Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2001-08-30
2003-04-29
Sanders, Kriellion A. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S102000, C524S291000, C524S427000
Reexamination Certificate
active
06555603
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a resin composition for producing agricultural films. The composition provides films in which reduction in weatherability caused by sulfur fumigation or acid rain is suppressed. More particularly, the present invention relates to a resin composition for producing agricultural films exhibiting excellent long-term weatherability, which composition contains an adduct obtained through addition of a nitroxy compound to a predetermined polymer, the adduct serving as a polymer stabilizer.
BACKGROUND ART
Films formed from a polyethylene thermoplastic resin, such as polyethylene or an ethylene-vinyl acetate copolymer, or films formed from a polyester resin are used as agricultural films for forming, for example, a greenhouse or a plastic tent, since such films exhibit excellent transparency, heat-insulating ability, and mechanical strength. However, such a resin film cannot be used for a long period of time, because of deterioration caused by UV rays; e.g., impairment of transparency or breakage of the film.
As is well known, such impairment of the films can be suppressed by addition of an antioxidant, a UV absorber, a hindered amine compound, or a hydrotalcite compound. For example, Japanese Patent Application Laid-Open (kokai) No. Showa63-175072 discloses a method in which a hindered amine compound and hydrotalcite are incorporated in combination into a resin film, thereby stabilizing the film. U.S. Pat. No. 5,096,950 discloses a method in which a hindered amine compound having a nitroxyalkyl structure is incorporated into an agricultural polyolefin film.
However, the aforementioned additives fail to satisfactorily exert the effect of stabilizing agricultural resin films. When agricultural chemicals are sprinkled or sulfur fumigation is carried out for exterminating pests, agricultural resin films are impaired within a short period of time. Therefore, there has been demand for further stabilization of such agricultural films.
A nitroxy compound serving as a hindered amine compound exhibits an excellent effect of imparting light resistance to a resin film. However, a resin film containing a nitroxy compound is considerably colored, and thus in practice a nitroxy compound is not used in agricultural films.
From the viewpoint of conservation of resources, there has been demand for agricultural films exhibiting more excellent weatherability than ever.
DISCLOSURE OF THE INVENTION
An object of the present invention is to provide a resin composition for producing agricultural films, which are resistant to deterioration in weatherability caused by sulfur fumigation or acid rain.
In view of the foregoing, the present inventors performed extensive studies, and have found that a synthetic resin film containing a high-molecular-weight hindered amine stabilizer obtained through addition of a nitroxy compound to a polymer exhibits excellent long-term weatherability, and deterioration in weatherability of the resin film is small even when the resin film is subjected to sulfur fumigation. The present invention has been accomplished on the basis of this finding.
A first invention provides a resin composition for agricultural films, which composition comprises 100 parts by mass of a synthetic resin (A) and the below-specified amount of a polymer stabilizer (B).
Polymer stabilizer (B): an adduct obtained by adding a compound (b1) represented by the following formula (I) to a polymer (b2) having a molecular weight (mass average molecular weight, which has been conventionally called “weight average molecular weight”) of at least 300:
(wherein n represents an integer of 1-4; X represents —O— or —NH—; and R represents a hydrogen atom, a C1-C20 aliphatic acyl group, a C1-C20 aliphatic polyacyl group, a C1-C20 aromatic acyl group, or a C1-C20 aromatic polyacyl group).
Amount of polymer stabilizer (B): such an amount that makes the amount of nitrogen atoms contained in the polymer stabilizer (B) 0.0005-1 part by mass.
A second invention is drawn to a specific embodiment of the resin composition for agricultural films according to the first invention, wherein the polymer (b2) is a polyolefin.
A third invention is drawn to a specific embodiment of the resin composition for agricultural films according to the first or second invention, wherein the synthetic resin (A) is any one selected from among linear chain low-density polyethylene, low-density polyethylene, and an ethylene-vinyl acetate copolymer.
A fourth invention is drawn to a specific embodiment of the resin composition for agricultural films according to any one of the first to third inventions, wherein a hydrotalcite compound is further added to the composition.
A fifth invention is drawn to a specific embodiment of the resin composition for agricultural films according to any one of the first to fourth inventions, wherein a benzoate compound represented by the following formula (II) is added to the composition:
(wherein R
1
represents a C8-C30 linear chain or branched alkyl group).
A sixth invention provides a film formed from the resin composition for agricultural films as recited in any one of the first to fifth inventions.
BEST MODE FOR CARRYING OUT THE INVENTION
The present invention will next be described in detail.
Examples of the synthetic resin (A) employed in the present invention include polyolefins such as linear chain low-density polyethylene, low-density polyethylene, and polypropylene; ethylene-vinyl acetate copolymers; and polyesters. Of these, linear chain low-density polyethylene, low-density polyethylene, or an ethylene-vinyl acetate copolymer is preferred. Low-density polyethylene is particularly preferred.
Examples of aliphatic carboxylic acids for providing the aliphatic acyl group or aliphatic polyacyl group represented by R of the compound (b1) of formula (I) employed in the present invention include aliphatic monocarboxylic acids such as formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, eicosanoic acid, acrylic acid, methacrylic acid, crotonic acid, oleic acid, and cyclohexanecarboxylic acid; and aliphatic polycarboxylic acids including aliphatic dicarboxylic acids such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, maleic acid, and fumaric acid; aliphatic tricarboxylic acids such as propane-1,2,3-tricarboxylic acid, butane-1,2,3-tricarboxylic acid, and pentane-1,3,5-tricarboxylic acid; and aliphatic tetracarboxylic acids such as butanetetracarboxylic acid. Examples of aromatic carboxylic acids for providing aromatic carboxylic acid residues include aromatic monocarboxylic acids such as benzoic acid, p-methylbenzoic acid, p-tert-butylbenzoic acid, and naphthylic acid; and aromatic polycarboxylic acids such as phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, and pyromellitic acid.
Specific examples of the compound represented by formula (I) include the following compound Nos. 1 through 7. However, these examples should not be construed as limiting the present invention thereto.
Examples of the polymer (b2) employed in the present invention include polyolefins such as polypropylene, high-density polyethylene, low-density polyethylene, and linear-chain low-density polyethylene; and polymers having an unsaturated bond such as ethylene-propylene-diene rubber, polybutadiene, and acrylonitrile-butadiene-styrene copolymers. Particularly, in consideration of compatibility between the resultant polymer stabilizer and the synthetic resin (A), the polymer (b2) is preferably a polymer similar to the synthetic resin (A). From the viewpoint of attaining a long-term stabilizing effect which is obtainable when the polymer (b2) is satisfactorily retained in the resin, the mass average molecular weight of the polymer (b2) is preferably 300 or more. The upper limit of the molecular weight is not particularly limited, so long as the polymer stabilizer (B) is compatible with the synthetic resin (A).
The me
Dai Naoko
Kikkawa Kazumi
Matsuura Tsutomu
Yukino Toshinori
Asahi Denka Kogyo K.K.
Nixon & Vanderhye PC
Sanders Kriellion A.
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