Drug – bio-affecting and body treating compositions – Preparations characterized by special physical form – Matrices
Reexamination Certificate
2001-02-16
2003-07-01
Page, Thurman K. (Department: 1615)
Drug, bio-affecting and body treating compositions
Preparations characterized by special physical form
Matrices
C424S484000
Reexamination Certificate
active
06586007
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a specific combination of two different polyolefin clarifying and nucleating agents, namely bis-3,4-dimethyldibenzylidene sorbitol and bis-p-methyldibenzylidene sorbitol. Such a combination surprisingly provides improved clarification and crystallization temperatures to polypropylene articles and formulations, better than bis-p-methyldibenzylidene sorbitol alone and equivalent or better than 3,4-dimethyldibenzylidene sorbitol alone. Such a combination of compounds thus permits the utilization of a new additive for the purpose of modifying polyolefin properties, such as polypropylene clarification and nucleation. The inventive combination may be introduced within any polyolefin composition, again preferably polypropylene, which may then be molded into any shape or form. A method of producing a polyolefin plastic utilizing the inventive combination of compounds is also provided.
BACKGROUND OF THE PRIOR ART
Dibenzylidene sorbitol acetals (“DBS”), substituted DBS, such as can be made with alkyl substituted aromatic aldehydes, and related acetals have found utility as nucleating agents, clarifying agents, gelling agents, processing aids, and strength modifiers in polyolefin resins, polyester resins, deodorant, and antiperspirant compositions; hydrocarbon fuels; waste liquids, especially those containing organic impurities; and paint.
Such compounds are utilized to provide nucleation sites for polyolefin crystal growth during cooling of a molten formulation. Without being limited to one specific scientific theory, it is believed that DBS compounds form fibrous networks within the molten polyolefin (such as polypropylene) at a temperature well above that required for polyolefin crystal formation. The fibrous networks appear to act as sites for more ordered and faster polyolefin crystallization during cooling. During the process of crystallization, polymer crystals organize into larger superstructures which are referred to as spherulites. The more uniform, and preferably smaller, the spherulite size, the reduced possibility for light to be scattered. In such a manner, optical opacity of the polyolefin article itself can be controlled. Thus, DBS compounds are very important to the polyolefin industry in order to provide such desired nucleation and clarification properties.
DBS derivative compounds are typically prepared by the condensation reaction of two moles of an aromatic aldehyde with one mole of a polyhydric alcohol, such as xylitol or sorbitol. Examples of suitable processes may be found in Murai et al., U.S. Pat. No. 3,721,682; Murai et al., U.S. Pat. No. 4,429,140; Machell, U.S. Pat. No. 4,562,265; Kobayashi et al., U.S. Pat. No. 4,902,807; and Scrivens et al., U.S. Pat. No. 5,731,474. All of these references are hereby incorporated by reference in their entirety.
Specific clarifying and nucleating agents for polyolefins include bis-3,4-dimethyldibenzylidene sorbitol (3,4-DMDBS) and bis-p-methyldibenzylidene sorbitol (MDBS). These specific compounds and polyolefins containing such compounds have been taught previously in U.S. Pat. No. 4,371,645 to Mahaffey and U.S. Pat. No. 5,049,605 to Rekers, respectively. Such compounds are thus individually well known as polyolefin additives and exhibit excellent low haze measurements within polyolefins (as low as about 8.0% for 3,4-DMDBS and about 10% for MDBS in random polypropylene copolymer injection molded 50 mil thick plaques having 2000 ppm of clarifier added).
However, there are drawbacks from utilizing MDBS as a clarifying agent since degradation of such a compound into the benzaldehyde and sorbitol components creates a problem with migration of such benzaldehydes from the target polyolefin. In such a situation, foul odors and tastes are generated such that the target polyolefin is limited in its end-use function to non-food contact applications. To combat this, Milliken & Company developed 3,4-DMDBS. Such a compound appears to suffer from the same type of degradation possibilities; however, the resultant benzaldehyde, being 3,4-dimethyl substituted, does not create the same organoleptic problems as its p-methylbenzaldehyde counterpart. As a result, 3,4-DMDBS has become the primary clarifying agent throughout the polyolefin market.
Unfortunately, though, 3,4-DMDBS is relatively expensive to manufacture. The manufacturing costs required to produce 3,4-DMDBS are above those for MDBS. As a result, there remains a great desire to develop a more cost-effective, yet acceptable clarifying agent or composition for polyolefins which exhibits similar haze results as either of the two compounds individually. To date, there has been no teaching or fair suggestion for any such improvements to lower the amount of 3,4-DMDBS in order to reduce the costs of such a composition solely comprising such a polyolefin clarifying agent without sacrificing clarification ability. There does exist a combination of 3,4-DMDBS with bis(p-chlorobenzylidene) sorbitol in Japanese Application Hei 8[1996]-199003 to Kobayashi; however, such a composition provides deleterious results from an organoleptic perspective. Japanese Application Hei 8[1996]-32415, also to Kobayashi, teaches a combination of MDBS with bis-p-chlorodibenzylidene sorbitol as a polyolefin additive as well. Again, organoleptics are problematic with such a composition. Neither teaching shows or fairly suggests the combination of 3,4-DMDBS and MDBS. The only other teachings concerning such polyolefin clarifying compounds have been as individually utilized compounds within polyolefin compositions and articles, as noted above. Thus, there remains a desire to provide a more cost-effective but similarly performing clarifying agent comprising the excellent clarifier 3,4-DMDBS.
OBJECTS OF THE INVENTION
Therefore, an object of the invention is to provide a lower cost alternative to a polyolefin clarifier containing 3,4-DMDBS alone exhibiting excellent clarifying capabilities for the same polyolefin articles and compositions. Another object of the invention is to provide a polyolefin composition or article exhibiting a haze measurement of below 10% comprising a clarifying combination of 3,4-DMDBS and MDBS.
Accordingly, this invention encompasses a polyolefin additive composition comprising a combination of both bis(3,4-dimethylbenzylidene) sorbitol and bis(4-methylbenzylidene) sorbitol. More specifically, this invention encompasses such a combination consisting of from 5 to 95% by weight of the total combination of bis(3,4-dimethylbenzylidene) sorbitol and from 5 to 95% by weight of the total combination of bis(4-methylbenzylidene) sorbitol. Finished solid articles of polyolefins, such as, preferably, though not necessarily, polypropylene, comprising such an additive composition are also contemplated within this invention. Furthermore, such an invention is also defined and thus encompasses a polyolefin nucleator composition comprising at least 1000 ppm of a mixture of compounds, wherein said compounds are bis(3,4-dimethylbenzylidene) sorbitol and bis(p-methylbenzylidene) sorbitol, wherein said polyolefin nucleator composition provides a crystallization onset temperature within a target polyolefin article formulation above the crystallization onset temperature provided for a comparative polyolefin article comprising the same polyolefin formulation but comprising bis(p-methylbenzylidene) sorbitol as its sole polyolefin nucleator component, wherein the concentration of said sole polyolefin nucleator component within said comparative polyolefin article is equivalent to the total concentration of the polyolefin nucleator mixture within said target polyolefin article. Also contemplated is a polyolefin nucleator composition comprising at least 1000 ppm of a combination of compounds, wherein said compounds are bis(3,4-dimethylbenzylidene) sorbitol and bis(p-methylbenzylidene) sorbitol, wherein said polyolefin nucleator composition provides a peak crystallization temperature within a target polyolefin article formulation above the peak crystallizat
Kochanowicz Christopher Thomas
Lake, Jr. K. David
Mehl Nathan A.
Fubara Blessing
Page Thurman K.
Parks William S.
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