Production process of freezing-resistant damp-proof coated white board paper

Abstract

The technical scheme provided by the invention belongs to the technical field of papermaking processes, and provides a production process of a freezing-resistant moisture-proof coated white board paper, which comprises the following steps: preparing materials, forming on a net, squeezing and drying, coating, calendering to form paper, and slitting. According to the embodiment of the invention, the raw material structures of the surface layer and the core layer and the sizing process are optimized to meet the index requirements of finished paper strength, water resistance and the like, so that certain toughness can be maintained in a freezing environment, the erosion of water vapor can be resisted, and meanwhile, stable physical properties can be maintained in a humid and hot environment to prevent deformation due to damp.

Description

Technical Field

[0001] This invention relates to the field of papermaking technology, specifically to a process for producing freeze-resistant and moisture-proof coated whiteboard paper. Background Technology

[0002] Coated white cardboard belongs to the category of packaging paperboard. It is made by coating the surface of the original paperboard with white paint and then finishing it. Its basis weight is ≥200g / m³. 2 The coating thickness is ≥0.1mm. Its coating surface has high whiteness, smoothness and ink absorption, and is suitable for the production of single-sided color printed packaging boxes such as offset printing and gravure printing.

[0003] In today's booming consumer market, grey-coated white cardboard, with its excellent printability, has become a core material for packaging boxes in industries such as food, daily chemicals, and electronics. From biscuit gift boxes to electronic product outer boxes, from cosmetic packaging to pharmaceutical boxes, its applications cover almost every corner of life.

[0004] The diverse application scenarios pose stringent challenges to gray-coated white cardboard: it must maintain its toughness in the low-temperature environment of a refrigerator and resist moisture erosion; it must also maintain its physical properties in the hot and humid climate of the south and prevent it from deforming due to moisture; and it must meet the requirements of single-sheet box forming process, possessing excellent folding and bursting strength to ensure that the packaging remains stable and reliable during transportation and storage. Summary of the Invention

[0005] The purpose of this invention is to provide a production process for freeze-resistant and moisture-proof coated whiteboard paper to solve the above-mentioned technical problems. The technical solution adopted by this invention is as follows: A process for producing freeze-resistant and moisture-proof coated whiteboard paper includes the following steps: Preparation of materials: DMOW pulp is prepared using the DMOW production line, the first DIP pulp is prepared using the first DIP production line, the second DIP pulp is prepared using the second DIP production line, the core pulp is prepared using the core layer pulp, and the wood pulp is prepared using the wood pulp production line. Internet access formation: The above slurry is sprayed onto the forming mesh, and the surface layer, lining layer, core layer, bottom lining layer and bottom layer are formed simultaneously. The above 5 layers are then combined into a long mesh forming composite. Press drying: After being vacuum-absorbed, the wet paper web enters the press section for pressing treatment, which includes three pressing processes: vacuum pressing, shoe pressing, and light pressing. After the pressing treatment reaches a dryness of 50%, it enters the drying section for drying treatment. Coating: Coating is applied to the surface of the dried paper web; Calendering into paper: After coating and drying, the paper web is calendered to obtain paper. Slicing: Cut according to the predetermined width.

[0006] Furthermore, in the material preparation step, the DMOW pulp is prepared from 100% domestic waste mixed colored paper via the DMOW production line; the first DIP pulp is prepared from 100% colored paper via the first DIP production line to obtain 65-degree pulp; the second DIP pulp is prepared from 90% domestic waste colored paper and 10% recycled wet pulp via the second DIP production line to obtain 50-degree pulp; the core layer pulp is prepared from 60% Grade A cardboard, 20% corrugated paper, and 20% AOCC dry-refined pulp via the core pulp production line; and the wood pulp is prepared from 70% Northern Long White Rolls and 30% Northern Short White Pulpboard via the wood pulp line.

[0007] Furthermore, in the material preparation step, the freeness settings are as follows: DMOW slurry: 300±20 CSF; First DIP paste: 300±20CSF; Second DIP paste: 300±20CSF; Core layer slurry: 450±20 CSF; Wood pulp: 300-350 CSF.

[0008] Furthermore, in the web forming step, the surface layer slurry comprises 70% wood pulp and 30% DMOW slurry; the liner slurry comprises 100% first DIP slurry; the core layer and the underlayer slurry comprise 100% core layer slurry; and the bottom layer comprises 100% second DIP slurry.

[0009] Furthermore, in the pressing and drying step, the pressure loads of the three pressing processes—vacuum pressing, shoe pressing, and light pressing—are respectively: Vacuum pressing: 75±5kn / m Shoe press: 750±50kn / m; Light pressure: 30-45 kN / m. Furthermore, in the calendering process, the paper web undergoes both hard pressing and soft pressing in the calender. The hard pressing process involves a pressure load of 30-60 kN / m and a temperature of 150-200°C. The soft pressing process involves a pressure load of 25-35 kN / m and a temperature of 150-200°C.

[0010] Furthermore, in the web forming step, when forming the core layer, 15-20 kg / ton of dry strength agent and 0.2-0.5 kg / ton of retention aid are added to the core layer pulp; when forming the underlayer, 5-8 kg / ton of dry strength agent and 0.2-0.5 kg / ton of retention aid are added to the core layer pulp; when forming the top layer, underlayer, and bottom layer, 0.2-0.5 kg / ton of retention aid is added to the corresponding pulp.

[0011] Furthermore, in the coating step, the total coating amount is 38±1 g / m². 2 .

[0012] Furthermore, it also includes a sizing step, which includes in-pulp sizing treatment and surface sizing treatment. In the in-pulp sizing treatment, 1-2 kg / ton of AKD is added to the pulp during the surface layer web forming, and 4-5 kg / ton of AKD is added to the pulp during the bottom layer web forming. In the surface sizing treatment, the surface sizing agent is 1.6-2.1 kg / ton of paper, and the sizing amount on the front / back sides is 1.8-2 g / m². 2 .

[0013] The beneficial effects of this invention are as follows: This invention provides a production process for freeze-resistant and moisture-proof coated whiteboard paper. By optimizing the structure of the surface and core layers and the sizing process, the paper meets the requirements for strength and water resistance. This process enables the paper to maintain a certain degree of toughness in a freezing environment to resist moisture erosion, while also maintaining stable physical properties in a humid and hot environment to prevent deformation due to moisture. Attached Figure Description

[0014] Figure 1 This is a process flow diagram of the present invention.

[0015] Figure 2 This is a comparison table of three embodiments. Detailed Implementation

[0016] To facilitate understanding by those skilled in the art, the present invention will be further described below with reference to embodiments and accompanying drawings. The content mentioned in the embodiments is not intended to limit the present invention. The present invention will be described in detail below with reference to the accompanying drawings.

[0017] This invention provides a production process for freeze-resistant and moisture-proof coated whiteboard paper. By optimizing the structure of the surface and core layers and the sizing process, the paper meets the requirements for strength and water resistance. This process enables the paper to maintain a certain degree of toughness in a freezing environment to resist moisture erosion, while also maintaining stable physical properties in a humid and hot environment to prevent deformation due to moisture.

[0018] Example 1 The coating white paperboard production process provided in this embodiment mainly includes the following steps: Preparation steps: DMOW pulp is prepared through a DMOW production line, first DIP pulp is prepared through a first DIP production line, second DIP pulp is prepared through a second DIP production line, core pulp is prepared through a core layer production line, and wood pulp is prepared through a wood pulp production line.

[0019] The DMOW pulp is prepared from 100% domestic waste paper using the DMOW production line, with a freeness set at 300±20 CSF. The first DIP pulp is prepared from 100% waste paper using the first DIP production line to obtain 65-degree pulp, with a freeness set at 300±20 CSF. The second DIP pulp is prepared from 90% domestic waste paper and 10% recycled wet pulp using the second DIP production line at 50°C to obtain 50-degree pulp, with a freeness set at 300±20 CSF. The core pulp is prepared from 60% Grade A cardboard, 20% corrugated paper, and 20% AOCC dry pulp using the core pulp production line, with a freeness set at 450±20 CSF. The wood pulp is prepared from 70% Beihai long white rolls and 30% Beihai short white pulpboard using the wood pulp line, with a freeness of 300 CSF.

[0020] Steps to create an online website: The above-mentioned pulp is sprayed onto the forming wire, and the top layer, liner layer, core layer, underliner layer, and bottom layer are formed simultaneously. The above five layers are then formed into a long wire. The pulp of the top layer includes 70% wood pulp and 30% DMOW pulp. The addition of 70% wood pulp to the top layer increases the proportion of long fibers, thereby improving the folding endurance and bursting strength of the paper. The liner layer pulp includes 100% first DIP pulp. The pulp of the core layer and the underliner layer includes 100% core layer pulp, with 20% AOCC dry-refined pulp added to improve the strength of the core layer and increase the bursting index of the paper. The bottom layer includes 100% second DIP pulp.

[0021] Meanwhile, in the web forming step, when forming the core layer, 20 kg / ton of dry strength agent and 0.5 kg / ton of retention aid are added to the core layer pulp; when forming the bottom liner layer, 8 kg / ton of dry strength agent and 0.5 kg / ton of retention aid are added to the core layer pulp; when forming the top layer, liner layer, and bottom layer, 0.5 kg / ton of retention aid is added to the corresponding pulp.

[0022] Dry strength agents were added to the core and backing layers to improve the dry strength and burst strength of the paper; retention aids were added to each layer to improve the retention rate of the pulp in each layer.

[0023] In-slurry sizing treatment: During the surface layer forming process, 2 kg / ton of AKD is added to the pulp; During the bottom layer forming process, 5 kg / ton of AKD is added to the pulp; Adding a sizing agent to the slurry improves its water retention properties; Pressing and drying steps: The wet paper web, after vacuum dehydration, enters the press section for pressing, which includes three pressing processes: vacuum pressing, shoe pressing, and light pressing. After the pressing process reaches a dryness of 50%, it enters the drying section for drying. During the pressing process in the press section, the pressure loads for the three pressing processes—vacuum pressing, shoe pressing, and light pressing—are as follows: Vacuum pressing: 75±5kn / m Shoe press: 750±50kn / m; Light pressure: 45 kN / m. Surface adhesive treatment: The surface sizing agent is 2.1 kg / ton of paper, and the sizing amount on both the front and back sides is 2 g / m². 2 In this embodiment, adhesive is applied to both the front and back sides simultaneously, and the amount of adhesive applied is 2g / m². 2 By applying adhesive to the surface, a film is gradually formed during the drying process, which slows down the evaporation and absorption of moisture in different environments, so as to adapt to different application scenarios and storage environments.

[0024] Coating steps: The dried paper web surface is coated with a coating, with a total coating weight of 38±1 g / m². 2 A three-layer coating was applied, with the total coating weight controlled at 38±1 g / m². 2 Adding 9-13 parts of latex to each of the three coating formulations allows for gradual film formation during the drying process, thereby improving both the coating strength and the water resistance of the paper.

[0025] Calendering process: After coating and drying, the paper web enters a calender for calendering to obtain paper. In this step, the paper web undergoes hard pressing and soft pressing in the calender. The pressure load in the hard pressing is 65 kN / m and is carried out at a temperature of 200°C. The pressure load in the soft pressing is 35 kN / m and is carried out at a temperature of 200°C.

[0026] Slitting steps: The calendered paper web is cut into predetermined widths.

[0027] In this embodiment, the processing and production of coated white cardboard paper is completed through steps such as material preparation, wire forming, internal sizing, press drying, surface sizing, coating, calendering, and slitting. This technical solution uses wood pulp as raw material to improve paper strength and stiffness, meeting customers' demands for high folding and bursting resistance. The front absorbance of the finished paper is controlled at 45-55 g / m². 2 Back suction 40-80g / m 2 It has strong water resistance, preventing moisture absorption and deformation, and also preventing poor adhesion due to excessive moisture. It maintains a certain degree of toughness in frozen environments by resisting moisture erosion, and also maintains stable physical properties in humid and hot environments, preventing moisture-induced deformation. It meets the current needs for packaging boxes in diverse usage scenarios.

[0028] Example 2 In this embodiment, the processing technology for coating whiteboard paper is basically the same as in the previous embodiment, with only minor adjustments to certain step parameters to change the freeze resistance of the coated whiteboard paper.

[0029] The coating white paperboard production process provided in this embodiment mainly includes the following steps: Preparation steps: DMOW pulp is prepared through a DMOW production line, first DIP pulp is prepared through a first DIP production line, second DIP pulp is prepared through a second DIP production line, core pulp is prepared through a core layer production line, and wood pulp is prepared through a wood pulp production line.

[0030] The DMOW pulp is prepared from 100% domestic waste paper using a DMOW production line, with a freeness set at 300±20 CSF. The first DIP pulp is prepared from 100% waste paper using a first DIP production line to obtain 65-degree pulp, with a freeness set at 300±20 CSF. The second DIP pulp is prepared from 90% domestic waste paper and 10% recycled wet pulp using a second DIP production line at 50°C to obtain 50-degree pulp, with a freeness set at 300±20 CSF. The core pulp is prepared from 60% Grade A cardboard, 20% corrugated paper, and 20% AOCC dry-refined pulp using a core pulp production line, with a freeness set at 450±20 CSF. The wood pulp is prepared from 70% Northern Long White Rolls and 30% Northern Short White Pulp Board using a wood pulp line, with a freeness of 350 CSF.

[0031] Steps to create an online website: The above-mentioned pulp is sprayed onto the forming wire, and the top layer, liner layer, core layer, underliner layer, and bottom layer are formed simultaneously. The above five layers are then formed into a long wire. The pulp of the top layer includes 70% wood pulp and 30% DMOW pulp. The addition of 70% wood pulp to the top layer increases the proportion of long fibers, thereby improving the folding endurance and bursting strength of the paper. The liner layer pulp includes 100% first DIP pulp. The pulp of the core layer and the underliner layer includes 100% core layer pulp, with 20% AOCC dry-refined pulp added to improve the strength of the core layer and increase the bursting index of the paper. The bottom layer includes 100% second DIP pulp.

[0032] Meanwhile, in the web forming step, when forming the core layer, 15 kg / ton of dry strength agent and 0.2 kg / ton of retention aid are added to the core layer pulp; when forming the bottom liner layer, 5 kg / ton of dry strength agent and 0.2 kg / ton of retention aid are added to the core layer pulp; when forming the top layer, liner layer, and bottom layer, 0.2 kg / ton of retention aid is added to the corresponding pulp.

[0033] Dry strength agents were added to the core and backing layers to improve the dry strength and burst strength of the paper; retention aids were added to each layer to improve the retention rate of the pulp in each layer.

[0034] In-slurry sizing treatment: When forming the surface layer, add 1 kg / ton of AKD to the pulp; During the bottom layer forming process, 4 kg / ton of AKD is added to the pulp; Adding a sizing agent to the slurry improves its water retention properties; Pressing and drying steps: The wet paper web, after vacuum dehydration, enters the press section for pressing, which includes three pressing processes: vacuum pressing, shoe pressing, and light pressing. After the pressing process reaches a dryness of 50%, it enters the drying section for drying. During the pressing process in the press section, the pressure loads for the three pressing processes—vacuum pressing, shoe pressing, and light pressing—are as follows: Vacuum pressing: 75±5kn / m Shoe press: 750±50kn / m; Light pressure: 30-45 kN / m. Surface adhesive treatment: The surface sizing agent is 1.6-2.1 kg / ton of paper, and the sizing amount on both the front and back sides is 1.8 g / m². 2 In this embodiment, adhesive is applied to both the front and back sides simultaneously, and the amount of adhesive applied is 1.8 g / m². 2By applying adhesive to the surface, a film is gradually formed during the drying process, which slows down the evaporation and absorption of moisture in different environments, so as to adapt to different application scenarios and storage environments.

[0035] Coating steps: The dried paper web surface is coated with a coating, with a total coating weight of 38±1 g / m². 2 A three-layer coating was applied, with the total coating weight controlled at 38±1 g / m². 2 In each of the three coating formulations, 9-13 parts of latex are added. In this embodiment, the latex content is 9 parts. During the drying process, the latex gradually forms a film, which improves both the coating strength and the water resistance of the paper.

[0036] Calendering process: After coating and drying, the paper web enters a calender for calendering to obtain paper. In this step, the paper web undergoes hard pressing and soft pressing in the calender. The pressure load in the hard pressing is 45 kN / m and is carried out at a temperature of 150°C. The pressure load in the soft pressing is 35 kN / m and is carried out at a temperature of 150°C.

[0037] Slitting steps: The calendered paper web is cut into predetermined widths.

[0038] The coated whiteboard paper prepared in this embodiment has slightly lower gloss on the paper surface and is slightly less resistant to freezing and moisture erosion compared to Embodiment 1. However, it can still meet the needs of daily use, and its moisture-proof performance is not much different from that of the embodiment.

[0039] Example 3 In this embodiment, the processing technology for coating whiteboard paper is basically the same as in the previous embodiment, with only minor adjustments to certain step parameters to change the freeze resistance of the coated whiteboard paper.

[0040] The coating white paperboard production process provided in this embodiment mainly includes the following steps: Preparation steps: DMOW pulp is prepared through a DMOW production line, first DIP pulp is prepared through a first DIP production line, second DIP pulp is prepared through a second DIP production line, core pulp is prepared through a core layer production line, and wood pulp is prepared through a wood pulp production line.

[0041] The DMOW pulp is prepared from 100% domestic waste paper using the DMOW production line, with a freeness set at 300±20 CSF. The first DIP pulp is prepared from 100% waste paper using the first DIP production line to obtain 65-degree pulp, with a freeness set at 300±20 CSF. The second DIP pulp is prepared from 90% domestic waste paper and 10% recycled wet pulp using the second DIP production line at 50°C to obtain 50-degree pulp, with a freeness set at 300±20 CSF. The core pulp is prepared from 60% Grade A cardboard, 20% corrugated paper, and 20% AOCC dry pulp using the core pulp production line, with a freeness set at 450±20 CSF. The wood pulp is prepared from 70% Beihai long white rolls and 30% Beihai short white pulpboard using the wood pulp line, with a freeness of 330 CSF.

[0042] Steps to create an online website: The above-mentioned pulp is sprayed onto the forming wire, and the top layer, liner layer, core layer, underliner layer, and bottom layer are formed simultaneously. The above five layers are then formed into a long wire. The pulp of the top layer includes 70% wood pulp and 30% DMOW pulp. The addition of 70% wood pulp to the top layer increases the proportion of long fibers, thereby improving the folding endurance and bursting strength of the paper. The liner layer pulp includes 100% first DIP pulp. The pulp of the core layer and the underliner layer includes 100% core layer pulp, with 20% AOCC dry-refined pulp added to improve the strength of the core layer and increase the bursting index of the paper. The bottom layer includes 100% second DIP pulp.

[0043] Meanwhile, in the web forming step, when forming the core layer, 18 kg / ton of dry strength agent and 0.4 kg / ton of retention aid are added to the core layer pulp; when forming the bottom liner layer, 7 kg / ton of dry strength agent and 0.3 kg / ton of retention aid are added to the core layer pulp; when forming the top layer, liner layer, and bottom layer, 0.4 kg / ton of retention aid is added to the corresponding pulp.

[0044] Dry strength agents were added to the core and backing layers to improve the dry strength and burst strength of the paper; retention aids were added to each layer to improve the retention rate of the pulp in each layer.

[0045] In-slurry sizing treatment: When forming the surface layer, add 1.5 kg / ton of AKD to the pulp; During the bottom layer forming process, 4.5 kg / ton of AKD is added to the pulp; Adding a sizing agent to the slurry improves its water retention properties; Pressing and drying steps: The wet paper web, after vacuum dehydration, enters the press section for pressing, which includes three pressing processes: vacuum pressing, shoe pressing, and light pressing. After the pressing process reaches a dryness of 50%, it enters the drying section for drying. During the pressing process in the press section, the pressure loads for the three pressing processes—vacuum pressing, shoe pressing, and light pressing—are as follows: Vacuum pressing: 75±5kn / m Shoe press: 750±50kn / m; Light pressure: 30-45 kN / m. Surface adhesive treatment: The surface sizing agent is 1.8 kg / ton of paper, and the sizing amount on both the front and back sides is 1.8 g / m². 2 In this embodiment, adhesive is applied to both the front and back sides simultaneously, and the amount of adhesive applied is 1.8 g / m². 2 By applying adhesive to the surface, a film is gradually formed during the drying process, which slows down the evaporation and absorption of moisture in different environments, so as to adapt to different application scenarios and storage environments.

[0046] Coating steps: The dried paper web surface is coated with a coating, with a total coating weight of 38±1 g / m². 2 A three-layer coating was applied, with the total coating weight controlled at 38±1 g / m². 2 In this three-layer coating formulation, 9-13 parts of latex are added to each layer. In this embodiment, the latex content is 10 parts. During the drying process, the latex gradually forms a film, which improves both the coating strength and the water resistance of the paper.

[0047] Calendering process: After coating and drying, the paper web enters a calender for calendering to obtain paper. In this step, the paper web undergoes hard pressing and soft pressing in the calender. The pressure load in the hard pressing is 45 kN / m and is carried out at a temperature of 180°C. The pressure load in the soft pressing is 30 kN / m and is carried out at a temperature of 180°C.

[0048] Slitting steps: The calendered paper web is cut into predetermined widths.

[0049] The coated whiteboard paper prepared in this embodiment exhibits relatively uniform performance in terms of gloss and whiteness, resistance to freezing and moisture erosion, and moisture resistance, falling between that of Embodiment 1 and Embodiment 2.

[0050] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some changes or modifications to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and modifications made to the above embodiments based on the present invention without departing from the scope of the present invention are within the scope of the present invention.

Claims

1. A process for producing freeze-resistant and moisture-proof coated whiteboard paper, characterized in that, It includes the following steps: Preparation of materials: DMOW pulp is prepared using the DMOW production line, the first DIP pulp is prepared using the first DIP production line, the second DIP pulp is prepared using the second DIP production line, the core pulp is prepared using the core layer pulp, and the wood pulp is prepared using the wood pulp production line. Internet access formation: The above slurry is sprayed onto the forming mesh, and the surface layer, lining layer, core layer, bottom lining layer and bottom layer are formed simultaneously. The above 5 layers are then combined into a long mesh forming composite. Press drying: After being vacuum-absorbed, the wet paper web enters the press section for pressing treatment, which includes three pressing processes: vacuum pressing, shoe pressing, and light pressing. After the pressing treatment reaches a dryness of 50%, it enters the drying section for drying treatment. Coating: Coating is applied to the surface of the dried paper web; Calendering into paper: After coating and drying, the paper web is calendered to obtain paper. Slicing: Cut according to the predetermined width.

2. The production process of freeze-resistant and moisture-proof coated whiteboard paper according to claim 1, characterized in that, In the material preparation steps, DMOW pulp is prepared from 100% domestic waste mixed decal paper via a DMOW production line; the first DIP pulp is prepared from 100% decal paper via a first DIP production line to obtain a 65-degree pulp; the second DIP pulp is prepared from 90% domestic waste decal paper and 10% recycled wet pulp via a second DIP production line to obtain a 50-degree pulp; the core layer pulp is prepared from 60% Grade A cardboard, 20% corrugated paper, and 20% AOCC dry-refined pulp via a core pulp production line; and the wood pulp is prepared from 70% Beihai long white pulp rolls and 30% Beihai short white pulpboard via a wood pulp line.

3. The process for producing freeze-resistant and moisture-proof coated whiteboard paper according to claim 2, characterized in that, In the material preparation step, the freeness settings are as follows: DMOW slurry: 300±20 CSF; First DIP paste: 300±20CSF; Second DIP paste: 300±20CSF; Core layer slurry: 450±20 CSF; Wood pulp: 300-350 CSF.

4. The production process of freeze-resistant and moisture-proof coated whiteboard paper according to claim 1, characterized in that, In the web forming step, the surface layer slurry comprises 70% wood pulp and 30% DMOW slurry; the liner slurry comprises 100% first DIP slurry; the core layer and the underlayer slurry comprise 100% core layer slurry; and the bottom layer comprises 100% second DIP slurry.

5. The process for producing freeze-resistant and moisture-proof coated whiteboard paper according to claim 1, characterized in that, In the pressing and drying step, the pressure loads of the three pressing processes—vacuum pressing, shoe pressing, and light pressing—are respectively: Vacuum pressing: 75±5kn / m Shoe press: 750±50kn / m; Light pressure: 30-45 kN / m.

6. The production process of freeze-resistant and moisture-proof coated whiteboard paper according to claim 1, characterized in that, In the calendering process, the paper web undergoes both hard pressing and soft pressing in the calender. The hard pressing process has a pressure load of 30-60 kN / m and a temperature of 150-200℃. The soft pressing process has a pressure load of 25-35 kN / m and a temperature of 150-200℃.

7. The production process of freeze-resistant and moisture-proof coated whiteboard paper according to claim 1, characterized in that, In the web forming step, when forming the core layer, 15-20 kg / ton of dry strength agent and 0.2-0.5 kg / ton of retention aid are added to the core layer pulp; when forming the underlayer, 5-8 kg / ton of dry strength agent and 0.2-0.5 kg / ton of retention aid are added to the core layer pulp; when forming the top layer, underlayer, and bottom layer, 0.2-0.5 kg / ton of retention aid is added to the corresponding pulp.

8. The production process of freeze-resistant and moisture-proof coated whiteboard paper according to claim 1, characterized in that, In the coating step, the total coating amount is 38±1 g / m². 2 .

9. The process for producing freeze-resistant and moisture-proof coated whiteboard paper according to claim 1, characterized in that, The paper also includes a sizing step, which comprises in-pulp sizing and surface sizing. In the in-pulp sizing step, 1-2 kg / ton of AKD is added to the pulp during the top layer web forming process, and 4-5 kg / ton of AKD is added during the bottom layer web forming process. In the surface sizing step, the surface sizing agent is 1.6-2.1 kg / ton of paper, and the sizing amount on both the front and back sides is 1.8-2 g / m². 2 .

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