Chloroprene Polymer Molecular Weight Control via Functional Chain Transfer
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Solution Overview
Problem
Current chloroprene rubber production methods limit molecular weight adjustment and terminal functional group modification, resulting in polymers with insufficient molecular weight for industrial applications and poor durability and fatigue endurance.
Innovation Solution
A chloroprene-based polymer with a number average molecular weight of 150,000 to 300,000 and a specific functional group structure, produced using radical polymerization with a chain transfer agent, achieving a molecular weight distribution of 1.5 to 5.0, allowing for improved durability and fatigue endurance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If chain transfer agents such as mercaptans or xanthogen disulfides are used to adjust molecular weight in radical emulsion polymerization, then molecular weight can be controlled, but the terminal functional groups cannot be easily changed and the molecular weight is insufficient for industrial applications
Solution Approach 1:
The patent changes the chemical structure of the chain transfer agent from traditional mercaptans or xanthogen disulfides to compounds with specific functional groups (carboxyl, hydroxyl, amino, or isocyanate groups). This parameter change in the chain transfer agent structure enables both molecular weight control and introduction of desired terminal functional groups on the polymer, resolving the contradiction between molecular weight control and functional group adaptability
Solution Approach 2:
The patent uses a specially designed chain transfer agent as an intermediary substance that mediates between the polymerization process and the desired terminal functional groups. The chain transfer agent structure includes a polymerizable unsaturated bond and a specific functional group, allowing it to transfer chains while introducing the desired terminal functionality, thus solving the limitation of traditional chain transfer agents
2Adaptability or versatility
If RAFT polymerization is used to control terminal structure, then terminal structure can be controlled, but the obtained polymer has small number average molecular weight and does not have sufficient molecular weight for industrial applications
Solution Approach 1:
The patent changes the polymerization mechanism from RAFT polymerization to radical emulsion polymerization while using a specially designed chain transfer agent. This parameter change in the polymerization method, combined with the specific chain transfer agent structure (including polymerizable unsaturated bonds and functional groups), enables both terminal structure control and achievement of high molecular weight (Mn ≥ 100,000) suitable for industrial applications
Solution Approach 2:
The patent segments the chain transfer agent into distinct functional components: a polymerizable unsaturated bond for chain transfer capability and a specific functional group (carboxyl, hydroxyl, amino, or isocyanate) for terminal functionality. This segmentation allows the chain transfer agent to perform multiple functions simultaneously, achieving both terminal structure control and high molecular weight
3Ease of manufacture
If traditional chain transfer agents are used in radical emulsion polymerization, then molecular weight can be adjusted, but the polymer lacks sufficient molecular weight and durability for industrial applications
Solution Approach 1:
The patent changes the molecular weight parameter by optimizing the chain transfer agent structure and polymerization conditions, achieving Mn ≥ 100,000. This parameter change, combined with introducing specific terminal functional groups, simultaneously improves both ease of manufacture (molecular weight adjustment) and reliability (durability and fatigue endurance) of the chloroprene-based polymer
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The resulting polymer provides vulcanized rubber with enhanced durability and fatigue endurance, as well as adhesives with improved layer separation resistance, suitable for various industrial applications.
Implementation Method 1
a chain transfer agent represented by the general formula (3) or (4) below is added to 100 parts by mass of a total monomer to achieve a ratio of an amount of substance of the total monomer to that of the chain transfer agent [M]0/[CTA] at the start of polymerization of 5/1 to 500/1
Implementation Method 2
radical polymerization is performed, and 100 to 5000 parts by mass of a chloroprene monomer singly or of a chloroprene monomer and a monomer copolymerizable with the chloroprene monomer is/are additionally added
Implementation Method 3
500 to 5000 parts by mass of an aqueous solution (B) of 0.1 to 10% by mass of an emulsifier are mixed and emulsified
Data Source
AI summary
Provided is a chloroprene-based polymer having an industrially applicable sufficient molecular weight and capable of obtaining a vulcanized rubber excellent in durability and fatigue endurance and an adhesive excellent in layer separation resistance. A chloroprene-based polymer having a number average molecular weight Mn of 150000 to 300000 and comprising a functional group of a structure represented by the general formula (1) or (2) below:(wherein in the general formula (1), R1 shows hydrogen, chlorine, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted heterocyclyl group.)