| 摘要 |
<p>#CMT# #/CMT# A single- or multilayer, white, biaxially oriented polyester film, comprises thermoplastic polyester and a coating on at least one side, where the R value of the film is smaller than 43 daN/mm2>, the emax ratio of film is smaller than 2.5, and the coating on one or both surface(s) of film is adhesion-promoting, steam-sterilization-resistant layer composed of a hydrolyzed amino-functional silane. #CMT# : #/CMT# Independent claims are also included for: (A) a process for the production of a polyester film, comprising producing a single- or multilayer film via extrusion or coextrusion and shaping the melts to give flat melt films; coating of film with a water-soluble adhesion promoting coating; biaxially stretching the film in the machine direction and the transverse direction; and heat-setting the stretched film, where the coating process takes place prior to, during, or after the biaxial stretching process; and (B) packaging film for foods and for other consumable items comprising the polyester film. #CMT#USE : #/CMT# The polyester film is used for packaging film for foods and for other consumable items. The polyester film can be lid film for cup-shaped containers e.g. yoghurt cups. (All claimed) #CMT#ADVANTAGE : #/CMT# The polyester film has capability for cost-effective production, good winding capability, and good processibility; good adhesion of at least one side of the film to inks, adhesives, sealing lacquers; steam-sterilizable, i.e. even after steam-sterilization, where the film has good adhesion to inks, adhesive, primer, and metallic and ceramic layers; very good peel-from-cup performance, no delamination, no tearing and no tear-propagation; and good optical properties, in particular even when recycled identical film material is added during film production, and good light-stabilization properties. #CMT#DESCRIPTION OF DRAWINGS : #/CMT# The figure is a schematic illustration of film strip orientations used in the determination of the R value. #CMT#INORGANIC CHEMISTRY : #/CMT# Preferred Component: The polyester film further comprises titanium dioxide (TiO2) as white pigment or filler. Only the layer B of the film has a white pigment or filler. Preferred Composition: The polyester film comprises more than 3 wt.% of the white pigment, based on the total weight of the layer in which it is present. #CMT#ORGANIC CHEMISTRY : #/CMT# Preferred Component: The polyester film further comprises titanium dioxide (TiO2) as white pigment or filler. Only the layer B of the film has a white pigment or filler. Preferred Composition: The polyester film comprises more than 3 wt.% of the white pigment, based on the total weight of the layer in which it is present. #CMT#ORGANIC CHEMISTRY : #/CMT# Preferred Component: The adhesion-promoting layer is composed of a dried residue of a hydrolyzed aminosilane compound whose unhydrolyzed form has the formula (R1>)aSi(R2>)b(R3>). R : functional group having primary amino group; R2>hydrolyzable group from short-chain 1-8C alkoxy, acetoxy, or halide; R3>unreactive, non-hydrolyzable group from short-chain 1-8C alkyl or Ph; a,b : >=1; c : >=0; a+b+c : 4. Preferred Parameter: The total thickness is 10-120 mu m, and the yellowness index is less than 50. #CMT#POLYMERS : #/CMT# Preferred Component: The polyester film has a symmetrical layer structure ABA or ACBCA, where C are the intermediate layers and A are the outer layers of the film. The polyester contains units derived from ethylene glycol and terephthalic acid, and/or units derived from ethylene glycol and naphthalene-2,6-dicarboxylic acid. The polyester used for the layer B comprises polyethylene terephthalate. Preferred Parameter: The R value of the film is smaller than 42 daN/mm2> and the emax ratio of the film is smaller than 2.2. Preferred Composition: The layer B comprises >=80 wt.% of the thermoplastic polyester, based on the total weight of the layer. Preferred Method: In order to achieve the desired R value or emax ratio of the film, the stretching temperatures are increased and/or the stretching ratio in the longitudinal and/or transverse direction is lowered. The water-soluble, adhesion-promoting coating is applied in the form of an aqueous dispersion to one or both surfaces of the film. Prior to the transverse stretching process, one or both surface(s) of the film is/are coated with the water-soluble adhesion promoting and steam-sterilizable layer. The coating is applied in the form of an aqueous dispersion. Preferred Condition: The longitudinal stretching temperature i80-130[deg]C, the transverse stretching temperature is 80-135[deg]C, the longitudinal stretching ratio is 2.5-4, and the transverse stretching ratio is 3.5-4. #CMT#EXAMPLE : #/CMT# N-2-(Aminoethyl)-3-aminopropyltrimethoxysilane (AEAPTMS) was dispersed at 2 wt.% in customary tap water. For this, 5% strength acetic acid was added at 0.2 wt.% in order to facilitate hydrolysis. Chips composed of polyethylene terephthalate were dried at 160[deg]C to a residual moisture level below 50 ppm and fed to the extruder for the base layer B. A monoaxially oriented film was obtained via extrusion, followed by stepwise longitudinal orientation. The longitudinally stretched film was corona treated, using corona discharge equipment, and was then coated by the reverse gravure method with the hydrolyzed aminosilane solution. The corona-treated, longitudinally stretched, coated film was dried at 110[deg]C. The film was then stretched transversely in order to produce a biaxially oriented film. The thickness of the stretched film was 55 mu m. The biaxially oriented film was then heat-set at 230[deg]C. The dry application weight of the coating was 2.5 mg/m2>. The base layer B was composed of 85 wt.% polyethylene terephthalate and 15 wt.% polyethylene terephthalate masterbatch. A single-layer film was obtained with very good optical properties, with low coefficient of friction, with very good processing performance, and with very good winding quality. The film exhibited the desired behavior when peeled from the cup. The film did not tear during this process, and it exhibited no tendency to delaminate.</p> |
