阅读说明：本技术 纳米纤维素粉体材料及制备方法、包含其的再分散纳米纤维素浆料和应用 (Nano cellulose powder material, preparation method, re-dispersed nano cellulose pulp containing nano cellulose powder material and application ) 是由 唐磊 张金柱 张延伟 于 2019-10-10 设计创作，主要内容包括：本发明提供了一种纳米纤维素粉体材料及制备方法、包含其的再分散纳米纤维素浆料和应用,包括纳米纤维素和水溶性高分子材料；其中,所述水溶性高分子材料含有氢键和/或醚键。将本发明提供的纳米纤维素粉体材料应用于水性高分子涂料中,可以提高涂料的耐洗刷性能。(The invention provides a nano cellulose powder material, a preparation method thereof, re-dispersed nano cellulose pulp containing the nano cellulose powder material and an application of the nano cellulose powder material, wherein the nano cellulose powder material comprises nano cellulose and a water-soluble high polymer material; wherein the water-soluble polymer material contains a hydrogen bond and/or an ether bond. The nano cellulose powder material provided by the invention is applied to water-based high-molecular paint, and the washing resistance of the paint can be improved.)

1. A nano-cellulose powder material is characterized by comprising nano-cellulose and a water-soluble high polymer material;

wherein the water-soluble polymer material contains a hydrogen bond and/or an ether bond.

2. The nanocellulose powder material of claim 1, characterized in that, the mass percentage of said water-soluble polymer material is 7-21 wt% based on 100% of the total mass of said nanocellulose powder material;

preferably, the water-soluble polymer material is selected from any one or a combination of at least two of polyethylene glycol, polyvinyl alcohol, polyoxyethylene and polyvinylpyrrolidone, preferably polyvinyl alcohol;

preferably, the polyvinyl alcohol has an alcoholysis degree of 88 to 100 and a viscosity of 5 to 40 mPas, more preferably 88 and a viscosity of 5 mPas.

3. The nanocellulose powder material of claim 1 or 2, characterized in that the mass percentage of the nanocellulose is 70-90% by weight, based on the total mass of the nanocellulose powder material being 100%;

preferably, the diameter of the nano-cellulose is 8-20nm, and the aspect ratio is 100-200.

4. The nanocellulose powder material of any one of claims 1-3, further comprising a plasticizer in the nanocellulose powder material;

preferably, the plasticizer comprises any one or a combination of at least two of glycerol, hexylene glycol, ethylene glycol, terpineol or propylene glycol, and is further preferably ethylene glycol and/or glycerol;

preferably, the mass percentage of the plasticizer is 3-9 wt% based on 100% of the total mass of the nanocellulose powder material.

5. A method for the preparation of a nanocellulose powder material according to any of claims 1-4, characterized in that said method of preparation comprises the steps of:

and mixing the nano cellulose pulp with a water-soluble polymer aqueous solution, diluting, stirring, drying and crushing to obtain the nano cellulose powder material.

6. The production method according to claim 5, wherein the water-soluble polymer aqueous solution has a solid content of 15 to 25%;

preferably, a plasticizer is further dispersed in the aqueous solution of the water-soluble polymer;

preferably, the solid content of the nanocellulose pulp is 3-8%;

preferably, in the diluted solution, the solid content is 1-4%;

preferably, the stirring is performed using a high speed stirrer;

preferably, the stirring time is 30-50 min;

preferably, the temperature of the drying is 90-140 ℃, further preferably 120 ℃;

preferably, the drying mode is one of spray drying, oven atmospheric drying or freeze drying, and further preferably spray drying.

7. A re-dispersed nanocellulose pulp, characterized by comprising a nanocellulose powder material of any one of claims 1-4;

preferably, the content of the nanocellulose in the re-dispersed nanocellulose pulp is 1-4 wt%.

8. The method of preparing a re-dispersed nanocellulose pulp as claimed in claim 7, comprising dispersing the nanocellulose powder material of any one of claims 1-4 in a solvent to obtain a re-dispersed nanocellulose pulp;

preferably, the dispersing manner is any one or a combination of at least two of high-speed stirring, ball milling dispersion, ultrasonic dispersion or sand milling dispersion.

9. Use of a nanocellulose powder material of any one of claims 1-4 or a redispersed nanocellulose pulp of claim 7 in a modified coating;

preferably, the coating is an aqueous polymer coating.

10. A modified aqueous polymer coating comprising the nanocellulose powder material of any one of claims 1 to 4 or the re-dispersed nanocellulose pulp of claim 7;

preferably, in the modified aqueous polymer coating material, the mass percentage of the nanocellulose is 0.3-1%, and more preferably 0.7%.

Technical Field

The invention belongs to the technical field of modified coatings, and relates to a nano-cellulose powder material, a preparation method thereof, re-dispersed nano-cellulose pulp containing the nano-cellulose powder material and application of the nano-cellulose pulp.

Background

Along with the enhancement of the national environmental protection supervision and the increasing improvement of the quality of healthy life of people. The environment-friendly coating is more and more popular, and the water-based high polymer coating is a high polymer coating which uses water as a solvent or a dispersion medium, has few toxic volatile matters, has no pungent smell, is healthy and environment-friendly, is one of the most popular coatings in the market, is widely used for furniture and indoor and outdoor protection and decoration, and has good market development prospect in the future. However, compared with the traditional solvent-based coating, the principle of film formation is different, so that the water-based polymer coating is poor in the aspects of paint film strength, wear resistance and the like, and needs to be enhanced and modified.

Cellulose is a rich natural renewable biopolymer material that is widely distributed in higher plants, but also in marine animals, algae, bacteria, fungi, and invertebrates. Cellulose is transversely decomposed into sub-structure nanometer units of the cellulose through mechanical shearing and chemical action to generate the nanometer cellulose. Because the nanocellulose has the characteristics of high modulus, reproducibility, degradability and the like, the preparation and the application of the nanocellulose become hot points in recent years. However, the nano-cellulose has stronger agglomeration property as other nano-materials, the nano-cellulose prepared at present can only be dispersed in a solvent, mainly in water, and the prepared slurry has lower nano-cellulose content, generally 0.1-10%, which greatly hinders the application aspect and increases the transportation cost.

CN106905437A discloses a high heat-resistant recyclableThe method comprises the steps of carrying out acidolysis on cellulose by sulfuric acid, adding ionic liquid into the obtained cellulose nanocrystal suspension to enable the ionic liquid and the cellulose nanocrystal to form ionic bonds, and drying reaction liquid to obtain the powdery cellulose nanocrystal; the ionic liquids are AmimCI and [ OMim]BF₄、[BMIm]BF₄One or more of; the ionic liquid used as the raw material in the technology is expensive, and the product exists in an ionic bond, so that the coating is unstable in some water-based coatings, the storage stability of the water-based high polymer material is reduced, and the popularization and the application of the prepared product are not facilitated. CN109054584A discloses a nano-level cellulose functional doping modified coating and a preparation method thereof, wherein, 0.1 percent of hydrophilic nano-cellulose dispersion A or 0.1 percent of hydrophobic nano-cellulose dispersion B, 20 to 60 percent of water-based or solvent film forming agent, 0.05 to 1.5 percent of dispersing agent, 0.08 to 1.7 percent of coupling agent, 0.02 to 1.0 percent of drier, 0.01 to 2.5 percent of anti-settling agent, 0.5 to 1.5 percent of defoaming agent, 0.001 to 0.05 percent of preservative, 0.02 to 2.5 percent of anti-skinning agent, 0.01 to 3.5 percent of flatting agent and 10 to 70 percent of filler are mixed and then dispersed at high speed by a high-speed shearing machine, wherein the absolute dry mass of the nano-cellulose accounts for 0.01 to 1 percent of the absolute dry mass of the coating, and the nano-level cellulose functional doping modified coating is dripped into the water or organic solvent coating at the normal temperature at the speed of 0.01 to 10mL/min, after the dropwise addition is finished, the nano-cellulose function modified doped coating is obtained, the method is characterized in that nano-cellulose is used for preparing a coating product with excellent surface strength, but 0.1% of nano-cellulose dispersion liquid is used, the content of nano-cellulose in the dispersion liquid is low, modification work of the coating by researchers is not facilitated, long-distance transportation of the product is not facilitated, and transportation cost is increased.

Therefore, it is desirable to provide a re-dispersible nanocellulose that can be directly dispersed and applied to save transportation costs and facilitate application.

Disclosure of Invention

The invention aims to provide a nano cellulose powder material, a preparation method, re-dispersed nano cellulose pulp containing the nano cellulose powder material and application of the nano cellulose powder material. The nano cellulose powder material provided by the invention has the advantages of high nano cellulose content and low transportation cost, and can be dispersed in a solvent to form slurry, so that the application is convenient.

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

in a first aspect, the invention provides a nanocellulose powder material, which comprises nanocellulose and a water-soluble polymer material.

Wherein the water-soluble polymer material contains a hydrogen bond and/or an ether bond.

The nano cellulose powder material provided by the invention has redispersibility, can not agglomerate in dispersion liquid, can be applied by using the dispersion liquid in the practical application process, can also directly use powder, is convenient and simple, is different from nano cellulose dispersion liquid or pulp, and is convenient to transport.

The water-soluble polymer material has hydrogen bonds and/or ether bonds, the water-soluble polymer is added into the nano-cellulose, so that the hydrogen bonds are formed between the nano-cellulose and hydroxyl groups (ether bonds) on the water-soluble polymer, the hydrogen bonds formed by the mutual combination of the hydroxyl groups of the nano-cellulose can be shielded, meanwhile, the nano-cellulose is in a fibrous structure, molecular chains of the water-soluble polymer are spread in water, the groups on the molecular chains interact with the groups carried by the nano-cellulose, and simultaneously, the high molecular chains can be wound and coated on the surface of the nano-cellulose to form an IPN-like structure (interpenetrating polymer network structure), and the structure has a steric hindrance effect on the nano-cellulose, so that the agglomeration of the nano-cellulose is prevented through the two effects, and the powder provided by the invention can be redispersed in a solvent and cannot be agglomerated.

In the present invention, the water-soluble polymer material is contained in an amount of 7 to 21% by mass, for example, 8%, 10%, 12%, 14%, 16%, 18%, 20%, etc., based on 100% by mass of the total mass of the nanocellulose powder material.

If the content of the water-soluble polymer material is too low, dispersion of the nanocellulose is not facilitated, and if the content of the water-soluble polymer material is too high, the content of the nanocellulose is reduced, which increases the cost to some extent.

Preferably, the water-soluble polymer material is selected from any one or a combination of at least two of polyethylene glycol, polyvinyl alcohol, polyoxyethylene and polyvinylpyrrolidone, and is preferably polyvinyl alcohol.

Polyvinyl alcohol is preferred because it is cheaper and more readily available than other water-soluble polymers.

Preferably, the polyvinyl alcohol has an alcoholysis degree of 88 to 100, e.g., 90, 92, 94, 95, 96, 98, etc., and a viscosity of 5 to 40 mPas, e.g., 10 mPas, 15 mPas, 20 mPas, 25 mPas, 30 mPas, 35 mPas, etc., and more preferably has an alcoholysis degree of 88 and a viscosity of 5 mPas.

If the alcoholysis degree of the polyvinyl alcohol is too low or too high, the water solubility is poor, if the viscosity is too low, the steric hindrance effect of the polyvinyl alcohol on the nanocellulose is reduced, resulting in a reduction in the content of the nanocellulose in the redispersible nanocellulose particles, and if the viscosity of the polyvinyl alcohol is too high, resulting in difficulty in stirring during preparation.

In the present invention, the nanocellulose is present in a mass percentage of 70 to 90 wt%, such as 72 wt%, 75 wt%, 78 wt%, 80 wt%, 82 wt%, 85 wt%, 88 wt%, etc., based on 100% of the total mass of the nanocellulose powder material.

Preferably, the nanocellulose has a diameter of 8-20nm, such as 10nm, 12nm, 14nm, 16nm, 18nm, etc., and an aspect ratio of 100-200, such as 120, 140, 160, 180, etc.

In the present invention, a plasticizer is further included in the nanocellulose powder material.

Preferably, the plasticizer comprises any one or a combination of at least two of glycerol, hexylene glycol, ethylene glycol, terpineol or propylene glycol, and further preferably ethylene glycol and/or glycerol.

The plasticizer can improve the content of the nano cellulose in the nano cellulose powder material and can promote the redispersion process of the nano cellulose powder material provided by the invention. The selected plasticizer is a water (or other solvent) soluble micromolecular compound, and can be quickly dispersed into water (or other solvents) in the early redispersion stage of the redispersible nano cellulose powder due to small molecular weight and small moving steric hindrance, so that the water (or other solvents) can quickly replace the plasticizer in the powder particles, the contact area of the water (or other solvents) and the powder particles is increased, and the redispersion process is accelerated.

Preferably, the mass percentage of the plasticizer is 3 to 9 wt%, such as 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, etc., based on 100% of the total mass of the nanocellulose powder material.

In a second aspect, the present invention provides a method for producing a nanocellulose powder material according to the first aspect, said method for producing comprising the steps of:

and mixing the nano cellulose pulp with a water-soluble polymer aqueous solution, diluting, stirring, drying and crushing to obtain the nano cellulose powder material.

The water-soluble polymer in the invention can prevent the aggregation of the nano-cellulose in the drying process, and further, the finally obtained nano-cellulose powder material can be dispersed in the solvent again for application. The preparation method can prepare the powder material with higher nano-cellulose content, and compared with the nano-cellulose dispersion liquid, the cost for transporting the nano-cellulose powder material is greatly reduced.

The preparation method has the advantages of simple preparation process, non-ionic raw materials, low price, mild reaction conditions and low energy consumption. And moreover, the nonionic raw materials can ensure that the finally obtained nano cellulose powder material does not have ions, so that the defect that the performance of the coating is reduced due to the instability of the coating caused by the presence of the ions in the application process is avoided.

Preferably, the water-soluble polymer aqueous solution has a solid content of 15 to 25%, for example, 16%, 18%, 20%, 22%, 24%, etc.

Preferably, a plasticizer is further dispersed in the aqueous solution of a water-soluble polymer.

Preferably, the nanocellulose pulp has a solids content of 3-8%, such as 4%, 5%, 6%, 7%, etc.

Preferably, the solids content in the diluted solution is 1-4%, e.g., 2%, 3%, etc.

The solid content is too high, so that the dried powder particles are too compact, the redispersion time is prolonged, and even some powder cannot be redispersed; if the solid content is too low, the amount of water for dilution increases, and the drying efficiency decreases.

In the diluted solution, the solid content refers to the total solid content, namely the total solid content of the nanocellulose, the water-soluble polymer and the plasticizer.

Preferably, the stirring is performed using a high speed stirrer.

Preferably, the stirring time is 30-50min, such as 35min, 40min, 45min, etc.

Preferably, the drying temperature is 90-140 ℃, such as 100 ℃, 110 ℃, 120 ℃, 130 ℃, and the like, and more preferably 120 ℃.

Preferably, the drying mode is one of spray drying, oven atmospheric drying or freeze drying, and further preferably spray drying.

In a third aspect, the present invention provides a re-dispersed nanocellulose pulp comprising the nanocellulose powder material of the first aspect.

Preferably, the amount of nanocellulose in the re-dispersed nanocellulose pulp is 1-4 wt%, such as 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, etc.

In a fourth aspect, the present invention provides a method for preparing a re-dispersed nanocellulose pulp according to the third aspect, said method comprising dispersing the nanocellulose powder material of the first aspect in a solvent to obtain said re-dispersed nanocellulose pulp.

Preferably, the dispersing manner is any one or a combination of at least two of high-speed stirring, ball milling dispersion, ultrasonic dispersion or sand milling dispersion.

In a fifth aspect, the present invention provides the use of a nanocellulose powder material according to the first aspect or a redispersed nanocellulose pulp according to the third aspect in a modified coating.

Preferably, the coating is an aqueous polymer coating.

The nano cellulose powder material prepared by the invention can be directly applied to water-based high-molecular paint, does not cause adverse effect on the stability of the paint, and can achieve the effect of fixing the powder in the paint by forming a net structure in the paint through nano cellulose, thereby improving the performances of the paint, such as washing resistance, brushing resistance and the like.

In a sixth aspect, the invention provides a modified aqueous polymer coating, comprising the nano-cellulose powder material of the first aspect or the re-dispersed nano-cellulose pulp of the third aspect.

Preferably, in the modified aqueous polymer coating material, the nanocellulose is contained in an amount of 0.3 to 1% by mass, for example, 0.4%, 0.5%, 0.6%, 0.8%, 0.9%, and more preferably 0.7%.

Compared with the prior art, the invention has the following beneficial effects:

(1) the water-soluble polymer material has hydrogen bonds and/or ether bonds, the water-soluble polymer is added into the nano-cellulose, so that the hydrogen bonds are formed between the nano-cellulose and hydroxyl (ether bonds) on the water-soluble polymer, the hydrogen bonds formed by mutual combination of the hydroxyl of the nano-cellulose can be shielded, and simultaneously, an IPN (interpenetrating polymer network) structure can be formed between the water-soluble polymer chain and the nano-cellulose, so that the structure has a steric hindrance effect on the nano-cellulose, and the agglomeration of the nano-cellulose is prevented through the two effects, so that the powder provided by the invention can be redispersed in a solvent and cannot be agglomerated.

(2) The water-soluble polymer in the invention can prevent the aggregation of the nano-cellulose in the drying process, and further, the finally obtained nano-cellulose powder material can be dispersed in the solvent again for application. The preparation method can prepare the powder material with higher nano-cellulose content, and compared with the nano-cellulose dispersion liquid, the cost for transporting the nano-cellulose powder material is greatly reduced.

(3) The nano cellulose powder material provided by the invention is applied to a water-based high-molecular paint, and the washing resistance of the paint can be improved, wherein the washing resistance is 13200 times or more.

Drawings

Fig. 1 is a graph of the apparent morphology of the re-dispersed nanocellulose pulps provided in example 1 and comparative example 1.

FIG. 2 is a transmission electron micrograph of the nanocellulose pulp provided in preparation example 1.

Fig. 3 is a scanning electron micrograph of the redispersed nanocellulose pulp provided in example 1.

Detailed Description

The technical solution of the present invention is further explained by the following embodiments. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitations of the present invention.

Preparation example 1

A nano cellulose powder material consists of 85 wt% of nano cellulose, 12 wt% of water-soluble polymer and 3 wt% of plasticizer.

Wherein the diameter of the nano-cellulose is 8-20nm, and the length-diameter ratio is 100-200; the water-soluble polymer is polyvinyl alcohol PVA088-05, the alcoholysis degree is 88, and the viscosity is 5mPa & s; the plasticizer is glycerol.

The preparation method comprises the following steps:

(1) preparation of Water-soluble Polymer solution

Mixing the aqueous polymer, a plasticizer and distilled water to prepare an aqueous polymer solution with the concentration of 20%;

(2) preparation of powder Material

Mixing nano cellulose pulp with solid content of 4% with an aqueous polymer solution, and diluting with distilled water until the total solid content is 3.5%; stirring and dispersing the mixed solution at a high speed for 40min by using a high-speed stirrer (400 revolutions per minute) at room temperature; and then drying and crushing the mixture in an oven at 95 ℃ to obtain the nano cellulose powder material.

Preparation examples 2 to 4

The differences from preparation example 1 are that the polyvinyl alcohol of this preparation example had an alcoholysis degree of 100, a viscosity of 40 mPas (preparation example 2), an alcoholysis degree of 100, a viscosity of 50 mPas (preparation example 3), an alcoholysis degree of 85 and a viscosity of 3 mPas (preparation example 4).

Preparation examples 5 to 6

The difference from preparation example 1 is that in this preparation example, polyvinyl alcohol was replaced with polyethylene glycol (molecular weight 20000, preparation example 5) and polyvinylpyrrolidone K90 (preparation example 6).

Preparation examples 7 to 8

The difference from preparation example 1 is that glycerin was replaced with propylene glycol (preparation example 7) and terpineol (preparation example 8).

Preparation example 9

The difference from preparation example 1 is that glycerol was not added.

Preparation examples 10 to 13

The difference from preparation example 1 is that, in this preparation example, 70 wt% of nanocellulose, 21 wt% of water-soluble polymer, 9 wt% of plasticizer (preparation example 10), 90 wt% of nanocellulose, 7 wt% of water-soluble polymer (preparation example 11), 65 wt% of nanocellulose, 32 wt% of water-soluble polymer (preparation example 12), 92 wt% of nanocellulose, and 5 wt% of water-soluble polymer (preparation example 13).

Preparation examples 14 to 17

The difference from preparation 1 is that step (2) was diluted to a total solids content of 1% (preparation 14), 4% (preparation 15), 0.5% (preparation 16), 5% (preparation 17).

Comparative preparation example 1

The difference from preparation example 1 is that the water-soluble polymer and plasticizer were not added, and the preparation method was as follows:

diluting the nano cellulose pulp with the solid content of 4% to the solid content of 3.5%; stirring and dispersing at high speed for 40min at room temperature by using a high-speed stirrer (400 rpm); and then drying and crushing the mixture in an oven at 95 ℃ to obtain the nano cellulose powder material.

Comparative preparation example 2

The difference from preparation example 1 is that the water-soluble polymer was not added, and the preparation method was as follows:

(1) mixing plasticizer with distilled water to prepare 20% solution;

(2) mixing nano cellulose pulp with solid content of 4% with the solution in the step (1), and diluting by using distilled water until the total solid content is 3.5%; stirring and dispersing the mixed solution at a high speed for 40min by using a high-speed stirrer (400 revolutions per minute) at room temperature; and then drying and crushing the mixture in an oven at 95 ℃ to obtain the nano cellulose powder material.

Comparative preparation example 3

The difference from preparation example 1 is that the water-soluble polymer in preparation example 1 was replaced with alcohol ester-12.