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The effect of fine pulp, forming and pressing process on paper

In the squeezing pressure zone of the paper machine, the fiber is pressed flat and permanent deformation due to the compression of the fiber, resulting in the decrease of the thickness of the paper. The pressed paper expands after passing the pressure zone, but does not fully recover to its original thickness. So the loose thickness of dry paper is related to the strength of the wet press.

The tight state of paper in the process of wet crushing increases the bonding area of the fiber and enhances the strength of the dry finished products. Reducing the loose thickness of the paper is suitable for some products, but high quality paper is not the case, and the minimum thickness is provided for this paper. If you can't meet the required thickness of paper by modifying the operating conditions, it is necessary to increase the paper ration to meet the requirement.

The density of paper depends on the nature of the pulp and several operating parameters. The effect of fine pulp and pressure on the thickness and other properties of high paper is studied extensively. The effect of the wet press on the thickness of the pine is more obvious than the mechanical pulp.

Mill's practical experience and test paper machine's research shows that under the same line pressure area load, produced by hard pressure zone is shorter but stronger maximum pressure, than produced by soft pressure area or pressing shoe is longer, but the intensity of low pressure pulse can more greatly reduce the thickness. However, the influence of pressure zone load on the thickness of paper is not studied systematically.

The purpose of this study is that determine on the first and the last squeeze pressure the pressure pulse amplitude will affect how senior paper moisture removal and thickness of the dry and soft, and how these effects combined with a degree of seminal plasma.

Wet paper can be crushed in the crush area, and the front of the paper that leaves the single blanket is rougher than the roll. The advanced paper made of soft chemical pulp is easier to press than the newsprint made of hard mechanical pulp. The other purpose of this study is to determine the two sides of the roughness produced by advanced paper in the process of squeezing.

It was previously reported that, in the area of the no blanket squeeze, the surface of the blanket was better than the roll, although it was not clear why the improvement was caused. This better printing quality may be the result of a larger positive effect on paper.

This cascade is more evident in high-quantitative cardboard than on low-quantity printed paper. The displacement of paper surface fibers and small fibers can also improve the printing properties of the paper surface. It has been reported that the displacement of fine fibrous material in the squeezing process of vacuum squeezing has been reported, but no one has yet confirmed that the small fibers and the Z - direction of the filler are redistributed during the squeezing process. In this study, we found evidence of the Z movement of small fibers and fillings in a strong squeeze condition.

The influence of wet pressing on the two sides of paper is combined with the paper characteristics formed in the forming process. The effects of long net and double mesh forming on paper properties are well known. However, as far as we know, there has not been any study on the comprehensive effect of the changing of the forming and pressing conditions on the paper characteristics. In this study, we used a series of the same pressing conditions to study the paper and the high - level paper.

Test section

Advanced paper is made from bleached sulphate pulp containing 80% of the wood and 20% of the black spruce. Both are produced in eastern Canada; Hardwood pulp is transported in the form of undried wet slurry, while the conifer wood pulp is full dry form. Coniferous wood pulp is ground to the Canadian standard free degree 550mlCSF. Hardwood pulp is ground to two different degrees of dissociation: 350mlCSF and 250mlCSF. Under alkaline conditions, the paper quantified by the speed of 700m/min to produce the paper with a quantitative range of 60 ~ 70g/m2 with precipitation of calcium carbonate.

In these experiments, Beloit company's research and development center of the third experiment machine is configured with a concept Ⅲ flow slurry tank and a shaper, first used in long net machine, then immediately change to Bel spray forming on the Form. The concentration of the slurry box was 0.55% while on the sprayer, and 0.50% on the long net paper machine. For the low-slurry ingredients, the retention rate of the two formers was 84 percent. For the ingredients with high precision, the retention rate of the sprayer was 85 percent and the length of the paper machine was 77 percent.

The squeeze part includes a four - roll squeeze, followed by a fourth squeeze. A special set of closed traction systems, including a vacuum primer roll and a primer, will press the paper from four rolls to the fourth crushing blanket. The two kinds of grinding pulp are made into high quality paper respectively on the long net machine and the top spray forming machine. In the four experiments, each group adopted eight different crushing conditions, with 32 different test conditions.

The squeeze part of the paper machine, including a four - roll squeeze and a fourth squeeze followed. When the pressure zone load is zero, open the first blanket pressure area, the paper enters the press, and the second pressure area of the blanket is squeezed first

The pressure area load used in the test is shown in table 1. The paper is first pressed in the double blanket pressure area, unless the paper is first pressed in the second squeeze of the single blanket when it is bypassed the first crushing pressure zone.

The paper machine did not bake the cadre, and the pressed paper was rolled up without drying. The wet paper roll of each condition is collected and dried on a separate 14 - cylinder dryer. Dry paper calender in Paprican laboratory in a single pressure zone was calender, calender speed of 50 m/min, press section load 10 kn/m, roller temperature is 50 ℃.

Using standard procedure to measure paper, see below. Measure the roughness of the paper immediately before and after the pressure. When the load is 1000kPa (S10), the parkerprint-surf (PPS) instrument with soft paper billet is used to measure it. The quality of printing is determined by the field version on the IGT printing machine, and the ink color concentration is determined according to the procedure described in the literature.