Polypropylene Composition with Segmented Copolymer Fractions
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Solution Overview
Problem
Polypropylene compositions face challenges in achieving high hot tack strength, low heat sealing initiation temperature, and high processing speeds for biaxially oriented films, while also requiring high melting temperatures to prevent stickiness issues during film manufacture.
Innovation Solution
A polypropylene composition comprising a propylene homopolymer and a propylene copolymer with two fractions of different 1-hexene comonomer content, where the weight ratio of the copolymer to homopolymer is between 95/5 and 75/25, and the comonomer content is between 1.0 and 10.0 wt.%, specifically designed to enhance melting temperature, heat sealing initiation temperature, and crystallization temperature alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high melting temperature is used to avoid stickiness during film manufacture, then processing reliability is improved, but heat sealing initiation temperature increases making sealing difficult
Solution Approach 1:
The propylene copolymer is segmented into two distinct fractions with different comonomer contents: Fraction A (1.0-5.0 wt% comonomer) providing high melting temperature for processing reliability, and Fraction B (5.0-20.0 wt% comonomer) providing low heat sealing initiation temperature. This segmentation allows each fraction to specialize in one function, resolving the contradiction between high melting point and low sealing initiation temperature.
Solution Approach 2:
Different regions of the polymer composition have different properties: Fraction A with lower comonomer content provides high melting temperature (125-145°C) suitable for film processing, while Fraction B with higher comonomer content provides low heat sealing initiation temperature (90-110°C) for easy sealing. Each fraction contributes its specific local quality to the overall composition.
2Ease of operation
If low heat sealing initiation temperature is achieved for easy sealing, then sealing ease is improved, but hot tack strength decreases compromising seal integrity
Solution Approach 1:
The polymer is segmented into two fractions where Fraction B (higher comonomer content) enables low heat sealing initiation temperature for easy sealing, while Fraction A (lower comonomer content) provides high hot tack strength for seal integrity. The segmentation allows each fraction to fulfill its specific function without compromising the other.
Solution Approach 2:
The invention creates a composite polymer system combining two propylene copolymer fractions with different comonomer contents. This composite structure integrates the low-temperature sealing capability of high-comonomer Fraction B with the high-strength hot tack properties of low-comonomer Fraction A, achieving both sealing ease and seal integrity simultaneously.
3Productivity
If high processing speeds are achieved for biaxially oriented films, then productivity is improved, but stickiness problems increase during manufacture
Solution Approach 1:
The polymer composition is segmented into Fraction A with low comonomer content (1.0-5.0 wt%) that provides high melting temperature and resistance to stickiness during high-speed film processing, and Fraction B with higher comonomer content that provides other necessary properties. This segmentation allows high processing speeds without stickiness problems.
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 composition achieves high melting temperatures, low heat sealing initiation temperatures, and close crystallization to sealing initiation temperatures, ensuring strong seals and efficient film processing with reduced stickiness, thereby improving processing speeds and seal integrity.
Implementation Method 1
the crystallization temperature close to the heat sealing initiation temperature
Implementation Method 2
high melting temperature Tm
Data Source
Figure 1
Figure 2~3
AI summary
Polypropylene composition comprising propylene homopolymer(H-PP) and a propylene copolymer (C-PP), said copolmyer comprises (a) a propylene copolymer fraction (A) having a comonomer content of equal or above 1.0 wt.-%, the comomers are C5 to C12 a-olefins, and (b) a propylene copolymer fraction (B) having a comonomer content of 4.0 to 20.0 wt- %, the comomers are C5 to C12 a-olefins, wherein further (i) the comonomer content in propylene copolymer fraction (A) is lower compared to the comonomer content in the propylene copolymer fraction (B), (ii) the propylene copolymer (C-PP)has a comonomer content of at least 2.0 wt.-%, the comomers are C5 to C12 a-olefins, (iii) the weight ratio [(A)/(B)] of the propylene copolymer fraction (A) to the propylene copolymer fraction (B) is in the range of 20/80 to 80/20, and (iv) the weight ratio [(C-PP)/(H-PP)] of the propylene copolymer (C-PP) to the propylene homopolymer(H-PP) is in the range of 95/5 to 75/25.