JPH06341091A - Apparatus for forming paper layer - Google Patents

Abstract

PURPOSE:To obtain an apparatus for forming a paper layer, good in formation, having a high internal strength and readily keeping the purity. CONSTITUTION:In a twin-wire former capable of passing a stock liquid through both wires by the action of a fixed dehydrator arranged in each wire loop in a zone where the top and bottom two wire loops engage and travel and dehydrating the stock liquid, the upper side on the opposite side of the top wire loop (2) engaging with the bottom wire (1) is nearly horizontally run and table apparatuses are arranged in the loop. The stock liquid jetted from a secondary headbox (5a) is dehydrated to enable the formation of both the combined and single plies.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a paper layer forming apparatus for a papermaking machine.

[0002]

2. Description of the Related Art A conventional example will be described with reference to FIG. FIG. 2 is a diagram of a conventional multi-layer forming apparatus using a long net and a short net.
This device is the wet end of a paper machine called a typical multiformer, which is composed of long-mesh and short-mesh parts and performs paper making. Head box 24, 24a for both long net and short net
The raw material liquid ejected from the table is dehydrated by the table equipment 20, 20a to form a paper layer. The paper layer formed by the short-mesh portion travels on the short-mesh whose direction is changed downward by the suction couch roll 12c, and is further changed by the dandy roll 26 in the advancing direction of the long-mesh 17 while at the same time It is pressed against the raw material mat on the net.

Therefore, two layers of wet paper are made while re-dispersing the raw mat on the fourdrinier by the dandy roll 26 of the short-netted portion. The combined multi-layered paper is further dehydrated by the suction box 21 provided in the fourdrinier loop and sent to the press part which is the next step by the suction pickup roll 23a.

[0004]

The conventional technique has the following problems. (1) Since each paper layer is composed of the normal forming board, foil, table roll, and wet box from the table equipment 20, 20a, the formation is not good. (2) It is necessary to increase the density of the paper layer of the long-mesh portion to such an extent that crushing does not occur at the place of the dandy roll 26 that is combined with the paper layer of the short-mesh portion. It is necessary to lengthen the mesh part. In addition, the internal strength (adhesion strength between layers) is weak because it is a dry-on-dry machine.

(3) When the short-mesh portion is one unit and the middle layer is made of three-layer white board using a cheap raw material such as waste paper, the four-net head box 24 is used as the two-layer machine head box. In addition, since the length of the long-mesh part described in the preceding paragraph is long enough to be dehydrated, the two layers are easily mixed and it is difficult to maintain the purity. (Purity here means the degree to which different raw materials do not mix when different layers of different raw materials are combined. When whiteboard is made, generally virgin raw materials with high whiteness are placed on the mesh side (outside). The intermediate layer such as used paper raw material is flowed on top of it so that the raw material of the intermediate layer may be seen outside the white raw material. Depending on the degree, the purity becomes a serious problem.) An object of the present invention is to provide a paper layer forming apparatus which solves problems, has good formation of each layer, has a large internal strength, and is easy to maintain purity.

[0006]

In a twin wire former for dehydrating through two wires by the action of a fixed dehydrating device arranged in each wire loop in a zone where two upper and lower wire loops are engaged and run, a top wire The opposite side of the loop that engages with the bottom wire is run substantially horizontally, the table equipment is arranged in the top wire loop, and the raw material liquid ejected from the second head box is dehydrated to make a machine combination, Papermaking is characterized in that both single-layer papermaking is possible.

[0007]

[Action]

(1) The paper-making side (usually poor formation) of the paper layer formed on the top wire unit comes into contact with the raw material liquid (having a lower concentration than the conventional paper-making portion) on the bottom wire unit. The concentration decreases while running. After that, when a strong pressure pulse is applied to the second forming shoe 8 part, it is re-dispersed and the formation is improved, and at the same time, the internal strength of the paper making part is increased by the mixing effect. On the other hand, the paper layer formed on the bottom wire side (the formation is good because it is dispersed by the agitation effect of the table equipment while the raw material concentration is low) has a fairly high concentration and the paper layer network is strong, so even if it receives a strong pressure pulse. The network is not broken and there is no mixing, so the purity is maintained.

(2) A dewatering device provided in the bottom wire loop at a portion where the top wire engages with the bottom wire (for example, the first described in Japanese Patent Application No. 02-403649 "Twin wire former of paper machine"). A fixed dewatering device such as the forming shoe 7 is convex upward and has a large radius of curvature, so that the pressing force of the top wire at the combining portion is small and the downward movement is caused by a vacuum (natural leg or externally applied) suction action. Since the dehydration to the bottom wire is promoted, the performance of swallowing the raw material on the bottom wire is good and the low speed and high basis weight (according to the research of the inventors, 220 gr / m ² , about 6
Even at 0 m / min, there were no problems such as swallowing without any problems). (3) The problem of the purity when using the primary headbox for two-layer papermaking with whiteboard three-layer papermaking is that the distance of the initial dewatering part from the slice lip, which is the raw material ejection port, to the papermaking part is short. The mixing of is slightly improved.

(4) Since the dehydrating device provided above the top wire loop is arranged without wrapping with the wire running substantially horizontally, there is a problem that the sliding resistance is small and the wire is worn even if the raw material is not flowed. Absent. Therefore, a single-layer papermaking operation can be performed using only the primary headbox 5 without flowing the raw material from the secondary headbox 5a. At this time, the dewatering device provided in the twin section, the first forming shoe 7, the second forming shoe 8, the low vacuum suction box 9, the transfer box 10 have sufficient dewatering ability, and the leading blade of the forming board 6 has a special application. By using a wide blade having a curvature described in HEI 02-403649, the raw material jet can be smoothly landed and high speed operation is possible.

[0010]

Embodiment An embodiment according to the present invention will be described with reference to FIG. FIG. 1 is a front view of the paper layer forming apparatus of the embodiment. In the figure, 1 is a top wire loop, and 2 is a bottom wire loop, which is a twin wire former having a zone in which a raw material is sandwiched between them to run. 6 is a forming board, 7 is a first forming shoe, 9 is a low vacuum suction box, 10 is a transfer box, and 11 is a high vacuum suction box, all of which are arranged in the bottom wire loop. A forming roll 4 and a second forming shoe 8 are arranged in the top wire loop 2. The dehydrator is disclosed in Japanese Patent Application No. 02-40364.
9. A dehydrator as described in "Twin wire former of paper machine", in which pulse pressure is applied to the raw material liquid ejected from the primary head box 5 to promote fiber dispersion and dehydrate through both wires to form a paper layer. .

The upper surface of the top wire loop 2 runs substantially horizontally, and the forming board 6a, the foil box 14, the table roll 16, and the wet box 1 are below the top wire loop 2.
It is also possible to form a paper layer by arranging table equipment such as 5 to dehydrate the raw material liquid ejected from the secondary head box 5a.

The operation of the above embodiment will be described. When the paper machine is activated and the raw material is ejected from both head boxes 5 and 5a, a paper layer is formed on the top wire 2 and travels on the top wire whose direction has been changed downward by the suction couch roll 12a and the forming roll 4. The direction is changed in the same direction as that of the bottom wire 1, and the raw material liquid on the bottom wire 1 is mixed on the first forming shoe 7.

At the 7th part of the first forming shoe, white water permeates due to the dehydration pressure, so that the concentration of the papermaking part is lowered.
Therefore, when a strong pulse pressure is applied when passing through the second forming shoe 8, both dispersion inside the paper layer is promoted and the formation is improved. At this time, since fibers are mixed between the layers, sufficient interlayer strength can be obtained. If necessary, the concentration of the top layer can be increased by applying a vacuum to the second forming shoe 8.

On the other hand, the raw material liquid ejected from the primary head box 5 onto the bottom wire 1 is initially dehydrated by the forming board 6 to form an initial mat. After that, the first forming shoe 7 engages with the paper layer formed on the top wire, but the pressing force of the top wire is small, so the gap formed on the first forming shoe 7 has a dehydration resistance to the top wire side. Is swallowed smoothly even if the pressure is high, the fiber is dispersed mainly by the pulse pressure of the first forming shoe 7, and is mainly dehydrated downward.

If necessary, it is possible to accelerate the dehydration by applying a vacuum to the first forming shoe 7. As described above, the paper layer is further concentrated in the low vacuum suction box 9 while being made into a sheet, transferred to the bottom wire 1 by the transfer box 10 and transferred to the press part which is the next step by the suction pickup roll 23. Next, the case of performing single-layer papermaking will be described. When performing single-layer papermaking, the raw material does not flow from the secondary head box 5a and only the primary head box 5 is used to form a paper layer. In this case, Japanese Patent Application No. 02-4
Since it is a hybrid type operation described in 03649, details are not described.

Next, the case of performing three-layer papermaking will be described. When performing three-layer papermaking, the primary headbox 5 can be operated without problems by using a conventional two-layer papermaking headbox. According to the researches of the inventors, the best use of these combinations is 40 gr / m ^{2 for} thin paper, about 1000
m / min equivalent printing paper to thick paper 380 gr /
It has been confirmed that a multi-layered paper, which is assumed to be a paperboard having a m ² of about 60 m / min, can be produced.

[0017]

The effects of the present invention are as follows. (1) Single former and multi-layer paper making are possible with one former. (2) The top layer formation is improved by the pulse pressure of the second forming shoe 8, and the formation is improved as compared with the conventional case. Furthermore, the density of the top layer papermaking surface decreases due to the permeation of white water in the papermaking part, and the density of the bottom layer papermaking surface is low, which makes it close to wet on wet papermaking Internal strength (interlayer adhesion strength) is increased in combination with inter-layer fiber mixing.

(3) Since the raw material liquid on the first forming shoe is swallowed gently and the dehydration ability to the bottom wire side is high, the initial dehydration may be small and the total length may be short. (4) When the primary head box is made into two layers and three layers are made, the purity between layers can be improved. (5) Since a wide range of grammage is used, a wide range of paper types and paperboards can be made with one former according to the final paper characteristics, and flexibility is high. Therefore, the present invention can provide a paper layer forming apparatus in which the formation of the paper layer is good, the internal strength is large, and the purity can be easily maintained.

[Brief description of drawings]

FIG. 1 is a front view of a paper layer forming apparatus according to an embodiment of the present invention.

FIG. 2 is a front view of a conventional multi-layer paper forming apparatus using a long-mesh and a short-mesh.

[Explanation of symbols]

1 ... Bottom wire, 2 ... Top wire (or middle net, generically top wire unit), 3 ... Pressed roll, 3a
... pressed roll, 4 ... forming roll, 5 ... primary head box, 5a ... secondary head box, 6 ... forming board, 6a ... forming board, 7 ... first forming shoe, 8 ... second forming shoe, 9 ... low vacuum suction Box, 10 ... Transfer box, 11 ... High vacuum suction box,
12 ... Suction couch roll, 12a, 12b, 12
c ... suction couch roll, 13 ... read-out roll, 14 ... foil box, 15 ... wet box, 16 ... table roll, 16a ... table roll,
17 ... Long net, 18 ... Short net, 19 ... Prestrol, 19
a ... press roll, 20 ... table equipment, 20a ... table equipment, 21 ... suction box, 22 ... turning roll, 23 ... suction pickup roll, 2
3a ... Suction pickup roll, 24 ... Primary head box, 24a ... Secondary head box.

Claims (1)

[Claims] 1. A twin wire former for dewatering through two wires by the action of a fixed dewatering device disposed in each wire loop in a zone where two upper and lower wire loops are engaged and run, and a top wire loop (2 ) Runs substantially horizontally on the side opposite to that which engages the bottom wire (1), and a table device is arranged in the top wire loop (2) to dehydrate the raw material liquid ejected from the secondary head box (5a). A paper layer forming apparatus characterized in that it is possible to perform both of the paper making and the single-layer paper making.