Simplified method of producing biodegradable aliphatic polyesters

Abstract

A method of synthesizing biodegradable aliphatic polyesters from one or more aliphatic dicarboxylic acids or diesters of the said acids and one or more linear or branched aliphatic glycols, comprising a first esterification or transesterification step and a second deglycolation under vacuum step, in which the catalyst is monobutylstannoic acid both for the esterification or transesterification step and for the deglycolation under vacuum step.

1 . A method of synthesizing biodegradable aliphatic polyesters from one or more aliphatic dicarboxylic acids or diesters of the said acids and one or more linear or branched aliphatic glycols, comprising a first esterification or transesterification step and a second deglycolation under vacuum step, in which the catalyst is monobutylstannoic acid both for the esterification or transesterification step and for the deglycolation under vacuum step.  
     
     
         2 . A method according to  claim 1 , in which the esterification or transesterification step is carried out at atmospheric pressure, at temperatures of between 180° C. and 230° C., and in a stream of nitrogen, until distillation of the by-product is complete.  
     
     
         3 . A method according to any one of the preceding claims, in which the deglycolation step is carried out in a dynamic vacuum of <1 mm Hg and at temperatures of between 220° C. and 250° C.  
     
     
         4 . A method according to any one of the preceding claims, in which the catalyst is added before the deglycolation step.  
     
     
         5 . A method according to  claim 4 , in which the catalyst is added at the beginning of the esterification or transesterification step.  
     
     
         6 . A method according to any one of the preceding claims, for the synthesis of poly(alkylene-sebacates).  
     
     
         7 . A method according to  claim 6 , in which the saturated aliphatic polyester produced is polyethylene sebacate, polybutylene sebacate, polyhexamethylene sebacate, or polydecamethylene sebacate.  
     
     
         8 . A method according to any one of the preceding claims, in which the aliphatic glycol is used in quantities of between 1 and 1.5 moles per mole of diacid or diester.  
     
     
         9 . A method according to any one of the preceding claims, in which the saturated aliphatic polyester may contain up to 10% in moles of aliphatic hydroxy-acids.  
     
     
         10 . A method according to any one of the preceding claims, in which the hydroxy-acid is constituted by glycolic, hydroxybutyric, hydroxycaproic, hydroxyvaleric, 7-hydroxyheptanoic, 8-hydroxyoctanoic, 9-hydroxynonanoic, lactic, ricinoleic, or 9,10-dihydroxystearic acid.  
     
     
         11 . A method according to any one of-the preceding claims, in which the saturated aliphatic polyester may contain up to 1% in moles of trifunctional or polyfunctional comonomers.  
     
     
         12 . A method according to any one of the preceding claims, in which the monobutylstannoic acid catalyst is added in quantities of between 0.5-10 −4  and 5-10 −3  moles cat./mole dicarboxylic acid.  
     
     
         13 . A method according to  claim 12 , in which the monobutylstannoic acid catalyst is added in quantities of between 1-10 −4  and 2.5-10 −3  moles cat./mole dicarboxylic acid.  
     
     
         14 . Polyesters produced by a method according to the preceding claims, with inherent viscosities of between 0.8 and 1.5 dl/g, preferably between 0.9 and 1.3 dl/g and MFRs of between 0.1 g/10 min and 70 g/10 min, preferably between 2 g/10 min and 30 g/10 min.  
     
     
         15 . Polyesters according to  claim 14 , wherein the thermal stability measured as viscosity decrease is less than 10%.  
     
     
         16 . Polyesters according to  claim 15 , wherein the catalyst has been added in quantity less than 2.5×10 −3  moles cat./mole dicarboxylic acid.  
     
     
         17 . Polyesters according to each one of claims  14 - 16 , wherein the biodegradability is higher than 60% in 180 days.  
     
     
         18 . Polyesters according to  claim 17 , wherein the biodegradability is higher than 90% in 180 days.  
     
     
         19 . Use of polyesters according to any of the preceding claims for: 
 coatings produced by extrusion-coating,    multi-layer laminates with layers of paper, plastics material or paper/plastics material, aluminium and metallized films,    films as such and multi-layer films with other polymers materials,    sacks for organic refused and for grass cuttings with periods of use longer than 1 week,    single-layer and multi-layer food packaging comprising containers for milk, yoghurt, cheeses, meat and beverages, in which the layer in contact with the food or beverage is formed by the aliphatic polyester,    composites with gelatinized or destructured starch, and/or completed starch or natural starch as a filler,    mono-directional and bi-directional films, shrink films, stretch films,    semi-expanded and expanded products produced by physical and/or chemical means, by extrusion, injection, or agglomeration of pre-expanded particles,    expanded sheet and expanded containers for foods, for drugs, and for fast food,    fibres, fabrics and non-woven fabrics in the hygiene, sanitary and clothing fields,    composites with mineral and vegetable fillers,    thermoformed sheets for the food or fast-food packaging fields,    bottles for the food, cosmetics and pharmaceutical fields,    fishing nets,    containers for fruit and vegetables,    extruded sections usable in the fast-food field and irrigation pipes in the agricultural field.