Compositions: coating or plastic – Coating or plastic compositions – Carbohydrate or derivative containing
Reexamination Certificate
2001-05-31
2003-06-24
Mulcahy, Peter D. (Department: 1713)
Compositions: coating or plastic
Coating or plastic compositions
Carbohydrate or derivative containing
C524S108000
Reexamination Certificate
active
06582503
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 (3,4-DMDBS) and bis(3,4-dichlorodibenzylidene) sorbitol (3,4-DCDBS). Such a combination surprisingly provides improved clarification comparable to polypropylene articles and formulations, better than DCDBS alone and equivalent or better than DMDBS 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 that 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-dichlorodibenzylidene) sorbitol (3,4-DCDBS) and bis(3,4-dimethyldibenzylidene) sorbitol (3,4-DMDBS). These specific compounds and polyolefins containing such compounds have been taught previously in U.S. Pat. Nos. 4,371,645 to Mahaffey and 5,049,605 to Rekers, respectively. Such compounds are thus individually known as polyolefin additives and exhibit relatively low haze measurements within polyolefins (as low as about 8% for 3,4-DMDBS and about 9% for DCDBS in random copolymer polypropylene injection molded 50 mil thick plaques having 2000 ppm of clarifier added).
Surprisingly, 3,4-DCDBS does not present a significant organoleptic problem within target plastics. It is well known that p-chlorodibenzylidene sorbitol exhibits troublesome odor and taste problems due to degradation of the compound into its separate benzaldehyde and sorbitol components and migration of the resultant benzaldehyde within and from the target plastic. The p-chloro benzaldehyde itself exhibits highly undesirable organoleptics (foul taste and odor) such that the target polyolefin is limited in its end-use function to non-food contact applications. Such a problem is not exhibited by the dichloro benzaldehyde, particularly when present within the inventive mixture with 3,4-DMDBS. The 3,4-DCDBS appears to suffer from the same type of degradation possibilities as the p-chloro compound; however, again, the resultant benzaldehyde, surprisingly, does not create the same organoleptic problems.
Unfortunately, though, 3,4-DMDBS is relatively expensive to manufacture. 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 3,4-DMDBS, but mixed with another compound (or compounds) to reduce the amount of expensive 3,4-DMDBS present therein. 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 bis-p-methyldibenzylidene sorbitol 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 3,4-DCDBS. 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 comprising a combination of 3,4-DMDBS and 3,4-DCDBS exhibiting a haze measurement below that for the same amount of 3,4-DCDBS present as the sole clarifying agent.
Accordingly, this invention encompasses a polyolefin additive composition comprising a combination of both bis(3,4-dimethylbenzylidene) sorbitol and bis(3,4-dichlorobenzylidene) 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(3,4-dichlorobenzylidene) sorbitol. Finished solid articles of polyolefins, such as, preferably, though not necessarily, polypropylene, comprising such an additive composition are also contemplated within this invention. Further contemplated is a polyolefin clarifier composition comprising at least 100 ppm of a combination of nucleator compounds, wherein said compounds are bis(3,4-dimethylbenzylidene) sorbitol and bis(3,4-dichlorobenzylidene) sorbitol, wherein said polyolefin clarifier composition provides a haze measurement within a target polyolefin article formulation below the haze measurement provided for a comparative polyolefin article comprising the same polyolefin formulation but comprising bis(3,4-dichlorobenzylidene) sorbitol as its sole polyolefin clarifier component, wherein such haze measurements are made in accordance with ASTM Standard Test Method D1003-61, and 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. The importance of and definition of such haze measurements are discussed in greater detail below. Lastly, the invention encompasses a method of nucleating a polyolefin comprisi
Dotson Darin L.
Mehl Nathan A.
Milliken & Company
Moyer Terry T.
Mulcahy Peter D.
Parks William S.
LandOfFree
Polyolefin additive composition comprising... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Polyolefin additive composition comprising..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Polyolefin additive composition comprising... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3163876