Agricultural covering material

Details Agricultural covering material Agricultural covering material

2000-12-22

2002-10-08

Acquah, Samuel A. (Department: 1711)

Stock material or miscellaneous articles

Structurally defined web or sheet

Continuous and nonuniform or irregular surface on layer or...

C525S199000, C525S240000, C525S331700, C428S098000, C428S141000, C428S220000

Reexamination Certificate

active

06461719

ABSTRACT:

TECHNICAL FIELD
The present invention relates to an agricultural covering material. In particular, it relates to an agricultural covering material made of a fluoroplastic film with excellent flexibility, durability, dust resistance and light transmittance to be installed in agricultural and horticultural facilities such as tunnel houses, pipe houses and large-scaled greenhouses or used inside of a greenhouse as a greenhouse liner film.
BACKGROUND ART
Heretofore, as agricultural covering materials, films of polyethylene, ethylene-vinyl acetate copolymers, polyester resins, flexible vinyl chloride resins have been used, and the majority of agricultural covering materials are made of flexible vinyl chloride resin film for its superiority in ease of handling, price and thermal insulation over the other film materials. However, flexible vinyl chloride resin films have a problem of light transmittance reduction within a short term because their surfaces tend to be fouled by the plasticizers bleeding out of them.
The above-mentioned various films usually have to be renewed in a year or two due to deterioration by sunlight, atmospheric temperature, weather and oxidation although they include ultraviolet absorbers to improve in weatherability. Besides, these films including ultraviolet absorbers block out ultraviolet light to various degrees and therefore are unsuitable to crops that need ultraviolet light (such as eggplant and some kinds of flowers and ornamental plants) and crops (such as strawberry, melon, watermelon and bell pepper) that are pollinated through honeybees and
Eristalis cerealis
that need ultraviolet light for their activity.
On the other hand, practical large greenhouses have been introduced in recent years for labor-saving in greenhouse control, larger cultivated area and longer service life. In these large greenhouses, covering materials such as polyester resins, polycarbonate resins, rigid vinyl chloride resins, acrylic resins, fiber-reinforced plastics, sheet glass have been introduced for long-term use of at least 5 years. However, these covering materials are thick in thickness and heavy in weight and have to be installed in greenhouses with large frameworks made of special materials. Therefore, their installation is quite complicated, and they have a drawback of relatively high price. Besides, sheets of polyester resins, polycarbonate resins, rigid vinyl chloride resins and acrylic resins have drawbacks that they are easily cracked by hail and that cracks formed on them tend to spread.
In addition, these plastic sheets usually contain ultraviolet absorbers to improve in weatherability and are unsuitable to crops that need ultraviolet light (such as eggplant and some kinds of flowers and ornamental plants) and crops (such as strawberry, melon, watermelon and bell pepper) that are pollinated through honeybees and
Eristalis cerealis
that need ultraviolet light for their activity. Sheet glass is dangerous due to its fragility and requires stronger frameworks to be installed in greenhouses due to its weight heavier than those of plastic panels.
To overcome these problems, fluoroplastic films made of tetrafluoroethylene-ethylene copolymers (hereinafter referred to as ETFE) and vinyl fluoride polymers have been proposed as agricultural covering materials for their excellent properties such as durability and acid rain resistance, their proven service life of from 10 to 15 years, ease of being cleaned up by rainwater and resistance to breakage.
In general, when an agricultural covering material is installed in a pipe house or the like, it is fastened to the framework of the house with anchors so as not to loosen. However, some fluoroplastic films in use have to be stretched with great force to be fixed due to their poor flexibility resulting from their large moduli of elasticity.
Use of lining films inside of greenhouses is intended to prevent rapid temperature drops inside the greenhouses which frequently takes place during the day or at night, especially at night, in winter and to improve heating efficiency of the heater in the greenhouse, and sometimes to block part of excessive sunlight for the proper amount of insolation.
Thus, greenhouse lining films are frequently spread and folded during the day, in the evening or in the morning, and stiff films are difficult to fold and crease-prone.
DISCLOSURE OF THE INVENTION
The object of the present invention is to solve the above-mentioned problems by providing an agricultural covering material made of a fluoroplastic film with a small modulus of elasticity, excellent flexibility, a specific gravity smaller than that of a conventional fluoroplastic film and excellent handling property in installation. The present invention has made it possible to provide an agricultural covering material made of a fluoroplastic film excellent in not only flexibility but also toughness such as tensile strength.
Namely, the present invention provides an agricultural covering material made of a fluorine-containing polymer film having a dynamic viscoelastic modulus of from 1 to 70 kg/mm
2
, a tensile strength of from 1.5 to 5.0 kg/mm
2
, a specific gravity of from 1.0 to 2.0 and a contact angle with water of at most 106°.
BEST MODE FOR CARRYING OUT THE INVENTION
The fluorine-containing polymer film in the present invention is, for example, a film molded from a composition comprising 100 parts by weight of a tetrafluoroethylene(hereinafter referred to as TFE)-ethylene copolymer (hereinafter referred to as copolymer 1) and from 5 to 100 parts by weight of a tetrafluoroethylene-propylene elastic copolymer (hereinafter referred to as copolymer 2).
Copolymer 2 preferably comprises from 5 to 70 mol % of polymerization units derived from propylene.
Copolymer 1 may comprise polymerization units derived from TFE and polymerization units derived from ethylene in a (weight) ratio of from 70/30 to 30/70 and further comprise from 0.1 to 10 mol % of polymerization units derived from a compound represented by CH═CH—C
n
F
2n+1
(wherein n is an integer of from 2 to 10).
In the present invention, the amount of copolymer 2 is from 5 to 100 parts by weight in relation to 100 parts by weight of copolymer 1. If the amount is smaller than 5 parts by weight, the resulting film does not have appreciable flexibility, and if the amount is larger than 100 parts by weight, the resulting film tends to have poor strength.
Copolymer 1 preferably comprises polymerization units derived from TFE and polymerization units derived from ethylene in a (molar) ratio of from 70/30 to 30/70, in particular in a (molar) ratio of from 65/35 to 45/55. If the ratio is larger than 70/30, film formation is difficult, and if the ratio is smaller than 30/70, the resulting film tends to be poor in wetherability and acid rain resistance.
When copolymer 1 further comprises polymerization units derived from a compound represented by CH═CH—C
n
F
2n+1
(wherein n is an integer of from 2 to 10), the content is preferably from 0.1 to 10 mol %, in particular from 0.3 to 5 mol %. If the content is larger than 10 mol %, the resulting film tends to be poor in wetherability and acid rain resistance, and if content is smaller than 0.1 mol %, the resulting film tends to be poor in mechanical properties.
Copolymer 1 itself is not novel and can be obtained, for example, by the method disclosed in JP-B-59-50163. Various conventional polymerization techniques such as bulk polymerization, suspension polymerization, emulsion polymerization and solution polymerization are applicable to production of copolymer 1. Commercial products called “Aflon COP” (Asahi Glass Company) and “Aflon LM” (Asahi Glass Company) may be used as copolymer 1.
The molecular weight of copolymer 1 is not particularly limited but preferably corresponds to a flow rate by volume of from 1 to 300 mm
3
/sec, in particular from 1 to 100 mm
3
/sec, in view of physical properties and production of the film. The flow rate by volume is defined as an outflow by volume of copolymer 1 in a unit time (mm
3
/sec) through a nozzle

Affiliated with

Also associated with

Rating

Agricultural covering material does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Agricultural covering material, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Agricultural covering material will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2988941