A method for producing a low basis weight decorative base paper

Abstract

This invention relates to a method for preparing low-basis-weight decorative base paper, comprising the following steps: a. Water treatment: softening water; b. Preparation of titanium dioxide slurry: diluting positively charged titanium dioxide raw materials with the softened water obtained in step a, adjusting the pH, stirring, and setting aside; c. Preparation of post-beating wood pulp: breaking down fiber raw materials with the softened water obtained in step a, and pumping the pulp into a beating tank via a double-disc beating pump; d. In a remixing tank, sequentially pumping in post-beating wood pulp, titanium dioxide slurry, aluminum sulfate, wet strength agent, and a novel material, hydrated alumina, at intervals, stirring thoroughly, adjusting the pH, pumping into a pre-papering tank, and then sequentially passing through screening for slag removal, a headbox, a press section, a drying section, a calendering section, and winding to form low-basis-weight decorative base paper. The method provided by this invention enables the low-basis-weight decorative base paper to have a better titanium dioxide retention rate, which is beneficial for actual production and product performance.

Description

Technical Field

[0001] This invention relates to the technical field of decorative base paper, and in particular to a method for preparing low basis weight decorative base paper. Background Technology

[0002] Currently, decorative base paper is made by mixing softwood pulp, hardwood pulp, high-quality titanium dioxide, pigment paste, and auxiliary chemicals, and then forming it on a paper machine. The use of titanium dioxide in the production of decorative base paper can increase whiteness, gloss, print quality, and light and weather resistance, but it also results in low bonding strength between wood pulp fibers and lower tensile strength of the base paper.

[0003] In the preparation of low-basis-weight decorative base paper, the basis weight of the base paper gradually concentrates to 60-70 g / m², or even 50-55 g / m². Due to the low basis weight, fillers such as titanium dioxide are difficult to retain during the production process, resulting in low single-pass retention, low base paper strength, difficulty in white water sedimentation, high discharge concentration, and increased production costs. Therefore, a method for preparing low-basis-weight decorative base paper that can improve the titanium dioxide retention rate of the base paper is needed. Summary of the Invention

[0004] To address the problems mentioned above in the background art, the present invention provides a method for preparing low basis weight decorative base paper.

[0005] The present invention provides a method for preparing low-basis-weight decorative base paper, which adopts the following technical solution:

[0006] A method for preparing a low-basis-weight decorative base paper includes the following preparation steps:

[0007] a. Water treatment: softening water;

[0008] b. Preparation of titanium dioxide slurry: Dilute the positively charged titanium dioxide raw material with the softened water obtained in step a, adjust the pH, stir, and set aside.

[0009] c. Preparation of wood pulp after beating: The softened water obtained in step a is used to break down the fiber raw materials, which are then pumped into the beating tank through a double grinding disc for later use;

[0010] d. In the pulp mixing tank, the wood pulp after beating, titanium dioxide slurry, aluminum sulfate, wet strength agent, and new material hydrated alumina are pumped in sequence at intervals according to the proportion. After thorough stirring and pH adjustment, the mixture is pumped into the pre-paper tank. Then, it passes through the screening and slag removal, headbox, press section, drying section, calendering section, and winding section in sequence to form low basis weight decorative base paper.

[0011] By adopting the above technical solution, the water is first softened to avoid the adsorption of calcium and magnesium ions on the hydroxyl groups of the fibers in the production water, thereby improving the primary retention rate of titanium dioxide. The titanium dioxide slurry is prepared using positively charged titanium dioxide raw materials, which allows the slurry to carry a positive charge. This enables the titanium dioxide slurry to be fully mixed with the paper pulp, and then a suitable amount of hydrated alumina colloid is deposited on the mixture via chemical deposition. The hydrated alumina colloid fixes the loosely adsorbed titanium dioxide particles on the paper fibers, thus forcing the titanium dioxide particles to achieve a good three-dimensional distribution on the paper fibers. Simultaneously, it effectively reduces anionic waste in the white water.

[0012] Furthermore, in step a, sodium carbonate is used to soften the water, and the hardness of the softened water is 20-40 mg / L.

[0013] By adopting the above technical solution, calcium and magnesium ions in the water can react with carbonate ions to form calcium carbonate and magnesium carbonate precipitates, effectively removing calcium and magnesium ions from the production water and helping to reduce water hardness.

[0014] Furthermore, the titanium dioxide raw material is any one or more of anatase and rutile types.

[0015] By adopting the above technical solution, it is beneficial to ensure that the titanium dioxide in the titanium dioxide raw material carries a positive charge.

[0016] Furthermore, the concentration of the titanium dioxide slurry is (50±5)%, and the pH of the titanium dioxide slurry is 9.5±0.5.

[0017] By adopting the above technical solution, the pH value of titanium dioxide slurry can be adjusted by using caustic soda flakes, which is beneficial for the application of titanium dioxide slurry in the mixing tank and helps to maintain the pH value in the mixing tank.

[0018] Furthermore, the fiber raw material in step c is any one or a combination of two of softwood pulp and hardwood pulp.

[0019] By adopting the above technical solution, the method provided by the present invention can use different raw materials, which is beneficial to improving the practicality of the present invention.

[0020] Furthermore, the ratio of the softwood pulp to the hardwood pulp is (0-50):(50-100).

[0021] By adopting the above technical solution, it is beneficial to reduce the raw material cost of the present invention.

[0022] Furthermore, in step c, the beating degree of the slurry is 25–45°SR.

[0023] By adopting the above technical solution, it is convenient to process the pulp and also beneficial to the production of decorative base paper.

[0024] Furthermore, the novel material in step d is hydrated alumina.

[0025] By adopting the above technical solutions, hydrated alumina is non-toxic, odorless, and powdery, with characteristics such as large specific surface area and large pore volume. Its aqueous state is a thixotropic gel with strong adhesion, which is beneficial to the production of decorative base paper.

[0026] Further, in step d, the wet strength agent is any one or a combination of several of UF resin, MF resin, polyamide epichlorohydrin, and PEI resin.

[0027] By adopting the above technical solution, the practicality of this device can be improved and the range of wet strength agents that can be selected can be broadened.

[0028] In summary, the present invention has the following beneficial technical effects:

[0029] 1. The innovation of this invention lies in: by adjusting the hardness of the production water, using positively charged titanium dioxide, adjusting the position of the wet strength agent and adding hydrated alumina colloid, the retention rate of titanium dioxide in low basis weight decorative base paper is improved, thereby making the paper more delicate and uniform, and ensuring that the low basis weight decorative base paper has good opacity.

[0030] 2. This invention uses positively charged titanium dioxide to mix with pulp, which can deposit an appropriate amount of hydrated alumina colloid on the mixture by chemical deposition. The hydrated alumina colloid fixes the loosely adsorbed titanium dioxide particles on the paper fibers, thereby forcing the titanium dioxide particles to achieve a good three-dimensional distribution on the paper fibers, that is, the titanium dioxide has a better retention rate.

[0031] 3. The technical solution provided by this invention can effectively reduce anionic waste in white water, which helps to reduce the cost of white water treatment. Detailed Implementation

[0032] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0033] Unless otherwise specified in the examples, operations should be performed under conventional conditions familiar to those skilled in the art or as recommended by the manufacturer. All raw materials, reagents, or instruments used, unless otherwise specified by the manufacturer, were purchased commercially.

[0034] A method for preparing a low-basis-weight decorative base paper includes the following preparation steps:

[0035] a. Water treatment: Soften the water by adding calcium carbonate to the production water. The hardness of the softened water is (20-40) mg / L.

[0036] b. Preparation of titanium dioxide slurry: Dilute the positively charged titanium dioxide raw material with the softened water obtained in step a to a concentration of (50±5)%, adjust the pH value to (9.5±0.5), stir at high speed for 10 minutes, and set aside.

[0037] c. Preparation of beating wood pulp: The softened water obtained in step a is used to break down the fiber raw material. The concentration after breaking down is 4.5%. The pulp is pumped into the beating tank by a double grinding disc beating pump for later use. The beating degree is 25-45°SR, preferably 25-35°SR.

[0038] d. In the pulp mixing tank, the wood pulp after beating, titanium dioxide slurry, aluminum sulfate, wet strength agent, and new material hydrated alumina are pumped in sequence at intervals of 5 minutes. The mixture is stirred thoroughly and the pH value is adjusted to (6.5-6.8). The mixture is then pumped into the pre-paper tank and then passed through the screening and slag removal, headbox, press section, drying section, calendering section, and winding section in sequence to form low basis weight decorative base paper.

[0039] Additional notes:

[0040] The sodium carbonate used in step a was provided by Haizhiyuan Chemical Co., Ltd.

[0041] The titanium dioxide used in step b is rutile titanium dioxide produced by Longbai Group Co., Ltd.

[0042] The caustic soda flakes used in step b were from Zibo Benyuan Chemical Co., Ltd.

[0043] The wood pulp used in step c is Acacia wood pulp produced by Asia Pacific Resources International Ltd. (Shandong) Pulp & Paper Co., Ltd. The aluminum sulfate used in step d is iron-free aluminum sulfate produced by Strong Water Purification Materials Co., Ltd.

[0044] The wet strength agent used in step d is Dafeng PAE wet strength agent.

[0045] The novel material hydrated alumina used in step d was provided by Zibo Juying Aluminum Industry Co., Ltd.

[0046] Product performance testing:

[0047] Retention rate testing method: Take a sample from the headbox, measure the mass concentration C1 of the slurry before it is fed into the net, and measure the mass concentration C2 of the white water under the net. Calculate the retention rate = (C1-C2) / C1*100%.

[0048] 1. Adjusting the water hardness, under the same papermaking conditions, the single-pass retention rate results are shown in Table 1 below:

[0049] Table 1

[0050]

[0051] As can be seen from the data in Table 1 above, the hardness of the production water has a significant impact on the retention rate of titanium dioxide. That is, when the hardness of the production water is low, the retention rate of titanium dioxide is high, which means that the product has better hiding power and paper strength.

[0052] 2. The comparison of the retention effect of hydrated alumina in different brands of titanium dioxide is shown in Table 2 below:

[0053] Table 2

[0054]

[0055] As shown in Table 2 above, in low basis weight decorative paper, the retention rate of positively charged titanium dioxide on the surface is higher; the retention rate of the system with added hydrated alumina is higher than that without added hydrated alumina.

[0056] 3. Adjust the wet strength agent addition point; the retention rate comparison is shown in Table 3 below:

[0057] Table 3

[0058]

[0059] As shown in Table 3 above, after adjusting the wet strength agent to the pressure screen, the dosage decreased, the retention rate declined, fiber agglomeration became more pronounced, and the coverage deteriorated. The dosage of titanium dioxide needed to be increased to achieve the same coverage. Experiments demonstrate that the closer the wet strength agent is to the wire mesh, the lower the dosage, the more pronounced the fiber agglomeration, and the lower the titanium dioxide retention rate.

[0060] In summary, by adjusting the hardness of the production water, selecting positively charged titanium dioxide, adjusting the location of the wet strength agent, and adding hydrated alumina colloid, the retention rate of titanium dioxide in low basis weight decorative base paper was improved. Through overall scheme test operation, the single-pass retention rate increased from 64% to 69-70%. The uniformity of low basis weight decorative base paper was improved due to the increased retention rate, and the fineness of the paper was also improved. At the same time, the opacity of low basis weight decorative base paper was also guaranteed.

[0061] The adsorption process between fibers and titanium dioxide particles in the pulp is reversible, and the binding force is not strong. Large impacts, such as water suction during papermaking or competition from other positively charged substances, can cause desorption. Therefore, after controlling the adsorption of titanium dioxide, appropriate additives are needed to help fix it to counteract these adverse factors. The technical solution provided by this patent is to fully mix positively charged titanium dioxide with pulp, and deposit an appropriate amount of hydrated alumina colloid on the mixture by chemical deposition. The hydrated alumina colloid fixes the loosely adsorbed titanium dioxide particles on the paper fibers, thereby forcing the titanium dioxide particles to achieve a good three-dimensional distribution on the paper fibers. At the same time, it effectively reduces anionic waste in the white water, further improving the retention and utilization rate of titanium dioxide. Macroscopically, it improves the hiding power and optical performance release of titanium dioxide, thereby reducing the overall production cost.

[0062] The improved retention rate significantly enhanced the sedimentation effect of the circulating white water, reducing the solid content of the discharged white water from 0.03% to 0.01%. This effectively controlled the consumption per ton of paper, significantly reduced production costs, and improved market competitiveness.

[0063] The above description is merely an embodiment of this application, and the scope of protection of this application is not limited to these specific embodiments, but is determined by the claims of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the technical concept and principles of this application should be included within the scope of protection of this application.

Claims

1. A method for preparing a low-basis-weight decorative base paper, characterized in that: The preparation steps include the following: a. Water treatment: Water softening treatment; Sodium carbonate is used to soften the water, and the hardness of the softened water is 20-40 mg / L; b. Preparation of titanium dioxide slurry: Dilute the positively charged titanium dioxide raw material with the softened water obtained in step a, adjust the pH, stir, and set aside. c. Preparation of wood pulp after beating: The softened water obtained in step a is used to break down the fiber raw materials, which are then pumped into the beating tank through a double grinding disc for later use; d. In the pulp mixing tank, the pulp, titanium dioxide slurry, aluminum sulfate, wet strength agent, and hydrated alumina are pumped in sequence at intervals according to the proportion. The mixture is stirred thoroughly, and the pH value is adjusted to 6.5-6.

8. The mixture is then pumped into the pre-paper tank, and then passes through the screening and deslagging section, headbox, press section, drying section, calendering section, and winding section in sequence to form low basis decorative base paper. In step d, the hydrated alumina is used to deposit on a mixture of titanium dioxide and tapped wood pulp; The titanium dioxide raw material is any one or more of anatase and rutile types; The concentration of the titanium dioxide slurry is 50±5%, and the pH of the titanium dioxide slurry is 9.5±0.

5.

2. The method for preparing a low-basis-weight decorative base paper according to claim 1, characterized in that: The fiber raw material in step c is any one or a combination of two of softwood pulp and hardwood pulp.

3. The method for preparing a low-basis-weight decorative base paper according to claim 2, characterized in that: The ratio of the softwood pulp to the hardwood pulp is 0-50:50-100.

4. The method for preparing a low-basis-weight decorative base paper according to claim 1, characterized in that: In step c, the beating degree of the slurry is 25-45°SR.

5. The method for preparing a low-basis-weight decorative base paper according to claim 1, characterized in that: In step d, the wet strength agent is any one or a combination of several of UF resin, MF resin, polyamide epichlorohydrin, and PEI resin.

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