Resumen
PURPOSE: A polymeric thermal film for use in agriculture is provided, which is highly opaque in the infrared region of the spectrum, without substantially interfering the transmission of the visible light necessary for the photosynthesis, thereby being used to cover for a green house or the soil. CONSTITUTION: The film comprises at least an 85% in weight of 85-99 wt% of a polyolefin; and 1-15 wt% of at least one compound (part A) selected from the group consisting of borates and borax stable to the treatment temperature, and at least one compound (part B) selected from the group consisting of silica, silicates, carbonates and sulfates. The ratio of the part A to the part B is 1:5 to 50:1 by weight. Preferably the polyolefin is polyethylene, a copolymer of ethylene and alkyl acrylate, a copolymer of ethylene and alkyl methacrylate, a poly(vinyl chloride) or their mixtures. Preferably the additive of the part A is zinc borate and the additive of the part B is a calcined kaolin or silica.
Reivindicaciones
1. A thermal polymeric film for agricultural use that comprises a polyolefin and a mixture of, at least, a compound selected from the group made up of the borates stable at the processing temperature and anhydrous borax (group A) and, at least, a compound selected from the group made up of silica, silicates, carbonates and sulfates (group B) . 2. A polymeric film according to claim 1, in which its composition contains between, approximately, an 85% and, approximately, a 99% in weight of a polyolefin and between, approximately, 1% and, approximately, 15% in weight of the mixture of the compounds of group A and group B. 3. A polymeric film according to claims 1 and 2, in which the weight ratio of the compounds of group A and group B is comprised between approximately 1:5 and approximately 50:1. 4. A polymeric film according to claims 1 to 3, in which said polyolefin is polyethylene, a copolymer of ethylene and an alkyl acrylate, a copolymer of ethylene and an alkyl methacrylate, PVC or mixtures of them. 5. A polymeric film according to claims 1 to 4, in which the additive of group A is zinc borate and the additive of group B is calcined kaolin. 6. A polymeric film according to claims 1 to 4, in which the additive of group A is zinc borate and the additive of group B is silica. 7. A polymeric film according to claims 1 to 6, in which the polyolefin is polyethylene. 8. A polymeric film according to claims 1 to 6 which also comprises additives selected from the group made up of antioxidants, light stabilizers, antidrip additives, antistatics, lubricants and their mixtures. 9. A polymeric film according to claims 1 or 2 in which said film is a single layer film or a multilayer film.
