Chlorine-Free Polyurethane Adhesive for Foam Bonding
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Solution Overview
Problem
Current adhesive technologies, particularly polychloroprene dispersion adhesives, are not suitable for bonding foam substrates using the spray coagulation process, especially on non-polar surfaces, and lack sufficient adhesion and strength, especially on foams with high resilience, and also contain undesirable components like bisphenol A.
Innovation Solution
Aqueous adhesive formulations comprising a mixture of aqueous polyurethane or polyurethane-urea dispersion, plasticizer resin, and tackifier resin, with specific weight ratios and polymer characteristics, enabling effective bonding of foam substrates to non-polar surfaces through the spray coagulation process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polychloroprene dispersion adhesives are used for bonding foam substrates, then high initial strengths and good heat resistance are achieved, but the adhesives contain chlorine and are not suitable for ecolabel requirements
Solution Approach 1:
The invention changes the chemical composition parameters by replacing polychloroprene polymer with a specific polyurethane polymer that has a melting temperature of 30-50°C and specific enthalpy of melting >35 J/g, while maintaining the dispersion adhesive format and spray coagulation process to achieve comparable performance without chlorine
Solution Approach 2:
The invention uses a readily available polyurethane dispersion that can be processed through spray coagulation with common coagulants like calcium chloride, replacing the need for specialized polychloroprene formulations and enabling widespread adoption for ecolabel-compliant applications
2Object-affected harmful factors
If aqueous polyurethane dispersions are used for bonding foam substrates via spray coagulation, then chlorine-free alternatives are provided, but the adhesives do not coagulate quickly enough and lack sufficient adhesion on difficult substrates
Solution Approach 1:
The invention optimizes the polyurethane polymer parameters specifically - melting temperature of 30-50°C and enthalpy of melting >35 J/g - which control the coagulation behavior and adhesion properties, enabling rapid coagulation and strong bonding on difficult substrates like high resilience foam
Solution Approach 2:
The invention creates a composite adhesive system combining polyurethane dispersion with specific coagulants (calcium chloride, zinc sulfate, or aluminum sulfate) to achieve rapid coagulation and enhanced adhesion performance on challenging foam substrates
3Adaptability or versatility
If polyurethane dispersions with polar groups are used for bonding, then the adhesives are suitable for many substrates, but adhesion on non-polar surfaces like polypropylene is insufficient
Solution Approach 1:
The invention modifies the adhesive parameters by using a polyurethane dispersion with controlled melting temperature (30-50°C) and enthalpy of melting (>35 J/g) that enables the adhesive to coagulate rapidly on non-polar surfaces, overcoming the limitation of polar group-only adhesion mechanisms
4Reliability
If thermal activation process is used for polyurethane bonding, then adhesion is achieved after heating, but long waiting times are required for water evaporation and appropriate drying systems are needed
Solution Approach 1:
The invention utilizes phase transition of water from liquid to vapor through spray coagulation, where the adhesive and coagulant are mixed in the spray jet and water rapidly evaporates during the spraying process, eliminating the need for prolonged drying periods and complex drying systems
Solution Approach 2:
The invention replaces the thermal activation process with a mechanical spray coagulation process, where the adhesive is coagulated through chemical reaction with coagulant in the spray jet rather than through thermal heating, significantly reducing processing time and equipment 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 formulations provide sufficient immediate strength and adhesion on foam substrates with high density and resilience, as well as on non-polar surfaces like polypropylene, without the need for pre-treatment, and are suitable for various substrates including wood, textiles, and plastics.
Implementation Method 1
the adhesive and a coagulant are conveyed separately into a spray gun, mixed in the spray jet and coagulated
Implementation Method 2
after the water has completely evaporated, the adhesive layer is removed by heating
Data Source
Figure 1.1~1.2
AI summary
The invention relates to formulations of aqueous dispersion adhesives on the basis of aqueous polyurethane or polyurethane-urea dispersions and the use of the adhesive formulations for bonding foam substrates according to the spray coagulation method.