JP6888097B2 - Hollow resin particles, heat-sensitive recording material, and method for producing hollow resin particles - Google Patents

Description

The present invention relates to hollow resin particles, a heat-sensitive recording material, and a method for producing hollow resin particles. Specifically, the present invention relates to hollow resin particles, a heat-sensitive recording material provided with a heat insulating layer containing hollow resin particles, and a method for producing hollow resin particles. Regarding.

Conventionally, hollow resin particles have been used in many fields such as thermal recording materials such as thermal recording paper and thermal transfer receiving paper, pesticides, pharmaceuticals, fragrances, liquid crystals, and adhesives.

For such hollow resin particles, for example, an aromatic isocyanate as a protective film-forming substance is blended with a volatile solvent to obtain a dispersed phase, and separately, a dispersant is blended with water to obtain a continuous phase, and then , The dispersed phase is mixed with this continuous phase and dispersed to obtain a dispersion liquid, and then the dispersion liquid is reacted to obtain microcapsules containing a volatile solvent with a protective film-forming substance, and then volatilized. It is produced by vaporizing a sex solvent to make the inside of a microcapsule hollow (see, for example, Patent Document 1 below).

Japanese Unexamined Patent Publication No. 2006-326457

If the volume average particle diameter of such hollow resin particles is too large, for example, when a resin containing hollow resin particles is applied to a base material, the smoothness of the coating film is lowered. Further, if the volume average particle diameter of the hollow resin particles is too small, the absolute value of the thickness of the protective film becomes small when the hollow ratio is constant, so that the particles are easily crushed and easily deformed, and as a heat insulating material. When used, it is inferior in heat insulating properties. Therefore, it is required to adjust the volume average particle diameter of the hollow resin particles.

On the other hand, in the production method of Patent Document 1, a protective film-forming substance is blended with a volatile solvent and then dispersed using a dispersant. However, in such a method, it is difficult to prepare the volume average particle size because the dispersion becomes non-uniform and the distribution of the volume average particle size is widened.

The present invention provides hollow resin particles that can be adjusted to a desired volume average particle size, a heat-sensitive recording material provided with a heat insulating layer containing the hollow resin particles, and a method for producing hollow resin particles that can be adjusted to a desired volume average particle size. To do.

The present invention [1] is a hollow resin particle having a hollow inside and made of a urethane / urea resin, wherein the urethane / urea resin is a urethane prepolymer having an isocyanate group and a chain extension compound having an active hydrogen group. The urethane prepolymer is a reaction product of a polyisocyanate component and an active hydrogen group-containing component containing a carboxyl group, and is one of the polyisocyanate component and the active hydrogen group-containing component. , Hollow resin particles containing a compound having at least one of them having a ring structure.

According to the hollow resin particles, since the urethane / urea resin has a carboxyl group, the volume average particle diameter of the hollow resin particles is adjusted.

Further, since at least one of the polyisocyanate component and the active hydrogen group-containing component contains a compound having a ring structure, the strength is excellent.

In the present invention [2], the hollow resin particles according to the above [1], wherein the active hydrogen group-containing component contains a polyhydric alcohol and a carboxyl group-containing active hydrogen compound having a carboxyl group and two active hydrogen groups. Includes.

According to the hollow resin particles, since the active hydrogen group-containing component contains a polyhydric alcohol and a carboxyl group-containing active hydrogen compound having a carboxyl group and two active hydrogen groups, the volume average particle diameter of the hollow resin particles is large. It is further adjusted, and the volume average particle diameter of the hollow resin particles can be further reduced.

In the present invention [3], the polyhydric alcohol contains the hollow resin particles according to the above [2], which is characterized by having a ring structure.

According to the hollow resin particles, the polyhydric alcohol has a ring structure and is therefore excellent in strength.

In the present invention [4], the polyhydric alcohol contains the hollow resin particles according to the above [3], which have an alicyclic structure and / or an aromatic ring structure.

According to the hollow resin particles, the polyhydric alcohol has an alicyclic structure and / or an aromatic ring structure, and therefore has excellent strength.

In the present invention [5], the hollow resin according to the above [1], wherein the active hydrogen group-containing component does not contain a polyhydric alcohol and contains a carboxyl group-containing active hydrogen compound having a carboxyl group and two active hydrogen groups. Contains particles.

According to the hollow resin particles, since the active hydrogen group-containing component does not contain a polyhydric alcohol and contains a carboxyl group-containing active hydrogen compound having a carboxyl group and two active hydrogen groups, the volume average particle diameter of the hollow resin particles Has been adjusted.

The present invention [6] contains the hollow resin particles according to any one of the above [1] to [5], wherein the polyisocyanate component contains a polyisocyanate having a ring structure.

According to the hollow resin particles, the polyisocyanate component contains the polyisocyanate having a ring structure, and therefore has excellent strength.

In the present invention [7], the polyisocyanate component contains the hollow resin particles according to the above [6], which contains a diisocyanate having a ring structure.

According to the hollow resin particles, since the polyisocyanate component contains diisocyanate having a ring structure, the particle size of the hollow resin particles can be controlled and the strength is excellent.

In the present invention [8], the polyisocyanate component contains the hollow resin particles according to the above [7], which contains a diisocyanate having an alicyclic structure.

According to the hollow resin particles, since the diisocyanate has an alicyclic structure, it is possible to suppress yellowing of the hollow resin particles while maintaining the strength.

In the present invention [9], the diisocyanate contains the hollow resin particles according to the above [8], which contain a secondary isocyanate group.

According to the hollow resin particles, since the diisocyanate contains a secondary isocyanate group, the reactivity is low, the side reaction between the isocyanate group and water can be suppressed, and the particle size of the hollow resin particles can be controlled.

The hollow resin particles according to any one of the above [1] to [9], wherein the present invention [10] contains a compound in which both the polyisocyanate component and the active hydrogen group-containing component have a ring structure. Includes.

According to the hollow resin particles, since both the polyisocyanate component and the active hydrogen group-containing component contain a compound having a ring structure, the hollow resin particles are excellent in strength while suppressing yellowing.

The present invention [11] contains the hollow resin particles according to any one of the above [1] to [10], wherein the urethane prepolymer has an isocyanate group content of 10% by mass or more.

According to the hollow resin particles, the content of the isocyanate group of the urethane prepolymer is 10% by mass or more, so that the strength is excellent.

The present invention [12] contains the hollow resin particles according to any one of the above [1] to [11], wherein the urethane / urea resin is crosslinked with a cross-linking agent.

According to the hollow resin particles, the urethane / urea resin is crosslinked by a crosslinking agent, so that the strength is excellent.

In the present invention [13], the cross-linking agent is selected from the group consisting of i) a silane coupling agent, ii) a compound having at least one of a carbodiimide group, an oxazoline group and an epoxy group, and iii) a melamine compound. It contains the hollow resin particles according to the above [12], which is at least one kind.

According to the hollow resin particles, the urethane / urea resin is a group consisting of i) a silane coupling agent, ii) a compound having at least one of a carbodiimide group, an oxazoline group, and an epoxy group, and iii) a melamine compound. Since it is crosslinked by at least one cross-linking agent selected from the above, it has excellent strength.

The present invention [14] is hollow resin particles having a hollow inside and made of a urethane / urea resin having a carboxyl group and a ring structure.

According to the hollow resin particles, since the urethane / urea resin has a carboxyl group, the volume average particle diameter of the hollow resin particles is adjusted.

Further, since the urethane / urea resin has a ring structure, it has excellent strength.

The present invention [15] includes a support layer, a heat insulating layer, and a heat-sensitive recording layer in this order, and the heat insulating layer contains the hollow resin particles according to any one of the above [1] to [14]. Contains thermal recording material.

The present invention [16] is a step of reacting a polyisocyanate component with an active hydrogen group-containing component containing a carboxyl group to obtain a urethane prepolymer having an isocyanate group, in which the urethane prepolymer and a hydrophobic solvent are mixed. To prepare a mixed solution, add water to the mixed solution, and obtain urethane prepolymer droplets containing the hydrophobic solvent by the urethane prepolymer, a chain extension having the urethane prepolymer and an active hydrogen group. A step of reacting with a compound to obtain resin particles made of a urethane / urea resin containing the hydrophobic solvent, and removing the hydrophobic solvent contained in the resin particles to obtain the urethane / urea resin. Production of hollow resin particles comprising a step of obtaining hollow resin particles having a hollow inside, and containing a compound in which at least one of the polyisocyanate component and the active hydrogen group-containing component has a ring structure. The method.

According to this method for producing hollow resin particles, a urethane prepolymer having a carboxyl group is reacted with a chain extension compound having an active hydrogen group to obtain resin particles made of a urethane urea resin containing a hydrophobic solvent. Have a process.

Therefore, the volume average particle diameter of the hollow resin particles can be adjusted.

Further, since at least one of the polyisocyanate component and the active hydrogen group-containing component contains a compound having a ring structure, hollow resin particles having excellent strength can be obtained.

The hollow resin particles of the present invention are hollow resin particles made of urethane / urea resin, and the urethane / urea resin has a carboxyl group. Therefore, the volume average particle diameter of the hollow resin particles is adjusted. As a result, it is possible to prevent the hollow resin particles from becoming excessively large, so that, for example, when a resin containing the hollow resin particles is applied to the base material, the smoothness of the coating film is improved. Further, since the hollow resin particles can be prevented from becoming excessively small, an internal space can be secured and the heat insulating property is excellent.

Since the heat-sensitive recording material of the present invention includes a heat insulating layer containing the hollow resin particles of the present invention, it is excellent in heat insulating properties.

In the method for producing hollow resin particles of the present invention, a urethane prepolymer having a carboxyl group is reacted with a chain extension compound having an active hydrogen group to obtain resin particles made of a urethane urea resin containing a hydrophobic solvent. Have a process. Therefore, the volume average particle diameter of the hollow resin particles can be adjusted.

FIG. 1 is a cross-sectional view showing an embodiment of the heat-sensitive recording material of the present invention.

Hollow resin particles are a step of reacting a polyisocyanate component with an active hydrogen group-containing component containing a carboxyl group to obtain a urethane prepolymer having an isocyanate group, and a mixed solution of the urethane prepolymer and a hydrophobic solvent. Is prepared, water is added to the mixed solution, and a urethane prepolymer droplet containing a hydrophobic solvent is obtained by using a urethane prepolymer. The urethane prepolymer is reacted with a chain extension compound having an active hydrogen group. , A process of obtaining resin particles made of urethane / urea resin containing a hydrophobic solvent, and removing the hydrophobic solvent contained in the resin particles to make a hollow resin made of urethane / urea resin and having a hollow inside. It can be obtained by a production method including a step of obtaining particles.

In the step of reacting the polyisocyanate component with the active hydrogen group-containing component containing a carboxyl group to obtain a urethane prepolymer having an isocyanate group, the polyisocyanate component and the active hydrogen group-containing component containing a carboxyl group (hereinafter, active) It is a hydrogen group-containing component.) Is reacted. This gives a urethane prepolymer.

The polyisocyanate component is an organic polyisocyanate that has an affinity for a hydrophobic solvent (described later), and examples thereof include a polyisocyanate having a ring structure and a polyisocyanate having no ring structure.

The ring structure is a cyclic structure that forms the skeleton of the polyisocyanate monomer, and does not include a cyclic structure (such as an isocyanurate ring) formed by inducing the polyisocyanate monomer. Examples of the ring structure include an alicyclic structure and an aromatic ring structure.

Examples of the polyisocyanate having a ring structure include a polyisocyanate monomer having a ring structure and a polyisocyanate derivative having a ring structure.

Examples of the polyisocyanate monomer having a ring structure include a diisocyanate monomer having a ring structure.

Examples of the diisocyanate monomer having a ring structure include alicyclic diisocyanates, aromatic diisocyanates, and aromatic aliphatic diisocyanates.

The alicyclic diisocyanate contains an alicyclic structure such as a cyclohexane ring or a crosslinked cyclohexane ring, and examples thereof include an alicyclic diisocyanate containing a secondary isocyanate group and an alicyclic diisocyanate not containing a secondary isocyanate group. ..

The alicyclic diisocyanate containing a secondary isocyanate group contains at least one secondary isocyanate group, for example, cyclopentane diisocyanate (1,3- or 1,4-cyclopentane diisocyanate or a mixture thereof), cyclohexanediisocyanate. A second having one cyclo ring, such as (1,3- or 1,4-cyclohexanediisocyanate or a mixture thereof), methylcyclohexanediisocyanate (methyl-2,4- or methyl-2,6-cyclohexanediisocyanate or a mixture thereof). Two cyclocycles such as an alicyclic diisocyanate containing a secondary isocyanate group, for example, methylenebis (cyclohexylisocyanate) (4,4'-or 2,4'-methylenebis (cyclohexylisocyanate) or a mixture thereof) (H _{12 MDI).} An alicyclic diisocyanate containing two secondary isocyanate groups, such as an alicyclic diisocyanate containing a secondary isocyanate group having, such as 3-isocyanatomethyl-3,5,5-trimethylcyclohexylisocyanate (IPDI). Examples thereof include alicyclic diisocyanates having one secondary isocyanate group and one primary isocyanate group.

Examples of the alicyclic diisocyanate containing no secondary isocyanate group include bis (isocyanatomethyl) cyclohexane (1,3- or 1,4-bis (isocyanatomethyl) cyclohexane or a mixture thereof) (H ₆ XDI). , For example, bis (isocyanatoethyl) cyclohexane (1,3- or 1,4-bis (isocyanatoethyl) cyclohexane or a mixture thereof), bis (isocyanatomethyl) norbornan (2,5- or 2,6-bis). (Isocyanatomethyl) -bicyclo [2.2.1] heptane or a mixture thereof) (NBDI) and the like.

The alicyclic diisocyanate is preferably an alicyclic diisocyanate containing a secondary isocyanate group, more preferably an alicyclic diisocyanate having one secondary isocyanate group and one primary isocyanate group, and further. Preferably, 3-isocyanatomethyl-3,5,5-trimethylcyclohexylisocyanate (IPDI) is used.

The secondary isocyanate group is an isocyanate group (> CH-NCO) that is directly bonded to a carbon atom (secondary carbon atom) having one hydrogen atom.

Further, the primary isocyanate group is directly attached to the isocyanate group _(-CH 2 -NCO) to the carbon atom having two hydrogen atoms (the first carbon atom).

The aromatic diisocyanate contains an aromatic ring structure such as a benzene ring and a fused ring, and includes, for example, tolylene diisocyanate (2,4- or 2,6-toluene diisocyanate or a mixture thereof) (TDI), phenylenediisocyanate (m-,). p-phenylenediisocyanate or a mixture thereof), 4,4'-diphenyldiisocyanate, 1,5-naphthalenediisocyanate (NDI), diphenylmethane diisocyanate (4,4'-, 2,4'-or 2,2'-diphenylmethane) Diisosinate or a mixture thereof) (MDI), 4,4'-toluene diisocyanate (TODI), 4,4'-diphenyl ether diisocyanate and the like.

Aromatic aliphatic diisocyanates contain aliphatic substituted aromatic rings such as alkyl-substituted benzene, and include, for example, xylylene diisocyanate (1,3- or 1,4-xylene diisocyanate or a mixture thereof) (XDI), tetramethylxylene diisocyanate. (1,3- or 1,4-tetramethylxylene diisocyanate or a mixture thereof) (TMXDI), ω, ω'-diisocyanate-1,4-diethylbenzene and the like can be mentioned.

The polyisocyanate derivative having a ring structure is a derivative of the polyisocyanate monomer having the above-mentioned ring structure, and is, for example, a polyisocyanate derivative having a bifunctional ring structure or a polyisocyanate having a polyfunctional ring structure. Derivatives and the like can be mentioned.

Examples of the polyisocyanate derivative having a bifunctional ring structure include a dimer of a diisocyanate monomer having the above-mentioned ring structure (for example, a uretdione derivative) and a bifunctional allophanate derivative (for example, the above-mentioned ring structure). A biuret derivative (for example, an allophanate derivative produced by a reaction between a diisocyanate monomer having a ring structure and a monovalent alcohol), a biuret derivative (for example, a biuret derivative produced by a reaction between a diisocyanate monomer having a ring structure described above and a monovalent amine). Etc.), urea derivatives (for example, urea derivatives produced by the reaction of the above-mentioned diisocyanate monomer having a ring structure with diamine), oxadiazine trione derivatives (for example, diisocyanate monomers having the above-mentioned ring structure). Examples thereof include oxadiazine trione produced by a reaction with carbon dioxide gas), a carbodiimide derivative (such as a carbodiimide derivative produced by a decarbonization condensation reaction of a diisocyanate monomer having a ring structure described above).

The polyisocyanate derivative having a polyfunctional ring structure has three or more isocyanate groups, and is, for example, a trimerate of the diisocyanate monomer having the above-mentioned ring structure (for example, isocyanurate derivative, iminooxadiazine). Dione derivative), polyfunctional allophanate derivative (for example, allophanate derivative produced by reaction with the above-mentioned diisocyanate monomer having a ring structure and dihydric alcohol), polyfunctional biuret derivative (for example, the above-mentioned above). A biisocyanate derivative having a ring structure and a biurette derivative produced by a reaction with a divalent amine, a polyfunctional polyol derivative (for example, a diisocyanate monomer having a ring structure described above, and trimetylolpropane, etc.) Polyuloxide derivatives (alcohol adducts) produced by reaction with trivalent alcohol, uretonimine derivatives (for example, uretonimine derivatives produced by reaction of the above carbodiimide derivative with the above diisocyanate monomer having a ring structure) Can be mentioned.

The polyisocyanate derivative having a ring structure is preferably a polyisocyanate derivative having a bifunctional ring structure.

Polyisocyanates having a ring structure can be used alone or in combination of two or more.

Examples of the polyisocyanate having no ring structure include a polyisocyanate monomer having no ring structure and a polyisocyanate derivative having no ring structure.

Examples of the polyisocyanate monomer having no ring structure include aliphatic polyisocyanates.

Examples of the aliphatic polyisocyanate include ethylene diisocyanate, trimethylene diisocyanate, 1,2-propylene diisocyanate, and butylene diisocyanate (tetramethylene diisocyanate, 1,2-butylene diisocyanate, 2,3-butylene diisocyanate, and 1,3-butylene diisocyanate). ), 1,5-Pentamethylene diisocyanate (PDI), 1,6-hexamethylene diisocyanate (HDI), 2,4,4- or 2,2,4-trimethylhexamethylene diisocyanate, 2,6-diisocyanate methylcapate , An aliphatic diisocyanate such as dodecamethylene diisocyanate and the like.

The polyisocyanate derivative having no ring structure is the above-mentioned derivative of the polyisocyanate monomer having no ring structure.

Polyisocyanates having no ring structure can be used alone or in combination of two or more.

The polyisocyanate component preferably contains a polyisocyanate having a ring structure. That is, the polyisocyanate component preferably contains a compound having a ring structure.

Specifically, the blending ratio of the polyisocyanate having a ring structure is, for example, 50% by mass or more, preferably 90% by mass or more, and more preferably 100% by mass with respect to the polyisocyanate component.

If the polyisocyanate component contains a compound having a ring structure, the strength of the hollow resin particles is excellent.

More preferably, the polyisocyanate component contains a polyisocyanate monomer containing an alicyclic structure or a polyisocyanate derivative containing an alicyclic structure.

If the polyisocyanate component contains a polyisocyanate monomer containing an alicyclic structure or a polyisocyanate derivative containing an alicyclic structure, yellowing of the hollow resin particles can be suppressed.

Further, the polyisocyanate component preferably contains a diisocyanate monomer having a ring structure or a polyisocyanate derivative having a bifunctional ring structure, and more preferably contains a diisocyanate monomer having a ring structure.

If the polyisocyanate component includes a diisocyanate monomer having a ring structure or a polyisocyanate derivative having a bifunctional ring structure, the diisocyanate monomer having a ring structure and an active hydrogen group-containing component (preferably a dihydric alcohol) ) (Described later), the molecular weight of the urethane prepolymer can be easily prepared, and the particle size of the hollow resin particles can be controlled.

Particularly preferably, the polyisocyanate component contains a diisocyanate monomer (alicyclic diisocyanate) containing an alicyclic structure among the polyisocyanates having such a ring structure.

If the polyisocyanate component contains an alicyclic diisocyanate, the particle size of the hollow resin particles can be controlled, the yellowing of the hollow resin particles is suppressed, and the strength of the hollow resin particles is excellent.

Most preferably, the polyisocyanate component contains an alicyclic diisocyanate containing a secondary isocyanate group among such alicyclic diisocyanates.

If the polyisocyanate component contains an alicyclic diisocyanate containing a secondary isocyanate group, the reactivity can be lowered, the side reaction between the isocyanate group and water can be suppressed, and the particle size of the hollow resin particles can be controlled.

Examples of the active hydrogen group-containing component include a polyhydric alcohol as an optional component, a carboxyl group-containing active hydrogen compound having a carboxyl group as an essential component and two active hydrogen groups (hereinafter referred to as a carboxyl group-containing active hydrogen compound). .) And.

Examples of the polyhydric alcohol include a polyhydric alcohol having a ring structure and a polyhydric alcohol having no ring structure.

Examples of the polyhydric alcohol having a ring structure include a dihydric alcohol having a ring structure.

Examples of the dihydric alcohol having a ring structure include an alicyclic dihydric alcohol, an aromatic dihydric alcohol, and an aromatic alicyclic dihydric alcohol.

The alicyclic dihydric alcohol contains an alicyclic structure such as a cyclohexane ring and a crosslinked cyclohexane ring, and includes, for example, cyclohexanediol (1,2- or 1,3- or 1,4-cyclohexanediol or a mixture thereof), cyclohexanedi. Methanol (1,2- or 1,3- or 1,4-cyclohexanedimethanol or a mixture thereof), cyclohexanediethanol (1,2- or 1,3- or 1,4-cyclohexanedimethanol or a mixture thereof), hydrogenation Examples thereof include bisphenol A, spiroglycol and isosorbide.

The aromatic dihydric alcohol contains an aromatic ring structure such as a benzene ring and a condensed ring, and includes, for example, bisphenol A, an ethylene oxide adduct of bisphenol A, a propylene oxide adduct of bisphenol A, and 2,2-bis (4-polyoxy). Propyleneoxyphenyl) Propane and the like can be mentioned.

The aromatic alicyclic dihydric alcohol contains an aliphatic substituted aromatic ring such as alkyl-substituted benzene, and examples thereof include xylene glycol, bishydroxyethoxybenzene, and bishydroxyethylene terephthalate.

The dihydric alcohol having a ring structure is preferably an alicyclic dihydric alcohol, an aromatic dihydric alcohol, more preferably cyclohexanediol, cyclohexanedimethanol, or 2,2-bis (4-polyoxypropylene oxyphenyl). ) Propane, more preferably 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, 2,2-bis (4-polyoxypropyleneoxyphenyl) propane.

The dihydric alcohol having a ring structure can be used alone or in combination of two or more.

Examples of the polyhydric alcohol having no ring structure include aliphatic polyhydric alcohols.

Examples of the aliphatic polyhydric alcohol include ethylene glycol, propylene glycol (1,2- or 1,3-propanediol or a mixture thereof), butylene glycol (1,2- or 1,3- or 1,4-butylene). Glycol or a mixture thereof), 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, 2,2,2-trimethylpentanediol, 3,3-di Alcan diols such as methylol heptane, dihydric alcohols such as ether diols such as diethylene glycol, triethylene glycol, dipropylene glycol, and trihydric alcohols such as glycerin, trimethylolpropane, triisopropanolamine, eg tetramethylolmethane. (Pentaerythritol), tetravalent alcohols such as diglycerin, eg pentavalent alcohols such as xylitol, eg, hexavalent alcohols such as sorbitol, mannitol, aritol, iditor, darsitol, altritor, inositol, dipentaerythritol, eg Seven-valent alcohols such as persetol, for example, octavalent alcohols such as sucrose, are mentioned, preferably dihydric alcohols, more preferably alcandiols, and even more preferably ethylene glycols, butylene glycols, neopentyl glycols, among others. Preferably, ethylene glycol, 1,4-butylene glycol and neopentyl glycol are mentioned.

Multivalent alcohols that do not have a ring structure can be used alone or in combination of two or more.

The polyhydric alcohol preferably includes a polyhydric alcohol having a ring structure. That is, the polyhydric alcohol preferably has a ring structure, more preferably an alicyclic structure and / or an aromatic ring structure.

Specifically, the blending ratio of the polyhydric alcohol having a ring structure is, for example, 50% by mass or more, preferably 90% by mass or more, and more preferably 100% by mass with respect to the polyhydric alcohol.

If the polyhydric alcohol has a ring structure (preferably an alicyclic structure and / or an aromatic ring structure), the strength of the hollow resin particles is excellent.

The carboxyl group-containing active hydrogen compound is an organic compound having two active hydrogen groups (hydroxyl group, amino group, etc.) and one carboxyl group.

The carboxyl group may form a salt with a neutralizing agent described later.

Examples of the carboxyl group-containing active hydrogen compound include 2,2-dimethylol acetic acid, 2,2-dimethylol lactic acid, 2,2-dimethylol propionic acid, 2,2-dimethylol butanoic acid, dimethylol heptanic acid, and dimethylol. Examples include nonanoic acid, 2,2-dimethylol butyric acid, 2,2-dimethylol valeric acid, and preferably 2,2-dimethylol propionic acid.

These carboxyl group-containing active hydrogen compounds can be used alone or in combination of two or more.

The active hydrogen group-containing component contains a polyhydric alcohol and a carboxyl group-containing active hydrogen compound (first active hydrogen group-containing component), or does not contain a polyhydric alcohol and contains a carboxyl group-containing active hydrogen compound ( Second active hydrogen group-containing component).

The first active hydrogen group-containing component contains a polyhydric alcohol and a carboxyl group-containing active hydrogen compound, and preferably comprises a polyhydric alcohol and a carboxyl group-containing active hydrogen compound.

The second active hydrogen group-containing component does not contain a polyhydric alcohol, contains a carboxyl group-containing active hydrogen compound, and preferably comprises a carboxyl group-containing active hydrogen compound.

If the active hydrogen group-containing component contains a carboxyl group-containing active hydrogen compound, the volume average particle size of the hollow resin particles can be adjusted.

Further, if the active hydrogen group-containing component contains a polyhydric alcohol together with the carboxyl group-containing active hydrogen compound, the compatibility of the hydrophobic solvent described later is enhanced, so that the volume average particle size of the hollow resin particles can be further adjusted. , The volume average particle diameter of the hollow resin particles can be further reduced.

In the present invention, at least one of the polyisocyanate component and the active hydrogen group-containing component contains a compound having a ring structure.

Specifically, as a urethane prepolymer formulation, the polyisocyanate component contains a compound having a ring structure, the active hydrogen group-containing component does not contain a compound having a ring structure (first formulation), and the polyisocyanate component is A formulation that does not contain a compound having a ring structure and the active hydrogen group-containing component contains a compound having a ring structure (second formulation), and both the polyisocyanate component and the active hydrogen group-containing component have a ring structure. Examples thereof include a formulation containing a compound (third formulation).

That is, as a urethane prepolymer formulation, a formulation in which both the polyisocyanate component and the active hydrogen group-containing component do not contain a compound having a ring structure is not included in the present invention.

More specifically, the first formulation contains a polyisocyanate having a ring structure and a carboxyl group-containing active hydrogen compound having no ring structure, preferably a polyisocyanate having a ring structure and no ring structure. It contains a polyhydric alcohol and a carboxyl group-containing active hydrogen compound having no ring structure.

The second formulation contains a polyisocyanate having no ring structure, a polyhydric alcohol having a ring structure, and a carboxyl group-containing active hydrogen compound, preferably having a polyisocyanate having no ring structure and a ring structure. It contains a polyhydric alcohol having a ring structure and a carboxyl group-containing active hydrogen compound having no ring structure.

The third formulation contains a polyisocyanate having a ring structure, a polyhydric alcohol having a ring structure, and a carboxyl group-containing active hydrogen compound, preferably a polyisocyanate having a ring structure and a polyisocyanate having a ring structure. It contains a valent alcohol and a carboxyl group-containing active hydrogen compound having no ring structure.

If at least one of the polyisocyanate component and the active hydrogen group-containing component contains a compound having a ring structure, the strength of the hollow resin particles is excellent.

Among these formulations, preferred are formulations containing a compound in which the polyisocyanate component has a ring structure (that is, first formulation, third formulation).

If the polyisocyanate component contains a compound having a ring structure, the strength of the hollow resin particles is further improved.

Among these formulations, more preferably, a formulation containing a compound in which both the polyisocyanate component and the active hydrogen group-containing component have a ring structure (that is, a third formulation) can be mentioned.

If both the polyisocyanate component and the active hydrogen group-containing component contain a compound having a ring structure, the strength of the hollow resin particles can be further improved.

Then, in order to react the polyisocyanate component with the active hydrogen group-containing component, the equivalent ratio of the isocyanate group to the active hydrogen group (NCO / active hydrogen group) of the polyisocyanate component and the active hydrogen group-containing component is excessive. For example, 1.25 or more, preferably 1.55 or more, and for example, 21.2 or less, preferably 2.85 or less.

As reaction conditions, under atmospheric pressure, the reaction temperature is, for example, 40 ° C. or higher, preferably 60 ° C. or higher, and for example, 100 ° C. or lower. The reaction time is, for example, 1 hour or more, and for example, 24 hours or less.

In this reaction, for example, an amine-based, tin-based, or lead-based urethanization catalyst may be added as needed, and after the reaction is completed, unreacted poly may be added as needed. The isocyanate component can also be removed by a known removing means such as distillation or extraction.

As a result, the molecular end of the reaction product (that is, urethane prepolymer) becomes an isocyanate group. Preferably, both ends of the main chain of the reaction product are isocyanate groups.

In order for both ends of the main chain of the reaction product to form isocyanate groups, it is preferable to react diisocyanate with a carboxyl group-containing active hydrogen compound and, if necessary, a dihydric alcohol.

The urethane prepolymer may have an isocyanate group in the side chain (other than the molecular terminal).

The isocyanate group content (solid content conversion value) of the urethane prepolymer is, for example, 5% by mass or more, preferably 10% by mass or more, and for example, 35% by mass or less, preferably 20% by mass or less. Is.

The isocyanate group content can be measured by the n-dibutylamine method based on JIS K-1603 using a potentiometric titrator.

When the content of the isocyanate group of the urethane prepolymer is at least the above lower limit, the volume average particle diameter of the hollow resin particles can be adjusted, and the strength of the hollow resin particles is excellent.

Examples of the reaction method include known polymerization methods such as bulk polymerization and solution polymerization, and solution polymerization is preferable.

In solution polymerization, a polyisocyanate component, an active hydrogen group-containing component, and a solvent are mixed and polymerized, for example, in a nitrogen atmosphere.

Solvents include esters such as ethyl acetate and butyl acetate, ether esters such as propylene glycol monomethyl ether acetate and propylene glycol monoethyl ether acetate, aromatic hydrocarbons such as benzene, toluene and xylene, hexane and 2-ethylhexyl. , Cyclohexane, aliphatic hydrocarbons such as methylcyclohexane, preferably esters, aromatic hydrocarbons, aliphatic hydrocarbons, and more preferably ethyl acetate, xylene, cyclohexane, methyl. Cyclohexane can be mentioned.

The solvent can be used alone or in combination of two or more.

When the polyisocyanate component and the active hydrogen group-containing component are reacted in the solvent, the solid content concentration of the urethane prepolymer in the solvent is, for example, 50% by mass or more, preferably 70% by mass or more. Also, for example, it is 90% by mass or less.

In such a case, the urethane prepolymer can be used in the next step as it is in the reaction solution containing the solvent.

Next, in the step of mixing a urethane prepolymer and a hydrophobic solvent to prepare a mixed solution, adding water to the mixed solution, and obtaining urethane prepolymer droplets containing the hydrophobic solvent by the urethane prepolymer, urethane is used. The prepolymer and the hydrophobic solvent are mixed to prepare a mixed solution, and water is added to the mixed solution. As a result, urethane prepolymer droplets containing a hydrophobic solvent are obtained by the urethane prepolymer.

Specifically, first, a urethane prepolymer and a hydrophobic solvent are mixed to prepare a mixed solution.

Examples of the hydrophobic solvent include the same solvents as those described above.

The mixing ratio of the hydrophobic solvent (when the reaction solution is used as it is, the total amount of the solvent of the reaction solution and the hydrophobic solvent) is, for example, 150 parts by mass or more, preferably 150 parts by mass or more, based on 100 parts by mass of the urethane prepolymer. It is 200 parts by mass or more, and for example, 600 parts by mass or less.

Further, if necessary, a cross-linking agent may be added to the mixed solution.

When a cross-linking agent is added to the mixed solution, the urethane / urea resin (described later) is cross-linked by the cross-linking agent, so that the strength of the hollow resin particles is excellent.

Examples of the cross-linking agent include a silane coupling agent, for example, a compound having at least one of a carbodiimide group, an oxazoline group, and an epoxy group, for example, a melamine compound and the like.

Examples of the silane coupling agent include 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 2- (3,4-epoxycyclohexyl). Epoxy group-containing silane coupling agents such as ethyltrimethoxysilane, such as 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane, N. Amino group-containing silane coupling agents such as -2- (aminoethyl) -3-aminopropyltrimethoxysilane, 3-triethoxysilyl-N- (1,3-dimethylbutylidene) propylamine, for example, 3-acry. (Meta) acrylic group-containing silane coupling agents such as loxypropyltrimethoxysilane and 3-methacryloxypropyltriethoxysilane, eg, amineate group-containing silane coupling agents such as 3-isocyanatopropyltriethoxysilane, eg. Examples thereof include a mercapto group-containing silane coupling agent such as 3-mercaptopropyltrimethoxysilane.

Examples of the compound having at least one of a carbodiimide group, an oxazoline group, and an epoxy group include a carbodiimide-based cross-linking agent, an oxazoline-based cross-linking agent, and an epoxy-based cross-linking agent.

Examples of the melamine compound include an alkylated melamine resin such as a methylated melamine resin and a butylated melamine resin.

The cross-linking agent is preferably at least one selected from the group consisting of i) a silane coupling agent, ii) a compound having at least one of a carbodiimide group, an oxazoline group and an epoxy group, and iii) a melamine compound. Can be mentioned.

If the cross-linking agent is at least one selected from the group consisting of i) a silane coupling agent, ii) a compound having at least one of a carbodiimide group, an oxazoline group, and an epoxy group, and ii) a melamine compound, urethane. -Since the urethane resin (described later) is crosslinked by the above-mentioned cross-linking agent, the strength of the hollow resin particles is excellent.

The cross-linking agent is more preferably a silane coupling agent, more preferably an cyanate group-containing silane coupling agent, a mercapto group-containing silane coupling agent, and even more preferably 3-isocyanatopropyltriethoxysilane. Examples include 3-mercaptopropyltrimethoxysilane.

These cross-linking agents can be used alone or in combination of two or more.

The blending ratio of the cross-linking agent is, for example, 1 part by mass or more, preferably 5 parts by mass or more, and for example, 30 parts by mass or less with respect to 100 parts by mass of the urethane prepolymer.

Further, the cross-linking agent may be added after reacting the urethane prepolymer with the chain extension compound having an active hydrogen group, as described later.

When a cross-linking agent is added to the mixed solution, a cross-linking catalyst can be added, if necessary.

Examples of the cross-linking catalyst include amine salts of organic acids such as a triethylamine neutralized product of paratoluenesulfonic acid and a triethylamine neutralized product of dodecylbenzenesulfonic acid, and in particular, when the cross-linking agent is a melamine compound, Preferably, a triethylamine neutralized product of dodecylbenzenesulfonic acid is used.

These cross-linking catalysts can be used alone or in combination of two or more.

The blending ratio of the cross-linking catalyst is, for example, 1 part by mass or more, preferably 4 parts by mass or more, and for example, 20 parts by mass or less with respect to 100 parts by mass of the urethane prepolymer.

Further, the cross-linking catalyst may be added after reacting the urethane prepolymer with the chain extension compound having an active hydrogen group, as described later.

Then, water is added to the mixed solution all at once or in divided portions.

When the reactivity of the urethane prepolymer is high, the temperature of the mixed solution is adjusted to, for example, 20 ° C. or lower, if necessary.

At this time, while the hydrophobic solvent is dispersed in water, the molecular skeleton portion of the urethane prepolymer has an affinity with the hydrophobic solvent, and the carboxyl group has an affinity with water. Intervene between.

Specifically, the urethane prepolymer envelops a hydrophobic solvent in water.

As a result, urethane prepolymer droplets containing a hydrophobic solvent are obtained by the urethane prepolymer.

Such urethane prepolymer droplets are dispersed in water. That is, an aqueous dispersion containing urethane prepolymer droplets can be obtained.

Since the urethane prepolymer has a carboxyl group, the urethane prepolymer droplets can be easily dispersed by mixing with water without separately adding a dispersant.

Further, as described above, in the phase inversion emulsification method in which water is added to the mixed solution, the volume average particle size of the hollow resin particles can be adjusted as compared with the normal phase emulsification method in which the mixed solution is added to water.

Next, in the step of reacting the urethane prepolymer with the chain extension compound having an active hydrogen group to obtain resin particles made of urethane / urea resin containing a hydrophobic solvent, the urethane prepolymer has an active hydrogen group. It is reacted with a chain extension compound (hereinafter referred to as a chain extension compound). As a result, resin particles made of urethane / urea resin containing a hydrophobic solvent are obtained.

Examples of the chain extension compound include water, for example, a compound having two or more (preferably two) active hydrogen groups such as an amino group and a hydroxyl group.

Examples of the chain extension compound include an amino group-containing compound and a hydroxyl group-containing compound.

Examples of the amino group-containing compound include aromatic polyamines, aromatic aliphatic polyamines, alicyclic polyamines, aliphatic polyamines, amino alcohols, polyoxyethylene group-containing polyamines, primary amino groups, and primary amino groups. And an alkoxysilyl compound having a secondary amino group, hydrazine or a derivative thereof and the like.

Examples of the aromatic polyamine include aromatic diamines such as 4,4'-diphenylmethanediamine and tolylenediamine.

Examples of the aromatic aliphatic polyamine include aromatic aliphatic diamines such as xylylenediamine (1,3- or 1,4-xylylenediamine or a mixture thereof).

Examples of the alicyclic polyamine include 3-aminomethyl-3,5,5-trimethylcyclohexylamine (also known as isophoronediamine), 4,4'-dicyclohexylmethanediamine, and 2,5 (2,6) -bis (. Aminomethyl) bicyclo [2.2.1] heptane, 1,4-cyclohexanediamine, 1-amino-3-aminomethyl-3,5,5-trimethylcyclohexane, bis- (4-aminocyclohexyl) methane, diaminocyclohexane , 3,9-bis (3-aminopropyl) -2,4,8,10-tetraoxaspiro [5,5] undecane, 1,3- and 1,4-bis (aminomethyl) cyclohexane and mixtures thereof. Alicyclic diamines such as.

Examples of the aliphatic polyamine include ethylenediamine, propylenediamine, 1,3-propanediamine, 1,4-butanediamine, 1,5-pentanediamine, 1,6-hexamethylenediamine, and 1,8-octamethylenediamine. Aliphatic diamines such as 1,12-dodecamethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, 1,2-diaminoethane, 1,2-diaminopropane, and 1,3-diaminopentane can be mentioned.

Examples of the amino alcohol include 2-((2-aminoethyl) amino) ethanol (also known as N- (2-aminoethyl) ethanolamine) and 2-((2-aminoethyl) amino) -1-methylpropanol. (Also known as: N- (2-aminoethyl) isopropanolamine) and the like.

Examples of the polyoxyethylene group-containing polyamine include polyoxyalkylene ether diamines such as polyoxyethylene ether diamines.

Examples of the alkoxysilyl compound having a primary amino group or a primary amino group and a secondary amino group include γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, and N-phenyl-γ. An alkoxysilyl compound having a primary amino group such as −aminopropyltrimethoxysilane, N-β (aminoethyl) γ-aminopropyltrimethoxysilane (also known as N-2- (aminoethyl) -3-aminopropyltri). Methoxysilane), N-β (aminoethyl) γ-aminopropyltriethoxysilane (also known as N-2- (aminoethyl) -3-aminopropyltriethoxysilane), N-β (aminoethyl) γ-aminopropyl Methyldimethoxysilane (also known as N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane), N-β (aminoethyl) γ-aminopropylmethyldiethoxysilane (also known as N-2- (aminoethyl)) Examples thereof include an alkoxysilyl compound having a primary amino group and a secondary amino group such as -3-aminopropylmethyldiethoxysilane).

Examples of hydrazine or a derivative thereof include hydrazine (including hydrate), succinate dihydrazide, adipic acid dihydrazide and the like.

The amino group-containing compound is preferably hydrazine, and more preferably hydrazine monohydrate.

Examples of the hydroxyl group-containing compound include ethylene glycol, propylene glycol, 1,3-propanediol, butylene glycol (1,2- or 1,3- or 1,4-butylene glycol,), 1,5-pentanediol, and the like. 1,6-Hexanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, 2,2,2-trimethylpentanediol, 3,3-dimethylolheptan, alkane (C7-20) diol, 1, 3- or 1,4-cyclohexanedimethanol and mixtures thereof, 1,3- or 1,4-cyclohexanediol and mixtures thereof, bisphenol hydride A, 1,4-dihydroxy-2-butene, 2,6- Examples thereof include dihydric alcohols such as dimethyl-1-octene-3,8-diol, bisphenol A, diethylene glycol, triethylene glycol and dipropylene glycol.

These chain extension compounds can be used alone or in combination of two or more.

As the chain extension compound, an amino group-containing compound is preferable.

In this reaction, specifically, the chain extension compound is added to the water in which the urethane prepolymer droplets are dispersed, and the mixture is stirred.

Specifically, the equivalent ratio (isocyanate group / active hydrogen group) of the isocyanate group of the urethane prepolymer to the active hydrogen group of the chain extension compound is, for example, 0.50 or more, preferably 0.67 or more, or, for example. , 1.43 or less, preferably 1.35 or less, and the chain extension compound is added.

Further, in this reaction, if necessary, a dispersant such as a neutralizing agent and sodium polyacrylate is added, and if necessary, the mixture is heated and stirred.

The neutralizing agent is formulated to neutralize the carboxyl group, and examples thereof include tertiary amines.

Examples of the tertiary amine include tertiary amines such as trimethylamine, triethylamine, tripropylamine, tributylamine, N, N-dimethylcyclohexylamine, N-methylmorpholin, N-ethylmorpholin, N-methylpiperidine or N-ethylpiperidine. Examples of monoamines include tertiary diamines such as 1,3-bis- (dimethylamino) -propane, 1,4-bis- (dimethylamino) -butane, and N, N'-dimethylpiperazine.

The blending ratio of the neutralizing agent is, for example, 0.02 mol or more, and for example, 1 mol or less with respect to 1 mol of the urethane prepolymer.

The mixing ratio of the dispersant is, for example, 1 part by mass or more, preferably 5 parts by mass or more, and for example, 20 parts by mass or less with respect to 100 parts by mass of the urethane prepolymer.

The heating temperature is, for example, 10 ° C. or higher, and for example, 80 ° C. or lower.

The heating (stirring) time is, for example, 1 hour or more, and for example, 24 hours or less.

When the chain extension compound is water, the urethane prepolymer is mixed with a hydrophobic solvent, water is added to the mixture, and if necessary, the urethane prepolymer is heated and stirred under the above conditions. Reacts with the chain extension compound.

In this reaction, the urethane prepolymer and the chain extension compound are interfacially polymerized at the interface between the hydrophobic solvent and water. That is, the urethane prepolymer on the surface of the urethane prepolymer droplet reacts with the chain extension compound.

Therefore, by this reaction, resin particles made of urethane / urea resin containing a hydrophobic solvent can be obtained.

Such resin particles are dispersed in water.

The urethane / urea resin is a polymer containing a urethane group and / or a urea group.

Specifically, when the chain extension compound is water or an amino group-containing compound, the isocyanate group of the urethane prepolymer reacts with water or the amino group of the amino group-containing compound to form a urea bond. Is formed, and a urea resin is obtained (in consideration of the urethane group in the urethane polymer, it is also a urethane-urea resin (described later)).

When the chain extension compound is a hydroxyl group-containing compound, the isocyanate group of the urethane prepolymer reacts with the hydroxyl group of the hydroxyl group-containing compound to form a urethane bond, and a urethane resin is obtained.

When the chain extension compound is water or an amino group-containing compound and a hydroxyl group-containing compound, the isocyanate group of the urethane prepolymer reacts with water or the amino group of the amino group-containing compound, and urea While the bond is formed, the isocyanate group of the urethane prepolymer reacts with the hydroxyl group of the hydroxyl group-containing compound to form a urethane bond, and a urethane-urea resin is obtained.

That is, the urethane / urea resin contains a reaction product of the urethane prepolymer and the chain extension compound, and preferably comprises a reaction product of the urethane prepolymer and the chain extension compound.

If the urethane / urea resin contains a reaction product of the urethane prepolymer and the chain extension compound, the urethane / urea resin can contain a hydrophobic solvent.

In the resin particles, the content of the carboxyl group with respect to the total amount of the urethane urea resin and the hydrophobic solvent is, for example, 0.074% by mass or more, preferably 0.15% by mass or more, more preferably 0.22% by mass. Further, for example, 2.5% by mass or less, preferably 1.25% by mass or less, more preferably 0.58% by mass or less, still more preferably 0.44% by mass or less, particularly preferably. , 0.37% by mass or less.

When the content of the above-mentioned carboxyl group is not less than the above lower limit and not more than the above upper limit, the particle size of the hollow resin particles can be adjusted.

Next, in the step of removing the hydrophobic solvent contained in the resin particles to obtain the hollow resin particles made of urethane / urea resin and having a hollow inside, the hydrophobic solvent contained in the resin particles is removed. .. As a result, hollow resin particles made of urethane / urea resin and having a hollow inside are obtained.

To remove the hydrophobic solvent contained in the resin particles, reduce the pressure of the aqueous dispersion in which the resin particles composed of the urethane / urea resin containing the hydrophobic solvent are dispersed in water to make the urethane / urea resin. The contained hydrophobic solvent is vaporized and replaced with water. As a result, the inside of the resin particles becomes hollow.

As a result, hollow resin particles made of urethane / urea resin and having a hollow inside can be obtained.

Such hollow resin particles are dispersed in water.

This urethane / urea resin has a carboxyl group. Specifically, the urethane / urea resin has a carboxyl group derived from a carboxyl group-containing active hydrogen compound.

The content of the carboxyl group in the urethane / urea resin is 0.3% by mass or more, preferably 0.6% by mass or more, more preferably 0.89% by mass or more, and 10% by mass or less. It is preferably 5% by mass or less, more preferably 2.3% by mass or less, still more preferably 1.75% by mass or less, and particularly preferably 1.47% by mass or less.

When the content of the carboxyl group in the urethane / urea resin is not less than the above lower limit and not more than the above upper limit, the volume average particle size of the hollow resin particles can be adjusted.

The content of the carboxyl group in the urethane / urea resin can be calculated from the charged amount.

In the obtained hollow resin particles, since the urethane / urea resin has a carboxyl group, the volume average particle diameter of the hollow resin particles is adjusted. Specifically, the active hydrogen group-containing component contains an active hydrogen group. If the component is a first active hydrogen group-containing component, for example, it is 0.5 μm or more, preferably 1 μm or more, and for example, 10 μm or less, preferably 5 μm or less, and an active hydrogen group-containing component. However, if the active hydrogen group-containing component is a second active hydrogen group-containing component, it is 0.5 μm or more, preferably 1 μm or more, and for example, 30 μm or less, preferably 20 μm or less.

The method for measuring the volume average particle size will be described in detail in Examples described later.

When the volume average particle diameter of the hollow resin particles is not more than the above upper limit, the smoothness of the coating film is improved, for example, when a resin containing the hollow resin particles is applied to the base material.

When the volume average particle diameter of the hollow resin particles is at least the above lower limit, the heat insulating property is excellent.

Further, in this method for producing hollow resin particles, since the urethane prepolymer has a carboxyl group, it can be stably dispersed. Therefore, the volume average particle diameter of the hollow resin particles can be adjusted.

Further, the hollow resin particles are hollow inside. Since the volume average particle diameter of the hollow resin particles is adjusted in the hollow resin particles, the hollow resin particles have excellent strength even if the inside is hollow, and the internal space can be enlarged. , Excellent heat insulation.

The volume hollow ratio of the hollow resin particles is, for example, 30% or more, preferably 60% or more, and for example, 95% or less, preferably 85% or less.

When the volume hollow ratio of the hollow resin particles is not more than the above upper limit, the strength is excellent.

When the volume hollow ratio of the hollow resin particles is at least the above lower limit, the heat insulating property is excellent.

The method for measuring the volume hollow ratio will be described in detail in Examples described later.

Further, this urethane / urea resin has a ring structure. Specifically, the urethane / urea resin has a ring structure derived from at least one of a polyisocyanate component and an active hydrogen group-containing component.

In the obtained hollow resin particles, the urethane / urea resin has a ring structure, and therefore has excellent strength.

That is, such hollow resin particles are made of a urethane / urea resin having a hollow inside and having a carboxyl group and a ring structure.

Therefore, the volume average particle diameter of the hollow resin particles is adjusted, and the strength is excellent.

Further, a fragrance, a dye, a heat storage material, a chemical, an ultraviolet absorber, an inorganic pigment, or the like can be contained inside the hollow resin particles (hollow portion).

In the above description, a mixed solution is prepared by mixing a urethane prepolymer and a hydrophobic solvent, water is added to the mixed solution, and the urethane prepolymer droplets containing the hydrophobic solvent are prepared by the urethane prepolymer. In the obtaining step, the urethane prepolymer is dispersed without blending the dispersant, but the urethane prepolymer may be dispersed by blending the dispersant.

Further, in the above description, a mixed solution is prepared by mixing a urethane prepolymer and a hydrophobic solvent, water is added to the mixed solution, and the urethane prepolymer droplets containing the hydrophobic solvent are prepared by the urethane prepolymer. In the obtaining step, water is added to the mixed solution (phase inversion emulsification method), but the mixed solution may be added to water (normal phase emulsification method).

Such hollow resin particles can be used in the fields of, for example, heat-sensitive recording materials, pesticides, pharmaceuticals, fragrances, liquid crystals, adhesives, etc., and can be particularly preferably used for heat-sensitive recording materials.

Therefore, in a heat-sensitive recording material including a support layer, a heat insulating layer, and a heat-sensitive recording layer in this order, it is preferable to include the hollow resin particles in the heat-insulating layer.

Specifically, in FIG. 1, the heat-sensitive recording material 1 includes a support layer 2, a heat insulating layer 3, and a heat-sensitive recording layer 4 in this order.

The thermal recording material 1 is a material whose color is changed by heat, and examples thereof include thermal recording paper and thermal transfer receiving paper.

Examples of the support layer 2 include paper and a plastic sheet. The thickness of the support layer 2 is appropriately set according to the purpose and application.

The heat insulating layer 3 is a layer that prevents heat from being dissipated from the heat sensitive head in order to develop the color of the heat sensitive recording layer 4.

The heat insulating layer 3 contains the above-mentioned hollow resin particles and a binder resin such as polyvinyl alcohol, polyacrylamide, styrene / butadiene emulsion, and acrylic emulsion. The thickness of the heat insulating layer 3 is appropriately set according to the purpose and application.

The heat-sensitive recording layer 4 contains the above-mentioned binder resin, a dye, and a color developer.

Examples of the dye include known basic organic dyes such as fluorolan-based organic dyes, triallylmethane-based organic dyes, and phenoxyazine-based organic dyes.

The color developer is not particularly limited, and examples thereof include known color developers such as phenolic compounds and aromatic carboxylic acids.

The thickness of the thermal recording layer 4 is appropriately set according to the purpose and application.

In order to manufacture the heat-sensitive recording material 1, first, the heat insulating layer 3 is formed on the support layer 2.

To form the heat insulating layer 3, a mixture of hollow resin particles and a binder resin is applied by a known coating method such as a curtain coating method, a roll coating method, or a blade coating method, and then dried.

Next, the heat-sensitive recording layer 4 is formed on the heat insulating layer 3.

To form the heat-sensitive recording layer 4, a mixture of the above binder resin, dye, and color developer is applied by a known coating method such as a curtain coating method, a roll coating method, or a blade coating method, and then the mixture is applied. ,dry.

As a result, the thermal recording material 1 is obtained.

Then, in such a heat-sensitive recording material 1, the heat insulating layer 3 contains the above-mentioned hollow resin particles. Therefore, the heat-sensitive recording material 1 has excellent heat insulating properties.

Further, in the above description, the heat-sensitive recording material 1 is composed of the support layer 2, the heat insulating layer 3, and the heat-sensitive recording layer 4. For example, between the support layer 2 and the heat insulating layer 3, or between the heat insulating layer 3 and the heat sensitive recording layer. An intermediate layer (not shown) may be interposed between the four.

Further, an overcoat layer (not shown) may be arranged on the heat-sensitive recording layer 4. In such a case, the heat-sensitive recording material 1 includes a support layer 2, a heat insulating layer 3, a heat-sensitive recording layer 4, and an overcoat layer (not shown) in this order.

Further, a back coat layer (not shown) may be arranged under the support layer 2. In such a case, the heat-sensitive recording material 1 includes a back coat layer (not shown), a support layer 2, a heat insulating layer 3, and a heat-sensitive recording layer 4 in this order.

Further, the heat-sensitive recording material 1 may include both the above-mentioned overcoat layer (not shown) and the above-mentioned backcoat layer (not shown). In such a case, the heat-sensitive recording material 1 includes a backcoat layer (not shown), a support layer 2, a heat insulating layer 3, a heat-sensitive recording layer 4, and an overcoat layer (not shown) in this order. ..

Specific numerical values such as the compounding ratio (content ratio), physical property values, and parameters used in the following description are the compounding ratios (content ratio) corresponding to those described in the above-mentioned "Form for carrying out the invention". ), Physical property values, parameters, etc., can be replaced with the corresponding upper limit value (numerical value defined as "less than or equal to" or "less than") or lower limit value (numerical value defined as "greater than or equal to" or "excess"). it can. In addition, unless otherwise specified in the following description, "part" and "%" are based on mass.

1. 1. Details of components and apparatus The components used in each synthesis example, each example , each reference comparative example, and each comparative example are described below.
IPDI: 3-Isocyanatomethyl-3,5,5-trimethylcyclohexylisocyanate H ₆ XDI: 1,3-bis (isocyanatomethyl) cyclohexaneXDI: 1,3-xylylene diisocyanate HDI: 1,6-hexamethylenediisocyanate D-170N: Isocyanurate derivative of HDI CHDM: 1,4-Cyclohexanedimethanol BA-P2M: 2,2-Bis (4-polyoxypropyleneoxyphenyl) Propane NPG: Neopentylglycol EG: Ethyleneglycol 1,4- BG: 1,4-butylene glycol TMP: Trimethylol propane DMPA: 2,2-Dimethylol propionate EA: Ethyl acetate MCH: Methylcyclohexane CH: Cyclohexane XY: Xylene TEA: Triethylamine poison 530: Soda polyacrylate KBE-9007 : 3-Isocyanatopropyltriethoxysilane, KBM-803 manufactured by Shin-Etsu Chemical Industry Co., Ltd., 3-Mercaptopropyltrimethoxysilane, Cymel 325 manufactured by Shin-Etsu Chemical Industry Co., Ltd .: Methylated melamine resin, Euban 225 manufactured by allnex: Butylated melamine resin , Mitsui Chemicals Co., Ltd. 2. Preparation of Urethane Prepolymer Synthesis Example 1
Add 15.0 parts by mass of CHDM, 3.8 parts by mass of DMPA and 20.0 parts by mass of EA as a solvent to a glass flask equipped with an electromagnetic induction stirrer, a reflux condenser, and a nitrogen introduction tube, and raise the temperature to 40 ° C. under stirring. It was warm. Next, 61.2 parts by mass of IPDI was added and reacted at 70 to 80 ° C. in a nitrogen atmosphere until the isocyanate group concentration became 12.0% or less to obtain a urethane prepolymer. The solid content concentration was 79.1% and the NCO group concentration was 11.8%.

Synthesis Examples 2-13, 15, 16
A urethane prepolymer was obtained by treating in the same manner as in Synthesis Example 1 except that the formulation was changed according to the description in Table 1.

In Synthesis Example 10, XDI was added dropwise over about 1 hour and reacted at 50 to 60 ° C. in a nitrogen atmosphere until the NCO group concentration became 12.0% or less.

Further, in Synthesis Example 12, HDI was added dropwise over about 1 hour and reacted at 50 to 60 ° C. in a nitrogen atmosphere until the NCO group concentration became 12.0% or less.

Synthesis example 14
48.2 parts by mass of D-170N, 1.8 parts by mass of glycolic acid, and 50.0 parts by mass of EA were placed in a flask equipped with an electromagnetic induction stirrer and reflux cooling. Then, the urethane prepolymer was obtained by heating and stirring at 50 ° C. for 1 hour and further at 80 ° C. for 12 hours. The solid content concentration was 50.2% and the isocyanate group concentration was 11.4%.
3. 3. Production of Hollow Resin Particles Example 1
A mixed solution was prepared by mixing 75.0 parts by mass of the urethane prepolymer obtained in Synthesis Example 1, 55.0 parts by mass of EA, 70.0 parts by mass of MCH, and 2.2 parts by mass of TEA. Next, 240.0 parts by mass of distilled water was added to the mixture every 10 minutes while stirring at 1000 rpm using a TK homomixer (sawtooth type) manufactured by Tokushu Kagaku Kogyo Co., Ltd. .. As a result, an aqueous dispersion containing urethane prepolymer droplets containing EA and MCH was obtained from the urethane prepolymer.

Next, 5.4 parts by mass of hydrazine / monohydrate was added to the water in which the urethane prepolymer droplets were dispersed, and after stirring at room temperature for 2 hours, 8.2 parts by mass of Poise 530 was further added. The mixture was stirred for 30 minutes. Then, this aqueous dispersion was transferred to a flask equipped with a stirrer and reflux cooling, and stirred at 45 ° C. for 3 hours. As a result, an aqueous dispersion containing resin particles made of a urea resin (urethane-urea resin) containing EA and MCH was obtained.

Then, the pressure of the aqueous dispersion was reduced, and EA and MCH contained in the resin particles were distilled off to obtain an aqueous dispersion containing hollow resin particles.

Examples 2-8, 15-17, 19, 20 , Reference Comparative Examples 9-14, 18 and Comparative Examples 1-4
The formulation was treated in the same manner as in Example 1 except that the formulation was changed according to the description in Tables 2 to 4, to obtain an aqueous dispersion containing hollow resin particles.

In Examples 2 to 8, 15 to 17, 19, 20, and Reference Comparative Examples 9 to 14, 18 and Comparative Examples 1, 2 and 4, a cross-linking agent was blended together with the urethane prepolymer to prepare a mixed solution. ..

Further, in Example 15, distilled water was added while the temperature of the mixed solution was adjusted to 20 ° C. or lower.

Further, in Example 16, distilled water was added while adjusting the temperature of the mixed solution to 10 ° C. or lower.

Further, in Example 17, distilled water was added while the temperature of the mixed solution was adjusted to 15 ° C. or lower.

Further, in Examples 19 and 20, after adding Poise 530 and stirring for 30 minutes, 9.0 parts by mass of a triethylamine neutralized product of dodecylbenzenesulfonic acid was added, and the mixture was stirred for 30 minutes, and then an aqueous dispersion. Was transferred to a flask equipped with a stirrer and reflux cooling.

Further, in Comparative Example 1, distilled water was added while the temperature of the mixed solution was adjusted to 15 ° C. or lower.

Further, in Comparative Example 2, distilled water was added while the temperature of the mixed solution was adjusted to 15 ° C. or lower.

Further, in Comparative Example 3, distilled water was added while the temperature of the mixed solution was adjusted to 15 ° C. or lower.

Comparative Example 5 (external emulsification formula)
A mixed solution was prepared by mixing 20.0 parts by mass of D-170N, 20.0 parts by mass of propylene glycol monomethyl ether acetate, and 60.0 parts by mass of XY. Next, using a TK homomixer (sawtooth type) manufactured by Tokushu Kagaku Kogyo Co., Ltd., 6.0 parts by mass of polyvinylpyrrolidone (PVP) as a dispersant was dissolved in 296 parts by mass of distilled water while stirring at 1000 rpm. The mixed solution was added to the mixture, and the mixture was stirred for 5 minutes. Next, this was transferred to a flask equipped with a stirrer and reflux cooling, 16 parts by mass of a 5% aqueous solution of disodium hydrogen phosphate and 2.5 parts by mass of hydrazine / monohydrate were added, and the mixture was stirred at room temperature. A large amount of agglomerates were generated.
4. Evaluation (volume average particle size)
The volume average particle diameter of the hollow resin particles was measured for each Example , each Reference Comparative Example, and the hollow resin particles of each Comparative Example. Specifically, 1 g of the sample and 10 g of distilled water were collected in a 30 mL glass sample bottle, stirred with a magnetic stirrer for 5 minutes, and then the particle size was measured using a particle size analyzer Microtrac HRA (manufactured by Nikkiso Co., Ltd.) under the following conditions. Distribution measurement was performed.

Particle Transparency = Transsp
Sphere Particles = Yes
Particle Refractive Index = 1.50
Fluid Refractive Index = 1.333
The results are shown in Tables 2 to 4.

For Comparative Example 5, the particle size of 50 hollow resin particles randomly selected from the obtained aggregates was measured by an optical microscope.

The results are shown in Tables 2 to 4.
(Shape and volume hollow ratio)
For each Example , each Reference Comparative Example, and the hollow resin particles of each Comparative Example, the shape of the hollow resin particles was observed, and the volume hollow ratio thereof was measured. Specifically, an aqueous dispersion containing hollow resin particles was applied onto aluminum foil and dried at 40 ° C. for 12 hours or more to obtain a coating film. Next, this coating film was immersed in liquid nitrogen to freeze it, and then cut immediately, and the obtained cut surface was observed with an electron microscope. The particle size and the diameter of the hollow portion of 10 randomly selected hollow resin particles were measured, and the hollow ratio was calculated. The average value of the obtained hollow ratio was taken as the volume hollow ratio of the hollow resin particles.

Looking at the cut surface of Comparative Example 1, it was confirmed that the particles were hollow, but they were crushed and the hollow ratio could not be evaluated.

The results are shown in Tables 2 to 4.
(Particle size distribution)
The particle size distribution of the hollow resin particles was measured for each Example , each Reference Comparative Example, and the hollow resin particles of each Comparative Example.

Based on the integrated distribution data of the particle size obtained from the particle size measurement by the particle size analyzer Microtrac HRA (volume basis), when the peak top particle size of the main peak is A, A-0.5A to A + 0. The proportion of hollow resin particles belonging to the range of 5A was determined.

The superiority and inferiority of the particle size distribution was evaluated according to the following criteria. The results are shown in Tables 2 to 4.
⊚: 60% or more ○: 30% or more and less than 60% ×: less than 30% (strength evaluation)
(Measurement with scanning electron microscope)
The strength of the hollow resin particles was measured for each Example , each Reference Comparative Example, and the hollow resin particles of each Comparative Example. Specifically, an aqueous dispersion containing hollow resin particles was applied onto aluminum foil to a thickness of 20 to 30 μm, and dried at 40 ° C. for 12 hours or more to obtain a coating film. The surface of the obtained coating film and the cut surface of the coating film were observed with a scanning electron microscope at a magnification of 2000 times. The cut surface of the coating film was obtained by immersing the coating film in liquid nitrogen, freezing it, and then cutting it immediately.

The superiority and inferiority of the strength were evaluated according to the following criteria. The results are shown in Tables 2 to 4.
⊚: All surface particles maintain shape, cross section keeps voids ○: Surface particles are partially dented, cross section keeps voids △: All surface particles are dented, cross section keeps voids × All particles on the surface are dented, and the cross section cannot maintain voids (calender test)
The strength of the hollow resin particles was measured for each Example , each Reference Comparative Example, and the hollow resin particles of each Comparative Example. Specifically, an aqueous dispersion containing hollow resin particles adjusted to a non-volatile content of 10% with distilled water is ^{applied to one side of commercially available coated paper (basis weight 74 g / m 2} ), and the amount applied after drying is 2 g / m ^2. And dried at 80 ° C. for 1 minute by an air dryer method to provide a layer containing hollow resin particles (hollow resin particle layer) to obtain a coated paper coated with hollow resin particles. .. Using a calender device (“desktop calender veneer type” manufactured by Yuri Roll Co., Ltd.), this coated paper was subjected to calender treatment at room temperature, linear pressure of 200 kg / cm, and processing speed of 2 m / min. The surface of the coated paper after the calender treatment on the hollow resin particle layer side and the cut surface of the hollow resin particle layer were observed with a scanning electron microscope at a magnification of 2000 times. The cut surface of the hollow resin particle layer was obtained by immersing the coated paper in liquid nitrogen, freezing it, and then cutting it immediately.

The superiority and inferiority of the strength were evaluated according to the following criteria. The results are shown in Tables 2 to 4.
◯: Particles on the surface maintain their shape ×: All particles on the surface are crushed

5. Discussion It can be seen that in Examples 1 to 8, 15 to 17, 19 and 20 in which the urethane prepolymer has a carboxyl group, the volume average particle size can be adjusted to 1.2 μm or more and 18 μm or less.

On the other hand, in Comparative Example 5 (external emulsification formulation) in which an isocyanurate derivative of HDI having no carboxyl group was dispersed using a dispersant (polyvinylpyrrolidone (PVP)), the dispersion became non-uniform and a large amount of aggregates were present. Occurred in. Therefore, it can be seen that the volume average particle diameter of the hollow resin particles could not be adjusted.

Further, Examples 1 to 8, 15 to 17, 19 and 20 in which a diisocyanate, a carboxyl group-containing active hydrogen compound having two active hydrogen groups and one carboxyl group, and a dihydric alcohol were reacted, if necessary. It can be seen that the particle size distribution of the hollow resin particles was 30% or more, and the particle size of the hollow resin particles could be controlled accurately.

On the other hand, in Comparative Example 3 in which the isocyanurate derivative (trifunctional) of HDI was reacted with glycolic acid having one active hydrogen group and one carboxyl group, the particle size distribution of the hollow resin particles was less than 30%. It can be seen that the particle size of the hollow resin particles could not be controlled accurately.

Examples 1 to 8, 15 to 17, 19 and 20 containing a compound in which at least one of the polyisocyanate component and the active hydrogen group-containing component has a ring structure are the polyisocyanate component and the active hydrogen group-containing component. It can be seen that both are superior in strength as compared with Comparative Examples 1 to 4 which do not contain a compound having a ring structure.

Although the above invention has been provided as an exemplary embodiment of the present invention, this is merely an example and should not be construed in a limited manner. Modifications of the present invention that will be apparent to those skilled in the art are included in the claims below.

The hollow resin particles and the method for producing hollow resin particles of the present invention can be used in the fields of heat-sensitive recording materials, pesticides, pharmaceuticals, fragrances, liquid crystals, adhesives, etc., and are particularly preferably used for heat-sensitive recording materials. it can.

Further, the thermal recording material of the present invention is suitably used in the production of thermal recording paper, thermal transfer receiving paper and the like.

Claims (11)

Hollow resin particles that are hollow inside and are made of urethane / urea resin.
The urethane / urea resin is a reaction product of a urethane prepolymer having an isocyanate group and a chain extension compound having an active hydrogen group.
The urethane prepolymer is a reaction product of a polyisocyanate component and an active hydrogen group-containing component containing a carboxyl group.
The active hydrogen group-containing component contains a polyhydric alcohol and a carboxyl group-containing active hydrogen compound having a carboxyl group and two active hydrogen groups.
The carboxyl group-containing active hydrogen compound does not have a ring structure and has no ring structure.
The polyhydric alcohol has a ring structure and has a ring structure.
The content of the carboxyl group in the urethane / urea resin is 0.3% by mass or more and 10% by mass or less.
The volume average particle diameter, characterized in der Rukoto than 30μm below 0.5 [mu] m, the hollow resin particles. The hollow resin particles according to claim 1 , wherein the polyhydric alcohol has an alicyclic structure and / or an aromatic ring structure. The hollow resin particles according to claim 1 or 2 , wherein the polyisocyanate component contains a polyisocyanate having a ring structure. The hollow resin particles according to claim 3 , wherein the polyisocyanate component contains a diisocyanate having a ring structure. The hollow resin particles according to claim 4 , wherein the polyisocyanate component contains a diisocyanate having an alicyclic structure. The hollow resin particles according to claim 5 , wherein the diisocyanate contains a secondary isocyanate group. The hollow resin particles according to claims 1 to 6 , wherein the urethane prepolymer has an isocyanate group content of 10% by mass or more. The hollow resin particles according to claims 1 to 7 , wherein the urethane / urea resin is crosslinked by a crosslinking agent. The cross-linking agent is at least one selected from the group consisting of i) a silane coupling agent, ii) a compound having at least one of a carbodiimide group, an oxazoline group, and an epoxy group, and iii) a melamine compound. The hollow resin particles according to claim 8 , wherein the hollow resin particles are characterized by the above. A support layer, a heat insulating layer, and a thermal recording layer are provided in this order.
A heat-sensitive recording material, wherein the heat insulating layer contains the hollow resin particles according to claims 1 to 9. A step of reacting a polyisocyanate component with an active hydrogen group-containing component containing a carboxyl group to obtain a urethane prepolymer having an isocyanate group.
A step of mixing the urethane prepolymer and a hydrophobic solvent to prepare a mixed solution, adding water to the mixed solution, and obtaining urethane prepolymer droplets containing the hydrophobic solvent by the urethane prepolymer.
A step of reacting the urethane prepolymer with a chain extension compound having an active hydrogen group to obtain resin particles made of a urethane / urea resin containing the hydrophobic solvent, and
A step of removing the hydrophobic solvent contained in the resin particles to obtain hollow resin particles made of the urethane / urea resin and having a hollow inside is provided.
The active hydrogen group-containing component contains a polyhydric alcohol and a carboxyl group-containing active hydrogen compound having a carboxyl group and two active hydrogen groups.
The carboxyl group-containing active hydrogen compound does not have a ring structure and has no ring structure.
The polyhydric alcohol has a ring structure and has a ring structure.
The content of the carboxyl group in the urethane / urea resin is 0.3% by mass or more and 10% by mass or less.
The volume average particle diameter of the hollow resin particles, characterized in der Rukoto than 30μm below 0.5 [mu] m, the production method of the hollow resin particles.

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