| 摘要 |
Moisture-containing and moisture-emitting products normally subjected to refrigeration e.g. meat, poultry, fresh fruit, vegetables and flowers, bakery and dairy products, fish and seafoods are packaged in a polyolefin film formed by extrusion of a polyolefin resin at a temperature of from 550 DEG F. to 700 DEG F., a pressure of from 1,000 p.s.i. to 10,000 p.s.i. and a speed of at least 100 feet per minute, e.g. 100 to 600 feet per minute, coated with an antifogging coating capable of dispersing moisture condensed thereon into a thin transparent film. The extruded film may be drawn down to quench means at a draw-down time of at least 0.001 minutes, e.g. 0.001 to 0.1 minutes, and may be shielded from premature cooling during draw-down. The hot extruded film may be quenched rapidly. The film may be extruded on to a chill roll, an air knife being employed to force the film suddenly and rapidly against the chill roll. The polyolefin may have a density not greater than 0.923, e.g. 0.905 to 0.923, and may be polymers of ethylene or of propylene, from copolymers thereof, and from copolymers of ethylene and of propylene with other polymerizable monomers, examples of which are given. The anti-fogging coating may comprise at least one water-soluble cellulose ether, which may have at least one ether linkage per anhydro-glucose unit and at least one free hydroxyl group per anhydro-glucose unit, and may also include one or more water-soluble salts, e.g. inorganic salts, examples of which are given. The anti-fogging coating has a thickness of from 0.02 to 0.4 microns and may be applied to the film from aqueous solution or dispersion and thereafter dried. The coating composition may contain an anionic or non-ionic wetting agent, examples of which are given, and a water-soluble film-forming polymeric material such as resins, synthetic or natural gums, casein, pectin, algins, glues, gelatin, starch derivatives, polyacrylic acids, or mixtures thereof; carboxymethyl, carboxyethyl, hydromethyl or methylhydroxypopyl cellulose, polyvinyl pyrrolidone, and its copolymers, propylene glycol alginate, polyvinyl alcohol, polycarboxymethylene and polyoxyethylene. The composition is applied as a dispersion or solution, preferably in aqueous form, by dipping, spraying, brushing, roll coating, or gravure coating, excess being removed by squeeze rolls or doctor knives. The side of the polyolefin film that does not have the anti-fogging coating may be coated with various other coatings as desired.ALSO:A polyolefin film formed by extrusion of a polyolefin resin at a temperature of from 550 DEG F. to 700 DEG F., a pressure of from 1000 p.s.i. to 10,000 p.s.i. and a speed of at least 100 feet per minute, e.g. 100-600 feet per minute, is coated with an anti-fogging coating capable of dispersing moisture condensed thereon into a thin transparent film. The extruded film may be drawn down to quench means at a draw-down time of at least 0,001 minute, e.g. 0,001-0,1 minute, and may be shielded from premature cooling during drawdown. The hot extruded film may be quenched rapidly. The film may be extruded on to a chill roll, an air knife being employed to force the film suddenly and rapidly against the chill roll. The polyolefins may have a density not greater than 0,923, e.g. 0,905-0,923, and may be polymers of ethylene or of propylene, copolymers thereof, or copolymers of ethylene or of propylene with other polymerizable monomers, examples of which are given. The anti-fogging coating may comprise at least one water-soluble cellulose ether, which may have at least one ether linkage per anhydro-glucose unit and at least one free hydroxyl group per anhydro-gluoces unit, and may also include one or more water-soluble salts, e.g. inorganic salts, examples of which are given. The anti-fogging coating has a thickness of from 0,02 to 0,4 microns and may be applied to the film from aqueous solution or dispersion and thereafter dried. The coating composition may contain an anionic or non-ionic wetting agent, examples of which are given, and a water-soluble film-forming polymeric material, specified examples of which are resins, synthetic or natural gums, casein, pectin, algins, glues, gelatin, starch derivatives, polyacrylic acids, or mixtures thereof; carboxymethyl, carboxyethyl, hydroxymethyl or methylhydroxypropyl cellulose, polyvinyl pyrrolidone, and its copolymers, propylene glycol alginate, polyvinyl alcohol, polycarboxymethylene and polyoxyethylene. The composition is applied as a dispersion or solution, preferably in aqueous form, by dipping, spraying, brushing, roll coating, or gravure coating, excess being removed by squeeze rolls or doctor knives. The side of the polyolefin film that does not have the anti-fogging coating may be coated with various other coatings as desired. The coated film may be used for packaging moisture-containing and moisture-emitting products normally subjected to refrigeration such as meat, poultry, fresh fruit and vegetables, bakery and dairy products, fish, sea foods and fresh flowers.
|
