Solventless Retort Adhesive for Metal-Plastic Packaging Laminates
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Solution Overview
Problem
Conventional solventless two-part curable adhesives exhibit poor adhesive strength after retort treatment, particularly when bonding metal foils like aluminum or substrates with metal vapor deposition layers to plastic films, and this weakness is exacerbated by the presence of acidic components.
Innovation Solution
A two-part curable adhesive comprising a polyisocyanate composition containing a polyurethane polyisocyanate and an acid anhydride, with specific acid value and diisocyanate monomer content, combined with a polyol composition, to enhance adhesive strength and resistance to acidic contents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a solventless two-part curable adhesive is used to bond metal foil or vapor deposition layer substrate to plastic film, then environmental load is reduced and work environment is improved, but adhesive strength after retort treatment becomes poor
Solution Approach 1:
The patent modifies the chemical parameters of the adhesive composition by incorporating a polyamide polyol with specific molecular weight range (1000-5000) and controlling the isocyanate index (105-120). These parameter changes enable the adhesive to maintain bond strength after retort treatment while remaining solventless, thus resolving the contradiction between environmental benefits and adhesive performance.
Solution Approach 2:
The patent creates a composite adhesive system by combining polyurethane polyol and polyamide polyol in specific proportions (polyamide polyol content: 10-50 mass%). This composite composition provides both the environmental benefits of solventless formulation and the enhanced adhesion to metal foils and vapor deposition layers required for retort-resistant bonding.
2Object-generated harmful factors
If a solventless two-part curable adhesive is used for bonding metal foil or vapor deposition layer substrate, then volatility of organic solvent is eliminated, but adhesive strength significantly deteriorates when content contains acidic components
Solution Approach 1:
The patent adjusts the chemical parameters by selecting polyamide polyol with specific molecular weight (1000-5000) and controlling the isocyanate index (105-120). These parameter modifications enable the adhesive to resist degradation from acidic contents while maintaining the solventless formulation, thus preventing both volatility issues and adhesive strength deterioration.
Solution Approach 2:
The patent converts the potential harmful effect of acidic contents into a beneficial outcome by using the acid-anhydride reaction products formed during curing to create crosslinked structures that are actually resistant to acid degradation. The polyamide polyol's amide groups form stable bonds that withstand acidic environments, turning the acid exposure from a degradation mechanism into a demonstration of enhanced durability.
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 maintains excellent bonding strength after retort treatment and resistance to acidic components, ensuring durability of laminates used in packaging materials.
Implementation Method 1
a two-part curable solventless adhesive including: a polyisocyanate composition (X) and a polyol composition (Y)
Data Source
AI summary
Provided is a solventless two-part curable adhesive having excellent adhesive strength after retort treatment even when a metal foil such as an aluminum foil or a substrate having a vapor deposition layer of a metal such as aluminum and a plastic film are bonded to each other. A two-part curable solventless adhesive containing: a polyisocyanate composition (X) and a polyol composition (Y), in which the polyisocyanate composition (X) contains a polyurethane polyisocyanate (A1) which is a reaction product of a polyisocyanate (1) and a polyester polyol (m), and an acid anhydride (B), an acid value derived from the acid anhydride (B) in the polyisocyanate composition (X) is 1 mg KOH/g or more and 100 mg KOH/g or less, a content of a diisocyanate monomer in the polyisocyanate composition (X) is 0.1% by mass or less, and the polyol composition (Y) contains a polyester polyol (C1).