Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2002-02-12
2003-06-17
Zitomer, Fred (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S329000, C526S329400, C526S348800, C526S352000
Reexamination Certificate
active
06579960
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a novel tetrafluoroethylene (hereinafter referred to also as TEE)/ethylene copolymer (hereinafter referred to also as an EFT copolymer), and a film made of such an EFT copolymer excellent in flexibility, dust-proofing property, light transmittance, high strength, non-tackiness, etc. Further, it relates to an agricultural covering material, a release film and an interlayer for laminated glass, made of such a film.
BACKGROUND ART
Heretofore, as an agricultural covering material for a tunnel house or a pipe house, a film made of e.g. an ethylene/vinyl acetate copolymer, a polyester resin or a soft vinyl chloride resin, has been used. Especially, a soft vinyl chloride resin film is superior to films of other materials with respect to an application efficiency, price, warmth retaining property, etc. And thus is used mostly as an agricultural covering material. However, the soft vinyl chloride film contains a plasticizer and thus has a difficulty such that the film surface is likely to be soiled by bleeding out of the plasticizer, and the light transmittance tends to deteriorate soon.
Further, many of the above conventional films have an ultraviolet absorber incorporated to improve the weather resistance, but due to deterioration attributable to e.g. sunlight, atmospheric temperature, wind and rains, oxidation, etc., they have to be replaced usually in one to two years. Besides, such films having an ultraviolet absorber incorporated, shield ultraviolet rays inevitably, although there may be a difference in the degree of ultraviolet absorptively. Accordingly, such films are not suitable for cultivation of crop plants which require ultraviolet rays (such as eggplants or certain types of flowers) or for cultivation of crop plants to be pollinated by e.g. bees, Mahana-abu or drone flies which require ultraviolet rays (such as strawberries, melons, water melons or green peppers).
Further, in recent years, really large sized houses have been employed for the purpose of labor saving in house control, enlargement of the cultivation area and prolongation of useful life of houses. For such large sized houses, a covering material made of e.g. a polyester resin, a polycarbonate resin, a soft vinyl chloride resin, an acrylic resin, a fiber reinforced plastic or an inorganic sheet glass, has been used for application for a long period of at least 5 years. However, such a covering material is thick and heavy and has to be applied to a house having a large sized special base material framework, whereby the application work is complex and relatively expensive. Further, a covering material made of a polyester resin, a polycarbonate resin, a hard vinyl chloride resin, an acrylic resin or the like has a drawback that cracks are likely to form by e.g. hail, and the formed cracks are likely to propagate. Further, in the covering material of such a plastic plate contains an ultraviolet absorber in many cases, and thus has the same problem as the above described film containing an ultraviolet absorber.
For the purpose of solving such problems, a film of a fluorine resin is known which is excellent in weather resistance durability and acidic rain resistance and has a long useful life of from 10 to 15 years, and which has excellent characteristics that it is hardly soiled, or a soil can readily be removed by rain water, and it is scarcely breakable. Especially, a film of an EFT copolymer further has excellent characteristics such as heat resistance, weather resistance, light transmittance and non-tackiness and thus is proposed as an agricultural covering material and is partly commercialized.
On the other hand, when a film of an agricultural covering material is stretched over e.g. a pipe house, it is applied by fixing it to the framework of the house by means of a fixing member, while taking care so that the tension of the film will not loosen. However, a conventional film of an ETFE copolymer has a large tensile modulus of elasticity and is poor in flexibility, and there has been a practical problem that the film has to be fixed by a large tensile force.
Further, also in the field of release films to be used for formation of printed boards, a film of an ETFE copolymer is used from the viewpoint of the non-tackiness and heat resistance. Also in this case, conventional ETFE copolymers have a problem that the tensile modulus of elasticity is large, and the follow-up property to a board having a complicated shape is poor.
Further, also as an interlayer for laminated glass to be used for safety glass, conventional ETFE copolymers have had drawbacks that their tensile modulus of elasticity is large, they are hardly closely adhered to glass, and they are hardly processable, and the shock absorbing property at the time of breakage of the glass has not been sufficient, although the light transmittance is high and preferable.
From such a viewpoint, it is desired to lower the elastic modulus of the ETFE copolymer, and in order to lower the elastic modulus of a resin, it is generally proposed, for example, to blend an elastomer. In such a case, it is necessary to take into consideration the compatibility to the resin of the elastomer to be blended or the thermal stability at the molding temperature. Otherwise, deterioration of the light transmittance or the mechanical property such as the strength of the blend product, or an increase of the haze is likely to be brought about. In the case of the ETFE copolymer, selection of the elastomer to be blended, is difficult, and it has been difficult to solve the problems by this method.
On the other hand, it is known to lower the elastic modulus by copolymerizing a third component to the ETFE copolymer. For example, JP-B-8-5976 proposes an agricultural covering material made of a film of an ETFE copolymer wherein the ratio of the polymerized units based on TFE/the polymerized units based on ethylene is from 45/55 to 55/45 (molar ratio), and the copolymer contains from 0.1 to 10 mol % of polymerized units based on a (perfluoroalkyl)ethylene represented by CH
2
═CHC
n
F
2n+1
(n is an integer of from 2 to 10) as a third component. However, this third component is poor in copolymerization reactivity, and the perfluoroalkyl group is of a rigid structure, and in order to obtain sufficiently low tensile modulus of elasticity, the content in the copolymer is required to be high, whereby the productivity was low with high costs.
It is an object of the present invention to provide a novel ETFE copolymer which solves the above problems.
Another object of the present invention is to provide a film having a small tensile modulus of elasticity and being excellent in flexibility, light transmittance, high strength, non-tackiness, etc., by using such a novel ETFE copolymer, and an excellent agricultural covering material, a release film and an interlayer for laminated glass, employing such a film.
DISCLOSURE OF THE INVENTION
The present invention provides an ETFE copolymer characterized in that the ratio of the polymerized units based on tetrafluoroethylene/the polymerized units based on ethylene, is from 35/65 to 65/35 (molar ratio), and it contains from 1 to 10 mol % of polymerized units based on an alkyl vinyl ester (provided that the carbon number of the alkyl group is from 5 to 17, and when the alkyl group contains a branched structure, the carbon number is from 9 to 17), is crystalline and has a volumetric flow rate of from 1 to 1000 mm
3
/sec.
A film formed of the ETFE copolymer of the present invention has a tensile modulus of elasticity as low as from 1 to 70 kg/mm
2
and thus is flexible, and it is also excellent in dust-proofing property, light transmittance, strength and non-tackiness. Accordingly, it is useful for many applications. Especially, it is suitable as an agricultural covering material, a release film or an interlayer for laminated glass. The low tensile modulus of elasticity of the film of the present invention is believed to be attributable to the high copolymerization reactivity of the alkyl vinyl ester as
Kamiya Hiroki
Okada Shinji
Asahi Glass Company Limited
Zitomer Fred
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