A factory produces 230g/m2 double-sided coated white paperboard. The ratio of slurry for the original batter and base paste is 20% for NBKP pulp, 80% for LBKP pulp, and bleached batter pulp for core pulp. In order to improve the stiffness and bulk of the white cardboard, 350/80/00 ​​BCTMP pulp was added to the core slurry. The comparison of the data before and after its product quality is shown in Table 3. White paper can be seen from Table 3, the coated white cardboard with BCTMP is higher in stiffness, looseness, smoothness, and folding resistance than the coated white cardboard without BCTMP. The paper containing BCTMP is calendered. After the smoothness is better, and the production cost is basically the same as the original. (The price of Zhenjiang eucalyptus pulp is 3,800 yuan/ton, and the price of Xueshan brand BCTMP is 3,750 yuan/ton.)
Application of needle-broad-leaf BCTMP in white paperboard A factory produces coated white paperboard. The batter consists of bleached chemical pulp and bleached pulp, and the core pulp and bottom pulp are waste pulp. In order to improve the surface opacity, reduce the proportion of chemical pulp and increase the stiffness of coated white paperboard, the factory added 15% to 20% of Poplar BCTMP pulp to the dough. See the product quality comparison. Table 4 .
The use of BCTMP in other paper types It is well-known that the presence of lignin has a bad influence on the properties of the pulp. Pulp with too high lignin content is beaten slowly, the binding force between the fibers is poor, and the resulting paper is tight. The strength is poor; but on the other hand, the presence of lignin can reduce the swelling ability of the fiber and increase the stiffness of the paper. Recent studies have questioned the traditional view that the presence of lignin reduces the strength of the paper sheet, suggesting that the main cause of paper decomposition is the acidity of the paper rather than lignin. As a result, BCTMP has been widely used in traditional wood-free coated paper, copy paper, and carbonless paper. European and Japanese hardwood BCTMP pulps have been used for more than a decade in the production of silicone-coated anti-sticking base papers, transparent papers, labels, and similar specialty papers. With the continuous improvement of the quality of BCTMP and the deepening of the understanding of BCTMP by papermakers, by continuously exploring and summarizing the experience, the application of BCTMP in production will surely achieve better results.
Use good chemical additives to increase the bonding strength between the fibers and improve the stiffness of the white paper. The paper stiffener has a certain effect on the improvement of paper stiffness. In particular, the use of inter-layer spray starch not only increases the bond strength between layers, but also improves the stiffness of the board. Applying starch sprays between the layers and layers of the paperboard can increase the bond strength of the paper layer by 25%, while adding it to the pulp does not achieve this effect. There are many types of sprayed starches for different requirements. For example, spray corn starch from Jiangxi Yufan Chemicals: YF308 contains urethane, YF408 is a high viscosity ester-based product, and YF508 is a low viscosity ester-based product. Technical characteristics are shown in Table 5.

Table 5 Performance of several sprayed starches

Technical Index YF308 YF408 YF508
Appearance white powder white powder white powder moisture% ≤14 ≤14 ≤14
pH (5% emulsion) 6.0±1 7.0±0.5 7.0±0.5
Viscosity (6%, 85°C) mPa•s 3~25 25~55 5~25
Fineness (over 100 mesh)% ≥99 ≥99 ≥99
Pasting temperature °C ≤ 60 ≤ 50 ≤ 55

Table 6 Before and after comparison with YF-308 sprayed starch

The test item did not add spray starch plus spray starch quantitative g/m2 223 223
Whiteness% 88.6 88.8
Thickness μm 292 295
Stiffness mN•m 2.9 3.75
Sizing degree g/m2 28/38 30/40
Smoothness s 27.8/8.6 30/8
Folding times 50 53
Glossiness % 31.6 31.3
Moisture% 8.2 7.5

Note: The paper machine model 1600mm round net multi-cylinder paper machine; production 230g/m2 coated white paperboard; batter and bottom pulp are 20% medium long fiber wood pulp, 80% hardwood short fiber pulp; core pulp is 20 % Hardwood pulp pulp, 80% 350/80/100BCTMP.

Table 4 Matching with BCTMP350/85/100 coated white paperboard Data comparison test data Surface layer Slurry ratio Proportioning One Proportioning Two Proportioning Three
BCTMP % 0 15 20
NBKP % 44 41 36
LBKP % 35 25 44
Bleached pulp% 21 19 0
Whiteness %ISO 76.06 79.62 78.04
Opacity % 99.97 99.96 100.08
Split Length km Vertical 4.77 5.26 4.83
Lateral 10.07 10.06 10.23
Tear index mN•m 2/g Longitudinal 9.69 9.83 9.77
Lateral 18.84 18.40 24.94
Gurley stiffness N portrait 42.65 51.11 70.99
Lateral 18.84 18.40 24.94

The spray amount of sprayed starch is generally about 1g/m2 per layer, the concentration of starch slurry is generally controlled at 1% to 10%, and the starch concentration is about 2% to 3% for interlayer reinforcement, and the amount can be lower; The strength of the binding, especially when increasing the stiffness, should be around 5%. When using starch, cold water is first added to the dissolving tank, stirring is started, the sprayed starch is poured, the starch is dispersed into a suspension, and then steamed and gelatinized. After gelatinization, the starch retention rate is high and the use effect is better. However, it should be noted that if the dewatering capacity of the wet end of the paper machine is poor, the addition of the gelatinized spray starch may cause embossing of the wet paper sheet in the press section. In this case, it may not be pasted. After the starch slurry was filtered through a 120 mesh screen, it was pressure sprayed into the paper sheet.
The effect of atomization directly affects the use effect, so controlling atomization is critical. The purpose of uniform spraying is generally achieved through pressure control. A pressure regulating valve is installed between the spray head and the pump to control the optimal atomization. The pressure is generally controlled to be about 0.294 MPa. If the pressure is lower than 0.196 MPa, the atomization will be poor. If the pressure is higher than 0.392 MPa, the formed sheet will be damaged. The distance between the nozzles is 80-160mm, and the distance between the nozzle and the mesh surface depends on the condition of the paper surface covered by the spray. Cross coverage is required, usually 200-300mm.
Taking a 1600mm board machine as an example, the mesh surface is equipped with 20 nozzles. Each nozzle has a flow rate of Q=0.4 m3/h. The pump Q=10m3/h and h=50m are selected. A nozzle is installed between the batter and the lining, the lining and the core, the core and the core, the core and the base. At the same time, attention should be paid to the circulation of the sprayed starch slurry. The starch liquid recycled from the spray system to the starch preparation system should be two-thirds, and only one-third of the starch liquid should be sprayed onto the paperboard.
The application effects of YF-308 sprayed starch are shown in Table 6.
In summary, in the production process of white (card) paperboard (coating and non-coating), BCTMP commercial pulp with appropriate material species and grades is selected, suitable slurry proportioning and beating process conditions are formulated, and good chemistry is used. Additives to enhance the binding force between fibers, adjust the operation of the paper machine, properly reduce the press line pressure, calender line pressure, reduce the water into the paper properly, can improve the white board stiffness, bulk. Also increase surface opacity and hiding power. To improve product quality and reduce production costs, the effect is obvious.

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