JP6980402B2 - Core shell particles - Google Patents

Description

The present invention relates to core-shell particles composed of a core portion and a shell portion provided on the surface thereof.

In recent years, resin fine particles having a size of several μm or more have been used as modifiers in order to improve the mechanical properties and optical properties of plastic products, paints, inks, adhesives and the like.

As the resin fine particles that can be used as the modifier, for example, Patent Document 1 describes an inner layer mainly composed of an acrylic acid ester copolymer having a glass transition temperature of 0 ° C. or lower, and methacrylic acid having a glass transition temperature of 60 ° C. or higher. A multi-layered acrylic resin particles composed of an outer layer mainly composed of an ester copolymer are disclosed. Further, Patent Document 2 includes a rubber core made of a poly (meth) acrylic acid ester copolymer having a three-dimensional crosslinked structure and a glass transition temperature of 0 ° C. or lower, and a hard resin having a glass transition temperature of 60 ° C. or higher. A beaded thermoplastic polymer particle having a core-shell structure composed of a non-adhesive shell is disclosed.

Japanese Unexamined Patent Publication No. 2003-128736 Japanese Unexamined Patent Publication No. 2007-070624

When aiming at modifying the characteristics of a soft resin composition, soft resin fine particles are preferably used. However, the soft resin fine particles have a drawback that they become rubbery and difficult to handle as powder. In order to pulverize such soft resin fine particles, a method such as adding silica particles is adopted, but since inorganic particles such as silica particles are not fixed to the resin fine particles, the resin composition There is a problem that silica particles fall off in the object.

Therefore, soft resin fine particles having a size of several μm or more added to the soft resin composition exhibit high softness that can follow deformation such as mixing of the resin composition without causing the above problems. Is required. Preferably, it is further required to have handleability as a powder and solvent resistance required when mixed with a resin composition. The particles disclosed in Patent Documents 1 and 2 described above are polymer particles having a multilayer structure of an inner layer and an outer layer, and particles having a soft inner layer are disclosed, but the outer layer is hard and the softness thereof. It was still inadequate.

The present invention has been made by paying attention to the above circumstances, and has a size of several μm or more, exhibits excellent softness, and is preferably powder handling and solvent resistance. It is intended to provide excellent core-shell particles. Hereinafter, the core-shell particles of the present invention may be referred to as "resin particles".

The core-shell particles of the present invention are composed of a core portion and a shell portion provided on the surface thereof, and have a volume average particle diameter of 3 μm or more and 150 μm or less, and a coefficient of variation of the particle diameter of 20% or more. The 10% K value of any of the particles having a particle size of 10 ± 2 μm, 30 ± 2 μm, or 50 ± 2 μm, which is the closest to the volume average particle size, satisfies the following range.
The 10% K value of a particle with a particle diameter of 10 ± 2 μm is 830 N / mm ² or less. The 10% K value of a particle with a particle diameter of 30 ± 2 μm is 680 N / mm ² or less. / Mm ² or less

The core portion contains a copolymer having at least one kind of monofunctional (meth) acrylic monomer (C1) unit and at least one kind of crosslinkable (meth) acrylic monomer (C2) unit, and has a FOX formula. The glass transition temperature Tg of the polymer composed of only the monofunctional (meth) acrylic monomer (C1) calculated based on the above is less than 0 ° C., and the shell portion is the monofunctional (meth) acrylic monomer (S1). A weight containing at least one unit and a copolymer having at least one crosslinkable monomer (S2) unit, and consisting only of the monofunctional (meth) acrylic monomer (S1) calculated based on the FOX equation. It is preferable that the glass transition temperature Tg of the coalescence is 0 ° C. or higher and lower than 50 ° C.

Further, the core-shell particles of the present invention are composed of a core portion and a shell portion provided on the surface thereof, and the core portion includes at least one kind of monofunctional (meth) acrylic monomer (C1) unit. , A polymer containing at least one crosslinkable (meth) acrylic monomer (C2) unit and consisting only of the monofunctional (meth) acrylic monomer (C1) calculated based on the FOX equation. The glass transition temperature Tg is less than 0 ° C., and the shell portion has at least one monofunctional (meth) acrylic monomer (S1) unit and at least one crosslinkable monomer (S2) unit. Even those characterized in that the glass transition temperature Tg of the polymer containing only the monofunctional (meth) acrylic monomer (S1) including the coalescence and calculated based on the FOX equation is 0 ° C. or higher and lower than 50 ° C. be.

The monofunctional (meth) acrylic monomer (S1) in the shell portion is preferably an ester of an alcohol having 3 or more carbon atoms and (meth) acrylic acid.

It is preferable that the crosslinkable (meth) acrylic monomer unit is contained as the crosslinkable monomer (S2) unit of the shell portion.

The crosslinkable (meth) acrylic monomer in the shell portion is preferably polyethylene glycol di (meth) acrylate having 2 or more repetitions of ethylene glycol units.

The crosslinkable monomer (S2) unit of the shell portion is 1 to 50 parts by mass with respect to a total of 100 parts by mass of the monofunctional (meth) acrylic monomer (S1) unit and the crosslinkable monomer (S2) unit. Is preferable.

The core-shell particles of the present invention preferably have a proportion of particles that pass through a sieve having an opening of 1.18 mm in an amount of 80% by mass or more.

The core-shell particles of the present invention preferably have a MEK swelling rate of less than 3.0, which is calculated by the following solvent resistance test.
[Solvent resistance test]
Test tubes A and B having an inner diameter of 15 mm were prepared, and 2.5 g of core-shell particles and 20 ml of a 1% by mass emulsifier aqueous solution were placed in test tube A, and 2.5 g of core-shell particles and 20 ml of methyl ethyl ketone were placed in test tube B. , Test tubes A and B are each dispersed by ultrasonic waves for 5 minutes, left for 12 hours, then the height of the settled core-shell particles is measured, and the MEK swelling rate is calculated according to the following formula (1).
MEK swelling rate = (height of core-shell particles precipitated in methyl ethyl ketone (mm)) / (height of core-shell particles precipitated in an aqueous emulsifier solution (mm)) ... (1)

The core-shell particles of the present invention preferably have a ratio of the thickness of the shell portion to the volume average particle diameter of 0.03 or more and 0.12 or less.

The production method of the present invention is the method for producing the core-shell particles, which is a monofunctional (meth) acrylic monomer (C1), a crosslinkable (meth) acrylic monomer (C2), a polymerization initiator, and a water-soluble polymer. Step 1 of reacting a suspension of a mixture containing a system dispersion stabilizer and an aqueous solvent to form a core polymerized portion, and a monofunctional (meth) acrylic monomer (S1) unit, a crosslinkable monomer (S2) unit, It is characterized by including a step 2 of contacting an emulsion containing an emulsifier and an aqueous solvent with a reaction solution containing the core polymerized portion obtained in the above step 1 to form a shell polymerized portion on the surface of the core polymerized portion. And.

According to the present invention, it is possible to realize resin particles exhibiting excellent softness, preferably further excellent in powder handling and solvent resistance.

The core-shell particles of the present invention are core-shell particles composed of a core portion and a shell portion provided on the surface thereof, and have a volume average particle diameter of 3 μm or more and 150 μm or less, and a coefficient of variation of the particle diameter of 20% or more. The 10% K value of any particle having a particle size of 10 ± 2 μm, 30 ± 2 μm, or 50 ± 2 μm, which is the closest to the volume average particle size, satisfies the following range. Hereinafter, the core-shell particles of the present invention will be described in detail.
The 10% K value of a particle with a particle diameter of 10 ± 2 μm is 830 N / mm ² or less. The 10% K value of a particle with a particle diameter of 30 ± 2 μm is 680 N / mm ² or less. / Mm ² or less

The present invention is intended for core-shell particles having a volume average particle diameter of 3 μm or more and 150 μm or less. The lower limit of the volume average particle diameter is preferably 5 μm or more, and more preferably 8 μm or more. The upper limit of the volume average particle diameter is preferably 120 μm or less, more preferably 100 μm or less, and further preferably 80 μm or less.

Further, the coefficient of variation (CV value) of the particle size of the core-shell particles of the present invention is 20% or more. When the CV value of the particle diameter of the core-shell particles is 20% or more, when the core-shell particles are mixed with the resin composition, the fine particles enter the gaps between the particles, so that the packing density of the core-shell particles can be improved.

The coefficient of variation (CV value) of the particle size is a value obtained by the following formula from the standard deviation of the particle size based on the volume and the volume average particle size obtained by measuring the particles with a particle size distribution measuring device using the call counter method. Is.

Coefficient of variation of particle size (%) = (standard deviation of particle size based on volume / volume average particle size) x 100

The lower limit of the CV value of the particle size is preferably 23% or more, more preferably 25% or more. The upper limit of the CV value of the particle size is, for example, 60% or less, preferably 55% or less, and more preferably 53% or less.

The thickness of the shell portion is preferably 0.8 μm or more and 3.5 μm or less. By setting the thickness of the shell part to 0.8 μm or more, the effect of the shell part (particularly, the handling of powder and the solvent resistance are improved, and the excellent softness and handling of powder are compatible). Can be demonstrated more effectively. The thickness of the shell portion is more preferably 1.0 μm or more, still more preferably 1.3 μm or more. Further, it is preferable that the thickness of the shell portion is 3.5 μm or less because the softness of the core portion can be sufficiently exhibited. The thickness of the shell portion is more preferably 3.0 μm or less, further preferably 2.5 μm or less, still more preferably 2.0 μm or less.

The lower limit of the ratio (shell thickness / volume average particle diameter) between the thickness of the shell portion and the volume average particle diameter of the core shell particles is, for example, 0.02 or more, preferably 0.03 or more, and the upper limit is, for example, 0. It is 12 or less, preferably 0.10 or less.

Further, the core-shell particles of the present invention show a compressive elastic modulus at the initial stage of deformation, which can be used as an index of softness, particularly a small value of 10% K value obtained by the following method, which is not more than a certain value. As a result, it is possible to achieve excellent softness that can sufficiently follow the deformation of the soft resin composition.

Specifically, the 10% K value of any particle having a particle diameter of 10 ± 2 μm, 30 ± 2 μm, or 50 ± 2 μm, which is the closest to the volume average particle diameter, satisfies the following range.
The 10% K value of a particle with a particle diameter of 10 ± 2 μm is 830 N / mm ² or less. The 10% K value of a particle with a particle diameter of 30 ± 2 μm is 680 N / mm ² or less. / Mm ² or less

The above 10% K value is measured by applying a load toward the center of the test particle and measuring the load value when the compressive displacement becomes 10% of the particle diameter, and more specifically, by the method shown in the examples described later. , The compressive elastic modulus obtained by the following formula.

In the above formula, E is the compressive elastic modulus (N / mm ² ), F is the compressive load (N), S is the compressive displacement (mm), and R: the radius of the particles (mm).

When the volume average particle diameter is 20 μm, that is, an intermediate value between the particle diameter of 10 ± 2 μm and the particle diameter of 30 ± 2 μm, the 10% K value of the particles having a particle diameter of 10 ± 2 μm and the particle diameter of 30 ± 2 μm It is sufficient that any one of the 10% K values of the particles satisfies the above range. When the volume average particle diameter is 40 μm, that is, an intermediate value between the particle diameter of 30 ± 2 μm and the particle diameter of 50 ± 2 μm, the 10% K value of the particles having a particle diameter of 30 ± 2 μm and the particle diameter of 50 ± 2 μm It is sufficient that any one of the 10% K values of the particles satisfies the above range.

10% K value of the particles having a particle size of 10 ± 2 [mu] m is in the as 830N / mm ² below, preferably 825N / mm ² or less, and more preferably not more than 820N / mm ^2. The lower limit of the 10% K value is not particularly limited, but is, for example, 15 N / mm ² or more, preferably 50 N / mm ² or more, and more preferably 100 N / mm ² or more.

10% K value of the particles having a particle size of 30 ± 2 [mu] m is in the as 680N / mm ² below, preferably 675N / mm ² or less, and more preferably not more than 670N / mm ^2. The lower limit of the 10% K value is not particularly limited, but is, for example, 10 N / mm ² or more, preferably 50 N / mm ² or more, and more preferably 100 N / mm ² or more.

10% K value of the particles having a particle size of 50 ± 2 [mu] m is in the as 320N / mm ² below, preferably 315N / mm ² or less, and more preferably not more than 310N / mm ^2. The lower limit of the 10% K value is not particularly limited, but is, for example, 5 N / mm ² or more, preferably 50 N / mm ² or more, and more preferably 100 N / mm ² or more.

In the present invention, the 10% K value of the particle diameter closest to the volume average particle diameter satisfies the above range, and further, among the particle diameters of 10 ± 2 μm, 30 ± 2 μm, and 50 ± 2 μm, the volume average particle diameter It is preferable that the 10% K value of the particle diameter other than the particle diameter closest to is also satisfied with the above range. For example, when the volume average particle diameter is 35 μm and the particles have a particle diameter of 10 ± 2 μm but no particles having a particle diameter of 50 ± 2 μm, not only the 10% K value of the particles having a particle diameter of 30 ± 2 μm but also the 10% K value. It is preferable that the 10% K value of the particles having a particle diameter of 10 ± 2 μm also satisfies the above range. Further, when the volume average particle diameter is 35 μm and the particles have a particle diameter of 10 ± 2 μm and a particle having a particle diameter of 50 ± 2 μm, not only the 10% K value of the particles having a particle diameter of 30 ± 2 μm but also the particle diameter of 10 ± It is preferable that the 10% K value of the 2 μm particles and / or the particles having a particle diameter of 50 ± 2 μm also satisfies the above range.

Although the core-shell particles of the present invention have high softness as described above, they are excellent in powder handling. Specifically, the handleability of the powder can be evaluated by the ratio of the core-shell particles passing through the sieve. Since the core-shell particles of the present invention suppress agglomeration and have good fluidity, the proportion of core-shell particles passing through a sieve having an opening of 1.18 mm can be 80% by mass or more. The proportion of core-shell particles that pass through a 1.18 mm mesh sieve is more preferably 100% by weight.

Further, although the core-shell particles of the present invention have high softness as described above, they are superior in solvent resistance to particles of a soft material alone. That is, when the core-shell particles of the present invention are added to the solvent, it is possible to prevent the core-shell particles from swelling containing the solvent. As a specific index of solvent resistance, MEK (methyl ethyl ketone) swelling rate obtained by a solvent resistance test according to the following procedure can be used.

In the solvent resistance test, test tubes A and B having an inner diameter of 15 mm were prepared, 2.5 g of core-shell particles and 20 ml of a 1% by mass emulsifier aqueous solution were placed in test tube A, and 2.5 g of core-shell particles were placed in test tube B. And 20 ml of methyl ethyl ketone was added, test tubes A and B were each dispersed by ultrasonic waves for 5 minutes, left for 12 hours, then the height of the settled core-shell particles was measured, and the MEK swelling rate was calculated according to the following formula (1). do.

MEK swelling rate = (height of core-shell particles precipitated in methyl ethyl ketone (mm)) / (height of core-shell particles precipitated in an aqueous emulsifier solution (mm)) ... (1)

The core-shell particles of the present invention can have the above-mentioned MEK swelling rate of less than 3.0, preferably 2.8 or less, and more preferably 2.5 or less. The lower limit of the MEK swelling rate is not particularly limited and is preferably 1.0, but is usually about 1.1.

The emulsifier used in the above solvent resistance test is not particularly limited as long as the particles can be dispersed well, and is, for example, a polyoxyethylene alkyl ether sulfate ester salt (for example, "High Tenol (registered trademark) manufactured by Daiichi Kogyo Seiyaku Co., Ltd." ) N-08 ”) can be used, and as another preferably usable emulsifier, among the emulsifiers contained in the shell preemulsion exemplified in the method for producing core-shell particles described later, an emulsifier having a polyoxyethylene chain can be mentioned. Will be.

Next, the components of the core portion and the shell portion constituting the core-shell particles of the present invention will be described. In addition, in this specification, a monomer unit means a structural unit derived from the monomer in a polymer. Further, in the present specification, "(meth) acryloyl group", "(meth) acrylate", and "(meth) acrylic" are "acryloyl group and / or methacrylic acid group", "acrylate and / or methacrylate", and "acrylic", respectively. And / or methacrylic.

The core portion of the present invention may contain a copolymer having at least one monofunctional (meth) acrylic monomer (C1) unit and at least one crosslinkable (meth) acrylic monomer (C2) unit. preferable.

As the monofunctional (meth) acrylic monomer (C1), a C _1-12 alkyl ester of (meth) acrylic acid is preferable. Specifically, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, 2-ethylhexyl (meth). ) Acrylate, lauryl (meth) acrylate and the like can be mentioned, and one kind or two or more kinds can be used, and it is preferable to use two or more kinds in combination. As the monofunctional (meth) acrylic monomer unit (C1), the alkyl group is preferably linear and long chain, more preferably the alkyl has 3 or more carbon atoms, and the alkyl has 3 or more carbon atoms. Can be, for example, 10 or less, and further can be 8 or less. Particularly preferably, n-butyl acrylate and n-butyl methacrylate are used in combination.

The crosslinkable (meth) acrylic monomer (C2) means a compound having two or more (meth) acryloyl groups in one molecule. The two or more (meth) acryloyl groups are preferably bonded via a diol compound such as alkylene glycol or polyalkylene glycol; a triol compound; a tetraol compound; a polyol compound such as a hexaol compound. In particular, the crosslinkable (meth) acrylic monomer (C2) is preferably a 2 to 6 functional crosslinkable (meth) acrylic monomer.

Specific examples of the bifunctional crosslinkable (meth) acrylic monomer include ethylene glycol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, and 1,6-hexanediol di (meth) acrylate. Alcandiol di (meth) acrylates such as 1,9-nonanediol di (meth) acrylates; alkene glycol di (meth) acrylates such as 1,3-butylene glycol di (meth) acrylates; polyethylene glycol di (meth) acrylates ( The number of repetitions of the ethylene glycol unit is, for example, 2 to 150); and the like. Examples of the trifunctional crosslinkable (meth) acrylic monomer include trimethylolpropane tri (meth) acrylate, and examples of the tetrafunctional crosslinkable (meth) acrylic monomer include pentaerythritol tetra (meth) acrylate. Examples of the hexafunctional crosslinkable (meth) acrylic monomer include dipentaerythritol hexa (meth) acrylate. The crosslinkable (meth) acrylic monomer (C2) may be used alone or in combination of two or more.

As the crosslinkable (meth) acrylic monomer (C2), a 2 to 4 functional crosslinkable (meth) acrylic monomer is more preferable, and a bifunctional crosslinkable (meth) acrylic monomer is more preferable. Particularly preferably, it is a polyethylene glycol di (meth) acrylate having an ethylene glycol unit repetition number of 2 to 10, preferably 2 to 8.

In the present invention, it is preferable that the glass transition temperature Tg of the polymer composed of only the monofunctional (meth) acrylic monomer (C1) is less than 0 ° C. By setting the glass transition temperature Tg to less than 0 ° C., the core portion becomes soft. In the polymer composed of only the monofunctional (meth) acrylic monomer (C1), only the monofunctional (meth) acrylic monomer is extracted from the monomers constituting the core portion, and between the monofunctional (meth) acrylic monomers. It refers to a conceptual polymer obtained by (co) polymerizing only these (these) while maintaining the ratio of. This conceptual polymer means a homopolymer consisting of only one kind when only one kind is used as C1, and a copolymer consisting of two or more kinds of C1 when two or more kinds are used as C1. means.

In the present invention, the glass transition temperature Tg means a value obtained by converting the glass transition temperature Tga at the absolute temperature obtained by the following formula (a) into _{a temperature in degrees Celsius.}

1 / Tg _a = Σ (W _i / Tg _i ) ... (a)
In the above formula (a), Tg _a is the a monofunctional (meth) Glass transition temperature of the polymer composed only of the acrylic monomer (C1) (unit is an absolute temperature). Wi _i is the mass ratio of each monofunctional (meth) acrylic monomer i in the polymer composed of only the monofunctional (meth) acrylic monomer (C1). Tg _i is the glass transition temperature (unit: absolute temperature) of the homopolymer formed only from each monofunctional (meth) acrylic monomer i.

The above formula (a) is a formula called a FOX formula, and for each monomer constituting the polymer, the glass transition temperature of the polymer is based on the glass transition temperature _{Tg i of the homopolymer of the monomer.} is a formula for calculating the Tg _a, the details of which, bulletin-of-the-American physical Society, Series 2 (Bulletin of the American physical Society , Series 2), Vol. 1, No. 3, No. It is described on page 123 (1956). _{Further, the glass transition temperature (Tg i} ) of homopolymers of various monomers for calculation by the FOX formula is described in, for example, paints and paints (Paint Publishing Co., Ltd., 10 (No. 358), 1982). It is possible to adopt the numerical value etc.

The glass transition temperature Tg of the polymer composed of only the monofunctional (meth) acrylic monomer (C1), which is obtained by converting the glass transition temperature obtained by the FOX formula into the temperature in degrees Celsius, is more preferably −5 ° C. or lower. , −10 ° C. or lower is more preferable, and −15 ° C. or lower is even more preferable. The lower limit of Tg is, for example, −50 ° C. or higher, which may be −45 ° C. or higher, or −40 ° C. or higher.

The ratio of the monofunctional (meth) acrylic monomer (C1) unit in the copolymer of the core portion is, for example, 90% by mass or more, and by doing so, the core portion can be made softer. The ratio of the monofunctional (meth) acrylic monomer (C1) unit is preferably 92% by mass or more, more preferably 93% by mass or more, and most preferably 100% by mass.

Further, the ratio of the crosslinkable (meth) acrylic monomer (C2) unit to the copolymer of the core portion is preferably, for example, 10% by mass or less. By doing so, the core portion can be made softer. The ratio of the crosslinkable (meth) acrylic monomer (C2) unit is preferably 8% by mass or less, more preferably 7% by mass or less, and the lower limit is not particularly limited, but is, for example, 2% by mass or more.

Next, the components of the shell portion of the present invention will be described. The shell portion of the present invention preferably contains a copolymer having at least one monofunctional (meth) acrylic monomer (S1) unit and at least one crosslinkable monomer (S2) unit.

As the monofunctional (meth) acrylic monomer (S1), a C _1-12 alkyl ester of (meth) acrylic acid is preferable. Specifically, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, 2-ethylhexyl (meth). ) Acrylate, lauryl (meth) acrylate and the like can be mentioned, and one kind or two or more kinds can be used. As the monofunctional (meth) acrylic monomer unit (S1), it is preferable that the alkyl group is linear and long chain. The monofunctional (meth) acrylic monomer (S1) is preferably an ester of an alcohol having 3 or more carbon atoms and (meth) acrylic acid, and further has, for example, 10 or less carbon atoms and further 8 or less carbon atoms. It can be an ester of alcohol and (meth) acrylic acid. More preferably, it is n-butyl methacrylate.

The crosslinkable monomer (S2) may be any crosslinkable monomer, and specific examples thereof include a vinyl-based crosslinkable monomer containing at least a vinyl group, for example, a crosslinkable (meth) acrylic monomer and the like. Examples thereof include crosslinkable styrene-based monomers. It is preferably a crosslinkable (meth) acrylic monomer.

The crosslinkable (meth) acrylic monomer means a compound having two or more (meth) acryloyl groups in one molecule. The two or more (meth) acryloyl groups are preferably bonded via a diol compound such as alkylene glycol or polyalkylene glycol; a triol compound; a tetraol compound; a polyol compound such as a hexaol compound. In particular, the crosslinkable (meth) acrylic monomer is preferably a 2 to 6 functional crosslinkable (meth) acrylic monomer.

Examples of the bifunctional crosslinkable (meth) acrylic monomer include esters of an aliphatic diol having two or more carbon atoms between two hydroxyl groups and (meth) acrylic acid. Specifically, such as ethylene glycol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, and 1,9-nonanediol di (meth) acrylate. Alcandiol di (meth) acrylates; alkene glycol di (meth) acrylates such as 1,3-butylene glycol di (meth) acrylates; for example polyethylene glycol di (meth) acrylates containing 2 to 150 ethylene glycol units; etc. Be done.

Examples of the trifunctional crosslinkable (meth) acrylic monomer include trimethylolpropane tri (meth) acrylate, and examples of the tetrafunctional crosslinkable (meth) acrylic monomer include pentaerythritol tetra (meth) acrylate. Examples of the hexafunctional crosslinkable (meth) acrylic monomer include dipentaerythritol hexa (meth) acrylate. The crosslinkable (meth) acrylic monomer may be used alone or in combination of two or more.

As the crosslinkable (meth) acrylic monomer, a 2 to 4 functional crosslinkable (meth) acrylic monomer is more preferable, and a bifunctional crosslinkable (meth) acrylic monomer is more preferable.

In the bifunctional crosslinkable (meth) acrylic monomer, the alkyl group between the two (meth) acryloyl groups is preferably a straight chain and a long chain, and the number of carbon atoms between the two hydroxyl groups is 3 or more. More preferably, it is an ester of an aliphatic diol and (meth) acrylic acid. Further, an ester of an aliphatic diol having a carbon number of, for example, 10 or less, further 8 or less, and further 6 or less between two hydroxyl groups and (meth) acrylic acid can be mentioned. Alternatively, it is more preferable that the polyethylene glycol di (meth) acrylate has a number of repetitions of 2 or more in ethylene glycol units. The number of repetitions of the ethylene glycol unit of the polyethylene glycol di (meth) acrylate is more preferably 3 or more. The upper limit of the number of repetitions of the ethylene glycol unit can be, for example, 10 or less, further 8 or less, and further 6 or less.

Examples of the crosslinkable styrene-based monomer include divinylbenzene, divinylnaphthalene, and derivatives thereof.

It is preferable that the crosslinkable monomer (S2) contains a crosslinkable (meth) acrylic monomer unit because the handleability of the powder can be sufficiently improved. The ratio of the crosslinkable (meth) acrylic monomer to the crosslinkable monomer (S2) is preferably 80% by mass or more, more preferably 90% by mass or more, and most preferably 100% by mass.

The crosslinkable monomer (S2) unit of the shell portion shall be 1 to 50 parts by mass with respect to a total of 100 parts by mass of the monofunctional (meth) acrylic monomer (S1) unit and the crosslinkable monomer (S2) unit. Is preferable. By setting the crosslinkable monomer (S2) unit to 1 part by mass or more, the handleability and solvent resistance of the powder can be improved. The crosslinkable monomer (S2) unit is preferably 2 parts by mass or more. Further, by setting the crosslinkable monomer (S2) unit to 50 parts by mass or less, the softness of the resin particles can be enhanced. The crosslinkable monomer (S2) unit is preferably 45 parts by mass or less.

Further, in the shell portion of the present invention, it is preferable that the glass transition temperature Tg of the polymer composed of only the monofunctional (meth) acrylic monomer (S1) calculated based on the FOX equation is 0 ° C. or higher and lower than 50 ° C. .. That is, in the formula (a) used in the calculation of the glass transition temperature Tg in the core portion, the monofunctional (meth) acrylic monomer (C1) is replaced with the monofunctional (meth) acrylic monomer (S1). It is preferable that the calculated glass transition temperature Tg of the polymer composed of only the monofunctional (meth) acrylic monomer (S1) is 0 ° C. or higher and lower than 50 ° C. By setting the glass transition temperature Tg to 0 ° C. or higher, good handleability of the powder can be ensured. Further, by setting the glass transition temperature Tg to less than 50 ° C., the softness of the core portion can be sufficiently exhibited, and as a result, the softness of the resin particles can be sufficiently enhanced. The glass transition temperature Tg is more preferably 5 ° C. or higher, further preferably 10 ° C. or higher, and even more preferably 15 ° C. or higher. The upper limit of the glass transition temperature Tg is more preferably 45 ° C. or lower, still more preferably 40 ° C. or lower, and even more preferably 35 ° C. or lower.

In the polymer composed of only the monofunctional (meth) acrylic monomer (S1), only the monofunctional (meth) acrylic monomer is extracted from the monomers constituting the shell portion, and between the monofunctional (meth) acrylic monomers. It refers to a conceptual polymer obtained by (co) polymerizing only these (these) while maintaining the ratio of. This conceptual polymer means a homopolymer consisting of only one kind when only one kind is used as S1, and a copolymer consisting of two or more kinds S1 when two or more kinds are used as S1. means.

Next, a method for producing core-shell particles of the present invention, particularly core-shell particles in which the core portion and the shell portion satisfy the above-mentioned preferable components will be described. The manufacturing method is
(I) Monofunctional (meth) acrylic monomer (C1), crosslinkable (meth) acrylic monomer (C2), polymerization initiator, dispersion stabilizer (preferably water-soluble polymer dispersion stabilizer), and aqueous solvent. Step 1 to form a core polymerized portion by reacting a suspension of a mixture containing 2. The step 2; which comprises contacting the emulsion containing the above-mentioned step 1 with the reaction solution containing the core polymerized portion obtained in the above step 1 to form a shell polymerized portion on the surface of the core polymerized portion.

Each step of the above manufacturing method will be described in more detail below.
(I) Monofunctional (meth) acrylic monomer (C1), crosslinkable (meth) acrylic monomer (C2), polymerization initiator, dispersion stabilizer (preferably water-soluble polymer dispersion stabilizer), and aqueous solvent. Step 1 to form a core polymerized portion by reacting a suspension of a mixture containing

(I-1) Preparation of Suspension for Core First, in order to prepare a suspension for the core, a monofunctional (meth) acrylic monomer (C1), a crosslinkable (meth) acrylic monomer (C2), and polymerization A mixture containing an initiator, a dispersion stabilizer, and an aqueous solvent is placed in a container and stirred for a predetermined time to prepare a suspension.

Water is used as a medium for providing a place for suspension polymerization, and the aqueous solvent may be water alone or a combination of water and a non-aqueous solvent, but water alone is preferable. .. The amount of water is preferably 70 to 85 parts by mass in 100 parts by mass of the suspension.

The above-mentioned dispersion stabilizer is used to stably promote the polymerization reaction, and is, for example, a water-soluble polymer-based dispersion stable such as polyvinyl alcohol (PVA), polyvinylpyrrolidone, cellulose, gelatin, sodium polyacrylate, and sodium polymethacrylate. Agents; anionic surfactants such as sodium lauryl sulfate, polyoxyethylene alkylphenyl ether sulfate (eg, polyoxyethylene distyrylphenyl ether sulfate ammonium); cationic such as alkylamine salts, quaternary ammonium salts. Surfactants; Amphoteric ionic surfactants such as lauryldimethylamine oxide; Nonionic surfactants such as polyoxyethylene alkyl ethers; Other alginates, zeins, caseins; barium sulfate, calcium sulfate, barium carbonate, magnesium carbonate, Inorganic dispersants such as calcium phosphate, talc, clay, silica soil, bentonite, titanium hydroxide, thorium hydroxide, and metal oxide powder can be used. As the dispersion stabilizer, a water-soluble polymer-based dispersion stabilizer is preferable, more preferably one or more of PVA, polyvinylpyrrolidone, cellulose and gelatin, still more preferably one or more of PVA and polyvinylpyrrolidone, particularly. PVA is preferred. In addition, from the viewpoint of ensuring higher affinity with the organic resin as an additive, among the above, water-soluble polymer-based dispersion stabilizers, various surfactants, other alginates, zein, casein, etc. are used. It is preferable to use it.

The dispersion stabilizer is preferably, for example, 5 to 10 parts by mass in 100 parts by mass of the suspension for the core.

As the polymerization initiator, a radical polymerization initiator can be preferably used. The radical polymerization initiator is preferably a thermal polymerization initiator, and examples thereof include peroxide-based polymerization initiators and azo compound-based polymerization initiators. Examples of the peroxide-based polymerization initiator include benzoyl peroxide, lauroyl peroxide, octanoyl peroxide, orthochlorobenzoyl peroxide, orthomethoxybenzoyl peroxide, methyl ethyl ketone peroxide, diisopropylperoxydicarbonate, cumenehydroperoxide, cyclohexanone peroxide, and t-butylhydroperoxide. , Diisopropylbenzenehydroperoxide and the like. Examples of the azo compound-based polymerization initiator include 2,2'-azobisisobutyronitrile, 2,2'-azobis (2,4-dimethylvaleronitrile), and 2,2'-azobis (2,3-). Dimethylbutyronitrile), 2,2'-azobis- (2-methylbutyronitrile), 2,2'-azobis (2,3,3-trimethylbutyronitrile), 2,2'-azobis (2- Isobutyronitrile), 1,1'-azobis (cyclohexane-1-carbonitrile), 2,2'-4-methoxy-2,4-dimethylvaleronitrile), 2- (carbamoylazo) isobutyronitrile, Examples thereof include 4,4'-azobis (4-cyanovaleric acid), dimethyl-2,2'-azobisisobutyrate and the like.

The polymerization initiator is preferably 0.1 to 1 part by mass in 100 parts by mass of the suspension for the core.

The suspension may be agitated at about 200 to 400 rpm for about 1 to 3 hours using a paddle blade or the like, or may be agitated at a high speed of about 2000 to 4000 rpm for about 1 to 30 minutes. A known emulsification / dispersion device can be used for the high-speed stirring described above. Examples of the emulsification / dispersion device include Milder (manufactured by Ebara Corporation), T.I. K. High-speed shear turbine type disperser such as homomixer (manufactured by Primex); high-pressure jet homogenizer such as piston type high-pressure homogenizer (manufactured by Gorin), microfluidizer (manufactured by Microfluidix); ultrasonic homogenizer (Nissei Tokyo Office) An ultrasonic emulsification / disperser such as (manufactured by Mitsui Mfg. Co., Ltd.); a medium stirring disperser such as Atwriter (manufactured by Mitsui Mining Co., Ltd.); a forced gap passage type disperser such as a colloid mill (manufactured by Nissei Tokyo Office) can be used.

(I-2) Polymerization of Core Monomer After the core suspension is prepared, it is transferred to another container as necessary, and the temperature is raised in an inert gas atmosphere while stirring, and the core monomer is heated. Polymerize the components.

As the inert gas, nitrogen gas, a rare gas or the like can be used, and it is preferable to use nitrogen gas. The temperature rise temperature is, for example, 40 to 100 ° C, preferably 50 to 90 ° C.

The timing of mixing the core suspension and the mixture containing the shell monomer described later is preferably performed when the polymerization of the core monomer is sufficiently advanced. The polymerization rate of the core monomer can be estimated from the temperature change of the core suspension, and it is preferable to mix with the mixture containing the shell monomer immediately after the temperature of the core suspension reaches the maximum value.

(Ii) An emulsion containing a monofunctional (meth) acrylic monomer (S1) unit, a crosslinkable monomer (S2) unit, an emulsifier, and an aqueous solvent, and a reaction solution containing the core polymerized portion obtained in the above step 1. Step 2 to form a shell polymerized part on the surface of the core polymerized part by contacting

(Ii-1) Preparation of Preemulsion Containing Monomer Component for Shell The monomer component for shell contains a monofunctional (meth) acrylic monomer (S1) unit, a crosslinkable monomer (S2) unit, an emulsifier, and an aqueous solvent, and is polymerized. It is preferred that the initiator-free mixture be stirred at high speed and mixed with the core suspension as a preemulsion. By making the mixture containing the shell monomer into a pre-emulsion, the shell monomer component is uniformly dispersed in the core suspension, and the shell monomer component easily reaches the surface of the core particles.

The polymerization initiator remains in the core suspension, and the polymerization initiator promotes the polymerization of the shell monomer. Therefore, the shell preemulsion does not need to contain the polymerization initiator. Rather, if a polymerization initiator is contained, there is a risk that the shell monomer will polymerize alone and will not form a shell portion. The preemulsion does not require a polymerization initiator, but may be contained in a range that does not inhibit the formation of the shell portion.

The aqueous solvent may be water alone or a combination of water and a non-aqueous solvent, but water alone is preferable. The amount of water is preferably 40 to 60 parts by mass in 100 parts by mass of the preemulsion.

The emulsifiers are polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene sorbitan fatty acid ester, sorbitan fatty acid ester, polyoxysorbitan fatty acid ester, polyoxyethylene alkylamine, glycerin fatty acid ester, and oxyethylene-oxypropylene block copolymer. Nonionic surfactants such as: fatty acid salts, alkyl sulfate ester salts, alkylbenzene sulfonates, alkylnaphthalene sulfonates, alkane sulfonates, dialkyl sulfosuccinates, alkyl phosphate ester salts, naphthalene sulfonic acid formarin condensates. , Polyoxyethylene alkyl ether sulfate ester salt, polyoxyethylene phenyl ether sulfate ester salt, polyoxyethylene alkyl sulfate ester salt and other anionic surfactants, preferably anionic surfactants (particularly polyoxyethylene phenyl). Ether sulfate ester salt) is used.

The amount of the emulsifier is preferably 0.05 to 1.5 parts by mass (preferably 0.05 to 1 part by mass) in 100 parts by mass of the pre-emulsion.

For the pre-emulsification of the mixture containing the shell monomer component, the aqueous solvent and the emulsifier, for example, the same apparatus as that which can be used for high-speed stirring of the shell suspension described above can be used.

The amount of the shell pre-emulsion can be, for example, 8 to 20 parts by mass with respect to 100 parts by mass of the suspension for the core.

(Ii-2) Polymerization of Shell Monomer After mixing the core suspension and the shell preemulsion, the shell monomer is held at 40 to 100 ° C (preferably 50 to 90 ° C) for 1 to 3 hours. Can be polymerized. After the polymerization of the core and the shell is completed, filtration, centrifugation, drying and the like may be performed as appropriate. Drying may be carried out at, for example, 100 ° C. or lower (preferably 30 to 50 ° C.) for about 5 to 20 hours.

Hereinafter, the present invention will be described in more detail with reference to examples. The present invention is not limited by the following examples, and it is of course possible to carry out the present invention with appropriate modifications within a range that can be adapted to the above-mentioned purpose, and all of them are technical of the present invention. Included in the range.

The methods for measuring various physical properties performed in the following examples are as follows.

(1) Volume average particle size / coefficient of variation (CV value) of resin particles
To 0.1 part of the resin particles, 20 parts of a 1% aqueous solution of polyoxyethylene alkyl ether sulfate ammonium salt ("High Tenol (registered trademark) N-08" manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.), which is an emulsifier, is added. The dispersion liquid dispersed with a sound wave for 10 minutes was used as a measurement sample. The particle size (μm) of 30,000 particles was measured with a particle size distribution measuring device (“Coulter Multisizer Type III” manufactured by Beckman Coulter), and the volume average particle size was determined. As for the coefficient of variation of the particle size, the standard deviation of the particle size on a volume basis was obtained together with the volume average particle size, and the coefficient of variation (CV value) of the particle size was calculated according to the following formula.
Coefficient of variation of particle size (%) = (standard deviation of particle size based on volume / volume average particle size) x 100

(2) Measurement of shell thickness In the process of manufacturing polymer particles, which will be described later, the average value of the particle size measured by sampling the polymer solution immediately before adding the emulsion of the monomer component for the shell, and the weight finally obtained. The value obtained by dividing the difference from the average value of the particle diameters measured for the coalesced fine particles by 2 was defined as the shell thickness. Table 1 also shows the ratio of the thickness of the shell portion to the volume average particle diameter.

(3) 10% K value of resin particles A "soft surface" of one particle sprayed on a sample table (material: SKS flat plate) using a microcompression tester ("MCT-W500" manufactured by Shimadzu Corporation). In the "detection" mode, a circular flat plate indenter (material: diamond) with a diameter of 50 μm is used to apply a load toward the center of the particle at a constant load velocity (2.2295 mN / sec), and the compressive displacement becomes 10% of the particle diameter. The compressive load value (mN) at that time and the displacement amount (μm) at that time were measured. The diameter of the resin particles was measured using the caliper diameter calculation tool attached to the MCT-W500. The resin particles to be measured are as shown in "(4) Evaluation of softness of resin particles" below. Then, the obtained compressive load value (mN) is converted into a compressive load (N), the displacement amount (μm) obtained at that time is converted into a compressive displacement (mm), and the average particle diameter (μm) of the resin particles is obtained. The particle radius (mm) was calculated from the above, and calculated based on the following formula using these. The above measurement was performed in a constant temperature atmosphere of 25 ° C.

In the above formula, E: compressive elastic modulus (N / mm ² ), F: compressive load (N), S: compressive displacement (mm), R: particle radius (mm).

(4) Evaluation of softness of resin particles The softness is evaluated by the following procedure.
[1] As shown in (1) above, the volume average particle diameter is measured with a particle size distribution measuring device.
[2] Among the particle diameters of 10 ± 2 μm, 30 ± 2 μm, and 50 ± 2 μm, the particle diameter closest to the volume average particle diameter is selected.
[3] Ten resin particles having the above-selected particle diameters of 10 ± 2 μm, 30 ± 2 μm, or 50 ± 2 μm are measured with the MCT-W500 using the attached caliper diameter calculation tool.
[4] The 10% K value of each of the 10 resin particles measured above is calculated, and the average value is obtained.
For example, when the volume average particle diameter is 35 μm, 10 resin particles having a particle diameter of 30 ± 2 μm measured using the above tool are collected, and the 10% K value of these resin particles is measured, and the 10 particles are measured. The average value is a 10% K value of particles having a particle diameter of 30 ± 2 μm. Then, the softness is evaluated by the following index. In Table 1, in each example, in addition to the 10% K value of the particle diameter of 30 ± 2 μm, which is the closest to the volume average particle diameter, the 10% K value of the particles having a particle diameter of 10 ± 2 μm, and the particle diameter of 50 ± 2 μm. The 10% K value of the particles of is also shown.
[Softness index]
When the particle size is 10 ± 2 μm, “○” is for ^{830 N / mm 2} or less, and “×” is for more than ^{830 N / mm 2.}
When the particle size is 30 ± 2 μm, “○” is for ^{680 N / mm 2} or less, and “×” is for more than ^{680 N / mm 2.}
When the particle size is 50 ± 2 μm, “○” is for ^{320 N / mm 2} or less, and “×” is for more than ^{320 N / mm 2.}

(5) Evaluation of handleability of powder (resin particles) 100 g of polymer fine particles were placed on a sieve having a mesh size of 1.18 mm, shaken for 1 minute, and then the mass of the polymer fine particles passed through the sieve was measured. The pass rate was calculated by the following formula.

Pass rate (%) = (mass of polymer fine particles passed through a sieve (g) / 100 (g)) × 100

Those having a pass rate of 80 to 100% by mass were evaluated as "◯", and those having a pass rate of less than 80% by mass were evaluated as "x".

(6) Evaluation of solvent resistance of resin particles Test tubes A and B with an inner diameter of 15 mm were prepared, and 2.5 g of resin particles and polyoxyethylene alkyl ether sulfate ester ammonium salt (Daiichi Kogyo Seiyaku Co., Ltd.) were prepared in test tubes A. 20 ml of a 1% by mass aqueous solution of "Hitenol (registered trademark) N-08" manufactured by the same company was put in, and 2.5 g of resin particles and 20 ml of methyl ethyl ketone were put in test tube B, and then 5 test tubes A and 5 each were put. The particles were dispersed by ultrasonic waves for 1 minute and left for 12 hours. The height of the settled resin particles was measured, and the MEK swelling rate was calculated according to the following formula (1). In the following formula (1), the core-shell particles are expressed as resin particles.
MEK swelling rate = (height of resin particles precipitated in methyl ethyl ketone (mm)) / (height of resin particles precipitated in an aqueous emulsifier solution (mm)) ... (1)

Those with a MEK swelling rate of less than 3.0 were evaluated as "◯", and those with a MEK swelling rate of 3.0 or more were evaluated as "x".

(Manufacturing Example 1)
In a four-necked flask equipped with a cooling tube, a thermometer, and a dropping port, 666.7 parts of a 10% aqueous solution of polyvinyl alcohol ("Poval PVA-205" manufactured by Kuraray Co., Ltd.) (hereinafter, "part" is "mass part"). Meaning) was charged and kept at 25 ° C. Under stirring at 235 rpm, 47.5 parts of n-butyl acrylate (47.5% by mass of all core monomers) and 47.5 parts of n-butyl methacrylate (for all cores) as the core monomer components from the dropping port. 47.5% by mass in the monomer), 5.0 parts of triethylene glycol dimethacrylate (5% by mass in the monomer for all cores) and 2,2'-azobis (2,4-dimethylvaleronitrile) (Wako Pure Chemical Industries, Ltd.) A suspension was prepared by adding a solution prepared by dissolving 3.0 parts of "V-65" manufactured by the same company) and holding for 2 hours. The suspension was heated to 65 ° C. under continuous stirring and a nitrogen atmosphere to carry out radical polymerization of the monomer component for the core. The glass transition temperature of the homopolymer of n-butyl acrylate is 218.2K, and the glass transition temperature of the homopolymer of n-butyl methacrylate is 293.2K.

Next, in another flask, 1.3 parts of a 20% aqueous solution of polyoxyethylene styrene phenyl ether sulfate ammonium salt (“High Tenol (registered trademark) NF-08” manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) as an emulsifier was placed. In a solution dissolved in 50.0 parts of ion-exchanged water, 47.5 parts of n-butyl methacrylate (47.5 parts by mass with respect to a total of 100 parts by mass of core monomers) and triethylene as monomer components for shells. 2.5 parts of glycol dimethacrylate (2.5 parts by mass with respect to 100 parts by mass of the total of the monomer for the core) was added and emulsified and dispersed to prepare an emulsified solution of the monomer component for the shell.

Immediately after the polymerization of the monomer component for the core started, the temperature inside the flask reached the peak temperature and reached the maximum value, the emulsion of the monomer component for the shell was added. Radical polymerization of the monomer component for the shell was carried out by holding at 65 ° C. for 2 hours after the addition. The emulsion after radical polymerization was solid-liquid separated and vacuum-dried at 40 ° C. for 12 hours to obtain polymer fine particles (1). The physical characteristics of the obtained resin particles are as shown in Table 1.

(Manufacturing Examples 2 to 5)
Polymer fine particles (2) to (5) were obtained in the same manner as in Production Example 1 except that the type and amount of the monomer used were as shown in Table 1. The physical characteristics of the obtained polymer fine particles are as shown in Table 1.

(Manufacturing Example 6)
666.7 parts of a 10% aqueous solution of polyvinyl alcohol (“Poval PVA-205” manufactured by Kuraray Co., Ltd.) was charged in a four-necked flask equipped with a cooling tube, a thermometer, and a dropping port and kept at 25 ° C. Under stirring at 200 rpm, 60.0 parts of methyl methacrylate, 40.0 parts of ethylene glycol dimethacrylate and 2,2'-azobis (2,4-dimethylvaleronitrile) (Wako Pure Chemical Industries, Ltd.) as monomer components from the dropping port. A suspension was prepared by adding a solution prepared by dissolving 2.0 parts of "V-65" manufactured by Kogyo Co., Ltd. and holding for 2 hours. The suspension was heated to 65 ° C. under continuous stirring and a nitrogen atmosphere to carry out radical polymerization of the monomer components. The emulsion after radical polymerization was solid-liquid separated and vacuum-dried at 40 ° C. for 12 hours to obtain polymer fine particles (6). The physical characteristics of the obtained resin particles are as shown in Table 1.

(Manufacturing Example 7)
Polymer fine particles (7) were obtained in the same manner as in Production Example 6 except that the type and amount of the monomer used were as shown in Table 1. The physical characteristics of the obtained polymer fine particles are as shown in Table 1.

In Table 1, nBMA stands for n-butyl methacrylate, nBA stands for n-butyl acrylate, 3EG stands for triethylene glycol dimethacrylate, MMA stands for methyl methacrylate, EGDMA stands for ethylene glycol dimethacrylate, DVB stands for divinylbenzene, and St stands for St. Represents styrene. The degree of cross-linking of the shell is a value indicating the mass ratio of the content of the cross-linking monomer to the content of all the monomers in the shell as a percentage.

From Table 1, it can be seen that Examples 1 and 2 satisfying the requirements of the present invention both have good softness, excellent powder handling, low MEK swelling rate, and excellent solvent resistance.

On the other hand, in Comparative Examples 1 to 3, the softness was inferior because the 10% K value of the particles having a particle diameter of 30 ± 2 μm, which was the closest to the volume average particle diameter, was high. Further, when Example 1 and Comparative Example 2 are compared, in order to obtain resin particles having excellent softness and excellent powder handling property, the shell portion is divided into monofunctional (meth) acrylic monomer (S1) units. It is preferable to use a copolymer having at least one of the crosslinkable monomer (S2) units and at least one of the crosslinkable monomer (S2) units, and more preferably the crosslinkable monomer (S2) unit is a crosslinkable (meth) acrylic monomer unit. It turns out that it is preferable to have it.

Comparative Example 4 was inferior in softness because it had only a hard core portion and no shell portion. Further, Comparative Example 5 was inferior in powder handling and solvent resistance because it had only a soft core portion and not a shell portion.

The core-shell particles of the present invention are useful as additives (modifiers) for enhancing the mechanical properties and optical properties of rubber, films, paints, inks, adhesives and the like. Specifically, the core-shell particles of the present invention include, for example, ethylene-propylene-diene rubber, ethylene-propylene rubber, isoprene rubber, butyl rubber, styrene-butadiene rubber, polybutadiene rubber, NBR rubber, natural rubber, fluororubber chloroprene rubber, polyethylene resin, and the like. Polypropylene resin, acrylonitrile-butadiene-styrene resin, acrylonitrile-styrene resin, styrene-butadiene resin, polyacetal resin, polystyrene resin, vinyl chloride-vinyl acetate resin, acrylic resin, polymethylmethacrylate resin, polyester resin, polyamide resin, polyimide resin, As an additive (modifier) for improving the above characteristics by adding to polyurethane resin, epoxy resin, phenol resin, amino resin, polycarbonate resin, polyfluoroolefin resin, cellulose resin, alkyd resin, melamine resin, etc. It is useful.

Claims (9)

Core-shell particles composed of a core portion and a shell portion provided on the surface thereof.
The volume average particle diameter is 3 μm or more and 150 μm or less.
The 10% K value of any particle having a particle size of 10 ± 2 μm, 30 ± 2 μm or 50 ± 2 μm, which has a coefficient of variation of 20% or more and is closest to the volume average particle size, is in the following range. It meets,
The core portion contains a copolymer having at least one kind of monofunctional (meth) acrylic monomer (C1) unit and at least one kind of crosslinkable (meth) acrylic monomer (C2) unit, and has a FOX formula. The glass transition temperature Tg of the polymer composed of only the monofunctional (meth) acrylic monomer (C1) calculated based on this is less than 0 ° C.
The shell portion contains at least one of the monofunctional (meth) acrylic monomer (S1) units and at least one of the crosslinkable monomer (S2) units, and is calculated based on the FOX formula. A core-shell particle having a glass transition temperature Tg of 0 ° C. or higher and lower than 50 ° C. in a polymer composed of only the monofunctional (meth) acrylic monomer (S1).
The 10% K value of a particle with a particle diameter of 10 ± 2 μm is 830 N / mm ² or less. The 10% K value of a particle with a particle diameter of 30 ± 2 μm is 680 N / mm ² or less. / Mm ² or less The core-shell particles according to claim 1 , wherein the monofunctional (meth) acrylic monomer (S1) in the shell portion is an ester of an alcohol having 3 or more carbon atoms and (meth) acrylic acid. The core shell particle according to claim 1 or 2 , wherein the crosslinkable (meth) acrylic monomer unit is included as the crosslinkable monomer (S2) unit of the shell portion. The core-shell particles according to claim 3 , wherein the crosslinkable (meth) acrylic monomer in the shell portion is a polyethylene glycol di (meth) acrylate having 2 or more repetitions of ethylene glycol units. Claims that the crosslinkable monomer (S2) unit of the shell portion is 1 to 50 parts by mass with respect to a total of 100 parts by mass of the monofunctional (meth) acrylic monomer (S1) unit and the crosslinkable monomer (S2) unit. Item 2. The core-shell particle according to any one of Items 1 to 4. The core-shell particles according to any one of claims 1 to 5 , wherein the proportion of particles passing through a sieve having a mesh size of 1.18 mm is 80% by mass or more. The core-shell particle according to any one of claims 1 to 6 , which is calculated by the following solvent resistance test and has a MEK swelling rate of less than 3.0.
[Solvent resistance test]
Test tubes A and B having an inner diameter of 15 mm were prepared, and 2.5 g of core-shell particles and 20 ml of a 1% by mass emulsifier aqueous solution were placed in test tube A, and 2.5 g of core-shell particles and 20 ml of methyl ethyl ketone were placed in test tube B. , Test tubes A and B are each dispersed by ultrasonic waves for 5 minutes, left for 12 hours, then the height of the settled core-shell particles is measured, and the MEK swelling rate is calculated according to the following formula (1).
MEK swelling rate = (height of core-shell particles precipitated in methyl ethyl ketone (mm)) / (height of core-shell particles precipitated in an aqueous emulsifier solution (mm)) ... (1) The core-shell particle according to any one of claims 1 to 7 , wherein the ratio of the thickness of the shell portion to the volume average particle diameter is 0.03 or more and 0.12 or less. A suspension of a mixture containing a monofunctional (meth) acrylic monomer (C1), a crosslinkable (meth) acrylic monomer (C2), a polymerization initiator, a water-soluble polymer dispersion stabilizer, and an aqueous solvent is reacted. The emulsion containing the monofunctional (meth) acrylic monomer (S1) unit, the crosslinkable monomer (S2) unit, the emulsifier, and the aqueous solvent, and the emulsion obtained in the above step 1 are obtained in the step 1 of forming the core polymerized portion. Step 2 of forming a shell-polymerized portion on the surface of the core-polymerized portion by contacting the reaction solution containing the core-polymerized portion.
The method for producing core-shell particles according to any one of claims 1 to 8, wherein the method comprises.