Microfibrillated Cellulose Filler for High-Loading Paper
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Solution Overview
Problem
Current methods for preparing microfibrillated cellulose on an industrial scale are energy-intensive due to the high viscosity of the starting material and product, and there is a need for economical methods to produce fillers for paper that can be used at high loading levels without compromising physical, mechanical, and optical properties.
Innovation Solution
A method involving the microfibrillation of a fibrous cellulose substrate in the presence of an inorganic particulate material, such as calcium carbonate, to create an aqueous suspension suitable for use as a filler in paper products, which reduces energy input and allows for high loading levels while maintaining or improving paper properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high amounts of filler are added to paper products to reduce cost, then cost savings increase, but physical, mechanical and optical requirements deteriorate
Solution Approach 1:
The invention uses a composite filler system combining hydrophobized cellulose microfibrils with inorganic particulate filler. The cellulose microfibrils form a network structure that binds inorganic particles together, creating a composite filler that maintains paper strength even at high loading levels (up to 80% or more by weight). This composite approach allows cost reduction through high filler content while preserving mechanical properties through the reinforcing cellulose network.
2Productivity
If microfibrillated cellulose is prepared using current industrial methods, then microfibrillated cellulose is produced, but energy consumption increases due to high viscosity
Solution Approach 1:
The invention changes the physical and chemical parameters of cellulose during processing. Specifically, it uses hydrophobization treatment to modify cellulose surface properties, reducing inter-fibril adhesion and viscosity. This parameter change allows microfibrillation to proceed with lower energy input while maintaining productivity, as the modified cellulose requires less mechanical energy to separate into microfibrils.
Solution Approach 2:
The invention partially replaces mechanical microfibrillation with chemical/physical modification through hydrophobization. By treating cellulose with hydrophobizing agents before or during microfibrillation, the process reduces reliance on high-energy mechanical breakdown, substituting some mechanical work with chemical modification that facilitates easier separation and reduces viscosity-related energy demands.
Data Source
AI summary
A method for preparing an aqueous suspension may include providing a fibrous substrate comprising cellulose having a Canadian Standard freeness equal to or less than 450 cm3, and microfibrillating the fibrous substrate in an aqueous environment by grinding in the presence of a grinding medium consisting essentially of mullite. The grinding may be carried out in the absence of grindable inorganic particulate material. The grinding medium may be present in an amount of at least about 10% by volume of the aqueous environment. The microfibrillated cellulose may have a fibre steepness of from about 20 to about 50.