WO2012067072A1

WO2012067072A1 - Softened thermosetting resin particles

Info

Publication number: WO2012067072A1
Application number: PCT/JP2011/076195
Authority: WO
Inventors: 林　寿人; 将大飛田; 小澤　雅昭
Original assignee: 日産化学工業株式会社
Priority date: 2010-11-15
Filing date: 2011-11-14
Publication date: 2012-05-24
Also published as: JPWO2012067072A1; JP6040773B2

Abstract

[Problem] To provide particles having a hardness which is intermediate between the low hardness of conventional thermoplastic resin particles comprising a styrene resin, an acrylic resin or the like and the high hardness of conventional thermosetting resin particles comprising a melamine resin or the like, namely, particles which combine sufficient hardness and softness. [Solution] Softened thermosetting resin particles obtained by a manufacturing process which includes: a step of reacting a monomer compound that contains at least one bifunctional monomer with an aldehyde compound under basic conditions in the presence of suspended colloidal silica having a mean particle diameter of 5 to 70nm to form an aqueous solution of a water-soluble melamine resin precondensate; and a step of adding an acid catalyst to the aqueous solution to deposit spherical softened thermosetting resin particles.

Description

Thermosetting resin softening particles

The present invention relates to novel resin particles obtained by reacting an amino compound such as acetoguanamine and an aldehyde compound such as formaldehyde, and more particularly to resin particles having a medium hardness.

Conventionally, spherical melamine-based cured resin particles obtained by reacting amino-based compounds with aldehyde-based compounds utilize properties such as hardness, heat resistance, and solvent resistance, and are used for matting agents, light diffusing agents, and polishing. It is used in applications such as a filler, a coating agent for various films, a filler such as polyolefin, polyvinyl chloride, various rubbers, various paints and toners, as well as a rheology control agent and a colorant.
Such spherical melamine-based cured resin particles are known to be produced by various methods. For example, an initial condensate obtained by reacting an amino compound with formaldehyde is emulsified into an emulsion, A method of adding a curing catalyst to cause a curing reaction is disclosed (Patent Documents 1 to 4, etc.).

JP 49-57091 A JP 50-45852 A JP-A-4-211450 JP 2002-327036 A

The conventional method disclosed above has the merit that particles having sufficient hardness can be produced, but on the other hand, depending on the application, the hardness may be too high and damages the target object, equipment or device used. There is a problem that there is a risk of giving.
In addition, since particles made of general-purpose thermoplastic resins such as styrene resin particles, acrylic resin particles, and urethane resin particles that have been used in various fields have low hardness, there is a problem that desired performance cannot be achieved depending on applications. is there.

The present invention has been made in view of the above circumstances, and includes thermoplastic resin particles (low hardness) made of conventional styrene resin, acrylic resin, etc., and thermosetting resin particles (high hardness) made of melamine resin, etc. It is an object of the present invention to provide particles having a medium hardness between, ie, particles having sufficient hardness and flexibility.

As a result of intensive studies to achieve the above object, the present inventors have adopted a bifunctional monomer compound such as acetoguanamine as an essential amino compound used in conventional spherical melamine-based cured resin particles. did. In producing the particles, an aqueous solution of an initial condensate of water-soluble melamine resin is prepared from the monomer compound and the aldehyde compound in an aqueous medium containing colloidal silica, and then cured by adding an acid catalyst. By conducting the (condensation polymerization) reaction, it was found that particles having an appropriate hardness can be obtained, and that the particles become the above-mentioned target particles, and the present invention has been completed.

That is, as a first aspect of the present invention, a monomer compound containing at least one bifunctional monomer and an aldehyde compound are reacted under basic conditions in a suspension of colloidal silica having an average particle diameter of 5 to 70 nm, Thermosetting obtained by a production method comprising a step of forming an aqueous solution of an initial condensate of melamine resin soluble in water and a step of depositing spherical thermosetting resin softening particles by adding an acid catalyst to the aqueous solution It relates to resin softening particles.
As a second aspect, a monomer compound containing at least one bifunctional monomer and at least one polyfunctional monomer and an aldehyde compound under basic conditions in a suspension of colloidal silica having an average particle diameter of 5 to 70 nm. It is obtained by a production method comprising a step of reacting to form an aqueous solution of an initial condensate of melamine resin that is soluble in water, and a step of adding an acid catalyst to the aqueous solution to precipitate spherical thermosetting resin softening particles. The thermosetting resin softening particles.
As a third aspect, the invention relates to the thermosetting resin softening particles according to the first aspect or the second aspect, in which 0.5 to 100 parts by mass of colloidal silica is present with respect to 100 parts by mass of the monomer compound.
As a 4th viewpoint, it is related with the thermosetting resin softening particle | grains as described in a 1st viewpoint or a 2nd viewpoint using aqueous silica sol as said colloidal silica.
As a fifth aspect, the bifunctional monomer is selected from the group consisting of guanamine, acetoguanamine, benzoguanamine, urea, thiourea, and ethylene urea, and the thermosetting resin softening particles according to the first aspect or the second aspect. About.
As a sixth aspect, the polyfunctional monomer relates to a thermosetting resin softening particle according to the second aspect selected from the group consisting of melamine, CTU guanamine and CMTU guanamine.
As a seventh aspect, the inner matrix of the particles is a thermosetting resin, the colloidal silica is a spherical particle unevenly distributed on the particle surface portion, the particle has an average particle diameter of 0.05 to 100 μm, and the particle The particles relate to thermosetting resin softening particles having a 10% displacement hardness of 30 to 84 MPa.
As an eighth aspect, the present invention relates to the thermosetting resin softening particle according to the seventh aspect, wherein the colloidal silica is present in the vicinity of the particle surface within a depth of 0.3 μm from the outermost surface of the particle.
As a ninth aspect, the thermosetting resin relates to a thermosetting resin softening particle according to the seventh aspect, which is formed from a monomer compound containing at least one bifunctional monomer and an aldehyde compound.
As a tenth aspect, the thermosetting resin is formed from a monomer compound containing at least one bifunctional monomer and at least one multifunctional monomer and an aldehyde compound, and the thermosetting resin softening according to the seventh aspect Concerning particles.
As an eleventh aspect, the bifunctional monomer is selected from the group consisting of guanamine, acetoguanamine, benzoguanamine, urea, thiourea, and ethylene urea, and the thermosetting resin softening particles according to the ninth aspect or the tenth aspect About.
As a twelfth aspect, the polyfunctional monomer relates to a thermosetting resin softening particle according to the tenth aspect selected from the group consisting of melamine, CTU guanamine and CMTU guanamine.

The thermosetting resin softening particles of the present invention have a hardness lower than the hardness of conventional spherical melamine-based cured resin particles and higher than the hardness of particles made of a thermoplastic resin such as styrene, that is, a medium hardness.

For this reason, the thermosetting resin softening particles of the present invention have a surface roughness of a roller surface resin layer used in an electrophotographic apparatus such as a copying machine or a laser beam printer, for example, in a range of particles requiring a medium hardness. It can be expected to be suitably used as particles added for the purpose of adjusting the thickness, charging characteristics, wear resistance, and the like.

1 is a scanning electron micrograph of the thermosetting resin particles obtained in Example 1. FIG. 2 is a scanning electron micrograph of the thermosetting resin particles obtained in Example 2. FIG. FIG. 3 is a view showing a scanning electron micrograph of the thermosetting resin particles obtained in Example 3. 4 is a view showing a scanning electron micrograph of the thermosetting resin particles obtained in Example 4. FIG. FIG. 5 is a scanning electron micrograph of the thermosetting resin particles obtained in Example 5. 6 is a view showing a scanning electron micrograph of the thermosetting resin particles obtained in Example 6. FIG. FIG. 7 is a scanning electron micrograph of the thermosetting resin particles obtained in Example 7. FIG. 8 is a transmission electron micrograph of the vicinity of the particle surface of the thermosetting resin particle cross section obtained in Example 1. FIG. 9 is a transmission electron micrograph of the vicinity of the particle surface of the thermosetting resin particle cross section obtained in Example 2. FIG. 10 is a transmission electron micrograph of the vicinity of the particle surface of the thermosetting resin particle cross section obtained in Example 3. 11 is a transmission electron micrograph of the vicinity of the particle surface of the thermosetting resin particle cross section obtained in Example 5. FIG. 12 is a transmission electron micrograph of the vicinity of the particle surface of the thermosetting resin particle cross section obtained in Example 7. FIG.

Hereinafter, embodiments of the present invention will be described in detail.
The heat-curing resin softening particles of the present invention are obtained by reacting a monomer compound and an aldehyde compound under basic conditions in a suspension of colloidal silica having an average particle diameter of 5 to 70 nm. And (b) adding an acid catalyst to the aqueous solution to precipitate spherical thermosetting resin softening particles.

The monomer compound used in the step (a) contains at least one bifunctional monomer as an essential component, and may contain a polyfunctional monomer in addition to the bifunctional monomer.
Examples of the bifunctional monomer used herein include 6-substituted guanamines such as guanamine, acetoguanamine, and benzoguanamine, and ureas such as urea, thiourea, and ethylene urea, and are produced industrially. Inexpensive guanamine, acetoguanamine, and benzoguanamine are preferable.
Polyfunctional monomers include melamine and CTU guanamine (3,9-bis [2- (3,5-diamino-2,4,6-triazaphenyl) ethyl] -2,4,8,10-tetra Oxaspiro [5,5] undecane), CMTU guanamine (3,9-bis [(3,5-diamino-2,4,6- 卜 riazaphenyl) methyl] -2,4,8,10-tetraoxaspiro [ An amine-substituted triazine compound such as 5,5] undecane) can be used, and among them, melamine capable of forming a rigid crosslinking point is most preferable from the viewpoint of improving particle hardness.
In the present invention, the monomer compound may be one or two or more types of bifunctional monomers, or one or two or more types of bifunctional monomers and one or more types of multifunctional monomers. May be used in combination.

The thermosetting resin softening particles of the present invention are, in other words, an initial stage obtained by adding formaldehyde to a bifunctional monomer such as acetoguanamine or benzoguanamine, or a polyfunctional monomer such as these bifunctional monomers and melamine. Resin particles obtained by condensation polymerization and curing of a condensate with an acid catalyst.
The initial condensate is a methylolated product obtained by adding formaldehyde to a bifunctional monomer such as acetoguanamine or benzoguanamine, and a polyfunctional monomer such as these bifunctional monomers and melamine, and the methylolated product is This refers to those condensed with each other to form a quantifier (oligomer).

Here, when the methylolated product obtained by adding formaldehyde to a bifunctional monomer or polyfunctional monomer is insoluble in an aqueous medium (for example, when CTU guanamine or CMTU guanamine is used), methylol having higher hydrophilicity is used. A hydrophilic initial condensate (quantity) can be obtained by simultaneously adding and co-condensing guanamine, acetoguanamine, and melamine from which chemical forms are obtained. It is more preferable that the initial condensate is hydrophilic, because the particles obtained through the subsequent steps are, as a result, spherical and have a uniform particle size distribution with little variation in particle size.
Accordingly, in order to obtain a hydrophilic initial condensate, for example, a hydrophobic monomer that becomes insoluble in an aqueous medium when forming a methylolated product, such as CTU guanamine, and acetoguanamine or melamine from which a more hydrophilic methylolated product can be obtained. The mixing ratio with the hydrophilic monomer such as is preferably 40:60 to 99: 1 in terms of the mass ratio of hydrophilic monomer: hydrophobic monomer. From the viewpoint of particle formation, when the amount of hydrophilic monomer is larger than this mixing ratio, the resin obtained by condensation polymerization is dissolved in the aqueous medium, so that the resin is difficult to precipitate and it is difficult to obtain resin particles. On the other hand, if the ratio of the hydrophobic monomers is too large, the initial condensate becomes hydrophobic, so that the resin obtained by condensation becomes indeterminate, precipitates as a lump, and resin particles cannot be obtained. More preferably, the weight ratio of hydrophilic monomer: hydrophobic monomer is 50:50 to 90:10.

In addition, when the condensation product (target resin) of the above initial condensate is easily soluble in an aqueous medium (for example, when guanamine or acetoguanamine is used), a melamine from which a condensation polymer with lower aqueous medium solubility can be obtained. , Benzoguanamine, CTU guanamine, and CMTU guanamine are simultaneously added, and subjected to initial condensation and condensation polymerization, whereby a condensation polymer (target resin) is precipitated in an aqueous medium, and spherical resin particles with little dissolution loss can be obtained. From the viewpoint of obtaining resin particles having a small particle size variation and a uniform particle size distribution with low loss, for example, a polycondensation product (target resin) such as guanamine or acetoguanamine is easily soluble in an aqueous medium. The mixing ratio of the hydrophilic resin monomer and the hydrophobic resin monomer such as melamine or benzoguanamine from which a copolycondensation product with lower aqueous medium solubility is obtained is expressed by a mass ratio of hydrophilic resin monomer: hydrophobic resin monomer 1: It is preferably 99 to 99: 1. More preferably, the weight ratio of hydrophilic resin monomer: hydrophobic resin monomer is 5:95 to 80:20.

In addition, when using a bifunctional monomer and a polyfunctional monomer together, from the viewpoint of particle hardness control obtained by the addition of the polyfunctional monomer, the polyfunctional monomer is 30 with respect to the total mass of the monomer compound. If the content is less than mass%, the crosslinking concentration is low and appropriate particle hardness cannot be obtained. If the content exceeds 99 mass%, the flexibility of the particles due to the addition of the bifunctional monomer cannot be obtained. Preference is given to using polyfunctional monomers. When the bifunctional monomer and the polyfunctional monomer are used in combination, it is particularly preferable to use the polyfunctional monomer in the range of 50 to 95% by mass with respect to the total mass of the monomer compound.

Examples of the aldehyde compound used in the step (a) include formaldehyde, paraformaldehyde, acetaldehyde, benzaldehyde, furfural and the like, but formaldehyde and paraformaldehyde that are inexpensive and have good reactivity with the above-described monomer compounds are preferable. . As the aldehyde compound, it is preferable to use an aldehyde compound having an amount of 1.1 to 6.0 mol, particularly 1.2 to 4.0 mol, per effective aldehyde group with respect to 1 mol of the monomer compound.

Water is most preferable as the medium used in the step (a). Also, a mixed solution in which a part of water is replaced with an organic solvent soluble in water can be used. In this case, it is preferable to select an organic solvent capable of dissolving the above-mentioned initial condensate. Preferred organic solvents include alcohols such as methanol, ethanol, isopropanol and propanol, ethers such as dioxane, tetrahydrofuran and 1,2-dimethoxyethane, and polar solvents such as N, N-dimethylformamide and dimethyl sulfoxide.

Colloidal silica having an average particle diameter of 5 to 70 nm is used.

Here, the average particle diameter of colloidal silica is a specific surface area diameter obtained by measurement by a nitrogen adsorption method (BET method). The average particle diameter (specific surface area diameter) (Dnm) is given by the formula D = 2720 / S from the specific surface area Sm ² / g measured by the nitrogen adsorption method. Although powdered colloidal silica such as precipitated silica powder and vapor phase method silica powder can be used, it is preferable to use a colloidal silica sol stably dispersed to the primary particle level in a medium. There are two types of colloidal silica sols: aqueous silica sol and organosilica sol, both of which can be applied. However, when an aqueous medium is used for the production of melamine resin, the aqueous silica sol may be used from the viewpoint of dispersion stability of the colloidal silica sol. Most preferred. The silica concentration in the colloidal silica sol is preferably from 5 to 50% by mass because it is generally commercially available and can be easily obtained.

When the average particle diameter of colloidal silica exceeds 70 nm, the thermosetting resin softening particles that precipitate in the subsequent step (b) are difficult to become spherical particles. The average particle size of the thermosetting resin softening particles generally tends to be smaller as the monomer compound (ie, melamine resin) concentration is lower and the average particle size of colloidal silica is smaller.

The amount of colloidal silica added is preferably 0.5 to 100 parts by mass, particularly 1 to 50 parts by mass with respect to 100 parts by mass of the monomer compound. If the addition amount is less than 0.5 parts by mass, it becomes difficult to obtain the thermosetting resin softening particles in the step (b). Further, particles can be obtained even when the addition amount exceeds 100 parts by mass. In this case, however, fine, non-spherical aggregated particles are produced as a by-product compared to the thermosetting resin softening particles obtained under optimum conditions, which is not preferable.

In the step (a), the reaction between the monomer compound and the aldehyde compound is preferably performed under basic conditions, that is, by adjusting the pH of the reaction solution to 7 to 10. As the basic catalyst, for example, sodium hydroxide, potassium hydroxide, aqueous ammonia and the like can be suitably used. The reaction is usually carried out at 50 to 100 ° C. As a result, an aqueous solution of an initial condensate soluble in water having a molecular weight of about 200 to 700 is prepared.

Examples of the acid catalyst used in the curing reaction in the step (b) include mineral acids such as hydrochloric acid, sulfuric acid, nitric acid and phosphoric acid, methanesulfonic acid, benzenesulfonic acid, paratoluenesulfonic acid, alkylbenzenesulfonic acid, sulfamic acid and the like. Examples include sulfonic acids, formic acid, oxalic acid, benzoic acid, and organic acids such as phthalic acid.

In the step (b), an acid catalyst is added to the aqueous solution of the initial condensate obtained in the step (a) to perform a curing (condensation polymerization) reaction. Particles are deposited. The curing reaction is preferably performed at 70 to 100 ° C. by adjusting the pH of the reaction solution to 3 to 7 with an acid catalyst.

The thermosetting resin softening particles of the present invention obtained through the above steps (a) and (b) are particles in which colloidal silica is unevenly distributed in the vicinity of the particle surface, and are obtained by drying a solid content obtained by general filtration or centrifugation. Or by directly spray-drying an aqueous dispersion slurry of resin particles, it can be obtained as powder particles. If the dried powder particles are agglomerated between particles, such as mixers with shearing force such as homomixers, Henschel mixers, and Laedige mixers, pin disc mills, pulverizers, inomizers, counter jet mills, etc. When appropriately treated with a pulverizer, interparticle aggregation can be loosened without destroying the spherical particles.

The present invention is also directed to thermosetting resin softening particles in which the internal matrix of the particles is a thermosetting resin and colloidal silica is unevenly distributed on the particle surface portion.
The thermosetting resin that is the internal matrix of the particles is preferably formed from the monomer compound and the aldehyde compound described above.
The particles are particles having an average particle diameter of 0.05 to 100 μm, and the average particle diameter (μm) is a 50% volume diameter (median diameter) obtained by measurement by a laser diffraction / scattering method based on Mie theory. ).
The particles have a 10% displacement hardness of 30 to 84 MPa, particularly preferably 10% displacement hardness of 50 to 80 MPa. Here, the 10% displacement hardness is a test force when a displacement amount reaches 10% of the particle diameter when a test force is applied to one particle at a loading speed of 0.223 mN / sec in a compression test.

The above-mentioned thermosetting resin softening particles in which the colloidal silica is unevenly distributed on the particle surface portion are primary particles that are spherical and independent, have no pores, and the colloidal silica is about 0.3 μm from the particle outermost surface. It means that it exists near the particle surface within the depth. Although colloidal silica is embedded in the thermosetting resin near the particle surface or exists on the particle surface, the outermost surface component is usually a thermosetting resin.

The thermosetting resin softening particle of the present invention is a particle having the flexibility of a two-dimensional structure caused by a bifunctional monomer, and further has such a flexible three-dimensional crosslinked structure caused by a polyfunctional monomer. Thermosetting resin that combines the properties of a thermosetting resin, such as wear resistance and heat resistance, with the characteristics of a thermoplastic resin, such as moderate flexibility that deforms the shape due to excessive load. Softening particles.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to only these examples.

[Example 1]
In a 100 mL reaction flask equipped with a stirrer, a reflux condenser and a thermometer, 4.51 g of melamine, 1.53 g of acetoguanamine, 11.58 g of 37% formalin, 20% by mass aqueous silica sol [manufactured by Nissan Chemical Industries, Snow Tex (registered trademark) ST-N (trade name), average particle size 12 nm, pH 9.5] 0.93 g, water 37.1 g, and 25% aqueous ammonia 67.2 μL were charged. Thereafter, the temperature of the mixture was increased while stirring, the temperature was kept at 70 ° C., and the mixture was reacted for 30 minutes to prepare an aqueous solution of an initial condensate of melamine resin. Next, while maintaining the temperature at 70 ° C., 3.59 g of 5 mass% para-toluenesulfonic acid aqueous solution was added to the obtained aqueous solution of the initial condensate. After about 5 minutes, the reaction system became cloudy and copolycondensation amino resin particles were precipitated. Thereafter, the temperature was raised to 90 ° C. and the curing reaction was continued for 3 hours. After cooling, the resulting reaction solution was filtered and dried to obtain white cured resin particles.

[Example 2]
In a 30 mL reaction flask equipped with a stirrer, reflux condenser and thermometer, 0.50 g of melamine, 0.52 g of guanamine, 1.93 g of 37% formalin, 20% by mass aqueous silica sol [manufactured by Nissan Chemical Industries, Snowtex (Registered trademark) ST-N (trade name), average particle diameter 12 nm, pH 9.5] 0.17 g, water 6.17 g, and 25% aqueous ammonia 20 μL were charged. Thereafter, the temperature of the mixture was increased while stirring, the temperature was kept at 70 ° C., and the mixture was reacted for 30 minutes to prepare an aqueous solution of an initial condensate of melamine resin. Next, while maintaining the temperature at 70 ° C., 0.58 g of a 5 mass% paratoluenesulfonic acid aqueous solution was added to the obtained aqueous solution of the initial condensate. After about 2 minutes, the reaction system became cloudy and copolycondensation amino resin particles were precipitated. Thereafter, the temperature was raised to 90 ° C. and the curing reaction was continued for 3 hours. After cooling, the resulting reaction solution was filtered and dried to obtain white cured resin particles.

Example 3
Into a 200 mL reaction flask equipped with a stirrer, a reflux condenser and a thermometer, 1.00 g of benzoguanamine, 1.00 g of acetoguanamine, 1.00 g of melamine, 5.18 g of 37% formalin, 20 mass% aqueous silica sol [Nissan Chemical ( Snowtex (registered trademark) ST-N (trade name), average particle diameter 12 nm, pH 9.5] 0.46 g, water 38.7 g, and 25% aqueous ammonia 34 μL were charged. Thereafter, the mixture was heated to 90 ° C. while stirring to prepare an aqueous solution of an initial condensate of melamine resin. Next, while maintaining the temperature at 90 ° C., 2.34 g of a 5 mass% paratoluenesulfonic acid aqueous solution was added to the obtained aqueous solution of the initial condensate. After about 40 seconds, the reaction system was clouded and copolycondensation amino resin particles were precipitated. Thereafter, the curing reaction was continued for 3 hours while maintaining the temperature at 90 ° C. After cooling, the resulting reaction solution was filtered and dried to obtain white cured resin particles.

Example 4
To a 200 mL reaction flask equipped with a stirrer, a reflux condenser and a thermometer, 1.00 g of benzoguanamine, 1.00 g of acetoguanamine, 2.00 g of melamine, 7.11 g of 37% formalin, 20 mass% aqueous silica sol [Nissan Chemical Industry ( Snowtex (registered trademark) ST-N (trade name), 0.62 g of pH9.5], 52.2 g of water, and 45 μL of 25% ammonia water were prepared. Thereafter, the mixture was heated to 90 ° C. while stirring to prepare an aqueous solution of an initial condensate of melamine resin. Next, while maintaining the temperature at 90 ° C., 2.34 g of a 5 mass% paratoluenesulfonic acid aqueous solution was added to the obtained aqueous solution of the initial condensate. After about 30 seconds, the reaction system became cloudy and copolycondensation amino resin particles were precipitated. Thereafter, the curing reaction was continued for 3 hours while maintaining the temperature at 90 ° C. After cooling, the resulting reaction solution was filtered and dried to obtain white cured resin particles.

Example 5
To a 100 mL reaction flask equipped with a stirrer, a reflux condenser and a thermometer, 0.30 g of benzoguanamine, 0.30 g of acetoguanamine, 1.81 g of melamine, 4.13 g of 37% formalin, 20% by mass aqueous silica sol [Nissan Chemical Industry ( Snowtex (registered trademark) ST-N (trade name), average particle diameter 12 nm, pH 9.5] 0.38 g, water 39.7 g, and 25% aqueous ammonia 0.024 g were charged. Thereafter, the mixture was heated to 80 ° C. while stirring, and further stirred for 5 minutes to prepare an aqueous solution of an initial condensate of melamine resin. Next, while maintaining the temperature at 80 ° C., 1.41 g of a 5 mass% paratoluenesulfonic acid aqueous solution was added to the obtained aqueous solution of the initial condensate. After about 3 minutes, the reaction system became cloudy and copolycondensation amino resin particles were precipitated. Thereafter, the temperature was raised to 90 ° C. and the curing reaction was continued for 3 hours. After cooling, the resulting reaction solution was filtered and dried to obtain white cured resin particles.

Example 6
In a 200 mL reaction flask equipped with a stirrer, a reflux condenser and a thermometer, 0.50 g of CTU guanamine, 4.50 g of acetoguanamine, 9.04 g of 37% formalin, 20 mass% aqueous silica sol [manufactured by Nissan Chemical Industries, Ltd., Snowtex (registered trademark) ST-N (trade name), average particle size 12 nm, pH 9.5] 0.78 g, water 65.6 g, and 25% aqueous ammonia 56 μL were charged. Thereafter, the mixture was heated to 90 ° C. while stirring to prepare an aqueous solution of an initial condensate of acetoguanamine resin. Next, 2.92 g of 5 mass% para-toluenesulfonic acid aqueous solution was added to the obtained aqueous solution of the initial condensate while maintaining the temperature at 90 ° C. After about 10 minutes, the reaction system became cloudy and copolycondensation amino resin particles were precipitated. Thereafter, the curing reaction was continued for 3 hours while maintaining the temperature at 90 ° C. After cooling, the resulting reaction solution was filtered and dried to obtain white cured resin particles.

Example 7
Into a 500 mL reaction flask equipped with a stirrer, a reflux condenser and a thermometer, 5.00 g of benzoguanamine, 6.50 g of 37% formalin, 20% by mass aqueous silica sol [manufactured by Nissan Chemical Industries, Snowtex (registered trademark) ST -N (trade name), average particle diameter 12 nm, pH 9.5] 0.78 g, water 355.1 g, and 25% aqueous ammonia 56 μL were charged. Thereafter, the mixture was heated to 95 ° C. while stirring to prepare an aqueous dispersion of an initial condensate of benzoguanamine resin. Next, 2.92 g of 5 mass% para-toluenesulfonic acid aqueous solution was added to the obtained aqueous dispersion of the initial condensate while maintaining the temperature at 95 ° C. Immediately after the addition, the reaction system became cloudy and benzoguanamine resin particles were precipitated. Thereafter, the temperature was kept at 95 ° C. and the curing reaction was continued for 3 hours. After cooling, the resulting reaction solution was filtered and dried to obtain white cured resin particles.

[Shape observation]
The shape of each of the cured resin particles prepared in each example was observed with a scanning electron microscope (SEM) [manufactured by JEOL Ltd., JSM-7400F]. SEM images of the cured resin particles prepared in Examples 1 to 7 are shown in FIGS. 1 to 7, respectively.
Referring to the scanning electron micrographs shown in FIG. 1 to FIG. 7, the cured resin particles obtained in Examples 1 to 7 have a uniform particle diameter, and the spherical particles are the same under any production conditions. The result was obtained.

[Cross-section observation]
For each of the cured resin particles prepared in Examples 1 to 3, Example 5, and Example 7, each particle was embedded in a resin, and then a slice piece was prepared, and a transmission electron microscope (TEM) [ The cross section was observed with Hitachi, Ltd., H-8000]. TEM images of the cured resin particles prepared in Examples 1 to 3, Example 5, and Example 7 are shown in FIGS. 8 to 12, respectively.
8 to 12 are enlarged views of the surface portion of the particle, and FIG. 8 shows the inside of the resin particle on the left side of the screen, and the image of the adjacent gray aggregate with the surface layer of the particle (see FIG. 8). The resin particle boundary is indicated by a dotted line). Similarly, FIG. 9 shows the inside of the resin particles on the upper right side of the screen, FIG. 10 shows the inside of the resin particles on the lower right side of the screen, FIG. 11 shows the inside of the resin particles on the upper side of the screen, and FIG. In each figure, the boundary of the resin particles is indicated by a dotted line.
Referring to the transmission electron micrographs shown in FIG. 8 to FIG. 12, in any of the photographs, black contrast is seen near the particle surface compared to the inside of the resin particle, and colloidal silica is unevenly distributed on the particle surface. Was confirmed.

[Specific gravity measurement]
About each of the cured resin particle prepared by each Example and the comparative example, the density measurement was performed with the dry-type automatic densimeter [Corporation | KK Shimadzu Corp. make, Accupic 1330]. Note that, as Comparative Example 1, Optobeads (registered trademark) 3500M manufactured by Nissan Chemical Industries, Ltd. was adopted, and the density measurement was performed in the same manner. The results (average values of five measurements each) are shown in Table 1.

(Particle hardness measurement)
About each of the cured resin particle prepared in each Example, the particle hardness measurement was performed with the micro compression tester [Shimadzu Corporation make, MCT]. As Comparative Example 1 and Comparative Example 2, Nissan Chemical Industries, Ltd., Opto Beads (registered trademark) 3500M (Comparative Example 1), Air Water Co., Ltd., Bell Pearl S (Comparative Example 2) were adopted. Similarly, the particle hardness was measured. Table 2 shows the results of measurement of 10% displacement hardness (* 1) and restoration rate (* 2) after 5 mN load (average value of five measurements each).
<* 1: 10% displacement hardness>
In the compression test, when a test force is applied to one particle at a load speed of 0.223 mN / sec, the test force when the displacement reaches 10% of the particle diameter <* 2: Restoration rate after 5 mN load>
In the load-unload test, a test force is applied to one particle at a load speed of 0.223 mN / sec, and the displacement obtained when the test force becomes 0.49 mN is L ₀ (μm), a maximum of 5.0 mN The displacement when the test force is reached is L ₁ (μm), the unloading speed is 0.223 mN / sec, and the displacement obtained when the test force is 0.49 mN is L ₂ (μm). Where L ₁ -L ₂ is divided by L ₁ -L ₀ to give a value of 100 minutes (100 * (L ₁ -L ₂ ) / (L ₁ -L ₀ ): restoration rate)

As shown in Table 2, the 10% displacement hardness of the cured resin particles obtained in each of Examples 1 to 7 decreased in comparison with the melamine resin (single) particles (Comparative Example 1). When the cured resin particles containing melamine obtained in Examples 1 to 5 and the melamine resin (single) particles of Comparative Example 1 were compared, the particle hardness increased with an increase in the melamine composition ratio in the particles. The result was obtained.
Moreover, the restoration rate after 5 mN load is compared with the melamine ratio increase in particle | grains, when the cured resin particle containing the melamine obtained in Example 3 and Example 4 and the melamine resin (simple substance) particle | grains of the comparative example 1 are compared. As a result, the result that the restoration rate increased was obtained.

Claims

Initial condensation of a water-soluble melamine resin by reacting a monomer compound containing at least one bifunctional monomer with an aldehyde compound under a basic condition in a suspension of colloidal silica having an average particle size of 5 to 70 nm. Producing an aqueous solution of the product,
Adding an acid catalyst to the aqueous solution and precipitating spherical thermosetting resin softening particles.
Thermosetting resin softening particles.
In a suspension of colloidal silica having an average particle size of 5 to 70 nm, a monomer compound containing at least one bifunctional monomer and at least one polyfunctional monomer and an aldehyde compound are reacted under basic conditions, and are then added to water. Generating an aqueous solution of an initial condensate of a soluble melamine resin;
Adding an acid catalyst to the aqueous solution and precipitating spherical thermosetting resin softening particles.
Thermosetting resin softening particles.
The thermosetting resin softening particles according to claim 1 or 2, wherein 0.5 to 100 parts by mass of colloidal silica is present with respect to 100 parts by mass of the monomer compound.
The thermosetting resin softening particles according to claim 1 or 2, wherein an aqueous silica sol is used as the colloidal silica.
The thermosetting resin softening particles according to claim 1 or 2, wherein the bifunctional monomer is selected from the group consisting of guanamine, acetoguanamine, benzoguanamine, urea, thiourea, and ethylene urea.
The thermosetting resin softening particles according to claim 2, wherein the polyfunctional monomer is selected from the group consisting of melamine, CTU guanamine, and CMTU guanamine.
The inner matrix of the particles is a thermosetting resin, the colloidal silica is a spherical particle unevenly distributed on the particle surface portion,
The particles have an average particle size of 0.05 to 100 μm;
The particles are softened thermosetting resin particles having a 10% displacement hardness of 30 to 84 MPa.
The thermosetting resin softening particle according to claim 7, wherein the colloidal silica is present in the vicinity of the particle surface within a depth of 0.3 µm from the outermost surface of the particle.
The thermosetting resin softening particles according to claim 7, wherein the thermosetting resin is formed from a monomer compound containing at least one bifunctional monomer and an aldehyde compound.
The thermosetting resin softening particles according to claim 7, wherein the thermosetting resin is formed from a monomer compound containing at least one bifunctional monomer and at least one polyfunctional monomer and an aldehyde compound.
The thermosetting resin softening particle according to claim 9 or 10, wherein the bifunctional monomer is selected from the group consisting of guanamine, acetoguanamine, benzoguanamine, urea, thiourea and ethyleneurea.
The thermosetting resin softening particle according to claim 10, wherein the polyfunctional monomer is selected from the group consisting of melamine, CTU guanamine, and CMTU guanamine.