Process for producing ethylene-&agr;-olefin interpolymer films

Details Process for producing ethylene-&agr;-olefin interpolymer films Process for producing ethylene-&agr;-olefin interpolymer films

2001-12-21

2003-11-18

Seidleck, James J. (Department: 1711)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Mixing of two or more solid polymers; mixing of solid...

C525S069000, C525S070000, C525S285000, C525S242000

Reexamination Certificate

active

06649694

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to a process for producing films of ethylene-&agr;-olefin interpolymers having, in combination, the properties of improved surface haze, improved stiffness, and improved color. The process involves forming a film from a composition comprising an ethylene-&agr;-olefin interpolymer and an amount of from about 0.1% to less than 1% by weight, based on the composition, of a functionalized ethylene homopolymer or a functionalized ethylene-&agr;-olefin interpolymer.
BACKGROUND OF THE INVENTION
Ethylene-&agr;-olefin interpolymer films are often employed in packaging and other applications where appearance is important. Usually in the case of packaging, it is desired that the film be optically transparent and glossy so that the product packaged within will be more attractive. Accordingly, it is desirable to provide a film that has not only improved surface haze properties, but also improved stiffness and color.
SUMMARY OF THE INVENTION
The novel process of the present invention for the production of ethylene-&agr;-olefin interpolymer films having improved surface haze, improved stiffness and improved color is comprised as follows. A composition comprising an ethylene-&agr;-olefin interpolymer and an amount of from about 0.1 to less than 1% by weight, based on the composition, of a functionalized ethylene homopolymer or a functionalized ethylene-&agr;-olefin interpolymer, as defined herein, is prepared. The composition is then formed into a film in any manner known in the art. In a preferred embodiment of the process, the film is formed utilizing the well-known blown film technique.
DETAILED DESCRIPTION OF THE INVENTION
The novel process of the present invention for the production of ethylene-&agr;-olefin interpolymer films having improved surface haze, improved stiffness and improved color is comprised as follows. A composition comprising an ethylene-&agr;-olefin interpolymer and an amount of from about 0.1 to less than 1% by weight, based on the composition, of a functionalized ethylene homopolymer or a functionalized ethylene-&agr;-olefin interpolymer, as defined herein, is prepared. The composition is then formed into a film in any manner known in the art. In a preferred embodiment of the process, the film is formed utilizing the well-known blown film technique.
More particularly, the ethylene-&agr;-olefin interpolymer used in preparing the compositions, that are formed into the films of the present invention, is any ethylene-&agr;-olefin interpolymer comprising ethylene and at least one, or more, other &agr;-olefin wherein the ethylene content is at least about 50% by weight of the total monomers comprising the interpolymer. Preferably, the ethylene content of the interpolymer ranges from greater than about 50% to about 99% by weight of the total monomers comprising the interpolymer. The &agr;-olefin monomer(s) preferably contain from 3 to about 16 carbon atoms. Exemplary &agr;-olefins that may be utilized herein are propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 4-methyl-1-pentene, 1-decene, 1-dodecene, 1-hexadecene and the like. Also utilizable herein as the &agr;-olefin monomer are non-conjugated dienes and olefins formed in situ in the polymerization medium. The ethylene-&agr;-olefin interpolymers may be linear or may contain Theologically significant long chain branches, such as the “substantially linear” polymers, and may be produced by any process, such as solution, gas phase, or slurry loop, and with any olefin polymerization catalyst, such as the constrained geometry, metallocene type, Ziegler Natta types, or chromium oxide types. The ethylene-&agr;-olefin interpolymer is present in the compositions utilized to form the films of the present invention, in an amount of from about greater than 99% to about 99.9% by weight of the composition.
The functionalized ethylene homopolymer or functionalized ethylene-&agr;-olefin interpolymer suitable for use herein are defined as follows. The polyethylene that is functionalized may be any homopolymer of ethylene. The interpolymer of ethylene that is functionalized and is suitable for use in preparing the compositions from which the films of the present invention are formed is any ethylene-&agr;-olefin interpolymer comprising ethylene and at least one, or more, other &agr;-olefin wherein the ethylene content is at least about 50% by weight of the total monomers comprising the interpolymer. Preferably, the ethylene content of the interpolymer ranges from greater than about 50% to about 99% by weight of the total monomers comprising the interpolymer. The &agr;-olefin monomer(s) preferably contain from 3 to about 16 carbon atoms. Exemplary &agr;-olefins that may be utilized herein are propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 4-methyl-1-pentene, 1-decene, 1-dodecene, 1-hexadecene and the like. Also utilizable herein as the &agr;-olefin monomer are non-conjugated dienes and olefins formed in situ in the polymerization medium. The ethylene-&agr;-olefin interpolymers may be linear or may contain Theologically significant long chain branches, such as the “substantially linear” polymers, and may be produced by any process, such as solution, gas phase, or slurry loop, and with any olefin polymerization catalyst, such as the constrained geometry, metallocene types, Ziegler Natta types, or chromium oxide types.
In preparing the functionalized ethylene homopolymers or ethylene-&agr;-olefin interpolymers suitable for use herein, there may be utilized as the functionalizing agent any unsaturated monomer containing one or more carboxylic acid, carboxylic acid ester, or acid anhydride group. Examples of suitable functionalizing agents herein are carboxylic acids such as acrylic and methacrylic acid, carboxylic acid esters such as methyl acrylate and methyl methacrylate, and acid anhydrides such as maleic anhydride. Further exemplary functionalizing agents suitable for use herein are unsaturated monocarboxylic acids and polycarboxylic acids and cyclic acid anhydrides. Specifically included herein are acids such as maleic acid, fumaric acid, himic acid, itaconic acid, citraconic acid, mesaconic acid, acrylic acid, methacrylic acid, crotonic acid, isocrotonic acid, and acid anhydrides such as maleic anhydride and himic anhydride. Preferred for use herein as the functionalizing agent is maleic anhydride. Mixtures of functionalizing agents may be utilized in the present invention. The functionalizing agent is utilized in any amount that will functionalize the ethylene homopolymer and/or interpolymer such that the functionalized ethylene homopolymer and/or interpolymer will contain from about 0.01 to about 3% by weight of the at least one functionalizing agent, based on the functionalized ethylene homopolymer or copolymer. Preferably, the functionalizing agent will be utilized in an amount of from about 0.20 to about 10 weight percent, based on the weight of the ethylene component in order to produce the desired functionalized polymer.
The functionalized ethylene homopolymers and ethylene-&agr;-olefin interpolymers utilized herein may be prepared by any process known in the art. Exemplary of such processes for preparing functionalized ethylene homopolymers and copolymers are U.S. Pat. Nos. 4,612,155; 4,762,890; 5,180,788; 5,705,565; and 5,728,776; and International Publication No. WO 01/36495 A1.
The functionalized ethylene homopolymer or ethylene-&agr;-olefin interpolymer is present in the compositions utilized to form the films of the present invention, in an amount of from about 0.1 to less than 1% by weight of the composition.
The compositions, from which the novel films are formed, comprising from greater than 99 to about 99.9% by weight of the composition, of the ethylene-&agr;-olefin interpolymer described herein, and from about 0.1 to less than 1% by weight of the composition, of the functionalized ethylene homopolymer or functionalized ethylene-&agr;-olefin interpolymer described herein are prepared by any method known in the art. For example, the components of the

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