Special paper for food barrel and preparation process thereof

Abstract

The invention belongs to the technical field of papermaking, and particularly relates to special paper for a food barrel and a preparation process thereof. Wherein the basis weight of the special paper for the food barrel is 240 + / -3g / m < 2 >, the tightness is 0.76 + / -0.02 g / cm < 3 >, the interlayer bonding strength is greater than or equal to 235J / m < 2 >, the water absorption value per minute is greater than or equal to 200g / m < 2 >, the burst index is greater than or equal to 2.5 Kpa.m < 2 > / g, and the water content is 7.8-8.4%. The preparation process of the special paper for the food barrel has the beneficial effects that by controlling the ratio of the raw materials, the paper has relatively high folding resistance, so that the cracking of the food barrel during 180-degree flanging is prevented; according to the preparation process of the special paper for the food barrel, stickers are controlled in all stages, and the situation that normal operation of a paper machine is affected due to the fact that the stickers adhere to a forming net or a guide roller is prevented; gluing is not carried out in the preparation process of the special paper for the food barrel, and meanwhile, silica sol is used in a net part, so that the produced paper is high in air permeability, and the glue absorbency of the paper is further improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of papermaking, and particularly relates to a special paper for food cylinders and a preparation process thereof. Background Art

[0002] With the rapid economic development of our country, paper cores and paper tubes have been widely used in the papermaking industry, packaging industry, and textile and chemical fiber industries due to their advantages such as low cost, light weight, easy recycling, and pollution-free. It can be used as the inner core of various reel papers and cardboard, and can also be used to produce food cylinders for potato chip packaging, and gradually replaces the original plastic packaging bags. The food cylinder replacing plastic packaging is more upscale and more environmentally friendly.

[0003] However, the special paper for food cylinders has high requirements for the folding resistance of the paper and the cleanliness of the paper surface. A large amount of cartons and wrapping papers are contained in the raw materials used for the special paper for food cylinders. Since glue is needed in the processing of such raw materials, adhesives will be brought into the papermaking system during use. When the forming wire or the guide roll is adhered with adhesives, it will have a negative impact on the production operation of the paper machine. For example, when the surface of the forming wire is adhered with adhesives, water filtration cannot be carried out at this place, resulting in wet spots on the paper surface, and serious crushing and paper breakage. For example, when adhesives accumulate on the surface of the guide roll, the paper will be adhered when the paper passes through the guide roll, resulting in black spots on the surface at the lightest, and paper breakage at the heaviest. In addition, to meet the bonding requirements, the special paper for food cylinders needs to increase the glue absorption amount. Summary of the Invention

[0004] The present invention aims at the above problems and provides a special paper for food cylinders and a preparation process thereof.

[0005] The present invention relates to a preparation process of a special paper for food cylinders, which comprises the following steps: (1) Pulping: putting recycled pulp waste paper, OCC waste paper, and grade B waste paper into a pulper according to a ratio, then screening and purifying through a discharge tank, a high-concentration slag remover, and a coarse screen, further screening and purifying through a fine screen, then concentrating the fibers through a multi-disc, and grinding the concentrated pulp through a double-disc refiner to fully disintegrate until the beating degree reaches the requirement of 42±1°SR, and then entering a pulp tower for standby; (2) Paper formation: The pulp is pumped from the pulp tower through a pulp pump into the reserve tank and the pre - forming tank in sequence, and then transferred into the corresponding head boxes, white water towers, pulp - jet pumps and pressure screens for the surface, liner and base through a pulp pump in sequence. The pulp purified by the pressure screen is transported to the corresponding head boxes of the surface, liner and base; then it is transferred into the wire section, press section, drying section and calender in sequence. The wire section adopts a triple - layer wire. The weight ratio of the pulp for the surface, liner and base is 15:45:40. The vacuum degree of the wire section is 0.04 - 0.05 Mpa. The press section has a total of four press nips, and the linear pressure of the press nips is 70, 80, 280, 280 KN / m respectively. The vacuum of the press section is 0.04 - 0.05 Mpa; finally, through coiling, the special paper for food cylinders is obtained, and then through slitting and winding with film, the finished product is obtained.

[0006] Preferably, in the step (1), the weight ratio of the recycled pulp waste paper, OCC waste paper and Grade B waste paper is 2:2:1. The Grade B waste paper is mixed waste paper, and the mixed waste paper includes office paper and packaging paper.

[0007] Preferably, in the step (1), the pulping concentration of the pulper is 3.5 - 3.8%; the coarse screen selects a 2.0 - mm sieve hole, the incoming pulp concentration is 3.0 - 3.5%, the incoming pulp pressure is 0.15 - 0.3 MPa, and the pressure difference is 0.05 - 0.09 MPa; the fine screen selects a 0.2 - mm sieve slot, the incoming pulp concentration < 2.0%, the incoming pulp pressure is 0.1 - 0.25 MPa, and the pressure difference is 0.02 - 0.04 MPa; the incoming pulp concentration of the multi - disc is 1.5 - 2.7%, the outlet concentration is 5.2 - 5.3%, and the white water concentration ≤ 0.03%; during the pulping process, two double - disc refiners are started. The pulping power of each refiner is 450 kW / h.

[0008] Preferably, in the step (1), an adhesive - control enzyme is added to the discharge tank, and the addition amount is 150 g / ton of paper.

[0009] Preferably, in the step (2), a dry - strength agent and a deodorant are added to the pre - forming tank; the addition amount of the dry - strength agent is 6 kg / ton of paper, and the addition amount of the deodorant is 60 g / ton of paper.

[0010] Preferably, in the step (2), a dry - strength agent is added before the pulp - jet pump of the liner layer, and the addition amount is 4 kg / ton of paper; sizing starch is added before the pulp - jet pumps of the surface, liner and base respectively, and the total addition amount is 40 kg / ton of paper. The distribution ratio of the surface, liner and base layers is 1:6:3; an adhesive - control agent is added before the pulp - jet pumps of the surface, liner and base respectively, and the total addition amount is 200 g / ton of paper. The distribution ratio of the surface, liner and base layers is 1:3:1; an auxiliary agent is added before the pressure screens of the surface, liner and base respectively, and the total addition amount is 450 g / ton of paper. The distribution ratio of the surface, liner and base layers is 1:5:4.

[0011] Preferably, in step (2), starch spray is applied separately on the forming wires of the surface, liner, and base layers. The addition amount of the spray starch is 20 kg per ton of paper, and the distribution ratio of the surface, liner, and base layers is 1:1:3. The forming wires of the surface, liner, and base layers are sprayed with a wire section isolation aid online, with an addition amount of 1 ml / m·min. The wire section uses silica sol, with an addition amount of 3 kg per ton of paper.

[0012] Preferably, in step (2), a dryer cylinder release agent is sprayed online at the dryer section, including four points: the draw-in cylinder, the first cylinder, the upper dry wire of the first dryer, and the lower dry wire of the first dryer. The addition amount at the draw-in cylinder is 6 ml / min, and the addition amounts at the first cylinder, the upper dry wire of the first dryer, and the lower dry wire of the first dryer are all 4 ml / min.

[0013] Preferably, in step (2), the upper and lower press felts of the pre-press section are cleaned online with a felt cleaner, with an addition amount of 10 ml / m·min. A dryer cylinder release agent is sprayed online at the calender, with a spraying amount of 4 ml / min.

[0014] The present invention also relates to a special paper for food cans, which is prepared by using the preparation process of the special paper for food cans. The basis weight of the special paper for food cans is 240 ± 3 g / m 2 , the bulk density is 0.76 ± 0.02 g / cm 3 , the interlayer bonding strength ≥ 235 J / m 2 , the water absorption value per minute ≥ 200 g / m 2 , the bursting index ≥ 2.5 Kpa·m 2 / g, and the moisture content is 7.8 - 8.4%.

[0015] Compared with the prior art, the advantages and positive effects of the present invention are as follows: (1) The preparation process of the special paper for food cans controls the raw material ratio, making the paper have strong folding resistance, thereby preventing bursting when the food can is processed with a 180-degree flanging; (2) The preparation process of the special paper for food cans controls the adhesives at each stage, preventing the forming wire or the guide roll from sticking with adhesives and affecting the normal operation of the paper machine; (3) In the preparation process of the special paper for food cans, sizing is not carried out, and silica sol is used in the wire section, so the produced paper has high air permeability and further improves the glue absorption of the paper. Specific Embodiments

[0016] In order to more clearly understand the above objects, features, and advantages of the present invention, the following further illustrates the present invention with reference to embodiments.

[0017] In the following description, many specific details are set forth in order to provide a thorough understanding of the present invention. However, the present invention may be practiced in other ways different from those described herein. Therefore, the present invention is not limited by the limitations of the specific embodiments disclosed in the following specification.

[0018] Example 1 The following further describes the present invention. A preparation process for special paper for food cans includes the following steps: (1) Pulping: Put recycled pulp waste paper, OCC waste paper, and Class B waste paper into a pulper according to a ratio, then screen and purify through a discharge tank, a high-concentration slag remover, and a coarse screen, and further screen and purify through a fine screen. After that, the fibers are concentrated by a multi-disc, and the concentrated pulp is ground by a double-disc refiner to be fully disintegrated to reach the requirement of beating degree of 42±1°SR, and then enter the pulp tower for standby; (2) Papermaking: The pulp enters the reserve tank and the pre-coating tank from the pulp tower through a pulp pump in sequence, and then is transferred to the corresponding head boxes, white water towers, pulp pumps, and pressure screens for the surface, liner, and bottom through a pulp pump in sequence. The pulp purified by the pressure screen is transported to the corresponding head boxes for the surface, liner, and bottom; Then it is transferred to the forming section, pressing section, drying section, and calender in sequence. The forming section uses a three-layer forming wire. The weight ratio of the pulp for the surface, liner, and bottom is 15:45:40. The vacuum degree in the forming section is 0.04 - 0.05 Mpa. The pressing section has a total of four press nips, and the line pressure of the press nips is 70, 80, 280, 280 KN / m respectively. The vacuum in the pressing section is 0.04 - 0.05 Mpa; Finally, through winding, the special paper for food cans is obtained, and then through slitting and winding with film, the finished product is obtained.

[0019] In step (1), the weight ratio of the recycled pulp waste paper, OCC waste paper, and Class B waste paper is 2:2:1. The Class B waste paper is mixed waste paper, and the mixed waste paper includes office paper and packaging paper.

[0020] In step (1), the pulping concentration of the pulper is 3.5 - 3.8%; the coarse screen selects a 2.0 mm screen hole, the incoming pulp concentration is 3.0 - 3.5%, the incoming pulp pressure is 0.15 - 0.3 MPa, and the pressure difference is 0.05 - 0.09 MPa; the fine screen selects a 0.2 mm screen slot, the incoming pulp concentration < 2.0%, the incoming pulp pressure is 0.1 - 0.25 MPa, and the pressure difference is 0.02 - 0.04 MPa; the incoming pulp concentration of the multi-disc is 1.5 - 2.7%, the outlet concentration is 5.2 - 5.3%, and the white water concentration ≤ 0.03%; During the grinding process, two double-disc refiners are turned on, and the grinding power of each refiner is 450 kW / h.

[0021] In step (1), an adhesive control enzyme is added to the discharge tank, and the addition amount is 150 g / ton of paper.

[0022] In step (2), dry strength agent and deodorant are added to the approach pond; the addition amount of the dry strength agent is 6 kg per ton of paper, and the addition amount of the deodorant is 60 g per ton of paper.

[0023] In step (2), dry strength agent is added before the pulp pump of the liner layer, and the addition amount is 4 kg per ton of paper; sizing starch is respectively added before the pulp pumps of the top, liner, and bottom layers, and the total addition amount is 40 kg per ton of paper, and the distribution ratio of the top, liner, and bottom layers is 1:6:3; stickies control agent is respectively added before the pulp pumps of the top, liner, and bottom layers, and the total addition amount is 200 g per ton of paper, and the distribution ratio of the top, liner, and bottom layers is 1:3:1; additives are respectively added before the pressure screens of the top, liner, and bottom layers, and the total addition amount is 450 g per ton of paper, and the distribution ratio of the top, liner, and bottom layers is 1:5:4.

[0024] In step (2), spraying starch is respectively sprayed on the forming wires of the top, liner, and bottom layers, and the addition amount of the spraying starch is 20 kg per ton of paper, and the distribution ratio of the top, liner, and bottom layers is 1:1:3; web part isolation additives are sprayed online on the forming wires of the top, liner, and bottom layers, and the addition amount is 1 ml / m·min; silica sol is used in the web part, and the addition amount is 3 kg per ton of paper.

[0025] In step (2), dryer section cylinder release agent is sprayed online, including four points: the draw-in cylinder, the first cylinder, the upper drying wire of the first dryer, and the lower drying wire of the first dryer. The addition amount of the draw-in cylinder is 6 ml / min, and the addition amounts of the first cylinder, the upper drying wire of the first dryer, and the lower drying wire of the first dryer are all 4 ml / min.

[0026] In step (2), the upper and lower press felts of the press section are cleaned online with felt cleaner, and the addition amount is 10 ml / m·min; dryer section cylinder release agent is sprayed online at the calender, and the spraying amount is 4 ml / min.

[0027] In step (2), the concentrations of sizing starch and spraying starch in the storage tank are both 40%. When used on the machine, the concentrations are adjusted to 20% online through dilution water; the additives are prepared by mixing solid additives and clear water through solution, stirring, and aging to prepare an additive solution with a concentration of 0.4%; the web part isolation additives are diluted 10,000 times with dilution water before use; the original solution pH of the felt cleaner is > 12, and it is used after being diluted 20 times with clear water, and the pH after dilution is > 9.

[0028] After testing the main indicators of the special paper for food cans prepared by the above preparation process, the results are shown in Table 1.

[0029] Table 1 In Table 1, the column of "standard value" is the standard values of each index of the special paper for food cans.

[0030] The "detected value" column in Table 1 is the average detected value after multiple detections of each index of the special paper for food cans.

[0031] It can be seen from Table 1 that the basis weight of the special paper for food cans prepared in this embodiment is well controlled, the formed paper has a low tightness, the interlayer bonding strength is much higher than the standard value, the water absorption control is higher than the minimum value, the burst index and the longitudinal folding endurance are both higher than the standard value, and the moisture control is on the upper limit.

[0032] As mentioned above, it is only a preferred embodiment of the present invention, and it is not a limitation of the present invention in other forms. Any person skilled in the art may use the disclosed technical content to make changes or modifications into equivalent embodiments with equivalent changes and apply them to other fields. However, as long as it does not depart from the technical solution content of the present invention, any simple modification or equivalent change made to the above embodiments based on the technical essence of the present invention still belongs to the protection scope of the technical solution of the present invention.

Claims

1. A preparation process for special paper for food cylinders, characterized in that, It includes the following steps: (1) Pulping: Put the recycled pulp waste paper, OCC waste paper and Class B waste paper into the pulper according to the proportion, then pass through the discharge tank, high-concentration slag remover, and coarse screen for screening and purification, and further screen and purify through the fine screen. After that, the fibers are concentrated by a multi-disc, and the concentrated pulp is ground by a double-disc refiner to be fully disintegrated, reaching the requirement of beating degree of 42±1°SR, and then enter the pulp tower for standby; (2) Paper forming: The pulp is pumped from the pulp tower into the reserve tank and the pre-coating tank in sequence by a pulp pump, and then transferred into the corresponding head boxes, white water towers, filling pumps and pressure screens for the surface, liner and bottom in sequence by a pulp pump. The pulp purified by the pressure screen is transported to the corresponding head boxes for the surface, liner and bottom; then it is transferred into the wire section, press section, drying section and calender in sequence. The wire section adopts a triple wire. The weight ratio of the pulp for the surface, liner and bottom is 15:45:

40. The vacuum degree of the wire section is 0.04 - 0.05 Mpa. The press section has a total of four press nips, and the linear pressure of the press nips is 70, 80, 280, 280 KN / m respectively. The vacuum of the press section is 0.04 - 0.05 Mpa; finally, it is wound to obtain the special paper for food cans, and then it is cut and wound with film to obtain the finished product.

2. The preparation process of the special paper for food cans according to claim 1, characterized in that In the step (1), the weight ratio of the recycled pulp waste paper, OCC waste paper and Class B waste paper is 2:2:

1. The Class B waste paper is mixed waste paper, and the mixed waste paper includes office paper and packaging paper.

3. The preparation process of the special paper for food cans according to claim 1 is characterized in that, In the step (1), the pulping concentration of the pulper is 3.5 - 3.8%; the coarse screen selects a 2.0 mm screen hole, the incoming pulp concentration is 3.0 - 3.5%, the incoming pulp pressure is 0.15 - 0.3 MPa, and the pressure difference is 0.05 - 0.09 MPa; the fine screen selects a 0.2 mm screen slot, the incoming pulp concentration < 2.0%, the incoming pulp pressure is 0.1 - 0.25 MPa, and the pressure difference is 0.02 - 0.04 MPa; the incoming pulp concentration of the multi-disc is 1.5 - 2.7%, the outlet concentration is 5.2 - 5.3%, and the white water concentration ≤ 0.03%; During the grinding process, two double-disc refiners are started, and the grinding power of each refiner is 450 kW / h.

4. The preparation process of the special paper for food cylinders according to claim 1, characterized in that, In the step (1), an adhesive control enzyme is added to the discharge tank, and the addition amount is 150 g / ton of paper.

5. The preparation process of the special paper for food cylinders according to claim 1, characterized in that, In the step (2), a dry strength agent and a deodorant are added to the pre-coating tank; the addition amount of the dry strength agent is 6 kg / ton of paper, and the addition amount of the deodorant is 60 g / ton of paper.

6. The preparation process of the special paper for food cylinders according to claim 1, characterized in that In the step (2), a dry strength agent is added before the filling pump of the liner layer, and the addition amount is 4 kg / ton of paper; sizing agents are added before the filling pumps of the surface, liner and bottom respectively, and the total addition amount is 40 kg / ton of paper. The distribution ratio of the three layers of the surface, liner and bottom is 1:6:3; adhesive control agents are added before the filling pumps of the surface, liner and bottom respectively, and the total addition amount is 200 g / ton of paper. The distribution ratio of the three layers of the surface, liner and bottom is 1:3:1; additives are added before the pressure screens of the surface, liner and bottom respectively, and the total addition amount is 450 g / ton of paper. The distribution ratio of the three layers of the surface, liner and bottom is 1:5:

4.

7. The preparation process of the special paper for food cans according to claim 1, characterized in that, In the step (2), starch spray is respectively sprayed on the forming wires of the surface, liner and base layers. The addition amount of the spray starch is 20 kg per ton of paper, and the distribution ratio of the surface, liner and base layers is 1:1:

3. The forming wires of the surface, liner and base layers are sprayed with a wire section isolation aid online, and the addition amount is 1 ml / m·min. The wire section uses silica sol, and the addition amount is 3 kg per ton of paper.

8. The preparation process of the special paper for food cans according to claim 1, characterized in that, In the step (2), a dryer cylinder release agent is sprayed online in the drying section, including four points: the draw-in cylinder, the No. 1 cylinder, the upper drying wire of the first dryer and the lower drying wire of the first dryer. The addition amount of the draw-in cylinder is 6 ml / min, and the addition amounts of the No. 1 cylinder, the upper drying wire of the first dryer and the lower drying wire of the first dryer are all 4 ml / min.

9. The preparation process of the special paper for food cylinders according to claim 1, characterized in that, In the step (2), the upper and lower press felts in the press section are cleaned online with a felt cleaner, and the addition amount is 10 ml / m·min. A dryer cylinder release agent is sprayed online at the calender, and the spraying amount is 4 ml / min.

10. A special paper for food cans, characterized in that, Prepared by the preparation process of the special paper for food cylinders described in any one of claims 1 to 9, the basis weight of the special paper for food cylinders is 240 ± 3 g / m 2 , the tightness is 0.76 ± 0.02 g / cm 3 , the interlayer bonding strength ≥ 235 J / m 2 , the water absorption value per minute ≥ 200 g / m 2 , the bursting strength index ≥ 2.5 Kpa·m 2 / g, and the moisture content is 7.8 - 8.4%.

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