Application of the hottest neutral sizing in speci

Research on the application of AKD neutral sizing in special packaging paper

Abstract: the sizing mechanism of AKD and its application in special packaging paper were studied

with the rapid development and progress of social economy, people have higher and higher requirements for the quality of special packaging paper, and the use of special packaging paper with traditional rosin sizing technology has been difficult to meet the requirements of users. In the past 10 years, a major trend in wet end chemistry research of papermaking is to complete the transformation from acid sizing to neutral sizing. The paper is made under the condition of high pH value of neutral sizing. The advantages are that the corrosion of the equipment is reduced, the fiber can obtain good swelling, the strength is greatly improved, the filler content is increased, the paper is easy to dry, the speed is increased, the output is increased, the energy consumption is reduced, and the pollution is reduced. In addition, the use of aluminum sulfate avoids the yellowing and embrittlement of the paper, which is convenient for long-distance transportation and long-term preservation of the paper. AKD neutral sizing is one of its typical representatives. It is reported that as early as 1997, neutral sizing was used in the global production of cultural paper, 95% in Europe, 72% - 75% in North America and 35% in Japan. China began to use imported AKD to make medium and high-grade paper in 1986, and achieved success

although Minfeng special paper company has a history of more than 70 years, it still adopts the traditional acid sizing process in the production of special packaging paper. Special packaging paper is one of the leading products of Minfeng special paper company's series of packaging paper, and its final products are mainly exported to South Korea, Japan, the United States and other countries and Taiwan. Recently, users have repeatedly reported that the special packaging paper is easy to turn yellow and brittle, and the appearance quality is poor after printing and storage, which affects the normal use of customers. Through the application research of AKD neutral sizing technology in special packaging paper, it not only solves the problems reflected by users, but also expands the selectivity of product raw materials, which greatly improves the internal quality, appearance, hand feel, etc. of special packaging paper. At the same time, the production cost is reduced and the waste water pollution load is reduced

1akd sizing mechanism

akd is the abbreviation of alkyl ketene dimer, which belongs to fiber reactive synthetic sizing agent. Under alkaline conditions, its reactive functional groups can react with hydroxyl groups on cellulose, form covalent bonds, bind and fix on the fiber, and form a stable film on the fiber surface, so that the fiber changes from hydrophilicity to hydrophobicity, so as to obtain water resistance of paper

akd has functional groups that can directly react with cellulose hydroxyl, but they basically do not react in the wet end of the paper machine. After AKD lotion is added to the size, the sizing agent particles are only dispersed in the size system, and multiple sizing agent particles can form relatively large agglomerates. These agglomerates and single sizing agent particles are adsorbed on the surface of fine fibers, fillers and fibers, and then remain in the wet paper with the retention of fines. At this time, AKD only exists in the form of electrostatic adsorption and dissociation, and the covalent bond between AKD and cellulose has not been formed. In the drying section, with the gradual reduction of moisture in the paper, AKD particles melt and expand on the fiber surface under the influence of drying temperature. The reactive functional groups of molecules face the fiber, the hydrophobic group part faces outward, and the reactive functional groups facing the fiber react with the hydroxyl group of cellulose to form covalent bonds, so as to fix on the fiber surface and complete the sizing process

2akd neutral adhesive production and application

2.1 introduction to special packaging paper special packaging paper is a kind of high-grade special packaging paper, which is mainly characterized by high whiteness of appearance, smooth and exquisite surface, high smoothness, non-destructive packaging and folding, good single-sided printing performance, high strength, and paper is not easy to turn yellow. See Table 1 for main technical indicators

2.2 production process conditions

raw material ratio: w=60% bleached wood pulp, w=40% bleached straw pulp

beating and mixing process conditions:

(1) crusher: industrialization of key technologies of key new materials with great market potential and high added value is carried out at the bottom of each row Five packs of Russian bleach needles, and then turn the upper plate down to the adjusted spacing position within 1s. Leaf wood pulp and 0.5 packs of domestic bleached straw pulp. Control the discharge concentration of 14 ~ 18G, and use the special packaging paper for uniform matching. Add 1200ml of ss-02 imported dye to each row. Adding method of ss-02 imported dye: take 1kg of ss-02 imported dye and add 10kg of water to dilute it into the required dye. Take 1kg of the prepared dye and add it into the slurry after 100 mesh filtration when the crusher is half loaded. It is strictly forbidden to add it too early or too late to avoid color difference

(2) pulping: the pulping degree of wood pulp is controlled at 26 ~ 30 ° Sr, and the wet weight is 4.5 ~ 5.5G. The pulp degree of straw pulp is controlled at 22 ~ 26 ° Sr, and the wet weight is 2.0 ~ 3.0g. (3) Mixing: after the wood pulp pump in the mixing tank is full, first add sn-01 cationic starch w=1% (for absolutely dry pulp), (sn-01 cationic starch dissolution method: take a packet of 25kg starch in the tank between rosin, add water to dissolve it into half a barrel, heat it and stir it until it is special and transparent. Pump it into the upper barrel of the mixing tank for use), Then add 50kg of n-03 calcium carbonate [dissolution method of n-03 calcium carbonate: add 2 bags of n-03 calcium carbonate (50kg) into the filler dissolution barrel of the paper machine, add water, stir and dissolve evenly, and add it to the pulp pool through filtration]. Control the ash content of paper ≤ 6%; The domestic AKD neutral collagen solution is added in the high-level box, the flow rate is 120ml/min (liquid glue, solid content 15%), and the control and slurry concentration is 12.0 ~ 15.0g

2.3 special packaging paper making equipment

long single cylinder paper machine, speed 40 ~ 80m/min, adjust the height and angle of lip cloth backing plate, can copy 30 ~ 90g/m2 packaging paper, control the sizing speed pressure by the liquid level of high-level box, and the surface temperature of drying cylinder is 60 ~ 120 ℃, equipped with stripping agent cylinder surface spray device. In production, the ration is 60g/m2, and the actual speed is 80m/min

2.4 control and use of AKD in production

1) before AKD is added, a small amount of preservative MS-5 is added to the slurry to reduce the production of rotten pulp, shorten the washing time and improve the effective operation time of the paper machine

2) AKD sizing lags behind, and continues after the paper roll is off the machine, reaching the best value in 6 ~ 10 days, so the sizing control is subject to the empirical reference value

3) AKD dosage w=0.15% ～ 0.25% (for absolutely dry pulp), dilute the stock solution twice and stir it, add it from the high-level tank with a metering pump to prevent hydrolysis loss, and add alkali to control the pH value of the pulp between 7.0 and 7.5

2.5 testing instruments and methods

Whiteness: yq-z-48a whiteness color tester (Hangzhou Qingtong instrument development company); Bursting strength: yq-z-23a electric paper bursting strength tester (Hangzhou light industry testing instrument factory)

quantitative: yq-z-45 paper quantitative determination standard sample sampler (Sichuan Changjiang paper instrument factory) and electronic balance (Sichuan Changjiang paper instrument factory)

tearing degree: yq-z-20 paper tearing degree tester (Sichuan Changjiang paper instrument factory)

smoothness: yq-z-30a smoothness tester (Hangzhou Qingtong instrument development company)

ash is determined by combustion method, moisture is determined by conventional method, and pH value of paper is determined by colorimetry. The laboratory is constant temperature and humidity, with temperature of 23 ± 1 ℃ and humidity of (50 ± 2)%. All test items are determined according to the current national standards

2.6 results and discussion of AKD application

2.6.1akd sizing effect test

1) see Table 6 for the comparison of AKD sizing effect test, target determination and original acid sizing

2) see Fig. 2 ~ Fig. 4 for the comparison between the effect of AKD sizing and some indicators of original acid sizing

3) user trial results. A total of 17T special packaging paper was produced this time, which has a good effect in the process of coating, coating or printing. At the same time, through trial, users in Shanghai, Wenzhou, Beijing and other places are satisfied with the high whiteness of the base paper and the difficulty of returning to yellow

2.6.2 economic benefit analysis

1) the product has been sent to many users for trial use in recent years, which basically meets the special requirements of customers

2) the improvement of whiteness and other indicators has opened up a direction for the production of rice and wheat straw pulp

3) the production cost is reduced, and the cost per ton of paper is reduced by about 80 yuan

4) it avoids the corrosion of acid papermaking on mechanical equipment and prolongs the service life of mechanical equipment and special equipment; (potential benefits)

5) reduce environmental pollution (BOD, COD, Ss are reduced by more than 50%), which is in line with the development trend of international paper industry. Due to the first trial production of special packaging paper with AKD neutral sizing, there are still many problems in the actual production and user use process. There is a certain deviation in the addition of AKD and cationic starch. During the use of some special packaging paper material factories, it is reflected that our paper sheets cannot be firmly combined with plastic film, which is easy to cause film peeling. In the future, it is necessary to study the addition amount of AKD, retention aid and other process conditions, and improve the operation level of the paper machine on the basis of the original experience, improve the product grade and stabilize the product quality

3 conclusion

through the application research of AKD, some experience has been accumulated for the future copying of AKD neutral sizing paper. At the same time, the problems of special packaging paper that cannot add brightener, whiteness cannot meet user requirements, and pH value of the paper cannot meet user requirements have been solved, which improves the product grade and user applicability of the paper. On the other hand, the research on the application of AKD neutral sizing technology in special packaging paper has significantly reduced the production cost and the waste water pollution load, increased economic benefits, reduced the environmental pollution load, facilitated the long-term development of the enterprise, benefited the children and even led the development of the industry for future generations

about the author: Ren Jianhua (1957-), male, engineer, is currently the director of the production department of Zhejiang Jiaxing Minfeng special Co., Ltd., mainly engaged in paper production management,:

Ren Jianhua, Nie Yongjun

(Minfeng Special Paper Co., Ltd.

reproduced from: O5