Stock material or miscellaneous articles – Structurally defined web or sheet – Including components having same physical characteristic in...
Reexamination Certificate
1999-08-05
2003-06-03
Kelly, Cynthia H. (Department: 1774)
Stock material or miscellaneous articles
Structurally defined web or sheet
Including components having same physical characteristic in...
C428S423700, C428S412000, C525S439000, C528S176000, C528S196000, C528S198000
Reexamination Certificate
active
06572956
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to weatherable multilayer resinous articles and their preparation. More particularly, it relates to articles in sheet form having a protective arylate polymer coating.
Various polymeric articles have a problem of long term color instability. This causes yellowing of the polymer, detracting from its transparency and attractiveness. Loss of gloss can also be an undesirable long term phenomenon.
Yellowing of polymers is often caused by the action of ultraviolet radiation, which is why such yellowing is frequently designated “photoyellowing”. Numerous means for suppressing photoyellowing have been employed and proposed. Many of these involve incorporation in the polymer of ultraviolet absorbing compounds (UVA's). For the most part, UVA's are low molecular weight compounds and they must be employed at relatively low levels, typically up to 1% by weight, to avoid degradation of the physical properties of the polymer such as impact strength and high temperature properties as reflected in heat distortion temperature. Such levels may be inadequate to afford sufficient protection. Another problem of concern with polymers such as aromatic polycarbonates and addition polymers of alkenylaromatic compounds such as styrene is susceptibility to attack by organic liquids.
One way of protecting a resinous article against photoyellowing and loss of gloss is to apply a coating of a weatherable second polymer, the term “weatherable” as used herein signifying resistance to such phenomena. Weatherable polymers suitable for this purpose include resorcinol isophthalate/terephthalate copolyarylates. This is the subject of Cohen et al.,
J. Poly. Sci., Part A
-1, 9, 3263-3299 (1971), and certain related US patents of Monsanto Company including U.S. Pat. Nos. 3,444,129, 3,460,961, 3,492,261 and 3,503,779.
The only method disclosed therein for the application of the weatherable polymer, however, is by solution coating followed by evaporation of the solvent. This method has numerous deficiencies, some of which are mentioned in the Cohen et al. paper at page 3267: namely, the necessity to use high priced and toxic solvents, the inherently low concentration of the arylate polymer in the solvent and the tendency of the solutions to gel. Accordingly, the described copolyarylates were considered “unacceptable coating candidates”.
Other serious deficiencies of solvent coating have been discovered since the publication of the Cohen et al. paper and related patents. A principal one is an inherent property of the use of a solvent: it cannot possibly be completely removed by any procedure occurring at a level below the glass transition temperature of the substrate, which is impractical since it causes physical distortion.
Therefore, the solvent remains present in sufficient quantities to adversely affect the properties of the substrate polymer. This can occur by way of volatilization of the remaining traces of solvent during subsequent heat treatment such as thermoforming, lamination, in-mold decoration or baking in a paint oven. On a cosmetic level, the results can include blistering, bubbling, cracking and void formations within the substrate and coating, degrading the appearance of the resulting article. Other adverse results can be degradation of physical properties by crazing, cracking and embrittlement of the substrate polymer.
Since the publication of the Cohen et al. paper, the industry has further recognized the desirability of recycling resinous articles by regrinding, to minimize the deposition of non-biodegradable waste in landfills. Many multilayer resinous articles cannot be recycled, since the substrate and the coating are often incompatible with each other and the recycle operation, which includes conversion to a blend of the two polymers, produces a material with inferior physical properties.
Japanese Kokai 1/199,841 discloses articles having a substrate layer comprising at least 90 mole percent poly(ethylene terephthalate) and a gas barrier coating layer which is a polyester of resorcinol and isophthalic acid, optionally with copolyester units derived from another dicarboxylic acid such as terephthalic acid, naphthalenedicarboxylic acid or various other specifically named dicarboxylic acids. The disclosed articles may be prepared by a series of operations including co-injection molding which are essentially performed entirely in the melt, thereby overcoming the aforementioned deficiencies of solution coating. However, the only types of articles disclosed are bottles, which are produced from a co-injection molded parison by subsequent blow molding. Larger articles intended for outdoor use, such as external automobile body parts, are not disclosed and no method for their production is suggested, nor are articles in which the substrate layer is anything other than poly(ethylene terephthalate).
It remains of interest, therefore, to develop a method for preparing weatherable, solvent resistant multilayer articles which are capable of use for such varied purposes as body parts for outdoor vehicles and devices such as automobiles, and which can be prepared without adverse solvent effects. It is further of interest to prepare articles which include only mutually compatible polymers, making them suitable for recycle.
SUMMARY OF THE INVENTION
The present invention provides multilayer resinous articles which are weatherable, solvent-free and resistant to solvent action by organic liquids. Said articles are also recyclable by reason of the compatibility of the discrete layers therein.
In one of its aspects, the invention includes multilayer articles comprising:
a substrate layer comprising a first material and
a coating layer thereon, said coating layer comprising a thermoplastic polyester different from said first material and comprising structural units derived from a 1,3-dihydroxybenzene organodicarboxylate,
with the proviso that said coating layer and a 25-micron portion of said substrate layer nearest to said coating layer are substantially free from volatile organic compounds.
Included as part of this aspect are articles in which the coating layer consists of 1,3-dihydroxybenzene organodicarboxylate units, a maximum of 75% by weight, if any, of the substrate layer being poly(ethylene terephthalate). Also included are articles in which the coating layer comprises a block copolyestercarbonate, said substrate limitation not applying thereto.
Another aspect of the invention is a method for preparing a multilayer resinous article which comprises applying in the melt a thermoplastic coating layer to a layer comprising a second material, said coating layer comprising a polyester comprising structural units derived from a 1,3-dihydroxybenzene organodicarboxylate and the above-described substrate limitation existing correspondingly depending on the structure of the coating layer. Still another aspect is multilayer resinous articles prepared by the aforementioned method.
DETAILED DESCRIPTION
Multilayer articles of the invention include, but are not limited to, those which comprise a substrate layer and a coating layer thereon; those which comprise a substrate layer with a coating layer on each side of said substrate layer; and those which comprise a substrate layer and at least one coating layer with at least one interlayer between a substrate layer and a coating layer. Any interlayer may be transparent and/or may contain an additive, for example a colorant or decorative material such as metal flake. If desired, an overlayer may be included over the coating layer, for example to provide abrasion or scratch resistance. The substrate layer, coating layer, and any interlayers or overcoating layers are preferably in contiguous superposed contact with one another.
The first material comprising the substrate layer in the articles of this invention may be, subject to the proviso hereinafter with respect to polyesters, any material capable of receiving an adherent arylate polymer coating. Suitable materials include metals, ceramics, cellulosic products and resi
Carter Randall Lee
Hoefflin Frank Axel
Olson Daniel Robert
Pickett James Edward
Wang Hua
Cabou Christian G.
Kelly Cynthia H.
Nguyen Kimberly
LandOfFree
Weatherable multilayer resinous articles and method for... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Weatherable multilayer resinous articles and method for..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Weatherable multilayer resinous articles and method for... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3102725