Propylene Block Copolymer Flow Mark Reduction
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Solution Overview
Problem
Existing polypropylene resin compositions for automobile parts face challenges in reducing flow marks while maintaining high-quality large-sized moldings and excellent moldability, as previous solutions either sacrifice mechanical properties or fail to adequately address flow mark issues.
Innovation Solution
A propylene block copolymer with a high-fluidity crystalline propylene polymer portion and a high-molecular-weight propylene-ethylene random copolymer portion, having a specific molecular weight distribution and viscosity ratio, is used as a molding appearance modifier to improve the appearance of polypropylene resin compositions without compromising original properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high fluidity material (ICP with increased MFR) is used to improve moldability and obtain thinner moldings, then moldability is improved, but flow marks appear on the surface
Solution Approach 1:
The patent applies parameter changes by precisely controlling the MFR of the crystalline propylene polymer portion (10-200 g/10min) and the viscosity ratio between crystalline and random copolymer portions (0.1-5.0). This optimization allows the material to have sufficient fluidity for thin-walled molding while preventing flow marks through controlled viscous flow characteristics during injection molding.
Solution Approach 2:
The patent uses composite materials by formulating a propylene block copolymer consisting of two distinct components: a crystalline propylene polymer portion and a propylene-ethylene random copolymer portion. The crystalline portion provides necessary fluidity for moldability, while the random copolymer portion suppresses flow mark formation, creating a synergistic composite material that resolves the contradiction between moldability and surface quality.
2Loss of time
If ICP with high MFR is used to achieve thinner moldings in shorter molding time, then molding time is reduced, but flow marks appear reducing commercial value
Solution Approach 1:
The patent optimizes the MFR parameter of the crystalline propylene polymer portion to a specific range (10-200 g/10min) that enables rapid filling of thin-walled molds, significantly reducing molding cycle time. Simultaneously, the viscosity ratio parameter is controlled (0.1-5.0) to ensure smooth flow that prevents flow mark formation, thus achieving both time efficiency and appearance quality.
Solution Approach 2:
The composite propylene block copolymer structure combines a high-fluidity crystalline portion for rapid molding with a propylene-ethylene random copolymer portion that maintains surface quality. This composite approach allows thin-walled parts to be molded quickly without sacrificing appearance, thereby reducing loss of time while maintaining commercial value.
3Manufacturing precision
If molding appearance modifier is added to improve flow mark characteristic, then appearance is improved, but original physical properties may be compromised
Solution Approach 1:
The patent carefully controls the viscosity ratio parameter between the crystalline propylene polymer portion and the propylene-ethylene random copolymer portion within the range of 0.1-5.0. This precise parameter control ensures that the modifier effectively suppresses flow marks while maintaining the mechanical properties and physical characteristics of the original polypropylene resin, avoiding compromise of reliability.
Solution Approach 2:
The patent develops a composite propylene block copolymer where the crystalline propylene polymer portion serves as the base material retaining original physical properties, and the propylene-ethylene random copolymer portion acts as the modifier improving flow mark characteristic. The synergistic combination in specific proportions allows simultaneous achievement of appearance improvement and property preservation.
Data Source
AI summary
Provided are a molding appearance modifier for resins capable of controlling appearance of large-sized molded parts only by small addition, and a polypropylene resin composition capable of providing good appearance to, for example, automobile exterior parts, and has excellent molding processability. The invention relates to a propylene block copolymer having a crystalline propylene polymer portion and a propylene•ethylene random copolymer portion, wherein the crystalline propylene polymer portion has an intrinsic viscosity [η]homo of 1.2 dl/g or less; the propylene•ethylene random copolymer portion has an ethylene content of 30 to 70 wt. %, has an intrinsic viscosity [η]copoly of 2.5 to 7.0 dl/g, and is added in an amount of 40 to 80 wt. % based on the whole propylene block copolymer; and the propylene block copolymer, in its entirety, has a melt flow rate of 0.1 to 10 g/10 min; and a [η]copoly/[η]homo ratio falls within a range of 2.5 to 10; and a polypropylene resin composition using the propylene block copolymer as a molding appearance modifier.