JP4173793B2 - Milky white film for curtain - Google Patents

Description

  The present invention relates to a milky film for curtains, and more particularly to a milky film for curtains that has excellent heat retention, can withstand high temperature use in summer, is inexpensive, and has excellent durability and weather resistance.

  Conventionally, film materials and fiber net materials have been used as agricultural light shielding curtain materials.

  The film materials are mainly transparent products, and the main purpose is to keep the heat at night by forming a so-called convection heat-dissipating layer between the house outer film and the curtain film. The actual situation is also using.

  If only heat retention is considered, an aluminum vapor-deposited film or an aluminum powder kneaded film (these may be simply referred to as an aluminum film) is preferable. This is because the effect of preventing heat radiation by infrared radiation from the ground and plants is great.

  However, aluminum vapor-deposited films and aluminum powder-kneaded films are opaque, so they cannot be used during the day, and nerves must be used when opening and closing in the morning and evening. For example, it must open in the morning with sunrise (5-6 am), and if it is closed until 7-8 am, it will cause poor growth. This is probably because early morning photosynthesis is said to be the most active and important part of the day.

  Next, it is also possible to use a film material during the day for the purpose of light shielding. From the viewpoint of cost and light shielding performance, a black film or the aluminum film can be considered.

  However, the curtains of black film or aluminum powder kneaded film have a convection heat radiation blocking layer and a large heat insulating space, or the curtain itself becomes a heat storage body, and the heating element is placed on the ceiling in the house. There is a problem that the house becomes hot.

  Furthermore, the aluminum film curtain has a problem that the temperature in the house becomes higher by suppressing infrared radiation.

  As mentioned above, the use of light-shielding film materials for daytime curtains causes problems of high temperature inside the house, especially in the summer, high temperatures and high humidity, which are very difficult for plants and workers. It will be a bad environment.

  From the above situation, there are very few cases where the film material is used as a light shielding curtain material.

  Next, as a light-shielding curtain material, since it has been mainly used in summer when the sun is strong, a net material that is mainly black colored with ventilation and water permeability has been known.

  Since it is a net material, it naturally has a problem that the above-mentioned heat retention performance is inferior to that of a film.

  On the other hand, in recent years, so-called “nonwoven fabric” having excellent heat retention has been used. Another reason is that it is generally cheaper than net materials. Regarding non-woven fabrics, uncolored products (uncolored non-woven fabrics) are often used in consideration of heat retention, but heat retention performance equivalent to that of film materials cannot be obtained.

  Furthermore, in the nonwoven fabric product, each individual fiber is as thin as several tens of microns or less, and is not yet drawn. For this reason, the strength is weak and the weather resistance is not good (about 2 years), and moisture is retained as a cloth (so-called wet elephant), so it becomes heavy as a curtain material, and the opening and closing work is also difficult.

  The following facts have been found by investigating and examining the light shielding and heat retaining case of the non-colored nonwoven fabric curtain.

  First, the time when it is used as a light shielding material is a short period of summer or spot use. In other words, it is used for about 10 days after the seedlings are planted until the roots are settled, and while watching the weather conditions to prevent burning in sunny weather (high temperature).

  Secondly, conventionally, vinyl chloride resin films for agriculture have been used for the house outer layer, and many have ultraviolet (UV) cutting properties. However, since the number of UV light transmission-type special polyolefin films for agriculture has increased dramatically over the past 10 years, the deterioration of materials in the house has been promoted, and naturally the nonwoven fabric (for example, product name “Love Sheet” manufactured by Unitika) is also agricultural. It has been used in vinyl chloride resin film houses for 4-5 years, but it has been about 2 years in agricultural polyolefin special film houses.

However, on the consumer side, it is too expensive to replace a much more expensive non-woven fabric in 2 years than a film, and a curtain material that is cheaper and more durable than the non-woven fabric is required. This is the current situation.
Japanese Patent Laid-Open No. 9-234829 Black and white multilayer curtain film Japanese Patent Laid-Open No. 9-239890 Three-layer curtain film of black and white silver JP, 11-196679, A Tape yarn net curtain JP, 2001-181967, A Non-woven curtain

  Therefore, an object of the present invention is to provide a milky white film for curtains that is excellent in heat retention, can withstand high temperature use in summer, is inexpensive in cost, and has excellent durability and weather resistance.

  The above problems are solved by the following inventions.

(Claim 1) A two-layer structure of a low-density polyethylene layer (LDPE layer) and a polyethylene-vinyl acetate copolymer layer (EVA layer), and titanium oxide (TiO 2) on the polyethylene-vinyl acetate copolymer layer (EVA layer). ₂ ) (however, the LDPE layer does not contain titanium oxide) , and the TiO ₂ content is in the range of 0.2 to 10 parts by weight with respect to 100 parts by weight of the polyethylene-vinyl acetate copolymer, A milk white film for curtains having a thickness of 30 to 100 μm and a light shielding rate of 20 to 60%.

(Claim 2) A three-layer structure of a low-density polyethylene layer (LDPE layer), a polyethylene-vinyl acetate copolymer layer (EVA layer), and a low-density polyethylene layer (LDPE layer), and a polyethylene-vinyl acetate copolymer layer (EVA layer) contains titanium oxide (TiO ₂ ) ( however, the LDPE layer does not contain titanium oxide) , and the TiO ₂ content is 0.2 with respect to 100 parts by weight of the polyethylene-vinyl acetate copolymer. A milky film for curtain, characterized in that it is in the range of 10 to 10 parts by weight, has a thickness of 30 to 100 μm, and has a light shielding rate of 20 to 60%.

  According to the present invention, it is possible to provide a milky film for curtains that is excellent in heat retention, can withstand high temperature use in summer, is inexpensive in cost, and has excellent durability and weather resistance.

  Embodiments of the present invention will be described below.

  The milky white film for curtains of the present invention is a polyolefin resin film and may be a single layer film or a multilayer film.

  Examples of the single layer polyolefin-based resin film include a low density polyethylene (LDPE) film, a linear low density polyethylene (L-LDPE) film, and an ethylene-vinyl acetate copolymer (EVA) film. Low density polyethylene (LDPE) is a polyethylene film having a density in the range of 0.910 to 0.930 g / cc, and a film called “agricultural poly” can be used. As the ethylene-vinyl acetate copolymer, those having a vinyl acetate monomer content of about 3 to 15% by weight are preferred.

  The multi-layer polyolefin resin film is preferably a special polyolefin film for agriculture (so-called “agriculture PO” or “agriculture PO film”: registered trademarks of Mikaka Chemical Co., Ltd. and 5 other companies). -Vinyl acetate copolymer (EVA) film, low density polyethylene (LDPE) film for inner and outer layers, linear low density polyethylene (L-LDPE) film for inner and outer layers, or low density polyethylene (LDPE) film for inner layers, outer layer The example which arrange | positioned the linear low density polyethylene (L-LDPE) film in is mentioned. Specific examples include layer configurations such as LDPE / EVA / LDPE, L-LDPE / EVA / L-LDPE, LDPE / EVA / L-LDPE, L-LDPE / EVA / LDPE.

The curtain milky film of the present invention contains titanium oxide (hereinafter sometimes simply referred to as TiO ₂ ) in a polyolefin resin film. TiO ₂ is preferably contained as particles in the range of 0.1 μm to 1 μm.

In the case of a single-layer film, TiO ₂ is contained in the film. The content is preferably in the range of 0.1 to 10 parts by weight, more preferably in the range of 0.2 to 5 parts by weight with respect to 100 parts by weight of the polyolefin resin.

In the present invention, when the polyolefin-based resin film is a multilayer film, examples of the embodiment containing TiO ₂ include the following preferred embodiments.

The first aspect, in the multilayer film has a L-LDPE layer is to contain TiO ₂ at least the L-LDPE layer.

The TiO ₂ content is preferably in the range of 0.2 to 20 parts by weight, more preferably in the range of 0.3 to 10 parts by weight with respect to 100 parts by weight of L-LDPE. In this embodiment, the layer other than the L-LDPE layer may contain TiO ₂ slightly (up to 0.5 parts by weight or less).

The second aspect is, in the multilayer film has a EVA layer is to contain TiO ₂ at least the EVA layer.

The TiO ₂ content is preferably in the range of 0.2 to 10 parts by weight, more preferably in the range of 0.3 to 5 parts by weight with respect to 100 parts by weight of EVA. In this embodiment, the layer other than the EVA layer may contain TiO ₂ slightly (up to 0.5 parts by weight or less).

According to a third aspect, in the first or second aspect, the multilayer film has an LDPE layer, and at least the LDPE layer contains TiO ₂ , and the TiO ₂ content is 100 parts by weight of LDPE. The amount is preferably 0.4 parts by weight or less, more preferably 0.3 parts by weight or less, and a small amount is preferable from the viewpoint of improving weather resistance.

In the present invention, as in the first and second aspects described above, the reason for the selective consideration regarding the polyolefin resin film that is a target containing TiO ₂ is inferred as follows.

Generally, the weather resistance of a polyolefin resin film containing TiO ₂ decreases. This is because TiO ₂ basically absorbs ultraviolet (UV) light in sunlight and is activated by itself to generate active oxygen on the surface of TiO ₂ particles (also referred to as filler). It is thought to be due to chemical degradation.

In this deterioration phenomenon, it is important to study the interaction between the polyolefin resin and TiO ₂ . The present inventor has found that when the material is sufficiently “familiar” with the TiO ₂ surface, the strength decrease due to deterioration is slow and the weather resistance is excellent.

Specifically, in the case of “unsuitable”, from a microscopic viewpoint, it is considered that there is an “air gap” between the TiO ₂ and the surrounding resin, and this is caused by many “defects (notches)” or “ It has a “bubble” and is very disadvantageous in strength. Further, it is considered that the active oxygen is easily generated.

Looking at the polyolefin resin films individually, in the case of LDPE, HP-LDPE is a low-density PE with a long-chain branching structure and a wide molecular weight distribution. The weather resistance is not enough. For this reason, it can be said that it is preferable to add a small amount of the TiO ₂ filler to the “LDPE layer having a large decrease in weather resistance, as described in the third embodiment.

L-LDPE has no long chain branching, a narrow low-density PE molecular weight distribution, relative to the melt viscosity LDPE, very low, weather resistance decreases in "familiar good" and TiO ₂ is very small (the first 1 embodiment).

EVA has a vinyl acetate content of 3 to 15% for films (basically LDPE structure), but the surface of TiO ₂ filler (generally chemically active) due to the polarity of vinyl acetate. It has a strong interaction with “phenomenon common to inorganic fillers”, is “familiar”, and is less susceptible to a weather resistance lowering effect (the second aspect). However, it tends to be inferior to L-LDPE.

  Next, it will be clarified that the first and second embodiments are preferable embodiments from the viewpoint of film moldability.

That is, when a polyolefin resin and a TiO ₂ filler are kneaded and formed into a film by inflation molding, the tension of the molten film is increased, the molten tube is stabilized, and the film moldability is improved. That is, film width and thickness fluctuations, wrinkles, and meandering are reduced. L-LDPE or EVA, which has a strong interaction with the TiO ₂ filler, has a large stabilizing effect.

This phenomenon is because the polyolefin-based resin has a strong interaction with the TiO ₂ filler surface, which acts as a “crosslink” in the rubber, increasing the strength of the molten film, that is, the tension. It is thought to be because.

  In addition, you may mix | blend other polyolefin resin suitably with the main polyolefin resin which forms each film layer of the said single layer film and multilayer film.

  Next, the milky white film for curtains of the present invention has a light shielding rate in the range of 20 to 60%, preferably in the range of 30 to 50%.

  The light blocking ratio is calculated from an average value obtained by measuring a transmittance in a so-called visible light region having a wavelength of 400 to 700 nm using a spectrophotometer (for example, Hitachi U-2800 type). The light shielding rate is obtained from the formula of light shielding rate = 100−average transmittance.

  When the shading rate is less than 20%, the shading property is insufficient, and when it exceeds 60%, growth is adversely affected by lack of sunshine even in the summer when the sunlight is strong. Also, since the temperature is high in summer, if it exceeds 60%, the respiratory exhaustion of the plant body is large, resulting in a physical exhaustion phenomenon.

Since the milky-white film for curtains of the present invention contains TiO ₂ , it is not only a heat accumulator but also a light reflector as long as it is within the above light-shielding rate range. Therefore, compared with a black or silver colored film, there is an effect that the interior of the curtain is brightened even with the same light shielding rate.

  The thickness of the milky-white film for curtains of the present invention is in the range of 30 to 100 μm, and preferably in the range of 40 to 75 μm. If the thickness is less than 30 μm, the strength and durability are inferior. On the other hand, if the thickness exceeds 100 μm, there is a problem that the stretch workability, the open / close workability, and the convergence (less shade when converged) are deteriorated.

  The thickness in the present invention means the total thickness in the case of a multilayer film. In the case of a multilayer film, it is preferable that each layer has a thickness of about 5 μm or more, considering the function of each layer resin and molding accuracy.

In addition to TiO ₂ , particles used for agricultural plastic films such as SiO ₂ , CaCO ₃ , talc, mica and hydrotalcite can be added to the film of the present invention. The antifogging agent for imparting antifogging properties may be kneaded into the film and added, or a coating treatment method (post treatment method and inline coating treatment method) may be used.

  The film of the present invention can be produced by film formation (molding) using an inflation molding method or a T-die molding method.

  Hereinafter, the effects of the present invention will be illustrated by examples.

Example 1
Film 1
A single layer film was formed using LDPE (MFR 2.0, density 0.924) as the base resin.
TiO ₂ was added in an amount of 0.2 part by weight with respect to 100 parts by weight of LDPE, and the film was formed by inflation molding so that the film thickness was 100 μm.
The light shielding rate of the film was measured with a spectrophotometer (Hitachi U-2800 type).
30%.

Film 2
A multilayer film composed of an LDPE layer and an L-LDPE layer was formed by inflation molding.
TiO ₂ was contained in the L-LDPE layer. The TiO ₂ content was 0.4 parts by weight with respect to 100 parts by weight of L-LDPE.
The total film thickness is 50 μm, and the thickness of each layer is LDPE 10 μm and LLDPE 40 μm.
The light shielding rate of the film was measured with a spectrophotometer (Hitachi U-2800 type).
25%.

Film 3
A multilayer film composed of an LDPE layer and an L-LDPE layer was formed by inflation molding.
TiO ₂ was contained in the L-LDPE layer. The TiO ₂ content was 9 parts by weight with respect to 100 parts by weight of L-LDPE.
The total film thickness is 50 μm, and the thickness of each layer is 40 μm for the LDPE layer and 10 μm for the L-LDPE layer.
The light shielding rate of the film was measured with a spectrophotometer (Hitachi U-2800 type).
50%.

Film 4
A multilayer film composed of an LDPE layer and an EVA layer was formed by inflation molding.
The EVA layer contained TiO ₂ . The TiO ₂ content was 0.4 parts by weight with respect to 100 parts by weight of EVA.
The total film thickness is 60 μm, and the thickness of each layer is 40 μm for the LDPE layer and 20 μm for the EVA layer.
The light shielding rate of the film was measured with a spectrophotometer (Hitachi U-2800 type).
40%.

Film 5
A multilayer film composed of an LDPE layer and an EVA layer was formed by inflation molding.
The EVA layer contained TiO ₂ . The TiO ₂ content was 4.5 parts by weight with respect to 100 parts by weight of EVA.
The total film thickness is 60 μm, and the thickness of each layer is 40 μm for the LDPE layer and 20 μm for the EVA layer.
The light shielding rate of the film was measured with a spectrophotometer (Hitachi U-2800 type).
40%.

Film 6
A multilayer film composed of an LDPE layer, an EVA layer, and an LDPE layer was formed by inflation molding.
TiO ₂ was contained in the LDPE layer and the EVA layer. The TiO ₂ content was 0.3 parts by weight with respect to 100 parts by weight of LDPE and 1 part by weight with respect to 100 parts by weight of EVA.
The total film thickness is 75 μm, and the thickness of each layer is 25 μm for the LDPE layer, 25 μm for the EVA layer, and 25 μm for the LDPE layer.
The light shielding rate of the film was measured with a spectrophotometer (Hitachi U-2800 type).
35%.

Film 7
A single layer film was formed using LDPE (MFR 2.0, density 0.924) as the base resin.
0.5 parts by weight of TiO ₂ was added to 100 parts by weight of LDPE, and the film was formed by inflation molding so that the film thickness was 50 μm.
The light shielding rate of the film was measured with a spectrophotometer (Hitachi U-2800 type).
60%.

Film 8
A multilayer film composed of an LDPE layer and an L-LDPE layer was formed by inflation molding.
TiO ₂ was contained in the L-LDPE layer. The TiO ₂ content was 9 parts by weight with respect to 100 parts by weight of L-LDPE.
The total film thickness is 50 μm, and the thickness of each layer is LDPE 10 μm and LLDPE 40 μm.
The shading rate of the film was measured with a spectrophotometer (Hitachi U-2800 type).
50%.

Film 9
A multilayer film composed of an LDPE layer and an EVA layer was formed by inflation molding.
The EVA layer contained TiO ₂ . The TiO ₂ content was 4.5 parts by weight with respect to 100 parts by weight of EVA.
The total film thickness is 60 μm, and the thickness of each layer is 20 μm for the LDPE layer and 40 μm for the EVA layer.
The light shielding rate of the film was measured with a spectrophotometer (Hitachi U-2800 type).
40%.

Comparative Example 1
Film 10
A single layer film was formed using LDPE (MFR 2.0, density 0.924) as the base resin.
1 part by weight of TiO ₂ was added to 100 parts by weight of LDPE, and the film was formed by inflation molding so that the film thickness was 20 μm.
The light shielding rate of the film was measured with a spectrophotometer (Hitachi U-2800 type).
30%.

Film 11
A single layer film was formed using LDPE (MFR 2.0, density 0.924) as the base resin.
4 parts by weight of TiO ₂ was added to 100 parts by weight of LDPE, and the film was formed by inflation molding so that the film thickness was 120 μm.
The light shielding rate of the film was measured with a spectrophotometer (Hitachi U-2800 type).
50%.

(Evaluation)
The relationship between the light shielding rate and the weather resistance of each of the above films was examined, and the results are shown in Table 1.

Evaluation of weather resistance The weather resistance was determined in a situation one year after each film was spread horizontally on the upper part of the house.
◎ No change from the initial stage
○ + Slightly whitish
○ Elongation drops slightly when pulled
× torn

Claims (2)

It has a two-layer structure consisting of a low-density polyethylene layer (LDPE layer) and a polyethylene-vinyl acetate copolymer layer (EVA layer). The polyethylene-vinyl acetate copolymer layer (EVA layer) contains titanium oxide (TiO ₂ ). (However, the LDPE layer does not contain titanium oxide.) The TiO ₂ content is in the range of 0.2 to 10 parts by weight with respect to 100 parts by weight of the polyethylene-vinyl acetate copolymer, and the thickness is 30 to 100 μm. A milky white film for curtains having a light shielding rate of 20 to 60%. It has a three-layer structure consisting of a low-density polyethylene layer (LDPE layer), a polyethylene-vinyl acetate copolymer layer (EVA layer), and a low-density polyethylene layer (LDPE layer), and a polyethylene-vinyl acetate copolymer layer (EVA layer). Titanium oxide (TiO ₂ ) is contained ( however, the LDPE layer does not contain titanium oxide) , and the TiO ₂ content is 0.2 to 10 parts by weight with respect to 100 parts by weight of the polyethylene-vinyl acetate copolymer. An opalescent milky film having a thickness of 30 to 100 μm and a light shielding rate of 20 to 60%.