JP2988166B2 - 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-crosslinkable polymer precipitate obtained by the above-mentioned production method has a property of agglomeration, and is not a powder when dried but a bulk agglomerated from a gel, which is pulverized to 0.1 mm. However, if the size is further reduced, the fluidity at the time of molding is improved, but the pulverization causes considerable damage to the structure of the metal ion crosslinked polymer, which may adversely affect the physical properties of the molded product. .

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 process for producing a metal ion-crosslinked polymer fine powder which solves the above-mentioned problems comprises reacting metal ions in an aqueous solution of a hydroxide of at least one of an alkali metal and an alkaline earth metal. A sol-like ultrafine particle by vibrating the gel-like precipitate of the obtained metal ion-crosslinked polymer by virtue of the precipitation step of reacting the polymer material capable of being crosslinked with metal ions to precipitate the metal-ion-crosslinked polymer; It is characterized by comprising a vibration step of forming a precipitate and a drying step of atomizing and drying the sol-like ultrafine particle precipitate.

Polyacrylic acid is typically used as a polymer material that can be crosslinked by reacting with metal ions.
This polyacrylic acid is 80-100 mol% 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 material, such as polymethacrylic acid, polystyrene carboxylic acid, and polystyrene sulfonic acid, which can be dissolved 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 activates a functional group of a polymer raw material to promote a reaction with a metal ion supplied from a metal salt. , Li, Ca, Ba,
A metal such as Sr is used. Especially basic N
It is preferable to use metals such as a and K. Examples of metal ions that react with and crosslink with the above polymer raw materials include Zn, M
g, Ca, Ba, Sn, Fe, Pb, Cu, Co, Ni
Salts of divalent metals such as Mn, Cr, Al, and La
Metal ions dissociated from salts of valent metals, salts of tetravalent metals such as Ti, Zr, Te, and Ru can be used.

The mixing ratio between the metal ion and the polymer raw material is as follows:
The ratio of the metal ion can be 0.1 to 20 equivalents to 1 equivalent of the carboxyl group of the polymer raw material. In the precipitation step, the polymer raw material and metal ions react in a solution, and a metal ion crosslinked polymer is precipitated and precipitated. It is also preferable that a fibrous or powdery reinforcing material coexist in the solution. By doing so, the reinforcing material is taken in and precipitated simultaneously with the precipitation of the metal ion crosslinked polymer, and the metal ion crosslinked polymer fine powder containing the reinforcing material can be easily produced.

[0010] The precipitation of the metal ion-crosslinked polymer is as follows:
It is aggregated to form a gel, and if dried as it is, only an aggregated coarse aggregate can be obtained. Therefore, in the present invention, a vibrating step of vibrating the obtained precipitate is performed. By this vibration, the gel-like precipitate is loosened to form a sol. In addition, as a vibration condition, a sound wave vibration of about 5 to 10 kHz may be used, but an ultrasonic vibration of about 20 to 50 kHz is preferable.
This is because the sol formation proceeds more quickly than the sound wave excitation and the noise is small.

In the drying step, the obtained sol-like ultrafine particle precipitate is sprayed and dried in a wet state before drying. For example, the precipitate is pumped up by a pump or the like and sprayed into a hot air stream. The precipitate may be sprayed and dried under a reduced-pressure atmosphere, or may be sprayed on a rotating heat drum surface to be dried. In addition, impurities such as by-products and unreacted raw materials during the synthesis of the polymer are sufficiently removed by filtering and washing the gel precipitate prior to the spraying step.

[0012]

According to the method for producing a metal ion-crosslinked polymer fine powder of the present invention, the aggregated gel-like precipitate of the metal ion-crosslinked polymer becomes a sol-like ultrafine particle precipitate by vibration. Then, by spraying and drying it, it is dried while maintaining the state of ultrafine particles, and a very fine metal ion crosslinked polymer fine powder is obtained.

[0013]

The present invention will be specifically described below with reference to examples. Example (1) Precipitation Step In a polyethylene beaker, 3400 cc of an aqueous solution containing 31.4 g of polyacrylic acid having a number average molecular weight of 250,000, and N
1100 cc of an aqueous solution containing 20 g of aOH is charged and sufficiently stirred. Then, while continuing stirring, AlCl ₃ 60
2600 cc of an aqueous solution containing g is gradually dropped, and polyacrylic acid is reacted with AlCl ₃ . Stirring is continued for about 10 minutes even after the entire amount has been dropped, to converge the reaction. As a result, the reaction product precipitates, and when the stirring is stopped, an Al ion crosslinked product of polyacrylic acid is obtained as a gel precipitate. The gel was washed with water and filtered to remove by-products and unreacted substances.

[0014] The mixing ratio of each raw material used in the above synthesis, polyacrylic acid 0.44 eq, NaOH0.52 equivalents are AlCl ₃ 1.36 eq, excess of a NaOH and AlCl ₃ to polyacrylic acid Was blended in. (2) Vibration Step The obtained undried gel-like precipitate was put into 2000 cc of water, and placed in an ultrasonic vibration tank 5 along with the beaker 4 as shown in FIG. Excited. Then, the gel precipitate became a sol as an aggregate of ultrafine particles. (3) Drying Step As shown in FIG. 1, the sol-like ultrafine particle precipitate 40 in the beaker 4 in which the ultrasonic vibration is continuously performed is pumped up using the pump 3 and is sent from the spray nozzle 30 to the drying device. Sprayed.

The drying apparatus comprises a drying chamber 1 having a heater 10 on the wall surface as shown in FIG. 1, and a supply path 2 opening on the upper side wall of the drying chamber 1. Is provided with a breathable collection bag 11. Hot air of 250 ° C. is supplied to the supply path 2 from one end toward the drying chamber 1. The supply path 2 has a reduced diameter portion 20 at an intermediate portion, and an injection nozzle 30 connected to the pump 3 is connected to the reduced diameter portion 20 so as to communicate therewith. A heater 21 is also provided downstream of the reduced diameter portion 20 of the supply path 2. Pump 3
A heater 31 is also provided in a flow path from the nozzle to the injection nozzle 30.

In the above-mentioned drying apparatus, the temperature inside the drying chamber 1 and the downstream side of the reduced diameter portion 20 of the supply path 2 is set to 200 ° C.
It is preheated to 0 ° C. Then, the blowing speed of the hot air was set to 60 m / sec in the vicinity of the injection nozzle 30, and the precipitate 40 was sprayed into fine particles from the injection nozzle 30 at a flow rate of 10 cc / sec.

The precipitate sprayed in the form of fine particles has a reduced diameter portion 2
From 0, it is blown out to the supply path 2 together with hot air, and is supplied to the drying chamber 1 in the form of mist. The precipitate which was dried in the drying chamber 1 and turned into fine powder was collected in the collection bag 11. As a result, 40 g of Al ion crosslinked polymer fine powder was obtained.
As a result of microscopic observation, the average particle size of the obtained fine powder was 3 μm
And very fine particles.

After the fine powder is directly produced from the synthetic product, the drying step may be carried out by repeating filtration and washing with water. Then 1
A mold having a cavity of 0 × 80 × 60 mm in depth was prepared, and 4 g of the obtained fine powder was charged. Then, it was heated and held at 250 ° C. while reducing the pressure in the vacuum chamber,
Vacuum heat compression molding was performed at 7000 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 obtained by performing a three-point bending test 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) A gel precipitate obtained in the same manner as in the example was filtered as it was, washed repeatedly with pure water and washed, and then heated to 150 ° C. in a hot air drying oven and dried. did.

The obtained Al ion crosslinked polymer is strongly agglomerated and cannot be said to be a powder. Then, it was pulverized with a mortar to obtain a powder having an average particle size of about 300 μm. A molded body (sample Nos. A to A) 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
(Examples Nos. K to C) 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.
In addition, the molded article formed in Comparative Example 2 shows better results than Comparative Example 1, and it can be seen that the same compactness as in the example can be obtained by molding at a pressure of 5000 kg / cm ² or more.

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 still 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 clear that a compact and high-strength compact is formed even when compacted at a low pressure. This is the effect obtained by the two effects of the small diameter and the intactness of the polymer structure.

[0023]

According to the production method of the present invention, extremely fine metal ion-crosslinked polymer fine powder can be produced easily and reliably. 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 vibration device and a drying device used in one embodiment of the present invention.

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

[Explanation of symbols]

1: Drying room 2: Supply path 3: Pump
5: Ultrasonic vibration tank

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-259818 (JP, A) JP-A-51-31756 (JP, A) JP-A-62-74905 (JP, A) JP-A 62-259905 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) Japanese Patent Publication No. 27-1138 (JP, B1) (58) Field surveyed (Int. Cl. ⁶ , DB name) C08F 8/44 C08J 3/12-8/16 C08J 3/24

Claims (1)

(57) [Claims] 1. A crosslinkable polymer material reacts with metal ions in an aqueous solution of a hydroxide of at least one of an alkali metal and an alkaline earth metal to react with the metal ions to precipitate a metal ion crosslinked polymer. A sol-like ultrafine particle precipitate by vibrating the gel-like precipitate of the obtained metal ion-crosslinkable polymer; and atomizing and drying the sol-like ultrafine particle precipitate. A method for producing a metal ion crosslinked polymer fine powder, comprising: a drying step.