Water-based lubricant for paper coating and application thereof

Abstract

The application provides a water-based lubricant for paper coating and application thereof. The water-based lubricant for paper coating comprises, in parts by weight, 13-18 parts of water-based oxidized polyethylene copolymer, 3-8 parts of surfactant, 5-7 parts of bactericide, 10-12 parts of initiator and 100 parts of water; the preparation method of the water-based oxidized polyethylene copolymer comprises the following steps: (1) mixing ethylene oxide and oxidized polyethylene, and then sequentially performing mixing reaction and standing to obtain a reaction solution; (2) mixing amide and the reaction solution, and performing modification reaction to obtain the water-based oxidized polyethylene copolymer. The lubricant provided by the application solves the problem of poor flowability in the coating process, reduces or even avoids the appearance of streaks, orange peel and rolling marks in the coating process, and the accompanying appearance of shrinkage, pinhole and flow hanging in the drying process.

Description

Technical Field

[0001] The invention belongs to the technical field of lubricants and relates to a paper coating lubricant, in particular to a water-based lubricant for papermaking coating and application thereof. Background Art

[0002] As the domestic papermaking industry continues to expand, demand for coated paper continues to rise, and coated paper machines are operating at increasingly faster speeds. Coating fluidity during the coating process is crucial for uniform coating. Every coating has a fixed point, and this varies with different properties or coating components. The fixed point of a coating generally ranges from 80% to 87% solids content, and leveling is only possible before the coating reaches the fixed point during drying. Leveling produces a regular flow pattern. As the solvent evaporates, a higher surface tension forms on the surface of the coating, and the viscosity increases. Simultaneously, the temperature drops, creating a temperature difference between the inner and outer layers, as well as differences in surface tension and viscosity. This results in poor leveling, resulting in streaks, orange peel marks, and rolling marks during application. During the drying process, craters and pinhole sagging can also occur. To prevent paper defects caused by poor coating fluidity during coating, it is necessary to enhance coating fluidity.

[0003] This has led to increasingly stringent requirements for coating lubricity, necessitating the addition of lubricants. Lubricants can reduce the coating's coefficient of friction, improve its rheological properties, and ultimately enhance coating smoothness and the gloss of the finished paper. However, to reduce production costs, paper mills are continuously increasing the solids content of their coatings. However, commercially available lubricants only have a maximum solids content of 50%, which is difficult to meet market demands. Furthermore, high-solids coatings significantly reduce their lubricity, necessitating the development of more efficient lubricants to meet these market demands.

[0004] At present, there are three main types of lubricants used in coated paper types such as coated white board paper, coated paper, and light coated paper: one is calcium stearate lubricants; one is oxidized polyethylene wax lubricants; and the other is fatty acid polyoxyethylene ether lubricants. The first type of lubricant is mainly prepared by reacting stearic acid with sodium hydroxide to form sodium stearate, which is then reacted with calcium chloride at a very low concentration of sodium stearate to form calcium stearate. The resulting product is then washed multiple times, centrifuged and dried in a drying oven to obtain relatively pure calcium stearate. Finally, water and an emulsifier are added to the calcium stearate and emulsified using a high-pressure homogenizer. This entire process is complex and tedious, generating large amounts of wastewater and product loss. In addition, when the solids content of the lubricant exceeds 50%, the viscosity of the lubricant is very high, which does not meet the requirements of use. The second type of lubricant contains waxy substances, which have a certain impact on the ink absorbency of the paper and cannot meet the production requirements of modern high-speed coated paper machines. Although the solids content of the third type of lubricant can be achieved at around 55%, the cost is too high, which adds a significant cost burden to the manufacturer. In addition, the rheological properties of this lubricant are poor, and paper defects such as streaks, orange peel, and rolling marks are easily caused during the coating process.

[0005] In summary, it is necessary to provide a new type of high-efficiency lubricant for papermaking to reduce or avoid the occurrence of streaks, orange peel, rolling marks, etc. during application. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention provides a water-based lubricant for papermaking coatings and its application. The lubricant provided by the present invention solves the problem of poor fluidity during coating application, reducing or even eliminating streaks, orange peel, and rolling marks that occur during application, as well as shrinkage craters and pinhole sagging that occur during drying.

[0007] To achieve this object, the present invention adopts the following technical solutions:

[0008] In a first aspect, the present invention provides a method for preparing a water-based lubricant for papermaking coating. The water-based lubricant for papermaking coating comprises, by weight, 13 to 18 parts of a water-based oxidized polyethylene copolymer, 3 to 8 parts of a surfactant, 5 to 7 parts of a bactericide, 10 to 12 parts of an initiator, and 100 parts of water.

[0009] Exemplarily, the weight proportion of the aqueous oxidized polyethylene copolymer in the aqueous lubricant for papermaking coating is 13 to 18 parts, for example, 13 parts, 13.5 parts, 14 parts, 14.5 parts, 15 parts, 15.5 parts, 16 parts, 16.5 parts, 17 parts, 17.5 parts or 18 parts, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0010] In the present invention, the water-based oxidized polyethylene copolymer is the main component of the water-based lubricant for paper coating, is easily soluble in water, and is an anionic organic substance; in the water-based lubricant for paper coating, if the content of the water-based oxidized polyethylene copolymer is too high, the pH value of the water-soluble lubricant will be too high. When the pH is greater than 9.5, the viscosity of the water-soluble lubricant increases, and when mixed with paper coating for coating, phenomena such as streaking will occur; if the content of the water-based oxidized polyethylene copolymer is too low, the water-based lubricant will not be able to play a lubricating role.

[0011] The weight ratio of the surfactant is 3 to 8 parts, for example, 3 parts, 3.5 parts, 4 parts, 4.5 parts, 5 parts, 5.5 parts, 6 parts, 6.5 parts, 7 parts, 7.5 parts or 8 parts, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable;

[0012] The surfactant includes hydrogen peroxide and / or caustic soda.

[0013] The weight ratio of the fungicide is 5 to 7 parts, for example, 5 parts, 5.5 parts, 6 parts, 6.5 parts or 7 parts, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable;

[0014] In the present invention, there is no specific limitation on the type of the bactericide, as long as it can sterilize the water-based lubricant without affecting the function of the water-based lubricant.

[0015] The weight portion of the initiator is 10 to 12 parts, for example, 10 parts, 10.5 parts, 11 parts, 11.5 parts or 12 parts, but is not limited to the values ​​listed, and other values ​​not listed within the numerical range are also applicable;

[0016] The initiator includes dimethyl azobisisobutyrate and / or azobisisobutyramidine hydrochloride.

[0017] As a preferred technical solution of the present invention, the solid content of the water-based lubricant for papermaking coating is 23 to 28 wt%, for example, it can be 23 wt%, 24 wt%, 25 wt%, 26 wt%, 27 wt% or 28 wt%, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0018] Preferably, the viscosity of the aqueous lubricant for papermaking coating is ≤300cps, for example, it can be 300cps, 280cps, 260cps, 240cps, 220cps or 200cps, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0019] Preferably, the pH value of the aqueous lubricant for papermaking coating is 7 to 10, for example, it can be 7, 7.3, 7.6, 7.9, 8.2, 8.5, 8.8, 9.1, 9.4, 9.7 or 10, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0020] In the present invention, the water-based lubricant can improve the fluidity and leveling properties of the coating, make the paper coating smooth and uniform, improve the smoothness of the paper surface, reduce the cracking of the dry coating, reduce the shedding and powdering phenomenon during the printing process, and facilitate the preparation of high-solid content coatings;

[0021] In addition, the solid content of the water-based lubricant of the present invention is 23-28wt%. If the solid content is lower than 23wt%, the lubricating effect of the water-based lubricant will be reduced, and the coating lubrication effect cannot be achieved; if the solid content is too high, the cost and pH value will increase. When the pH value is greater than 9.5, the water-based lubricant affects the dispersibility of the papermaking coating, resulting in the coating not being dispersed, thereby affecting the use effect.

[0022] It is worth noting that the water-based oxidized polyethylene copolymer of the present invention is acidic or neutral, but after being mixed with water, surfactant, bactericide and initiator, the resulting water-based lubricant is alkaline. The reason is that after adding surfactant and initiator, OH - The reaction is promoted so that the lubricant is alkaline.

[0023] As a preferred technical solution of the present invention, the preparation method of the water-based oxidized polyethylene copolymer comprises:

[0024] (1) mixing ethylene oxide and polyethylene oxide, and then sequentially performing a mixing reaction and standing to obtain a reaction solution;

[0025] (2) mixing the amide and the reaction solution obtained in step (1), and performing a modification reaction to obtain the water-based oxidized polyethylene copolymer.

[0026] As a preferred technical solution of the present invention, the mass ratio of the ethylene oxide, amide and polyethylene oxide is 1.8-2.2:1:2.8-3.2, for example, it can be 1.8:1:2.8, 1.8:1:3.2, 2:1:3, 2:1:2.9, 2.2:1:3, 2.2:1:3.2 or 1.9:1:3.1, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0027] As a preferred technical solution of the present invention, the temperature of the mixing reaction in step (1) is 60-70°C, for example, it can be 60°C, 62°C, 64°C, 66°C, 68°C or 70°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0028] Preferably, the stirring rate of the mixing reaction in step (1) is 800 to 1200 r / min, for example, it can be 800 r / min, 900 r / min, 1000 r / min, 1100 r / min or 1200 r / min, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0029] Preferably, the mixing reaction time in step (1) is 8 to 12 minutes, for example, 8 minutes, 9 minutes, 10 minutes, 11 minutes or 12 minutes, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0030] Preferably, the standing time in step (1) is 5 to 10 minutes, for example, 5 minutes, 6 minutes, 7 minutes, 8 minutes, 9 minutes or 10 minutes, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0031] As a preferred technical solution of the present invention, the temperature of the modification reaction in step (2) is 25-30°C, for example, it can be 25°C, 26°C, 27°C, 28°C, 29°C or 30°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0032] Preferably, the modification reaction time in step (2) is 30 to 50 min, for example, 30 min, 34 min, 38 min, 42 min, 46 min or 50 min, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0033] Preferably, the stirring rate of the modification reaction in step (2) is 700-800 r / min, for example, it can be 700 r / min, 720 r / min, 740 r / min, 760 r / min, 780 r / min or 800 r / min, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0034] Preferably, the pH value of the modification reaction in step (2) is 5 to 7, for example, 5, 5.2, 5.4, 5.6, 5.8, 6, 6.2, 6.4, 6.6, 6.8 or 7, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0035] In the present invention, the water-based oxidized polyethylene copolymer prepared by amide modification has the characteristics of low temperature resistance and can be stored at a temperature of 0 to 5°C without affecting the use effect; the temperature during the modification reaction is 25 to 30°C. When the temperature is too high, the chemical properties of the modifier (amide) will be destroyed, causing it to lose its modification effect; the pH value of the modification reaction is 5 to 7. If the pH value is too high, the hydroxide content will be too high, which will prevent the decomposition and modification of the amide; if the pH value is too low, the modifier will react with the acid first and then be modified, and the effect will be weakened.

[0036] It is worth noting that the modification environment of the modification reaction in step (2) of the present invention can be neutral or acidic. When the modification environment is acidic, the pH of the modification environment can be adjusted by adding an acid-base regulator to the mixed reaction in step (1).

[0037] In a second aspect, the present invention provides a use of the aqueous lubricant for paper coating provided in the first aspect in paper coating, the use comprising the following steps:

[0038] (a) mixing alkali liquor, papermaking coating and the papermaking coating aqueous lubricant to obtain a coating solution;

[0039] (b) applying the coating solution obtained in step (a) to at least one side of the paper layer with a roller to obtain a paper layer with a coating layer.

[0040] As a preferred technical solution of the present invention, the addition amount of the water-based lubricant for papermaking coating in step (a) is 0.05-0.15% of the mass of the papermaking coating, for example, it can be 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14% or 0.15%, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0041] Preferably, the pH value of the coating solution in step (a) is 8.8 to 9.2, for example, 8.8, 8.9, 9.0, 9.1 or 9.2, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0042] Preferably, the alkali solution in step (a) comprises sodium hydroxide and / or calcium hydroxide.

[0043] As a preferred technical solution of the present invention, the roller coating in step (b) includes primer coating, mid-coating and top coating performed sequentially.

[0044] Preferably, the temperature of the roller coating in step (b) is 58-65°C, for example, it can be 58°C, 59°C, 60°C, 61°C, 62°C, 63°C, 64°C or 65°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0045] Preferably, the interval between two adjacent roller coatings is 3 to 5 seconds, for example, 3 seconds, 3.4 seconds, 3.8 seconds, 4.2 seconds, 4.6 seconds or 5 seconds, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0046] As a preferred technical solution of the present invention, the thickness of the coating obtained by each roller coating is 40-60 μm, for example, it can be 40 μm, 42 μm, 44 μm, 46 μm, 48 μm, 50 μm, 52 μm, 54 μm, 56 μm, 58 μm or 60 μm, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0047] The numerical range described in the present invention includes not only the point values ​​listed above, but also any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0048] The system refers to an equipment system, a device system or a production device.

[0049] Compared with the prior art, the present invention has the following beneficial effects:

[0050] (1) The water-based lubricant provided by the present invention can effectively improve the fluidity and leveling properties of papermaking coatings, making the paper coating smooth and uniform, thereby improving the smoothness of the paper surface and reducing cracking of the coating and hair loss and powdering during the printing process;

[0051] (2) The water-based lubricant provided by the present invention has a high solid content, so that the papermaking coating used in conjunction with it also has a high solid content;

[0052] (3) The water-based lubricant provided by the present invention has excellent stability and can be used normally in the temperature range of 20 to 200°C without affecting its lubricating effect;

[0053] (4) The water-based lubricant provided by the present invention is low in cost and is conducive to industrial application. DETAILED DESCRIPTION

[0054] The technical solution of the present invention is further described below by way of specific embodiments. It should be understood by those skilled in the art that the embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0055] Example 1

[0056] This embodiment provides an aqueous lubricant for papermaking coating, which comprises, by weight, 15 parts of an aqueous oxidized polyethylene copolymer, 5 parts of a surfactant, 6 parts of a bactericide, 11 parts of an initiator, and 100 parts of water.

[0057] The water-based lubricant for papermaking coating has a solid content of 25 wt %, a viscosity of 280 cps, and a pH value of 8.5;

[0058] The preparation method of the water-based oxidized polyethylene copolymer comprises the following steps:

[0059] (1) mixing ethylene oxide and polyethylene oxide, and then performing a mixing reaction at a temperature of 65° C. and a stirring rate of 1000 r / min for 10 minutes, and standing for 8 minutes to obtain a reaction solution; (2) mixing amide and the reaction solution obtained in step (1), and performing a modification reaction at a temperature of 25° C., a stirring rate of 750 r / min and a pH value of 6 for 40 minutes to obtain the water-based polyethylene oxide copolymer;

[0060] Wherein, the mass ratio of the ethylene oxide, amide and polyethylene oxide is 2:1:3.

[0061] Example 2

[0062] This embodiment provides an aqueous lubricant for papermaking coating, which comprises, by weight, 13 parts of an aqueous oxidized polyethylene copolymer, 3 parts of a surfactant, 5 parts of a bactericide, 10 parts of an initiator, and 100 parts of water.

[0063] The water-based lubricant for papermaking coating has a solid content of 23 wt %, a viscosity of 240 cps, and a pH of 10;

[0064] The preparation method of the water-based oxidized polyethylene copolymer comprises the following steps:

[0065] (1) mixing ethylene oxide and polyethylene oxide, and then performing a mixing reaction at a temperature of 60° C. and a stirring rate of 1200 r / min for 12 minutes, and standing for 10 minutes to obtain a reaction solution; (2) mixing amide and the reaction solution obtained in step (1), and performing a modification reaction at a temperature of 30° C., a stirring rate of 700 r / min and a pH value of 7 for 50 minutes to obtain the water-based polyethylene oxide copolymer;

[0066] Wherein, the mass ratio of the ethylene oxide, amide and polyethylene oxide is 1.8:1:2.8.

[0067] Example 3

[0068] This embodiment provides an aqueous lubricant for papermaking coating, which comprises, by weight, 18 parts of an aqueous oxidized polyethylene copolymer, 8 parts of a surfactant, 7 parts of a bactericide, 12 parts of an initiator, and 100 parts of water.

[0069] The water-based lubricant for papermaking coating has a solid content of 28 wt %, a viscosity of 300 cps, and a pH value of 7;

[0070] The preparation method of the water-based oxidized polyethylene copolymer comprises the following steps:

[0071] (1) mixing ethylene oxide and polyethylene oxide, and then performing a mixing reaction at a temperature of 70° C. and a stirring rate of 800 r / min for 8 minutes, and standing for 5 to 10 minutes to obtain a reaction solution; (2) mixing amide and the reaction solution obtained in step (1), and performing a modification reaction at a temperature of 25° C., a stirring rate of 800 r / min and a pH value of 5 for 30 minutes to obtain the water-based polyethylene oxide copolymer;

[0072] Wherein, the mass ratio of the ethylene oxide, amide and polyethylene oxide is 2.2:1:3.2.

[0073] Example 4

[0074] This embodiment provides a water-based lubricant for papermaking coating. The difference between the water-based lubricant for papermaking coating and that of Example 1 is as follows:

[0075] In this embodiment, the temperature of the modification reaction in step (2) is adjusted to 40°C.

[0076] The aqueous lubricant provided in this embodiment has a solid content of 25 wt %, a viscosity of 260 cps, and a pH value of 8.5.

[0077] The modification reaction temperature in this embodiment is too high, which causes the structure of the modifier amide to be destroyed, thereby losing the modification ability.

[0078] Example 5

[0079] This embodiment provides a water-based lubricant for papermaking coating. The difference between the water-based lubricant for papermaking coating and that of Example 1 is as follows:

[0080] In this embodiment, the temperature of the modification reaction in step (2) is adjusted to 20°C.

[0081] The aqueous lubricant provided in this embodiment has a solid content of 25 wt %, a viscosity of 200 cps, and a pH value of 6.5.

[0082] Example 6

[0083] This embodiment provides a water-based lubricant for papermaking coating. The difference between the water-based lubricant for papermaking coating and that of Example 1 is as follows:

[0084] In this embodiment, the pH value of the modification reaction in step (2) is adjusted to 3.

[0085] The aqueous lubricant provided in this embodiment has a solid content of 25 wt %, a viscosity of 198 cps, and a pH value of 6.

[0086] Example 7

[0087] This embodiment provides a water-based lubricant for papermaking coating. The difference between the water-based lubricant for papermaking coating and that of Example 1 is as follows:

[0088] In this embodiment, the pH value of the modification reaction in step (2) is adjusted to 8.

[0089] The aqueous lubricant provided in this embodiment has a solid content of 25.5 wt %, a viscosity of 230 cps, and a pH value of 8.4.

[0090] Example 8

[0091] This embodiment provides a water-based lubricant for papermaking coating. The difference between the water-based lubricant for papermaking coating and that of Example 1 is as follows:

[0092] In this embodiment, the mass ratio of ethylene oxide, amide and polyethylene oxide is adjusted to 1.5:2:2.

[0093] The aqueous lubricant provided in this embodiment has a solid content of 24.5 wt %, a viscosity of 240 cps, and a pH value of 8.

[0094] Example 9

[0095] This embodiment provides a water-based lubricant for papermaking coating. The difference between the water-based lubricant for papermaking coating and that of Example 1 is that:

[0096] In this embodiment, the mass ratio of ethylene oxide, amide and polyethylene oxide is adjusted to 2.5:2:3.6.

[0097] The aqueous lubricant provided in this embodiment has a solid content of 25 wt %, a viscosity of 290 cps, and a pH value of 9.

[0098] Comparative Example 1

[0099] This embodiment provides a water-based lubricant for papermaking coating. The difference between the water-based lubricant for papermaking coating and that of Example 1 is as follows:

[0100] In this comparative example, the modification reaction described in step (2) is omitted, that is, the water-based oxidized polyethylene copolymer in the water-based lubricant for papermaking coating is not modified.

[0101] The aqueous lubricant provided in this comparative example has a solid content of 26 wt %, a viscosity of 270 cps, and a pH value of 8.8.

[0102] Application Example 1

[0103] This application example provides an application of the aqueous lubricant for paper coating provided in Example 1 in paper coating, and the application comprises the following steps:

[0104] (a) mixing an alkali solution, a papermaking coating, and an aqueous lubricant for papermaking coating to obtain a coating solution having a pH value of 9;

[0105] Wherein, the addition amount of the water-based lubricant for paper coating is 0.1% of the mass of the paper coating;

[0106] (b) applying the coating solution obtained in step (a) to at least one side of the paper layer with a roller to obtain a paper layer with a coating layer;

[0107] The roller coating includes primer coating, mid-coating and top coating in sequence; the temperature of the roller coating is 60° C., the interval between two adjacent roller coatings is 4 seconds; and the thickness of the coating obtained by each roller coating is 50 μm.

[0108] Application Example 2

[0109] This application example provides an application of the aqueous lubricant for paper coating provided in Example 1 in paper coating, and the application comprises the following steps:

[0110] (a) mixing an alkali liquor, a papermaking coating, and an aqueous lubricant for papermaking coating to obtain a coating solution having a pH value of 8.8;

[0111] Wherein, the addition amount of the water-based lubricant for paper coating is 0.05% of the mass of the paper coating;

[0112] (b) applying the coating solution obtained in step (a) to at least one side of the paper layer with a roller to obtain a paper layer with a coating layer;

[0113] The roller coating includes primer coating, mid-coating and top coating in sequence; the temperature of the roller coating is 58° C., the interval between two adjacent roller coatings is 5 seconds; and the thickness of the coating obtained by each roller coating is 60 μm.

[0114] Application Example 3

[0115] This application example provides an application of the aqueous lubricant for paper coating provided in Example 1 in paper coating, and the application comprises the following steps:

[0116] (a) mixing an alkali liquor, a papermaking coating, and an aqueous lubricant for papermaking coating to obtain a coating solution having a pH value of 9.2;

[0117] Wherein, the addition amount of the water-based lubricant for paper coating is 0.15% of the mass of the paper coating;

[0118] (b) applying the coating solution obtained in step (a) to at least one side of the paper layer with a roller to obtain a paper layer with a coating layer;

[0119] The roller coating includes primer coating, mid-coating and top coating in sequence; the temperature of the roller coating is 65° C., the interval between two adjacent roller coatings is 3 seconds; and the thickness of the coating obtained by each roller coating is 40 μm.

[0120] Application Examples 4-9

[0121] An application of the aqueous lubricant for paper coating provided by Examples 4-9 in paper coating, wherein the operating steps of the application are the same as those of Application Example 1.

[0122] Application Example 10

[0123] This application example provides an application of the aqueous lubricant for paper coating provided in Example 1 in paper coating. The difference between this application and Application Example 1 is that:

[0124] In this application example, the amount of the aqueous lubricant added for paper coating in step (a) is adjusted to 2% of the mass of the paper coating.

[0125] Application Example 11

[0126] This application example provides an application of the aqueous lubricant for paper coating provided in Example 1 in paper coating. The difference between this application and Application Example 1 is that:

[0127] In this application example, the amount of the aqueous lubricant added for paper coating in step (a) is adjusted to 0% of the mass of the paper coating.

[0128] Application Example 12

[0129] This application example provides an application of the aqueous lubricant for paper coating provided in Example 1 in paper coating. The difference between this application and Application Example 1 is that:

[0130] In this application example, the pH value of the coating solution in step (a) is adjusted to 10.

[0131] Application Example 13

[0132] This application example provides an application of the aqueous lubricant for paper coating provided in Example 1 in paper coating. The difference between this application and Application Example 1 is that:

[0133] In this application example, the pH value of the coating solution in step (a) is adjusted to 7.

[0134] Application Example 13

[0135] This application example provides an application of the aqueous lubricant for paper coating provided in Example 1 in paper coating. The difference between this application and Application Example 1 is that:

[0136] In this application example, the thickness of the coating obtained by each roller coating in step (b) is adjusted to 30 μm.

[0137] Application Example 14

[0138] This application example provides an application of the aqueous lubricant for paper coating provided in Example 1 in paper coating. The difference between this application and Application Example 1 is that:

[0139] In this application example, the thickness of the coating obtained by each roller coating in step (b) is adjusted to 70 μm.

[0140] Comparative Application Example 1

[0141] This comparative application example provides an application of the aqueous lubricant for paper coating provided in Comparative Example 1 in paper coating, and the operating steps of the application are the same as those of Application Example 1.

[0142] Coating performance test:

[0143] The coating performance test of the coated paper provided in the above application examples and comparative application examples was conducted using the national standard method. The results are shown in Table 1:

[0144] Among them, the paper used in the coating process is: gray-based white board paper.

[0145] Table 1

[0146]

[0147]

[0148] According to Table 1, we can know the following points:

[0149] (1) Comprehensive analysis of Application Examples 1-3 shows that the whiteness of the coated paper layer obtained by using the lubricant provided by the present invention is 78.4-78.6%, the smoothness is 220-240s, the roughness is 1.00-1.04μm, and the gloss is 51-52GU. This shows that the lubricant provided by the present invention can improve the fluidity and leveling properties of the coating, make the paper coating smooth and uniform, and improve the smoothness of the paper surface.

[0150] (2) Comprehensive analysis of Application Example 1, Application Examples 4-7 and Comparative Application Example 1 shows that adjustment of the preparation parameters of the water-based oxidized polyethylene copolymer in the water-based lubricant will affect the performance of the water-based oxidized polyethylene copolymer, and thus affect the effect of the lubricant;

[0151] Among them, if the temperature of the modification reaction is too high or too low (such as in Application Example 4-5) or the pH value of the modification reaction is too high or too low, the whiteness, glossiness and smoothness of the coated paper will decrease, and the roughness will also increase.

[0152] If the modification process is omitted (such as in Comparative Example 1), the smoothness and glossiness will be greatly reduced, and the roughness will increase.

[0153] (3) Comprehensive analysis of Application Example 1 and Application Examples 10-14 shows that the selection of process parameters during the coating process will also affect the effect of the lubricant, that is, the whiteness of the paper layer after coating and other paper indicators;

[0154] In the coating process, if the amount of water-based lubricant added is too high or too low (such as in Application Examples 10-11), the smoothness will decrease and the roughness will increase.

[0155] During the coating process, if the pH value of the coating solution is too high (such as in Application Example 12), it will result in high roughness, low whiteness and low gloss; if the coating solution is neutral (such as in Application Example 13), it will result in reduced gloss and smoothness and increased roughness;

[0156] In summary, the lubricant provided by the present invention solves the problem of poor fluidity during coating application, reduces or even avoids streaks, orange peel, and rolling marks that occur during the application process, and the accompanying phenomena of shrinkage craters, pinhole sagging, etc. during the drying process.

[0157] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A water-based lubricant for papermaking coating, characterized in that: The water-based lubricant for papermaking coating comprises, by weight: 13 to 18 parts of water-based oxidized polyethylene copolymer, 3 to 8 parts of surfactant, 5 to 7 parts of bactericide, 10 to 12 parts of initiator and 100 parts of water; The preparation method of the water-based oxidized polyethylene copolymer comprises the following steps: (1) mixing ethylene oxide and polyethylene oxide, and then sequentially performing a mixing reaction and standing to obtain a reaction solution; (2) mixing the amide and the reaction solution obtained in step (1), and subjecting the mixture to a modification reaction to obtain the aqueous oxidized polyethylene copolymer; the modification reaction temperature is 25-30° C., and the pH value is 5-7; The mass ratio of the ethylene oxide, amide and polyethylene oxide is 1.8-2.2:1:2.8-3.

2.

2. The aqueous lubricant for papermaking coating according to claim 1, characterized in that The solid content of the water-based lubricant for papermaking coating is 23-28 wt %.

3. The aqueous lubricant for papermaking coating according to claim 1, characterized in that The viscosity of the water-based lubricant for papermaking coating is ≤300 cps.

4. The aqueous lubricant for papermaking coating according to claim 1, characterized in that The pH value of the water-based lubricant for papermaking coating is 7-10.

5. The aqueous lubricant for papermaking coating according to claim 1, characterized in that The temperature of the mixing reaction in step (1) is 60-70°C.

6. The aqueous lubricant for papermaking coating according to claim 1, characterized in that The stirring rate of the mixing reaction in step (1) is 800~1200r / min.

7. The aqueous lubricant for papermaking coating according to claim 1, characterized in that The mixing reaction time in step (1) is 8 to 12 minutes.

8. The aqueous lubricant for papermaking coating according to claim 1, characterized in that The standing time in step (1) is 5 to 10 minutes.

9. The aqueous lubricant for papermaking coating according to claim 1, characterized in that The modification reaction time in step (2) is 30 to 50 minutes.

10. The aqueous lubricant for papermaking coating according to claim 1, characterized in that The stirring rate of the modification reaction in step (2) is 700-800 r / min.

11. Use of the aqueous lubricant for paper coating according to any one of claims 1 to 10 in paper coating, characterized in that: The application comprises the following steps: (a) mixing alkali liquor, papermaking coating and the water-based lubricant for papermaking coating to obtain a coating solution with a pH value of 8.8 to 9.2; the amount of the water-based lubricant for papermaking coating to be added is 0.05 to 0.15% of the mass of the papermaking coating; (b) applying the coating solution obtained in step (a) to at least one side of the paper layer by a roller to obtain a paper layer with a coating layer; The roller coating comprises primer coating, intermediate coating and top coating performed sequentially; the thickness of the coating obtained by each roller coating is 40-60 μm.

12. The use according to claim 11, characterized in that The temperature of the roller coating in step (b) is 58-65°C.

13. The use according to claim 11, characterized in that The interval between two adjacent roller coatings is 3~5s.

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