Solar-reactive mulch film

Abstract

A solar reactive mulch film comprising one or more layers of heat shrink material pre-strained at a predetermined temperature and tension. Immediately cooling the pre-strained layers retains molecular deformation stresses in the material which facilitate shrinkage but not expansion on exposure to solar radiation. The mulch film adapted to be laid over longitudinal growing beds and held tautly by burying its side edges in soil. Exposure of uncovered portions of film to solar radiation causes shrinkage in one or more directions whereby in combination with the weight of the soil holding it down, maintains tautness of the mulch over a growing period. Methods of manufacture and use of the same.

1 - 20 . (canceled) 
     
     
         21 . A method of creating a solar-reactive agricultural mulch film, comprising:
 heating one or more polymers beyond a melting temperature of each polymer to produce one or more melted polymers, wherein one or more of the polymers is a linear low density polyethylene (LLDPE) and/or a metallocene linear low density polyethylene (mLLDEP) having dispersed therein carbon black particles in an amount that ranges between 2% and 8% by weight;   extruding one or more of the melted polymers to produce a film that includes one or more layers of LLDPE and/or mLLDPE having dispersed therein the carbon black particles;   heating the film to a stretching temperature;   stretching, at the stretching temperature, the film in a longitudinal direction beyond a yield point of each of one or more of the layers of LLDPE and/or mLLDPE such that main chain molecules of LLDPE and/or mLLDPE and/or side branched molecules of LLDPE and/or mLLDPE in each of the one more layers of LLDPE and/or mLLDPE are elongated in the longitudinal direction;   cooling the stretched film;   maintaining a stretching tension throughout the stretched film while cooling the stretched film such that resultant plastic deformation stresses, resulting from stretching beyond the yield point, are retained and each of the one or more layers of LLDPE and/or mLLDPE does not shrink until one or more of the layers of LLDPE and/or mLLDPE having dispersed therein the carbon black particles to absorb radiant energy from sunlight and convert the radiant energy to heat, such that a surface temperature of one or more of the layers of LLDPE and/or mLLDPE is raised to at least a shrinking temperature of at least 40 degrees Celsius.   
     
     
         22 . The method of creating the solar-reactive agricultural mulch film of claim  1 , wherein the extruding further comprises:
 extruding one or more melted polymers through a circular die;   drawing one or more of the extruded polymers upwards as a bubble;   cooling and solidifying the collapsed tube by a cooling air ring; and   collapsing the bubble into a tubular configuration through a set of collapsing boards.   
     
     
         23 . The method of creating a solar-reactive agricultural mulch film of claim  1 , wherein the extruding further comprises:
 extruding one or more melted polymers through a flat die; and   passing the one or more of the extruded polymers onto chilled rollers wherein it cools and solidifies.   
     
     
         24 . The method of creating the solar-reactive agricultural mulch film of claim  1 , further comprising adding, to one or more of the polymers, at least one material selected from a group comprising an anti-oxidation additive, an ultraviolet light stabilizer, an ultraviolet light absorber, a plasticizer, and a lubricant. 
     
     
         25 . The method of creating the solar-reactive agricultural mulch film of claim  1 , wherein the film is heated to a stretching temperature that ranges from between 20 degrees Celsius and 120 degrees Celsius. 
     
     
         26 . The method of creating the solar-reactive agricultural mulch film of claim  1 , wherein the film is heated to a stretching temperature that ranges from between 40 degrees Celsius and 90 degrees Celsius. 
     
     
         27 . The method of creating the solar-reactive agricultural mulch film of claim  1 , wherein the film is heated to a stretching temperature that ranges from between 60 degrees Celsius and 70 degrees Celsius. 
     
     
         28 . The method of creating the solar-reactive agricultural mulch film of claim  1 , wherein the stretching includes stretching using a machine direction orientation machine having a heated infeed nip roller and a chilled outfeed nip roller rotating at a faster velocity than the infeed nip roller such that the outfeed nip roller has a surface linear velocity that is greater than the infeed nip roller, thereby stretching the film. 
     
     
         29 . The method of creating the solar-reactive agricultural mulch film of  claim 28 , wherein the outfeed nip roller surface linear velocity is between 1.25 and 10 times faster than the infeed nip roller linear speed velocity. 
     
     
         30 . The method of creating the solar-reactive agricultural mulch film of  claim 28 , wherein the infeed nip roller is rotated at the same velocity as a haul off nip roller employed during the extruding. 
     
     
         31 . The method of creating the solar-reactive agricultural mulch film of claim  1 , wherein the film is cooled to a temperature that ranges between 10 degrees Celsius and 40 degrees Celsius after the film has been stretched and while the resultant plastic deformation stresses are retained in the film. 
     
     
         32 . The method of creating the solar-reactive agricultural mulch film of claim  1 , wherein the film is cooled to a temperature that ranges between 15 degrees Celsius and 20 degrees Celsius after the film has been stretched and while the resultant plastic deformation stresses are retained in the film. 
     
     
         33 . The method of creating the solar-reactive agricultural mulch film of claim  1 , further including printing planting lines longitudinally along the film. 
     
     
         34 . The method of creating the solar-reactive agricultural mulch film of claim  1 , further including trimming away edges of the film to ensure the film is of substantially uniform thickness across its width. 
     
     
         35 . The method of creating the solar-reactive agricultural mulch film of claim  1 , further including rolling the film onto a spool. 
     
     
         36 . The method of creating the solar-reactive agricultural mulch film of claim  1 , further comprising subjecting the cooled film to a relaxing process to remove residual elastic forces entrapped in the film by some polymer molecules being stretched to below their yield point. 
     
     
         37 . The method of creating the solar-reactive agricultural mulch film of claim  1 , wherein the sheet is not subjected to any post orientation process designed to anneal, de-stress, or pre-relax shrinking forces entrapped in the plastic sheet. 
     
     
         38 . The method of creating the solar-reactive agricultural mulch film of claim  1 , wherein the film is a single wound sheet. 
     
     
         39 . The method of creating the solar-reactive agricultural mulch film of claim  1 , wherein the film is a double wound sheet bonded together to form a single sheet. 
     
     
         40 . The method of creating the solar-reactive agricultural mulch film of claim  1 , wherein the stretching includes aligning the main chain molecules of LLDPE and/or mLLDPE and/or the side branched molecules of LLDPE and/or mLLDPE in each of one more of the layers of LLDPE and/or mLLDPE.