JPS6313832B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an agricultural film mainly composed of an olefin resin that has improved heat retention, transparency, and abrasion resistance. Conventionally, polyolefin resin films such as polyvinyl chloride films, polyethylene films, and ethylene-vinyl acetate copolymer films have been mainly used as greenhouse covering materials for greenhouse cultivation such as agricultural greenhouses and tunnel houses. Among these, polyvinyl chloride film has been widely used in this field until recently because it has excellent heat retention, transparency, toughness, and durability. however,
Polyvinyl chloride film has the disadvantage that during use, the plasticizer contained in the film bleeds onto the film surface, which attracts dust, which significantly impairs light transmittance, and prevents the temperature from rising inside the greenhouse, and it must be incinerated after use. There is a problem in that it is difficult to dispose of because hydrochloric acid gas is generated during treatment. Furthermore, it loses its flexibility at low temperatures and has poor impact resistance, making it unsuitable for use in cold regions. On the other hand, 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. Furthermore, among olefin resins, ethylene-vinyl acetate copolymer film has been recognized for its advantages such as transparency, flexibility, and cold resistance, and has recently attracted attention as an agricultural covering material, but its heat retention properties are lower than that of polyvinyl chloride. In addition to the above-mentioned problem of inferiority, there is also the problem of inferior friction strength. Specifically, when the covering material is opened and closed for ventilation at the pipe part of a pipe house or the car wire holding part, or when it is blown by the wind, it is rubbed. There is a problem that the film is damaged. 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. 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 addition of inorganic fillers makes it difficult to use ordinary films. In processing methods such as the T-die casting method and the inflation method, the molten resin is cooled and solidified while being stretched, so that the surface of the film becomes uneven. For this reason, the film is more likely to be damaged due to friction at the pipe section of the house or the car wire holding section, and more importantly, the transparency of the film, especially its parallel light transmittance, is lower than that of polyvinyl chloride film or ethylene-vinyl acetate copolymer film. This is inferior to the combined film. Generally, the light transmittance required for agricultural covering films is 80~80 in terms of total light transmittance.
It is said that 85% or more is required, but even if the total light transmittance satisfies this requirement, the impact on crops will depend on whether the contribution is greater, parallel light transmittance or scattered light transmittance. are very different. For example, fruits and vegetables, including tomatoes, cucumbers, and watermelons, which are originally summer crops, generally prefer to grow using parallel light, and when using scattered light,
Problems with coloration and fruit growth often occur.
In addition, it has gradually become clear in recent years that scattered light is preferable for raising seedlings of leafy vegetables such as lettuce and cabbage, and paddy 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 for improving the heat retention, which was a drawback of polyolefin films, by adding a specific inorganic filler to polyolefins as described above has been provided for a long time, it is still not generally used. It is. 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 polymeric 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, and
In order to provide an agricultural film with excellent heat retention, parallel light transmittance, and abrasion resistance at a low price, we have conducted extensive research and found that the primary particle size is 40 mμ or less, and the average secondary particle size is more than 5 μm and 10 μm or less. , and substantially 20μ
By providing an ionomer resin on the inner and outer surfaces of a film made of a composition containing silicon oxide that does not contain the above secondary particles, the film has superior parallel light transmittance, heat retention, and friction resistance properties compared to conventional technology. They discovered that a film could be obtained and completed the present invention. The first feature of the present invention is that although an inorganic filler is added to the olefin resin, by providing a resin layer that does not contain filler on the inner and outer surfaces, surface irregularities generated during film processing are significantly improved, resulting in reduced external haze. This significantly reduces the transmittance of parallel light, making it possible to obtain a transparent film with excellent parallel light transmittance.In addition, heat retention, which was a drawback of conventional polyolefin films, has been greatly improved and is now comparable to that of polyvinyl chloride film. At the point. The second feature of the present invention is that by providing a filler-free resin layer with excellent friction resistance on the inner and outer surfaces, the friction resistance of the resulting film is significantly improved, and its toughness is comparable to that of polyvinyl chloride film. The point is that it can be improved to the extent that it is possible. The third feature of the present invention is that silicon oxide having a desired particle size can be generally obtained at low cost by a manufacturing method known in the prior art, and that it can be added to olefin resins as an additive when manufacturing agricultural films. Since it can be added at the same time during formulation, the manufacturing process of the conventional technology can be used as is, and it is generally easy to form a film.As a result, the present invention has greatly improved performance at a price not much different from that of conventional olefin resin agricultural films. The point is that it can provide film. 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. In the present invention, the olefin resin used in the intermediate layer includes an α-olefin homopolymer,
It is a copolymer with different monomers mainly composed of α-olefin, such as polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-butene copolymer, ethylene-4-methyl-1-
Examples include pentene copolymers, ethylene-vinyl acetate copolymers, ethylene-acrylic acid copolymers, 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 good for transparency, weather resistance, and price. From this point of view, it is preferable as an agricultural film. 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 particularly preferred in terms of transparency, flexibility, weather resistance, etc. In the present invention, the resin used for the inner and outer layers is preferably a resin that does not impair the heat retention properties of the intermediate layer and has good friction resistance. According to the findings of the present inventors, the house covering materials include house aggregates (e.g. iron pipes, bamboo, etc.) and holding cords (usually called mica wire) used to stabilize the film between the aggregates. Friction occurs when the hem is opened and closed for ventilation, the film vibrates due to the wind, etc., and the friction causes heat generation and abrasion of the resin.Furthermore, the film is heated by sunlight, which causes deterioration and breakage. The ionomer resin used for the inner and outer layers in the present invention is a resin having a metal ion crosslinked structure of α-olefin and α,β-unsaturated carboxylic acid copolymer. Usually, the α-olefin is ethylene,
A copolymer using methacrylic acid as the α,β-unsaturated carboxylic acid and containing 1 to 5 mol% of methacrylic acid, and using Na ⁺ and Zn ⁺⁺ as the metal ions is available from DuPont Co., Ltd., for example. It is sold under the trade name Surlyn. Those preferably used in the present invention have a density of 0.935 g/cm ³ or more.
It is preferably 0.975 g/cm ³ or less, a melt index of 0.5/10 min or more and 7 g/10 min or less, and the metal ion is preferably of the Na ⁺ or Zn ⁺⁺ type. The silicon oxide used in the present invention preferably has primary particles of 40 μm or less, substantially no secondary particles of 20 μm or more, and an average secondary particle size of more than 5 μm and 10 μm or less. Among these, substantially amorphous silicon oxide is particularly suitable for the present invention. Generally, the refractive index of olefin resin (20℃ D line)
is between 1.48 and 1.52, and the refractive index of low-density polyethylene and ethylene-vinyl acetate copolymer, which are commonly used for agricultural purposes, is between 1.49 and 1.51. On the other hand, the refractive index of silicon oxide commonly used for resin fillers is in the range of 1.45 to 1.48. However, this does not apply to special crystalline silicon oxides such as quartz.
For this reason, light scattering occurs at the filler/resin interface, so in addition to light scattering on the film surface (which can be quantified by external haze), there is also the problem of light scattering within the film (which can be quantified by internal haze). occurs. Because of these problems, in order to achieve one of the objects of the present invention, it is necessary to use silicon oxide having a specific particle size as described above to relatively reduce the internal haze, and at the same time to reduce the inner and outer haze. It is necessary to significantly reduce the external haze by providing a resin layer that does not contain filler. The blending ratio of the silicon oxide to the olefin resin is preferably 2 to 25 parts by weight, more preferably 3 to 15 parts by weight, based on 100 parts by weight of the olefin resin.
If the amount of the compound is less than 2 parts by weight, the effect of improving the heat retention of the resulting film is not very noticeable,
Moreover, if the amount is more than 25 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 the olefin resin and silicon oxide powder 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 calender processing. , and is formed into a film using a normal forming method such as T-die processing. Usually film processing is suitably carried out at a processing temperature of 130 to 250°C. Methods for providing ionomer resin on the inner and outer surfaces of a film made of olefin resin containing silicon oxide include a method of forming each film into a laminated film by dry lamination, heat lamination, etc.; Existing techniques may be used, such as extrusion lamination of an ionomer resin onto a resin film, or simultaneous molding of a laminated film using a multilayer extrusion method.In particular, a multilayer extrusion method is preferred because of its ease of molding and the resulting film. It is preferable in terms of interlayer adhesion, transparency, cost, etc. Furthermore, since wide films are preferred for agricultural applications, a multilayer inflation process is desirable. In addition, the thicknesses of the film (intermediate layer) made of the olefin resin containing silicon oxide and the resin layers (inner and outer layers) provided on the inner and outer surfaces are determined depending on the end use and purpose, and are not necessarily specified. The layers depend on the required level of heat retention and the ratio of silicon oxide to the resin, but usually 30μ to 200μ is sufficient, and the inner and outer layers have a level that reduces the external haze of the middle layer and has abrasion resistance. The thickness can be any thickness that allows the expression to occur, and usually a thickness of about 10μ to 20μ is sufficient. In the film obtained as described above, in order to improve the dispersion of silicon oxide in the intermediate layer,
For example, it is also effective to use a dispersant such as sorbitan fatty acid ester such as sorbitan monostearate or glycerin fatty acid ester such as glycerin monostearate by adding 0.2 to 2 parts by weight to the composition of the present invention, It is also effective to mix appropriate stabilizers, ultraviolet absorbers, antistatic agents, and, if necessary, water drop preventive agents into both the intermediate layer and the inner and outer layers. When the olefin resin film obtained by the present invention is used as a film for multiple applications such as temperature control and greenhouses, 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 absorbs water, its parallel light transmittance is comparable to that of polyvinyl chloride, and its change over time is even better than that of polyvinyl chloride film.Additionally, inorganic fillers are added to the olefin resin for heat retention. The parallel light transmittance is significantly better than that of technologies that attempt to improve the film, and the abrasion resistance and toughness are also significantly better and are comparable to polyvinyl chloride film, making it 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]. Transparency 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 In addition, a water drop prevention test was conducted by the method shown below. 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. ×: A small number of droplets adhere to the entire surface. Furthermore, the friction resistance performance was measured using the following method. A pre-weighed sample film was fixed by attaching it to the circular section of a 200φmm cylindrical jig without wrinkles, and a ring-shaped 100φmm iron rotor was thoroughly polished with #180 paper on the surface that would contact the film. the fixed film perpendicularly from the film surface.
After pressing down 20 mm, pour 20 c.c. of water onto the film surface to prevent extreme temperature rise due to frictional heat generation.
The film was rotated at a speed of 240 rpm, and the time until the film was torn and the loss of film abrasion per hour were measured. Example 1 In 100 parts by weight of ethylene-vinyl acetate copolymer (MI = 2 g/10 min) with a vinyl acetate content of 15% by weight, there are particles with a primary particle size of 16 mμ, a secondary particle size of 6 μ, and particles of 20 μ or more 8 parts by weight of amorphous silicon oxide,
Add 0.3 parts by weight of glycerin monostearate as a dispersant to a resin temperature of 130 to 150 using a Banbury mixer.
After kneading at ℃ for 10 minutes, granulated pellets were produced using an extruder. Hereinafter, the above mixture will be referred to as filler mixed resin. Using a multilayer inflation device equipped with a two- and three-layer inflation die (diameter 150mm), the filler mixed resin was passed through an extruder with a diameter of 40mm into the middle layer of the die, and the weight of the filler mixture was 9 kg at a melting zone of 180℃ and a die temperature of 190℃. /hr, and Mitsui Polychemical's Himilan 1650 (density 0.95,
Melt index 1.5, Zn ion type of ethylene-methacrylic acid copolymer) melting zone 215
The resin supplied to each layer was laminated inside the die to form a tubular body with a three-layer sandwich structure at a blow-out ratio of 2.4 and a frost line distance. 200 mm, taken at a taking speed of 4.9 m/min, folded diameter: 365 mm, thickness of each layer: inner layer 0.013 mm, middle layer 0.05 mm, outer layer 0.013
A film with a three-layer sandwich structure composed of mm was obtained. Table 1 summarizes the results of measuring the heat retention, total light transmittance, parallel light transmittance, haze, tear strength, punching impact strength, and abrasion resistance of the obtained film.
It was shown to. Example 2 In Example 1, Himilan 1707 (density 0.95 g/cm ³ , melt index 0.9 g/10 minutes, Na ion type of ethylene-methacrylic acid copolymer) was used instead of Himilan 1650 for the inner and outer layers, and the extrusion conditions were changed. A film was obtained by repeating Example 1 except that the melting zone was changed to 220°C and the die was changed to 195°C. The physical properties of the obtained film are summarized in Table 1. Comparative Example 1 Using the ethylene-vinyl acetate copolymer alone used as the base of the filler mixed resin used for the intermediate layer in Example 1, a melting zone was produced using a 50 mm diameter extruder equipped with a 100 mm diameter spiral die.
The tubular body was taken at a blow-up rate of 2.4, a frost line distance of 200 mm, and a take-up speed of 5 m/min under conditions of 180° C. and 177° C. to obtain a single-layer film with a thickness of 0.075 mm. The physical properties of the obtained film are summarized in Table 1. Comparative Example 2 Filler mixed resin pellets were produced by the method of Example 1, except that the blending ratio of amorphous silicon oxide in the filler mixed resin used for the intermediate layer in Example 1 was changed to 5.4 parts by weight, and the pellets were A monolayer film of filler-mixed resin was obtained using the extruder and extrusion conditions of Comparative Example 1. The obtained film had a slightly matte texture. The physical properties of the film are summarized in Table 1. Comparative Example 3 In place of the amorphous silicon oxide in the filler mixed resin used for the intermediate layer in Example 1, an average particle size of 15μ was used.
Example 1 was repeated except that the same amount of quartz powder was used to obtain a film. The resulting film was opaque. The physical properties are summarized in Table 1. Comparative Example 4 Himilan used for the inner and outer layers in Example 1
Except that high-pressure low-density polyethylene (Sumikasen F208-1) with a density of 0.925 g/cm ³ and a melt index of 1.7 g/10 min was used instead of 1650, and the extrusion conditions were changed to a melt zone of 173°C and a die of 168°C. Example 1 was repeated to obtain a film. The physical properties of the obtained film are summarized in Table 1. Comparative Example 5 Himilan used for the inner and outer layers in Example 1
Ethylene-4-methyl-1-pentene copolymer (4-methyl-1-pentene content 9% by weight) obtained with a Ziegler catalyst system with a density of 0.920 g/cm ³ and a melt index of 2 g/10 min instead of 1650. ) using extrusion conditions: melt zone 175℃, die 168℃
A film was obtained by repeating Example 1 except for changing the following. The physical properties of the obtained film are summarized in Table 1. Comparative Example 6 Himilan used for the inner and outer layers in Example 1
Instead of 1650, an ethylene-butene copolymer (butene-1 content 10% by weight) polymerized with a Ziegler catalyst with a density of 0.920 g/cm ³ and a melt index of 1.5 g/10 min was used, and the extrusion conditions were changed to melt zone.
A film was obtained by repeating Example 1 except that the temperature was changed to 175°C and the die temperature to 168°C. The physical properties of the obtained film are summarized in Table 1. Comparative Example 7 Himilan used for the inner and outer layers in Example 1
Instead of 1650, an ethylene-vinyl acetate copolymer with a density of 0.94 g/cm ³ , a melt index of 0.6 g/10 min, and a vinyl acetate content of 15% by weight was used, and the extrusion conditions were set to 175°C in the melt zone and 168°C in the die. A film was obtained by repeating Example 1 except for changing the following. The physical properties of the obtained film are summarized in Table 1. Comparative Example 8 Himilan used for the inner and outer layers in Example 1
Instead of 1650, an ethylene-acrylic acid copolymer with a melt index of 10 g/10 minutes and an acrylic acid content of 20% by weight was used, and the extrusion conditions were set to a melt zone of 170°C,
A film was obtained by repeating Example 1 except that the die temperature was changed to 168°C. The physical properties of the obtained film are summarized in Table 1. Comparative Example 9 In place of the ethylene-vinyl acetate copolymer used as the base of the filler mixed resin used for the intermediate layer in Example 1, the density was 0.925 g/cm ³ , the melt index was 1.7 g/10 min, and the refractive index was n. _A 1.501 high-pressure polyethylene (Sumikasen F208-1) was used, and the same Sumikasen F208-1 was used instead of Himilan 1650 used for the inner and outer layers, and the extrusion conditions were changed for the inner and outer layers.
A transparent film was obtained by repeating Example 1 except that for both the intermediate layer, the melting zone was changed to 173°C and the die temperature was changed to 168°C. The physical properties of the obtained film are summarized in Table 1. 【table】

Claims (1)

[Claims] 1. Primary particles are 40 mμ or less and the average secondary particle diameter is more than 5 μm based on 100 parts by weight of olefin resin.
Ionomer resin layers are provided on the inner and outer surfaces of a film made of a composition containing 2 to 25 parts by weight of silicon oxide with a particle size of 10μ or less and substantially free of secondary particles of 20μ or more. An agricultural film characterized by having a carbon content of 70% or more. 2. The agricultural film according to claim 1, wherein the olefin resin is a low-density polyethylene or an ethylene-α-olefin copolymer having a density of 0.935 g/cm ³ or less. 3. The agricultural film according to claim 1, wherein the olefin resin is an ethylene-vinyl acetate copolymer. 4 The ionomer resin used for the inner and outer layers is a resin with a zinc ion or sodium ion crosslinked structure of ethylene-methacrylic acid copolymer, and has a high density.
Agricultural use according to claim 1, which is a resin having characteristic values of 0.935 g/cm ³ or more and 0.975 g/cm ³ or less, and a melt index of 0.5 g/10 minutes or more and 7 g/10 minutes or less. film.