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
2001-07-03
2003-02-18
Szekely, Peter (Department: 1714)
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...
C524S108000, C524S109000, C524S110000, C252S182120, C252S182130, C252S182140, C252S182150, C252S182160, C252S182230, C252S182240, C252S182260, C252S182170
Reexamination Certificate
active
06521685
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to certain thermoplastic additives that induce simultaneously low clarity and high nucleation efficacy. Such additives include combinations of certain bicyclic salts (which by themselves induce very high nucleation efficacy) and thermoplastic clarifying agents, including certain dibenzylidene sorbitol acetals and derivatives (hereinafter collectively referred to as “DBSs”)(which alone provide very low haze measurements and thus highly desirable clarity characteristics). In comparison, other types of standard thermoplastic nucleators, such as sodium benzoate and sodium 2,2′-methylene-bis-(4,6-di-tert-butylphenyl)phosphate provide relatively high peak crystallization temperatures, but do not combine synergistically with clarifiers, such as DBSs, to provide the same results as for the inventive combination of bicyclic salts and DBSs. Thermoplastic compositions as well as thermoplastic additive packages comprising such inventive nucleator compounds, as well as methods of producing polypropylene compositions and articles made therefrom, 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, polyolefins (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 polyolefins, 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 unnucleated 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. Highly efficient nucleation of thermoplastics, being very important to the thermoplastic industry in order to provide enhanced physical properties and/or faster processing to the target thermoplastic article or composition, is highly desirable in order to reduce costs and provide improved plastics in terms of durability, impact resistance, and the like.
Furthermore, for applications that require good clarity of the thermoplastic (e.g., polyolefin) article itself, there is also a need to provide an additive that induces low haze measurements within the ultimate polyolefin product. A combination of high nucleation efficacy and low haze (e.g., good clarity) is highly desirable; however, to date there are very few alternatives individually to provide effective low haze or high peak crystallization temperatures within the target polyolefin and no real alternatives that provides an effective combination of such characteristics.
The most effective clarifying agent known to the industry and available commercially at this time is also a type of nucleator, namely dibenzylidene sorbitol acetal derivative compounds (again, “DBSs”). Such compounds are typical nucleator compounds, particularly for polypropylene end-products, and include, without limitation. Compounds such as 1,3-O-2,4-bis(3,4-dimethylbenzylidene)sorbitol, available from Milliken Chemical under the trade name Millad® 3988 (hereinafter referred to as 3,4-DMDBS), 1,3-O-2,4-bis(p-methylbenzylidene)sorbitol, also available from Milliken & Company under the trade name Millad® 3940 (hereinafter referred to as p-MDBS). Again, such compounds provide excellent clarification and relatively effective nucleation characteristics for target polypropylenes and other polyolefins. However, the peak crystallization temperatures provided by such compounds for the aforementioned polyolefins (e.g., polypropylene) could be much lower than for comparative standard and also commercially available nucleators (which, again, do not provide effective clarification measurements). Such nucleators include sodium benzoate, sodium 2,2′-methylene-bis-(4,6-di-tert-butylphenyl)phosphate (from Asahi Denka Kogyo K. K., known as and hereinafter referred to as NA-11), aluminum bis[2,2′-methylene-bis-(4,6-di-tert-butylphenyl)phosphate] with lithium myristate (also from Asahi Denka Kogyo K. K., which is understood to be known as and hereinafter referred to as NA-21), talc, and the like. Such compounds all impart the desirable high polyolefin crystallization temperatures indicative of excellent nucleation capabilities. Attempts have been made to develop a nucleating packaging that exhibits simultaneous high nucleating efficacy and good clarity. One such attempt was to blend commercial nucleating agents (NA-11, NA-21, and the like) with DBSs. Unfortunately, upon mixing and compounding within polypropylene, the resultant formulation with such blends exhibited much worse clarity characteristics than that of DBSs alone. Thus, there was no simultaneous exhibition of inducement of both high peak crystallization temperatures (or other characteristics associated with excellent nucleation efficacy) as well as low haze within target polyolefins. To date, the best all around high nucleating and clarifying agent remains 3,4-DMDBS or p-MDBS. There thus exists a need to develop such simultaneous high-performing polyolefin thermoplastic additives.
Furthermore, a certain class of unsaturated 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 are embodied in disodium bicyclo[2.2.1 ]heptene dicarboxylate and camphanic acid.
The efficacy of nucleating agents is 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. Compounds mentioned above all impart relatively high polyolefin crystallization temperatures
Milliken & Company
Moyer Terry T.
Parks William S.
Szekely Peter
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