Chopped carbon fiber bundles and method for producing chopped carbon fiber bundles
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Solution Overview
Problem
The production of chopped carbon fiber bundles with high fluidity and productivity is challenging when using carbon fiber bundles with a large number of filaments and high total fineness, as they tend to have low flatness, leading to issues with sizing agent penetration, cohesion, and increased shear forces, resulting in fibrillation and clogging during compounding.
Innovation Solution
A chopped carbon fiber bundle with a total fineness of 25,000 to 45,000 dtex and a sizing agent deposit of 1% to 5% by mass, characterized by a length of 1 mm to 50 mm, a diameter ratio of 6.0 to 18.0, and an orientation parameter of 4.0 or less, using thermoplastic resin-based sizing agents, and a method involving primary and secondary sizing agent application followed by cutting and drying to achieve uniform cohesion and handleability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If carbon fiber bundles with a large number of filaments and high total fineness are used to reduce production cost, then cost reduction is achieved, but the bundles have low flatness leading to poor sizing agent penetration and low cohesion
Solution Approach 1:
The patent applies parameter changes by controlling the flatness of carbon fiber bundles within a specific range (0.05 to 0.2 mm) and optimizing the sizing agent composition (combining wax and coupling agent in specific ratios) to achieve both cost reduction through high total fineness (24,000-48,000 dtex) and adequate sizing agent penetration while maintaining bundle cohesion
2Manufacturing precision
If the carbon fiber bundle shape is made flat to improve sizing agent penetration, then sizing agent penetration is improved, but fluidity and bundling properties decrease
Solution Approach 1:
The patent optimizes the flatness parameter within a specific range (0.05 to 0.2 mm) to balance sizing agent penetration and fluidity. Additionally, the sizing agent composition is modified by combining wax and coupling agent in specific ratios, which reduces surface friction and improves fluidity while maintaining adequate penetration
3Volume of stationary object
If the cross-sectional shape approaches circular to increase bulk density, then bulk density is increased, but sizing liquid penetration becomes difficult and cohesion becomes irregular
Solution Approach 1:
The patent controls the flatness parameter within a specific range (0.05 to 0.2 mm) to prevent excessive circularity while maintaining adequate bulk density. The optimized sizing agent composition (wax and coupling agent combination) ensures uniform penetration and regular cohesion by reducing surface friction and improving wettability
4Productivity
If shear force is increased during compounding to improve mixing, then mixing is improved, but carbon fiber bundles are easily fibrillated and fiber balls are generated
Solution Approach 1:
The patent uses wax and coupling agents as intermediary substances that coat the carbon fiber bundle surface, reducing surface friction and acting as a lubricant during compounding. This allows for adequate mixing efficiency while preventing excessive shear force from causing fibrillation or fiber ball generation
5Stability of the object's composition
If a large amount of sizing agent is applied to improve cohesion, then cohesion is improved, but handling and fluidity are negatively affected
Solution Approach 1:
The patent optimizes the sizing agent composition by combining wax and coupling agent in specific ratios, which enhances cohesion through chemical bonding while the wax component reduces surface friction to maintain good handleability and fluidity. This eliminates the need for excessive sizing agent application
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 solution enhances the processability and handleability of the chopped carbon fiber bundles, resulting in improved mechanical characteristics and increased productivity during compounding, while maintaining stability and dispersibility with a reduced amount of sizing agent.
Implementation Method 1
the sizing agent can easily penetrate into the interior of the carbon fiber bundle
Data Source
AI summary
Provided are: chopped carbon fiber bundles which have high fluidity without decreasing the dispersibility of carbon fibers and the physical properties of a molded product; and a method for producing chopped carbon fiber bundles with high productivity. Chopped carbon fiber bundles, each of which contain a carbon fiber bundle having a total fineness of from 25,000 dtex to 45,000 dtex (inclusive) and a sizing agent in an amount of from 1% by mass to 5% by mass (inclusive) relative to the total mass of the chopped carbon fiber bundle. The length (L) of each chopped carbon fiber bundle along the fiber direction of the carbon fiber bundle is from 1 mm to 50 mm (inclusive); the ratio of the longest diameter (Dmax) to the shortest diameter (Dmin) of a cross section perpendicular to the fiber direction of each chopped carbon fiber bundle, namely Dmax/Dmin is from 6.0 to 18.0 (inclusive); and the orientation parameter of the single fibers present in the surface of each chopped carbon fiber bundle is 4.0 or less.