Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Including a second component containing structurally defined...
Reexamination Certificate
1994-10-25
2004-02-17
Chen, Vivian (Department: 1773)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Including a second component containing structurally defined...
C428S323000, C428S324000, C428S325000, C428S331000, C428S332000, C428S335000, C428S339000, C428S363000, C428S403000, C428S404000, C428S421000, C428S500000, C428S515000, C428S520000, C428S522000, C428S910000, C428S918000
Reexamination Certificate
active
06692824
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a light-permeable, light-scattering, IR-reflecting body with a whitish appearance which contains a base material with high light-permeability and further contains particles which reflect IR and are disposed parallel to the surface of the sheet. The invention also relates to the use of such a body as a thermally insulating and sunlight-protecting roofing material.
2. Description of the Background
Ger. Pat. 2,544,245 discloses a sheet of the above-described type, comprised of polymethyl methacrylate (PMMA) having a quantity of light-reflecting particles oriented parallel to the surface. The particles have a thickness chosen such that they transmit most of the incident visible light but reflect most of the incident IR radiation.
The known body contains the light-reflecting particles in the base material comprised of PMMA. They are introduced into the liquid methyl methacrylate monomer which is then charged to a polymerization chamber formed from parallel glass plates and is partially polymerized. Up to this point the particles have sunk to the lower glass plate. The plates are shifted in a mutually parallel fashion, whereby the particles are oriented parallel to the surface and are maintained in this position while the polymerization is continued. This treatment step renders the manufacturing process costly in terms of resources and economics.
Eur. OS 340,313 describes sunlight-protective coatings for ships, fluid tanks, buildings, and the like, which are intended to reduce heating in sunlight. The coatings contain a binder, a heat-reflecting pigment, and possible coloring pigments where desired.
According to Eur. OS 428,937, polyethylene sheets for greenhouses can be produced by treating the basic material with a brushed (or similarly spread on) or sprayed coating containing light-reflecting pigments in a matrix comprising a paint binder. Because the application process does not orient the pigment particles, they have only a shading action, and do not transmit to a satisfactory degree. Because ordinary paint binders do not adhere well to polyethylene, the coating can be easily removed from the coated sheet with a stream of water. A need therefore continues to exist for a light permeable weather resistant body which possesses high IR reflection.
SUMMARY OF THE INVENTION
Accordingly, one object of the present invention is to provide weather-resistant IR-reflecting bodies which have high light permeability and which can be easily manufactured. In particular, high IR reflection must be combined with maximal transmissivity (T) in the visible 380-780 nm range, only limited overall energy permeability (g), and a selectivity index, expressed by the ratio T/g, of >1.15.
Briefly, this object and other objects of the invention as hereinafter will become more readily apparent can be attained in a light-permeable IR-reflecting body comprised of a stiff amorphous base material comprised of light-permeable plastic and IR-reflecting particles oriented parallel to the surface, the light-permeable IR-reflecting body having a transmissivity (T) in the visible range of 45-75%, an overall energy permeability (g) of 30-60%, and a T/g ratio of >1.15. The IR-reflecting particles oriented parallel to the surface are disposed in a coating layer comprised of a transparent water-insoluble binder, which layer is 5-40 micron thick and adheres to the base material. Red-reflecting particles with a layer of titanium dioxide 60-120 nm thick on a platelet-shaped carrier pigment are present in the aforesaid coating layer in the amount of 20-40 wt. % of the coating layer.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The amount of visible light which passes through the body of the present invention in relation to the total energy permeability can be increased by a critical adjustment of the thickness of the coating layer, by the content of IR-reflecting particles in the coating layer, and by the size distribution of the particles. This adjustment is expressed in the claimed values of T, g, and T/g.
If the coating thickness or the pigment content is increased, T is decreased. If the coating thickness or the pigment content is decreased, g is decreased undesirably. If the pigment particles are too small or too large, T/g decreases. This is attributable to light refraction and light scattering effects, and to the susceptibility of larger pigment particles to breakage during handling or processing, wherewith the resulting small particles cause an unfavorable T/g ratio. Only in the narrow range of parameters of the present invention has it been possible to achieve high permeability to visible light in combination with relatively low IR-permeability.
An additional advantage of the present invention is in the category of easy manufacturability. The known method of producing IR-reflecting sheets having high light-permeability is suffering from the disadvantage that the production of the base body by a special polymerization method is encompassing the production of the IR-reflecting structure. Thus, in order to produce differently sized bodies the whole production method had to be varied accordingly. In contrast, the IR-reflecting sheets of the invention may be produced starting from any available light-permeable base body and requiring only conventional coating methods to produce a wide variety of differently sized IR-reflecting bodies. In particular, possible methods include the following:
A previously manufactured light-permeable body is coated by means of paint technology with a coating suitable for forming the coating layer.
Light-permeable PMMA or polycarbonate plastics are co-extruded with a coating material.
The reflecting structure is produced here also by a shear treatment of the still-liquid coating, which coating is not subjected to additional processes but arises in the necessary manner in the course of suitable coating and co-extrusion operations.
According to the invention, light-permeable bodies of any arbitrary shape may be rendered IR-reflecting, and not merely “cast” sheets of PMMA produced by polymerization in sheet-shaped chambers. In this way, products economically produced by extrusion, such as extruded sheets or double skin sheets, can be rendered IR-reflecting.
The production of the IR-reflecting orientation by parallel displacement of the narrow-chamber walls is a method which is more difficult and can be accomplished only with special equipment. Because the polymerizing base material is liquid over its entire thickness, major shear displacement is required in order to orient the IR-reflecting particles. In contrast, the coating layer in the manufacture of the present bodies can be kept very thin, so that a substantial orienting effect can be obtained from a minor shear displacement. The possibilities for shear displacement are numerous and may be optimally adapted to the particular characteristics of the body which is to be coated and the production method which is to be used. Thus, e.g., a coating zone and a shearing zone may be readily provided in an extrusion line, by simple means. Accordingly, the apparatus cost is substantially reduced and the IR-reflecting bodies can be supplied at competitive prices.
The high light-permeability of the present bodies makes them suitable as, e.g., durable roofing materials, particularly for greenhouses. By means of the present invention it is not necessary to provide for the temporary removal of the coating to enable more intense light penetration.
Light-permeability and IR-reflection Properties:
The term “light-permeable” concerns the visible region of the spectrum, for which the wavelength range 380-780 nm is used for characterization, particularly 550 nm. The light permeability, here designated (T), is generally symbolized as &tgr;
D65
in the scientific literature. The base material and the binder material should have light permeability (T)=at least 50%, preferably 60-94%. It is advantageous if they are substantially transparent. As used in connection
Benz Volker
Meier-Kaiser Michael
Müller Michael
Scharnke Wolfgang
Chen Vivian
Roehm GmbH & Co. KG
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