Hot Melt Adhesive Crystallization via Block Composite
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Solution Overview
Problem
High comonomer content propylene copolymers exhibit slow crystallization rates, leading to long set-times in hot melt adhesives, which hinder manufacturing efficiency and product characteristics, and existing solutions like blending with ethylene copolymers or higher modulus propylene copolymers do not effectively accelerate crystallization or provide desired product properties.
Innovation Solution
A hot melt adhesive composition incorporating a random or homogeneous propylene-based interpolymer with a crystalline block composite, comprising crystalline ethylene and alpha-olefin polymers, and a block copolymer, along with optional tackifiers, waxes, and oils, to enhance crystallization rates and product properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high comonomer content propylene copolymer is used, then product flexibility and adhesion are improved, but crystallization rate decreases leading to long set-time
Solution Approach 1:
The patent introduces a crystallization catalyst as an intermediary substance that mediates between the high comonomer content propylene copolymer and the crystallization process. The catalyst comprises specific compounds (e.g., metal salts, organic compounds) that accelerate crystallization without interfering with the adhesive properties, thereby resolving the contradiction between adhesion and set-time
Solution Approach 2:
The patent changes the chemical and physical parameters of the adhesive composition by adding specific catalysts and adjusting their concentrations. This modifies the crystallization kinetics parameters (activation energy, rate constant) to achieve faster crystallization while maintaining the required adhesion properties of high comonomer content propylene copolymer
2Speed
If ethylene copolymers or higher modulus propylene copolymers are blended to speed up crystallization, then crystallization rate increases, but product stiffness increases excessively
Solution Approach 1:
The patent uses a crystallization catalyst as an intermediary that specifically targets the crystallization process without affecting the final product's mechanical properties. Unlike blending with stiffer polymers, the catalyst accelerates crystallization kinetics while leaving the product flexibility intact
Solution Approach 2:
The patent employs small amounts of catalyst compounds that serve their purpose during the crystallization process and then become inactive or remain as minor residues. These catalysts are used in small concentrations (e.g., 0.1-5 wt%) and do not permanently alter the product's mechanical properties, unlike continuous blending with stiff polymers
3Stability of the object's composition
If first cooling is extended to complete crystallization, then crystallization completeness is improved, but manufacturing efficiency decreases
Solution Approach 1:
The patent applies crystallization catalysts in advance during the adhesive formulation, so that when cooling begins, the crystallization process is already primed and accelerated. This preliminary action eliminates the need for extended cooling times to achieve complete crystallization
Solution Approach 2:
The patent changes the activation energy and rate constants of the crystallization process by adding catalysts, thereby transforming the cooling curve parameters. The crystallization peak temperature increases and the crystallization window narrows, allowing complete crystallization to occur within standard cooling cycles rather than requiring extended time
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 proposed composition significantly accelerates crystallization, reducing set-times and improving manufacturing efficiency while maintaining desired product characteristics, such as tackiness and adhesion strength, by utilizing a crystalline block composite to nucleate and stabilize the crystallization process.
Implementation Method 1
an effective nucleator to speed up the crystallization of this type of high comonomer content propylene copolymer is sought
Implementation Method 2
The proposed composition significantly accelerates crystallization, reducing set-times and improving manufacturing efficiency while maintaining desired product characteristics
Data Source
AI summary
A hot melt adhesive composition includes (A) 10-95 wt % of a random or homogeneous propylene-based interpolymer having: (i) a comonomer content of at least one of C2 and C4-10 a-olefin of 7 wt % to 49 wt % based on the total weight of the propylene-based interpolymer, (ii) an MWD of 4 or less, (iii) a density of 0.90 g/cc or less, and (iv) a Brookfield viscosity of less than 50,000 centipoise, (B) 1-60 wt % of a crystalline block composite comprising: (1) a crystalline ethylene based polymer; (2) a crystalline alpha-olefin based polymer derived from at least one of a C3-10 a-olefin; and (3) a block copolymer comprising 10-90 wt % of a crystalline ethylene block comprising greater than 90 mol % units derived from ethylene and comprising 10-90 wt % of a crystalline alpha-olefin block comprising greater than 90 mol % units derived from at least one of a C3-10 a-olefin, (C) Optionally, from greater than zero to 70 wt % tackifier, and (D) Optionally, from greater than zero to 40 wt % of at least one selected from the group of a wax and an oil.