JPH0717723B2 - Process for producing cured resin spherical fine particles having a uniform particle size - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention is a uniform particle made of a melamine or benzoguanamine-based amino resin, which is useful in various applications such as a slipperiness improving agent for plastic films and spacers for liquid crystal display devices. The present invention relates to a method for producing spherical fine particles of a cured resin having a diameter.

(Prior Art) Conventionally, various methods have been proposed as a method for producing spherical fine particles having a uniform particle diameter. For example, JP-A-59-
As disclosed in No. 59741 of thermoplastic resin fine particles obtained by emulsion polymerization of a specific vinyl monomer, a method for producing spherical fine particles by an emulsion polymerization method is known. However, in the emulsion polymerization method, it is not possible to obtain tough spherical fine particles having excellent heat resistance and solvent resistance even if the crosslinkable monomer is partially used.

Various attempts have also been made to obtain spherical fine particles of amino resin, which is a thermosetting resin. For example, a method of advancing the condensation in the presence of a water-soluble acid catalyst to a dilute aqueous solution of an N-methylol derivative of melamine, and adding a large amount of water at the moment when the transparent aqueous solution starts to become cloudy (Japanese Patent Publication No. 32-5743), Melamine-
A method (JP-B-43-29159) in which an aqueous solution of formaldehyde is reacted in the presence of a protective colloid at a pH value of 6.0 to 8.0 until a solid phase is formed has been proposed.

(Problems to be Solved by the Invention) In the emulsion polymerization method as described above, spherical fine particles having a uniform particle diameter can be relatively easily obtained, but heat resistance and solvent resistance are insufficient, and strength is limited. In particular, it is not suitable for use as a modifier or pigment used in plastics or kneaded with a polar solvent.

Further, it is practically difficult to obtain spherical fine particles having a uniform particle diameter by the method for obtaining spherical fine particles of amino resin described above. For example, in the method of Japanese Examined Patent Publication (Kokoku) No. 32-5743, since the condensation of the melamine resin is prevented by adding a large amount of water to prevent the coarsening of the spherical fine particles, the obtained spherical fine particles have poor heat resistance and solvent resistance. Further, it is difficult to take out the powder as powder while completely preventing the coarsening of the fine particles, and spherical fine particles having a substantially uniform particle size cannot be obtained. Further, in the method of Japanese Patent Publication No. 43-29159, the reaction is carried out at a high temperature until the precipitate of the melamine resin is formed, but since the reaction is not carried out in a stable suspension state, the spherical fine particles produced during the reaction Causes agglomeration and fusion, and it is very difficult to obtain spherical fine particles having a practically uniform particle size, and in fact, only powder having a large bulk density can be obtained.

The present invention solves the above-mentioned problems of the prior art. Accordingly, an object of the present invention is to provide cured resin spherical fine particles having excellent heat resistance and solvent resistance and having a uniform particle size as a powder that can be used for various purposes.

(Means for Solving the Problems) The present inventors have conducted research to obtain spherical fine particles via a stable emulsion of a cured resin having a uniform particle size,
The present invention is based on the finding that a water-affinity precondensate of melamine and / or benzoguanamine and formaldehyde undergoes a specific interfacial chemical behavior with a specific sulfonic acid in an aqueous liquid to form a stable emulsion. Is completed.

That is, the present invention condenses a water-affinity initial condensate of melamine and / or benzoguanamine and formaldehyde in an aqueous liquid containing a surfactant in the presence of an alkylbenzenesulfonic acid having an alkyl group having 10 to 18 carbon atoms. The present invention relates to a method for producing spherical fine particles of a cured resin having a uniform particle diameter, which comprises curing and forming an emulsion of a cured resin, and separating the cured resin from the emulsion and drying.

The water-affinity initial condensate of melamine and / or benzoguanamine and formaldehyde used in the present invention is a water-soluble or water-dispersible product obtained by reacting melamine or benzoguanamine or a mixture thereof with formaldehyde according to a conventional method. It is a resinous material. The degree of water affinity is generally measured by adding water to the initial condensate at 15 ° C and then adding the amount of water to the initial condensate in terms of weight% (hereinafter referred to as water miscibility) with respect to the initial condensate. Will be
The water miscibility of the initial condensate suitable for the present invention is 100% or more. An initial condensate with a water miscibility of less than 100% can be obtained in the final stage, even if dispersed in an aqueous solution containing a surfactant, only a non-uniform emulsion with a relatively large particle size is formed. Spherical particles are less likely to have a uniform particle size. Also,
As the formaldehyde, any formaldehyde, such as formalin, trioxane, and paraformaldehyde, can be used.

The surfactant used in the present invention is not particularly limited, and all surfactants such as anionic surfactant, cationic surfactant, nonionic surfactant and amphoteric surfactant can be used, but especially Anionic or nonionic surfactants or mixtures thereof are preferred. Examples of the anionic surfactant include alkali metal alkyl sulphates such as sodium dodecyl sulphate and potassium dodecyl sulphate; ammonium alkyl sulphates such as ammonium dodecyl sulphate; sodium dodecyl polyglycol ether sulphate; sodium sulpholysino Alkyl sulfonates such as alkali metal salts of sulfonated paraffins and ammonium salts of sulfonated paraffins; fatty acid salts such as sodium laurate, triethanolamine oleate, triethanolamine abietate; sodium dodecylbenzene sulfonate; Alkyl aryl sulfonates such as alkali phenol hydroxyethylene alkali metal sulphates; high alkyl naphthales Sulfonates; naphthalene sulfonic acid formalin condensates; dialkyl sulfosuccinates; polyoxyethylene alkyl sulphate salts; polyoxyethylene alkyl aryl sulphate salts and the like can be used, and nonionic surfactants include polyoxyethylene alkyl Ethers; polyoxyethylene alkylaryl ethers; sorbitan fatty acid esters; polyoxyethylene sorbitan fatty acid esters; fatty acid monoglycerides such as glycerol monolaurate; polyoxyethyleneoxypropylene copolymers; ethylene oxide and fatty amines, amides or acids A condensation product with and the like can be used.

The amount of the surfactant used is not particularly limited, but is preferably in the range of 0.01 to 10 parts by weight with respect to 100 parts by weight of the initial condensate. If the amount is less than 0.01 parts by weight, a stable emulsion of the cured resin may not be obtained, and if the amount is more than 10 parts by weight, the emulsion may cause unnecessary foaming or the final spherical fine particles may be obtained. The physical properties of may be adversely affected.

The alkylbenzene sulfonic acid having an alkyl group having 10 to 18 carbon atoms used in the present invention exerts a unique surface-active ability in the aqueous liquid of the initial condensation product to form a stable emulsion of a cured resin. It is an essential component for the purpose of using, for example, one or more selected from decylbenzenesulfonic acid, dodecylbenzenesulfonic acid, tetradecylbenzenesulfonic acid, hexadecylbenzenesulfonic acid, octadecylbenzenesulfonic acid, etc. can do.

The amount of alkylbenzene sulfonic acid used is 10
0.1 to 20 parts by weight relative to 0 parts by weight, more preferably 0.
It is in the range of 5 to 10% by weight. If the amount is less than 0.1 part by weight, the condensation curing takes a long time, and a stable emulsion of the cured resin cannot be obtained, and only aggregated and coarse particles are finally obtained. Further, when the amount is more than 20 parts by weight, the alkylbenzene sulfonic acid is excessively distributed in the resin particles in the produced emulsion, and as a result, the resin particles are plasticized and agglomerate or melt between the particles during condensation curing. Adhesion tends to occur, and spherical fine particles having a uniform particle size cannot be finally obtained.

To condense and cure the water-affinity precondensate in the present invention in the present invention, the surfactant and alkylbenzenesulfonic acid are added to an aqueous solution of the precondensate or a milky white dispersion in which the precondensate is finely dispersed in water. Then, the temperature may be maintained from a low temperature of 0 ° C. to a high temperature of 100 ° C. or higher under pressure with stirring. The method of adding the surfactant and the alkylbenzene sulfonic acid is not particularly limited, and for example, a method of previously mixing the surfactant and the alkylbenzene sulfonic acid in the aqueous liquid and then adding the initial condensate to the aqueous liquid may be used. Alternatively, a method may be used in which the initial condensate is mixed in the aqueous liquid and then the surfactant or the alkylbenzene sulfonic acid is added. Further, the concentration of the initial condensate in the aqueous liquid is preferably 5 to 20% by weight in consideration of the ease of handling the obtained emulsion and the economical efficiency of the operation.

Condensation curing is generally completed by raising the temperature to 90 ° C. or higher and holding it for a certain period of time, but curing at a high temperature is not always necessary, and even at a low temperature for a short time, an emulsion It is sufficient that the resin particles therein are cured to the extent that they do not swell with methanol or acetone.

In the emulsion of the cured resin obtained as described above, spherical fine particles having a uniform particle size are present in a very stable manner without aggregation. A known method may be used for separating and drying the cured resin from the emulsion of the cured resin, for example, various separation methods such as natural sedimentation or centrifugal sedimentation and separation by decantation, separation by filtration, natural drying, and reduced pressure. Various drying methods such as drying and hot air drying can be freely adopted. Further, prior to the separation, a flocculant such as aluminum sulfate may be added to accelerate the separation.

The cured resin obtained by drying can be easily made into fine particles having the same spherical and uniform particle diameter as the cured resin particles in the emulsion with an extremely light force such as ball mol.

(Function) In the present invention, the reason why a stable emulsion of a cured resin having a uniform particle size of melamine and / or benzoguanamine and formaldehyde can be obtained by using a surfactant and a specific alkylbenzene sulfonic acid is as follows. Not clear. However, if condensation curing is performed using another acid instead of alkylbenzene sulfonic acid, considering that the emulsion that has just formed immediately aggregates or the cured resin particles in the emulsion become coarse. It is clear that the alkylbenzene sulfonic acid acts interfacially with the precondensate to keep the cured resin particles in the resulting emulsion stable.

As a result of the presence of a part of the alkylbenzene sulfonic acid oriented near the interface of the cured resin particles in the emulsion, the properties of the interface of the cured resin particles are melamine- or benzoguanamine-based amino resin originally emulsified. It is speculated that it is because the surfactant used in the present invention is changed to a property that is stable and easily emulsified due to the difficult property. But,
For this reason, the present invention is not limited at all, but the synergistic effect of the surfactant used in the present invention and the stabilization of the cured resin particles of the specific alkylbenzene sulfonic acid in the emulsion is surprising. Is.

(Effects of the Invention) According to the method of the present invention, curing having a uniform particle diameter can be achieved by adjusting the condensation degree of the initial condensate, that is, the degree of water affinity, and the amount of the surfactant or dodecylbenzenesulfonic acid used. The resin spherical microparticles can be prepared with any particle size in the range of 0.1 to 20 microns. Further, the effect resin spherical fine particles obtained by the method of the present invention, heat resistance originally possessed by melamine or benzoguanamine-based amino resin,
In addition to having excellent properties such as water resistance and solvent resistance, it has a uniform spherical shape and is extremely excellent in dispersibility in various media such as water, organic solvents, and plastics. Therefore,
The cured resin spherical fine particles obtained by the method of the present invention are various modifiers such as a slip film improving agent for plastic film sheets, an anti-blocking agent, a matte finishing agent, a light diffusing agent and a surface hardness improving agent; liquid crystal display. Spacer for device; useful for various purposes such as standard particles for measurement / analysis, and also, before or after each step in the present invention, an acidic dye,
It is also possible to make spherical particles of cured resin colored by adding various dyes such as basic dyes, fluorescent dyes and optical brighteners, and these colored particles are used as pigments for paints, inks and plastic coloring. You can also do it.

Hereinafter, the present invention will be described in more detail with reference to examples.
Unless otherwise specified, parts are parts by weight and% is% by weight.
Represents

Example 1 In a four-necked flask equipped with a stirrer, a reflux condenser and a thermometer, 150 parts of melamine, 290 parts of formalin having a concentration of 37% and a concentration of 28
% Aqueous ammonia solution (1.5 parts) was added to prepare a mixture, and the system pH was adjusted to 8.0. 70 ° C. with stirring this mixture
The temperature was raised to 0 ° C., and the reaction was carried out at the same temperature for 30 minutes to obtain an initial condensate having a water miscibility of ∞%.

Separately, 12 parts of anionic surfactant Neoperex 05 powder (Kao Soap Co., Ltd., sodium dodecylbenzene sulfonate) was dissolved in 2240 parts of water, and the temperature of the surfactant aqueous solution was raised to 90 ° C and stirred. did. The above initial condensate was added to a surfactant aqueous solution under stirring condition, then 75 parts of 10% dodecylbenzenesulfonic acid aqueous solution was added, and the temperature was gradually raised and held at 90 ° C for 2 hours for condensation curing to obtain a cured resin. To obtain an emulsion. This emulsion is light microscope (magnification
When observed at 800 parts), it was found that the particles consisted of spherical fine particles with a particle size of about 0.5μ, and each fine particle was violently in Brownian motion.

This emulsion was cooled to 30 ° C., 200 parts of a 1% aqueous solution of aluminum sulfate was added thereto, and suction filtration was carried out to perform solid-liquid separation. The separated cured resin was dried with a hot air dryer at 160 ° C. for 2 hours to obtain an aggregate of 183 parts of cured resin spherical fine particles. This agglomerate was disaggregated and agglomerated with a ball mill to obtain a powder of white cured resin spherical fine particles. When the powder was examined by a scanning electron microscope, it was confirmed that the powder was uniform spherical fine particles having an average particle diameter of 0.5 μ. The cured resin spherical fine particles are not swollen or dissolved by various organic solvents such as methanol, ethanol, isopropyl alcohol, butanol, ethyl acetate, butyl acetate, methyl cellosolve, ethyl cellosolve, acetone, methyl ethyl ketone, toluene, xylene and dimethylformamide. There was nothing. Furthermore, even if the cured resin spherical fine particles were heated to a temperature of 250 ° C. or higher, no phenomenon such as fusion or melting was observed.

Example 2 Melamine was placed in the same four-necked flask used in Example 1.
75 parts, benzoguanamine 75 parts, concentration 37% formalin 29
The pH of the system was adjusted to 8.0 by adding 0 parts and 1.16 parts of a 10% aqueous sodium carbonate solution as a mixture. While stirring this mixture, the temperature was raised to 85 ° C. and the mixture was reacted at the same temperature for 1.5 hours,
An initial condensate having a water miscibility of 200% was obtained. Separately, 7.5 parts of nonionic surfactant Emulgen 430 (manufactured by Kao Soap Co., Ltd., polyoxyethylene oleyl ether) is dissolved in 2455 parts of water, and the temperature of this surfactant aqueous solution is raised to 50 ° C. and stirred. did. The above-mentioned initial condensate was added to a surfactant aqueous solution under stirring to obtain an emulsion of the initial condensate. To this was added 90 parts of a 5% aqueous solution of dodecylbenzenesulfonic acid, and the mixture was kept at a temperature of 50 to 60 ° C. for 3 hours for condensation curing to obtain an emulsion of cured resin. This emulsion was poured into 3000 parts of cold water and rapidly cooled. This cooled emulsion is then examined under an optical microscope (magnification 600
It was found that the particles consisted of very uniform spherical fine particles having a particle size of about 8 μ. Then, the paste obtained by sedimentation of the cured resin from this emulsion, emulgen 430, 7.5 parts and dodecylbenzenesulfonic acid 4.5 parts ultrasonic dispersion in an aqueous solution obtained by dissolving 2000 parts in water. Dispersed using. The emulsion obtained by dispersion was gradually heated to 90 ° C. with stirring and kept at the same temperature for 1 hour to be completely cured to obtain a sufficiently cured resin suspension. From this emulsion, the hardened resin was centrifuged and separated, and
It was dried with a hot air dryer at 150 ° C. for 4 hours to obtain 120 parts of an aggregate of cured resin spherical fine particles. This agglomerate was disaggregated and agglomerated with a ball mill to obtain a powder of white cured resin spherical fine particles.

The fineness distribution of this powder is measured by a particle size distribution measuring instrument (Coulter Counter Model TA-II, C-1000, Coulter Electronics).
Inc.), average particle size 8.0μ, standard deviation 0.5
It was μ, and it was found that the particle size distribution was very narrow.

Further, when the powder was examined by a scanning electron microscope, it was confirmed that the powder was uniform spherical fine particles having an average particle diameter of 8 μ.

The cured resin spherical fine particles are not swollen or dissolved by various organic solvents such as methanol, ethanol, isopropyl alcohol, butanol, ethyl acetate, butyl acetate, methyl cellosolve, ethyl cellosolve, acetone, methyl ethyl ketone, toluene, xylene and dimethylformamide. It was In addition, 25 particles of cured resin spherical particles
No phenomenon such as fusion or melting was observed even when heated to a temperature of 0 ° C. or higher.

Example 3 250 parts of melamine-formaldehyde initial condensate (Nikaresin S-260 manufactured by Nippon Carbide Co., Ltd.) and Emulgen 930 (polyoxyethylene nonylphenyl ether manufactured by Kao Soap Co., Ltd.) 7.5 which is a nonionic surfactant. Part 234
In addition to 0 parts, the temperature was raised to 70 ° C. with stirring to dissolve.
To the obtained aqueous solution of the initial condensate, 90 parts of a 5% aqueous solution of dodecylbenzenesulfonic acid was added, and the mixture was kept at 70 ° C. for 30 minutes, then gradually heated to 90 ° C. and kept at 90 ° C. for 1 hour for condensation curing.

When an emulsion of the cured resin obtained by condensation curing was observed with an optical microscope, it was found that the emulsion consisted of uniform spherical fine particles having a particle diameter of about 1 μm. This emulsion was cooled to 30 ° C., 200 parts of a 1% aqueous solution of aluminum sulfate was added thereto, and then centrifugal sedimentation was performed to perform solid-liquid separation. The separated cured resin was dried for 3 hours with a hot air dryer at 160 ° C. to obtain an aggregate of 178 parts of cured resin spherical fine particles. This agglomerate was disaggregated and agglomerated with a ball mill to obtain a powder of white cured resin spherical fine particles.

When the powder was examined by a scanning electron microscope, it was confirmed that the powder was uniform spherical fine particles having an average particle diameter of 1.0 μ.

In addition, particle size distribution measuring machine (Coulter counter model TA
-II), average particle size 1.0μ, standard deviation
It was found that the particles were spherical particles of cured resin having a narrow particle size distribution of 0.2μ. The cured resin spherical fine particles are not swollen or dissolved by various organic solvents such as methanol, ethanol, isopropyl alcohol, butanol, ethyl acetate, butyl acetate, methyl cellosolve, ethyl cellosolve, acetone, methyl ethyl ketone, toluene, xylene and dimethylformamide. It was Furthermore, even when the cured resin spherical fine particles were heated to a temperature of 250 ° C. or higher, no phenomenon such as fusion or melting was observed.

Comparative Example 1 Condensation curing was carried out in the same manner as in Example 1 except that 10 parts of 10% sulfuric acid aqueous solution was added instead of 10% dodecylbenzenesulfonic acid aqueous solution in Example 1, but immediately after emulsification of the cured resin. Aggregation of the cured resin occurred, sedimentation and adhesion to the vessel wall and stirrer occurred, and stirring became impossible.

Comparative Example 2 The procedure of Example 2 was repeated except that 60 parts of a 5% aqueous solution of sulfamic acid was added instead of the 5% aqueous solution of dodecylbenzene sulfonic acid, and condensation curing was carried out in the same manner as in Example 2 except that the cured resin was emulsified. Immediately, the cured resin agglomerated, settling out and adhering to the vessel wall and the stirrer, which made stirring impossible.

Comparative Example 3 Condensation curing was carried out in the same manner as in Example 3 except that 90 parts of a 5% aqueous solution of ammonium chloride was added instead of the 5% aqueous solution of dodecylbenzenesulfonic acid in Example 3, but after the emulsion of the cured resin was obtained. Immediately, the cured resin agglomerated, settling out and adhering to the vessel wall and the stirrer, which made stirring impossible.

Example 4 Except for adding 1.5 parts of a fluorescent whitening agent (Kayalite ACR, manufactured by Nippon Kayaku Co., Ltd.) to the initial condensate in Example 1, the procedure was exactly the same as in Example 1 except that fluorescent whiteness was high. A powder of cured resin spherical fine particles was obtained. When examined by a scanning electron microscope, it was confirmed that the particles were uniform spherical particles having an average particle diameter of 0.5 μ.

Claims (1)

[Claims] 1. A water-affinity initial condensate of melamine and / or benzoguanamine and formaldehyde is condensed in an aqueous liquid containing a surfactant in the presence of an alkylbenzenesulfonic acid having an alkyl group having 10 to 18 carbon atoms. Cure
A method for producing spherical fine particles of a cured resin having a uniform particle diameter, which comprises producing an emulsion of a cured resin, separating the cured resin from the emulsion and drying the emulsion.