High-strength environment-friendly craft paper production process with low bleached hardwood pulp consumption
By optimizing the slurry ratio and treatment process, combining heat dispersion and additives, the problem of high consumption of natural coniferous pulp in the production of high-strength environmentally friendly ketchup paper is solved, and the effect of low-cost, high-strength and good interlayer combination is achieved.
Patent Information
- Application Number
- CN202510944712.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-09
- Publication Date
- 2025-08-12
AI Technical Summary
In the production of existing high-strength environmentally friendly ketchup paper, the natural conifer pulp is high, resulting in an increase in production costs and poor interlayer bonding strength, making it difficult to maintain high strength while reducing the amount of conifer pulp.
The natural sulfate method conifer pulp is used to use 20%-30% and 70%-80% of the recycled pulp. The pulp is beaten in series through three conical refiners and sieved in a graded manner. Combined with heat dispersion treatment and adhesive control enzyme use, the surface, core and bottom slurry ratio is adjusted, and aluminum sulfate and dry strength agent are added during the molding process of the net, and finally the surface is glued and hard calendered.
Production of high-strength environmentally friendly paper with a breakage index of 2.8kPa.m2/g at low natural color conifer slurry consumption reduces production costs while maintaining good interlayer bonding strength and paper smoothness.
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of papermaking, and in particular to a production process for high-strength and environmentally friendly kraft paper with low bleached broadleaf pulp consumption. Background Art
[0002] High-strength kraftliner is a high-end containerboard packaging base paper produced using a modern, advanced stacking machine. Its primary raw material is recycled paper. Compared to traditional containerboard packaging base paper, high-strength, environmentally friendly kraftliner features a distinct non-woven mesh structure and a smooth surface, making it highly printable. It is suitable for packaging high-end gifts, electronic products, and other products. While maintaining the strength and quality of high-end containerboard packaging base paper, high-strength, environmentally friendly kraftliner reduces the use of virgin wood pulp, thereby reducing the use of forest resources. Key criteria for evaluating the quality of a white-faced kraftliner include hue, interlayer bond strength, burst resistance, and folding resistance. Currently, this paper is typically produced using a stacking machine using waste paper pulp and unbleached softwood pulp. Recycled pulp is used for the core and bottom layers, while unbleached softwood pulp is used for the top and core layers, with the unbleached softwood pulp comprising approximately 40%-50%. High-strength, environmentally friendly kraftliner produced using this production method exhibits a high burst resistance index and uniform hue. It has some disadvantages, mainly: the paper machines used are mostly headboxes with dilution water in the core layer, and the core layer and bottom layer raw materials are very different, which leads to poor bonding strength between the paper layers; the production cost is also high, and the natural coniferous pulp must account for 40-50% of the raw materials to achieve a paper bursting strength of 2.8 kPa·m 2 / g or above. Due to the significant price difference between unbleached softwood pulp and recycled pulp, while ensuring product quality, the lower the amount of unbleached softwood pulp used, the lower the cost of high-strength environmentally friendly linerboard. As the use of virgin wood pulp gradually increases, raw material costs are rising, and the production cost of high-strength environmentally friendly linerboard is increasing, which places higher demands on its production. Therefore, the high-strength environmentally friendly paper market urgently needs to develop a high-strength environmentally friendly linerboard with lower unbleached softwood pulp consumption while maintaining the current paper strength requirements. Summary of the Invention
[0003] The purpose of the present invention is to address the defects and shortcomings of the existing technology, provide a high-strength and environmentally friendly kraft paper production process with low bleached broadleaf pulp consumption, develop high-strength and environmentally friendly kraft paper with low natural color coniferous pulp consumption, and solve the problem of natural color coniferous pulp consumption in the conventional method.
[0004] To achieve the above object, the present invention adopts the following technical solution: it comprises the following steps: Step 1: Pulp ratio: Use 20%-30% by weight of natural kraft softwood pulp (NUKP) and 70%-80% by weight of recycled paper pulp (OCC); Step 2: Beating: Unbleached kraft softwood pulp is beaten using three conical refiners in series; recovered pulp is graded and screened into long, medium and short fibers for later use; Step 3: Using a heat disperser to heat disperse the recovered pulp after the classification process; Step 4: Adding a stickies control enzyme to the recovered pulp after heat dispersion treatment at a rate of 10-30 mL / min; Step 5. Slurry preparation: The slurry ratios of the surface, core and bottom layers are: surface layer is 100% NUKP, core layer is 50% long fiber + 50% medium fiber + bottom layer is 100% short fiber; Step 6: Threading: To ensure the PCD of the paper machine system, add 3kg / t of aluminum sulfate to the surface layer in the pipeline of the wet-end system of the threading forming process. Since the core and bottom layers contain more recycled pulp, add 12kg / t of aluminum sulfate to these layers. To ensure the bursting strength of the finished paper, add 20kg / t of dry strength agent to the above pipeline. The threading concentration of the surface and bottom layers is controlled at 0.5%±0.1%. Since the core layer is a headbox with dilution water, the core layer pulp concentration is controlled at 0.8%±0.2%. Step 7: Paper pressing; Step 8: Surface sizing: The line pressure of the sizing machine is controlled at 42-45kN / m, and the gluing flow rate is 100±20m 3 / h, using film transfer sizing to ensure that the amount of starch glue on the surface is 1.5-2g / m 2 ; Step 9: Hard calendering, and finally forming and rolling.
[0005] Furthermore, the beating concentration in step 2 is 4.2±0.3%, and the beating degree is 420±10 mL.
[0006] Furthermore, the recovered pulp concentration of the heat dispersion treatment in step 3 is 25%-35%, the treatment temperature is 100-110° C., the cutter head gap is 0.2 mm, and the back pressure is 1.0-1.8 bar.
[0007] Furthermore, the step seven is divided into two pressing steps, the first pressing is controlled at 1000±50 kN / m, and the second pressing is 1150±50 kN / m.
[0008] Furthermore, the hard pressing light pressure in step nine is 40±5 kN / m, and the temperature is set at 170±10°C.
[0009] Compared with the prior art, the present invention has the following advantages: the present invention provides a high-strength and environmentally friendly kraft paper production process with low bleached broadleaf pulp consumption, which can produce high-strength and environmentally friendly kraft paper with a bursting index of 2.8 kPa.m under the premise of low natural coniferous pulp consumption. 2 / g of high-strength environmentally friendly kraft paper; the prepared high-strength environmentally friendly kraft paper has the advantages of low cost and market demand. DETAILED DESCRIPTION
[0010] The technical solutions of the present invention are described clearly and completely below. The preferred embodiments described are only used as examples. All other embodiments obtained by those skilled in the art without making any creative work are within the scope of protection of the present invention. Example 1
[0011] This embodiment adopts the following technical solution: it includes the following steps: Step 1: Pulp ratio: 30% by weight of natural kraft softwood pulp (NUKP) and 70% by weight of recycled paper pulp (OCC); Step 2: Beating: Unbleached kraft softwood pulp is beaten using three conical refiners in series, with a beating concentration of 3.9% and a beating degree of 410 mL; the recovered pulp is graded and sieved into long, medium and short fibers for later use; Step 3: Use a heat disperser to heat disperse the recovered pulp after classification. The recovered pulp concentration during heat dispersion is 25%, the processing temperature is 100°C, the blade gap is 0.2mm, and the back pressure is 1.0bar. Step 4: Add stickies control enzyme to the recovered pulp after heat dispersion treatment at a rate of 10 mL / min. The above operation is a key step in reducing large-sized stickies in the pulp.
[0012] Step 5: The slurry ratios for the surface, core and bottom layers are: 100% NUKP for the surface layer, 50% long fiber + 50% medium fiber for the core layer, and 100% short fiber for the bottom layer; Step 6: Wire mesh: To ensure the PCD of the paper machine system, 3kg / t of aluminum sulfate is added to the surface layer in the pipeline of the wet-end system of the wire mesh forming system. Since the core and bottom layers contain more recycled pulp, 12kg / t of aluminum sulfate is added to the core and bottom layers. To ensure the bursting strength of the finished paper, 20kg / t of dry strength agent is added to the above pipeline. The surface and bottom pulp concentrations on the wire mesh are controlled at 0.4%. Since the core layer is a headbox with dilution water, the pulp concentration of the core layer is controlled at 0.6%. Step 7: Paper pressing: First press at 950 kN / m, second press at 1100 kN / m; Step 8: Surface sizing: The line pressure of the sizing machine is controlled at 42kN / m, and the gluing flow rate is 8m 3 / h, using film transfer sizing to ensure that the surface starch coating amount is 1.5g / m 2 ; Step 9. Hard calendering: To ensure the smoothness of the paper surface, use the hard calendering process with a line pressure of 35kN / m and a temperature setting of 160°C. Finally, form and roll. Example 2
[0013] This embodiment adopts the following technical solution: it includes the following steps: Step 1: Pulp ratio: 20% by weight of natural kraft softwood pulp (NUKP) and 80% by weight of recycled paper pulp (OCC); Step 2: Beating: Unbleached kraft softwood pulp is beaten in series using three conical refiners with a beating concentration of 4.5% and a beating degree of 430 mL; recovered pulp is graded and sieved into long, medium and short fibers for later use; Step 3: Use a heat disperser to heat disperse the recovered pulp after classification. The recovered pulp after heat dispersion treatment has a concentration of 35%, a treatment temperature of 110°C, a blade clearance of 0.2mm, and a back pressure of 1.8bar. Step 4: Add stickies control enzyme to the recovered pulp after heat dispersion treatment at a rate of 30 mL / min. The above operation is a key step in reducing large-sized stickies in the pulp.
[0014] Step 5: The slurry ratios for the surface, core and bottom layers are: 100% NUKP for the surface layer, 50% long fiber + 50% medium fiber for the core layer, and 100% short fiber for the bottom layer; Step 6: Wire mesh: To ensure the PCD of the paper machine system, 3kg / t of aluminum sulfate is added to the surface layer in the pipeline of the wet-end system of the wire mesh forming system. Since the core and bottom layers contain more recycled pulp, 12kg / t of aluminum sulfate is added to the core and bottom layers. To ensure the bursting strength of the finished paper, 20kg / t of dry strength agent is added to the above pipeline. The surface and bottom pulp concentrations on the wire mesh are controlled at 0.6%. Since the core layer is a headbox with dilution water, the pulp concentration of the core layer is controlled at 1.0%. Step 7: Paper pressing: First press is controlled at 1050 kN / m, second press is 1200 kN / m; Step 8: Surface sizing: The line pressure of the sizing machine is controlled at 45kN / m, and the gluing flow rate is 120m 3 / h, using film transfer sizing to ensure that the surface starch coating amount is 2g / m 2 ; Step 9. Hard calendering: To ensure the smoothness of the paper surface, use the hard calendering process with a line pressure of 45kN / m and a temperature setting of 180°C. Finally, form and roll. Example 3
[0015] This embodiment adopts the following technical solution: it includes the following steps: Step 1: Pulp ratio: 25% by weight of natural kraft softwood pulp (NUKP) and 75% by weight of recycled paper pulp (OCC); Step 2: Beating: Unbleached kraft softwood pulp is beaten using three conical refiners in series, with a beating concentration of 4.2% and a beating degree of 420 mL; the recovered pulp is graded and sieved into long, medium and short fibers for later use; Step 3: Use a heat disperser to heat disperse the recovered pulp after classification. The recovered pulp concentration during heat dispersion treatment is 30%, the treatment temperature is 105°C, the blade gap is 0.2mm, and the back pressure is 1.5bar. Step 4: Add stickies control enzyme to the recovered pulp after heat dispersion treatment at a rate of 20 mL / min. The above operation is a key step in reducing large-sized stickies in the pulp.
[0016] Step 5: The slurry ratios for the surface, core and bottom layers are: 100% NUKP for the surface layer, 50% long fiber + 50% medium fiber for the core layer, and 100% short fiber for the bottom layer; Step 6: Wire mesh: To ensure the PCD of the paper machine system, 3kg / t of aluminum sulfate is added to the surface layer in the pipeline of the wet-end system of the wire mesh forming system. Since the core and bottom layers contain more recycled pulp, 12kg / t of aluminum sulfate is added to the core and bottom layers. To ensure the bursting strength of the finished paper, 20kg / t of dry strength agent is added to the above pipeline. The surface and bottom pulp concentrations on the wire mesh are controlled at 0.5%. Since the core layer is a headbox with dilution water, the core layer pulp concentration is controlled at 0.8%. Step 7: Paper pressing: First press is controlled at 1000kN / m, second press is controlled at 1150kN / m; Step 8: Surface sizing: The line pressure of the sizing machine is controlled at 43kN / m, and the gluing flow rate is 100m 3 / h, using film transfer sizing to ensure that the surface starch coating amount is 1.8g / m 2 ; Step 9. Hard calendering: To ensure the smoothness of the paper surface, use the hard calendering process with a line pressure of 40kN / m and a temperature setting of 170°C. Finally, form and roll up.
[0017] Compared with the prior art, the present invention has the following advantages: the present invention provides a high-strength and environmentally friendly kraft paper production process with low bleached broadleaf pulp consumption, which can produce high-strength and environmentally friendly kraft paper with a bursting index of 2.8 kPa.m under the premise of low natural coniferous pulp consumption. 2 / g of high-strength environmentally friendly kraft paper; the prepared high-strength environmentally friendly kraft paper has the advantages of low cost and market demand.
[0018] For those skilled in the art, they can modify the technical solutions described in the aforementioned embodiments and make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.
Claims
1. A process for producing high-strength and environmentally friendly kraft paper with low bleached broadleaf pulp consumption, characterized by: It includes the following steps: Step (1), pulp ratio: using 20%-30% by weight of natural kraft softwood pulp and 70%-80% by weight of recycled pulp; Step (2), beating: Unbleached kraft softwood pulp is beaten using three conical refiners in series; recovered pulp is graded and screened into long, medium and short fibers for later use; Step (3), using a heat disperser to heat disperse the recovered pulp after the classification treatment; Step (4), adding a stickies control enzyme to the recovered pulp after the heat dispersion treatment at a rate of 10-30 mL / min; Step (5), slurry preparation: the slurry ratios of the surface, core and bottom layers are: the surface layer is 100% NUKP, the core layer is 50% long fiber + 50% medium fiber, and the bottom layer is 100% short fiber; Step (6) Wire mesh: In the pipeline of the wet-end system for wire mesh forming, add 3kg / t of aluminum sulfate to the surface layer. Since the core and bottom layers contain more recycled pulp, add 12kg / t of aluminum sulfate to the core and bottom layers. Add 20kg / t of dry strength agent to the above pipelines. The surface and bottom pulp concentrations on the wire mesh are controlled at 0.5%±0.1%. Since the core layer is a headbox with dilution water, the core layer pulp concentration is controlled at 0.8%±0.2%. Step (seven), paper pressing; Step (eight), surface sizing: the sizing machine line pressure is controlled at 42-45kN / m, and the sizing flow rate is 100±20m 3 / h, using film transfer sizing to ensure that the amount of starch glue on the surface is 1.5-2g / m 2 ; Step (9), hard calendering, and finally forming and rolling.
2. The process for producing high-strength and environmentally friendly kraft paper with low bleached broadleaf pulp consumption according to claim 1, characterized in that: The beating concentration in the step (ii) is 4.2±0.3%, and the beating degree is 420±10 mL.
3. The process for producing high-strength and environmentally friendly kraft paper with low bleached broadleaf pulp consumption according to claim 1, characterized in that: The recovered pulp concentration of the heat dispersion treatment in step (iii) is 25%-35%, the treatment temperature is 100-110°C, the cutter disc gap is 0.2mm, and the back pressure is 1.0-1.8bar.
4. The process for producing high-strength and environmentally friendly kraft paper with low bleached broadleaf pulp consumption according to claim 1, characterized in that: The step (seven) is divided into two pressing steps, the first pressing is controlled at 1000±50kN / m, and the second pressing is 1150±50kN / m.
5. The process for producing high-strength and environmentally friendly kraft paper with low bleached broadleaf pulp consumption according to claim 1, characterized in that: The hard pressing light pressure in step (9) is 40±5 kN / m, and the temperature is set at 170±10°C.