Direct plating paper capable of being coated at high speed as well as preparation method and application of direct plating paper

Abstract

The invention belongs to the technical field of label materials, and discloses direct plating paper capable of being coated at a high speed as well as a preparation method and application thereof. The direct plating paper sequentially comprises a back coating layer, a body paper layer, a bottom coating layer, an aluminum plating layer and a surface coating layer from bottom to top, the bottom coating is formed by drying a water-based paint film, and the water-based paint comprises an alkali-resistant emulsion, a leveling emulsion, a defoaming agent and an alcohol solvent; the alkali-resistant emulsion comprises a monomer, an initiator, an emulsifier, a cross-linking agent and a functional monomer; the leveling emulsion comprises a monomer, an initiator, an emulsifier and a cross-linking agent. High-speed coating can be achieved, the coating speed is larger than or equal to 600 m / min, compared with a traditional coating speed of 120 m / min, the production efficiency is remarkably improved by 5 times or above, the production period can be greatly shortened, and the yield can be greatly increased; meanwhile, the obtained direct plating paper has excellent alkali resistance, high glossiness and good wear resistance, and meets the application requirements of beer labels.

Description

Technical Field

[0001] The invention belongs to the technical field of label materials, and in particular relates to a direct-plated paper capable of high-speed coating, and a preparation method and application thereof. Background Art

[0002] At present, the more common packaging materials on the market include aluminum foil, paper-plastic composite packaging film, aseptic packaging materials, aluminum foil and direct-plated paper. Direct-plated paper is made by performing multi-layer coating treatment on the base paper and plating aluminum on a specific layer to form direct-plated paper with metallic luster and barrier properties.

[0003] In the relevant technologies, the production process of direct-plated paper is relatively mature, but it mainly has problems such as low production efficiency (coating speed is about 120m / min), poor coating uniformity, unstable quality of aluminum coating, poor alkali resistance, etc. As the market's requirements for packaging material performance continue to increase, it is necessary to improve the performance of direct-plated paper while improving production efficiency. Summary of the invention

[0004] The present invention aims to solve at least one of the technical problems existing in the above-mentioned prior art. To this end, the present invention provides a high-speed coated direct-plated paper and a preparation method and application thereof, wherein the direct-plated paper has excellent alkali resistance, high gloss and good wear resistance.

[0005] According to a first aspect of the present invention, there is provided a direct-plated paper, which comprises, from bottom to top, a back coating layer, a base paper layer, a primer layer, an aluminum-plated layer and a top coating layer; the primer layer is formed by drying a water-based paint film, and the water-based paint comprises an alkali-resistant emulsion, a leveling emulsion, a defoaming agent and an alcohol solvent; the alkali-resistant emulsion comprises a monomer, an initiator, an emulsifier, a cross-linking agent and a functional monomer; the leveling emulsion comprises a monomer, an initiator, an emulsifier and a cross-linking agent; the monomer comprises at least one of methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, styrene and isooctyl acrylate, and the functional monomer comprises at least one of hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxypropyl acrylate and hydroxyethyl acrylate.

[0006] In some embodiments of the present invention, the water-based coating comprises, by weight percentage, 50-80% of alkali-resistant emulsion, 10-30% of leveling emulsion, 0.2-0.8% of defoaming agent and 1-5% of alcohol solvent.

[0007] Specifically, the alkali-resistant emulsion selected in the present invention can enhance the resistance of paper to alkaline environment, so that it can still maintain good physical and chemical properties under alkaline conditions. By interacting with paper fibers, the alkali-resistant emulsion can strengthen the bonding force between fibers, thereby improving the overall strength of the paper. The alkali-resistant emulsion helps to protect the paper from corrosion by alkaline substances, thereby extending its service life. Paper treated with the alkali-resistant emulsion can better absorb ink during the printing process, thereby improving the quality of printed products.

[0008] Specifically, the leveling emulsion selected in the present invention can reduce the tension of the surface of the paper coating, making it easier to form a flat and smooth coating. During the paper coating process, the leveling emulsion helps to reduce the generation of defects such as bubbles and orange peel, improve the quality of the coating, increase the gloss of the paper, and increase the hardness of its surface, enhance the resistance of the paper coating to moisture and scratches, thereby increasing its service life.

[0009] Specifically, if the addition ratio of defoaming agent is too high, it will cause emulsification, stratification or gelation of the coating, so that the foam in the coating is overly suppressed, resulting in certain properties of the coating (such as leveling) being affected; if the addition ratio is insufficient, the expected defoaming effect cannot be achieved, and there will still be a lot of foam in the coating, affecting the quality and appearance of the coating, causing defects such as pinholes and bubbles to appear on the coating surface, reducing the density and aesthetics of the coating.

[0010] Specifically, alcohol solvents can reduce the surface tension of foam, destroy the stability of foam, and cause the foam to burst quickly. In the paper coating process, alcohol defoamers can effectively control the generation of foam and improve production efficiency. They also have a plasticizing effect and can increase the flexibility and plasticity of paper, which helps to improve the folding performance and tear resistance of paper.

[0011] In some embodiments of the present invention, the water-based paint further comprises a preservative and water, wherein the preservative accounts for 0.1-0.5% of the weight of the water-based paint, and the water accounts for 20-40% of the weight of the water-based paint.

[0012] Specifically, the preservative added in the present invention can destroy the cell structure of microorganisms or inhibit their metabolic activities, thereby effectively inhibiting the growth and reproduction of microorganisms and extending the shelf life of the coating; adding water to the coating can effectively reduce its viscosity, making the coating smoother during the construction process, reducing brush marks and roller marks, thereby obtaining a smoother and more uniform coating effect, reducing defects such as bubbles and pinholes in the coating, and improving the overall quality of the coating. An appropriate amount of water can reduce the hardness of the coating, improve the flexibility of the coating, reduce costs, etc., but excessive addition of water may cause the coating's scrub resistance, stain resistance, weather resistance, hiding power, coating effect and other performance to decrease.

[0013] In some embodiments of the present invention, the preservative includes at least one of kasonite, BIT, benzoic acid and its salts, and sulfite preservatives.

[0014] In some embodiments of the present invention, in the alkali-resistant emulsion, the monomer accounts for 35-45% of the weight of the alkali-resistant emulsion, the initiator accounts for 0.1-1% of the weight of the monomer, the emulsifier accounts for 0.5-2% of the weight of the monomer, the cross-linking agent accounts for 0.1-1% of the weight of the monomer, and the functional monomer accounts for 0.5-5% of the weight of the monomer.

[0015] In some embodiments of the present invention, in the leveling emulsion, the monomer accounts for 20-30% of the weight of the leveling emulsion, the initiator accounts for 0.1-1% of the weight of the monomer, the emulsifier accounts for 0.5-2% of the weight of the monomer, and the crosslinker accounts for 0.1-1% of the weight of the monomer.

[0016] In some embodiments of the present invention, the defoaming agent includes at least one of a mineral oil defoaming agent, a silicone defoaming agent, a polyether defoaming agent and a surfactant defoaming agent.

[0017] In some embodiments of the present invention, the alcohol solvent includes at least one of methanol, ethanol, isopropanol and butanol.

[0018] In some embodiments of the present invention, the initiator includes at least one of ammonium persulfate, potassium persulfate and benzoyl peroxide.

[0019] In some embodiments of the present invention, the emulsifier includes at least one of alkyl polyoxyethylene ether, fatty alcohol polyoxyethylene ether and allyloxy hydroxypropyl sulfonate.

[0020] In some embodiments of the present invention, the cross-linking agent includes at least one of ethylene glycol dimethacrylate and glycidyl methacrylate.

[0021] In some embodiments of the present invention, the solid content of the water-based coating is 32-38%, and the viscosity (coating 4 cups) is 13-17s. If the viscosity of the water-based coating of the present invention is too high, it is difficult to spread evenly during the coating process, resulting in inconsistent coating thickness, which in turn affects the flatness of the paper surface, resulting in poor gloss, spots, stripes and other quality problems, affecting the appearance and quality of the product; too low viscosity will directly affect the thickness and uniformity of the coating, thereby reducing the strength, gloss and durability of the coating.

[0022] A second aspect of the present invention provides a method for preparing the direct-plated paper according to the first aspect of the present invention, comprising the following steps:

[0023] S1, coating the water-based coating on the surface of the base paper, and obtaining a primer layer after the water-based coating is dried;

[0024] S2, aluminum plating is performed on the surface of the primer layer to obtain an aluminum plating layer;

[0025] S3, applying a topcoat on the surface of the aluminum-plated layer, and obtaining a topcoat after drying;

[0026] S4, performing back coating on the back side of the base paper to obtain a back coating layer, thereby producing the direct-plated paper.

[0027] Specifically, the base paper of the present invention is selected from 35-120 g / m 2 Wet-strength paper base material, as the base layer of paper, paper moisture content: 4.5±0.5%, curling time: ≥15s, smoothness (front) ≥900s, Cobb60" (back) 17±3g / m 2 , wet tensile strength (longitudinal) ≥12N / 15mm, wet tensile strength (transverse) ≥9N / 15mm; if the wet tensile strength is too low, paper breakage is likely to occur during processing.

[0028] In some embodiments of the present invention, the method for preparing the water-based coating comprises the following steps:

[0029] The alkali-resistant emulsion, the leveling emulsion, the defoamer and the alcohol solvent are mixed to obtain the water-washable coating.

[0030] In some embodiments of the present invention, the method for preparing the alkali-resistant emulsion comprises the following steps:

[0031] S1, pre-emulsifying a portion of the emulsifier, the monomer, the functional monomer and the cross-linking agent to obtain a pre-emulsified liquid;

[0032] S2, mix water and another part of the emulsifier, heat to 75-90°C, stir until completely dissolved, then drop the pre-emulsified liquid of step S1, and simultaneously drop the initiator, the dropping time is 2-2.5h, and keep warm for 20-40min after the dropping is completed to obtain an alkali-resistant emulsion.

[0033] In some embodiments of the present invention, the method for preparing the leveling emulsion comprises the following steps:

[0034] S1, pre-emulsifying a portion of the emulsifier, the monomer and the cross-linking agent to obtain a pre-emulsified liquid;

[0035] S2, mix water and another part of the emulsifier, heat to 75-90°C, stir until completely dissolved, then drop the pre-emulsified liquid of step S1, and at the same time drop the initiator, the dropping time is 1-1.5h, and keep warm for 20-40min after the dropping is completed to obtain a leveling emulsion.

[0036] In some embodiments of the present invention, in step S1, the coating method is air knife coating, the coating speed is 600-1000 m / min, and the coating dry glue amount is 0.7-1.5 g / m 2 The drying temperature is 70-120℃. The coating method is air knife coating, which is characterized by the use of advanced automatic control systems, which can achieve precise control of the coating process and monitor the coating quality. Air knife coating can form a coating with uniform thickness and smooth surface, accurately control the distribution of coating on the paper surface and remove excess coating, so that the coating thickness and uniformity error can be very accurately controlled to ≤0.2g / m 2 , high-precision coating not only improves the aesthetics of the product, but also enhances its durability and functionality.

[0037] Specifically, the drying method of the present invention adopts the existing suspension drying technology, so that the paper can maintain a stable and contactless state during the coating process, avoiding possible paper deformation and damage problems. The oven of this technology adopts an upper and lower air outlet design, and the hot air can be evenly blown to the surface and back of the paper to ensure that the coating can evaporate quickly; at the same time, the temperature control system in the oven can accurately adjust the temperature to meet the drying requirements of different types of coatings.

[0038] In some embodiments of the present invention, the coating is a secondary coating, that is, after the first coating and drying, the second coating and drying are repeated.

[0039] In some embodiments of the present invention, after the coating in step S1, the transverse shrinkage of the paper is ≤3mm, the glossiness is ≥50%, and the moisture content of the paper is 2.5-3.5%. Too high a moisture content of the paper will affect the processing quality of the next step of aluminum plating, such as yellowing, coloring, uneven aluminum plating, etc.

[0040] In some embodiments of the present invention, in step S2, the aluminum plating method is vacuum aluminum plating, and the aluminum plating thickness is

[0041] Specifically, the paper coated in step S1 is placed in a vacuum aluminum coating machine, and a vacuum pump is used to evacuate the paper so that the vacuum degree in the coated paper reaches a certain requirement (e.g., 1.3×10 -3 Pa), in a vacuum chamber, heat the evaporation boat to a high temperature (such as 1300-1400℃), so that the high-purity aluminum wire melts and evaporates into gaseous aluminum; the gaseous aluminum dust particles are deposited on the surface of the paper and are restored by refrigeration to form a glossy metal aluminum layer. The thickness of the aluminum coating can be adjusted by controlling the evaporation rate of the aluminum, the movement rate of the paper and the vacuum value of the aluminum coating chamber, which is generally controlled at If the aluminum coating is too thick, it will make the transfer and absorption of ink difficult during the printing process, affecting the printing effect; at the same time, in the subsequent processing, such as cutting, folding, coding, etc., the excessively thick aluminum layer may also increase the difficulty and complexity of the operation. If the thickness of the aluminum coating is too low, its barrier properties and glossiness will not meet the needs of the product, making the product vulnerable to external environmental influences, such as oxidation and deterioration.

[0042] In some embodiments of the present invention, in step S3, the top coating has a solid content of 18-30% and a coating dry weight of 0.8-1.5 g / m 2 The water-based acrylic resin, the drying temperature is 70-90°C.

[0043] In some embodiments of the present invention, the coating speed during top coating is 600-1000 m / min.

[0044] In some embodiments of the present invention, after the surface coating in step S3, the transverse shrinkage of the paper is ≤1 mm, the glossiness is ≥8%, and the water content of the paper is 2.5-4.5%.

[0045] In some embodiments of the present invention, the paper after back coating in step S4 is subjected to moisture regain treatment to ensure that the moisture and flatness of the paper meet the requirements of printing and labeling.

[0046] A third aspect of the present invention provides an application of direct-plated paper in a beer label, wherein the direct-plated paper is the direct-plated paper described in the first aspect of the present invention.

[0047] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0048] The present invention obtains a specific water-based coating by compounding an alkali-resistant emulsion, a leveling emulsion, a defoamer and an alcohol solvent, so that high-speed coating can be achieved, and the coating speed is ≥600m / min. Compared with the traditional coating speed of 120m / min, the production efficiency is significantly improved by more than 5 times, and the production cycle can be greatly shortened and the output can be increased. At the same time, the direct-plated paper obtained by the present invention has excellent performance, wherein the alkali permeability test is 50-120s, the wear resistance number is ≥70 times, the flatness is maintained at -6mm~+2mm in an environment with a humidity of 30-80%, and the water curl is ≥4s, which meets the application requirements of beer labels. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 This is a schematic structural diagram of the direct-plated paper according to Example 1 of the present invention.

[0050] Reference numerals: 100, back coating layer; 200, base paper layer; 300, primer layer; 400, aluminum plating layer; 500, top coating layer. DETAILED DESCRIPTION

[0051] In order to make the technical scheme of the present invention more clearly understood by those skilled in the art, the following embodiments are listed for illustration. It should be pointed out that the following embodiments do not limit the protection scope of the present invention.

[0052] Unless otherwise specified, the raw materials, reagents or devices used in the present invention can be obtained from conventional commercial channels or by existing known methods.

[0053] The base paper used in the following embodiments of the present invention is 80 g / m 2 Wet-strength paper, paper moisture content: 4.5%, curling time: 15s, smoothness (front): 900s, Cobb60" (back): 17g / m 2 , wet tensile strength (longitudinal): 12N / 15mm, wet tensile strength (transverse): 9N / 15mm.

[0054] Example 1

[0055] like Figure 1 As shown, a direct-plated paper includes, from bottom to top, a back coating 100, a base paper layer 200, a primer layer 300, an aluminum-plated layer 400 and a top coating layer 500; the primer layer 300 is formed by drying a water-based paint film, and the water-based paint is mixed by 50% alkali-resistant emulsion, 20% leveling emulsion, 0.2% defoamer, 1% alcohol solvent, 0.1% preservative and the remainder water by weight percentage, and the solid content of the water-based paint is 35%, and the viscosity (coating 4 cups) is 15s; wherein, the defoamer is a silicone defoamer, the alcohol solvent is ethanol, and the preservative is a Kathon preservative.

[0056] Among the raw materials of the alkali-resistant emulsion in this example, the monomer accounts for 40% of the weight of the alkali-resistant emulsion, and the monomer is composed of methyl methacrylate, isooctyl acrylate and styrene in a mass ratio of 1:1:1; the initiator accounts for 0.5% of the weight of the monomer, and the initiator is ammonium persulfate; the emulsifier accounts for 1% of the weight of the monomer, and the emulsifier is composed of sodium allyloxyhydroxypropyl sulfonate and fatty alcohol polyoxyethylene ether in a mass ratio of 1:1; the cross-linking agent accounts for 0.5% of the weight of the monomer, and the cross-linking agent is ethylene glycol dimethacrylate; the functional monomer accounts for 2.5% of the weight of the monomer, and the functional monomer is hydroxyethyl acrylate; the balance is water.

[0057] The preparation method of the alkali-resistant emulsion of this example comprises the following steps:

[0058] S1, pre-emulsifying the mixture of sodium allyloxyhydroxypropyl sulfonate, methyl methacrylate, hydroxyethyl acrylate, isooctyl acrylate, styrene and ethylene glycol dimethacrylate to obtain a pre-emulsified liquid;

[0059] S2, mixing water and fatty alcohol polyoxyethylene ether, heating to 85°C, stirring until completely dissolved, then dripping the pre-emulsified liquid of step S1, and simultaneously dripping ammonium persulfate, the dripping time is 2h, and after dripping, keeping warm for 30min, to obtain an alkali-resistant emulsion.

[0060] Among the raw materials of the leveling emulsion in this example, the monomer accounts for 25% of the weight of the leveling emulsion, and the monomer is composed of methyl methacrylate, butyl acrylate and styrene in a mass ratio of 1:1:1; the initiator accounts for 0.5% of the weight of the monomer, and the initiator is ammonium persulfate; the emulsifier accounts for 1% of the weight of the monomer, and the emulsifier is composed of sodium allyloxyhydroxypropyl sulfonate and fatty alcohol polyoxyethylene ether in a mass ratio of 1:1; the cross-linking agent accounts for 0.5% of the weight of the monomer, and the cross-linking agent is glycidyl methacrylate; the balance is water.

[0061] The preparation method of the leveling emulsion of this example comprises the following steps:

[0062] S1, pre-emulsifying the mixture of sodium allyloxyhydroxypropyl sulfonate, methyl methacrylate, butyl acrylate, styrene and glycidyl methacrylate to obtain a pre-emulsified liquid;

[0063] S2. Mix water and fatty alcohol polyoxyethylene ether, heat to 85° C., stir until completely dissolved, then drop the pre-emulsified liquid of step S1, and simultaneously drop ammonium persulfate for 1 hour. After the dropwise addition, keep warm for 30 minutes to obtain a leveling emulsion.

[0064] The preparation method of the direct-plated paper of this example comprises the following steps:

[0065] S1. Use a high-speed coating machine to coat the surface of the base paper twice with water-based coating, and the amount of dry glue coated once is 1g / m 2 , the suspension drying temperature is 100℃, the parameters of the secondary coating are the same as those of the primary coating, the coating method is air knife coating, the coating machine speed is 600m / min, and the base coating is obtained; after coating, the transverse shrinkage of the paper is 3mm, the glossiness is 50%, and the moisture content is 3%;

[0066] S2, placing the paper coated in step S1 in a vacuum aluminum coating machine, and evacuating the paper by a vacuum pump to a vacuum degree of 1.3×10 -3 Pa, in a vacuum chamber, the evaporation boat is heated to 1350°C to melt the high-purity aluminum wire and evaporate it into gaseous aluminum. After deposition, a thickness of Aluminum coating;

[0067] S3. Use a high-speed coating machine to coat the surface of the aluminum-plated paper. The solid content of the top coating is 25% and the coating dry weight is 1.2g / m 2The water-based acrylic resin was coated at a speed of 600 m / min and dried at 80°C to obtain the top coating. After the top coating, the paper had a transverse shrinkage of 1 mm, a glossiness of 8%, and a moisture content of 3%.

[0068] S4. Use a high-speed coating machine to perform back coating on the back of the paper after top coating. The coating machine speed is 600m / min to obtain a back coating layer, and then perform a moisture reconditioning treatment to obtain a direct-plated paper.

[0069] Example 2

[0070] A direct-plated paper comprises, from bottom to top, a back coating, a base paper layer, a primer layer, an aluminum-plated layer and a top coating layer; the primer layer is formed by drying a water-based paint film, and the water-based paint is mixed by weight percentage with 50% alkali-resistant emulsion, 20% leveling emulsion, 0.2% defoamer, 1% alcohol solvent, 0.1% preservative and the remainder water, the solid content of the water-based paint is 35%, and the viscosity (coating 4 cups) is 15s; wherein, the defoamer is an organosilicon defoamer, the alcohol solvent is ethanol, and the preservative is a Kathon preservative.

[0071] Among the raw materials of the alkali-resistant emulsion in this example, the monomer accounts for 35% of the weight of the alkali-resistant emulsion, and the monomer is composed of methyl methacrylate, isooctyl acrylate and styrene in a mass ratio of 1:1:1; the initiator accounts for 0.1% of the weight of the monomer, and the initiator is ammonium persulfate; the emulsifier accounts for 0.5% of the weight of the monomer, and the emulsifier is composed of sodium allyloxyhydroxypropyl sulfonate and fatty alcohol polyoxyethylene ether in a mass ratio of 1:1; the cross-linking agent accounts for 0.1% of the weight of the monomer, and the cross-linking agent is ethylene glycol dimethacrylate; the functional monomer accounts for 0.5% of the weight of the monomer, and the functional monomer is hydroxyethyl acrylate; the balance is water.

[0072] The preparation method of the alkali-resistant emulsion of this example comprises the following steps:

[0073] S1, pre-emulsifying the mixture of sodium allyloxyhydroxypropyl sulfonate, methyl methacrylate, hydroxyethyl acrylate, isooctyl acrylate, styrene and ethylene glycol dimethacrylate to obtain a pre-emulsified liquid;

[0074] S2, mixing water and fatty alcohol polyoxyethylene ether, heating to 75°C, stirring until completely dissolved, then dripping the pre-emulsified liquid of step S1, and simultaneously dripping ammonium persulfate, the dripping time is 2h, and after dripping, keeping warm for 20min, to obtain an alkali-resistant emulsion.

[0075] Among the raw materials of the leveling emulsion in this example, the monomer accounts for 20% of the weight of the leveling emulsion, and the monomer is composed of methyl methacrylate, butyl acrylate and styrene in a mass ratio of 1:1:1; the initiator accounts for 0.1% of the weight of the monomer, and the initiator is ammonium persulfate; the emulsifier accounts for 0.5% of the weight of the monomer, and the emulsifier is composed of sodium allyloxyhydroxypropyl sulfonate and fatty alcohol polyoxyethylene ether in a mass ratio of 1:1; the cross-linking agent accounts for 0.1% of the weight of the monomer, and the cross-linking agent is glycidyl methacrylate; the balance is water.

[0076] The preparation method of the leveling emulsion of this example comprises the following steps:

[0077] S1, pre-emulsifying the mixture of sodium allyloxyhydroxypropyl sulfonate, methyl methacrylate, butyl acrylate, styrene and glycidyl methacrylate to obtain a pre-emulsified liquid;

[0078] S2. Mix water and fatty alcohol polyoxyethylene ether, heat to 75° C., stir until completely dissolved, then drop the pre-emulsified liquid of step S1, and simultaneously drop ammonium persulfate for 1 hour. After the dropwise addition, keep warm for 20 minutes to obtain a leveling emulsion.

[0079] The preparation method of the direct-plated paper of this example comprises the following steps:

[0080] S1. Use a high-speed coating machine to coat the surface of the base paper with water-based coating twice, and the amount of dry glue coated once is 0.7g / m 2 , the suspension drying temperature is 70℃, the parameters of the secondary coating are the same as those of the primary coating, the coating method is air knife coating, the coating machine speed is 800m / min, and the base coating is obtained; after coating, the transverse shrinkage of the paper is 2mm, the glossiness is 50%, and the moisture content is 2.5%;

[0081] S2, placing the paper coated in step S1 in a vacuum aluminum coating machine, and evacuating the paper by a vacuum pump to a vacuum degree of 1.3×10 -3 Pa, in a vacuum chamber, the evaporation boat is heated to 1350°C to melt the high-purity aluminum wire and evaporate it into gaseous aluminum. After deposition, a thickness of Aluminum coating;

[0082] S3. Use a high-speed coating machine to coat the surface of the aluminum-plated paper. The solid content of the top coating is 18% and the coating dry weight is 0.8g / m 2 The water-based acrylic resin was coated at a speed of 800 m / min and dried at 80°C to obtain the top coating. After the top coating, the paper had a transverse shrinkage of 1 mm, a glossiness of 8%, and a moisture content of 2.5%.

[0083] S4. Use a high-speed coating machine to perform back coating on the back of the paper after top coating. The coating machine speed is 800m / min to obtain a back coating layer, and then perform a moisture reconditioning treatment to obtain a direct-plated paper.

[0084] Example 3

[0085] A direct-plated paper comprises, from bottom to top, a back coating, a base paper layer, a primer layer, an aluminum-plated layer and a top coating layer; the primer layer is formed by drying a water-based paint film, and the water-based paint is mixed by weight percentage with 50% alkali-resistant emulsion, 20% leveling emulsion, 0.2% defoamer, 1% alcohol solvent, 0.1% preservative and the remainder water, the solid content of the water-based paint is 35%, and the viscosity (coating 4 cups) is 15s; wherein, the defoamer is an organosilicon defoamer, the alcohol solvent is ethanol, and the preservative is a Kathon preservative.

[0086] Among the raw materials of the alkali-resistant emulsion in this example, the monomer accounts for 45% of the weight of the alkali-resistant emulsion, and the monomer is composed of methyl methacrylate, isooctyl acrylate and styrene in a mass ratio of 1:1:1; the initiator accounts for 1% of the weight of the monomer, and the initiator is ammonium persulfate; the emulsifier accounts for 2% of the weight of the monomer, and the emulsifier is composed of sodium allyloxyhydroxypropyl sulfonate and fatty alcohol polyoxyethylene ether in a mass ratio of 1:1; the cross-linking agent accounts for 1% of the weight of the monomer, and the cross-linking agent is ethylene glycol dimethacrylate; the functional monomer accounts for 5% of the weight of the monomer, and the functional monomer is hydroxyethyl acrylate; the balance is water.

[0087] The preparation method of the alkali-resistant emulsion of this example comprises the following steps:

[0088] S1, pre-emulsifying the mixture of sodium allyloxyhydroxypropyl sulfonate, methyl methacrylate, hydroxyethyl acrylate, isooctyl acrylate, styrene and ethylene glycol dimethacrylate to obtain a pre-emulsified liquid;

[0089] S2, mixing water and fatty alcohol polyoxyethylene ether, heating to 90°C, stirring until completely dissolved, then dripping the pre-emulsified liquid of step S1, and simultaneously dripping ammonium persulfate, the dripping time is 2.5 hours, and keeping warm for 40 minutes after dripping to obtain an alkali-resistant emulsion.

[0090] Among the raw materials of the leveling emulsion in this example, the monomer accounts for 30% of the weight of the leveling emulsion, and the monomer is composed of methyl methacrylate, butyl acrylate and styrene in a mass ratio of 1:1:1; the initiator accounts for 1% of the weight of the monomer, and the initiator is ammonium persulfate; the emulsifier accounts for 2% of the weight of the monomer, and the emulsifier is composed of sodium allyloxyhydroxypropyl sulfonate and fatty alcohol polyoxyethylene ether in a mass ratio of 1:1; the cross-linking agent accounts for 1% of the weight of the monomer, and the cross-linking agent is glycidyl methacrylate; the balance is water.

[0091] The preparation method of the leveling emulsion of this example comprises the following steps:

[0092] S1, pre-emulsifying the mixture of sodium allyloxyhydroxypropyl sulfonate, methyl methacrylate, butyl acrylate, styrene and glycidyl methacrylate to obtain a pre-emulsified liquid;

[0093] S2, mix water and fatty alcohol polyoxyethylene ether, heat to 90°C, stir until completely dissolved, then drop the pre-emulsion of step S1, and simultaneously drop ammonium persulfate for 1.5 hours. After the dropwise addition, keep warm for 40 minutes to obtain a leveling emulsion.

[0094] The preparation method of the direct-plated paper of this example comprises the following steps:

[0095] S1. Use a high-speed coating machine to coat the surface of the base paper with water-based coating twice, and the amount of dry glue coated once is 1.5g / m 2 The suspension drying temperature is 120℃. The parameters of the secondary coating are the same as those of the primary coating. The coating method is air knife coating. The coating machine speed is 1000m / min to obtain the base coating. The transverse shrinkage of the coated paper is 3mm, the glossiness is 50%, and the moisture content is 3.5%.

[0096] S2, placing the paper coated in step S1 in a vacuum aluminum coating machine, and evacuating the paper by a vacuum pump to a vacuum degree of 1.3×10 -3 Pa, in a vacuum chamber, the evaporation boat is heated to 1350°C to melt the high-purity aluminum wire and evaporate it into gaseous aluminum. After deposition, a thickness of Aluminum coating;

[0097] S3. Use a high-speed coating machine to coat the surface of the aluminum-plated paper. The top coating has a solid content of 30% and a coating dry weight of 1.5g / m 2 The water-based acrylic resin was coated at a speed of 1000 m / min and dried at 80°C to obtain a top coating. After the top coating, the paper had a transverse shrinkage of 1 mm, a glossiness of 8%, and a moisture content of 4.5%.

[0098] S4. Use a high-speed coating machine to perform back coating on the back of the paper after top coating. The coating machine speed is 1000m / min to obtain a back coating layer, and then perform a moisture reconditioning treatment to obtain a direct-plated paper.

[0099] With reference to the vacuum aluminum-plated paper industry standard (BB / T 0054-2010), the moisture content of the direct-plated paper prepared in Examples 1-3 of the present invention is 3.5-4.5%, the wear resistance is ≥70 times, the flatness is maintained at -6mm to +2mm in an environment with a humidity of 80%, and the water curl is ≥4s, which meets the application requirements of beer labels.

[0100] Alkali resistance test

[0101] The detection method is as follows:

[0102] 1. Add 200 mL of 2.5% NaOH solution to the beaker, and then place it together with the beaker in a constant temperature water bath and heat to 80°C;

[0103] 2. Use the quantitative sample sampler to accurately cut 5 samples of 100mm×100mm from the sample to be tested. When cutting the samples, pay attention to cutting quantitative specification samples from the top, bottom, left, right and middle of the sample to be tested. When taking the samples, ensure that the sampling distance is more than 2cm from the edge of the sample to be tested;

[0104] 3. Place the front side of the sample facing down, fold a line along the four sides 25mm away from the edge to the back, use 15mm wide single-sided transparent tape to stick the fold on the front side of the sample, then fold up the four sides and stick them into a boat shape;

[0105] 4. Use a small brush to spread phenolphthalein powder evenly inside the boat, then put the boat into a 2.5% NaOH solution heated to 80°C, so that the boat floats steadily on the surface of the solution, with the front of the sample in full contact with the solution, and start timing with a stopwatch;

[0106] 5. When red spots appear on the inner surface of the boat, stop the timing and record the time. Follow the above steps to complete the test of 5 samples and take the average of the results.

[0107] The alkali permeability of the direct-plated paper prepared in Example 1 of the present invention is 110s, the alkali permeability of the direct-plated paper prepared in Example 2 is 102s, and the alkali permeability of the direct-plated paper prepared in Example 3 is 98s; compared with the alkali permeability of 10-50s of traditional direct-plated paper, the alkali resistance of the direct-plated paper prepared in the present invention is significantly stronger; one of the reasons may be that the acrylic emulsion used in the base coating of traditional direct-plated paper contains carboxyl functional monomers, while the present invention introduces functional monomers containing hydroxyl groups such as hydroxyethyl acrylate and hydroxyethyl methacrylate, does not contain carboxyl functional monomers, and the emulsion acid value is low, thereby improving the alkali resistance.

[0108] The preferred embodiments of the present invention are specifically described above, but the invention is not limited to the embodiments. Those skilled in the art can make various equivalent modifications or substitutions without violating the spirit of the invention. These equivalent modifications or substitutions are all included in the scope defined by the claims of this application.

Claims

1. A direct-plated paper, characterized in that: The invention comprises, from bottom to top, a back coating layer, a base paper layer, a primer layer, an aluminum-plated layer and a top coating layer; the primer layer is formed by drying a water-based paint film, and the water-based paint comprises an alkali-resistant emulsion, a leveling emulsion, a defoamer and an alcohol solvent; the alkali-resistant emulsion comprises a monomer, an initiator, an emulsifier, a cross-linking agent and a functional monomer; the leveling emulsion comprises a monomer, an initiator, an emulsifier and a cross-linking agent; the monomer comprises at least one of methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, styrene and isooctyl acrylate, and the functional monomer comprises at least one of hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxypropyl acrylate and hydroxyethyl acrylate.

2. The direct-plated paper according to claim 1, characterized in that: Calculated by weight percentage, the water-based paint comprises 50-80% of alkali-resistant emulsion, 10-30% of leveling emulsion, 0.2-0.8% of defoaming agent and 1-5% of alcohol solvent.

3. The direct-plated paper according to claim 1, characterized in that: In the alkali-resistant emulsion, the monomer accounts for 35-45% of the weight of the alkali-resistant emulsion, the initiator accounts for 0.1-1% of the weight of the monomer, the emulsifier accounts for 0.5-2% of the weight of the monomer, the crosslinker accounts for 0.1-1% of the weight of the monomer, and the functional monomer accounts for 0.5-5% of the weight of the monomer.

4. The direct-plated paper according to claim 1, characterized in that: In the leveling emulsion, the monomer accounts for 20-30% of the weight of the leveling emulsion, the initiator accounts for 0.1-1% of the weight of the monomer, the emulsifier accounts for 0.5-2% of the weight of the monomer, and the crosslinker accounts for 0.1-1% of the weight of the monomer.

5. The direct-plated paper according to claim 1, characterized in that: The defoaming agent includes at least one of mineral oil defoaming agent, silicone defoaming agent, polyether defoaming agent and surfactant defoaming agent; the alcohol solvent includes at least one of methanol, ethanol, isopropanol and butanol.

6. The direct-plated paper according to claim 1, characterized in that: The initiator includes at least one of ammonium persulfate, potassium persulfate and benzoyl peroxide; the emulsifier includes at least one of alkyl polyoxyethylene ether, fatty alcohol polyoxyethylene ether and allyloxy hydroxypropyl sulfonate; the crosslinking agent includes at least one of ethylene glycol dimethacrylate and glycidyl methacrylate.

7. The method for preparing direct-plated paper according to any one of claims 1 to 6, characterized in that: The following steps are involved: S1, coating the water-based coating on the surface of the base paper, and obtaining a primer layer after the water-based coating is dried; S2, aluminum plating is performed on the surface of the primer layer to obtain an aluminum plating layer; S3, applying a topcoat on the surface of the aluminum-plated layer, and obtaining a topcoat after drying; S4, performing back coating on the back side of the base paper to obtain a back coating layer, thereby producing the direct-plated paper.

8. The preparation method according to claim 7, characterized in that: In step S1, the coating method is air knife coating, the coating speed is 600-1000 m / min, and the coating dry glue amount is 0.7-1.5 g / m 2 , the drying temperature is 70-120°C.

9. The preparation method according to claim 7, characterized in that: In step S3, the top coating has a solid content of 18-30% and a coating dry weight of 0.8-1.5 g / m 2 The water-based acrylic resin, the drying temperature is 70-90°C.

10. Application of direct-plated paper in beer labels, characterized in that: The direct-plated paper is the direct-plated paper according to any one of claims 1 to 6.

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