Polypropylene Adhesive Laminate Thermal Stability
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Solution Overview
Problem
Adhesive layers used in laminates with polyester resin substrates, such as PET, experience reduced adhesiveness after thermal history processes like retorting or boiling, which affects their stability and durability.
Innovation Solution
A laminate production method involving a polypropylene adhesive layer with a specific composition, including 97-70% propylene copolymer (A) and 3-30% butene copolymer (B), along with a polymer (C) derived from unsaturated carboxylic acids, and a heat treatment step at 80-140°C for 5-120 minutes, ensuring high initial and stable adhesiveness after heat treatment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a soft rubber component is compounded with PP to improve initial adhesiveness, then the reactivity with EVOH or PA increases and initial adhesiveness is improved, but the adhesiveness reduces under thermal history at 40°C or more
Solution Approach 1:
The invention changes the chemical composition parameters of the adhesive layer by incorporating specific copolymers with controlled butene content and introducing polymers with carboxylic acid groups. This chemical parameter modification enables the adhesive to maintain both high initial adhesiveness and stability after thermal history, resolving the contradiction between initial bonding strength and thermal durability.
Solution Approach 2:
The invention creates a composite adhesive system combining multiple polymer components: propylene copolymer (A), butene copolymer (B) with specific butene content, and polymer (C) with carboxylic acid groups. This multi-component composite approach synergistically improves both initial adhesiveness to polar polymers and resistance to thermal degradation, simultaneously addressing both requirements.
2Ease of operation
If propylene copolymer with low butene content is used to maintain flexibility, then the melting point is reduced and processability is improved, but the adhesiveness to polyester resin substrates deteriorates
Solution Approach 1:
The invention introduces polymer (C) with carboxylic acid groups as a chemical intermediary that mediates the bonding between the propylene copolymer matrix and the polyester resin substrate. This intermediary component provides the necessary chemical reactivity for strong adhesion to polar substrates while allowing the base propylene copolymer to maintain its processability and flexibility characteristics.
Solution Approach 2:
The invention applies local quality enhancement by adding specific functional components (polymer C with carboxylic acid groups) only in the adhesive layer where chemical bonding is needed, while the bulk propylene copolymer maintains its inherent processability and mechanical properties. This localized functional modification achieves improved adhesiveness without compromising overall processability.
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 method produces laminates with high initial adhesiveness to polyester resin substrates that maintain stability and adhesiveness even after heat treatments like boiling or retorting, reducing content leakage and enhancing durability.
Implementation Method 1
a heat treatment step of performing a heat treatment under a temperature condition of 80 to 140°C for 5 to 120 minutes
Implementation Method 2
the adhesive layer (I) comprises 97 to 70% by weight of a propylene copolymer (A), and 3 to 30% by weight of a copolymer (B) having a structural unit derived from butene
Data Source
Figure 1~2
AI summary
A method of producing a laminate comprising a polypropylene adhesive layer (I) and a substrate layer (II), the method comprising a heat treatment step of performing a heat treatment under a temperature condition of 80 to 140°C for 5 to 120 minutes, wherein the laminate satisfies at least the following requirements (1) to (5): (1) the adhesive layer (I) includes 97 to 70% by weight of a propylene copolymer (A) and 3 to 30% by weight of a copolymer (B) having a structural unit derived from butene (where the total of copolymers (A) and (B) is 100% by weight), (2) the copolymer (A) has a melting point (TmA) of 70 to 120°C measured with a differential scanning calorimeter (DSC), and includes less than 1 mol % of a structural unit derived from butene, (3) the copolymer (B) has a melting point (TmB) of 130°C or less measured with a differential scanning calorimeter (DSC), and includes 1 mol % or more of the structural unit derived from butene, (4) the adhesive layer (I) includes a polymer (C)having a structural unit derived from at least one graft monomer selected from the group consisting of unsaturated carboxylic acids and derivatives thereof, and (5) the substrate layer (II) includes a polyester resin.