CN115992453A - Hydrophobic nanocellulose powder and preparation method thereof - Google Patents
Hydrophobic nanocellulose powder and preparation method thereof Download PDFInfo
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Abstract
The invention discloses hydrophobic nano cellulose powder and a preparation method thereof. The method comprises the steps of immersing fiber raw materials in an aqueous suspension of calcium hydroxide, dissociating the immersed slurry by adopting a mechanical method, adding a bonding agent into the dissociated slurry under a certain condition, reacting for a period of time, adding a catalyst and a modifier, and continuously reacting for a period of time at a certain temperature. Washing, concentrating and drying the reacted slurry to obtain the hydrophobic nano cellulose powder. The length-diameter ratio of the nanocellulose in the obtained hydrophobic nanocellulose powder is more than or equal to 50, calcium stearate particles with the diameter less than or equal to 100nm are adsorbed on the surface of the nanocellulose, the average particle diameter of the powder is less than or equal to 1 mu m, and the water contact angle is more than or equal to 90 degrees. The hydrophobic nano cellulose powder obtained by the invention can be used as lubricant, emulsifier, stabilizer, release agent, accelerator, plasticizer, reinforcing agent, cosmetic base material and the like for industries such as food, medicine, cosmetics, papermaking, paint, plastic rubber and the like.
Description
Technical Field
The invention belongs to the field of cellulose modification, and particularly relates to hydrophobic nano cellulose powder and a preparation method thereof.
Background
Cellulose is the most abundant, renewable, biocompatible and biodegradable natural polymer on earth, and with the advent and development of nanotechnology, cellulose has received increasing attention in the new form of "nanocellulose". The nanocellulose has the advantages of wide sources of cellulose, no toxicity, water insolubility, reproducibility, degradability and the like, and also has the characteristics of high comparison area, large length-diameter ratio, good water retention, low density, high strength and the like. The nanocellulose has a large number of hydroxyl groups on the surface, and is a hydrophilic material, so that the nanocellulose can be uniformly mixed with polar substances. However, it does not disperse well in weakly polar solvents and polymer media, greatly limiting its range of applications. In addition, nanocellulose is in a gel form because of good water retention, and when dried into powder by various methods, hydroxyl groups on the surface of nanocellulose are easy to form hydrogen bonds to cause aggregation, so that the original filament-like form of nanocellulose is difficult to maintain.
Based on this, it is necessary to hydrophobically modify nanocellulose in order to prevent irreversible agglomeration between nanocellulose during drying and to improve its compatibility with weak polar solvents, polymer matrices. The invention patent CN201810526183.9 discloses a preparation method of cellulose micro-nano crystals with hydrophobically modified surfaces, which comprises the steps of hydrolyzing cellulose powder in phosphoric acid to obtain a cellulose micro-nano crystal suspension, adding absolute ethyl alcohol and stearic acid for heating reaction, centrifuging and drying to obtain the hydrophobically modified cellulose micro-nano crystals. The cellulose micro-nano crystal obtained by the method can improve the hydrophobicity of the starch film, but a large amount of ethanol is used in the whole process, which is not beneficial to practical application and production. The invention patent CN201811487427.3 discloses a preparation method and application of sugarcane She Shushui modified nanocellulose, which comprises the steps of adding sugarcane leaf nanocellulose and stearic acid into an organic solvent according to the mass part of 0.5-2:1, modifying for 60-100min at 20-70 ℃, filtering, washing and drying to obtain the modified nanocellulose, wherein a large amount of organic solvent is also used in the process. Therefore, the existing method for modifying the nanocellulose in a hydrophobic way is mostly completed in an organic solvent system, and has certain problems of environmental pollution and effective recovery of solvents.
The nanocellulose has great application prospect and potential in the aspect of weak polar or nonpolar polymers, so that a simpler and green hydrophobic nanocellulose powder and a preparation method thereof are needed to be searched.
Disclosure of Invention
In view of the above problems, an object of the present invention is to provide a hydrophobic nanocellulose powder and a preparation method thereof. The method does not need to use a large amount of organic solvents in the implementation process, has mild conditions, is suitable for large-scale production, can keep the fibril form of the nanocellulose, has hydrophobic surface, can be uniformly dispersed in a weak polar or nonpolar polymer matrix, has good interfacial compatibility with the polymer, and can play a remarkable role in strengthening.
In order to achieve the above purpose, the invention adopts the following technical scheme:
a hydrophobic nano cellulose powder and a preparation method thereof are characterized by comprising the following steps:
(1) Adsorption and dissociation: immersing the fiber raw material in an aqueous suspension of calcium hydroxide, wherein the solid content of the fiber raw material is 0.1-5wt%, the dosage of the calcium hydroxide is 0.1-10 times of the mass of the fiber raw material, the immersion temperature is 10-30 ℃, and the immersion time is 2-4h; dissociating the impregnating slurry by a mechanical method;
(2) Modification: heating the slurry to a certain temperature, adding a binding agent, reacting for a period of time, adding a catalyst and a modifier, continuously stirring, and reacting for a period of time at a certain temperature;
(3) And (3) drying: washing, concentrating and drying the reacted slurry to obtain hydrophobic nano cellulose powder;
the length-diameter ratio of the nanocellulose in the obtained hydrophobic nanocellulose powder is more than or equal to 50, calcium stearate particles with the diameter less than or equal to 100nm are adsorbed on the surface of the nanocellulose, the average particle diameter of the powder is less than or equal to 1 mu m, and the water contact angle is more than or equal to 90 degrees; the obtained hydrophobic nanocellulose powder can be used as lubricant, emulsifier, stabilizer, release agent, accelerator, plasticizer, reinforcing agent, cosmetic base material and the like in industries of food, medicine, cosmetics, papermaking, paint, plastic rubber and the like.
The fiber raw material is at least one of bleached or unbleached needle pulp, broad leaf pulp, cotton pulp, bamboo pulp, wheat straw pulp, waste paper pulp or wood powder, bamboo powder, plant straw, corn cob and xylose waste residue, wherein the block and powder raw materials are crushed to 40-80 meshes.
The mechanical dissociation method comprises the following steps: one or more of disc milling, fine milling and ball milling; wherein the mass concentration of the materials subjected to disc grinding and fine grinding treatment is 1-50wt%, the gap between the grinding discs is-150-0 mu m, and the rotating speed of the grinding discs is 1000-2000rpm; the mass concentration of the ball-milling material is 1-50wt% and the speed is 100-600 rpm.
The binding agent is one or more of gamma-aminopropyl triethoxysilane, gamma- (2, 3-epoxypropoxy) propyl trimethoxysilane and gamma-methacryloxypropyl trimethoxysilane, and the amount of the binding agent based on calcium hydroxide is 0-5wt%, preferably 2-4wt%; the reaction time is 10min-2h, preferably 30min-1h; the reaction temperature is 50-70℃and preferably 55-65 ℃.
The catalyst is one or more of diethanolamine, hydrogen peroxide, glycerol, propylene glycol, ammonium chloride and ammonium hydroxide, and the catalyst is 0-200wt% based on calcium hydroxide, preferably 10-50wt%.
The modifier is one or more of stearic acid and stearate, and the dosage of the modifier is 0.1-10 times of the mass of calcium hydroxide, preferably 2-6 times; the reaction time is 10min-5h, preferably 2-3h; the reaction temperature is 50 to 100℃and preferably 55 to 80 ℃.
The drying method comprises the following steps: at least one of spray drying, supercritical drying, vacuum freeze drying, microwave drying, infrared drying, fluidized bed drying, flash drying, and oven drying.
Compared with the prior art, the invention has the following advantages and beneficial effects:
1. the hydrophobic nanocellulose powder and the preparation method thereof provided by the invention have the advantages of strong applicability to raw materials, mild pretreatment conditions, high medicine utilization rate, simple process, environmental friendliness and contribution to industrial production.
2. The main components of the hydrophobic nano cellulose powder provided by the invention are nano cellulose and calcium stearate, and the calcium stearate is coated on the surface of the nano cellulose, so that the nano cellulose still maintains the slender fibrillar shape. Compared with single-component nano cellulose powder, the nano cellulose in the nano cellulose powder provided by the invention is not easy to agglomerate, the slender fibril shape is still reserved, and the nano cellulose is hydrophobic and can be dispersed in a weak polar solvent and a nonpolar solvent and a polymer due to the coating of calcium stearate; the nanocellulose and the calcium stearate in the nanocellulose powder have good synergistic effect, namely, the nanocellulose and the calcium stearate have the application effects of using the calcium stearate as a lubricant, an emulsifier, a stabilizer, a release agent, an accelerator, a plasticizer and the like, and also have the application effects of using the nanocellulose as a reinforcing agent, namely, the effect is superior to that of a single nanocellulose powder and is also superior to that of a single calcium stearate.
3. According to the hydrophobic nano cellulose powder and the preparation method thereof, calcium hydroxide participates in the cellulose dissociation process in the early dissociation process, so that the hydrophobic nano cellulose powder plays a role in alkali swelling and grinding. In the dissociation process, the hydroxyl exposed on the surface of the newly dissociated cellulose fiber forms a hydrogen bond with the hydroxyl of the peripheral calcium hydroxide, and the calcium hydroxide is firmly adsorbed on the surface of the fiber; in the subsequent modification process, calcium hydroxide adsorbed on the surface of the nanocellulose is reacted in situ under the action of a binding agent and a modifier to generate calcium stearate, and the nanocellulose is tightly combined with the calcium stearate and is not easy to fall off. The adsorption and the cladding of the calcium stearate can shield the hydroxyl on the surface of the nanocellulose, and can avoid the agglomeration between the nanocellulose and the nanocellulose due to the formation of hydrogen bonds in the drying process, thereby retaining the fibrillar form of the nanocellulose and being beneficial to playing the reinforcing role of nanocellulose powder. The powder obtained by simply mixing and co-grinding cellulose fibers or nanocellulose and calcium stearate does not have the effect, and the nanocellulose and the calcium stearate are difficult to form tight adsorption, so that the effect that the nanocellulose surface is completely coated by the calcium stearate can not be achieved, and the hydrophobic modification and the retention of fibril morphology of the nanocellulose can not be achieved.
4. Compared with other hydrophobically modified nanocellulose, the hydrophobic nanocellulose powder and the preparation method thereof provided by the invention have the advantage that an organic solvent is not needed in the modification process. Through the co-dissociation of calcium hydroxide and the fibers between the calcium hydroxide and the fibers, the adsorption and the coating of the calcium hydroxide on the surface of the nanocellulose are realized. The binding agent is added before modification, and contains two different active groups, namely a hydrolyzable group (reacting with inorganic matters) and an organic functional group (reacting with organic matters), so that the connection between the inorganic matters and the organic matters can be established, and the cohesiveness of the organic polymer and the inorganic filler is enhanced. By precisely controlling the adding position, adding amount, reaction time and reaction temperature of the bonding agent, the tight combination of the nanocellulose and the surface adsorption calcium hydroxide and calcium stearate is realized, the nanocellulose is prevented from falling off from the fiber surface in the subsequent modification, drying and application processes, the hydroxyl on the fiber surface is effectively shielded, namely the hydrophobic nanocellulose is prepared by hydrophobically modifying the calcium hydroxide on the nanocellulose surface, and the agglomeration of the nanocellulose in the drying process is effectively prevented.
5. According to the hydrophobic nanocellulose powder and the preparation method thereof, the nanocellulose in the obtained powder is in a fibrillar shape, and the hydrophobic calcium stearate coated on the surface of the nanocellulose is beneficial to the uniform dispersion of the nanocellulose powder in the nonpolar organic polymer on one hand, and the interfacial compatibility of the nanocellulose and the nonpolar polymer is increased, so that the nanocellulose powder can play a good role in enhancing the nonpolar polymer. In addition, when the amount of calcium hydroxide is large, free calcium stearate is also present in the powder finally produced, and calcium stearate itself can be used as a lubricant, an emulsifier, a stabilizer, a mold release agent, an accelerator, a plasticizer, and the like. Therefore, the hydrophobic nano-cellulose powder prepared by the invention can be used as lubricant, emulsifier, stabilizer, release agent, accelerator, plasticizer, reinforcing agent, cosmetic base stock and the like in the industries of food, medicine, cosmetics, papermaking, coating, plastic rubber and the like.
Drawings
The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification, but are not to be construed as limiting the invention. In the drawings:
fig. 1 is a scanning electron micrograph of a hydrophobic nanocellulose powder at a magnification of x 10,000 showing the nanocellulose fibril surface coated with calcium stearate.
Detailed Description
The present invention will be described in further detail with reference to specific examples, but is not limited thereto.
Example 1
(1) Adsorption and dissociation: dipping the bleached needle pulp into an aqueous suspension of calcium hydroxide, wherein the solid content of the fiber raw material is 2wt%, the dosage of the calcium hydroxide is 3 times of the mass of the fiber raw material, the dipping temperature is 30 ℃, and the dipping time is 3 hours; adopting fine grinding to dissociate the fiber slurry, wherein the grinding mass concentration of the material is 8wt%, the gap between grinding discs is-100 mu m, and the rotating speed of the grinding discs is 2000rpm;
(2) Modification: heating the slurry to 60 ℃, adding a binding agent gamma-aminopropyl triethoxysilane, the dosage of which is 2.0wt% of that of calcium hydroxide, reacting for 30min, adding a catalyst hydrogen peroxide, the dosage of which is 80wt% based on that of the calcium hydroxide, adding a modifier stearic acid, the dosage of which is 2 times that of the calcium hydroxide, and continuously stirring and reacting for 3h at 75 ℃;
(3) And (3) drying: washing and concentrating the reacted slurry, and spray drying to obtain hydrophobic nano cellulose powder;
the aspect ratio of the nanocellulose in the obtained hydrophobic nanocellulose powder is=95, calcium stearate with the diameter of about 50nm is adsorbed on the surface of the nanocellulose, the average particle diameter of the powder is=0.9 mu m, and the water contact angle is=97 degrees; the powder can be added into polyethylene to play the roles of lubricant, release agent and reinforcing agent; when the powder amount is 0.1%, the tensile strength of the sample is improved by 7% compared with that of pure polyethylene.
Example 2
(1) Adsorption and dissociation: dipping bleached broadleaf pulp into aqueous suspension of calcium hydroxide, wherein the solid content of the fiber raw material is 5wt%, the dosage of the calcium hydroxide is 5 times of the mass of the fiber raw material, the dipping temperature is 20 ℃, and the dipping time is 3 hours; dissociating the fiber raw material by adopting ball milling, wherein the grinding mass concentration of the material is 30wt% and the speed is 500rpm;
(2) Modification: heating the slurry to 65 ℃, adding a bonding agent gamma- (2, 3-glycidoxy) propyl trimethoxy silane, wherein the dosage is 2.5wt% of that of calcium hydroxide, reacting for 1h, adding a catalyst hydrogen peroxide and glycerol, wherein the dosage of hydrogen peroxide is 50wt% based on that of calcium hydroxide, the dosage of glycerol is 70wt% based on that of calcium hydroxide, adding a modifier stearic acid, the dosage of which is 6 times that of calcium hydroxide, and continuing stirring and reacting for 3h at 60 ℃;
(3) And (3) drying: washing and concentrating the reacted slurry, and drying by supercritical carbon dioxide to obtain hydrophobic nano-cellulose powder;
the aspect ratio of the nanocellulose in the obtained hydrophobic nanocellulose powder is=80, calcium stearate with the diameter of about 20nm is adsorbed on the surface of the nanocellulose, the average particle diameter of the powder is=0.7 mu m, and the water contact angle is=95 degrees; the powder can be added into polyvinyl chloride to play the roles of a heat stabilizer, a lubricant and a reinforcing agent; when the powder consumption is 3.5%, the tensile strength of the sample is improved by 16% compared with pure polyvinyl chloride.
The above embodiments are only exemplary embodiments of the present invention and are not intended to limit the present invention, the scope of which is defined by the claims. Various modifications and equivalent arrangements of this invention will occur to those skilled in the art, and are intended to be within the spirit and scope of the invention.
Claims (7)
1. A hydrophobic nano cellulose powder and a preparation method thereof are characterized by comprising the following steps:
(1) Adsorption and dissociation: immersing the fiber raw material in an aqueous suspension of calcium hydroxide, wherein the solid content of the fiber raw material is 0.1-5wt%, the dosage of the calcium hydroxide is 0.1-10 times of the mass of the fiber raw material, the immersion temperature is 10-30 ℃, and the immersion time is 2-4h; dissociating the impregnating slurry by a mechanical method;
(2) Modification: heating the slurry to a certain temperature, adding a binding agent, reacting for a period of time, adding a catalyst and a modifier, continuously stirring, and reacting for a period of time at a certain temperature;
(3) And (3) drying: washing, concentrating and drying the reacted slurry to obtain hydrophobic nano cellulose powder;
the length-diameter ratio of the nanocellulose in the obtained hydrophobic nanocellulose powder is more than or equal to 50, calcium stearate particles with the diameter less than or equal to 100nm are adsorbed on the surface of the nanocellulose, the average particle diameter of the powder is less than or equal to 1 mu m, and the water contact angle is more than or equal to 90 degrees; the obtained hydrophobic nanocellulose powder can be used as lubricant, emulsifier, stabilizer, release agent, accelerator, plasticizer, reinforcing agent, cosmetic base material and the like in industries of food, medicine, cosmetics, papermaking, paint, plastic rubber and the like.
2. The hydrophobic nanocellulose powder and the preparation method thereof according to claim 1, wherein in the step (1), the fiber raw material is at least one of bleached or unbleached needle pulp, broad-leaved pulp, cotton pulp, bamboo pulp, wheat straw pulp, waste paper pulp or wood flour, bamboo powder, plant straw, corncob and xylose waste residues, and the blocky and powdery raw materials need to be crushed to 40-80 meshes.
3. The hydrophobic nanocellulose powder and the preparation method thereof according to claim 1, wherein the mechanical dissociation method adopted in said step (1) comprises: one or more of disc milling, fine milling and ball milling; wherein the mass concentration of the materials subjected to disc grinding and fine grinding treatment is 1-50wt%, the gap between the grinding discs is-150-0 mu m, and the rotating speed of the grinding discs is 1000-2000rpm; the mass concentration of the ball-milling material is 1-50wt% and the speed is 100-600 rpm.
4. The hydrophobic nanocellulose powder and the preparation method thereof according to claim 1, wherein in the step (2), the binding agent is one or more of gamma-aminopropyl triethoxysilane, gamma- (2, 3-glycidoxy) propyl trimethoxysilane and gamma-methacryloxypropyl trimethoxysilane, the amount of the binding agent based on calcium hydroxide is 0-5wt%, the reaction time is 10min-2h, and the reaction temperature is 50-70 ℃.
5. The hydrophobic nanocellulose powder and the preparation method thereof according to claim 1, wherein the catalyst in the step (2) is one or more of diethanolamine, hydrogen peroxide, glycerol, propylene glycol, ammonium chloride and ammonium hydroxide, and the catalyst is 0-200wt% based on the dosage of calcium hydroxide.
6. The hydrophobic nanocellulose powder and the preparation method thereof according to claim 1, wherein in the step (2), the modifier is one or more of stearic acid and stearate, the dosage of the modifier is 0.1-10 times of the mass of calcium hydroxide, the reaction time is 10min-4h, and the reaction temperature is 50-100 ℃.
7. The hydrophobic nanocellulose powder and the preparation method thereof according to claim 1, wherein the drying method adopted in the step (3) comprises: at least one of spray drying, supercritical drying, vacuum freeze drying, microwave drying, infrared drying, fluidized bed drying, flash drying, and oven drying.
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| CN117510996A (en) * | 2023-12-25 | 2024-02-06 | 广东扬格新材料科技有限公司 | Preparation method and application of modified cellulose |
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| CN117510996A (en) * | 2023-12-25 | 2024-02-06 | 广东扬格新材料科技有限公司 | Preparation method and application of modified cellulose |
| CN117510996B (en) * | 2023-12-25 | 2024-05-03 | 广东扬格新材料科技有限公司 | Preparation method and application of modified cellulose |
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