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
2001-11-29
2004-02-24
Seidleck, James J. (Department: 1711)
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...
C524S409000, C524S432000
Reexamination Certificate
active
06696513
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a polymer composition for use as a capstock material for making plastic laminates.
BACKGROUND OF THE INVENTION
Low cost plastics, such as poly(vinyl chloride) (PVC), have many commercial uses but often require capping with other materials if the intended use is likely to prompt unreasonably rapid deterioration of the base plastic or if it is desired to impart colour, gloss, weatherability or some other property to the base plastic.
For example PVC is suitable, because of its low cost, rigidity, ease of processing (for example, by extrusion) and other mechanical properties, for use in a variety of building materials and products. Examples are window systems, including profiles for all types of windows, door sets and associated items; roofline and cladding products, such as fascia, bargeboards, soffits, shiplap and vee groove cladding; rainwater systems, such as guttering, downpipes and accessories; and piping systems, such as waste water and process piping for use above and below ground. Often such products utilise expanded PVC so as to save material and reduce the weight of such products. However, PVC is relatively unstable to heat and light and does not have good durability or resistance to weathering. This may present particular problems when the appearance of the building product, such as a window frame, is important. Deterioration of PVC involves yellowing of the material and may be unsightly, Similarly, the problem of poor weatherability may be of particular concern in, for example, guttering. Deterioration of the PVC guttering may lead to cracks in the material which may ultimately allow egress of water from the guttering.
Other base plastics which may be used in place of, or as well as, PVC in such applications include polybutene, prolypropylene polybutylene terephthalate (PBT), polyamides, and styrene-based polymers, such as acrylonitrile-butadiene-styrene copolymers, high impact polystyrene, and styrene-acrylonitrile copolymers. Such materials may be foamed for cost or weight considerations. These materials generally have one or more of PVC's disadvantages.
One conventional solution to the problem of low durability of the base plastic is to coat the plastic with a thin layer of a capstock material, i.e. another material having better resistance to weathering and perhaps other is desirable properties such as colour or gloss. Such capstock materials are known in the art.
U.S. Pat. No. 3,458,391 discloses a laminated article which comprises in superimposed relationship a rigidity imparting base member having bonded thereto a protective film of a blend of from 90% to 40% by weight of poly (methyl methacrylate) (PMMA) or poly (ethyl methacrylate) and from 10% to 60% by weight of poly (vinylidene fluoride).
U.S. Pat. No. 5,322,899 teaches a capstock polymer composition comprising 30 to 80% of a fluoropolymer component, 5 to 50% of poly (methyl methacrylate) and 5 to 50% of poly (ethyl methacrylate).
International Patent Application No. WO93/05959 discloses a plastic composite comprising an extrusion product having at least two layers including a layer of a first polymeric substance comprising from 1 to 70% by weight of an acrylic material, a fluoropolymer and an inorganic pigment in contact with a second polymeric layer.
Another capstock material containing polyvinylidene fluoride is disclosed in European Patent Specification. No. 0151812 A2.
U.S. Pat. No. 5,132,164 also discloses a fluorine resin type film having a multi-layer structure.
Coextrusion methods for producing composite polymers are also known, as described for example in British Patent Specification No. 2071007 A.
Thermoforming a plastic substrate with simultaneous formation of an integral coating on a surface of the thermoplastic is taught in U.S. Pat. No. 5,268,203.
A review of developments in plastic window frames, Is including PVC, coextruded and PMMA-coated profiles, PVC extrusion equipment, expandable PVC, and stabilisers can be found in Macplas Int., June 1991, pages 57 to 64. Blends of self-extinguishing PVC with high impact polystyrene, PMMA and their rheological properties are disclosed in a paper entitles “Fire Retardant Blends, Alloys and Thermoplastic Elastomers”, Conference Proceedings Hilton Head Island S.C., 17
th
to 20
th
March 1991, pages 59 to 84.
Whilst fluoropolymers have been suggested widely as capstock ingredients because of their weatherability and chemical resistance, they are extremely expensive in relation to other polymers.
One particularly important property of capstock materials is fire retardancy. In U.S. Pat. No. 4,965,309 a smoke depressant additive for plastics is proposed which comprises an inorganic zinc compound, an inorganic magnesium compound other than magnesium oxide, an inorganic molybdenum compound, and an inorganic cooper compound. Incorporation of such a smoke depressant additive in PVC is proposed.
Japanese Unexamined Patent Specification No. 54/034359 discloses a composition which comprises 100 parts by weight of a polymer mixture consisting of 95-3S parts by weight polytetramethylene terephthalate and 5-65 parts by weight of a methacrylate polymer containing at least 50 weight a of a polymer of methyl methacrylate, 3-40 parts by weight of a halogen compound, such as a bisphenol-A type brominated epoxy resin, 1-30 parts by weight of an antimony compound, such as antimony trioxide, and 3-70 weight % (of total resin) of non-electrically conductive inorganic filler, such as glass fibre and talc.
I. N. Razinskaya et al., Plast Massy, No. 2 (1983), pages 49 to 50, investigated synergism with the simultaneous action of three fireproofing agents, i.e. antimony trioxide, trichloroethylphosphate and polyvinylchloride, in compositions with methyl methacrylate.
Arakawa et al., Kobunshi Ronbunshu (Japanese Polymer Science and Technology), Vol. 31, No. 10 (1974), pages 643 to 647, made a quantitative study of the synereric effect of chlorine and phosphorus or antimony in conferring self-extinguishing properties on poly(methyl methacrylate), using a blend of poly(methyl methacrylate) and a vinyl chloride-vinylidene chloride copolymer.
While acrylic polymers, such as poly(methyl methacrylate), have many of the properties desired in a capstock material, their flammability is a drawback to their use. This drawback can be mitigated, to some extent, by formulating such acrylic polymer capstocks as coextrudates with halogen-donating materials, for example a halogen-containing polymer such as PVC. The halogen-donating polymer provides a source of halogen atoms which can act as a chain breaker in a free radical combustion reaction, in the event of the capstock being exposed to fire. If the base plastic is PVC and the halogen-donating polymer is PVC, a strong bond is formed between identical ingredients of the base plastic and the capstock. However, in order to meet stringent fire safety regulations in many countries, it will often be necessary to include quite large quantities (typically at least about 70% by weight) of halogen-donating polymer in the capstock. Whilst the incorporation of large amounts of, for example, PVC in the composition may have an improving effect upon the fire retardance of the capstock, it may also lead to increased deterioration of the capstock on exposure to U.V. light or other adverse environmental conditions.
It is particularly important for many building materials and products to be resistant to the spread of flame. Ideally, polymer composites for use in such materials and products should meet the standards of BS476 Part 7 in the United Kingdom and should pass corresponding fire safety tests in other countries.
Accordingly, there is a need for capstock materials which exhibit fire retardance, good weatherability and durability, which are cost effective to manufacture, which have good appearance, and which may include colour.
It is therefore an object of the present invention to provide a polymer capstock which is fire retardant and which meets ore or more of these other needs.
SUMMARY OF THE I
Dodd Keith Herbert
Welton Nicholas Jason
H. B. Fuller Coatings Ltd.
Rajguru U. K.
Seidleck James J.
Senniger Powers Leavitt & Roedel
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