JP2015174871A - Method for producing thermoplastic polymer fine particle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing thermoplastic polymer fine particles at high yield, in which method a particle size distribution of the thermoplastic polymer fine particles is made uniform by stabilizing a polymer emulsion which was unstable up to now.SOLUTION: The method for producing thermoplastic polymer fine particles comprises: a first step of dissolving a thermoplastic polymer in an organic solvent to obtain a polymer solution; a second step of adding a part of surfactant-incorporated water to the polymer solution while agitating the polymer solution by using agitation power Pso that a drop water-in-oil type emulsion becomes a drop oil-in-water type emulsion; a third step of adding the whole of the surfactant-incorporated water and reducing the agitation power of the drop oil-in-water type emulsion to 50% or lower; and a fourth step of adding the drop oil-in-water type emulsion to a poor solvent to precipitate thermoplastic polymer fine particles and separating/recovering the precipitated thermoplastic polymer fine particles.

Description

  The present invention relates to a method for producing thermoplastic polymer fine particles having a uniform particle size distribution with high yield.

  The thermoplastic polymer fine particles are fine particles made of various thermoplastic polymers, and generally have a diameter ranging from several tens of nanometers to several hundreds of micrometers.

  And, unlike polymer molded products such as films, fibers, injection molded products, and extrusion molded products, thermoplastic polymer fine particles have a large specific surface area, and by utilizing the structure of the fine particles, It is used for the purpose of improvement. Specific main applications include cosmetic modifiers, toner additives, rheology modifiers such as paints, medical diagnostic inspection agents, additives for molded products such as automotive materials and building materials. . In particular, in recent years, it has come to be used as a raw material for rapid prototyping and rapid manufacturing, which is a technique for making a custom-made molded product in combination with a laser processing technique by utilizing the fine particle structure of polymer fine particles.

  Conventional production methods of thermoplastic polymer fine particles are roughly classified into build-up processes such as emulsion polymerization, and top-down processes such as mechanical pulverization, melt-kneading, dissolution precipitation, and emulsion-precipitation. be able to.

  As a typical build-up process, a radical polymerization method of vinyl polymer such as emulsion polymerization can be mentioned. Such radical polymerization has been widely used as a method for producing colloidal particles for a long time, and it is possible to produce particles of several tens to several μm. Polymer fine particles produced by the radical polymerization method have been studied for a long time in applications such as modifiers for ABS resins, spacer materials for liquid crystal displays, and emulsion paints. is there.

  However, there has been a problem that polymers studied by these techniques are limited to vinyl polymers made from acrylic, styrene, or the like.

  A method that is easily used as a typical top-down process is a mechanical pulverization method. In this method, polymer pellets are frozen with liquid nitrogen and mechanically pulverized.

  However, this technique may require freezing the polymer, which is energy cost and the resulting pulverized product generally has an irregular shape.

  On the other hand, melt kneading methods (for example, see Patent Document 1), dissolution precipitation methods (for example, see Patent Document 2), emulsion methods, and the like have been developed as methods for obtaining spherical polymer fine particles.

  However, the melt-kneading method described in Patent Document 1 uses an extruder to melt and knead a polymer component incompatible with a polymer at a high temperature to form a sea-island structure, dissolve the sea component, Although it is a production method for taking out the internal particles, this melt-kneading method requires a high temperature, the particle size distribution of the obtained fine particles is large, and kneading is performed under conditions of high viscosity. There were problems such as difficulty in miniaturizing the diameter.

  In addition, the dissolution precipitation method described in Patent Document 2 is a method in which a polymer is heated to high temperature in the presence of a solvent to form a polymer solution and cooled to obtain fine particles. In many cases, the productivity is inferior because it is limited to the solubility of the polymer in the solvent.

  Furthermore, after dissolving a polymer or a thermosetting polymer precursor in an organic solvent or melting the polymer, an emulsion is formed with the solution or melt and water, and then the polymer particles are kept in shape. Emulsion methods have been known for a long time, and as this method, a polyurethane resin is dissolved in an organic solvent to form an emulsion in water (for example, see Patent Document 3), or amorphous nylon is dissolved in an organic solvent. A method of adding an emulsifier and making an emulsion (for example, see Patent Document 4) is known.

  However, in order to take out the emulsified particles, a step of precipitating the particles is necessary. A typical precipitating step is a method of volatilizing the solvent and precipitating the particles due to a difference in solubility, or an emulsion solution ( Hereinafter, there is a method of adding an emulsion). The methods described in Patent Documents 3 and 4 are both methods for volatilizing and precipitating the solvent in the emulsion, and in this method, the particles are easily fused together, and spherical particles are difficult to obtain. In addition to the problems, there was a problem that continuous production was not possible and productivity was poor. In addition, in the latter method, since the emulsion must be gradually added to the poor solvent, there is a waiting time for the emulsion, and if it is an unstable emulsion, the particle size distribution deteriorates during the waiting. Furthermore, there is a problem that the dissolved polymer is precipitated.

JP 2005-162840 A JP-A-2005-054153 JP-A-63-75038 Japanese Patent Publication No. 7-47643

  An object of the present invention is to provide a method for producing thermoplastic polymer fine particles having a uniform particle size distribution in a high yield by stabilizing a polymer emulsion which has been unstable in the past.

In order to achieve the above object, according to the present invention, there is provided a method for producing thermoplastic polymer fine particles characterized by sequentially performing the following first to fourth steps.
(A) a first step in which a thermoplastic polymer is dissolved in an organic solvent to obtain a polymer solution;
(B) a second step of adding water containing a surfactant to the polymer solution (a) with stirring at a stirring power P ₀ and emulsifying from the water-in-oil emulsion to the oil-in-water emulsion,
(C) The third step of dropping the stirring power of the emulsified liquid (b) to 50% or less after adding all of the water containing the surfactant.
(D) A fourth step in which the emulsion (c) is added to a poor solvent to precipitate polymer particles, and then the thermoplastic polymer particles are separated and recovered.

In the method for producing the thermoplastic polymer fine particles of the present invention,
The thermoplastic polymer in the first step is amorphous nylon;
The boiling point of the organic solvent in the first step is less than 100 ° C. and is hardly soluble or insoluble in water,
The preferable conditions are that the surfactant in the second and third steps is polyvinyl alcohol, and that the poor solvent in the fourth step is water or water containing a surfactant. .

According to the present invention, as described below, by devising the stirring power P ₀ when adding water containing a surfactant to a polymer solution, a previously unstable polymer emulsion can be stabilized. Therefore, thermoplastic polymer fine particles having a uniform particle size distribution can be produced with high yield.

  The thermoplastic polymer applied to the first step of the present invention is water-insoluble and has a glass transition temperature (Tg) of at least 30 ° C. of the thermoplastic polymer as the main component and is soluble in an organic solvent described later. Specific examples include polysulfone resins, polyamide resins, polyarylate resins, styrene resins, vinyl resins, polyester resins, cellulose derivatives, polyacetal resins, polycarbonate resins and polyphenylene oxides. It is not limited. These polymers may be used alone or in admixture of two or more. If the Tg of the main component polymer is lower than 30 ° C., the polymer fine particles finally obtained may cause fusion. Here, the main component is a polymer having a most heavy component when the polymer is a mixture of two or more kinds.

  In particular, among these thermoplastic polymers, at least one selected from an aromatic polysulfone resin, an amorphous polyamide resin, and an amorphous polyarylate resin is preferable from the viewpoint of excellent heat resistance and toughness.

  The aromatic polysulfone-based resin is a resin having a diallylsulfone group in the molecule as a structural unit, and specific examples include polysulfone, polyethersulfone, and polyallylsulfone, but are not limited thereto. Absent. These can be synthesized as needed or those commercially available can be used. As commercial products, Udel (Union Carbide), Victrex (ICC) Astrel (Carborundum), Radel (Union Carbide) and the like are known.

  As an amorphous polyamide resin, a polyamide that gives a transparent molded product regardless of thickness under normal melt molding conditions, and that the molded product does not cause devitrification due to post-crystallization even during heat treatment and hydrothermal treatment. In order to satisfy such properties, it is a resin, and isophthalic acid, terephthalic acid, metaxylylenediamine, 1,3-bisaminomethylcyclohexane, isophoronediamine, 2,2,4- or 2,4,4-trimethyl At least one component selected from hexamethylenediamine, 4,4′-diaminodicyclohexylmethane, 4,4′-diamino-3,3′-dimethyldicyclohexylmethane, and 4,4′-diaminodicyclohexylpropane is used as a constituent component. It is preferable. These can be synthesized according to the required properties, or those commercially available as amorphous nylon can be used. As commercially available products, TROGAMID-T (Dymit Nobel), ZYTEL-330 (Du Pont), GRILAMID-TR55 (Emser Chemie) and the like are known.

  The amorphous polyarylate resin is usually obtained by polycondensation of a divalent phenol and an aromatic dicarboxylic acid. Examples of the divalent phenol include bisphenol A, bisphenol F, and alkyl-substituted products thereof. On the other hand, examples of the aromatic dicarboxylic acid include, but are not limited to, terephthalic acid and isophthalic acid. These can be synthesized according to the required properties, or commercially available ones can be used. As commercially available products, U polymer (Unitika), Adel (UCC), Arilev (Solvay), APE (Bayer), Durel (Celanese), Arilon (DuPont), NAP resin (Kaneka) and the like are known.

  The organic solvent used in the first step of the present invention may be any organic solvent as long as its main component is substantially insoluble or hardly soluble in water and has a boiling point of less than 100 ° C. Organic solvents that satisfy these characteristics include hydrocarbons such as pentane, hexane, heptane, benzene, cyclohexane, petroleum ether, methylene chloride, chloroform, dichloroethane, dichloroethylene, 1,1,1-trichloroethane, trichloroethylene, carbon tetrachloride. Halogenated hydrocarbons such as diethyl ether, ethers such as diethyl ether, esters such as ethyl acetate, ketones such as methyl ethyl ketone, and the like may be used as a mixture of two or more. In addition, in order to further improve the solubility of the thermoplastic polymer in the organic solvent, it is possible to use a small amount of an organic solvent miscible with water. In the method of the present invention, if 60% by weight or more of the organic solvent to be used is insoluble in water, the operation can be performed without any problem.

  The organic solvent to be used is appropriately selected depending on the type of polymer, and the temperature during emulsification is not particularly limited as long as it is not higher than the boiling point of water, but is preferably not higher than the boiling point of the main organic solvent.

  In the method of the present invention, examples of the surfactant used in the second and third steps include polyvinyl alcohol, carboxymethylcellulose, hydroxypropylcellulose, hydroxyethylcellulose, modified starch, polyvinylpyrrolidone, gelatin, gum arabic, and casein. . The water containing the surfactant is continuously or intermittently added to the polymer solution stirred with a predetermined stirring power. The amount of water finally added is preferably 50% by weight or more based on the polymer solution. A feature of the present invention is that water is added to a polymer solution having a relatively high viscosity. First, a water-in-oil emulsion is formed, and then the phase is changed to an oil-in-water emulsion as the amount of added water increases. Thus, a solvent-containing polymer emulsion having a predetermined particle size can be obtained. The obtained emulsion is added to a poor solvent while reducing the pressure as necessary to precipitate particles.

  The addition rate (g / h) at this time is preferably 5 (1 / h) or less, more preferably 1 (1 / h) or less, with respect to the poor solvent amount (g). If it exceeds 5 (1 / h), the mass or string of substances increases, and it is difficult to obtain spherical particles.

  For this reason, the emulsion has a waiting time of 1 to 2 hours until the particles are precipitated, and if the emulsion formed is unstable, the polymer dissolved during this time will precipitate and the yield will deteriorate significantly. There is also. In the present invention, it is important to reduce the stirring power of the emulsion during this standby, and preferably, the emulsion can be stably present by reducing the stirring power to 50% or less to obtain spherical particles with high yield. It can be done.

The stirring power Pv (kw / m ³ ) in the present invention refers to the stirring power per unit volume, and is obtained from the required power (P) and the liquid volume (V) by the following formula (1). Value. The required power (P) is obtained from the required power for stirring (Np), the liquid density ρ (kg / m ³ ), the rotational speed n (rps), and the stirring blade diameter d (m) as in the following formula (2).
Pv = P / V (1)
P = Np · ρ · n ³ · d ⁵ (2)

  Moreover, the power required for stirring (Np) here can be obtained by the following formula (Ref. 6th edition, Chemical Engineering Handbook, p430-431, Chemical Engineering Society, edited by Maruzen Co., Ltd.).

  In order to precipitate polymer fine particles, the poor solvent used in the fourth step of the present invention is a solvent having low solubility of the polymer used, and is an aromatic hydrocarbon solvent, an aliphatic hydrocarbon solvent, an alcohol solvent. And a solvent containing at least one selected from water. Among these, water is preferable from the viewpoint of efficiently precipitating the particles, and a surfactant may be contained in the water in order to improve the dispersibility of the particles.

  In producing the thermoplastic polymer fine particles of the present invention, an appropriate amount of an uncured body of a thermosetting resin that is cured by external energy such as heat or light and at least partially forms a three-dimensional cured product is dissolved in the polymer solution, A spherical polymer fine powder having improved heat resistance, chemical resistance, water absorption rate, strength, and the like can be obtained by forming a hardened body by performing a curing treatment such as heating after the spherical fine powder is formed. Thermosetting resins include epoxy resins containing epoxy curing agents, maleimide resins, acetylene-terminated resins, nadic acid-terminated resins, cyanate ester-terminated resins, vinyl-terminated resins, allyl-terminated resins. And so on. In particular, an epoxy resin containing an epoxy curing agent is preferably used. The amount of the thermosetting resin used is preferably 150 parts by weight or less, more preferably 50 parts by weight or less with respect to 100 parts by weight of the thermoplastic polymer. If the thermosetting resin exceeds 150 parts by weight, the original properties of the thermoplastic polymer may be deteriorated, which is not preferable.

  In producing the thermoplastic polymer fine particles of the present invention, pigments, dyes, antioxidants, lubricants, antistatic agents, plasticizers and the like may be further dispersed and dissolved in the polymer solution. It is also possible to improve the dispersibility and fluidity by adsorbing or spraying ultrafine powder such as silica or alumina on the surface of the fine powder in the emulsion and / or dry state.

  Examples will be given below, but the present invention is not limited thereto.

[Example 1]
34.4 g of amorphous nylon (trade name “GRILAMID-TR55”, manufactured by EMSER WERKE) was dissolved in a mixed solvent of 205 g of chloroform and 88 g of methanol to obtain an amorphous nylon solution. While the temperature of the solution was adjusted to 34 ° C. and stirred at a stirring power of 2.7 kw / m ³ , 362 g of a 7% polyvinyl alcohol aqueous solution was continuously added over 45 minutes. From the initial water-in-oil emulsion, Finally, an oil-in-water emulsion was obtained. Next, the emulsion was cooled to 20 ° C., the stirring power was lowered to 0.1 kw / m ^3, and the amount of polymer precipitated after 1 hour was measured to be 0.8 g. The polymer deposited here is in the form of a lump and cannot be formed into fine particles, so that the amount of polymer deposited here is preferably small. The emulsion was continuously added to water at 1 (1 / h) to obtain spherical amorphous nylon particles having a median diameter of 11 μm.

[Example 2]
In the same manner as in Example 1, after adding the whole amount of the polyvinyl alcohol aqueous solution, the stirring power of the emulsion was dropped to 0.8 kw / m ³ and the amount of polymer precipitated after 1 hour was measured. It was. The emulsion was continuously added to water at 1 (1 / h) to obtain spherical amorphous nylon particles having a median diameter of 16 μm.

[Comparative Example 1]
In the same manner as in Example 1, after adding the whole amount of the polyvinyl alcohol aqueous solution, the stirring power of the emulsion was dropped to 1.4 kw / m ^3, and the amount of polymer precipitated after 1 hour was measured to be 2.0 g. It was. The emulsion was continuously added to water at 1 (1 / h) to obtain spherical amorphous nylon particles having a median diameter of 16 μm.

[Comparative Example 2]
In the same manner as in Example 1, the total amount of the polyvinyl alcohol aqueous solution was added, the stirring power of the emulsion was dropped to 2.1 kw / m ^3, and the amount of polymer precipitated after 1 hour was measured to be 5.1 g. It was. The emulsion was continuously added to water at 1 (1 / h) to obtain spherical amorphous nylon particles having a median diameter of 15 μm.

[Comparative Example 3]
In the same manner as in Example 1, after adding the whole amount of the polyvinyl alcohol aqueous solution, the stirring power of the emulsion was kept at 2.7 kw / m ³ , and the amount of polymer precipitated after 1 hour was measured to be 7.8 g. there were. The emulsion was continuously added to water at 1 (1 / h) to obtain spherical amorphous nylon particles having a median diameter of 14 μm.

  The experimental results of Example 1-2 and Comparative Example 1-3 are summarized in Table 1.

As is clear from the results in Table 1, according to Example 1-2, it was unstable in the prior art by devising the stirring power P ₀ when adding water containing a surfactant to the polymer solution. Since the polymer emulsion was stabilized, thermoplastic polymer fine particles having a uniform particle size distribution can be produced with high yield.

  On the other hand, in the case of Comparative Example 1-3 in which the stirring power of the emulsion (b) is not dropped to 50% or less after the total amount of water containing a surfactant is added, the polymer emulsion cannot be stabilized. The amount of polymer precipitated before being added to the poor solvent is increased, and the yield of the thermoplastic polymer fine particles is remarkably lowered.

  Since the thermoplastic polymer fine particles obtained by the present invention have a good yield and a uniform particle size distribution, they can be widely used for applications intended to modify and improve various materials.

Claims (5)

The manufacturing method of the thermoplastic polymer microparticle characterized by performing the following 1st process-4th process sequentially.
(A) a first step in which a thermoplastic polymer is dissolved in an organic solvent to obtain a polymer solution;
(B) a second step of adding water containing a surfactant to the polymer solution (a) with stirring at a stirring power P ₀ and emulsifying from the water-in-oil emulsion to the oil-in-water emulsion,
(C) The third step of dropping the stirring power of the emulsified liquid (b) to 50% or less after adding all of the water containing the surfactant.
(D) A fourth step in which the emulsion (c) is added to a poor solvent to precipitate polymer particles, and then the thermoplastic polymer particles are separated and recovered. The method for producing polymer fine particles according to claim 1, wherein the thermoplastic polymer in the first step is amorphous nylon. The method for producing fine polymer particles according to claim 1 or 2, wherein the boiling point of the organic solvent in the first step is less than 100 ° C and is hardly soluble or insoluble in water. The method for producing polymer fine particles according to any one of claims 1 to 3, wherein the surfactant in the second step and the third step is polyvinyl alcohol. The method for producing polymer fine particles according to any one of claims 1 to 4, wherein the poor solvent in the fourth step is water or water containing a surfactant.