Preparation method of multifunctional specialty paper coating

Abstract

The invention relates to a preparation method of a multifunctional specialty paper coating, which belongs to the technical field of papermaking, and comprises the following operation steps: 1, making backing paper, selecting bamboo pulp / jute pulp composite fibers as paper pulp fibers, and adding PLA (polylactic acid) short fibers into the paper pulp fibers for modification; and 2, preparing a film spraying solution. And 3, obtaining a film spraying liquid II, and introducing fluorine modified polysiloxane so that the film spraying layer can resist alternating from a low temperature of-40 DEG C to a high temperature of 200 DEG C. And 4, obtaining a film spraying liquid III, and then magnetically stirring the film spraying liquid for 30 minutes. And 5, carrying out film spraying treatment. And 6, carrying out drying treatment. And 7, curing treatment is carried out, the dried paper is conveyed to an ultraviolet curing chamber, and cross-linked substances in the film spraying liquid are subjected to cross-linking curing. By means of the bamboo and hemp fiber compounding and nano modification technology, the technical bottleneck that traditional coated paper is non-degradable and single in function is solved, and the coated paper has the flame-retardant, antibacterial and wide-temperature-range tolerance characteristics and replaces plastic packaging in the high-end fields of electronics, medical treatment and the like.

Description

Technical Field

[0001] The invention relates to the technical field of papermaking, and in particular to a method for preparing a multifunctional special paper coating. Background Art

[0002] Multifunctional specialty paper coatings, by applying specific materials to the paper surface, impart multiple functions such as waterproofing, antifouling, chemical resistance, high-temperature resistance, flame retardancy, and super-hydrophobicity. These coatings are widely used in packaging, printing, industry, and environmental protection. With its customizable functionality and environmental advantages, specialty paper has become a key material in packaging, medical, electronics, and other fields.

[0003] Driven by the "plastic restriction" policy, demand for products such as food greaseproof paper and medical dialysis paper has surged, with the global market expected to exceed 200 billion yuan in 2024. However, high-end products still rely on imports. In recent years, with increasing environmental protection requirements, water-based coating materials have become a research hotspot, as they reduce volatile organic compound (VOC) emissions and align with the trend of green manufacturing.

[0004] Current research focuses on technologies such as water-based coatings and nanofiber reinforcement to address pollution and import issues with traditional PE coatings. The development of biodegradable, high-temperature-resistant specialty paper can not only meet the needs of cutting-edge industries such as aerospace, but also promote the green transformation of the packaging industry, with dual strategic significance for achieving the "dual carbon" goals and industrial upgrading. Summary of the Invention

[0005] The present invention mainly solves the deficiencies in the existing technology and provides a method for preparing a multifunctional specialty paper coating. By combining bamboo and hemp fibers with nano-modification technology, it solves the technical bottleneck of non-degradable and single-function traditional coated paper. Its flame retardant (UL94 V-0), antibacterial (antibacterial rate > 99%) and wide temperature tolerance (-40~200°C) properties can replace plastic packaging in high-end fields such as electronics and medical care. Functionally, it integrates the PLA-PBAT copolymer coating system with the graphene conductive network to achieve mechanical strength (Shore D65), antistatic (10 6 The synergistic optimization of Ω / sq) and biodegradation has demonstration value in promoting the green transformation of the packaging industry.

[0006] The above technical problems of the present invention are mainly solved by the following technical solutions: A method for preparing a multifunctional specialty paper coating comprises the following steps: The first step is to create the base paper. The pulp fibers are a bamboo / hemp pulp composite, modified by the addition of PLA staple fibers. This enhances the interfacial bonding with the plant fibers, increasing the fiber density and tear resistance. After thorough mixing, the paper is rolled and ready for use without drying.

[0007] The second step is to prepare the coating solution. PLA-PBAT copolymer is used as the film-forming material. 2-3 wt% of nanocellulose crystals (CNC) are introduced to enhance the coating's puncture resistance through hydrogen bonding. A mixture of ethanol and water is added as a diluent to adjust the coating solution's viscosity and ensure uniform coating.

[0008] Step 3: Add biodegradable polyester and hexamethylene diisocyanate to the coating liquid I and mix them thoroughly. The ratio of PBAT-based polyester and hexamethylene diisocyanate is 1:1 to 1:2. Add a certain amount of trimethylolpropane to obtain coating liquid II, introduce fluorine-modified polysiloxane, and the addition amount of fluorine-modified polysiloxane is 3wt% to make the coating layer withstand the alternating temperature from -40°C to 200°C.

[0009] Step 4: Add needle-shaped crystalline calcium carbonate to the coating solution II. The aspect ratio of the needle-shaped crystalline calcium carbonate is greater than 15:1. The amount of needle-shaped crystalline calcium carbonate added is 4-6wt%. After uniform dispersion, the coating hardness can be improved to achieve a Shore D hardness of ≥65.

[0010] At the same time, 0.3wt% polyether modified siloxane leveling agent was added to solve the wetting and spreading problem of the coating liquid on the paper base with high fiber content. 0.5wt% graphene was added to reduce the surface resistance to 10 6 Ω / sq, meeting the anti-static requirements. Obtain coating solution III, which is then magnetically stirred for 30 minutes.

[0011] By controlling the powder particle size and distribution, the uniformity and adhesion of the coating layer can be optimized, imparting waterproof and oil-resistant properties to paper products. Nano-calcium carbonate is low-cost and provides a certain degree of adhesion.

[0012] Step 5: Carry out laminating treatment. Preheat the paper prepared in the first step to 60-80°C, and then use a shower to spray laminating liquid III. The amount of laminating liquid III used is 20-30g per square meter of paper.

[0013] Step 6: Drying treatment: Place the paper after the spraying treatment in the third step in a drying oven for drying treatment at a temperature of 50 to 80°C.

[0014] Step 7: Curing treatment: send the dried paper to the UV curing room to cross-link and cure the cross-linked substances in the coating solution.

[0015] Preferably, the PLA-PBAT copolymer ratio is 3:7, which has both high ductility and rapid degradation performance, and the high ductility means the elongation at break is greater than 300%; the ratio of ethanol to water is 1:1 to 1:3.

[0016] Preferably, 1 to 2 wt% of phosphorus-based flame retardant is added to give the material UL94 V-0 flame retardant properties; 0.5 wt% of nano zinc oxide particles are mixed to achieve antibacterial function, with an antibacterial rate of >99%.

[0017] Functional additive: Disodium lauryl sulfosuccinate surfactant, with low degreasing power, strong hard water tolerance, and strong biodegradability. Curing agent: Environmentally friendly fluorine-free waterproof coating curing agent: Accelerates resin cross-linking reaction, improving the mechanical strength and heat resistance of the film. Defoaming agent: Polyether-modified silicone oil: Compatible with water-based and solvent-based coatings, suppresses spray foam while preventing craters and dynamic surface tension. Heat these materials in a magnetic stirrer to 60-80°C and mix thoroughly for 5-6 hours. Allow to cool naturally to obtain coating solution I.

[0018] Preferably, polyester PET powder is added, which has high mechanical strength and chemical corrosion resistance and is used for special packaging requiring high barrier properties and durability.

[0019] Preferably, a three-zone gradient heating is set during the curing process: 120°C → 140°C → 130°C, with a stay of 15 seconds in each zone to avoid thermal deformation of the PLA fiber; the radiation distance is adjusted to 12±1cm, and the heat flux is stabilized at 900-1100W / m²5; a staged cooling is adopted: 120°C → 80°C air cooling → 50°C water mist cooling, and the cooling rate is controlled to be ≤5°C / second.

[0020] Preferably, a dual-frequency coupling mode with a power of 100kHz / 300kHz is adopted to achieve gradient curing of the coating layer, with the surface curing degree >95% and the bottom layer >85%; a dynamic pressure of 0.4-0.6MPa is applied simultaneously, and the holding time is shortened to 6-8 seconds.

[0021] Preferably, the mass ratio of bamboo pulp / hemp pulp composite fiber is 6:4.

[0022] The present invention can achieve the following effects: The present invention provides a method for preparing a multifunctional specialty paper coating. Compared with the existing technology, the invention solves the technical bottleneck of non-degradability and single function of traditional coated paper through bamboo and hemp fiber composite and nano-modification technology. Its flame retardant (UL94 V-0), antibacterial (antibacterial rate > 99%) and wide temperature tolerance (-40 ~ 200 ° C) properties can replace plastic packaging in high-end fields such as electronics and medical care. Functionally, it innovatively integrates the PLA-PBAT copolymer coating system with the graphene conductive network to achieve mechanical strength (Shore D65), antistatic (10 6 The synergistic optimization of Ω / sq) and biodegradation has demonstration value in promoting the green transformation of the packaging industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1It is the tearing strength corresponding to different PLA staple fiber contents of the present invention.

[0024] Figure 2 It is the puncture strength corresponding to different CNC contents of the present invention.

[0025] Figure 3 These are the flame retardant grades corresponding to the addition of different hexachlorocyclotriphosphazenes in the present invention.

[0026] Figure 4 It is the surface resistance corresponding to different graphene additions in the present invention. DETAILED DESCRIPTION

[0027] The technical solution of the invention is further described in detail below through embodiments and in conjunction with the accompanying drawings.

[0028] Example: Figure 1-4 As shown, a method for preparing a multifunctional specialty paper coating includes the following steps: Step 1: Prepare the base paper. The pulp fibers are a bamboo pulp / hemp pulp composite fiber with a weight ratio of 6:4. PLA staple fibers are added for modification. The diameter of the PLA staple fibers is ≤0.5 mm, and the PLA content is 25-30% by weight. After thorough mixing, the paper is prepared. After rolling, the paper is ready for use without drying.

[0029] The second step is to prepare the coating solution, using a PLA-PBAT copolymer as the film-forming material in a 3:7 ratio. This copolymer exhibits both high ductility and rapid degradation, with high ductility (elongation at break exceeding 300%). 2-3wt% nanocellulose crystals are introduced to enhance the coating's puncture resistance through hydrogen bonding. A mixture of ethanol and water is added as a diluent, with a ratio of ethanol to water ranging from 1:1 to 1:3.

[0030] Adding 1-2 wt% of phosphorus-based flame retardant imparts UL94 V-0 flame retardancy to the material. Mixing in 0.5 wt% of nano zinc oxide particles provides antibacterial properties.

[0031] Step 3: Add biodegradable polyester and hexamethylene diisocyanate to the coating liquid I and mix them thoroughly. The ratio of PBAT-based polyester and hexamethylene diisocyanate is 1:1 to 1:2. Add a certain amount of trimethylolpropane to obtain coating liquid II, introduce fluorine-modified polysiloxane, and the addition amount of fluorine-modified polysiloxane is 3wt% to make the coating layer withstand the alternating temperature from -40°C to 200°C.

[0032] Adding polyester PET powder, it has high mechanical strength and chemical corrosion resistance, and is used for special packaging that requires high barrier properties and durability, such as anti-static packaging for electronic products.

[0033] Step 4: Add needle-shaped crystalline calcium carbonate to the coating liquid II, and the addition amount of needle-shaped crystalline calcium carbonate is 4-6wt%; at the same time, add 0.3wt% polyether modified siloxane leveling agent and 0.5wt% graphene; obtain coating liquid III, and then the coating liquid needs to be magnetically stirred for 30 minutes.

[0034] Step 5: Carry out laminating treatment. Preheat the paper prepared in the first step to 60-80°C, and then use a shower to spray laminating liquid III. The amount of laminating liquid III used is 20-30g per square meter of paper.

[0035] Step 6: Drying treatment: Place the paper after the spraying treatment in the third step in a drying oven for drying treatment at a temperature of 50 to 80°C.

[0036] Step 7: Curing treatment: send the dried paper to the UV curing room to cross-link and cure the cross-linked substances in the coating solution.

[0037] The curing process utilizes a three-zone gradient heating system: 120°C → 140°C → 130°C, with a dwell time of 15 seconds in each zone to prevent thermal deformation of the PLA fibers. The radiation distance is adjusted to 12±1cm, and the heat flux is stabilized at 900-1100W / m²5. A dual-frequency coupling mode with a power of 100kHz / 300kHz is used to achieve gradient curing of the coating layer, with a cure rate of >95% for the surface layer and >85% for the base layer. A dynamic pressure of 0.4-0.6MPa is simultaneously applied, reducing the dwell time to 6-8 seconds.

[0038] Use staged cooling: 120℃→80℃ air cooling→50℃ water mist cooling, and control the cooling rate to ≤5℃ / second.

[0039] Figure 1 The tear strength test results of specialty paper with different PLA staple fiber contents are presented. The results show that PLA staple fiber content has a significant impact on the tear strength of specialty paper. After comprehensively considering performance and cost, the PLA staple fiber content was selected to be 25-30%.

[0040] Figure 2 The effects of varying cellulose nanocrystal (CNC) content on the puncture resistance of specialty paper coatings are reported. The results show that the CNC content significantly influences the puncture resistance of specialty paper coatings. After considering both performance and cost, a CNC content of 2 to 3 wt% was selected.

[0041] Figure 3 The effects of different hexachlorocyclotriphosphazene contents on the flame retardancy of specialty paper are reported. The results show that the hexachlorocyclotriphosphazene content significantly influences the flame retardancy of specialty paper. After considering both performance and cost, a hexachlorocyclotriphosphazene content of 1 to 2 wt% was selected.

[0042] Figure 4 The results of tests comparing the surface resistance of specialty paper with varying graphene content are presented. The results show that graphene content significantly influences the surface resistance of specialty paper. When 0.5 wt% graphene is added, the surface resistance drops to 6.68 × 10⁷ Ω / sq, meeting antistatic requirements and capable of shielding some electromagnetic signals. Therefore, after comprehensive cost considerations, a 0.5 wt% graphene content was selected.

[0043] In summary, the preparation method of the multifunctional specialty paper coating adopts a PLA staple fiber content of 25-30 wt% to enhance the interfacial bonding force with the plant fiber and improve the fiber interweaving density and tear strength.

[0044] By introducing 1-2 wt% of phosphorus-based flame retardants (such as hexachlorocyclotriphosphazene) into the laminating liquid of paper products, the material is given UL94 V-0 flame retardant properties, significantly improving the flame retardant properties of special paper materials.

[0045] By introducing 2-3 wt% nanocellulose crystals (CNC) into the paper product coating solution, the puncture resistance of the coating can be effectively improved by utilizing hydrogen bonds and intermolecular interactions between surface groups.

[0046] During the curing process, the traditional one-step heating and cooling treatment method is abandoned, and gradient heating, gradient curing and step-by-step cooling methods are adopted, which is beneficial to the ductility and uniformity of the specialty paper coating and ultimately improves the service life of the specialty paper.

[0047] The above description is only a specific embodiment of the present invention, but the structural features of the present invention are not limited thereto. Any changes or modifications made by any technician in this field within the scope of the present invention are included in the patent scope of the present invention.

Claims

1. A method for preparing a multifunctional specialty paper coating, characterized in that The steps are as follows: The first step is to make the base paper. The pulp fiber is selected as bamboo pulp / hemp pulp composite fiber, and PLA short fiber is added to it for modification. After thorough mixing, it is prepared into paper. After the paper is rolled, it does not need to be dried for use. Step 2: Prepare the coating solution, using PLA-PBAT copolymer as the film-forming substance, introducing 2-3wt% nanocellulose crystals to enhance the coating's puncture resistance through hydrogen bonding; and adding a mixture of ethanol and water as a diluent. Step 3: Add biodegradable polyester and hexamethylene diisocyanate to the coating solution I and mix thoroughly. The ratio of PBAT-based polyester and hexamethylene diisocyanate is 1:1 to 1:

2. A certain amount of trimethylolpropane is added to obtain coating solution II. Fluoro-modified polysiloxane is introduced. The addition amount of fluorine-modified polysiloxane is 3wt%, so that the coating layer can withstand the alternating temperature from -40°C to 200°C. Step 4: Add 4-6 wt% of needle-shaped calcium carbonate to the coating solution II; add 0.3 wt% of polyether-modified siloxane leveling agent and 0.5 wt% of graphene at the same time; The leaching solution III is obtained, and then the leaching solution is magnetically stirred for 30 minutes; Step 5: Laminating treatment: preheat the paper in the first step to 60-80℃, then use a shower to spray the laminating liquid III. The amount of laminating liquid III used is 20-30g per square meter of paper. Step 6: Drying treatment: Place the paper after the spraying treatment in the third step in a drying oven for drying at a temperature of 50-80°C; Step 7: Curing treatment: send the dried paper to the UV curing room to cross-link and cure the cross-linked substances in the coating solution.

2. The method for preparing a multifunctional specialty paper coating according to claim 1, wherein: The diameter of the PLA staple fiber is ≤0.5 mm, and the PLA staple fiber content is 25-30 wt%.

3. The method for preparing a multifunctional specialty paper coating according to claim 1, wherein: The PLA-PBAT copolymer ratio is 3:7, which has both high ductility and rapid degradation performance. High ductility means elongation at break is greater than 300%; the ratio of ethanol to water is 1:1 to 1:

3.

4. The method for preparing a multifunctional specialty paper coating according to claim 1, wherein: Adding 1-2wt% phosphorus flame retardant gives the material UL94 V-0 flame retardant properties; mixing 0.5wt% nano zinc oxide particles to achieve antibacterial function.

5. The method for preparing a multifunctional specialty paper coating according to claim 1, wherein: The addition of polyester PET powder provides high mechanical strength and chemical resistance, and is used for special packaging requiring high barrier properties and durability.

6. The method for preparing a multifunctional specialty paper coating according to claim 1, wherein: The curing process was set up with three-zone gradient heating: 120℃→140℃→130℃, with a dwell time of 15 seconds in each zone to avoid thermal deformation of the PLA fiber; the radiation distance was adjusted to 12±1cm, and the heat flux was stabilized at 900~1100W / m²5; a staged cooling method was adopted: 120℃→80℃ air cooling→50℃ water mist cooling, and the cooling rate was controlled to be ≤5℃ / second.

7. The method for preparing a multifunctional specialty paper coating according to claim 1, wherein: A dual-frequency coupling mode with a power of 100kHz / 300kHz is adopted to achieve gradient curing of the coating layer, with the surface curing degree >95% and the bottom layer >85%; 0.4~0.6MPa dynamic pressure is applied simultaneously, and the pressure holding time is shortened to 6~8 seconds.

8. The method for preparing a multifunctional specialty paper coating according to claim 1, wherein: The mass ratio of bamboo pulp / hemp pulp composite fiber is 6:4.

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