JP2004067878A - Preparation method of hydrated gel particle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of converting at a low cost fine powders of a water-soluble polymer, such as an organic polymer coagulant, into particles within product specifications. <P>SOLUTION: The preparation method of hydrated gel particles is characterized by obtaining a hydrated gel mass having a stress of 0.1-300Pa by kneading a mixture with a kneader which consists of water-soluble polymer powders and water and contains water in a proportion of 20-80mass% based on the total amount thereof and then by pulverizing the hydrated gel mass. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for converting a powder of a water-soluble polymer into hydrogel particles, for example, a fine powder generated in a sieving step or the like to obtain a powder product such as an organic polymer flocculant as hydrogel particles. In the case of recovery, it can be suitably used.
[0002]
[Prior art and its problems]
Generally, the organic polymer coagulant is one or two selected from the group consisting of (meth) acrylic acid and / or a salt thereof, a tertiary or quaternary salt of (meth) acrylamide and dialkylamino (meth) acrylate. It is produced by homopolymerizing or copolymerizing at least one kind of ethylenically unsaturated monomer. The polymerization of the ethylenically unsaturated monomer is usually carried out in an aqueous medium, and the polymerization product is obtained as a hydrogel having a water concentration of about 20 to 80% by mass.
Most organic polymer flocculants are shipped as powdered products, and the hydrogel obtained by the above method is usually refined through the following steps. That is, the hydrogel is first cut into an appropriate size for drying, dried, and further pulverized. Thereafter, polymer particles having a particle size of 150 μm to 2 mm are separated by sieving to obtain a flocculant product.
Discarding the powder that has passed through the sieve in the sieving step (hereinafter sometimes referred to as fine powder) leads to an increase in manufacturing cost, and thus recycling of such fine powder is one of the technical issues.
[0003]
The number of proposals for recycling organic polymer flocculants fines is surprisingly small. JP-A-1-315426 discloses that by contacting fine powder having a particle size of less than 50 μm with water, the surface of the fine powder is first made tacky, and then the fine powder is aggregated to form a particle having a particle size of at least 200 μm or at least 500 μm. It has been proposed to convert to aggregates, often at least 700 μm. Since such agglomerates are loose agglomerates of the fine powder, they are again decomposed into the original fine powder in an aqueous medium, so that the dissolution rate in water is excellent, and the aggregation performance is higher than that of a general polymer flocculant product. It is also somewhat better in point.
However, the agglomerates described in the above patent publication have poor mechanical strength, and thus have a problem that they are converted into fine powder again by operations such as a drying step and sieving, and have the same particle size as ordinary polymer flocculant products. It cannot be adopted by the method of reusing fine powder as a product.
[0004]
JP-A-49-83681 also discloses a method of processing a fine powder of an organic polymer flocculant to produce a granular flocculant having much higher solubility than a polymer flocculant product obtained by a usual production method. Has been proposed. Specifically, a water-containing hydrophilic organic solvent obtained by adding water to methanol or ethanol is added to the fine powder of the organic polymer flocculant and kneaded, and then dried and then crushed or dried after granulation. The technical means of doing so is disclosed. In this case as well, there is a problem similar to that described with reference to Japanese Patent Application Laid-Open No. 1-315426, and the range of application is limited.
[0005]
On the other hand, polymer particles obtained by polymerizing a water-soluble vinyl monomer similar to the monomer constituting the organic polymer flocculant and introducing a cross-linked structure are excellent in water absorption performance, and absorb water in disposable diapers, sanitary products and the like. Although it is widely used as an agent, there is a similar problem of fine powder with respect to the water-absorbing polymer particles, and many proposals have been made regarding recycling of the fine powder (JP-A-2001-79829, JP-A-3-152104). And JP-A-4-41532. However, since the technical means disclosed in these publications basically target a crosslinked polymer, application to a water-soluble polymer was expected to be impossible.
[0006]
[Problems to be solved by the invention]
An object of the present invention is to provide a method of processing fine powder of an organic polymer flocculant into particles of a product standard at low cost.
[0007]
[Means for Solving the Problems]
The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, completed the present invention.
That is, the present invention kneads a mixture composed of a water-soluble polymer powder and water and having a water ratio of 20 to 80% by mass based on the total amount thereof with a kneader to reduce the stress to 0.1. A method for producing hydrous gel particles, characterized in that after obtaining a hydrogel mass of up to 300 Pa (Pascal), the hydrogel mass is refined.
Hereinafter, the present invention will be described in more detail.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
Representative examples of the water-soluble polymer that can be used in the present invention include cationic polymer flocculants, cationic polymers used as anionic polymer flocculants and nonionic polymer flocculants, anionic polymers and Nonionic polymers are mentioned, and such polymers are obtained by polymerizing water-soluble ethylenically unsaturated monomers as exemplified below.
Examples of the ethylenically unsaturated monomer include (meth) acrylic acid, maleic acid, maleic anhydride, itaconic acid, crotonic acid, 2- (meth) acryloylethanesulfonic acid, and 2- (meth) acrylamido-2-methyl. Acidic monomers such as propanesulfonic acid, vinylsulfonic acid and styrenesulfonic acid, and their alkali metal salts, alkaline earth metal salts, ammonium salts and alkylamine salts, N, N-dimethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylamide and the like, and quaternary salts thereof, N-alkylvinylpyridinium halide, hydroxymethyl (meth) acrylate, 2-hydroxy Ethyl (meth) acrylate, 2-hydroxyp Pill (meth) acrylate, (meth) acrylamide, N-ethyl (meth) acrylamide, N-propyl (meth) acrylamide, methoxypolyethylene glycol (meth) acrylate, polyethylene glycol mono (meth) acrylate, vinylpyridine, N-vinylpyrrolidone And these can be used alone or in combination of two or more.
[0009]
The monomer is subjected to radical polymerization by heat in the presence of a radical polymerization initiator in an aqueous medium or by ultraviolet polymerization in the presence of a photopolymerization initiator, whereby a water-soluble polymer in a gel state (this The water content is 20 to 80% by mass). When radical polymerization is initiated by heat, a combination of a redox initiator and an azo initiator is preferred. Examples of the oxidizing agent in the redox initiator include hydrogen peroxide, ammonium persulfate, sodium persulfate, potassium persulfate, t-butyl hydroperoxide, and the like.As the reducing agent, sodium bisulfite, ascorbic acid and the like Salts, triethanolamine and ferrous sulfate. The amount of the redox initiator and the azo-based initiator to be used is preferably 100 to 200 ppm of the redox initiator and 500 to 1000 ppm of the azo-based initiator based on the mass of the whole monomer. By performing the radical polymerization under the above conditions, a water-soluble polymer having a weight average molecular weight of 1,000,000 or more can be obtained.
[0010]
The water-soluble polymer in a gel state is finally processed into dry particles having a particle size of 150 μm to 2 mm through a pulverizing step, a drying step, a sieving step, and the like as described in the description of the related art. In the present invention, fine powder (usually a powder having a water content of 2 to 10% by mass and an average particle size of 150 μm or less) generated in the sieving step or the like is kneaded with water by the method described below. In the present invention, the polymer kneaded with water is a water-soluble polymer, and the water-insoluble polymer is out of the scope of the present invention. In the case of a water-insoluble polymer, for example, a water-absorbing raw resin, simply kneading it with water in the manner described below results in gelation of each water-absorbing resin particle while maintaining the particle form. The gel-like particles of the water-absorbent resin do not coalesce and transform into a uniform gel mass as a whole, and may return to the original fine powder in the following fine-graining step, drying step, sieving step, etc. As a result, the effect of the present invention cannot be obtained.
In the present invention, the powder to be kneaded with water is not limited to fine powder, and any dry powder that is desired to be returned to the hydrogel can be used without any particular limitation.
[0011]
In the present invention, a water-containing gel mass having a stress described below of 0.1 to 300 Pa (Pascal) is obtained by kneading the water-soluble polymer powder and water by a method described below. The hydrogel having such stress is in a very homogeneous state, and its appearance, touch, and the like are similar to those of the hydrogel immediately after polymerization. In the present invention, the more preferable stress of the hydrogel mass is 40 to 200 Pa. If the stress is less than 0.1 Pa, it will be difficult to reduce the grain size in the next step. On the other hand, if the stress exceeds 300 Pa, an excessive load is applied to the kneading machine, and the machine stops. In addition, the property of the hydrogel mass in the range of 0.1 to 300 Pa is that the gel is torn in the marginal portion when pulled by a stress higher than the stress, but is slightly deformed when pressed below the stress. However, it keeps the original shape of the gel mass and does not disperse in the raw material powder. When pressed with a force higher than the stress, the gel is not scattered in the powder of the raw material, and the whole gel mass is crushed in a senbei shape while maintaining a uniform state.
[0012]
The stress relating to the hydrogel mass in the present invention is a value measured by a card meter, and is a numerical value approximating the hardness felt when pressing the hydrogel mass with a finger. A card meter is generally used as a device for quantitatively measuring the hardness of cream, tofu, miso, sheep, pudding, agar, kamaboko, sausage, and the like.For example, a card meter / max model from Iio Electric Co., Ltd. ME-303 is commercially available.
The conceptual diagram showing the configuration of the card meter is as shown in FIG. 1. In the card meter, a pressure-sensitive shaft having a diameter of 3 mmφ, 8 mmφ, or 11.3 mmφ, which is a portion for applying a load to the sample, is brought into contact with the sample, The stress from the sample is measured while increasing the load applied to the sample at a constant rate. That is, by raising the sample stage on which the sample is mounted by the pulse motor at a constant speed, the load applied to the sample via a spring (a precision spring is used to detect stress) is increased at a constant speed, and the pressure-sensitive shaft is increased. A change in stress when the sample enters the sample or crushes the sample is detected by a stress detector via the spring. The hardness of the sample, that is, the stress, is obtained by the following equation by such measurement.
Stress = A ₂ / A ₁ · K / L
However, K is the spring constant, L is the circumferential length of the sensitive application shaft, A ₁ is a load to the sample when the sample has caused significant deformation by the load, also A ₂ for temporarily loading the sample a load to the sample at the same time as when a ₁ measurement in the case of that a solid is not deformed at all.
[0013]
The ratio of the water-soluble polymer and water in the kneading is 20 to 80% by mass of the water-soluble polymer and 80 to 20% by mass of water based on the total amount of both. If the proportion of the water-soluble polymer is less than 20% by mass, the compressive force applied during kneading is absorbed by the moisture side, and the kneading operation is hindered. On the other hand, when the proportion of the water-soluble polymer exceeds 80% by mass, the stress becomes too high, which causes an overload of the kneader. More preferable ratios of the water-soluble polymer and water are 40 to 60% by mass of the water-soluble polymer and 60 to 40% by mass of water.
Since the stress of the hydrous gel mass varies depending on the type of water-soluble polymer that forms the gel, the average molecular weight, the amount of water contained in the gel, and the like, the amount of water to be added and the temperature and time of kneading are appropriately selected. By doing so, the stress is adjusted to be 0.1 to 300 Pa.
[0014]
In the present invention, the kneading apparatus used when kneading the water-soluble polymer powder and water is not particularly limited, as long as the kneading apparatus can be kneaded under a compressive force, specifically, a twin-screw mixer, Examples include a twin-screw assembled blade mixer, a single-screw screw mixer, and a twin-screw return screw mixer. A particularly preferred mixer is a twin screw mixer. About 5 to 15 minutes is sufficient for the time required for mixing. In kneading without compressive force, it is difficult for the water-soluble polymer and water to form a uniform gel mass, and the water-soluble polymer gel obtained by such kneading returns to the original fine powder again in the subsequent steps, Poor recovery.
[0015]
The hydrated gel mass is discharged as a rod-like material from the outlet of the kneader, but a material having a stress of 0.1 to 0.5 Pa is cut into a length of about 5 to 50 cm by its own weight to form a columnar gel mass. The gel lump having such a size can be used as it is in the next step, that is, the step of refining. The water-containing gel mass discharged from the kneading machine without being cut in such a length as a rod is cut into an appropriate size or cut without being cut into a shredder in the next granulation step. Can be put in.
[0016]
The hydrogel gel mass obtained by the above-mentioned method is finely granulated so that the hydrogel mass can be efficiently dried in a later step. In the case of fine granulation, in order to stabilize the quality of the granular product obtained through the subsequent steps, the hydrogel mass obtained by processing the powder by the above method and the hydrogel obtained by polymerization are mixed. It is preferable to make them finer at the same time. The preferred particle size of the gel particles obtained by the fine graining is 2 to 10 mm.
The means for grain refinement is not limited, but a device provided with a perforated plate having small holes having a diameter of 3 to 10 mm and a rotary cutter at the outlet of the screw extruder (sometimes called a meat chopper) is used. It is inexpensive to use the extruder to extrude the gel particles in the direction of the outlet while making the gel finer by means of a perforated plate at the outlet and a rotary cutter.
[0017]
When the hydrogel particles obtained by the above method are to be processed again into a product of an organic polymer flocculant, the water content is reduced to 10 by heating at a temperature of 60 to 100 ° C. for 3 to 12 hours in a hot air drying oven or the like. After drying to a mass% or less, it may be pulverized and further sieved to convert into polymer particles having a particle size of 150 μm to 2 mm. The drying and pulverizing steps and the like may be performed in a state where the hydrogel particles obtained from the fine powder are mixed with fresh hydrogel particles obtained by polymerization.
Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples of the present invention.
[0018]
Embodiment 1
A co-kneader (manufactured by Neotec Co., Ltd .; 3.7 kW (rated 14.2 A, no load 5.6 A), a kneader having two stirring shafts alternately provided with a return screw), a cylinder inner diameter of 125 mm, a screw rotation speed 60 rpm], the fine powder of the cationic polymer flocculant and water in an 80 mesh pass (180 μm or less) are charged into the kneader at an addition rate of 800 g / min at a mass ratio of 50 to 50, respectively. Kneading was performed.
Five minutes later, a hydrogel mass having a stress of 100 Pa was continuously discharged from the outlet at 1600 g / min. The obtained rod-like hydrated gel mass was directly introduced into a meat chopper, whereby the hydrated gel mass was cut into particles having a particle size of 3 to 6 mm.
The obtained hydrogel particles were dried with a hot air drier at 80 ° C. for 5 hours. The dried particles were pulverized and classified again with an 80-mesh sieve, and as a result, a fine powder of the polymer flocculant was recovered as a 95% product.
[0019]
Embodiment 2
Into the same kneader as in Example 1, the fine powder of the polymer flocculant was continuously supplied at 1,200 g / min and the water at 800 g / min (the ratio of the fine polymer powder and water was 60 parts by mass to 40 parts by mass). After 5 minutes, a rod-shaped hydrogel having a stress of 200 Pa was continuously discharged from the outlet at 2,000 g / min. Thereafter, the same operation as in Example 1 was performed to recover fine powder as a product, and as a result, the recovery rate was 93%.
[0020]
[Comparative Example 1]
Into a kneader similar to that in Example 1, the fine powder of the polymer flocculant was continuously supplied at 1,800 g / min and the water at 200 g / min (the ratio of the fine polymer powder to water was 90 parts by mass. 10 parts by mass). The hydrogel discharged from the outlet of the kneader contains a large number of powder aggregates, and the same operation as in the following examples resulted in a fine powder recovery rate of only 70%.
[0021]
【The invention's effect】
According to the present invention, not only the fine powder of the polymer flocculant but also other dry particles of the water-soluble polymer can be returned to the hydrogel particles again by an easy operation. The obtained hydrogel particles are processed into dried particles of a desired shape at a high recovery rate and converted into products.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram illustrating a schematic configuration of a card meter.
Also, 1 to 10 in the figure respectively indicate the following components.
1; load cell (stress detector) 2: pulse motor 3; precision spring 4: connecting shaft 5; wire 6; weight 7; pressure-sensitive shaft 8; sample 9; movable base 10;

Claims (3)

A mixture of a water-soluble polymer powder and water, in which the proportion of water based on the total amount thereof is 20 to 80% by mass, is kneaded with a kneader, so that a hydrogel mass having a stress of 0.1 to 300 Pa is obtained. Obtaining a water-containing gel mass, and then finely crushing the water-containing gel mass. The method for producing hydrogel particles according to claim 1, wherein the water-soluble polymer has a weight average molecular weight of 1,000,000 or more. The water-soluble polymer is an anionic polymer containing a unit based on (meth) acrylic acid and / or a salt thereof, a nonionic polymer mainly containing a unit based on (meth) acrylamide, and a dialkylamino (meth) acrylate. The method for producing hydrogel particles according to claim 1 or 2, which is a polymer selected from the group consisting of cationic polymers containing units based on tertiary or quaternary salts.

Images