Aqueous Dispersion Crystallisable Block Copolymers
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Solution Overview
Problem
Existing methods for preparing aqueous dispersions of crystallisable polymers for coatings and packaging face challenges in achieving desired physical properties such as heat sealability, flexibility, and non-tackiness, often requiring high amounts of crystalline polymers and using environmentally undesirable organic solvents or toxic iodine-based processes.
Innovation Solution
The use of reversible addition-fragmentation chain transfer (RAFT) polymerisation to synthesise vinyl block copolymers with crystallisable blocks, allowing for the formation of aqueous dispersions that can provide crystallinity at low monomer concentrations, enabling heat-sealable and flexible films without the need for high crystalline polymer content or toxic reagents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high amounts of crystalline polymer are used to achieve heat sealability and film formation, then the heat seal properties improve, but the coating coherency is compromised when heated above the melting temperature
Solution Approach 1:
The invention divides the polymer system into two distinct components: a crystalline polymer component (providing heat sealability) and an amorphous polymer component (providing film coherency and stability). This segmentation allows each component to perform its specific function without interfering with the other, resolving the contradiction between heat seal properties and coating coherency.
Solution Approach 2:
The invention creates a composite coating composition combining crystalline polymer and amorphous polymer in specific ratios (1:4 to 4:1 weight ratios). The amorphous polymer acts as a matrix that maintains film integrity above the melting temperature of the crystalline polymer, while the crystalline polymer provides heat sealability. This composite approach allows both heat seal properties and coating coherency to coexist.
2Ease of manufacture
If organic solvents are used to dissolve SCC polymers for coating applications, then the polymer can be applied and formed into films, but environmental concerns and the need for specific controlling measures arise
Solution Approach 1:
The invention changes the solvent parameter from organic to aqueous. The coating composition uses water as the continuous phase instead of organic solvents, maintaining the ability to apply and form films while eliminating environmental hazards. The crystalline and amorphous polymers are dispersed or dissolved in water, allowing the composition to be applied by conventional coating methods without organic solvents.
Solution Approach 2:
The invention replaces expensive and hazardous organic solvents with water, which is abundant, inexpensive, and environmentally benign. This substitution maintains the functional requirements for coating application while eliminating the need for special handling and environmental controls associated with organic solvents.
3Stability of the object's composition
If crosslinking is used to control film coherency above the melting temperature, then film stability improves, but polymer diffusion is hindered and heat seal properties are lost
Solution Approach 1:
The invention segments the functional roles: the amorphous polymer provides film coherency and stability through its rubbery properties above the crystalline polymer's melting temperature, while the crystalline polymer provides heat sealability. This segmentation eliminates the need for crosslinking to maintain coherency, preserving polymer diffusion and heat seal properties.
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 allows for the creation of films with improved heat-sealability and flexibility at lower crystallisable monomer concentrations, maintaining structural integrity above the melting temperature, while avoiding the use of organic solvents and toxic substances.
Implementation Method 1
at least a crystallisable block [A] is obtained by a controlled radical polymerisation of at least one vinyl monomer via a reversible addition-fragmentation chain transfer (RAFT) mechanism in solution
Implementation Method 2
at least a crystallisable block [A] is obtained by a controlled radical polymerisation of at least one vinyl monomer via a reversible addition-fragmentation chain transfer (RAFT) mechanism in solution
Data Source
AI summary
An aqueous dispersion comprising a crystallisable vinyl block copolymer - polymer which comprises: i) a vinyl block copolymer comprising at least blocks [A]x [B] y , wherein at least a crystallisable block [A] is obtained by a controlled radical polymerisation of at least one vinyl monomer via a reversible addition-fragmentation chain transfer (RAFT) mechanism in solution, in the presence of a control agent and a source of free radicals; and wherein the vinyl block copolymer comprises 2 to 50 wt % of vinyl monomers bearing at least a crystallisable side chain by weight of the vinyl block copolymer - polymer; wherein crystallisable block [A] has an average degree of polymerisation x, wherein x is an integer in the range of from 3 to 80; wherein block [B] has an average degree of polymerisation y, wherein y is an integer = 3; and ii) a vinyl polymer [P] obtained by the free radical emulsion polymerisation of one or more vinyl monomers in the presence of the vinyl block copolymer; and wherein the block copolymer : polymer weight ratio is in the range of from 10:90 to 70:30.