阅读说明：本技术 高浓度微纤化纤维素分散液的制备方法 (Method for preparing high-concentration microfibrillated cellulose dispersion ) 是由 吴国勇 刘丽萍 覃献慧 于 2019-11-28 设计创作，主要内容包括：本发明公开一种高浓度微纤化纤维素分散液的制备方法,涉及化学产品生产技术领域。它包括在植物纤维中加入氢氧化钠和水,煮沸后加水稀释成纤维悬浮液；在纤维悬浮液中加入蔗糖甘油酯,经过磨浆机粗磨、胶体磨细磨、射流均质机微细化研磨获得低浓度植物微纤化纤维素-蔗糖甘油酯分散液；然后调节pH值在1～4之间,液体分为上下两层,经分液漏斗分离,得到上清液和下层淡黄色半固体凝状物；下层半固体凝状物用离心机离心沉降。本发明可以解决现有技术难以制备高浓度、高度分散的微纤化纤维素分散液的问题,进而达到降低运输、储存成本的目的。(The invention discloses a preparation method of a high-concentration microfibrillated cellulose dispersion, and relates to the technical field of chemical product production. Adding sodium hydroxide and water into plant fibers, boiling, and adding water to dilute into fiber suspension; adding sucrose glyceride into the fiber suspension, and carrying out coarse grinding by a pulping machine, fine grinding by a colloid mill and fine grinding by a jet flow homogenizer to obtain a low-concentration plant microfibrillated cellulose-sucrose glyceride dispersion liquid; then adjusting the pH value to be 1-4, dividing the liquid into an upper layer and a lower layer, and separating by a separating funnel to obtain a supernatant and a lower layer of a faint yellow semi-solid condensate; the lower semi-solid gel was centrifuged and sedimented by a centrifuge. The invention can solve the problem that the prior art is difficult to prepare the microfibrillated cellulose dispersion with high concentration and high dispersion, thereby achieving the purpose of reducing the transportation and storage costs.)

1. A method for preparing a high-concentration microfibrillated cellulose dispersion is characterized by comprising the following steps:

A. adding sodium hydroxide and water into plant fibers, boiling, and adding water to dilute into a fiber suspension;

B. adding sucrose glyceride into the fiber suspension obtained in the step A, and carrying out coarse grinding by a pulping machine, fine grinding by a colloid mill and fine grinding by a jet flow homogenizer to obtain a low-concentration plant microfibrillated cellulose-sucrose glyceride dispersion liquid;

C. regulating the pH value of the low-concentration plant microfibrillated cellulose-sucrose glyceride dispersion liquid obtained in the step B to be 1-4, dividing the liquid into an upper layer and a lower layer, and separating by a separating funnel to obtain a supernatant and a lower layer coagulated substance;

D. and C, centrifuging and settling the lower-layer coagulum obtained in the step C by using a centrifuge.

2. The method for producing a highly concentrated microfibrillated cellulose dispersion according to claim 1, wherein: and step A, adding the sodium hydroxide in an amount which is 5 to 15 percent of the mass fraction of the plant fiber.

3. The method for producing a high-concentration microfibrillated cellulose dispersion liquid according to claim 1 or 2, wherein: and step A, adding the water in an amount which is 20-30 times of the mass of the plant fiber.

4. The method for producing a highly concentrated microfibrillated cellulose dispersion according to claim 3, wherein: and B, the HLB value of the sucrose glyceride in the step B is 7-16, and the concentration of the sucrose glyceride is 0.5-15%.

5. The method for producing a highly concentrated microfibrillated cellulose dispersion according to claim 4, wherein: the mass ratio of the plant fibers to the sucrose glyceride is 1: 0.05-10 in terms of dry matter.

6. The method for producing a highly concentrated microfibrillated cellulose dispersion according to claim 5, wherein: and D, the rotating speed of a centrifuge used in the centrifugal sedimentation process is 3000 rpm.

7. The method for producing a highly concentrated microfibrillated cellulose dispersion according to claim 6, wherein: and step A, adding sodium hydroxide and water into the plant fibers, boiling, and adding water to dilute into a fiber suspension with the plant fiber mass fraction of 0.5%.

Technical Field

The invention relates to the technical field of chemical product production, in particular to a preparation method of a high-concentration microfibrillated cellulose dispersion.

Background

Plant microfibrillated Cellulose (MFC) is a novel Cellulose fiber with nanoscale, and has a promising application prospect in advanced composite materials due to its high strength, high rigidity, light weight, biodegradability and renewability, and thus has received wide attention.

In the known literature, methods for producing microfibrillated cellulose are generally used in which a pretreatment of the fibers is combined with a mechanical treatment in order to reduce the energy consumption during the production of microfibrillated cellulose.

The fiber pretreatment adopts enzymolysis and chemical methods, wherein the chemical method is most convenient and economic in alkali liquor treatment.

Microfibrillated cellulose has various problems in the preparation and application processes, such as strong polarity, uneven dispersion or agglomeration in a non-polar or low-polar matrix, loss of the nanometer scale of the MFC, and influence on the performance of the MFC, which limit the development of the MFC in the field of nanocomposites. The preparation process of the microfibrillated cellulose is usually carried out in a liquid medium, the concentration of the obtained microfibrillated cellulose in a suspension or gel is low so as to ensure a highly dispersed state of fibers in the liquid medium and maintain the nanometer size of the fibers, and the existing method cannot prepare the microfibrillated cellulose with high dispersion and nanometer size in a high concentration state, which is one of the main reasons for the low concentration of the microfibrillated cellulose. The low concentration of microfibrillated cellulose not only affects its use, but also increases transportation and storage costs.

Disclosure of Invention

The invention aims to provide a preparation method of a high-concentration microfibrillated cellulose dispersion, which can solve the problem that the high-concentration and high-dispersion microfibrillated cellulose dispersion is difficult to prepare in the prior art, and further achieves the purpose of reducing the transportation and storage costs.

In order to solve the problems, the technical scheme adopted by the invention is as follows:

it comprises the following steps:

A. adding sodium hydroxide and water into plant fibers, boiling, and adding water to dilute into a fiber suspension;

B. adding sucrose glyceride into the fiber suspension obtained in the step A, and carrying out coarse grinding by a pulping machine, fine grinding by a colloid mill and fine grinding by a jet flow homogenizer to obtain a low-concentration plant microfibrillated cellulose-sucrose glyceride dispersion liquid;

C. regulating the pH value of the low-concentration plant microfibrillated cellulose-sucrose glyceride dispersion liquid obtained in the step B to be 1-4, dividing the liquid into an upper layer and a lower layer, and separating by a separating funnel to obtain a supernatant and a lower layer coagulated substance;

D. and C, centrifuging and settling the lower-layer coagulum obtained in the step C by using a centrifuge.

In the above technical solution, a more specific technical solution may also be: and step A, adding the sodium hydroxide in an amount which is 5 to 15 percent of the mass fraction of the plant fiber.

Further, the adding amount of the water in the step A is 20-30 times of the mass of the plant fiber.

Further, the HLB value of the sucrose glyceride in the step B is 7-16, and the concentration of the sucrose glyceride is 0.5-15%.

Further, the mass ratio of the plant fibers to the sucrose glyceride is 1: 0.05-10 in terms of dry matter.

Further, the rotating speed of a centrifuge used in the centrifugal sedimentation process in the step D is 3000 rpm.

Further, in the step A, sodium hydroxide and water are added into the plant fibers, and the mixture is boiled and then diluted by adding water to obtain a fiber suspension with the plant fiber mass fraction of 0.5%.

Due to the adoption of the technical scheme, compared with the prior art, the invention has the following beneficial effects:

1. according to the invention, the plant fiber is added with the sodium hydroxide with the plant fiber mass fraction of 5-15% and the water with the plant fiber mass fraction of 20-30 times, and after boiling for 30min, the water is added to dilute the plant fiber into the fiber suspension with the plant fiber mass fraction of 0.5%, so that the advantages of quantitatively adding less sodium hydroxide, achieving the purposes of dissolving out lignin, pectin and hemicellulose in a shorter time and reducing cellulose hydrolysis and separating from cellulose under the conditions of higher concentration and boiling are achieved, thereby improving the yield of plant microfibrillated cellulose and reducing the environmental load.

2. The fiber suspension is diluted into the fiber suspension with the plant fiber mass fraction of 0.5% by adding water, so that the measurement is convenient, more importantly, the alkali concentration is reduced to avoid excessive hydrolysis of cellulose, the mechanical grinding treatment is carried out under low concentration, the microfibrillated cellulose is obtained, and the mechanical abrasion is reduced; the sucrose glyceride is added to disperse microfibrillated cellulose formed in the process of mechanically and repeatedly grinding plant fibers in the sucrose glyceride emulsion, so that the fiber winding degree is reduced, the subsequent treatment is facilitated, and the mechanical abrasion is also facilitated to be reduced.

3. The invention obtains the low-concentration plant microfibrillated cellulose-sucrose glyceride dispersion liquid by coarse grinding of a refiner, fine grinding of a colloid mill and micronization grinding of a jet homogenizer, performs cellulose pre-refining by utilizing the advantage of high grinding efficiency of the refiner and the colloid mill, and is beneficial to solving the problems of high energy consumption and low efficiency of microfibrillated cellulose prepared by adopting single equipment of the jet homogenizer.

4. The plant fiber is effectively dispersed in water as much as possible and avoids excessive winding of the fiber in the refining process due to the existence of the sucrose glyceride serving as the surfactant in the mechanical repeated grinding process, and the formed microfibrillated cellulose is in a dispersed state and is also beneficial to reducing mechanical abrasion.

5. In the invention, in the low-concentration sucrose glyceride microfibrillated cellulose dispersion liquid, the pH value of the material is adjusted, the sucrose glyceride and the microfibrillated cellulose form a semisolid gel which is separated from a water phase, and the high-concentration microfibrillated cellulose sucrose glyceride dispersion liquid is obtained through centrifugal sedimentation, so that the microfibrillated cellulose is also in a dispersed state in the high-concentration dispersion liquid and maintains the nanometer size of the microfibrillated cellulose.

6. The high-concentration microfibrillated cellulose dispersion has good affinity to water, non-polar and low-polar substrates due to the presence of the nonionic surfactant sucrose glyceride: wherein the sucrose glyceride shows different dispersion forms along with the change of pH value in water: the sucrose glyceride can be uniformly dispersed in water at a pH value of 5-8 to form stable emulsion; when the pH value of the emulsion is reduced to be below 5, the sucrose glyceride forms a semisolid coagulum and is separated from water, and when the pH value is reduced to be below 1, the sucrose glyceride is precipitated; when the pH value is recovered to be more than 7, the sucrose glyceride is re-dispersed into the water to form good emulsion, so that the problem of uneven dispersion or agglomeration of the microfibrillated cellulose is effectively solved, the microfibrillated cellulose is re-dispersed, and the application of the microfibrillated cellulose to the nano composite material is facilitated.

Detailed Description

The present invention will be described in more detail with reference to specific examples, but the technical scope of the present invention is not limited to these examples.