Propylene-Ethylene Copolymer Adhesives With High Strength and Low Viscosity
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Solution Overview
Problem
Existing polyolefin polymers used in hot melt adhesives lack desirable tensile strength and mechanical properties, and their performance degrades with aging, particularly in hygiene applications, necessitating the need for secondary polymers that increase processing complexity and energy consumption.
Innovation Solution
Development of propylene-ethylene copolymers with specific compositions and properties, including 77 to 90% propylene, triad tacticity of 52% to 75%, Brookfield viscosity of 2,000 to 7,000 cP, and tensile strength of at least 4 MPa, which can be used alone or as a primary component in adhesive formulations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If higher tensile polyolefin polymers are utilized, then tensile strength is improved, but processing becomes more difficult due to higher viscosities and energy consumption
Solution Approach 1:
The patent applies parameter changes by precisely controlling the ethylene content (5-30 wt%) and triad tacticity (mm%) of the propylene-ethylene copolymer to achieve optimal balance between tensile strength and viscosity. By adjusting these parameters, the copolymer attains sufficient tensile strength (≥2.0 MPa) while maintaining manageable Brookfield viscosity (2,000-7,000 cP) for easy processing.
2Strength
If secondary polymers are added to improve tensile strength, then mechanical properties are improved, but device complexity and processing complexity increase
Solution Approach 1:
The patent extracts and eliminates the need for secondary polymers by developing a propylene-ethylene copolymer with inherently sufficient tensile strength through controlled ethylene content and triad tacticity. The copolymer achieves ≥2.0 MPa tensile strength as a single component, removing the complexity of multi-polymer formulations while maintaining required mechanical properties.
3Strength
If polyolefin polymers with higher ring and ball softening point temperatures are used, then tensile strength is improved, but energy consumption increases due to higher melting temperatures
Solution Approach 1:
The patent applies parameter changes by controlling the ethylene content (5-30 wt%) and triad tacticity to achieve an optimal Ring and Ball softening point range (95-125°C). This parameter optimization allows the copolymer to maintain high tensile strength while reducing the energy required for melting and processing compared to polymers with higher softening points.
4Ease of manufacture
If existing polyolefin polymers are used, then processing is easier, but adhesive strength decreases unacceptably with ageing
Solution Approach 1:
The patent applies parameter changes by optimizing the triad tacticity (mm%) and ethylene content to achieve superior adhesive strength retention after ageing. The copolymer maintains ≥80% of initial adhesive strength after 24 hours at 38°C, while preserving easy processing characteristics through controlled Brookfield viscosity in the 2,000-7,000 cP range.
Data Source
AI summary
Propylene-ethylene copolymers are provided that exhibit superior tensile strength and mechanical properties due to their specific propylene and ethylene content, triad tacticity, viscosity, and crystallinity. Moreover, we have discovered that certain processing conditions, such as polymerization temperature and external donor to catalyst ratios, can facilitate the production of the high tensile strength propylene-ethylene copolymers described herein. Furthermore, the high tensile strength propylene-ethylene copolymers may be used to produce a variety of hot melt adhesives, such as those for hygiene applications, woodworking applications, lamination applications, and packaging applications, which exhibit unique and superior mechanical properties.