Nitrile Rubber Vulcanization Control via Magnesium Coagulation
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Solution Overview
Problem
Current processes for producing nitrile rubbers do not effectively control the vulcanization rate and property profile, particularly the difference between initial and full vulcanization rates, leading to suboptimal processing and properties in vulcanizates.
Innovation Solution
The process involves emulsion polymerization with specific alkyl thiols and coagulation using magnesium salts to set the pH and temperature, resulting in nitrile rubbers with controlled cation content and ion index, which enhances vulcanization rates and properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional coagulation methods are used, then nitrile rubber can be produced, but the vulcanization rate and property profile cannot be effectively controlled
Solution Approach 1:
The patent applies parameter changes by precisely controlling the pH value (setting to 6-7 before coagulation) and temperature (maintaining 0-40°C during coagulation) during the coagulation process. These parameter adjustments enable effective control of the vulcanization rate and property profile, resolving the technical contradiction between manufacturing precision and process complexity.
2Productivity
If polyvalent metal ions are used for coagulation, then coagulation efficiency is improved, but emulsifier inclusion in the product increases
Solution Approach 1:
The patent uses divalent metal ions (Ca²⁺ or Mg²⁺) at controlled concentrations (0.1-5% by weight based on rubber content) with specific pH adjustment (6-7) before coagulation. This parameter optimization achieves both efficient coagulation and minimal emulsifier inclusion, resolving the contradiction between productivity and substance loss.
Solution Approach 2:
The patent employs a composite coagulation system combining divalent metal salts with optional auxiliary agents (0.01-1% by weight) to enhance coagulation efficiency while controlling emulsifier inclusion. This composite approach allows simultaneous achievement of high productivity and low emulsifier retention.
3Loss of substance
If monovalent metal ions are used for coagulation, then emulsifier inclusion is reduced, but significantly larger amounts of electrolyte are required
Solution Approach 1:
The patent uses divalent metal ions (Ca²⁺ or Mg²⁺) which have higher coagulation efficiency per unit mass compared to monovalent ions. By controlling the concentration at 0.1-5% by weight and adjusting pH to 6-7, the patent achieves effective coagulation with minimal electrolyte amounts while maintaining low emulsifier inclusion.
4Productivity
If rapid vulcanization is achieved, then productivity is improved, but control over property profile is reduced
Solution Approach 1:
The patent achieves both rapid vulcanization and precise property profile control through optimized parameter settings: pH 6-7 before coagulation, temperature 0-40°C during coagulation, and controlled metal ion concentration (0.1-5% by weight). These parameters work synergistically to enable fast vulcanization while maintaining excellent control over mechanical properties and product quality.
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
This approach yields nitrile rubbers with fast initial and full vulcanization, along with improved vulcanizate properties such as high modulus, addressing the limitations of previous methods.
Implementation Method 1
DD 154 702 discloses a process for the free-radical copolymerization of butadiene and acrylonitrile in emulsion
Implementation Method 2
the latex which is initially obtained in the polymerization and contains the nitrile rubber being subjected to coagulation and the coagulated nitrile rubber obtained subsequently being washed
Implementation Method 3
In the coagulation of latices by means of metal salts, it is known that significantly larger amounts of electrolyte are required in the case of monovalent metal ions
Data Source
AI summary
An improved polymerization and work-up process makes it possible to produce specific nitrile rubbers which have a particular ion index and a particular magnesium content which is responsible for an excellent vulcanization rate and leads to vulcanizates having an advantageous property profile.