KR960007015B1 - Three-layer film - Google Patents

Abstract

The three layered film for agriculture has good optical property, weatherability, working strength, and excellent transparency at daytime and infrared absorption at night for keeping warmth. The multilayer film comprises the mixture of more than one or two compounds which are selected from LDPE(low density polyethylene), LLDPE(linear low density polyethylene), EVA(ethylene vinyl acetate), and the thickness ratio of each layer is 1:1-4:1-3. The melt flow index of the used LDPE and LLDPE resin is 0.1-5.9 g/10min, and the their density is 0.914-0.926. The melt index of 5-17 wt% EVA is 0.2-5.0 g/10min.

Description

Agricultural 3-layer film

The present invention relates to an agricultural film, and more particularly, to produce a film having a three-layer structure, by appropriately mixing and using a resin and additives for each layer to exhibit the various physical properties that the agricultural film should have at the same time a variety of consumers It relates to a three-layer film for agriculture that can meet the needs.

Resin used in the conventional agricultural monolayer film is mainly polyethylene, ethylene vinyl acetate (EVA) copolymer, polyvinyl chloride and the like. However, polyethylene is inferior to ethylene vinyl copolymer in terms of heat retention, transparency and oil repellency, and ethylene vinyl copolymer is inferior to polyvinyl chloride in terms of thermal insulation and work strength.

In addition, polyvinyl chloride has excellent heat insulation, transparency, and working strength, but generates halogen gas and incombustibility during disposal, and plasticizer leaches to the surface of the film, causing dust to stick to it, resulting in a sudden decrease in light transmittance and poor cold resistance. There was a restriction.

In order to make up for the shortcomings of polyethylene and ethylene vinyl acetate copolymers used as single-layer films, it is possible to maintain the thermal insulation properties by using a silica-based additive (Japanese Patent Publication 47-13853) or an absorbent resin (Japanese Patent Publication No. 61-81446) And improved oil repellency and the like, but it was not able to maintain heat retention and oil repellency, such as polyvinyl chloride, and also had a disadvantage in inferior commerciality due to a sudden drop in transparency.

Japanese Unexamined Patent Publication No. 57-160638 describes a film in which a polyolefin layer containing a oil repellent agent and a polyolefin layer containing a metal organic compound are described. It was difficult to obtain a film that satisfies all of the strength and the like. In addition, Japanese Patent Laid-Open No. 62-179939 improves oil repellency by adding a superabsorbent resin to the flame resistance of the multilayer film, but still does not solve the problem of lowering transparency. In Japanese Patent Application Laid-Open No. 63-115743 and Japanese Patent Laid-Open No. 63-149148, all of heat retention, transparency, and ruins are enhanced, but since the emphasis is placed on heat retention, transparency is lowered. It was not able to control the disadvantage that the oil residue was discharged to the surface of the film and the transparency changes with time.

On the other hand, Japanese Unexamined Patent Publication No. 4-47936 improves oil repellency by evenly adding the oil repellent agent to each layer of the three-layer film, but has not overcome the disadvantage of lack of heat retention and transparency.

The present inventors supplement the disadvantages of the conventional agricultural multi-layer film, while suppressing the change of transparency due to the film surface discharge of the oil-repellent agent to excellent transparency, which is the biggest disadvantage of the multi-layer film, and improve the initial oil-resistance and long-term oil persistence To prepare a multilayer film.

That is, an object of the present invention, while maintaining the excellent optical properties of the film, at the same time can exhibit the daytime warming effect due to the optical properties of the film and the night warming effect due to infrared absorption at night, and improved weather resistance and work intensity 3 To provide a layer film.

The three-layer film of the present invention for achieving the above object of the present invention is an agricultural multilayer film, the outer layer, middle layer and inner layer resin is low density polyethylene (LDPE) resin, linear low density polyethylene (LLDPE) resin and ethylene vinyl acetate resin It consists of 1 type, or 2 or more types of mixtures chosen from.

Looking at the present invention in more detail as follows.

Agricultural film according to the present invention has a three-layer structure, each layer is divided into an outer layer (weather resistance) and a middle layer (heat insulation layer). The hot bed coextrusion film may have different resins for each layer, and the use and blending ratios of the additives may be different for each layer, so the selection and blending ratio of appropriate layered resins and additives are very important.

The most basic and important thing in the development of the present invention is what resin is selected and used in each composition layer in addition to the additive properties. The biggest disadvantage of the three-layer film is that the optical and mechanical strength of the film is weakened because a large amount of additives are impregnated in one film. Therefore, the first consideration in selecting a layered resin is the optical and mechanical strength of each layered resin, and in particular, the opticality is more important because it has a decisive effect on crop growth.

In the present invention, an ethylene vinyl acetate copolymer of 0.914-0.926 g / cc and 0.1 g / 10 min-5.0 g / 10 min is used as the base resin.

When the resin is applied to each layer of resin, a single resin or two or more resins may be appropriately mixed and the thickness ratio of each layer may be adjusted to improve optical and mechanical strength. Resin applied as the outer layer can improve the optical and mechanical strength of the three-layer film by using alone or mixed low-density polyethylene and linear low-density polyethylene, the mixing ratio can be changed according to the thickness ratio of the three-layer film.

In the middle layer, the additive is impregnated with a large amount of additives such as a warming agent. The impregnation ability of the additive is very important, and the optical and mechanical strength of the three-layer film can be improved by using ethylene vinyl acetate copolymer alone or mixed with low density polyethylene. have. The mixing ratio of the resin varies depending on the thickness ratio of the three-layer film and the amount of the additive used.

The inner layer is a layer in which the oil-resistance activity occurs directly, and the oil-based additive is prescribed. Therefore, ethylene vinyl acetate copolymer and low-density polyethylene are used alone or in combination to maintain the impregnation ability and the initial and continuous oil-resistance of the additive. . Mixing the resin differently according to the thickness ratio of the three-layer film and the amount of the additive used can be expected to improve the optical properties and the additive activity of the film.

The thickness ratio of the three-layer film is based on the thickness of the outer layer: middle layer: inner layer as "1", the thickness of the middle layer may have a thickness of 1-4.5 and the thickness of the inner layer may have a thickness of 1-3. . When the thickness ratio is outer layer: middle layer: inner layer = 1: 1: 1, the best optical and mechanical properties may be exhibited when the outer layer is used as the low density polyethylene, the middle layer and the inner layer as the ethylene vinyl acetate copolymer, respectively. However, when the thermal insulation agent is added to the oil repellent agent, the optical properties and the oil persistence are adversely affected. Therefore, when the thickness ratio is 1: 1: 1, the thermal insulation agent is not added to the inner layer.

If the thickness of the outer layer and inner layer is 1, and the thickness ratio of the middle layer is 1.5-4.0, the use of a low density polyethylene and a linear low density polyethylene as a resin of the outer layer is excellent in optical properties and additive activity, and the optimum mixing ratio is low density polyethylene: linear Low density polyethylene = 100-10: 0-90 parts by weight. It is preferable to use 100% ethylene vinyl acetate copolymer as the resin in the middle layer, but when a large amount of the heat-adding additive is not added, it is preferable to mix and use the low density polyethylene: ethylene vinyl acetate = 0-80: 100-20 parts by weight. As the resin of the inner layer, it is preferable to mix the ethylene vinyl acetate copolymer with low density polyethylene: vinyl acetate = 100-10: 0-90 parts by weight, rather than using low density polyethylene alone.

In addition, when the thickness of the outer layer is 1 based on the thickness of the middle layer is 2-4.5 and the inner layer has a thickness of 1.5-3, low density polyethylene resin: linear low density polyethylene = 100-10: 0-90 parts by weight It is good for optical and additive properties. Low-density polyethylene is a low-density polyethylene: ethylene vinyl acetate = 80-0: 20-100 weight part, and resin of the inner layer is low-density polyethylene: ethylene vinyl acetate = 100-20: 0-80 weight with ethylene vinyl acetate copolymer as a middle layer resin It is good to mix them together.

When the resin and thickness ratio of each layer of the film having a three-layer structure is determined, the additives may be maximized without changing the optical properties of the film by impregnating the impregnating agent, the warming agent, and the oil-repellent agent for each layer. In addition, since the resin and thickness ratio of each layer of the film may be determined accordingly when the impregnation amount of the additive is determined, the determination of the type of resin, the thickness ratio of each layer, and the content of the additive should be determined at the same time.

Here, the weathering agent may be impregnated only in the outermost layer of the three-layer film, but evenly impregnating the same amount in the three layers may further improve the inter-late period and the optical properties of the film are not deteriorated. The oil-repellent agent and the heat-retaining agent can be impregnated only in the middle layer or the inner layer, but in order for the effect of the oil drop to be effected early and continuously, the impregnation of the middle layer and the inner layer is appropriate. It may not be greatly reduced. That is, when emphasizing heat retention and initial oil repellency, it is preferable to add a larger amount of oil repellent agent to the inner layer, a relatively large amount of heat retainer to the middle layer, and a small amount of oil repellent agent. When emphasizing the persistence rather than the initial relicability, it is better to add a larger amount of retardant to the middle layer, a relatively small amount to the inner layer, and to add the thermal insulation to the middle layer and the inner layer evenly. It does not degrade much.

In the present invention, using a light stabilizer of the HALS (Hindered Amine Light Stabilizer) system as a weathering agent is added 0.1-0.8% by weight to each layer of the three-layer film. In order to improve the dispersibility in the hydrotalside system, the heat insulating agent was surface treated with a surfactant such as fatty acid ester and 5-15% was added to the middle layer and inner layer of the three-layer film. The oil-and-water agent is a 1: 1 mixture of glycerin fatty acid ester and sorbitan fatty acid ester, and adds 0.4-1.5 wt% to the three-layer film.

When the weathering agent is added in the same amount to the outer layer, the middle layer, and the inner layer, the oil-in-water agent is added to the middle layer in the 1-3 weight ratio compared to the inner layer, and the warming agent is added to the inner layer in the 0-1 weight ratio compared to the middle layer.

In addition, when the weathering agent is added in an outer layer: middle layer: inner layer in a weight ratio of 1: 0.1-1: 0-1, the heat insulating agent is added only to the middle layer, and the oil-reducing agent is added in the same weight ratio to the inner layer and the middle layer, or the heat insulating agent is the middle layer. Compared to the inner layer in the 0-1 weight ratio, and the oil-in-water is added to the middle layer in the 1-3 weight ratio.

Hereinafter, the present invention will be described in more detail with reference to the following examples, which are not intended to limit the present invention.

Example 1: When the thickness of each layer of the three-layer film is the same

Film production was carried out in a three-layer blown co-extruder having an extruder of 40 mm, 40 mm, and 40 mm in size of the outer layer, the middle layer, and the inner layer, the diameter of the die, and the die gap of 1.5 mm. The resin used had a melt index of 0.8 g / 10 min and a density of 0.920 g / cc for low density polyethylene, a linear low density polyethylene with a melt index of 1.0 g / min and a density of 0.920 g / cc. Was 1.5 g / 10 min, and the VA content was 15%. In the film production, the expansion ratio was 2.0 and the processing temperature conditions for each layer were adjusted from 140 ° C to 220 ° C. The total thickness of the film was 60 µ, and the thickness of each layer was kept the same, that is, each thickness of the outer layer, the middle layer, and the inner layer was 20 µ. Resin for each layer used low density polyethylene, linear low density polyethylene, and ethylene vinyl acetate individually or in mixture of 2 or more as shown in Table 1. In each case, the additive was used in the same manner for each layer or only in the outer layer and the middle layer, and the oil-repellent agent was evenly penetrated into each layer or added only to the middle layer and the inner layer to change the addition ratio. The warming agent was evenly added to each layer, or the middle layer, the inner layer only, or the middle layer only.

The higher it is, the higher the temperature inside the house can be maintained during the night. It is common to measure the thermal insulation of ordinary film by comparing infrared absorption rate with other films, but here, the house was actually installed (width 2m, length 5m, height 1.5m) and the temperature was measured after installing thermometers in three places inside the house. The highest temperature was recorded during the day and the lowest temperature at night. Temperature recording conditions were measured for one day after 7 days of house installation and averaged three thermometers.

Relics of film: Relics are the ability of water droplets on the film surface to flow through the film surface. The oil repellency varies depending on the type and amount of oil repellent added to the film. As a comparison of high-temperature ruins performance, 2/3 of water is packed in a 500cc beaker, wrapped in a film, installed at a 15 ° incline in a thermostat, and then maintained at 25 ° C outside of the film and 40 ° C in the thermostat. In order to compare the low-temperature ruins, the film was packed with a film of 2/3 of water in a 500cc beaker and installed at an inclined angle of 15 ° in a thermostat. The temperature of the thermostat was changed to 4 ° C., 15 ° C., and 30 ° C. at intervals of 8 hours. Remaining performance was recorded when the water droplets formed more than 30% of the total film area on the film surface.

Mechanical strength of the film: The strength of the film was measured for tensile strength, elongation, tensile strength, drop impact strength, and Elmendorf tear strength. All the measurement standards were carried out according to the test method according to KS ASTM.

TABLE 1

[Example 2: When only the thickness of the middle layer in the three-layer film is relatively thick]

Except for using the components shown in Table 2, using the same method as in Example 1 according to the impregnated amount of the resin and additives of each layer while changing only the middle layer to 2.0-4.0 when the thickness of the outer layer, inner layer based on "1" The physical properties of the film were measured, and the results are shown in Table 2.

TABLE 2

Example 3

When the thickness of the middle layer and the inner layer in the three-layer film is thicker than the outer layer, the thickness of the middle layer is determined by using the same method as in Example 1 except for using the components shown in Table 3 below. The physical properties of the film were measured when the thickness was changed to 2.0-4.0 and the thickness of the inner layer was also changed to 2-3 at the same time. The results are shown in Table 3.

TABLE 3

[Comparative Example: Comparison of Characteristics of Three-Layer Film with Conventional Agricultural Film]

The overall physical properties of the low density polyethylene, ethylene vinyl acetate special film, and three-layer film currently used as agricultural films in Korea were compared with some of the films prepared in Examples 1, 2, and 3 in the same manner as in Example 1. Table 4 was as follows.

TABLE 4

As can be seen from the above table, the agricultural three-layer film according to the present invention is superior in overall physical properties compared to conventional low density polyethylene, ethylene vinyl acetate monolayer special film, and three-layer thermal insulation film, in particular, excellent in optical properties and additive properties. (Weather resistance, warmth, oil repellency) is also very good, it was able to maintain the characteristics superior to the conventional agricultural film.

Claims (9)

In the agricultural multilayer film, the outer layer, the middle layer and the inner layer resin are one or two or more kinds selected from low density polyethylene resin, linear low density polyethylene resin and ethylene vinyl acetate resin, each having a thickness ratio of 1: 1-4: 1-3. Agricultural three-layer film, characterized in that. The melt index of the low density polyethylene resin and the linear low density polyethylene resin is 0.1-5.9g / 10min, the density is 0.914-0.926, the melt index of the ethylene vinyl acetate resin is 0.2-5.0g / 10min, acetic acid Agricultural three-layer film, characterized in that the vinyl content of 5-17% by weight. The agricultural three-layer film according to claim 1, wherein when the thickness ratio of the outer layer: middle layer: inner layer is the same, the resin of the outer layer is a low density polyethylene resin, and the resin of the middle layer and the inner layer is ethylene vinyl acetate resin. The method of claim 1, wherein when the thickness ratio of the outer layer to the middle layer is 1: 1.5-4: 1, the resin of the outer layer is low density polyethylene: linear low density polyethylene = 100-10: 0-90 parts by weight, Resin is a low density polyethylene: ethylene vinyl acetate = 0-80: 100-20 parts by weight, and the resin of the inner layer is a low density polyethylene: ethylene vinyl acetate = 100-10: 0-90 parts by weight. The method of claim 1, wherein when the thickness ratio of the outer layer: middle layer: inner layer is 1: 1.5-4: 1.5-3, the resin of the outer layer is a low density polyethylene resin: linear low density polyethylene = 100-10: 0-90 parts by weight, The middle layer of the resin is low density polyethylene: ethylene vinyl acetate = 80-0: 20-100 parts by weight and the resin of the inner layer is low density polyethylene: ethylene vinyl acetate = 100-20: 0-80 parts by weight film. The agricultural three-layer film according to claim 1, further comprising 0.1-0.8% by weight of weathering agent, 5-15% by weight of warming agent and 0.4-1.5% by weight of oil-repellent agent alone or in combination. The method according to claim 1, wherein the weathering agent is added to the outer layer, the middle layer, and the inner layer by the same amount, the oil-repellent agent is added to the inner layer in 1-3 weight ratio compared to the inner layer, and the warming agent is added to the inner layer in 0-1 weight ratio compared to the middle layer. Agricultural three-layer film characterized in that. The method according to claim 6, wherein the weathering agent is added in a weight ratio of outer layer: middle layer: inner layer in a ratio of 1: 0.1-1: 0-1, the oil-repellent agent is added to the inner layer and the middle layer in the same weight ratio, and the warming agent is added only to the middle layer. The agricultural three-layer film characterized by. The method according to claim 6, wherein the weathering agent is added in a weight ratio of outer layer: middle layer: inner layer in a ratio of 1: 0.1-1: 0-1, the oil-repellent agent is added in a 1-3 weight ratio to the middle layer compared to the inner layer, and the warming agent is a middle layer Agricultural three-layer film, characterized in that added to the inner layer at a weight ratio of 0-1.