JPH06143509A - Agricultural film - Google Patents

Abstract

PURPOSE:To provide an ethylene-vinyl acetate copolymer agricultural film, which has high beam transmittance and in which direct transmittance is reduced, and the flexible agricultural film having high stength and excellent heat-retaining properties. CONSTITUTION:At least one layer of an outemost layer is composed of the mixture of an ethylene-vinyl acetate copolymer (A) having 20-35wt.% vinyl acetate content and a melt flow rate(MFR) of 4-50g/10min and low-density polyethylene (B) having the MFR of 0.04-2.0g/10min. An agricultural film has multilayer structure consisting of a mixture layer having the mixing ratio of (A) and (B) of (A)/(B)=35-90/65-10 (a weight ratio), the mean vinyl acetate content of 12-22wt.% of said mixture and the MFR ratio (the MFR of (A)/the MFR of (B))=10-100 of (A) and (B) and another olefin resin layer, and the agricultural film has not less than 80% overall beam transmittance and a not more than 10% transmittance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ethylene / vinyl acetate copolymer-based agricultural film having a small amount of direct light and a high light transmittance.

[0002]

2. Description of the Related Art Generally, as an agricultural film, one having a high light transmittance is desired, but depending on the type of crop, it is desired to reduce the proportion of direct light as much as possible and increase the proportion of scattered light. There is. For example, in a nursery house for soft vegetables such as leaf tobacco and lettuce, in order to prevent sunburn of leaves, and in a dry house of leaf tobacco to prevent rapid drying, or to prevent production of loose leaves and combed leaves, respectively. It is essential to use an agricultural film with a small amount of direct light, and a satin type film has been generally used. Many of the conventional satin-finished films are produced by a method of roughening the film surface with an embossing roll during film processing, and a polyvinyl chloride film containing a plasticizer has predominantly been used. Therefore, from a practical point of view, when it is spread in a house or a tunnel, the film surface is contaminated by dust in the air, which causes a decrease in light transmittance with time.

As a method for improving such a defect, there is a method of using a blend of two or more kinds of olefin resins without taking a mechanical means such as embossing.
It is proposed in Japanese Patent No. 5146. In this proposal, the use of high-density polyethylene is indispensable, so that there is a drawback that the selection range of quality design is narrow with regard to the flexibility of the film. Further, the heat retaining agents and antifogging agents that are often added to agricultural films have high hygroscopicity, but since the proposal requires film processing to be performed at high temperatures, foaming trouble occurs when such additives are blended. There was a fear that it would occur. Furthermore, it cannot be said that the light transmittance is always sufficiently high.

[0004]

DISCLOSURE OF INVENTION Problems to be Solved by the Invention The inventors of the present invention have attracted attention as a substitute material for a polyvinyl chloride film having problems with waste treatment and stain resistance. Multilayer agriculture based on ethylene / vinyl acetate copolymer. In the film for film, the method for reducing the direct light was examined without using a mechanical processing means such as embossing which may cause dust adhesion and keeping the light transmittance at a very high level. As a result, they have found that the object can be achieved by providing the following ethylene / vinyl acetate copolymer layer on at least one outermost layer of the agricultural film.

Accordingly, an object of the present invention is to provide an ethylene / vinyl acetate copolymer-based agricultural film having a high light transmittance and a small amount of direct light. Another object of the present invention is to
It is intended to provide an agricultural film that is flexible and has excellent strength and heat retention.

[0006]

In the present invention, at least one of the outermost layers has a vinyl acetate content of 20 to 35% by weight and a melt flow rate (MFR) of 4 to 50 g / 10 min. Combined (A) and MFR is 0.04
It is composed of a mixture of low density polyethylene (B) of about 2.0 g / 10 minutes, and the mixing ratio of (A) and (B) is (A) /
(B) = 35-90 / 65-10 (weight ratio), the average vinyl acetate content of the mixture is 12-22% by weight, and its MFR ratio (MFR of (A) / MFR of (B)) = 10. ~
The present invention relates to an agricultural film having a multilayer structure composed of a mixture layer of 100 and another olefin resin layer and having a total light transmittance of 80% or more and a transformer of 10% or less.

[0007]

In the present invention, a resin mixture layer is used as at least one of the outermost layers of the film.
That is, the resin mixture layer is used for either the outermost layer or the innermost layer in the case of forming a tunnel or a house, or a portion corresponding to both layers. One component of the resin mixture has a vinyl acetate content of 20-35% by weight, preferably 24-
34% by weight, more preferably 26-32% by weight, MFR
Of 4 to 50 g / 10 min, preferably 6 to 30 g / 10 min of ethylene / vinyl acetate copolymer is used. It is difficult to obtain a film having desired light transmission properties even when a copolymer having a vinyl acetate content less than the above range is used, and conversely, when a copolymer having a vinyl acetate content larger than the above range is used, blocking occurs. This is not preferable because it increases the property and makes it easier for dust to adhere. In addition, M of the copolymer
If the FR is smaller than the above range, it is difficult to obtain a film having a desired light transmission property, and conversely, if the FR is larger than that, fish eyes are generated, which is not preferable.

Other components of the resin mixture layer include MFR
Is 0.04 to 2.0 g / 10 minutes, preferably 0.1 to
Low density polyethylene of 1.0 g / 10 min is used.
When the MFR having a MFR smaller than the above range is used, fish eyes are likely to occur, and when the MFR having a MFR larger than the above range is used, it becomes difficult to obtain a film having desired optical performance. Low density polyethylene has a density of 0.900 to
0.935 g / cc, preferably 0.905 to 0.93
It may be 0 g / cc, and may be high-pressure polyethylene or linear low-density polyethylene produced by copolymerization of ethylene and α-olefin having about 3 to 10 carbon atoms by the medium-low pressure method. Good.

The mixing ratio of the component (A) and the component (B) is
(A) / (B) = 35-90 / 65-10 (weight ratio),
Preferably (A) / (B) = 40-80 / 60-20 and the average vinyl acetate content is 12-22.
% By weight, and MFR of (A) / MFR of (B) = 10
It should be in the range of 100, preferably 20-90. If the average vinyl acetate content is less than the above range or the ratio of MFR is less than the above range,
It is difficult to obtain a film having desired optical characteristics. On the other hand, if the average vinyl acetate content is larger than the above range, the blocking tendency becomes strong and dust is easily attached, which is not preferable. Further, if the MFR ratio is larger than the above range, fish eyes are likely to occur, which is not preferable.

The resin mixture layer of the present invention comprises the above (A),
As long as the content of both components (B) is within the above range, 100 parts by weight of low-density polyethylene different from component (B) per 100 parts by weight of both components (A) and (B) is used within a range that does not impair optical characteristics. The following may be added, preferably at a ratio of 50 parts by weight or less. Such low density polyethylene has an MFR of more than 2.0 g / 10 min, preferably 20 g / 10 min or less, more preferably 1 g / min.
It is 0 g / 10 minutes or less. By blending the low density polyethylene, the fusion resistance of the resin mixture layer can be improved without impairing the optical characteristics.

In the present invention, it is important from the viewpoint of optical properties to provide a resin mixture containing the components (A) and (B) as the outermost layer of the film. That is, even if such a resin mixture layer is used as an intermediate layer of a multilayer film having three or more layers, it is not possible to obtain one having desired optical performance.

In the present invention, a film having a multi-layer structure is provided in which another olefin resin layer is provided in addition to the resin mixture layer. By using a laminate with another olefin resin layer rather than using the resin mixture as a single-layer film, it is easy to obtain the required properties such as mechanical strength, durability, and heat retention property suitable for the agricultural film. Generally, it has a two-layer or three-layer structure, and it is common that the resin mixture layer is formed as a relatively thin layer and the olefin resin layer is formed as a thick layer.

As the olefin resin, an ethylene / vinyl acetate copolymer having a vinyl acetate content of 20% by weight or less, preferably 15% by weight or less, a low density polyethylene, an ethylene / (meth) acrylic acid ester copolymer, an ionomer Alternatively, a mixture thereof or the like can be given as a preferable example. It is preferable to use those having an MFR of about 0.5 to 20 g / 10 minutes, especially about 1 to 10 g / 10 minutes.
Among them, when used as the intermediate layer, the ethylene / vinyl acetate copolymer is most preferably used in consideration of affinity with the heat retaining agent, economy, interlayer adhesion with the resin mixture layer, and the like. When the resin layer is used as one of the outermost layers, it is desirable to select from ethylene / vinyl acetate copolymer or low density polyethylene.

The thickness of the resin mixture layer is about 3 to 100 μm, especially about 10 to 100 μm, and the thickness of the olefin resin layer is about 20 to 200 μm, especially 30 to 15 μm.
The thickness is preferably about 0 μm (the total thickness of two or more layers). A heat retaining agent, an antioxidant, an ultraviolet absorber, a light resistance stabilizer, an antifogging agent, an antifog agent and the like are appropriately added to each layer. As the heat retaining agent, a known one having a refractive index similar to that of the resin layer can be used, but particularly the heat retaining property is good,
Most preferred is the use of hydrotalcite which does not adversely affect the light transmission. The amount of heat insulating agent used is 10
0.1 to 10 parts by weight, especially 0.2 to 0 parts by weight
It is desirable to set the ratio to 7 parts by weight, but 30 parts by weight or less per 100 parts by weight of the resin component in the outer layer and the intermediate layer when expanded in the three-layer film and in the outer layer when expanded in the two-layer film, It is desirable that the amount of the compound is 20 parts by weight or less.

According to the present invention, by adopting the above constitution, the total light transmittance is 80% or more, usually 90% or more, preferably 92% or more, the transformer is 10% or less, usually 3% or less, preferably. Can easily provide less than 1%. Further, a haze value of 30% or more, generally 40% or more, preferably 45% or more can be easily provided.

[0016]

According to the present invention, it is possible to provide an agricultural film which is excellent in flexibility, fusion resistance and heat retention, has a high total light transmittance, and has a small amount of direct light. By making use of such characteristics, it can be used for tunnel tensioning and house tensioning as a heat-retaining film for raising soft vegetables and leaf tobacco, rice and other seedlings that do not want direct sunlight, and for drying leaf tobacco.

[0017]

EXAMPLES Next, examples will be described, but the present invention is not limited thereto. Evaluation method Total light transmittance and haze (HAZE) ・ ・ ・ Compliant with JIS K6714-77 Trans ・ ・ ・ Transparency measured according to ASTM D1746 (T
ransmittance) Thermal insulation ... Emissivity meter Dand S. The longwave emissivity determined using the AERD model was used as a measure of heat retention. Dirt resistance: A small arch-type agricultural pipe house with a frontage of 2 m, height of 2 m, and length of 9 m was built in Ichihara, Chiba prefecture.
It was stretched from July 1990 to July 1991, and the total light transmittance after one year was measured and used as the scale.

Example 1 (Manufacture of Multilayer Film) Using a multi-layer insulation device equipped with a three-kind three-layer inflation die (diameter 150 mm) and passing through an extruder having a diameter 45 mm, the melting zone temperature 14
The following composition was supplied to each layer under conditions of 0 ° C. and a die temperature of 140 ° C., and a tubular body having a three-layer structure obtained by coalescing in a die was inflation-molded under the condition of blow-up ratio 2.8, and folded. The diameter of the outer layer is 650 mm and the thickness of each layer is 0.
A multilayer film having a thickness of 02 mm, a middle layer of 0.02 mm and an inner layer of 0.06 mm was obtained.

Outer layer: ethylene / vinyl acetate copolymer (vinyl acetate content 28% by weight, MFR 15 g / 10
Min., EVAFLEX P2807 manufactured by Mitsui DuPont Polychemical Co., Ltd.)
39.2% by weight, low density polyethylene (density 0.922
g / cc, MFR 0.25 g / 10 min, Nippon Petrochemical Lexron F102 26.1 wt% and low density polyethylene (density 0.923 g / cc, MFR 3.7 g / 10
Min, Mitsui Petrochemical Co., Ltd. Mirason 16 28.0% by weight
And 0.1% by weight of a benzophenone-based ultraviolet absorber, 0.1% by weight of a hindered amine-based light stabilizer, and a heat retaining agent (DHT-4A manufactured by Hydrotalcite Kyowa Chemical Co., Ltd.)
6.5% by weight.

Intermediate layer: Ethylene / vinyl acetate copolymer (vinyl acetate content: 14.5% by weight, MFR: 1.3 g / 10
Min, EVAFLEX P1403 manufactured by Mitsui DuPont Polychemical Co., Ltd.)
85.6% by weight, antifogging agent 1.1% by weight, benzophenone-based UV absorber 0.05% by weight, hindered amine-based light stabilizer 0.15% by weight, anti-fusing agent 0.1% by weight And a heat retaining agent (hydrotalcite DH manufactured by Kyowa Chemical Co., Ltd.
T-4A) 13% by weight.

Inner layer: ethylene / vinyl acetate copolymer (vinyl acetate content 9.1% by weight, MFR 1.5 g / 10)
Min, EVAFLEX V340 manufactured by Mitsui DuPont Polychemical Co., Ltd. 9
6.29% by weight, antifogging agent 1.41% by weight, benzophenone-based UV absorber 0.05% by weight, hindered amine-based light stabilizer 0.15% by weight, anti-fusing agent 0.1% by weight And 2% by weight of heat retaining agent (DHT-4A). The physical properties of the obtained film are, as shown in Table 1, high total light transmittance,
The constant axis light transmittance (direct light transmittance) was low, and high heat retention characteristics were exhibited.

(Test as a house) Using the multilayer film of the above-mentioned Example 1 (the second year of use), it was spread so that the outer layer surface was the outside of the house, and 80 square meters (4 m
X 20 m) and a 2.2 m high camouflage-type leaf tobacco drying house was prepared, which was designated as the present invention group. In contrast,
As a control, an agricultural polyvinyl chloride film (pear-skin type, 0.1 mm thick, second year of use) was used, and a dry house having the same structure as that of the present invention was used as a control. The total light transmittance measured at the start of the test was 81% and 48% in the present invention group and the control group, respectively. In addition, the total light transmittances of the multilayer film of Example 1 and the agricultural polyvinyl chloride film at the time of manufacture were 96% and 75%, respectively. It had deteriorated considerably.

Then, 700 kg of barley-type tobacco synthetic leaves were respectively hung in the present invention group and the control group without being subjected to the "coarse draining" treatment in advance and dried. The test is 19
It was carried out in Towada City, Aomori Prefecture from August 8 to August 20, 1992, and drying control such as hem opening of both the present invention zone and the control zone was performed in the same manner. In addition, 6 days out of 13 days of the drying period were fine sunny days, and therefore a light-shielding curtain (light-shielding rate 90%) was coated in both the present invention group and the control group to prevent high temperature.

Table 2 shows the average values of the daytime temperature and the nighttime temperature and the maximum and minimum temperature of the day during the drying period of 13 days.
Compared with the control group, the present invention group has a high total light transmittance due to the high dust-proof property of the film as described above, so that the average value of the daytime temperature and the average value of the maximum temperature are about 3 ° C. and about 7 ° C., respectively. ℃ was high. Further, since the heat-retaining property of the multilayer film of the present invention is almost the same as that of the agricultural polyvinyl chloride film, there was no difference in the night temperature and the minimum temperature between the two sections.

[0025] Fig. 1 shows the cloudy day on the 9th day after the start of drying (the progress of leaf tobacco drying is 70% browning), and Fig. 2 shows the 10th day after the start of drying (the progress of leaf tobacco drying is 80% browning). The temperature change in the house from 6 am to 6 pm on a rainy day is shown together with the outside air temperature. A is the present invention group, B is the control group, and C is the outside air temperature. The shading curtain was not worn on both days. Compared with the control group, the temperature of the present invention was higher on the cloudy day and the rainy day in the house of the present invention, which was in agreement with the above-mentioned average value.

The results of an examination of the quality of the dried leaves at the end of the drying are shown in Table 3 as the type-based 1000 division ratio and the price ratio per kg. As is clear from Table 3, since the temperature inside the house was higher than that of the control group and the dry management such as exhaustion was easy to perform, the dry leaves of the present invention group had less generation of mottled leaves and dull leaves than the control group. . For this reason, the most high-quality A type was produced, and the price ratio per kg of the present invention group was higher than that of the control group.

Further, Table 4 shows the results of investigations on the suitability of use of the multilayer film of the present invention and the agricultural polyvinyl chloride film of the control. Damage situation of multilayer film of the present invention,
The dust resistance, cold resistance and stickiness were considerably better than those of the control agricultural PVC film. Also, there was no difficulty in opening and closing, which is often seen in vinyl acetate films (adhesion between films due to blocking). In addition, the poor elasticity often seen in polyolefin films was not recognized.

In addition, the drying house of the present invention was installed in March 1992.
When we raised seedlings of Burley tobacco as a house for raising seedlings on the moon, no sunburn was seen in the seedlings due to little direct light transmission, and healthy seedlings were produced. On the other hand, when a Burley seed tobacco was raised as a control drying house in the same manner as the house of the present invention, the dust resistance of the film was poor, and since a large amount of dust in the air was attached, the light transmittance was low, and the house Due to the lack of light inside, the seedlings grew soft and became high-pitched seedlings.

Example 2 In Example 1, the resin component for the outer layer was ethylene / vinyl acetate copolymer (vinyl acetate content 28% by weight, MFR1).
5g / 10 minutes, Mitsui DuPont Polychemical EVAFL
EX P2807) 56.0% by weight, low-density polyethylene (density 0.922 g / cc, MFR 0.25 g / 10 minutes, Lexron F102 manufactured by Nippon Petrochemical Co., Ltd.) 37.3% by weight, and benzophenone-based ultraviolet absorber 0. Film formation was carried out in the same manner as in Example 1 except that 1% by weight, 0.1% by weight of a hindered amine light stabilizer and 6.5% by weight of a heat retaining agent (hydrotalcite) were used. The physical properties of the obtained film were, as shown in Table 1, high total light transmittance, low constant axis light transmittance, and high heat retention.

Example 3 In Example 1, the ethylene / vinyl acetate copolymer (EVAFLEXP1403) for the intermediate layer and the ethylene / vinyl acetate copolymer (EVAFLEX V340) for the inner layer were replaced,
EVAFLEX V340 as the resin for the middle layer and EVAFLE as the resin for the inner layer
Film molding was performed in the same manner as in Example 1 except that XP1403 was used. The physical properties of the obtained film were, as shown in Table 1, high total light transmittance, low constant axis light transmittance, and high heat retention.

Example 4 In Example 1, except that the layer thickness was 0.01 mm for the outer layer, 0.03 mm for the intermediate layer, and 0.06 mm for the inner layer, and the use of the heat retaining agent (hydrotalcite) was stopped for the outer layer. Film molding was performed in the same manner as in Example 1. As shown in Table 1, the physical properties of the obtained film were such that the total light transmittance was high, the constant axis light transmittance was low, and high heat retention characteristics were exhibited.

Example 5 In Example 1, as the resin component of the inner layer, ethylene / vinyl acetate copolymer (EVAFLEX P2807), low density polyethylene (Lexron F102) and low density polyethylene (Mirason 16) 42/28 / The mixed resin of 30 was used, and 1.5% by weight of an antifogging agent, 0.1% by weight of a benzophenone-based UV absorber, and 0.1% by weight of a hindered amine-based light resistance stabilizer were used. The content of the heat retaining agent was 6.3% by weight, and the thickness of each layer was 0.02 mm in the outer layer, 0.06 mm in the intermediate layer, and 0.02 mm in the inner layer to produce a three-layer film. The physical properties of the obtained film showed excellent properties as shown in Table 1.

Comparative Example 1 Film formation was performed in the same manner as in Example 1 except that the resin component of the outer layer was changed to low density polyethylene (Millason 16), and the outer layer was 0.02 mm, the middle layer was 0.02 mm, and the inner layer was 0.02 mm. A 06 mm three-layer film was obtained. As shown in Table 1, the physical properties of the obtained film were such that the constant axis light transmittance was high and the film was non-satin-like.

Comparative Example 2 In Example 1, ethylene resin was used as the resin component of the outer layer.
While using vinyl acetate copolymer (EVAFLEX BRV340), mixed resin component of 60% by weight of ethylene / vinyl acetate copolymer (EVAFLEX P2807) and 40% by weight of low density polyethylene (LEXRON F102) was used as the resin component of the intermediate layer. The same procedure as in Example 1 was carried out except that it was used to obtain a three-layer film having an outer layer of 0.02 mm, an intermediate layer of 0.02 mm and an inner layer of 0.06 mm. As to the physical properties, as shown in Table 1, the film had a high constant axis light transmittance and was a non-satin-like film.

[0035]

[Table 1]

[0036]

[Table 2] Note) 1. Measurement position: 50 cm below the roof covering material 2. Measurement period: August 8 to August 20, 1992 3. Measurement place: Towada City, Aomori Prefecture 4. Daytime temperature: 6:00 to 18:00 Nighttime temperature: 18:00 to 5:00 Average temperature: average value of measured values every 30 minutes 6. Maximum temperature: average of 13 days of maximum value of the day 7. Minimum temperature: The average value of 13 days of the lowest value of the day

[0037]

[Table 3] A: Normal leaf, B: Mildly deteriorated leaf, C:
Moderately deteriorated leaves, D: Severely deteriorated leaves (* The price ratio per kilogram was calculated by the purchase price of leaf tobacco by leaf type in 1992.)

[0038]

[Table 4]

[Brief description of drawings]

FIG. 1 is from 6 o'clock to 18 o'clock on a cloudy day on the ninth day after the start of drying in Example 1 (the progress of leaf tobacco drying is 70% browning).
It is a graph which shows the temperature change in the house up to time together with the outside air temperature, where A is the present invention group, B is the control group, and C is the outside air temperature.

[FIG. 2] From 6 o'clock on a rainy day on day 10 after the start of drying in Example 1 (progress of leaf tobacco drying is 80% browning)
It is a graph which shows the temperature change in a house by 8 o'clock with the outside temperature, A is this invention group, B is a control group, C is outside temperature.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location B32B 27/32 E 8115-4F // C08L 23/08 LDF 7107-4J LDJ 7107-4J

Claims (4)

[Claims] 1. At least one of the outermost layers has a vinyl acetate content of 20 to 35% by weight and a melt flow rate (MF).
R) is a mixture of an ethylene / vinyl acetate copolymer (A) having 4 to 50 g / 10 min and a low density polyethylene (B) having MFR of 0.04 to 2.0 g / 10 min, and (A) and The mixing ratio of (B) is (A) / (B) = 35-9
0 / 65-10 (weight ratio), the average vinyl acetate content of the mixture is 12-22% by weight, and its MFR ratio ((A)
(MFR of (B) / (MFR of (B)) = 10 to 100 and a multilayer structure composed of another olefin resin layer, and having a total light transmittance of 80% or more and a transformer of 10% or less. Film. 2. The mixture layer according to claim 1, wherein 100 parts by weight or less of low density polyethylene having an MFR of more than 2.0 g / 10 minutes is used per 100 parts by weight of (A) and (B) in total. Agricultural film. 3. The agricultural film according to claim 1, wherein at least one layer contains a heat retaining agent. 4. The agricultural film according to claim 3, wherein the heat retaining agent is hydrotalcite.