JPS5836452A - Water absorbing sheet and its manufacture - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a water-absorbent sheet and a method for producing the same, and more specifically to a water-absorbent sheet formed by inserting a polymer absorbent between two sheets, at least one of which is a water-permeable sheet. The present invention relates to a water-absorbing sheet that does not cause cough polymer absorbent to fall off and is highly flexible, and a manufacturing method for economically manufacturing such a sheet.

A polymer absorbent, that is, a granular or short fibrous water-absorbing polymer material such as a polyacrylic acid polymer, OMO, or a starch derivative, is used as an absorbent between two sheets, at least one of which is a water-permeable sheet. The method of stably stabilizing the zero-carrying polymer absorbent used in sanitary products and sanitary products such as disposable diapers by inserting it into a water absorbent sheet without falling off is to insert the polymer absorbent into one sheet. After spraying the agent, the other sheet is combined and embossed, which is generally called a dry method, or by using the above method, a small amount of moisture is added before or after embossing, and the basic characteristics of the polymer absorbent are applied. Wet methods, which are commonly referred to as processing methods that take advantage of the property of gelling due to certain moisture, are considered. Processing using the wet method allows the polymer absorbent to exhibit its gelation property due to water, which is a basic property of the polymer absorbent. This is an appropriate method for immobilizing iron water absorbent sheets within the absorbent sheet without falling off.@K uses the wet method to process iron water absorbent sheets. The water-absorbing sheet is manufactured by a method of incorporating it into a 1n-4in method, or by a special method of spraying water. ff −1
There are two possible cases: 1n/Law.

In order to produce an economical and flexible water absorbent sheet using a wet method, the 1n-une method should be used in principle, and the amount of water sprayed should be adjusted to fix the polymer absorbent. This is done in the minimum necessary amount to prevent the decrease in flexibility of the water absorbent sheet due to excessive swelling of the polymer absorbent, and also from a process standpoint.
A method that does not require a drying step is considered appropriate. Processing using the cough wet method is a spray method, published in Japanese Patent Publication No. 54-125'19.
Publication No. 5 (Mitsubishi Ren), Japanese Patent Application Laid-open No. 51-40497 (Unicharm), Japanese Patent Application Publication No. 1410-1982? However, both inventions are device-wise,
It takes the form of off-14n.

In the spray method called water spraying, it is possible to spray a fixed amount of water under a certain fixed line. etc. production machine) or a dedicated machine for axillary water absorbent sheets (0ff
In principle, it is possible to spray a constant amount onto the water-absorbing sheet itself by linking the production speed with the change in the internal pressure of the spray (for example, in the case of -11no). .

However, a certain amount of water-absorbing sea) K which is subject to water spraying
When spraying water, the main machine (processing machine 4 or special machine)
When controlling the amount of water sprayed at a constant level by linking the production speed with the internal pressure of the sprayer, when the mother machine becomes faster, that is, the internal pressure of the sprayer increases, and the amount of sprayed water spreads. Yes, water will be scattered around.

Therefore, in order to deal with the nuclear problem, it is possible to control the amount of spray by adjusting the height of the spray, but this requires a large-scale equipment. In addition, spraying does not spray water in the form of a mist, and does not allow water droplets to scatter around the area.Even if a cover is installed to prevent scattering, it may cause water droplets to aggregate, and mechanical measures are required. be. If the parent unit suddenly stops due to some kind of accident, the system spray I will be activated due to the residual pressure in the sprayer.
The water droplets remaining in IcW4 drip off, and the amount of water sprayed onto the water absorbent sheet increases by a predetermined amount. Because of the controllability of the water spray amount itself, a dryer is required after water is sprayed on the water absorbent sheet, which poses problems in terms of equipment and economic efficiency.

The present inventors have conducted various studies based on the above-mentioned problems, and have found that in order to accurately spray water over the width of the predetermined water-absorbent sheet and stably fix the polymer absorbent within the predetermined water-absorbent sheet, The present invention has completed an extremely economical water sprinkling method that can spray the minimum amount of effective water with high accuracy and does not require the introduction of a dryer into the cough processing process when processing the water-absorbent sheet. reached.

That is, in the present invention, a water-absorbing polymer substance is sandwiched between a flexible first sheet and a flexible and water-permeable second sheet, and water is added in a columnar flow state. A water-absorbent sheet is prepared by spraying a Kll water-based polymer material on a flexible first sheet and covering it with a flexible and water-permeable second sheet. The present invention provides a method for producing a water-absorbing sheet, characterized in that water is added in a columnar flow state from a nozzle.

Hereinafter, the present invention will be explained in more detail with reference to the drawings. Figs. 1 and 2 show examples of nozzles used in the present invention. FIG. 1 is a cross-sectional view of the needle-shaped nozzle 1, and FIG. 2 is a cross-sectional view of the disk-shaped nozzle 4. Here, 2 is a water inlet, and 5 is a water outlet. A nozzle capable of spraying water in such a columnar flow is attached to a nozzle head 5 shown in FIG. 5. here 6
7 is a packing, and 7 is a nozzle mounting part. Figure 4 shows the disk-shaped nozzle 4 attached to the nozzle head 5.
8 is a strainer. The state of water spraying by the nozzle head 5 equipped with the cough nozzle 4 is as shown in FIG.

According to the nuclear force formula, water is distributed in a columnar flow 10 from the orifice-like structure of the nozzle as shown in Figure 1 or Figure 2, and water scattering in the form of a mist seen in spraying is a problem. do not become. Furthermore, the amount of spraying is fixed across the width of the nozzle head 5, and even if the internal pressure within the nozzle head 5 changes, there is no variation as seen in sprays. Therefore, if the width of the nozzle head is made the same as the width of the absorbent body to be sprayed, uniform spraying on the absorbent body will be achieved.

On the other hand, when spraying with a mosquito nozzle, the trajectory of water sprayed onto the absorbent body becomes a linear trajectory at the moment of spraying, but water spreads on the surface layer of the absorbent body, and as a result, water is sprayed uniformly. situation,
That is, the state is the trajectory 12 toward the water absorbent sheet 11 shown in FIG.

The height of the absorber to be sprayed from the nozzle head 5 is set at 5 m/cm in order to obtain a stable columnar flow of water through the nozzle.
m ~ 300 m/m is preferable 〇 Furthermore, the water delivery method accompanying the spraying is a pressurized method from the viewpoint of controllability that controls the amount of water sprayed according to the application speed of the mother machine. Alternatively, a metering pump system such as a gear pump is preferable.

The pressurization method takes the signal of the motor rotation speed, that is, the motor rotation speed of the mother machine, converts this electrical signal into air pressure, and sends pressurized air according to the rotation speed to a pressurization tank containing water. The water according to the water injection pipe 9 is fed into the nozzle head 5 equipped with a nozzle as shown in Fig. 1 or Fig. It becomes dispersion. Also, in the metering pump system, the rotational speed of the metering pump is linked to the rotational speed of the mother machine, and as a result, the water pumped out from the water storage tank by the metering pump is pumped through the water injection pipe 9 as shown in FIG.
Nozzle head 5 equipped with one nozzle as shown in Fig. 2
The amount of water is sprayed according to the speed of the mother machine. Figure 6 shows the correlation between the air pressure, that is, the discharge pressure, and the amount of water discharged when water is supplied using the pressurized method.
- For example, diameter 120μφ, N@e+11e length 27 m
The needle-shaped nozzle 1 shown in FIG. 1 with a width of 60 m/ms
This is the case when the nozzle head 5 shown in FIG. 5, which has a length of 115 $m and a thickness of s o m/m, is attached to send water. Figure 7 shows a metering pump system with a diameter of 80 μφ and a thickness of O,!
In/m, the plate nozzle 4 shown in FIG. 2 has a width of 60 m/!
! 1% length 115m1! E1. The third layer has a thickness of 50m/m.
This figure illustrates the correlation between the motor rotation speed and the amount of water discharged when 12 nozzles are attached to the nozzle head 5 shown in the figure to send water.

In both cases, there is a linear correlation between the amount of water discharged and the speed with the mother machine, and it can be seen that the controllability of the amount of water discharged is excellent.

On the other hand, in order to stably fix the cough polymer absorbent in the water absorbent sheet without falling off and to obtain a flexible sheet, the conditions for the amount of water sprayed are such that the polymer absorbent is slightly swollen and mosquito The minimum amount of water sprayed (Twin) for joining the upper and lower sheets with a polymer absorbent interposed in the state,
Furthermore, when the cough polymer absorbent absorbs water and dies, it retains the water within the cough polymer structure, which is a characteristic of mosquito polymers, and after absorbing water, it is necessary to do so within the limit (Wmax) that does not release water even when pressurized. There is. The characteristics of the absorbent, which is generally referred to as a polymer absorbent, is that it exhibits stable swelling behavior in the presence of a small amount of water, and exhibits wet swelling behavior in a saturated state of absorption of several tens of times its own weight.

In addition, in the structure of the cough water absorbent sheet, if water is sprayed below the saturated absorption capacity of the wrinkled polymer absorbent, the absorbing power of the polymer absorbent will actively absorb the water present in the absorbent paper, etc. , the entire water-absorbing sheet shows almost no moisture, exhibiting the characteristic of being in a dry state.

Utilizing these characteristics mentioned above, in the iron water absorbent sheet containing the armpit polymer absorbent, the twin and Wmax of the water spray amount can be adjusted.
The limit is 10 to 70 seconds (for the polymer absorbent sprayer). That is, in terms of performance, the water-absorbent sheet containing a chain polymer absorbent according to the present invention can be made stable and flexible without shedding of the polymer absorbent, and at the same time, the water-absorbent sheet can be made flexible. A highly economical processing technique that does not involve the introduction of a dryer in the processing process requires a controlled water distribution method that matches the water behavior of the polymeric absorbent. In an iron water-absorbing sheet where one side is at least hydrophilic, the amount of water sprayed from the hydrophilic sheet side slightly swells the polymeric absorbent contained in the water-absorbing sheet and causes the tI temperature to rise. The upper and lower layers that make up the axillary water-absorbent sheet are bonded together at the appropriate time to form a stable water-absorbent sheet, and as the water absorption of the polymer absorbent progresses, the water-absorbent properties The sheet can be formed in a state where it can hardly be wetted.

In the shape of the nozzle capable of water column spraying as shown in FIGS. 1 and 2, the size of the discharge port 3 and the needle length in FIG. 1 depend on the amount of water sprayed. As shown in the figure,
There is a correlation between the nozzle diameter and the amount of water discharged through the nozzle diameter using the nozzle head pressure as a parameter. Here 1
is when the head pressure is 0.2%/Om2, and b is when the head pressure is 0.2%/Om2.・For 410n”, C is head pressure 2, OI
Therefore, there is no need to limit the required water spray amount by the nozzle diameter or needle length, but if the nozzle diameter is 0.05mm to 0.2mm.
Preferably, it is within the range of mm.

The water spraying location is on the processing machine shown in FIG. A permeable or water-impermeable sheet may be used, and the polymeric absorbent may be sprayed onto the sheet after insertion.

The upper layer is a water-permeable sheet, the lower layer is a water-permeable or water-impermeable sheet, and after inserting a cough polymer absorbent between them, press four with a slight press pressure if necessary.
If the water-absorbent sheet is introduced in 01'14, a more stable water-absorbent sheet can be obtained, and the water spraying location may be provided after the pressure roll. Specifically, on the processing machine shown in FIG. 9, water can be sprayed at either 21.22 or 2!5, but preferably 22.25.

l'i! (d) Either a press on the press or an embossing roll may be used.

Hereinafter, the present invention will be explained in more detail with reference to Examples.

Example 1 A nozzle having the shape shown in FIG. 2 with a diameter of 70 μm and a plate thickness of 100 μm was used to have a width of 70 m/m under the conditions of the mother machine speed and water spray amount as indicated by the straight line d in FIG. 10.

110 nozzles were attached to the nozzle head shown in Fig. 5 with a length of b o m/m and a thickness of 50 m/II, and were heated using a pressurizing method.
Y pressure 0, 2 b/am” O'Jk condition, I
Attached S 1t/Wl” % crepe rate 40%, width 70
After spraying polyacrylic acid-based polymer absorbent (4 Wonder Zeel'' made by Chemical Soap Co., Ltd.) on a water-permeable sheet of m/m in 17 furnace/-S-, the same water-permeable sheet was put together and processed. Water was sprayed on the sheet after introduction between press rollers with a pressure of 1 KI/Cml 1. The results are shown in Table 1 with AIK.
An extremely stable water-absorbing sheet which is flexible and does not have the polymer absorbent falling off is obtained. The amount of water sprayed under the improved processing conditions was 14% by weight per scissors polymer absorbent, and the water spraying situation was as follows:
It was a stable columnar flow and there was no water scattering around it.Example-2 Under the conditions of the mother machine speed and the water spray amount as shown in the straight line f in Fig. 10, that is, the diameter of 140μ as shown in Fig. 1, 18 nozzles with a needle length of 27 m/m as shown in Figure 5, medium 200 Vm, length 60
When attached to a nozzle head with a thickness of m/m and a head pressure of 1.6 m/m using a pressurizing method, the crepe rate StS is 200 m/m. After uniformly spraying acrylic acid and starch copolymer-based polymer absorbent (Sunwet, manufactured by Sanyo Kaisha, Ltd.) at 26 f/IEI onto a water-resistant sheet, the same water-permeable sheet as used in Example 1 was applied. Water was sprinkled on top of the mixture, and then introduced into a pressure roller having an upper embossing throw of 2-/- with a pressure of 1-/-.

The result is 1! A flexible and extremely stable water-absorbing sheet with no polymer shedding was obtained as shown in No. 42 of -1. Same tX
The amount of water sprayed under the conditions is 481g of cough polymer absorbent (F)
The water spraying situation was a stable columnar flow with no water splashing around. Example 5 Under the conditions of the mother machine speed and the water spray amount as shown in the straight line in Figure 10, That is, 12 nozzles having a diameter of 80 μm and a thickness of 100 μm and having the shape shown in FIG. 2 were used with a width of 70 m/m.

It was attached to the nozzle head shown in Fig. 3 with a length of 60 t/ms and a thickness of 50 t/m, and under the conditions of water supply using a metering pump method, the fabric weight was 51 t/m'', the crepe rate was 40 inches, and the width was y o.
100 f/m of polyacrylic acid-based polymer absorbent (Wonder Zeel manufactured by Chemical Soap) on a water-permeable sheet of m/m.
After spraying on step 8, put the same water permeable sheet above together and pressurize 1.
p after introduction between 1Ey/all” press rollers
) was sprayed with water.

As a result, a flexible and extremely stable water-absorbing sheet F without the polymer absorbent falling off was obtained as shown in column 5 of Table 1.

The mosquito water spraying conditions are as follows: The metering pump rotation speed is linked to the speed of the base machine, and the water spray amount of 50 oo/ml corresponds to the metering pump rotation speed of 475 orpm.The water spray amount is also per polymer absorbent. 30-, and the water spraying condition was a stable columnar flow with no scattering around the area.

Comparative example 1 (wet method; off -1ine,
Manufacture of water absorbent sheet by spray method) Fabric weight: 31f/
! I2. On a water-permeable sheet with a crepe rate of 40% and a width of 500xy'm, 17 tons/- of a polyacrylic acid-based polymer absorbent ('Wonder Zell' manufactured by Kako Soap) was uniformly sprinkled, and the same water permeability as above was obtained. After putting the sheets together and introducing them between the press rows of 1 and 10, 7Bt was applied with a spray nozzle.
/m", the polymer absorption capacity! After spraying 1001g of water, dry it in a dryer with a temperature of 130℃ and a length of 2ml to obtain a water-absorbent sheet. 90 breast varnish beads are 2Qm
/It was a win. The physical properties of the obtained sheet were evaluated in the same manner as in Example 1, and the results are shown in Table 1.

Comparative Example 2 (Dry method; Manufacture of water absorbent sheet using only press roller K at 1fi-1in@) Area weight s
A polyacrylic acid-based polymer absorbent (
Wonder Zeel 1) made from chemical soap was uniformly spread at 17 f/-, and the same water-permeable sheets described above were put together, one side was heated to 180°C, and pressurized 2. sW4/+- to obtain a water absorbent sheet between pressure rollers. The speed between both breasts was 60 ru/wim. The physical properties of the obtained nine sheets were evaluated in the same manner as in Example 1, and the results are shown in Table 1.

Table-1 Note) Middle 1 Flexibility: Based on the cantilever method.

As shown in FIG.
5 at a constant speed V = S mrs/sea, and the length L at the time of contact with the slope is displayed. The shorter the L value, the more flexible it is.

Here, θ is 45°.

Medium 2: Removal of polymer absorbent; by shaker method.

As shown in FIG. 12, the water absorbent sheet 24 (width 70q/m x length 1yo$m% weight) is attached to the shaker device 26 (cover 28-L1l) as indicated by the arrow 27. The weight W of the water absorbent sheet 24 after being vibrated in the direction S minutes at goo rpm is measured.

Amount of polymer absorbent falling off Wetl-Ws ・Water-absorbent seams with the amount of chain shedding This is used as a guide to the stability of the target.

[Brief explanation of the drawing]

Figure 1 is a sectional view of the needle nozzle, Figure 2 is a sectional view of the plate nozzle, Figure 5 is a perspective view of the nozzle head, and Figure 4 is a sectional view of the plate nozzle attached to the nozzle head. , 5th
The figure is a perspective view showing the water spraying situation according to the method of the present invention, Figure 6 is a correlation diagram between water discharge amount and discharge pressure, Figure 7 is a correlation diagram between water discharge volume and metering pump motor rotation speed, and Figure 8 is a correlation diagram between water discharge amount and metering pump motor rotation speed. The figure shows the correlation between water discharge amount and nozzle diameter using nozzle head pressure as a parameter, Figure 9 shows the locations where water can be sprayed on the processing machine, and Figure 10 shows the correlation between base machine speed and water spray amount. Figure 11 is a schematic front view of the device used for evaluating flexibility.
FIG. 2 is a schematic front view of a nine-shaker device used to evaluate the shedding property of a polymer absorbent. 1... Needle nozzle, 2... Water inlet, 5... Water outlet, 4... Plate nozzle, 5... Nozzle head, 9
...Water injection pipe, 1o...Column flow, 11.Hinaga permeable sheet, I! - Sheet roll, 16... Water-permeable or water-impermeable sheet, 17... Guide roll, 18... Water spray nozzle head, 19... Polymer absorbent sprayer, 20... Press roll, 21, 22.
23...Place where water can be sprayed Applicant's agent Kaoru Furuya 10th
Figure 0 20 40 60
80 Mother machine speed (m/mtn) Figure 11 4

Claims (1)

[Claims] 1. A water-absorbing polymer material is sandwiched between a flexible first sheet and a flexible and water-permeable second sheet,
A water absorbent sheet made by adding water in a columnar flow state. 2. The water absorbent sheet according to claim 1, wherein water is added from the surface of a 1L2 sheet. 5 Claim 1 in which the first sheet is water permeable
Water-absorbing sheet described in Section 0 4 A water-absorbing polymer material is sprinkled on a flexible first sheet, and then covered with a flexible and water-permeable second sheet to absorb water. A method for producing a water absorbent sheet, which comprises adding water in a columnar flow from a nozzle when producing the sheet. 5. The manufacturing method according to claim 4, wherein water is added from the surface of the second sheet. 6. The manufacturing method according to claim 4, wherein water is added in an amount of 10 to 70 times the weight of the water-absorbing polymeric material. 7. The manufacturing method according to claim 4, wherein the nozzle has a diameter of 0, osmm to 0.2.