Low Molecular Weight Ethylene Copolymer Plasticizer
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Solution Overview
Problem
Polyolefins, particularly polypropylene homopolymers and copolymers, face challenges due to high glass transition temperatures, leading to brittleness at low temperatures and difficult processing, while high molecular weight polyolefins are hard to process due to high melt viscosities. Existing plasticizers often crystallize or volatilize, causing polymer deterioration and loss of properties over time.
Innovation Solution
Development of ethylene-C3-C10 alpha-olefin copolymers with specific characteristics, including a number average molecular weight of less than 5,000 g/mol, ethylene content less than 80 mol%, and a crossover temperature of -20°C or lower, which are used to plasticize polyolefins, improving processability and maintaining properties across a wide temperature range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional plasticizers are used to lower the Tg of polyolefins, then processability and low-temperature impact toughness are improved, but the plasticizers tend to crystallize or form structure at low temperatures, causing viscosity increase and brittleness
Solution Approach 1:
The invention changes the molecular parameters of the plasticizer by controlling the number average molecular weight (Mn) to be less than 5,000 g/mol and the weight average molecular weight (Mw) to be less than 10,000 g/mol. This parameter optimization prevents crystallization at low temperatures while maintaining low viscosity and effective Tg reduction, resolving the contradiction between processability improvement and low-temperature toughness maintenance.
2Productivity
If the number average molecular weight of the plasticizer is decreased to better lower the Tg of the polymer, then plasticization efficiency is improved, but the plasticization durability is adversely affected due to increased tendency to migrate and volatilize
Solution Approach 1:
The invention optimizes the molecular weight parameters by setting Mn < 5,000 g/mol and Mw < 10,000 g/mol with controlled polydispersity. This parameter range achieves effective Tg reduction and plasticization efficiency while the controlled molecular weight distribution and unsaturation content reduce migration and volatilization tendencies, maintaining plasticization durability.
3Strength
If high molecular weight polyolefins are used to provide desired polymer properties, then mechanical strength is improved, but processability deteriorates due to high melt viscosities
Solution Approach 1:
The invention uses a specifically designed low molecular weight copolymer as an intermediary substance (plasticizer) that interacts with the high molecular weight polyolefin. This intermediary reduces the overall melt viscosity of the system by disrupting polymer chain entanglements and increasing free volume, enabling processability of high molecular weight polymers while maintaining their mechanical strength properties.
4Strength
If plasticizers are added to improve impact strength and processability, then low-temperature brittleness is reduced, but blooming or diffusion to the surface occurs, resulting in long-term deterioration of polymer properties
Solution Approach 1:
The invention changes the chemical and physical parameters of the plasticizer by incorporating unsaturated groups (vinylidene or tri-substituted vinylidene terminal groups) and optimizing molecular weight. These parameter changes enhance compatibility with the polyolefin matrix through increased chemical similarity, reducing blooming and diffusion to the surface while maintaining impact strength improvement.
Data Source
AI summary
A copolymer including ethylene units and units of one or more C3-10 alpha-olefins. The copolymer has a number average molecular weight of less than 5,000 g/mol, as measured by GPC. The ethylene content of the copolymer is less than 80 mol %. At least 70% of molecules of the copolymer have an unsaturated group, and at least 70% of said unsaturated groups are located in a terminal vinylidene group or a tri-substituted isomer of a terminal vinylidene group. The copolymer has a crossover temperature of −20° C. or lower and/or a certain ethylene run length. Also disclosed are a method for making the copolymer and polyolefins plasticized with 1-40 wt % of the copolymer.