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Method combining formic acid preprocessing and high-pressure homogenization to prepare nano-crystalline cellulose fibrils

A technology of nanocellulose and cellulose, applied in the field of natural polymer material preparation, can solve the problems of far less enhancement effect, complicated reaction system, small length and diameter of CNCs, etc., to increase interface compatibility, easy control of reaction, Excellent effect

Active Publication Date: 2016-06-29
QINGDAO INST OF BIOENERGY & BIOPROCESS TECH CHINESE ACADEMY OF SCI
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Problems solved by technology

In Carbohydrate Polymers, 2015, 133, 605-612, Li et al. disclosed a method for preparing nano-cellulose microcrystals (cellulosenanocrystals, CNCs) by hydrolyzing cellulose raw materials with formic acid, but the reaction time is longer and the concentration of formic acid is higher (98%)
For this reason, Chinese invention patents 2014106492298 and 201510680481.X respectively disclose adding a small amount of inorganic acid to the hydrolysis of formic acid to speed up the reaction and adding metal salts to reduce the concentration of formic acid, but the added inorganic acid or metal salt will complicate the reaction system. The long-diameter ratio of prepared CNCs is small, and the reinforcement effect in composite materials is far less than that of CNFs with large long-diameter ratio.

Method used

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  • Method combining formic acid preprocessing and high-pressure homogenization to prepare nano-crystalline cellulose fibrils
  • Method combining formic acid preprocessing and high-pressure homogenization to prepare nano-crystalline cellulose fibrils
  • Method combining formic acid preprocessing and high-pressure homogenization to prepare nano-crystalline cellulose fibrils

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preparation example Construction

[0038] In step 1) of the method for preparing CNFs according to the present invention: the weight ratio of the added cellulose raw material to the added formic acid solution is 1:10-100, when the weight ratio is less than 1:10, that is, the amount of formic acid solution added is insufficient , the reaction is not complete enough; and when the weight ratio is greater than 1:100, that is, the amount of formic acid solution is excessive, it is not economical enough.

[0039] In the prior art, in order to realize the defibrillation of cellulose in formic acid solution, catalysts, such as metal salt catalysts, inorganic acids, etc. must be used. Although the use of catalyst can shorten the time of defibrillation, it will inevitably remain in the final product, which will adversely affect the performance of the product. In order to overcome the problem of catalyst residue, the reaction product must be post-treated such as filtration step, the catalyst has been removed. However, th...

Embodiment 1

[0045] Weigh 3 g of absolute dry bleached spruce wood pulp into a 250 mL round bottom flask, add 100 mL of 88% (w / w) formic acid solution, and stir magnetically at 95° C. for 6 h. After the reaction, the flask was quickly placed in a cold water bath to cool to room temperature, and then the reaction mixture was transferred into a centrifuge tube and centrifuged at 5000 rpm for 5 min. The hydrolyzate can be directly returned to pretreat the next batch of cellulosic raw material. The precipitated jelly was washed by centrifugation with distilled water until neutral, and the centrifuged product was diluted with distilled water to a concentration of 0.2 wt%, and then homogenized 10 times by a high-pressure homogenizer at 60 MPa to obtain a viscous CNFs product. The yield of CNFs prepared in this example was 88% (relative to the original dry bleached spruce wood pulp). The FTIR pictures before and after hydrolysis are shown in the attachment figure 2 , as attached figure 2 Sho...

Embodiment 2

[0047] Weigh 3 g of absolute dry bleached eucalyptus pulp into a 250 mL round bottom flask, add 60 mL of 85% (w / w) formic acid solution, and magnetically stir at 90° C. for 5 h. After the reaction, the flask was quickly placed in a cold water bath to cool to room temperature, and then the reaction mixture was moved into a centrifuge tube and centrifuged at 5000 rpm for 10 min. The hydrolyzate can be directly returned to pretreat the next batch of cellulosic raw material. The precipitated jelly was centrifuged and washed with distilled water until neutral, and the centrifuged product was diluted with distilled water to a concentration of 0.5 wt%, and then homogenized 8 times by a high-pressure homogenizer at 80 MPa to obtain a viscous CNFs product. The yield of CNFs obtained in this example is 85% (relative to the original absolute dry bleached eucalyptus pulp), and the crystallinity is increased to 72% of CNFs from 65% of the original slurry (Pulp). The XRD patterns before and...

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Abstract

The invention relates to a green, economical and sustainable method for preparing nano-crystalline cellulose fibrils. The method includes the steps of firstly, cellulose raw material is added into a formic acid solution, and heating and stirring are performed for hydrolysis to obtain preprocessed cellulose; secondly, the preprocessed cellulose is separated from hydrolysate through centrifugal settling, the settled cellulose is centrifugally washed with water, and the washed cellulose is diluted into a cellulose suspension with certain concentration; thirdly, the separated hydrolysate can be directly recycled at least once, the recycled hydrolysate can recycle formic acid through reduced-pressure distillation, and the recycled formic acid can be recycled; fourthly, the cellulose suspension obtained in the second step is homogenized for certain times under certain pressure through a high-pressure homogenizing machine to obtain the colloidal nano-crystalline cellulose fibrils. The method has the advantages that no catalysts are used, and the method is relatively mild in reaction condition, easy in reaction control, simple to operate and environmental friendly.

Description

technical field [0001] The invention relates to the field of preparation of natural polymer materials, in particular to a new method for preparing nano-cellulose fibrils by using formic acid to pretreat cellulose raw materials combined with high-pressure homogenization. Background technique [0002] Cellulose senanofibrils (CNFs) are due to their unique structural properties (such as nanoscale, high specific surface area, high aspect ratio, low density, superior mechanical properties) and their wide range of raw materials (such as wood, cotton, Straw, bacteria, industrial and agricultural waste, etc.), biodegradable characteristics, has received more and more attention and research. Klemm et al. reported in Angewandte Chemie-international Edition, 2011, 50, 5438-5466 that CNFs can be widely used in nanomaterials, such as aerogels, food packaging materials, nanopaper and various nanocomposites. [0003] The most commonly used method for preparing CNFs is the mechanical metho...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C08B15/02C08B3/04
CPCC08B3/04C08B15/02
Inventor 杜海顺李滨刘超牟新东龚文博
Owner QINGDAO INST OF BIOENERGY & BIOPROCESS TECH CHINESE ACADEMY OF SCI
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