Preparation method of cellulose microspheres

Abstract

The invention discloses a preparation method of cellulose microspheres, and belongs to the technical field of polymer functional materials. The invention aims to solve the problem that cellulose microspheres with excellent monodispersity are difficult to quickly prepare on the premise of ensuring uniform particle size of the microspheres in the existing microsphere preparation process. The method comprises: 1, preparing a cellulose solution; 2, spraying the cellulose solution into a circulating coagulating bath; the method is used for preparing the cellulose microspheres.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of high polymer functional materials. BACKGROUND

[0002] Cellulose is a natural polymer with high content. Cellulose polymer has the advantages of environmental friendliness, stable structure, low production cost, easy reaction modification with other substances, etc., so that cellulose and its derivatives are widely used in medicine, food, chemical industry, textile and other fields. The morphology of the products is various, including cellulose film, cellulose column, cellulose gel, cellulose microspheres, etc. Among these products, cellulose microspheres have the characteristics of clear particle size and distribution, spherical shape, highly porous structure, large specific surface area, chemical reactivity, good functionalization possibility and high mechanical strength.

[0003] The core defect of the existing cellulose microsphere preparation process is that under the premise of ensuring the uniform particle size of the microspheres, it is difficult to quickly prepare cellulose microspheres with excellent monodispersity. SUMMARY

[0004] The application aims to solve the problem that under the premise of ensuring the uniform particle size of the microspheres in the existing microsphere preparation process, it is difficult to quickly prepare cellulose microspheres with excellent monodispersity, and further provides a preparation method of cellulose microspheres.

[0005] A preparation method of cellulose microspheres, which is carried out according to the following steps:

[0006] I. Under stirring conditions, cellulose powder is dissolved in a solvent to achieve no swelling phenomenon, and then vacuum is applied to remove bubbles in the solution, thereby obtaining a cellulose solution;

[0007] The solvent is dimethyl sulfoxide or a co-solvent system of dimethyl sulfoxide;

[0008] II. Under the conditions that the diameter of the nozzle is 500-1000 μm, the air flow pressure is 0.2-0.8 MPa, and the distance between the nozzle and the surface of the coagulation bath is 8-20 mm, the cellulose solution is sprayed into a coagulation bath with a temperature of 20-40 ℃ and circulating flow, thereby obtaining cellulose microspheres;

[0009] The coagulation bath is a mixture of dimethyl sulfoxide and water.

[0010] The application has the following beneficial effects:

[0011] The cellulose microsphere preparation method can produce at least 100 cellulose microspheres per minute, and the cellulose microspheres are uniform in particle size, good in monodispersity, 100-1000 mu m in size, good in sphericity, can be kept running for a long time (more than 2 hours) without blocking, and the like.

[0012] Compared with the prior art, the cellulose microsphere preparation method can realize preparation of cellulose microspheres without using other desolventizing agents or adding, is simple in operation, high in raw material utilization rate, can save a drying step in a general production process, realizes large-scale rapid production, is high in applicability, and has a wide development prospect in the microsphere field.

[0013] The cellulose microsphere preparation method is used. DETAILED DESCRIPTION

[0014] Figure 1 A practical diagram for producing a large amount of cellulose microspheres in a coagulation bath in step two of the embodiment;

[0015] Figure 2 An optical micrograph of the cellulose microspheres prepared in step two of the embodiment. DETAILED DESCRIPTION

[0016] Specific embodiment one: the cellulose microsphere preparation method is performed according to the following steps:

[0017] I. Under stirring, cellulose powder is dissolved in a solvent to realize no swelling phenomenon, and then vacuum is extracted to remove bubbles in the solution, to obtain a cellulose solution;

[0018] The solvent is dimethyl sulfoxide or a cosolvent system of dimethyl sulfoxide.

[0019] II. The cellulose solution is sprayed into a coagulation bath circulating at a temperature of 20-40 DEG C under the conditions that the nozzle diameter is 500-1000 mu m, the gas flow pressure is 0.2-0.8 MPa, and the distance between the nozzle and the surface of the coagulation bath is 8-20 mm, to obtain cellulose microspheres.

[0020] The coagulation bath is a mixture of dimethyl sulfoxide and water.

[0021] The chemical formula of dimethyl sulfoxide (DMSO) is (CH3)2SO, and the dipole moment is as high as 3.96 D (very strong polarity), which belongs to aprotic polar solvent. Due to the strong polar double bond formed by the electronegativity of sulfur atom and oxygen atom, the charge distribution in the molecule is highly uneven, resulting in a significant dipole effect. Both DMSO and water are strong polar substances, and the similarity in polarity makes the intermolecular interaction force between them strong, which overcomes the intermolecular force of itself to achieve mutual solubility. In addition, during the mixing of DMSO and water, the oxygen atom of DMSO can form a hydrogen bond with the hydroxyl group (-OH) in the water molecule, constructing a mixed hydrogen bond network, and the dipole-dipole interaction force between the polar molecules by attracting each other through positive and negative charge ends, so that DMSO and water can be completely and efficiently mixed.

[0022] The present embodiment relates to a method for rapidly preparing cellulose microspheres. By dissolving various types of cellulose such as cellulose acetate, nitrocellulose, ethyl cellulose, microcrystalline cellulose, hydroxypropyl cellulose, etc. in DMSO or its co-solvent system, a uniform cellulose solution is obtained, and then the release of the cellulose solution is controlled, the released solution enters a certain proportion of coagulation bath, and under the action of surface tension, spherical shape is formed. In this process, the solvent in the cellulose solution and the coagulation bath quickly exchange solvents, and the surface of the microsphere can be quickly solidified and formed. That is, the principle of high-efficiency mixing of DMSO and water can make the surface of the released droplet quickly solidify and form, and cellulose microspheres can be rapidly and massively prepared. In addition, since DMSO and water are completely miscible, the desolventizing step in the general preparation method can be omitted, which is more convenient, fast and efficient, and has broad development potential.

[0023] The present embodiment has the following advantages:

[0024] The method for preparing cellulose microspheres in the present embodiment can produce at least 100 cellulose microspheres per minute, and the particle size is uniform, the monodispersity is good, the size of the cellulose microspheres is 100 μm to 1000 μm, which can be adjusted and controlled by changing the volume of the sprayed solution, the sphericity of the microspheres is good, and the microspheres can be kept running for a long time (more than 2 hours) without blocking, etc.

[0025] Compared with the prior art, the present embodiment can realize the preparation of cellulose microspheres without using other desolvents or adding other substances, the preparation method is simple to operate, the raw material utilization rate is high, the drying step in the general production process can be omitted, large-scale rapid production can be realized, and the method has strong applicability and broad development prospects in the field of microspheres.

[0026] Specific embodiment two: the difference between the present embodiment and the specific embodiment one is that the cellulose powder in step one is one or a combination of several of the following: cellulose acetate, nitrocellulose, ethyl cellulose, hydroxypropyl methyl cellulose, carboxymethyl cellulose, microcrystalline cellulose and hydroxypropyl cellulose. The others are the same as in the specific embodiment one.

[0027] Specific embodiment three: the cellulose powder in step one is cellulose powder screened through a 500 mesh~1000 mesh screen. The other aspects are the same as specific embodiment one or two.

[0028] Specific embodiment four: the cellulose powder in step one and the solvent have a mass ratio of 1:(5~20). The other aspects are the same as specific embodiment one to three.

[0029] Specific embodiment five: the co-solvent system of dimethyl sulfoxide in step one is a mixed solution of dimethyl sulfoxide and ethyl acetate, a mixed solution of dimethyl sulfoxide and water, a dimethyl sulfoxide and sodium chloride solution; and the mass percentage of dimethyl sulfoxide in the co-solvent system of dimethyl sulfoxide is 70%~90%. The other aspects are the same as specific embodiment one to four.

[0030] Specific embodiment six: in step one, the cellulose powder is added to the solvent 5~10 times under the condition of stirring speed of 300 rpm~500 rpm, dissolved for 1 h~3 h, and no swelling phenomenon is achieved, then the gas bubbles in the solution are removed under the condition of temperature of 20℃~30℃ and vacuum degree of 1 mbar~10 mbar. The other aspects are the same as specific embodiment one to five.

[0031] Specific embodiment seven: the mass percentage of dimethyl sulfoxide in the coagulation bath in step two is 20%~50%. The other aspects are the same as specific embodiment one to six.

[0032] The mass percentage of dimethyl sulfoxide in the coagulation bath in the present embodiment is 20%~50%, too much will make the droplets dissolve in the coagulation bath and not form spherical shape, too little will make the droplets solidify too fast and the sphericity is poor.

[0033] Specific embodiment eight: the circulating flow speed of the coagulation bath in step two is 0.05 m / s~0.2 m / s. The other aspects are the same as specific embodiment one to seven.

[0034] Specific embodiment nine: the volume ratio of the cellulose solution sprayed and the coagulation bath in step two is 1:(500~1000). The other aspects are the same as specific embodiment one to eight.

[0035] Embodiment ten differs from one of the embodiments one to nine in that: in step two, the point glue machine is used to spray the cellulose solution into the coagulation bath with a temperature of 20℃ to 40℃ and circulating flow under the conditions of nozzle diameter of 500μm to 1000μm, air flow pressure of 0.2MPa to 0.8MPa and the distance between the nozzle and the surface of the coagulation bath of 8mm to 20mm. The others are the same as the embodiments one to nine.

[0036] The following examples are used to verify the beneficial effects of the present application:

[0037] Example 1:

[0038] A preparation method of cellulose microspheres, which is carried out according to the following steps:

[0039] I. Under the condition of stirring speed of 300rpm, the cellulose powder is added into the solvent for dissolution for 1h in 5 times and no swelling phenomenon is realized, and then the vacuum is extracted under the conditions of temperature of 30℃ and vacuum degree of 10mbar to remove the bubbles in the solution, so as to obtain the cellulose solution;

[0040] The solvent is dimethyl sulfoxide;

[0041] The cellulose powder is cellulose acetate;

[0042] The cellulose powder is the cellulose powder screened through the 800 mesh screen;

[0043] The mass ratio of the cellulose powder to the solvent is 1:10;

[0044] II. The point glue machine is used to spray the cellulose solution into the coagulation bath with a temperature of 30℃ and circulating flow under the conditions of nozzle diameter of 800μm, air flow pressure of 0.4MPa and the distance between the nozzle and the surface of the coagulation bath of 10mm, so as to obtain the cellulose microspheres;

[0045] The coagulation bath is the mixture of dimethyl sulfoxide and water, and the mass percentage of dimethyl sulfoxide in the coagulation bath is 20%;

[0046] The circulating flow speed of the coagulation bath is 0.1m / s;

[0047] The volume ratio of the sprayed cellulose solution to the coagulation bath is 1:500.

[0048] Figure 1 It is the actual picture of a large number of cellulose microspheres generated in the coagulation bath in step II of the example. As can be seen from the picture, the preparation method can quickly prepare the cellulose microspheres with good monodispersity, uniform particle size, and the size of the cellulose microspheres is about 500μm.

[0049] Figure 2 An optical micrograph of the cellulose microspheres prepared in Step 2 of the example; it can be seen from the figure that the cellulose microspheres prepared by the method have good sphericity.

[0050] In this example, more than 100 cellulose microspheres per minute were produced, and the operation was carried out continuously for 8 hours without blockage and the like.

Claims

1. A method for preparing cellulose microspheres, characterized by It is carried out according to the following steps: I. Under stirring, the cellulose powder is added into the solvent to be dissolved and to realize no swelling phenomenon, and then vacuum is applied to remove the bubbles in the solution to obtain a cellulose solution; The solvent is dimethyl sulfoxide or a co-solvent system of dimethyl sulfoxide; II. Under the conditions that the nozzle diameter is 500-1000 μm, the gas flow pressure is 0.2-0.8 MPa, and the distance between the nozzle and the surface of the coagulation bath is 8-20 mm, the cellulose solution is sprayed into the coagulation bath with a temperature of 20-40 ℃ and a circulating flow to obtain cellulose microspheres. The coagulation bath is a mixture of dimethyl sulfoxide and water.

2. The method for preparing cellulose microspheres according to claim 1, characterized in that... The cellulose powder in step I is one or a combination of several of cellulose acetate, nitrocellulose, ethyl cellulose, hydroxypropyl methyl cellulose, carboxymethyl cellulose, microcrystalline cellulose and hydroxypropyl cellulose.

3. The method for preparing cellulose microspheres according to claim 1, characterized in that... The cellulose powder in step I is screened through a 500-1000 mesh screen.

4. The method for preparing cellulose microspheres according to claim 1, characterized in that... The mass ratio of the cellulose powder to the solvent in step I is 1:(5-20).

5. The method for preparing cellulose microspheres according to claim 1, characterized in that... The co-solvent system of dimethyl sulfoxide in step I is a mixed solution of dimethyl sulfoxide and ethyl acetate, a mixed solution of dimethyl sulfoxide and water, or a dimethyl sulfoxide and sodium chloride solution, and the mass percentage of dimethyl sulfoxide in the co-solvent system is 70-90%.

6. The method for preparing cellulose microspheres according to claim 1, characterized in that... In step I, the cellulose powder is added into the solvent in 5-10 portions under stirring at a speed of 300-500 rpm for 1-3 h to be dissolved and to realize no swelling phenomenon, and then vacuum is applied at a temperature of 20-30 ℃ and a vacuum degree of 1-10 mbar to remove the bubbles in the solution.

7. The method for preparing cellulose microspheres according to claim 1, characterized in that... The mass percentage of dimethyl sulfoxide in the coagulation bath in step II is 20-50%.

8. The method for preparing cellulose microspheres according to claim 1, characterized in that... The circulating flow speed of the coagulation bath in step II is 0.05-0.2 m / s.

9. The method for preparing cellulose microspheres according to claim 1, characterized in that... The volume ratio of the cellulose solution to the coagulation bath in step II is 1:(500-1000).

10. The method of claim 1, wherein In step II, the cellulose solution is sprayed into the coagulation bath with a temperature of 20-40 ℃ and a circulating flow by using a point glue machine under the conditions that the nozzle diameter is 500-1000 μm, the gas flow pressure is 0.2-0.8 MPa, and the distance between the nozzle and the surface of the coagulation bath is 8-20 mm.

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