Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2001-04-27
2004-01-06
Mullis, Jeffrey (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S071000, C525S080000
Reexamination Certificate
active
06673868
ABSTRACT:
The present invention relates to polymeric compositions which can be melt processed to provide plastic films or layers having excellent optical, printing, weathering, and tensile impact resistance characteristics. The present invention also relates to processes for preparing plastic films of the compositions of the present invention. The present invention also relates to composite articles having the plastic films of the present invention and an underlying substrate.
Poly(vinyl chloride) resin (“PVC”) has a combination of properties which make it particularly useful as a structural material which can be readily extruded or formed into a variety of articles; for example as siding for buildings, shutters, profiles for window and door frames, rain carrying systems (e.g., gutters and downspouts), and fencings.
Unfortunately, PVC compositions have relatively poor weatherability characteristics, particularly poor color retention in darker grade colors. The color is imparted to the PVC composition, for instance, by the use of colorants such as pigments or dyes, but exposure to sunlight causes unappealing changes in the colors. Poor weathering characteristics also causes reduction in tensile impact resistance leading to embrittlement and cracking and/or mechanical failure of the articles prepared from such compositions. Thus, there is a need for improving the weathering characteristics of such materials.
One solution is to provide a laminated film or coextruded layer for PVC profile (e.g., used in building and construction applications), the film or coextruded layer having transparency, weatherability, impact resistance, good printability, and adhesion to the PVC. The film or coextruded layer can also provide UV barrier capabilities allow the use of less expensive nonweatherable substrate materials, such as PVC.
The capstock generally is much thinner than the substrate plastic, typically being about 0.1 to about 25% of the total thickness of the composite. Suitable polymeric compositions for use as capstock must be melt processable using calendering, extrusion, or coextrusion processes to forms films or layers. Capstocks which are melt calendered or extruded into a film are subsequently laminated to the substrate. Alternatively, if the substrate is comprised of a thermoplastic resin such as PVC, the polymer composition can be co-extruded with the substrate. As well, the polymer compositions must adhere well to the substrate and have excellent weathering characteristics, high tensile impact resistance, and good clarity (low haze).
One remedy has been to apply a protective polymethyl methacrylate (“PMMA”) homopolymer, or copolymer-based films or layers (“capstock”) over PVC articles (“substrate”) to improve its weathering characteristics. U.S. Pat. No. 5,318,737 to Rohm and Haas Company describes a method for preparing a plastic composite by feedblock coextrusion of a molten acrylic based capstock overlying and integrally bonded to an underlying structural plastic ply. The composition of the capstock contains from about 40 to about 88 wt. % of an acrylic polymer having a molecular weight of at least about 125,000 g/mol, and from about 12 to about 60 wt. % of an acrylate-based impact modifier resin in the form of discrete multi-layered polymeric particles.
Japanese Kokai Publication Hei 9-100,385 discloses acrylic polymer compositions having an acrylic resin, a lubricant, and optionally a plasticizer and vinyl chloride resin for calendering molding sheets and films having weatherability, transparency, and high tensile impact resistance for applying to wallpaper and outdoor signs. This publication discloses that a lubricant allows the acrylic resin to be calendered into film and sheet by reducing sticking of the acrylic resin to the calender rolls, thereby improving the metal release property. However, I have discovered that the range of various lubricants disclosed in this publication (e.g., all-acrylic polymers, calcium stearate, and polyethylene wax) cause high haze in polymer compositions.
I have now discovered new polymeric compositions which can be calendered or extruded into film and sheet, or alternatively coextruded with thermoplastic resins, to provide a protective capstock layer having superb weatherability, tensile impact resistance, and transparency (low haze). Specifically, I have discovered that particular vinyl aromatic (“VA”) copolymer lubricants in combination with processing aid polymers enable acrylic core-shell graft-co-polymers to be calendered or extruded into film and sheet having superb weatherability, tensile impact resistance, and transparency (low haze).
I have also discovered that the new polymeric compositions can further contain acrylic impact modifiers to substantially increase its tensile impact resistance without decreasing its weatherability. These impact-modified compositions can also be calendered and extruded into film and sheet, and can be coextruded with thermoplastic resins to provide capstock film and capped articles.
Therefore, one object of the present invention is to provide a polymeric composition which can be calendered or extruded into film or sheet, or which can be coextruded with thermoplastic resins, the film or sheet having superb weatherability, tensile impact resistance, and transparency (low haze).
A second object of the invention is to provide a polymeric composition which can be calendered or extruded into film or sheet, or which can be coextruded with thermoplastic resins, the film or sheet having superb weatherability and exceptional tensile impact resistance.
A third object of the invention is to provide a plastic film or sheet having superb weatherability, tensile impact resistance, and transparency (low haze).
A fourth object of the invention is to provide composite articles having superb weatherability and excellent tensile impact resistance.
A fifth object of the invention is to provide a process for preparing the plastic films of the present invention.
These and other objects, as will become apparent from the following disclosure, are achieved by the present invention.
In the present invention, the problem of providing polymeric compositions which can be calendered or extruded into film or sheet, or which can be coextruded with thermoplastic resins, the film or sheet having superb weatherability, tensile impact resistance, and transparency (low haze) is solved by providing particular vinyl aromatic copolymer lubricants in combination with particular processing aid polymers that enable the the melt-processing (calendering, extrusion, or coextrusion) of acrylic core-shell graft-co-polymer matrix resins.
In a first aspect of the present invention, there is provided a polymeric composition, comprising:
(A) 100 parts by weight of an acrylic core-shell graft-co-polymer, comprising
(i) from 20% to 70% by weight of an acrylic rubbery core polymer based on the total weight of the acrylic core-shell graft-co-polymer and
(ii) from 30% to 80% by weight of an acrylic hard shell polymer based on the total weight of the acrylic core-shell graft-co-polymer;
(B) from 1 to 40 parts by weight of a processing aid polymer, wherein the molecular weight of the processing aid polymer is greater than 1 million g/mol; and
(C) from 0.1 to 10 parts by weight of a VA lubricating copolymer, comprising
(i) from 20% to 70% by weight of polymerizable units derived from one or more vinyl aromatic monomers; and
(ii) from 30% to 80% by weight of polymerizable units derived from one or more ethylenically unsaturated monomers,
wherein the molecular weight of the VA lubricating copolymer is in the range of from 20,000 g/mol to 1 million g/mol.
In a second aspect of the present invention, there is provided a polymeric composition, comprising:
(A) 100 parts by weight of an acrylic core-shell graft-co-polymer, comprising
(i) from 35% to 45% by weight of an acrylic rubbery core polymer based on the total weight of the acrylic core-shell graft-co-polymer; and
(ii) from 55% to 65% by weight of an acrylic hard shell polymer based on the total weight of the acrylic core
Hemenway Carl P.
Mullis Jeffrey
Rohm and Haas Company
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