Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
1999-09-14
2002-05-07
Reddick, Judy M. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S111000, C524S275000, C524S276000, C524S277000
Reexamination Certificate
active
06384120
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a synthetic resin film for agriculture and, more particularly, to a synthetic resin film for agriculture having good long-lasting transparency and anti-clouding and anti-fogging properties which is suited for use as a covering material for greenhouses or the like.
BACKGROUND OF THE INVENTION
Accelerated, semi-accelerated or retarding culture has conventionally been popularly conducted for the purpose of raising productivity or marketability of agricultural products. These cultures has been carried out in greenhouses or tunnels using covering materials such as vinyl chloride resin, polyethylene or ethylene/vinyl acetate copolymer resin. In the culture using greenhouses or tunnels, the greenhouses or tunnels are tightly closed by the covering material. The water vapor which is transpired from the soil and plants is, therefore, not discharged, the atmosphere within greenhouses or tunnels is saturated with the water vapor, and the water vapor condenses to form droplets of water on the inner surface of a cold film. Water droplets on the film not only seriously reduce the amount of incident sunlight due to irregular reflection but the droplets fall on the plants resulting in occurrence of diseases. To avoid formation of water droplets on the inner surface of the covering material film to thereby increase the amount of incident sunlight and, even if water droplets are formed on the inner surface of the film, to allow the droplets to flow downward along the inner surface of the film, it has widely been conducted to coat an anti-clouding agent on the inner surface of the film or to incorporate the anti-clouding agent in the film itself. However, in the case of using the anti-clouding agent, generation of fog which is liable to occur within the greenhouses or tunnels due to rapid change of the outside temperature is more promoted resulting in frequent generation of fog. When fog is generated within the greenhouses or tunnels, stems, leaves, flowers, fruits, etc. of cultivated plants get wet, which can cause occurrence or propagation of plant diseases. Thus, it has been conducted to use a anti-fogging agent together with the anti-clouding agent.
In order to prevent or reduce fog generation to be caused by the synthetic resin film for agriculture, various anti-clouding agents and anti-fogging agents are known. For example, Japanese Examined Patent Publication No. S59-35573 describes synthetic resin-made covering materials for agriculture having incorporated therein a fluorine-containing surfactant as an anti-fogging agent and other nonionic surfactant as an anti-clouding agent. In this publication, esters of higher fatty acids such as stearic acid with alcohols such as sorbitan, glycerin, polyethylene glycol, trimethylolpropane or pentaerythritol are described as the nonionic surfactants. However, the higher fatty acid ester compounds or the fluorine-containing surfactants specifically described in the publication difficultly provide enough lasting efficiency to the covering materials when previously incorporated as the anti-clouding agent or anti-fogging agent. According to the evaluation of the covering materials by accelerated test, there is obtained durability of only 4 to 7 months.
Japanese Unexamined Patent Publication No. H4-272946 describes to incorporate a fluorine-containing compound, a nonionic surfactant and a hindered amine compound in polyolefin resin to thereby retain anti-clouding property and anti-fogging property for a longer period of time. However, actual exposure tests on anti-clouding property conducted under similar conditions to that described in the publication have revealed that the anti-clouding property lasts for only 60 days at the longest both at a lower temperature and at a normal temperature. Also, actual exposure tests on anti-fogging property conducted under the conditions described in the publication revealed that anti-fogging property lasts for about 7 months after spreading. Thus, the polyolefin resin films are not said to have satisfactorily long-lasting effects.
On the other hand, as a method for attaining long-lasting anti-clouding property or anti-fogging property, Japanese Unexamined Patent Publication Nos. S60-96682 and H2-279733, etc. describe a so-called coating method of coating a composition having anti-clouding property or both anti-clouding property and anti-fogging property on agricultural film. This coating method can impart good long-lasting anti-clouding property and anti-fogging property to synthetic resin film for agriculture based on electrostatic mutual action between inorganic fine powder of hydrotalcite or the like incorporated in the base film and an effective ingredient such as inorganic hydrophilic colloid contained in the coating composition. It is necessary, however, to spray-coat or roller-coat the composition after spreading the agricultural films. In spray-coating, a lot of coating solution is used with such a low efficiency that spray-coating method has the defects that, in comparison with incorporating method, it is economically disadvantageous, it requires a long coating time, and causes coating unevenness which can deteriorate the anti-dripping effect. The same applies to the roller-coating method.
An object of the present invention is to provide a synthetic resin film for agriculture having good transparency, good anti-clouding property, good anti-fogging property and long lasting effect thereof, which can be obtained by a conventional incorporation process with excellent cost advantages, handling easiness, workability and uniformity in performance.
DISCLOSURE OF THE INVENTION
As a result of intensive investigations, the inventors have found that a synthetic resin film for agriculture can be obtained by previously kneading an anti-clouding agent and an anti-fogging agent into a resin, by which the film exhibits anti-clouding and anti-fogging properties for a duration as long as, or longer than, that attained by the coating method, using a specific higher fatty acid ester as anti-clouding agent and a fluorine-containing surfactant as anti-fogging agent, thus having achieved the present invention.
That is, the present invention is a synthetic resin film for agriculture which contains kneaded therein (a) at least one compound selected from the group consisting of (1) an ester of sorbitan with acid wax derived from montan wax, i.e., higher fatty acid mainly containing 24 to 34 carbon atoms (montanic acid wax), (2) an ester of glycerin with montanic acid wax, (3) an alkylene oxide adduct to the ester of sorbitan with montanic acid wax, (4) an alkylene oxide adduct to the ester of glycerin with montanic acid wax, and (5) an ester of polyoxyalkylene with montanic acid wax and (b) a fluorine-containing surfactant.
In the present invention, (c) at least one compound selected from the group consisting of esters of sorbitan with higher fatty acids containing 12 to 22 carbon atoms, esters of glycerin with higher fatty acids containing 12 to 22 carbon atoms, and alkylene oxide adducts thereto may further be incorporated in addition to the above-described ingredients (a) and (b) for more improving the anti-clouding and anti-fogging properties of the film.
As is described above, the fatty acid constituting component (a) is required to be montanic. acid wax containing higher fatty acids having 24 to 34 carbon atoms as a major component. The montanic acid wax is a natural mineral wax usually extracted and purified from brown coal, and has the longest carbon chain of the industrially available higher fatty acids. In the present invention, the number of carbon atoms of the fatty acid is limited to 24 to 34 because, if the number of carbon atom of the fatty acid used as a major component is 22 or less, long-lasting anti-clouding property, which is intended in the present invention, can not be attained , whereas higher fatty acids containing more than 34 carbon atoms are difficult to be industrially available. Further, in the present invention, the ester products of montanic acid wax (here
Hoga Takuya
Nakamura Masaki
Ohsawa Hiroshi
Bisulca Anthony A.
Reddick Judy M.
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