阅读说明：本技术 一种不含氟碳化合物且可生物降解的防油纸及其制备方法 (Fluorocarbon-free biodegradable oil-proof paper and preparation method thereof ) 是由 童树华 华飞果 张宇 童力 孟育 倪永浩 何志斌 于 2020-03-13 设计创作，主要内容包括：本发明涉及一种不含氟碳化合物且可生物降解的防油纸及其制备方法,该方法是在纤维素基纸上先预涂一层变性淀粉类的增强预涂层,经干燥处理后再进行纳米纤维素/聚乙烯醇配合的防油层涂布。采用本发明,通过纳米纤维素与增强预涂层中的阳离子化合物的相互作用,减少了主要成分为PVA的抗油层涂布过程中的聚乙烯醇渗透问题,并且在涂料中起到对PVA抗油脂的增强作用,以大幅度提高抗油层抗油脂渗透的效果；由于不含任何氟碳化合物添加剂,并且对环境友好,对人体无毒害作用,可用作各种目的的防油纸。(The invention relates to fluorocarbon-free biodegradable oil-proof paper and a preparation method thereof. By adopting the invention, the problem of polyvinyl alcohol permeation in the coating process of the oil-resistant layer with PVA as the main component is reduced through the interaction of the nano-cellulose and the cationic compound in the reinforced precoat layer, and the oil-resistant coating plays a role in reinforcing the grease resistance of the PVA in the coating so as to greatly improve the effect of the oil-resistant layer on grease resistance; the oil-proof paper does not contain any fluorocarbon additive, is environment-friendly and has no toxic or harmful effect on human bodies, and can be used as oil-proof paper for various purposes.)

1. A fluorocarbon-free biodegradable oil-proof paper and a preparation method thereof are characterized in that a layer of modified starch type enhanced precoating paint is precoated on cellulose-based paper to obtain an enhanced precoating layer, and then nano-cellulose/polyvinyl alcohol matched oil-proof paint is coated to obtain an oil-proof layer.

2. The fluorocarbon-free biodegradable oilproof paper and the method for preparing the same according to claim 1, wherein: the preparation method of the reinforced precoating paint comprises the following steps: adding deionized water into cationic starch or other cationic high molecular polymers according to the mass ratio of 1-10: 90-99, and stirring at 70-100 ℃ until a uniform solution, a glue solution or a dispersion solution is obtained.

3. The fluorocarbon-free biodegradable oilproof paper and the method for making the same as claimed in claim 2, wherein the mixing method comprises but is not limited to mechanical mixing, ultrasonic mixing and high pressure homogenizer mixing after adding deionized water.

4. The fluorocarbon-free biodegradable oil-proof paper and the preparation method thereof as claimed in claim 1, wherein the oil-proof coating is prepared by the following steps: (1) adding water into polyvinyl alcohol according to the mass ratio of 5-20: 80-95, stirring at 80-100 ℃ until a uniform solution is obtained, (2) waiting for the polyvinyl alcohol solution to be cooled to room temperature, and (3) after cooling, adding nano-cellulose according to the solid content ratio of 20-100: 1 of polyvinyl alcohol to nano-cellulose, and mixing to be uniform under the condition of ice water cooling.

5. The fluorocarbon-free biodegradable oilproof paper and the preparation method thereof according to claim 4, wherein in the step (3), the mixing method includes but is not limited to mechanical mixing, ultrasonic mixing and high pressure homogenizer mixing.

6. A fluorocarbon-free biodegradable oilproof paper and its preparation method as claimed in claim 1, wherein said polyvinyl alcohol can be any one or a mixture of two or more polyvinyl alcohols, and the degree of hydrolysis and molecular weight of the polyvinyl alcohol can be changed according to the requirements of product production.

7. A fluorocarbon-free biodegradable grease barrier paper and its preparation method as claimed in claim 1, wherein the nanocellulose can be any one of nanocellulose including but not limited to Cellulose Nanocrystals (CNC), Cellulose Nanofibrils (CNF) and TEMPO oxidized cellulose nanofibrils.

8. A fluorocarbon-free biodegradable oilproof paper and its preparation method as claimed in claim 1, wherein the cellulose-based paper can be any one of the cellulose-based paper materials including but not limited to copy paper, filter paper, kraft paper, cardboard and coated paper, and the fiber source can be virgin or recycled.

9. The fluorocarbon-free biodegradable oilproof paper and the preparation method thereof according to claim 1, wherein the specific steps are as follows: (1) coating of the reinforcing precoat: coating the prepared enhanced precoating paint on cellulose-based paper by using a multifunctional coating machine and then drying; (2) coating of an oil-proof layer: and (3) coating the prepared oil-proof coating compounded by the nano-cellulose/polyvinyl alcohol by using a multifunctional coating machine, and drying.

10. The fluorocarbon-free biodegradable oilproof paper and the method for making the same as claimed in claim 9, wherein the drying method is any one of drying methods including but not limited to hot plate drying, drying cylinder drying, hot air drying and natural drying.

11. A fluorocarbon-free biodegradable oilproof paper and method of making the same as claimed in claim 9, wherein said enhanced precoat is applied at a basis weight of 0.1g/m²To 10g/m²(ii) a The coating weight of the oil-repellent layer is 0.2g/m²To 20g/m²。

Technical Field

The invention relates to fluorocarbon-free biodegradable oil-proof paper and a preparation method thereof, in particular to a surface treatment process taking cellulose-based paper as an object and application thereof.

Background

In general, a cellulose-based paper is a paper mainly composed of cellulose and other small compounds, and is a material having pores on the surface thereof without having oil-repellent properties. In industry, coated oil-resistant paper is a product obtained by surface modification of base paper by using an oil-resistant coating through a coating method, and in general, the oil-resistant performance of an oil-resistant layer of the coated paper is mainly provided by fluorine-containing compounds or latex or paraffin, but the fluorine-containing compounds or latex or paraffin are toxic and harmful to human bodies and the environment, or the produced oil-resistant paper has poor recycling performance and biodegradation performance. In recent years, the environmental protection problem of disposable plastic products is emphasized all over the world, and the agenda for forbidden plastic products is put forward, so that the disposable plastic products can be replaced to a certain extent.

In order to obtain oil-repellent properties on base paper without oil-repellent properties, it is necessary to apply an oil-repellent component to the surface of the base paper. Specifically, the following treatment methods have been reported so far.

Patent document 1 (U.S. Pat. No. 5,674,961) and patent document 2 (U.S. Pat. No. 5,330,622) propose a surface modification method in which fluorocarbon is attached to the surface of base paper by impregnation or coating to obtain grease resistance of the base paper. Although fluorocarbon paper modification processes are well established and effective, fluorocarbons are harmful to the human body and the environment and can migrate and accumulate with food chains. Some developed countries, such as the health canada, the environmental protection agency of the united states, the german federal risk assessment research institute, have identified fluorocarbons as potentially hazardous compounds. Therefore, it is necessary to develop a non-fluorocarbon grease-resistant paper coating modification process.

Patent document 3 (U.S. Pat. No. 4418119A) proposes a coating process in which the active ingredients of the coating are mainly composed of polyvinyl alcohol and silicone grease, and the grease-resistant effect of the base paper is improved by using the grease-resistant properties provided by the two components by the coating technique. However, this method requires the use of an easily vaporizable organic solvent such as heptane or toluene at the time of handling the mixed silicone grease components, which is very high in the air purification requirement for the production environment and has a production safety problem.

Patent document 4 (chinese patent CN 103669105A) proposes a coating process in which a coating material composed of starch, a plasticizer, a film-forming aid, and a fluorine-containing compound is coated on base paper, and then the base paper is dried to obtain finished paper. The fluorine-containing compound is perfluoropolyether phosphate and fluorine-containing acrylate, and the solid content of the coating is 5-15%. However, this coating process, while not using fluorocarbons, still uses fluorine-containing compounds, which can be potentially harmful, as well as some other potential hazards due to the use of plasticizers and some other additives.

Patent document 5 (chinese patent CN 110258184A) proposes a coating process in which a base paper is coated with components such as modified starch and chitosan and then dried to obtain food-grade oil-proof paper. However, due to the fact that the cost of chitosan is too high, applicable scenes are limited, and the limit grease resistance of the method is limited.

In addition, in the conventional coating process of the polyvinyl alcohol solution, the polyvinyl alcohol solution can be dried to form a smooth and compact film, and when the film is covered on the top layer of the base paper, the film has a good grease-resistant effect.

As mentioned above, the existing coated greaseproof papers all have some problems. With the increasing living standard of people, people hope to use environment-friendly, biodegradable and oil-proof paper with high oil resistance, not only on food packaging, but also in industrial application, such as base paper of sand paper. Therefore, the original coating process using the fluorine-containing compound and the volatile organic solvent needs to be replaced by a novel environment-friendly high-performance coating oilproof paper process.

Disclosure of Invention

The invention aims to provide a simple surface modification process aiming at the technical problems of non-green environmental protection, poor recycling performance and difficult biodegradation of the existing oil-proof paper, which can improve the grease resistance of food packaging base paper or superfine sand paper base paper while avoiding using fluorocarbon, silicone grease and volatile organic compounds in the coating process, and does not lose the pulping capacity of the base paper for recycling under the condition of not losing the binding capacity with other high molecular compounds (such as polyurethane), thereby being the oil-proof paper which does not contain fluorocarbon and can be biodegraded and a preparation method thereof.

In order to solve the technical problems, the invention adopts the following technical scheme: a fluorocarbon-free biodegradable oil-proof paper and a preparation method thereof are characterized in that a modified starch type enhanced pre-coating paint is pre-coated on cellulose-based paper to obtain an enhanced pre-coating layer, and then a nano-cellulose/polyvinyl alcohol-compounded oil-proof paint is coated to obtain an oil-proof layer.

The fluorocarbon-free biodegradable oil-proof paper and the preparation method thereof are characterized in that the preparation method of the reinforced precoating paint comprises the following steps: adding deionized water into cationic starch or other cationic high molecular compounds according to the mass ratio of 1-10: 90-99, adding magnetons, and dissolving on a magnetic heating stirrer at 70-90 ℃ until uniform solution, glue solution or dispersion liquid is obtained.

The fluorocarbon-free biodegradable oil-proof paper and the preparation method thereof are characterized in that the preparation of the oil-proof coating comprises the following specific steps: (1) adding deionized water into polyvinyl alcohol according to the mass ratio of 5-20: 80-95, stirring at 80-100 ℃ until a uniform solution is obtained, (2) waiting for the polyvinyl alcohol solution to be cooled to room temperature, and (3) after cooling, adding nanocellulose according to the solid content ratio of 20-100: 1 of polyvinyl alcohol to nanocellulose, and carrying out ultrasonic treatment to be uniform under the condition of ice water cooling. The polyvinyl alcohol can be any one polyvinyl alcohol or a mixture of two or more polyvinyl alcohols, and the hydrolysis degree and the molecular weight of the polyvinyl alcohol can be changed according to the production requirements of products; the nanocellulose may be any one of nanocelluloses including, but not limited to, Cellulose Nanocrystals (CNC), Cellulose Nanofibrils (CNF), and TEMPO oxidized cellulose nanofibrils.

The fluorocarbon-free biodegradable oil-proof paper and the preparation method thereof are characterized in that the cellulose-based paper can be any one of cellulose-based paper materials, including but not limited to copy paper, filter paper, kraft paper, paperboard and coated paper, and the fiber source can be native or regenerated.

The fluorocarbon-free biodegradable oil-proof paper and the preparation method thereof are characterized in that the preparation method comprises the following specific steps: (1) coating of the reinforcing precoat: post-drying (including but not limited to hot plate drying, cylinder drying, hot air drying, and natural drying) the cellulose-based paper by applying the prepared enhanced precoating coating (i.e., cationic starch solution) using a multifunctional coater; (2) coating of an oil-proof layer: coating the prepared nano-cellulose/polyvinyl alcohol oil-proof coating by using a multifunctional coating machine, drying (including but not limited to heating plate drying, drying cylinder drying, hot air drying and natural drying), then carrying out heat treatment on a heating plate at 103-107 ℃ or in a drying cylinder, or directly carrying out heat treatment, and finally transferring to a standard test environment for standing for 12-24 hours to reconstruct hydrogen bonds among components of the coated paper and level the paper; wherein the reinforcing precoat layer is applied in a quantitative of 0.1g/m²To 10g/m²The quantitative amount of the oil-repellent layer applied was 0.2g/m²To 20g/m²。

Compared with other methods, the method has the beneficial technical effects that:

(1) the oil-proof paper obtained by the invention can pass the highest level 12 in a TAPPI T559 oil and grease proofing test and has excellent oil and grease resistance, while the polyvinyl alcohol coated paper with the same amount can only pass the TAPPIT559 oil and grease proofing test of the level 4 to 7 according to different base papers.

(2) The invention adds the charge effect of the nano-cellulose and the cationic starch. Through the electrostatic action, the starch with the positive points can act with the nano-cellulose with the negative electricity, so that the permeation effect of the nano-cellulose/polyvinyl alcohol solution is greatly prevented or delayed, and the polyvinyl alcohol forms a more compact and thick oil-resistant layer on the top of the base paper, thereby achieving a stronger oil-resistant effect.

(3) According to the invention, the nano-cellulose and the polyvinyl alcohol are mixed, and the viscosity of the polyvinyl alcohol/nano-cellulose mixed solution is enhanced through hydrogen bonding, so that the coating is less prone to permeating into paper, and further, the polyvinyl alcohol can generate a better anti-grease layer on the surface of the base paper along with drying.

(4) The invention adds the mixture of nano-cellulose and polyvinyl alcohol, and the shear thinning effect of the polyvinyl alcohol/nano-cellulose mixed solution is strengthened by hydrogen bond combination. In the coating, the solution viscosity becomes lower as the shearing force of the coating blade (bar) becomes higher, and the coating becomes easier.

(5) All the raw materials used in the invention can be naturally and gradually degraded into carbon dioxide and water, and no micro plastic is generated.

(6) All the raw materials used in the invention have no toxic or harmful effect, and the obtained oil-proof paper can be used for industrial application, such as base paper of sand paper, and can also be used in the field of food packaging.

(7) The method has simple coating process and easy operation, and can be used for producing special paper coating enterprises without purchasing other equipment and using volatile organic solvent to ensure green production.

Detailed Description

The following further illustrates and contrasts the conventional processes with the present invention in detail with reference to specific examples, including but not limited to the examples.

First, the following examples one to three are illustrative of grease resistance ratings of grease-proof papers under conventional polyvinyl alcohol coating processes.

Embodiment one.

1. Preparing an oil-proof coating: (1) adding deionized water into polyvinyl alcohol with hydrolysis degree of 87-89% and molecular weight of 8 ten thousand 5-12 ten thousand 4 according to the mass ratio of 10:90, and stirring at 95 ℃ until a uniform 10% polyvinyl alcohol solution is obtained; (2) waiting for the polyvinyl alcohol solution to cool to room temperature.

2. And (3) standby base paper: the gram weight is 90g/m²Density of 0.763g/cm³Copy paper having a Gurley air permeability of 18.6 s/100 ml.

3. The coating process comprises the following steps: coating the prepared polyvinyl alcohol oil-proof coating with a K303 multifunctional coating machine by using a JS10 scraper at the speed of 3m/min, naturally drying, performing heat treatment on a heating plate at 105 ℃ for 5 minutes, and finally transferring to a standard test environment for standing for 12-24 hours to reestablish hydrogen bonds among the components of the coated paper and level the paper, wherein the coating weight is 2g/m²。

4. And (3) testing: the greaseproof paper obtained in this example passed the grease resistance test TAPPI T559 with a maximum rating of 7.

(II) example II.

1. Preparing an oil-proof coating: (1) adding deionized water into polyvinyl alcohol with hydrolysis degree of 87-89% and molecular weight of 8 ten thousand 5-12 ten thousand 4 according to the mass ratio of 10:90, and stirring at 95 ℃ until a uniform 10% polyvinyl alcohol solution is obtained; (2) waiting for the polyvinyl alcohol solution to cool to room temperature.

2. And (3) standby base paper: the gram weight is 50g/m²Density of 0.722g/cm³Unbleached packaged kraft paper having a Gurley air permeability of 36.5 s/100 ml.

3. The coating process comprises the following steps: coating the prepared polyvinyl alcohol oil-proof coating with a K303 multifunctional coating machine by using a JS10 scraper at the speed of 3m/min, naturally drying, performing heat treatment on a heating plate at 105 ℃ for 5 minutes, and finally transferring to a standard test environment for standing for 12-24 hours to reestablish hydrogen bonds among the components of the coated paper and level the paper, wherein the coating weight is 2g/m²。

4. And (3) testing: the greaseproof paper obtained in this example passed the grease resistance test TAPPI T559 with a maximum rating of 7.

(III) example III.

1. Preparing an oil-proof coating: (1) adding deionized water into polyvinyl alcohol with hydrolysis degree of 87-89% and molecular weight of 8 ten thousand 5-12 ten thousand 4 according to the mass ratio of 10:90, and stirring at 95 ℃ until a uniform 10% polyvinyl alcohol solution is obtained; (2) waiting for the polyvinyl alcohol solution to cool to room temperature.

2. And (3) standby base paper: a waste pulp paperboard having a grammage of 170g/m2, a density of 0.656g/cm3, and a Gurley air permeability of 20.5 s/100 ml.

3. The coating process comprises the following steps: coating the prepared polyvinyl alcohol oil-proof coating with a K303 multifunctional coating machine by using a JS10 scraper at the speed of 3m/min, naturally drying, performing heat treatment on a heating plate at 105 ℃ for 5 minutes, and finally transferring to a standard test environment for standing for 12-24 hours to reestablish hydrogen bonds among the components of the coated paper and level the paper, wherein the coating weight is 2g/m²。

4. And (3) testing: the greaseproof paper obtained in this example passed the grease resistance test TAPPI T559 with a maximum rating of 4.

And (IV) concluding the step one.

Based on examples one to three, we can conclude that conventional paper surface coating processes based on polyvinyl alcohol do not give paper products with sufficiently high grease resistance.

Second, the following examples, fourth through sixth, illustrate grease resistance ratings of grease-proof papers under the nanocellulose/polyvinyl alcohol coatings and processes of the present invention.

Example (a) is four.

1. Preparing an oil-proof coating: (1) adding deionized water into polyvinyl alcohol with hydrolysis degree of 87-89% and molecular weight of 8 ten thousand 5-12 ten thousand 4 according to mass ratio of 19:81, and stirring at 95 ℃ until a uniform 19% polyvinyl alcohol solution is obtained; (2) waiting for the polyvinyl alcohol solution to cool to room temperature; (3) after cooling, adding nanofiber (cellulose nanofibrils oxidized by a TEMPO method, TEMPO-CNF, provided by the university of Bureau of America) according to the solid content ratio of the polyvinyl alcohol to the nanocellulose of 19-1, and then carrying out ultrasonic treatment to be uniform by using a Q1375 (Qsonica) ultrasonic crusher under the ice water cooling condition. Wherein the coating solids content is the same as the coating in example one above.

2. Preparation of the reinforced precoating paint: (1) adding deionized water into cationic starch (HI CAT 5283A) according to the mass ratio of 2:98, adding magnetons, and placing on a magnetic heating stirrer at the temperature of 80 ℃ for dissolving for 30 minutes until the mixture is uniform; (2) wait for the cationic starch solution to cool to room temperature.

3. And (3) standby base paper: the gram weight is 90g/m²Density of 0.763g/cm³Copy paper having a Gurley air permeability of 18.6 s/100 ml.

4. The coating process comprises the following steps: (1) coating of the reinforcing precoat: coating the prepared cationic starch reinforced precoating paint with a K303 multifunctional coating machine by using a JS10 scraper at the speed of 3m/min, and naturally drying; (2) coating of an oil-proof layer: and (3) coating the prepared nano-cellulose/polyvinyl alcohol oil-proof coating by using a K303 multifunctional coating machine with a JS10 bar at the speed of 3m/min, naturally drying, carrying out heat treatment on a heating plate at 105 ℃ for 5 minutes, and finally, transferring to a standard test environment for standing for 12-24 hours to reestablish hydrogen bonds among the components of the coated paper and flatten the paper. The total coating weight is 2.4g/m²0.4g/m of reinforcing precoat²Oil-proof layer 2g/m²。

5. And (3) testing: the greaseproof paper obtained in this example passes the greaseproof test TAPPI T559 with a maximum rating of 12,

the highest grease resistance rating for this test standard. Meanwhile, the base paper subjected to only the precoating treatment had a grease resistance rating of 0.

(II) example five.

1. Preparing an oil-proof coating: (1) adding deionized water into polyvinyl alcohol with hydrolysis degree of 87-89% and molecular weight of 8 ten thousand 5-12 ten thousand 4 according to mass ratio of 19:81, and stirring at 95 ℃ until a uniform 19% polyvinyl alcohol solution is obtained; (2) waiting for the polyvinyl alcohol solution to cool to room temperature; (3) after cooling, adding nanocellulose (the cellulose nanofibrils oxidized by a TEMPO method, TEMPO-CNF, provided by the university of Bureau of America) according to the solid content ratio of the polyvinyl alcohol to the nanocellulose of 19-1, and then carrying out ultrasonic treatment to the nanocellulose to be uniform by using a Q1375 (Qsonica) ultrasonic crusher under the ice water cooling condition. Wherein the coating solids content is the same as the coating in example one above.

2. Preparation of the reinforced precoating paint: (1) adding deionized water into cationic starch (HI CAT 5283A) according to the mass ratio of 2:98, adding magnetons, and placing on a magnetic heating stirrer at the temperature of 80 ℃ for dissolving for 30 minutes until the mixture is uniform; (2) wait for the cationic starch solution to cool to room temperature.

3. And (3) standby base paper: unbleached packaged kraft paper having a grammage of 50g/m2, a density of 0.722g/cm3, and a Gurley air permeability of 36.5 s/100 ml.

4. The coating process comprises the following steps: (1) coating of the reinforcing precoat: coating the prepared cationic starch reinforced precoating paint with a K303 multifunctional coating machine by using a JS10 scraper at the speed of 3m/min, and naturally drying; (2) coating of an oil-proof layer: and (3) coating the prepared nano-cellulose/polyvinyl alcohol oil-proof coating by using a K303 multifunctional coating machine with a JS10 bar at the speed of 3m/min, naturally drying, then carrying out heat treatment on a heating plate at 105 ℃ for 5 minutes, and finally transferring to a standard test environment for standing for 12-24 hours to reestablish hydrogen bonds among the components of the coated paper and flatten the paper. The total coating weight is 2.4g/m²Wherein the reinforcing precoat layer is 0.4g/m²Oil-proof layer 2g/m²。

5. And (3) testing: the greaseproof paper obtained in this example passes the greaseproof test TAPPI T559 with a maximum rating of 12,

the highest grease resistance rating for this test standard. Meanwhile, the base paper subjected to only the precoating treatment had a grease resistance rating of 0.

(III) example six.

1. Preparing an oil-proof coating: (1) adding deionized water into polyvinyl alcohol with hydrolysis degree of 87-89% and molecular weight of 8 ten thousand 5-12 ten thousand 4 according to mass ratio of 19:81, and stirring at 95 ℃ until a uniform polyvinyl alcohol solution with 19% is obtained; (2) waiting for the polyvinyl alcohol solution to cool to room temperature; (3) after cooling, adding nanocellulose (the cellulose nanofibrils oxidized by a TEMPO method, TEMPO-CNF, provided by the university of Bureau of America) according to the solid content ratio of the polyvinyl alcohol to the nanocellulose of 19-1, and then carrying out ultrasonic treatment to the nanocellulose to be uniform by using a Q1375 (Qsonica) ultrasonic crusher under the ice water cooling condition. Wherein the coating solids content is the same as the coating in example one.

2. Preparation of the reinforced precoating paint: (1) adding deionized water into cationic starch (HI CAT 5283A) according to the mass ratio of 2:98, adding magnetons, and placing on a magnetic heating stirrer at the temperature of 80 ℃ for dissolving for 30 minutes until the mixture is uniform; (2) wait for the cationic starch solution to cool to room temperature.

3. And (3) standby base paper: the gram weight is 170g/m²Density of 0.656g/cm³Waste pulp paperboard having a Gurley air permeability of 20.5 s/100 ml.

4. The coating process comprises the following steps: (1) coating of the reinforcing precoat: coating the prepared cationic starch reinforced precoating paint with a K303 multifunctional coating machine by using a JS10 scraper at the speed of 3m/min, and naturally drying; (2) coating of an oil-proof layer: and (3) coating the prepared nano-cellulose/polyvinyl alcohol oil-proof coating by using a K303 multifunctional coating machine with a JS10 bar at the speed of 3m/min, naturally drying, carrying out heat treatment on a heating plate at 105 ℃ for 5 minutes, and finally, transferring to a standard test environment for standing for 12-24 hours to reestablish hydrogen bonds among the components of the coated paper and flatten the paper. The total coating weight is 2.4g/m²Wherein the reinforcing precoat layer is 0.4g/m²Oil-proof layer 2g/m²。

5. And (3) testing: the greaseproof paper obtained in this example passed the grease resistance test TAPPI T559 with a maximum rating of 10. Meanwhile, the base paper subjected to only the precoating treatment had a grease resistance rating of 0.

And (IV) a conclusion of II.

By comparing the first, second and third examples with the fourth, fifth and sixth examples, the grease resistance grade based on the TAPPI T559 standard is greatly improved under the condition of similar total coating amount and under the condition of the same grease resistance layer coating amount, and even the grease resistance grade of the grease resistant paper taking kraft paper and copy paper as base paper reaches the highest standard of the standard. Examples four to six illustrate the importance of the charge effect of nanocellulose and cationic starch in the present invention, from which the improvement of the grease resistance mainly comes.

Third, the following examples seven to nine are illustrative of the grease resistance rating of the grease resistant paper without the addition of nanocellulose under the improved nanocellulose/polyvinyl alcohol coating and process of the present invention.

Example (a) seventh.

1. Preparing an oil-proof coating: (1) adding 87-89% of polyvinyl alcohol with the hydrolysis degree and the molecular weight of 8 ten thousand 5-12 ten thousand 4 into deionized water according to the mass ratio of 10:90, placing the mixture into a baking oven at the temperature of 95 ℃, and thoroughly stirring the mixture once every half hour until the mixture is uniformly stirred to obtain a 10% polyvinyl alcohol solution; (2) waiting for the polyvinyl alcohol solution to cool to room temperature. Wherein the coating solids content is the same as the coating in example one above.

2. Preparation of the reinforced precoating paint: (1) adding deionized water into cationic starch (HI CAT 5283A) according to the mass ratio of 2:98, adding magnetons, and placing on a magnetic heating stirrer at the temperature of 80 ℃ for dissolving for 30 minutes until the mixture is uniform; (2) wait for the cationic starch solution to cool to room temperature.

3. And (3) standby base paper: the gram weight is 90g/m²Density of 0.763g/cm³Copy paper having a Gurley air permeability of 18.6 s/100 ml.

4. The coating process comprises the following steps: (1) coating of the reinforcing precoat: coating the prepared cationic starch reinforced precoating paint with a K303 multifunctional coating machine by using a JS10 scraper at the speed of 3m/min, and naturally drying; (2) coating of an oil-proof layer: and (3) coating the prepared polyvinyl alcohol oil-proof coating by using a K303 multifunctional coating machine with a JS10 bar at the speed of 3m/min, naturally drying, then carrying out heat treatment on a heating plate at 105 ℃ for 5 minutes, and finally transferring to a standard test environment for standing for 12-24 hours to reconstruct hydrogen bonds among the components of the coated paper and flatten the paper. The total coating weight is 2.4g/m²Wherein the reinforcing precoat layer is 0.4g/m²Oil-proof layer 2g/m²。

5. And (3) testing: the greaseproof paper obtained in this example passes the greaseproof test TAPPI T559 with a maximum rating of 8, slightly higher than that of example one, but much lower than that of example four.

(II) example eight

1. Preparing an oil-proof coating: (1) adding deionized water into polyvinyl alcohol with hydrolysis degree of 87-89% and molecular weight of 8 ten thousand 5-12 ten thousand 4 according to the mass ratio of 10:90, and stirring at 95 ℃ until a uniform 10% polyvinyl alcohol solution is obtained; (2) waiting for the polyvinyl alcohol solution to cool to room temperature. The solids content of the coating was the same as in the first example.

2. Preparation of the reinforced precoating paint: (1) adding deionized water into cationic starch (HI CAT 5283A) according to the mass ratio of 2:98, adding magnetons, and placing on a magnetic heating stirrer at the temperature of 80 ℃ for dissolving for 30 minutes until the mixture is uniform; (2) wait for the cationic starch solution to cool to room temperature.

3. And (3) standby base paper: unbleached packaged kraft paper having a grammage of 50g/m2, a density of 0.722g/cm3, and a Gurley air permeability of 36.5 s/100 ml.

4. The coating process comprises the following steps: (1) coating of the reinforcing precoat: coating the prepared cationic starch reinforced precoating paint with a K303 multifunctional coating machine by using a JS10 scraper at the speed of 3m/min, and naturally drying; (2) coating of an oil-proof layer: and (3) coating the prepared polyvinyl alcohol oil-proof coating by using a K303 multifunctional coating machine with a JS10 bar at the speed of 3m/min, naturally drying, then carrying out heat treatment on a heating plate at 105 ℃ for 5 minutes, and finally transferring to a standard test environment for standing for 12-24 hours to reconstruct hydrogen bonds among the components of the coated paper and flatten the paper. The total coating weight is 2.4g/m²Wherein the reinforcing precoat layer is 0.4g/m²Oil-proof layer 2g/m²。

The greaseproof paper obtained in this example passed the grease resistance test TAPPI T559 with a maximum rating of 7, which is the same as in example two but much lower than in example five.

EXAMPLE III

1. Preparing an oil-proof coating: (1) adding deionized water into polyvinyl alcohol with hydrolysis degree of 87-89% and molecular weight of 8 ten thousand 5-12 ten thousand 4 according to the mass ratio of 10:90, and stirring at 95 ℃ until a uniform 10% polyvinyl alcohol solution is obtained; (2) waiting for the polyvinyl alcohol solution to cool to room temperature. The solids content of the coating was the same as in the first example.

2. Preparation of the reinforced precoating paint: (1) adding deionized water into cationic starch (HI CAT 5283A) according to the mass ratio of 2:98, adding magnetons, and placing on a magnetic heating stirrer at the temperature of 80 ℃ for dissolving for 30 minutes until the mixture is uniform; (2) wait for the cationic starch solution to cool to room temperature.

3. And (3) standby base paper: the gram weight is 170g/m²Density of 0.656g/cm³Waste pulp paperboard having a Gurley air permeability of 20.5 s/100 ml.

4. The coating process comprises the following steps: (1) coating of the reinforcing precoat: coating the prepared cationic starch reinforced precoating paint with a K303 multifunctional coating machine by using a JS10 scraper at the speed of 3m/min, and naturally drying; (2) coating of an oil-proof layer: and (3) coating the prepared polyvinyl alcohol oil-proof coating by using a K303 multifunctional coating machine with a JS10 bar at the speed of 3m/min, naturally drying, then carrying out heat treatment on a heating plate at 105 ℃ for 5 minutes, and finally transferring to a standard test environment for standing for 12-24 hours to reconstruct hydrogen bonds among the components of the coated paper and flatten the paper. The total coating weight is 2.4g/m²Wherein the reinforcing precoat layer is 0.4g/m²Oil-proof layer 2g/m²。

5. And (3) testing: the greaseproof paper obtained in this example passes the greaseproof test TAPPI T559 with a maximum rating of 7, which is higher than example three, but much lower than example six.

And fourthly, a conclusion of the third step.

By means of the seven to nine examples, the invention is carried out without adding nanocellulose, and the grease resistance grade based on TAPPI T559 standard is obviously reduced under the condition of similar total coating weight and the same oil-proof layer coating weight, thereby illustrating the importance of the nanocellulose in the coating process of the invention.

Fifth, the following examples, tenth to twelfth, illustrate grease resistance ratings of grease-proof paper without a cationic starch precoating with the nanocellulose/polyvinyl alcohol coating and process of the present invention.

Example (a) ten.

1. Preparing an oil-proof coating: (1) adding deionized water into polyvinyl alcohol with hydrolysis degree of 87-89% and molecular weight of 8 ten thousand 5-12 ten thousand 4 according to mass ratio of 19:81, and stirring at 95 ℃ until a uniform 19% polyvinyl alcohol solution is obtained; (2) waiting for the polyvinyl alcohol solution to cool to room temperature; (3) after cooling, adding nanocellulose (the cellulose nanofibrils oxidized by a TEMPO method, TEMPO-CNF, provided by the university of Bureau of America) according to the solid content ratio of the polyvinyl alcohol to the nanocellulose of 19-1, and then carrying out ultrasonic treatment to the nanocellulose to be uniform by using a Q1375 (Qsonica) ultrasonic crusher under the ice water cooling condition. The solids content of the coating was the same as in the first example.

2. And (3) standby base paper: the gram weight is 90g/m²Density of 0.763g/cm³Copy paper having a Gurley air permeability of 18.6 s/100 ml.

3. The coating process comprises the following steps: and (3) coating the prepared nano-cellulose/polyvinyl alcohol oil-proof coating by using a K303 multifunctional coating machine with a JS10 bar at the speed of 3m/min, naturally drying, then carrying out heat treatment on a heating plate at 105 ℃ for 5 minutes, and finally transferring to a standard test environment for standing for 12-24 hours to reestablish hydrogen bonds among the components of the coated paper and flatten the paper. The above coating amount was 2g/m²。

4. And (3) testing: the greaseproof paper obtained in this example passed the grease resistance test TAPPI T559 with a maximum rating of 8, which is higher than that of example one but lower than that of example four.

Example two eleven.

1. Preparing an oil-proof coating: (1) adding deionized water into polyvinyl alcohol with hydrolysis degree of 87-89% and molecular weight of 8 ten thousand 5-12 ten thousand 4 according to mass ratio of 19:81, and stirring at 95 ℃ until a uniform 19% polyvinyl alcohol solution is obtained; (2) waiting for the polyvinyl alcohol solution to cool to room temperature; (3) after cooling, adding nanocellulose (the cellulose nanofibrils oxidized by a TEMPO method, TEMPO-CNF, provided by the university of Bureau of America) according to the solid content ratio of the polyvinyl alcohol to the nanocellulose of 19-1, and then carrying out ultrasonic treatment to the nanocellulose to be uniform by using a Q1375 (Qsonica) ultrasonic crusher under the ice water cooling condition. The solids content of the coating was the same as that of the coating in example one above.

2. And (3) standby base paper: unbleached packaged kraft paper having a grammage of 50g/m2, a density of 0.722g/cm3, and a Gurley air permeability of 36.5 s/100 ml.

3. The coating process comprises the following steps: coating the prepared nano-cellulose with JS10 bar at 3m/min by using K303 multifunctional coating machineThe oil-proof polyvinyl alcohol coating is naturally dried, then is subjected to heat treatment for 5 minutes on a heating plate with the temperature of 105 ℃, and finally is transferred to a standard test environment to stand for 12-24 hours, so that hydrogen bonds among components of the coated paper are reestablished and the paper is leveled. The above coating amount was 2g/m²。

4. And (3) testing: the maximum grade of the greaseproof paper obtained in the example, which can pass the grease resistance test TAPPI T559, is 8, is slightly higher than that of the second example, but is greatly lower than that of the fifth example.

(III) example twelve.

1. Preparing an oil-proof coating: (1) adding deionized water into polyvinyl alcohol with hydrolysis degree of 87-89% and molecular weight of 8 ten thousand 5-12 ten thousand 4 according to mass ratio of 19:81, and stirring at 95 ℃ until a uniform 19% polyvinyl alcohol solution is obtained; (2) waiting for the polyvinyl alcohol solution to cool to room temperature; (3) after cooling, adding nanocellulose (the cellulose nanofibrils oxidized by a TEMPO method, TEMPO-CNF, provided by the university of Bureau of America) according to the solid content ratio of the polyvinyl alcohol to the nanocellulose of 19-1, and then carrying out ultrasonic treatment to the nanocellulose to be uniform by using a Q1375 (Qsonica) ultrasonic crusher under the ice water cooling condition. The solids content of the coating was the same as in the first example.

2. And (3) standby base paper: a waste pulp paperboard having a grammage of 170g/m2, a density of 0.656g/cm3, and a Gurley air permeability of 20.5 s/100 ml.

3. The coating process comprises the following steps: and (3) coating the prepared nano-cellulose/polyvinyl alcohol oil-proof coating by using a K303 multifunctional coating machine with a JS10 bar at the speed of 3m/min, naturally drying, then carrying out heat treatment on a heating plate at 105 ℃ for 5 minutes, and finally transferring to a standard test environment for standing for 12-24 hours to reestablish hydrogen bonds among the components of the coated paper and flatten the paper. The above coating amount was 2g/m²。

4. And (3) testing: the maximum grade of the greaseproof paper obtained in the example, which can pass the grease resistance test TAPPI T559, is 8, which is higher than that of the third example, but is greatly lower than that of the sixth example.

Sixthly, a conclusion of four.

The ten to twelve examples show that the grease resistance rating based on TAPPI T559 standard is significantly reduced without precoating treatment at similar total coating weights at the same coating weights of the grease resistant layer, indicating that the grease resistance improvement is mainly derived from charge interaction, indicating the importance of cationic starch in the coating process system of the present invention.

The following example 13 was coated with different kinds of polyvinyl alcohol to demonstrate that the kind of polyvinyl alcohol has no influence on the grease-repellent property.

Seventhly, the following example thirteen is to illustrate that under the nano-cellulose/polyvinyl alcohol coating and the process of the invention, the grease resistance grade of the oil-proof paper with the base paper being the copy paper is not affected by changing the kind of polyvinyl alcohol.

The thirteenth embodiment.

1. Preparing an oil-proof coating: (1) adding deionized water into polyvinyl alcohol with the hydrolysis degree of 98-99% and the molecular weight of 8 ten thousand 5-12 ten thousand 4 according to the mass ratio of 19:81, and stirring at 95 ℃ until a uniform 19% polyvinyl alcohol solution is obtained; (2) waiting for the polyvinyl alcohol solution to cool to room temperature; (3) after cooling, adding nanocellulose (the cellulose nanofibrils oxidized by a TEMPO method, TEMPO-CNF, provided by the university of Bureau of America) according to the solid content ratio of the polyvinyl alcohol to the nanocellulose of 19-1, and then carrying out ultrasonic treatment to the nanocellulose to be uniform by using a Q1375 (Qsonica) ultrasonic crusher under the ice water cooling condition. The solids content of the coating was the same as in the first example.

2. Preparation of the reinforced precoating paint: (1) adding deionized water into cationic starch (HI CAT 5283A) according to the mass ratio of 2:98, adding magnetons, and placing on a magnetic heating stirrer at the temperature of 80 ℃ for dissolving for 30 minutes until the mixture is uniform; (2) wait for the cationic starch solution to cool to room temperature.

3. And (3) standby base paper: the gram weight is 90g/m²Density of 0.763g/cm³Copy paper having a Gurley air permeability of 18.6 s/100 ml.

4. The coating process comprises the following steps: (1) coating of the reinforcing precoat: coating the prepared cationic starch reinforced precoating paint with a K303 multifunctional coating machine by using a JS10 scraper at the speed of 3m/min, and naturally drying; (2) coating of an oil-proof layer: by using the K303 multifunctional coater,and coating the prepared nano-cellulose/polyvinyl alcohol oil-proof coating with a JS10 scraper at the speed of 3m/min, naturally drying, performing heat treatment on a heating plate at 105 ℃ for 5 minutes, and finally transferring to a standard test environment for standing for 12-24 hours to reestablish hydrogen bonds among the components of the coated paper and flatten the paper. The total coating weight is 2.4g/m²Wherein the reinforcing precoat layer is 0.4g/m²Oil-proof layer 2g/m²。

5. Test-the greaseproof paper obtained in this example was able to pass the grease resistance test TAPPI T559 with a maximum rating of 12,

the grease resistance rating was the highest grease resistance rating for this test standard, whereas the base paper, which was only precoated, had a grease resistance rating of 0.

And eighthly, a conclusion of five.

The importance of the charge effect of negatively charged nanocellulose and positively charged cationic starch in the coating process system of the present invention is demonstrated by comparing examples four to six with examples seven to twelve. The permeability of the nano-cellulose/polyvinyl alcohol coating is greatly reduced due to the charge effect of the nano-cellulose and the cationic starch above the cationic starch enhancement layer, and then compared with the traditional polyvinyl alcohol coating process, the dried oil-proof layer forms a thicker polyvinyl alcohol oil-proof layer under the same coating weight so as to achieve a higher oil-proof grade.

Meanwhile, by using polyvinyl alcohols with different molecular weights and different degrees of hydrolysis to carry out coating experiments, the theory, effect and grease resistance of the obtained paper are not affected, so that in actual production, the type of the polyvinyl alcohol can be changed according to the actual requirements of products. If the product requires better water resistance, polyvinyl alcohol with higher hydrolysis degree can be used; lower molecular weight polyvinyl alcohols can be used if lower viscosities are required for equipment requirements in the production.