A writing paper that protects eyesight and its preparation method

Abstract

This invention discloses a writing paper that protects eyesight and its preparation method. The preparation method includes the following steps: uniformly coating the upper and lower surfaces of 100% bleached wood pulp paper with a carbon black coating. The carbon black coating includes pretreated carbon black, kaolin, latex, polyvinyl alcohol, and a crosslinking agent, glyoxal. The pretreated carbon black is prepared by mixing carbon black stock solution and styrene-acrylic emulsion at a mass ratio of 100:10, stirring and reacting in a reactor for 60-120 minutes while maintaining the temperature at 70-80℃. This invention effectively reduces the whiteness of 100% bleached wood pulp paper by coating the 100% bleached wood pulp substrate layer with a coating containing pretreated carbon black, thus protecting the eyes and making the writing paper more visually comfortable. It also increases opacity, preventing the writing paper from being too transparent. Furthermore, the carbon black coating layer is prepared by coating, avoiding the impact of directly adding carbon black to the pulp on the entire paper machine system. It eliminates the need to clean the entire paper machine system, resulting in low production costs, less environmental pollution, convenient cleaning, and energy savings.

Description

Technical Field

[0001] This invention belongs to the field of papermaking technology, specifically relating to a writing paper that protects eyesight and its preparation method. Background Technology

[0002] High-quality writing paper not only requires few impurities, high purity, high strength, and a premium feel, but also low whiteness to protect eyesight and high opacity to prevent see-through. High strength requires a large amount of bleaching chemical pulp; paper made from 100% bleached chemical pulp has a whiteness of 86.5% (R457), which is detrimental to eye protection. Using mechanical pulp results in low whiteness but many impurities, which significantly reduces paper strength. As for high opacity, chemicals such as titanium dioxide can be added to the paper surface coating to improve opacity, but this is costly. Currently, writing papers with good strength tend to have high whiteness; those with low whiteness lack the strength required for writing.

[0003] Currently, some papers alter their whiteness and opacity by adding pigments to the pulp. For example, Chinese patent application number 202110206362.6 discloses an optical anti-myopia paper, which adds light-absorbing fillers such as carbon black to the pulp and produces optical anti-myopia paper on a paper machine. However, because carbon black is added to the pulp, the entire paper machine system is affected by the carbon black. When changing products, the entire paper machine system needs to be cleaned, which is inconvenient and not energy-efficient. Summary of the Invention

[0004] In view of the above-mentioned problems in the prior art, the present invention provides a writing paper that protects eyesight and a method for preparing the same.

[0005] The objective of this invention is achieved by the following method: a method for preparing writing paper that protects eyesight, comprising the following steps: uniformly coating the upper and lower surfaces of 100% bleached wood pulp paper with a carbon black coating, wherein the carbon black coating comprises 0.15-0.35 parts of pretreated carbon black, 85-88 parts of kaolin, 8.5-10.5 parts of latex, 3.1-4.0 parts of polyvinyl alcohol, and 0.35-0.45 parts of glyoxal as a crosslinking agent; wherein the pretreated carbon black is prepared by mixing carbon black stock solution with styrene-acrylic emulsion at a mass ratio of 100:10, stirring and reacting in a reactor for 60-120 minutes while maintaining the temperature at 70-80°C.

[0006] The stirring speed is 20-80 rpm.

[0007] The carbon black stock solution in the pretreated carbon black is liquid water-based carbon black S350 with a particle size D90≤1.0μm and a viscosity of 100-500cps.

[0008] The single-sided coating weight of carbon black coating on 100% bleached wood pulp paper is 2.5-4.0 g / m². 2 .

[0009] A type of writing paper that protects eyesight, prepared using the method described above.

[0010] The writing paper R457 has a whiteness of 70.0-80.0% and an opacity of 92.0-98.0%.

[0011] Compared to existing technologies, this invention effectively reduces the whiteness of paper made from 100% bleached wood pulp by coating a 100% bleached wood pulp base layer with a coating containing pretreated carbon black, thus protecting the eyes and making the paper more visually comfortable. At the same time, it increases the opacity, preventing the paper from being too transparent. Furthermore, the carbon black coating layer is prepared by coating, avoiding the impact of adding carbon black directly to the pulp on the entire paper machine system. It eliminates the need to clean the entire paper machine system, resulting in lower production costs, less environmental pollution, easier cleaning, and energy savings. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of the structure of the present invention. Detailed Implementation

[0013] like Figure 1 As shown, a writing paper for protecting eyesight includes a base paper 1, with carbon black coating layers 2 formed on the upper and lower surfaces of the base paper 1 by coating with carbon black coating. The base paper 1 is 100% bleached wood pulp paper. The writing paper has an R457 whiteness of 70.0-80.0% and an opacity of 92.0-98.0%.

[0014] A method for preparing a writing paper that protects eyesight includes the following steps: uniformly coating the upper and lower surfaces of 100% bleached wood pulp paper with a carbon black coating, wherein the carbon black coating comprises 0.15-0.35 parts of pretreated carbon black, 85-88 parts of kaolin, 8.5-10.5 parts of latex, 3.1-4.0 parts of polyvinyl alcohol with a solid content of 8.0-9.0%, and 0.35-0.45 parts of glyoxal as a crosslinking agent.

[0015] Preparation of pretreated carbon black: Mix carbon black stock solution and styrene-acrylic emulsion at a mass ratio of 100:10, maintain the temperature at 70-80℃ in the reactor, and stir for 60-120 minutes. The preferred stirring speed is 20-80 rpm, so that the carbon black stock solution and styrene-acrylic emulsion are fully mixed, the styrene-acrylic emulsion coats the carbon black, and then they adhere to each other.

[0016] Preparation of carbon black coating: To achieve more uniform dispersion, dilute the prepared pretreated carbon black 100 times with cooling water and stir for no less than 10 minutes, preferably 10-30 minutes. After stirring evenly, add it to the coating made of kaolin, latex, polyvinyl alcohol and crosslinking agent glyoxal, and stir evenly to form carbon black coating.

[0017] Preferably, the carbon black stock solution in the pretreated carbon black is liquid water-based carbon black S350 with a particle size D90 ≤ 1.0 μm and a viscosity of 100-500 cps. Water-based carbon black is a black particulate substance, mainly formed by the heating of hydrocarbon compounds such as alkyl styrene, styrene, and isoprene.

[0018] Styrene-acrylic emulsions are mainly composed of acrylate, a soft monomer that provides strong adhesion, and styrene, a high-strength hard monomer.

[0019] The preparation process of pretreated carbon black involves heating, stirring, and homogenization to uniformly disperse the carbon black stock solution in a styrene-acrylic emulsion, giving the carbon black good stability and processability. This pretreatment process results in writing paper with uniform and firm coloring, good surface strength, low whiteness, and high opacity.

[0020] Preferably, the single-sided coating weight of carbon black coating on 100% bleached wood pulp paper is 2.5-4.0 g / m². 2 .

[0021] When uniformly coating the upper and lower surfaces of 100% bleached wood pulp paper with carbon black coating, the carbon black coating can be fed into the coating system of the paper machine and then coated via film transfer, or it can be coated off-machine for secondary forming. Adding carbon black in the coating section of the paper machine has a much smaller impact on the system than adding carbon black to the pulp, and cleaning is also much simpler.

[0022] Example 1

[0023] (1) Preparation of pretreated carbon black: carbon black: styrene-acrylic emulsion = 100:10 by mass ratio, mix evenly, stir at low speed of 50 rpm in the reactor, keep warm at 70~80℃ for 2 hours, and continue stirring during the warming process.

[0024] (2) Preparation of carbon black coating: 85 parts of kaolin, 10.5 parts of styrene-butadiene latex, 4.0 parts of polyvinyl alcohol (PVA), 0.35 parts of glyoxal crosslinking agent, and 0.15 parts of pretreated carbon black. Kaolin, styrene-butadiene latex, polyvinyl alcohol and glyoxal crosslinking agent are mixed evenly in proportion. The pretreated carbon black prepared in step (1) is diluted 100 times with condensed water and then added to the mixture of kaolin, styrene-butadiene latex, polyvinyl alcohol and glyoxal crosslinking agent. The mixture is stirred together for 30 minutes to obtain carbon black coating.

[0025] (3) A type of writing paper for protecting eyesight, made from 100% bleached wood pulp, which is pulped and formed into a base paper. The base paper then enters the coating section, where the carbon black coating obtained in step (2) is applied using a film transfer coating method. The double-sided coating amount is 5.5 g / m². 2After drying, the resulting paper has a whiteness R457 of 80.5% and an opacity of 92.8%. The entire process only involves adding carbon black coating in the coating stage, without requiring any changes to the preceding and following stages. It is simple to operate, has low production costs, and achieves the effect of low whiteness and high opacity, protecting eyesight and avoiding see-through problems on writing paper.

[0026] Example 2

[0027] The only difference between Example 2 and Example 1 is that the double-sided coating amount is 7.0 g / m². 2 The resulting paper had a whiteness R457 of 78.8% and an opacity of 93.6%.

[0028] Example 3

[0029] The difference between Example 3 and Example 1 is that the amount of kaolin pigment in the carbon black coating is 84.8 parts, the amount of pretreated carbon black is 0.35 parts, and the double-sided coating weight is 7.0 g / m². 2 The resulting paper had a whiteness R457 of 75.2% and an opacity of 95.0%.

[0030] Compared with Example 1, Example 2 uses the same papermaking process and the same amount of pretreated carbon black in the coating, but the coating amount is increased, resulting in a decrease in paper whiteness R457 and an increase in opacity. Compared with Example 3, Example 2 uses the same coating amount, but the amount of pretreated carbon black is increased, resulting in a decrease in paper whiteness R457 and an increase in opacity.

[0031] The difference between Comparative Example 1 and Example 1 is that the amounts of carbon black stock solution and pretreated carbon black are shown in Table 1. The carbon black stock solution group was not pretreated. The mass ratio of carbon black stock solution to styrene-acrylic emulsion was 100:10. The carbon black stock solution was diluted 100 times with cooling water and then added to a mixture of kaolin, styrene-butadiene latex, styrene-acrylic emulsion, polyvinyl alcohol, and glyoxal as a crosslinking agent. The mixture was stirred together for 30 minutes to obtain a carbon black coating.

[0032]

[0033] The difference between Comparative Example 2 and Example 1 is that the amounts of carbon black stock solution and pretreated carbon black are shown in Table 2. The carbon black stock solution group was not pretreated; the mass ratio of carbon black stock solution to styrene-acrylic emulsion was 100:10. The carbon black stock solution was diluted 100 times with cooling water and then added to a mixture of kaolin, styrene-butadiene latex, styrene-acrylic emulsion, polyvinyl alcohol, and glyoxal (a crosslinking agent). The mixture was stirred for 30 minutes to obtain the carbon black coating. The double-sided coating weight was 7.0 g / m². 2 .

[0034]

[0035] The difference between Comparative Example 3 and Example 1 is that the amounts of carbon black stock solution and pretreated carbon black are shown in Table 1. The carbon black stock solution group was not pretreated; the mass ratio of carbon black stock solution to styrene-acrylic emulsion was 100:10. The carbon black stock solution was diluted 100 times with cooling water and then added to a mixture of kaolin, styrene-butadiene latex, styrene-acrylic emulsion, polyvinyl alcohol, and glyoxal (a crosslinking agent). The mixture was stirred for 30 minutes to obtain the carbon black coating. The double-sided coating weight was 7.0 g / m². 2 .

[0036]

[0037] IGT, or In-Gravity Test, is a test of the strength of printed surfaces. Specific testing methods are described in standard GB / T 22365. For wet rubbing resistance, the Taber 5135 abrasion tester manufactured by Taber Systems, Inc. (USA) is used.

[0038] Comparative Examples 1-3 show that, to achieve similar whiteness and opacity, the amount of pretreated carbon black used is less than that of untreated carbon black solution, and the surface strength and wet rubbing resistance of paper using pretreated carbon black are superior to those using untreated carbon black solution. The comprehensive properties of paper coatings using pretreated carbon black, including abrasion resistance, water resistance, and surface strength, are significantly improved compared to paper using untreated carbon black solution. This is because during the formation of pretreated carbon black, the styrene-acrylic emulsion and carbon black solution are thoroughly mixed, the emulsion encapsulates the carbon black, and they then adhere to each other. Through processes such as heating, stirring, and homogenization, the carbon black is evenly dispersed in the styrene-acrylic emulsion, giving it good stability and processability. Coatings made with pretreated carbon black result in writing paper with uniform and firm coloring, good surface strength, low whiteness, and high opacity.

[0039] This invention adds pretreated carbon black to the coating to reduce its whiteness, effectively weakening the whiteness of paper made from 100% bleached wood pulp, thus protecting the eyes and making it more visually comfortable. It also increases opacity, preventing see-through distortion on writing paper. While coating the paper surface is common in the papermaking industry, this invention achieves low whiteness and high opacity by adding pretreated carbon black to the coating. Compared to adding other chemicals to the entire paper machine system or using other chemicals in the coating, this eye-protecting invention is significantly more effective, eliminates the need to clean the entire paper machine system, has lower production costs, less environmental pollution, a smaller system that is easier to clean, and saves energy.

[0040] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several changes and improvements without departing from the overall concept of the present invention, and these should also be considered within the scope of protection of the present invention.

Claims

1. A method for producing a writing paper for protecting eyesight, characterized by: The method comprises the following steps: uniformly coating carbon black paint on the upper and lower surfaces of 100% bleached wood pulp paper, wherein the carbon black paint comprises 0.15-0.35 parts of pretreated carbon black, 85-88 parts of kaolin, 8.5-10.5 parts of latex, 3.1-4.0 parts of polyvinyl alcohol and 0.35-0.45 parts of crosslinking agent glyoxal; the pretreated carbon black is obtained by mixing carbon black stock solution and phenylpropyl emulsion at a mass ratio of 100:10, stirring and reacting in a reactor for 60-120 minutes while keeping the temperature at 70-80 DEG C; the carbon black stock solution in the pretreated carbon black is liquid water-based carbon black S350 with a particle size D90 of less than or equal to 1.0 microns and a viscosity of 100-500 cps; the phenylpropyl emulsion is mainly composed of soft monomer acrylate for providing firm adhesion and high-strength hard monomer styrene; the phenylpropyl emulsion is fully mixed with the carbon black stock solution, the emulsion wraps the carbon black, and the carbon black is adhered to each other, so that the carbon black is uniformly dispersed in the phenylpropyl emulsion through heating, stirring and homogenization process, and the carbon black has good stability and processability; the carbon black paint prepared by using the pretreated carbon black makes the writing paper have the advantages of uniform and firm coloring, good surface strength, low whiteness, high opacity and excellent surface strength and wet rubbing resistance.

2. The method for preparing a vision-protecting writing paper according to claim 1, characterized in that: The stirring speed is 20-80 rpm.

3. The method for preparing a vision-protecting writing paper according to claim 1, characterized in that: The single side coating weight of carbon black coating on 100% bleached wood pulp paper was 2.5-4.0 g / m 2 .

4. A writing paper for protecting eyesight prepared by the method of any one of claims 1-3.

5. The paper for writing for protecting eyesight according to claim 4, wherein: The writing paper R457 has a whiteness of 70.0-80.0% and an opacity of 92.0-98.0%. The writing paper R457 has a whiteness of 70.0-80.0% and an opacity of 92.0-98.0%.

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