Multilayer rotational moulding

Abstract

This invention discloses a multilayer article prepared by rotational moulding that comprises: a) a layer A that is a polyolefin(PO)-based layer prepared from a composition comprising:—from 40 to 100 wt % of polyolefin (PO) or a mixture thereof and—from 60 to 0 wt % of a functionalised polyolefin (FPO) or of a PO grafted to a non-polyolefin (NPO) in the form of a block copolymer (PO)g-NPO); b) a layer B comprising:—a PO that is dissimilar from that of layer A or a NPO or a mixture thereof; —optionally a FPO or a (PO-g-NPO); c) optionally a layer C prepared from a polymer that is dissimilar from that of layer A and that is similar to or dissimilar from that of layer B and is adjacent to layer A and/or layer B and, if present, is characterised in that it has good adhesion to layer A and/or to layer B and is not a blend of layer A and layer B. It also discloses a method for preparing these articles.

1 - 14 . (canceled)  
     
     
         15 . A multilayer article prepared by rotational molding comprising: 
 (a) a primary layer A prepared from a composition comprising at least 40 wt. % of a first polymer component comprising a non-fimctionalized polyolefin no more than 60 wt. % of a second polymer component comprising a functionalized polyolefin having reactive functional units with acid, anhydride or epoxy functions, or of a non-functionalized polyolefin (PO) grafted to a non-olefinic polymer (NPO) in the form of a block copolymer ((PO)g-NPO); and    (b) a secondary layer B prepared from a composition comprising at least one of an olefin polymer different from that of layer A and a non-olefinic polymer.    
     
     
         16 . The multilayer article of  claim 15  wherein the secondary layer B further comprises a functionalized polyolefin having reactive functional units with acid, anhydride or epoxy functions, or a non-functionalized polyethylene (PO) grafted to a non-olefinic polymer (NPO) in the form of a block copolymer ((PO)g-NPO).  
     
     
         17 . The multilayer article of  claim 15  further comprising a tertiary layer C prepared from a composition comprising a polymer which is different from the composition of layer A and has good adhesion to at least one of layer A or layer B and is adjacent to at least one of layer A and B.  
     
     
         18 . The multilayer article of  claim 17  wherein the primary and secondary layers A and B are adjacent to one another and the tertiary layer C is adjacent to one of the primary layers A and B and is not interposed between said primary and said secondary layers.  
     
     
         19 . The multilayer article of  claim 15  wherein said primary layer A comprises polyethylene or polypropylene prepared with a Ziegler-Natta or metallocene-based catalyst system.  
     
     
         20 . The multilayer article of  claim 15  wherein said primary layer A comprises at least 75 wt. % of a metallocene-produced polyethylene and no more than 25 wt. % of a functionalized polyethylene.  
     
     
         21 . The multilayer article of  claim 20  wherein said metallocene-produced polyethylene is produced with a metallocene catalyst component having a bis(tetrahydroindenyl) or bis(n-butyl-cyclopentadienyl) ligand structure.  
     
     
         22 . The multilayer article of  claim 15  wherein said primary layer A comprises at least 75 wt. % of an isotactic or syndiotactic homopolymer or copolymer of propylene and no more than 25 wt. % of a functionalized polypropylene.  
     
     
         23 . The multilayer article of  claim 15  wherein said secondary layer B is formed of a composition comprising a polyamide in an amount within the range of 75-100 wt. % of said composition.  
     
     
         24 . The multilayer article of  claim 23  wherein said polyamide is a condensation product of an amino acid and a lactam or of a diamine and a dicarboxylic acid.  
     
     
         25 . The multilayer article of  claim 24  wherein said polyamide is a diamine polyamide.  
     
     
         26 . The multilayer article of  claim 23  wherein secondary layer B further comprises a functionalized polyolefin or a polyolefin-graft-polyamide amide block copolymer in an amount of no more than 25 wt. %.  
     
     
         27 . The multilayer article of  claim 15  wherein said primary layer A is prepared from a composition comprising polyethylene or polypropylene and a functionalized polyolefin, and layer B is prepared from a composition comprising polyamide or a fluoropolymer containing functional groups selected from the group consisting of an acid, anhydride, alcohol, amine and an epoxy.  
     
     
         28 . The multilayer article of  claim 15  wherein said secondary layer B is prepared from a polymer selected from the group consisting of a thermoplastic polyester, liquid crystal polymer, fluoropolymer, polycarbonate, acrylic, polyamide, aromatic or aliphatic polyketone, polyether ketone, polyethylene vinyl alcohol, and a polyphenylene sulfide.  
     
     
         29 . The multilayer article of  claim 15  wherein each of said layers A and B has a thickness of at least 0.5 mm.  
     
     
         30 . The multilayer article of  claim 15  wherein said primary layer is prepared from a composition comprising polyethylene, isotactic polypropylene or syndiotactic polypropylene in an amount within the range of 70-98 wt. % and a functionalized polyolefin in an amount within the range of 2-30 wt. %.  
     
     
         31 . The multilayer article of  claim 30  wherein said primary layer comprises said polyethylene, isotactic polypropylene or syndiotactic polypropylene in an amount within the range of 80-95 wt. % and said functionalized polyolefin in an amount within the range of 5-20 wt. %.  
     
     
         32 . A method for preparing a multilayer rotationally molded article comprising: 
 (a) providing a primary layer composition comprising at least 40 wt. % of a first polymer component comprising a non-functionalized polyolefin no more than 60 wt. % of a second polymer component comprising a functionalized polyolefin having reactive functional units with acid, anhydride or epoxy functions, or of a non-functionalized polyolefin (PO) grafted to a non-olefinic polymer (NPO) in the form of a block copolymer ((PO)g-NPO);    (b) providing a secondary layer composition comprising at least one of an olefin polymer different from that of the primary layer composition and a non-olefinic polymer;    (c) supplying said primary layer and said secondary layer composition into the cavity of a rotational mold in one shot; and    (d) operating said rotational mold under temperature conditions above the melting temperature of said primary layer and secondary layer compositions and thereafter cooling said rotational mold to produce a multilayer article.    
     
     
         33 . The method of  claim 32  for preparing a two-layer rotomolded article wherein layer A is the outer layer and is a polyethylene composition and layer B is the inner layer and is polyamide, polyvinylidene fluoride, or fluoropolymer-containing functional groups, further comprising: 
 (a) providing a particulate primary layer polyethylene composition comprising from 70-98 wt. % of polyethylene and from 2-30 wt. % of functionalized polyethylene, said polyethylene composition having an average particle diameter (DPE) and a melting point of less than 145° C.;    (b) providing a particulate secondary layer composition comprising polyamide, polyvinylidene fluoride or a functional fluoropolymer having an average particle diameter (DPA) and a melting point of at least 145° C., wherein the ratio DPE/DPA is no more than 2:3 and the melting point of the primary layer composition is at least 15° C. lower than the melting point of the secondary layer composition;    (c) physically mixing said primary and secondary layers;    (d) feeding the mixture formed in subparagraph (c) to a rotational mold under rotation; and    (e) retrieving the rotomolded article from said mold.    
     
     
         34 . A process for preparing a two-layer rotomolded article comprising an outer layer A formed of a polyethylene composition comprising polyethylene and a functionalized polyolefin having reactive functional units with acid, anhydride or epoxy functions or a non-functionalized polyolefin (PO) grafted to a non-olefinic polymer (NPO) in the form of a block copolymer ((PO)g-NPO), and an inner layer B formed of a polyamide, a polyvinylidene fluoride, or a fluoropolymer-containing functional group: 
 (a) supplying the polyethylene composition for layer A to a rotational mold;    (b) increasing the peak internal air temperature in said mold to a temperature that is from 15-50° C. higher than the melting temperature of the layer A composition in order to fully melt said layer A composition;    (c) adding the layer B composition to said mold by means of a drop-box;    (d) increasing the peak internal air temperature in said mold to a temperature that is greater than the melting temperature of said layer B composition in order to fully melt said layer B composition;    (e) cooling said mold with water spray in order to solidify said layers A and B; and    (f) retrieving the rotomolded article from said mold.