Block Composite Nucleator for Propylene Interpolymer Crystallization
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Solution Overview
Problem
High comonomer content propylene-based interpolymers exhibit slow crystallization rates, making them difficult to pelletize and store, and limiting their use in applications requiring fast crystallization, such as fiber spinning, due to their slow crystallization kinetics.
Innovation Solution
A composition comprising 30-95 wt% of a random or homogeneous propylene-based interpolymer blended with 5-70 wt% of a block composite nucleator, which includes a first polymer of polypropylene, a second alpha-olefin-based polymer, and a block copolymer with a hard segment predominantly derived from ethylene, acting as a nucleating agent to enhance crystallization rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If high comonomer content propylene-based interpolymer is used to achieve homogeneous composition distribution and narrow molecular weight distribution, then polymer quality is improved, but crystallization rate deteriorates
Solution Approach 1:
A block composite nucleator comprising polypropylene, ethylene-based polymer, and block copolymer is introduced as an intermediary substance to mediate between the high comonomer content propylene interpolymer and the crystallization process. The nucleator provides heterogeneous nucleation sites that accelerate crystallization without requiring changes to the polymer's composition or structure, thus resolving the contradiction between maintaining homogeneous composition and achieving fast crystallization.
Solution Approach 2:
The invention changes the nucleation parameters by introducing a multi-component nucleator system with specific composition ratios (30-95 wt% propylene interpolymer, 5-70 wt% block composite nucleator). The block copolymer segment with at least 80 wt% ethylene units creates favorable thermodynamic conditions for nucleation, enabling fast crystallization at lower supercooling degrees while maintaining the high comonomer content and homogeneous composition of the base polymer.
2Productivity
If conventional nucleating agents or ethylene copolymers are added to accelerate crystallization, then crystallization rate is improved, but product stiffness increases undesirably
Solution Approach 1:
The block composite nucleator exhibits local quality differentiation through its multi-component structure. The block copolymer segment with at least 80 wt% ethylene units provides localized nucleation activity at specific sites within the polymer matrix, accelerating crystallization only where needed without uniformly increasing the stiffness of the entire product. This localized action allows fast crystallization while preserving the desired flexibility and processability of the final product.
3Stability of the object's composition
If slow crystallization occurs in high comonomer content propylene copolymer, then homogeneous composition is maintained, but pelletization and storage become difficult
Solution Approach 1:
The block composite nucleator performs preliminary action by creating nucleation sites before the actual crystallization and pelletization processes. The presence of the nucleator pre-establishes the conditions for rapid crystallization during cooling, ensuring that the polymer crystallizes quickly enough to be properly pelletized and stored without blocking, while the nucleator itself is designed to be compatible with the homogeneous composition requirements of the high comonomer content propylene interpolymer.
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 block composite nucleator significantly accelerates the crystallization process of high comonomer content propylene-based interpolymers, enabling faster pelletization, improved storage, and expanded application possibilities by modifying the crystalline structure and physical properties.
Implementation Method 1
The onset of crystallization is known as nucleation (i.e., a nucleus for starting a crystalline formation process), and this may occur randomly throughout the polymer matrix as the individual polymer molecules begin to align. Alternatively, nucleation may occur at the interface of a foreign impurity or an intentionally added nucleating agent.
Implementation Method 2
The proper use of nucleating agents can result in unique and desirable crystalline structures and promote the efficiency of a given process (e.g., by shortening process times and/or initiating nucleation at higher temperatures).
Data Source
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AI summary
A composition includes (A) 30-95 wt% of a random or homogeneous propylene-based interpolymer having: (i) a comonomer content of at least one of C2 and C4-10 α-olefins of 7 wt% to 49 wt% based on the total weight of the propylene-based interpolymer, (ii) a density of 0.90 g/cc or less, and (iii) an MFR of 1 g/10 min or greater (230°C/2.16 kg); and (B) 5-70 wt% of a block composite nucleator comprising: (1) a first polymer that includes polypropylene; (2) a second polymer that includes an alpha-olefin based polymer, the alpha-olefin being selected from at least one of a C2 and C4-10 α-olefins, and (3) a block copolymer having a first segment and a second segment, the first segment of the block copolymer having the same composition as the first polymer in the block composite nucleator and the second segment of the block copolymer having the same composition as the second polymer of the block composite nucleator.