Polymer Composition For Producing Gel Extruded Articles and Polymer Articles Made Therefrom

Abstract

A polymer composition for producing gel extruded articles is described. The polymer composition contains polyethylene particles combined with a plasticizer. The polyethylene particles are particularly selected so that the particles rapidly form a homogeneous gel-like material when combined with the plasticizer during gel processing. In one embodiment, the polyethylene used to produce the particles has a relatively low bulk density. Alternatively or in addition, the particles can have a carefully controlled particle size distribution. Polymer articles such as fibers and films can be produced having little to no imperfections.

1 .- 21 . (canceled) 
     
     
         22 . A polymer composition for producing gel extruded articles comprising:
 a plasticizer; and   high density polyethylene particles combined with the plasticizer, the high density polyethylene particles having a bulk density of less than about 0.35 g/cm 3  and a median particle size (d50) of greater than 60 microns, and wherein the high density polyethylene has an average molecular weight of greater than about 1,500,000 g/mol.   
     
     
         23 . A polymer composition as defined in claim  1 , wherein the high density polyethylene particles have a bulk density of less than about 0.33 g/cm 3 . 
     
     
         24 . A polymer composition as defined in claim  1 , wherein the high density polyethylene particles have a bulk density of less than about about 0.28 g/cm 3 . 
     
     
         25 . A polymer composition as defined in claim  1 , wherein the high density polyethylene particles have a median particle size (d50) of greater than about 70 microns. 
     
     
         26 . A polymer composition as defined in claim  1 , wherein the high density polyethylene particles have a median particle size (d50) of greater than about 95 microns. 
     
     
         27 . A polymer composition as defined in claim  1 , wherein 90% of the high density polyethylene particles have a particle size of less than about 180 microns. 
     
     
         28 . A polymer composition as defined in claim  1 , wherein, when tested according to a solubility test, the high density polyethylene particles have a solubility of less than about 3 mins. 
     
     
         29 . A polymer composition as defined in claim  1 , wherein the high density polyethylene particles are present in the composition in an amount up to about 50% by weight. 
     
     
         30 . A polymer composition as defined in claim  1 , wherein the plasticizer comprises mineral oil, a paraffinic oil, a hydrocarbon, an alcohol, an ether, an ester, or mixtures thereof. 
     
     
         31 . A polymer composition as defined in claim  1 , wherein the high density polyethylene has a molecular weight of greater than about 2,000,000 g/mol. 
     
     
         32 . A polymer composition as defined in claim  1 , wherein the high density polyethylene is a Ziegler-Natta catalyzed ultrahigh molecular weight polyethylene. 
     
     
         33 . A polymer composition as defined in claim  1 , wherein the plasticizer comprises decaline, xylene, dioctyl phthalate, dibutyl phthalate, stearyl alcohol, oleyl alcohol, decyl alcohol, nonyl alcohol, diphenyl ether, n-decane, n-dodecane, octane, nonane, kerosene, toluene, naphthalene, tetraline, monochlorobenzene, camphene, methane, dipentene, methylcyclopentandiene, tricyclodecane, 1,2,4,5-tetramethyl-1,4-cyclohexadiene, or mixtures thereof. 
     
     
         34 . A process for producing polymer articles comprising:
 forming the polymer composition as defined in claim  1  into a gel-like composition;   extruding the gel-like composition through a die to form a polymer article, the polymer article comprising fibers, a film, or a membrane.   
     
     
         35 . A process as defined in  claim 34 , further comprising the step of removing at least part of the plasticizer from the polymer article. 
     
     
         36 . A polymer article comprising a fiber, a film, or a membrane, the polymer article being produced by:
 combining a plasticizer with high density polyethylene particles to form a gel-like composition, the high density polyethylene particles having bulk density of less than about 0.35 g/cm 3  and a median particle size (d50) of greater than 60 microns, wherein the high density polyethylene has an average molecular weight of greater than about 1,500,000 g/mol; and   extruding the gel-like composition through a die to form the polymer article.   
     
     
         37 . A polymer article as defined in  claim 36 , wherein the high density polyethylene particles have a bulk density of less than about 0.28 g/cm 3 . 
     
     
         38 . A polymer article as defined in  claim 36 , wherein the high density polyethylene particles have a median particle size (d50) of greater than about 70 microns. 
     
     
         39 . A polymer article as defined in  claim 36 , wherein the polymer article comprises a membrane. 
     
     
         40 . A polymer article as defined in  claim 36 , wherein the polymer article comprises fibers.