High modulus weatherable polyester carbonate articles

Stock material or miscellaneous articles – Structurally defined web or sheet – Including components having same physical characteristic in...

Reexamination Certificate

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C528S190000, C528S194000, C528S206000, C528S219000, C528S298000, C528S302000, C528S308000, C528S308600, C525S439000, C525S450000, C524S442000, C524S449000, C428S412000, C428S423700

Reexamination Certificate

active

06627303

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to article with high stiffness and strength having high retention of color and gloss when exposed to weathering.
BACKGROUND OF THE INVENTION
Fiber reinforced thermoplastic resins have long been used in a wide variety of applications. The combination of rigid fibers, especially glass fibers, with thermoplastic polymers has joined the easy molding and forming of recyclable plastics with the strength and stiffness of the fiber.
However one drawback to this combination is the poor weathering of the fiber resin combination when used in outdoor applications. After a relatively short period of time the surface of fiber filled thermoplastic articles begin to erode. The erosion process exposes the fiber giving an article that has poor appearance and may no longer serve its intended purpose. For example a surface designed for seating will become uncomfortable as glass fibers begin to protrude from its surface as a result of weathering. Similarly a rigid part designed to carry a load in a structural application may alter its appearance due to loss of gloss or changes of color as the thermoplastic resin weathers to expose the glass fibers in the mixture. Changes in gloss and color may often make the article unacceptable for its intend use.
Fiber reinforced plastics (FRP), when exposed to outdoor weathering, often suffer loss of gloss, discoloration and loss of strength. Poor FRP weathering is thought to occur mainly due to the following reasons. First, fiber and polymer resin do not erode at the same rate, with weathering the surface of the FRP is roughened, leading to loss of gloss and exposing fibers. Second, UV induced degradation of the resin surface leads to crazing and erosion, exposing the fiber. The fibers exposed at the surface and create multiple wicking sites which allow moisture to penetrate beneath the exposed surface of the article formed from the polymer resin fiber mixture. The moisture absorbed may further reduce the interfacial bonding between the resin matrix and the individual reinforcing fibers, resulting loss of strength. Third, photochemical induced degradation of the resin also often leads to discoloration. The loss of gloss due to unequal rate of erosion is a problem of FRP.
The traditional method to address the problem of erosion of the surface of weathering articles formed from fiber filled thermoplastic resins is to apply a coating or protective layer. To address the poor weatherability of FRP, U.S. Pat. No. 4,369,224 teaches application of a gel coat to the surface of FRP product to provide resistance to the deterioration from UV exposure; U.S. Pat. No. 4,117,185 teaches application of a film or a layer of fluoro-plastic materials to provide the resistance to weathering.
This approach is effective, paints or thin films are very commonly used to protect plastic parts used in outdoor applications. However, application of such coatings adds complexity and cost to the article. In addition the issue of coating adhesion to the fiber filled resin substrate must be addressed. Despite many inventions in the area, loss of protective coatings is still common.
SUMMARY OF THE INVENTION
We have found that articles made from a combination of fibers with a specific resorcinol based polyester resins have high strength and stiffness, as indicated by flexural strength and modulus with surprisingly good retention of color and gloss when exposed to weathering.
Even though the fiber and the resorcinol based polyester resin: should have different erosion rates, the invented articles defy the expected observation, showing excellent weatherability in terms of gloss retention and resistance to discoloration compared with the similar compositions based on polycarbonate resins.
DETAILED DESCRIPTION OF THE INVENTION
The composition of the invention may comprise from 1-60% by weight of the composition of fiber. Any rigid fiber may be used for example, glass fibers, carbon fibers, metal fibers, ceramic fibers or whiskers. Preferred fibers will not add color when combined to the polycarbonate ester resin. In one embodiment of the invention glass fibers are employed. In other embodiments of the invention borosilicate glass fibers are used Preferred fibers of the invention will have modulus of grater than or equal to 1,000,000 psi. The fiber may be chopped or continuous. The fiber may have various cross-sections for example, round, crescent, bilobal, trilobal, rectangular and hexagonal.
Preferred fibers will have a diameter of from 5-25 microns with diameter of 6-17 microns being most preferred. In some applications it may be desirable to treat the surface of the fiber with a chemical coupling agent to improve adhesion to the polyester carbonate resin. Examples of useful coupling agents are alkoxy silanes and alkoxy zirconates. Amino, epoxy, amide, or thio functional alkoxy silanes are especially useful.
The composition of the invention will further comprise 99-40% by weight of the entire mixture of a resorcinol based polyarylate resin. The resin should contain at least 30 mole % of units derived from the reaction product of resorcinol, or functionalized resorcinol, with an aryl dicarboxylic acid or dicarboxylic acid derivatives suitable for the formation of aryl ester linkages, for example, carboxylic acid halides, carboxylic acid esters and carboxylic acid salts.
The resorcinol based polyarylate may further contain carbonate linkages derived from reaction of a bisphenol and a carbonate forming species, such as phosgene. In another embodiment of the invention resorcinol polyarylate carbonate copolymers will be comprised of the reaction products of iso and tere phthalic acid, resorcinol and optionally, bisphenol A and phosgene. The resorcinol polyester carbonate copolymer will be made in such a way that the number of bisphenol dicarboxylic ester linkages is minimized, for example by pre-reacting the resorcinol moiety with the dicarboxylic acid moiety to form a polyester block and then reacting a said block with the bisphenol and carbonate moiety to form the polycarbonate part of the copolymer.
Most preferred compositions will have 60-90% resorcinol based polyester with from 10-40% glass fiber.
In one of its aspects the article of the present invention is comprised of polymers containing arylate polyester chain members. Said chain members comprise at least one diphenol residue in combination with at least one aromatic dicarboxylic acid residue. In one embodiment the diphenol residue is derived from a 1,3-dihydroxybenzene moiety, as illustrated in Formula I, commonly referred to throughout this specification as resorcinol or resorcinol moiety. Resorcinol or resorcinol moiety as used within the context of the present invention should be understood to include both unsubstituted 1,3-dihydroxybenzene and substituted 1,3-dihydroxybenzenes unless explicitly stated otherwise.
In Formula I R is at least one of C
1-12
alkyl, C
6
-C
24
aryl, alkyl aryl or halogen, and n is 0-3.
Suitable dicarboxylic acid residues include aromatic dicarboxylic acid residues derived from monocyclic moieties. In various embodiments suitable dicarboxylic acid residues include those derived from isophthalic acid, terephthalic acid, or mixtures of isophthalic and terephthalic acids. Suitable dicarboxylic acid residues also include those derived from polycyclic moieties, illustrative examples of which include diphenyl dicarboxylic acid, diphenylether dicarboxylic acid, and naphthalenedicarboxylic acid, especially naphthalene-2,6-dicarboxylic acid. In some embodiments the aromatic dicarboxylic acid residues are derived from mixtures of isophthalic and/or terephthalic acids as typically illustrated in Formula II.
Therefore, in one embodiment the present invention provides thermally stable polymers comprising resorcinol arylate polyester chain members as typically illustrated in Formula III wherein R and n are as previously defined:
In one of its aspects the present invention provides an article made of a resin prepared using an interfacial polymerization method preparing polymers

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