Stock material or miscellaneous articles – Composite – Of addition polymer from unsaturated monomers
Reexamination Certificate
2001-02-05
2002-09-24
Nakarani, D. S. (Department: 1773)
Stock material or miscellaneous articles
Composite
Of addition polymer from unsaturated monomers
C428S519000, C428S520000
Reexamination Certificate
active
06455171
ABSTRACT:
FIELD OF INVENTION
This invention relates to multilayer structures and polymer compositions for making the same. More particularly, the present invention concerns a multilayer structure having an acrylic polymer cap layer, polyolefin core layer, and an intermediate tie layer.
BACKGROUND OF THE INVENTION
Multilayered structures formed from blended polymers are useful in preparing parts for: the automotive industry; communications such as telephones, radio, TV, cassettes, etc.; power tools; appliances; business machines; toys; furniture; medical devices, etc. When preparing multilayer structures, the layers of the structures must adhere securely to each other. If the layers of the structure do not adhere to each other a special adhesive, or in other cases a tie layer, may be used to join the layers of the multilayer structure together.
Multilayer structures formed by blends of different polymer compositions are known in the prior art. Examples of such multilayer structures may be found, for example, in Chundury et al. U.S. Pat. Nos. 5,264,280, 5,374,680 and 5,385,781. Generally speaking, these patent references disclose multilayer structures comprising olefinic core layers and cap layers comprising polymers of vinyl aromatic compounds such as polystyrene.
The present invention provides a new and useful multilayer structure which provides the physical properties of an olefinic core layer and the glossy, scratch and chemical resistive properties of an acrylic cap layer. Furthermore, the acrylic cap layer serves to further enhance the thermoformability of the olefin or olefin blend cap layer.
SUMMARY OF THE INVENTION
The present invention provides a new and useful multilayer thermoformable structure comprising: (A) a cap layer comprising from 50% to about 100% by weight of a polymethacrylate ester, polyacrylate ester, their copolymers, or blends thereof; (B) a core layer comprising from 30% to about 100% by weight of a polyolefin; and (C) a tie layer intermediate the cap layer and core layer. The present invention also provides various ways in which to form the multilayer thermoformable structure.
In one preferred embodiment of the present invention, the tie layer (C) comprises a polymer composition selected from the group consisting of: (Ci) an olefin acrylate copolymer; (Cii) a block polymer of a vinyl aromatic monomer and an aliphatic conjugated diene, a selectively hydrogenated derivative thereof, or a selectively hydrogenated derivative thereof to which has been grafted an unsaturated carboxylic reagent; and blends of (Ci) and (Cii).
The multilayer structures of the present invention are useful in preparing thermoformed articles and are particularly useful in applications that require the thermoformability of an olefin and the gloss, scratch resistance and chemical resistance of an acrylic polymer. Applications for the multilayer structures of the present invention include, for example, automotive parts, plumbing fixtures and parts such as shower stalls, and appliance parts such as control panels, housings and lids, and medical applications.
The foregoing and other features of the invention are hereinafter more fully described and particularly pointed out in the claims, the following description setting forth in detail certain illustrative embodiments of the invention, these being indicative, however, of but a few of the various ways in which the principles of the present invention may be employed.
DETAILED DESCRIPTION
Unless the context clearly indicates otherwise, as used in the instant specification and in the appended claims, the term “olefin-containing” or “olefinic” means that the material contains one or more thermoplastic polymers derived from olefin monomers. Olefin-containing materials can be homopolymers of olefin monomers, copolymers derived in part from olefin monomers, and polymer alloys that contain such olefinic homopolymers and/or copolymers alloyed with other polymers. Olefin-containing materials of this type are sometimes referred to herein as olefin alloys. As noted above, this application claims benefit of U.S. Provisional Application Serial No. 60/179,978, filed Feb. 3, 2000, which is hereby incorporated by reference in its entirety.
As noted above, the present invention provides a new and useful multilayer thermoformable structure comprising: (A) a cap layer of a polymer composition comprising 50% to about 100% by weight of a polymethacrylate ester or polyacrylate ester polymer or their copolymers or blends thereof; (B) a core layer comprising from about 30% to about 100% by weight of at least one polyolefin; and (C) a tie layer intermediate the cap layer and core layer. The tie layer (C), which is free of any solvents, is utilized to adhere the cap layer (A) to the core layer (B). The components of the multilayer thermoformable multilayer structure of the present invention, as well as the most preferred embodiments thereof, are separately discussed in greater detail below.
Cap Layer (A)
The cap layer (A) comprises from about 50% to about 100%, and preferably, from about 70% to about 100% by weight of a polymethacrylate ester or polyacrylate ester polymer or their copolymers or blends thereof. Preferably, the cap layer (A) comprises one or more acrylate copolymers formed from methyl methacrylate (MMA) monomer. It will be appreciated that various acrylate comonomers may be copolymerized with MMA to lower the glass transition temperature (T
g
) of the acrylic polymer and thus confer some degree of flexibility to the formulated cap layer (A). Suitable acrylate comonomers are those, when polymerized into homopolymers, have a T
g
of less than about 373° K (i.e., about 100° C.), and which will readily copolymerize with MMA. Several examples of acrylate monomers that meet these requirements include, but are not limited to, those listed in Table 1 below:
TABLE 1
Monomer
T
g
Butyl Acrylate
219° K.
Ethyl Acrylate
218° K.
Heptyl Acrylate
213° K.
2-Heptyl Acrylate
233° K.
Hexadecyl Acrylate
308° K.
Hexyl Acrylate
216° K.
Isobutyl Acrylate
230° K.
Isopropyl Acrylate
267-270° K.
4-Methoxy Phenyl Acrylate
198° K.
Nonyl Acrylate
215° K.
Octyl Acrylate
208° K.
Pentyl Acrylate
216° K.
Phenyl Acrylate
330° K.
Propyl Acrylate
236° K.
Many other acrylate comonomers having suitable T
g
values are listed in the
Polymer Handbook,
4
th Edition,
J. Brandrup, E. H. Immergut, E. A. Grulke, Akihiro Abe, and D. Bloch, Editors (1999), pages 198-205, Section II, that portion of which is incorporated by reference herein.
In many applications where ultraviolet light or thermo/oxidative stability is required, it has been found that low T
g
methacrylate comonomers are preferred over acrylate comonomers. Several examples of suitable methacrylate comonomers include, but are not limited to, those listed in Table 2 below:
TABLE 2
Monomer
T
g
Butyl Methacrylate
293° K.
Sec-Butyl Methacrylate
333° K.
Cyclohexyl Methacrylate
256° K.
Decyl Methacrylate
203° K.
Dodecyl Methacrylate
208° K.
2Ethylhexyl Methacrylate
263° K.
Ethyl Methacrylate
338° K.
2-Hydroxy Propyl Methacrylate
311-359° K.
Isobutyl Methacrylate
281-326° K.
Octyl Methacrylate
308° K.
Octadecyl Methacrylate
173° K.
Phenyl Methacrylate
268° K.
Other suitable methacrylate monomers are listed in the
Polymer Handbook,
4
th Edition,
that portion of which was previously incorporated by reference above.
When used as comonomers in the copolymerization of MMA monomer, the comonomers identified in Tables 1 and 2, as well as those comonomers listed in the incorporated portion of the
Polymer Handbook,
4
th Edition,
tend to lower the T
g
of the acrylic copolymer according to the following empirical equation:
1/
T
g(CP)
°K=W
(CM A))
/T
g(HP A)
°K+W
(CM B)
/T
g(HP B)
°K+ . . .
where:
T
g(CP)
=the glass transition temperature of the copolymer in °K;
W
(CM A)
=the weight fraction of comonomer A in the copolymer;
T
g(HP A)
=the glass transition temperature of the homopolymer of comonomer A in °K;
W
(CM B)
=the weight fraction of comonomer B in the compolymer; and
T
g(HP B)
=the g
Birch Timothy W.
Scheibelhoffer Anthony S.
Ferro Corporation
Nakarani D. S.
Rankin, Hill Porter & Clark LLP
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