Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1995-06-20
2002-08-27
Yamnitzky, Marie (Department: 1774)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C523S205000, C428S323000, C428S324000, C428S325000, C428S331000, C428S913000, C252S582000, C047S009000, C047S017000, C047S029100, C047SDIG006
Reexamination Certificate
active
06441059
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a polymeric substance and an additive for the screening of solar radiation with the aim of influencing plant growth and the morphogenesis.
2. Brief Description of the Related Art
It is necessary for a controllable growth of plants to set up special light conditions to affect plant growth and morphogenesis. Special light conditions for plant growth, for example, within a greenhouse or under a mulch film include some which are of particular interest. The temperature within the enclosed area and the light intensity and the spectral distribution of the incoming light are important factors for the plant growth.
Plants, grown in a greenhouse build a resistance to the variations in temperature. From this it follows that the plants stay back in growth. Thus, for the photosynthesis in greenhouses the photosynthetically active radiation (PAR) is only desired while other parts of the solar light should be screened because they have mainly a negative influence on the microclimate. Therefore the following objectives have to be achieved. Firstly, the intensive irradiation by sunlight in particular by NIR radiation needs to be screened, in order to avoid too high temperatures within the enclosed area. Secondly, the incoming light beams are to be scattered in order to prevent burnings on plants. Thirdly, heat within the area is to be stored at night.
However, in case of mulch films the opposite effect is desired. The PAR should be screened and all other parts of the solar light should be transmitted. Mulch films are used in agriculture to improve the growing conditions of the useful plants and to minimize the use of chemical herbicides.
For certain crop growers want to intervene in the plant morphogenesis. Morphogenesis is the influence from environmental factors on the shape and appearance of the plant. One of them is the light quality. It means that the spectral energy distribution has an effect on the growth of plants.
Raviv and Allingham describe in “Plastic Culture”, No. 59, September 1989, pp. 3 to 12, that diffuse light is favourable for a steady growth of plants. Furthermore, it turned out that diffuse light has the advantage that the plants are not going to be damaged. Hancock describes in “Plastic Culture”, No. 79, 1988, pp. 4 to 14, that special additives in LDPE have a favourable effect on the microclimate in greenhouses because of the generation of diffuse light and the creation of a favourably thermic effect in the greenhouses. Suitable additives are aluminosilicate in the form of kaolin, calcium carbonate, talc and kaolin clay.
Greenhouses made of glass already fulfil some of the above-mentioned conditions by virtue of the inherent physical properties of inorganic glasses. Furthermore, constructive measures, for example knurled glass or shadow cloth are known.
If the enclosing material is plastic, such as, for example, polyethylene, polyethylene/vinyl acetate copolymers, polyvinyl chloride, polycarbonate or polyacrylate, it is much more difficult to meet these requirements. The high transparency of many plastics for IR radiation results in good heat transmission which, in the case of films, is additionally assisted by the low film thickness.
A polymethyl methacrylate glazing material for buildings and vehicles containing an interference pigment for the screening of NIR radiation of a wave length between 800 and 1500 nm is disclosed in DE 2,544,245.
The pigment used has a blue-red colour and the light transmitted through the glazing material has a yellow-green colour. When used in greenhouses, this glazing material has the disadvantage that portions of visible light which cannot be utilized by the plant are transmitted and, on the other hand, the red portion of visible light which can be utilized by the plant is screened off by said glazing material. Furthermore, the transmitted green portion has the additional disadvantage that it contributes to heating of the greenhouse by virtue of its conversion into long wave light.
EP-A 0,428,937 describes a grey-white coating composition for greenhouses consisting of a polymer substrate and reflecting particles suspended therein. These particles are aluminium platelets or mica platelets coated with titanium dioxide. The coating composition is used for temporary coatings in extreme weather conditions (summer). In winter, it can again be removed by washing it off with a water jet. More details regarding the pigment used are not given.
The coating composition has the disadvantage that not only the IR beams but also a substantial portion of the visible light which can be utilized by the plant are reflected by the metal particles. The green portion of the transmitted light cannot be utilized by the plant and contributes to heating of the greenhouse.
EP-A-03 98 243 describes polymeric mulch sheets and mulch films for use in agriculture which have a green absorption colour and contain a UV stabilizer. The green sheets and films absorb a large part of the solar radiation which promotes photosynthesis and plant development (PAR), and transmits enough solar radiation so as to heat the soil beneath such films and sheets. Such mulch films and sheets reduce weed growth but they have the disadvantage that the photosynthetically active radiation is absorbed and is lost for the useful plant.
L. M. Mortensen and E. Stromme describe in Scientia Horticulturae 33 (1987), 27-36 the effects of light quality on some greenhouse crops. Different light qualities were established in growth chambers placed outdoors by selective screening of the natural light spectrum in the chambers. The PAR level was the same at all light qualities. Blue light containing a high red/far-red ratio reduced the dry weight compared to natural (N), green, yellow and red light in chrysanthemum, tomato and lettuce. Plant height in chrysanthemum and tomato was strongly reduced by blue compared to N light, and strongly increased by green and yellow light.
SUMMARY OF THE INVENTION
The aim of the invention is.,to provide a composite material for the screening of intensive irradiation by sunlight, which material reflects, apart from the IR portion, also a green portion of visible light which cannot be utilized by the plant.
A further aim of the invention is to provide a composite material useful as mulch film or mulch sheet which do not absorb the photosynthetically active radiation.
Lastly, it is the aim of the invention to provide a composite material useful as covering material for the influencing of plant morphogenesis.
This object is achieved according to the invention by a composite material comprising a polymer and an additive and the customary stabilizers and processing aids necessary for the particular polymer.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION
The additive according to the invention is a platelet-shaped material or a platelet-shaped material coated with one or more metal oxides.
Usually the platelet-shaped material consists of layered silicate, synthetic mica, glass platelets, ceramic platelets and silicia platelets.
Preferably the layered silicate is mica, pyrophillite, sericite, talc or kaolin.
The platelet-shaped material coated with one or more metal oxides is preferably an interference pigment.
The preferably used interference pigments are platelet-like pigments consisting of platelet-like substrate, such as for example, mica, kaoline or talc, and one or more metal oxide films thereon.
The metal oxides which can be used are only those oxides which allow the preparation of interference pigments, for example, oxides of the metals tin, titanium, zirconium, chromium, cerium, iron or tungsten.
In order to be able to produce interference colours, a certain film thickness is necessary. This film thickness depends on the metal oxide used. If titanium dioxide is used, it is for example advantageous to apply a film in a thickness of 120 to 160 nm for obtaining a pigment having a green interference colour.
In the invention the substrate preferably has a diameter of from 1
Daponte Tony Leon Filip
Edler Gerhard
Kieser Manfred
Verschaeren Patrick Corneel Mathilde
Merck Patent Gesellschaft mit Beschrankter Haftung
Pitney Hardin Kipp & Szuch LLP
Yamnitzky Marie
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