Two-Pack Curable Adhesive for Packaging Materials
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Solution Overview
Problem
Solvent-free adhesives used in packaging materials often suffer from air bubble entrapment and printing layer dissolution issues, leading to appearance defects and reduced adhesive strength, especially when used with metal vapor deposition layers.
Innovation Solution
A two-pack curable adhesive comprising a polyisocyanate composition with a urethane prepolymer and a polyol composition, where the polyester polyol contains diethylene glycol in high proportions, is developed to minimize air bubbles and prevent printing layer dissolution, ensuring a strong and defect-free laminate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a solvent-free adhesive is used to eliminate dry steps and reduce environmental load, then energy consumption is reduced and no solvent discharge is needed, but air bubbles are likely to remain in the cured coating film causing appearance defects
Solution Approach 1:
The patent changes the chemical composition parameters of the adhesive by specifying that polyester polyol contains 50-90 mass% of diethylene glycol and polyether polyol contains 10-50 mass% of diethylene glycol. This parameter optimization allows the adhesive to achieve low viscosity for easy coating while preventing air bubble entrapment and maintaining appearance quality without requiring solvent evaporation steps.
Solution Approach 2:
The patent uses a composite adhesive system combining polyester polyol and polyether polyol with specific proportions and compositions. This composite formulation creates an adhesive that maintains low viscosity for easy application while the specific combination of polyols prevents air bubble formation and ensures high appearance quality, resolving the contradiction between energy efficiency and manufacturing precision.
2Ease of manufacture
If polyol with low molecular weight is used to achieve coating at low temperature, then coating can be performed at 40-100°C, but polyol easily re-dissolves the printing layer causing darkening
Solution Approach 1:
The patent optimizes the molecular weight and composition parameters of the polyol by specifying that polyester polyol contains 50-90 mass% diethylene glycol and polyether polyol contains 10-50 mass% diethylene glycol. This parameter control ensures the adhesive has low enough viscosity for coating at 40-100°C while the specific polyol composition prevents excessive dissolution of the printing layer, maintaining its appearance.
Solution Approach 2:
The patent applies different polyol compositions to different functional requirements: the adhesive formulation is designed to have low viscosity for easy coating (40-100°C processing) while the specific polyol composition (50-90% diethylene glycol in polyester polyol, 10-50% in polyether polyol) provides sufficient bonding strength without causing printing layer dissolution, achieving local optimization of properties.
3Ease of manufacture
If adhesive viscosity is reduced for easy coating at low temperature, then coating can be performed at 40-100°C, but air bubbles are more likely to be entrapped and aggregated
Solution Approach 1:
The patent changes the viscosity and composition parameters of the adhesive by controlling the polyol content and diethylene glycol proportion. This optimization allows the adhesive to flow easily for coating at low temperatures (40-100°C) while the specific composition prevents air bubble entrapment and aggregation, maintaining high appearance quality.
Solution Approach 2:
The patent uses a composite polyol system with polyester polyol (50-90 mass% diethylene glycol) and polyether polyol (10-50 mass% diethylene glycol). This composite formulation achieves the right balance of viscosity for easy coating while preventing air bubble problems, resolving the contradiction between manufacturing ease and appearance 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
The adhesive effectively suppresses air bubble aggregation and ink re-dissolution, maintaining excellent adhesive strength and appearance even with high gas barrier films and metal vapor deposition layers, enhancing the reliability of packaging materials.
Implementation Method 1
a polyisocyanate composition (A) containing a urethane prepolymer (A1), which is a reaction product of polyester polyol (a1), polyether polyol (a2), and a polyisocyanate compound (a3); and a polyol composition (B) containing polyester polyol (B1), which is a reaction product of a monomer composition containing a polycarboxylic acid (b1-1) and polyol (b1-2)
Implementation Method 2
it is necessary to design components used in the solvent-free adhesive to have a low molecular weight such that a viscosity is obtained at which coating can be performed when heated to approximately 40° C. to 100° C.
Implementation Method 3
there is a concern that polyol with a low molecular weight easily re-dissolves the printing layer, and causes the appearance defect such as darkening in the printing layer
Implementation Method 4
maintaining excellent adhesive strength and appearance even with high gas barrier films and metal vapor deposition layers
Data Source
AI summary
Provided is a two-pack curable adhesive less likely to cause an appearance defect due to air bubbles or the dissolution of a printing layer. A two-pack curable adhesive, containing: a polyisocyanate composition (A) containing a urethane prepolymer (A1), which is a reaction product of polyester polyol (a1), polyether polyol (a2), and a polyisocyanate compound (a3); and a polyol composition (B) containing polyester polyol (B1), in which polyhydric alcohol (a1-2) used in the synthesis of the polyester polyol (a1) and polyhydric alcohol (b1-2) used in the synthesis of the polyester polyol (B1) contain 80% by mass or more of diethylene glycol, respectively, and the compound amount of the polyester polyol (a1) is 50% by mass or more and 90% by mass or less with respect to the total amount of the polyester polyol (a1) and the polyether polyol (a2).