Production process of fast-growing eucalyptus packaging paper

Abstract

The invention discloses a production process of fast-growing eucalyptus packaging paper. The production process is characterized by comprising the following steps: S1, pretreating raw materials; s2, chemical pretreatment; s3, pulping is carried out; s4, performing bleaching treatment; and S5, preparing and processing. Efficient large-scale utilization of the low-quality fast-growing eucalyptus residues is achieved, the pulp yield is increased, the production energy consumption is reduced, the bleaching whiteness and the fiber strength are balanced, the core contradiction of a traditional process is solved, and it is ensured that the finished paper quality meets the core requirement of packaging paper.

Description

Technical Field

[0001] This invention belongs to the field of fast-growing eucalyptus packaging paper production technology, and specifically relates to a production process for fast-growing eucalyptus packaging paper. Background Technology

[0002] Fast-growing eucalyptus is a general term for hybrid eucalyptus varieties, native to Australia. It is characterized by its extremely rapid growth and is widely planted in southern my country (especially Guangxi), forming a complete industrial chain from seedlings to processing. As an economic tree species, its timber is widely used in construction and furniture manufacturing and is a core raw material for the board processing industry. However, it generates a huge amount of processing waste such as tail branches and sapwood every year. Currently, most of these wastes are disposed of at low prices as fuel, with extremely low economic value. This not only causes a serious waste of forest resources but also fails to fully realize the material potential of fast-growing eucalyptus.

[0003] Fast-growing eucalyptus has excellent pulping and papermaking properties, with its pulp exhibiting advantages such as good bulk, softness, flexibility, good sheet formation, and high opacity. However, low-quality raw materials, such as sapwood and twigs, have uneven composition and significant morphological differences, leading to drastic fluctuations in pulp quality during the pulping process, making it difficult to meet the requirements of large-scale production. Furthermore, existing pulping processes are not optimized for the characteristics of fast-growing eucalyptus residues, resulting in low pulp yield and excessive energy consumption. At the same time, there is an inherent contradiction between whiteness and fiber strength during the bleaching process. Traditional processes either result in insufficient whiteness or severe fiber damage leading to a decrease in paper strength, failing to meet the core quality requirements for packaging paper. Therefore, there is an urgent need for a fast-growing eucalyptus packaging paper production process to solve the above problems. Summary of the Invention

[0004] In view of the problems mentioned in the background art above, the purpose of this invention is to provide a production process for fast-growing eucalyptus packaging paper.

[0005] To achieve the above-mentioned technical objectives, the technical solution adopted by the present invention is as follows: A production process for fast-growing eucalyptus packaging paper, characterized by the following steps: S1: Raw material pretreatment: Select fast-growing eucalyptus branches and sapwood residues, sort and clean them to remove impurities, and then pre-soak them in warm water at 40-50℃ for 30-40 minutes. Then, steam treatment and extrusion treatment are carried out in sequence. The steam treatment temperature is 105-110℃ and the time is 10-12 minutes. The compression ratio of the extrusion treatment is 1:4.0-1:4.5. After extrusion, a pretreated raw material with a moisture content of 42-48% is obtained. S2: Chemical pretreatment, the pretreatment raw material in S1 is immersed in alkaline hydrogen peroxide solution at a temperature of 100-150℃ for 120-160 min to obtain chemical pretreatment raw material; S3: Pulping. The chemically pretreated raw materials from S2 are subjected to two stages of refining. The first stage is high-consistency refining with a concentration of 32-35%, a refining pressure of 0.3-0.5 MPa, and a refining disc gap of 0.8-1.2 mm. The second stage is medium-consistency refining with a concentration of 19-21%, a refining pressure of 0.1-0.2 MPa, and a refining disc gap of 0.3-0.5 mm. The average fiber length of the pulp after refining is 0.8-1.2 mm, resulting in fast-growing eucalyptus mechanical pulp. S4: Bleaching treatment, employing a two-stage bleaching process. Both the first and second stage bleaching systems contain NaOH, H2O2, and the chelating agent DTPA. In the first stage bleaching, H2O2 accounts for 60-70% of the total amount, and NaOH accounts for 55-65%. In the second stage bleaching, H2O2 accounts for 30-40% of the total amount, and NaOH accounts for 35-45%. The total mass ratio of NaOH to H2O2 is controlled at 0.9:1 to 1.1:1. The total amount of H2O2 is 5.2-5.8% of the oven-dry weight of the raw material, and the total amount of DTPA is 0.3-0.4% of the oven-dry weight of the raw material. The bleaching temperature is 68-72℃, the first stage bleaching time is 80-100 min, the second stage bleaching time is 70-90 min, and the total bleaching time is 150-190 min, yielding bleached pulp with a whiteness ≥75% ISO. S5: Forming and papermaking treatment. Fast-growing eucalyptus mechanical pulp and hardwood pulp are mixed at a mass ratio of 35:65 to 45:55. A reinforcing agent is added, which is a composite system of cationic starch and polyacrylamide. The amount of cationic starch is 1.5 to 2.5% of the oven-dry weight of the pulp, and the amount of polyacrylamide is 0.1 to 0.2% of the oven-dry weight of the pulp. After beating to 38 to 42°SR and controlling the pulp freeness to 350 to 450 mL, the pulp is sequentially formed, pressed, and dried. The drying is carried out in stages. The first stage drying temperature is 90 to 100°C, the second stage drying temperature is 110 to 120°C, and the total drying time is 25 to 35 min. After drying, the pulp is calendered to obtain fast-growing eucalyptus packaging paper with a bursting index ≥2.19 kPa·m² / g and a tear index ≥4.38 mN·m² / g.

[0006] Further specified, in S1, the pH value of the warm water used for pre-soaking is 6.5 to 7.5, and sodium dodecylbenzenesulfonate surfactant is added to the warm water at 0.05 to 0.1% of the oven-dry weight of the raw material.

[0007] Further specified, in S1, the extrusion process uses a twin-roll extruder with a twin-roll speed of 30-50 r / min and the roll surface temperature is maintained at 60-70°C.

[0008] Further specifying, in S2, the alkaline hydrogen peroxide solution is 15% Na2SO3 + 3% NaOH + liquid ratio 1:4.

[0009] Further specifying that in S3, after both stages of grinding, screening is performed using a 40-60 mesh screen, and the remaining material after screening is returned to the corresponding grinding equipment for re-grinding.

[0010] Further specified, in S4, the initial pH value of the first stage of bleaching is 10.5 to 11.5, the initial pH value of the second stage of bleaching is 9.5 to 10.5, the pH value is detected every 30 minutes during the bleaching process, and the pH value is maintained by adding NaOH solution.

[0011] Further specified, in S5, the calendering process is performed using a two-roll calender, with a calendering temperature of 80-90℃, a calendering pressure of 0.2-0.3MPa, and a calendering speed of 20-30m / min.

[0012] The beneficial effects of this invention are as follows: 1. This invention employs a combined pretreatment process of warm water pre-soaking, steaming, and extrusion to achieve uniform softening and preliminary purification of low-quality raw materials, obtaining pretreated raw materials with stable moisture content. This effectively solves the problem of pulp quality fluctuations caused by uneven composition and large morphological differences in low-quality raw materials such as fast-growing eucalyptus branches and sapwood. It transforms previously unusable residues into qualified packaging paper raw materials, not only improving the comprehensive utilization rate of fast-growing eucalyptus resources but also reducing raw material costs.

[0013] 2. This invention utilizes a synergistic process of chemical pretreatment and two-stage refining. The chemical pretreatment gently removes some lignin, reducing the difficulty of refining and minimizing fiber damage and energy consumption during the refining process. Furthermore, the segmented design of high-consistency refining for initial fiber dissociation and medium-consistency refining for fiber refinement avoids excessive fiber damage or insufficient dissociation caused by improper single refining parameters, thereby improving pulp yield. In addition, a screening and reflux device is added after the two-stage refining process to further improve raw material utilization and reduce raw material loss.

[0014] 3. This invention employs a two-stage bleaching process with precise parameter control. By rationally allocating the dosage of the reagents and stabilizing the bleaching pH value, the whiteness of the bleached pulp is guaranteed to be ≥75% ISO while minimizing fiber damage and increasing the fiber strength retention rate of the bleached pulp by 10-15%.

[0015] 4. This invention achieves a final product with a bursting index ≥2.19KPa·m² / g, a tear index ≥4.38mN·m² / g, and meets the standards for smoothness and density by using a reasonable ratio of fast-growing eucalyptus mechanical pulp and hardwood pulp, the synergistic effect of composite reinforcing agents, and precise control of drying and calendering parameters. This fully meets the requirements of packaging paper for core indicators such as strength and appearance. Attached Figure Description

[0016] The present invention can be further illustrated by the non-limiting embodiments given in the accompanying drawings; Figure 1 This is a schematic flowchart illustrating a production process for fast-growing eucalyptus packaging paper according to an embodiment of the present invention. Detailed Implementation

[0017] To enable those skilled in the art to better understand the present invention, the technical solution of the present invention will be further described below in conjunction with the accompanying drawings and embodiments. Example

[0018] A process for producing packaging paper for fast-growing eucalyptus trees includes the following steps: S1: Raw material pretreatment: Select fast-growing eucalyptus branches and sapwood residues, sort and clean them to remove impurities, and then soak them in 40℃ warm water with a pH of 6.5 for 40 minutes. Add 0.05% of sodium dodecylbenzenesulfonate surfactant by oven-dry weight of the raw materials to the warm water. Then, steam treatment is carried out at a temperature of 105℃ for 12 minutes. Finally, extrusion treatment is carried out using a two-roll extruder with a roller speed of 30 r / min, a roller surface temperature of 60℃, and a compression ratio of 1:4.0. After extrusion, a pretreated raw material with a moisture content of 42% is obtained. S2: Chemical pretreatment, the pretreatment raw material in S1 is immersed in alkaline hydrogen peroxide solution (Na2SO3 15% + NaOH 3% + liquid ratio 1:4) at 100℃ for 160 min to obtain chemical pretreatment raw material; S3: Pulping. The chemically pretreated raw materials in S2 are subjected to two stages of refining. The first stage is high-consistency refining with a concentration of 32%, a refining pressure of 0.3 MPa, and a grinding disc gap of 1.2 mm. The second stage is medium-consistency refining with a concentration of 19%, a refining pressure of 0.1 MPa, and a grinding disc gap of 0.5 mm. After both stages of refining, the materials are screened using a 40-mesh sieve. The residue after screening is returned to the corresponding refining equipment for re-refining. The average fiber length of the pulp after refining is 0.8 mm, resulting in fast-growing eucalyptus mechanical pulp. S4: Bleaching treatment, employing a two-stage bleaching process. Both the first and second stage bleaching systems contain NaOH, H2O2, and the chelating agent DTPA. The total amount of H2O2 used is 5.2% of the raw material's oven-dry weight, the total amount of NaOH used is 4.68% of the raw material's oven-dry weight (NaOH to H2O2 mass ratio is 0.9:1), and the total amount of DTPA used is 0.3% of the raw material's oven-dry weight. In the first stage bleaching, H2O2 accounts for 60% of the total amount used, and NaOH accounts for the remaining percentage. The initial pH value was 10.5, the amount of H2O2 used in the second stage of bleaching accounted for 40% of the total amount, the amount of NaOH used accounted for 45% of the total amount, the initial pH value was 9.5, the bleaching temperature was 68℃, the first stage of bleaching time was 100 min, the second stage of bleaching time was 90 min, and the total bleaching time was 190 min. The pH value was checked every 30 min during the bleaching process, and the pH value was maintained by adding NaOH solution to keep it stable, resulting in a bleached pulp with a whiteness of 75% ISO. S5: Forming and papermaking process: Fast-growing eucalyptus mechanical pulp and hardwood pulp are mixed at a mass ratio of 35:65. A reinforcing agent (a composite system of cationic starch and polyacrylamide) is added. The amount of cationic starch is 1.5% of the oven-dry weight of the pulp, and the amount of polyacrylamide is 0.1% of the oven-dry weight of the pulp. After beating to 38°SR and controlling the pulp freeness to 450mL, the pulp is sequentially formed, pressed, and dried. The drying is carried out in stages, with the first stage drying temperature at 90℃ and the second stage drying temperature at 110℃, for a total drying time of 35min. After drying, the pulp is calendered using a two-roll calender at a calendering temperature of 80℃, a calendering pressure of 0.2MPa, and a calendering speed of 20m / min to obtain fast-growing eucalyptus packaging paper.

[0019] The fast-growing eucalyptus packaging paper obtained in this embodiment has a bursting strength index of 2.25 kPa·m² / g and a tear index of 4.42 mN·m² / g, which meets the quality requirements for packaging paper. Example

[0020] A process for producing packaging paper for fast-growing eucalyptus trees includes the following steps: S1: Raw material pretreatment: fast-growing eucalyptus branches and sapwood residues are selected, sorted, cleaned to remove impurities, and then pre-soaked in 45℃ warm water with pH 7.0 for 35 minutes. Sodium dodecylbenzenesulfonate surfactant at 0.08% of the raw material's oven-dry weight is added to the warm water. Subsequently, steam treatment is carried out at 108℃ for 11 minutes. Finally, a two-roll extruder is used for extrusion treatment at a roller speed of 40 r / min, roller surface temperature is maintained at 65℃, and compression ratio is 1:4.3. After extrusion, a pretreated raw material with a moisture content of 45% is obtained. S2: Chemical pretreatment, the pretreatment raw material in S1 is immersed in alkaline hydrogen peroxide solution (Na2SO3 15% + NaOH 3% + liquid ratio 1:4) at 125℃ for 140 min to obtain chemical pretreatment raw material; S3: Pulping. The chemically pretreated raw materials from S2 are subjected to two stages of refining. The first stage is high-consistency refining with a concentration of 34%, a refining pressure of 0.4 MPa, and a disc gap of 1.0 mm. The second stage is medium-consistency refining with a concentration of 20%, a refining pressure of 0.15 MPa, and a disc gap of 0.4 mm. After both stages of refining, the pulp is screened using a 50-mesh sieve. The residue is returned to the corresponding refining equipment for re-refining. The average fiber length of the pulp after refining is 1.0 mm, resulting in fast-growing eucalyptus mechanical pulp. S4: Bleaching treatment, employing a two-stage bleaching process. Both the first and second stage bleaching systems contain NaOH, H2O2, and the chelating agent DTPA. The total amount of H2O2 used is 5.5% of the raw material's oven-dry weight, the total amount of NaOH used is 6.05% of the raw material's oven-dry weight (the total mass ratio of NaOH to H2O2 is 1.1:1), and the total amount of DTPA used is 0.35% of the raw material's oven-dry weight. In the first stage bleaching, H2O2 accounts for 65% of the total amount used, and NaOH accounts for... The initial pH value was 11.0, accounting for 60% of the total amount of H2O2 used in the second stage of bleaching. The initial pH value was 10.0. The bleaching temperature was 70℃, the first stage of bleaching time was 90 min, the second stage of bleaching time was 80 min, and the total bleaching time was 170 min. The pH value was measured every 30 min during the bleaching process, and the pH value was maintained by adding NaOH solution to keep it stable, resulting in a bleached pulp with a whiteness of 78% ISO. S5: Forming and papermaking process: Fast-growing eucalyptus mechanical pulp and hardwood pulp are mixed at a mass ratio of 40:60, and a reinforcing agent (a composite system of cationic starch and polyacrylamide) is added. The amount of cationic starch is 2.0% of the oven-dry weight of the pulp, and the amount of polyacrylamide is 0.15% of the oven-dry weight of the pulp. After beating to 40°SR and controlling the pulp freeness to 400mL, the pulp is sequentially formed, pressed, and dried. The drying process is carried out in stages, with the first stage drying temperature at 95℃ and the second stage drying temperature at 115℃, for a total drying time of 30min. After drying, the pulp is calendered using a two-roll calender at a calendering temperature of 85℃, a calendering pressure of 0.25MPa, and a calendering speed of 25m / min to obtain fast-growing eucalyptus packaging paper.

[0021] The fast-growing eucalyptus packaging paper obtained in this embodiment has a bursting strength index of 2.32 kPa·m² / g, a tearing index of 4.55 mN·m² / g, uniform whiteness, smooth appearance, and excellent overall performance. Example

[0022] A process for producing packaging paper for fast-growing eucalyptus trees includes the following steps: S1: Raw material pretreatment: fast-growing eucalyptus branches and sapwood residues are selected, sorted, cleaned to remove impurities, and then pre-soaked in 50℃ warm water with pH 7.5 for 30 minutes. Sodium dodecylbenzenesulfonate surfactant at 0.1% of the raw material's oven-dry weight is added to the warm water. Subsequently, steam treatment is carried out at 110℃ for 10 minutes. Finally, a two-roll extruder is used for extrusion treatment at a speed of 50 r / min, a roll surface temperature of 70℃, and a compression ratio of 1:4.5. After extrusion, a pretreated raw material with a moisture content of 48% is obtained. S2: Chemical pretreatment, the pretreatment raw material in S1 is immersed in alkaline hydrogen peroxide solution (Na2SO3 15% + NaOH 3% + liquid ratio 1:4) at 150℃ for 120 min to obtain chemical pretreatment raw material; S3: Pulping. The chemically pretreated raw materials from S2 are subjected to two stages of refining. The first stage is high-consistency refining with a concentration of 35%, a refining pressure of 0.5 MPa, and a grinding disc gap of 0.8 mm. The second stage is medium-consistency refining with a concentration of 21%, a refining pressure of 0.2 MPa, and a grinding disc gap of 0.3 mm. After both stages of refining, the pulp is screened using a 60-mesh sieve. The residue after screening is returned to the corresponding refining equipment for re-refining. The average fiber length of the pulp after refining is 1.2 mm, resulting in fast-growing eucalyptus mechanical pulp. S4: Bleaching treatment, employing a two-stage bleaching process. Both the first and second stage bleaching systems contain NaOH, H2O2, and the chelating agent DTPA. The total amount of H2O2 used is 5.8% of the raw material's oven-dry weight, the total amount of NaOH used is 6.38% of the raw material's oven-dry weight (NaOH to H2O2 mass ratio is 1.1:1), and the total amount of DTPA used is 0.4% of the raw material's oven-dry weight. In the first stage bleaching, H2O2 accounts for 70% of the total amount, and NaOH accounts for the remaining percentage. The initial pH value was 11.5, with 65% of the total amount of H2O2 and 35% of the total amount of NaOH used in the second stage of bleaching. The initial pH value was 10.5. The bleaching temperature was 72℃, the first stage of bleaching time was 80 min, the second stage of bleaching time was 70 min, and the total bleaching time was 150 min. The pH value was measured every 30 min during the bleaching process, and the pH value was maintained by adding NaOH solution to keep it stable, resulting in a bleached pulp with a whiteness of 80% ISO. S5: Forming and papermaking process: Fast-growing eucalyptus mechanical pulp and hardwood pulp are mixed at a mass ratio of 45:55, and a reinforcing agent (a composite system of cationic starch and polyacrylamide) is added. The amount of cationic starch is 2.5% of the oven-dry weight of the pulp, and the amount of polyacrylamide is 0.2% of the oven-dry weight of the pulp. After beating to 42°SR and controlling the pulp freeness to 350mL, the pulp is sequentially formed, pressed, and dried. The drying is carried out in stages, with the first stage drying temperature at 100℃ and the second stage drying temperature at 120℃, for a total drying time of 25min. After drying, the pulp is calendered using a two-roll calender at a calendering temperature of 90℃, a calendering pressure of 0.3MPa, and a calendering speed of 30m / min to obtain fast-growing eucalyptus packaging paper.

[0023] The fast-growing eucalyptus packaging paper obtained in this embodiment has a bursting index of 2.40 kPa·m² / g, a tear index of 4.68 mN·m² / g, high and uniform whiteness, and excellent strength, fully meeting the quality requirements of high-end packaging paper.

[0024] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A production process for fast-growing eucalyptus packaging paper, characterized in that: Includes the following steps: S1: Raw material pretreatment: Select fast-growing eucalyptus branches and sapwood residues, sort and clean them to remove impurities, and then pre-soak them in warm water at 40-50℃ for 30-40 minutes. Then, steam treatment and extrusion treatment are carried out in sequence. The steam treatment temperature is 105-110℃ and the time is 10-12 minutes. The compression ratio of the extrusion treatment is 1:4.0-1:4.

5. After extrusion, a pretreated raw material with a moisture content of 42-48% is obtained. S2: Chemical pretreatment, the pretreatment raw material in S1 is immersed in alkaline hydrogen peroxide solution at a temperature of 100-150℃ for 120-160 min to obtain chemical pretreatment raw material; S3: Pulping. The chemically pretreated raw materials from S2 are subjected to two stages of refining. The first stage is high-consistency refining with a concentration of 32-35%, a refining pressure of 0.3-0.5 MPa, and a refining disc gap of 0.8-1.2 mm. The second stage is medium-consistency refining with a concentration of 19-21%, a refining pressure of 0.1-0.2 MPa, and a refining disc gap of 0.3-0.5 mm. The average fiber length of the pulp after refining is 0.8-1.2 mm, resulting in fast-growing eucalyptus mechanical pulp. S4: Bleaching treatment, employing a two-stage bleaching process. Both the first and second stage bleaching systems contain NaOH, H2O2, and the chelating agent DTPA. In the first stage bleaching, H2O2 accounts for 60-70% of the total amount, and NaOH accounts for 55-65%. In the second stage bleaching, H2O2 accounts for 30-40% of the total amount, and NaOH accounts for 35-45%. The total mass ratio of NaOH to H2O2 is controlled at 0.9:1 to 1.1:

1. The total amount of H2O2 is 5.2-5.8% of the oven-dry weight of the raw material, and the total amount of DTPA is 0.3-0.4% of the oven-dry weight of the raw material. The bleaching temperature is 68-72℃, the first stage bleaching time is 80-100 min, the second stage bleaching time is 70-90 min, and the total bleaching time is 150-190 min, yielding bleached pulp with a whiteness ≥75% ISO. S5: Forming and papermaking treatment. Fast-growing eucalyptus mechanical pulp and hardwood pulp are mixed at a mass ratio of 35:65 to 45:

55. A reinforcing agent is added, which is a composite system of cationic starch and polyacrylamide. The amount of cationic starch is 1.5 to 2.5% of the oven-dry weight of the pulp, and the amount of polyacrylamide is 0.1 to 0.2% of the oven-dry weight of the pulp. After beating to 38 to 42°SR and controlling the pulp freeness to 350 to 450 mL, the pulp is sequentially formed, pressed, and dried. The drying is carried out in stages. The first stage drying temperature is 90 to 100°C, the second stage drying temperature is 110 to 120°C, and the total drying time is 25 to 35 min. After drying, the pulp is calendered to obtain fast-growing eucalyptus packaging paper with a bursting index ≥2.19 kPa·m² / g and a tear index ≥4.38 mN·m² / g.

2. The production process for fast-growing eucalyptus packaging paper according to claim 1, characterized in that: In S1, the pH value of the warm water used for pre-soaking is 6.5 to 7.5, and sodium dodecylbenzenesulfonate surfactant is added to the warm water at 0.05 to 0.1% of the oven-dry weight of the raw material.

3. The production process for fast-growing eucalyptus packaging paper according to claim 2, characterized in that: In S1, the extrusion process uses a twin-roll extruder with a twin-roll speed of 30-50 r / min and the roll surface temperature maintained at 60-70°C.

4. The production process for fast-growing eucalyptus packaging paper according to claim 3, characterized in that: In S2, the alkaline hydrogen peroxide solution is 15% Na2SO3 + 3% NaOH + liquid ratio 1:

4.

5. The production process for fast-growing eucalyptus packaging paper according to claim 4, characterized in that: In S3, after both stages of grinding, a screening process is performed using a 40-60 mesh screen. The remaining material after screening is returned to the corresponding grinding equipment for re-grinding.

6. The production process for fast-growing eucalyptus packaging paper according to claim 5, characterized in that: In S4, the initial pH value of the first stage of bleaching is 10.5 to 11.5, and the initial pH value of the second stage of bleaching is 9.5 to 10.

5. The pH value is detected every 30 minutes during the bleaching process, and the pH value is maintained by adding NaOH solution.

7. The production process for fast-growing eucalyptus packaging paper according to claim 6, characterized in that: In S5, the calendering process is performed using a two-roll calender, with a calendering temperature of 80–90°C, a calendering pressure of 0.2–0.3 MPa, and a calendering speed of 20–30 m / min.

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