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A green method for continuously dissolving natural polymer materials

A technology of natural polymer and viscosity-average molecular weight, which is applied in the field of polymer materials, can solve the problems of shortening the dissolution time of cellulose, easy gelation, easy gelation, gelation time within 1 hour, etc., to achieve gelation The effect of prolonging the curing time and improving the solubility

Active Publication Date: 2021-03-12
SICHUAN UNIV
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  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

However, it has the following defects: 1) the system is in a metastable state, and it is easy to gel at low or high temperatures, and the dissolution processing window is narrow; 2) the dissolution temperature is harsh, and cellulose and solvent need to be mixed quickly, and once it exceeds a specific temperature, it will not dissolve; 3) The resulting system after mixing the solvent with cellulose, etc. is difficult to carry out subsequent defoaming and filtration processes, so industrial production cannot be realized; in addition, the solubility of cellulose with a molecular weight of 90,000 is only 4-5 %, and the solution is easy to gel, and the gel time is within 1 hour, making it impossible to spin normally
[0003] In response to this defect, LiOH and urea systems are often used to replace NaOH and urea systems in the prior art. For example, Chinese patent 200301115678 discloses a lithium hydroxide and urea composition solvent and its use for dissolving cellulose. The method of directly dissolving cellulose and preparing cellulose or film, although this method is simple and easy, but because LiOH is expensive and costly, it cannot meet the industrial requirements
NaOH, urea and thiourea systems are also used to replace NaOH and urea systems. For example, Donghua University has proposed a continuous low-temperature alkali urea method, which is to add a certain amount of thiourea to the alkali / urea dissolution system to directly dissolve the fiber Suspension is made of raw material and alkali / urea / thiourea / water solution, and then the temperature is quickly lowered to the dissolution temperature; in this system, a spherical complex is formed between sodium hydroxide, urea, thiourea and water, in which thiourea It is the main part to form the outer complex, which greatly shortens the dissolution time of cellulose and improves the production efficiency (the preparation and performance research of cellulose film such as Tong Xiantao; a kind of cellulose composite solvent system and its application such as Yu Muhuo); but due to The solvent system must add thiourea, and thiourea is toxic, and the use of thiourea has certain pollution problems, so its industrial production is not environmentally friendly
[0004] From the above analysis, it can be seen that there is no relevant report in the prior art about "using only NaOH and urea system as solvents, without adding non-toxic additives, the continuous industrial production of natural polysaccharide polymers such as cellulose can be realized"; And if this technical problem can be solved, it will have excellent industrialization value, because it is not only low in cost, but also environmentally friendly and non-toxic

Method used

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  • A green method for continuously dissolving natural polymer materials
  • A green method for continuously dissolving natural polymer materials
  • A green method for continuously dissolving natural polymer materials

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0044] Add 14 kg of NaOH to the stirred tank, add 24 kg of urea, add 162 liters of water, continue to stir until the urea is completely dissolved; obtain a cellulose solvent whose weight ratio of NaOH is 7wt%, and the weight ratio of urea is 12wt%; finally add dry 10 kilograms of cellulose pulp with a molecular weight of 90,000, stirred at a stirring speed of 50 RPM for half an hour at 15-25° C. to obtain a cellulose pulp porridge, and then milled for one hour with a milling pump (to ensure that the pulp porridge can pass smoothly through a hole diameter of 5 mm) The screen will not be blocked during the metering and conveying and the whole pulp and porridge components are stable and uniform); then the screw pump is accurately metered, and the pulp and porridge is injected into the screw extruder at a constant flow rate of 50 liters / hour, and the screw extruder The temperature of each stage is: 1-5 stage: -18°C, 6-8 stage: -12°C, the twin-screw shear speed is 800rpm; the cellul...

Embodiment 2

[0046] Add 14 kg of NaOH into the stirring tank, add 50 liters of water, stir at room temperature, then add 1.6 kg of zinc oxide, continue stirring, wait for the complete dissolution of zinc oxide, add 24 kg of urea, add 110.4 liters of water, continue stirring until Urea is all dissolved; Obtaining NaOH weight ratio is 7wt%, and urea weight ratio is 12wt%, and the cellulose solvent that zinc oxide weight ratio is 0.8wt%; Finally add 10 kilograms of dried 90,000 molecular weight cellulose pulp, 15-25 After stirring for half an hour at a stirring speed of 50RPM at ℃, the cellulose porridge was obtained, and then milled for one hour with a milling pump (to ensure that the porridge can pass through the sieve with an aperture of 5mm smoothly, and that it will not be blocked during metering and transportation and that the entire porridge group Stable and uniform); then accurately metered by the screw pump, inject the porridge into the screw extruder at a constant speed of 50 liters / ...

Embodiment 3

[0052] Add 14 kg of NaOH to the stirred tank, add 24 kg of urea, add 162 liters of water, continue to stir until the urea is completely dissolved; obtain a cellulose solvent whose weight ratio of NaOH is 7wt%, and the weight ratio of urea is 12wt%; finally add dry 13 kilograms of the 70,000 molecular weight cellulose pulp that has been passed, stirred at a stirring speed of 50 RPM for half an hour at 15-25° C. to obtain a cellulose pulp porridge, and then used a milling pump to grind for one hour (guaranteeing that the pulp porridge can pass through the aperture smoothly is 5 mm) sieve); then accurately metered by the screw pump, inject the porridge into the screw extruder at a constant speed of 30 liters / hour, and the temperatures of each section of the screw extruder are: 1-5 section: -18°C, 6- Section 8: -12°C, twin-screw shear speed at 800rpm; dissolving in a twin-screw extruder for 1 to 3 minutes to obtain a cellulose solution containing a small amount of air bubbles; at t...

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Abstract

The invention relates to a method capable of continuously dissolving natural polymer materials, belonging to the field of polymer materials. The invention provides a method for continuously dissolving natural polymer materials. The method is as follows: first stirring and mixing the solvent and natural polymer material powder or natural polymer pulp at room temperature to obtain a natural polymer material suspension; Liquid milling until its particle size is ≤5mm; then the milled suspension is sheared at a high speed at a shear rate of 600-1000rpm in a twin-screw extruder at -20--12°C, within 1-3min Dissolving the natural polymer material to prepare a transparent natural polymer solution; wherein, the natural polymer material in the natural polymer material powder or natural polymer pulp is a natural polymer material that can be dissolved by a low-temperature alkali urea aqueous solution. The invention provides a green and environment-friendly method capable of industrially dissolving natural polymers such as cellulose continuously, and the method is simple and feasible.

Description

technical field [0001] The invention relates to a method capable of continuously dissolving natural polymer materials, belonging to the field of polymer materials. Background technique [0002] Natural polysaccharide polymer materials such as cellulose and chitin; due to the large number of hydrogen bonds in the molecule, the decomposition temperature is higher than the melting temperature, and only special solvents can dissolve it. Among them, the sodium hydroxide / urea / water low-temperature dissolution system has low cost due to the solvent , environmental friendliness, safety and non-toxic advantages, and has a good industrialization prospect. However, it has the following defects: 1) the system is in a metastable state, and it is easy to gel at low or high temperatures, and the dissolution processing window is narrow; 2) the dissolution temperature is harsh, and cellulose and solvent need to be mixed quickly, and once it exceeds a specific temperature, it will not dissolv...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C08J3/03C08L1/02
CPCC08J3/03C08J2301/02
Inventor 傅强谢康陈枫
Owner SICHUAN UNIV