Papermaking method for improving sizing efficiency of rosin size of food card

Abstract

The invention discloses a papermaking method for improving the sizing efficiency of rosin size of a food card, and relates to the technical field of papermaking. Adjusting the refluxing proportion of the ground pulp to 10%-15%; setting the quantity of the surface layer and the bottom layer to be 23-30 / 27-36, and adding 70% cationic starch with the concentration of 1.0-1.5% into the prepared slurry; the dosage ratio of aluminum sulfate to rosin size is dynamically adjusted, the surface layer ratio is (0.9-1.1): 1, and the core layer ratio is (1.1-1.3): 1; performing dilution; forming on a net; performing squeezing; a three-section temperature curve is adopted for control, the temperature ranges from 100 DEG C to 105 DEG C to 110 DEG C to 115 DEG C to 105 DEG C to 115 DEG C in sequence, and the corresponding drying rate ranges from 30% to 35% to 70% to 75% to 100%; sizing on the surface; performing post-drying; carrying out hard calendaring; coating is conducted; carrying out soft calendering; and performing subsequent treatment. The problems that in existing food card production, rosin size is low in sizing efficiency, large in using amount and unstable in product performance, and consequently paper machine operation efficiency is reduced, and environmental protection pressure is increased are solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of papermaking, in particular to a papermaking method for improving the sizing efficiency of food carton rosin size. BACKGROUND

[0002] Food carton is a kind of packaging paper with special use function, and its core requirement is to have good liquid resistance to prevent leakage when containing liquid (such as beverage, soup, etc.). At present, the industry generally uses the method of adding rosin size in pulp to realize sizing, which utilizes the chemical properties of rosin acid to react with cellulose fibers to form a hydrophobic layer on the fiber surface, thereby giving the paper liquid resistance. However, in the existing paper machine system, the sizing efficiency of rosin size is low. In order to meet the requirements of liquid resistance of food carton, enterprises have to increase the amount of rosin size, which brings a series of problems: Excessive use of rosin size causes a large amount of foam in the paper machine system, affecting the action efficiency of other chemical agents (such as dry strength agent, retention aid); Foam will hinder the dewatering of the wet end of the paper machine, reduce the production efficiency, and affect the uniformity and strength of the finished paper; The increase of rosin size directly increases the production cost, and the excessive sizing agent will increase the load of the back-end water treatment, which does not meet the environmental protection requirements; The unstable sizing efficiency leads to fluctuations in the liquid resistance of the product, affecting the consistency of product quality.

[0003] Therefore, it is of great significance to develop a method for improving the sizing efficiency of rosin size without changing the hardware of the paper machine, by optimizing the process, to reduce the amount of rosin size under the premise of ensuring the liquid resistance of the finished paper, to optimize the production process, reduce the cost, and meet the environmental protection requirements. SUMMARY

[0004] The present application aims to solve the problems of low sizing efficiency, large amount of rosin size, unstable product performance, and the resulting decrease in paper machine operation efficiency and increase in environmental pressure in the production of existing food carton, by providing a papermaking method for improving the sizing efficiency of food carton rosin size.

[0005] To achieve the above-mentioned purpose, the present application adopts the following technical scheme: its operation steps are as follows: Step one, pulping: using the white water separated in the forming process as pulping water, and controlling the pulping concentration to be 5%; Step two, grinding: adjusting the grinding backflow ratio to 10%-15% to avoid excessive fiber disintegration caused by repeated grinding of the pulp; Step 3, Slurry Preparation: Set the top and bottom layer slurry quantities to 23-30 / 27-36, the top layer slurry formula to 15-35NB + 85-65LB, the bottom layer slurry formula to 15-35NB + 85-65LB, and the core layer slurry formula to 55-70BCT + 45-30BK; add 1.0-1.5% of 70% cationic starch to the prepared slurry to eliminate anionic waste and improve slurry strength; Step 4, Chemical Addition: Add rosin resin to the three layers (top, core, and bottom) at a rate of 13-25 kg / t, 13-25 kg / t, and 13-25 kg / t respectively; dynamically adjust the ratio of aluminum sulfate to rosin resin, with the top layer at 0.9-1.1:1 and the core layer at 1.1-1.3:1; simultaneously add 0-15 kg / t of dry strength agent, 0-200 kg / t of filler, and 0-10 kg / t of silica sol. Step 5, Dilution: The surface and bottom layer slurries are diluted from 3.2±0.2% to 0.3±0.05% after mixing, and the core layer slurry is diluted from 3.7±0.2% to 1.0±0.2% after mixing. Cationic starch, AKD (alkyl ketene dimer), and GCC filler coated with filler pretreatment agent are added sequentially before the three-layer slurry pump, and thoroughly mixed by high-speed shearing of the slurry pump. CPAM (cationic polyacrylamide) is added after the slurry pump, and Silica (silica sol) is added after the pressure sieve. Step 6, Web forming: After the pulp enters the three-layer headbox and is distributed, it is introduced into the forming wire and dewatered by gravity; the core layer is first laminated with the surface layer, and starch is sprayed onto the surface layer before lamination to improve the lamination strength, and then laminated with the bottom layer to form the base paper; Step 7, Pressing: The base paper is dewatered by two shoe presses (first and second presses), and then by a third gloss press (coated ceramic rollers) to eliminate wire marks and felt marks, controlling the dryness of the base paper to 45-48% after pressing; Step 8, Pre-drying: A three-stage temperature curve is used for control, successively 100-105℃ → 110-115℃ → 105-115℃, corresponding to drying rates of 30-35% → 70-75% → 100% respectively; Step 9, Surface sizing: Enzymatically converted cassava starch is used as the surface sizing agent. The viscosity of the prepared sizing solution is 210±10 cps, and the solid content is 28±1%. The machine temperature is controlled at 75±3℃, the machine viscosity is 35±5 cps, and the machine solid content is 12±2%. The sizing amount on the front side is 4.8±0.5 g / ㎡, and the sizing amount on the back side is 4.8±0.5 g / ㎡. Step 10, Post-drying: Control the temperature at 100-120℃ to ensure the adhesive is fully cured; Step 11, Hard calendering: Control the temperature at 170-190℃ and the pressure at 20-30kN / m; Step 12, Coating: For the primer, use a hard scraper with a coating amount of 11.5-13.5 g / ㎡; for the topcoat, use a soft scraper with a coating amount of 13-15 g / ㎡. Step 13, Soft calendering: The temperature of both the front and back sides is controlled at 140-160℃, and the pressure is 20-30kN / m; Step Fourteen, Post-processing: After curling, rewinding, and slitting, the product is stored in the warehouse.

[0006] Preferably, in step four, the ratio of aluminum sulfate to rosin is 1:1 for the surface layer and 1.2:1 for the core layer.

[0007] Preferably, the filler in step four is calcium carbonate, preferably GCC (ground calcium carbonate).

[0008] Preferably, the temperatures of the three stages of pre-drying in step eight are precisely controlled at 100℃, 110℃, and 105℃, respectively, with a heating rate of 5℃ / min and a cooling rate of 3℃ / min.

[0009] Preferably, in step nine, the solid content of the gel prepared by enzyme conversion of cassava starch is 28%, the machine temperature is 75°C, and the viscosity is 35 cps.

[0010] Preferably, in step twelve, the amount of the primer coating is 12.5 g / m², and the amount of the topcoat coating is 14 g / m².

[0011] Compared with the prior art, the beneficial effects of the present invention are: 1. Significantly improved sizing efficiency: By optimizing parameters such as the ratio of aluminum sulfate to rosin and the drying temperature curve, the bonding efficiency between rosin and fiber is improved, and the edge leakage (distance method) of the paper is ≤6.0mm, which meets the liquid resistance requirements of food-grade cardboard. 2. Reduced rosin usage: The amount of rosin used per ton of paper can be reduced by 2-3 kg. Based on an annual production capacity of 200,000 tons, this can save 400-600 tons of rosin annually. At the same time, it can improve steam utilization and is expected to generate an annual economic benefit of 5 million yuan. 3. Improved paper machine operating efficiency: Reduced rosin usage, significantly reduced foaming in the paper machine system, improved wet end dewatering efficiency, enhanced paper strength and uniformity, and improved product quality stability; 4. Optimized environmental performance: The amount of rosin used is reduced, which reduces the pressure of sizing agents on downstream water treatment and complies with environmental policy requirements; 5. Low implementation cost: No changes are required to the paper machine hardware; it can be achieved simply by optimizing process parameters, making it easy to promote and apply in existing production lines. Detailed Implementation

[0012] The technical solutions of the present invention will be clearly and completely described below. The preferred embodiments described are only examples. All other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Example 1:

[0013] The operation steps in this embodiment are as follows: Step 1, Pulping: Use the white water separated during the wire mesh forming process as the pulping water, and control the pulp concentration to 5%; Step 2, Pulping: Adjust the pulp reflow ratio to 12% to avoid excessive fiber fragmentation caused by repeated pulping; Step 3, Pulp Preparation: Set the top and bottom layer weights to 27 / 30. The top layer pulp formula is 25% NBKP (Northern Bleached Sulfate Softwood Pulp) + 75% LBKP (Southern Bleached Sulfate Hardwood Pulp). The bottom layer pulp formula is 25% NBKP + 75% LBKP. The core layer pulp formula is 64% BCTMP (Bleached Chemithermal Mechanical Pulp) + 36% BK (Bleached Sulfate Pulp). Add 1.2% of 70% cationic starch to the prepared pulp to eliminate anionic waste and improve pulp strength. Step 4, Chemical Addition: Add rosin resin to the three layers (top, core, and bottom) at amounts of 15 kg / t, 16 kg / t, and 15 kg / t respectively; dynamically adjust the ratio of aluminum sulfate to rosin resin, with the top layer at 1:1 and the core layer at 1.2:1; simultaneously add 10 kg / t of dry strength agent, 80 kg / t of GCC, and 4.4 kg / t of silica sol. Step 5, Dilution: The surface and bottom layer slurries are diluted from 3.2±0.2% to 0.3±0.05% after mixing, and the core layer slurry is diluted from 3.7±0.2% to 1.0±0.2% after mixing. Cationic starch, AKD (alkyl ketene dimer), and GCC filler coated with filler pretreatment agent are added sequentially before the three-layer slurry pump, and thoroughly mixed by high-speed shearing of the slurry pump. CPAM (cationic polyacrylamide) is added after the slurry pump, and Silica (silica sol) is added after the pressure sieve. Step 6, Web forming: After the pulp enters the three-layer headbox and is distributed, it is introduced into the forming wire and dewatered by gravity; the core layer is first laminated with the surface layer, and starch is sprayed onto the surface layer before lamination to improve the lamination strength, and then laminated with the bottom layer to form the base paper; Step 7, Pressing: The base paper is dewatered by two shoe presses (first and second presses), and then by a third gloss press (coated ceramic rollers) to eliminate wire marks and felt marks, controlling the dryness of the base paper to 45-48% after pressing; Step 8, Pre-drying: A three-stage temperature curve is used for control, successively 100℃→110℃→105℃, corresponding to drying rates of 30%→70%→100% respectively; Step 9, Surface sizing: Enzymatically converted cassava starch is used as the surface sizing agent. The viscosity of the prepared sizing solution is 210 cps and the solid content is 28%. The machine temperature is controlled at 75℃, the machine viscosity is 35 cps, and the machine solid content is 12%. The sizing amount on the front side is 4.8 g / ㎡, and the sizing amount on the back side is 4.8 g / ㎡. Step 10, Post-drying: Control the temperature at 100℃ to ensure the adhesive is fully cured; Step 11, Hard calendering: Control the temperature at 180℃ and the pressure at 25kN / m; Step 12, Coating: The primer is applied using a hard scraper with a coating amount of 12.5 g / ㎡; the topcoat is applied using a soft scraper with a coating amount of 14 g / ㎡. Step 13, Soft calendering: The temperature of both the front and back sides is controlled at 150℃, and the pressure is 25kN / m; Step Fourteen, Post-processing: After curling, rewinding, and slitting, the product is stored in the warehouse.

[0014] Test results: Rosin dosage: 22kg / ton of pulp (current technology conventional dosage is 25kg / ton of pulp); Paper edge bleeding: 5.2mm by distance method, 1.5kg / m² by weight method; Dry strength of the paper: transverse ring crush strength ≥ 8.5 N·m / g, longitudinal breaking length ≥ 6.5 km; Paper machine wet end dewatering efficiency: 10% improvement over existing technologies; System foam volume: reduced by 30% compared to existing technologies. Example 2:

[0015] The process steps in this embodiment are the same as those in the first embodiment. The difference lies in some process parameters, as detailed below: 1. Pulping reflow ratio: 10%; 2. Cationic starch concentration: 1.0%; 3. Ratio of aluminum sulfate to rosin: surface layer 0.9:1, core layer 1.1:1; 4. Pre-drying temperature curve: 100℃ (drying rate 30%) → 110℃ (drying rate 70%) → 105℃ (drying rate 100%), heating rate 5℃ / min, cooling rate 3℃ / min; 5. Surface application: The adhesive solution has a solid content of 27% and a viscosity of 200 cps; the machine temperature is 72℃, the viscosity is 32 cps, and the solid content is 11%; the application amount for both the front and back sides is 4.5 g / ㎡. 6. Coating: Primer coating amount 11.5g / ㎡, topcoat coating amount 13g / ㎡; 7. Hard calendering: Temperature 170℃, Pressure 20kN / m; 8. Soft calendering: Temperature 140℃, pressure 20kN / m.

[0016] Test results: Rosin dosage: 23 kg / ton of slurry; Paper edge bleeding: 5.5mm by distance method, 1.6kg / m² by weight method; Dry strength of the paper: transverse ring crush strength ≥ 8.2 N·m / g, longitudinal breaking length ≥ 6.3 km; Paper machine wet end dewatering efficiency: 8% improvement over existing technologies; System foam volume: reduced by 25% compared to existing technologies. Example 3:

[0017] The process steps in this embodiment are the same as those in the first embodiment. The difference lies in some process parameters, as detailed below: 1. Pulping reflow ratio: 15%; 2. Cationic starch concentration: 1.5%; 3. Ratio of aluminum sulfate to rosin: surface layer 1.1:1, core layer 1.3:1; 4. Pre-drying temperature curve: 100℃ (drying rate 30%) → 110℃ (drying rate 70%) → 105℃ (drying rate 100%), heating rate 5℃ / min, cooling rate 3℃ / min; 5. Surface application: The adhesive solution has a solid content of 29% and a viscosity of 220 cps; the machine temperature is 78℃, the viscosity is 38 cps, and the solid content is 13%; the application amount for both the front and back sides is 5.0 g / ㎡. 6. Coating: Primer application rate 13.5g / ㎡, topcoat application rate 15g / ㎡; 7. Hard calendering: Temperature 190℃, Pressure 30kN / m; 8. Soft calendering: Temperature 160℃, pressure 30kN / m.

[0018] Test results: Rosin dosage: 21 kg / ton of slurry; Paper edge bleeding: 4.8mm by distance method, 1.4kg / m² by weight method; Dry strength of the paper: transverse ring crush strength ≥ 8.8 N·m / g, longitudinal breaking length ≥ 6.7 km; Paper machine wet end dewatering efficiency: 12% higher than existing technology; System foam volume: reduced by 35% compared to existing technologies.

[0019] Comparative test (existing technology) Using existing conventional processes, the amount of rosin gum used is 25 kg / ton of slurry, the ratio of aluminum sulfate to rosin gum is uniformly 1.0:1, the pre-drying temperature is kept constant at 110℃, and other parameters are the same as in Example 1.

[0020] Test results: Paper edge bleeding: 6.8mm by distance method, 1.9kg / m² by weight method; Dry strength of the paper: transverse ring crush strength 7.8 N·m / g, longitudinal breaking length 6.0 km; Paper machine wet end dewatering efficiency: baseline value; System foam quantity: baseline value.

[0021] The results of the above three embodiments and comparative tests show that the process of the present invention can significantly reduce the amount of rosin glue used while improving the liquid resistance and physical strength of the paper and improving the operating efficiency of the paper machine, thus having significant technical advantages and economic benefits.

[0022] For those skilled in the art, modifications can be made to the technical solutions described in the foregoing embodiments, and equivalent substitutions can be made to some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this invention should be included within the protection scope of this invention.

Claims

1. A papermaking process for improving the sizing efficiency of food casson gum, characterized by: Its operation steps are as follows: Step (one), pulping: the white water separated in the forming process is used as pulping water, and the pulping concentration is controlled to be 5%; Step (two), grinding: the grinding backflow ratio is adjusted to 10%-15% to avoid excessive fiber disintegration caused by repeated grinding of pulp; Step (three), pulp preparation: the face and bottom layer dosages are set to be 23-30 / 27-36, the face layer pulp formula is 15-35NB+85-65LB, the bottom layer pulp formula is 15-35NB+85-65LB, and the core layer pulp formula is 55-70BCT+45-30BK; 70% cationic starch with a concentration of 1.0-1.5% is added to the prepared pulp to eliminate anionic garbage and improve the strength of the pulp; Step (four), chemical addition: rosin size is added to the face / core / bottom layers respectively, and the dosage is 13-25kg / t, 13-25kg / t, and 13-25kg / t respectively; the dosage ratio of aluminum sulfate to rosin size is dynamically adjusted, and the face layer is 0.9-1.1:1, and the core layer is 1.1-1.3:1; dry strength agent 0-15kg / t, filler 0-200kg / t, and silica sol 0-10kg / t are also added; Step (five), dilution: the face and bottom layer pulp is diluted from 3.2±0.2% after preparation to 0.3±0.05%, and the core layer pulp is diluted from 3.7±0.2% after preparation to 1.0±0.2%; cationic starch, AKD, and GCC filler coated with filler pretreatment agent are added in sequence before the three-layer pulp pump, and they are fully mixed by high-speed shearing of the pulp pump; CPAM is added after the pulp pump, and Silica is added after the pressure screen; Step (six), wire forming: the pulp enters the three-layer headbox and is distributed on the forming wire, and is dewatered by gravity; the core layer is first compounded with the face layer, and the face layer is sprayed with starch before compounding to improve the compounding strength, and then the bottom layer is compounded to form the base paper; Step (seven), pressing: the base paper is sequentially pressed by one-press and two-press boot-type presses to dewater, and then is pressed by three-press glossy press to eliminate wire marks and felt marks, and the dryness of the base paper after pressing is controlled to be 45-48%; Step (eight), pre-drying: a three-stage temperature curve is used for control, and the temperature is 100-105℃→110-115℃→105-115℃ in sequence, and the corresponding drying rates are 30-35%→70-75%→100%; Step (nine), surface sizing: enzyme-converted cassava starch is used as surface sizing agent, and the viscosity of the sizing solution is 210±10cps, and the solid content is 28±1%; the machine temperature is controlled to be 75±3℃, the machine viscosity is 35±5cps, and the machine solid content is 12±2%; the front side sizing amount is 4.8±0.5g / ㎡, and the back side sizing amount is 4.8±0.5g / ㎡; Step (ten), post-drying: the temperature is controlled to be 100-120℃ to fully cure the sizing solution; Step (eleven), hard calendering: the temperature is controlled to be 170-190℃, and the pressure is 20-30kN / m; Step (twelve), coating: the bottom coating uses a hard doctor blade, and the coating amount is 11.5-13.5g / ㎡; the face coating uses a soft doctor blade, and the coating amount is 13-15g / ㎡; Step (thirteen), soft calendering: the temperature of front and back surface is controlled at 140-160℃, and the pressure is 20-30kN / m; Step (fourteen), subsequent processing: after crimping, rewinding, slitting, it is stored in warehouse.

2. The papermaking process for improving the sizing efficiency of casson gum as claimed in claim 1, wherein the said process is characterized by: The papermaking method for improving the sizing efficiency of food casone gum according to claim 1 is characterized in that the ratio of the use amount of aluminum sulfate to the casone gum in the step (four) is preferably 1:1 for the surface layer and preferably 1.2:1 for the core layer.

3. The papermaking process for improving the sizing efficiency of casson gum as claimed in claim 1, wherein the said process is characterized by: The filler in the step (four) is calcium carbonate.

4. The papermaking process for improving the sizing efficiency of casson gum as claimed in claim 1, wherein the said process is characterized by: The three-stage temperature of the pre-drying in the step (eight) is accurately controlled at 100℃, 110℃ and 105℃ respectively, the temperature rising rate is 5℃ / min, and the temperature falling rate is 3℃ / min.

5. The papermaking process for improving the sizing efficiency of casson gum as claimed in claim 1, wherein the said process is characterized by: The glue solution prepared by the enzyme conversion of cassava starch in the step (nine) has a solid content of 28%, the machine temperature is 75℃, and the viscosity is 35cps.

6. The papermaking process for improving the sizing efficiency of casson gum of a food according to claim 1, characterized in that: The coating amount of the base coating in the step (twelve) is 12.5g / ㎡, and the coating amount of the top coating is 14g / ㎡.