Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2001-06-05
2003-06-24
Mulcahy, Peter D. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S285000, C524S396000, C524S399000, C524S378000, C524S381000, C524S382000, C524S398000, C524S400000, C556S115000, C556S132000, C556S170000, C562S502000
Reexamination Certificate
active
06583206
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to compounds and compositions comprising specific salts of saturated [2.2.2] dicarboxylate in order to provide highly desirable properties within thermoplastic (e.g., polyolefin) articles. The inventive salts and derivatives thereof are useful as nucleating and/or clarifying agents for such thermoplastics, are easy to produce and handle, and relatively inexpensive to manufacture. Such compounds induce high peak crystallization and improved stiffness within thermoplastics. Also, thermoplastic compositions comprising such novel nucleating agents exhibit improved heat distortion properties and clarity levels in comparison with the closest unsaturated salt nucleating agents. Thermoplastic additive compositions and methods of producing thermoplastics with such compounds are also contemplated within this invention.
BACKGROUND OF THE PRIOR ART
All U.S. patents cited below are herein entirely incorporated by reference.
As used herein, the term “thermoplastic” is intended to mean a polymeric material that will melt upon exposure to sufficient heat but will retain its solidified state, but not prior shape without use of a mold or like article, upon sufficient cooling. Specifically, as well, such a term is intended solely to encompass polymers meeting such a broad definition that also exhibit either crystalline or semi-crystalline morphology upon cooling after melt-formation. Particular types of polymers contemplated within such a definition include, without limitation, polyolefin (such as polyethylene, polypropylene, polybutylene, and any combination thereof), polyamides (such as nylon), polyurethanes, polyesters (such as polyethylene terephthalate), and the like (as well as any combinations thereof).
Thermoplastics have been utilized in a variety of end-use applications, including storage Containers, medical devices, food packages, plastic tubes and pipes, shelving units, and the like. Such base compositions, however, must exhibit certain physical characteristics in order to permit widespread use. Specifically within polyolefin, for example, uniformity in arrangement of crystals upon crystallization is a necessity to provide an effective, durable, and versatile polyolefin article. In order to achieve such desirable physical properties, it has been known that certain compounds and compositions provide nucleation sites for polyolefin crystal growth during molding or fabrication. Generally, compositions containing such nucleating compounds crystallize at a much faster rate than un-nucleated polyolefin. Such crystallization at higher temperatures results in reduced fabrication cycle times and a variety of improvements in physical properties, such as, as one example, stiffness.
Such compounds and compositions that provide faster and or higher polymer crystallization temperatures are thus popularly known as nucleators. Such compounds are, as their name suggests, utilized to provide nucleation sites for crystal growth during cooling of a thermoplastic molten formulation. Generally, the presence of such nucleation sites results in a larger number of smaller crystals. As a result of the smaller crystals formed therein, clarification of the target thermoplastic may also be achieved, although excellent clarity is not always a result. The more uniform, and preferably smaller, the crystal size, the less light is scattered. In such a manner, the clarity of the thermoplastic article itself can be improved. Thus, thermoplastic nucleator compounds are very important to the thermoplastic industry in order to provide enhanced clarity, physical properties and/or faster processing.
As an example of one type of nucleator, dibenzylidene sorbitol derivative compounds are typical nucleator compounds, particularly for polypropylene end products. Compounds such as 1,3-O-2,4-bis(3,4-dimethylbenzylidene) sorbitol, available from Milliken Chemical under the trade name Millad® 3988, provide excellent nucleation characteristics for target polypropylenes and other polyolefin. Other well known compounds include sodium benzoate, sodium 2,2′-methylene-bis-(4,6-di-tert-butylphenyl) phosphate (from Asahi Denk Kogyo K.K., known as NA-11), aluminum bis[2,2′-methylene-bis-(4,6-di-tert-butylphenyl)phosphate] (also from Asahi Denka Kogyo K.K., known as NA-21), talc, and the like. Such compounds all impart high polyolefin crystallization temperatures; however, each also exhibits its own drawback for large-scale industrial applications.
Other acetals of sorbitol and xylitol are typical nucleators for polyolefin and other thermoplastics as well. Dibenzylidene sorbitol (DBS) was first disclosed in U.S. Pat. No. 4,016,118 by Hamada, et al. as effective nucleating and clarifying agents for polyolefin. Since then, large numbers of acetals of sorbitol and xylitol have been disclosed. Representative references of such other compounds include Mahaffey, Jr., U.S. Pat. No. 4,371,645 [di-acetals of sorbitol having at least one chlorine or bromine substituent].
As noted above, another example of the effective nucleating agents are the metal salts of organic acids. Wijga in U.S. Pat. Nos. 3,207,735, 3,207,736, and 3,207,738, and Wales in U.S. Pat. Nos. 3,207,737 and 3,207,739, suggest that aliphatic, cycloaliphatic, and aromatic carboxylic, dicarboxylic or higher polycarboxylic acids, and corresponding anhydrides and metal salts, are effective nucleating agents for polyolefin. They further state that benzoic acid type compounds, in particular sodium benzoate, are the best nucleating agents for their target polyolefin.
Another class of nucleating agents was suggested by Nakahara, et al. in U.S. Pat. No. 4,463,113, in which cyclic bis-phenol phosphates was disclosed as nucleating and clarifying agents for polyolefin resins. Kimura, et al. then suggests in U.S. Pat. No. 5,342,868 that the addition of an alkali metal carboxylate to basic polyvalent metal salt of cyclic organophosphoric ester can further improve the clarification effects of such additives. Compounds that are based upon this technologies are marketed under the trade name NA-11 and NA-21.
Furthermore, a certain class of bicyclic compounds, such as bicyclic dicarboxylic acid and salts, have been taught as polyolefin nucleating agents as well within Patent Cooperation Treaty Application WO 98/29494, 98/29495 and 98/29496, all assigned to Minnesota Mining and Manufacturing. The best working examples of this technology is embodied in disodium bicyclo[2.2.1]heptene dicarboxylate, disodium bicyclo[2.2.2]octene dicarboxylated and camphanic acid. Formulations with such compounds are also contemplated within the inventions.
The efficacy of the nucleating agents are typically measured by the peak crystallization temperature of the polymer compositions containing such nucleating agents. A high polymer peak crystallization is indicative of high nucleation efficacy, which generally translates into fast processing cycle time and more desirable physical properties, such as stiffness/impact balance etc., for the fabricated parts.
It is also very desirable that the nucleating agents induce improved clarity in the fabricated parts. DBS based Nucleating agents are known to provide excellent clarity in polypropylene articles. For example, 3,4-dimethyl DBS, marketed under the trade name Millad 3988 is an exceptional clarifier. However, DBS based nucleating agents generally suffer from higher level of migration and certain ones [for example bis(p-methyl benzylidene) sorbitol)] from highly undesirable taste and odor transfer. Site nucleators, which are loosely defined as nucleating agents that are not soluble in molten polyolefin, provide better performance in migration, taste and odor transfer. Typically site nucleators include Na-11, sodium benzoate and alike. Site nucleators generally do not afford sufficient clarification effect in polyolefin articles. Therefore, there is a long felt need for a site nucleating agents with improved clarification property.
Depending upon the application
Milliken & Company
Moyer Terry T.
Mulcahy Peter D.
Parks William S.
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