JP3297192B2 - Method for transporting and drying hydrated gel polymer and conveyor-type drying apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for transporting and drying a hydrogel polymer and a conveyor type drying apparatus. The method for transporting and drying the hydrogel polymer and the conveyor-type drying apparatus can be suitably used when transporting or drying the hydrogel polymer that is a precursor of the water-absorbing resin.

[0002]

2. Description of the Related Art Water-absorbent resins include absorbent materials, sanitary materials (paper diapers, sanitary napkins, sanitary cotton, bandages, incontinence pads, paper towels, etc.), freshness preserving agents, absorbents for water leakage from foods, and the like. It is widely used in many fields.

As a method for producing this water-absorbing resin, for example, a method is known in which a monomer such as acrylic acid or sodium acrylate is polymerized in an aqueous solution together with a crosslinking agent to form a hydrogel polymer, dried, and pulverized to an appropriate particle size. Are known. This type of manufacturing method is generally desirable in that it does not handle organic solvents that are toxic and hazardous to disaster prevention for workers.
As a method for drying the hydrogel polymer, as shown in FIG. 3, a gel is placed on a parallel two-axis drum dryer, and heated while compressing the gel between rotating drums to stretch the thin film. Method (Japanese Unexamined Patent Publication (Kokai) No. 1-163615), a circulating drying method or a tray drying method in which gels are laminated on shelves in a drying chamber, hot air is circulated, and drying is performed for each batch. The gel is sent from the top of the machine, hot air is blown from below, and the gel is cut along the spiral inner wall and dried while falling down. A conveyor-type drying method is known in which hot air is blown onto a gel through holes in a tray and dried during transportation.

In the thin film drying method, since the gel is continuously formed into a thin film between the drums, it is possible to dry the hydrogel polymer in a short time. In the case of a gel or a high-strength gel, since uniform stretching is difficult, drying unevenness may occur between the inside and the surface of the gel.

[0005] The circulating drying method or the tray drying method only circulates hot air by placing a gel on a shelf in a fixed position.
The air can pass only from either the upper part or the lower part of the gel. Therefore, it takes a long time to completely dry the inside of the gel. When the drying time is prolonged, it is necessary to increase the input amount of one batch as much as possible in mass production. In addition, the dryer is large and inefficient, and the polymer is deteriorated by cutting, thermal crosslinking, oxidation and the like. Such deterioration of the polymer lowers the commercial value of the water absorbent resin. For example, this is because excessive water-induced crosslinking lowers the water absorption performance, or the polymer is cut to increase the amount of water-soluble components, resulting in stickiness during water absorption.

Further, the hydrogel polymer is not easily cut because of its high adhesiveness and toughness. Therefore, in the case of the spin-drying method, the gel is integrated during the spinning and the specific surface area is reduced. As a result, a long time is required for the drying, and the polymer is deteriorated in the same manner as described above.

[0007] In this regard, the conveyor drying method differs from the thin film drying method in that it does not depend on the elasticity or strength of the gel, and unlike the circulation drying method, it can continuously charge the gel. Are not integrated. In addition, only the conveyor-type drying method can continuously perform other steps such as spraying a medicine before and after the drying operation during transportation. Therefore, it is excellent as a method for drying a hydrogel polymer.

[0008]

In a conveyor type drying apparatus, it is necessary to spread the gel uniformly on the conveyor, which is a necessary condition for efficient drying in a short time. Regardless of whether or not the medicine is dried, for example, even if the medicine is sprayed during transportation, if the gel is not spread evenly, the medicine concentration in the gel becomes non-uniform and the product performance varies. . For this reason, conventionally, a belt conveyor that swings in a pendulum type is provided on a starting point of the conveyor, and the gel is shaken down onto the conveyor by the pendulum type belt conveyor.

However, in such a sorting method, it is easy to spread the non-adhesive substance evenly, but in the case of a gel polymer having strong adhesiveness, the gel is formed into a dumpling or a drop when the gel is supplied or dropped. It was mountain-like and difficult to distribute uniformly. Therefore, in the drying operation, hot air mainly passes through the gap between the gel and the tray or a thin portion of the gel, and the drying time is prolonged or drying unevenness occurs. Also, in the drug spraying operation, the drug is sprayed even on the portion where the gel is not spread, thereby wasting the drug, and the drug does not sufficiently penetrate into the gel inside the portion in the shape of a dumpling or a mountain. I did.

An object of the present invention is to solve the above-mentioned problems in the method of transporting or drying a hydrogel polymer using a conveyor, and to spread the gel uniformly on the conveyor in the initial stage of transportation.
An object of the present invention is to provide a conveying method, a drying method, and a conveyor-type drying apparatus that can efficiently perform post-processes such as drying.

[0011]

In order to achieve the object, a method for transporting a hydrogel polymer according to the present invention is a method for transporting a hydrogel polymer placed on a conveyor.
A plurality of pins protrude on the peripheral surface, and a roll whose rotation axis is orthogonal to the conveying direction of the conveyor is arranged on the conveying start point of the conveyor,
The hydrogel polymer is placed in front of the roll while the conveyor is operated and the roll is rotated, and is passed between the roll and the conveyor in the initial stage of transport.

In this method, it is preferable that the conveyor and the roll are operated so that V−v becomes a positive value, where V is the conveying speed of the conveyor, and v is the peripheral speed of the pin tip when the conveyor is closest to the conveyor. And rotating.

The method for drying a hydrogel polymer according to the present invention is a method for drying a hydrogel polymer while placing and transporting the hydrogel polymer on a conveyor. A roll with a rotating shaft perpendicular to the conveyor conveyance direction is placed on the conveyor start point, the conveyor is operated, and the roll is rotated, and the hydrogel polymer is placed in front of the roll and conveyed. It is characterized in that it is dried after passing between a roll and a conveyor at an early stage.

[0014] A conveyor-type drying apparatus suitable for this drying method is a drying apparatus including a conveyor for transporting an object to be dried and a heat source for heating the object to be dried during transportation. A roll whose rotation axis is orthogonal to the conveying direction of the conveyor is provided on the conveying start point of the conveyor.

Here, the system for driving the conveyor may be any of a chain drive, a belt drive and a roller drive. As means for heating the hydrogel polymer with a heat source,
Hot air may be transmitted from a heat source as in a conventional conveyor-type drying apparatus, but the present invention is not limited to this, and radiant heat from an infrared heater may be used. It is preferable that the roll body and the pin are themselves non-adhesive resin (for example, fluororesin) or coated with a non-adhesive resin in order to prevent the gel from adhering.

[0016]

When the conveyor is operated and the roll is rotated and the hydrogel polymer is placed in front of the roll, the gel passes under the roll immediately after the start of transport. Then, at the time of passing, the pin provided on the roll cuts the gel, and at the same time, the peripheral surface of the roll is combined with the tray of the conveyor to hold down the gel and level the gel. Therefore, the thickness of the gel passing under the roll becomes uniform. Therefore, when a drying operation is performed in the subsequent transport process, heat is uniformly applied to the gel regardless of whether it is hot air or radiation. Also, when spraying a drug,
The drug falls uniformly on the gel.

The roll may be rotated in either clockwise or counterclockwise direction. However, the above-mentioned condition is desirable for the difference between the conveyor speed and the peripheral speed of the pin end of the roll. That is, when the circulating conveyor is fed in the positive direction of the velocity vector and returned in the negative direction, the velocity V
This is because if the conveyor and the roll are operated and rotated so that −v becomes a positive value, the gel that has passed through the roll is transported without accumulation. For example, when the conveyor is circulated clockwise and the roll is also rotated clockwise, V-v is always a positive value because v is a negative value with respect to a positive value of V.
On the other hand, when only the roll is rotated counterclockwise, V-v becomes a positive value by increasing the conveying speed of the conveyor more than the peripheral speed of the tip of the pin. The thickness of the gel after passing through the roll can be adjusted by the conveyor speed, the peripheral speed of the tip of the pin, the interval between the roll and the tray, and the height of the pin.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a drying method and a conveyor-type drying apparatus according to the present invention will be described with reference to the drawings. FIG. 1 is a perspective view showing a main part of a conveyor-type drying apparatus used in the drying method of this embodiment, and FIG. 2 is a cross-sectional view taken along a line XY of FIG. Although FIG. 2 shows a gel, it is omitted in FIG.

The conveyor type drying apparatus 1 includes a tray 2 with holes.
1 in a conveying direction, a roll 3 provided with a rotating shaft 31 on the conveyor starting point so as to be orthogonal to the conveying direction of the conveyor 2, and a heater as a heat source for heating the surrounding gas (Not shown) and a blower (not shown) are provided in a tunnel (not shown), and air (hot air) heated by a heater is supplied to the tray 2 by the blower.
1 is sent.

A sealing material that slides on the side surface of the tray 21 is provided in a strip shape on the wall of the tunnel. The gap between the tray 21 and the tunnel wall is kept airtight, and hot air does not pass through the gap. (For convenience of illustration, the holes 22 are arranged in five rows and one row in one tray, but it is desirable that a plurality of holes 22 having a smaller diameter are arrayed vertically and horizontally.)
Is passed preferentially. Roll 3
Pins 32 projecting in a cross-shaped cross section around the rotation shaft 31 are arranged on the peripheral surface in the rotation axis direction. The peripheral surface of the roll 3 and the surface of the pin 32 are coated with a fluororesin. The pins 32 do not necessarily have to be arranged on the same peripheral surface of the roll 3, and the number of pins 32 may be larger. Next, a situation in which the gel is dried using the conveyor-type drying apparatus of this embodiment will be described.

First, the conveyor 2 is driven counterclockwise toward FIG. 2, the tray 21 is circulated, the power of the heater is turned on, and the blower is rotated. The roll 3 is also rotated counterclockwise. Then, at the position immediately before the roll 3, the hydrogel G is loaded on the empty tray 21 which has returned after finishing the transport of the dried gel. Then, the gel G placed on the tray 21 passes below the roll 3.
At the time of passing, the pin 32 provided on the roll 3 cuts the gel G, and at the same time, the peripheral surface of the roll 3 is
Of the gel G in combination with the tray 21 of FIG.
Therefore, the thickness d of the gel G passing under the roll 3 becomes uniform.

Subsequently, hot air is sent to the gel G from above the tray 21. When the hot air permeates the gel G, the gel G is heated to evaporate the water in the gel G and pass through the holes 22 to dry the gel G. Since the thickness of the gel G is uniform as described above, the drying speed of each part of the gel is also uniform. Therefore, if the temperature and the speed of the hot air are appropriately set, no undried portion remains in the gel, and no deterioration portion of the polymer occurs due to overheating.

In order to confirm the effect of this example, the hydrogel polymer was actually transported and dried in the following manner. First, the roll 3 in which a pin 32 having a length of 20 cm protrudes from a peripheral surface having a radius of 15 cm, and the axial center of the roll 3 is positioned 37 mm from the surface of the tray 21.
cm, and was rotated in the direction of the arrow in FIG. 2 (counterclockwise) so that the peripheral speed at the tip of the pin 32 was 1300 m / hour. Acrylic acid was graft-polymerized to the starch and then neutralized with an aqueous sodium hydroxide solution to obtain a gel polymer having a water content of 70%.
The transfer was started at a rate of 30 kg per 1 m ^{2 of the} area of one tray on the conveyor 2 driven at 0 m / hour (the direction from right to left in FIG. 2 is the positive value of the velocity vector).

When the gel thickness d immediately after passing under the roll 3 was measured at three arbitrary positions, 9.8 c
m, 10.1 cm and 10.5 cm. Subsequently, hot air at a temperature of 150 ° C. and a wind speed of 2 m / sec was sent from above the tray 21 to the gel G, and was passed through the gel G and the holes 22 to dry the gel G. When the water content of the gel G after the transportation was measured at three arbitrary points, 4.6% and 4.8 were measured.
%, 4.9%. The transfer time was about 30 minutes. Thus, according to the method of this example, the gel can be spread all over the conveyor. In addition, it is possible to dry uniformly uniformly in a short time thereafter.

For comparison, a conventional pendulum-type belt conveyor was provided in place of the roll 3, and the gel was transported under the same conditions as in this example. The belt conveyor made 10 reciprocations per minute. Then, the thickness d of the gel immediately after sorting by the belt conveyor was measured at any three places, and it was 8.4 cm, 10.2 cm, and 13.1 cm. Further, when the water content of the gel G after the conveyance was measured at three arbitrary points, it was 2.7%, 5.6%, and 8.8%, and there was considerable variation.

[0026]

As described above, according to the conveying method, the drying method and the conveyor-type drying apparatus of the present invention, the hydrogel polymer can be uniformly spread on the conveyor, and the drying operation can be performed in a short time. And can be dried efficiently and uniformly.

[Brief description of the drawings]

FIG. 1 is a perspective view illustrating a main part of a conveyor type drying apparatus used in a conveying method and a drying method according to an embodiment.

FIG. 2 is a cross-sectional view taken along a line XY of FIG.

FIG. 3 is a diagram illustrating a conventional thin film drying method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Conveyor type drying device 2 ... Conveyor 21 ... Tray 22 ... Hole 3 ... Roll 31 ... Rotation axis 32 ... Pin G ... Gel

────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Kenji Tanaka 11 Sanyo Kasei Kogyo Co., Ltd., 11-11 Hitotsubashi-Honcho, Higashiyama-ku, Kyoto (56) References JP-A-60-210961 (JP, A) Akira Tokubo 31-5120 (JP, B1) Jiko 11-2950 (JP, Y1) (58) Fields investigated (Int. Cl. ⁷ , DB name) F26B 17/02 F26B 23/04

Claims (7)

(57) [Claims] 1. A method for transporting a hydrogel polymer by placing the hydrogel polymer on a conveyor, comprising disposing a roll having a plurality of pins projecting from a peripheral surface and a rotation axis orthogonal to the transport direction of the conveyor at a transport start point of the conveyor. Transporting the hydrogel polymer, wherein the conveyor is operated and the rolls are rotated, the hydrogel polymer is placed in front of the rolls, and is passed between the rolls and the conveyor in the initial stage of conveyance. Method. 2. When the conveying speed of the conveyor is V, and the peripheral speed of the pin tip when the conveyor is closest to the conveyor is v, V-
The method for conveying a hydrogel polymer according to claim 1, wherein the conveyor and the roll are operated and rotated so that v becomes a positive value. 3. A method for drying a hydrogel polymer while placing and transporting the hydrogel polymer on a conveyor, wherein a plurality of pins protrude from a peripheral surface and a rotation axis is orthogonal to a conveyance direction of the conveyor. Deploy the roll on the conveyor start point, operate the conveyor, and rotate the roll,
A method for drying a hydrogel polymer, comprising placing a hydrogel polymer in front of a roll, passing the roll between a roll and a conveyor at an early stage of transport, and then drying. 4. In a drying apparatus provided with a conveyor for transporting a material to be dried and a heat source for heating the material to be dried during the transportation, a plurality of pins project from a peripheral surface, and a rotation axis is orthogonal to a transport direction of the conveyor. A conveyor-type drying device, wherein a roll to be rolled is disposed on a conveyor start point. 5. The roll body and the pin are non-adhesive.
Resin or coated with non-stick resin
The transport method according to claim 1. 6. The roll body and the pin are non-adhesive.
Resin or coated with non-stick resin
The drying method according to claim 3. 7. The roll body and the pin are non-adhesive.
Resin or coated with non-stick resin
The drying device according to claim 4.