JPS638992B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to synthetic resin materials with excellent visible light transmittance (hereinafter referred to as "translucent properties") and heat retention properties, particularly synthetic resins with excellent light transmittance and heat retention properties used for agricultural purposes, etc. The present invention relates to a synthetic resin material suitable for obtaining a film. Films used for agricultural greenhouses and tunnels are required to have heat retention and translucency in order to increase the temperature inside the greenhouse and tunnel and promote photosynthesis. In order to improve heat retention, it is necessary to block the heat escaping from the inside of the house or tunnel to the outside air. Heat dissipation can be divided into radiation, conduction, and convection, but in agricultural greenhouses and the like, heat retention can be greatly improved by suppressing radiation. It is well known that most of the energy of the great sunlight is distributed in the wavelength range of 0.3 to 2.5μ, and that radiation from materials at room temperature contains energy in the long wavelength range of 3μ or more. Therefore, by imparting transparency in the wavelength range of 0.3 to 2.5 μm and opacity to infrared rays with a wavelength of 3 μm or more to the film, excellent heat retaining ability and translucency can be obtained. By using such a film, the temperature inside the house or tunnel can be increased both during the day and night, and at the same time, the temperature rise after sunrise can be increased. In practical terms, this results in faster crop growth, increased yields, and reduced heating costs. The infrared spectrum emitted from the ground is approximated to the blackbody radiation spectrum and is expressed by the blank blackbody radiation formula. For example, the spectrum emitted from the ground at 10℃ is approximately expressed as shown in Figure 1, with a wavelength range of 5μ (wavenumber 2000cm ^-1 ) to 50μ
(wavelength 200cm ^-1 ) contains most of the energy. Conventionally, by adding substances that absorb and reflect infrared rays to agricultural films, it has been possible to prevent the transmission and dissipation of infrared rays and improve the heat retention properties of the film.
And such substances include silicic anhydride, phosphoric acid, aluminosilicic anhydride, polyacetal,
PVA etc. are known. The additives used for this purpose must have the following properties: absorb infrared rays over a wide range of 5μ to 50μ, have a refractive index that matches that of the base resin so as not to reduce the translucency of the film, and be suitable for outdoor use. In order to use it, it must satisfy three conditions: it must be water resistant. However, there is no known infrared absorbing material that satisfies these three requirements at the same time. For example, silicic anhydride has a satisfactory refractive index and water resistance, but has a narrow infrared absorption wavelength range and poor heat retention. Calcium phosphate has a refractive index different from that of synthetic resins, so it becomes cloudy, and potassium phosphate has a defect of poor water resistance and whitening during use. The present inventors have conducted various studies on heat retention improving additives that satisfy the above three conditions, and have already created a synthetic resin material that satisfies the above three conditions by adding phosphate glass. However, although this phosphate glass has excellent performance, there are some difficulties in manufacturing it. For example, the furnace material is eroded during melt synthesis, which significantly shortens the life of the furnace, and the composition changes because phosphorus tends to evaporate due to high temperatures. In order to overcome the manufacturing difficulties mentioned above, we investigated the glass composition and found that by limiting the composition of silicic acid glass, infrared absorption and
The present invention has been achieved by making it possible to obtain a glass composition that satisfies the three requirements of refractive index and water resistance and is easy to melt. That is, the present invention is a synthetic resin material having excellent light transmittance and heat retention, which is obtained by adding borosilicate glass powder to a transparent synthetic resin. The transparent synthetic resin in the present invention refers to a synthetic resin that can be formed into a film with high translucency, such as low-density polyethylene, medium-density polyethylene, high-density polyethylene, ethylene acetic acid, etc. Examples include vinyl copolymers, polyolefins such as polypropylene, polyvinyl chloride, polyesters, polyamides, and polymethyl methacrylate. The borosilicate glass used in the present invention is a glass whose main components are silicon dioxide (SiO ₂ ) and boron oxide (B ₂ O ₃ ), with SiO ₂ 10 to 80 mol%, preferably 20 to 70% mol, B ₂ O ₃ from 5 to 50 preferably 10
~50 mol%, 0 to 30 mol% of one or both of aluminum oxide (Al ₂ O ₃ ) and zinc oxide (ZnO), and 1 mol% of alkali metal and alkaline earth metal oxides as modified oxides. Those containing ~60 mol% are used. In the present invention, mol% refers to the silicic acid component and boric acid component, which are the main components, as SiO ₂ and B ₂ O ₃ , respectively.
The components added to this are basic oxides such as B ₂ O ₃ ,
Calculated by displaying Al ₂ O ₃ , K ₂ O, CaO, etc. Here, boron oxide mainly has the effect of widening the absorption range of infrared rays and making the glass brittle so that it can be easily shattered, but when it is in excess, water resistance decreases. Aluminum oxide and zinc oxide have the effect of improving water resistance and further broadening the infrared absorption range, while making the glass harder and less likely to shatter.
Addition of an alkali metal or alkaline earth metal oxide lowers the melting point, facilitates vitrification, and has the effect of adjusting the refractive index in balance with the above two components. Since P ₂ O ₅ has the effect of widening the absorption width of infrared rays, P ₂ O ₅ can be added up to about 40 mol % for use. This borosilicate glass is desirably finely powdered in view of its miscibility with synthetic resins, and its particle size is 50 μm or less, preferably 10 μm or less.
Further, the fine powder of borosilicate glass may be treated with a surface treatment agent such as paraffin, fatty acid, polyhydric alcohol, or silane coupling agent, depending on the case. Powders subjected to such treatment have improved dispersibility in synthetic resins, as well as improved interfacial adhesion with synthetic resins, and can improve the tensile strength of molded products. The material to which borosilicate glass according to the present invention is added has wide absorption in the infrared wavelength range of 5μ to 50μ, has excellent heat retention, and can transmit light because the refractive index of the added glass can be matched to that of the base synthetic resin. It has excellent properties and water resistance. The amount of borosilicate glass powder added is adjusted depending on the type of synthetic resin, the wall thickness of the molded body, etc. Naturally, it is necessary to increase the addition ratio if the thickness of the film is thin. For example, when molding a low-density polyethylene film with a thickness of 100 μm, adding 10% by weight of borosilicate glass powder can provide good infrared absorption and therefore good heat retention. Furthermore, for example, polyvinyl chloride itself has higher infrared absorption than polyolefin, so the amount of borosilicate glass powder added can be reduced. Generally, 1.0% by weight or more is used, and when used as a material for forming films or sheet-like products, 2.0% by weight or more is used.
Approximately 25% by weight is appropriate. When adding borosilicate glass, it may be uniformly dispersed in a film or sheet, or the concentration may be distributed in the thickness direction. For example, by increasing the concentration of the middle layer of a laminated film and making the concentration of the two outer layers low or zero, the surface can be made smooth, light scattering can be suppressed, and transparency can be increased. Even if the concentration is distributed in this way, if the average concentration is the same, the infrared absorbency will not be different from the case of uniform dispersion. In the present invention, various additives can be added to the synthetic resin material before molding. For example, in order to improve the dispersibility of the borosilicate glass powder into the synthetic resin, a dispersant such as a fatty acid metal salt can be added. The dispersant may be added after being mixed with the borosilicate glass powder, or may be added during kneading of the borosilicate glass powder and the resin. Addition of a dispersant improves the dispersibility of the borosilicate glass powder, thereby improving the translucency of the molded product. In addition, the material of the present invention can be kneaded by various methods, and can be kneaded using an extruder, roll, kneader, etc. The mixed material is usually in the form of pellets, and can be used as is or as needed. It is diluted with raw resin pellets and used for molding. The thus obtained material of the present invention can be formed by T-die molding,
Using various molding methods such as extrusion molding such as inflation molding, blow molding, and calendar molding,
It can be molded into a desired shape depending on the application. The material of the present invention has excellent translucency and allows sunlight to pass through it well, but it also absorbs infrared rays emitted from objects at room temperature over a wide wavelength range, so it has extremely excellent heat retention properties. In addition, because it has excellent water resistance, it can be advantageously used in various applications that take advantage of these properties, such as covering materials for greenhouse cultivation and tunnel cultivation, resource-saving greenhouse materials,
It can be used as a material for solar water heaters, etc. The shape of the molded product may vary depending on the purpose of use, such as a film shape or other various shapes such as a flat plate shape,
It can be shaped like a curved plate. Next, an explanation will be given by giving Examples and Comparative Examples. Example 1 Low density polyethylene (manufactured by Mitsubishi Yuka Co., Ltd., trade name Yucalon AH-40) with an average particle size of 90% by weight
3μ, composition: SiO ₂ 65 mol%, B ₂ O ₃ 27 mol%,
A mixture of 10% by weight of borosilicate glass powder containing 7% by mole of Al ₂ O ₃ and 1% by mole of CaO was formed into a film by an inflation method at a temperature of 170°C to obtain a film with a thickness of 0.1 mm. Example 2 Low-density polyethylene (manufactured by Mitsubishi Yuka Co., Ltd., trade name, Yucalon AH-40) with an average particle size of 90% by weight
3μ, the composition is SiO ₂ 29 mol%, B ₂ O ₃ 29 mol%,
Al ₂ O ₃ 10 mol%, ZnO 5 mol%, CaO 6 mol%,
A mixture of 10% by weight of borosilicate glass powder, which is 1% by mole of K ₂ O, was formed into a film at a temperature of 170° C. by an inflation method to obtain a film with a thickness of 0.1 mm. Example 3 Soft polyvinyl chloride (35% DOP as plasticizer)
(wt% content) 95 wt%, average particle size 3μ, composition
SiO ₂ 45 mol%, B ₂ O ₃ 23 mol%, Al ₂ O ₃ 9 mol%,
A mixture of 5% by weight of borosilicate glass powder containing 3% by mole of BaO was formed into a film by an inflation method at a temperature of 150°C to obtain a film with a thickness of 0.1 mm. Example 4 The same raw materials as in Example 2 were used, and the film thickness ratio was 1:2 using the die lamination inflation method.
A film with a thickness of 100 μm was obtained, with the middle layer being a mixture of 80% by weight of resin and 20% by weight of glass powder, and the outer layer being made only of resin. Comparative Example 1 The same low-density polyethylene as used in Example 1 was formed into a film by an inflation method at a temperature of 170° C. to obtain a film for normal concentration use with a thickness of 0.1 mm. Comparative Example 2 A film with a thickness of 0.1 mm was obtained by using 10% by weight of silicon oxide powder with an average particle size of 2 μm in place of the borosilicate glass powder in Example 1, and otherwise forming a film in the same manner as in Example 1. Ta. Comparative Example 3 A film with a thickness of 0.1 mm was obtained by using 10% by weight of boron oxide powder with an average particle size of 3 μm in place of the borosilicate glass powder in Example 1, and otherwise forming a film in the same manner as in Example 1. Ta. Comparative Example 4 The soft polyvinyl chloride used in Example 3 was used alone, and the film was otherwise formed in the same manner as in Example 3 to obtain a 0.1 mm thick ordinary agricultural polyvinyl chloride film. . The average blackbody radiant energy transmittance at 283 mm of the films obtained in each Example and Comparative Example was measured. The results were as shown in Table 1. Furthermore, a small tunnel was made using the films obtained in each of the Examples and Comparative Examples, and the temperature inside the tunnel was measured under the same conditions.The results were as shown in Table 1. Next, we measured the natural light transmittance of the film to examine its translucency and water resistance.
The natural light transmittance of the film was measured after soaking it in warm water at 60°C. The results were as shown in Table 2. As is clear from the results shown in Tables 1 and 2, the films of the Examples are excellent in heat retention, translucency, and water resistance, whereas the films of the Comparative Examples are , heat retention, translucency, and water resistance.

【table】

【table】 [Brief explanation of the drawing]

The figure shows a curve showing the radiant energy of a black body at 283〓.

Claims (1)

[Scope of Claims] 1. A synthetic resin material with excellent light transmittance and heat retention, which is made by adding borosilicate glass powder to a transparent synthetic resin. 2 The borosilicate glass contains 10 to 80 mol% of silicon dioxide, 5 to 50 mol% of boron oxide, and 1 to 60 mol% of one or more oxides of alkali metals and alkaline earth metals. A synthetic resin material with excellent light transmittance and heat retention properties as claimed in claim 1. 3 Borosilicate glass contains 20 to 80 mol% of silicon dioxide, 5 to 50 mol% of boron oxide, 1 to 30 mol% of one or both of aluminum oxide and zinc oxide, and oxidation of alkali metals and alkaline earth metals. thing 1
A synthetic resin material having excellent light transmittance and heat retention according to claim 1, which contains 1 to 60 mol% of one or more species.