A sealable gummed paper for a sterile barrier system and a method of making the same

Abstract

The present application belongs to the technical field of polyester-coated paper, and particularly relates to a sealable coated paper for a sterile barrier system and a preparation method thereof. The present application aims to solve the problem that the air permeability and durability of the existing coated paper are difficult to be considered simultaneously. The present application first beats bleached softwood pulp, adds oxidized nanocellulose and other additives, and applies glue to form a paper base material; the paper base material is subjected to plasma treatment to obtain a modified paper base material; a dihydric alcohol monomer and a diacid monomer are subjected to melt polycondensation to obtain a copolyester resin, which is emulsified and dispersed after being blended with functional fillers to obtain a coating agent; the coating agent is ultrasonically sprayed on the surface of the modified paper base material, and is dried to form a film to obtain a sealable coated paper. The sealable coated paper provided by the present application has good air permeability and sealing durability, and has high application value.

Description

Technical Field

[0001] This invention belongs to the field of polyester coated paper technology, specifically relating to a sealable coated paper for sterile barrier systems and its preparation method. Background Technology

[0002] Coated paper, as part of a sterile barrier system, allows sterilizing agents to penetrate during sterilization while effectively preventing microbial invasion after sterilization, ensuring that medical devices remain sterile before use. This type of paper is of great importance in the medical and pharmaceutical industries, playing a crucial role in preventing infection and cross-contamination. The coating of coated paper can be made from various polymer materials. Coatings prepared from ethylene-acrylic acid copolymers and unsaturated polyesters can give coated paper excellent heat-sealing properties while providing a microbial barrier, ensuring a sterile environment within the barrier, and forming an organically combined layered structure with the paper substrate, exhibiting good air permeability.

[0003] Currently, coated paper used in aseptic barrier systems requires not only good coating performance but also excellent tear strength and durability. The pore structure design of coated paper must allow sterilizing gases to pass through while preventing the penetration of bacteria and other microorganisms, and it must also withstand the mechanical stresses during packaging, transportation, and storage, exhibiting good tear and puncture resistance. Therefore, the pore structure and coating design of coated paper need to meet the requirements of air permeability and barrier performance, especially maintaining consistent performance under different sterilization methods; simultaneously, it is necessary to improve its tear and puncture resistance while keeping the paper thin and lightweight. These technical requirements are mutually restrictive, making it difficult to obtain coated paper products that simultaneously meet all these technical requirements.

[0004] Currently, the difficulty in balancing air permeability and durability in existing coated paper remains a significant challenge for the industry.

[0005] Therefore, a sealable coated paper for sterile barrier systems and its preparation method are proposed. Summary of the Invention

[0006] The purpose of this invention is to provide a sealable coated paper for sterile barrier systems and its preparation method. The invention first involves pulping bleached softwood pulp, adding oxidized nanocellulose and other additives, and then sizing to obtain a paper substrate. The paper substrate is then subjected to plasma treatment to obtain a modified paper substrate. A copolyester resin is obtained by melt polycondensation of diol monomers and diacid monomers, and then emulsified and dispersed with functional fillers to prepare a coating agent. The coating agent is ultrasonically sprayed onto the surface of the modified paper substrate, and dried to form a film, resulting in the sealable coated paper.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A method for preparing a sealable coated paper for a sterile barrier system includes the following steps:

[0009] Unless otherwise specified, all parts in this invention refer to parts by mass, and all average molecular weights refer to exponential molecular weights.

[0010] After bleached softwood pulp is pulped, oxidized nanocellulose is added, dispersed, and then wet strength agent and sizing agent are added. After sizing and molding, paper substrate is obtained.

[0011] The wet strength agent is an aqueous solution of glyoxal; the sizing agent includes cationic starch, alkyl ketone dimer, and polyvinyl alcohol; the mass concentration of the glyoxal aqueous solution is 22 wt%, and the added mass is 3% of the bleached softwood pulp; the cationic starch is quaternary ammonium cationic potato starch with an average molecular weight of 3.3 × 10⁻⁶. 4 Da, added at 1% by mass of bleached softwood pulp; alkyl ketene dimer in emulsion form, with a solid content of 40%, added at 1% by mass of bleached softwood pulp; polyvinyl alcohol with an average molecular weight of 85,000, added at 1.2% by mass of bleached softwood pulp.

[0012] Among them, the bleached softwood pulp is bleached sulfate softwood pulp; the oxidized nanocellulose is TEMPO oxidized nanocellulose with an average molecular weight of 3000; the mass ratio of bleached softwood pulp to oxidized nanocellulose is 7:1.5-2.8.

[0013] The paper substrate is subjected to plasma treatment to obtain a modified paper substrate.

[0014] The plasma treatment process involves treating the paper substrate with a mixed gas of N2 and O2, where the gas flow rate is 50-60 SLM and the discharge power density is 5 W / cm². 2 The linear speed of the roll material is 25 m / min, and the electrode gap is 2 mm; the flow ratio of N2 to O2 is 3:1.

[0015] Copolyester resin is obtained by melt polycondensation of diol monomers and dicarboxylic acid monomers.

[0016] The molar ratio of added diol monomers to diacid monomers is 1.05-1.1:1.

[0017] The diol monomers include ethylene glycol, 1,4-butanediol, and cyclohexanediol; the dicarboxylic acid monomers include terephthalic acid, adipic acid, and sebacic acid; the molar ratio of ethylene glycol, 1,4-butanediol, and cyclohexanediol is 2:2.3-3.5:1.2; the molar ratio of terephthalic acid, adipic acid, and sebacic acid is 1:1.4:0.5-0.8.

[0018] After blending copolyester resin with functional fillers, emulsification and dispersion are carried out to obtain a coating agent.

[0019] The functional filler is nano-silica with an average particle size of 80nm. The emulsification and dispersion process is as follows: 100 parts of copolyester resin and 10 parts of deionized water are mixed and stirred at 400-600 rpm under nitrogen protection, and the temperature is raised to 90-110℃. After treatment for 45 minutes, the stirring speed is increased to 3500-4200 rpm, 55 parts of deionized water and 3 parts of nano-silica are added, and after treatment for 60 minutes, the stirring speed is reduced to 300 rpm and cooled to 25℃ to obtain the coating agent.

[0020] The adhesive is sprayed onto the surface of the modified paper substrate through an ultrasonic spraying process to obtain the adhesive-coated paper precursor;

[0021] The adhesive paper precursor is dried to form a film, resulting in a sealable adhesive paper.

[0022] Preferably, the sizing and molding process is as follows: bleached softwood pulp is pulped, oxidized nanocellulose is added and mixed evenly, and diluted to a solid content of 1.0-1.5% to obtain a mixed pulp; while stirring the mixed pulp, glyoxal aqueous solution, cationic starch and alkyl ketone dimer are added sequentially to adjust the pH value of the mixed pulp to 7-8.5, then polyvinyl alcohol is added, and after mixing evenly, the mixed pulp is evenly sprayed onto a forming wire, dehydrated and formed, and then pressed to obtain pre-made paper; the pre-made paper is dried at 80-120℃ to obtain a paper substrate.

[0023] Preferably, the melt copolymerization process is as follows: the diol monomer and the diacid monomer are mixed and dissolved, and 0.25% of tetrabutyl titanate by mass of the diol monomer is added. The mixture is heated to 150-220°C under nitrogen protection and reacted for 3-4 hours. After heating to 240-260°C, the operating pressure of the reaction system is reduced to 0.05 atm, and the reaction is continued to be stirred for 2 hours. After removing the solvent, the copolyester resin is obtained.

[0024] Preferably, the ultrasonic spraying process is as follows: after spraying a 0.5 wt% ethyl acetate solution of isophorone diisocyanate onto the surface of the modified paper substrate and drying it, the adhesive is treated through a 25 μm filter head and then sprayed onto the surface of the modified paper substrate at an ultrasonic frequency of 40 kHz and a nitrogen gas flow pressure of 0.5-0.8 psi. The distance from the nozzle to the surface of the modified paper substrate is 35 mm, and the ultrasonic power is 10 W, thus obtaining the coated paper precursor.

[0025] Preferably, the drying and film-forming process is as follows: the adhesive paper precursor is dried at 50-70℃ for 25s, then heated to 80-90℃ and purged with nitrogen for 60s, and then cooled to 25℃ and kept at that temperature for 60s to obtain a sealable adhesive paper.

[0026] A sealable coated paper for a sterile barrier system comprises: an adhesive layer and a modified paper substrate; the adhesive layer is obtained by spraying an adhesive agent onto the surface of the modified paper substrate. The coated paper product prepared by this invention has an average thickness of 0.3 mm and exhibits good heat-sealing properties and sealing durability.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] 1. By introducing oxidized nanocellulose and bleached softwood pulp to form a fiber network, and by using nano-silica filler in the sizing agent to form a composite physical barrier in the sizing layer, the ability of the coated paper to block microorganisms is comprehensively improved, and the mechanical strength of the coated paper is guaranteed.

[0029] 2. By using specific types and proportions of diol monomers and diacid monomers, a hydroxyl-terminated copolyester resin was synthesized through melt polycondensation. This synergistically improved the adhesion and heat-sealing performance of the coating agent while ensuring that the air permeability of the coated paper product remained unaffected. Different monomer selections and specific proportions gave the coating agent good flowability and non-crystallization properties. Furthermore, the use of ultrasonic spraying technology achieved highly uniform coating, resulting in a stable and highly durable coated paper product.

[0030] 3. The synergistic effect of oxidized nanocellulose and polyvinyl alcohol improved the surface structure of the paper substrate, providing a good foundation for subsequent processing and coating. The plasma treatment increased the surface energy of the paper substrate, significantly improving the bonding strength between the coating layer and the paper substrate. This achieved a synergistic effect of strong chemical bonding and physical adsorption from paper fibers to polyester adhesive layer, ensuring extremely high interfacial bonding strength.

[0031] 4. By adding cationic starch and ethyl acetate solution of isophorone diisocyanate pre-sprayed during ultrasonic spraying, and combining it with a multi-stage drying film-forming process, uniform film formation is ensured, which synergistically strengthens the interfacial bonding between the coating layer and the paper substrate and the sealing durability of the coated paper product. Attached Figure Description

[0032] Figure 1 This is a flowchart illustrating the preparation process of the sealable coated paper in this invention. Detailed Implementation

[0033] The technical solution of the present invention will be clearly and completely described below through some embodiments and experimental examples. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0034] Reference Figure 1 The process flow diagram shown illustrates that this invention provides a sealable coated paper for aseptic barrier systems and its preparation method. The technical solution is as follows:

[0035] Example 1

[0036] Bleached softwood pulp was pulped, and oxidized nanocellulose was added and mixed evenly. The mixture was then diluted to a solid content of 1.0% to obtain a mixed pulp. While stirring the mixed pulp, glyoxal aqueous solution, cationic starch, and alkyl ketone dimer were added in sequence. The pH of the mixed pulp was adjusted to 7, and then polyvinyl alcohol was added. After mixing evenly, the mixed pulp was sprayed evenly onto a forming wire, dehydrated, formed, and pressed to obtain pre-made paper. The pre-made paper was dried at 80°C to obtain paper substrate.

[0037] The wet strength agent is an aqueous solution of glyoxal; the sizing agent includes cationic starch, alkyl ketone dimer, and polyvinyl alcohol; the mass concentration of the glyoxal aqueous solution is 22 wt%, and the added mass is 3% of the bleached softwood pulp; the cationic starch is quaternary ammonium cationic potato starch with an average molecular weight of 3.3 × 10⁻⁶. 4 Da, added at 1% by mass of bleached softwood pulp; alkyl ketene dimer in emulsion form, with a solid content of 40%, added at 1% by mass of bleached softwood pulp; polyvinyl alcohol with an average molecular weight of 85,000, added at 1.2% by mass of bleached softwood pulp.

[0038] Among them, the bleached softwood pulp is bleached sulfate softwood pulp; the oxidized nanocellulose is TEMPO oxidized nanocellulose with an average molecular weight of 3000; the mass ratio of bleached softwood pulp to oxidized nanocellulose is 7:1.5.

[0039] The paper substrate was treated with a mixture of N2 and O2 gases at a flow rate of 50 SLM and a discharge power density of 5 W / cm². 2 The linear speed of the roll material is 25 m / min, and the electrode gap is 2 mm; the flow ratio of N2 to O2 is 3:1.

[0040] Diol monomers and diacid monomers were mixed and dissolved. Tetrabutyl titanate at 0.25% of the mass of the diol monomers was added. The mixture was heated to 150°C and reacted for 3 hours under nitrogen protection. After heating to 240°C, the operating pressure of the reaction system was reduced to 0.05 atm, and the reaction was continued to be stirred for 2 hours. After removing the solvent, copolyester resin was obtained.

[0041] The molar ratio of the added diol monomer to the diacid monomer is 1.05:1.

[0042] The diol monomers include ethylene glycol, 1,4-butanediol, and cyclohexanediol; the dicarboxylic acid monomers include terephthalic acid, adipic acid, and sebacic acid; the molar ratio of ethylene glycol, 1,4-butanediol, and cyclohexanediol is 2:2.3:1.2; the molar ratio of terephthalic acid, adipic acid, and sebacic acid is 1:1.4:0.5.

[0043] Mix 100 parts copolyester resin and 10 parts deionized water, stir at 400 rpm under nitrogen protection, and heat to 90°C. After 45 min of treatment, increase the stirring speed to 3500 rpm, add 55 parts deionized water and 3 parts nano silica, and treat for 60 min. Then reduce the stirring speed to 300 rpm and cool to 25°C to obtain the coating agent.

[0044] After spraying a 0.5 wt% ethyl acetate solution of isophorone diisocyanate onto the surface of a modified paper substrate and drying it, the coating agent was treated through a 25 μm filter and then sprayed onto the surface of the modified paper substrate at an ultrasonic frequency of 40 kHz and a nitrogen gas flow pressure of 0.5 psi. The distance from the nozzle to the surface of the modified paper substrate was 35 mm, and the ultrasonic power was 10 W, thus obtaining the coated paper precursor.

[0045] After drying the adhesive paper precursor at 50°C for 25 seconds, the temperature is raised to 80°C and purged with nitrogen for 60 seconds. The temperature is then lowered to 25°C and held for 60 seconds to obtain the sealable adhesive paper.

[0046] Examples 2-20 differ from Example 1 in terms of operating parameters. The specific parameter changes are summarized in Tables 1-3.

[0047] Table 1. Changes in operating parameters for Examples 1-20 (Part 1)

[0048]

[0049] Table 2. Changes in operating parameters for Examples 1-20 (II)

[0050]

[0051] Table 3. Changes in operating parameters for Examples 1-20 (Part 3)

[0052]

[0053] Comparative Example 1

[0054] Unlike Example 1, nanocellulose was used instead of TEMPO to oxidize nanocellulose, while other process parameters remained unchanged.

[0055] Comparative Example 2

[0056] Unlike Example 1, no nano-silica was added, but other process parameters remained unchanged.

[0057] Comparative Example 3

[0058] Unlike Example 1, TEMPO-oxidized nanocellulose and nano-silica were not added, while other process parameters remained unchanged.

[0059] Comparative Example 4

[0060] Unlike Example 6, 1,4-butanediol was not added to the diol monomer, while other process parameters remained unchanged.

[0061] Comparative Example 5

[0062] Unlike Example 6, sebacic acid was not added to the dicarboxylic acid monomer, while other process parameters remained unchanged.

[0063] Comparative Example 6

[0064] Unlike Example 6, the molar ratio of the added diol monomer and diacid monomer was changed to 1.4:1, while other process parameters remained unchanged.

[0065] Comparative Example 7

[0066] Unlike Example 11, polyvinyl alcohol was not added, but other process parameters remained unchanged.

[0067] Comparative Example 8

[0068] Unlike Example 11, no plasma treatment was performed, but other process parameters remained unchanged.

[0069] Comparative Example 9

[0070] Unlike Example 16, cationic starch was not added, but other process parameters remained unchanged.

[0071] Comparative Example 10

[0072] Unlike Example 16, an ethyl acetate solution of isophorone diisocyanate was sprayed onto the surface of the modified paper substrate after ultrasonic spraying treatment, while other process parameters remained unchanged.

[0073] Comparative Example 11

[0074] Unlike Example 16, the drying film formation process only involves single-stage drying at 83°C and purging with nitrogen for 85 seconds, while other process parameters remain unchanged.

[0075] Experimental Example 1

[0076] The mechanical strength and barrier properties of the coated paper products prepared in Examples 1-5 and Comparative Examples 1-3 were tested, and the results are summarized in Table 4.

[0077] The mechanical strength test method is as follows: Cut a rectangular sample with a width of 15 mm and a length of 200 mm from the coated paper product, and use a tensile testing machine to measure its tensile strength. The clamp spacing is 100 mm, the tensile speed is 100 mm / min, and the maximum tensile force (N / m) and elongation at break (%) are recorded.

[0078] The barrier properties test method is as follows: Cut a circular sample with a diameter of 60 mm from the coated paper product, and add 1 mL of a 1×10⁻⁶ m³ solution. 7 A CFU / mL Staphylococcus aureus suspension was dropped onto the sample surface and incubated at 37°C for 24 hours. The liquid in the receiving chamber was collected, colony counts were performed, and the microbial penetration number (CFU / mL) was calculated.

[0079] Table 4 shows the mechanical strength and barrier properties of the coated paper products prepared in Examples 1-5 and Comparative Examples 1-3.

[0080]

[0081] As shown in Table 4, the coated paper products prepared in Examples 1-5 exhibit good tensile strength and barrier properties. In Comparative Example 1, replacing TEMPO-oxidized nanocellulose with nanocellulose reduced the maximum tensile strength to 1627 N / m, while increasing the microbial penetration count to 0.1 CFU / mL. In Comparative Example 2, without the addition of nano-silica, the maximum tensile strength was 1856 N / m, and the microbial penetration count increased to 0.4 CFU / mL. In Comparative Example 3, removing both TEMPO-oxidized nanocellulose and nano-silica resulted in a maximum tensile strength of only 1108 N / m, but a significantly increased microbial penetration count of 1.8 CFU / mL. Examples 1-5 demonstrated significant advantages in both mechanical strength and barrier properties, which is attributed to the synergistic effect of oxidized nanocellulose, bleached softwood pulp, and nano-silica. The introduction of TEMPO oxidized nanocellulose effectively improves the mechanical properties of the paper substrate, directionally strengthens the basic fiber support structure provided by bleached softwood pulp, enhances the bonding force between fiber networks, and improves the overall strength of coated paper products. The addition of nano silica constructs an effective physical barrier in the coating layer, significantly improving the coating paper's ability to block microorganisms. The synergistic effect of these three elements ensures both the mechanical strength of the coated paper and its excellent microbial barrier performance, thereby meeting the application requirements of aseptic barrier systems.

[0082] Experiment Example 2

[0083] The heat-sealing performance and air permeability of the coated paper products prepared in Examples 6-10 and Comparative Examples 4-6 were tested, and the results are summarized in Table 5.

[0084] The test method for heat sealing performance is as follows: cut a sample of coated paper product with a size of 25mm×150mm, and heat sealing parameters are: temperature 130℃, pressure 0.3MPa, time 1s; record the heat sealing strength (N / m) of the sample.

[0085] The air permeability test method is as follows: Cut a circular sample with a diameter of 60 mm from the coated paper product, clamp the sample in an air permeability tester, and measure its air permeability (mL / s) within a 60-second air permeability time. The operating air pressure is 200 kPa, and the final air permeability (mL / (m²)) is calculated. 2 ·s)).

[0086] Table 5 shows the heat-sealing properties and air permeability of the coated paper products prepared in Examples 6-10 and Comparative Examples 4-6.

[0087]

[0088] As shown in Table 5, the heat-sealing strength and air permeability of the coated paper products prepared in Examples 6-10 are relatively stable. In Comparative Example 4, without the addition of 1,4-butanediol to the diol monomer, the heat-sealing strength decreased to 305 N / m, and the air permeability was 15.6 mL / (m²). 2 •s); Comparative Example 5, without the addition of sebacic acid to the dicarboxylic acid monomer, showed a decrease in heat-sealing strength to 287 N / m and air permeability to 12.5 mL / (m). 2 ·s); In Comparative Example 6, the molar ratio of diol monomer to diacid monomer was changed to 1.4:1, resulting in a decrease in heat-sealing strength to 294 N / m and an increase in air permeability to 20.3 mL / (m). 2 In summary, specific diol monomers (ethylene glycol, 1,4-butanediol, and cyclohexanediol) and diacid monomers (terephthalic acid, adipic acid, and sebacic acid) effectively improve the heat-sealing strength of coated paper products. Different monomers endow the copolyester resin with specific molecular structures and properties, thereby optimizing the adhesion and heat-sealing performance of the coating agent. At the same time, specific ratios help to adjust the crystallinity and melting behavior of the copolyester resin, thereby obtaining a good heat-sealing effect while ensuring the air permeability of the coated paper product. The melt polycondensation process controls the synthesis of the copolyester resin, specific monomer types endow the resin with specific chemical structures, and the monomer ratio further adjusts the physical properties of the resin, ultimately giving the coating agent good flowability and non-crystallization. Uniform coating is achieved through ultrasonic spraying, resulting in a coated paper product with stable performance and high durability.

[0089] Experimental Example 3

[0090] Referring to the test methods of Experimental Examples 1 and 2, the mechanical strength and heat-sealing properties of the coated paper products prepared in Examples 11-15 and Comparative Examples 7-8 were tested, and the results are summarized in Table 6.

[0091] Table 6 shows the mechanical strength and heat-sealing properties of the coated paper products prepared in Examples 11-15 and Comparative Examples 7-8.

[0092]

[0093] As shown in Table 6, the coated paper products prepared in Examples 11-15 have good mechanical strength and heat-sealing strength. Comparative Example 7, without the addition of polyvinyl alcohol, has a maximum tensile strength of 1804 N / m, an elongation at break of 9.2%, and a heat-sealing strength of 301 N / m. Comparative Example 8, without plasma treatment, has a maximum tensile strength of 1725 N / m, an elongation at break of 8.7%, and a heat-sealing strength of 283 N / m. Compared with the above data, Examples 11-15 showed superior overall performance in terms of mechanical strength and heat-sealing properties. This indicates that the combined effect of oxidized nanocellulose and polyvinyl alcohol can effectively improve the surface properties of the paper substrate and the bonding performance of the coating layer. At the same time, plasma treatment improves the wettability and adhesion of the paper substrate to the coating layer by increasing the surface energy of the paper substrate, thereby achieving strong chemical bonding and physical adsorption from paper fibers to polyester adhesive layer. The synergistic effect of oxidized nanocellulose and polyvinyl alcohol improves the surface properties of the paper substrate, providing a good foundation for coating. Plasma treatment further strengthens the bonding between the coating layer and the paper substrate, ultimately achieving a synergistic improvement in the surface smoothness of the paper substrate and the bonding strength between the coating layer and the paper substrate.

[0094] Experiment Example 4

[0095] Referring to the test method of Experimental Example 1, the sealing durability and mechanical strength of the coated paper products prepared in Examples 16-20 and Comparative Examples 9-11 were tested, and the results are summarized in Table 7.

[0096] The test method for sealing durability is as follows: referring to the test method for heat sealing performance, cut a rectangular sample of 25mm×150mm from the coated paper product, heat seal it and put it in a test chamber with a temperature of 40℃ and a humidity of 75%. Take samples at 0 days, 7 days and 14 days respectively to test the heat sealing performance, record its heat sealing strength (N / m), and calculate the heat sealing strength retention rate corresponding to different days.

[0097] Table 7. Sealing durability and mechanical strength of the coated paper products prepared in Examples 16-20 and Comparative Examples 9-11

[0098]

[0099] As shown in Table 7, the coated paper products prepared in Examples 16-20 exhibited good sealing durability and mechanical strength. Comparative Example 9, without the addition of cationic starch, had a heat-sealing strength of 309 N / m, a 7-day heat-sealing strength retention rate of 97.7%, a 14-day heat-sealing strength retention rate of 89.6%, a maximum tensile strength of 1915 N / m, and an elongation at break of 11.2%. Comparative Example 10, after ultrasonic spraying treatment, had an ethyl acetate solution of isophorone diisocyanate sprayed onto the surface of the modified paper substrate, resulting in a heat-sealing strength of... The heat seal strength of the first example was 272 N / m, with a 7-day heat seal strength retention rate of 93.1% and a 14-day heat seal strength retention rate of 81.2%. The maximum tensile strength was 1842 N / m, and the elongation at break was 10.4%. The second example, Comparative Example 11, underwent a single-stage drying process at 83°C followed by nitrogen purging for 85 seconds. Its heat seal strength was 288 N / m, with a 7-day heat seal strength retention rate of 98.1% and a 14-day heat seal strength retention rate of 84.7%. The maximum tensile strength was 1904 N / m, and the elongation at break was 9.2%.

[0100] In summary, cationic starch, as a wet strength agent, also possesses the functionality of a sizing agent. Its addition helps improve the performance of the paper substrate and enhances the uniformity of the coating layer. The application of an ethyl acetate solution of isophorone diisocyanate before ultrasonic spraying strengthens the interfacial bond between the coating layer and the paper substrate, achieving in-situ cross-linking during the spraying process. The synergistic effect of these two processes ensures the formation of a uniform adhesive film. The multi-stage drying film-forming process better controls the evaporation rate of the solvent in the coating layer, reducing defects in the coating film and thus improving the sealing durability of the coated paper product. The combined effect of these three factors ensures a uniform adhesive film formation and synergistically strengthens the interfacial bond between the coating layer and the paper substrate, ultimately improving the sealing durability of the coated paper product.

[0101] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a sealable coated paper for a sterile barrier system, characterized in that: The preparation method is as follows: After bleached softwood pulp is pulped, oxidized nanocellulose is added, dispersed, and then wet strength agent and sizing agent are added. After sizing and molding, paper substrate is obtained. The mass ratio of the bleached softwood pulp to the oxidized nanocellulose is 7:1.5-2.

8. The paper substrate is subjected to plasma treatment to obtain a modified paper substrate; A copolyester resin is obtained by melt polycondensation of diol monomers and dicarboxylic acid monomers. The molar ratio of the added diol monomer to the added dicarboxylic acid monomer is 1.05-1.1:1; The diol monomers include ethylene glycol, 1,4-butanediol, and cyclohexanediol; the dicarboxylic acid monomers include terephthalic acid, adipic acid, and sebacic acid; wherein the molar ratio of ethylene glycol, 1,4-butanediol, and cyclohexanediol is 2:2.3-3.5:1.2; and the molar ratio of terephthalic acid, adipic acid, and sebacic acid is 1:1.4:0.5-0.

8. The copolyester resin is blended with functional fillers and then emulsified and dispersed to obtain a coating agent; The functional filler is nano-silica; The adhesive is sprayed onto the surface of the modified paper substrate through an ultrasonic spraying process to obtain an adhesive-coated paper precursor. In the ultrasonic spraying process, an ethyl acetate solution of isophorone diisocyanate is first sprayed onto the surface of the modified paper substrate and then dried, and then the adhesive is sprayed onto the same surface of the modified paper substrate. The coated paper precursor is dried to form a film, resulting in a coating layer. The coating layer and the modified paper substrate together constitute a sealable coated paper.

2. The method for preparing a sealable coated paper for a sterile barrier system according to claim 1, characterized in that: The wet strength agent is an aqueous solution of glyoxal; the sizing agent includes cationic starch, alkyl ketone dimer, and polyvinyl alcohol; the sizing and molding process is as follows: the bleached softwood pulp is pulped, the oxidized nanocellulose is added and mixed evenly, and diluted to a solid content of 1.0-1.5% to obtain a mixed pulp; the mixed pulp is stirred, and the aqueous solution of glyoxal, the cationic starch, and the alkyl ketone dimer are added sequentially to adjust the pH value of the mixed pulp to 7-8.5, then the polyvinyl alcohol is added, and after mixing evenly, the mixed pulp is evenly sprayed onto a forming wire, dehydrated and formed, and then pressed to obtain a pre-made paper; the pre-made paper is dried at 80-120℃ to obtain the paper substrate.

3. The method for preparing a sealable coated paper for a sterile barrier system according to claim 1, characterized in that: The plasma treatment process involves treating the paper substrate with a mixed gas of N2 and O2, wherein the gas flow rate is 50-60 SLM and the discharge power density is 5 W / cm². 2 The linear speed of the roll material is 25 m / min, and the electrode gap is 2 mm.

4. The method for preparing a sealable coated paper for a sterile barrier system according to claim 1, characterized in that: The melt copolymerization process is as follows: the diol monomer and the diacid monomer are mixed and dissolved, tetrabutyl titanate is added, and the mixture is heated to 150-220°C under nitrogen protection for 3-4 hours. After heating to 240-260°C, the operating pressure of the reaction system is reduced to 0.05 atm, and the reaction is continued to be stirred for 2 hours. After removing the solvent, the copolyester resin is obtained.

5. The method for preparing a sealable coated paper for a sterile barrier system according to claim 1, characterized in that: The emulsification and dispersion process is as follows: 100 parts by mass of the copolyester resin and 10 parts by mass of deionized water are mixed and stirred at 400-600 rpm under nitrogen protection, and the temperature is raised to 90-110℃. After treatment for 45 min, the stirring speed is increased to 3500-4200 rpm, 55 parts by mass of deionized water and 3 parts by mass of nano-silica are added, and after treatment for 60 min, the stirring speed is reduced to 300 rpm and the mixture is cooled to 25℃ to obtain the coating agent.

6. The method for preparing a sealable coated paper for a sterile barrier system according to claim 1, characterized in that: The ultrasonic spraying process is as follows: First, a 0.5 wt% ethyl acetate solution of isophorone diisocyanate is sprayed onto the surface of the modified paper substrate and dried. Then, the adhesive is treated through a 25 μm filter and sprayed onto the same surface of the modified paper substrate at an ultrasonic frequency of 40 kHz and a nitrogen gas flow pressure of 0.5-0.8 psi. The distance from the nozzle to the surface of the modified paper substrate is 35 mm, and the ultrasonic power is 10 W, thus obtaining the adhesive paper precursor. The drying and film-forming process is as follows: The adhesive paper precursor is dried at 50-70℃ for 25 s, then heated to 80-90℃ and purged with nitrogen for 60 s, and then cooled to 25℃ and held for 60 s to obtain the sealable adhesive paper.

7. A sealable coated paper for use in a sterile barrier system, characterized in that: The sealable coated paper is prepared by the preparation method according to any one of claims 1-6; the sealable coated paper includes: a coating layer and a modified paper substrate; the coating layer is obtained by spraying an adhesive onto the surface of the modified paper substrate and then drying it to form a film.

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