JPS5837814B2 - Agricultural covering material with excellent heat retention, dehumidification, and drip-free properties and its manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an agricultural covering material excellent in heat retention, moisture removal and drip-free properties, and a method for producing the same.

After the war, Japan's agriculture has achieved remarkable development centered on facility farming, but under the recent harsh environment surrounding oil,
Due to the abnormally high price of heavy oil, it is no longer possible to maintain agricultural management with conventional facility cultivation that relies on heavy oil.

In this difficult situation, all kinds of measures to realize energy-saving agriculture are being considered mainly by national and public research institutes and cultivation farmers. is one of them.

On the other hand, measures to prevent over-humidity, high humidity, and dew condensation within the coating have been an important problem in the conventional cultivation of crops in facilities.

In other words, in a closed environment where crops are flourishing, the humidity is always 8.
Humidity conditions of 0 to 90% or more are likely to occur, and this high humidity condition not only encourages the propagation of pathogenic bacteria in crops and inhibits the stable growth of crops, but in some cases may even lead to complete extinction due to withering.

Particularly in the low-temperature season, gray mold, which attacks various fruits and vegetables, as well as late blight of tomatoes, downy mildew of cucumbers, and sclerotinia are induced by humid or overhumid conditions, and the crops themselves are also exposed to humid conditions. Because of this, efforts are being made to lower the humidity as much as possible, as this results in soft growth.Especially in the future, when it is essential to realize energy-saving agriculture as mentioned above, prevention of high humidity, overhumidity, and dew condensation will become an increasingly important issue. It's coming.

Under the recent agricultural management environment as explained above, synthetic fibers such as polyester and polypropylene are used as agricultural covering materials that have heat retention and dehumidification properties to realize energy-saving agriculture and prevent high humidity and excessive humidity within the sealed covering, and prevent dew condensation. However, such nonwoven fabrics have the following drawbacks and are not yet completely satisfactory as agricultural covering materials that meet the above objectives.

That is, first of all, the fatal drawback is that it has voids and is breathable, so solar energy stored during the day can be easily released at night due to convection heat transfer and the transmission of infrared rays in the 6-17μ wavelength range. For example, in the case of polyester non-woven fabric, it varies depending on the humidity inside the coating, but the humidity is 6.
At a humidity of 0 to 70%, it is equivalent to a polyethylene synthetic resin film with low heat retention as an agricultural covering material, and at a humidity of 80 to 70%.
In a state of 90% or more, the heat retention property is inferior to that of a polyethylene synthetic resin film.

On the other hand, if we eliminate the voids and make them non-breathable, as we will discuss later, the material has no moisture absorption, moisture permeability, or water absorption, so the dehumidification property is completely impaired, and there is no way to prevent humidity, excessive humidity, or dew condensation. It doesn't have any effect either.

Furthermore, another drawback is that conventional agricultural covering materials made of non-woven fabrics have moisture permeability due to air-permeable voids or water retention properties due to capillary action to prevent moisture build-up and dew condensation within the covering. However, since the material itself does not have hygroscopic or water absorbing properties, its effects are also not completely satisfactory.

The present inventors have completed the present invention as a result of intensive studies to eliminate the above-mentioned drawbacks of existing agricultural covering materials made of non-woven fabrics, and the purpose thereof is to provide heat retention,
It is an object of the present invention to provide a new agricultural covering material with excellent dehumidification and drip-free properties.

Another object of the present invention is to provide air permeability with voids when dry, for example during the day, but to automatically close most of the voids when swollen, for example at night, thereby providing heat retention, The purpose of the present invention is to provide an excellent agricultural covering material that has both dehumidification and drip-free properties.

Furthermore, another object of the present invention is to provide an effective manufacturing method including heat treatment for manufacturing the novel agricultural covering.

Other objects and effects of the present invention will be made clear in the following description, but it goes without saying that the present invention may be modified as appropriate without departing from the object.

The features of the present invention that achieve the above-mentioned objects are as follows:
The base material is a nonwoven fabric with a porosity of 0.01 to 0.7, and the constituent fibers and/or their intersections have a porosity of 0.01 to 0.7 based on the weight of the nonwoven fabric.
This is achieved by an agricultural coating coated with a heat-treated polyvinyl alcohol-coated resin film of 3 to 3 times the porosity of o. oi～0
．． After applying a solution containing polyvinyl alcohol synthetic resin as a main component to the nonwoven fabric of No. 7, the polyvinyl alcohol synthetic resin is once solidified and then heat treated at a temperature of 140 to 220°C to form the nonwoven fabric fibers or their intersections. This is achieved by a method of forming and coating a heat-treated polyvinyl alcohol synthetic resin film of 0.3 to 3 times the weight of the nonwoven fabric.

The nonwoven fabric used in the present invention is made of synthetic resin fibers such as polyester, polyolefin, polyvinyl alcohol, polyamide, and polyacrylonitrile, chemical fibers such as rayon and acetate, or natural fibers such as cotton and linen, and has a fineness of 1 to 10. denier, preferably 2 to 6 denier, by a known method such as a needle punch method, stitching method, adhesive method, spunbond method, etc., but preferably a moisture absorbing material as described later. In terms of properties and water absorption, nonwoven fabrics made of hydrophilic fibers such as polyvinyl alcohol, rayon, acetate, etc. are preferred.

Furthermore, an important property of the above-mentioned nonwoven fabric used in the present invention is a porosity of about 0.01 to 0.7, preferably 0.01 to 0.7.
It is important that it be about 0.03 to 0.5.

The porosity referred to here is the apparent specific gravity divided by the true specific gravity, and it indicates the bulkiness, so to speak, but this value is also related to the thickness, so it is difficult to define it unambiguously.
If the porosity is less than 0.01, it will be insufficient as a skeleton and unfavorable in terms of strength properties, and if the porosity is less than 0.7
If the size is larger, when a solution containing polyvinyl alcohol synthetic resin as the main component is applied, it is difficult to completely and uniformly form and coat the polyvinyl alcohol synthetic resin film on the fibers constituting the nonwoven fabric or their intersections, and the resulting product However, it lacks flexibility and is impractical, both of which are undesirable.

In the present invention, the solution containing polyvinyl alcohol synthetic resin as its main component preferably has an average degree of polymerization of 1 from the viewpoint of water resistance.
000 or more and a saponification degree of 98% or more as the main component, and if necessary, inorganic or organic coloring, bactericide, fiber powder, pore shape or auxiliary agent, etc. are blended into the solution. means.

This polyvinyl alcohol synthetic resin is hygroscopic, moisture permeable,
In addition to having excellent water absorption properties, it also has excellent ability to block infrared transmission in the 6 to 17 micron wavelength range, and also has the property of swelling when absorbing moisture and water. A polyvinyl alcohol synthetic resin film is formed on the fibers that make up the nonwoven fabric or their intersections.
As will be described later, coating is the most important requirement for the present invention, and the same effects as the present invention cannot be achieved by forming and coating a film made of other materials.

Furthermore, an important requirement of the present invention is that after applying a solution containing polyvinyl alcohol composite or resin as a main component to a nonwoven fabric, it is once solidified and then heat treated at a temperature of 140 to 220°C.

That is, although polyvinyl alcohol synthetic resin has the above-mentioned properties, it has poor water resistance and absorbs moisture, elution and blocking due to water absorption. There is a practical problem if it is coated, and at least 1
It is important to perform heat treatment at a temperature of 40° C. to impart practical water resistance; temperatures lower than 140° C. are not preferred from the viewpoint of insufficient crystallization and practical water resistance.

However, if the temperature exceeds 220°C, the polyvinyl alcohol synthetic resin will be easily decomposed, so it is also not preferable.

In addition, as a method of making polyvinyl alcohol synthetic resin water resistant, there is a method of acetalizing it in the presence of a catalyst such as sulfuric acid or phosphoric acid using an aldehyde such as formaldehyde or acetaldehyde, but although this method can impart water resistance, it is difficult to synthesize polyvinyl alcohol. Since the OH groups possessed by the resin are reduced, the hygroscopicity, moisture permeability, and water absorption properties are significantly lowered, and the resin also lacks swelling properties when absorbing moisture and water, so that the same effects as those of the present invention cannot be expected.

The agricultural covering material according to the present invention is formed by forming and covering the above-described nonwoven fabric constituent fibers or their intersections, or both, with a film mainly composed of heat-treated polyvinyl alcohol synthetic resin. The explanation is as follows.

Figures 1 to 3 are explanatory diagrams showing one example of the agricultural covering material of the present invention. In the figures, 1 is the nonwoven fabric constituent fiber, 2 is the intersection of the nonwoven fabric constituent fiber, and 3 is the heat-treated polyvinyl alcohol synthetic resin film. , 4 indicates the voids between the constituent fibers, 5 indicates the pores, and 6 indicates the aluminum powder. P synthetic resin
The agricultural covering material shown in Fig. 2 is made by adding a pore-forming agent to a solution mainly composed of PVA to form pores in the heat-treated PVA film. In addition, the agricultural covering material shown in Fig. 3 is one in which aluminum powder is further blended into a solution mainly composed of PVA, so that the heat-treated PVA film has pores and aluminum powder. If necessary, colorants, fungicides, fiber powder, etc. may be added to these ingredients.

The characteristics and effects of the agricultural covering material of the present invention reside in forming and covering the nonwoven fabric fibers or their intersections with a film mainly composed of heat-treated PVA obtained as described above. This is effective, but I will explain this next.

First of all, heat-treated PVA has excellent hygroscopicity, moisture permeability, and water absorption, so the agricultural covering material of the present invention has a high affinity for moisture in the air, and has better moisture permeability due to the voids of conventional agricultural covering materials made of nonwoven fabric. In addition to water retention due to capillary action, heat-treated PVA itself exhibits excellent water retention, so it has dehumidifying properties.
This makes it a highly drip-free agricultural covering material.

In this case, the fiber material constituting the nonwoven fabric is not particularly limited as mentioned above, but it is a hydrophilic fiber material with good moisture absorption and water absorption properties in terms of dehumidification and non-droplet properties, such as polyvinyl alcohol, rayon, etc. A fiber material such as acetate is more suitable.

In addition, heat-treated PVA has low infrared transmittance in the 6-17μ wavelength range and has a high ability to prevent radiation cooling at night, so the agricultural covering material of the present invention has superior heat retention compared to conventional agricultural covering materials made of non-woven fabric. This is an even more important characteristic regarding heat retention.
The effects are as follows.

That is, heat-treated PVA swells when it absorbs moisture and water, depending on the heat treatment temperature, so the agricultural covering material of the present invention absorbs moisture that condenses when the temperature drops at night and swells, filling all or most of the voids in the nonwoven fabric. The biggest drawback of conventional agricultural covering materials made of non-woven fabric is the lack of heat retention due to convection heat transfer or infrared transmission in the 6-17μ wavelength range due to the air permeability of the voids. This, combined with the above characteristics, results in an agricultural covering material with extremely excellent heat retention properties.

In order to fill and seal the voids in the nonwoven fabric when the temperature drops at night, it is effective to appropriately design and combine the porosity of the nonwoven fabric, the heat treatment temperature for the PVAO heat treatment, in other words, the degree of swelling, and the amount of coverage.

In addition, as in the agricultural covering material of the present invention shown in FIG.
A film in which pores are formed acts as a heat insulating layer, resulting in an agricultural covering material with even higher heat retention properties.Furthermore, as shown in the agricultural covering material of the present invention shown in Fig. 3, aluminum A heat-treated PVA film containing pores and aluminum powder by blending the powder has aluminum's excellent infrared shielding properties in the 6-17μ wavelength range, and is suitable as an agricultural covering material with even better heat retention. be.

Hereinafter, specific embodiments of the method of the present invention will be described in more detail. First, PVA having preferably an average degree of polymerization of 1000 or more and a degree of saponification of 98% or more is dissolved in water to form a solution of 10 to 15%. An inorganic or organic coloring agent, a pore-forming aid, a fiber powder, a bactericide, etc. are added to this aqueous solution as necessary to form a solution mainly containing PVA.

When mixing pore-forming aids, for example, those that decompose and foam at a certain temperature to generate gas, such as sodium bicarbonate or butane gas microcapsules, can be used, but in order to prevent decomposition and foaming during the solution preparation stage, it is necessary to mix them at a temperature below the decomposition and foaming temperature. It is important to mix them together.

In addition, when aluminum powder is blended, it is preferable that the average particle diameter of the aluminum powder used is 10 to 50 μm, and if it is smaller than 10 μm, it lacks light reflectivity.6 to 17
The infrared shielding properties in the μ wavelength range are poor, and if the thickness is greater than 50 μm, the adhesiveness is poor and it is easy to fall off, so both are not preferred.

To apply the PVA-based solution obtained in this way to a nonwoven fabric, any conventional liquid application method can be used, such as a dipping method, a spray method, a coating method, etc. In the case of the example, it is also good to perform leveling and impregnation with a squeezing roll, doctor, etc. as appropriate.

In addition, the application amount should be adjusted appropriately by adjusting the concentration of the stock solution, the amount of squeezing, the amount of spray, etc. so that the amount of heat-treated PVA film formed and covered after solidification and heat treatment is 0.3 to 3 times the weight of the nonwoven fabric. <<If it is less than 0.3 times, it will have poor moisture absorption, water absorption, and water retention properties, and the amount of swelling during moisture absorption and water absorption will be small, which is undesirable.If it is more than 3 times, the resulting product will have poor flexibility, which is undesirable from the point of view of practicality.

PVA is fixed to the nonwoven fabric coated with the solution containing PVA as a main component obtained as described above by a wet method or a dry method, and then heat treatment is performed to impart water resistance to the PVA.

To solidify by dry method, cylinder drying or hot air drying at a temperature of about 80 to 100°C may be used, and to solidify by wet method, use a saturated aqueous solution of salts that have a high solidifying ability for PVA, such as ammonium sulfate and Glauber's salt. The material may be solidified by being immersed in the liquid at a temperature of about room temperature to 80°C, but in the latter wet method, it is necessary to wash thoroughly with water to remove salts.

As mentioned above, the heat treatment conditions can be set appropriately within the temperature range of 140 to 220 degrees Celsius, but in order to promote crystallization in a short period of time and provide effective water resistance, the open method using hot air is preferable. It is also said that it is preferable to use the heated cylinder method.

When a pore-forming aid is added to form pores, it may be carried out by decomposing and foaming the PVA during solidification or heat treatment as described above.

The thus obtained agricultural covering material of the present invention is made by coating the nonwoven fibers or their intersections with a film mainly composed of PVA in a specific ratio, and its thickness is usually 57 nm.
11L or less, around 3 meters is suitable for practical use. PVA's high hygroscopicity, moisture permeability, and water absorption properties provide excellent dehumidification and drip-free properties, as well as PVA's non-transmission of infrared rays in the 6-17μ wavelength range. It has the advantage of exhibiting extremely good heat retention by absorbing moisture when the temperature drops at night, and sealing by water absorption and swelling. It can be widely used for applications such as curtains inside houses, small tunnels inside buildings, etc.

Hereinafter, the present invention will be explained by examples.

In addition, the various physical property values in the examples were measured by the following methods.

(Moisture absorption rate) The weight (W1) when the sample was left for 24 hours at 20°C and 65% RH and the absolute dry weight (WO) when the same sample was vacuum-dried at 50°C for 10 hours were measured and calculated using the following formula. I asked for more.

(Maximum water retention rate) The weight (W,) when a sample is immersed in water at 20°C for 10 hours and the interval between drops of water is 10 seconds or more, and the weight (W,) when the same sample is vacuum-dried at 70°C for 24 hours. Bone dry weight (Wo)
was measured and calculated from the following formula.

(Water absorption rate) Cut the sample into 10 x 150 mm, and insert the sample from the bottom at 20 mm.
Draw a base line at the gate and draw another line 5Qmm from the base line.

Soak the sample in 20°C water up to the baseline. Measure the time (sand) for the water to penetrate to a line 50 degrees above the baseline using a stopwatch and display it.

(Temperature retention) The minimum nighttime temperature (t1) under a covered tunnel with a width of approximately 1.2mm, height of approximately 0.6m, and total length of approximately 20m and the long nighttime low temperature (t2) under an uncovered tunnel are calculated at a height of 10 CrIL above ground. The values were measured using the following formula.

(Usability) Samples were distributed to 30 people, and practical tests were carried out using tunnel coverings and interior curtains, and the results were categorized based on questionnaires regarding expansibility, opening/closing properties, etc.

(Durability) This is the result of conducting a 3-month extension test using the same tunnel covering as the one used for maintaining temperature, and examining the state of damage caused by rain, wind, etc.

Example 1 Completely saponified PV with average polymerization degree of 1700 and saponification degree of 99.9%
A was dispersed in water, heated to 98° C. with stirring to dissolve, and cooled to 40° C. to prepare a 9% PVA aqueous solution.

On the other hand, a polyester nonwoven fabric having a fiber length of 507I17L, a fineness of 3 denier, and a porosity of 0.1 was prepared as a roll, and after the nonwoven fabric was continuously introduced into the PVA aqueous solution, it was squeezed between two rolls. A certain amount of PVA aqueous solution was impregnated.

Next, the PVA aqueous solution was solidified at a surface temperature of 100° C. using a Teflon-coated steam heating cylinder, and then heat-treated for 30 seconds on an Etotherm heating cylinder to produce a product of the present invention.

In this case, the present invention products 1 and 1 where the heat treatment temperature is 160°C
Inventive product 2 was obtained at 80°C, and inventive product 3 was obtained at 200°C.

Incidentally, the amount of PVA deposited was 1.2 times the weight of the nonwoven fabric in all of Invention Products 1 to 3.

The hygroscopicity, water absorption, and heat retention properties of the products 1 to 3 of the present invention were examined, and the results are shown in Table 1.

For comparison, only the nonwoven fabrics used in Invention Products 1 to 3, polyester nonwoven fabrics (manufactured by Unitika, trade name: Roughsheet), and polyolefin nonwoven fabrics (manufactured by Mitsui Petrochemicals, trade name: Roughsheet), which have been conventionally used as agricultural covering materials. Similar measurements were also performed on the Syntax Sheet), and the results are also listed in Table 1.

As shown in Table 1, the product of the present invention has extremely superior moisture absorption, water absorption, and heat retention properties compared to conventional products, and is clearly a suitable covering material for crop cultivation in the severe cold season. be.

Example 2 When producing the product of the present invention in the same manner as in Example 1, the heat treatment temperature was kept constant at 180°C, and the PVA aqueous solution used was PVA
Inventive product 4, PVA, which is a 9% aqueous solution with 2% butane gas microcapsules (foaming temperature 70°C)
2% butane gas microcapsules and 5% in 9% aqueous solution
A product 5 of the present invention was obtained in which aluminum powder (average particle size 20 to 30 μm) was added.

The hygroscopicity, water absorption, and heat retention properties of the products 4 to 5 of the present invention were measured according to the description above, and the measurement results are shown in Table 2.As is clear from the table, the products 4 to 5 of the present invention have hygroscopicity, water absorption, and heat retention. In terms of water absorption, it is good, being on the same level as products 1 to 3 of the present invention, and in terms of heat retention, it has insulation properties due to the formed pores, and furthermore, due to the shielding property of infrared rays in the 6 to 17μ wavelength range due to the aluminum powder. It is confirmed that this product exhibits a heat retention property that is one step higher than that of products 1 to 3 of the present invention, and is a more suitable agricultural covering material.

Example 3 A product of the present invention was produced in the same manner as in Example 1, except that the heat treatment temperature was kept constant at 160° C. and the nonwoven fabric used was variously changed.

In this case, the nonwoven fabric used has a fiber length of 70 mm and a fineness of 3.
Denier, porosity 0.1 polyvinyl alcohol fiber (
A product 6 of the present invention using a nonwoven fabric made of vinylon fiber) and a product 7 of the present invention using a nonwoven fabric made of rayon fiber having a fiber length of 50 am, a fineness of 5 denier, and a porosity of 0.1 were obtained.

Products 6 to 7 of the present invention exhibited good performance comparable to that of products 1 to 3 of the present invention in terms of heat retention, and in terms of hygroscopicity and water absorption, the measurement results are shown in Table 3. Since a nonwoven fabric made of hydrophilic fibers was used, this product exhibited superior performance to Invention Products 1 to 3, and is a more suitable agricultural covering material.

Example 4 In Example 1, the heat treatment temperature was kept constant at 160°C, and PVA
Inventive products 8 to 10 and comparative products 1 to 2 were produced in the same manner except that the amount of aqueous solution applied was varied.

The obtained product was examined for hygroscopicity, water absorption, heat retention, and usability, and the results are shown in Table 4.

As shown in Table 4, it can be seen that the weight ratio of the nonwoven fabric and the amount of PVA deposited is within a certain range and is particularly effective*.

Example 5 Inventive products 11 to 13 and comparative products 3 to 4 were manufactured in the same manner as in Example 1, except that nonwoven fabrics with various porosities as shown in Table 5 were used, and heat treatment was performed at a temperature of 160°C. did.

Table 5 shows the results of examining the hygroscopicity, water absorption, heat retention, usability, and durability of the obtained material.As is clear from the table, good results were obtained within a certain range of porosity of the nonwoven fabric. is obtained.

[Brief explanation of the drawing]

1 to 3 are explanatory diagrams showing examples of the agricultural covering material of the present invention. DESCRIPTION OF SYMBOLS 1... Nonwoven fabric fiber, 2... Crossing part of nonwoven fabric fiber, 3... Heat treated PVA film, 4...
... Vacancy, 5... Pore, 6...
Aluminum powder.

Claims (1)

[Scope of Claims] 1. A nonwoven fabric having a porosity of 0.01 to 0.7, with a porosity of 0.3 to the weight of the nonwoven fabric in the nonwoven fabric constituent fibers and/or their intersections.
A heat-treated polyvinyl alcohol synthetic resin film of ~3 times the strength is formed and coated, and when the film dries, it has voids between the constituent fibers of the nonwoven fabric, but when it swells, it fills at least most of the voids. An agricultural covering material with excellent heat retention, dehumidification, and drip-free properties, which is characterized by being closed in part and virtually non-ventilated over the entire surface. 2. An agricultural covering material with excellent heat retention, dehumidification, and drip-free properties according to claim 1, wherein the nonwoven fabric is a nonwoven fabric made of hydrophilic fibers. 3. Agricultural coating with excellent heat retention, dehumidification, and drip-free properties according to claim 1 or 2, wherein the coating material made of nonwoven fabric and heat-treated polyvinyl alcohol synthetic resin film has a thickness of 5 cm or less. Material. 4 After applying a solution containing polyvinyl alcohol synthetic resin as the main component to a nonwoven fabric with a porosity of 0.01 to 0.7,
The polyvinyl alcohol synthetic resin is solidified and then 1
Heat treatment is performed at a temperature of 40 to 220°C, and the fibers constituting the nonwoven fabric or/and their intersections are coated with 0.3 to 0.3% of the weight of the nonwoven fabric.
A method for manufacturing an agricultural covering material having excellent heat retention, dehumidification, and drip-free properties, which is formed and coated with a 3x heat-treated polyvinyl alcohol synthetic resin film. 5. The method for producing an agricultural covering material with excellent heat retention, dehumidification, and drip-free properties according to claim 4, wherein the nonwoven fabric is a nonwoven fabric made of hydrophilic fibers. 6. Production of an agricultural covering material with excellent heat retention, dehumidification, and drip-free properties according to claim 4 or 5, wherein the solution containing polyvinyl alcohol synthetic resin as a main component contains a pore-forming aid. Method. 7. Heat retention, dehumidification, and non-droplet properties according to claim 4, item 5 or 6, wherein the solution whose main component is polyvinyl alcohol synthetic resin contains aluminum powder with an average particle size of 10 to 50μ. How to make superior agricultural coverings.