JP6415132B2 - Method for producing polymer emulsion and polymer emulsion obtained thereby, and method for producing hollow particle and hollow particle obtained thereby - Google Patents

Description

  The present invention relates to a method for producing a polymer emulsion containing polymer particles containing a sufficient amount of a specific compound as compared with the conventional method, a polymer emulsion obtained thereby, and the production of hollow particles having a higher porosity than the conventional method. The present invention relates to a method and hollow particles obtained thereby.

  Until now, polymer particles having voids inside (hereinafter referred to as “hollow particles”) have been used for applications such as water-based paint compositions or paper coating compositions, and are used as hiding agents or white pigments with a high hiding degree as hollow particles. Have been utilized in addition to the ingredients of these compositions.

  For example, as a method for producing hollow particles used as a concealing agent added to paper, a polymer having a polar functional group as a polymerization initiator is used to assemble the polar functional groups in polymer particles, and water is attached thereto. As described above, a method has been proposed in which polymer particles having water gaps are produced by allowing water to be taken into polymer particles and drying the water-containing polymer particles (Patent Document 1).

JP 2007-270096 A

  However, the manufacturing method disclosed in Patent Document 1 basically has a gap only for the water volume incorporated. That is, because it does not contain a sufficient amount of a specific compound that thermally expands when heated, particle expansion is insufficient when heated, and the proportion of water entering the interior when shrinking when cooled is reduced. As a result, the porosity of the particles was insufficient, and hollow particles having a high porosity were not obtained.

  And the hollow particle obtained by the said patent document 1 also had the problem that it was inferior also in terms of concealment property, since the porosity was inadequate.

  Therefore, the present invention was obtained under such a background, and compared with the prior art, a method for producing a polymer emulsion containing polymer particles containing a sufficient amount of a specific compound, and a polymer emulsion obtained thereby, In addition, an object of the present invention is to provide a method for producing hollow particles having a higher porosity than in the prior art and hollow particles obtained thereby.

  However, the present inventors have conducted extensive studies in view of such circumstances, and as a result, in the emulsion polymerization, the polyoxyalkylene alkyl ether (b) having 14 or more carbon atoms, which is usually used as a nonionic emulsifier, has a temperature higher than the cloud point. By exposing to the bottom and using it for emulsion polymerization after having no original emulsion performance (non-emulsifier emulsion polymerization), the above-mentioned component (b) having no emulsion performance is formed in the polymer particles formed by polymerization. It was determined that a fully incorporated polymer emulsion was formed. In the polymer emulsion obtained by this production method, since the component (b) is sufficiently incorporated into the polymer particles, the component (b) is thermally expanded by heating the polymer emulsion to a specific temperature. By expanding the polymer shell portion and then cooling the polymer emulsion to room temperature, the shell portion is left intact and water is taken in when component (b) shrinks, thereby diluting component (b). . And the polymer emulsion which removes the water inside a polymer particle by drying the polymer emulsion, and can obtain the polymer particle which has a high porosity compared with the past was obtained, and it reached | attained this invention.

That is, the gist of the present invention is a method for producing a polymer emulsion containing polymer particles obtained by polymerization using the following components (a) to (d), wherein the polymerization is carried out by clouding the component (b). The present invention relates to a method for producing a polymer emulsion performed at a temperature equal to or higher than a point.
(A) Monomer.
(B) A polyoxyalkylene alkyl ether having an alkyl group with 14 or more carbon atoms.
(C) A polymerization initiator.
(D) Water.

  In the present invention, there is also provided a polymer emulsion obtained by the above-described production method, wherein the polymer particles in which the component (b) is encapsulated in a polymer shell are dispersed. It is to provide.

Furthermore, the present invention also provides a method for producing hollow particles having a polymer shell part structure in which the inside becomes hollow by passing through the following steps [I] to [III] using the polymer emulsion. .
[I] A step of heating at a temperature not lower than the cloud point of the component (b) and not less than 10 ° C. lower than the glass transition temperature of the polymer.
[II] A step of cooling to room temperature.
[III] A step of performing at least one of heat drying and vacuum drying.

  And the hollow particle obtained by the manufacturing method of the said hollow particle is also provided.

  The present invention is a method for producing a polymer emulsion containing polymer particles obtained by polymerization using the components (a) to (d), wherein the polymerization is performed at a temperature equal to or higher than the cloud point of the component (b). Therefore, according to this production method, a polymer emulsion containing polymer particles containing a sufficient amount of the specific compound can be obtained according to this production method.

  Then, by using the obtained polymer emulsion, hollow particles having a polymer shell part structure in which the inside becomes hollow by passing through the steps [I] to [III] can be produced. With the hollow particle production method, hollow particles having a higher porosity can be obtained compared to the conventional method.

The description of the constituent requirements described below is an example (representative example) of the embodiment of the present invention, and is not limited to these contents.
Hereinafter, the present invention will be described in detail.

<< Manufacture of polymer emulsion >>
In the present invention, a polymer emulsion is obtained by performing a polymerization reaction using a monomer component (a), a polyoxyalkylene alkyl ether (b) having 14 or more alkyl groups, a polymerization initiator (c), and water (d). Manufacturing. And the said polymerization reaction is performed at the temperature more than the cloud point of the said polyoxyalkylene alkyl ether (b), It is characterized by the above-mentioned.
The above (a) to (d), which are constituent materials of the polymer emulsion, will be described in order below.

<Monomer component (a)>
Examples of the monomer component (a) include styrene monomers such as styrene and α-methylstyrene; vinyl formate, vinyl acetate, vinyl propionate, vinyl valerate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, capric acid. Vinyl ester monomers such as vinyl, vinyl laurate, vinyl stearate, vinyl benzoate, vinyl versatic acid, vinyl 2-ethylhexanoate; methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate , I-butyl (meth) acrylate, t-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, cyclohexyl (meth) acrylate, lauryl (meth) acrylate, octyl (meth) acrylate, stearyl (meth) acrylate Aliphatic (meth) acrylate monomers such as, aromatic (meth) acrylate monomers such as phenoxy (meth) acrylate, (meth) acrylic monomers such as trifluoroethyl (meth) acrylate; and functional Group-containing monomers and the like, and these may be used alone or in combination of two or more. Among these, a styrene monomer is preferable, and a styrene monomer is particularly preferably used.

  In the present invention, (meth) acryl refers to acryl or methacryl, and (meth) acrylate refers to acrylate or methacrylate.

  Examples of the functional group-containing monomer include monomers having two or more vinyl groups in the molecular structure, glycidyl group-containing monomers, allyl group-containing monomers, hydrolyzable silyl group-containing monomers, acetoacetyl group-containing monomers, hydroxyl groups. Group-containing monomers, carboxyl group-containing monomers, and the like.

  Among these, it is preferable to use a monomer having two or more vinyl groups in the molecular structure or a hydrolyzable silyl group-containing monomer from the viewpoint of excellent stability during polymerization.

  Examples of the monomer having two or more vinyl groups in the molecular structure include divinylbenzene, and examples of the monomer having two or more allyl groups include diallyl phthalate, triallyl cyanurate, triallyl isocyanurate, Triallyloxyethylene, diallyl maleate, tetraallyloxyethane and the like can be mentioned. Examples of the monomer having two or more (meth) acrylate groups include ethylene glycol di (meth) acrylate, 1,2-propylene glycol di ( (Meth) acrylate, 1,3-propylene glycol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, tri Methylolup Pantori (meth) acrylate, and the like, Examples of the monomer having two or more different polymerizable groups, for example, allyl (meth) acrylate and the like.

  Among these, ethylene glycol di (meth) acrylate, 1,2-propylene glycol di (meth) acrylate, 1,3-propylene glycol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, 1, 6-hexanediol di (meth) acrylate, neopentylglycol di (meth) acrylate, and trimethylolpropane tri (meth) acrylate are preferable in that they are excellent in copolymerizability with (meth) acrylate monomers.

  Examples of the glycidyl group-containing monomer include glycidyl (meth) acrylate, glycidyl (meth) allyl ether, 3,4-epoxycyclohexyl (meth) acrylate, and the like.

  Examples of the allyl group-containing monomer include allyl glycidyl ether and allyl acetate.

  Examples of the hydrolyzable silyl group-containing monomer include vinyl-based silyl group-containing monomers such as vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (β-methoxyethoxy) silane, and vinylmethyldimethoxysilane; γ- (meth) (Meth) acryloxy systems such as acryloxypropyltrimethoxysilane, γ- (meth) acryloxypropylmethyldimethoxysilane, γ- (meth) acryloxypropyltriethoxysilane, γ- (meth) acryloxypropylmethyldiethoxysilane Examples thereof include silyl group-containing monomers.

  Among these, a (meth) acryloxy-based silyl group-containing monomer is preferable because it is excellent in copolymerizability with a (meth) acrylate-based monomer.

  Examples of the acetoacetyl group-containing monomer include acetoacetate vinyl ester, acetoacetate allyl ester, diacetoacetate allyl ester, acetoacetoxyethyl (meth) acrylate, acetoacetoxyethyl crotonate, acetoacetoxypropyl (meth) acrylate, acetoacetoxy Examples thereof include propyl crotonate and 2-cyanoacetoacetoxyethyl (meth) acrylate.

  Examples of the hydroxyl group-containing monomer include (meth) acrylates such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and the like during emulsion polymerization. From the viewpoint of protective colloidal action and washability, 2-hydroxyethyl acrylate and 2-hydroxyethyl methacrylate are preferred.

  Examples of the carboxyl group-containing monomer include (meth) acrylic acid, acrylic acid dimer, crotonic acid, maleic acid, maleic anhydride, fumaric acid, citraconic acid, glutaconic acid, itaconic acid, acrylamide-N-glycolic acid, silica Among these, acrylic acid and methacrylic acid are preferred from the viewpoint of easily imparting mechanical stability during emulsion polymerization.

  As the content ratio of the other monomer component (a), for example, when the styrene monomer and the other monomer component (X) are used, the use ratio is styrene monomer / X based on weight. = 100/0 to 50/50, particularly preferably 95/5 to 70/30. When there is too little styrene-type monomer, there exists a tendency for the porosity to fall.

<Polyoxyalkylene alkyl ether (b) having 14 or more carbon atoms in the alkyl group>
The alkyl group polyoxyalkylene alkyl ether is 14 or more carbon atoms of (b) _{is, RO - ((C m H} 2m) O) n -H (R is C14 or more alkyl groups, m is 1-4, n is represented by 1 to 50), and examples thereof include polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether and the like. These may be used alone or in combination of two or more.

  Moreover, although carbon number of the alkyl group of the said (b) component is 14 or more as mentioned above, Preferably it is 14-22 from a viewpoint that the solubility with respect to the water in the temperature more than a cloud point is low, More preferably, it is 16-20. Among these, as the component (b), polyoxyethylene oleyl ether is preferable because it can easily move together with the monomer. Specifically, Emulgen 409PV (cloud point 55 ° C.) (manufactured by Kao Corporation) can be mentioned.

  In the present invention, the cloud point of the polyoxyalkylene alkyl ether (b) is preferably from 20 to 70 ° C, particularly preferably from 30 to 60 ° C. When the cloud point is too high, it tends to be difficult to incorporate the polyoxyalkylene alkyl ether (b) into the produced polymer particles. When the cloud point is too low, the polyoxyalkylene alkyl ether ( b) is easy to enter, but when the polyoxyalkylene alkyl ether (b) incorporated in the subsequent step is removed and the interior of the polymer particles is hollowed out, the polyoxyalkylene alkyl ether (b) remains more. There is a tendency for the porosity to decrease.

  Furthermore, the degree of hydrophobicity (HLB) of the polyoxyalkylene alkyl ether (b) is preferably 5 to 20, particularly preferably 6 to 19. If the HLB of the polyoxyalkylene alkyl ether (b) is too high, it tends to be difficult to encapsulate inside the particle, and if the HLB is too low, the residue tends to increase in the particle at the time of hollowing and the porosity decreases. Is seen.

  Moreover, as said polyoxyalkylene alkyl ether (b), the thing whose solubility with respect to the water of the hydrophobic group is 0.0001-10 mg / L is preferable, Most preferably, it is 0.001-5 mg / L. If the solubility of the hydrophobic group in water is too high, it tends to be difficult to incorporate the polyoxyalkylene alkyl ether (b) inside the polymer particle, and if the solubility of the hydrophobic group in water is too low, the polymer particle is not filled in the polymer particle. Oxyalkylene alkyl ether (b) is easy to enter, but when polyoxyalkylene alkyl ether (b) is removed and the inside of the polymer particles is hollowed out, the residual polyoxyalkylene alkyl ether (b) increases and the porosity decreases. There is a tendency to

  The amount of the polyoxyalkylene alkyl ether (b) used is preferably 2 to 40 parts by weight, particularly preferably 4 to 20 parts by weight, and more preferably 5 parts per 100 parts by weight of the monomer component (a). ~ 15 parts by weight. If the amount used is too small, the porosity tends to decrease, and if it is too large, the stability during polymerization tends to decrease.

<Polymerization initiator (c)>
As the polymerization initiator (c), either water-soluble or oil-soluble can be used. For example, alkyl peroxide, t-butyl hydroperoxide, cumene hydroperoxide, p-methane hydroperoxide, lauroyl peroxide, 3,5,5-trimethylhexanoyl peroxide, octanoyl peroxide, t-butyl cumi Ruperoxide, benzoyl peroxide, dichlorobenzoyl peroxide, dicumyl peroxide, di-t-butyl peroxide, 1,1-bis (t-butylperoxy) -3,3,5-trimethylcyclohexane, 3, 3,5-trimethylcyclohexanone peroxide, methylcyclohexanone peroxide, di-isobutyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, t-butylperoxyisobutyrate, etc. Organic peroxides, 2,2'-azobisisobutyronitrile, dimethyl-2,2'-azobisisobutyrate, 2,2'-azobis (2,4-dimethylvaleronitrile), 2,2 ' -Azobis (2-methylbutyronitrile), potassium persulfate, sodium persulfate, ammonium persulfate, hydrogen peroxide, ammonium (amine) salt of 4,4'-azobis-4-cyanovaleric acid, 2,2 ' -Azobis (2-methylamidooxime) dihydrochloride, 2,2'-azobis (2-methylbutanamidoxime) dihydrochloride tetrahydrate, 2,2'-azobis {2-methyl-N- [1,1- Bis (hydroxymethyl) -2-hydroxyethyl] -propionamide}, 2,2′-azobis [2-methyl-N- (2-hydroxyethyl) ) -Propionamide], various redox catalysts (in this case, as an oxidizing agent, ammonium persulfate, potassium persulfate, sodium persulfate, hydrogen peroxide, t-butyl hydroperoxide, benzoyl peroxide, cumene hydroperoxide, p-methane hydroperoxide and the like, and sodium sulfite, acidic sodium sulfite, Rongalite, ascorbic acid and the like are used as the reducing agent. These polymerization initiators (c) may be used alone or in combination of two or more.

  Of these, potassium persulfate, ammonium persulfate, sodium persulfate, redox catalyst (oxidizer: potassium persulfate, sodium persulfate, reducing agent: sodium sulfite, acidic sodium sulfite, Rongalite, ascorbine are excellent in polymerization stability. Acid) and the like are preferably used.

  The amount of the polymerization initiator (c) used is preferably 0.01 to 10 parts by weight, particularly preferably 0.03 to 7 parts by weight, more preferably 100 parts by weight of the monomer component (a). Is 0.05 to 5 parts by weight. When the amount of the polymerization initiator (c) used is too small, the polymerization rate tends to be slow, and when it is too large, the molecular weight of the resulting copolymer tends to be low and the water resistance tends to decrease.

  In addition, as a use aspect of the said polymerization initiator (c), you may add beforehand in a superposition | polymerization can, may be added just before the start of superposition | polymerization, and may be added in the middle of superposition | polymerization as needed. Good. Alternatively, it may be added in advance to the monomer component (a) or may be added to the emulsion comprising the monomer component (a). In addition, when adding the polymerization initiator (c), the polymerization initiator (c) is separately dissolved in a solvent or the monomer component (a) and added, or the dissolved polymerization initiator (c) is further emulsified. Or may be added.

<Water (d)>
As a constituent material of the polymer emulsion of the present invention, water (d) is an essential component in addition to the above (a) to (c). Examples of the water (d) include pure water such as ion exchange water, ultrafiltration water, reverse osmosis water, and distilled water, ultrapure water, well water from which foreign matters are removed, and tap water. Of these, ion-exchanged water is preferred from the viewpoints of economy and production stability. These may be used alone or in combination of two or more.

  As content of the said water (d), it is preferable that it is 50-20000 weight part with respect to 100 weight part of monomer components (a), Most preferably, it is 100-10000 weight part, More preferably, it is 200-5000 weight part Part. If the amount of water used is too small, the stability during polymerization tends to decrease, and if too large, the economic efficiency during industrialization tends to decrease.

<Other ingredients>
In the method for producing the polymer emulsion of the present invention, an emulsifier having an action as a surfactant may be used. As the emulsifier, various surfactants conventionally used as surfactants may be used. For example, anionic, cationic, and nonionic reactive surfactants, anionic, cationic, and nonionic types Non-reactive surfactants.
Among these, it is preferable to use a nonionic non-reactive surfactant in terms of excellent polymerization stability, and the cloud point is preferably higher than the polymerization temperature in the polymerization reaction described later.

  Examples of the emulsifier include, as polyoxyethylene alkyl ethers, Emulgen 120 (cloud point 98 ° C.), Emulgen 123P (cloud point> 100 ° C.), Emulgen 130K (cloud point> 100 ° C.), Emulgen 147 (cloud point> 100 ° C), Emulgen 150 (cloud point> 100 ° C), Emulgen 1118S-70 (cloud point> 100 ° C), Emulgen 1135S-70 (cloud point> 100 ° C), Emulgen 1150S-60 (cloud point> 100 ° C) ( (Both manufactured by Kao Corporation). These may be used alone or in combination of two or more.

  In addition, as the addition method of the said emulsifier, you may add to the emulsion monomer liquid which consists of a monomer component (a), may add to the superposition | polymerization can previously, and may use both together.

  About the usage-amount of the said emulsifier, it is preferable that it is 0-10 weight part with respect to 100 weight part of said monomer components (a), Most preferably, it is 0-5 weight part. When there is too much said usage-amount, emulsifier-free polymerization does not advance and there exists a tendency for emulsion polymerization to be performed.

  In the method for producing a polymer emulsion of the present invention, for example, a polymerization regulator can be used in addition to the above components. Examples of the polymerization regulator include chain transfer agents and pH buffering agents.

  Examples of the chain transfer agent include alcohols such as methanol, ethanol, propanol and butanol; aldehydes such as acetaldehyde, propionaldehyde, n-butyraldehyde, furfural and benzaldehyde; n-dodecyl mercaptan, thioglycolic acid and thioglycolic acid And mercaptans such as octyl and thioglycerol. These may be used alone or in combination of two or more.

  The use of the chain transfer agent is effective in terms of carrying out the polymerization stably, but may reduce the degree of polymerization of the resin and reduce the elastic modulus of the resulting coating film. Therefore, specifically, the amount of the chain transfer agent used is preferably 1 part by weight or less, particularly preferably 0.5 parts by weight or less, more preferably 100 parts by weight of the monomer component (a). 0.3 parts by weight or less. When there is too much usage-amount of the said chain transfer agent, there exists a tendency for the reactivity fall and the elasticity modulus of particle | grains to fall.

  Examples of the pH buffering agent include soda ash (sodium carbonate), sodium bicarbonate, potassium bicarbonate, monosodium phosphate, monopotassium phosphate, disodium phosphate, trisodium phosphate, sodium acetate, acetic acid. Examples include ammonium, sodium formate, and ammonium formate. These may be used alone or in combination of two or more.

  The amount of the pH buffer used is preferably 10 parts by weight or less, particularly preferably 5 parts by weight or less, and further preferably 3 parts by weight or less, based on 100 parts by weight of the whole monomer component (a). When there is too much usage-amount of the said pH buffer agent, there exists a tendency which is easy to inhibit reaction.

<Method for producing polymer emulsion>
As described above, the polymer emulsion of the present invention comprises a monomer component (a), a polyoxyalkylene alkyl ether (b) having an alkyl group having 14 or more carbon atoms, a polymerization initiator (c), water (d), and if necessary. Using the other components, a polymer emulsion is produced by conducting a polymerization reaction under a temperature condition higher than the cloud point of the polyoxyalkylene alkyl ether (b).

<Polymerization reaction conditions>
The temperature condition for the polymerization reaction depends on the cloud point of the polyoxyalkylene alkyl ether (b) contained in the polymer particles, but for example, in the range of 40 to 100 ° C. under normal pressure. Is more preferable, and 60-90 ° C is more preferable.

  The time required for the polymerization reaction is preferably, for example, 3 to 48 hours, and more preferably 5 to 24 hours. The time required for the polymerization reaction may be a time for which the monomer component (a) to be used is consumed for the reaction. If the time is too short, the residual ratio of the monomer component (a) increases and the yield decreases. Tend.

  In the above polymerization reaction, the pressure of the reaction system is preferably normal pressure, and the stirring conditions during the polymerization reaction are preferably set earlier than the state in which the monomer component (a) during polymerization is emulsified, For example, it is preferable that the polymerization reaction container be 300 rpm or more when the scale is 300 mL.

  The apparatus used for producing the polymer emulsion of the present invention may be an ordinary stirring apparatus. For example, a paddle-type, turbine-type, impeller-type rod, plate, or propeller-like stirrer rotates in a tank.

<Physical properties of polymer emulsion>
A polymer emulsion is obtained by the method for producing a polymer emulsion of the present invention. This polymer emulsion is in a state where polymer particles in which the component (b) is encapsulated in a polymer shell are dispersed.

  The average particle diameter of the polymer particles is preferably 0.05 to 50 μm, more preferably 0.1 to 10 μm, from the viewpoint of easy formation of a hollow.

  Since the polymer particles are substantially spherical, the particle size can be obtained using a sphere as a basic shape, the average particle diameter is a weight average particle diameter, and the weight average particle diameter is a dynamic light scattering particle. It can be measured by a diameter distribution measuring device.

  The polymer constituting the shell portion of the polymer particles is preferably a weight average molecular weight of 10,000 to 300,000, more preferably 50,000 to 200,000, and particularly preferably 80,000 to 170,000. . If the weight average molecular weight is too low, the shell of the polymer particles tends to be weak, and if it is too high, the temperature of the heat treatment tends to increase.

In addition, said weight average molecular weight is a weight average molecular weight by standard polystyrene molecular weight conversion, a column: TSK SuperMultiporeHZ-H (exclusion limit molecular weight: 4 * 10) in size exclusion chromatography (Tosoh Corporation make, "HLC-8320GPC". ⁷ ) Measured by using two series of filler materials: styrene-divinylbenzene copolymer, filler particle size: 6 μm.

  The glass transition temperature (Tg) of the polymer constituting the shell portion of the polymer particles is preferably 40 ° C. or higher, more preferably 60 ° C. or higher, and particularly preferably 80 ° C. or higher. If the Tg is too low, the polymer particles tend to fuse with each other. Further, the upper limit of Tg is usually 150 ° C. or lower.

The glass transition temperature (Tg) of the polymer used was a value calculated by the Fox equation shown in the following equation (1).
1 / Tg = W1 / Tg1 + W2 / Tg2 + ... + Wn / Tgn (1)
In the above formula (1), W1 to Wn represent the weight fraction of each monomer used, and Tg1 to Tgn represent the glass transition temperature of each monomer homopolymer (unit is absolute temperature “ K "). The absolute temperature is calculated as absolute temperature “K” = Celsius temperature “° C.” + 273.15.

<Method for producing hollow particles>
Next, by using the obtained polymer emulsion, hollow particles having a polymer shell portion structure in which the inside becomes hollow can be produced through the following steps [I] to [III].
[I] A step of heating at a temperature not lower than the cloud point of the component (b) and not less than 10 ° C. lower than the glass transition temperature of the polymer.
[II] A step of cooling to room temperature.
[III] A step of performing at least one of heat drying and vacuum drying.

  The heating temperature of [I] above is a temperature equal to or higher than the cloud point in normal pressure and a pressurized state, and is equal to or higher than a temperature 10 ° C. lower than the glass transition temperature (Tg) of the polymer constituting the shell portion, Further, the temperature is preferably 5 ° C. lower than Tg, particularly preferably Tg or higher. The upper limit of the heating temperature is preferably Tg + 50 ° C. or less, more preferably Tg + 40 ° C. or less, and particularly preferably Tg + 30 ° C. or less. If the heating temperature is too low, the polymer tends to hardly expand in the glass state, and if it is too high, the particles tend to fuse and aggregates are formed.

  The heating time of the above [I] may be influenced by the Tg and composition of the polymer constituting the shell part, but in the case of normal pressure, it is preferably heated for 5 to 24 hours, and further 6 to 20 hours It is preferable to overheat. In the case of pressurization (1 Pa to 200 kPa), the time is preferably 30 minutes to 2 hours, and more preferably 40 minutes to 1 hour. When the heating time is too short, the polymer particles tend not to expand sufficiently, and when the heating time is too long, the expansion stability of the polymer particles decreases and the porosity tends to decrease.

  The above-mentioned [II] cooling to room temperature means, for example, exposing the polymer emulsion heated in the step [I] to ambient air at room temperature of 25 ° C. ± 10 ° C., cooling or freezing the heated polymer emulsion. Exposure to a heated fluid (such as, but not limited to, liquid, air, nitrogen, oxygen, or combinations thereof), a heated polymer emulsion to a temperature controlled chamber (tube, pipe, or conduit, Or a bath). These may be used alone or in combination of two or more.

  Examples of the drying step [III] include drying by heating using a circulating dryer, spray dryer, fluidized bed dryer, etc., and vacuum drying using a vacuum dryer, etc. It is done. As the heating conditions, for example, when a circulating dryer is used, it is preferable to heat and dry at 30 to 90 ° C. for 3 to 20 hours. In the case of using a vacuum dryer, it is preferable to heat and dry at a temperature of 10 to 90 ° C. for 3 to 20 hours.

  When the polymer emulsion undergoes the steps [I] to [III], the polymer particles in the emulsion can be hollowed out. The hollowing mechanism will be described as follows. By heating [I] above, the polyoxyalkylene alkyl ether (b) encapsulated inside the polymer particles expands to expand the polymer shell. Thereafter, by cooling to the room temperature of [II] above, the shell part takes in water when the component (b) contracts while leaving the shell as it is, thereby diluting the component (b). At this time, the component (b) inside the shell is further diluted by the concentration gradient between the diluted component (b) inside the shell and the water component outside the shell. Then, by drying [III], the water component inside the shell part evaporates, and a cavity is formed inside the shell part, so that a polymer particle having a hollow polymer shell part, that is, hollow particles can be obtained. become.

  In addition, the hollow particles obtained by the above-mentioned drying are highly likely to be adhered to the surface of the shell portion, etc., so that the target hollow particles are obtained by washing with a solvent such as alcohol. It will be obtained.

<Physical properties of hollow particles>
The porosity of the hollow particles obtained above is preferably 4 to 70%, more preferably 6 to 70%, and particularly preferably 8 to 70%. If the porosity is too high, the thickness of the shell is reduced, the strength of the particle shell is reduced, and the particles may be broken.

  In addition, the said porosity is "the area ratio of the shell part and space part by binary image processing of a SEM image by observing a some hollow particle with a magnification of 100,000 times or more with a transmission electron microscope (TEM). Then, the porosity of the mixed film is calculated, and the average value is taken as the porosity. ”

  In addition, since the above hollow particles are advantageous in optical properties such as concealability (light non-transmitting property) when the porosity is high, it is also required that the porosity is high and the liquid floating rate correlated therewith is high. Is done.

  Accordingly, the floating rate of the hollow particles in the liquid is such that the hollow particles have a floating rate of 40% or more after 24 hours when 0.2 g of the obtained hollow particles are added to 20 mL of a 1 wt% aqueous sodium lauryl sulfate solution. Preferably there is. It is preferable that the floating rate is further 40 to 100%, particularly 50 to 100%, particularly 70 to 100%. If the floating rate in the liquid is too low, the porosity tends to decrease.

  The hollow particles of the present invention are hollowed out by producing a polymer emulsion containing polymer particles containing a sufficient amount of the compound (b), etc., and then heating, cooling, and drying. Therefore, hollow particles having a high porosity can be obtained as compared with the prior art.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist. In the examples, “parts” and “%” mean weight standards.

[Example 1]
<Manufacture of polymer emulsion>
A solution was prepared by dissolving 10 parts of polyoxyethylene oleyl ether (“Emulgen 409PV” (18 carbon atoms of alkyl group, cloud point 55 ° C.)) as surfactant A (b) in 100 parts of styrene. Then, 360 parts of deionized water in a reaction vessel, 1 part of polyoxyethylene lauryl ether [manufactured by Kao Corporation, “Emulgen 150”: (carbon number of alkyl group 12, cloud point> 100 ° C.)] as surfactant D Dissolved and heated to 70 ° C. Into this, the previously prepared solution was blended, and further, 66.7 parts of 3% aqueous potassium persulfate solution was blended as a polymerization initiator α to initiate polymerization. During the polymerization, the internal temperature was maintained at 70 ° C., and the polymerization was carried out for about 24 hours.

  The non-volatile content [SC; Solid Content (%)] of the obtained polymer emulsion was 21%, and the Tg of the polymer of the obtained polymer emulsion was 100 ° C.

<Manufacture of hollow particles>
The same amount of deionized water was added to 100 parts of the emulsion obtained above, and stirring was continued at 94 ° C. for 9 hours, followed by heat treatment. Thereafter, the heat-treated emulsion was allowed to cool at room temperature (25 ° C.), and the solid (polymer) and aqueous solution were separated using a centrifuge. And two types of hollow particles were obtained by the following methods (1) and (2).
(1) The solid content was collected and dried at 50 ° C. for about 24 hours to obtain hollow particles.
(2) The solid content was collected and stirred in methanol at 25 ° C. for 24 hours, and then the solid content was similarly collected and dried at 50 ° C. for about 24 hours to obtain hollow particles.

[Example 2]
Polymerization was carried out in the same manner as in Example 1 except that the polymerization initiator α in Example 1 was changed to the polymerization initiator β (3% ammonium persulfate aqueous solution) to obtain hollow particles. The results are shown in Table 1.

Example 3
Polymerization was carried out in the same manner as in Example 1 except that the surfactant D (Emulgen 150) of Example 1 was not used to obtain hollow particles. The results are entered in a table.

Example 4
Polymerization was carried out in the same manner as in Example 1 except that the surfactant A (Emulgen 409PV) in Example 1 was increased by 1.25 times to obtain hollow particles. The results are entered in a table.

[Comparative Example 1]
Since the polymerization temperature is 45 ° C. lower than the cloud point of the surfactant A and the reaction activity needs to be increased due to the low temperature, the polymerization initiator is polymerized with 66.7 parts of a polymerization initiator α (3% potassium persulfate aqueous solution). Initiator θ (3% sodium hydrogen sulfite aqueous solution) was 66.7 parts of redox reaction. Otherwise, the polymerization was carried out in the same manner as in Example 1. As a result, there was a sudden exotherm and a stable emulsion could not be obtained, so no hollow particles were obtained.
In addition, when the polymerization temperature of Example 1 was 45 degreeC lower than the cloud point of surfactant A, since the polymerization initiator did not decompose | disassemble and it did not superpose | polymerize, it superposed | polymerized using the said redox reaction.

[Comparative Example 2]
In Comparative Example 1, in order to make the polymerization reaction mild, only the styrene monomer was dropped over 3 hours to carry out the polymerization to obtain an emulsion. Otherwise, hollow particles were obtained in the same manner as in Example 1. The non-volatile content (%) of the obtained emulsion was 19%.

[Comparative Example 3]
Surfactant A of Example 1 (Emulgen 409PV) was added to polyoxyethylene lauryl ether ["Emulgen 108" (12 carbon atoms, cloud point 40 ° C)] in which the alkyl group of surfactant C has less than 14 carbon atoms. Except for the change, polymerization was carried out in the same manner as in Example 1 to obtain hollow particles. Note that the non-volatile content (%) of the obtained emulsion was 21%.

[Comparative Example 4]
Surfactant A (Emulgen 409PV) of Example 1 was changed to polyoxyethylene lauryl ether [“Emulgen 109P” (carbon number of alkyl group 12, cloud point 83 ° C.) of surfactant B having less than 14 carbon atoms] Except that, polymerization was performed in the same manner as in Example 1 to obtain hollow particles. Note that the non-volatile content (%) of the obtained emulsion was 21%.

<Floating rate in liquid>
The hollow particles obtained above were subjected to a liquid floating rate test according to the following method, and the results are shown in Table 1 below.

  About the hollow particles obtained through the drying steps (1) and (2) above, 0.2 g of the hollow particles were weighed into a 30 mL glass bottle, and about 20 mL of 1% sodium dodecyl sulfate aqueous solution was added. The floating rate after 3 days from the addition of the 1% sodium dodecyl sulfate aqueous solution was determined visually according to the following evaluation criteria. The result of the drying step (1) is shown as “floating rate a”, and the result of the drying step (2) is shown as “floating rate b” in Table 1 below.

<Evaluation criteria>
Floating rate 80% to 100%: ◎
Floating rate 50% or more and less than 80%: ○
Floating rate 20% or more and less than 50%: △
Floating rate less than 20%: ×

  Furthermore, for the hollow particles of Example 1 and Comparative Example 4, “a plurality of hollow particles were observed with a transmission electron microscope (TEM) at a magnification of 100,000 times or more, and binarized image processing of the SEM image was performed. The void ratio of the mixed film was calculated from the area ratio of the shell part and the space part by the above method, and the average value thereof was defined as the void ratio. " As a result, 30% was obtained in Example 1 and 3% was obtained in Comparative Example 4.

  From the above results, the hollow particles of the examples using the polyoxyalkylene alkyl ether (b) having an alkyl group with 14 or more carbon atoms were mostly in a state of floating in the liquid with both the floating ratios a and b. It was.

  On the other hand, in Comparative Examples 1 and 2 in which the polymerization temperature is less than the cloud point of the component (b), Comparative Example 1 cannot obtain a stable emulsion due to rapid heat generation, and Comparative Example 2 has both the floating rates a and b. It was x and the hollow particles were almost precipitated.

  Also in Comparative Examples 3 and 4 using polyoxyalkylene alkyl ethers having less than 14 carbon atoms, the floatability a and b were both x or Δ, and the hollow particles settled in the liquid or mostly settled. It was in a state.

  In Comparative Examples 2 to 4, since the polymer particles could not contain a sufficient amount of polyoxyalkylene alkyl ether (b) during the emulsion, sufficient voids were obtained even when the particles were hollow. This is because the rate was not obtained. That is, the high floating rate of the hollow particles of the example product also indicates the high porosity of the hollow particles.

  According to the method for producing a polymer emulsion of the present invention, a polymer emulsion containing polymer particles containing a sufficient amount of a specific compound can be obtained as compared with the conventional method, and the resulting hollow particles have a high porosity. Therefore, it is useful as a material used for various applications such as paints, film-forming materials, sheet-forming materials, and concealing materials.

Claims (1)

Following (a) ~ (d) in the method for producing a polymer emulsion containing a heavy combined and made polymer particles using the components, the polymerization and the (b) polymer I cloud point or more rows at a temperature of component emulsion Manufacture and
In the produced polymer emulsion, polymer particles in which the component (b) is encapsulated in a polymer shell portion are dispersed,
A hollow characterized in that hollow particles having a hollow shell structure are produced by using the polymer emulsion produced above, through the following steps [I] to [III]. Particle production method.
(A) Monomer.
(B) A polyoxyalkylene alkyl ether having an alkyl group with 14 or more carbon atoms.
(C) A polymerization initiator.
(D) Water.
[I] A step of heating at a temperature not lower than the cloud point of the component (b) and not less than 10 ° C. lower than the glass transition temperature of the polymer.
[II] A step of cooling to room temperature.
[III] A step of performing at least one of heat drying and vacuum drying.