A high-strength transparent antibacterial ultra-thin paper and its preparation method

Abstract

The present invention provides a high-strength transparent antibacterial ultra-thin paper and a preparation method thereof, relating to the field of ultra-thin paper. The preparation method of the high-strength transparent antibacterial ultra-thin paper comprises the following steps: preparing carboxyl-modified cellulose nanofibers, preparing dialdehyde cellulose nanocrystals, preparing an antibacterial composite coating, preparing an ultra-thin paper base paper, and forming. The preparation method of the high-strength transparent antibacterial ultra-thin paper of the present invention can improve the mechanical properties and antibacterial properties of the ultra-thin paper while further improving the transparency of the ultra-thin paper; the obtained high-strength transparent antibacterial ultra-thin paper has the characteristics of high strength, good flexibility, and appropriate transparency, and the antibacterial rate can reach 99.9%.

Description

Technical Field

[0001] The present invention relates to the field of ultra-thin paper, and particularly to a high-strength transparent antibacterial ultra-thin paper and a preparation method thereof. Background Art

[0002] Infections caused by Escherichia coli (Gram-negative bacteria) cause tens of thousands of people to fall ill every year, leading to a large number of hospitalizations and deaths every year. There are many solutions to treat these infections, but they all require high economic costs. Vaccination is one of the effective ways to solve these infections, but it also costs tens of billions of yuan every year, and the cost is also relatively high; moreover, tens of millions of children around the world cannot be vaccinated every year. In the prior art, there is also a more feasible epidemic prevention method, which is to prepare daily necessities with bactericidal functions, especially toilet paper and its related paper-based products, which are the most consumed by people daily. Among them, toilet paper and paper towels are essential daily necessities for people. According to statistics, the annual per capita consumption of toilet paper in China exceeds 8.4 kg. At the same time, due to people's increasing attention to a healthy lifestyle, the toilet paper market is growing every year, but there are very few toilet paper products with bactericidal properties.

[0003] In our daily life, the safety and antibacterial properties of sanitary products are very important for our physical health, and the need to effectively control the spread of infectious diseases is becoming increasingly urgent. Among them, in people's daily life, the most used are toilet paper and its related paper-based products. In order to minimize the use of paper products, it is of great technical significance and application value to prepare ultra-thin paper with high strength and good antibacterial properties.

[0004] Ultra-thin paper prepared by using modified cellulose is disclosed in the prior art. By adding modified cellulose in the pulp and through the interaction between the surface groups of the modified cellulose and the raw materials, the mechanical strength of the ultra-thin paper is improved. The cellulose-based ultra-thin paper prepared based on this method shows unique properties and physical characteristics, such as transparency, density, mechanical strength, etc., and is expected to be applied in the fields of medical treatment, hygiene, electronics, and intelligent packaging. However, the aforementioned cellulose paper-based materials still have many deficiencies, such as low mechanical properties and lack of functionality.

[0005] Chitosan is prepared by deacetylating chitin from the shells of crustaceans such as shrimp and crab shells. It is a type of natural polysaccharide with very rich reserves and strong antibacterial properties. Currently, there are two antibacterial mechanisms. One is that chitosan molecules contain a large number of NH2 active functional groups, which are protonated and positively charged, and can produce electrostatic interactions with negatively charged anions such as sialic acid phospholipids that make up the bacterial cell wall, thereby restricting the free movement of microorganisms and hindering their reproduction. Another mechanism is that low-molecular-weight chitosan can penetrate into bacterial cells, hinder the transcription of bacterial DNA to RNA, and block the growth and reproduction of bacteria. In the prior art, it has been disclosed that chitosan is used as an antibacterial agent in the preparation of paper-based materials, thereby endowing the paper-based materials with certain antibacterial functions. However, the antibacterial performance of paper-based materials using only chitosan is still insufficient, and the addition of existing composite antibacterial components will have an adverse impact on the transparency of ultra-thin paper; at the same time, while improving the antibacterial performance and transparency of ultra-thin paper, the mechanical properties of ultra-thin paper also need to be further improved. Summary of the Invention

[0006] To solve the technical problems existing in the prior art, the present invention provides a high-strength transparent antibacterial ultra-thin paper and a preparation method thereof, which can improve the mechanical properties and antibacterial properties of ultra-thin paper while further improving the transparency of ultra-thin paper.

[0007] To solve the above technical problems, the technical solutions adopted by the present invention are as follows:

[0008] A preparation method of a high-strength transparent antibacterial ultra-thin paper includes the following steps: preparing carboxyl-modified cellulose nanofibers, preparing dialdehyde cellulose nanocrystals, preparing an antibacterial composite coating, preparing an ultra-thin paper base paper, and forming.

[0009] The method for preparing carboxyl-modified cellulose nanofibers is to treat cellulose pulp with a citric acid-oxalic acid mixed organic acid solvent to obtain carboxyl-modified cellulose nanofibers.

[0010] The method for preparing dialdehyde cellulose nanocrystals is to contact and react sodium periodate with cellulose nanocrystals and then dialyze to obtain dialdehyde cellulose nanocrystals.

[0011] The method for preparing the antibacterial composite coating is to put chitosan and dialdehyde cellulose nanocrystals into acetic acid solution to obtain the antibacterial composite coating.

[0012] The method for preparing the ultra-thin paper base paper is to mix bleached kraft pine pulp, bleached kraft acacia pulp, and carboxyl-modified cellulose nanofibers to obtain the ultra-thin paper base paper.

[0013] The forming method is to coat the antibacterial composite coating on the ultra-thin paper base paper and then dry it, and then perform plasma treatment to obtain the high-strength transparent antibacterial ultra-thin paper.

[0014] Preferably, in the preparation of carboxyl-modified cellulose nanofibers, the citric acid content in the citric acid-oxalic acid mixed organic acid solvent is 25-50 wt%, and the oxalic acid content is 2-10 wt%; more preferably, the citric acid content is 25-30 wt%, the oxalic acid content is 2-4 wt%, and the balance is water;

[0015] Preferably, the treatment temperature of the cellulose pulp with the citric acid-oxalic acid mixed organic acid solvent is 110-130 °C, and the treatment time is 1.5-3 h.

[0016] Preferably, in the preparation of carboxyl-modified cellulose nanofibers, the cellulose pulp is the absolute dry pulp of bleached kraft pine pulp, the ISO brightness of the bleached kraft pine pulp is at least 86%, the fiber length is 2.25 mm, the fiber width is 28.0 μm, and the coarseness is 265 mg / km.

[0017] Preferably, in the preparation of dialdehyde cellulose nanocrystals, the contact reaction temperature of sodium periodate with cellulose nanocrystals is 25-60 °C, and the contact reaction time is 2-4 h;

[0018] The cut-off molecular weight of dialysis is 12000-14000 Da, and the dialysis time is 48-80 h.

[0019] Preferably, in the preparation of dialdehyde cellulose nanocrystals, the dosage of sodium periodate is at least 1.1 times the weight of cellulose nanocrystals;

[0020] The average particle size of cellulose nanocrystals is 150 nm, the aldehyde group content is 1.5 mmol / g, and the potential is -13 mV.

[0021] Preferably, in the preparation of the antibacterial composite coating, the concentration of chitosan in the antibacterial composite coating is 0.6-0.85 wt%, and the concentration of dialdehyde cellulose nanocrystals is 0.15-0.4 wt%.

[0022] Preferably, in the preparation of the ultra-thin paper base paper, by weight, the dosage of bleached kraft pine pulp is 70-80 parts; the dosage of bleached kraft acacia pulp is 20-30 parts; the dosage of carboxyl-modified cellulose nanofibers is 0.1-1 part.

[0023] Preferably, after the antibacterial composite coating is coated on the ultra-thin paper base paper and dried, the weight parts of chitosan in the antibacterial composite coating in the high-strength transparent antibacterial ultra-thin paper are 0.6-0.85 parts, and the weight parts of dialdehyde cellulose nanocrystals in the high-strength transparent antibacterial ultra-thin paper are 0.15-0.4 parts.

[0024] Preferably, in the forming, the plasma atmosphere of the plasma treatment is composed of helium and oxygen;

[0025] The discharge power of the plasma treatment is 100 - 200 W, the discharge frequency is 25 - 30 kHz, the treatment time is 10 - 30 min, and the treatment temperature is room temperature.

[0026] Further, the method for preparing carboxyl - modified cellulose nanofibers is as follows: after treating cellulose pulp with a citric acid - oxalic acid mixed organic acid solvent, it is diluted with deionized water and filtered to obtain a filter residue; after the filter residue is washed to neutrality, it is diluted with deionized water and ultrasonically treated to prepare a carboxyl - modified cellulose nanofiber aqueous suspension.

[0027] Preferably, the concentration of the carboxyl - modified cellulose nanofiber aqueous suspension is at least 0.8 wt%.

[0028] Preferably, the ultrasonic treatment power is 800 - 1000 W, and the ultrasonic treatment time is 20 - 40 min.

[0029] Further, the method for preparing dialdehyde cellulose nanocrystals is as follows: sodium periodate is added to an aqueous solution of cellulose nanocrystals for contact reaction, diluted with ethylene glycol, and then dialyzed to obtain dialdehyde cellulose nanocrystals.

[0030] Preferably, the concentration of the aqueous solution of cellulose nanocrystals is at least 1 wt%.

[0031] Preferably, the mass - to - volume ratio of sodium periodate to the aqueous solution of cellulose nanocrystals is 1.3 g:100 mL.

[0032] Further, in the preparation of the ultra - thin paper base paper, bleached kraft pine pulp, bleached kraft acacia pulp and the carboxyl - modified cellulose nanofiber aqueous suspension are mixed evenly and then made into the ultra - thin paper base paper.

[0033] Preferably, in the preparation of the ultra - thin paper base paper, the ISO brightness of the bleached kraft pine pulp is at least 86%, the fiber length is 2.25 mm, the fiber width is 28.0 μm, and the coarseness is 265 mg / km; the ISO brightness of the bleached kraft acacia pulp is at least 85%, the fiber length is 1.1 mm, the fiber width is 16.5 μm, and the fiber coarseness is 150 mg / km.

[0034] Further, the forming method is as follows: after the ultra - thin paper base paper is statically balanced, an antibacterial composite coating is coated on the ultra - thin paper base paper and then dried, and then plasma - treated to obtain a high - strength transparent antibacterial ultra - thin paper.

[0035] Preferably, the temperature of the static balance is room temperature and the relative humidity is 60%.

[0036] A high-strength transparent antibacterial ultra-thin paper is prepared by the aforementioned preparation method; the high-strength transparent antibacterial ultra-thin paper, by weight, comprises the following components: 70-80 parts of bleached sulfate pine pulp; 20-30 parts of bleached sulfate acacia pulp; 0.1-1 part of carboxyl-modified cellulose nanofibers; 0.6-0.85 part of chitosan; 0.15-0.4 part of dialdehyde cellulose nanocrystals.

[0037] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0038] 1) In the preparation method of the high-strength transparent antibacterial ultra-thin paper of the present invention, a high-strength transparent antibacterial ultra-thin paper is prepared by using all-natural polymer materials. During the preparation process, carboxyl-modified cellulose nanofibers are added to the ultra-thin paper base paper to improve the strength; and the ultra-thin paper base paper is treated with a natural composite antibacterial coating including chitosan and dialdehyde cellulose nanocrystals. Among them, dialdehyde cellulose has certain antibacterial properties, and after mixing dialdehyde cellulose nanocrystals in the coating, the synergistic effect of the two can be fully exerted. In addition to further enhancing the antibacterial property of the paper-based material, it can moderately offset the hydrophobicity of chitosan and maintain fiber formation and water absorption. Further, the inventors have found through research that the hydrophilicity of microorganisms and substrates is one of the key factors to enhance the sensitivity of chitosan as an antibacterial agent. The inventors have found through a large number of experimental studies that after treating the coating formed by the composite antibacterial coating with oxygen plasma, the hydrophilicity of the ultra-thin paper can be effectively improved; and by spraying a composite antibacterial coating containing dialdehyde cellulose nanocrystals and chitosan on the surface of the ultra-thin paper base paper and cooperating with plasma treatment, the antibacterial performance of the ultra-thin paper can be further significantly improved, and finally an ultra-thin paper with high strength, moderate transparency, and good antibacterial performance (able to inhibit the growth of up to 99.9% of microorganisms) is obtained.

[0039] 2) In the preparation method of the high-strength transparent antibacterial ultra-thin paper of the present invention, carboxyl-modified nanocellulose is added to the mixed pulp (bleached sulfate pine pulp, bleached sulfate acacia pulp), and a composite antibacterial coating is applied, cooperating with plasma treatment, which can improve the mechanical properties and antibacterial properties of the ultra-thin paper while further improving the transparency of the ultra-thin paper; the prepared high-strength transparent antibacterial ultra-thin paper has the characteristics of high strength, good flexibility, and appropriate transparency, and the antibacterial rate can reach 99.9%.

[0040] 3) In the preparation method of the high-strength transparent antibacterial ultra-thin paper of the present invention, the required raw materials are all natural polysaccharide polymer materials, which belong to renewable resources; and the prepared high-strength transparent antibacterial ultra-thin paper belongs to a completely biodegradable material, which conforms to the concept of carbon reduction development.

[0041] 4) The high-strength transparent antibacterial ultra-thin paper of the present invention has excellent antibacterial properties and has application prospects in the fields of biology, medicine, electronics, and intelligent packaging. Detailed implementation manners

[0042] To have a clearer understanding of the technical features, objectives, and effects of the present invention, the specific embodiments of the present invention will now be described.

[0043] Example 1

[0044] This example provides a high-strength transparent antibacterial ultra-thin paper, which contains the following components by weight: 75 parts of bleached sulfate pine pulp; 25 parts of bleached sulfate acacia pulp; 0.1 part of carboxyl-modified cellulose nanofibers; 0.85 part of chitosan; 0.15 part of dialdehyde cellulose nanocrystals.

[0045] This example also provides a method for preparing a high-strength transparent antibacterial ultra-thin paper, specifically as follows:

[0046] (1) Preparation of carboxyl-modified cellulose nanofibers

[0047] Cellulose pulp is treated with a citric acid-oxalic acid mixed organic acid solvent. Specifically, 30 g of citric acid, 3 g of oxalic acid, and 67 g of deionized water are mixed and stirred at 50 °C for 30 min to obtain a mixed organic acid solvent; then 10 g of dry cellulose pulp is added to 100 mL of the above mixed organic acid solvent, and the reaction is carried out in a polytetrafluoroethylene reaction kettle at a temperature of 120 °C and a rotation speed of 500 rpm for 2 h. After the reaction is completed, the reaction product is added to 1000 mL of deionized water and stirred at a rotation speed of 500 rpm for 1 h, and then vacuum filtered to obtain a filter residue, which is washed with deionized water until the pH is neutral; the filter residue is diluted with deionized water to a concentration of 0.8 wt%; then it is ultrasonically treated with an ultrasonic emulsifier at a power of 900 w for 30 min to obtain a carboxyl-modified cellulose nanofiber (C-CNF) aqueous suspension, and the concentration of C-CNF in this C-CNF aqueous suspension is 0.8 wt%.

[0048] The cellulose pulp is the dry pulp of bleached sulfate pine pulp. The ISO whiteness of the bleached sulfate pine pulp is 86%, the fiber length is 2.25 mm, the fiber width is 28.0 μm, and the coarseness is 265 mg / km.

[0049] (2) Preparation of dialdehyde cellulose nanocrystals

[0050] Under dark and light-shielded conditions, 1.3 g of sodium periodate is dissolved in 100 mL of an aqueous solution of cellulose nanocrystals (the mass fraction of cellulose nanocrystals is 1.0 wt%), the pH value of the system is adjusted to 3.0, and the reaction is carried out at 25 °C for 4 h. After the reaction is completed, the reaction is terminated with 200 mL of ethylene glycol, and then the obtained product is dialyzed with deionized water for 72 h (the cut-off molecular weight of the dialysis bag is 12000 - 14000 Da) to obtain dialdehyde cellulose nanocrystals.

[0051] Among them, in the aqueous solution of cellulose nanocrystals, the average particle size of cellulose nanocrystals is 150 nm, the aldehyde group content is 1.5 mmol / g, and the potential is -13 mV.

[0052] (3) Preparation of antibacterial composite coating

[0053] Chitosan is put into acetic acid solution with a volume concentration of 1%, stirred evenly to obtain a chitosan solution with a concentration of 0.85 wt%; then the prepared dialdehyde cellulose nanocrystals are put into the chitosan solution, and stirred and mixed at a speed of 500 rpm for 30 min using a stirrer to obtain an antibacterial composite coating.

[0054] Among them, the chitosan is medium molecular weight chitosan with a deacetylation degree of 97%.

[0055] In the antibacterial composite coating, the concentration of chitosan is 0.85 wt%, and the concentration of dialdehyde cellulose nanocrystals is 0.15 wt%.

[0056] (4) Preparation of ultra-thin paper base paper

[0057] According to the weight parts of the foregoing components, 75 parts of bleached kraft pine pulp, 25 parts of bleached kraft acacia pulp and a carboxyl-modified cellulose nanofiber aqueous suspension (the content of carboxyl-modified cellulose nanofibers in the aqueous suspension is 0.1 part) are mixed evenly, and a hand sheet mold is used to make a quantitative ultra-thin paper base paper of 15 g / m 2 of.

[0058] Among them, the ISO whiteness of the bleached kraft pine pulp is 86%, the fiber length is 2.25 mm, the fiber width is 28.0 μm, and the coarseness is 265 mg / km.

[0059] The ISO whiteness of the bleached kraft acacia pulp is 85%, the fiber length is 1.1 mm, the fiber width is 16.5 μm, and the fiber coarseness is 150 mg / km.

[0060] The total addition amount of the carboxyl-modified cellulose nanofiber aqueous suspension is added according to the content of carboxyl-modified cellulose nanofibers in the carboxyl-modified cellulose nanofiber aqueous suspension being 0.1 part (relative to the other components of the foregoing high-strength transparent antibacterial ultra-thin paper).

[0061] (5) Shaping

[0062] The ultra-thin paper base paper is placed in an environment of 20 °C at room temperature and 60% relative humidity, and left to stand and balance for 12 h; then the antibacterial composite coating is evenly coated on the ultra-thin paper base paper after standing and balancing, and then placed in a drying oven at 110 °C for drying to obtain the coated ultra-thin paper base paper; then the coated ultra-thin paper base paper is subjected to surface modification treatment using a plasma system to obtain a high-strength transparent antibacterial ultra-thin paper.

[0063] Among them, the coating amount of the antibacterial composite coating is coated according to 0.85 parts of chitosan content in the antibacterial mixed coating (relative to other components of the aforementioned high-strength transparent antibacterial ultra-thin paper) and 0.15 parts of dialdehyde cellulose nanocrystals (relative to other components of the aforementioned high-strength transparent antibacterial ultra-thin paper).

[0064] In the surface modification treatment, the plasma atmosphere consists of helium and oxygen, the volume ratio of helium to oxygen is 6:4, and the flow rate of the plasma atmosphere is 5 L / min; the discharge power of the plasma is 100 W, the discharge frequency is 25 kHz, the surface modification treatment time is 15 min, the surface modification treatment temperature is room temperature, and the plasma atmosphere pressure is maintained at 100 Pa.

[0065] Example 2

[0066] The preparation method of the high-strength transparent antibacterial ultra-thin paper in this example adopts the technical solution of Example 1, and the difference lies in that: in the step of preparing the ultra-thin paper base paper, the total addition amount of the carboxyl-modified cellulose nanofiber aqueous suspension is added according to 0.25 parts of the carboxyl-modified cellulose nanofiber content in the carboxyl-modified cellulose nanofiber aqueous suspension (relative to other components of the aforementioned high-strength transparent antibacterial ultra-thin paper).

[0067] Example 3

[0068] The preparation method of the high-strength transparent antibacterial ultra-thin paper in this example adopts the technical solution of Example 1, and the difference lies in that: in the step of preparing the ultra-thin paper base paper, the total addition amount of the carboxyl-modified cellulose nanofiber aqueous suspension is added according to 0.5 parts of the carboxyl-modified cellulose nanofiber content in the carboxyl-modified cellulose nanofiber aqueous suspension (relative to other components of the aforementioned high-strength transparent antibacterial ultra-thin paper).

[0069] Example 4

[0070] The preparation method of the high-strength transparent antibacterial ultra-thin paper in this example adopts the technical solution of Example 1, and the differences are as follows: 1) In the step of preparing the ultra-thin paper base paper, the total addition amount of the carboxyl-modified cellulose nanofiber aqueous suspension is added according to 0.5 parts of the carboxyl-modified cellulose nanofiber content in the carboxyl-modified cellulose nanofiber aqueous suspension (relative to other components of the aforementioned high-strength transparent antibacterial ultra-thin paper). 2) In the step of preparing the antibacterial composite coating, the concentration of chitosan is 0.75 wt%, and the concentration of dialdehyde cellulose nanocrystals is 0.25 wt%; and in the coating and forming step, the coating amount of the antibacterial composite coating is coated according to 0.75 parts of chitosan content in the antibacterial mixed coating (relative to other components of the aforementioned high-strength transparent antibacterial ultra-thin paper) and 0.25 parts of dialdehyde cellulose nanocrystals (relative to other components of the aforementioned high-strength transparent antibacterial ultra-thin paper).

[0071] Example 5

[0072] The preparation method of the high-strength transparent antibacterial ultra-thin paper in this example adopts the technical solution of Example 1, and the differences are as follows: 1) In the step of preparing the ultra-thin paper base paper, the total addition amount of the carboxyl-modified cellulose nanofiber aqueous suspension is added according to the content of carboxyl-modified cellulose nanofibers in the carboxyl-modified cellulose nanofiber aqueous suspension being 0.5 parts (relative to other components of the aforementioned high-strength transparent antibacterial ultra-thin paper). 2) In the step of preparing the antibacterial composite coating, the concentration of chitosan is 0.65 wt%, and the concentration of dialdehyde cellulose nanocrystals is 0.35 wt%; and in the coating and forming step, the coating amount of the antibacterial composite coating is coated according to the content of chitosan in the antibacterial mixed coating being 0.65 parts (relative to other components of the aforementioned high-strength transparent antibacterial ultra-thin paper) and dialdehyde cellulose nanocrystals being 0.35 parts (relative to other components of the aforementioned high-strength transparent antibacterial ultra-thin paper).

[0073] Comparative Example 1

[0074] The preparation method of the ultra-thin paper in Comparative Example 1 adopts the technical solution of Example 3, and the difference is that in the step of preparing the ultra-thin paper base paper, the addition of the carboxyl-modified cellulose nanofiber aqueous suspension is omitted.

[0075] Comparative Example 2

[0076] The preparation method of the ultra-thin paper in Comparative Example 2 adopts the technical solution of Example 3, and the differences are that the step of preparing dialdehyde cellulose nanocrystals is omitted, and in the step of preparing the antibacterial composite coating, cellulose nanocrystals are used to replace dialdehyde cellulose nanocrystals.

[0077] Comparative Example 3

[0078] The preparation method of the ultra-thin paper in Comparative Example 3 adopts the technical solution of Example 3, and the difference is that in the coating and forming step, the surface modification treatment of the coated ultra-thin paper base paper by the plasma system is omitted.

[0079] Comparative Example 4

[0080] The preparation method of the ultra-thin paper in Comparative Example 4 adopts the technical solution of Example 3, and the differences are as follows: 1) In the step of preparing the ultra-thin paper base paper, the addition of the carboxyl-modified cellulose nanofiber aqueous suspension is omitted. 2) The preparation and use of dialdehyde cellulose nanocrystals and the antibacterial composite coating are omitted, and in the forming step, the ultra-thin paper base paper is directly subjected to plasma surface modification treatment.

[0081] The tensile index, Escherichia coli antibacterial rate and transparency of the ultra-thin papers prepared in Examples 1-5 and Comparative Examples 1-4 were detected, and the specific technical means comparison and detection results are shown in the following table:

[0082]

[0083] As can be seen from the data in the above table, the addition of carboxyl-modified cellulose nanofibers in the pulp and the nano-antibacterial composite coating significantly improve the antibacterial performance of the ultra-thin paper made from the mixed pulp. At the same time, they can improve the tensile strength of the ultra-thin paper without significantly affecting the transparency of the ultra-thin paper. In addition, the ultra-thin paper with carboxyl-modified cellulose nanofibers added in the pulp has advantages in terms of the improvement of various properties compared with the ultra-thin paper without the addition of carboxyl-modified cellulose nanofibers and only coated with the antibacterial composite coating. And the plasma surface modification treatment of the coated ultra-thin paper base paper can further improve the antibacterial performance of the ultra-thin paper.

[0084] As can be seen from the above table, when carboxyl-modified cellulose nanofibers are added in the pulp and the content of dialdehyde cellulose nanocrystals in the antibacterial composite coating is 0.25 - 0.35 wt%, the prepared high-strength transparent antibacterial ultra-thin paper has better mechanical properties and antibacterial performance, and the transparency change of the ultra-thin paper is not obvious.

[0085] Unless otherwise specified, the percentages used in the present invention are all mass percentages.

[0086] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or perform equivalent replacements for some of the technical features. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing high-strength transparent antibacterial ultra-thin paper, characterized in that: The method comprises the following steps: preparing carboxyl-modified cellulose nanofibers, preparing dialdehyde cellulose nanocrystals, preparing antibacterial composite coatings, preparing ultra-thin paper base paper, and forming; The method for preparing carboxyl-modified cellulose nanofibers comprises treating cellulose pulp with a citric acid-oxalic acid mixed organic acid solvent to prepare carboxyl-modified cellulose nanofibers; The method for preparing dialdehyde cellulose nanocrystals comprises: contacting sodium periodate with cellulose nanocrystals and then dialyzing to obtain dialdehyde cellulose nanocrystals; The method for preparing the antibacterial composite coating comprises: adding chitosan and dialdehyde cellulose nanocrystals into an acetic acid solution to prepare the antibacterial composite coating; The method for preparing the ultra-thin paper base paper comprises: mixing bleached kraft pine pulp, bleached kraft acacia pulp and carboxyl modified cellulose nanofibers to prepare the ultra-thin paper base paper; In the preparation of the ultra-thin paper base paper, the amount of bleached kraft pine pulp is 70-80 parts by weight; the amount of bleached kraft acacia pulp is 20-30 parts; the amount of carboxyl modified cellulose nanofiber is 0.1-1 part; The forming method comprises applying the antibacterial composite coating to the ultra-thin paper base paper, drying the base paper, and subjecting the base paper to plasma treatment to obtain the high-strength transparent antibacterial ultra-thin paper; In the molding, the antibacterial composite coating is applied to the ultra-thin paper base and then dried. The weight portion of chitosan in the antibacterial composite coating is 0.6-0.85 parts, and the weight portion of dialdehyde cellulose nanocrystals in the high-strength transparent antibacterial ultra-thin paper is 0.15-0.4 parts.

2. The method for preparing the high-strength transparent antibacterial ultra-thin paper according to claim 1, characterized in that: In the preparation of the carboxyl-modified cellulose nanofibers, the citric acid content of the citric acid-oxalic acid mixed organic acid solvent is 25-50wt%, the oxalic acid content is 2-10wt%, and the balance is water; The treatment temperature of the citric acid-oxalic acid mixed organic acid solvent for the cellulose pulp is 110-130° C., and the treatment time is 1.5-3 h.

3. The method for preparing the high-strength transparent antibacterial ultra-thin paper according to claim 1, characterized in that: In the preparation of carboxyl-modified cellulose nanofibers, the cellulose pulp is an absolute dry pulp of bleached kraft pine pulp, the bleached kraft pine pulp has an ISO whiteness of at least 86%, a fiber length of 2.25 mm, a fiber width of 28.0 μm, and a coarseness of 265 mg / km.

4. The method for preparing the high-strength transparent antibacterial ultra-thin paper according to claim 1, characterized in that: In the preparation of dialdehyde cellulose nanocrystals, the contact reaction temperature of sodium periodate and cellulose nanocrystals is 25-60° C., and the contact reaction time is 2-4 hours; The molecular weight cut-off for dialysis is 12000-14000Da, and the dialysis time is 48-80h.

5. The method for preparing the high-strength transparent antibacterial ultra-thin paper according to claim 1, characterized in that: In the preparation of dialdehyde cellulose nanocrystals, the amount of sodium periodate used is at least 1.1 times the weight of the cellulose nanocrystals; The average particle size of cellulose nanocrystals is 150 nm, the aldehyde content is 1.5 mmol / g, and the potential is -13 mV.

6. The method for preparing the high-strength transparent antibacterial ultra-thin paper according to claim 1, characterized in that: In the preparation of the antibacterial composite coating, the concentration of chitosan in the prepared antibacterial composite coating is 0.6-0.85wt%, and the concentration of dialdehyde cellulose nanocrystals is 0.15-0.4wt%.

7. The method for preparing the high-strength transparent antibacterial ultra-thin paper according to claim 1, characterized in that: In the molding, the plasma atmosphere of the plasma treatment is composed of helium and oxygen; The discharge power of the plasma treatment is 100-200W, the discharge frequency is 25-30kHz, the treatment time is 10-30min, and the treatment temperature is room temperature.

8. A high-strength transparent antibacterial ultra-thin paper, characterized in that: The high-strength transparent antibacterial ultra-thin paper is prepared by the preparation method described in any one of claims 1 to 7; the high-strength transparent antibacterial ultra-thin paper comprises the following components by weight: 70-80 parts of bleached sulfate pine pulp; 20-30 parts of bleached sulfate acacia pulp; 0.1-1 parts of carboxyl-modified cellulose nanofibers; 0.6-0.85 parts of chitosan; and 0.15-0.4 parts of dialdehyde cellulose nanocrystals.

Images