Wako Pure Chemical Industries, Ltd.) 10 mass PVA aqueous solution (PVA concentration is 10% by mass) containing 12 parts by mass and glycerin was dried on a metal roll at 60 ° C. to obtain a film having a thickness of 75 μm. The obtained film was fixed to a frame and heat-treated at 120 ° C. for 3 minutes.
Using the film after heat treatment, the softening point, penetration resistance and nutrient permeability of the film were measured or evaluated by the above-described method, and a penetration test using roots was performed. The results are shown in Table 1.

  In Examples 1 to 7, all the evaluation results of penetration resistance, nutrient permeability, and penetration test with roots were “◯” (good), and the film strength was high and root penetration could be suppressed. Thus, a film suitable for a plant cultivation film having excellent nutrient permeability and good plant growth was obtained. On the other hand, in Comparative Examples 1 to 12, a PVA film having good penetration resistance, nutrient permeability, and penetration test using roots was not obtained.

  The film of the present invention has high film strength and can suppress penetration of roots, and also has excellent nutrient permeability and good plant growth. It can be preferably used as a plant cultivation film in the cultivation of leafy vegetables.

Claims (8)

  A film formed by using polyvinyl alcohol and a polycarboxylic acid whose carboxyl group may be neutralized in a mass ratio of 65:35 to 95: 5 and having a softening point of 75 to 90 ° C.   The polycarboxylic acid in which the carboxyl group may be neutralized is at least one of a poly (meth) acrylic acid polymer and a neutralized product of a poly (meth) acrylic acid polymer. Film.   After immersion in water at 20 ° C. for 1 minute, the penetration resistance measured as the maximum load when piercing a thick iron round nail (CN65) specified in JIS A5508: 2009 is the value when the thickness is 60 μm. The film according to claim 1 or 2 which is 17.0N or more when converted.   The film according to any one of claims 1 to 3, which is a plant cultivation film.   A film formed from a stock solution containing polyvinyl alcohol and a polycarboxylic acid whose carboxyl group may be neutralized in a mass ratio of 65:35 to 95: 5, at a temperature in the range of 130 to 170 ° C. The manufacturing method of a film including the process of heat-processing for 6 to 14 minutes.   The polycarboxylic acid in which the carboxyl group may be neutralized is at least one of a poly (meth) acrylic acid polymer and a neutralized product of a poly (meth) acrylic polymer. Manufacturing method.   The manufacturing method of Claim 5 or 6 which is a manufacturing method of the film for plant cultivation.   A plant cultivation method for cultivating a plant so that the plant and the film of claim 4 are in direct contact with each other.