Transparent films

Abstract

The invention relates to an optically transparent polymer film or extrudate product made of a polymer composition comprising a semi-crystalline polyamide having a melting temperature of at least 270° C. or a blend of the semi-crystalline polyamide (A) and a second polymer (B), and optionally at least one additive, wherein the semi-crystalline polyamide (A) is present in an amount of more than 50 wt. %, relative to the total weight of the polymer composition, the polymer composition in the optically transparent polymer film or extrudate product has a melting temperature (Tm-C) in the range of 270-340 ° C., and wherein the film or a part of the extrudate product has a haze of less than 12% and a light transmittance, of at least 88% measured with the method according to ASTM D1003A.

1 . Optically transparent polymer film or extrudate product made of a polymer composition comprising a semi-crystalline polyamide (A) wherein the semi-crystalline polyamide (A) has a melting temperature (Tm-A) of at least 270° C. and is present in an amount of respectively at least 60 wt. % in case the semi-crystalline polyamide (A) consists of a semi-aromatic semi-crystalline polyamide or of a blend of a semi-aromatic semi-crystalline polyamide and an aliphatic semi-crystalline polyamide, or at least 75 wt. % the case the semi-crystalline polyamide (A) consists of an aliphatic semi-crystalline polyamide, wherein the wt. % is relative to the total weight of the polymer composition, the polymer composition has a melting temperature (Tm-C) of at least 270° C., and the film or a part of the extrudate product has a haze of less than 12% and a light transmittance of at least 88%, measured with the method according to ASTM D1003A. 
     
     
         2 . Film or product according to  claim 1 , wherein the polymer composition has a melting enthalpy, of at least 25 J/g, measured according to ASTM D3418-03 by DSC in the second heating run with a heating rate of 10° C./min. 
     
     
         3 . Film or product according to  claim 1 , wherein the semi-crystalline polyamide (A) is a semi-crystalline semi-aromatic copolyamide comprising repeat units derived from:
 (a) 25-45 mole % terephthalic acid,   (b) 5-25 mole % of an aromatic dicarboxylic acid different from terephthalic acid, and/or an aliphatic dicarboxylic acid,   (c) 5-30 mole % of an diamine chosen from the group consisting of ethylene diamine, trimethylene diamine, tetramethylene diamine and pentamethylene diamine,   (d) 20-45% of a diamine comprising at least 6 C-atoms, and optionally   (e) 0-10 mole % of one or more aminocarboxylic acids and or lactams   (f) 0-3 mole % of compounds being mono-functional or tri-functional in amino and/or carboxylic acid groups;   wherein the mole % of each of a-f is relative to the total of a-f.   
     
     
         4 . Film or product according to  claim 1 , wherein the semi-crystalline polyamide (A) is polytetramethylene adipamide, or a copolyamide thereof, comprising (i) repeat units derived form tetramethylene diamine and adipic acid and (ii) repeat units derived from other diacids, diamines and/or amino carboxylic acids and/or lactams, wherein the repeat units (i) derived from tetramethylene adipamide are present in an amount of at least 75 wt. %, relative to the total weight of the copolyamide. 
     
     
         5 . Film or product according to  claim 1 , wherein the polymer composition comprises at least one other polymer and/or at least one additive. 
     
     
         6 . Film or product according to  claim 1 , wherein the polymer composition comprises an amorphous semi-aromatic polyamide and/or a semi-crystalline aliphatic or semi-aromatic polyamide having a melting temperature below 270° C. 
     
     
         7 . Film or product according to  claim 1 , wherein the polymer composition consists of
 (A) 60-100 wt. % of the semi-crystalline polyamide,   (B) 0-40 wt. % of at least one other polymer   (C) 0-10 wt. % of the at least one additive   wherein the wt. % are relative to the total weight of the polymer composition.   
     
     
         8 . Film or product according to  claim 1 , wherein the film or a part of the product has a thickness of at most 500 μm. 
     
     
         9 . Film or product according to  claim 1 , wherein the film or a part of the product has a haze of less than 5% and a light transmittance of at least 90% when measured according to ASTM D1003A. 
     
     
         10 . Process for preparing a transparent polymer film, comprising steps wherein
 (1) a polymer composition as according to  claim 1  is heated and melt-extruded through a slit die to form an extruded polymer layer;   (2) the extruded polymer layer is led over a chilling role having a temperature below 40° C., thereby forming a polymer film, and   (3) the polymer film is collected,   wherein the polymer film has a haze of less than 12% and a light transmittance of at least 88% when measured according to ASTM D1003A.   
     
     
         11 . Process according to  claim 10 , wherein the slit die and the chilling role are separated from each other by a distance of at most 1.3 cm and the chilling role has a surface temperature of at most 8° C., more preferably the chilling role is cooled with ice water. 
     
     
         12 . Process for after-treatment of a polymer film, wherein a transparent polymer film according to  claim 1  is subjected to a drawing step wherein the film is stretched, and/or a heat setting and/or an annealing step, wherein transparent polymer film, having a glass transition temperature (Tg) and a melting temperature (Tm), is heated to or kept for a certain period at a temperature between the Tg and Tm. 
     
     
         13 . Process for preparing an extrudate product comprising steps wherein
 i. a polymer composition as according to  claim 1  is melt extruded through a die;   ii. the extruded polymer composition is led through a quenching liquid having a temperature below 40° C., thereby forming a solid product, and   iii. the solid product is collected,   wherein the solid product comprises a part having a haze of less than 12% and a light transmittance of at least 88% when measured according to ASTM D1003A.   
     
     
         14 . Steam-sterilizable medical article comprising an extrudate product according to  claim 1 . 
     
     
         15 . Packaging materials or electrical or electronic components comprising a transparent polymer film according to  claim 1 .