CN111364268A - Production process of low-basis-weight middle partition paper - Google Patents

Abstract

The invention provides a production process of low-basis-weight middle partition paper, which comprises the steps of proportioning, disintegrating, screening and purifying, concentrating, pulping, pulp proportioning, delivering, forming and compoundingThe method comprises the following steps of squeezing, drying, surface sizing, reeling and the like, wherein in the batching step, OCC waste paper with different grades is matched according to the determined raw material proportion of a produced product according to the fiber quality and the impurity content, the OCC waste paper comprises domestic waste paper and imported waste paper with the dosage of 10-30%, the imported waste paper comprises American waste paper, European waste paper and hong Kong waste paper, and the low-basis-weight intermediate paper produced by the production process of the low-basis-weight intermediate paper has the main physical indexes that: quantitative (60-65) +/-3 g/square meter, tightness greater than or equal to 0.50g/cm³The transverse ring pressure index is more than or equal to 3.0Nm/g, the longitudinal fracture length is more than or equal to 3.5km, the moisture content is 7.5-10.0 percent, and the water absorption is as follows: less than or equal to 50g per square meter, the quantitative rate of the septal paper product is reduced as much as possible on the premise that the strength index of the product meets the use purpose, and the use area of the product is obviously increased under the condition of the same weight, so that the development of low-carbon economy can be promoted.

Description

A kind of production process of low-quantity intermediate paper

【Technical field】

The invention relates to a pulp and paper production process, in particular to a production process of low-quantity intermediate paper.

【Background technique】

From the perspective of pollutant emission reduction, the fresh water consumption of waste paper pulping and papermaking is small, and the pollution load and treatment difficulty of waste paper pulping and papermaking wastewater are significantly lower than those of chemical pulping. Therefore, natural waste paper pulping conforms to the cycle. Characteristics of economic development, comprehensive utilization of resources and cleaner production.

Separator paper refers to the paper used to make the sandwich paper between the corrugated cores of corrugated cardboard, which is made of natural pulp. From the structural analysis of corrugated cardboard, the contribution rate of its flat compressive strength and edge compressive strength mainly comes from corrugated paper, surface layer paper and bottom layer paper. Not only to meet the use of the combined carton production line, which requires sufficient tensile strength, but also to maintain appropriate water absorption, to meet the needs of rapid bonding of starch glue. It can be seen that the separator paper has its own characteristics in terms of use and product characteristics, which is different from the corrugated core (original) paper in the general sense. In traditional corrugated cardboard manufacturing, corrugated core (original) paper with a basis weight of 100g/m ² or more is generally used for intermediate paper, which cannot adapt to the current paper product packaging industry to continuously reduce product weight, improve product quality, and reduce product packaging weight and packaging costs. demand.

[Content of the invention]

The technical problem to be solved by the present invention is to provide a production process of low-quantity intermediate paper, so as to overcome the deficiencies that the existing products for corrugated cardboard intermediate paper have high quantitative and cannot meet the needs of the current paper product packaging market.

The object of the present invention is achieved in this way:

A production process of low-quantity intermediate paper, comprising the following steps:

A: Ingredients, according to fiber quality and impurity content, different grades of OCC waste paper are matched according to the raw material ratio determined by the produced products;

B: Disintegration, adding the mixed waste paper into white water, under the action of mechanical and hydraulic forces, through infiltration, friction and dispersal, the waste paper is turned into coarse pulp with a beating degree of 22-28° SR;

C: Screening and purification, using outflow pressure screen, fiber separator, slag separator and low-consistency desander pulping equipment to purify and sort the coarse pulp;

D: Concentration, the long fiber pulp and short fiber pulp obtained by screening and purification are concentrated and washed by a multi-disc thickener, and the concentration of the pulp after dilution is 3.5-4.5%;

E: Beating, the long-fiber pulp is beaten by a double-disc mill, so as to purify the fibers and increase the binding force of the fibers, so that the beating degree of the long-fiber pulp is 36-42° SR;

F: pulping, matching the long fiber pulp and the short fiber pulp in proportion, and sending it to the pulping tower for standby use, and the beating degree of the obtained pulp is 34-38° SR;

G: Streaming, the qualified pulp will be thickened, punched, screened before the screen, evenly distributed and pressure-streamed;

H: Forming, the pulp is formed into a uniform wet paper sheet on the forming plate of the Fourdrinier former, and a large amount of dewatering is carried out through the wiper, wet vacuum box, vacuum box and vacuum couch roll, so that the dryness of the wet paper sheet reaches 18 -twenty two%;

I: Compound press, the wet paper sheet from the wire section is transferred and transferred through the papermaking felt, and the wet paper sheet is dehydrated by a combination of vacuum pressing and blind hole pressing, so that the dryness of the wet paper sheet sent out from the press section reaches 44-46% ;

J: Drying, using a drying cylinder with a surface temperature of 60-120°C to carry out convection and radiation mass transfer of the moisture in the wet paper, so that the dryness of the paper reaches 90-94%;

K: Surface sizing, using starch glue for surface treatment on the paper sheet, in the process of surface sizing, the starch glue solution is immersed in the paper sheet, and then forms a film on the surface of the paper sheet through post-drying, thereby improving the ring compressive strength of the paper sheet ;

L: Reeling, the sheets are formed into finished rolls on a horizontal reel.

A production process of the above-mentioned low-quantity intermediate separator paper, in the batching step, the OCC waste paper of different grades includes domestic waste paper and imported waste paper with a proportion of 10-30%. Paper includes US waste paper, European waste paper and Hong Kong waste paper.

A kind of production process of the above-mentioned low-quantity intermediate paper, described disintegration step comprises the steps:

B1: Dry screening, use a baler to break up the waste paper, remove heavy impurities such as soil and sand brought into the waste paper, and use a bag filter for dust removal;

B2: High-consistency pulping, adding OCC mixed waste paper and white water to the drum pulper, and disintegrating the waste paper into pulp at a concentration of 14-18%;

B3: High-consistency sand removal, the crushed pulp is sent to the high-consistency sand remover through a discharge pump to remove iron, sand and other heavy impurities in the pulp;

B4: Store pulp, store the crushed pulp in a pulp tower for later use, and fully infiltrate the fibers.

A kind of production process of the above-mentioned low-quantity intermediate paper, described screening purification step comprises the steps:

C1: Coarse sieve, the crushed pulp is coarsely sorted at a concentration of 2.5-3.5% using a hole sieve with a hole diameter of Φ2.0-3.0mm, which uses a fiber separator and a slag separator to carry out the second and third stage tailing Further disintegration of pulp to recover qualified fibers;

C2: Medium-consistency sand removal, use medium-consistency sand remover to further purify the coarsely screened pulp at a concentration of 2.0-2.5% to remove heavy impurities such as box nails and staples, and protect subsequent equipment;

C3: Classification of long and short fibers, using a grading screen with a screen gap of 0.25-0.30mm to classify pulp fibers at a concentration of 2.0-2.5%, strengthen the follow-up treatment of long fibers, simplify the treatment process of short fibers, and effectively protect the fiber length and width to avoid excessive damage to fibers, especially short fibers;

C4: One-stage multi-stage low-concentration sand removal, using the principle of gravity sedimentation, using a low-concentration desander group for purification at a concentration of 1.0-1.5%, and the second, third and fourth stages of low-concentration desander for the sequence. Further separation of tailings, recovery of qualified fibers;

C5: One-stage multi-stage fine sieve, the long fiber pulp is selected at a concentration of 1.0-1.5% using a fine screen with a screen gap of 0.20-0.25mm, which uses a two-stage fine screen, a fiber separator and a slag separator. Further dispersal and separation of tailings, and recovery of qualified fibers.

The production process of the above-mentioned low-quantity intermediate paper, the flow step comprises the following steps:

G1: Concentration adjustment. In the future, the qualified pulp from the pulping workshop will be transferred to the pulp making tank, and concentrated white water will be used for concentration adjustment. The target concentration is 3.5-4.5%;

G2: Pulp punching, send the papermaking pulp into the punching tank, and adjust the pulp concentration to 0.6-1.5% of the upper net pulp concentration under the action of the punching pump by mixing with the white water under the wire;

G3: Add papermaking chemicals. Add cationic electrolytes such as aluminum sulfate to neutralize negative charges in the pulp and anionic retention and drainage aids such as polyacrylamide for retention and drainage in the pulping tank and the pulp feeding pipeline. , the addition amount of the cationic electrolyte and retention and drainage aid agent is 0.05-0.10% and 0.02-0.06% respectively according to the weight percentage of the original solution and the finished paper production;

G4: Screening in front of the screen, the final screening of the qualified pulp is carried out in an internal flow pressure screen with a screen gap of 0.15-0.20mm;

G5: Distributor and headbox, the pulp is sent to the cone tube distributor for leveling to form micro-turbulence, and is sprayed to the forming wire through the hydraulic headbox with uniform pressure over the entire width.

A kind of production process of the above-mentioned low-quantity intermediate paper, the forming step comprises the steps:

H1: Fourdrinier wire forming, pulp forming and dewatering of wet paper sheets are completed on the forming wire reciprocatingly rotated under the action of net driving roller and vacuum couch roll, and the white water under the wire is discharged into the pulping tank;

H2: Vacuum dehydration. According to the vacuum degree requirements of different parts, the water ring vacuum pump performs vacuum dehydration on the wire vacuum suction box, vacuum couch roll, vacuum suction roll, composite press vacuum roll, and press felt suction box.

A kind of production process of the above-mentioned low-quantity intermediate paper, the drying step comprises the steps:

J1: The front drying section is dried, and the wet paper sheet from the press section is dried by a drying cylinder group, and the front drying section has 1 to 2 groups of drying cylinders using a single hanging drying cylinder, a paper web stabilizer and a cleaning roll device;

J2: Drying in the post-drying section, using a drying cylinder group to dry the wet paper sheets with a dryness of 60-65% after surface sizing, so that the dryness of the paper sheets reaches 90-94%, improving the strength of the paper sheets and improving the paper The surface properties of the page, the post-drying section has 1 to 2 sets of drying cylinders using chrome-plated drying cylinders;

J3: Multi-stage steam ventilation, combined with steam pressure, temperature, dosage and condensate flash volume, etc., design multi-stage steam ventilation process, so that the temperature of the surface of the dryer group rises slowly from low to high, so as to ensure the paper strength and other quality indicators.

A kind of production process of the above-mentioned low-quantity intermediate paper, described surface sizing step comprises the steps:

K1: Preparation of sizing material, conversion, dilution and storage of cassava or corn native starch under the action of a-amylase or oxidant;

K2: Sizing, adjust the starch glue to the required viscosity, temperature and solid content, use a screw pump to feed it into an immersion or film transfer surface sizing machine, and apply single- or double-sided sizing to the paper sheet from the pre-drying section , the applied amount of starch glue is 0.3-0.6% according to the weight percentage of the raw starch and the finished paper production;

K3: Functional chemical addition, adding functional papermaking chemicals such as waterproof and moisture resistance to starch or starch glue, the functional papermaking chemicals include surface sizing agents such as styrene acrylate or AKD, PVA or hard Moisture-proof agents such as sodium fatty acid, etc., the amount of surface sizing agent and moisture-proof agent added is 0.01-0.04% and 0.02-0.08% respectively according to the weight percentage of the original solution or solid and the finished paper, so as to further improve the finished paper after surface sizing. Page surface properties such as water absorption.

Compared with the prior art, the present invention has the following characteristics:

1. The main physical indicators of the low-quantity intermediate paper produced by the production process of the low-quantity intermediate paper of the present invention: quantitative (60-65)±3g/㎡, tightness≥0.50g/cm ³ , transverse ring pressure Index ≥3.0Nm/g, longitudinal fracture length ≥3.5km, moisture 7.5-10.0%, water absorption: ≤50g/㎡.

2. On the premise that the product strength index satisfies the use purpose, the quantification of the intermediate paper product is reduced as much as possible, and the use area of the product is significantly increased under the same weight, thereby promoting the development of a low-carbon economy.

3. The present invention uses OCC waste paper and other secondary fiber raw materials, develops advanced and applicable pulping and papermaking technology, and produces low-quantity intermediate paper of ^60-65g /m2, which increases the use area of the product and saves resources such as energy and forest trees. It reduces the adverse impact of traditional pulping on the environment and is very environmentally friendly.

4. Compared with the 100g/m2 product of the low-quantity intermediate paper produced by the present invention and the traditional 100g/ ^m2 product for corrugated cardboard intermediates, under the same weight, the use area of the 60-65g/m2 low-quantity intermediate paper increases by 67- 54%, promote energy conservation and emission reduction in the papermaking and paper product packaging industry, implement a circular economy and a low-carbon economy, and realize the sustainable development of the papermaking industry.

5. The present invention adopts a specific raw material formula, uses OCC waste paper raw materials and an optimized pulping process to effectively protect the fiber length and remove various impurities in the waste paper.

6. It is suitable for all kinds of papermaking equipment. The running speed of the paper machine producing low-quantity intermediate paper can reach 400-800m/min, and the equipment running rate of the ratio of normal papermaking time to equipment running time can reach more than 88%.

7. The low-quantity intermediate paper product produced by the present invention has stable quality and meets the rapidly developing market demands of industrial packaging such as household appliances and express logistics.

【Description of drawings】

The specific embodiments of the present invention will be described in further detail below in conjunction with the accompanying drawings, wherein:

Fig. 1 is one of the process flow schematic diagrams of the present invention;

Fig. 2 is the second schematic diagram of the process flow of the present invention.

【Detailed ways】

A first specific embodiment of a production process of low-quantity intermediate paper, comprising the steps:

1. Ingredients. According to fiber quality and impurity content, different grades of OCC waste paper are matched according to the raw material ratio determined by the produced products. Under the premise of product cost control, the effect of improving the physical strength index of the product can be achieved by using imported waste paper raw materials containing high-quality wood pulp fiber, and the amount used is 10-30%. The imported waste paper includes AOCC (American waste paper), EOCC (European waste paper) and HOCC (Hong Kong waste paper). The specific waste paper ratio is EOCC (European waste paper) 10%, HOCC (Hong Kong waste paper) 20%, and LOCC (domestic waste paper) 70%.

2. Disintegration. The mixed waste paper is added to the white water, and under the action of mechanical and hydraulic forces, the waste paper is transformed into coarse pulp through infiltration, friction, and dispersal, and the beating degree of the obtained pulp is 22-28° SR.

2.1. Dry screening, using a bulk bag machine to break up the waste paper to remove heavy impurities such as soil and sand brought into the waste paper, and supporting a bag filter;

2.2. High-consistency pulping, OCC mixed waste paper and white water are added to the drum pulper, and the waste paper is disintegrated into pulp at a concentration of 14-18%;

2.3. High-consistency sand removal, the crushed pulp is sent to the high-consistency sand remover through the discharge pump to remove iron, sand and other heavy impurities in the pulp;

2.4. Storing pulp, store the crushed pulp in the pulp tower for use, and fully infiltrate the fibers.

3. Screening and purification. According to the characteristics of fiber shape and density, pulping equipment such as outflow pressure screen, fiber separator, slag separator and low-consistency desander are used to further purify and sort the coarse pulp. combination.

3.1. Coarse sieving, the pulp after crushing is coarsely selected at a concentration of 2.5-3.5% using a hole sieve with an aperture of Φ2.0-3.0mm. Further dispersal of the third stage tailing pulp to recover qualified fibers;

3.2. Medium-consistency sand removal, further purify the coarsely screened pulp with a medium-consistency sand remover at a concentration of 2.0-2.5% to remove heavy impurities such as box nails and staples, and protect subsequent equipment;

3.3. Classification of long and short fibers. According to the characteristics of fiber length, use a grading screen with a screen gap of 0.25-0.30mm to classify pulp fibers at a concentration of 2.0-2.5%, strengthen the follow-up treatment of long fibers, and simplify the treatment process of short fibers. Effective Protect fiber length and width from excessive damage to fibers, especially short fibers;

3.4. One-stage multi-stage low-concentration sand removal, using the principle of gravity sedimentation, and using a low-concentration desander group for purification at a concentration of 1.0-1.5%. The low-concentration sand removal process adopts the second, third and fourth stages of low concentration. The desander further separates the tailings and recovers qualified fibers;

3.5. One-stage multi-stage fine sieving, long-fiber pulp is selected at a concentration of 1.0-1.5% using a fine sieve with a screen gap of 0.20-0.25mm. The slag separator further disperses and separates the tailings and recovers qualified fibers.

4. Concentrate. The purified and screened pulp is concentrated and washed through a multi-disc thickener, and the pulp concentration after dilution is 3.5-4.5%.

5. Beating. The long-fiber pulp is beaten by a Φ720mm double-disc mill to purify the fibers and increase the binding force of the fibers. The beating degree of the obtained pulp is 36-42°SR.

6, with pulp. According to the requirements of the produced products, the long and short fiber pulps are matched in proportion and sent to the pulping tower for use. The beating degree of the obtained pulp is 34-38°SR.

7. Streaming. The qualified pulp is adjusted, washed, screened before the screen, evenly distributed and conveyed by pressure.

7.1. Concentration adjustment. In the future, the qualified pulp from the pulping workshop will be transferred to the pulp making tank, and concentrated white water will be used to adjust the concentration. The target concentration range is 3.5-4.5%;

7.2. Pulp pulping, send the papermaking pulp into the pulping tank, and adjust the pulp concentration to 0.6-1.5% of the online pulp concentration under the action of the pulping pump by mixing with the white water under the wire;

7.3. Add papermaking chemicals. Add cationic electrolytes such as Alum (aluminum sulfate) to neutralize the negative charge in the pulp and PAM (polyacrylamide) for retention and drainage in the pulping tank and the pulp feeding pipeline. Anionic retention and drainage aid, the addition amount of the cationic electrolyte and retention and drainage aid agent is 0.05-0.10% and 0.02-0.06% respectively according to the weight percentage of the original solution and the finished paper production;

7.4. Screening before the screen, the qualified pulp is finally screened in the internal flow pressure screen with a screen gap of 0.15-0.20mm;

7.5. Pulp distributor and headbox, send the pulp into the cone tube pulper for leveling, form micro-turbulence, and spray it to the forming net through the hydraulic headbox with uniform pressure over the entire width.

8. Forming. The pulp is formed into a uniform wet sheet on the forming plate of the Fourdrinier former and is dewatered in a large amount by the wiper, wet vacuum box, vacuum box and vacuum couch roll, and the dryness of the wet sheet reaches 18-22%.

8.1. Fourdrinier wire forming, pulp forming and dewatering of wet paper sheets are completed on the forming wire reciprocatingly rotated under the action of net driving roller and vacuum couch roll, and the white water under the wire is discharged into the pulping tank;

8.2. Vacuum dehydration. According to the vacuum degree requirements of different parts, the water ring vacuum pump separately dehydrates the wire vacuum suction box, vacuum couch roll, vacuum suction roll, composite press vacuum roll, and press felt suction box.

9. Compound pressing. The wet paper sheet from the wire part is transferred and transferred through the papermaking felt, and the compound press can be a three-roll K-press structure + a large-roll blind-hole press or a four-roll three-press structure, and the wet paper sheet is subjected to vacuum pressing + blind hole pressing. Combined dehydration, the dryness of the wet paper sheet at the press section reaches 44-46%.

10. Dry. It is divided into a front drying part and a rear drying part. Using the thermal conductivity of the drying cylinder, the surface temperature of the drying cylinder reaches 60-120 °C, and the moisture in the wet paper sheet is convectively and radiatively transferred. The fan is discharged, and the dryness of the paper sheet reaches 90-94%.

10.1. Drying in the front drying section. According to the drying curve, a group of drying cylinders are used to dry the wet paper sheets from the pressing section. The drying cylinders in the 1-2 groups of the front drying section use a single-hanging drying cylinder, a paper web stabilizer and a cleaning roller device. ;

10.2. Drying in the post-drying section. According to the drying curve, a dryer group is used to dry the wet paper sheet with a dryness of 60-65% after surface sizing, and the dryness of the paper sheet reaches 90-94%, which improves the strength of the paper sheet and improves the The surface properties of the paper sheet, the 1-2 groups of drying cylinders in the post-drying section are chrome-plated drying cylinders;

10.3. Multi-stage steam ventilation, in order to ensure the paper strength and other quality indicators, make full use of the latent heat of steam, and design a multi-stage steam ventilation process according to the paper drying curve, combined with steam pressure, temperature, dosage and condensate flash volume, etc. The surface temperature rises slowly from low to high.

11. Surface sizing. The surface of the paper sheet is treated with starch glue. In the process of surface sizing, the starch glue is immersed in the paper sheet, and then dried to form a film on the surface of the paper sheet to improve the ring pressure strength of the paper sheet and other indicators.

11.1. Preparation of sizing material, conversion, dilution and storage of cassava or corn native starch under the action of α-amylase or oxidant;

11.2. For sizing, adjust the starch glue to the required viscosity, temperature and solid content, send it into the immersion or film transfer surface sizing machine with a screw pump, and apply single-sided or double-sided sizing to the paper sheet from the front drying section , the applied amount of starch glue is 0.3-0.6% according to the weight percentage of the raw starch and the finished paper production;

11.3. Addition of functional chemicals, in order to further improve the surface properties such as water absorption of the finished paper sheet after surface sizing, add functional papermaking chemicals such as water and moisture resistance to starch or starch glue solution. The functional papermaking chemicals Such as surface sizing agents such as styrene acrylate or AKD (alkyl ketene dimer), moisture-proofing agents such as PVA (polyvinyl alcohol) or sodium stearate, etc. or solids) and the weight percent of the finished paper production are 0.01-0.04% and 0.02-0.08%, respectively.

12. Coiling. The sheets are formed into finished rolls on a horizontal reel.

Another specific embodiment of a production process of low-quantity intermediate paper, comprising the following steps:

1. Ingredients. According to fiber quality and impurity content, different grades of OCC waste paper are matched according to the raw material ratio determined by the produced products. Under the premise of product cost control, the effect of improving the physical strength index of the product can be achieved by using imported waste paper raw materials containing high-quality wood pulp fiber, and the proportion of the product is 10-30%. The imported waste paper includes AOCC (American waste paper), EOCC (European waste paper) and HOCC (Hong Kong waste paper). The specific waste paper ratio is EOCC (European waste paper) 20%: LOCC (domestic waste paper) 80%.

2. Disintegration. The mixed waste paper is added to the white water, and under the action of mechanical and hydraulic forces, the waste paper is transformed into coarse pulp through infiltration, friction, and dispersal, and the beating degree of the obtained pulp is 22-28° SR.

2.1. Dry screening, using a bulk bag machine to break up the waste paper to remove heavy impurities such as soil and sand brought into the waste paper, and supporting a bag filter;

2.2. High-consistency pulping, OCC mixed waste paper and white water are added to the drum pulper, and the waste paper is disintegrated into pulp at a concentration of 14-18%;

2.3. High-consistency sand removal, the crushed pulp is sent to the high-consistency sand remover through the discharge pump to remove iron, sand and other heavy impurities in the pulp;

2.4. Storing pulp, store the crushed pulp in the pulp tower for use, and fully infiltrate the fibers.

3. Screening and purification. According to the characteristics of fiber shape and density, pulping equipment such as outflow pressure screen, fiber separator, slag separator and low-consistency desander are used to further purify and sort the coarse pulp. combination.

3.1. Coarse sieving, the pulp after crushing is coarsely selected at a concentration of 2.5-3.5% using a hole sieve with an aperture of Φ2.0-3.0mm. Further dispersal of the third stage tailing pulp to recover qualified fibers;

3.2. Medium-consistency sand removal, further purify the coarsely screened pulp with a medium-consistency sand remover at a concentration of 2.0-2.5% to remove heavy impurities such as box nails and staples, and protect subsequent equipment;

3.3. Classification of long and short fibers. According to the characteristics of fiber length, use a grading screen with a screen gap of 0.25-0.30mm to classify pulp fibers at a concentration of 2.0-2.5%, strengthen the follow-up treatment of long fibers, and simplify the treatment process of short fibers. Effective Protect fiber length and width from excessive damage to fibers, especially short fibers;

3.4. One-stage multi-stage low-concentration sand removal, using the principle of gravity sedimentation, and using a low-concentration desander group for purification at a concentration of 1.0-1.5%. The low-concentration sand removal process adopts the second, third and fourth stages of low concentration. The desander further separates the tailings and recovers qualified fibers;

3.5. One-stage multi-stage fine sieving, long-fiber pulp is selected at a concentration of 1.0-1.5% using a fine sieve with a screen gap of 0.20-0.25mm. The slag separator further disperses and separates the tailings and recovers qualified fibers.

4. Concentrate. The purified and screened pulp is concentrated and washed through a multi-disc thickener, and the pulp concentration after dilution is 3.5-4.5%.

5. Beating. The long-fiber pulp is beaten by a Φ720mm double-disc mill to purify the fibers and increase the binding force of the fibers. The beating degree of the obtained pulp is 36-42°SR.

6, with pulp. According to the requirements of the produced products, the long and short fiber pulps are matched in proportion and sent to the pulping tower for use. The beating degree of the obtained pulp is 34-38°SR.

7. Streaming. The qualified pulp is adjusted, washed, screened before the screen, evenly distributed and conveyed by pressure.

7.1. Concentration adjustment. In the future, the qualified pulp from the pulping workshop will be transferred to the pulp making tank, and concentrated white water will be used to adjust the concentration. The target concentration range is 3.5-4.5%;

7.2. Pulp pulping, send the papermaking pulp into the pulping tank, and adjust the pulp concentration to 0.6-1.5% of the online pulp concentration under the action of the pulping pump by mixing with the white water under the wire;

7.3. Add papermaking chemicals. Add cationic electrolytes such as Alum (aluminum sulfate) to neutralize the negative charge in the pulp and PAM (polyacrylamide) for retention and drainage in the pulping tank and the pulp feeding pipeline. Anionic retention and drainage aid, the addition amount of the cationic electrolyte and retention and drainage aid agent is 0.05-0.10% and 0.02-0.06% respectively according to the weight percentage of the original solution and the finished paper production;

7.4. Screening in front of the screen, the final screening of the qualified pulp is carried out in the internal flow pressure screen with a screen gap of 0.15-0.20mm;

7.5. Pulp distributor and headbox, send the pulp into the cone tube pulper for leveling, form micro-turbulence, and spray it to the forming net through the hydraulic headbox with uniform pressure over the entire width.

8. Forming. The pulp is formed into a uniform wet sheet on the forming plate of the Fourdrinier former and is dewatered in a large amount by the wiper, wet vacuum box, vacuum box and vacuum couch roll, and the dryness of the wet sheet reaches 18-22%.

8.1. Fourdrinier wire forming, pulp forming and dewatering of wet paper sheets are completed on the forming wire reciprocatingly rotated under the action of net driving roller and vacuum couch roll, and the white water under the wire is discharged into the pulping tank;

8.2. Vacuum dehydration. According to the vacuum degree requirements of different parts, the water ring vacuum pump separately dehydrates the wire vacuum suction box, vacuum couch roll, vacuum suction roll, composite press vacuum roll, and press felt suction box.

9. Compound press, which transfers and transfers wet paper sheets from the wire through the papermaking felt. The compound press can be a three-roll K-press structure + a large-roll blind-hole press or a four-roll three-press structure, and the wet paper sheet is vacuum-pressed + Combined dehydration of blind hole press, the dryness of the wet paper sheet at the press section reaches 44-46%.

10. Dry. It is divided into a front drying part and a rear drying part. Using the thermal conductivity of the drying cylinder, the surface temperature of the drying cylinder reaches 60-120 °C, and the moisture in the wet paper sheet is convectively and radiatively transferred. The fan is discharged, and the dryness of the paper sheet reaches 90-94%.

10.1. Drying in the front drying section. According to the drying curve, a group of drying cylinders are used to dry the wet paper sheets from the pressing section. The drying cylinders in the 1-2 groups of the front drying section use a single-hanging drying cylinder, a paper web stabilizer and a cleaning roller device. ;

10.2. Drying in the post-drying section. According to the drying curve, a dryer group is used to dry the wet paper sheet with a dryness of 60-65% after surface sizing, and the dryness of the paper sheet reaches 90-94%, which improves the strength of the paper sheet and improves the The surface properties of the paper sheet, the 1-2 groups of drying cylinders in the post-drying section are chrome-plated drying cylinders;

10.3. Multi-stage steam ventilation, in order to ensure the paper strength and other quality indicators, make full use of the latent heat of steam, according to the paper drying curve, combine the steam pressure, temperature, dosage and condensate flash volume, etc. to design a multi-stage steam ventilation process, so that the drying cylinder group The surface temperature rises slowly from low to high.

11. Surface sizing. The surface of the paper sheet is treated with starch glue. In the process of surface sizing, the starch glue is immersed in the paper sheet, and then dried to form a film on the surface of the paper sheet to improve the ring pressure strength of the paper sheet and other indicators.

11.1. Preparation of sizing material, conversion, dilution and storage of cassava or corn native starch under the action of α-amylase or oxidant;

11.2. For sizing, adjust the starch glue to the required viscosity, temperature and solid content, send it into the immersion or film transfer surface sizing machine with a screw pump, and apply single-sided or double-sided sizing to the paper sheet from the front drying section , the amount of starch glue applied is 0.3 to 0.6% by weight of the raw starch and the finished paper production;

11.3. Addition of functional chemicals, in order to further improve the surface properties such as water absorption of the finished paper sheet after surface sizing, add functional papermaking chemicals such as water and moisture resistance to starch or starch glue solution. The functional papermaking chemicals Such as surface sizing agents such as styrene acrylate or AKD (alkyl ketene dimer), moisture-proofing agents such as PVA (polyvinyl alcohol) or sodium stearate, etc. or solids) and the weight percent of the finished paper production are 0.01-0.04% and 0.02-0.08%, respectively.

12. Coiling. The sheets are formed into finished rolls on a horizontal reel.

Another specific embodiment of a production process of a low-quantity intermediate paper, comprising the following steps:

1. Ingredients. According to fiber quality and impurity content, different grades of OCC waste paper are matched according to the raw material ratio determined by the produced products. Under the premise of product cost control, the effect of improving the physical strength index of the product can be achieved by using imported waste paper raw materials containing high-quality wood pulp fiber, and the proportion of the product is 10-30%. The imported waste paper includes AOCC (American waste paper), EOCC (European waste paper) and HOCC (Hong Kong waste paper). The specific waste paper ratio is AOCC (American waste paper) 10%: LOCC (domestic waste paper) 90%.

2. Disintegration. The mixed waste paper is added to the white water, and under the action of mechanical and hydraulic forces, the waste paper is transformed into coarse pulp through infiltration, friction, and dispersal, and the beating degree of the obtained pulp is 22-28° SR.

2.1. Dry screening, using a bulk bag machine to break up the waste paper to remove heavy impurities such as soil and sand brought into the waste paper, and supporting a bag filter;

2.2. High-consistency pulping, OCC mixed waste paper and white water are added to the drum pulper, and the waste paper is disintegrated into pulp at a concentration of 14-18%;

2.3. High-consistency sand removal, the crushed pulp is sent to the high-consistency sand remover through the discharge pump to remove iron, sand and other heavy impurities in the pulp;

2.4. Storing pulp, store the crushed pulp in the pulp tower for use, and fully infiltrate the fibers.

3. Screening and purification. According to the characteristics of fiber shape and density, pulping equipment such as outflow pressure screen, fiber separator, slag separator and low-consistency desander are used to further purify and sort the coarse pulp. combination.

3.1. Coarse sieving, the pulp after crushing is coarsely selected at a concentration of 2.5-3.5% using a hole sieve with an aperture of Φ2.0-3.0mm. Further dispersal of the third stage tailing pulp to recover qualified fibers;

3.2. Medium-consistency sand removal, further purify the coarsely screened pulp with a medium-consistency sand remover at a concentration of 2.0-2.5% to remove heavy impurities such as box nails and staples, and protect subsequent equipment;

3.3. Classification of long and short fibers. According to the characteristics of fiber length, use a grading screen with a screen gap of 0.25-0.30mm to classify pulp fibers at a concentration of 2.0-2.5%, strengthen the follow-up treatment of long fibers, and simplify the treatment process of short fibers. Effective Protect fiber length and width from excessive damage to fibers, especially short fibers;

3.4. One-stage multi-stage low-concentration sand removal, using the principle of gravity sedimentation, and using a low-concentration desander group for purification at a concentration of 1.0-1.5%. The low-concentration sand removal process adopts the second, third and fourth stages of low concentration. The desander further separates the tailings and recovers qualified fibers;

3.5. One-stage multi-stage fine sieving, long-fiber pulp is selected at a concentration of 1.0-1.5% using a fine sieve with a screen gap of 0.20-0.25mm. The slag separator further disperses and separates the tailings and recovers qualified fibers.

4. Concentrate. The purified and screened pulp is concentrated and washed through a multi-disc thickener, and the pulp concentration after dilution is 3.5-4.5%.

5. Beating. The long-fiber pulp is beaten by a Φ720mm double-disc mill to purify the fibers and increase the binding force of the fibers. The beating degree of the obtained pulp is 36-42°SR.

6, with pulp. According to the requirements of the produced products, the long and short fiber pulps are matched in proportion and sent to the pulping tower for use. The beating degree of the obtained pulp is 34-38°SR.

7. Streaming. The qualified pulp is adjusted, washed, screened before the screen, evenly distributed and conveyed by pressure.

7.1. Concentration adjustment. In the future, the qualified pulp from the pulping workshop will be transferred to the pulp making tank, and concentrated white water will be used to adjust the concentration. The target concentration range is 3.5-4.5%;

7.2. Pulp pulping, send the papermaking pulp into the pulping tank, and adjust the pulp concentration to 0.6-1.5% of the online pulp concentration under the action of the pulping pump by mixing with the white water under the wire;

7.3. Add papermaking chemicals. Add cationic electrolytes such as Alum (aluminum sulfate) to neutralize the negative charge in the pulp and PAM (polyacrylamide) for retention and drainage in the pulping tank and the pulp feeding pipeline. Anionic retention and drainage aid, the addition amount of the cationic electrolyte and retention and drainage aid agent is 0.05-0.10% and 0.02-0.06% respectively according to the weight percentage of the original solution and the finished paper production;

7.4. Screening before the screen, the qualified pulp is finally screened in the internal flow pressure screen with a screen gap of 0.15-0.20mm;

7.5. Pulp distributor and headbox, send the pulp into the cone tube pulper for leveling, form micro-turbulence, and spray it to the forming net through the hydraulic headbox with uniform pressure over the entire width.

8. Forming. The pulp is formed into a uniform wet sheet on the forming plate of the Fourdrinier former and is dewatered in a large amount by the wiper, wet vacuum box, vacuum box and vacuum couch roll, and the dryness of the wet sheet reaches 18-22%.

8.1. Fourdrinier wire forming, pulp forming and dewatering of wet paper sheets are completed on the forming wire reciprocatingly rotated under the action of net driving roller and vacuum couch roll, and the white water under the wire is discharged into the pulping tank;

8.2. Vacuum dehydration. According to the vacuum degree requirements of different parts, the water ring vacuum pump separately dehydrates the wire vacuum suction box, vacuum couch roll, vacuum suction roll, composite press vacuum roll, and press felt suction box.

9. Compound pressing. The wet paper sheet from the wire part is transferred and transferred through the papermaking felt, and the compound press can be a three-roll K-press structure + a large-roll blind-hole press or a four-roll three-press structure, and the wet paper sheet is subjected to vacuum pressing + blind hole pressing. Combined dehydration, the dryness of the wet paper sheet at the press section reaches 44-46%.

10. Dry. It is divided into a front drying part and a rear drying part. Using the thermal conductivity of the drying cylinder, the surface temperature of the drying cylinder reaches 60-120 °C, and the moisture in the wet paper sheet is convectively and radiatively transferred. The fan is discharged, and the dryness of the paper sheet reaches 90-94%.

10.1. Drying in the front drying section. According to the drying curve, a group of drying cylinders are used to dry the wet paper sheets from the pressing section. The drying cylinders in the 1-2 groups of the front drying section use a single-hanging drying cylinder, a paper web stabilizer and a cleaning roller device. ;

10.2. Drying in the post-drying section. According to the drying curve, a dryer group is used to dry the wet paper sheet with a dryness of 60-65% after surface sizing, and the dryness of the paper sheet reaches 90-94%, which improves the strength of the paper sheet and improves the The surface properties of the paper sheet, the 1-2 groups of drying cylinders in the post-drying section are chrome-plated drying cylinders;

10.3. Multi-stage steam ventilation, in order to ensure the paper strength and other quality indicators, make full use of the latent heat of steam, and design a multi-stage steam ventilation process according to the paper drying curve, combined with steam pressure, temperature, dosage and condensate flash volume, etc. The surface temperature rises slowly from low to high.

11. Surface sizing. The surface of the paper sheet is treated with starch glue. In the process of surface sizing, the starch glue is immersed in the paper sheet, and then dried to form a film on the surface of the paper sheet to improve the ring pressure strength of the paper sheet and other indicators.

11.1. Preparation of sizing material, conversion, dilution and storage of cassava or corn native starch under the action of α-amylase or oxidant;

11.2. For sizing, adjust the starch glue to the required viscosity, temperature and solid content, send it into the immersion or film transfer surface sizing machine with a screw pump, and apply single-sided or double-sided sizing to the paper sheet from the front drying section , the applied amount of starch glue is 0.3-0.6% according to the weight percentage of the raw starch and the finished paper production;

11.3. Addition of functional chemicals, in order to further improve the surface properties such as water absorption of the finished paper sheet after surface sizing, add functional papermaking chemicals such as water and moisture resistance to starch or starch glue solution. The functional papermaking chemicals Such as surface sizing agents such as styrene acrylate or AKD (alkyl ketene dimer), moisture-proofing agents such as PVA (polyvinyl alcohol) or sodium stearate, etc. or solids) and the weight percent of the finished paper production are 0.01-0.04% and 0.02-0.08%, respectively.

12. Coiling. The sheets are formed into finished rolls on a horizontal reel.

Claims (8)

1. A production process of low-basis weight middle partition paper is characterized by comprising the following steps:

a: proportioning, namely, according to the fiber quality and the impurity content, matching OCC waste paper of different grades according to the determined raw material proportion of the produced product;

b: crushing, namely adding the mixed waste paper into white water, and changing the waste paper into coarse pulp with the beating degree of 22-28 DEG SR through infiltration, friction and defibering under the mechanical and hydraulic effects;

c: screening and purifying, namely purifying and sorting the coarse pulp by adopting pulp making equipment of an outward flow type pressure screen, a fiber separator, a slag discharge separator and a low-concentration desander;

d: concentrating, namely concentrating and washing long fiber slurry and short fiber slurry obtained by screening and purifying by using a multi-disc concentrator, wherein the concentration of the diluted slurry is 3.5-4.5%;

e: pulping, namely pulping the long fiber pulp through a double disc grinder so as to brood fibers and increase the bonding force of the fibers, so that the pulping degree of the long fiber pulp is 36-42 DEG SR;

f: pulp mixing, namely matching long fiber pulp and short fiber pulp in proportion, and sending the mixture into a pulp forming tower for later use, wherein the beating degree of the obtained paper pulp is 34-38 DEG SR;

g: flow conveying, namely performing concentration regulation, pulp flushing, pre-screening, uniform pulp distribution and pressure flow conveying on qualified paper pulp;

h: forming, namely forming uniform wet paper sheets on a forming plate of a fourdrinier former by the paper pulp, and dehydrating the wet paper sheets in a large amount through a scraping plate, a wet vacuum box, a vacuum box and a vacuum couch roll to ensure that the dryness of the wet paper sheets reaches 18-22 percent;

i: composite pressing, namely transferring and transferring the wet paper sheet from the net part through a papermaking felt, and performing combined dewatering of vacuum pressing and blind hole pressing on the wet paper sheet to ensure that the dryness of the wet paper sheet sent out of the pressing part reaches 44-46 percent;

j: drying, namely performing convection and radiation mass transfer on the moisture in the wet paper sheet by using a drying cylinder with the surface temperature of 60-120 ℃ to ensure that the dryness of the paper sheet reaches 90-94%;

k: surface sizing, namely performing surface treatment on paper sheets by adopting starch glue solution, summarizing the surface sizing process, immersing the starch glue solution into the paper sheets, and forming a film on the surfaces of the paper sheets through after-drying, thereby improving the ring crush strength of the paper sheets;

l: and (4) reeling, wherein the paper sheets form a finished paper roll on a horizontal winder.

2. The process of claim 1, wherein in the blending step, the different grades of OCC waste paper comprise domestic waste paper and 10-30% imported waste paper, and the imported waste paper comprises American waste paper, European waste paper and hong Kong waste paper.

3. The process for producing a low basis weight middle barrier paper according to claim 1, wherein said disintegrating step comprises the steps of:

b1: dry screening, namely scattering waste paper by using a bag scattering machine, removing heavy impurities such as soil, sand grains and the like brought in the waste paper, and removing dust by using a bag-type dust remover;

b2: high-concentration pulping, adding OCC mixed waste paper and white water into a drum pulper, and pulping the waste paper into paper pulp at the concentration of 14-18%;

b3: high-concentration desanding, namely conveying the crushed paper pulp into a high-concentration desander through a discharge pump to remove iron, sand and other large heavy impurities in the paper pulp;

b4: storing pulp, storing the crushed pulp in a pulp tower for later use, and fully soaking the fiber.

4. The process for producing a low basis weight middle barrier paper according to claim 1, wherein the screening and purifying step comprises the steps of:

c1: coarse screening, namely performing coarse screening on the crushed paper pulp by using a hole screen with the hole diameter of phi 2.0-3.0mm under the concentration of 2.5-3.5%, further defibering two-stage and three-stage tail pulp by adopting a fiber separator and a slag discharge separator, and recovering qualified fibers;

c2: medium concentration desanding, namely further purifying the paper pulp subjected to coarse screening by using a medium concentration desander under the concentration of 2.0-2.5%, removing heavy impurities such as box nails, staples and the like, and protecting subsequent equipment;

c3: classifying long and short fibers, and classifying the pulp fibers by using a classifying screen with a screen slot of 0.25-0.30mm under the concentration of 2.0-2.5%, so as to strengthen the subsequent treatment of long fibers, simplify the treatment process of short fibers, effectively protect the length and width of the fibers and avoid excessive damage to the fibers, particularly the short fibers;

c4: the first-stage multi-section low-concentration desanding is carried out by using a low-concentration desander group under the concentration of 1.0-1.5% to purify by utilizing the gravity settling principle, and two-section, three-section and four-section low-concentration desanders are sequentially adopted to further separate tailings and recycle qualified fibers;

c5: the first stage multi-section fine screen is used for fine screening of long fiber pulp with a screen gap of 0.20-0.25mm under the concentration of 1.0-1.5%, and the second stage fine screen, a fiber separator and a slag discharging separator are used for further defibering and separating tailings to recover qualified fibers.

5. A process for producing a low basis weight middle barrier paper according to claim 1, wherein said flowing step comprises the steps of:

g1: concentration adjustment, namely transferring qualified paper pulp from a pulp making workshop to a pulp making pool, and adjusting concentration by using concentrated white water, wherein the concentration of a target range is 3.5-4.5%;

g2: flushing, namely feeding the papermaking pulp into a flushing tank, and regulating the pulp concentration to 0.6-1.5% of the pulp concentration of the upper net under the action of a flushing pump by blending with the net white water;

g3: adding papermaking chemicals, namely adding cationic electrolytes such as aluminum sulfate and the like for neutralizing negative charges in pulp and anionic retention and filtration aids such as polyacrylamide and the like for retention and filtration aid into a pulp flushing tank and a pulp inlet pipeline respectively, wherein the addition amounts of the cationic electrolytes and the retention and filtration aids are 0.05-0.10% and 0.02-0.06% respectively according to the weight percentage of the pulp making amount of stock solution and finished paper;

g4: screening before a screen, namely performing final screening on qualified paper pulp in an internal flow type pressure screen with a screen gap of 0.15-0.20 mm;

g5: the pulp distributor and the pulp flowing box send pulp into the taper pipe pulp distributor for homogenization to form micro-turbulence, and the pulp is sprayed on a forming net through the hydraulic pulp flowing box with full-width uniform pressure.

6. The process for producing a low basis weight middle barrier paper according to claim 1, wherein the forming step comprises the steps of:

h1: forming a fourdrinier wire, wherein paper pulp is formed and dewatered on a forming wire which rotates in a reciprocating manner under the action of a wire driving roller and a vacuum couch roll, and white water under the wire is discharged into a pulp flushing groove;

h2: and (3) performing vacuum dehydration, namely performing vacuum dehydration on the net part vacuum suction box, the vacuum couch roll, the vacuum suction transfer roll, the composite press vacuum roll and the press felt suction box by a water ring vacuum pump according to the vacuum degree requirements of different parts.

7. The process for producing a low basis weight middle barrier paper according to claim 1, wherein the drying step comprises the steps of:

j1: a front drying part for drying the wet paper from the pressing part by adopting a drying cylinder group, wherein the front drying part comprises 1 to 2 groups of drying cylinders which adopt a single-hanging drying cylinder, a paper web stabilizer and a cleaning roller device;

j2: drying in a post-drying part, namely drying the wet paper with the surface sizing dryness of 60-65% by using a drying cylinder group to ensure that the dryness of the paper reaches 90-94%, improving the strength of the paper and improving the surface performance of the paper, wherein 1-2 groups of drying cylinders in the post-drying part adopt chromium-plated drying cylinders;

j3: and multi-section steam ventilation is carried out, and a multi-section steam ventilation flow is designed by combining steam pressure, temperature, dosage, condensate water flash evaporation amount and the like, so that the temperature on the surface of the cylinder group is slowly increased from low to high, and the quality indexes such as paper strength and the like are ensured.

8. A process for producing a low basis weight intermediate paper according to claim 1, wherein said surface sizing step comprises the steps of:

k1: preparing a sizing material, namely converting, diluting and storing the raw cassava or corn starch under the action of alpha-amylase or an oxidant;

k2: sizing, adjusting starch glue solution to required viscosity, temperature and solid content, feeding the starch glue solution into a soaking type or film transfer surface sizing machine by a screw pump, and performing single-side or double-side sizing on paper sheets from a front drying part, wherein the application amount of the starch glue is 0.3-0.6 percent of the weight percentage of the original starch and the papermaking amount of finished paper;

k3: adding functional chemicals, namely adding functional papermaking chemicals such as water resistance and moisture resistance into starch or starch glue solution, wherein the functional papermaking chemicals comprise surface sizing agents such as styrene acrylate or AKD (alkyl ketene dimer) and the like, moisture-proof agents such as PVA (polyvinyl alcohol) or sodium stearate and the like, and the addition amounts of the surface sizing agents and the moisture-proof agents are respectively 0.01-0.04% and 0.02-0.08% according to the weight percentage of stock solution or solid and the papermaking amount of a finished paper, so that the surface properties such as water absorption and the like of the finished paper after surface sizing are further improved.

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