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
2001-03-29
2003-05-13
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...
C524S374000, C524S436000, C524S437000
Reexamination Certificate
active
06562890
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to compositions comprising specific disodium salts of hexahydrophthalic acid (HHPA) in combination with acid scavengers (such as organic calcium salts or dihydrotalcite complexes) that provide highly desirable and effective nucleating properties within polymer articles (such as polyolefins). Surprisingly, such a combination of a disodium HHPA salt and acid scavenger provides high crystallization temperatures, low haze, and high flexural modulus to the finished polymer product. Other sodium salt polymer nucleators (such as sodium benzoate and NA-11) deleteriously react with calcium organic salt acid scavengers such that characteristically high crystallization temperatures are drastically reduced when in combination with calcium salts (such as calcium stearate). Also, sodium benzoate, when combined with dihydrotalcite (DHT4-A) acid scavengers produce extremely high haze levels in the finished target polymer article, whereas the inventive compositions surprisingly reduce haze. The finished polymer articles comprising such an inventive composition are also contemplated within this invention.
BACKGROUND OF THE PRIOR ART
All U.S. patents cited below are herein fully 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, crystalline morphology uniformity 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 polyolefins. 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 nucleators 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 (DBS) compounds are common, particularly for polypropylene end-products. Compounds such as 1,3-O-2,4-bis(3,4-dimethylbenzylidene) sorbitol (hereinafter DMDBS), available from Milliken Chemical under the trade name Millad® 3988, provide excellent nucleation characteristics for target polypropylenes and other polyolefins. Other well known compounds include sodium benzoate, sodium 2,2′-methylene-bis-(4,6-di-tert-butylphenyl) phosphate (from Asahi Denka 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.
For example, although disodium hexahydrophthalate has been taught within U.S. Pat. No. 3,207,739 to Wales, as well as within Beck, H. N., “Heterogeneous Nucleating Agents for Polypropylene Crystallization,”
Journal of Applied Polymer Science
, Vol. 11, pp. 673-685 (1967), as a possible, though not preferred, nucleator for polymers, such disclosures are directed more specifically to sodium benzoate and other like aromatic compounds as better nucleators. Furthermore, neither reference discusses the presence of any acid scavenger compounds other than the salts themselves; in order to provide any effective dual function of acid scavenger and nucleator, these references require very high addition amounts of such salts within the target polymer (in both instances homopolymer polypropylene). There is no discussion of the utilization of such compounds (which range from the preferred sodium benzoate to the possible, much less desired disodium salts of cycloaliphatic dicarboxylic acids) in combination with any acid scavengers in order to retain the amount of nucleator present within the polymer melt or within the finished article.
Of great interest to this invention is the compatibility of nucleators with different acid scavenger additives widely used within typical thermoplastic (e.g., polyolefins, such as polypropylene, polyethylene, and the like, polyesters, such as polyethylene terephthalate) and thermoset (e.g., polyurethanes, and the like) articles. For instance, calcium stearate, being a very popular, inexpensive acid scavenger and neutralizer present within typical polypropylene formulations to protect the end product from catalyst residue attack, is utilized or greatly desired as a component within polypropylene and other polyolefin formulations. Unfortunately, compatibility between such a calcium salt and sodium-based nucleators is highly questionable. Utilizing sodium benzoate or NA-11 without acid scavenger in polypropylene compositions, albeit at high levels, results in a relatively high peak crystallization temperature for adequate, effective nucleation. However, acid scavengers are necessary to protect the stabilizing additives, such as antioxidants and light stabilizers, from acidic catalyst residue attack during polymer processing. Thus, such acid scavengers must be present. When sodium benzoate or NA-11 is added in combination with calcium stearate (or other calcium organic salts) the resultant polymer crystallization temperature is reduced significantly (about 3-4° C.) from that of the polymer when the nucleator is used without acid scavenger, thereby rendering the nucleation capability of the sodium-based compounds nearly ineffective and certainly well below the performance required of such compounds. When no acid scavenger is used, however, much higher use levels of nucleator are required, and while the said nucleator may still give desirable performance in terms of higher crystallization temperatures, much of the active nucleator is consumed by acid scavenger, and plate-out and blooming often results. Regarding calcium stearate compatibility, it is not known specifically why this phenomenon occurs, however, it is speculated (without intending to be bound to any particular scientific theory) that the calcium and sodium ions exchange places in their respective compounds. Thus, w
Milliken & Company
Moyer Terry T.
Parks William S.
Szekely Peter
LandOfFree
Disodium hexahydrophthalate salt compositions and nucleated... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Disodium hexahydrophthalate salt compositions and nucleated..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Disodium hexahydrophthalate salt compositions and nucleated... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3069600