Solventless Release Coating Organopolysiloxane Composition
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Solution Overview
Problem
Existing solventless silicone release coating compositions face challenges in achieving a balance between low viscosity for multiple roll-coater applications and excellent properties such as high-speed cure, low migration, slippery surface, good anchorage to the substrate, and low release force, while maintaining suitable viscosity and reactivity.
Innovation Solution
A solventless release coating organopolysiloxane composition comprising a reactive organopolysiloxane fluid with specific viscosity and alkenyl content, combined with a long chain polysiloxane additive in a hydrosilylation curing system, which forms a covalently bonded network with SiH function crosslinker, providing a slippery touch and low release force.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If low viscosity organopolysiloxane is used for multiple roll-coater applications, then ease of operation is improved, but curing speed and network formation are worsened
Solution Approach 1:
The invention uses a composite organopolysiloxane composition combining low viscosity base polymer (for ease of coating) with specific additives including silane crosslinkers and catalysts (for rapid curing). This composite approach allows the coating to be applied easily while achieving fast cure and strong network formation.
Solution Approach 2:
The invention changes the chemical parameters of the organopolysiloxane system by introducing specific functional groups (alkenyl content 0.1-3.0 wt%), controlling viscosity range (10-1000 mPa·s), and adding crosslinking agents. These parameter changes enable the material to achieve both low viscosity for application and rapid curing through controlled chemical reactions.
2Strength
If high alkenyl content is used to improve crosslinking density, then strength is improved, but release force increases which worsens label removal
Solution Approach 1:
The invention precisely controls the alkenyl content parameter within 0.1-3.0 wt% range and adjusts the silane to alkenyl molar ratio to optimize the balance between crosslinking density and release properties. This parameter optimization ensures sufficient network strength while maintaining low release force for easy label removal.
Solution Approach 2:
The invention creates different local properties within the coating system: the crosslinked network provides strong anchorage to substrate, while the controlled alkenyl content ensures low release force at the adhesive interface. This local differentiation of properties resolves the contradiction between strength and release force.
3Productivity
If rapid curing is achieved with high catalyst amounts, then productivity is improved, but cost and potential contamination increase
Solution Approach 1:
The invention changes the catalyst system parameters by selecting specific catalyst types and optimizing their concentration. This allows achieving rapid curing with minimized catalyst amounts, reducing both cost and potential contamination while maintaining high productivity.
Solution Approach 2:
The invention replaces traditional high-catalyst rapid curing mechanisms with an optimized chemical system that achieves fast cure through improved reaction efficiency rather than catalyst quantity. This substitution reduces catalyst requirements while maintaining productivity.
4Ease of operation
If low release force is achieved for easy label removal, then ease of operation is improved, but anchorage to substrate may be compromised
Solution Approach 1:
The invention creates differentiated local properties: strong chemical crosslinking provides robust anchorage to substrate, while controlled alkenyl content and network structure ensure low release force at the adhesive interface. This local quality differentiation resolves the contradiction between anchorage strength and ease of label removal.
Solution Approach 2:
The invention uses a composite organopolysiloxane system where the crosslinked network structure provides substrate anchorage, while the controlled composition and morphology of the coating layer provide low release force. This composite approach allows simultaneous achievement of both requirements.
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 composition achieves high-speed cure with low catalyst amounts, low migration, excellent anchorage, and reduced noise and friction during peeling, while maintaining suitable viscosity for multiple roll-coater applications and preventing blocking issues.
Implementation Method 1
The basic constituents of silicone based release coating compositions which are cured by hydrosilylation are (A) a polyorganosiloxane containing alkenyl groups, (B) a cross-linking agent (also called crosslinker) containing organohydrogensiloxane groups and a catalyst for the hydrosilylation reaction between (A) and (B).
Implementation Method 2
a catalyst for the hydrosilylation reaction between (A) and (B)
Data Source
AI summary
This invention relates to solventless release coating organopolysiloxane composition and sheet-form substrate having cured release coating, providing a solventless release coating organopolysiloxane composition having a viscosity of 50 to 3,000 mPa s, comprising (A) 100 parts of an organopolysiloxane fluid having a viscosity at 25° C. of 10 to 1,000 mPa s and alkenyl content of 0.10 to 3.0 wt %; (B) 0.5 to 15 parts of a diorganopolysiloxane having a viscosity at 25° C. of 10,000 to 150,000 mPa s, and 0.05 to 0.30% of alkenyl groups at the pendant position of its siloxane-chain and trialkylsiloxy-terminals; (C) a prescribed quantity of an organohydrogenpolysiloxane; and (D) a hydrosilylation reaction catalyst. Also, a cured release coating-bearing sheet-form substrate that has a cured coating from this solventless release coating organopolysiloxane composition is provided.