Process for producing single-side high-gloss food-grade base paper on a long net cylinder machine

Abstract

The application belongs to the technical field of papermaking, and particularly relates to a process for producing single-side high-gloss food-grade composite base paper by a long net cylinder paper machine. The production process flow is as follows: pulp board -> chain plate conveying -> pulper -> unloading pool -> refiner -> pulp pool -> pre-pulping pool -> pulp pump -> pressure screen -> headbox -> net section -> press section -> cylinder -> calender -> winding section -> rewinding -> packaging and warehousing. The application uses acid sizing of rosin size and aluminum sulfate, the viscosity of rosin size is large, and the viscosity of slurry can be uniformly increased after adding, so that the adhesion between paper sheet and cylinder is increased when the paper sheet is dried at the cylinder, the contact between the paper sheet and the cylinder is more close, the ironing effect of the cylinder on the paper sheet is improved, and the gloss of the paper sheet is increased. The free rosin acid particles soften at high temperature in the drying section, react with aluminum ions, position the rosin molecules, turn the hydrophobic group to the outside of the fiber, and firmly combine the hydrophilic group with the fiber to form a hydrophobic layer. The rosin size itself has high gloss after melting and spreading.

Description

Technical Field

[0001] This invention belongs to the field of papermaking technology, specifically relating to a process for producing single-sided high-gloss food-grade composite base paper using a long-wire large-cylinder paper machine. Background Technology

[0002] With the rapid development of the food packaging industry, consumers have increasingly higher requirements for the aesthetics and safety of food packaging. Food-grade composite base paper, as an important packaging material, has been widely used in the food packaging field due to its environmentally friendly and recyclable characteristics. However, existing single-sided high-gloss food-grade composite base paper technologies face some technical bottlenecks, limiting its application in high-end food packaging. Existing food-grade composite base paper typically has low gloss (less than 20Gs), which leads to insufficient color reproduction during printing, affecting the visual effect of the final product. Due to insufficient smoothness, existing food-grade composite base paper is prone to uneven ink coverage and dull colors during printing, which not only affects the aesthetics of the packaging but also reduces the product's market competitiveness. After printing, existing food-grade composite base paper often fails to exhibit rich color gradations and textures. The low gloss and poor smoothness of food-grade composite base paper, failing to provide good color texture, not only affect the overall quality of food packaging but also restrict the innovation and development of food packaging materials. Summary of the Invention

[0003] To address the shortcomings of existing technologies, the present invention aims to provide a process for producing single-sided high-gloss food-grade composite base paper using a long-wire large-cylinder paper machine. This base paper exhibits higher gloss and smoothness, meeting the printing requirements of high-end food packaging. By employing a special production process and material formulation, the composite base paper of this invention achieves higher color fidelity and richer color texture, thereby enhancing the overall quality and market competitiveness of food packaging.

[0004] The process for producing single-sided high-gloss food-grade composite base paper using a long-wire large-cylinder paper machine according to the present invention is as follows:

[0005] Pulp sheet → Chain conveyor → Pulper → Unloading tank → Refining mill → Pulp forming tank → Pre-pulping tank → Pulp pump → Pressure screen → Headbox → Wire section → Press section → Large cylinder → Calender → Winding section → Rewinding → Packaging and warehousing;

[0006] Process flow diagram as follows Figure 1 As shown.

[0007] Add 8-12 kg of cationic starch per ton of slurry and 30-40 kg of aluminum sulfate per ton of slurry to the pipeline between the slurry forming tank and the pre-slurry forming tank;

[0008] Add 15-20 kg / ton of anionic dispersed rosin gum to the pipeline between the pre-filling pool and the slurry pump.

[0009] In the pulp board process described above, the pulp board ratio is: 20 wt.% bleached sulfate softwood pulp and 80 wt.% bleached sulfate hardwood pulp.

[0010] The pulping process described above is as follows: three DD720 double-disc mills are connected in series for pulping. The first disc mill uses cutting fin-type grinding discs, and the second and third disc mills use broom-type grinding discs. The freeness is 34-38°SR, and the wet weight is 2.5-3.5g.

[0011] Add 200-300g of cationic retention aid per ton of slurry to the pipeline between the slurry pump and the pressure screen.

[0012] Add 200-300g / ton of anionic retention aid to the pipe between the pressure screen and the headbox.

[0013] In the large-cylinder process, an adhesion promoter is sprayed onto the large cylinder, and the amount of adhesion promoter sprayed is 100-300g / ton of paper.

[0014] Food-grade wet strength agent 10-18 kg / ton of pulp and wax emulsion LW-101 3-8 kg / ton of pulp are added to the pipeline between the pulping tank and the pre-pulping tank.

[0015] The paper machine operating parameters are as follows:

[0016] (1) Vehicle speed 450-550m / min;

[0017] (2) The steam pressure of the large cylinder is 550-590 kPa;

[0018] The wet end air temperature of the large cylinder hood is 220-280℃, and the dry end air temperature is 220-280℃.

[0019] The dryness of the product exiting the large cylinder is 94-96%.

[0020] The calender is a dual-pressure zone soft calender. The first pressure zone has a hard roller pressing the front side of the paper (the side with higher paper smoothness), and the second pressure zone has a hard roller pressing the back side of the paper (the side with lower paper smoothness). The first pressure is 50-70 kN / m and the temperature is 120℃; the second pressure is 50-70 kN / m and the temperature is 120℃.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] 1. This invention uses 100% wood pulp fiber. During the drying process in large vats, the wood pulp fiber is ironed in large vats, making it easier for its surface to develop a "mirror" effect. The resulting paper has a gloss level far superior to paper containing fillers.

[0023] 2. This invention uses an acidic sizing agent composed of rosin and aluminum sulfate. Firstly, the high viscosity of rosin increases the viscosity of the pulp uniformly when added, thereby increasing the adhesion between the paper sheet and the drying vat, resulting in a tighter contact and improved ironing effect, thus enhancing the paper's gloss. Furthermore, the sizing mechanism of rosin involves the softening of free rosin acid particles at high temperatures in the drying section, followed by a reaction with aluminum ions. This repositions the rosin molecules, causing the hydrophobic groups to flank the fibers while the hydrophilic groups firmly bond with the fibers, forming a good hydrophobic layer. Rosin itself also has high gloss after melting and spreading. Therefore, after drying in the vat, a water-resistant layer similar to a rosin film is formed on the paper surface, further improving the paper's gloss.

[0024] 3. The food-grade wet strength agent used in this invention, in addition to providing the required wet strength of the paper, also uniformly increases the viscosity of the pulp, thereby increasing the adhesion between the paper and the large vat during drying, making the contact between the paper and the large vat more compact, improving the ironing effect of the large vat on the paper, and enhancing the gloss of the paper.

[0025] 4. The wax emulsion LW-101 used in this invention adheres to the fiber surface in the thick pulp and is remelted and spread through a heating process in a large vat. Due to the reflective properties of wax, the surface gloss of the paper is increased.

[0026] 5. This invention uses a dual-pressure zone soft calender, which improves the gloss of the paper while also improving its smoothness and flatness, and enhances the bonding strength between the base paper and other composite materials.

[0027] 6. In this invention, an adhesion promoter is sprayed at the large cylinder. After the pulp viscosity reaches a high level under the condition of ensuring operation, the adhesion promoter is sprayed to further improve the adhesion between the paper sheet and the large cylinder during the drying process, thereby improving the ironing effect of the large cylinder and increasing the gloss of the paper sheet.

[0028] 7. Single-sided glossy food-grade composite base paper, meeting food-grade requirements, with a chloropropanol content of less than 10ppm, is a green, recyclable, and environmentally friendly material. Attached Figure Description

[0029] Figure 1 This is a process flow diagram of the long-wire large-cylinder paper machine described in this invention for producing single-sided high-gloss food-grade composite base paper;

[0030] Figure 2 For comparison example 1, a process flow diagram of the production of single-sided food-grade composite base paper by a long-wire large-cylinder paper machine;

[0031] Figure 3 For comparison example 2, a process flow diagram of the production of single-sided food-grade composite base paper by a long-wire large-cylinder paper machine. Detailed Implementation

[0032] The present invention will be further described below with reference to the embodiments, but these embodiments do not limit the implementation of the present invention.

[0033] The raw material procurement information used in the examples and comparative examples is as follows:

[0034] Cationic starch is MYZ-307 high molecular weight cationic starch product of Guangxi Nongken Mingyang Biochemical Group Co., Ltd.

[0035] The cationic retention aid PC301L-AP was purchased from Solis Company.

[0036] The food-grade wet strength agent 888ULX was purchased from Solis Company.

[0037] Anionic retention aid SP8338-AP was purchased from Solis Company.

[0038] The wax emulsion LW-101 was purchased from Nanjing Tianshi New Material Technology Co., Ltd.

[0039] AKD is a commercially available product of Kemira Corporation;

[0040] The adhesion promoter, polymin SK polyamide polyamine epichlorohydrin resin, was purchased from BASF.

[0041] The anionic dispersed rosin adhesive was purchased from Hangzhou Hanghua Halima Chemical Co., Ltd.

[0042] Test method:

[0043] 1. Tightness: The calculation formula is: Tightness = Basis Weight / Thickness (Basis Weight: GB / T 451.2-2002; Thickness: GB / T 451.3-2002);

[0044] 2. Wet tensile strength: GB / T465.2-2008;

[0045] 3. Tensile strength: GB / T12914-2008;

[0046] 4. Water absorption: GB / T 1540-2002;

[0047] 5. Smoothness: GB / T 456-2002;

[0048] 6. Gloss: GB / T 8941-2013.

[0049] Example 1

[0050] The process for producing single-sided high-gloss food-grade composite base paper using the long-wire large-cylinder paper machine is as follows:

[0051] Pulp sheet → Chain conveyor → Pulper → Unloading tank → Refining mill → Pulp forming tank → Pre-pulping tank → Pulp pump → Pressure screen → Headbox → Wire section → Press section → Large cylinder → Calender → Winding section → Rewinding → Packaging and warehousing;

[0052] Process flow diagram as follows Figure 1 As shown.

[0053] 15 kg / ton of anionic dispersed rosin gum was added to the pipeline between the pre-filling pool and the slurry pump.

[0054] In the pulp board process described above, the pulp board ratio is: 20 wt.% Canadian bleached sulfate softwood pulp (Moon brand) and 80 wt.% Brazilian bleached sulfate hardwood pulp (Parrot brand).

[0055] In the aforementioned pulping process, the pulping process is as follows: three DD720 double-disc mills are connected in series for pulping. The first disc mill uses cutting fin-type grinding discs, and the second and third disc mills use broom-type grinding discs. The freeness is 36°SR and the wet weight is 3.1g.

[0056] 200g of cationic retention aid per ton of slurry is added to the pipeline between the slurry pump and the pressure screen.

[0057] Add 200g / ton of anionic retention aid to the pipe between the pressure screen and the headbox.

[0058] In the large-cylinder process, an adhesion promoter is sprayed onto the large cylinder, and the spraying amount of the adhesion promoter is 300g / ton of paper.

[0059] The pipeline between the pulping tank and the pre-pulping tank contains 10 kg / ton of cationic starch, 30 kg / ton of aluminum sulfate, 10 kg / ton of food-grade wet strength agent, and 3 kg / ton of wax emulsion LW-101.

[0060] The paper machine operating parameters are as follows:

[0061] (1) Vehicle speed 500m / min;

[0062] (2) The steam pressure of the large cylinder is 580 kPa;

[0063] The wet end air temperature of the large cylinder hood is 260℃, and the dry end air temperature is 260℃.

[0064] The dryness of the product exiting the large cylinder is 95%.

[0065] The calender is a dual-pressure zone soft calender. The first pressure zone has a hard roller pressing the front side of the paper (the side with higher paper smoothness), and the second pressure zone has a hard roller pressing the back side of the paper (the side with lower paper smoothness). The first pressure is 60 kN / m and the temperature is 120℃; the second pressure is 60 kN / m and the temperature is 120℃.

[0066] Example 2

[0067] The process for producing single-sided high-gloss food-grade composite base paper using the long-wire large-cylinder paper machine is as follows:

[0068] Pulp sheet → Chain conveyor → Pulper → Unloading tank → Refining mill → Pulp forming tank → Pre-pulping tank → Pulp pump → Pressure screen → Headbox → Wire section → Press section → Large cylinder → Calender → Winding section → Rewinding → Packaging and warehousing;

[0069] Process flow diagram as follows Figure 1 As shown.

[0070] 20 kg / ton of anionic dispersed rosin gum was added to the pipeline between the pre-filling pool and the slurry pump.

[0071] In the pulp board process described above, the pulp board ratio is: 20 wt.% Canadian bleached sulfate softwood pulp (Moon brand) and 80 wt.% Brazilian bleached sulfate hardwood pulp (Parrot brand).

[0072] In the aforementioned pulping process, the pulping process is as follows: three DD720 double-disc mills are connected in series for pulping. The first disc mill uses cutting fin-type grinding discs, and the second and third disc mills use broom-type grinding discs. The freeness is 36°SR and the wet weight is 3.1g.

[0073] 200g of cationic retention aid per ton of slurry is added to the pipeline between the slurry pump and the pressure screen.

[0074] Add 200g / ton of anionic retention aid to the pipe between the pressure screen and the headbox.

[0075] In the large-cylinder process, an adhesion promoter is sprayed onto the large cylinder, and the spraying amount of the adhesion promoter is 300g / ton of paper.

[0076] The pipeline between the pulping tank and the pre-pulping tank contains 10 kg / ton of cationic starch, 40 kg / ton of aluminum sulfate, 18 kg / ton of food-grade wet strength agent, and 8 kg / ton of wax emulsion LW-101.

[0077] The paper machine operating parameters are as follows:

[0078] (1) Vehicle speed 500m / min;

[0079] (2) The steam pressure of the large cylinder is 580 kPa;

[0080] The wet end air temperature of the large cylinder hood is 260℃, and the dry end air temperature is 260℃.

[0081] The dryness of the product exiting the large cylinder is 95%.

[0082] The calender is a dual-pressure zone soft calender. The first pressure zone has a hard roller pressing the front side of the paper (the side with higher paper smoothness), and the second pressure zone has a hard roller pressing the back side of the paper (the side with lower paper smoothness). The first pressure is 60 kN / m and the temperature is 120℃; the second pressure is 60 kN / m and the temperature is 120℃.

[0083] Example 3

[0084] The process for producing single-sided high-gloss food-grade composite base paper using the long-wire large-cylinder paper machine is as follows:

[0085] Pulp sheet → Chain conveyor → Pulper → Unloading tank → Refining mill → Pulp forming tank → Pre-pulping tank → Pulp pump → Pressure screen → Headbox → Wire section → Press section → Large cylinder → Calender → Winding section → Rewinding → Packaging and warehousing;

[0086] Process flow diagram as follows Figure 1 As shown.

[0087] Anionic dispersed rosin gum of 18 kg / ton of slurry is added to the pipeline between the pre-filling pool and the slurry pump.

[0088] In the pulp board process described above, the pulp board ratio is: 20 wt.% Canadian bleached sulfate softwood pulp (Moon brand) and 80 wt.% Brazilian bleached sulfate hardwood pulp (Parrot brand).

[0089] In the aforementioned pulping process, the pulping process is as follows: three DD720 double-disc mills are connected in series for pulping. The first disc mill uses cutting fin-type grinding discs, and the second and third disc mills use broom-type grinding discs. The freeness is 36°SR and the wet weight is 3.1g.

[0090] 200g of cationic retention aid per ton of slurry is added to the pipeline between the slurry pump and the pressure screen.

[0091] Add 200g / ton of anionic retention aid to the pipe between the pressure screen and the headbox.

[0092] In the large-cylinder process, an adhesion promoter is sprayed onto the large cylinder, and the spraying amount of the adhesion promoter is 200g / ton of paper.

[0093] The pipeline between the pulping tank and the pre-pulping tank contains 10 kg / ton of cationic starch, 36 kg / ton of aluminum sulfate, 14 kg / ton of food-grade wet strength agent, and 5.5 kg / ton of wax emulsion LW-101.

[0094] The paper machine operating parameters are as follows:

[0095] (1) Vehicle speed 500m / min;

[0096] (2) The steam pressure of the large cylinder is 580 kPa;

[0097] The wet end air temperature of the large cylinder hood is 260℃, and the dry end air temperature is 260℃.

[0098] The dryness of the product exiting the large cylinder is 95%.

[0099] The calender is a dual-pressure zone soft calender. The first pressure zone has a hard roller pressing the front side of the paper (the side with higher paper smoothness), and the second pressure zone has a hard roller pressing the back side of the paper (the side with lower paper smoothness). The first pressure is 60 kN / m and the temperature is 120℃; the second pressure is 60 kN / m and the temperature is 120℃.

[0100] Comparative Example 1

[0101] Compared with Example 3, talc powder (18 wt.% Canadian bleached sulfate softwood pulp, 72 wt.% Brazilian bleached sulfate hardwood pulp, and 10 wt.% talc powder) was added to the pulper while other conditions remained unchanged. The process flow diagram is as follows. Figure 2 As shown.

[0102] Comparative Example 2

[0103] Compared with Example 3, aluminum sulfate and rosin were replaced with AKD sizing agent. The AKD dosage was 18 kg / ton of paper, and other conditions remained unchanged. The process flow diagram is as follows. Figure 3 As shown.

[0104] Comparative Example 3

[0105] Compared with Example 3, no wet strength agent was added, and other conditions remained unchanged.

[0106] Comparative Example 4

[0107] Compared with Example 3, no wax emulsion was added, and other conditions remained unchanged.

[0108] Comparative Example 5

[0109] Compared with Example 3, the calender was not used, but other conditions remained the same.

[0110] Comparative Example 6

[0111] Compared with Example 3, no adhesion promoter was used, and other conditions remained the same.

[0112] The paper produced in the examples and comparative examples was subjected to performance tests, and the results are shown in Table 1 below.

[0113] Table 1 Performance Test Results

[0114]

[0115] The above test data shows that the solution of this invention is effective.

[0116] By comparing Comparative Example 1 and Example 3, it can be found that after the paper is filled, the fiber ratio decreases, the "mirror" ratio formed by the fibers decreases, and the gloss level drops to 17.8 Gs, which does not meet the standard of gloss level ≥20 Gs.

[0117] By comparing Comparative Example 2 and Example 3, it can be found that after using neutral AKD sizing, the viscosity of the pulp is greatly reduced, the adhesion of the paper to the cylinder is greatly reduced, and the sizing and film-forming properties of rosin glue are also lost, resulting in a significant decrease in the smoothness and gloss of the paper, with a gloss of only 15.3 Gs, which does not meet the standard of gloss ≥20 Gs.

[0118] By comparing Comparative Example 3 with Example 3, it can be found that without adding wet strength agent, the wet strength of the paper sheet is lower, the viscosity of the pulp is reduced, the ironing effect at the large cylinder is reduced, and the gloss is also reduced to 18.4Gs, which does not meet the standard of gloss ≥20Gs.

[0119] By comparing Comparative Example 4 with Example 3, it can be found that without the addition of wax emulsion, the reflective properties of the wax emulsion disappear, resulting in a decrease in gloss to 18.7 Gs, which does not meet the standard of gloss ≥20 Gs.

[0120] By comparing Comparative Example 5 with Example 3, it can be found that without using a calender, the paper sheet loses one ironing and smoothing process, resulting in reduced smoothness and gloss. The gloss level is 17.4 Gs, which does not meet the standard of gloss level ≥20 Gs.

[0121] By comparing Comparative Example 6 with Example 3, it can be found that spraying at the large cylinder without using an adhesion promoter leads to a decrease in the adhesion of the paper sheet at the large cylinder, thereby weakening the ironing effect of the large cylinder and reducing the gloss to 17.1 Gs, which does not meet the standard of gloss ≥20 Gs.

Claims

1. A process for producing single-sided high-gloss food-grade composite base paper using a long-wire large-cylinder paper machine, characterized in that, The production process is as follows: Pulp sheet → Chain conveyor → Pulper → Unloading tank → Refining mill → Pulp forming tank → Pre-pulping tank → Pulp pump → Pressure screen → Headbox → Wire section → Press section → Large cylinder → Calender → Winding section → Rewinding → Packaging and warehousing; Add 8-12 kg / ton of cationic starch and 30-40 kg / ton of aluminum sulfate to the pipeline between the pulping tank and the pre-pulping tank; Add 15-20 kg / ton of anionic dispersed rosin gum to the pipeline between the pre-filling pool and the slurry pump; In the aforementioned pulp board process, the pulp board ratio is: 20 wt.% bleached sulfate softwood pulp and 80 wt.% bleached sulfate hardwood pulp. In the aforementioned pulping process, the pulping process is as follows: three DD720 double-disc mills are connected in series for pulping. The first disc mill uses cutting fin-type grinding discs, and the second and third disc mills use broom-type grinding discs. The freeness is 34-38°SR, and the wet weight is 2.5-3.5g. In the large-cylinder process, the adhesion promoter polymin SK polyamide polyamine epichlorohydrin resin is sprayed onto the large cylinder, and the spraying amount of the adhesion promoter is 100-300g / ton of paper. Add 10-18 kg / ton of wet strength agent and 3-8 kg / ton of wax emulsion to the pipeline between the pulping tank and the pre-pulping tank. The calender described is a dual-pressure zone soft calender. The first pressure zone has a hard roller pressing the front side of the paper, and the second pressure zone has a hard roller pressing the back side of the paper. The first pressure is 50-70 kN / m and the temperature is 120℃; the second pressure is 50-70 kN / m and the temperature is 120℃.

2. The process for producing single-sided high-gloss food-grade composite base paper using a long-wire large-cylinder paper machine according to claim 1, characterized in that, Add 200-300g of cationic retention aid per ton of slurry to the pipeline between the slurry pump and the pressure screen.

3. The process for producing single-sided high-gloss food-grade composite base paper using a long-wire large-cylinder paper machine according to claim 1, characterized in that, Add 200-300g / ton of anionic retention aid to the pipe between the pressure screen and the headbox.

4. The process for producing single-sided high-gloss food-grade composite base paper using a long-wire large-cylinder paper machine according to claim 1, characterized in that, The paper machine operating parameters are as follows: (1) Vehicle speed 450-550m / min; (2) The steam pressure of the large cylinder is 550-590 kPa; The wet end air temperature of the large cylinder hood is 220-280℃, and the dry end air temperature is 220-280℃. The dryness of the product from the large cylinder is 94-96%.

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