Void-containing polyester shrink film with improved density retention

Abstract

Disclosed are void-containing polyester shrink films which show excellent density retention upon exposures to high temperatures. The films have high shrinkage and retain their low density after processing under conditions of temperature and moisture used in typical recycling processes. The films are useful for sleeve label and other shrink film applications, and their lower density allows them to be readily separated from soft drink bottles, food containers and the like during recycling operations. Also disclosed is a process for void-containing polyester shrink films having high shrinkage and low density after exposure to elevated temperatures.

1 . A void-containing shrink film comprising an oriented polyester having dispersed therein about 5 to about 35 weight percent, based on the total weight of the film, of a voiding agent wherein said film has a shrinkage of at least 40% after 5 seconds in water bath at 95° C. and a density of 1.05 g/cc or less after 15 minutes in a water bath at 85° C.  
   
   
       2 . The shrink film of  claim 1  wherein said polyester comprises (i) diacid residues comprising at least 80 mole percent, based on the total moles of diacid residues, of the residues one or more diacids selected from terephthalic acid, naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, and isophthalic acid; and (ii) diol residues comprising about 10 to 100 mole percent, based on the total moles of diol residues, of the residues of one or more diols selected from 1,4-cyclohexanedimethanol, neopentyl glycol, and diethylene glycol; and 0 to 90 mole percent of the residues of one or more diols selected from: ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, 2,2,4-trimethyl-1,3-pentanediol, 2,2,4,4-tetramethyl-1,3-cyclobutanediol, 1,3-cyclohexanedimethanol, bisphenol A, and polyalkylene glycol.  
   
   
       3 . The shrink film of  claim 2  wherein said diol residues comprise about 10 to about 99 mole percent of residues of 1,4-cyclohexanedimethanol, 0 to about 90 mole percent of residues of ethylene glycol, and about 1 to about 25 mole percent of residues of diethylene glycol.  
   
   
       4 . The shrink film of  claim 2  wherein said diacid residues further comprise 0 to about 20 mole percent of one or more residues of a modifying diacid containing 4 to 40 carbon atoms.  
   
   
       5 . The shrink film of  claim 4  wherein said modifying diacid is selected from the group consisting of succinic acid, glutaric acid, adipic acid, suberic acid, sebacic acid, azelaic acid, dimer acid, and sulfoisophthalic acid.  
   
   
       6 . The shrink film of  claim 5  wherein said polyester further comprises at least one additive selected from the group consisting of antioxidants, melt strength enhancers, branching agents, chain extenders, flame retardants, fillers, dyes, colorants, pigments, nanoclays, antiblocking agents, flow enhancers, impact modifiers, antistatic agents, processing aids, mold release additives, and plasticizers.  
   
   
       7 . The shrink film of  claim 3  wherein said voiding agent comprises at least one polymer selected from the group consisting of: cellulosic polymers, starch, esterified starch, polyketones, polyester, polyamides, polysulfones, polyimides, polycarbonates, olefinic polymers, and copolymers thereof.  
   
   
       8 . The shrink film of  claim 3  wherein said voiding agent comprises least one inorganic compound selected from the group consisting of talc, silicon dioxide, titanium dioxide, calcium carbonate, barium sulfate, kaolin, wollastonite, and mica.  
   
   
       9 . The shrink film of  claim 7  wherein said voiding agent comprises at least one polymer selected from the group consisting of cellulose acetate, cellulose triacetate, cellulose acetate proprionate, cellulose acetate butyrate, polyethylene, polystyrene, polypropylene, ethylene vinyl acetate, ethylene vinyl alcohol copolymer, ethylene methyl acrylate copolymer, ethylene butyl acrylate copolymer, ethylene acrylic acid copolymer, ionomer, and copolymers thereof.  
   
   
       10 . The shrink film of  claim 9  wherein said voiding agent comprises cellulose acetate, polypropylene, and ethylene methyl acrylate copolymer.  
   
   
       11 . The shrink film of  claim 3  wherein said diacid residues comprise at least 95 mole percent of the residues of terephthalic acid; said the diol residues comprise about 10 to about 40 mole percent of the residues of 1,4-cyclohexanedimethanol, about 1 to about 25 mole percent of the residues of diethylene glycol, and about 35 to about 89 mole percent of the residues ethylene glycol; said voiding agent comprises cellulose acetate, polypropylene, and ethylene methyl acrylate copolymer.  
   
   
       12 . The shrink film of  claim 11  wherein said film has a shrinkage of at least 50% after 5 seconds in a water bath at 95° C.  
   
   
       13 . The shrink film of  claim 2  wherein said film is stretched in at least one direction.  
   
   
       14 . The shrink film of  claim 2  wherein said film comprises a plurality of layers in which at least one layer comprises said voiding agent.  
   
   
       15 . The film of  claim 2  wherein said film is produced by extrusion, calendering, casting, drafting, tentering, or blowing.  
   
   
       16 . A sleeve or roll-fed label comprising said shrink film of  claim 1 .  
   
   
       17 . The sleeve or label of  claim 16 , wherein said sleeve or label is seamed by solvent bonding, hot-melt glue, UV-curable adhesive, radio frequency sealing, heat sealing, or ultrasonic bonding.  
   
   
       18 . A void-containing shrink film, comprising: (a) an oriented polyester comprising diacid and diol residues, wherein said diacid residues comprise at least 95 mole percent, based on the total moles of diacid residues, of the residues of terephthalic acid; and said diol residues comprise about 10 to about 40 mole percent, based on the total moles of diol residues, of the residues of 1,4-cyclohexanedimethanol, about 1 to about 25 mole percent of the residues of diethylene glycol, and about 35 to about 89 mole percent of the residues ethylene glycol; and (b) about 5 to about 35 weight percent, based on the total weight of the film, of a voiding agent dispersed within said polyester, wherein said voiding comprises about 40 to about 60 weight percent cellulose acetate, about 20 to about 40 weight percent polypropylene, and about 5 to about 40 weight percent ethylene methyl acrylate copolymer; wherein said film has a shrinkage of at least 40% after 5 seconds in water bath at 95° C. and a density of 1.05 g/cc or less after 15 minutes in a water bath at 85° C.  
   
   
       19 . The shrink film of  claim 18  wherein said film has a shrinkage of at least 60% after 5 seconds in a water bath at 95° C.  
   
   
       20 . The shrink film of  claim 18  wherein said film has a density of 1.03 g/cc or less after 15 minutes in a water bath at 85° C.  
   
   
       21 . The shrink film of  claim 20  wherein said film comprises 20 to 30 weight percent of voiding agent, based on the total weight of said film.  
   
   
       22 . A process for a void-containing shrink film, comprising: (i) mixing a polyester and 5 to 35 weight percent, based on the total weight of said film, of a voiding agent at a temperature at or above the Tg of said polyester to form a uniform dispersion of said voiding agent within said polyester; (ii) forming a film; and (iii) orienting said film of step (ii) in one or more directions; and (iv) annealing said film from step (iii) at a temperature of about 75 to about 110° C., wherein said film has a shrinkage of at least 40% after 5 seconds in water bath at 95° C. and a density of 1.05 g/cc or less after 15 minutes in a water bath at 85° C.  
   
   
       23 . The process of  claim 22  wherein said film formation step (ii) is by extrusion, calendering, casting, or blowing.  
   
   
       24 . The process of  claim 23  wherein said polyester comprises (i) diacid residues comprising at least 80 mole percent, based on the total moles of diacid residues, of the residues of one or more residues selected from terephthalic acid, naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, and isophthalic acid; and (ii) diol residues comprising about 10 to 100 mole percent, based on the total moles of diol residues, of the residues of one or more diols selected from 1,4-cyclohexanedimethanol, neopentyl glycol, and diethylene glycol; and 0 to 90 mole percent of the residues of one or more diols selected from ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, 2,2,4-trimethyl-1,3-pentanediol, 2,2,4,4-tetramethyl-1,3-cyclobutanediol, 1,3-cyclohexanedimethanol, bisphenol A, and polyalkylene glycol.  
   
   
       25 . The process of  claim 24  wherein said diol residues comprise about 10 to about 99 mole percent of residues of 1,4-cyclohexanedimethanol, 0 to about 90 mole percent of residues of ethylene glycol, and about 1 to about 25 mole percent of residues of diethylene glycol.  
   
   
       26 . The process of  claim 24  wherein said diacid residues further comprise 0 to about 20 mole percent of one or more residues of a modifying diacid containing 4 to 40 carbon atoms.  
   
   
       27 . The process of 26 wherein said modifying diacid is selected from succinic acid, glutaric acid, adipic acid, suberic acid, sebacic acid, azelaic acid, dimer acid, and sulfoisophthalic acid.  
   
   
       28 . The process of  claim 24  wherein said polyester further comprises one or more additives selected from the group consisting of antioxidants, melt strength enhancers, branching agents, chain extenders, flame retardants, fillers, dyes, colorants, pigments, nanoclays, antiblocking agents, flow enhancers, impact modifiers, antistatic agents, processing aids, mold release additives, and plasticizers.  
   
   
       29 . The process of  claim 24  wherein said voiding agent comprises least one inorganic compound selected from the group consisting of talc, silicon dioxide, titanium dioxide, calcium carbonate, barium sulfate, kaolin, wollastonite, and mica.  
   
   
       30 . The process of  claim 25  wherein said voiding agent comprises at least one polymer selected from the group consisting of: cellulosic polymers, starch, esterified starch, polyketones, polyester, polyamides, polysulfones, polyimides, polycarbonates, olefinic polymers, and copolymers thereof.  
   
   
       31 . The process of  claim 30  wherein said voiding agent comprises at least one polymer selected from the group consisting of cellulose acetate, cellulose triacetate, cellulose acetate proprionate, cellulose acetate butyrate, polyethylene, polystyrene, polypropylene, ethylene vinyl acetate, ethylene vinyl alcohol copolymer, ethylene methyl acrylate copolymer, ethylene butyl acrylate copolymer, ethylene acrylic acid copolymer, ionomer, and copolymers thereof.  
   
   
       32 . The process of  claim 31  wherein said voiding agent comprises about 40 to about 60 weight percent cellulose acetate, about 20 to about 40 weight percent polypropylene, and about 5 to about 40 weight percent ethylene methyl acrylate copolymer.  
   
   
       33 . The process of  claim 24  wherein said film is a roll fed label or shrink sleeve.  
   
   
       34 . The process of  claim 27  wherein said film has a shrinkage of at least 50% after 5 seconds in water bath at 95° C.  
   
   
       35 . The process of  claim 34  wherein said film has a density of 1.03 g/cc or less after 15 minutes in a water bath at 85° C.  
   
   
       36 . The process of  claim 35  wherein said voiding agent is about 20 to about 30 weight percent of the total weight of said film.  
   
   
       37 . The process of  claim 25  wherein said film comprises a plurality of layers in which at least one layer comprises a voiding agent.  
   
   
       38 . The process of  claim 22  wherein the film is oriented in one direction, annealed at a temperature of 75° C. or higher, and oriented a second time in one or more directions.  
   
   
       39 . The process of  claim 22  wherein the film is annealed at a temperature of about 80° C. to about 105° C.  
   
   
       40 . The process of  claim 22  wherein the film is annealed at a temperature of about 80° C. to about 85° C. or about 95° C. to about 100° C.