JP2002187980A - Agricultural polyolefin film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prepare an agricultural film having good transparency, being excellent in low-temperature antifogging properties and the retentivity of antifogging properties, and not undergoing blocking due to bleeding. SOLUTION: There is provided an agricultural film containing 100 pts.wt. polyolefin resin and 0.5-5 pts.wt. antifogging agent comprising a partial ester compound obtained by mixing a polyglycerol having an average degree of polymerization of 2-10 with at least two 8-22C fatty acids. It is preferable that the antifogging agent is a partial ester compound (degree of esterification of 15-60%) in which a 14-22C saturated fatty acid constitutes at least 50 wt.% of the at least two fatty acids and a 14-22C unsaturated fatty acid constitutes 10-35 wt.% of the at least two fatty acids.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an agricultural film which is excellent in transparency, excellent in low-temperature antifogging properties and antifogging durability, and does not cause film blocking by bleeding.

[0002]

2. Description of the Related Art Ethylene-vinyl acetate copolymers, polyethylene and the like are used as polyolefin resins used as agricultural films used in greenhouse horticulture such as house cultivation and tunnel cultivation. Since these polyolefin resins are hydrophobic, moisture evaporating from the soil and crops aggregates on the film surface, forming fine water droplets and fogging, lowering the transparency and hindering the transmission of sunlight. In addition to impairing the growth of cultivated crops, water drops may cause crop damage. for that reason,
Generally, a method of applying a surface active substance such as a surfactant to the film surface as an antifogging agent, and a method of kneading a polyolefin resin with an antifogging agent to form a film are used to make the film surface easily wettable.

A method of applying an antifogging agent has a good initial antifogging effect and is an inexpensive method. In general, a method of kneading an antifogging agent with a polyolefin resin to form a film is generally used because the property is easily lowered. As an agricultural film, it exhibits anti-fog properties even in winter and summer, and the anti-fog agent is less likely to run off due to water droplets adhering to the inner surface of the film. The agent must transfer and maintain its performance in the long term.

[0004] In order to impart anti-fogging properties, it is necessary that the anti-fogging agent to be blended has an appropriate compatibility with the polyolefin resin. When the compatibility is good, the amount of the antifogging agent transferred to the film surface is small, and the transparency is good, but the antifogging property is poor. When the compatibility is poor, the transfer speed of the anti-fogging agent to the film surface is high, and although there is anti-fogging property, the transparency of the film deteriorates due to whitening, and the film surface becomes sticky due to stickiness of the film surface and workability. , And the handling becomes poor. Therefore, in order to impart an appropriate anti-fogging property and transparency to the film, the bleeding property and the compatibility of the anti-fogging agent blended with the polyolefin resin must be balanced. Until now, there is no problem with anti-fogging properties, but for the purpose of improving the transparency of the film in which whitening is a problem, liquid type anti-fog agents and the like have been used, but the anti-fogging persistence deteriorates, Sufficient results were not obtained due to blocking between the films. In order to develop the anti-fogging property of the film, it is necessary to always transfer the anti-fogging agent from the inside of the film toward the surface. However, at low temperatures, the anti-fogging agent hardly bleeds on the film surface. Sorbitan or glycerin-based anti-fogging agents were added in specific amounts and in specific mixing ratios to improve haze and anti-fogging durability, but satisfactory anti-fogging properties have not yet been obtained That was the current situation.

[0005]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and has good transparency by blending a polyolefin resin with a suitable antifogging agent.
Further, it is an object of the present invention to provide an agricultural film which is excellent in antifogging property and antifogging durability at low temperature, and in which the bleeding property of the antifogging agent works properly to reduce blocking between films.

[0006]

According to the present invention, an average degree of polymerization is 2 to 10 with respect to 100 parts by weight of a polyolefin resin.
Of 0.5 to 5 parts by weight of a partial ester compound obtained by mixing the polyglycerin and two or more fatty acids having 8 to 22 carbon atoms. The anti-fog agent is a partial ester compound having a degree of esterification of 15 to 60%, and two or more fatty acids having 8 to 22 carbon atoms constituting the partial ester compound are 50% by weight of a saturated fatty acid having 14 to 22 carbon atoms.
That is, the unsaturated fatty acid is 10 to 35% by weight. The degree of esterification is represented by the following formula (1): degree of esterification (%) = (number of ester bonds per mole of polyglycerin / polyglycerin 1 before esterification)
Average number of hydroxyl groups per mole) × 100 (1) A polyolefin-based resin, an ethylene-vinyl acetate copolymer having a vinyl acetate content of 30% by weight or less,
1 of low-density polyethylene or ethylene-α-olefin copolymer having a density of 0.910 to 0.930 g / cm ³
It is an agricultural film characterized by comprising a seed or two or more kinds.

The polyolefin resins used in the present invention include polyethylene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, and ethylene-4-methyl-1-pentene copolymer. A coalesced ionomer resin or the like can be used, and among these, the low-density polyethylene or ethylene-α-olefin copolymer having a density of 0.910 to 0.930 g / cm ³ and the vinyl acetate content is 30% by weight or less. Is more preferred from the viewpoint of strength, transparency and weather resistance.

[0008] Among the antifogging agents used in the agricultural film of the present invention, the degree of esterification obtained by mixing polyglycerin having an average degree of polymerization of 2 to 10 and two or more fatty acids having 8 to 22 carbon atoms. 15 to 60% of a partial ester is obtained by subjecting polyglycerin and a fatty acid to an esterification reaction by a conventional method, and mainly contains a compound in which a part of the hydroxyl group of polyglycerin is ester-bonded to the fatty acid. I do.
When the degree of esterification is lower than 15%, the anti-fogging property is poor, and when it is higher than 60%, the anti-fogging property is poor. As polyglycerin, diglycerin, tetraglycerin, hexaglycerin, decaglycerin and the like can be used, but diglycerin and tetraglycerin are preferred from the viewpoints of antifogging property, economy and the like. Examples of the fatty acid having 8 to 22 carbon atoms include caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, and behenic acid. Among the above fatty acids,
A mixture of two or more fatty acids containing 50% by weight or more of a saturated fatty acid having 14 to 22 carbon atoms and containing 10 to 35% by weight of an unsaturated fatty acid is used as a saturated fatty acid having 14 to 22 carbon atoms. The saturated fatty acids having 14 to 22 carbon atoms may be used alone or in combination. Among them, palmitic acid and stearic acid are preferred. As the unsaturated fatty acid, oleic acid, linoleic acid, linolenic acid, ricinoleic acid, stearolic acid, erucic acid and the like can be used. Among them, oleic acid is preferable. Examples of oleic acid include industrial oleic acid and distilled oleic acid obtained by separating decomposed fatty acids obtained from animal and vegetable fats and oils by distillation and the like.
Those containing 5% or more are preferred. Average degree of polymerization is 2
When a saturated fatty acid having 14 to 22 carbon atoms is used as the fatty acid used in the ester with polyglycerin No. 10, the transparency of the film is significantly deteriorated due to whitening. When only unsaturated fatty acids are used, the transparency of the film is improved, but the antifogging durability is extremely poor and the film becomes sticky. In addition, a polyglycerin saturated fatty acid ester and a polyglycerin unsaturated fatty acid ester are mixed with an ester obtained by mixing the polyglycerin of the present invention and two or more kinds of fatty acids so as to have a similar fatty acid composition and a similar degree of esterification. Even when used, the antifogging property and the transparency deteriorate, and the same effect as the specific polyglycerin mixed fatty acid ester of the present invention cannot be obtained. The agricultural film of the present invention is obtained by blending 0.5 to 5% by weight of a specific polyglycerin-mixed fatty acid ester as an antifogging agent with respect to 100 parts by weight of a polyolefin-based resin to form a film. If the addition amount is less than 0.5 part by weight, the antifogging performance is insufficient, and if it is more than 5 parts by weight, no extreme improvement effect of the antifogging property is seen,
Conversely, the stickiness of the film becomes severe, and a blocking phenomenon due to bleeding of the anti-fog agent easily occurs during storage of the film in a high temperature state such as in summer.

[0009] The agricultural film of the present invention comprises the above-mentioned polyolefin resin as a substrate, and a specific antifogging agent added thereto in an amount of 0.5 to 0.5%.
Although 5% by weight is added, antioxidants (such as phenolic compounds) and ultraviolet absorbers (benzophenone-based compounds) generally used when forming a polyolefin-based resin into a film as far as the effects of the present invention are not impaired. , Benzotriazole compounds, etc.), antifog agents, light stabilizers (hindered amine compounds, etc.), light transmittance improvers (β-diketone compounds, etc.), lubricants, stabilizers, heat insulators, anti-blocking agents, antistatic agents , A colorant, a fungicide, and the like.

The agricultural film of the present invention is obtained by blending 0.5 to 5% by weight of an antifogging agent and various necessary additives with a polyolefin resin, and then mixing and forming a film. The method of mixing includes, for example, a method of mixing with a tumbler mixer, a Banbury mixer, a super mixer, and the like, and the method of forming a film includes a T-die method, an inflation method, a calender roll method, and the like.

[0011]

Next, the present invention will be described in detail with reference to examples and comparative examples, but the present invention is not limited to these examples. In the examples and comparative examples, evaluation of the formed films was performed by the following method.

(Evaluation of Transparency)
The haze of the film which was allowed to stand in a constant temperature room at 3 ° C. and a humidity of 50% for one month was measured, and the transparency was evaluated. Evaluation criteria ○: Haze value less than 30% ×: Haze value 30% or more

(Evaluation of Stickiness of Film) The stickiness of the film surface after standing in a constant temperature room at 23 ° C. and a humidity of 50% for one month was evaluated by touch. Evaluation criteria ○: No stickiness of the film. X: The film is sticky.

(Low-temperature antifogging property) 23 ° C., 50% humidity after film formation
After standing for 10 days in a constant temperature room, the film was placed on a 450 ml glass bottle opening containing 150 ml of water at 15 ° C.
After being placed in a constant temperature water bath at 15 ° C. with an inclination of 10 °, it was left still in a low temperature room at 4 ° C., and the surface state of the film was observed over time. The antifogging property was evaluated on the following four levels. Evaluation criteria A: The surface is uniformly transparent and there is no adhesion of water droplets. ：: The surface is almost transparent, but appears uneven and distorted. Δ: Large water droplets partially adhered to the surface. ×: Water droplets adhered to the entire surface, and the bottom was difficult to see.

(High temperature anti-fog persistence) 23 ° C., humidity 5 after film formation
After leaving the film in a 0% constant temperature room for 10 days,
After placing it in a 450 ml glass bottle opening containing 150 ml of water at 150 ° C. and placing it at an inclination of 10 ° in a constant temperature water bath at 40 ° C., it was allowed to stand still in a constant temperature room at 23 ° C. Was observed. The antifogging property was evaluated on the following four levels. Evaluation criteria A: The surface is uniformly transparent and there is no adhesion of water droplets. ：: The surface is almost transparent, but appears uneven and distorted. Δ: Large water droplets partially adhered to the surface. ×: Water droplets adhered to the entire surface, and the bottom was difficult to see.

[0016]

Examples 1 to 5 To 100 parts by weight of an ethylene-vinyl acetate copolymer resin (vinyl acetate content: 5% by weight), a predetermined amount of a compound comprising the components shown in Table 1 was added and mixed. This was kneaded using a twin screw extruder to produce extruded pellets. Further, screw temperature 210 ° C., die temperature 210
A film having a thickness of 100 μm was formed by a T-die-extruder method at 0 ° C., and the haze of the film was determined for the obtained film.
The whitening, stickiness of the film, low-temperature antifogging property, and high-temperature antifogging durability were evaluated. Table 2 shows the results.

[0017]

[Table 1]

[0018]

[Table 2]

[0019]

Comparative Examples 1 to 6 To 100 parts by weight of an ethylene-vinyl acetate copolymer resin (vinyl acetate content: 5% by weight), a predetermined amount of a compound comprising the components shown in Table 1 was added and mixed. This was kneaded using a twin screw extruder to produce extruded pellets. Further, screw temperature 210 ° C., die temperature 210
A film having a thickness of 100 μm was formed by a T-die-extruder method at 0 ° C., and the haze of the film was determined for the obtained film.
The whitening, stickiness of the film, low-temperature antifogging property, and high-temperature antifogging durability were evaluated. Table 2 shows the results.

[0020]

Industrial Applicability The present invention has an excellent effect as an antifogging agent for agricultural films which has good transparency, excellent low-temperature antifogging properties and antifogging durability, and does not cause film blocking by bleeding.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) C08L 23/08 C08L 23/08 F term (Reference) 2B024 DB01 EA01 2B029 EB02 EC02 EC09 EC16 4F071 AA15X AA18 AA28X AE10 AH01 BC01 4J002 BB031 BB051 BB061 EH056 FD206 FD316 GQ01

Claims (3)

[Claims] 1. A polyglycerol having an average degree of polymerization of 2 to 10 and a carbon number of 8 based on 100 parts by weight of a polyolefin resin.
An agricultural film comprising 0.5 to 5 parts by weight of an anti-fogging agent comprising a partial ester compound obtained by mixing two or more fatty acids of the formula (1) to (2). 2. The antifogging agent is a partial ester compound having a degree of esterification of 15 to 60%, and two or more fatty acids having 8 to 22 carbon atoms constituting the partial ester compound have 14 to 14 carbon atoms.
The agricultural film according to claim 1, wherein the saturated fatty acid is 22% by weight or more and the unsaturated fatty acid is 10 to 35% by weight. 3. An ethylene-vinyl acetate copolymer in which the polyolefin resin has a vinyl acetate content of 30% by weight or less,
1 of low-density polyethylene or ethylene-α-olefin copolymer having a density of 0.910 to 0.930 g / cm ³
3. The agricultural film according to claim 1, comprising at least one species.