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Process for improving the clarity of sheet extrusion and thermoformed parts by adding an additional clarifying agent to a previously nucleated polypropylene resin

IP.com Disclosure Number: IPCOM000247324D
Publication Date: 2016-Aug-23
Document File: 2 page(s) / 139K

Publishing Venue

The IP.com Prior Art Database

Abstract

Nucleating agents enable modest improvements to the optical properties of polypropylene resins (homopolymer and copolymer); however, these improvements can be substantially enhanced by adding a clarifying agent to work alongside the nucleating agent. The improvement on optical properties for polypropylenes containing this dual-additive clarifying system is most apparent in extruded sheet or when the manufacturing process of said part imposes lower levels of orientation on the polymer, but enhancements can occur at higher levels of orientation as well. Addition of the clarifying agent can occur during polymer finishing, polymer compounding, or sheet extrusion steps.

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Process for improving the clarity of sheet extrusion and thermoformed parts by adding an

additional clarifying agent to a previously nucleated polypropylene resin

 

Nucleating agents enable modest improvements to the optical properties of polypropylene resins (homopolymer and copolymer); however, these improvements can be substantially enhanced by adding a clarifying agent to work alongside the nucleating agent. The improvement on optical properties for polypropylenes containing this dual-additive clarifying system is most apparent in extruded sheet or when the manufacturing process of said part imposes lower levels of orientation on the polymer, but enhancements can occur at higher levels of orientation as well. Addition of the clarifying agent can occur during polymer finishing, polymer compounding, or sheet extrusion steps.

The nucleated polypropylene resin can be nucleated by an aromatic carboxylate (such as sodium benzoate or bis(4-tert-butyl-benzoate)aluminum hydroxide), a dicarboxylate salt (such as sodium bicyclo[2.2.1]heptane dicarboxylate or calcium hexahydrophthalate), or a phosphate ester (such as sodium 2,2′-methylene-bis-(4,6-di-tert-butylphenyl) phosphate or lithium 2,2′-methylene-bis-(4,6-di- tert-butylphenyl) phosphate).

Examples of commercially available nucleating agents containing such compounds or a combination of such compounds may include, but are not limited to, Hyperform® HPN-20E nucleating agent, Hyperform® HPN-68l nucleating agent, and Hyperform® HPN-600ei nucleating agent.

Clarifying agents suitable for use in the composition of the invention include, but are not limited to, trisamides, bisphenol phosphates, and acetal compounds. Suitable trisamide clarifying agents include, but are not limited to, amide derivatives of benzene-1,3,5-tricarboxylic acid, derivatives of N-(3,5-bis- formylamino-phenyl)-formamide (e.g., N-[3,5-bis-(2,2-dimethyl-propionylamino)-phenyl]-2,2-dimethyl- propionamide), derivatives of 2-carbamoyl-malonamide (e.g., N,N-bis-(2-methyl- cyclohexyl)-2-(2- methyl-cyclohexylcarbamoyl)-malonamide), and mixtures thereof. Suitable bisphenol phosphate clarifying agents include, but are not limited to, aluminum 2,2'-methylenebis-(4,6-di-tert-butylphenyl) phosphate, lithium 2,2'-methylenebis(4,6-di-tert-butylphenyl) phosphate, and mixtures thereof. Clarifying agents suitable for use in the composition of the invention include the acetal compounds produced by the condensation reaction of a polyhydric alcohol and an aromatic aldehyde. Polyhydric alcohols suitable for producing such acetal clarifying agents include, but are not limited to, acyclic polyols, such as xylitol, sorbitol, 1,2,3-trideoxynonitol, and 1,2,3-trideoxynon-1-enitol. Aromatic aldehydes suitable for producing such acetal clarifying agents include, but are not limited to, aromatic aldehydes containing a single aldehyde group with the remaining positions on the aromatic ring being either unsubstituted or substituted. Thus...