Preparation method of white cardboard surface sizing agent

Abstract

The invention discloses a preparation method of a white cardboard surface sizing agent, and relates to the technical field of preparation of white cardboard surface sizing agents. Preparing starch liquid; adding the primary polymer and the surface glue starch liquid into a comprehensive reaction kettle at the same time, keeping the reaction temperature at 50-80 DEG C and the reaction time for 1-2 hours, finally adding hydroquinone accounting for 0.1-0.8% of the total absolute dry amount, and reacting for 10 minutes to obtain a finished product. A pre-polymerized hydrophobic compound is grafted on starch through a free radical reaction, so that the starch has a sizing effect, the COBB value of base paper is reduced, the surface water absorption is reduced, and the absorption of the base paper to a coating adhesive is controlled, and the prepared sizing agent has relatively good compatibility, can improve the characteristics of hardening and brittleness, and is beneficial to improving the folding strength of a paperboard.

Description

Technical Field

[0001] The invention relates to the technical field of preparation of a white cardboard surface sizing agent, and in particular to a preparation method of a white cardboard surface sizing agent. Background Art

[0002] Double-sided coated white cardboard is mainly used for tobacco and alcohol packaging, book and magazine covers, business cards, hangtags, calendars, handbags, etc. In addition, white cardboard can also be used for food packaging, common liquid milk cartons, etc. The front is generally printed with exquisite patterns, and some packaging cardboards are gold-plated or coated. The production and related technologies of white cardboard also belong to the field of papermaking.

[0003] At present, according to the requirements of cardboard printing, surface coating is generally carried out in production to increase the smoothness and glossiness of the paper surface and reduce the roughness of the paper surface; the purpose of surface sizing of base paper is mainly to control the absorption and penetration of moisture and adhesive in the coating by the base paper during the coating process, reduce the proportion of adhesive consumption in the coating process, and reduce the phenomenon of hair loss and powder loss in the paper printing process. The surface sizing agent needs to have good compatibility with the coating and surface starch, and should not have a negative impact on the strength performance of the base paper. The amount of base paper sizing will affect the folding resistance of the paper, and cardboard, as a high-end packaging paper for daily use, needs to be folded into packaging boxes of different specifications. Summary of the invention

[0004] The purpose of the present invention is to address the defects and shortcomings of the prior art and provide a method for preparing a surface sizing agent for white cardboard. Pre-polymerized hydrophobic compounds are grafted onto starch through free radical reactions so that the starch has a sizing effect, reduces the COBB value of base paper, reduces surface water absorption, and controls the absorption of coating adhesives by base paper. The prepared sizing agent has good compatibility, can improve the hardening and brittle properties, and helps to improve the folding resistance of cardboard.

[0005] To achieve the above object, the present invention adopts the following technical scheme: its operation steps are as follows:

[0006] Step 1, synthesis and preparation of the primary polymer: first add 20-30 parts by mass of deionized water, heat to 40-60°C, add 0.2-0.8 parts of methyl persulfate or ammonium persulfate, then slowly add 10-18 parts of styrene, 20-28 parts of butyl acrylate and 4-8 parts of myristic acid respectively, after the temperature rises, react for 2-3 hours and set aside;

[0007] Step 2, preparation of starch solution: first add 50 parts of softened water, then add 45 parts of corn starch or cassava starch to prepare starch solution, heat the starch solution to 30-35°C, add 10% NaOH solution to adjust the pH value to 8-9; then add 2-8% acetic anhydride of the absolute dry starch, and continuously add alkali solution to maintain the pH value at 8-9, keep reacting for 10-30 minutes, and then add 0.1-0.5% ammonium persulfate or methyl persulfate of the absolute dry starch to obtain the surface gelatin starch solution;

[0008] Step 3, preparation of finished product: add the primary polymer and the surface starch solution into the integrated reactor at the same time, maintain the reaction temperature at 50-80°C, react for 1-2 hours, finally add 0.1-0.8% of the total absolute dry amount of hydroquinone, and react for another 10 minutes to obtain the finished product.

[0009] Preferably, in step 1, the temperature is raised to 50°C.

[0010] Preferably, the solid content of the finished product is 18-30%.

[0011] Preferably, the mass ratio of the primary polymer to the surface starch liquid in step three is 1:3-1:6.

[0012] Preferably, both the primary polymer preparation reactor and the starch solution preparation reactor are equipped with a pressure transmitter to give the CPU a pressure control signal, and the flow meter PLC sets the flow control. When the flow reaches the set flow, the centrifugal pump stops automatically, and the addition time of each synthetic component is maintained at 1-2 hours.

[0013] Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention provides a method for preparing a surface sizing agent for white cardboard, by grafting pre-polymerized hydrophobic compounds onto starch through free radical reaction, so that the starch has a sizing effect, reduces the COBB value of base paper, reduces the surface water absorption and controls the absorption of the base paper by the coating adhesive, and the prepared sizing agent has good compatibility, can improve the hardening and brittle characteristics, and helps to improve the folding resistance of the cardboard. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a test comparison picture table of the compatibility of the present invention with starch liquid.

[0015] Figure 2 The present invention provides a comparative table of COBB values ​​of the surface sizing agent prepared in the present invention and the existing styrene-based surface sizing agent respectively coated on unsizing base paper of cardboard.

[0016] Figure 3 The present invention is used to prepare the surface sizing agent. The surface sizing agent is used to prepare the surface sizing agent. The surface sizing agent is used to prepare the surface sizing agent. DETAILED DESCRIPTION

[0017] The technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. The preferred embodiments in the description are only used as examples, and all other embodiments obtained by those skilled in the art without making any creative work are within the scope of protection of the present invention.

[0018] This specific implementation adopts the following technical solution: its operation steps are as follows:

[0019] Step 1, synthesis and preparation of the primary polymer: first add 20-30 parts by mass of deionized water, heat to 40-60°C, add 0.2-0.8 parts of methyl persulfate or ammonium persulfate, then slowly add 10-18 parts of styrene, 20-28 parts of butyl acrylate and 4-8 parts of myristic acid respectively, wait until the temperature rises to 50°C, react for 2-3 hours and then set aside;

[0020] Step 2, preparation of starch solution: first add 50 parts of softened water, then add 45 parts of corn starch or cassava starch to prepare starch solution, heat the starch solution to 30-35°C, add 10% NaOH solution to adjust the pH value to 8-9; then add 2-8% acetic anhydride of the absolute dry starch, and continuously add alkali solution to maintain the pH value at 8-9, keep reacting for 10-30 minutes, and then add 0.1-0.5% ammonium persulfate or methyl persulfate of the absolute dry starch to obtain the surface gelatin starch solution;

[0021] Step 3, preparation of finished product: add the primary polymer and the surface starch liquid into the comprehensive reaction kettle at the same time, the mass ratio of the primary polymer and the surface starch liquid is 1:3-1:6, maintain the reaction temperature at 50-80°C, the reaction time is 1-2 hours, and finally add 0.1-0.8% of the total absolute dry amount of hydroquinone, and react for another 10 minutes to obtain the finished product, and the solid content of the finished product is 18-30%.

[0022] Experimental test:

[0023] 1. The surface sizing agent prepared by the present invention is tested for compatibility with starch solution and coating. Figure 1 It can be seen that the surface sizing agent prepared by the present invention has no compatibility problem with starch solution and coating.

[0024] 2. The COBB values ​​of the surface sizing agent prepared by the present invention and the existing styrene-based surface sizing agent are measured. The specific evaluation and comparison method is as follows: the starch glue solution after on-site cooking is taken, and the surface sizing agent prepared by the present invention and the existing styrene-based surface sizing agent are added at solid contents of 4%, 8%, 12%, and 20% respectively, and mixed for 5 minutes. The mixed surface sizing solution is coated on the unsizing base paper of the cardboard, and then the COBB values ​​of different schemes are measured. For details, see Figure 2It can be seen that compared with the existing styrene-based surface sizing agents, the surface sizing agent prepared by the present invention can effectively reduce the COBB value of paper. When the dosage is 4%, the COBB relative value of the surface sizing agent prepared by the present invention increases by 8%. When the dosage is 20%, the COBB relative increase of the surface sizing agent prepared by the present invention is 35%. The surface sizing agent prepared by the preparation method of the present invention has a better sizing effect.

[0025] 3. The surface sizing agent prepared by the present invention and the existing styrene-based surface sizing agent were tested on a machine. Figure 3 It can be seen that the surface sizing agent prepared by the present invention has good sizing performance, can significantly improve the folding resistance of the finished paper, the folding resistance is increased from the original 22 times to 35 times, meeting the product requirement of ≥15 times; the IGT and IR of the finished paper are significantly improved. The starch-based characteristics of the surface sizing agent prepared by the present invention can not only give it better compatibility with other chemicals, but also have a reinforcing effect. The transparent toughness of the esterified starch can give the white cardboard better folding resistance, reducing the folding explosion phenomenon that occurs during conventional applications.

[0026] After adopting the above process, the beneficial effects of this specific embodiment are as follows:

[0027] 1. The surface sizing agent prepared by the present invention has a relatively good sizing effect;

[0028] 2. The surface sizing agent prepared by the present invention has a significant effect on enhancing the folding resistance and surface strength of white cardboard;

[0029] 3. The surface sizing agent prepared by the present invention can also reduce the bursting phenomenon that occurs during the application process of paperboard.

[0030] For those skilled in the art, they can modify the technical solutions described in the aforementioned embodiments and make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a white cardboard surface sizing agent, characterized in that: Its operation steps are as follows: Step (i) Synthesis and preparation of the primary polymer: first add 20-30 parts by mass of deionized water, heat to 40-60° C., add 0.2-0.8 parts of methyl persulfate or ammonium persulfate, then slowly add 10-18 parts of styrene, 20-28 parts of butyl acrylate and 4-8 parts of myristic acid respectively, after the temperature rises, react for 2-3 hours and set aside; Step (ii), preparation of starch solution: first add 50 parts of softened water, then add 45 parts of corn starch or cassava starch to prepare starch solution, heat the starch solution to 30-35°C, add 10% NaOH solution to adjust the pH value to 8-9; then add 2-8% acetic anhydride of the absolute dry starch, and continuously add alkali solution to maintain the pH value at 8-9, keep reacting for 10-30 minutes, and then add 0.1-0.5% ammonium persulfate or methyl persulfate of the absolute dry starch to obtain the surface gelatin starch solution; Step (iii), preparation of the finished product: add the primary polymer and the surface starch solution into a comprehensive reaction kettle at the same time, maintain the reaction temperature at 50-80°C, react for 1-2 hours, and finally add 0.1-0.8% of the total absolute dry amount of hydroquinone, and react for another 10 minutes to obtain the finished product.

2. The method for preparing a white cardboard surface sizing agent according to claim 1, characterized in that: In the step (i), the temperature is raised to 50°C.

3. The method for preparing a white cardboard surface sizing agent according to claim 1, characterized in that: The solid content of the finished product is 18-30%.

4. The method for preparing a white cardboard surface sizing agent according to claim 1, characterized in that: The mass ratio of the primary polymer to the surface starch liquid in the step (iii) is 1:3-1:

6.

5. The method for preparing a white cardboard surface sizing agent according to claim 1, characterized in that: The primary polymer preparation reactor and the starch solution preparation reactor are both equipped with pressure transmitters to give the CPU pressure control signals. The flow meter PLC sets the flow control. When the flow reaches the set flow, the centrifugal pump stops automatically. The addition time of each synthetic component is maintained at 1-2 hours.

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