Preparation method and application of fluorine-free antibacterial paper

Abstract

The application provides a preparation method of fluorine-free antibacterial paper and application thereof, and the preparation method is characterized in that: a first coating liquid containing hydrophobic cellulose nanocrystals and cationic starch modified AKD is coated on raw paper in a step-by-step coating manner, then a second coating liquid containing hydrophobic cellulose nanocrystals and polyvinyl alcohol is coated, and the content of each component in the first coating liquid and the second coating liquid is controlled, so that the packaging paper with high physical strength, good oil resistance and water resistance is finally prepared. Since no fluorine-containing raw materials are used in the above preparation process, the packaging paper can be further made into food packaging paper.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of packaging paper preparation, and particularly relates to a preparation method of fluorine-free antibacterial paper and application thereof. BACKGROUND

[0002] Food packaging paper must meet the food hygiene standard requirements, and also has good barrier properties (water and oil resistance) and necessary mechanical strength. At present, the oil-proof food packaging paper is mainly realized by spraying PE or PP plastic film on the surface of paper or applying fluorine-containing water and oil repellent agent. However, the PE or PP spraying film product has problems of non-degradability, non-pulping, and recycling difficulty. Although the fluorine-containing oil repellent agent has good oil resistance effect, the molecular chain of the fluorine-containing oil repellent agent is broken at high temperature to form PFOA (perfluorooctanoic acid ammonium) and PFOS (perfluorooctanesulfonate) which are harmful to the human body. Therefore, from the requirements of food safety and green environmental protection, fluorine-free oil-proof food packaging paper base material is the inevitable trend of development.

[0003] Therefore, it is necessary to design an improved preparation method of fluorine-free antibacterial paper and application thereof to solve the above problems. SUMMARY

[0004] The present application aims to provide a preparation method of fluorine-free antibacterial paper and application thereof.

[0005] To achieve the above-mentioned purpose, the present application provides a preparation method of fluorine-free antibacterial paper, comprising the following steps:

[0006] S1, adding AKD powder into an organic solvent, uniformly mixing, then adding modified starch, using esterification reaction between AKD and modified starch to prepare modified starch / AKD powder; dispersing the modified starch / AKD powder in a first nanocellulose suspension to prepare a first coating liquid; the modified starch is cationic starch;

[0007] S2, dispersing polyvinyl alcohol in a second nanocellulose suspension to prepare a second coating liquid;

[0008] S3, first coating the first coating liquid on the base paper, then coating the second coating liquid after drying, and drying to prepare the fluorine-free antibacterial paper.

[0009] As an embodiment of the present application, the mass percentage of the first nanocellulose suspension is 0.1-0.15%, and the mass percentage of the second nanocellulose suspension is 0.01-0.05%.

[0010] As an embodiment of the present application, in step S1, the first coating liquid is configured according to the following rule: 2-4 g of modified starch / AKD powder is added to 100 mL of the first nanocellulose suspension.

[0011] As an embodiment of the present application, the modified starch / AKD powder is prepared by dissolving the AKD powder in an organic solvent, adding the modified starch, obtaining a mixture, stirring the mixture at 70-80 ℃ for 1.0-1.5 h; after the reaction is completed, the product is collected by centrifugation, and then dried to obtain the modified starch / AKD powder.

[0012] As an embodiment of the present application, the mass percentage of AKD in the mixture is 5-10%, and the mass percentage of the modified starch in the mixture is 1-3%.

[0013] As an embodiment of the present application, in step S2, the second coating liquid is configured according to the following rule: 0.2-0.4 g of polyvinyl alcohol is added to 100 mL of the second nanocellulose suspension.

[0014] As an embodiment of the present application, the first nanocellulose suspension and the second nanocellulose suspension are both water suspensions configured from hydrophobic cellulose nanocrystals, and the hydrophobic cellulose nanocrystals are prepared by dispersing cellulose nanocrystals in a modified solution, mixing under ultrasonic conditions for 15-20 min, collecting the product by centrifugation, and drying at room temperature to obtain the modified hydrophobic cellulose nanocrystals; the modified solution is a polydimethylsiloxane solution containing fumed silica, and the viscosity of the modified solution is 300-400 cps.

[0015] As an embodiment of the present application, in step S3, the coating amount of the first coating liquid is 3-10 g / m 2 , the drying temperature after coating is 25-30 ℃, and the drying time is 12-24 h; the coating amount of the second coating liquid is 1.5-3 g / m 2 , the drying temperature after coating is 25-30 ℃, and the drying time is 12-24 h.

[0016] As an embodiment of the present application, in step S1, the organic solvent is one of benzene, toluene, diethyl ether, and chloroform.

[0017] In particular, the fluorine-free antibacterial paper prepared by the preparation method of the present application can be applied to the field of food packaging paper.

[0018] The present application has the following beneficial effects:

[0019] 1. The preparation method of the fluorine-free antibacterial paper provided by the application, by adopting the step-by-step coating mode, a first coating liquid containing hydrophobic cellulose nanocrystals and cationic starch modified AKD is coated on the base paper first, then a second coating liquid containing hydrophobic cellulose nanocrystals and polyvinyl alcohol is coated, and by adjusting the content of each component in the first coating liquid and the second coating liquid, the packaging paper with the advantages of high physical strength, good oil resistance, water resistance, etc. is finally prepared. Since the above preparation process does not use fluorine-containing raw materials, it has high safety, and can be further made into food packaging paper.

[0020] 2. The preparation method of the fluorine-free antibacterial paper provided by the application, by coating the coating liquid containing hydrophobic cellulose nanocrystals and cationic starch modified AKD first, the hydrophobic cellulose nanocrystals and the modified starch modified AKD can be fixed on the fibers of the paper together. Since the size of the hydrophobic cellulose nanocrystals is small, part of the cellulose nanocrystals will also enter the fiber gap of the paper, so as to adjust the pore size of the paper, make the structure inside the paper more uniform, and give the paper certain hydrophobicity. At the same time, since the cellulose nanocrystals have certain flexibility, by using them to treat the paper, the influence of surface coating on the flexibility of the paper itself can be reduced, and the mechanical strength of the paper can be enhanced; by coating the first coating liquid and the second coating liquid containing hydrophobic cellulose nanocrystals on the paper in steps, not only can the adhesion between the first coating layer formed after the first coating and the paper be improved by using the interaction between the hydrophobic cellulose nanocrystals in the first coating liquid and the paper fibers, but also the paper can be secondarily strengthened by using the cellulose nanocrystals during the second coating. This process fully utilizes the strengthening effect of cellulose nanocrystals on the strength of the paper, and gives the paper excellent comprehensive performance. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical scheme and advantages of the application clearer, the application will be described in detail below with specific examples.

[0022] Here, it also needs to be explained that, in order not to obscure the application due to unnecessary details, only the structures and / or processing steps closely related to the scheme of the application are shown in the text, and other details not closely related to the application are omitted.

[0023] In addition, it also needs to be explained that the term "comprise", "include" or any other variant thereof is intended to cover non-exclusive inclusion, so that the process, method, article or equipment including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such process, method, article or equipment.

[0024] The preparation method of the fluorine-free antibacterial paper provided by the application comprises the following steps:

[0025] S1, preparing a first coating liquid: adding AKD (hexadecyl alkene ketone dimer) into an organic solvent, uniformly mixing, then adding modified starch, using esterification reaction between AKD and modified starch to prepare modified starch / AKD powder; dispersing the modified starch / AKD powder in a first nanocellulose suspension to prepare the first coating liquid;

[0026] S2, preparing a second coating liquid: dispersing polyvinyl alcohol in a second nanocellulose suspension to prepare the second coating liquid;

[0027] S3, preparing a fluorine-free antibacterial paper: first coating the first coating liquid on the base paper, drying, then coating the second coating liquid, drying to prepare the fluorine-free antibacterial paper.

[0028] As an embodiment of the present application, in step S1, the modified starch is cationic starch, specifically, introducing cationic groups such as tertiary amino groups and quaternary ammonium groups into starch macromolecules. It should be noted that the modified starch of the present application is prepared by using traditional starch modification method, and therefore detailed description is not given here.

[0029] As an embodiment of the present application, in steps S1 and S2, the first nanocellulose suspension and the second nanocellulose suspension are both water suspensions prepared by using hydrophobic cellulose nanocrystals (CNC), and the mass percentage of the first nanocellulose suspension is 0.1-0.15%, and the mass percentage of the second nanocellulose suspension is 0.01-0.05%.

[0030] Further, the preparation method of the hydrophobic cellulose nanocrystals is as follows: dispersing cellulose nanocrystals in a modified solution, mixing under ultrasonic conditions for 15-20 min, then collecting the product by centrifugation, drying at room temperature to obtain modified hydrophobic cellulose nanocrystals; wherein the modified solution is a polydimethylsiloxane solution containing fumed silica, the viscosity of the modified solution is 300-400 cps, preferably, the mass percentage of the modified solution is 3-4%. It should be noted that the cellulose nanocrystals in the above steps are prepared by using traditional sulfuric acid hydrolysis of cellulose method, and dried by freeze dryer.

[0031] In the above process, by controlling the concentration of the first nanocellulose suspension and the second nanocellulose suspension in a specific range and making the concentration of the first nanocellulose suspension greater than that of the second nanocellulose suspension, the hydrophobic cellulose nanocrystals and the modified starch modified AKD can be fixed on the fibers of the paper at the first coating, and due to the small size of the hydrophobic cellulose nanocrystals, part of the cellulose nanocrystals will also enter the interstitial space of the fibers of the paper, giving the paper certain hydrophobicity; at the same time, due to the flexibility of the cellulose nanocrystals, the mechanical strength of the paper can be enhanced without affecting the flexibility of the paper after the paper is treated with the cellulose nanocrystals.

[0032] As an embodiment of the present application, in step S1, the organic solvent is one of benzene, toluene, diethyl ether, and chloroform.

[0033] As an embodiment of the present application, in step S1, the preparation process of the modified starch / AKD powder is as follows: the cetyl alkene ketone dimer powder is dissolved in an organic solvent, the modified starch is added to obtain a mixture, the mixture is magnetically stirred at 70-80°C for 1.0-1.5h to make the modified starch and the cetyl alkene ketone dimer fully react; after the reaction is completed, the product is collected by centrifugation, and then dried to obtain the modified starch / AKD powder. In the mixture, the mass percentage of the cetyl alkene ketone dimer is 5-10%, and the mass percentage of the modified starch in the mixture is 1-3%.

[0034] In the above process, the esterification reaction between the hydroxyl group of the modified starch and the cetyl alkene ketone dimer can be used to stabilize the cetyl alkene ketone dimer and avoid its hydrolysis, and the stabilized cetyl alkene ketone dimer of the modified starch is easier to deposit on the fibers of the paper, making the sizing easier to perform, improving the retention rate after sizing, and shortening the sizing curing time. Secondly, since the modified starch contains cations and the cetyl alkene ketone dimer also carries positive charges, the use of the modified starch to treat the cetyl alkene ketone dimer can reduce the influence on the cetyl alkene ketone dimer during the treatment process.

[0035] As an embodiment of the present application, in step S1, the configuration rule of the first coating liquid is that the amount of the modified starch / AKD powder added in 100mL of the first nanocellulose suspension is 2-4g.

[0036] As an embodiment of the present application, in step S2, the second coating liquid is configured by adding 0.2-0.4 g of polyvinyl alcohol to 100 mL of the second nanocellulose suspension, and the process of dispersing the polyvinyl alcohol in the suspension can be performed in an ultrasonic oscillation environment. In other embodiments, other ways of accelerating the mixing efficiency can also be used as long as the purpose of uniform dispersion is achieved, which is not limited herein.

[0037] In the above process, by adding polyvinyl alcohol to the second coating liquid, the good film-forming property of polyvinyl alcohol can be utilized to form a protective film with solvent resistance, friction resistance and antibacterial properties on the surface of the paper; secondly, during the drying process after the second coating, the film-forming process of polyvinyl alcohol can be utilized to make the cellulose nanocrystals in the second nanocellulose suspension adhere to the paper, thereby enhancing the bonding of the cellulose nanocrystals to the paper; most importantly, both the polyvinyl alcohol protective film and the cellulose nanocrystals have certain mechanical strength, and utilizing both of them to coat the paper can not only improve the surface properties of the paper, but also improve the mechanical strength of the paper.

[0038] As an embodiment of the present application, in step S3, the coating amount of the first coating liquid is 3-10 g / m 2 , the drying temperature after coating is 25-30℃, and the drying time is 12-24 h; the coating amount of the second coating liquid is 1.5-3 g / m 2 , the drying temperature after coating is 25-30℃, and the drying time is 12-24 h.

[0039] In particular, the fluorine-free antibacterial paper prepared by the preparation method of the present application can be further made into food packaging paper, and the packaging paper has the following properties: basis weight of 40±2 g / m 2 , tightness ≥0.7 g / cm 3 , transverse tear resistance ≥160 mN, longitudinal tear length ≥8.0 km, longitudinal wet tear length ≥0.8 km, oil resistance (kit) ≥6, water absorption ≤21 g / m 2 , and front surface smoothness ≥50 s.

[0040] The preparation method of the fluorine-free antibacterial paper and its application provided by the present application will be further described below in conjunction with specific embodiments:

[0041] Embodiment 1

[0042] In this embodiment, a fluorine-free antibacterial paper is prepared, and the specific preparation method includes the following steps:

[0043] S1, 8 g of cetyl alkene ketone dimer powder is uniformly mixed with 100 mL of toluene, 2 g of quaternary ammonium group modified starch is added to obtain a mixture, the mixture is magnetically stirred at 70°C for 1.5 h, so that the modified starch and cetyl alkene ketone dimer are fully reacted; after the reaction is completed, the product is collected by centrifugation, and then dried to obtain modified starch / AKD powder; 3 g of modified starch / AKD powder is dispersed in 100 mL of a first nanocellulose suspension with a mass percentage of 0.1% to obtain a first coating liquid;

[0044] It should be noted that the process of quaternary ammonium group modified starch in this step only needs to be implemented by using the modification method known in the art, so the detailed modification steps are not given here;

[0045] S2, 0.2 g of polyvinyl alcohol is added to 100 mL of a second nanocellulose suspension with a mass percentage of 0.02%, and after being uniformly dispersed, a second coating liquid is prepared; wherein the preparation methods of the first nanocellulose suspension and the second nanocellulose suspension are as follows: cellulose nanocrystals are dispersed in a polydimethylsiloxane solution with a mass percentage of 3% and with fumed silica dispersed therein, the viscosity of the polydimethylsiloxane solution is 300 cps, the mixture is mixed under ultrasonic conditions for 15 min, and then the product is collected by centrifugation and dried at room temperature to obtain hydrophobic cellulose nanocrystals; this process can adhere fumed silica particles to the surface of the cellulose nanocrystals by the viscosity of the polydimethylsiloxane solution, and during the subsequent drying process, the fumed silica particles with hydrophobicity are fixed on the surface of the cellulose nanocrystals as the polydimethylsiloxane solution is further solidified on the surface of the cellulose nanocrystals;

[0046] S3, first coat the first coating liquid on the base paper, dry at 25°C, then coat the second coating liquid, dry at 25°C, to obtain a fluorine-free antibacterial paper. Wherein the coating amount of the first coating liquid is 5 g / m 2 , and the coating amount of the second coating liquid is 2 g / m 2 .

[0047] Examples 2 to 4

[0048] The difference between Examples 2 to 4 and Example 1 is only that the concentration of the first nanocellulose suspension in step S1 is different from that of Example 1, and other steps are the same as those of Example 1, which will not be repeated here. The mass percentage of the first nanocellulose suspension of Examples 1 to 4 and the performance of the fluorine-free antibacterial paper prepared under the corresponding conditions are shown in Table 1. As can be seen from the data in the table, when the concentration of the first nanocellulose suspension is within a certain range, a paper with excellent oil-proof performance and high strength can be prepared. With the increase of the concentration of the first nanocellulose suspension, the strength of the paper slightly decreases, and the surface front smoothness (i.e., the side of the paper surface subjected to coating treatment) decreases, because when the concentration of the first nanocellulose suspension reaches a certain value, the cellulose nanocrystals are prone to aggregation and even wrinkle during the coating process, the cellulose nanocrystals are not uniformly distributed on the paper, the effect of improving the strength of the paper is limited, and the front smoothness of the paper is affected.

[0049] Table 1: Comparison of the mass percentage of the first nanocellulose suspension of Examples 1 to 4 and the performance of the fluorine-free antibacterial paper prepared under the corresponding conditions

[0050]

[0051] Examples 5 to 7

[0052] The difference between Examples 5 to 7 and Example 1 is only that the concentration of the second nanocellulose suspension in step S2 is different from that of Example 1, and other steps are the same as those of Example 1, which will not be repeated here. The mass percentage of the second nanocellulose suspension of Example 1 and Examples 5 to 7 and the performance of the fluorine-free antibacterial paper prepared under the corresponding conditions are shown in Table 2. As can be seen from the data in the table, increasing the concentration of the second nanocellulose suspension can enhance the strength of the paper, but when the concentration is greater than 0.05%, the strength of the paper does not increase much, and the smoothness of the paper decreases, because when the concentration of the second nanocellulose suspension is too large, aggregation occurs during the coating process, resulting in uneven distribution of cellulose nanocrystals, which affects the smoothness of the paper.

[0053] Secondly, the performance of the packaging paper prepared in Examples 1 to 7 is as follows: transverse tear resistance ≥ 160 mN, longitudinal breaking length ≥ 8.0 km, longitudinal wet breaking length ≥ 0.8 km, oil resistance (kit) ≥ 6 levels, water absorption ≤ 21 g / m 2 , front smoothness ≥ 50 s, in addition, the basis weight and tightness of the above packaging paper are also tested, wherein the basis weight of the packaging paper prepared in Examples 1 to 7 is 40 ± 2 g / m 2 , tightness ≥ 0.7 g / cm 3 .

[0054] Table 2 Mass percentage of the second nanocellulose suspension of Example 1 and Examples 5 to 7 and comparison of properties of the fluorine-free antibacterial paper produced under the corresponding conditions

[0055]

[0056]

[0057] Comparative Example 1

[0058] The difference between Comparative Example 1 and Example 1 is only that the coating liquid in the second coating process is different from that of Example 1, and the content of hydrophobic cellulose nanocrystals in the first coating liquid of Comparative Example 1 is the same as the total content of hydrophobic cellulose nanocrystals in the first coating liquid and the second coating liquid of Example 1, that is, the content of hydrophobic cellulose nanocrystals in the coating liquid used in the coating process of Comparative Example 1 and Example 1 is the same, and the coating process of Comparative Example 1 is carried out in the following manner: first, a coating liquid with the same content of hydrophobic cellulose nanocrystals as the total content of hydrophobic cellulose nanocrystals in the first coating liquid and the second coating liquid of Example 1 is coated on the base paper, then 100 mL of polyvinyl alcohol solution is coated, and the concentration of the polyvinyl alcohol solution is the same as the content of polyvinyl alcohol in the second coating liquid of Example 1, and the remaining experimental conditions are the same as those of Example 1, which will not be repeated here.

[0059] Comparative Example 2

[0060] The difference between Comparative Example 2 and Example 1 is only that the first coating liquid of Comparative Example 2 is a modified starch / AKD suspension, and the content of hydrophobic cellulose nanocrystals in the second coating liquid is the sum of the content of hydrophobic cellulose nanocrystals in the first coating liquid and the second coating liquid of Example 1, that is, the content of hydrophobic cellulose nanocrystals in the coating liquid used in the coating process of Comparative Example 1 and Example 1 is the same, and the coating process of Comparative Example 2 is carried out in the following manner: first, a solution prepared using modified starch / AKD is coated on the surface of the base paper, and then a hydrophobic cellulose nanocrystal suspension containing polyvinyl alcohol dispersed therein is coated, and the content of cellulose nanocrystals in the hydrophobic cellulose nanocrystal suspension is the same as the total content of hydrophobic cellulose nanocrystals in the first coating liquid and the second coating liquid of Example 1.

[0061] The performance of the packaging paper prepared in Example 1 and Comparative Examples 1-2 is compared as shown in Table 3. It is found that the comprehensive performance of the packaging paper prepared in Example 1 is the best, although the same amount of hydrophobic cellulose nanocrystals is coated in the three preparation methods. In Comparative Example 1, the cellulose nanocrystals are coated on the paper at the first time. At this time, the cellulose nanocrystals are not easy to be dispersed in the coating liquid due to the high content of cellulose nanocrystals in the coating liquid, and the cellulose nanocrystals are easy to aggregate. In Comparative Example 2, the modified starch / AKD solution is coated first. At this time, the pores between the fibers of the paper are occupied by the starch modified hexadecyl enone dimer to form a glue layer. The cellulose nanocrystals in the coating liquid are distributed on the surface of the glue layer at the second time, and cannot be connected with the fibers of the paper. In this case, the cellulose nanocrystals cannot fully play the role of enhancing the strength of the paper, so the comprehensive performance of the packaging paper in Comparative Examples 1 and 2 is not as good as that in Example 1.

[0062] Table 3 Performance comparison of packaging paper prepared in Example 1 and Comparative Examples 1-2

[0063]

[0064] The above examples are only used to illustrate the technical solutions of the present application and not limit the present application. Although the present application has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solutions of the present application can be modified or replaced equivalently without departing from the spirit and scope of the technical solutions of the present application.

Claims

1. A method for producing a fluorine-free antibacterial paper, characterized by, It comprises the following steps: S1, adding AKD powder into an organic solvent, adding modified starch after mixing uniformly, using esterification reaction between AKD and modified starch to prepare modified starch / AKD powder; dispersing the modified starch / AKD powder in a first nanocellulose suspension to prepare a first coating liquid; the modified starch is cationic starch, the mass percentage of the first nanocellulose suspension is 0.1-0.15%, and the configuration rule of the first coating liquid is that the addition amount of modified starch / AKD powder in 100 mL of the first nanocellulose suspension is 2-4 g; the preparation process of the modified starch / AKD powder is as follows: dissolving the AKD powder in the organic solvent, adding the modified starch to obtain a mixture, stirring the mixture at 70-80℃ for 1.0-1.5 h; after the reaction is completed, the product is collected by centrifugation, and then dried to prepare the modified starch / AKD powder; the mass percentage of AKD in the mixture is 5-10%, and the mass percentage of modified starch in the mixture is 1-3%; S2, dispersing polyvinyl alcohol in a second nanocellulose suspension to prepare a second coating liquid; The first nanocellulose suspension and the second nanocellulose suspension are both water suspensions prepared from hydrophobic cellulose nanocrystals, and the preparation of the hydrophobic cellulose nanocrystals is as follows: dispersing cellulose nanocrystals in a modified solution, mixing under ultrasonic conditions for 15-20 min, then collecting the product by centrifugation, and drying at room temperature to obtain modified hydrophobic cellulose nanocrystals; The modified solution is a polydimethylsiloxane solution containing fumed silica, and the viscosity of the modified solution is 300-400 cps; The mass percentage of the second nanocellulose suspension is 0.01-0.05%, and the configuration rule of the second coating liquid is that 0.2-0.4 g of polyvinyl alcohol is added in 100 mL of the second nanocellulose suspension; S3, first coating the first coating liquid on the base paper, then coating the second coating liquid after drying, and drying to prepare a fluorine-free antibacterial paper.

2. The method for preparing a fluorine-free antibacterial paper according to claim 1, characterized by, In step S3, the coating amount when the first coating liquid is coated is 3 to 10 g / m 2 , the drying temperature after coating is 25 to 30°C, and the drying time is 12 to 24 h; the coating amount when the second coating liquid is coated is 1.5 to 3 g / m 2 , the drying temperature after coating is 25 to 30°C, and the drying time is 12 to 24 h.

3. The method of claim 1, wherein the fluorine-free antibacterial paper is prepared by adding 0.1 to 0.5 parts by weight of the quaternary ammonium salt to 100 parts by weight of the base paper. In step S1, the organic solvent is one of benzene, toluene, diethyl ether, and chloroform.

4. The application of the fluorine-free antibacterial paper prepared by the preparation method of any one of claims 1-3 in the field of food packaging paper.

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