Bacteriostatic coated paper, calcium carbonate slurry and preparation method thereof

Abstract

The invention provides antibacterial coated paper, calcium carbonate slurry and a preparation method thereof, and belongs to the technical field of functionalization of inorganic nonmetallic mineral fillers. The superfine calcium carbonate slurry is prepared by wet grinding, calcium carbonate particles in the slurry are subjected to bacteriostatic grinding modification twice in a liquid phase environment, and the calcium carbonate slurry subjected to bacteriostatic grinding modification in the front stage is directly used as a filler and is mixed with paper pulp fibers to make paper. And the back-stage bacteriostatic grinding modification is further bacteriostatic superfine grinding on the basis of the calcium carbonate slurry of the front-stage grinding, and organic and inorganic matters are attached to the surface of the calcium carbonate through the bacteriostatic grinding modification, so that the calcium carbonate not only has the bacteriostatic performance, but also contributes to retention of the calcium carbonate filler in the paper. The antibacterial agent modified calcium carbonate slurry is used for paper preparation and paper coating liquid, and the obtained paper not only has excellent paper performance, but also has a remarkable antibacterial effect.

Description

Technical Field

[0001] The invention relates to the technical field of functionalization of inorganic non-metallic mineral fillers, and in particular to an antibacterial coated paper, a calcium carbonate slurry and a preparation method thereof. Background Art

[0002] With the improvement of the quality of life, consumers are paying more and more attention to health, and the use rate of antibacterial materials is generally increasing. Among them, antibacterial paper is a common packaging material, which is widely used in food packaging, daily necessities, medical and other industries. It is closely related to daily life, especially in the post-epidemic era, and the requirements for antibacterial are even higher. From the development of domestic antibacterial paper, mildew inhibitors have a history of use for many years. In the early days, in order to prevent the production of rotten pulp and mildew of paper products in the papermaking system, some mildew inhibitors were added to prevent mildew caused by long-term storage of paper. As an environmentally friendly daily antibacterial material, the proportion of paper-based antibacterial materials will continue to increase. Research on the preparation and application of antibacterial paper has become a hot topic in the papermaking industry. At present, some paper mills have prepared antibacterial paper with antibacterial properties, mainly through paper surface treatment and in-pulp addition method. The in-pulp addition method is to mix the antibacterial agent with pulp and then make paper through papermaking process. However, this method has low utilization rate of antibacterial agent and high production cost due to the large loss of antibacterial agent during the paper drying process. The surface treatment method is to prepare the antibacterial agent into a coating and attach the antibacterial agent to the surface of the paper by coating and sizing the surface of the paper. Compared with the in-pulp addition method, the utilization rate of the antibacterial agent can be improved, but the long-term antibacterial effect is not as good as the in-pulp addition method because the antibacterial agent only stays on the surface of the paper. Both methods have their own advantages and disadvantages.

[0003] There are many types of antimicrobial agents, and antibacterial agents can be roughly divided into two categories: inorganic antimicrobial agents and organic antimicrobial agents. Inorganic antimicrobial agents are mainly preparations in which metals or metal ions with antimicrobial properties are loaded on inorganic carriers, and calcium carbonate is a commonly used inorganic filler in papermaking. Calcium carbonate can be selected as an inorganic carrier, and the antimicrobial agent is loaded on calcium carbonate to prepare calcium carbonate fillers with antimicrobial properties. Although the domestic coating process is mature, for calcium carbonate used for coating, paper mills only stay at the stage of grinding into ultrafine slurry, and the calcium carbonate slurry is not subjected to antibacterial treatment. If the ultrafinely ground calcium carbonate slurry can be subjected to antibacterial treatment, long-term antibacterial effect of paper can be achieved. Antimicrobial agents need to be selected according to the characteristics of paper-based materials. While considering the high antibacterial efficiency of paper, the performance of paper must be taken into account. It is difficult to achieve high-efficiency antibacterial by relying solely on inorganic antimicrobial agents, and organic antimicrobial agents need to be combined to improve the high antibacterial efficiency. Summary of the invention

[0004] The object of the present invention is to provide an antibacterial coated paper, a calcium carbonate slurry and a preparation method thereof, so as to solve the technical problems of poor antibacterial effect and paper performance and high cost of antibacterial paper in the prior art.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The present invention provides a method for preparing a calcium carbonate slurry, comprising the following steps:

[0007] Step 1): the calcite ore is roughly crushed to obtain powder;

[0008] Step 2): the powder obtained in step 1) is mixed with water to obtain a slurry, the obtained slurry is mixed with a grinding aid and then subjected to antibacterial grinding, and then cationic starch and an antibacterial agent are added in sequence for grinding to obtain a front-stage calcium carbonate slurry;

[0009] Step 3): continue to add antibacterial agent to the front-stage calcium carbonate slurry obtained in step 2), perform secondary antibacterial grinding, and obtain the back-stage calcium carbonate slurry.

[0010] Furthermore, in step 1), the whiteness of the calcite ore is ≥95%, and the calcium carbonate content is ≥98%.

[0011] Furthermore, in step 1), the particle size of the powder is 325-425 mesh.

[0012] Furthermore, in step 2), the rotation speed of the primary antibacterial grinding is 90 to 120 r / min, and the grinding time is 15 to 20 min;

[0013] The temperature for grinding by adding cationic starch is 95-105°C, and the grinding time is 20-25 minutes;

[0014] The temperature for grinding by adding the antibacterial agent is 70-80° C., and the grinding time is 10-15 minutes.

[0015] Furthermore, in step 2), the grinding aid includes one or two of sodium polyacrylate, ethylene glycol, and triethanolamine, and the amount of the grinding aid added is 0.8-1.0% of the mass of the powder;

[0016] The amount of cationic starch added is 1.5-2.5% of the mass of the absolute dry calcium carbonate in the powder;

[0017] The antibacterial agent comprises chitosan quaternary ammonium salt, and the added amount of the antibacterial agent is 2-3% of the mass of the absolutely dry calcium carbonate in the powder.

[0018] Furthermore, in step 2), the solid content of the front-stage calcium carbonate slurry is 60-65%, and the particle size D50 of the calcium carbonate in the front-stage calcium carbonate slurry is 6-8 μm.

[0019] Furthermore, in step 3), the amount of the antibacterial agent added is 5-7% of the mass of the absolute dry calcium carbonate in the calcium carbonate slurry in the previous stage;

[0020] The secondary antibacterial grinding temperature is 70-80°C, the time is 20-25min, and the speed is 90-120r / min;

[0021] The solid content of the latter calcium carbonate slurry is 65-73%, and the content of calcium carbonate with a particle size of 2 μm in the latter calcium carbonate slurry is ≥95wt%.

[0022] The present invention provides a calcium carbonate slurry prepared by the above-mentioned preparation method, comprising a front-stage calcium carbonate slurry and a rear-stage calcium carbonate slurry.

[0023] The present invention provides a method for preparing antibacterial coated paper, comprising the following steps:

[0024] The aforementioned front-stage calcium carbonate slurry is mixed with pulp fiber to make paper to obtain a paper sample; the aforementioned rear-stage calcium carbonate slurry is mixed with an emulsion, a dispersant, a defoamer, and a water repellent to prepare a coating, and the paper sample is coated, dried, and calendered in sequence to obtain an antibacterial coated paper;

[0025] The emulsion includes styrene acrylic emulsion or styrene butadiene emulsion.

[0026] The present invention also provides an antibacterial coated paper prepared by the above preparation method.

[0027] Beneficial effects of the present invention:

[0028] The present invention only needs to perform antibacterial treatment on the calcium carbonate slurry in the liquid phase, and the slurry does not need to be dried into powder and can be directly transported to the paper machine, thereby avoiding the agglomeration of the powder during the drying process and the influence on the antibacterial effect of the antibacterial agent;

[0029] The calcium carbonate slurry ground by antibacterial treatment in the front stage is used as papermaking filler and added to paper, and the ultra-fine calcium carbonate slurry ground by antibacterial treatment in the back stage is used as paper coating, so that both the inside and the surface of the paper have antibacterial effects;

[0030] Grinding cationic starch with modified calcium carbonate can not only improve the retention rate of fillers, but also integrate the negatively charged groups on the surface of the grinding aids used in the grinding process, making more -NH3 + Still positively charged, -NH3 + It can adsorb onto negatively charged bacteria through electrostatic interaction, thus playing an antibacterial role. DETAILED DESCRIPTION

[0031] The present invention provides a method for preparing a calcium carbonate slurry, comprising the following steps:

[0032] Step 1): the calcite ore is roughly crushed to obtain powder;

[0033] Step 2): the powder obtained in step 1) is mixed with water to obtain a slurry, the obtained slurry is mixed with a grinding aid and then subjected to antibacterial grinding, and then cationic starch and an antibacterial agent are added in sequence for grinding to obtain a front-stage calcium carbonate slurry;

[0034] Step 3): continue to add antibacterial agent to the front-stage calcium carbonate slurry obtained in step 2), perform secondary antibacterial grinding, and obtain the back-stage calcium carbonate slurry.

[0035] In the present invention, in step 1), the calcite ore is roughly crushed and then dry-ground into powder by Yifeng Mill.

[0036] In the present invention, the grinding, the primary antibacterial grinding and the secondary antibacterial grinding in step 2) and step 3) are all wet grinding.

[0037] In the present invention, the wet grinding equipment is a JM vertical spiral stirring mill purchased from Changsha Institute of Mining and Metallurgy, which adopts a full ceramic lining and a zirconia bead as the medium.

[0038] In the present invention, in step 1), the whiteness of the calcite ore is ≥95%, preferably ≥97%, and the calcium carbonate content is ≥98%, preferably ≥99%.

[0039] In the present invention, in step 1), the particle size of the powder is 325-425 mesh, preferably 350-400 mesh, and more preferably 375 mesh.

[0040] In the present invention, in step 2), the rotation speed of the primary antibacterial grinding is 90 to 120 r / min, preferably 100 to 110 r / min, more preferably 105 r / min, and the grinding time is 15 to 20 min, preferably 18 min;

[0041] The temperature for grinding by adding cationic starch is 95-105°C, preferably 100°C, and the grinding time is 20-25min, preferably 23min;

[0042] The temperature for grinding by adding the antibacterial agent is 70-80° C., preferably 75° C., and the grinding time is 10-15 min, preferably 13 min.

[0043] In the present invention, the cationic starch undergoes gelatinization and swelling during grinding, so that the starch coats the calcium carbonate.

[0044] In the present invention, in step 2), the grinding aid comprises one or two of sodium polyacrylate, ethylene glycol, and triethanolamine, preferably sodium polyacrylate and / or ethylene glycol, more preferably sodium polyacrylate and ethylene glycol, and the addition amount of the grinding aid is 0.8-1.0% of the mass of the powder, preferably 0.9%;

[0045] The amount of cationic starch added is 1.5-2.5% of the mass of the absolute dry calcium carbonate in the powder, preferably 1.8-2.3%, and more preferably 2%;

[0046] The antibacterial agent includes chitosan quaternary ammonium salt, preferably chitosan quaternary ammonium salt, and the added amount of the antibacterial agent is 2-3% of the mass of the absolute dry calcium carbonate in the powder, preferably 2.5%.

[0047] In the present invention, in step 2), the solid content of the front-stage calcium carbonate slurry is 60-65%, preferably 63%, and the particle size D50 of the calcium carbonate in the front-stage calcium carbonate slurry is 6-8 μm, preferably 7 μm.

[0048] In the present invention, in step 3), the amount of the antibacterial agent added is 5-7% of the mass of the absolute dry calcium carbonate in the previous calcium carbonate slurry, preferably 6%;

[0049] The temperature of the secondary antibacterial grinding is 70-80°C, preferably 75°C, the time is 20-25min, preferably 23min, the speed is 90-120r / min, preferably 100-115r / min, more preferably 110r / min;

[0050] The solid content of the latter calcium carbonate slurry is 65-73%, preferably 70%, and the content of calcium carbonate with a particle size of 2 μm in the latter calcium carbonate slurry is ≥95wt%, preferably ≥97%.

[0051] The present invention provides a calcium carbonate slurry prepared by the above-mentioned preparation method, comprising a front-stage calcium carbonate slurry and a rear-stage calcium carbonate slurry.

[0052] The present invention provides a method for preparing antibacterial coated paper, comprising the following steps:

[0053] The aforementioned front-stage calcium carbonate slurry is mixed with pulp fiber to make paper to obtain a paper sample; the aforementioned rear-stage calcium carbonate slurry is mixed with an emulsion, a dispersant, a defoamer, and a water repellent to prepare a coating, and the paper sample is coated, dried, and calendered in sequence to obtain an antibacterial coated paper;

[0054] The emulsion comprises styrene acrylic emulsion or styrene butadiene emulsion, preferably styrene acrylic emulsion.

[0055] In the present invention, the dispersant includes polyacrylamide, preferably polyacrylamide.

[0056] In the present invention, the defoaming agent includes polysiloxane, preferably polysiloxane.

[0057] In the present invention, the water repellent comprises melamine formaldehyde resin, preferably melamine formaldehyde resin.

[0058] The present invention also provides an antibacterial coated paper prepared by the above preparation method.

[0059] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0060] Example 1

[0061] The calcite ore with a whiteness of 96% and a calcium carbonate content of ≥98% was washed, dried, and roughly broken, and then ground to obtain a powder with a particle size of 325 meshes, the powder was mixed with water to obtain a slurry, sodium polyacrylate was added to the slurry as a grinding aid, the addition amount was 1% of the mass of the powder, and the slurry was ground at a speed of 100r / min for 15min, then 2% of the mass of the absolute dry calcium carbonate in the powder was added to the slurry, and the grinding temperature was 100°C for 10min, and then 2% of the mass of the absolute dry calcium carbonate in the powder was added to the slurry. Chitosan quaternary ammonium salt was added, and the powder particle size D50 in the slurry was measured to be 7.4μm, and the solid content of the slurry was 65%, so as to obtain the front-stage calcium carbonate slurry;

[0062] Take part of the front-stage calcium carbonate slurry, add 6% chitosan quaternary ammonium salt to the slurry (based on the mass of absolute dry calcium carbonate in this part of the slurry), and perform secondary antibacterial grinding at 70°C for 25 minutes. The content of calcium carbonate with a particle size of 2 μm in the slurry is measured to be 96.3%, and the solid content of the slurry is 69%, thus obtaining the back-stage calcium carbonate slurry.

[0063] Example 2

[0064] The calcite ore with a whiteness of 95% and a calcium carbonate content of ≥98% was washed, dried, and roughly broken, and then ground to obtain a powder with a particle size of 400 meshes, and the powder was mixed with water to obtain a slurry, and sodium polyacrylate and ethylene glycol were added to the slurry in a mass ratio of 1:1 as grinding aids. The total added mass of the grinding aids was 0.9% of the powder. The slurry was ground at a speed of 120r / min for 20min, and then 1.5% of the mass of the absolute dry calcium carbonate in the powder was added to the slurry. The slurry was ground at a grinding temperature of 100°C for 25min, and then 3% of the mass of the absolute dry calcium carbonate in the powder was added. Chitosan quaternary ammonium salt was added, and the slurry was ground at 80°C for 15min. The powder particle size D50 in the slurry was measured to be 6.5μm, and the solid content of the slurry was 63%, so as to obtain the front-stage calcium carbonate slurry;

[0065] Take part of the front-stage calcium carbonate slurry, add 6% chitosan quaternary ammonium salt to the slurry (based on the mass of absolute dry calcium carbonate in this part of the slurry), and perform secondary antibacterial grinding at 80°C for 25 minutes. The content of calcium carbonate with a particle size of 2 μm in the slurry is measured to be 97.5%, and the solid content of the slurry is 71%, thereby obtaining the back-stage calcium carbonate slurry.

[0066] Comparative Example 1

[0067] The calcite ore with a whiteness of 95% and a calcium carbonate content of ≥98% was washed, dried, and roughly broken, and then ground to obtain a powder with a particle size of 325 meshes, and the powder was mixed with water to obtain a slurry, and sodium polyacrylate was added to the slurry as a grinding aid, and the added mass was 0.9% of the absolute dry calcium carbonate in the powder, and the slurry was ground at a speed of 120r / min for 20min, and then cationic starch of 1.5% of the mass of the absolute dry calcium carbonate in the powder was added to the slurry, and the slurry was ground at a grinding temperature of 100°C for 25min, and the powder particle size D50 in the slurry was measured to be 7.7μm, and the solid content of the slurry was 60%, so as to obtain the front-stage calcium carbonate slurry;

[0068] Take part of the front-stage calcium carbonate slurry, add 6% chitosan quaternary ammonium salt (based on the mass of absolute dry calcium carbonate in the slurry) to the slurry, perform secondary antibacterial grinding at 70°C for 25 minutes, and measure the content of calcium carbonate with a particle size of 2 μm in the slurry to be 97.3%, and the solid content of the slurry is 70%, thus obtaining the back-stage calcium carbonate slurry.

[0069] Comparative Example 2

[0070] The calcite ore with a whiteness of 95% and a calcium carbonate content of ≥98% was washed, dried, and roughly broken, and then ground to obtain a powder with a particle size of 400 meshes, and the powder was mixed with water to obtain a slurry, and sodium polyacrylate and ethylene glycol were added to the slurry in a mass ratio of 1:1 as grinding aids. The total added mass of the grinding aids was 0.9% of the absolute dry calcium carbonate in the powder. The slurry was ground at a speed of 120r / min for 20min, and then chitosan quaternary ammonium salt of 3% of the absolute dry calcium carbonate in the powder was added to the slurry, and the slurry was ground at 80°C for 15min. The powder particle size D50 in the slurry was measured to be 7.5μm, and the solid content of the slurry was 61%, so as to obtain the front-stage calcium carbonate slurry;

[0071] Take part of the front-stage calcium carbonate slurry, add 6% chitosan quaternary ammonium salt to the slurry (based on the mass of absolute dry calcium carbonate in this part of the slurry), and perform secondary antibacterial grinding at 80°C for 25 minutes. The content of calcium carbonate with a particle size of 2 μm in the slurry is measured to be 97.1%, and the solid content of the slurry is 70%, thus obtaining the back-stage calcium carbonate slurry.

[0072] Comparative Example 3

[0073] The calcite ore with a whiteness of 95% and a calcium carbonate content of ≥98% was washed, dried, and roughly broken, and then ground to obtain a powder with a particle size of 400 meshes, and the powder was mixed with water to obtain a slurry, and sodium polyacrylate was added to the slurry as a grinding aid, and the added mass was 1% of the powder, and the slurry was ground at a speed of 120r / min for 20min, and then cationic starch of 1.5% of the mass of the absolute dry calcium carbonate in the powder was added to the slurry, and the slurry was ground at a grinding temperature of 100°C for 35min, and the powder particle size D50 in the slurry was measured to be 7.7μm, and the solid content of the slurry was 60%, so as to obtain the front-stage calcium carbonate slurry;

[0074] Take part of the front-stage calcium carbonate slurry and continue grinding for 30 minutes until the content of calcium carbonate with a particle size of 2 μm in the slurry is 96.3% and the solid content of the slurry is 69%, thereby obtaining the back-stage calcium carbonate slurry.

[0075] The antibacterial coated paper was prepared using the calcium carbonate slurries in Examples 1 to 2 and Comparative Examples 1 to 3, respectively. The preparation method comprises the following steps:

[0076] Step 1): Mix the broadleaf pulp and coniferous pulp in a mass ratio of 1:3, and beat and dilute to a beating degree of 40 O SR, pulp with a mass concentration of 3%, to which the calcium carbonate slurry of the previous stage is added in a ratio of 30% of the mass of calcium carbonate to the absolute dry paper, and then papermaking is carried out to obtain a paper sample;

[0077] Step 2): The latter calcium carbonate slurry is used to prepare a coating (the coating is composed of the following components by mass fraction: 85% calcium carbonate slurry, 14.85% styrene-butadiene latex, 0.05% polyacrylamide, 0.05% polysiloxane, and 0.05% melamine formaldehyde resin), and the above-mentioned paper sample is coated, dried, and calendered in sequence to obtain an antibacterial coated paper.

[0078] The whiteness, ash content and antibacterial effect of the antibacterial coated paper prepared by the calcium carbonate slurry of Examples 1 to 2 and Comparative Examples 1 to 3 were tested, wherein the smoothness, folding resistance, whiteness, ash content and antibacterial effect were tested according to the national standards GB / T456-2008, GB / T457-2008, GB / T7974-2002, GB / T742-2008 and GB / T12661-2008, respectively. Table 1 shows the performance test results of the antibacterial coated paper prepared by the calcium carbonate slurry of Examples 1 to 2 and Comparative Examples 1 to 3.

[0079] Table 1 Performance test results of antibacterial coated paper prepared from calcium carbonate slurry of Examples 1 to 2 and Comparative Examples 1 to 3

[0080]

[0081] As can be seen from the table, the smoothness, folding resistance, whiteness, ash content and antibacterial effect of the paper samples in Examples 1 to 2 are better than those in Comparative Examples 1 to 3, and the ash content of Comparative Example 1 is higher than that of 2 and 3, indicating that starch modification helps to improve the retention rate of fillers. The number of colonies in Comparative Example 1 is more than that in Comparative Example 3, indicating that the antibacterial effect of adding antibacterial modified calcium carbonate inside the paper and coating the paper surface with antibacterial treatment is better than that of simply coating the surface with antibacterial coating.

[0082] It can be seen from the above embodiments that the present invention provides an antibacterial coated paper, a calcium carbonate slurry and a preparation method thereof. The present invention utilizes wet grinding to prepare ultrafine calcium carbonate slurry, and the calcium carbonate particles in the slurry are subjected to antibacterial grinding and modification twice in a liquid environment. The calcium carbonate slurry subjected to antibacterial grinding and modification in the front stage is directly used as a filler and mixed with pulp fibers to make paper, and the antibacterial grinding and modification in the back stage is further antibacterial ultrafine grinding based on the calcium carbonate slurry ground in the front stage. The antibacterial grinding and modification allows organic and inorganic substances to adhere to the surface of calcium carbonate, so that calcium carbonate not only has antibacterial properties, but also helps to retain calcium carbonate fillers in paper. The calcium carbonate slurry modified with an antibacterial agent is used as the preparation of paper and paper coating liquid, and the resulting paper not only has excellent paper properties, but also has a significant antibacterial effect, which solves the technical problems of poor antibacterial effect, poor paper performance and high cost of antibacterial paper in the prior art.

[0083] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a calcium carbonate slurry, characterized in that: The following steps are involved: Step 1): the calcite ore is roughly crushed to obtain powder; Step 2): the powder obtained in step 1) is mixed with water to obtain a slurry, the obtained slurry is mixed with a grinding aid and then subjected to antibacterial grinding, and then cationic starch and an antibacterial agent are added in sequence for grinding to obtain a front-stage calcium carbonate slurry; Step 3): continue to add antibacterial agent to the front-stage calcium carbonate slurry obtained in step 2), perform secondary antibacterial grinding, and obtain the back-stage calcium carbonate slurry.

2. The method for preparing a calcium carbonate slurry according to claim 1, characterized in that: In step 1), the whiteness of the calcite ore is ≥95%, and the calcium carbonate content is ≥98%.

3. The method for preparing a calcium carbonate slurry for antibacterial coated paper according to claim 1 or 2, characterized in that: In step 1), the particle size of the powder is 325-425 mesh.

4. The method for preparing a calcium carbonate slurry according to claim 1, characterized in that: In step 2), the rotation speed of the primary antibacterial grinding is 90-120 r / min, and the grinding time is 15-20 min; The temperature for grinding by adding cationic starch is 95-105°C, and the grinding time is 20-25 minutes; The temperature for grinding by adding the antibacterial agent is 70-80° C., and the grinding time is 10-15 minutes.

5. The method for preparing a calcium carbonate slurry according to claim 1 or 4, characterized in that: In step 2), the grinding aid includes one or two of sodium polyacrylate, ethylene glycol, and triethanolamine, and the amount of the grinding aid added is 0.8-1.0% of the mass of the powder; The amount of cationic starch added is 1.5-2.5% of the mass of the absolute dry calcium carbonate in the powder; The antibacterial agent comprises chitosan quaternary ammonium salt, and the added amount of the antibacterial agent is 2-3% of the mass of the absolutely dry calcium carbonate in the powder.

6. The method for preparing a calcium carbonate slurry according to claim 1, characterized in that: In step 2), the solid content of the front-stage calcium carbonate slurry is 60-65%, and the particle size D50 of the calcium carbonate in the front-stage calcium carbonate slurry is 6-8 μm.

7. The method for preparing a calcium carbonate slurry according to claim 1, characterized in that: In step 3), the amount of the antibacterial agent added is 5-7% of the mass of the absolute dry calcium carbonate in the calcium carbonate slurry in the previous stage; The secondary antibacterial grinding temperature is 70-80°C, the time is 20-25min, and the speed is 90-120r / min; The solid content of the latter calcium carbonate slurry is 65-73%, and the content of calcium carbonate with a particle size of 2 μm in the latter calcium carbonate slurry is ≥95wt%.

8. The calcium carbonate slurry prepared by the preparation method according to any one of claims 1 to 7, characterized in that: It includes front-end calcium carbonate slurry and back-end calcium carbonate slurry.

9. A method for preparing antibacterial coated paper, characterized in that: The following steps are involved: The front-end calcium carbonate slurry of claim 8 is mixed with pulp fiber to make paper to obtain a paper sample; the back-end calcium carbonate slurry of claim 8 is mixed with an emulsion, a dispersant, a defoamer, and a water repellent to prepare a coating, and the paper sample is coated, dried, and calendered in sequence to obtain an antibacterial coated paper; The emulsion includes styrene acrylic emulsion or styrene butadiene emulsion.

10. The antibacterial coated paper prepared by the preparation method according to claim 9.

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