JPH04194093A - Twin wire former of paper-making machine - Google Patents

Abstract

PURPOSE:To produce paper having small difference of paper properties between the top and back surfaces and relatively high interlaminar strength without degrading the formation by placing a dehydration-suppressing shoe and a double- side dehydration shoe, in a wire loop composed of a pair of wire sheets. CONSTITUTION:A paper raw material ejected from a head box 3 is formed in the form of paper in wet state between wires 1,2. A dehydration-suppressing shoe 6 for suppressing the dehydration to the side of the wire 1 is placed in the wire loop of the wire 1 and a double-side dehydration shoe 7 is placed in the wire loop of the wire 2 at the downstream side of the former shoe.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a twin-wire former of a paper machine that performs wet paper web formation between two wires.

(Prior Art) Based on FIG. 4, the configuration of a twin wire former with a shoe-type dewatering device, which is one type of conventional twin wire former, is shown in the figure. As shown in the figure, each twin wire former forms a loop. It has a top wire 1 and a bottom wire 2. A raw material liquid is ejected from the head box 3 between the breast roll 5 that guides the top wire 1 and the forming roll 4 that guides the bottom wire 1.
The raw material liquid is sandwiched between both wires 1.2.

The dehydration suppressing shoe 6 is provided close to the breast roll 5 within the loop of the top wire 1. As shown in FIG. 5, the shoe 6 has a plurality of land portions 40'a that support the wire, and a wedge-shaped space where the wire entry surface of each land portion 40'a is in the width direction with respect to the wire surface. a plurality of sawtooth plates 40' having sloped portions 40'b forming a
It is made up of.

Following the dehydration suppressing shoe 6, two suction boxes 20, 21, a first vacuum roll 12, and a transfer box 22 are sequentially provided in the loop of the bottom wire 2, and the transfer box 22 is further provided with A second vacuum roll 24 is also provided on the downstream side.

On the other hand, a return roll 2 of the top wire 1 is placed between the transfer box 22 and the second vacuum roll 24.
A suction pickup roll 25 is provided downstream of the second vacuum roll 24 to suck the wet paper.

Reference numeral 26 denotes a saveall provided within the loop of the bottom wire 2 at the position of the dehydration suppressing shoe 6.

Further, the top wire 1 side of the suction box 20, 21, first vacuum roll 12, and transfer box 22 is open to the atmosphere.

In this example, the raw material ejected from the head box 3 for supplying the paper raw material is immediately sandwiched between the two wires, the top wire 1 and the bottom wire 2, and the land portion 40' of the plate 40' of the dehydration suppressing shoe 6. When passing through a, pressure acts on the raw material in the two wires due to the reaction force of the wire tension, etc., and water is squeezed out to both sides of the two wires. Among these, the white water that once flows out to the top wire l side where the dehydration suppressing shoe 6 is installed travels together with the wire, and is then formed by the inclined surface 40'b of the plate 40' of the shoe 6 and the wire surface. It is pushed back toward the raw material by the wedge effect of the space. As a result, dehydration to the top wire 1 side is suppressed.

On the other hand, since there is nothing to suppress dehydration on the bottom wire 2 side facing the top wire 1, the wire tension and the pulsating pressure generated when the white water once discharged to the top wire 1 side enters the wedge space Free dehydration is allowed.

By repeating this action several times, a mat is formed sequentially from the bottom wire 2 side.

The dehydrated water is collected in the saveall 26 and discharged outside the system.

Furthermore, there is a suction box 2 as a suction dehydrator on the downstream side.
0, 21, and a first vacuum roll 12 are provided, and most of the water in the raw material is dehydrated to the bottom wire 2 side by the suction boxes 20, 21 and the first vacuum roll 12.

Further, at this time, due to the centrifugal force of the rotating vacuum roll, some water is removed toward the top wire 1 side, and a water break line is formed.

In addition, from the viewpoint of improving the profile in the width direction, it is preferable to partially dewater the jet landing part toward the top wire l side using the breast roll 4. In this case, centrifugal dewatering toward the top wire side using the rolls also occurs. In the case of this example, it is possible to perform one-sided dehydration of up to about 95% up to a linear acid, and high interlaminar strength can be obtained. After this, transfer box 22. The second vacuum roll 24 further dewaters the bottom wire side to form a paper web with an increased matte density of 18 to 20%, and the paper web is sucked by the pickup linen 25 and separated from the bottom wire 2 for the next process. Transported to the press part.

(Problems to be Solved by the Invention) The conventional shoe-type twin ear former described above performs wet paper paper formation using pulsed dewatering pressure generated by the dehydration suppressing shoe blade 6. However, in this method, the amount of movement of the fibers is large, the paper is well-formed, and dehydration is performed on one side to about 95%, so high interlaminar strength is obtained, but on the other hand, the properties of the front and back sides of the formed paper (For example, the content of fine fibers and ash) is different, and the amount of ink consumed during printing is different between the front and back sides.

The present invention aims to provide a twin wire former that can produce paper with relatively high interlaminar strength and little difference between the front and back sides of the paper without disturbing the formation.

(Means for Solving the Problems) Therefore, the present invention provides a paper making method in which paper stock material ejected from a head box is sandwiched between two dewatering wires forming a loop, and water is dehydrated between the wires to form a wet paper. In the machine, a shoe for suppressing dewatering toward the first wire side is provided in the first wire loop, and a shoe for dewatering to both sides is provided in the second wire loop subsequent to the shoe, so that This is a means to solve problems.

(Function) Regarding the dewatering of the twin wire former, in the wet paper forming process up to the formation of the water cut line (called a dry line in the paper industry), the dewatering ratio to one side (the dewatering rate relative to the jetting flow rate of the head box) is When the ratio of water amount exceeds 70%, the interlaminar strength improves approximately in proportion to the increase in the dewatering ratio, and when it exceeds about 90%, it is on the same level as paper that is completely dehydrated on one side, such as those produced by a Fourdrinier paper machine. The interlaminar strength is obtained. In the present invention, following a stationary shoe that supports the first wire in the loop of the first wire and suppresses dehydration to the first wire side, dehydration is carried out to both sides in the loop of the second wire. Since it is equipped with a stationary shoe and a vacuum suction dehydration device, it is possible to make the dehydration ratio asymmetric and adjust the dehydration ratio as desired to obtain the above-mentioned interlaminar strength or the desired strength. You can give the history of shoe blades on both sides of the paper for the same purpose.

(Example) The present invention will be described in detail below with reference to the drawings. FIG. 1 is an overall configuration diagram of a twin former of a paper machine according to this embodiment.

In the figure, this embodiment includes a first wire 1 and a second wire 2 that form each loop, a forming roll 5 that guides the first wire 1, and a second wire 2.
A raw material liquid is ejected from the head box 3 between the breast rolls 40 that guide the wires 1. It seems to be sandwiched between 2.

The dehydration suppressing shoe 6 is provided close to the forming roll 5 within the loop of the first wire 1 . This shoe 6 has the same structure as the one filed by the inventors in Japanese Patent Application No. 63-285871, and detailed explanation thereof will be omitted here.

Following the dehydration suppressing shoe 6, a shoe 7 is provided within the loop of the second wire to allow dehydration to occur on both sides of the first wire 1 and the second wire 2. Further downstream, there are provided a transfer box 9 for ensuring transfer of the wet paper paper to the second wire 2 by vacuum suction, and a vacuum suction dewatering roll 12 for driving the second wire 2 to travel. Further, a dewatering roll 8 is provided within the first loop. On the other hand, a return roll 11 for the first wire 1 is provided at an intermediate position between the transfer box 9 and the vacuum suction dewatering roll 12. 13 is the first
A saveall that collects white water discharged to the wire 1 side,
10 is a saveall that collects white water discharged to the second wire 2 side by the dehydration suppressing shoe 6.

In this embodiment, the paper stock material ejected from the head box 3 is immediately sandwiched between two wires, the first wire 1 and the second wire 2, and the dehydration suppressing shoe 6 is moved in the direction of the second wire 2 (in the figure). dehydration is performed in the downward direction). The dehydrated white water is collected in the saveall 10 and discharged outside the system.

Furthermore, a shoe 7 capable of dewatering on both sides is arranged on the downstream side, and is designed to mainly dewater the first wire 1 side and also dewater the second wire 2 side. Next, the rotating non-porous dewatering roll 8 dewaters the paper to the second wire 2 side, the transfer box 9 suctions the paper web to the second wire 2 side, and finally the vacuum suction dewatering roll 12 dewaters the paper web to a density of 18~ It improves to 20% and is transported to the next process, the press part.

A second embodiment of the invention is shown in FIG. In this embodiment, a vacuum suction box 14 is provided on the second wire 2 side between the dehydration suppressing shoe 6 and the shoe 7 capable of double-sided dehydration. A dewatering ratio adjustment function is added to the wire 2 side.

(Effects of the Invention) The present invention achieves the following excellent effects in a twin wire former of a paper machine by arranging a dewatering suppressing shoe in the initial dewatering section and a dewatering shoe on both sides in the opposite wire loop on the downstream side. or can be obtained.

(1) As shown in the conceptual diagram of the relationship between dewatering ratio and interlaminar strength in Figure 3, it is possible to operate in such a way that the one-side dewatering ratio can be increased to a maximum of about 95%. You can gain strength between the eyebrows.

(2) Since wet paper is formed by giving the same history to both sides of the paper, the difference in properties between both sides of the paper can be minimized.

(3) High-speed operation is possible because the raw material liquid ejected from the head box is sandwiched between two wires before it is disturbed.

(4) Previously filed dehydration control shoe (patent application 1986-28)
5871), it is possible to obtain paper quality equivalent to that of a conventional double-sided dewatering twin wire former.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram of a twin wire former of a paper machine according to a first embodiment of the present invention, FIG. 2 is an overall configuration diagram of a twin wire former of a paper machine according to a second embodiment of the invention, and FIG. The figure is a conceptual diagram showing the relationship between dehydration ratio and interlaminar strength, FIG. 4 is an overall view of a conventional twin wire former, and FIG. 5 is a diagram showing the structure of a dehydration suppressing shoe. Explanation of the main parts of the diagram 1 ・-First wire (top wire) 2 ・-Second wire
Wire (bottom wire) 3 - Head box 4 - Breast roll 5 - Forming roll 6 - Dehydration suppression shoe 7 - Double-sided dehydration shoe 8 - Dehydration roll 9 - Transfer box 12 - Vacuum suction roll 14 - Vacuum suction It is the same as Box Figure 3C.

Claims (1)

[Claims] In a paper machine in which paper material ejected from a head box is sandwiched between two dewatering wires forming two loops and dewatered between the two wires to form a wet paper, the first wire loop contains a first A twin-wire former for a paper machine, characterized in that a shoe for suppressing dewatering to the wire side is provided, and, following the shoe, a shoe for dewatering to both sides is provided in the loop of a second wire.