KR101778826B1 - Dry cellulose gel and process for producing same - Google Patents

Abstract

A step of adding 15 to 25 wt% of a cellulose powder while spraying mist water in a water kneading machine and kneading the water and the cellulose powder under vacuum to obtain a cellulose kneaded product; To obtain a crosslinked cellulose gel; and drying the crosslinked cellulose gel to obtain a dry cellulose gel.

Description

[0001] DRY CELLULOSE GEL AND PROCESS FOR PRODUCING SAME [0002]

The present invention relates to a dry cellulosic gel, and more particularly to a dry cellulosic gel having excellent water absorbency and a method for producing the same.

A method of producing a self-crosslinking alkyl cellulose derivative using irradiation of radiation has been proposed (Patent Documents 1 and 2).

In the method described in Patent Document 1, a mixture containing 5 to 2,000 parts by weight of water relative to 100 parts by weight of an alkyl cellulose derivative is irradiated with γ-ray radiation of 0.1 kGy and dried. In the case of the alkyl cellulose derivative alone, a hydroxy radical is generated in the presence of water to cause self-crosslinking reaction although it is decomposed by irradiation.

In the method described in Patent Document 2, as a modification of the method described in Patent Document 1 by the present inventors, in order to solve the complicated process of the drying step to the molding step after self-crosslinking by irradiation, the gel after irradiation with radiation is granulated Then, a method of drying is proposed. In the method described in Patent Document 2, the cellulose powder and water are kneaded with extruder, and then cross-linked by irradiating? -Ray, X-ray or electron beam from cobalt 60, in particular, into cellulose gel, . However, as a result of repeating the experiments by the present inventors, it has been found that the absorption rate of the obtained cellulose gel is not uniform and can not be mass-produced.

Japanese Laid-Open Patent Publication No. 2001-2703 Japanese Laid-Open Patent Publication No. 2009-179706

There is a problem that the dry cellulose gel obtained by the methods described in Patent Documents 1 and 2 has a low absorption power and a variation in absorption power and can not be mass-produced. Therefore, an object of the present invention is to provide a dry cellulose gel having excellent water absorbability and a production method for mass-producing the dried cellulose gel.

DISCLOSURE OF THE INVENTION The inventors of the present invention have made intensive studies for solving the problems, and as a result, they found that the cause of the decrease in water absorbability and the deviation is the nonuniformity of the alkyl cellulose derivative-water mixture and the presence of bubbles upon irradiation with radiation.

That is, according to the present invention, 15 to 25 wt% of a cellulose powder is added to a water kneading machine while spraying mist water, and then water and a cellulose powder are kneaded under vacuum to obtain a paste-like cellulose kneaded product A step of irradiating the cellulose kneaded product with electron beams to obtain a crosslinked cellulose gel, and a step of drying the crosslinked cellulose gel to obtain a dry cellulose gel.

In the present invention, by performing kneading of water and cellulose powder under vacuum, bubbles can be discharged out of the kneaded paste-like cellulose-based kneaded product, and unevenness in degree of crosslinking resulting from the presence of bubbles upon irradiation of electron beams can be eliminated have.

When water is firstly introduced into the kneader and cellulose powder is introduced, the cellulose powder is scattered so that not only a predetermined amount of cellulose powder can be introduced, but also the cellulose powder is vacuum-sucked when kneaded under vacuum. In order to enable kneading under vacuum, it is possible to spray water in the form of mist over the cellulose powder at the time of introducing the cellulose powder into the kneader, to prevent the cellulose powder from scattering, and to prevent the wettability of the water and the cellulose powder Can be improved.

The powdered cellulose is preferably a carboxyalkylcellulose, particularly preferably sodium carboxymethylcellulose.

Further, since the carboxyalkyl cellulose reacts with chlorine, the water to be directly introduced into the kneader and the water to be sprayed are preferably water not containing chlorine or alcohol, and more preferably water having been desalted or deaerated.

Water and powdered cellulose for vacuum kneading are adjusted so that the content of powdered cellulose is 15 to 25 wt%. If the content of the powdered cellulose is excessively large, the crosslinking reaction by the electron beam irradiation does not proceed, and the decomposition reaction of the cellulose takes precedence. On the other hand, if the content of the powdered cellulose is too small, a large amount of electron beam irradiation is required to cause a crosslinking reaction by electron beam irradiation, and the cost becomes high.

In the present invention, by using an electron beam in the cellulose kneaded product, crosslinking can be performed by irradiation for a very short time. The dose of the electron beam differs depending on the content of the powdered cellulose, and it is preferably 9 to 16 kGy in the range of 15 to 25 wt% of the powdered cellulose. If the amount of electron beam irradiation is large, the net of the crosslinked structure becomes small, and if the amount of electron beam irradiation is small, the net of the crosslinked structure becomes large. Within this range, the absorption rate of the dry cellulose gel can be increased.

The production method of the present invention preferably further comprises a step of molding the cellulose kneaded product under vacuum. By forming under vacuum, it is possible to avoid the occurrence of extra bubbles in the cellulose kneaded product containing water.

According to the production method of the present invention, a dry cellulose gel having an absorption capacity of 150 or more, which is obtained by dividing the gel absorbed for 24 hours by the initial weight before absorption, is obtained.

According to the present invention, there is provided an apparatus for producing a dry cellulosic gel of the present invention, comprising: a kneading kiln provided with a stirring blade; a water pipe formed along the inner periphery; A vacuum chucking device having a vacuum suction unit; An electron beam irradiating device including an electron beam irradiating section and an electron beam source; a belt conveyor for conveying the cellulose kneaded material taken out from the vacuum kneading apparatus; And a drying device having a breathable belt conveyor for conveying the cellulose gel taken out from the electron beam irradiating device and a circulating fan for blowing hot air from above the belt conveyor.

By using the production method of the present invention and the production apparatus for carrying out the production method, it is possible to suppress the variation of the water absorption rate and mass-produce the dry cellulose gel having excellent water absorbability.

1 is a schematic flow chart showing a manufacturing process of the present invention.
Fig. 2 is an explanatory view schematically showing the entire manufacturing apparatus used in the present invention. Fig.
Fig. 3 (A) is a schematic front view showing a vacuum kneading apparatus used in the present invention, Fig. 3 (B) is a schematic side view thereof, and Fig. 3 (C) is a sectional view taken along line A of Fig.
4A is a schematic cross-sectional view showing an electron beam irradiating apparatus used in the present invention.
4B is a schematic plan view thereof.
5 is a schematic sectional view showing an extrusion apparatus used in the present invention.
6 is a schematic sectional view showing a drying apparatus used in the present invention.
7A is a bar graph showing the measurement results of the absorption magnification according to the first embodiment.
7B is a bar graph showing measurement results of the absorption magnification according to the first embodiment.
7C is a bar graph showing measurement results of the absorption magnification according to the first embodiment.

The manufacturing method and apparatus of the present invention will be described with reference to the drawings.

First, the manufacturing apparatus of the present invention will be described with reference to Figs. 2 to 5. Fig.

2, the manufacturing apparatus of the present invention includes a vacuum kneading apparatus 10, an electron beam irradiating apparatus 100, and a drying apparatus 200. [

3, the vacuum kneading apparatus 10 includes a kneading kiln 20, a lid 30, a lifting cylinder 40 for lifting the lid 30, a hydraulic / vacuum unit 50, , And a kneading motor (60). The lid 30 is provided with a stirring blade 31, a raw material inlet port 32, a water pipe 34 formed in the inner portion of the lid above the raw material inlet port 32, And a water spraying portion 33 formed on the water spray portion 33. In use, the lid 30 is lowered to the position of the kneading kiln 20 by the lifting cylinder 40. The lid 30 and the kneading kiln 20 are sealed together and then the inside of the kneading kiln 20 is vacuumed by the hydraulic and vacuum unit 50 and the stirring wing 31 is rotated by the kneading motor 60, .

4, the electron beam irradiating apparatus 100 includes a belt conveyor 110 for conveying the cellulose kneaded product prepared by the vacuum kneading apparatus 10, an electron beam irradiating unit 120 for irradiating the cellulose kneaded product with electron beams, , And an electron beam source (130). The electron beam irradiating unit 120 and the electron beam source 130 are accommodated in a shielding enclosure 140 for preventing the electron beam from leaking to the outside. Inside the shielding enclosure 140, a belt conveyor 110 is disposed so as to have a length sufficient to impart a desired electron beam irradiation amount. For example, the belt conveyor 110 may be a straight path, a curved path, a U-turn path, or a plurality of solid paths.

The manufacturing apparatus of the present invention may be provided with an extrusion apparatus 150 for molding the crosslinked crosslinked cellulose gel in the electron beam irradiating apparatus 100 into a shape easy to dry processing. 5, the extruding apparatus 150 includes a hopper 152 for housing a crosslinked cellulose gel, a slicer 154 formed under the hopper 152 for cutting the crosslinked cellulose gel, An extruding portion 156 for extruding the cellulose gel into a spherical shape, and an outlet 158. The extruded portion 156 includes a cylindrical main body 156a and an extrusion screw 156b rotatably formed inside the cylindrical main body. In the discharge port 158, a plate-like member 158a having a circular hole for extruding the crosslinked cellulose gel into a spherical shape is formed. The feed pitch P1 in the front half of the extruding screw 156b is about half the feed pitch P2 in the back half, so that the extrusion pressure at the tip end side is increased. A space portion 156d in the shape of a skirt is formed between the tip end of the screw 156b and the die die 156c. A plurality of molding holes 156e for granulation are formed in the die mold 156c. Each of the molding holes 156e is formed in the thickness direction of the molding hole 156e from the rear surface of the screw 156b side The intermediate position is a tapered hole tapered slightly toward the front. A straight hole having a constant diameter from the intermediate position to the front surface of the dies 156c is formed. The diameter of the molding hole 156e differs depending on the use of the drying gel, and the die 156c having a desired diameter is replaceably mounted on the extruding device.

6, the drying apparatus 200 includes an air-permeable belt conveyor 210 for receiving and conveying the crosslinked cellulose gel molded in the granular form in the extrusion apparatus 150, and a ventilating belt conveyor 210 for blowing hot air from above the belt conveyor 210. [ , An exhaust duct (230), and an outlet (240) for taking out the dried crosslinked cellulose gel. The air-permeable belt conveyor 210 may be a punching metal or mesh-metal sheet, and may be configured to vent hot air from the circulating fan 220. The exhaust duct 230 is formed above the circulation fan 220 and removes moisture containing moisture removed from the crosslinked cellulose from the drying apparatus 200 when hot air is blown against the crosslinked cellulose gel. It is preferable to form a plurality of circulating fans and individually adjust the temperature depending on the degree of drying of the crosslinked cellulose gel.

Next, the manufacturing process of the present invention will be described with reference to Fig. S1 is a vacuum kneading step of kneading the cellulose powder and water under vacuum, and is preferably carried out in the vacuum kneading apparatus 10 shown in Fig. S2 is an electron beam irradiation process for irradiating the knitted cellulose product with an electron beam, and is preferably performed in the electron beam irradiation device 100 shown in Fig. S3 is a drying step for drying the crosslinked cellulose gel, and is preferably carried out in the drying apparatus 200 shown in Fig.

<S1>

Water is previously introduced into the kneading kiln 20 of the vacuum kneading apparatus 10, and then powdered cellulose is introduced from the raw material input port 32. When introducing the powdered cellulose into the kneading kiln 20, mist water is sprayed from the water spraying portion 33 formed in the lid 30 to suppress scattering of the powdered cellulose and wet the powdered cellulose, And improves the wettability with water in the kneading kiln 20.

After the water and the powdered cellulose are introduced into the kneading kiln 20, the lid 30 is lowered and the inside of the kneading kiln 20 is vacuum-sucked by the hydraulic / vacuum unit 50 and the stirring wing 31 is kneaded And is driven by a motor 60 for driving. The vacuum state in the present invention can be realized by applying a pressure in the range of 500 Pa to 0.13 Pa, more preferably in the range of 130 Pa to 1 Pa by means of a vacuum pump, and the kneading time is preferably 30 to 60 minutes It is 40 to 50 minutes.

Subsequently, the kneaded cellulose compound obtained by vacuum kneading is formed into a size and shape suitable for electron beam irradiation. The molding may be carried out by using a vacuum press machine, a vacuum extruder, or the like, but the kneading kiln 20 in a vacuum state may be pressed to cut the cellulose kneaded material out of the lower extrusion port.

<S2>

The molded cellulose kneaded product is loaded on a belt conveyor 110 and transported into the electron beam irradiating apparatus 100 to be irradiated with an electron beam from the electron beam source 130 in the electron beam irradiating unit 120.

<S3>

The crosslinked cellulose gel obtained by electron beam irradiation is conveyed to the hopper 152 of the extruding apparatus 150 while being stuck in the belt conveyor 110 and is put into the hopper 152. The crosslinked cellulose gel put into the hopper 152 is cut by the slider 154 under the hopper 152 and fed into the extrusion apparatus 150 main body. The crosslinked cellulose gel supplied to the extruding portion 156 of the main body of the extruding device 150 is extruded by the extruding screw 156b toward the discharge port 158, Is extruded from the circular hole of the member 158a, and is discharged in a spherical shape. At this time, the crosslinked cellulose gel is crushed by the rotating screw 156b, and is pushed to the front of the cylindrical main body 156a while being kneaded. Since the feed pitch P1 in the front half of the screw 156b is about half of the feed pitch P2 in the back half, the pressing force against the kneaded product of the crosslinked cellulose gel becomes gradually higher, The cross-linked cellulose gel is extruded from each of the molding holes 156e of the through-hole 156c. At the time of this extrusion, the cross-linked cellulose gel is not continuously elongated in the relation of the moisture content or the viscoelastic strength of the cross-linked cellulose gel, but is short-cut to form a granular gel and extruded.

The spherical crosslinked cellulose gel is received in the breathable belt conveyor 210 of the drying apparatus 200 and conveyed into the drying apparatus 200. The spherical crosslinked cellulose gel is exposed to warm air at a predetermined temperature of 60 to 90 DEG C in each drying chamber in the drying apparatus 200, becomes a dry crosslinked cellulose gel, and is taken out from the outlet 240. At this time, the hot air flows repeatedly from the upper side of the air-permeable belt conveyor 210 downward and from the lower side to the upper side, so that the particulate crosslinked cellulose gel is dried to a residual moisture content of about 10 wt% while moving at low speed.

Example

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples.

[Example 1]

A dry crosslinked cellulose gel was prepared by changing the content of the carboxyalkyl cellulose sodium as the cellulose powder to 15 wt% to 30 wt% and changing the electron beam dose to 7 kGy to 16 kGy using the production apparatus shown in Fig. . That is, 10.5 to 12.75 liters of water were poured into the kneading kiln and 2.25 to 4.5 kg of sodium carboxyalkyl cellulose sodium powder was added while spraying mist water. Then, the lid of the kneading kiln was closed, vacuum suction was performed and vacuum kneading was performed for 40 minutes . Subsequently, the kneaded cellulose compound obtained by vacuum kneading was transferred to an electron beam irradiating device, and irradiated with a predetermined electron beam to be crosslinked to obtain a crosslinked cellulose gel. Subsequently, the crosslinked cellulose gel was transferred to an extruder and formed into a spherical shape, which was then conveyed by a drying device and dried to obtain a dry cellulose gel.

&Lt; Absorption magnification &gt;

For each sample, the absorbed power of the gel absorbed for 24 hours was divided by the initial weight before absorption. Production conditions and measurement results are shown in Table 1. 7 (a) to (c), the relationship between the content of the powdered cellulose in Table 1 and the electron beam irradiation amount was shown as a bar graph for each type of powdered cellulose.

7 shows that the combination of the content of the cellulose powder and the electron beam irradiation amount which is optimal for attaining a high absorption magnification decreases depending on the type of the cellulose powder to be the raw material but decreases as the content of the cellulose powder increases .

In Table 1, &quot; 2200 &quot; represents &quot; Carboxymethylcellulose sodium CMC2200 manufactured by Daicel Fine Chem Co., Ltd. &quot;, &quot; 1350 &quot; represents carboxymethylcellulose sodium CMC1350 manufactured by Daicel Fine Chemicals Co., Carboxymethylcellulose sodium F350HC-4 &quot;

In Table 1, the evaluation item &quot;? &Quot; indicates that it has an absorption magnification of 350 times or more, particularly suitable for applications requiring absorption ability, &quot;? &Quot; has an absorption magnification of 150 to 350 times, , And &quot; DELTA &quot; indicates that it has an absorption magnification of 90 to 150 times.

&Lt; Evaluation of dry gel &gt;

In the material part number 2200, the gel as it is after the irradiation is comparatively firm, but the absorption power as a dry gel is inferior among the three kinds of materials.

In the material part number 1350, the gel as it is after irradiation is soft compared with 2200 times. Among the three kinds of materials, the absorption power of the dried gel tends to vary.

The material part number 350 shows stable high absorption magnification in both the gel and the dry gel as they are after irradiation.

&Lt; Use of dry gel &gt;

The dry gel obtained in the evaluation of "⊚" in Table 1 is particularly useful for applications requiring high liquid absorption performance, for example, paper diapers and sanitary articles, substitutes for soil used for countermeasures against floods, And the like.

The dry gel obtained in the evaluation of &quot; DELTA &quot; in Table 1 has flexibility and strength, and is slow in decomposition, so that it is suitable as a repair material for plants.

<Swelling degree>

Further, 1 g of the dry cellulose gel of the present invention was immersed in 1600 g of well water for 18 hours, and the swellability (= mass after immersion / mass before immersion) was calculated by measuring the mass before and after swelling. The measurement results of the representative examples are shown in Table 2.

[Comparative Example 1]

A dried cellulose gel was obtained in the same manner as in Example 1 except that the kneading was carried out in the atmosphere, and the absorption magnification and swelling degree were measured. The results are shown in Tables 3 and 4. The evaluation of the absorption magnification was &quot; DELTA &quot;, but the water retention property was insufficient, and decomposition occurred overnight at a high temperature and a high humidity exceeding 30 DEG C, such as a summer night.

As shown in Tables 3 and 4, in the dry cellulose gel obtained by kneading in the air, both the absorption magnification and the swelling degree are lower than those of the dry cellulose gel of the present invention.

Claims (7)

After adding carboxymethylcellulose sodium powder while spraying mist water in a kneading container filled with water, water and carboxymethylcellulose sodium powder were kneaded under vacuum to knead the carboxymethylcellulose sodium containing 15 to 25 wt% A step of obtaining water, a step of irradiating the kneaded product with electron beams to obtain a crosslinked cellulose gel, and a step of drying the crosslinked cellulose gel to obtain a dry cellulosic gel. The method according to claim 1,
Wherein the dose of the electron beam is 9 to 16 kGy. The method according to claim 1,
Wherein the drying is carried out at a temperature of 60 to 90 占 폚. The method according to claim 1,
And a step of forming the kneaded product under vacuum. A dry cellulosic gel obtained by the production method according to any one of claims 1 to 4, which is obtained by dividing the mass of the gel absorbed for 24 hours by the initial mass before absorption, is 150 or more and is immersed for 18 hours A dry cellulosic gel having a degree of swelling of 290 or more, which is obtained by dividing the mass of the gel by the initial mass before immersion. An apparatus for carrying out the method for producing a dry cellulosic gel according to any one of claims 1 to 4,
A vacuum kneading apparatus having a mixing kneader, a stirring blade, a raw material input port, a lid having a water pipe formed along an inner peripheral portion above the material input port and a water spray portion formed at equal intervals in the water pipe, and a vacuum suction unit;
An electron beam irradiating device including an electron beam irradiating section and an electron beam source; a belt conveyor for conveying the cellulose kneaded product prepared in the vacuum kneading apparatus; And
An air vent belt conveyor for conveying the crosslinked cellulose gel prepared by the electron beam irradiating apparatus, a circulating fan for blowing hot air from above the belt conveyor, and a drying device having an exhaust duct. The method according to claim 6,
Further comprising an extruding device for kneading the crosslinked cellulose gel taken out from the electron beam irradiating device and shaping the gel into a spherical shape.

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