Methods of forming an article comprising melt-processable thermoplastic compositions
Methods of making articles are described comprising the steps of applying a capstock material over a layer of a substrate material and then calendaring said capstock material and said substrate material with calendaring rolls to form an article, wherein said capstock material contacts said calendar rolls for a shorter period of time than said substrate material. The capstock material comprises a melt-processable thermoplastic composition comprising a) 50-99.5 wt. % of a melt-processable thermoplastic polymer and b) 0.5-50 wt. % of a particulate polymer comprising the residues of a monomer mixture comprising 50-100 wt. % of MMA, at least 0-50 % of an ethylenically unsaturated comonomer comprising at least one alkyl acrylate or methacrylate and 0-10 wt. % of a copolymerisable cross-linking monomer said particles having a maximum dimension of 5 mm.
1. A method of forming an article which includes a substrate and a capstock material, wherein said substrate material comprises a polymer which is different than the capstock material and said capstock material comprises a melt-processable thermoplastic composition comprising:
(a) 50-99.5 wt % of a melt-processable thermoplastic polymer; and
(b) 0.5 to 50 wt % of a particulate polymer comprising a homopolymer of methyl methacrylate or a copolymer comprising the residues of a monomer mixture comprising at least 50 wt % methyl methacrylate and up to 50 wt % of a copolymerisable acrylic comonomer comprising at least one alkyl acrylate or methacrylate and 0 to 10 wt % of a copolymerisable cross-linking monomer, said particles having a maximum dimension of 5 mm and having a weight averaged diameter of between 100 μm and 500 μm;
the method comprising the steps of applying the capstock material over a layer of the substrate material and then calendaring said capstock material and said substrate material with calendaring rolls to form said article, wherein said capstock material contacts said calendar rolls for a shorter period of time than said substrate material.
2. A method as claimed in claim 1 wherein said particulate polymer further includes at least 0.1 wt % to 10 wt % of a copolymerisable cross-linking monomer.
3. A method as claimed in claim 2 wherein the particulate polymer comprises a copolymer formed from the residues of a monomer mixture comprising 70 to 95 wt % methyl methacrylate, 5 to 30 wt % of said copolymerisable acrylic comonomer and 0.1 to 5 wt % of said copolymerisable cross-linking monomer.
4. A method as claimed in claim 3 wherein said copolymerisable acrylic comonomer of the particulate polymer comprises at least one alkyl acrylate.
5. A method as claimed in claim 4 wherein said alkyl acrylate is selected from the group consisting of ethyl acrylate or butyl acrylate.
6. A method as claimed in claim 3 wherein said copolymerisable acrylic comonomer is present in an amount of at least 12 wt % and less than 18 wt % of said particulate polymer.
7. A method as claimed in claim 2 wherein said particulate polymer comprises a copolymer comprising 5 wt % and less than 20 wt % of said copolymerisable acrylic comonomer and at least 0.3 wt % and 1 wt % or less of said copolymerisable cross-linking monomer.
8. A method as claimed in claim 1 wherein the particulate polymer comprises a copolymer and said copolymerisable acrylic comonomer comprises at least one alkyl acrylate.
9. A method as claimed in claim 8 wherein said alkyl acrylate is selected from the group consisting of ethyl acrylate or butyl acrylate.
10. A method as claimed in claim 8 wherein said copolymerisable acrylic comonomer is present in an amount of at least 12 wt % and less than 18 wt % of said particulate polymer.
11. A method as claimed in claim 1 wherein said particles have a maximum dimension which is less than 1 mm.
12. A method as claimed in claim 1 wherein the weight average diameter of said particles of the particulate polymer is greater than 150 μm as measured in accordance with ASTM D1921.
13. A method as claimed in claim 1 wherein at least 20 wt % of said particles of the particulate polymer are between 60 (250 μm) and 80 (177 μm) mesh.
14. A method as claimed in claim 2 wherein said particulate polymer comprises a copolymer formed from the residues of a monomer mixture comprising at least 79.9 wt % methyl methacrylate.
15. A method as claimed in claim 7 wherein said particulate polymer comprises a copolymer formed from the residues of a monomer mixture comprising at least 79.9 wt % methyl methacrylate.
16. A method as claimed in claim 1 wherein said particulate polymer is present in an amount of at least 3 wt % and less than 20 wt % of said melt-processable thermoplastic composition.
17. A method as claimed in claim 1 wherein the melt-processable thermoplastic polymer forms a matrix and is a polymethyl methacrylate homopolymer or a copolymer derived from a monomer mixture comprising at least 60 wt % methyl methacrylate and up to 40 wt % of at least one other copolymerisable alkyl acrylate or methacrylate.
18. A method as claimed in claim 7 wherein the melt-processable thermoplastic polymer forms a matrix and is a polymethyl methacrylate homopolymer or a copolymer derived from a monomer mixture comprising at least 60 wt % methyl methacrylate and up to 40 wt % of at least one other copolymerisable alkyl acrylate or methacrylate.
19. A method as claimed in claim 1 wherein the melt-processable thermoplastic composition is formed by mixing said melt-processable polymer and said particulate polymer by extrusion under conditions such that said particles of the particulate polymer are broken down.
20. A method as claimed in claim 1 wherein a surface of the article formed of said melt-processable thermoplastic composition has a surface gloss measured at 75° observation angle (according to ASTM D3679) of less than 65.
21. A method as claimed in claim 1 wherein said article is a component for use in construction and is co-extruded component wherein said substrate is made of PVC, HIPS, or ABS.