JPH0347703A - Compaction method of powder - Google Patents

Abstract

PURPOSE:To enable high-density compaction in the vicinity of the optimum moisture ratio, by a method wherein a polymer under a water absorption state and a dried powder are mixed up with each other uniformly under a dried state and water contained in the polymer is fed to the surrounding dried powder with a pressurizing action after that. CONSTITUTION:A water absorption polymer still keeping particle independent properties under a water absorption state performs powder mixture with a dried powder such as a dried clay material or dried bentonite. A dried powdery polymer mixture obtained through the powder mixture is pressurized, the water absorption polymer in a dried powdery polymer mixture is caused to discharge outside the water in an absorbed state into the water absorption polymer and to act the discharged water upon the dried powder so that the dried powder is compacted. With this construction, since the water is fed under a state where the water is connoted into the water absorption polymer, the water absorption polymer can be mixed up with the dried powder under a dried state substantially and a uniform state. Compaction of the dried powder can be performed in the vicinity of the optimum moisture ratio without passing through a specific device and process and a compaction product whose drying density is high becomes possible.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a method for compacting powder suitable for use in producing ceramic clay, high-density bentonite, and the like.

(b), Conventional technology Conventionally, this type of compaction is performed by adding water to the raw material powder, but the compaction density at this time is close to the optimum water content ratio, which is the maximum dry density. preferable. However, since it is difficult to uniformly mix water into the powder, it is unavoidable to mix in excess water than the optimum water content ratio, or knead with an excess of water using methods such as a filter press. A method is used in which the water is dehydrated to reach the optimum moisture content.

(C) 0 Problems to be Solved by the Invention However, this method has the disadvantage of requiring extra labor such as pressing in order to obtain a powder with an optimum water content ratio.

In order to eliminate the above-mentioned drawbacks, the present invention aims to provide a compaction method for powder that does not require extra effort such as pressing other than kneading and is capable of high-density compaction near the optimum water content ratio. This is the purpose.

(d) Means for solving the zero problem, that is, the present invention involves mixing a dry powder with a dry powder in a water-absorbing state using a water-absorbing polymer that maintains particle independence even in a water-absorbing state; The dried powder polymer mixture is pressurized, and the pressure causes the water absorbent polymer in the dry powder polymer mixture to discharge the water absorbed by the water absorbent polymer to the outside, and the discharged water is dried. It is configured to act on powder to compact dry powder.

Note that the numbers in parentheses are for convenience and indicate corresponding elements in the drawings, and therefore, this description is not limited to the descriptions on the drawings. r (e) below
The same applies to the column ``, action''.

(e) 0 effect With the above-described configuration, the present invention allows the water-absorbed polymer and dry powder to be uniformly mixed in a substantially dry state, and the water contained in the polymer to be absorbed by the subsequent pressurizing action to dry the surrounding area. It acts as if it were supplied to the powder.

(f), Example Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a diagram showing the glass transition point of each monomer.

To manufacture viscous materials such as ceramic clay and high-density bentonite, dry powders such as dry clay powder and bentonite powder are used as raw materials, and water-absorbing polymers that include water in their structure are used. Mix the powder. When mixing the powders, the dry powder and the water-enclosing polymer maintain particle independence even in a water-absorbed state, so that both are mixed in a substantially dry state. The amount of water to be absorbed by the water-absorbing polymer is such that the water content ratio is optimal for compacting the dry powders to be mixed together.

The water-absorbing polymer used here can be obtained by the following method. That is, an acrylic copolymer is dissolved in an aliphatic hydrocarbon, an aqueous solution of acrylic acid and its alkali metal salt is dispersed, and reverse phase suspension polymerization is carried out, followed by crosslinking with a crosslinking agent in the presence or absence of an inorganic substance and drying. be. below,
The manufacturing method of the water-absorbing polymer will be explained in detail.

The acrylic copolymer used as a dispersant in the production of the water-absorbing polymer used in the present invention is (a) an acrylic acid alkyl ester or a methacrylic acid alkyl ester, a monomer in which the alkyl group has 8 or more carbon atoms. 40 to 95% by weight (bl carboxyl group, amino group or quaternary group)
5 to 40% by weight of one type or 2m or more monomer selected from acrylic acid derivatives, methacrylic acid derivatives, acrylamide derivatives, and methacrylamide derivatives containing an ammonium group or a hydroxyl group (0) Above (a) It is a copolymer containing 0 to 40% by weight of an unsaturated monomer that can be copolymerized with ) and (b).

The acrylic acid or methacrylic acid alkyl ester of component (a) may be used as long as the number of carbon atoms in the alkyl group is 8 or more. , lauryl acrylate, lauryl methacrylate, tridecyl acrylate, tridecyl methacrylate, mixed ester of lauryl/tridecyl acrylate, stearyl acrylate, and stearyl methacrylate.

When selecting component (a), it is advantageous that the glass transition point is as high as possible, since blocking of beads is less likely to occur when a dispersant is synthesized by aqueous suspension polymerization. The glass transition temperature of each monomer is shown in FIG.

Examples include 2-ethylhexyl methacrylate, lauryl acrylate, lauryl/tridecyl acrylate mixed ester, tridecyl acrylate, stearyl acrylate, and stearyl methacrylate.

Acrylic acid derivatives, methacrylic acid derivatives, or acrylamide derivatives or methacrylamide derivatives containing a carboxyl group, an amino group, a quaternary ammonium group, or a hydroxyl group as the component (b) include acrylic acid, methacrylic acid, and itacon. Acid, dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, diethylaminoethyl acrylate, diethylaminoethyl methacrylate, trimethylaminoethyl chloride acrylate, trimethylaminoethyl chloride methacrylate, 2-droxyethyl acrylate, 2-hydroxy methacrylate Ethyl, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate,
These include acrylamide, dimethylacrylamide, dimethylaminopropylacrylamide, dimethylaminopropylmethacrylamide, trimethylaminopropylacrylamide chloride, trimethylaminopropylmethacrylamide chloride, and the like.

Examples of the monomer of component (e) include methacrylic acid alkyl esters having a high glass transition point and affinity for aliphatic hydrocarbon solvents with an alkyl group having 4 or less carbon atoms, and vinyl acetate. Examples include methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, and vinyl acetate. Preferably, methyl methacrylate, ethyl methacrylate, and isobutyl methacrylate are suitable.

(Al, (bl, (The composition ratio of the C1 component is determined by the dispersion solubility in an aliphatic hydrocarbon solvent, the colloidal dispersibility of polymerization, the physical properties of the water-absorbing polymer, such as water absorption capacity, particle independence during water absorption, It has a large effect on particle strength, particle size, etc.

Usually, (a) component 40-95% by weight, (b) component 5-4
0% by weight, (C) component 0-40% by weight, more preferably (a) component 45-70% by weight, (bl component 5-40% by weight)
25% by weight, (20 to 40% by weight of the Cl component is appropriate. If the (41) component is less than 40% by weight, the dispersion solubility in the solvent decreases, and if it exceeds 95% by weight, it is relatively (
b) When the component is less than 5% by weight, colloidal dispersibility deteriorates;
In both cases, it becomes difficult to continue reverse phase suspension polymerization. In the range of 40 to 95% by weight, the higher the content, the better the dispersion and solubility in the solvent, and the particle independence and strength of the particles during water absorption of the water-absorbing polymer tend to improve.The lb component is less than 5% by weight. In this case, the colloidal dispersibility deteriorates as described above, and if it exceeds 40% by weight, the dispersion solubility in the solvent decreases, making it difficult to continue reverse-phase suspension polymerization.

In the range of 5 to 40% by weight, the higher the amount, the better the colloidal dispersibility of the polymerization9.The water absorption rate of the water-absorbing polymer increases, but the particle independence and particle strength during water absorption decreases, and the particle size becomes finer. Tend. If the content of component (c) exceeds 40% by weight, the proportion of component (a) will decrease relatively, resulting in poor dispersibility in the solvent.In the range of 0 to 40% by weight, the higher the content, the stronger the particle strength of the water-absorbing polymer. will be uploaded.

The acrylic copolymer used as a dispersant is synthesized by an aqueous suspension polymerization method. Solvent remained in solution polymerization9.
Low molecular weight polymers may have poor functionality as a dispersant. To give an example of the aqueous suspension polymerization method, partially saponified polyvinyl alcohol is dissolved in ion-exchanged water under weight, and after nitrogen substitution, azo or ζ peroxide is added to the monomers of (al, (bl, and el) components. A solution of the system's polymerization initiator is dropped and dispersed, and the polymerization is completed by keeping it warm.After cooling, the solid matter is filtered and washed with water, and then dried under reduced pressure to form a bead-shaped acrylic copolymer, that is, a dispersant. obtain.

The dispersant obtained by the above method is dispersed and dissolved in an aliphatic hydrocarbon solvent for reverse phase gluster polymerization. The amount of the dispersant used is in the range of 0.1 to 10% by weight, preferably O, S to 5% by weight, based on the monomer of acrylic acid and its alkali metal salt. If the amount of the dispersant is less than 0.1% by weight, the colloidal dispersion of the polymerization will become unstable, and 10F! If the amount exceeds %, the particle size becomes too fine, which is economically disadvantageous.

An aqueous solution of acrylic acid and its alkali metal salt is prepared by partially neutralizing an acrylic acid monomer with an aqueous solution of sodium hydroxide, potassium hydroxide, or the like. The degree of neutralization is preferably 60 to 85% in consideration of water absorption capacity and safety. The monomer concentration in the aqueous solution is 35 to 75% by weight, preferably 4% by weight.
It is preferably 0 to 70% by weight.

Further, within the scope of producing a water-absorbing polymer, an unsaturated monomer that can be copolymerized with acrylic acid and an alkali metal salt monomer of acrylic acid may be copolymerized.

When carrying out reverse-phase suspension polymerization of acrylic acid and its aqueous alkali metal solution, water-soluble persulfates such as potassium persulfate and ammonium persulfate are used as polymerization initiators, as they are self-crosslinking types that do not use crosslinking monomers. or hydrogen peroxide are preferred. The amount of the polymerization initiator used is 0.1 to 2.0% by weight, preferably 0.2 to 1.0% by weight based on the monomer.

Examples of aliphatic hydrocarbon solvents for reverse phase suspension polymerization include aliphatic hydrocarbons such as n-pentane, n-hexane, n-hebutane, and n-octane, and alicyclic hydrocarbons such as cyclohexane, methylcyclohexane, and decalin. For example,
Preferred are n-hexane, n-hebutane, and cyclohexane.

Another particularly important requirement when producing a water-absorbing polymer is to carry out a crosslinking reaction with a crosslinking agent in the presence or absence of an inorganic substance after completion of reverse phase suspension polymerization.

The crosslinking agent is a carboxyl group (or carboxylate group)
Any compound may be used as long as it has two or more functional groups capable of reacting with. Examples of such crosslinking agents include polyglycidyl ethers such as ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, and glycerin triglycidyl ether; epichlorohydrin, α-
Examples include heloepoxy compounds such as methyl chlorohydrin; polyaldehydes such as geltaraldehyde and glyoxal; preferably, ethylene glycol glycidyl ether is suitable.

The amount of the crosslinking agent added varies depending on the type of crosslinking agent and the type of dispersant, but the appropriate range is usually 0.05 to 2% by weight based on the monomer of acrylic acid and its alkali metal salt.

If the amount of the crosslinking agent used is less than 0.05% by weight, the particle independence during water absorption and the strength of the particles will be poor, and if it is more than 2% by weight, the crosslinking density will be too high (too much) and the water absorption capacity will be significantly reduced.

Adding an inorganic substance during the crosslinking reaction further increases particle independence during water absorption. Inorganic substances include white carbon, talc, hydrotalcite, and finely divided silica. Further, at this time, a surfactant may be added, and a conventionally known Q nonionic surfactant or the like may be used.

The crosslinking reaction can be carried out by adding a crosslinking agent during conventionally known azeotropic dehydration or vacuum drying, and addition during azeotropic dehydration is easy.

Unlike commercially available polymers, the water-absorbing polymer used in the present invention exhibits particle independence when water is absorbed.
In addition, since the more the number of baffles are, the more effective it is, it is presumed that the sliding of the water-absorbed polymer is involved. of the dispersant (a
) component increases the water repellency of the water-absorbed polymer, and the crosslinking agent increases the degree of crosslinking of the polymer, thereby increasing the water absorption rate and reducing surface stickiness. Due to these effects, the bead-shaped polymers that have absorbed water have less water as a binder, so they slide against each other, creating voids and exhibiting particle independence and fluidity.

The present invention allows the water-absorbing polymer to absorb a necessary amount of water,
Of course, it may also be used by freezing it in a state where it remains in the form of independent fine particles. The amount of water that can be absorbed is determined by the water absorption capacity of the polymer (100 to 20% of the weight of the water absorbing polymer with ion exchange water)
0 times) is possible. Although it is sufficient to simply allow the water-absorbing polymer to absorb the necessary amount of water, it is desirable that the amount of water that can be absorbed to maintain independent fine particle form is less than half the water-absorbing capacity of the polymer.

The particle size of the water-absorbing polymer can be freely changed within the range of 0.03 to 39.0 mm depending on the particle size of the water-absorbing polymer and the amount of water to be absorbed, and can be adjusted to suit the working conditions when mixing with dry powder. You can choose.

In this way, when the dry powder and the water-absorbing polymer are powder-mixed to form a dry powder-polymer mixture, an operation is performed to compact the powder-polymer mixture. In addition, since the powder polymer mixture is mixed in a substantially dry state at the time of mixing, the water-absorbing polymer is mixed with the dry powder in a uniform state.

In this way, the powder polymer mixture is compacted under pressure using a punch rod, a vibrator, or the like. Then, due to the pressure compaction operation, the water included in the water-absorbing polymer in the powder polymer mixture is released to the outside by the pressure generated during compaction, and is supplied to the surrounding dry powder. As mentioned above, since the water-absorbing polymer is uniformly mixed with the dry powder in a substantially dry state, the water released from inside the polymer during compaction is uniformly distributed throughout the dry powder. Ru.

Therefore, even if the amount of water contained in the water-absorbing polymer corresponds to the optimum water content ratio required for optimal compaction of the dry powder, the amount of water is not too much or too little for the dry powder (supplied, The compaction operation proceeds smoothly and compaction with maximum dry density is possible.

(g) 0 Effects of the Invention As explained above, according to the present invention, a water-absorbing polymer that maintains particle independence even in a water-absorbed state can be mixed with a dry powder such as a dry viscosity material or dried bentonite in a water-absorbed state. Powders are mixed, the powder-mixed dry powder polymer mixture is pressurized,
The pressure causes the water absorbent polymer in the dry powder polymer mixture to discharge the water absorbed by the water absorbent polymer to the outside, and causes the discharged water to act on the dry powder to tighten the dry powder. Since it is configured to harden, the water is supplied in a state where it is included in the water-absorbing polymer, so the water-absorbing polymer can be uniformly mixed into the dry powder in a substantially dry state. It becomes possible to compact dry powder near the optimum moisture content without using special equipment and processes such as a filter press, and it becomes possible to provide compacted products with high dry density.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the glass transition point of each monomer.

Claims (1)

[Claims] A water-absorbing polymer that maintains particle independence even in a water-absorbed state is mixed with dry powder in a water-absorbed state, and the powder-mixed dry powder-polymer mixture is pressurized. Using pressure, the water-absorbing polymer in the dry powder-polymer mixture discharges the water absorbed by the water-absorbing polymer to the outside, and the discharged water acts on the dry powder to tighten the dry powder. A compaction method for powder that is configured to harden.