阅读说明：本技术 一种醋酸丁酸纤维素的沉析方法 (Precipitation method of cellulose acetate butyrate ) 是由 余炎冰 李丽 尹伊君 崔乾 陈来中 于 2021-10-28 设计创作，主要内容包括：本发明公开了一种醋酸丁酸纤维素的沉析方法,该方法将含有醋酸丁酸纤维素的待沉析液通过喷嘴喷入含有稳定剂的水中,所述喷嘴位于水面以上,同时在高速搅拌下沉析,得到醋酸丁酸纤维素颗粒。本发明方法在稳定剂和高速搅拌的条件下,使析出的CAB固体均匀分散,避免相互粘结、成团,保持颗粒状,得到的CAB产品颗粒均匀、堆密度高,且稳定剂可被水洗去,不影响产品性能。(The invention discloses a cellulose acetate butyrate precipitation method, which comprises the steps of spraying a solution to be precipitated containing cellulose acetate butyrate into water containing a stabilizing agent through a nozzle, wherein the nozzle is positioned above the water surface, and precipitating under high-speed stirring to obtain cellulose acetate butyrate particles. The method of the invention enables the precipitated CAB solid to be dispersed evenly under the conditions of the stabilizer and high-speed stirring, avoids mutual bonding and agglomeration, keeps granular shape, and the obtained CAB product has even granules and high bulk density, and the stabilizer can be washed by water without affecting the product performance.)

1. A cellulose acetate butyrate precipitation method is characterized in that a solution to be precipitated containing cellulose acetate butyrate is sprayed into water containing a stabilizer through a nozzle, the nozzle is located above the water surface, and the solution is precipitated under high-speed stirring to obtain cellulose acetate butyrate particles.

2. The precipitation method according to claim 1, wherein the stabilizer is any one or a combination of at least two of cetyltrimethylammonium bromide, sodium dodecylsulfonate, sodium allylsulfonate, preferably cetyltrimethylammonium bromide.

3. A precipitation method according to claim 1 or 2, wherein the mass concentration of the stabilizer in the stabilizer-containing water is 0.5-6%, preferably 1-3.5%, based on the mass of the stabilizer-containing water.

4. A precipitation method according to any one of claims 1-3, wherein the amount of water containing the stabilizing agent is 7-15 times, preferably 8-12 times the mass of the liquid to be precipitated.

5. A precipitation method according to any one of claims 1 to 4, wherein the solution to be precipitated containing cellulose acetate butyrate has a composition comprising 13 to 30% by mass of cellulose acetate butyrate, 60 to 85% by mass of butyric acid, 0.5 to 10% by mass of acetic acid, and 0.5 to 1% by mass of water, based on 100% by mass of the solution.

6. A precipitation process according to any one of claims 1-5, wherein said nozzle is a single fluid high pressure atomising nozzle, preferably a standard fan nozzle in the Japanese basin;

preferably, the feed pressure to the nozzle is from 0.15 to 0.3MPa (gauge), preferably from 0.18 to 0.24MPa (gauge);

preferably, the spray diffusion angle of the nozzle is 50-80 degrees, preferably 55-70 degrees, and the droplet diameter after spraying is 140-500 μm, preferably 250-470 μm;

preferably the outlet of the nozzle is directed vertically downwards, the nozzle outlet being located 1-8cm, preferably 3-5cm, above the water surface.

7. The method according to any one of claims 1 to 6, wherein the liquid flow rate at the outlet of the nozzle is 0.05 to 0.5m/s, preferably 0.1 to 0.35 m/s;

preferably, the spray flow rate per unit cross-sectional area is 0.2 to 0.5L/min m²Preferably 0.25 to 0.4L/min. m²；

Preferably, the settling-out residence time for continuing high-speed stirring after the feeding of the nozzle is finished is 3-10min, preferably 4-8 min.

8. A precipitation method according to any one of claims 1-7, wherein the high-speed stirring rotation speed is 400-1000r/min, preferably 500-800 r/min;

preferably, the high-speed stirring adopts any one or a combination of at least two of a slant blade paddle, a propelling paddle, a six-rear-bent blade opening turbine paddle, a straight blade disc turbine paddle, a slant blade disc turbine paddle, a tooth-shaped disc turbine paddle and a boolean-gold type paddle, and the straight blade disc turbine paddle and/or the slant blade disc turbine paddle are/is preferred.

9. A method according to any one of claims 1 to 8, wherein the precipitation is carried out in a stirred tank, the paddle being positioned at a height of 1/3 to 1/2 of the reaction tank, the paddle having a diameter of 2/3 to 3/4 of the diameter of the stirred tank.

10. A precipitation method according to any one of claims 1 to 9, wherein the precipitation method further comprises washing with water and drying after discharging through the discharge port to obtain cellulose acetate butyrate particles;

preferably, the cellulose acetate butyrate particles have an average particle size of 300-600 μm and a bulk density of 0.45-0.6Kg/m³Surface area of 0.3-0.5m²Acid number < 200ppm (based on acetic acid); the particle size distribution coefficient is 0.3-0.5.

Technical Field

The invention provides a precipitation method of cellulose acetate butyrate, belonging to the field of organic chemical synthesis.

Background

Cellulose Acetate Butyrate (CAB) is a derivative of cellulose, resulting from the esterification of the hydroxyl groups on cellulose with acetic acid and butyric acid. CAB is compatible with various resins, has good flexibility, cold resistance, leveling property and color retention, is anti-aging and non-yellowing, and can be used for manufacturing plastic substrates, thin films and leveling agents, film forming substances and the like of various coatings with high transparency and good weather resistance.

Generally, the production process of CAB comprises the steps of activation, esterification, hydrolysis, neutralization, precipitation, washing, drying and the like, and each step is strictly controlled to ensure that CAB products with good quality are obtained. One key product index is the appearance and bulk density of the product, and the powder CAB is beneficial to washing, deacidification and drying in the washing process and cannot be twisted together in the conveying process, so that the transmission efficiency is improved; CAB products with high bulk density can reduce the use of packaging bags and improve the space utilization rate. The CAB is added into a large amount of water in the traditional precipitation method, and is precipitated and dispersed under high-speed stirring or shearing, but most CAB products obtained at the moment are blocky or flocculent and need to be crushed in the next step, and the heat generated in the crushing process can exceed the glass transition temperature of the CAB by 85 ℃, so that the products are yellow and sticky, and equipment is locked, and the requirements on the crushing process and the equipment are strict. And the CAB product obtained by the traditional method has lower bulk density, needs more packaging volume under the same quality and influences the packaging efficiency. Patent CN111253616A adopts the method of two-step flash distillation to get rid of butyric acid and water from the product, avoids washing, filtering, stoving production waste water, reduces the energy consumption, but the product that obtains is fluffy cotton-shaped, has improved the dissolution rate of product in the use, but the cotton-shaped product is unfavorable for the transport and the packing of product.

Therefore, how to create a one-step precipitation method which can improve the appearance of the CAB product in the precipitation process and increase the bulk density of the product becomes a problem which needs to be solved urgently in the industry.

Disclosure of Invention

In order to solve the technical problems, the invention provides a method for precipitating cellulose acetate butyrate, which is used for improving the granularity of a precipitated product and increasing the bulk density of the precipitated product.

In order to achieve the above purpose, the invention adopts the following technical scheme:

the invention provides a cellulose acetate butyrate precipitation method, which comprises the following steps:

and (2) spraying the solution to be precipitated containing the cellulose acetate butyrate into water containing a stabilizer through a nozzle, wherein the nozzle is positioned above the water surface, and simultaneously precipitating under high-speed stirring to obtain cellulose acetate butyrate particles.

Further, the stabilizing agent is any one or a combination of at least two of cetyl trimethyl ammonium bromide, sodium dodecyl sulfonate and sodium allyl sulfonate, preferably cetyl trimethyl ammonium bromide; the stabilizing agent can form a film on the surface of a droplet of the precipitation liquid, so that the precipitation liquid droplet can keep a droplet shape and prevent the droplets from aggregating and condensing; the interface strength is increased, so that the precipitation liquid drops are not stretched along with the shearing force generated by stirring to separate out a flocculent product; the stabilizer is dissolved in water and can be removed from the surface of the product in a water washing mode, the quality and the performance of the product cannot be influenced, particularly, the cetyl trimethyl ammonium bromide has longer chain, stronger interface strength and longer liquid drop-shaped retention time, so the bulk density of the product is higher, and the quaternary ammonium salt can promote the dissolution of butyric acid in the water, so that the butyric acid wrapped by the product is less, and the water consumption for washing the product is reduced.

Further, the mass concentration of the stabilizer in the stabilizer-containing water according to the present invention is 0.5 to 6%, preferably 1 to 3.5%, based on the mass of the stabilizer-containing water.

Further, the amount of the water containing the stabilizing agent is 7-15 times, preferably 8-12 times of the mass of the liquid to be precipitated. The dosage of the stabilizer and the water needs to be controlled within the scope of the invention in the precipitation process, wherein the water content is not too low, because the water content is low, the concentration of acid in the precipitation liquid can be increased, CAB can be dissolved in the acid, and the precipitation product can be sticky and bonded together; the recovery difficulty and energy consumption are increased due to the overhigh precipitation water, and meanwhile, the granularity of a precipitation product is poor, the concentration is overhigh, the washing water consumption is increased, and the energy consumption is increased due to the overlow concentration of the stabilizer.

Further, the liquid to be precipitated containing the cellulose acetate butyrate is obtained by CAB production process, and the esterified liquid is obtained by hydrolysis, neutralization and filtration; specifically, after cellulose is activated by acetic acid, the cellulose is subjected to esterification reaction with butyric anhydride and acetic anhydride under the action of an acid catalyst to generate esterified liquid, and the esterified liquid is hydrolyzed, neutralized and filtered to obtain clear liquid to be precipitated;

the liquid to be precipitated containing the cellulose acetate butyrate comprises, by taking the total mass of the liquid to be precipitated as 100%, 13-30% of Cellulose Acetate Butyrate (CAB), 60-85% of butyric acid, 0.5-10% of acetic acid and 0.5-1% of water.

Furthermore, the nozzle is a single-fluid high-pressure atomizing nozzle, the liquid to be precipitated is dispersed into water through high-pressure atomizing spray to form liquid drops with smaller diameters, so that precipitation is carried out in a tiny volume, the outward diffusion of butyric acid is facilitated, and the residue of butyric acid in particles is reduced; preferably a standard fan nozzle as in the japanese tank;

preferably, the feed pressure to the nozzle is from 0.15 to 0.30MPa (gauge), preferably from 0.18 to 0.24MPa (gauge);

preferably, the spray diffusion angle of the nozzle is 50-80 degrees, preferably 55-70 degrees, and the droplet diameter after spraying is 140-500 μm, preferably 250-470 μm;

preferably the outlet of the nozzle is directed vertically downwards, the nozzle outlet being located 1-8cm, preferably 3-5cm, above the water surface.

Further, in the settling out of the invention, the flow rate of the liquid at the outlet of the nozzle is 0.05-0.5m/s, preferably 0.1-0.35 m/s;

preferably, the spray flow rate per unit cross-sectional area is 0.2 to 0.5L/min m²Preferably 0.25 to 0.4L/min. m²；

Preferably, the settling-out residence time for continuing high-speed stirring after the feeding of the nozzle is finished is 3-10min, preferably 4-8 min.

Further, the high-speed stirring rotating speed is 400-1000r/min, preferably 500-800 min;

preferably, the high-speed stirring is performed by adopting any one or a combination of at least two of a form of a stirring paddle of an inclined blade paddle, a form of a propulsion paddle, a form of a six-back-bent-blade opening turbine paddle, a form of a straight-blade disc turbine paddle, a form of an inclined-blade disc turbine paddle, a form of a tooth-shaped disc turbine paddle and a form of a boolean-gold type paddle, and preferably, the straight-blade disc turbine paddle and/or the inclined-blade disc turbine paddle; the proper stirring paddle can fully mix the materials, so that the separated CAB solid is uniformly dispersed, and mutual bonding and agglomeration are avoided.

Further, the settling process is carried out in a stirring kettle, wherein a stirring paddle is positioned at the height of 1/3-1/2 of the reaction kettle, and the diameter of the stirring paddle is 2/3-3/4 of the diameter of the stirring kettle.

According to the method, after the precipitation is finished and the material is discharged through the discharging opening, the cellulose acetate butyrate particle product is obtained by washing and drying; the cellulose acetate butyrate particle product has an average particle diameter of 300-600 mu m and a bulk density of 0.45-0.6Kg/m³Surface area of 0.3-0.5m²Acid value < 200ppm (calculated as acetic acid) and particle size distribution coefficient of 0.3-0.5.

The method has the advantages that the precipitation yield can reach more than 99.9 percent, and the purity can reach more than 99.9 percent.

Compared with the prior art, the technical scheme of the invention has the beneficial effects that:

the invention sprays the liquid to be precipitated containing cellulose acetate butyrate, butyric acid, acetic acid and water into the water containing the stabilizer by a high-pressure atomization method, and the precipitation is carried out in a tiny volume under the conditions of the stabilizer and high-speed stirring, thereby being beneficial to reducing the residue of butyric acid in the particles, and the obtained cellulose acetate butyrate particle product has uniform particles and high bulk density.

The precipitation method has the advantages of simplicity, convenience in operation, uniform granularity of the product and high bulk density.

Detailed Description

The present invention is further described with reference to the following examples, but the invention is not limited to the examples listed, and it is intended to include equivalent modifications and variations of the technical solutions defined in the claims appended to the present application.

Examples main raw material sources:

and (3) after precipitating the solution: after the cellulose is activated by acetic acid, the cellulose is subjected to esterification reaction with butyric anhydride and acetic anhydride under the action of an acid catalyst to generate an esterification solution, and the esterification solution is hydrolyzed, neutralized and filtered to obtain a clear solution to be precipitated, which is the existing method in the field and is not described in detail in the invention;

cetyl trimethylammonium bromide: (ii) alatin;

sodium allyl sulfonate: (ii) alatin;

sodium dodecyl sulfate: (ii) alatin;

the rest are common commercial raw materials unless otherwise specified.

The precipitation kettle used in the embodiment is a 20L cylindrical glass stirring kettle, the stirring paddle is positioned at the 1/2-height position of the reaction kettle, and the diameter of the stirring paddle is 2/3 of the diameter of the stirring kettle;

a nozzle: in the Japanese pond, the model is a standard fan-shaped nozzle;

stirring paddles: attson.

Example 1

The liquid to be precipitated containing cellulose acetate butyrate comprises 27% CAB, 70% butyric acid, 2% acetic acid and 1% water in percentage by mass.

The precipitation method comprises the following steps:

1Kg of the above-mentioned solution to be precipitated containing cellulose acetate butyrate was sprayed through a nozzle into 10Kg of water for precipitation containing a stabilizer, wherein the stabilizer was 0.35Kg of cetyltrimethylammonium bromide. The outlet of the atomizing nozzle is 4cm above the water surface, the spraying diffusion angle is adjusted to 60 ℃, the stirring paddle is an inclined blade disc turbine paddle, the rotating speed is set to 700r/min, stirring is started, the feeding pressure is set to be 0.2MPa, feeding is started, the liquid flow rate at the outlet of the nozzle is 0.25m/s, and the spraying flow rate of the unit cross section area is 0.4L/min m²And after 2.5min, continuing stirring for 5min, discharging through a discharge hole, washing the product for a plurality of times by using water, and drying to obtain the cellulose acetate butyrate particles.

The cellulose acetate butyrate particle product obtained was tested to have an average particle diameter of 378 μm, was in the form of particles, and had a bulk density of 0.57Kg/m³Surface area of 0.45m²Acid value 158ppm, particle size distribution coefficient 0.35.

The purity of the cellulose acetate butyrate particles obtained by precipitation was 99.9%, and the yield was 99.9%.

Example 2

The liquid to be precipitated containing cellulose acetate butyrate comprises 19.5% of CAB, 75% of butyric acid, 5% of acetic acid and 0.5% of water in percentage by mass.

The precipitation method comprises the following steps:

1Kg of the above-mentioned solution to be precipitated containing cellulose acetate butyrate was sprayed through a nozzle into 7Kg of water for precipitation containing a stabilizer, wherein the stabilizer was 0.21Kg of sodium allylsulfonate. Fog mistThe outlet of the chemical nozzle is 3cm above the water surface, the spray diffusion angle is adjusted to 70 ℃, the stirring paddle is an inclined blade disc turbine paddle, the rotating speed is set to 400r/min, the stirring is started, the feeding pressure is set to 0.18MPa, the feeding is started, the liquid flow rate at the outlet of the nozzle is 0.15m/s, and the spray flow of the unit cross section area is 0.2L/min m²And after 5min, continuously stirring for 7min, discharging through a discharge opening, washing the product for a plurality of times by using water, and drying to obtain the cellulose acetate butyrate particles.

The cellulose acetate butyrate particle product obtained was tested to have an average particle diameter of 546. mu.m, a granular shape, and a bulk density of 0.49Kg/m³Surface area of 0.55m²Acid value of 100ppm and particle size distribution coefficient of 0.45.

The purity of the cellulose acetate butyrate particles obtained by precipitation was 99.9%, and the yield was 99.9%.

Example 3

The liquid to be precipitated containing cellulose acetate butyrate comprises 29% CAB, 60% butyric acid, 10% acetic acid and 1% water in percentage by mass.

The precipitation method comprises the following steps:

1Kg of the above-mentioned solution to be precipitated containing cellulose acetate butyrate was sprayed through a nozzle into 15Kg of water for precipitation containing a stabilizer, wherein the stabilizer was 0.15Kg of sodium dodecylsulfate. The outlet of the atomizing nozzle is positioned 5cm above the water surface, the spraying diffusion angle is adjusted to 80 ℃, an inclined blade disc turbine impeller is adopted as a stirring impeller, the rotating speed is set to be 800r/min, stirring is started, the feeding pressure is set to be 0.24MPa, feeding is started, the liquid flow rate at the outlet of the nozzle is 0.3m/s, and the spraying flow of the unit cross section area is 0.33L/min m²And after 3min, continuously stirring for 8min, discharging through a discharge hole, washing the product for several times by using water, and drying to obtain the cellulose acetate butyrate particles.

The cellulose acetate butyrate granular product obtained by the test has the average grain diameter of 458 mu m, is granular and has the bulk density of 0.58Kg/m³Surface area of 0.32m²The acid value was 99ppm and the particle size distribution coefficient was 0.39.

The purity of the cellulose acetate butyrate particles obtained by precipitation was 99.9%, and the yield was 99.9%.

Example 4

The liquid to be precipitated containing cellulose acetate butyrate comprises 27% CAB, 70% butyric acid, 2% acetic acid and 1% water in percentage by mass.

1Kg of the above-mentioned solution to be precipitated containing cellulose acetate butyrate was sprayed through a nozzle into 10Kg of water for precipitation containing a stabilizer, wherein the stabilizer was 0.4Kg of cetyltrimethylammonium bromide. The outlet of the atomizing nozzle is 8cm above the water surface, the spraying diffusion angle is adjusted to 80 ℃, the stirring paddle is an inclined blade disc turbine paddle, the rotating speed is set to 1200r/min, stirring is started, the feeding pressure is set to 0.3MPa, feeding is started, the liquid flow rate at the outlet of the nozzle is 0.5m/s, and the spraying flow rate of the unit sectional area is 0.5L/min m²And after 2min, continuously stirring for 3min, discharging through a discharge opening, washing the product for a plurality of times by using water, and drying to obtain the cellulose acetate butyrate particles.

The cellulose acetate butyrate particle product obtained was tested to have an average particle diameter of 378 μm, was in the form of particles, and had a bulk density of 0.57Kg/m³Surface area of 0.45m²Acid value 158ppm, particle size distribution coefficient 0.35.

The purity of the cellulose acetate butyrate particles obtained by precipitation was 99.9%, and the yield was 99.9%.

Comparative example 1

Referring to the precipitation method of example 3, the difference from example 3 is that the precipitation water is not added with the stabilizer of sodium dodecyl sulfate, and other operation methods and conditions are completely the same, so as to obtain cellulose acetate butyrate particles.

The cellulose acetate butyrate particle product obtained by testing has the average particle size of 800 mu m, is flocculent and has the bulk density of 0.21Kg/m³Surface area of 1.0m²Acid value 420ppm, particle size distribution coefficient 1.28.

The purity of the cellulose acetate butyrate particles obtained by precipitation was 99.4%, and the yield was 99.1%.

Comparative example 2

Referring to the precipitation method of example 3, the difference from example 3 is that the stabilizer sodium dodecyl sulfate added to the precipitation water is replaced by sodium dodecyl benzene sulfonate with equal mass, and other operation methods and conditions are completely the same, so as to obtain cellulose acetate butyrate particles.

The cellulose acetate butyrate particle product obtained by the test has the average particle size of 980 mu m, is flocculent and has the bulk density of 0.17Kg/m³Surface area of 1.52m²The acid value was 700ppm and the particle size distribution coefficient was 1.48.

The purity of the cellulose acetate butyrate particles obtained by precipitation was 98.2%, and the yield was 98.9%.

Comparative example 3

Referring to the precipitation method of example 1, the precipitation method was different from example 1 only in that cetyl trimethyl ammonium bromide, which is a stabilizer added to the precipitation water, was replaced with dodecyl trimethyl ammonium bromide of an equal mass, and other operation methods and conditions were completely the same, to obtain cellulose acetate butyrate particles.

The cellulose acetate butyrate particle product obtained by the test has the average particle size of 745 mu m, is in the shape of short floccule and has the bulk density of 0.28Kg/m³Surface area of 0.78m²The acid value was 512ppm and the particle size distribution coefficient was 0.75.

The purity of the cellulose acetate butyrate particles obtained by precipitation was 98.9%, and the yield was 99.1%.

Comparative example 4

Referring to the precipitation method of example 2, the difference from example 2 is only that sodium allylsulfonate, a stabilizer added to the precipitation water, is replaced with sodium vinylsulfonate of equal mass, and other operation methods and conditions are completely the same, so that cellulose acetate butyrate particles are obtained.

The cellulose acetate butyrate particle product obtained by the test has the average particle size of 1203 mu m, is flocculent and has the bulk density of 0.13Kg/m³Surface area of 0.98m²Acid value was 1024ppm, and particle size distribution coefficient was 1.03.

The purity of the cellulose acetate butyrate particles obtained by precipitation was 98.1%, and the yield was 89.8%.

Comparative example 5

Referring to the precipitation method of example 3, the difference from example 3 is only that the high-speed stirring is replaced by the ordinary stirring, the set rotation speed is 100r/min, and other operation methods and conditions are completely the same, so as to obtain the cellulose acetate butyrate particles.

The cellulose acetate butyrate particulate product obtained was tested to have an average particle size of 1200 μm in the form of a cake having a bulk density of 0.19Kg/m³Surface area of 0.84m²Acid value 1000ppm, particle size distribution data 0.95.

The purity of the cellulose acetate butyrate particles obtained by precipitation was 99.1%, and the yield was 97.2%.