Rigid vinyl polymer compositions, such as polyvinyl chloride compositions, are utilized for producing a variety of structural articles such as plastic pipe, siding, containers, and sheets. These rigid compositions are substantially unplasticized. Sheets are typically made by calendering which involves passing the material between rollers, Because the resulting sheets are typically used for blister packs and credit cards, a very clear final product is highly desirable,
In order to stabilize vinyl polymer against the decomposing influence of heat and light, tin stabilizers including organotin stabilizers such as organotin mercaptides and organotin sulfides are used to stabilize vinyl polymers.
Lubricants are also added to vinyl polymers to facilitate the extrusion or other melt processing of the structural articles produced, Lubricants are generally classified as external or internal lubricants, An external lubricant provides a lubricating layer between the plastic melt and the metallic surfaces of the processing equipment. The external lubricant serves to coat the individual particles of the polymeric resin and inhibits their adherence to the metallic surfaces. In contrast, an internal lubricant reduces the effective melt viscosity of the vinyl polymer at the processing temperatures in order to improve its flow properties during processing as well as to promote fusion. An internal lubricant is generally needed only for thin extrusions such as films and thin-walled pipe.
The suitability of lubricants for vinyl polymer is determined by the type of stabilizer used in the vinyl polymer. For example, the PLASTICS ADDITIVE HANDBOOK, 3rd Edition (Hanser Publishers 1990) teaches that oxidized polyethylene waxes are suitable lubricants for tin stabilized polyvinyl chloride sheets.
Known tin stabilized rigid polyvinyl chloride calendered sheet formulations include compositions such as:
______________________________________ Rigid 4-Cell Resin 100 phr Organotin Stabilizer 2.0 Acrylic Processing Aid 3.0 ______________________________________
which is disclosed by David Hurwitz, "The Use of Low Molecular Weight Polyethylene in Rigid PVC Lubrication", Society of Plastics Engineers, 31st Annual Technical Conference, 349 (May 1973), and
______________________________________ PVC 100 phr Processing Aid 1.5 Glycerol Mono-Oleate 1.0 Octyl Sn Stabilizer 1.6 Impact Modifier 5-10 A-C .RTM. 316 (oxidized homopolymer 0.05-0.3 polyethylene wax, acid number of 16) ______________________________________
which is disclosed in A-C.RTM. POLYETHYLENES FOR PVC by AlliedSignal Inc. (1986). See also Technical Data on A-C.RTM. Polyethylenes and Copolymers for Plastics by AlliedSignal Inc. (1973) which teaches that A-C.RTM. 392A (high density oxidized polyethylene wax having an acid number of 30) is useful for tin stabilized polyvinyl chloride. See also Technical Data on A-C.RTM. Polyethylenes for Plastics by Allied (1984) which teaches that A-C.RTM. 31 6A (high density oxidized polyethylene wax having an acid number of 16) or A-C.RTM. 330 (high density oxidized polyethylene wax having an acid number of 30) is useful for tin stabilized calendered polyvinyl chloride.
U.S. Pat. No. 4,203,880 discloses tin stabilized polyvinyl chloride having a lubricant package comprising oxidized polyethylene wax having an acid number greater than 5 and a melt viscosity of 1,000 to 60,000 centipoises at 140.degree. C. and a known external lubricant such as paraffin oils, paraffin waxes, liquid and solid hydrocarbons, unoxidized polyethylene waxes, montan ester waxes, lead stearate, mineral oil, 12-hydroxystearic acid, ethylene bis-stearamide, and glycol esters of fatty acids that contain 10 to 20 or more carbon atoms.
It would be desirable to have a calendered vinyl polymer composition which has improved plate out resistance, clarity, release, and stability improved plate out resistance compared with currently used calendered vinyl polymer compositions.