Solvent-Free Silicone Release Coating Adhesion
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Solution Overview
Problem
Conventional solvent-free silicone compositions exhibit poor adhesion to plastic film substrates like polyester films and have storage stability issues due to separation of functional compounds during long-term storage or transportation.
Innovation Solution
A silicone composition comprising an alkenyl group-containing organopolysiloxane, an alpha-olefin as a compatibilizer, and an organohydrogenpolysiloxane with aryl groups, stored separately and mixed just before application, to enhance adhesion and prevent separation, ensuring high storage stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a silane coupling agent is added to a solvent-free silicone composition to improve adhesion to plastic films, then adhesion to the substrate is improved, but the composition still shows unsatisfactory adhesion and requires additional process steps for surface treatment
Solution Approach 1:
The invention changes the chemical parameters of the silicone composition by introducing a specific organohydrogenpolysiloxane with aryl groups (8-50% aryl groups by number of groups bonded to silicon atoms) and controlling the ratio of aryl-containing to non-aryl-containing polysiloxane at 0.01-10 parts by mass per 100 parts. This parameter optimization achieves good adhesion to plastic films without requiring additional surface treatment processes.
Solution Approach 2:
The invention creates a composite silicone composition system combining multiple components: alkenyl group-containing organopolysiloxane, organohydrogenpolysiloxane with aryl groups, and optional silane coupling agents. This composite approach achieves both good adhesion to plastic films and solvent-free characteristics, eliminating the need for separate surface treatment steps.
2Strength
If a functional compound with epoxide groups is added to enhance adhesion to film substrates, then adhesion is improved, but the functional compound separates from the silicone composition during long-term storage or transportation
Solution Approach 1:
The invention introduces an alpha-olefin as an intermediary compatibilizer that mediates between the alkenyl group-containing organopolysiloxane and the organohydrogenpolysiloxane with aryl groups. This compatibilizer prevents phase separation during storage while maintaining the adhesion-enhancing functionality of the aryl-containing polysiloxane when the composition is applied and cured.
Solution Approach 2:
The invention optimizes the concentration parameters by limiting the amount of organohydrogenpolysiloxane with aryl groups to 0.01-10 parts by mass per 100 parts of alkenyl group-containing organopolysiloxane, and controlling the H/Vi ratio (number of SiH groups to number of alkenyl groups) to 0.1-10. These parameter controls ensure storage stability while maintaining adhesion performance.
3Strength
If an organopolysiloxane with epoxy groups is added in small amounts to enhance adhesion, then adhesion to substrate is improved, but the composition shows low compatibility and separation issues during storage
Solution Approach 1:
The alpha-olefin acts as a compatibilizer that enables the coexistence of polysiloxanes with different functional groups (epoxide groups and alkenyl groups) without phase separation. This intermediary allows the composition to maintain both adhesion enhancement from epoxy groups and storage stability through proper compatibility.
Solution Approach 2:
The invention controls the ratio of different polysiloxane components and the H/Vi ratio within specific ranges (0.1-10) to maintain compositional homogeneity during storage. This parameter control ensures that the small amount of organopolysiloxane with epoxy groups remains compatible with the base silicone composition throughout storage and transportation.
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 excellent adhesion to plastic film substrates and maintains stability during long-term storage and transportation without separation of functional components, providing a solvent-free, environmentally friendly release coating.
Implementation Method 1
a releasable coating is formed on the substrate surface by the addition reaction between an organopolysiloxane having alkenyl groups and an organohydrogenpolysiloxane in the presence of a platinum-based catalyst
Implementation Method 2
an alpha-olefin which is liquid at 25 degrees C., in an amount of 0.05 to 15 parts by mass, relative to 100 parts by mass of component (A)
Data Source
AI summary
The object of the present invention is to provide a silicone composition which provides a release coating having excellent adhesion to a substrate, in particular a plastic film substrate, such as a polyester film. Further, an object of the present invention is to provide a release sheet having a cured coating of the silicon composition. It is also an object of the present invention to provide a silicone composition which has improved storage stability and does not cause separation of the functional compound during long-term storage or transportation. The present invention provides a silicone composition comprising the following components (A) to (C):(A) an organopolysiloxane having at least two alkenyl groups each bonded to a silicon atom in a molecule, having a viscosity at 25 degrees C. in the range of from 50 mPa·s to 10,000 mPa·s, and having no aryl nor aralkyl group bonded to a silicon atom, wherein a percentage of the number of the alkenyl groups relative to the number of groups each bonded to a silicon atom is from 0.01% to less than 4.5%;(B) a mixture comprising the following components (B1), (B2) and (B3):(B1) an alpha-olefin which is liquid at 25 degrees C., in an amount of 0.05 to 15 parts by mass, relative to 100 parts by mass of component (A),(B2) an organohydrogenpolysiloxane having at least three hydrogen atoms each bonded to a silicon atom in a molecule, and having no aryl nor aralkyl group bonded to a silicon atom, wherein a ratio of the number of the SiH groups present in component (B2) to a total number of the alkenyl groups present in components (A) and (B) is 0.5 to 10;(B3) an organohydrogenpolysiloxane having at least three hydrogen atoms each bonded to a silicon atom in a molecule, and having an aryl group and/or an aralkyl group each bonded to a silicon atom such that a percentage of the number of the aryl group and the aralkyl group relative to a total number of hydrogen atoms and groups each bonded to a silicon atom is 8% to 50%, wherein the amount of component (B3) is from 0.05 to 10 parts by mass, relative to 100 parts by mass of component (A), and a ratio of the number of the SiH groups present in component (B3) to a total number of the alkenyl groups present in components (A) and (B) is 0.1 to 2; and(C) a catalytic amount of a platinum group metal catalyst.