EVOH Pellet Cracking Prevention via Coagulation Control
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Solution Overview
Problem
Saponified ethylene-vinyl ester copolymer resin pellets are prone to cracking, chipping, and fine powder generation during transport due to their high crystallinity and brittleness, which complicates stable melt molding.
Innovation Solution
The pellets are processed to have an amount of fine powder of 400 ppm or less after a ball mill crushing test by optimizing the composition, coagulation temperature, and washing conditions, ensuring surface smoothness and preventing cracking and chipping during transport.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If EVOH resin is produced by extruding resin solution into coagulating liquid and cutting, then the resin can be formed into pellets, but the pellets become porous and hard/brittle due to high crystallinity, causing cracking and chipping during transport
Solution Approach 1:
The invention changes the physical and chemical parameters of the resin solution, coagulating liquid, and processing conditions (temperatures, concentrations, molecular weights) to optimize the crystallization process. This produces pellets with controlled crystallinity that maintain strength while preventing excessive brittleness and cracking during transport
Solution Approach 2:
The invention uses composite resin compositions containing specific ratios of EVOH resin and other polymers, creating a material that combines the gas barrier properties of EVOH with the toughness and flexibility of complementary materials, thereby reducing pellet brittleness and cracking
2Reliability
If EVOH resin pellets are transported in packaged form, then protection is provided, but temperature changes, loading state, and vibration still cause fusion, cracking, and chipping
Solution Approach 1:
The invention applies beforehand cushioning by optimizing pellet surface properties and internal structure to be more resistant to transport stresses. The pellets are designed with improved surface smoothness and internal flexibility that cushion against the effects of vibration, temperature changes, and mechanical stress during transport, preventing cracking and chipping before they occur
3Reliability
If EVOH resin has high crystallinity for excellent gas barrier property, then gas molecules are hard to pass through, but the resin becomes hard and brittle, making stable melt molding difficult
Solution Approach 1:
The invention optimizes processing parameters such as temperature, pressure, and cooling rates during pellet formation and molding to control the crystallization process. This creates a balanced structure with sufficient crystallinity for gas barrier properties while maintaining enough amorphous content and molecular mobility for stable melt molding
Solution Approach 2:
The invention uses composite resin systems that combine EVOH with other polymers having complementary properties. The composite structure provides the gas barrier performance of crystalline EVOH while the amorphous or less crystalline components provide melt flow and moldability
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 resulting pellets exhibit improved melt moldability and reduced cracking and chipping, maintaining their integrity during transport and processing.
Implementation Method 1
a method of cutting a strand-like material (continuous rod-like body) obtained by extruding the resin solution from a metal plate into a coagulating liquid to allow for deposition
Data Source
AI summary
The invention provides a saponified ethylene-vinyl ester copolymer pellet which can be inhibited from cracking, chipping and generation of fine powder at the time of transport and is excellent in melt moldability. The saponified ethylene-vinyl ester copolymer pellet of the invention is a pellet which is obtained from a resin composition containing a saponified ethylene-vinyl ester copolymer resin and in which an amount of fine powder after an impact crushing test with ball mill is 400 ppm or less with respect to the saponified ethylene-vinyl ester copolymer pellet.