JP3148463B2 - Agricultural film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an agricultural film of a saponified ethylene-vinyl acetate copolymer (hereinafter sometimes abbreviated as EVOH), and more particularly to a film having good transparency, good heat retention and dust. The present invention relates to an agricultural film which is excellent in anti-adhesion property, drip-free property and film strength, and is also safe for the environment during incineration.

[0002]

2. Description of the Related Art Conventionally, polyvinyl chloride films have been frequently used as agricultural films in terms of flexibility, transparency, economy, workability, and the like. However, on the other hand, it is also the fact that contamination (migration, seepage) by the plasticizer contained therein is the greatest disadvantage. As a measure to prevent this, it is conceivable to reduce the amount of the plasticizer, but this reduces the flexibility characteristic of the polyvinyl chloride film and loses its original properties. So, in order to prevent migration of plasticizer,
A film in which EVOH is laminated on polyvinyl chloride has been proposed (Japanese Patent Publication No. 4-56744). On the other hand, a polyolefin resin film is used instead of the polyvinyl chloride film. In this case, there is no concern about migration of the plasticizer or generation of toxic gas at the time of incineration, but it is inferior to the conventional polyvinyl chloride film in terms of heat retention. In order to solve this problem, attempts have been made to improve the heat retention by blending a compound absorbing infrared rays, glass beads, or the like into the olefin resin film.

[0003]

However, in the technique disclosed in Japanese Patent Publication No. 4-56744, although the prevention of the transfer of the plasticizer and the prevention of the adhesion of dust are recognized, the film is drip-free (the inside of the film cannot be removed). The resulting dew condensation water has an adverse effect on crops, so it is required to be drip-free so that no dew condensation water is generated.) Furthermore, no toxic gas is generated during incineration because polyvinyl chloride resin is used. Outbreaks cannot be avoided. On the other hand, in the method using a polyolefin-based resin, a compound that absorbs infrared rays or glass beads is blended in order to increase the heat retention, so that the transparency of the film is reduced, and the adhesion of dust and the drip-free property are reduced. The fact is that there are still problems with such things.

[0004]

The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems. As a result, at least one side of the polyolefin resin film has an ethylene content of 20 to 60 mol% and a saponification degree of 20 to 60 mol%. Is 90 mol% or more,
An agricultural film laminated with a saponified ethylene-vinyl acetate copolymer having a melting point (Tm) that satisfies the following formula is excellent in transparency, heat retention, dust adhesion prevention, drip resistance, and film strength. The present invention was found to be excellent and also excellent in safety to the environment during incineration, and completed the present invention. Tm <220-1.46Et + 3.31 (Sv-99.
6) Here, Tm: melting point (° C.) measured by a differential scanning calorimeter Et: ethylene content (mol%) Sv: saponification degree (mol%)

Hereinafter, the present invention will be described specifically.
EVOH used in the present invention has an ethylene content of 20-6.
0 mol%, preferably 25 to 55 mol%, and the degree of saponification of the vinyl acetate component is 90 mol% or more, preferably 95 mol%.
Must be at least. Ethylene content is 20 mol%
If it is less than 30, the water resistance at high temperatures is reduced, which hinders outdoor use as an agricultural film.
If it exceeds 30, sufficient heat retention and driplessness cannot be obtained, and if the saponification degree is less than 90 mol%, the heat retention and moisture resistance will be reduced. Moreover, in the present invention, the differential scanning calorimeter (DS
Melting point (Tm) calculated from peak temperature measured in C)
The greatest feature is that EVOH in a range satisfying the following expression defined by the ethylene content (Et mol%) and the degree of saponification (Sv mol%) is used.

Tm <220-1.46Et + 3.31
(Sv-99.6) When the Tm value is larger than the above range, the adhesive strength to the polyolefin-based resin film and the driplessness are reduced.
The object of the present invention cannot be achieved. Further, when a layer having poor gas barrier properties such as a polyolefin resin is laminated on the EVOH layer, it is necessary to impart gas barrier properties to the EVOH layer, and for this purpose, the Tm value is set to 120-1.46 Et.
+3.31 (Sv-99.6) <Tm <220-1.4
It is preferable to be in the range of 6Et + 3.31 (Sv-99.6). EVOH as defined in the present invention is generally not commercially available. That is, in the conventional EVOH, the melting point is higher than the melting point of the present invention regardless of the ethylene content and the degree of saponification, and the use of EVOH having such a high melting point achieves the object of the present invention. I can't get it.

Further, the EVOH may further contain a small amount of α-olefin such as propylene, isobutene, α-octene, α-dodecene, α-octadecene, unsaturated carboxylic acid or its salt, partial alkyl ester, complete alkyl ester, nitrile, Comonomers such as amides, anhydrides, unsaturated sulfonic acids or salts thereof may be included as copolymer components. As a method for obtaining EVOH satisfying the above Tm value, there is an arbitrary method, and the degree of polymerization may be controlled at the time of polymerization or saponification of EVOH, or the saponification degree distribution may be considered. It is advantageous to treat EVOH obtained by a conventional industrial production method with a peroxide. Hereinafter, such a method will be described in detail.

An ethylene content of 20 to 60 mol%, a saponification degree of 90 mol% or more, and a melting point (Tm) of 220-
Those having a melting point higher than the value calculated from 1.46 Et + 3.31 (Sv-99.6) (for example, an ethylene content of 38 mol% and a saponification degree of 99.6 mol%)
In the case of, the value of the above equation is 164.5 ° C., and a higher value, for example, having a melting point of 173 ° C., is converted to water and a lower alcohol (eg, ethyl alcohol, methyl alcohol, is
o-propyl alcohol, n-propyl alcohol, t
-Butyl alcohol) or a solvent such as dimethyl sulfoxide (DMSO) or N, N-dimethylformamide (DMF).

The concentration of the EVOH is suitably from 1 to 50% by weight. Hydrogen peroxide (usually 35% by weight aqueous solution) is added to the solution with EVOH / hydrogen peroxide (35% by weight).
% By weight) = 1 / 0.03 to 1/3 (weight ratio), and the mixture is treated with stirring at 40 to 90 ° C. for 1 to 50 hours. In some cases, a metal catalyst (CuCl ₂ , CuSo ₄ , MoO ₃ , FeSo ₄ , T
iCl ₄ , SeO _2, etc.) per solution to 1-5000 pp
m may be added. Also, water, alcohol,
The order of adding the solvent, EVOH and hydrogen peroxide is not limited to the above order. Of course, it is also possible to charge the above-mentioned composition at once. At the end of the treatment, one point is that the viscosity of the solution at the time of start becomes about 10% or less of the initial viscosity.

[0010] The EVOH solution thus obtained is composed of water-
It is a solution containing alcohol or DMSO, DMF, etc., and the solution can be directly used for producing a laminate with a polyolefin resin, or the solution is subjected to a known process using a fluidized bed dryer, a flash dryer, a freeze dryer, or the like. It is also possible to remove the solvent such as water-alcohol or DMSO or DMF by a method and to provide a solid EVOH for producing a laminate. The EVOH thus obtained is excellent in adhesiveness and heat sealability without blending any other resin. However, in order to further improve the performance and to improve the performance other than the above, other EVOH is used. Resins can also be blended. As the resin, a polyolefin resin, or a modified polyolefin resin graft-modified with an unsaturated carboxylic acid or a derivative thereof, polyamide, polyvinyl chloride, polyvinylidene chloride, polyester, polystyrene, polyacrylonitrile, polyurethane, polyacetal, polycarbonate, Examples thereof include a melt-moldable polyvinyl alcohol-based resin.

The polyolefin resin film used in the present invention includes linear low density polyethylene, low density polyethylene, medium density polyethylene, high density polyethylene, ethylene-vinyl acetate copolymer, ionomer, ethylene-propylene copolymer , Ethylene-acrylate copolymer, polypropylene, polypropylene-α
-Olefin (α-olefin having 4 to 20 carbon atoms) copolymers, homo- or copolymers of olefins such as polybutene, polypentene, or grafts of homo- or copolymers of these olefins with unsaturated carboxylic acids or esters thereof Films of polyolefin resins in a broad sense, such as modified ones, may be mentioned. Further, in the present invention, EVOH having the specific melting point (Tm) as described above is laminated with the polyolefin resin film, but the laminating method is not particularly limited. An example of the lamination method is as follows.

(Solution coating method) The water-alcohol (or solvent) -containing solution of EVOH obtained as described above is known in the art such as a roller coating method such as a Meyer bar, gravure and reverse roll method, a spray coating method, and a dip coating method. The polyolefin resin film is coated by the method described above to produce a laminate.
Thereafter, drying is performed by a known method. For example, the drying temperature is 40 to 180 ° C, preferably 60 to 140 ° C.
It may be heated for about 5 seconds to about 5 minutes. In this drying, the volatile components (water, alcohol or solvent) in the coating film are removed, and the drying is usually performed until the volatile component becomes 2% by weight or less. Thus, the EVOH layer is formed on the polypropylene resin film. The thickness of this layer is practically 0.5 to 20 .mu., Preferably about 1 to 10 .mu.m. In order to improve the adhesive strength between the EVOH and the polyolefin resin film, a usual anchor coating agent (polyurethane, polyester or the like) may be previously coated on the film.

(Extrusion coating method) The solid EVOH obtained as described above is subjected to 150-150
It is extruded from a die and coated on a polyolefin resin film at a temperature of about 250 ° C. to produce a laminate. At this time, the thickness of the layer is practically 1 to 20 μm. (Co-extrusion method) The solid EVOH obtained as described above is co-extruded with a polyolefin-based resin film at a temperature of about 150 to 300 ° C by a melt extruder equipped with a three-layer die to produce a laminate. At this time, the thickness of the EVOH layer is 1 to 20 μm.
Is practical. (Dry lamination method) From EVOH of the present invention to EVOH
Make a film (unstretched, uniaxially stretched, biaxially stretched),
A laminate is prepared by dry laminating a polyolefin resin film with a known adhesive such as an organic titanium compound, an isocyanate compound, or a polyester compound. At this time, the thickness of the EVOH layer is practically 5 to 20 μm.

The layer structure of the laminate obtained as described above includes an EVOH layer / polyolefin resin film, EV
Various configurations such as an OH layer / polyolefin resin film / EVOH layer can be adopted. The EVOH thus obtained
The laminate with the polyolefin resin film is transparent,
It is very useful as an agricultural film because of its excellent heat retention, dust adhesion prevention and drip-free properties, and film strength.
In order to further improve the driplessness, a normal surfactant may be blended. The thickness of the polyolefin resin film used for the above-mentioned agricultural film may be any EVO.
When the H lamination method is adopted, it is also suitably selected in the range of 20 to 200 μm.

[0015]

The agricultural film of the present invention is made by laminating an EVOH having a specific melting point and a polyolefin-based resin film, so that it has not only transparency and heat retention, but also anti-dust adhesion, drip-free (water droplets). It has excellent anti-condensation properties, film strength and environmental safety when incinerated.

[0016]

The present invention will be specifically described below with reference to examples. In the examples, “parts” and “%” are based on weight unless otherwise specified. Example 1 To 36 parts of a mixed solvent containing 50% of water and 50% of iso-propyl alcohol, 8 parts of EVOH (ethylene content: 29% by mole, saponification degree: 99.7% by mole, melting point: 188 ° C) was added, and 60 to 70 parts were added. The mixture was stirred at about 2 hours for about 2 hours to prepare a clear solution. Next, 6 parts of hydrogen peroxide (35% aqueous solution) was added to the solution, and the mixture was reacted at 80 ° C. with stirring for about 20 hours.
Further, catalase was added to be 3000 ppm,
The remaining hydrogen peroxide was removed to obtain an about 15% EVOH solution. The ethylene content of the obtained EVOH is 29 mol%,
The saponification degree was 99.7 mol%, and the melting point Tm was 158 ° C. as measured by DSC. This Tm value is defined in claim 1 of the present application.
The value satisfies the specified value Tm <178 ° C. calculated from the equation described.

Next, linear low-density polyethylene (LLD)
PE) The above EVOH is applied to the surface of the film (thickness: 50 μ).
The solution was applied with a gravure coater and dried at about 80 ° C. for 1 minute to obtain a laminate having a thickness of 5 μm of EVOH. The laminate was evaluated for transparency, dust adhesion (surface resistivity), driplessness (wetting index), and heat retention (visible light and infrared light transmittance). The film strength was evaluated based on the pencil scratch hardness of the EVOH layer surface of the laminate.

Examples 2-3 and 5-6 Using the EVOH as a starting material, an EVOH solution having the Tm value shown in Table 1 was obtained from the raw materials shown in Table 1 in the same manner as in Example 1. A laminate was prepared and evaluated. The same evaluation as in Example 1 was performed on the laminate. Example 4 In the same manner as in Example 1 except that the raw material EVOH shown in Table 1 was used, Table 1 was used.
An EVOH solution having a Tm value shown in Table 2 was obtained, and the solution was dried up (80 ° C., 90 minutes) to obtain a solid EVOH solution.
After obtaining the EVOH, the EVOH was co-extruded with a linear low-density polyethylene (single-screw extruder with feed block die, C ₁ /
_{C 2 / C 3 / C 4} / J / D = 150/170/180/1
90/190/190 (° C.)) to produce a laminate. The same evaluation as in Example 1 was performed on the laminate.

Comparative Example 1 In Example 1, a commercially available EVOH (ethylene content 2
EVOH of 9 mol%, saponification degree 99.5 mol%, melting point 188 ° C .; Tm value calculated as in Example 1 is Tm <178 ° C., and the melting point is out of the range specified in the present application.
A laminate was prepared and evaluated in the same manner as in Example 1 except that the solution was used. Comparative Example 2 The single-layer linear low-density polyethylene film of Example 1 (thickness: 50 μm) was evaluated in the same manner. Comparative Example 3 Evaluation of the polyvinyl chloride (PVC) film single layer (thickness: 50 μ) of Example 1 was performed in the same manner.

Comparative Example 4 In Example 1, 5% by weight of glass beads (GB) having a diameter of about 5 μm or less were blended with the intermediate layer of LLDPE,
A laminate of DPE (thickness 15 μ) / GB blend LLDPE (thickness 20 μ) / LLDPE (thickness 15 μ) was prepared and subjected to the same evaluation. Table 2 shows the respective evaluation results of the examples and the comparative examples. The evaluation method is as follows. (Transparency) The haze value was measured. (Dust Adhesion) The surface resistivity (Ω) of the surface of the EVOH layer and the single layer body of the laminate was measured by a surface resistivity meter. The measurement was performed at a standard condition of 20 ° C. and 65 RH%.

(Dripless) The wetting index (surface tension) of the surfaces of the EVOH layer and the monolayer of the laminate was measured according to JIS K6768. (Heat insulation) Visible light (546 mm) of laminate and single layer
And the transmittance (%) of infrared rays (8 to 12 μm) to visible light; UV-visible spectrophotometer U manufactured by JASCO Corporation U
VIDEC-650, infrared; measured using an infrared-visible spectrophotometer UVIDEC270-30 manufactured by Hitachi Spectroscopy. The larger the visible light transmittance and the smaller the infrared transmittance, the better the heat retention. (Film strength) It was measured according to the pencil scratch hardness of JIS K 5400. The film strength was evaluated only for the laminate having the EVOH layer.

[0022]

Table 1 EVOH Tm value of raw material Range of Tm value Et (mol%) Sv (mol%) Melting point (° C.) (° C.) (° C.) Example 1 29 99.7 188 158 Tm <178 Example 2 2999 .6 188 140 Tm <178 Example 3 299 99.4 188 123 Tm <177 Example 4 29 99.6 188 95 Tm <178 Example 5 38 99.6 173 143 Tm <165 Example 6 38 99.0 173 118 Tm <163 Comparative Example 1 29 99.5 188 188 Tm <177 Comparative Example 2 LLDPE Single Layer Comparative Example 3 PVC Single Layer Comparative Example 4 LLDPE / GB Blend LLDPE / LLDPE Note) Et and Sv are ethylene content and Represents the degree of saponification. The Tm value represents a melting point measured by a differential scanning calorimeter, and the range of the Tm value represents a range of the Tm value calculated from the expression of claim 1 of the present invention.

[0023]

Table 2 Transparency Surface resistivity Wetting index Light transmittance (%) Pencil scratching haze (%) (Ω) (dyn / cm) Visible light Infrared Hardness Example 1 6.38 8 × 10 ¹⁴ 49 81 37 HB Example 2 6.0 5 × 10 ¹⁴ 52 83 35 HB Example 3 6.0 3 × 10 ¹⁴ 52 83 34 HB Example 4 5.9 1 × 10 ¹⁴ 53 85 32 HB Example 5 6.2 7 × 10 ¹⁴ 48 81 38 HB Example 6 6.1 4 × 10 ¹⁴ 51 8237 HB Comparative Example 1 6.4 2 × 10 ¹⁵ 46 81 35 HB Comparative Example 2 5.5 5 × 10 ¹⁶ 38 38 82 85-Comparative Example 3 4.2 4 × 10 ¹⁶ 36 85 35 −Comparative Example 4 7.0 5 × 10 ¹⁶ 38 75 48 −

[0024]

According to the agricultural film of the present invention, since EVOH having a specific melting point and a polyolefin resin film are laminated, not only transparency and heat retention, but also dust adhesion prevention and drip-free ( It is also excellent in film strength and environmental safety during incineration.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-6-65452 (JP, A) JP-A-5-295119 (JP, A) JP-A-5-116258 (JP, A) JP-A-2- 255355 (JP, A) JP-A-56-89553 (JP, A) JP-A-54-159481 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B32B 1/00-35 / 00 A01G 9/14 A01G 13/02 EPAT (QUESTEL) WPI / L (QUESTEL)

Claims (2)

(57) [Claims] An ethylene-vinyl acetate copolymer having an ethylene content of at least 20 to 60 mol%, a saponification degree of at least 90 mol%, and a melting point (Tm) satisfying the following formula on at least one surface of the polyolefin resin film. An agricultural film characterized by laminating polymer saponified products. Tm <220-1.46Et + 3.31 (Sv-99.
6) Here, Tm: melting point (° C.) measured by a differential scanning calorimeter Et: ethylene content (mol%) Sv: saponification degree (mol%) 2. An ethylene-vinyl acetate copolymer having an ethylene content of 20 to 60 mol%, a saponification degree of 90 mol% or more and a melting point (Tm) satisfying the following formula on at least one surface of the polyolefin resin film. The agricultural film according to claim 1, wherein a saponified polymer is laminated. 120-1.46Et + 3.31 (Sv-99.6) <
Tm <220-1.46Et + 3.31 (Sv-99.
6)