JP2021055217A - Method for manufacturing web in paper machine - Google Patents

Abstract

To provide a method for manufacturing a web in which the moisture content of the webs is made constant, and in which the sticking and cracking of the sheets in the dryer are suppressed and the moisture content is promptly dehydrated to the target moisture content.SOLUTION: In a method for manufacturing a carbon fiber web according to the present invention, this paper making machine includes at least a wet part, a press part, and a dryer part, wherein the press part has at least a first suction device and a second suction device, and the first suction device dehydrates the moisture content to the upper limit of the target water content just before the dryer part, and then the second suction device dehydrates to the target moisture content, wherein a moisture measuring device for measuring the moisture content of wet paper is provided at least between the first and second suction devices.SELECTED DRAWING: Figure 1

Description

According to the present invention, in a paper machine including a wet part, a press part, and a dryer part, the press part is provided with a first suction device and a second suction device, the moisture content of the web is made constant, and the sheet is stuck on the dryer. This is a method for producing a web that suppresses cracking and quickly dehydrates to a target moisture content.

Paper making with a paper machine is required to have a uniform basis weight and thickness, and an optimum and uniform moisture content.

A suction device is provided in the wet part of the paper machine, and the suction device is arranged under the wet blanket to dehydrate the web formed in the paper layer through the wet blanket.

A press part is provided in the post-process of the wet part. The press part has a pair of press rolls, and the web is squeezed and dehydrated by passing the web through the nip portion between the press rolls together with the wet blanket.

In this way, the web is dehydrated, transported to the dryer part, and dried by the dryer. Originally, the moisture content of the web immediately before the dryer part ranges from 54 to 70%, for example. Even if dehydration is continued under the same conditions, the water content is constantly changing with the passage of time due to changes in the drainage degree of the raw material and dirt on the wet blanket.

In such a state where the moisture content is changing, the dryer cannot exert its ability, and the dryer cannot obtain uniform drying. Furthermore, depending on the moisture content of the web immediately before the dryer part, the web may crack due to insufficient drying, or may stick to the dryer due to overdrying. This is particularly remarkable when the web constituent fibers are rigid like carbon fibers and glass fibers or have a low softening point.

In such a state, when the drying is poor, the papermaking speed is reduced and the operation is performed. In addition, overdrying causes a problem that the paper machine must be stopped and the web attached to the dryer must be removed.

From such a problem, for example, in Patent Document 1, a moisture meter and a basis weight meter are installed side by side or independently on the wet paper at the end of the wet part of the paper machine, and the crown shape of the crown control roll is formed by the signal output. A control method for wet paper moisture that changes and changes the nip pressure is disclosed, whereby a uniform dry paper moisture can be obtained by controlling the moisture content in the width direction and the flow direction of the wet paper moisture. It is supposed to be done.

Further, in Patent Document 2, at the end of the wet part of the paper machine similar to the above, the wet paper moisture is linked to the press suction roll vacuum device, the wire suction box vacuum device, or the suction couture roll vacuum device. A control method for making the temperature constant is disclosed, and it is stated that the moisture content of the dry paper can be made uniform by controlling the moisture content of the wet paper before drying from the aspect of the water squeezing mechanism.

Further, Patent Document 3 discloses a control device in a paper machine in which one of a basis weight meter and a moisture meter is installed on the wet paper of a press part, and the paper charge outflow amount controller of the head box is controlled by the signal. It is said that it is possible to measure the moisture content or basis weight of the high-humidity paper of the press part, which occupies a large part of the paper quality determination, and to make the best paper quality paper based on the measured value.

Tokukousho 47-40565 Gazette Special Publication No. 47-40566 Special Publication No. 47-40567

However, the above-mentioned prior art method for adjusting suction dehydration of wet paper has the following problems. Since the moisture meter is located on the wet paper at the end of the wet portion immediately before the dryer, for example, after the wet paper reaches the moisture meter at a moisture content below the lower limit, the adjustment is delayed and overdrying occurs. If it exceeds the upper limit of the moisture content, wet paper exceeding the upper limit of the moisture content is sent to the dryer part between the time when the moisture content is measured with the moisture meter and the time when the moisture content is adjusted, resulting in poor drying.

In addition, when the target moisture content lower limit is obtained by suction dehydration with a wire suction box and suction couture roll, it is niped without suction in the subsequent press suction, so a slight dehydration is performed, so go to the dryer. There is a problem that the entering web becomes lower than the target moisture content.

The present invention has been devised in view of such conventional problems, and is a suction device that dehydrates to a target moisture content, and is provided with a first suction device and a second suction device to quickly and reliably retain water. This is a method for manufacturing a web whose rate can be adjusted.

That is, according to the present invention, in a paper making machine including at least a wet part, a press part, and a dryer part, the press part includes at least two or more suction devices, a first suction device and a second suction device, and the first suction device. A method for producing a web, which comprises dehydrating to a target moisture content upper limit immediately before a dryer part, and then dehydrating to the target moisture content in a second suction device.

Further, it is characterized in that a moisture measuring device capable of continuously measuring the moisture content of the web is provided between the first suction device and the second suction device.

According to the present invention, it is possible to quickly dehydrate the moisture content of the web to a target moisture content, and to produce a stable web without poor drying with a dryer or sticking.

According to the present invention, it is possible to produce a stable web even in a carbon fiber non-woven fabric in which sticking to a dryer or cracking of the web occurs remarkably when the moisture content of the web is unstable.

It is a schematic view which looked at the paper machine from the side.

Hereinafter, the method for producing a web of the present invention will be described in detail.

The paper machine according to the method for producing a web of the present invention includes at least a wet part, a press part, and a dryer part. The press part of the paper machine according to the present invention includes at least a first suction device and a second suction device as suction devices for dehydrating the web. Further, it is preferable to provide a moisture measuring device capable of continuously measuring the moisture content of the web between the first suction device and the second suction device.

The web manufacturing method of the present invention includes at least a first suction device and a second suction device in the press part, dehydrates the first suction device to the target moisture content upper limit immediately before the dryer part, and then in the second suction device the target. It is characterized by dehydration to a water content. The target moisture content of the web immediately before the dryer part varies depending on the basis weight of the web and the fiber composition, but it is generally preferable to set it to 54 to 70%. Therefore, in the present invention, when the water content range is set as the target water content range, dehydration above the upper limit of the target water content means dehydration by suction to a water content of 70% or more. At this time, the upper limit of the water content in the first suction device is preferably 75% or less. Further, dehydration to the target moisture content in the second suction device means dehydration by suctioning to 70% or less, and dehydration to a moisture content of 62%, which is the median value of the target moisture content range, or slightly lower than that. Is preferable.

More specifically, the first suction device can perform suction under certain conditions so that the moisture content falls within the range of 70 to 75%, and the moisture content of the web can be continuously measured between the first suction device and the second suction device. In the measurement by the moisture measuring device, if the moisture content when passing through the first suction device is 70% or less, the second suction device has a target moisture content lower limit of 54% or more, more preferably about 60 to 62%. When the moisture content when passing through the first suction device exceeds 70% of the target moisture content upper limit value, the target moisture content lower limit value of 54% or more in the second suction device is at least 70% or less of the target moisture content upper limit value. The suction is adjusted and dehydrated by the second suction device.

In the present invention, the moisture measuring device is provided not only between the first suction device and the second suction device, but also between the wet part up to the first suction device and between the second suction device and the dryer part. Moisture content may be measured. In particular, when suction is performed under certain conditions in the first suction device, the moisture measuring device reaches the first suction device, and the first suction device and the second suction device are used in order to deal with the dehydration in the second suction device in detail. It is preferable to measure at least two points between the suction devices.

The first suction device according to the present invention is not particularly limited as long as it is a suction device capable of dehydrating in a range of the target moisture content upper limit or more, more preferably the target moisture content upper limit to the target moisture content upper limit + 5%, but the suction press roll. Is preferable, and a suction box is more preferable.

Further, the second suction device according to the present invention can dehydrate to a moisture content within the range of the target moisture content, more preferably at least the lower limit of the target moisture content, preferably at the median value of the target moisture content range or slightly below it. The suction device is not particularly limited as long as it is a suction device, but a suction box or a suction device in which a press roll on the web side of a pair of press rolls is preferably a suction press roll is preferable.

In the press part according to the present invention, the suction device may be two, a first suction device and a second suction device, but three or more suction devices may be provided. In that case, it is preferable that the first suction device and the second suction device are continuous devices. More preferably, in the press part, the "first suction device" is the first suction device, that is, the suction device closest to the wet part, the "second suction device" is the subsequent suction device, and the suction following the second suction device. Optimally, the device is provided with a moisture measuring device immediately after the second suction device to lightly suck the moisture above the target moisture content lower limit, which contributes to the reduction of the drying burden of the dryer part.

Hereinafter, the method for producing a web of the present invention will be described in detail by taking a circular net paper machine as an example in the drawings. FIG. 1 is a schematic view of a circular net paper machine as viewed from the side.

The paper machine according to the present invention is composed of at least a wet part 4, a press part 8, a dryer part 6, and a reeler part 13.

In the wet part 4, the raw material is extracted by the circular net former 2 to form a web, and the web 1 (indicated by a thick line from the wet blanket 3 and the dryer blanket 5 in FIG. 1) is the circular net of the circular net former 2. It is transferred onto the transport support of the wet blanket 3 in contact.

The web 1 transferred to the wet blanket 3 is transported by the wet blanket 3 which is a transport support of the web 1, and is transported to the first suction device 9 and the moisture measuring device 11.

The moisture content of the transported web 1 is measured by the moisture measuring device 11. The signal measured by the moisture measuring device 11 is put into the dehydration control means (not shown), and the signal from the dehydration control means controls the degree of decompression of the vacuum system of the control means (not shown) of the first suction device 9. By this, suction dehydration is performed. Any target moisture content and range can be set for the dehydration control means.

It is desirable that the moisture measuring device 11 is at least necessary, and preferably another moisture measuring device 15 is installed on the upstream side of the first suction device 9. The first suction device 9 may be controlled by the measurement signal of the moisture measuring device 11, but by installing the moisture measuring device 15, the moisture content measurement information of the moisture measuring device 15 can be input to the moisture measuring device 11. 1 It becomes easier to control the suction device 9. Further, even when the first suction device is controlled under a certain condition (constant decompression degree), the moisture content measurement information of the moisture measuring device 15 makes it possible to quickly respond to the dehydration of the second suction device.

The water content measuring device 11 is a water content measuring device capable of continuously measuring, and may be, for example, a BM meter or a device using a change in the reflection and absorption of infrared rays. The same applies when, for example, a moisture measuring device 15 other than the moisture measuring device 11 is provided.

The web 1 sucked and dehydrated by the first suction device 9 is conveyed to the wet blanket 3 and dehydrated to the target moisture content by the second suction device 10. As shown in FIG. 1, when a configuration in which dehydration is performed by a nip of a roll pair of a suction press roll and a press roll is adopted as the second suction device, the nip is nipped between the suction press roll and the press roll 12.

The second suction device 10 measures the moisture content of the web 1 sucked and dehydrated by the first suction device 9 with the moisture measuring device 11, and the nip between the suction press roll and the press roll 12 with the signal measured by the measuring device. Dehydration within the target moisture content range by controlling the degree of vacuum of the suction part (not shown) in the suction press roll and the pressure dewatering.

The web 1 having a constant moisture content dehydrated to the target moisture content by the second suction device 10 is then peeled off from the wet blanket 3 and is closely dried by the dryer blanket 5 and the dryer 7 of the dryer part 6. The dried web is taken up by the reeler 14 of the reeler part 13.

1 Web 2 Circular net former 3 Wet blanket 4 Wet part 5 Dryer blanket 6 Dryer part 7 Dryer 8 Press part 9 1st suction device 10 2nd suction device 11, 15 Moisture measuring device 12 Press roll 13 Reeler Part 14 Reeler

Claims (3)

In a paper making machine including at least a wet part, a press part, and a dryer part, the press part has at least a first suction device and a second suction device, and the first suction device dehydrates the moisture content above the target moisture content immediately before the dryer part. Then, a method for producing a web, which comprises dehydrating to the target moisture content in a second suction device. The method for manufacturing a web according to claim 1, further comprising a moisture measuring device for measuring the moisture content of wet paper between at least the first suction device and the second suction device. The web manufacturing method according to claim 1 or 2, wherein the web is a carbon fiber web.

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