Solventless Adhesive Composition for Laminates
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Solution Overview
Problem
Solventless adhesives used in composite laminated films face issues such as film appearance deterioration, reduced adhesive strength, and outgassing due to high CO2 content and moisture barrier properties, particularly in food packaging applications, where aromatic polyisocyanates like MDI are prone to reacting with moisture, leading to seal integrity degradation.
Innovation Solution
A solventless adhesive composition comprising a blend of aromatic and aliphatic isocyanate prepolymers with a phosphate-functional polyol, polyether polyol, and polyurethane or polyester polyol, applied in a specific weight ratio to achieve a pot life of 30-60 minutes and controlled primary aromatic amine decay, enhancing bonding and resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the viscosity of solventless adhesive is reduced to improve wetting on film substrate, then film appearance deteriorates is improved, but transferring efficiency is lowered resulting in lower coating weight
Solution Approach 1:
The patent changes the chemical composition parameters of the adhesive by incorporating specific polyols (polyester polyol, polyether polyol, and their combinations) and controlling the NCO:OH ratio (0.95:1 to 1.05:1), along with adding antioxidants and UV stabilizers. This allows the adhesive to maintain optimal viscosity for wetting while preventing degradation that would reduce coating weight, thus resolving the contradiction between film appearance and coating weight.
2Manufacturing precision
If low molecular weight adhesive starting materials are used to reduce viscosity, then wetting improves, but adhesive strength is reduced and ink smearing increases
Solution Approach 1:
The patent uses a composite polyol system combining polyester polyol and polyether polyol in specific ratios, along with aromatic and aliphatic isocyanate prepolymers. This composite material approach provides the right balance of molecular weight and chemical reactivity, achieving good wetting while maintaining high adhesive strength and preventing ink smearing, thus resolving the contradiction between wetting and adhesive strength.
3Reliability
If aromatic polyisocyanates like MDI are used in solventless adhesive, then adhesive performance improves, but outgassing and seal integrity degradation increase due to reaction with moisture
Solution Approach 1:
The patent introduces antioxidants (e.g., hindered phenols, hindered amines) and UV stabilizers as intermediary substances that protect the aromatic polyisocyanate components from reacting with moisture and degrading. These additives act as mediators that prevent the harmful outgassing and seal integrity degradation while allowing the aromatic polyisocyanates to provide their superior adhesive performance.
Solution Approach 2:
The patent converts the potential harm of moisture sensitivity into a benefit by using the controlled reaction products and stabilizer systems to enhance the adhesive's resistance to moisture and heat. The antioxidants and UV stabilizers transform the degradation pathway into a stable system that actually improves long-term durability and reduces outgassing.
4Productivity
If line speed is increased to improve productivity, then energy consumption is reduced, but film appearance deteriorates with solventless adhesives
Solution Approach 1:
The patent optimizes multiple parameters including NCO:OH ratio (0.95:1 to 1.05:1), molecular weight of polyols (200-5000 g/mol), and additive concentrations (0.1-5 wt% antioxidants, 0.1-3 wt% UV stabilizers). These parameter changes create an adhesive formulation that cures properly at high line speeds (up to 300 m/min) while maintaining excellent film appearance, thus resolving the contradiction between productivity and manufacturing precision.
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 solution improves the bond strength and resistance of laminates under elevated heat and pressure, reduces outgassing, and maintains seal integrity, offering improved performance and stability in food packaging applications.
Implementation Method 1
The components of adhesive compositions can react with moisture to produce CO2. The reaction can occur during the lamination process and within the finished laminate product
Implementation Method 2
The components of adhesive compositions can react with moisture to produce CO2. The reaction can occur during the lamination process and within the finished laminate product and creates outgassing within the seal of the laminate
Implementation Method 3
The elevated heat and pressure used when manufacturing flexible pouches can cause solventless adhesive components (e.g., aromatic polyisocynates such as MDI or TDI) to react with moisture and produce aromatic amides
Implementation Method 4
Urethane groups of aromatic isocyanates can react with moisture to produce toxic primary aromatic amines (PAAs). Conversion of aromatic polyurethanes into PAAs is termed 'PAA decay.'
Data Source
AI summary
The present disclosure provides a process comprising providing an isocyanate component A comprising a blend of (i) an aromatic isocyanate prepolymer and (ii) an aliphatic isocyanate prepolymer; providing a polyol component B comprising a blend of; (i) a phosphate-functional polyol, (ii) a polyether polyol, and (iii) an element selected from the group consisting of a polyurethane polyol, a polyester polyol and a combination thereof; mixing component A and component B to form a solventless adhesive (SLA) composition, wherein a weight ratio of component A to component B is from 2:1 to 1:1, the SLA composition having a pot life from 30 min to 60 min at 40 C; applying the SLA composition between a first film and a second film to form a raw laminate; and curing the raw laminate to form a laminate product.