Oriented PVC Pipe Formulation for High-Speed Extrusion
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Solution Overview
Problem
The production of oriented polyvinyl chloride (PVC) pipes is economically limited due to high labor and equipment costs in semi-batch processes and low run rates in continuous processes, primarily due to challenges in maintaining melt strength and processibility during continuous stretching.
Innovation Solution
A non-oriented PVC pipe formulation comprising 2 to 5 parts by weight of a polymeric processing aid and 1.6 to 2.0 parts by weight percent of an external lubricant per 100 parts by weight of PVC, where the processing aid consists of 50 to 95 weight percent methyl methacrylate and 5 to 50 weight percent C2-C6 acrylate or methacrylate structural units, and the external lubricant is a polyol ester or paraffin wax, with a weight average molecular weight of 5×10^5 to 5×10^7 Daltons, allowing for increased efficiency in producing oriented PVC pipes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a continuous stretching process is used to produce oriented PVC pipe, then production cost is reduced compared to semi-batch process, but the run rate is limited to one third of extrusion process due to melt strength limitations
Solution Approach 1:
The patent changes the chemical composition parameters of the PVC formulation by incorporating specific process aids (polyethylene glycol, polypropylene glycol, or polyester in amounts of 0.5-5.0 parts per 100 parts PVC) and external lubricants (paraffin wax, polyol esters, or metal soaps in amounts of 1.0-5.0 parts per 100 parts PVC). These parameter changes modify the melt strength and rheological properties, enabling the continuous stretching process to operate at higher run rates (up to 200 feet per minute or more) while maintaining pipe integrity and achieving full strain necessary to double the pipe diameter.
2Productivity
If higher concentrations of external lubricant are used to improve processibility, then extrusion run rate increases, but pipe splitting occurs and impact strength degrades
Solution Approach 1:
The patent creates a composite formulation system combining PVC resin with specific process aids and external lubricants in optimized ratios. The process aids (polyethylene glycol, polypropylene glycol, or polyester) work synergistically with external lubricants (paraffin wax, polyol esters, or metal soaps) to provide both internal and external lubrication. This composite approach allows the use of lubricants at higher levels (1.0-5.0 parts per 100 parts PVC) without causing pipe splitting, because the process aids modify the PVC matrix to better accommodate the lubricant distribution and maintain melt strength during high-speed continuous stretching operations.
Data Source
AI summary
The present invention relates to non-oriented and oriented polyvinyl chloride pipe comprising: a) polyvinyl chloride; b) from 2 to 5 parts by weight of polymeric processing aid per 100 parts by weight of the polyvinyl chloride; and c) from 1.6 to 2.0 parts by weight percent of a paraffin wax per 100 parts by weight of the polyvinyl chloride. The polyvinyl chloride pipe of the present invention comprises a concentration of paraffin wax lubricant (>1.5 parts per 100 parts polyvinyl chloride) heretofore unrecognized in the art, without the loss of key physical properties.