JP2988137B2 - Method for producing metal ion crosslinked polymer fine powder - 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 producing a fine powder of a metal ion crosslinked polymer such as a metal polyacrylate.

[0002]

2. Description of the Related Art Polymers crosslinked at high density with metal ions such as metal polyacrylates are expected to be a metal substitute polymer because of their high heat resistance, isotropic and high elastic modulus. To produce this metal ion crosslinked polymer, for example, JP-A-62-74905 and JP-A-62-74905
As disclosed in JP-A-74906 and JP-A-62-259818, polyacrylic acid and an inorganic metal salt are reacted at a predetermined ratio in an aqueous solution of an alkali metal hydroxide to form a precipitate. This is filtered and dried to obtain a polymer powder.

[0003]

However, this metal ion cross-linked polymer powder is heat-infusible, so that a general resin molding method cannot be used. Further, since the particles have a large particle size, are indefinite, and have low fluidity at the time of molding, a high pressure of several thousand kg / cm ² or more is required at the time of heat compression molding, and the man-hour required for molding is large.

In order to improve the fluidity at the time of molding in order to reduce the pressure at the time of molding, the metal ion crosslinked polymer powder may be miniaturized. However, the metal ion-crosslinked polymer precipitate obtained by the above-mentioned production method has a property of agglomerating during drying, and the particle size of the obtained dry powder is as small as 0.1 mm. As a method of remaining fineness, there is a method of physically pulverizing. However, in this case, the fluidity during molding is improved,
The pulverization causes considerable damage to the structure of the metal ion crosslinked polymer, which may adversely affect the physical properties of the molded article.

The present invention has been made in view of the above circumstances, and has no fear of damaging the polymer structure.
It is intended to produce a fine metal ion crosslinked polymer powder.

[0006]

A method for producing a metal ion-crosslinked polymer fine powder which solves the above-mentioned problems comprises a method of crosslinking a metal ion-crosslinked polymer by reacting with a hydroxide or a metal ion of at least one of an alkali metal and an alkaline earth metal. A first aqueous solution in which a possible polymer raw material is dissolved, and a second aqueous solution in which a metal salt is dissolved, and a reaction step in which the first aqueous solution and the second aqueous solution are brought into contact with each other in an atomized state to react, and A drying step of continuously drying the obtained particulate reaction product.

[0007] As a polymer raw material dissolved in the first aqueous solution, polyacrylic acid is typically used. This polyacrylic acid is obtained by copolymerizing 80 to 100 mol% of acrylic acid and 20 to 0 mol of another vinyl monomer. The degree of polymerization of the polyacrylic acid is 500,000 to 1,250,000 in number average molecular weight, and preferably 100 or more.
In addition, any polymer, such as polymethacrylic acid, polystyrene carboxylic acid, and polystyrene sulfonic acid, which can be dissociated and dissolved in a solvent and can form an ion bond with a metal ion can be used.

The alkali metal or alkaline earth metal supplied as a hydroxide dissolved in the first aqueous solution activates the functional group of the polymer raw material and is supplied from the metal salt dissolved in the second aqueous solution. Na, K, Li, Ca, Ba, Sr
Metals such as are used. Particularly basic Na,
It is preferable to use a metal such as K.

The metal salts dissolved in the second aqueous solution include Zn, Mg, Ca, Ba, Sn, Fe, Pb, C
salts of divalent metals such as u, Co, Ni, Mn, Cr, A
salts of trivalent metals such as l, La, etc., Ti, Zr, Te, Ru
And the like, salts of tetravalent metals such as In the reaction step, the first aqueous solution and the second aqueous solution are brought into contact with each other in an atomized state. As a result, a reaction immediately occurs at the contact interface, and a fine powder of the metal ion-crosslinked polymer is generated. The atomization state can be achieved by air atomization using pressurized air or atomization by centrifugal force. In order to bring the two aqueous solutions into contact with each other in the atomized state, the flow directions of the pressurized air may be opposed to each other so that the two mist collide with each other.

The mixing ratio between the metal salt and the polymer raw material is such that the metal salt is 0.1 equivalent to 1 equivalent of the carboxyl group of the polymer raw material.
The ratio can be 1 to 20 equivalents. In the drying step, fine particulate products generated by contact of both mistes of the first aqueous solution and the second aqueous solution are dried continuously and continuously in the reaction step. In this way, drying is performed while maintaining the fine particle state, and a metal ion crosslinked polymer fine powder is obtained.
In this drying, the reaction product may be continuously supplied into a drying furnace, or may be dried by being brought into contact with a heating drum or the like.

It is preferable that a fibrous or powdery reinforcing material coexist in at least one of the first aqueous solution and the second aqueous solution. In this case, the reinforcing material is taken in simultaneously with the generation of the metal ion crosslinked polymer, and the metal ion crosslinked polymer fine powder containing the reinforcing material can be easily produced. The once dried metal ion crosslinked polymer fine powder does not agglomerate even if it is in a wet state during washing, and maintains a fine state after washing and drying. Therefore, the obtained metal ion crosslinked polymer fine powder can be subjected to molding after washing and drying.

[0012]

In the method for producing a metal ion-crosslinked polymer fine powder according to the present invention, the first aqueous solution and the second aqueous solution are each atomized, contacted and reacted with each other in the atomized state, and a reaction product is deposited. Therefore, the reaction product is in the form of fine particles substantially corresponding to the particle size of the mist. Furthermore, since the particles are in a wet state by the aqueous solution, they become almost spherical fine particles due to surface tension.

Then, a drying step is performed continuously to the reaction step. Therefore, the reaction product in the form of fine particles hardly aggregates and is dried in the state of fine particles, whereby a metal ion crosslinked polymer fine powder is obtained. Also, the once dried metal ion crosslinked polymer fine powder does not aggregate even if it is brought into a wet state again. Therefore, cleaning
By repeating the filtration, a substantially spherical metal ion crosslinked polymer fine powder having high purity can be obtained.

[0014]

The present invention will be specifically described below with reference to examples. (Embodiment) FIG. 1 shows a manufacturing apparatus used in this embodiment. The manufacturing apparatus includes a reaction tube 1 having a substantially cylindrical shape and an axial direction perpendicular to the ground, and a pair of spray nozzles provided at an upper end of the reaction tube 1 and positioned symmetrically with respect to a central axis. 1
0, 11; a cooling water passage 12 provided above the center of the reaction tube 1 for cooling the reaction tube 1; a heater 13 provided below the center of the reaction tube 1; And a collection bag 14 provided.

The spray nozzles 10 and 11 include:
Pressurized air 2 and a first aqueous solution 3 and a second aqueous solution 4, which will be described later, are supplied via pumps 30 and 40, respectively, and the first aqueous solution 3 and the second aqueous solution 4 are atomized, respectively, and Sprayed to face each other. The reaction product and unreacted mist fall by their own weight and fall into the collection bag 14.
Collected inside. (1) Reaction Step 3400 cc of an aqueous solution containing 31.4 g of polyacrylic acid having a number average molecular weight of 250,000 and an aqueous solution 1 containing 20 g of NaOH
100 cc was mixed and sufficiently stirred to obtain a first aqueous solution 3. On the other hand, 2600 cc of an aqueous solution containing 60 g of AlCl ₃
Was prepared and used as a second aqueous solution 4.

The first aqueous solution 3 and the second aqueous solution 4 are supplied to the spray nozzle 10 and the spray nozzle 11, respectively, and sprayed into the reaction tube 1. At this time, the first aqueous solution 3 was 1.7 cc /
The second aqueous solution 4 was discharged at 1.0 cc / sec. The pressure of the compressed air 2 is 5 kg / cm ²
It is. Thereby, the first aqueous solution 3 and the second aqueous solution 4 are atomized into fine mist, respectively, and collide with each other to progress the reaction. Since the upper part of the reaction tube 1 is cooled, the mist of both aqueous solutions is prevented from drying before the reaction, and the yield is improved.

[0017] The mixing ratio of each raw material used in the above reaction, polyacrylic acid 0.44 eq, NaOH0.52 equivalents are AlCl ₃ 1.36 eq, excess of a NaOH and AlCl ₃ to polyacrylic acid It was constituted so that it might become. (2) Drying step Unreacted mist and particulate Al precipitated by the reaction
The ionically crosslinked polymer falls in the reaction tube 1 by its own weight. At this time, the inside of the reaction tube 1 was heated to 200 ° C. by the heater 12.
, The particulate Al ion crosslinked polymer is continuously dried in that state and collected in the collection bag 14.

The obtained powder is repeatedly washed with pure water and filtered, and unreacted NaOH and AlCl ₃ and N of the reaction product are removed.
After eluting aCl, it was dried by heating again to obtain 40 g of Al.
An ionically crosslinked polymer fine powder was obtained. As a result of microscopic observation, the average particle size of the obtained fine powder was 3 μm. Next, a mold having a cavity of 10 × 80 × 60 mm in depth was prepared, and 4 g of the obtained fine powder was charged. Then, it was heated and kept at 250 ° C. while reducing the pressure in the vacuum chamber, and the contact pressure was set to 2000.
Vacuum heating compression molding was performed at 6000 kg / cm ² for 60 minutes each. Obtained molded body (samples No. a to
The specific gravity of e) was measured, and the results are shown in Table 1. FIG. 2 shows the results of a three-point bending test performed at room temperature on each molded body and measuring the bending strength. In addition, the thickness of the molded body is about 3 mm. (Comparative Example 1) The same first aqueous solution 3 as in the example was placed in a polyethylene beaker, and the second aqueous solution 4 was added dropwise with stirring to gradually react. Stirring was continued for about 10 minutes even after the dropwise addition of the entire amount, thereby converging the reaction. As a result, a reaction product was precipitated, and when the stirring was stopped, a gel-like precipitate was obtained.

The obtained precipitate was filtered as it was, washed repeatedly with pure water and filtered, and then heated to 150 ° C. in a hot air drying oven to be dried. Obtained Al
The ionically crosslinked polymer is agglomerated strongly and cannot be said to be a powder. Then, it was pulverized with a mortar to obtain a powder of about 300 μm. A compact (samples f to j) was formed from 4 g of the powder in the same manner as in the example, and the specific gravity and the three-point bending strength were measured in the same manner. The results are shown in Table 1 and FIG. Comparative Example 2 The powder obtained in Comparative Example 1 was further pulverized in a mortar to obtain a powder having an average particle size of about 30 μm. 4g of this powder
(Example Nos. K to o) were formed in the same manner as in Examples, and the specific gravity and the three-point bending strength were measured in the same manner. Table 1 shows the results
And FIG.

[0020]

[Table 1] (Evaluation) As shown in Table 1, the molded body formed in the example has a high specific gravity and a dense molded body regardless of the pressure during molding. However, in Comparative Example 1, the specific gravity varies greatly due to the pressure at the time of molding because the particle size of the powder is large.
The molded article formed in Comparative Example 2 shows better results than Comparative Example 1, but is inferior to Examples.

On the other hand, from FIG. 2, the molded body obtained in the example shows a substantially constant high strength regardless of the molding pressure. However, in the molded body obtained in Comparative Example 1, the voids increased at a low molding pressure, and strength was not obtained.
It can be used only at a molding pressure of g / cm ² or more. In Comparative Example 2, the particle size is smaller than that in Comparative Example 1, so that voids are small and high strength is obtained. However, since the Al ion crosslinked polymer was damaged during the pulverization, the strength was lower than that of the example.

That is, according to the Al ion-crosslinked polymer fine powder obtained by the production method of the example, it is apparent that a compact and high-strength compact is formed even when compacted at a low pressure.

[0023]

According to the production method of the present invention, it is possible to easily and reliably produce an extremely fine metal ion-crosslinked polymer fine powder having a substantially spherical shape. There is no risk that the polymer structure will be damaged.
Therefore, by using the metal ion-crosslinked polymer fine powder obtained by the production method of the present invention, it is possible to obtain a dense compact even if the pressure during the heat compression molding is reduced, and to improve the physical properties of the compact. And
Man-hours can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic structural explanatory view of a manufacturing apparatus used in one embodiment of the present invention.

FIG. 2 is a graph showing the relationship between the pressure at the time of molding and the three-point bending strength of the obtained molded body in Examples and Comparative Examples.

[Explanation of symbols]

1: reaction tube 2: pressurized air
3: First aqueous solution 4: Second aqueous solution 10: Injection nozzle 1
1: injection nozzle

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-259818 (JP, A) JP-A-51-31756 (JP, A) JP-A-48-95444 (JP, A) JP-A-62-259444 74905 (JP, A) JP-A-62-74906 (JP, A) JP-A-3-59006 (JP, A) JP-A-1-149805 (JP, A) JP-A-6-57034 (JP, A) JP-A-6-16864 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C08F 8/44 C08J 3/12-3/16 C08J 3/24

Claims (1)

(57) [Claims] 1. A first aqueous solution in which a polymer material capable of reacting with a hydroxide and / or a metal ion of at least one of an alkali metal and an alkaline earth metal is dissolved, and a second aqueous solution in which a metal salt is dissolved. A reaction step of contacting and reacting the first aqueous solution and the second aqueous solution with each other in an atomized state; and a drying step of continuously drying the particulate reaction product obtained in the reaction step. A method for producing a metal ion crosslinked polymer fine powder, comprising: