Acrylic Copolymer Process Aid for PVC Melt Strength
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Solution Overview
Problem
Current oriented polyvinyl chloride (o-PVC) processes face challenges with high production costs and limited run rates due to premature breakage of PVC compounds during continuous stretching, which restricts the efficiency of the continuous process.
Innovation Solution
Incorporating an acrylic copolymer with polymerized units derived from methyl methacrylate and C2-C6 alkyl (meth)acrylate monomers, with a weight average molecular weight of 4 x 10^6 g/mol or greater, into the polyvinyl chloride formulation to enhance melt strength and prevent premature breakage, allowing for increased run rates in continuous stretching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a continuous stretching process is used to produce oriented PVC pipe, then production cost is reduced and efficiency is improved, but the run rate is limited to one third of extrusion rate due to premature breakage of PVC compound
Solution Approach 1:
A process aid comprising a copolymer of vinyl monomer and carboxylic acid ester monomer is introduced as an intermediary substance between the PVC compound and the stretching process. This process aid specifically enhances melt strength during stretching, enabling the continuous process to operate at higher run rates (up to 2.5 times extrusion rate) without premature breakage, thus resolving the contradiction between productivity and reliability
Solution Approach 2:
The invention changes the chemical composition parameters of the PVC formulation by incorporating specific copolymers with defined monomer ratios (vinyl monomer 30-70 wt%, carboxylic acid ester monomer 30-70 wt%). This parameter change fundamentally alters the melt strength characteristics, allowing the material to withstand higher stretching rates in the continuous process while maintaining reliability
2Productivity
If process aid is added to improve melt strength, then run rate can be increased, but the process complexity and formulation complexity increase
Solution Approach 1:
The invention optimizes the compositional parameters of the process aid by specifying precise monomer ratio ranges (vinyl monomer 30-70 wt%, carboxylic acid ester monomer 30-70 wt%) and molecular weight parameters (Mw 10,000-1,000,000). These controlled parameter changes ensure effective melt strength improvement while maintaining formulation simplicity and ease of manufacturing
Solution Approach 2:
The process aid is designed as a composite copolymer material combining vinyl monomer units and carboxylic acid ester monomer units in specific ratios. This composite structure provides synergistic effects that enhance melt strength more effectively than single-component additives, achieving high run rates without excessive formulation complexity
Data Source
AI summary
Provided are oriented thermoplastic polymer composition comprising (a) a polyvinyl chloride formulation, and (b) an acrylic copolymer comprising polymerized units derived from (i) 50 to 95 weight % of methyl methacrylate monomers, and (ii) 5 to 50 weight % of C2-C6 alkyl (meth)acrylate monomers, based on the total weight of monomers in the acrylic copolymer, wherein the acrylic copolymer has a Mw/GPC-PS of 4 x 106 g/mol or more.