JPS625182B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an agricultural film mainly composed of an olefin resin with improved heat retention and drip-free properties.
More specifically, for 100 parts by weight of olefin resin (A), 2 to 20 parts of hydrated aluminum silicate gel (B)
parts by weight, the ratio of the refractive index _nA of the olefinic resin to the refractive index nB of the hydrous aluminum silicate gel, _nA / _{nB ,} is 0.99.
The present invention relates to an agricultural film formed from a composition having a molecular weight of 1.01 or less. Conventionally, olefin resin films such as polyvinyl chloride film, polyethylene film, and ethylene-vinyl acetate copolymer film have been used as covering materials for agricultural greenhouses, tunnel houses, etc.; The disadvantage is that the plasticizer contained in the film bleeds onto the film surface, attracting dust, which significantly impairs the light transmittance and prevents the temperature from rising inside the greenhouse.In addition, if the film is incinerated after use, it releases hydrochloric acid gas. There is a problem in that it is difficult to dispose of as it is generated. In addition, olefin resin film does not contain plasticizers and has a stable chemical structure, so its light transmittance hardly changes during long-term use, and no harmful gases are generated even when incinerated. Although it is superior to polyvinyl chloride film, this film is inferior to polyvinyl chloride film in terms of heat retention. Therefore, although olefin resin films have the above-mentioned advantage of long-lasting light transmittance, they have not been widely used as house covering films in the past. In general, the heat retention properties of the covering film for greenhouses and greenhouses are the properties that prevent the temperature inside the greenhouse from dropping at night. The temperature inside the house is kept higher than the temperature of the outside air by being radiated from the ground as radiation, but if the transmittance of the radiation radiating from the ground of the covering film is high, the radiation rays from the ground are As it dissipates outside the greenhouse, the soil temperature inside the greenhouse decreases, and as a result, it becomes impossible to maintain the temperature inside the greenhouse higher than the outside temperature. Therefore, the quality of the heat retaining property of the coating film depends on the radiation absorption or reflectance, and the higher the reflectance, the better. In addition, one of the characteristics required of a coating film for greenhouses and greenhouses is water drop resistance. The water droplet resistance of a coating film refers to the property that when the coating film is used as a house, it is difficult for small water droplets to form due to internal water vapor condensing on the film's inner surface, but olefin resin films have low wettability to water droplets. Therefore, it has been pointed out that the water droplet prevention property is inferior. For this reason, a water droplet prevention agent is usually mixed to improve the wetting of the film surface, but there are problems with the sustainability of the water droplet prevention effect and the excessive bleeding of the water droplet prevention agent onto the film surface, which reduces the light transmittance of the film. Because of the formation of spots, a film with good water droplet prevention properties has not yet been obtained. Examples of coating films with improved heat retention properties of olefin resin films include coating films made by adding specific inorganic fillers such as phosphate compounds, silicon oxide, and dehydrated kaolinite to olefin resins. However, although these methods have improved the heat retention properties of olefin resins, they are still insufficient compared to polyvinyl chloride films, and the biggest problem is that the resulting film The transparency, especially the parallel light transparency, is inferior to that of polyvinyl chloride film or ethylene-vinyl acetate copolymer film. In general, it is said that the light transmittance required for agricultural covering films is 80 to 85% or more in terms of total light transmittance, but even if the total light transmittance satisfies this requirement, The effects on crops vary greatly depending on which of light transmittance and scattered light transmittance contributes more. For example, fruits and vegetables, such as tomatoes, cucumbers, and watermelons, which are originally summer crops, generally prefer to grow under parallel light.If scattered light is used, problems often occur with color change and fruit growth; In recent years, it has gradually become clear that scattered light is preferable for raising seedlings of leafy vegetables such as cabbage and rice, as it improves the growth of the leaves. However, with the exception of wet rice cultivation, farmers still often use transparent polyvinyl chloride film, which has good parallel light transmittance, for not only fruit and vegetable crops but also for greenhouses and tunnels. This is also due to the fact that it has the great advantage of being able to see the growth status of crops inside from the outside. For this reason, although the technology to improve the heat retention, which was a drawback of polyolefin film, by adding a specific inorganic filler to polyolefin as described above has been provided for a long time, it is still not generally used. This is the current situation. Furthermore, the conventional technology in which a specific inorganic filler is added to polyolefin as described above does not provide water drop prevention properties, but water drop prevention properties are imparted by adding a large amount of a compound that is usually called a dripless agent or a wetting agent. Must. As a way to solve these problems, attempts have been made in recent years to improve parallel light transmittance and heat retention by adding specific polymer compounds such as polyacetal to polyolefin, but in this case, However, the effect of improving heat retention is still insufficient. The present inventors have removed the above-mentioned problems with olefin resins as agricultural films,
In order to provide agricultural films with excellent heat retention, parallel light transmittance, and water droplet resistance at low prices, we have conducted intensive research and developed a hydrated aluminum silicate gel powder that has a refractive index that is almost the same as that of olefin resins. The present invention was completed based on the discovery that by forming a film from a composition containing the following, a film having parallel light transmittance, heat retention, and water droplet prevention properties that are extremely superior to those of the prior art can be obtained. That is, the present invention provides a composition in which 2 to 20 parts by weight of aluminum silicate gel (B) is blended with 100 parts by weight of olefin resin (A), wherein the refractive index n _A of the olefin resin and aluminum silicate are The present invention relates to an agricultural film formed from a composition in which the ratio n _A /n _B of the gel refractive index n _B is in the range of 0.98 or more and 1.02 or less. The first feature of the present invention is that even though an inorganic filler is added to the olefin resin, a transparent film with very good parallel light transmittance can be obtained, and it also overcomes the drawbacks of conventional olefin resin films. The heat retention properties have been greatly improved and are comparable to those of polyvinyl chloride film. This heat retention improvement effect is due to the synergistic effect of the infrared opacity of water in addition to the infrared opacity of hydrated aluminum silicate gel, which greatly improves heat retention, since hydrated aluminum silicate gel adsorbs a large amount of water. It is considered that The second feature of the present invention is that the above-mentioned water-containing aluminum silicate gel contains a large amount of water, so that the film can have an effect of preventing water droplets. In addition, a small amount of non-drip agent is added for the purpose of providing remarkable water drop prevention performance.
When a humectant is used in combination, the moisturizing agent is adsorbed to the hydrous aluminum silicate gel and gradually released, resulting in excellent long-lasting effects. A third feature of the present invention is that a hydrous aluminum silicate gel having a desired refractive index is generally available at low cost by a manufacturing method known in the prior art;
Since it can be added to the olefin resin at the same time when formulating additives when manufacturing conventional agricultural films, the manufacturing process of the conventional technology can be used as is.
Since it is easy to form into a film, it is possible to provide a film according to the present invention which has greatly improved performance at a price not much different from that of conventional olefin resin agricultural films. The fourth feature of the present invention is that the composition of the present invention, which is mainly composed of olefin resin, is essentially easy to incinerate, and does not generate harmful substances such as hydrochloric acid gas when incinerated, making it easy to dispose of it after use. That's true. The above-mentioned features are advantages of the present invention over the prior art. The present invention will be explained in more detail below. The olefin resin used in the present invention is a homopolymer of α-olefin, or a copolymer with a different monomer containing α-olefin as a main component, such as polyethylene, polypropylene, or ethylene-propylene copolymer. Copolymer, ethylne-butene copolymer, ethylene-4-methyl-1-pentene copolymer, ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer and the like. Among these, low-density polyethylene with a density of 0.910 to 0.935, ethylene-α-olefin copolymer, and ethylene-vinyl acetate copolymer with a vinyl acetate content of 30% by weight or less are preferred in terms of transparency, weather resistance, and price. It is preferable as a film for kana agriculture. Further, among these, ethylene-vinyl acetate copolymers having a vinyl acetate content of 5% by weight or more and 25% by weight or less are more preferable in terms of transparency, flexibility, weather resistance, etc. The refractive index (25
℃D line) is generally between 1.48 and 1.52; for example, in low-density polyethylene with a density of 0.935 or less,
1.51 to 1.52 with vinyl acetate content of 30
The refractive index of the ethylene-vinyl acetate copolymer below weight percent is in the range of 1.48 to 1.51. The hydrous aluminum silicate gel used in the present invention is a hydrous composite oxide gel, and its composition is determined according to the gist of the present invention.
That is, the refractive index of the olefin resin used in carrying out the present invention is measured using, for example, a D(Na) ray at 25° C. and a relative humidity of 65%, and the refractive index n _A obtained is The composition of the hydrous aluminum silicate gel is determined so that it has a refractive index _nB as close as possible to that of the gel. In this case _, the ratio n _A and n _B is 0.98 or more _.
Unless a hydrous aluminum silicate gel having a composition with n _B of 1.02 or less, more preferably 0.99 or more and 1.01 or less is used, the parallel light transmittance of the resulting film will deteriorate, which is not preferable. The refractive index of olefin resin is generally 1.48~
1.52, and calculate the refractive index of the hydrous aluminum silicate gel corresponding to the most preferable refractive index ratio n _A /n _B of the composition of the present invention from 0.99 to 1.01 with respect to the refractive index n _A of this olefinic resin. n _B
is 1.47 to 1.54, and a hydrous aluminum silicate gel having a refractive index within these ranges is most suitable for the composition of the present invention. The composition of the hydrous aluminum silicate gel is the above n _B =
Uniquely determined from 1.47 to 1.54. i.e. n
The composition corresponding to _B is 1.47 is 90% by weight of silica, 7% by weight of alumina, 3% by weight of impurities, and _nB .
The composition corresponding to 1.54 is 60% by weight of silica, 37% by weight of alumina, and 3% by weight of impurities. Therefore, the most preferable composition of the hydrous aluminum silicate gel in the composition of the present invention is 90 to 60% by weight of silica and 7 to 60% by weight of alumina, excluding water.
It has a composition consisting of impurities of 37% by weight or less and 3% by weight or less, and furthermore, among these hydrous aluminum silicate gels, the adsorbed moisture at 25°C and 65% relative humidity is 10% or more, more preferably 20% or more. Those having the above are preferably used in the present invention. If the adsorbed water content is less than 10%, it is not preferable because the effect of improving heat retention and preventing water droplets, which are the gist of the present invention, is insufficient. Furthermore, when using such a hydrous aluminum silicate gel, it is necessary that it is a fine powder, and it is desirable that the average particle size is 10 μm or less, more preferably 5 μm or less. In addition, particles with a particle size exceeding 20μ are within 3% by weight of the total particles.
More preferably, it is within 0.1% by weight. If the average particle size exceeds this range, it is not preferable because it not only deteriorates the appearance of the resulting film and deteriorates parallel light transmittance due to surface irregularities, but also deteriorates the physical properties of the film. In addition, the blending ratio of the hydrous aluminum silicate gel to the olefin resin is
It is preferably 2 to 20 parts by weight, and 3 to 20 parts by weight per 100 parts by weight.
10 parts by weight is more preferred. The amount of the compound is 2
If the amount is less than 20 parts by weight, the effect of improving the heat retention and water droplet prevention properties of the resulting film will not be significant, and if the amount exceeds 20 parts by weight, the strength of the resulting film will decrease, which is not preferable. The method of carrying out the present invention is to mix an olefinic resin and a hydrous aluminum silicate gel by a conventional method such as mixing or kneading in a roll type or Banbury type mixer or extruder, and then, for example, by inflation processing or calendering. , and is formed into a film using a normal forming method such as T-die processing. Usually film processing is 130~250℃
Since the hydrous aluminum silicate gel used in the present invention desorbs adsorbed water in this temperature range, it is necessary to pre-dry it at a temperature around the processing temperature to remove the adsorbed water. In order to improve the dispersion of the hydrous aluminum silicate gel, the film obtained as described above contains, for example, sorbitan fatty acid esters such as sorbitan monostearate, glycerin fatty acid esters such as glycerin monostearate, etc. A dispersant is added to the composition of the present invention,
It is also effective to add 0.2 to 2 parts by weight, and it is also effective to mix in suitable stabilizers, ultraviolet absorbers, antistatic agents, and if necessary, water drop preventive agents. When the olefin resin film obtained by the present invention is used as a coating film for greenhouses, greenhouses, etc., it shows a remarkable improvement in heat retention compared to the conventional technology, and is comparable to polyvinyl chloride films. In addition to having excellent performance to the extent that it can absorb moisture, its parallel light transmittance is also equivalent to that of polyvinyl chloride, and its change over time is actually better than that of polyvinyl chloride film, and it also has excellent properties in terms of water drop resistance. It is extremely useful as an agricultural film. Next, the present invention will be explained with reference to Examples, but these Examples are merely illustrative and are not limited thereto. The heat retention measurements shown in the Examples and Comparative Examples were carried out using a heat retention measurement device in which a sample was placed on one side of a box approximately 30 cm cubic in size made of heat insulating material. The temperature change inside the device was measured using a thermistor. The temperature difference from the value shown by the standard sample glass plate (approximately 2 mm thick) was expressed as the heat retention property [△T°C]. Transmittance was measured by measuring haze value and total light transmittance using a haze meter in accordance with JIS K-6714. At this time, the parallel light transmittance was determined using the following formula. Parallel light transmittance = total light transmittance - haze value The refractive index of the inorganic powder was measured by the immersion method, and the refractive index of the polymer film was measured using an Abbe refractometer. The measurements were carried out in a room at 25° C. and 65% RH using the D line. In addition, a water drop prevention test was conducted using the following method. Fill a 100c.c. beaker with water (30℃), cover it with a sample film, and then place it in a constant temperature bath (30℃).
The beaker was placed in a sunny place and the condition was observed after a predetermined period of time. The evaluation results were expressed using the following criteria. ○: There are no small water droplets. △: Small water droplets are observed in some areas. ×: Small water droplets adhere to the entire surface. Example 1 Ethylene-vinyl acetate copolymer with a vinyl acetate content of 15% by weight (MI = 2 g/10 min, refractive index n _A =
1.498) 100 parts by weight and pre-dried at 150℃ for 2 hours
Hydrous aluminum silicate gel (refractive index _{n B} = 1.493 _{, 21} % adsorbed moisture at 25 °C relative temperature 65%, average particle size 4μ) and 0.3 parts by weight of glycerin monostearate as a dispersant were kneaded in a Brabender Plastograph at 150°C for 8 minutes, and then press-molded at 170°C to form a film with a thickness of 100μ. As shown in Table 1, the obtained film was transparent and had excellent heat retention and water droplet prevention properties. Example 2 In Example 1, the vinyl acetate content was 15% by weight.
Ethylene-vinyl acetate copolymer with a vinyl acetate content of 25% by weight instead of the ethylene-vinyl acetate copolymer (MI = 2 g/10 min, refractive index n _A = 1.489)
The thickness was 100μ in the same manner as in Example 1 except that
A film was prepared, film molded and measured, and the results are shown in Table 1. Example 3 In Example 1, the vinyl acetate content was 15% by weight.
Ethylene-vinyl acetate copolymer with a vinyl acetate content of 5% by weight instead of the ethylene-vinyl acetate copolymer (MI = 2 g/10 min, refractive index n _A = 1.505)
Film molding and measurement were carried out in the same manner as in Example 1, except that the following was used, and the results are shown in Table 1. Comparative Example 7 Same as Example 1 except that low density polyethylene with a density of 0.924 (MI = 1.8 g/10 min, refractive index n _A = 1.515) was used instead of the ethylene-vinyl acetate copolymer in Example 1. Film molding and measurements were carried out using the following methods, and the results are shown in Table 1. Example 4 Film molding and measurements were carried out in the same manner as in Example 1 except that the amount of hydrous aluminum silicate gel was changed to 15 parts by weight. The results are shown in Table 1. Example 5 Film molding and measurements were carried out in the same manner as in Example 1 except that the dispersant glycerin monostearate was not added, and the results are shown in Table 1. Comparative Examples 1-4 Film molding and measurements were carried out in the same manner as in Examples 1-3 and Comparative Example 7, except that the hydrous aluminum silicate gel was removed, and the results are shown in Table 1. . Comparative Example 5 Same as Example 1 except that the hydrous aluminum silicate gel was changed to silica gel (refractive index n _B = 1.465, adsorbed moisture 29% at 25° C. relative humidity 65%, average particle size 4 μ). Film molding and measurements were carried out using the following methods, and the results are shown in Table 1. Comparative Example 6 In Example 1, the hydrous aluminum silicate gel was replaced with anhydrous kaolinite (compositional formula: Al ₂ O ₃
2SiO ₂ 2H ₂ O, refractive index 1.560, 25℃, relative humidity 65
Film molding and measurement were carried out in the same manner as in Example 1, except that the adsorbed water content was changed to 3.0% (average particle size: 4 μm), and the results are shown in Table 1.

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Claims (1)

[Scope of Claims] 1. A composition comprising 100 parts by weight of an olefin resin (A) and 2 to 20 parts by weight of a hydrous aluminum silicate gel (B), wherein the olefin resin has a refractive index n. An agricultural film formed from a composition in which the ratio n _A /n _B of _A and the refractive index n _B of the hydrous aluminum silicate gel is in the range of 0.99 or more and 1.01 or less. 2. The olefin resin (A) is a low-density polyethylene with a density of 0.935 or less, an ethylene-α-olefin copolymer, or an ethylene-vinyl acetate copolymer, and the hydrous aluminum silicate gel has a composition excluding water, Silica 90~60
2. The agricultural film according to claim 1, which is a hydrous aluminum silicate gel comprising water as a component consisting of 7 to 37% by weight of alumina, and 3% by weight or less of impurities. 3. The agricultural film according to claims 1 and 2, wherein the hydrated aluminum silicate gel has an adsorbed moisture content of 10% or more at 25° C. and 65% relative humidity.