Solid state shear pulverization of multicomponent polymeric waste

Abstract

A method of making polymeric particulates wherein polymeric scrap material such as in the form of film waste is supplied to intermeshing pulverizer screws which are rotated to transport the polymeric material along their length and subject the polymeric material to solid state shear pulverization and in-situ polymer compatibilization. Uniform pulverized particulates are produced without addition of a pre-synthesized compatibilizing agent. The pulverized particulates are directly melt processable (as powder feedstock) and surprisingly yield a substantially homogeneous light color product. The polymeric film waste containing high proportions of LDPE yield molded articles of superior notched izod impact strength and elongation. Compatibilized polymeric particles can be formed even if the polymeric scrap material includes cellulose materials such as paper, cardboard and wood.

We claim:  
     
         1 . A method of preparing polymeric material comprising the steps of: 
 (a) providing a mixture of chemically distinct polymeric materials in the solid state, said mixture containing at least three chemically distinct polymeric materials and wherein low density polyethylene (LDPE) is present as the major component of said mixture;    (b) effecting a chemical change to said mixture by application of mechanical energy through solid state shear pulverization in the presence of cooling to maintain the polymeric materials in the mixture in the solid state during said change and thereby compatibilizing the mixture to form homogenous material upon effecting said chemical change; and    (c) discharging the resulting compatibilized polymeric material.    
     
     
         2 . The method of  claim 1 , wherein said mixture is provided in the form of chips, particles or flakes.  
     
     
         3 . The method of  claim 1 , wherein said polymeric material is discharged in the form of a powder.  
     
     
         4 . The method of  claim 1 , wherein the step of effecting a chemical change is effected by co-rotating, mechanical screws.  
     
     
         5 . The method of  claim 1 , wherein said mixture is provided from film waste.  
     
     
         6 . The method of  claim 5 , wherein said film waste comprises at least 50 wt. % LDPE.  
     
     
         7 . The method of  claim 5 , wherein said film waste comprises HDPE/LDPE/PP/PS/PVC in amounts of 5-25/50-75/5-25/0-10/0-10 percent by wt.  
     
     
         8 . The method of  claim 5 , wherein said mixture contains cellulosic material which is intimately bonded to at least a portion of said polymeric materials forming said mixture.  
     
     
         9 . The method of  claim 5 , wherein said mixture further contains 0-40 wt. % cellulosic material.  
     
     
         10 . The method of  claim 9 , wherein said cellulosic material is intimately bonded to said polymeric materials forming said mixture.  
     
     
         11 . The method of  claim 9 , wherein said mixture contains 0.5-15 wt. % of said cellulosic material.  
     
     
         12 . The method of  claim 9 , wherein said cellulosic material comprises paper, cardboard, wood, or mixture thereof.  
     
     
         13 . The method of  claim 2 , wherein said chips, particles, or flakes are formed by comminution of polymeric waste.  
     
     
         14 . The method of  claim 13 , wherein said plastic waste is a mixture of commingled, unsorted polymeric material, so as to form said mixture.  
     
     
         15 . The method of  claim 1 , wherein said mixture contains low density polyethylene (LDPE) as the major component and at least two polymeric materials selected from the group consisting of high density polyethylene (HDPE),  
       polypropylene (PP), polyethylene terephthalate (PET), polystyrene (PS) and polyvinyl chloride (PVC).  
     
     
         16 . The method of  claim 15 , wherein said mixture contains as a major component LDPE, and additionally each of HDPE, PP, PET, PS and PVC.  
     
     
         17 . The method of  claim 16 , wherein said mixture comprises HDPE/LDPE/PP/PET/PS/PVC in amounts of 10-30/30-50/10-20/5-15/5-20/4-15 percent by wt.  
     
     
         18 . The method of  claim 15 , wherein said mixture comprises LDPE as the major component and at least two additional polymeric materials selected from the group consisting of polypropylene, polystyrene and polyvinyl chloride.  
     
     
         19 . The method of  claim 18 , wherein said mixture is substantially devoid of high density polyethylene and polyethylene terephthalate.  
     
     
         20 . The method of  claim 18 , wherein said mixture comprises LDPE/PP/PS/PVC in amounts of 40-60/12-25/10-25/10-20 percent by wt.  
     
     
         21 . The method of  claim 15 , wherein said mixture may contain up to 2% by wt. each of additional polymeric materials.  
     
     
         22 . The method of  claim 15 , wherein said polymeric material is discharged as a powder.  
     
     
         23 . The method of  claim 5 , wherein said polymeric material is discharged as a powder.  
     
     
         24 . A compatibilized polymeric material formed by the method of  claim 1 .  
     
     
         25 . The compatibilized polymeric material of  claim 24  in the form of a powder.  
     
     
         26 . A compatibilized polymeric material formed by the method of  claim 5 .  
     
     
         27 . The method of  claim 1 , further comprising the steps of: (d) melting said discharged polymeric material; and (e) shaping said melted polymeric material by molding, extrusion or spray coating.  
     
     
         28 . The method of  claim 27 , wherein said melted polymeric material is shaped by injection molding, extrusion or blow molding.  
     
     
         29 . The method of  claim 3 , further comprising the steps of: (d) applying the powder of said polymeric material as a coating.  
     
     
         30 . The method of  claim 29 , wherein said polymeric material is applied as a powder coating.  
     
     
         31 . The method of  claim 1 , wherein said solid state shear pulverization is applied in the absence of a compatibilizing agent.  
     
     
         32 . The method of  claim 2 , wherein said mixture is provided at a rate of at least about 100 lbs. per hour.  
     
     
         33 . The method of  claim 5 , wherein said mixture is provided in the form of chips, particles or flakes.  
     
     
         34 . The method of  claim 33 , wherein said mixture is provided at a rate of at least about 100 lbs. per hour.  
     
     
         35 . A method of preparing polymeric material comprising the steps of: 
 (a) providing a mixture of chemically distinct polymeric materials in the solid state consisting essentially of film waste;    (b) effecting a chemical change to said mixture by application of mechanical energy through solid state shear pulverization in the presence of cooling to maintain the polymeric materials in the mixture in the solid state during said change and thereby compatibilizing the mixture to form homogenous material upon effecting said chemical change; and    (c) discharging the resulting compatibilized polymeric material, wherein articles molded from said compatibilized polymeric materials have a notched izod impact strength of at least 5.0 ft. lb./in.    
     
     
         36 . The method of  claim 35 , wherein articles molded from said compatibilized polymeric material have a notched izod impact strength of at least 8.0 ft. lb./in.  
     
     
         37 . The method of  claim 35 , wherein articles molded from said compatibilized polymeric material have an elongation of at least 100%.  
     
     
         38 . The method of  claim 35 , wherein said mixture contains at least 50 wt. % LDPE.  
     
     
         39 . The method of  claim 35 , wherein said mixture is provided in the form of chips, particles or flakes.  
     
     
         40 . The method of  claim 39 , wherein said chips, particles or flakes are formed by comminution of said film waste.  
     
     
         41 . The method of  claim 35 , wherein said compatibilized polymeric material is discharged in the form of a powder.  
     
     
         42 . The method of  claim 35 , wherein the step of effecting a chemical change is effected by co-rotating mechanical screws.  
     
     
         43 . The method of  claim 35 , wherein the step of effecting a chemical change is effected in the absence of a compatibilizing agent.  
     
     
         44 . The method of  claim 39 , wherein said mixture is provided at a rate of at least about 100 lbs. per hour.  
     
     
         45 . A method of preparing polymeric material comprising the steps of: 
 (a) providing a mixture of at least one polymeric material and cellulosic material in the solid state;    (b) effecting compatibilization of said mixture by application of mechanical energy through solid state shear pulverization in the presence of cooling to maintain the materials in the mixture in the solid state during said change, thereby compatibilizing the mixture to form homogenous material; and    (c) discharging the resulting compatibilized polymeric material.    
     
     
         46 . The method of  claim 45 , wherein said mixture contains 0.5 to 40 % by wt. cellulosic material.  
     
     
         47 . The method of  claim 45 , wherein said cellulosic material comprises paper, cardboard, wood or mixture thereof.  
     
     
         48 . The method of  claim 45 , wherein at least a portion of said cellulosic material is intimately bonded to said polymeric material forming said mixture.  
     
     
         49 . The method of  claim 45 , wherein said polymeric material is selected from the group consisting of HDPE, LDPE, PP, PET, PS, PVC and mixtures thereof.  
     
     
         50 . The method of  claim 49 , wherein said mixture contains at least two of said polymeric materials.  
     
     
         51 . The method of  claim 45 , wherein said mixture is provided in the form of chips, particles or flakes.  
     
     
         52 . The method of  claim 45 , wherein said polymeric material is discharged in the form of a powder.  
     
     
         53 . The method of  claim 45 , wherein the step of effecting a chemical change is effected by co-rotating mechanical screws.  
     
     
         54 . The method of  claim 50 , wherein said polymeric material is a mixture of commingled, unsorted polymeric waste.  
     
     
         55 . The method of  claim 45 , wherein the step of effecting a chemical change is effected in the absence of a compatibilizing agent.  
     
     
         56 . The method of  claim 45 , wherein said mixture is provided at a rate of at least about 100 lbs. per hour.  
     
     
         57 . A compatibilized polymeric material formed by the method of  claim 45 .  
     
     
         58 . A compatibilized polymeric material formed by the method of  claim 54 .  
     
     
         59 . A molded article comprising a thermoplastic polymer matrix having contained therein cellulosic particles.  
     
     
         60 . The molded article of  claim 59 , wherein said cellulosic particles are pulverized paper, wood or mixtures thereof mixed directly within said thermoplastic polymer matrix.  
     
     
         61 . The molded article of  claim 60 , wherein said thermoplastic polymer matrix is formed from comminuted thermoplastic polymeric scrap containing one or more thermoplastic polymers.  
     
     
         62 . The molded article of  claim 59  in the form of a thin film.  
     
     
         63 . The molded article of  claim 62 , wherein said thin film is transparent or translucent and wherein said cellulosic particles do not degrade the transparency of said film.  
     
     
         64 . The molded article of  claim 63 , wherein said cellulosic particles have a diameter of 1-100 microns.  
     
     
         65 . The molded article of  claim 64 , wherein said cellulosic particles have a diameter of 10-75 microns.  
     
     
         66 . The molded article of  claim 63 , wherein said thermoplastic polymer matrix and said cellulosic particles are formed from comminuted scrap.