JP2682640B2 - Method for producing fine particles of silicone resin - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to a method for efficiently producing silicone resin fine particles having an average particle diameter of 1 μm or less.

TECHNICAL BACKGROUND OF THE INVENTION AND PROBLEMS THEREOF Silicone fine particles are used as fillers in the fields of electronics, paints, inks, synthetic resins, rubbers, cosmetics and the like. In particular, in the electronics industry, the structure of elements and wiring has become finer recently, and in the paint industry, the coating film itself has become thinner. Therefore, as a filler for the purpose of improving various physical properties, the average particle size is Attention is focused on a silicone resin having a thickness of 1 μm or less.

Conventionally, as a method for producing silicone resin fine particles,
A method is known in which a silicone resin is frozen with dry ice or the like, or is ground as it is. However, these methods have problems that it is difficult to obtain a fine granular silicone resin, the shape is extremely uneven, and the productivity is poor.

In order to solve such a problem, JP-A-59-68333
The publication describes a method in which a polymer composition having an organosiloxane block is sprayed in a hot air stream or under irradiation with high energy to cure the composition. However, in this method, the particle diameter of the cured polymer obtained depends on the diameter of the sprayed droplets, and it is difficult to obtain a silicone resin having an average particle diameter of 1 μm or less. It was difficult to control the cure rate.

Further, JP-A-62-243621 discloses a method in which a liquid silicone rubber composition is made into an aqueous emulsion with a surfactant, and this aqueous emulsion is dispersed in warm water and cured. JP-A-62-257939 describes a method in which an organopolysiloxane composition is emulsified so as to have a particle size of 20 μm or less, and the emulsion is cured and then spray-dried, or is cured while being spray-dried. However, when an attempt is made to produce a silicone resin by the method as described above, the average particle diameter of the silicone resin does not usually become 1 μm or less, and even if it is 1 μm or less by a special method, the silicone resin particles are fused during the curing. Therefore, it has been difficult to obtain silicone resin fine particles having an average particle diameter of 1 μm or less.

An object of the present invention is to solve the problems associated with the prior art as described above, and to provide silicone resin fine particles having an average particle diameter of 1 μm or less or a granular silicone resin composed of the fine particles. It is an object of the present invention to provide a method for producing silicone resin fine particles that can be efficiently and economically obtained.

SUMMARY OF THE INVENTION The method for producing silicone resin fine particles having an average particle size of 1 μm or less according to the present invention is [A] A, C, D (in the formula, a + b + c + d = 5 to 500, a + b = 2-1)
00) having a linear or branched liquid organovinylpolysiloxane, and B ′, C ′, D '(wherein a' + b '+ c' + d '= 5 to 500,
a ′ + b ′ = 2 to 500), a linear, branched or cyclic liquid organohydropolysiloxane, and (iii) a platinum-based organopolysiloxane composition containing a catalyst and [B] a dispersion medium. Mixture with an average particle size of 1μ
m, and then the organopolysiloxane composition is cured in this emulsion to give an average particle size of 1
It is characterized by forming silicone resin fine particles having a size of not more than μm. That is, the present invention provides: (i) the specific linear or branched liquid organovinylpolysiloxane, (ii) the specific linear, branched or cyclic organohydropolysiloxane, and (iii) platinum A step of preparing an organopolysiloxane composition [A] containing a system catalyst, the organopolysiloxane composition [A] and the dispersion medium [B] are mixed and stirred, and the organopolysiloxane composition [A] To form an emulsion of the organopolysiloxane composition [A] by dispersing in a dispersion medium [B] with an average particle size of 1 μm or less. In the formed emulsion, the organopolysiloxane composition [A] Is a method for producing silicone resin fine particles, which comprises a step of curing the above to form silicone resin fine particles having an average particle diameter of 1 μm or less.

In order to obtain the silicone resin fine particles having a particle diameter of 1 μm or less as described above, it is necessary to make the emulsion diameter sufficiently small when the liquid organopolysiloxane composition is emulsified and cured. Since a mixture of a specific organopolysiloxane composition and a dispersion medium is stirred to form an emulsion having an average particle size of 1 μm or less and then cured, it is possible to obtain a silicone resin which is not easily fused and fused during curing. As a result, silicone resin fine particles having a particle diameter of 1 μm or less can be obtained in good yield.

DETAILED DESCRIPTION OF THE INVENTION The method for producing fine particles of silicone resin according to the present invention will be specifically described below.

The organovinylpolysiloxane used in the present invention has the following groups.

(Hereinafter referred to as group A) (Hereinafter referred to as group B) (Hereinafter referred to as C group) (Hereinafter referred to as D group) In this organovinylpolysiloxane, the A group is located at the end of the main chain or the end of the branched chain, and the D group is located at the end of the main chain or the end of the branched chain.

When the A group is located at the end of the branched chain, for example, When the D group is located at the end of the branched chain, It has a structure like.

In the organovinylpolysiloxane used in the present invention, A
The groups, B groups, C groups, and D groups may be randomly arranged or may be arranged in blocks. In addition, the number of A groups in this organovinylpolysiloxane is a
, The number of B groups is b, the number of C groups is c, and D
When the number of groups is d, a + b + c + d is preferably 5 to 500, and more preferably 5 to 100. Further, it is desirable that the number of vinyl groups contained in this organovinylpolysiloxane, that is, a + b, is 2 to 100, preferably 2 to 30.

When a + b + c + d exceeds 500, the viscosity of the organovinylpolysiloxane becomes too high, and it tends to be difficult to obtain a fine emulsion. In addition, the larger the number of vinyl groups (a + b) contained in the organovinylpolysiloxane, the easier it is to cure, the amount of unreacted raw materials decreases rapidly, the degree of cross-linking increases, and the emulsion particles become fused and become huge during curing. However, if (a + b) exceeds 100,
The degree of cross-linking increases so much that the silicone resin obtained after curing tends to have poor elasticity.

In the present invention, two or more kinds of the above organovinylpolysiloxane may be used in combination.

The organohydropolysiloxane used in the present invention has the following groups.

(Hereinafter referred to as E group) (Hereinafter referred to as F group) (Hereinafter referred to as G group) (Hereinafter referred to as H group) In this organohydropolysiloxane, the E group is located at the end of the main chain or the end of the branched chain, and the H group is located at the end of the main chain or the end of the branched chain. E
When the group is located at the end of the branched chain, for example, When the H group is located at the end of the branched chain, It has a structure like.

In the organohydropolysiloxane used in the present invention, the E groups, F groups, G groups, and H groups may be arranged randomly or in blocks.
When the number of E groups in this organohydropolysiloxane is a ', the number of F groups is b', the number of G groups is c ', and the number of H groups is d', a ′ + B ′
It is desirable that + c '+ d' is 5 to 500, preferably 5 to 50. The number (a '+ b') of hydrosilyl groups contained in this organohydropolysiloxane is preferably 2 to 500, and more preferably 3 to 50.

If a '+ b' + c '+ d' exceeds 500, the viscosity of the organohydropolysiloxane becomes too high, and it tends to be difficult to obtain a fine emulsion. Further, the larger the number of hydrosilyl groups (a '+ b') contained in the organohydropolysiloxane, the easier it is to cure, the amount of unreacted raw materials decreases rapidly, the degree of crosslinking increases, and the emulsion particles fuse during curing. Is prevented from becoming huge, but (a '
When + b ') exceeds 500, the degree of crosslinking increases too much, and the elasticity of the silicone resin obtained after curing tends to be poor.

In the present invention, two or more kinds of the above organovinylpolysiloxane may be used in combination.

The organopolysiloxane composition according to the present invention is cured by the addition of the hydrosilyl group of the organohydropolysiloxane to the vinyl group of the organovinylpolysiloxane. Here, the molar ratio of vinyl group to hydrosilyl group can vary from 1: 4 to 4: 1, but preferably from 1: 1.5 to
It is 1: 3 or 3: 1 to 1.5: 1.

In the present invention, when the number of vinyl groups in one molecule of organovinylpolysiloxane is a and the number of hydrosilyl groups of the organohydropolysiloxane is a ′, a>
If it is a ', it is preferable to use the organovinylpolysiloxane in excess, and if it is a <a', it is preferable to use the organohydropolysiloxane in excess.
In particular, when the number of vinyl groups in one molecule of the organovinylpolysiloxane is 2, an organohydropolysiloxane having 3 or more hydrosilyl groups in one molecule is used in an excess amount with respect to the organovinylpolysiloxane. It is preferable to use. When the number of hydrosilyl groups in one molecule of the organohydropolysiloxane is 2, an organovinylpolysiloxane having 3 or more vinyl groups in one molecule is used in an excess amount with respect to the organohydropolysiloxane. It is preferable to use.

In the present invention, as the platinum-based catalyst, for example, chloroplatinic acid or a chloroplatinic acid solution obtained by dissolving it in a solvent such as alcohol or ketone, or one obtained by aging this solution,
A complex of chloroplatinic acid with an aldehyde, an olefin, an alkenyl siloxane, a diketone, platinum black, or one in which platinum is supported on a carrier is used.

Such a platinum-based catalyst is preferably mixed with an organovinylpolysiloxane and an organohydropolysiloxane at a temperature of preferably -30 ° to 10 ° C to prepare an organopolysiloxane composition.

The platinum-based catalyst is 0.1 to 1000 ppm by weight as platinum metal, preferably 1 to 10 relative to the mixture of organovinylpolysiloxane and organohydropolysiloxane.
It is desirable to add it in an amount of 0 ppm by weight.

If the amount of platinum-based catalyst added is less than 0.1 ppm by weight, the curing rate will slow down, the amount of unreacted raw materials will increase, the degree of crosslinking will decrease, and the emulsion particles will tend to become fused and become huge before the completion of the curing reaction. On the other hand, if it exceeds 1000 ppm by weight, it tends to be uneconomical.

In the present invention, water is mainly used as the dispersion medium, but a mixture of water and an organic solvent such as alcohol, or an organic solvent such as alcohol can also be used.

In the present invention, the dispersion medium as described above is preferably used in an amount of 10 to 0.5 parts by weight, preferably 7 to 4 parts by weight, based on 1 part by weight of the organopolysiloxane composition. If the amount of the dispersion medium is too small, the emulsion particles tend to become fused and become huge before the completion of curing, while if the amount of the dispersion medium is too large, it takes time to separate the silicone resin after curing. There is.

A surfactant is preferably present in such a dispersion system, and the surfactant is not particularly limited, but is preferably HLB (Hydrophile Lypophile Balance).
Is a nonionic surfactant having 10 to 17 such as polyoxymethylene octyl phenyl ether, polyoxyethylene trimethyl nonyl ether, and polyexethylene sorbitan stearate.
You may use these surfactants in mixture of 2 or more types.

A mixture of the organopolysiloxane composition according to the present invention and a dispersion medium, if necessary, for suppressing the curing of the emulsion, as a curing inhibitor, acetylene compounds, hydrazines, triazoles, phosphines, mercaptans, etc. , A heat-resistant agent, flame retardant,
A plasticizer or the like may be added.

In the present invention, a mixture of the above-mentioned organopolysiloxane composition and a dispersion medium is stirred to have an average particle size of 1 μm.
The following minute droplets (emulsion particles) are formed.

To make a mixture of the organopolysiloxane composition and the dispersion medium into fine emulsion particles having an average particle size of 1 μm or less, for example, the mixture is divided into a plurality of liquid streams under a high pressure of 10 to 2000 kg / cm ² , How to make this liquid collide in the collision area (Microfluidization American Paint &
Coating Journal P24 ~ 26), a method of spraying with a spray nozzle, a method of rapidly flushing to atmospheric pressure, a method of flushing to atmospheric pressure and at the same time colliding with a baffle plate are adopted.

As described above, before the mixture of the organopolysiloxane composition and the dispersion medium is made into emulsion particles having an average particle size of 1 μm or less, the organopolysiloxane composition and the dispersion medium are mixed and stirred by a usual stirring operation in advance. It is preferable to use emulsion particles having an average particle size larger than 1 μm.

The liquid temperature during emulsification as above is -10 to 90 ° C.
It is preferably in the range of 0 to 40 ° C. If the temperature of the mixture at the time of emulsification is less than −10 ° C., the viscosity of the mixture tends to be too high.
If the temperature is higher than 0 ° C, the curing reaction will proceed during the emulsification, and it tends to be difficult to obtain a fine silicone resin.

The emulsion particles thus prepared having an average particle size of 1 μm or less are cured by heating the emulsion. This curing is 30-300 ℃, preferably 50-200
The curing time is 1 minute to 6 hours, preferably 5 minutes to 3 hours. This curing reaction may be carried out under pressure if necessary. If the curing temperature is lower than 30 ° C., the curing speed will be slow, and fusion of particles tends to occur during curing.

The silicone resin obtained as described above has an average particle size of 1 μm or less, which is extremely small. For this reason, it is very difficult to collect and handle, but with or without heating the resulting suspension of silicone resin particles,
Part of the dispersion medium such as water may be distilled off and the particles may be collected in an aggregated state. In addition, after agglomeration in this manner, or by agglomeration without agglomeration, the particles can be granulated and recovered by spray drying.

The silicone fine particles thus aggregated in the granular form can be dispersed again by applying a small stress. It can be dispersed again into single particles in a kneading step during use.

The fine particles or the granular aggregated particles thereof collected as described above may be washed with a low boiling point polar solvent such as acetone, if necessary, separated, and vacuum dried.

The silicone resin fine particles or granular agglomerates thereof obtained as described above are excellent in properties such as elasticity, lubricity, water repellency, electric insulation, heat resistance, and chemical resistance, and thus are synthetic resin fillers. In particular, since the particle size is extremely small, it can be used as a filler for various electronic materials.

EFFECTS OF THE INVENTION In the present invention, a mixture of a composition of an organopolysiloxane having a specific structure and water is emulsified by stirring, has an extremely small diameter, and is unlikely to fuse and become huge during curing. Particle size of 1μm
The following silicone resin fine particles or their granular aggregated particles can be obtained efficiently and economically.

EXAMPLES Hereinafter, the present invention will be described with reference to Examples, but the present invention is not limited to these Examples.

In addition, "part" in the examples means "part by weight".

Example 1 Average composition formula(Ie a = 2, b = 3, c = 30, d = 0)
50 parts vinyl polysiloxane and average composition formula(That is a '= 0, b' = 35, c '= 0, d' = 2)
9 parts of vinyl polysiloxane represented by
The hydrosilyl group / vinyl group molar ratio of the resiloxane is 1.
5) and a platinum-vinylsiloxer with a platinum content of 30%
Complex 9 × 10^-FourAnd the HLB = 14.9 surfactant
Lioxyethylene sorbitan stearate (flower
Mix with 1.5 parts of King Leo Doll TW-S120) with ice cooling
Then, add 480 parts of water to the obtained mixture and homogenize.
Stir for about 10 seconds at room temperature, then microfluidizer
(Microfluidics Corporation M-11
0H type) with a feed rate of 50 ml / min.
Therefore, emulsification was performed at room temperature.

100 g of this emulsion was placed in a flask and heated with stirring at 90 ° C. for 1 hour to cure.

Using a spray dryer (Mini Spray GA-31 type manufactured by Yamato Scientific Co., Ltd.), the suspension thus obtained was supplied at a liquid feed rate of 10 g / min and a hot air flow rate of 0.5 m ³ / min (inlet temperature
Water was removed by evaporation at 150 ° C and an outlet temperature of 80 ° C.

As a result of observing the obtained granular particles by SEM, most of the simple particles had a particle size of 1 μm or less.

Example 2 Average composition formula (That is, a = 2, b = 3, c = 65, d = 0) is used (hydrosilyl group / vinyl group molar ratio of the two polysiloxanes is 2.9) at 70 ° C.
Granular particles were obtained in the same manner as in Example 1 except that the material was heat-cured for 3 hours.

As a result of observing the obtained particles by SEM, most of the particles alone had a particle size of 1 μm.

Comparative Example 1 Average composition formula (Ie, a = 2, b = 0, c = 600, d = 0) except that 50 parts of the vinyl polysiloxane represented by the formula (1) and 0.4 part of the hydropolysiloxane used in Example 1 were used (two kinds of poly The molar ratio of hydrosilyl group / vinyl group of siloxane is
2.8), and granular particles were obtained in the same manner as in Example 1.

As a result of observing the obtained particles by SEM, the average particle size was 70.
μm.

Claims (2)

(57) [Claims] 1. (i) (In the formula, a + b + c + d = 5 to 500, a + b = 2 to 100)
A linear or branched liquid organovinylpolysiloxane having (ii) (Where a '+ b' + c '+ d' = 5 to 500, a '+ b'
= 2-500) having a linear, branched or cyclic organohydropolysiloxane, and (iii) a platinum-based catalyst, the step of preparing an organopolysiloxane composition [A], the above organopolysiloxane composition [A] and the dispersion medium [B] are mixed and stirred, and the organopolysiloxane composition [A] is dispersed in the dispersion medium [B] to have an average particle size of 1 μm or less. A method for producing fine silicone resin particles, which comprises a step of forming an emulsion of [A], and a step of curing the organopolysiloxane composition [A] in the formed emulsion to form fine silicone resin particles having an average particle diameter of 1 μm or less. . 2. The vinyl polysiloxane according to claim 1, wherein a + b + c + d = 5 to 100, a + b = 2 to 3
0, in hydroxypolysiloxane, a '+ b' +
The method for producing silicone resin fine particles according to claim 1, wherein c ′ + d ′ = 5 to 50, a ′ + b ′ = 3 to 50, and a surfactant is contained in the dispersion system.