High-barrier direct plating paper and preparation method thereof

Abstract

The invention discloses high-barrier direct plating paper and a preparation method thereof, and relates to the technical field of packaging materials. The preparation method of the high-barrier direct plating paper comprises the following steps: coating the surface of paper with a priming coat to obtain a pretreated base material; coating the surface of the pretreated coating with a moisture-resistant and oxygen-resistant coating to obtain a base material with the moisture-resistant and oxygen-resistant coating on the surface; and aluminizing the surface of the moisture-resistant and oxygen-resistant coating to obtain the high-barrier direct-plated paper. The bottom coating is prepared from the following raw materials: montmorillonite modified polyvinyl alcohol, an ethylene-vinyl alcohol copolymer, a curing agent, a cross-linking agent, a tackifier, a dispersing agent and a wetting agent; the paper is treated before aluminum plating, so that the barrier property of the direct plating paper to water vapor, oxygen and grease is improved, the adhesive force between the paper and an aluminum plating layer and the large smoothness of the aluminum plating layer are improved, and the integrity of the aluminum plating layer is ensured.

Description

Technical Field

[0001] The present invention relates to the technical field of packaging materials, and in particular to a high-barrier direct-plated paper and a preparation method thereof. Background Art

[0002] With the development of science and technology and the improvement of people's living standards, people pay more and more attention to the sustainable development of resources and the protection of the living environment, and require green production and green consumption. Food packaging paper is a packaging material with paper and paperboard as the main raw materials. It can effectively prevent food from being damaged by external oxygen, water vapor, potential harmful migrants, grease and other substances during storage and transportation, and play a role in delaying food deterioration and ensuring food quality and safety. Paper materials are interwoven with fibers, and the hydrophilicity and capillary action of the fibers themselves make the paper absorbent. The loose and porous structure also aggravates the penetration of oil and grease. Therefore, untreated paper does not have any water and oil barrier ability. In order to meet the needs of high barrier and functional transformation of food packaging paper, direct plating paper (also known as direct vacuum aluminum-plated paper) is mainly composed of base paper, aluminum layer and coating. It is to improve the surface flatness and brightness of the paper by pre-coating the paper surface, and then place the paper in a vacuum aluminum plating machine for direct aluminum plating on its surface to obtain a paper material with a strong metallic feel. Direct-plated paper has the advantages of good gloss and smoothness, good flexibility, beautiful appearance and environmental protection, as well as good printing and machining properties. Therefore, it is widely used in the packaging of products such as tobacco, alcohol, tea, food, and cosmetics.

[0003] However, in order to enhance its barrier properties (such as waterproof, gas-proof, oil-resistant, etc.), it is necessary to optimize the formulation and preparation process of its surface coating. At present, common paper barrier coating materials are mainly divided into two categories. One category is natural biopolymers, such as cellulose, starch, chitosan and sodium alginate, which form dense films through the molecular structure characteristics of the polymer itself, thereby playing a barrier role. However, these materials are mostly hydrophilic substances, and have the disadvantages of poor water resistance, strong crystallinity, high brittleness and poor melt stability, which are not easy to achieve industrial-scale production and application; the other category is artificially synthesized polymers, such as polyvinyl alcohol (PVA), polylactic acid (PLA), polyhydroxybutyrate (PHB), acrylate copolymers, etc. Among them, polyvinyl alcohol has regular molecular chain stacking, high crystallinity, good film-forming properties, and excellent oxygen barrier properties, which are suitable for flexible packaging coating. However, due to the presence of hydrophilic hydroxyl groups in polyvinyl alcohol, polyvinyl alcohol will absorb environmental moisture when exposed to humid conditions, and water molecules will enter the interior of the molecule to swell and dissolve the hydrogen bonds between molecules, greatly destroying its barrier ability. Summary of the invention

[0004] The purpose of the present invention is to provide a high-barrier direct-plated paper and a preparation method thereof to solve the following technical problems: Hydrophilic polyvinyl alcohol is added as a base material in existing barrier coatings. Polyvinyl alcohol absorbs environmental moisture in a humid environment, resulting in a significant reduction in the barrier capacity of the barrier coating.

[0005] The purpose of the present invention can be achieved through the following technical solutions: A method for preparing high-barrier direct-plated paper comprises the following steps: S1: coating a primer layer and a moisture and oxygen barrier layer on the surface of paper in sequence to obtain a pretreated substrate; S2: Aluminum is plated on the surface of the moisture and oxygen barrier layer of the pre-treated substrate to obtain high barrier direct-plated paper; The primer layer comprises the following raw materials in parts by weight: 75-85% of montmorillonite-modified polyvinyl alcohol, 10-15% of ethylene-vinyl alcohol copolymer, 1-3% of curing agent, 2-4% of cross-linking agent, 2-4% of tackifier, 0.1-0.3% of dispersant, and 0.3-0.5% of wetting agent; The preparation method of montmorillonite-modified polyvinyl alcohol comprises the following steps: A1: Add acidified montmorillonite, anhydrous ethanol, deionized water and N,N-diethyl-3-aminopropyltrimethoxysilane into a reaction kettle and disperse them evenly. Control the temperature at 60-80°C, keep the temperature for 2-4 hours, wash with water, and dry to obtain organic montmorillonite. A2: In a nitrogen atmosphere, add the organic montmorillonite and methanol into a reaction kettle and disperse them evenly. Control the temperature at 45-55°C, add epichlorohydrin, keep the temperature for 3-6 hours, cool to room temperature, filter, wash and dry to obtain modified montmorillonite. A3: Add polyvinyl alcohol and dimethyl sulfoxide into a reaction kettle and disperse them evenly. Control the temperature at 85-95°C. Stir and dissolve. Control the temperature at 55-65°C. Add modified montmorillonite and sodium hydroxide solution. Keep the temperature for 3-6 hours. Filter, wash and dry to obtain montmorillonite-modified polyvinyl alcohol.

[0006] As a further solution of the present invention: the addition ratio of acidified montmorillonite, anhydrous ethanol, deionized water, and N,N-diethyl-3-aminopropyltrimethoxysilane in A1 is 10 g: 20-40 mL: 80-160 mL: 4-8 g.

[0007] As a further solution of the present invention: the addition ratio of the organized montmorillonite, methanol and epichlorohydrin in A2 is 10g:50-100mL:1.5-3g.

[0008] As a further solution of the present invention: the sodium hydroxide solution in A3 is a 10-15wt% sodium hydroxide solution; the addition ratio of polyvinyl alcohol, dimethyl sulfoxide, modified montmorillonite, and sodium hydroxide solution is 10g:100-150mL:1-2g:10-20mL.

[0009] As a further solution of the present invention: the acidified montmorillonite is obtained by washing the montmorillonite with water and then treating it with hydrochloric acid.

[0010] As a further solution of the present invention: the curing agent is a polyamide-epoxy resin copolymer; the crosslinking agent is a melamine formaldehyde resin; the tackifier is carboxymethyl cellulose; the dispersant is a polyacrylate ammonium salt dispersant; and the wetting agent is sodium dodecyl sulfate.

[0011] As a further embodiment of the present invention, the molar fraction of ethylene in the ethylene-vinyl alcohol copolymer is 20-40%, and the molar fraction of vinyl alcohol is 60-80%.

[0012] As a further solution of the present invention: the specific method of aluminum plating in S2 is: physical vapor deposition aluminum plating under a vacuum environment, and the aluminum plating thickness is 200-400Å.

[0013] As a further embodiment of the present invention, the water vapor permeability of the moisture and oxygen barrier layer is 0.5-1.5 g / m 2 ˙24h, oxygen permeability is 0.8-1.2 cm 3 / (m 2 ˙24h˙0.1MPa).

[0014] As a further solution of the present invention: the primer layer is obtained by dry molding method, and the specific steps of the dry molding method are: applying a pretreatment coating on the surface of the film carrier, compounding the film carrier with paper, and then peeling the film carrier and the paper and drying them to form a primer layer on the surface of the paper; the film carrier is BOPP or PET film.

[0015] As a further solution of the present invention: the coating dry weight of the pretreatment coating is 1.5-2.5g / m 2 , the solid content of the pretreatment coating is 35-50%.

[0016] A method for preparing high-barrier direct-plated paper, prepared by any one of the above preparation methods.

[0017] Beneficial effects of the present invention: (1) The present application uses hydrochloric acid to acidify montmorillonite to obtain acidified montmorillonite; and uses N,N-diethyl-3-aminopropyltrimethoxysilane to organically treat the acidified montmorillonite. The alkoxy group of N,N-diethyl-3-aminopropyltrimethoxysilane is hydrolyzed in a water-alcohol solution to generate silanol, which then reacts with the silanol group on the end face of the acidic montmorillonite and is dehydrated at high temperature to obtain an organic montmorillonite. The main chain of the organic montmorillonite contains Si-O-Si bonds, which effectively reduces the water absorption and swelling characteristics of the montmorillonite; the present application then uses epichlorohydrin to react with the tertiary amine between the organic montmorillonite layers to obtain a modified montmorillonite. The modified montmorillonite prepared in the present application not only has antibacterial groups and epoxy groups, but also further increases the interlayer distance of the montmorillonite and reduces the polarity of the montmorillonite through modification with epichlorohydrin; the present application utilizes the epoxy groups of the modified montmorillonite to react with the hydroxyl groups of polyvinyl alcohol to obtain montmorillonite-modified polyvinyl alcohol; the present application cross-links the polyvinyl alcohol and the modified montmorillonite, and introduces montmorillonite to effectively inhibit the swelling of the coating after contacting water, thereby improving the density of the coating; the addition of montmorillonite makes the molecular diffusion channel more tortuous, prolongs the diffusion distance of the molecules per unit time, and the permeation flux of the coating is reduced accordingly.

[0018] The present application utilizes montmorillonite-modified polyvinyl alcohol as a base material, and polyvinyl alcohol has excellent oxygen barrier properties; the modification of montmorillonite increases the montmorillonite interlayer spacing, which helps the penetration of polyvinyl alcohol molecular chains and forms a tighter intermolecular force, and the montmorillonite fills the micro-gaps in the coating to reduce the air permeability; after polyvinyl alcohol is treated with modified montmorillonite, the oxygen permeability and water vapor permeability of the coating are significantly reduced, and the mechanical properties, thermal stability and surface flatness are significantly improved, effectively improving the barrier properties of direct-plated paper and the flatness of subsequent aluminum plating.

[0019] (2) The present application sets a primer layer and a moisture and oxygen barrier layer between the paper and the aluminum-plated layer, which effectively improves the barrier properties of the material. The prepared direct-plated paper has good barrier properties against water vapor, oxygen and grease, and can extend the shelf life of the contents. The present application uses the prepared montmorillonite-modified polyvinyl alcohol as the base material of the primer layer to effectively improve the adhesion and smoothness of the coating and ensure the integrity of the subsequent aluminum-plated layer. The direct-plated paper prepared by the present application can be more widely used in food, medicine and industrial packaging, and meet the demand for high barrier materials.

[0020] (3) This application utilizes the synergistic effect of montmorillonite-modified polyvinyl alcohol and EVOH (ethylene-vinyl alcohol copolymer) and polyamide-epoxy resin copolymer to give the base coating excellent gas barrier properties, water vapor barrier properties and moisture resistance. This application adds melamine formaldehyde resin as a cross-linking agent to improve the mechanical strength and moisture resistance of the coating; adds carboxymethyl cellulose as a tackifier to improve the adhesion of the coating; adds polyacrylate ammonium salt as a dispersant to ensure uniform dispersion of the barrier material; and adds sodium dodecyl sulfate as a wetting agent to enhance the uniformity of the coating coating. DETAILED DESCRIPTION

[0021] The following will be described clearly and completely in conjunction with the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] Example 1 The preparation method of montmorillonite-modified polyvinyl alcohol comprises the following steps: A1: Disperse 10 g of sodium montmorillonite in 50 mL of deionized water, wash by centrifugation, add 10 mL of 1 mol / L hydrochloric acid aqueous solution to acidify, and wash with water to obtain acidified montmorillonite; A2: Add 10g of acidified montmorillonite, 20mL of anhydrous ethanol, 80mL of deionized water, and 4g of N,N-diethyl-3-aminopropyltrimethoxysilane (CAS: 41051-80-3) into a reaction kettle and disperse them evenly. Control the temperature at 60°C, keep the reaction warm for 2h, wash with water, and dry to obtain organic montmorillonite. A3: In a nitrogen atmosphere, 10 g of organic montmorillonite and 50 mL of methanol were added to a reactor and dispersed evenly. The temperature was controlled at 45 °C, 1.5 g of epichlorohydrin was added, and the reaction was kept warm for 3 h. The temperature was cooled to room temperature, filtered, washed, and dried to obtain modified montmorillonite. A4: Add 10g polyvinyl alcohol (alcoholysis degree 88%) and 100mL dimethyl sulfoxide into a reactor and disperse them evenly. Control the temperature at 85℃ and stir to dissolve. Control the temperature at 55℃ and add 1g modified montmorillonite and 10mL 10wt% sodium hydroxide solution. Keep the temperature and react for 3h. Filter, wash and dry to obtain montmorillonite-modified polyvinyl alcohol.

[0023] Example 2 The preparation method of montmorillonite-modified polyvinyl alcohol comprises the following steps: A1: Disperse 10 g of sodium montmorillonite in 50 mL of deionized water, wash by centrifugation, add 10 mL of 1 mol / L hydrochloric acid aqueous solution to acidify, and wash with water to obtain acidified montmorillonite; A2: Add 10g of acidified montmorillonite, 30mL of anhydrous ethanol, 120mL of deionized water, and 6g of N,N-diethyl-3-aminopropyltrimethoxysilane (CAS: 41051-80-3) into a reaction kettle and disperse them evenly. Control the temperature at 70°C, keep the reaction warm for 3h, wash with water, and dry to obtain organic montmorillonite. A3: In a nitrogen atmosphere, 10 g of organic montmorillonite and 70 mL of methanol were added to a reactor and dispersed evenly. The temperature was controlled at 50 °C, 2 g of epichlorohydrin was added, and the reaction was kept warm for 4 h. The temperature was cooled to room temperature, filtered, washed, and dried to obtain modified montmorillonite. A4: Add 10g polyvinyl alcohol (alcoholysis degree 88%) and 120mL dimethyl sulfoxide into a reactor and disperse them evenly. Control the temperature at 90℃ and stir to dissolve. Control the temperature at 60℃ and add 1.5g modified montmorillonite and 15mL 10wt% sodium hydroxide solution. Keep the temperature and react for 4h. Filter, wash and dry to obtain montmorillonite-modified polyvinyl alcohol.

[0024] Example 3 The preparation method of montmorillonite-modified polyvinyl alcohol comprises the following steps: A1: Disperse 10 g of sodium montmorillonite in 50 mL of deionized water, wash by centrifugation, add 10 mL of 1 mol / L hydrochloric acid aqueous solution to acidify, and wash with water to obtain acidified montmorillonite; A2: Add 10g of acidified montmorillonite, 40mL of anhydrous ethanol, 160mL of deionized water, and 8g of N,N-diethyl-3-aminopropyltrimethoxysilane (CAS: 41051-80-3) into a reaction kettle and disperse them evenly. Control the temperature at 80°C, keep the reaction for 4h, wash with water, and dry to obtain organic montmorillonite. A3: In a nitrogen atmosphere, 10 g of organic montmorillonite and 100 mL of methanol were added to a reactor and dispersed evenly. The temperature was controlled at 55 °C, 3 g of epichlorohydrin was added, and the reaction was kept warm for 6 h. The temperature was cooled to room temperature, filtered, washed, and dried to obtain modified montmorillonite. A4: Add 10g polyvinyl alcohol (alcoholysis degree 88%) and 150mL dimethyl sulfoxide into a reactor and disperse them evenly. Control the temperature at 95℃ and stir to dissolve. Control the temperature at 65℃ and add 2g modified montmorillonite and 20mL 10wt% sodium hydroxide solution. Keep the temperature and react for 6h. Filter, wash and dry to obtain montmorillonite-modified polyvinyl alcohol.

[0025] Example 4 The preparation method of melamine formaldehyde resin comprises the following steps: Add 60 mL of 37 wt% formaldehyde aqueous solution and 0.15 g of urotropine (also known as hexamethylenetetramine) into a reaction bottle and disperse them evenly. Add 35 g of melamine, control the temperature to 80°C, stir to dissolve, and keep warm to react until the precipitation ratio reaches 2:2. Add triethanolamine to adjust the pH to 8 to obtain melamine formaldehyde resin.

[0026] Example 5 A method for preparing high-barrier direct-plated paper comprises the following steps: S1: 78.1 g of montmorillonite-modified polyvinyl alcohol prepared in Example 1, 12 g of ethylene-vinyl alcohol copolymer (ethylene mole fraction 32%, density 1.19 g / cm 3), 3g polyamide epoxy curing agent NP-650, 3g melamine formaldehyde resin prepared in Example 4, 3.2g carboxymethyl cellulose, 0.3g polyacrylate ammonium salt dispersant, 0.4g sodium dodecyl sulfate, and deionized water were blended to obtain a pre-treated coating with a solid content of 40%; the pre-treated coating was applied on the surface of the PET film and then mixed with paper (liner paper 60g / m 2 ) Composite, pre-treatment coating dry weight 2g / m 2 , then the film carrier and the paper are peeled off and dried to form a primer layer on the surface of the paper; S2: A moisture barrier and oxygen barrier layer is applied on the surface of the primer layer. The moisture barrier and oxygen barrier layer is TAKELAC WPB-341 manufactured by Mitsui Chemicals. The water vapor permeability of the moisture barrier and oxygen barrier layer is 1 g / m 2 ˙24h, oxygen permeability is 1cm 3 / (m 2 ˙24h˙0.1MPa) to obtain the pretreated substrate; S3: The surface of the moisture barrier and oxygen barrier layer of the pretreated substrate is aluminum-plated by physical vapor deposition under vacuum conditions with a thickness of 200Å to obtain high-barrier direct-plated paper.

[0027] Example 6 A method for preparing high-barrier direct-plated paper comprises the following steps: S1: 78.1 g of montmorillonite-modified polyvinyl alcohol prepared in Example 2, 12 g of ethylene-vinyl alcohol copolymer (ethylene mole fraction 32%, density 1.19 g / cm 3 ), 3g polyamide epoxy curing agent NP-650, 3g melamine formaldehyde resin prepared in Example 4, 3.2g carboxymethyl cellulose, 0.3g polyacrylate ammonium salt dispersant, 0.4g sodium dodecyl sulfate, and deionized water were blended to obtain a pre-treated coating with a solid content of 40%; the pre-treated coating was applied on the surface of the PET film and then mixed with paper (liner paper 60g / m 2 ) Composite, pre-treatment coating dry weight 2g / m 2 , then the film carrier and the paper are peeled off and dried to form a primer layer on the surface of the paper; S2: A moisture barrier and oxygen barrier layer is applied on the surface of the primer layer. The moisture barrier and oxygen barrier layer is TAKELAC WPB-341 manufactured by Mitsui Chemicals. The water vapor permeability of the moisture barrier and oxygen barrier layer is 1 g / m 2 ˙24h, oxygen permeability is 1cm 3 / (m 2 ˙24h˙0.1MPa) to obtain the pretreated substrate; S3: The surface of the moisture barrier and oxygen barrier layer of the pretreated substrate is aluminum-plated by physical vapor deposition under vacuum conditions with a thickness of 200Å to obtain high-barrier direct-plated paper.

[0028] Example 7 A method for preparing high-barrier direct-plated paper comprises the following steps: S1: 78.1 g of montmorillonite-modified polyvinyl alcohol prepared in Example 3, 12 g of ethylene-vinyl alcohol copolymer (ethylene mole fraction 32%, density 1.19 g / cm 3 ), 3g polyamide epoxy curing agent NP-650, 3g melamine formaldehyde resin prepared in Example 4, 3.2g carboxymethyl cellulose, 0.3g polyacrylate ammonium salt dispersant, 0.4g sodium dodecyl sulfate, and deionized water were blended to obtain a pre-treated coating with a solid content of 40%; the pre-treated coating was applied on the surface of the PET film and then mixed with paper (liner paper 60g / m 2 ) Composite, pre-treatment coating dry weight 2g / m 2 , then the film carrier and the paper are peeled off and dried to form a primer layer on the surface of the paper; S2: A moisture barrier and oxygen barrier layer is applied on the surface of the primer layer. The moisture barrier and oxygen barrier layer is TAKELAC WPB-341 manufactured by Mitsui Chemicals. The water vapor permeability of the moisture barrier and oxygen barrier layer is 1 g / m 2 ˙24h, oxygen permeability is 1cm 3 / (m 2 ˙24h˙0.1MPa) to obtain the pretreated substrate; S3: The surface of the moisture barrier and oxygen barrier layer of the pretreated substrate is aluminum-plated by physical vapor deposition under vacuum conditions with a thickness of 200Å to obtain high-barrier direct-plated paper.

[0029] Comparative Example 1 The preparation method of montmorillonite-modified polyvinyl alcohol comprises the following steps: A1: Disperse 10 g of sodium montmorillonite in 50 mL of deionized water, wash by centrifugation, add 10 mL of 1 mol / L hydrochloric acid aqueous solution to acidify, and wash with water to obtain acidified montmorillonite; A2: 10 g of acidified montmorillonite, 20 mL of anhydrous ethanol, 80 mL of deionized water, and 4 g of γ-glycidyloxypropyltrimethoxysilane were added to a reaction kettle and dispersed evenly. The temperature was controlled at 60°C, and the reaction was kept warm for 2 h. The mixture was washed with water and dried to obtain an organic montmorillonite. A3: Add 10g polyvinyl alcohol (alcoholysis degree 88%) and 100mL dimethyl sulfoxide into a reactor and disperse them evenly. Control the temperature at 85℃ and stir to dissolve. Control the temperature at 55℃ and add 1g organic montmorillonite and 10mL 10wt% sodium hydroxide solution. Keep the temperature and react for 3h. Filter, wash and dry to obtain montmorillonite-modified polyvinyl alcohol.

[0030] Comparative Example 2 The preparation method of montmorillonite-modified polyvinyl alcohol comprises the following steps: A1: Add 10g montmorillonite, 20mL anhydrous ethanol, 80mL deionized water, and 4g N,N-diethyl-3-aminopropyltrimethoxysilane (CAS: 41051-80-3) into a reaction kettle and disperse evenly. Control the temperature at 60℃, keep the reaction for 2h, wash with water, and dry to obtain organic montmorillonite. A2: In a nitrogen atmosphere, 10 g of organic montmorillonite and 50 mL of methanol were added to a reactor and dispersed evenly. The temperature was controlled at 45 °C, 1.5 g of epichlorohydrin was added, and the reaction was kept warm for 3 h. The temperature was cooled to room temperature, filtered, washed, and dried to obtain modified montmorillonite. A3: Add 10g polyvinyl alcohol (alcoholysis degree 88%) and 100mL dimethyl sulfoxide into a reactor and disperse them evenly. Control the temperature at 85℃ and stir to dissolve. Control the temperature at 55℃ and add 1g modified montmorillonite and 10mL 10wt% sodium hydroxide solution. Keep the temperature and react for 3h. Filter, wash and dry to obtain montmorillonite-modified polyvinyl alcohol.

[0031] Comparative Example 3 The preparation method of montmorillonite-modified polyvinyl alcohol comprises the following steps: A1: Disperse 10 g of sodium montmorillonite in 50 mL of deionized water, wash by centrifugation, add 10 mL of 1 mol / L hydrochloric acid aqueous solution to acidify, and wash with water to obtain acidified montmorillonite; A2: Add 10g of acidified montmorillonite, 20mL of anhydrous ethanol, 80mL of deionized water, and 4g of N,N-diethyl-3-aminopropyltrimethoxysilane (CAS: 41051-80-3) into a reaction kettle and disperse them evenly. Control the temperature at 60°C, keep the reaction warm for 2h, wash with water, and dry to obtain organic montmorillonite. A3: Add 10g polyvinyl alcohol (alcoholysis degree 88%) and 100mL dimethyl sulfoxide into a reactor and disperse them evenly. Control the temperature at 85℃ and stir to dissolve. Control the temperature at 55℃ and add 1g organic montmorillonite and 10mL 10wt% sodium hydroxide solution. Keep the temperature and react for 3h. Filter, wash and dry to obtain montmorillonite-modified polyvinyl alcohol.

[0032] Comparative Example 4 Compared with Example 6, in Comparative Example 4, only the montmorillonite-modified polyvinyl alcohol prepared in Example 2 added in Example 6 is replaced by the montmorillonite-modified polyvinyl alcohol prepared in Comparative Example 1 in an equal amount, and the other components and preparation method are completely the same as those in Example 6.

[0033] Comparative Example 5 Compared with Example 6, in Comparative Example 5, only the montmorillonite-modified polyvinyl alcohol prepared in Example 2 added in Example 6 is replaced by the montmorillonite-modified polyvinyl alcohol prepared in Comparative Example 2 in an equal amount, and the other components and preparation method are completely the same as those in Example 6.

[0034] Comparative Example 6 Compared with Example 6, Comparative Example 6 only replaces the montmorillonite-modified polyvinyl alcohol prepared in Example 2 added in Example 6 with the montmorillonite-modified polyvinyl alcohol prepared in Comparative Example 3 in an equal amount, and the other components and preparation method are completely the same as those of Example 6.

[0035] Performance Testing (1) Barrier properties: According to BB / T 0030-2019 “Aluminum-coated films for packaging”, the primer layers prepared in Examples 5-7 and Comparative Examples 4-6 were tested using a W3 / 060 water vapor transmission rate tester and a VAC-V1 differential pressure gas permeability tester to measure water vapor transmission rate (WVTR) and oxygen transmission rate (OTR). The test results are shown in Table 1. Table 1: Statistical table of barrier performance test data of Examples 5-7 and Comparative Examples 4-6

[0036] As can be seen from Table 1, the primer layer prepared using the pretreated coating of the present application as raw material has excellent water vapor and oxygen barrier properties, and effectively improves the problem of the existing coating using polyvinyl alcohol as the base material being easily swollen when exposed to water.

[0037] (2) Oil resistance: According to the oil penetration test of Q / HYG 002-2019 "Oil-proof Paper", the oil barrier effect is tested. The test results are shown in Table 2; Table 2: Statistical table of oil resistance test data of Examples 5-7 and Comparative Examples 4-6

[0038] It can be seen from Table 2 that the primer layer prepared in the present application has excellent oil and water resistance.

[0039] (3) Mechanical properties: ① Smoothness: The base coating was tested according to GB / T 456-2002 "Determination of smoothness of paper and paperboard (Buick method)", and the test results are shown in Table 3; ② Interlayer adhesion: The adhesion of the base coating and paper was tested according to the ASTM D3359-02 X-scratch method. The test results are shown in Table 3; ③ Antibacterial property: The antibacterial properties of the primers prepared in Examples 5-7 and Comparative Examples 4-6 against Escherichia coli and Staphylococcus aureus were tested by agar plate diffusion method. The primers were cut into 8 mm discs and sterilized by ultraviolet light. The coating concentration was 1.0×10 8 CFU / mL bacterial suspension was placed at 37°C for 24 h, and the diameter of the inhibition zone was measured. The test results are shown in Table 3; Table 3: Statistical table of physical and chemical performance test data of Examples 5-7 and Comparative Examples 4-6

[0040] The base coating prepared in the present application has good surface smoothness and strong adhesion to paper, which is convenient for subsequent aluminum plating. In addition, the base coating has excellent antibacterial properties. The packaging paper prepared in the present application has water and oil barrier capabilities and antibacterial and fresh-keeping capabilities as food packaging paper.

[0041] The above is a detailed description of an embodiment of the present invention, but the content is only a preferred embodiment of the present invention and cannot be considered to limit the scope of implementation of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the patent coverage of the present invention.

Claims

1. A method for preparing high-barrier direct-plated paper, characterized in that: The steps include: S1: coating a primer layer and a moisture and oxygen barrier layer on the surface of paper in sequence to obtain a pretreated substrate; S2: Aluminum is plated on the surface of the moisture and oxygen barrier layer of the pre-treated substrate to obtain high barrier direct-plated paper; The primer layer comprises the following raw materials in parts by weight: 75-85% montmorillonite-modified polyvinyl alcohol, 10-15% ethylene-vinyl alcohol copolymer, 1-3% curing agent, 2-4% cross-linking agent, 2-4% tackifier, 0.1-0.3% dispersant, and 0.3-0.5% wetting agent; The preparation method of the montmorillonite-modified polyvinyl alcohol comprises the following steps: A1: Add acidified montmorillonite, anhydrous ethanol, deionized water and N,N-diethyl-3-aminopropyltrimethoxysilane into a reaction kettle and disperse them evenly. Control the temperature at 60-80°C, keep the temperature for 2-4 hours, wash with water, and dry to obtain organic montmorillonite. A2: In a nitrogen atmosphere, add the organic montmorillonite and methanol into a reaction kettle and disperse them evenly. Control the temperature at 45-55°C, add epichlorohydrin, keep the temperature for 3-6 hours, cool to room temperature, filter, wash and dry to obtain modified montmorillonite. A3: Add polyvinyl alcohol and dimethyl sulfoxide into a reaction kettle and disperse them evenly. Control the temperature at 85-95°C. Stir and dissolve. Control the temperature at 55-65°C. Add modified montmorillonite and sodium hydroxide solution. Keep the temperature for 3-6 hours. Filter, wash and dry to obtain montmorillonite-modified polyvinyl alcohol.

2. The method for preparing high-barrier direct-plated paper according to claim 1, characterized in that: The addition ratio of acidified montmorillonite, anhydrous ethanol, deionized water, and N,N-diethyl-3-aminopropyltrimethoxysilane in A1 is 10 g: 20-40 mL: 80-160 mL: 4-8 g.

3. The method for preparing high-barrier direct-plated paper according to claim 1, characterized in that: The addition ratio of the organized montmorillonite, methanol and epichlorohydrin in A2 is 10g:50-100mL:1.5-3g.

4. The method for preparing high-barrier direct-plated paper according to claim 1, characterized in that: The sodium hydroxide solution in A3 is 10-15wt% sodium hydroxide solution; The addition ratio of polyvinyl alcohol, dimethyl sulfoxide, modified montmorillonite and sodium hydroxide solution is 10g:100-150mL:1-2g:10-20mL.

5. The method for preparing high-barrier direct-plated paper according to claim 1, characterized in that: The curing agent is a polyamide-epoxy resin copolymer; the cross-linking agent is a melamine formaldehyde resin; the tackifier is carboxymethyl cellulose; the dispersant is a polyacrylate ammonium salt dispersant; and the wetting agent is sodium dodecyl sulfate.

6. The method for preparing high-barrier direct-plated paper according to claim 1, characterized in that: The specific method of aluminum plating in S2 is: physical vapor deposition aluminum plating under a vacuum environment, and the aluminum plating thickness is 200-400Å.

7. The method for preparing high-barrier direct-plated paper according to claim 1, characterized in that: The water vapor permeability of the moisture and oxygen barrier layer is 0.5-1.5 g / m 2 ˙24h, oxygen permeability is 0.8-1.2 cm 3 / (m 2 ˙24h˙0.1MPa).

8. The method for preparing high-barrier direct-plated paper according to claim 1, characterized in that: The primer layer is obtained by dry molding, and the specific steps of the dry molding are: coating the surface of the film carrier with a pretreatment coating, compounding the film carrier with paper, and then peeling the film carrier and the paper and drying them to form a primer layer on the surface of the paper; the film carrier is a BOPP or PET film.

9. The method for preparing high-barrier direct-plated paper according to claim 8, characterized in that: The dry coating weight of the pretreatment coating is 1.5-2.5g / m 2 , the solid content of the pretreatment coating is 35-50%.

10. A method for preparing high-barrier direct-plated paper, characterized in that: Prepared by the preparation method described in any one of claims 1 to 9.

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