Laser coding white cardboard coating

Abstract

The invention discloses a laser coding white cardboard coating. The coating is divided into a pre-coating coating, a middle coating coating, a back coating coating and a surface coating coating. The surface coating coating comprises the following components and weight proportions: 15-35 parts of china clay, 65-85 parts of 95-grade heavy calcium carbonate, 0.08-0.2 parts of a dispersant, 0.05-0.12 parts of a defoamer, 0.05-0.2 parts of a rheological agent, 0.1-0.5 parts of hydroxymethyl cellulose, 12-14 parts of latex, 0.15-0.3 parts of polyaluminium chloride, 0.1-0.5 parts of a water repellent, 0.1-0.5 parts of a lubricant and 0-0.05 parts of a dye. The surface strength of the paper is 3.3-3.5 m / s, the glossiness is 51-53.8%, and the smoothness is 554-679s. All the above indicators meet the requirements of packaging paper. When the paper is laser coded, no problems such as smoking and sparks will occur, and the content after coding is clear and regular.

Description

Technical Field

[0001] The invention relates to a coating, in particular to a laser coding white cardboard coating. Background Art

[0002] White cardboard is an important material for making commodity packaging and is widely used in commodity packaging. Due to the rapid development of my country's industry, the market demand for white cardboard has been very strong in recent years. The substantial increase in demand reflects the huge market demand. Electronic supervision code management system is generally used in commodity packaging to complete product status query, traceability and management, which is unique. At present, supervision codes are usually printed on commodity packaging boxes using laser coding technology. Laser coding is a method of digital information processing on coated paper or paperboard using optical means such as lasers. This processing method is widely used in the post-printing processing of the outer packaging of various high-end products at home and abroad.

[0003] The working principle of laser coding machine is to use laser to gather extremely high energy density on the surface of the object to be marked, gasify the surface material through burning and etching, and accurately burn out patterns or texts by controlling the effective displacement of the laser beam. It has the characteristics of clarity, firmness and not easy to erase. However, laser coding has high requirements on the heat resistance, printing adaptability and flatness of the paper surface. Therefore, the coating formula and production and processing method of coated white cardboard used for commodity packaging have not been specially treated and cannot be used for laser coding processing, otherwise there will be problems such as sparks and smoke on the paper surface and unclear coding information.

[0004] At present, the coating used in the preparation process of coated white cardboard for laser coding adopts a formula of low amount of porcelain clay and high amount of calcium carbonate; the calcium carbonate particles of the coated white cardboard prepared by this method cannot be burned off in time under the laser, which ultimately causes the coding information of the finished white cardboard to be unclear, such as Figure 2 shown. Summary of the invention

[0005] Purpose of the invention: The purpose of the present invention is to provide a white cardboard coating suitable for improving the clarity of laser coding.

[0006] Technical solution: The laser coding white cardboard coating described in the present invention is divided into a pre-coating coating, a mid-coating coating, a back coating and a top coating, wherein the top coating composition and weight ratio are: 15-35 parts of china clay, 65-85 parts of 95-grade heavy calcium carbonate, 0.08-0.2 parts of dispersant, 0.05-0.12 parts of defoaming agent, 0.05-0.2 parts of rheological agent, 0.1-0.5 parts of hydroxymethyl cellulose, 12-14 parts of latex, 0.15-0.3 parts of polyaluminium chloride, 0.1-0.5 parts of water repellent, 0.1-0.5 parts of lubricant and 0-0.05 parts of dye.

[0007] Furthermore, the top coating also includes 0-1.0 part of a brightener.

[0008] Furthermore, the coating amount of the top coating is 13.5-14.5 g / m 2 .

[0009] Furthermore, the pre-coating coating composition and weight ratio are: 40-50 parts of 70-grade heavy calcium carbonate, 50-60 parts of 65-grade heavy calcium carbonate, 0.08-0.2 parts of dispersant, 0.05-0.12 parts of defoamer, 0.1-0.5 parts of hydroxymethyl cellulose, 0.1-0.5 parts of water repellent, 0.1-0.5 parts of lubricant and latex; the latex weight is ≥300g / m 2 , the dosage is 10-14 parts; the latex weight is less than 300g / m 2 , the dosage is 10-13 parts.

[0010] Furthermore, the components and weight proportions of the mid-coat coating are: 40-50 parts of 70-grade heavy calcium carbonate, 50-60 parts of 65-grade heavy calcium carbonate, 0.08-0.2 parts of dispersant, 0.05-0.12 parts of defoamer, 0.05-0.2 parts of rheological agent, 0.1-0.5 parts of hydroxymethyl cellulose, 0.15-0.3 parts of polyaluminium chloride, 0.1-0.5 parts of water repellent, 0.1-0.5 parts of lubricant, 0-0.05 parts of dye and latex; the latex weight is ≥300g / m 2 , the dosage is 11-13 parts; the latex weight is less than 300g / m 2 , the dosage is 10.5-13 parts; it is expected that the middle material will use relatively rough 70-grade heavy calcium carbonate and 65-grade heavy calcium carbonate. First, it saves costs. Second, such a combination makes the surface friction of the paper greater, which is conducive to the front layers of coating to hang on. If it is too fine, the surface layer cannot be coated, and the coating amount will decrease, which will easily cause streaks. If it is too rough, it will easily damage the scraper and the water retention performance of the coating will also decrease.

[0011] Furthermore, the back coating composition and weight ratio are: 8-15 parts of 95-grade heavy calcium carbonate, 85-92 parts of 70-grade heavy calcium carbonate, 0.08-0.2 parts of dispersant, 0.05-0.12 parts of defoamer, 0.1-0.5 parts of hydroxymethyl cellulose, 0.15-0.3 parts of polyaluminium chloride, 0.1-0.5 parts of water repellent, 0-0.05 parts of dye and latex; the latex weight is ≥300g / m 2 , the dosage is 12-14 parts; the latex weight is less than 300g / m 2 , the dosage is 11-13 parts.

[0012] Furthermore, the pH values ​​of the pre-coating, mid-coating, back-coating and top-coating are all 9.2-9.6.

[0013] Furthermore, the coating amount of the pre-coating coating is 12-16 g / m 2 The coating amount of the intermediate coating is 10.5-14.5g / m 2 .

[0014] Furthermore, the coating amount of the back coating is 15.0-16.5 g / m 2 .

[0015] Furthermore, the pre-coating coating and the back-coating coating include 0-1.0 parts of a brightener.

[0016] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: the surface strength of the paper prepared by the coating is 3.3-3.5m / s; the glossiness is 51-53.8%; the smoothness is 554-679s, and the above indicators all meet the requirements of packaging paper; and the obtained paper will not have problems such as smoking and sparks when laser coding, and the content after coding is clear and regular. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Prepare flow charts for paper;

[0018] Figure 2 This is the effect of laser coding after the existing coating is prepared into paper;

[0019] Figure 3 This is a picture of the effect of laser coding after the coating of Example 1 is prepared into paper. DETAILED DESCRIPTION

[0020] The technical solution of the present invention is further described below in conjunction with embodiments.

[0021] Example 1

[0022] The coating formula is shown in Table 1, where the latex weight is 250g / m 2 Specific papermaking process parameters, the amount of each coating and the final paper index test data are shown in Table 8, and the coding content of the paper obtained in Example 1 is clearly visible after coding, see Figure 3 .

[0023] Table 1

[0024]

[0025] The base paper of the present invention is made of three layers: surface layer, core layer and bottom layer; the coating is divided into four layers: pre-coating, middle coating, surface coating and back coating; the specific paper preparation process is as follows Figure 1 As shown, the following steps are included:

[0026] (1) Production of base paper

[0027] The broadleaf pulp board and the coniferous pulp board enter the pulper for crushing and dispersion into pulp, and are transported to the mill for further refining according to actual needs. After the pulping is completed, it passes through the paper machine pulp tank, desander, pulp pump, pressure screen, headbox in sequence, and then goes to the net for dehydration. In order to improve the opacity, brightness, smoothness, printing adaptability (such as improving absorbency and ink absorption), softness and uniformity of the paper, 65-grade calcium carbonate is used as filler, and the amount of filler added is 50-200kg / t; the formed wet paper web enters the pressing section, and the pressed paper is steam dried before surface sizing, and the front sizing is controlled at 3.0-7.0g / m 2 , the amount of glue applied on the back side is controlled at 2.0-5.0g / m 2 Surface base paper weight (including sizing) 30-45g / m 2 , the basis weight of the bottom base paper (including sizing) is 21-36g / m 2 After the gluing is completed, the paper enters the post-drying stage. After drying, the paper is hard pressed again. The pressure is controlled at 50kn / m and the temperature is controlled at 160℃. After the drying is completed, it enters the coating stage.

[0028] (2) Coating

[0029] The paper after hard calendering is coated, and the coating is divided into four layers: pre-coating, middle coating, top coating, and back coating; the four layers of coating are applied according to the coating formula in Table 1.

[0030] Among them: for calcium carbonate grade 95 and above, the fineness of dry powder must be ≥99.9%, the whiteness must reach 95±2%, the solid content of slurry calcium must be 75±1.5%, and the viscosity must be 180±50cp; for calcium carbonate grade 70 and above, the fineness of dry powder must be ≥99.9%, the whiteness must reach 95±2%, the solid content of slurry calcium must be 75±1.5%, and the viscosity must be 110±40cps; for calcium carbonate grade 65 and above, the fineness of dry powder must be ≥99.9%, the whiteness must reach 88±2%, the solid content of slurry calcium must be 75±1.5%, and the viscosity must be 60±30cps.

[0031] The coating scraper uses a ceramic scraper. Due to the high requirements for the coating amount and glossiness of the finished paper, a hard blade is used for pre-coating and mid-coating. In order to improve the poor flatness, a soft blade is used for top coating and back coating. The specific coating amount is shown in Table 6. After coating, soft calendering is performed with a soft calendering pressure of 10-30KN / M and a soft calendering temperature of 140-180℃, and finally winding is performed.

[0032] Example 2

[0033] The coating formula is shown in Table 2, where the latex weight is 300g / m 2Specific papermaking process parameters, the amount of each coating and the final paper index test data are shown in Table 6.

[0034] Table 2

[0035]

[0036] Example 3

[0037] The coating formula is shown in Table 3, where the latex weight is 350g / m 2 Specific papermaking process parameters, the amount of each coating and the final paper index test data are shown in Table 6.

[0038] Table 3

[0039]

[0040]

[0041] Comparative Example 1

[0042] The coating formula is shown in Table 4, where the latex weight is 250g / m 2 Specific papermaking process parameters, the amount of each coating and the final paper index test data are shown in Table 6.

[0043] Table 4

[0044]

[0045]

[0046] Comparative Example 2

[0047] The coating formula is shown in Table 5, where the latex weight is 300g / m 2 Specific papermaking process parameters, the amount of each coating and the final paper index test data are shown in Table 6.

[0048] Table 5

[0049]

[0050] The specific parameters of the paper production process are shown in Table 6, where various parameters are adjusted in real time according to different coating ratios, and the final paper index test data are shown in Table 6. The relevant indexes are explained as follows:

[0051] IGT (paper surface strength): Applicable to the evaluation of the surface strength of paper and paperboard. It refers to the ability of paper to resist linting, powdering, pilling and delamination when subjected to the tension of ink peeling during the printing process. It is usually evaluated by the paper's linting speed, with the unit of m / s or cm / s.

[0052] Gloss: It refers to the ratio of the luminous flux reflected from the surface of the paper sample into the specified aperture to the luminous flux incident on the standard mirror under the same conditions. It is expressed in %, which is a measure of the image clarity and color vividness of color printing.

[0053] Smoothness: refers to the degree of smoothness of the paper surface. It is an indicator for evaluating the concave-convex characteristics of the paper or paperboard surface, and is also an important indicator for the printing adaptability of paper and paperboard. Under specific conditions, a certain amount of air is allowed to pass through a certain area of ​​small holes between the smooth glass surface and the paper surface, and the time required for the air to pass is measured in seconds. The longer the time required, the higher the smoothness.

[0054] Table 6

[0055]

[0056] The coating formula of the present invention is used to obtain products. After actual testing, the surface strength of the surface layer of paper is 3.3-3.5m / s, and the surface strength of the papers obtained in this scheme is not much different; the glossiness is 51-53.8%, which is slightly better than the comparative paper; the smoothness is 554-679s, and the smoothness of the paper of the present invention is significantly better than the smoothness of the comparative paper; and the obtained product is laser-coded, and the obtained content is clear and regular, and there is no abnormality; each coating and filler uses calcium carbonate of different particle sizes, which are reasonably matched and used in proportion, and corresponding process production standards are formulated according to calcium carbonate of different particle sizes, the fineness of calcium carbonate is adjusted and controlled, and a suitable scraper is selected to make the IGT (>1.7m / s), glossiness (50±5%), smoothness (400-1000s) and other indicators within the standard range; and the coating reduces the production cost under the premise of ensuring the demand for laser coding.

Claims

1. A laser coding white cardboard coating, the coating comprising a pre-coating coating, a mid-coating coating, a back coating and a top coating; characterized in that: The top coating composition and weight ratio are: 35 parts of china clay, 65 parts of 95-grade heavy calcium carbonate, 0.2 parts of dispersant, 0.12 parts of defoamer, 0.2 parts of rheological agent, 0.3 parts of carboxymethyl cellulose, 12 parts of latex, 0.25 parts of PVA, 0.3 parts of water repellent PAPU, 0.2 parts of lubricant, 0.015 parts of dye, and 0.5 parts of whitening agent; The pre-coating coating composition and weight ratio are: 40 parts of 70-grade heavy calcium carbonate, 60 parts of 65-grade heavy calcium carbonate, 0.1 parts of dispersant, 0.06 parts of defoamer, 0.3 parts of carboxymethyl cellulose, 0.1 parts of water repellent PAPU, 0.1 parts of lubricant, 12 parts of latex, 0.015 parts of dye, and 0.5 parts of brightener; The components and weight proportions of the mid-coat coating are: 40 parts of 70-grade heavy calcium carbonate, 60 parts of 65-grade heavy calcium carbonate, 0.1 parts of dispersant, 0.06 parts of defoamer, 0.07 parts of rheological agent, 0.3 parts of carboxymethyl cellulose, 0.15 parts of PVA, 0.1 parts of water repellent PAPU, 0.1 parts of lubricant, 0.015 parts of dye, 12.7 parts of latex, and 0.5 parts of brightener; The back coating composition and weight ratio are: 8 parts of 95-grade heavy calcium carbonate, 92 parts of 70-grade heavy calcium carbonate, 0.08 parts of dispersant, 0.05 parts of defoamer, 0.3 parts of carboxymethyl cellulose, 0.015 parts of dye, 11.5 parts of latex, and 0.5 parts of brightener.

2. A laser coding white cardboard coating, the coating comprising a pre-coating coating, a mid-coating coating, a back coating and a top coating; characterized in that: The top coating composition and weight ratio are: 21 parts of china clay, 79 parts of 95-grade heavy calcium carbonate, 0.2 parts of dispersant, 0.12 parts of defoamer, 0.2 parts of rheological agent, 0.25 parts of carboxymethyl cellulose, 12 parts of latex, 0.3 parts of PVA, 0.35 parts of water repellent PAPU, 0.3 parts of lubricant, 0.015 parts of dye, and 0.5 parts of whitening agent; The pre-coating coating composition and weight ratio are: 45 parts of 70-grade heavy calcium carbonate, 55 parts of 65-grade heavy calcium carbonate, 0.12 parts of dispersant, 0.07 parts of defoamer, 0.25 parts of carboxymethyl cellulose, 0.2 parts of water repellent PAPU, 0.1 parts of lubricant, 12.5 parts of latex, 0.015 parts of dye, and 0.5 parts of brightener; The components and weight proportions of the mid-coat coating are: 45 parts of 70-grade heavy calcium carbonate, 55 parts of 65-grade heavy calcium carbonate, 0.12 parts of dispersant, 0.07 parts of defoamer, 0.07 parts of rheological agent, 0.25 parts of carboxymethyl cellulose, 0.13 parts of PVA, 0.15 parts of water repellent PAPU, 0.2 parts of lubricant, 0.015 parts of dye, 13 parts of latex, and 0.5 parts of brightener; The back coating composition and weight ratio are: 10 parts of 95-grade heavy calcium carbonate, 90 parts of 70-grade heavy calcium carbonate, 0.08 parts of dispersant, 0.05 parts of defoamer, 0.25 parts of carboxymethyl cellulose, 0.2 parts of PVA, 0.015 parts of dye, 12 parts of latex, and 0.5 parts of brightener.

3. A laser coding white cardboard coating, the coating comprising a pre-coating coating, a mid-coating coating, a back coating and a top coating; characterized in that: The top coating composition and weight ratio are: 15 parts of china clay, 85 parts of 95-grade heavy calcium carbonate, 0.2 parts of dispersant, 0.12 parts of defoamer, 0.2 parts of rheological agent, 0.4 parts of carboxymethyl cellulose, 12 parts of latex, 0.3 parts of PVA, 0.5 parts of water repellent PAPU, 0.4 parts of lubricant, 0.03 parts of dye, and 0.8 parts of whitening agent; The pre-coating coating composition and weight ratio are: 50 parts of 70-grade heavy calcium carbonate, 50 parts of 65-grade heavy calcium carbonate, 0.1 parts of dispersant, 0.1 parts of defoamer, 0.4 parts of carboxymethyl cellulose, 0.2 parts of water repellent PAPU, 0.2 parts of lubricant, 12 parts of latex, 0.03 parts of dye, and 0.8 parts of brightener; The components and weight proportions of the mid-coat coating are: 50 parts of 70-grade heavy calcium carbonate, 50 parts of 65-grade heavy calcium carbonate, 0.1 parts of dispersant, 0.1 parts of defoamer, 0.1 parts of rheological agent, 0.4 parts of carboxymethyl cellulose, 0.2 parts of PVA, 0.2 parts of water repellent PAPU, 0.3 parts of lubricant, 0.03 parts of dye, 13 parts of latex, and 0.8 parts of brightener; The back coating composition and weight ratio are: 15 parts of 95-grade heavy calcium carbonate, 85 parts of 70-grade heavy calcium carbonate, 0.08 parts of dispersant, 0.08 parts of defoamer, 0.4 parts of carboxymethyl cellulose, 0.03 parts of dye, 12.2 parts of latex, and 0.8 parts of brightener.

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