Method for producing polymer-coated particles

Abstract

To provide a method for producing polymer-coated particles suitable for use as a filler in paint or the like.SOLUTION: A method for producing polymer-coated particles includes polymerizing a radically polymerizable monomer (a) in the presence of an inorganic powder (b), a wetting dispersant (c), and a radical polymerization initiator (d). The wetting dispersant (c) has an acid value of 132 mgKOH / g or less and / or an amine value of 94 mgKOH / g or less. The usage amount of the radically polymerizable monomer (a) is 5 pts.wt. or more and 400 pts.wt. or less relative to 100 pts.wt. of the total amount of the inorganic powder (b).SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a method for producing polymer-coated particles.

Background Art

[0002] Paints are used for purposes such as protecting an object, improving its aesthetics, and imparting functions. For example, Patent Document 1 is an invention related to a paint used for a sliding part, in which the amount of wear is reduced by adding a certain amount of titanium oxide powder, and the anti-seizure property is improved by using a solid lubricant. On the other hand, since molybdenum disulfide or graphite is used as a solid lubricant, it has a black appearance, and it has been difficult to apply it to applications where it is desired to improve the aesthetics by coloring. Therefore, there has been a demand for an additive that can improve lubricity without affecting the aesthetics.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] An object of the present invention is to provide a method for producing polymer-coated particles suitable for use as a filler for paints and the like.

Means for Solving the Problems

[0005] The present invention is a method for producing polymer-coated particles, which comprises polymerizing a radically polymerizable monomer (a) in the presence of an inorganic powder (b), a wetting dispersant (c) and a radical polymerization initiator (d).

Effects of the Invention

[0006] By the production method of the present invention, polymer-coated particles suitable for filler applications of paints and the like can be easily obtained. In particular, it is excellent in that it does not require special equipment and is easy to produce polymer-coated particles by combining various inorganic powders and polymer species.

Embodiments for Carrying Out the Invention

[0007] The production method of the present invention is characterized in that a radically polymerizable monomer (a) is polymerized in the presence of an inorganic powder (b), a wetting dispersant (c) and a radical polymerization initiator (d).

[0008] The radically polymerizable monomer (a) may be a known one, and can be appropriately selected according to the miscibility with other resin components in which the polymer-coated particles of the present invention are used and the properties to be imparted. For example, carboxyl group-containing monomers such as acrylic acid and methacrylic acid, n-linear alkyl group monomers such as methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, and n-butyl (meth) acrylate, branched alkyl group monomers such as isobutyl (meth) acrylate and 2-ethylhexyl acrylate, alicyclic skeleton monomers such as cyclohexyl (meth) acrylate and isobornyl (meth) acrylate, hydroxyl group-containing monomers such as 2-hydroxyethyl (meth) acrylate and 4-hydroxybutyl (meth) acrylate, halogen-substituted group-containing monomers such as hexachlorobutyl (meth) acrylate, and aromatic-containing monomers such as styrene, etc. can be mentioned, and they can be used alone or in combination of two or more.

[0009] As the radically polymerizable monomer, a polyfunctional monomer may be included. Examples of usable polyfunctional monomers include alkylene glycol di(meth)acrylates such as ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate; polyalkylene glycol di(meth)acrylates such as diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate; polyol poly(meth)acrylates such as trimethylolpropane di(meth)acrylate, pentaerythritol tetra(meth)acrylate; allyl compounds such as allyl (meth)acrylate, allyl maleate, diallyl fumarate, diallyl itaconate, triallyl isocyanurate; aromatic divinyl monomers such as divinylbenzene, and the like.

[0010] The amount of the radically polymerizable monomer used is preferably 5 parts by weight or more, more preferably 10 parts by weight or more, and still more preferably 20 parts by weight or more and 400 parts by weight or less with respect to 100 parts by weight of the total amount of the inorganic powder (b) described later. If the blending amount of the monomer is less than 5 parts by weight, the polymer component may be insufficient, making it difficult to perform coating. By setting the blending amount of the monomer within the above weight part range, it becomes easier to sufficiently secure the polymer component for coating the surface of the inorganic powder, facilitating the production of polymer-coated particles.

[0011] The inorganic powder (b) preferably has a particle diameter of 0.2 to 500 μm, more preferably 0.2 to 250 μm, and still more preferably 0.2 to 100 μm. If it is less than 0.2 μm, it becomes difficult to form a structure in which the surface of the inorganic powder is coated with a polymer. On the other hand, if it is larger than 500 μm, coarse particles may be generated, and the quality of the polymer-coated particles may vary. The particle shape of the inorganic powder is not particularly limited as long as it is within the range of the particle diameter of the inorganic powder, and may be an irregular granular shape with a mixture of plate-like and needle-like shapes, preferably substantially spherical, and more preferably spherical.

[0012] The possible inorganic powders are not particularly limited as long as they can be produced with the above-mentioned particle size. For example, metal powders such as iron powder, zinc powder, silver powder, copper powder, tin powder, aluminum powder, inorganic oxides such as titanium oxide, zinc oxide, iron oxide, magnesium oxide, tin oxide, indium oxide, silica, alumina, inorganic salts such as aluminum hydroxide, calcium hydroxide, magnesium hydroxide, calcium carbonate, magnesium carbonate, mica, talc, barium sulfate, iron oxalate, etc. can be exemplified. One of these may be used alone, or two or more may be used in combination.

[0013] The present invention uses a wetting dispersant (c). By using the wetting dispersant, the above-mentioned radically polymerizable monomer can interact with the surface of the inorganic powder, enabling the production of polymer-coated particles. Further, it is preferable to pre-mix and use the wetting dispersant with the above-mentioned monomer. The wetting dispersant may be one that is dispersed, dissolved or miscible with the above-mentioned monomer, and its component composition may be such that a part elutes into the aqueous layer. The wetting dispersant may be used alone or in combination of two or more, but it is necessary that the acid value as the wetting dispersant is less than 132 mgKOH / g, or the amine value is less than 94 mgKOH / g, or it has an acid value and an amine value within both ranges.

[0014] As the wetting dispersant, any one having the aforementioned acid value and amine value may be used. Effective examples include commercially available products such as DISPERBYK-101N, DISPERBYK-102, DISPERBYK-106, DISPERBYK-108, DISPERBYK-110, DISPERBYK-111, DISPERBYK-118, DISPERBYK-140, DISPERBYK-142, DISPERBYK-145, DISPERBYK-161, DISPERBYK-162, DISPERBYK-163, DISPERBYK-164, DISPERBYK-167, DISPERBYK-170, DISPERBYK-174, DISPERBYK-180, DISPERBYK-182, DISPERBYK-184, DISPERBYK-185, DISPERBYK-2000, DISPERBYK-2001, D-2008, DISPERBYK-2009, DISPERBYK-2013, DISPERBYK-2014, DISPERBYK-2022, DISPERBYK-2023, DISPERBYK-2025, DISPERBYK-2026, DISPERBYK-2050, DISPERBYK-2055, DISPERBYK-2096, DISPERBYK-2150, DISPERBYK-2157, DISPERBYK-2159, DISPERBYK-2163, DISPERBYK-2164, DISPERBYK-9076, DISPERBYK-9077, DISPERBYK-220S (all of the above are manufactured by ALTANAAG), Borchi Gen911,Borchi Gen0755, BorchiGen 1051, Borchi Gen 1251, Borchi Gen 1252, Borch Gen AP (all manufactured by Milliken & Company), TEGO Dispers 610S, TEGO Dispers 630, TEGO Dispers 662C, TEGO Dispers 670, TEGO Dispers 685, TEGO Dispers 700, TEGO Dispers 710 (all manufactured by Evonik Industries AG), Floren AF-1000, Floren AF-1005, Floren DOPA-15B, Floren DOPA-15BHFS, Floren DOPA-17HF, Floren DOPA -22, Floren DOPA-35, Floren G-700, Floren G-820XF, Floren GW-1500, Floren KDG-2400 (all manufactured by Kyoeisha Chemical Co., Ltd.), Disparon 1831, Disparon 1850, Disparon 1860, Disparon DA-234, Disparon DA-325, Disparon DA-375, Disparon DA-703-50 (all manufactured by Kusumoto Chemicals, Ltd.), Ajisper PB821, Ajisper PB822, Ajisper PB824, Ajisper PB881, Ajisper PN411, Ajisper PA111 (all manufactured by Ajinomoto Fine-Techno Co., Inc.), Hinact KF-1000, Hinact KF-1300M, Hinact KF-1500, Hinact T-6000, Hinact T-8000, Hinact T-8000E, Hinact R-242, Hinact Ri242 (all manufactured by Kawaken Fine Chemicals Co., Ltd.), etc. may be mentioned, and these can be used alone or in combination of two or more kinds.,

[0015] As the amount of the wetting dispersant used, 0.5 parts by weight or more is preferable, 1 part by weight or more is more preferable, and further 2 parts by weight or more and 30 parts by weight or less is more preferable with respect to 100 parts by weight of the total amount of the inorganic powder (b). If the amount of the wetting dispersant used is less than 0.5 parts by weight, the polymer coating on the surface of the inorganic powder may become non-uniform and the quality may become unstable. By setting the amount of the wetting dispersant within the above-mentioned parts by weight range, the monomer easily interacts with the surface of the inorganic powder, and polymer-coated particles are easily formed.

[0016] The radical polymerization initiator (d) is not particularly limited, but can be roughly classified into an oil-soluble radical initiator and a water-soluble radical initiator. Examples of the oil-soluble radical initiator include organic peroxides such as benzoyl peroxide, o-methoxybenzoyl peroxide, o-chlorobenzoyl peroxide, lauroyl peroxide, and cumene hydroperoxide, and azo compounds such as 2,2'-azobisisobutyronitrile and 2,2'-azobis(2,4-dimethylvaleronitrile). These can be used alone or in combination of two or more. Examples of the water-soluble radical initiator include ammonium persulfate, sodium persulfate, potassium persulfate, 2,2'-azobis(2-methylpropionamidine) dihydrochloride, and 2,2'-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride. These can be used alone or in combination of two or more.

[0017] As the compounding amount of the radical polymerization initiator, 0.01 to 1 part by weight is preferable, and 0.02 to 2 parts by weight is more preferable with respect to 100 parts by weight of the total amount of the radically polymerizable monomer (a). Regarding the addition method of the radical polymerization initiator, it is preferable to premix and dissolve the oil-soluble radical initiator in the monomer in advance. Regarding the water-soluble radical polymerization initiator, known methods such as a method of charging the total amount all at once into the mixed system of the aqueous dispersion of the inorganic powder and the monomer emulsion described above, a method of adding a part in portions from the initial stage to the middle stage to the final stage of the reaction, and a method of adding intermittently can be adopted.

[0018] As a method for producing polymer-coated particles in the present invention, for example, it is a method in which an inorganic powder (b) dispersed in an aqueous layer and a radically polymerizable monomer (a) are mixed, and polymerization is carried out using a radical polymerization initiator (d). It is preferable that the wetting dispersant (c) is previously mixed with the radically polymerizable monomer (a).

[0019] As the water that is the dispersion medium when dispersing the inorganic powder in the aqueous layer, purified water such as distilled water or ion-exchanged water is common. The amount of water used may be appropriately adjusted according to the type of inorganic powder. However, in order for the inorganic powder to be in a uniform dispersion state, it is preferably 100 parts by weight or more, more preferably 200 parts by weight or more, and even more preferably 300 parts by weight or more with respect to 100 parts by weight of the total inorganic powder. Also, depending on the inorganic powder used, a surfactant, a dispersion stabilizer, etc. may be appropriately added to ensure dispersibility in water. The adjustment of the inorganic powder aqueous dispersion can be carried out by known methods, and stirring by a stirrer, ultrasonic dispersion, homomixer stirring, disper stirring, etc. can be applied without particular limitation.

[0020] The radically polymerizable monomer is preferably previously mixed with the wetting dispersant. After blending the aforementioned wetting dispersant, it is preferably mixed with an aqueous layer containing a surfactant and a dispersion stabilizer and adjusted to a monomer emulsion for use. Further, this aqueous layer may be the aqueous dispersion containing the aforementioned inorganic powder. The preparation of the monomer emulsion can be carried out by known methods such as stirring by a stirrer, ultrasonic dispersion, disper stirring, homomixer stirring.

[0021] Regarding the aforementioned monomer emulsion, if it is a water-in-oil type emulsion in which the monomer is in the form of particles in the aqueous layer, there are no restrictions on the monomer particle size, emulsion concentration, etc., and it can be used. It may also be an oil-in-water type emulsion in which the aqueous layer components are in the form of particles in the monomer, but there is a possibility that the polymerization proceeds without the monomer coating the inorganic powder and separation occurs, making it difficult to produce uniform polymer-coated particles in some cases.

[0022] Examples of surfactants include anionic surfactants, cationic surfactants, nonionic surfactants, amphoteric surfactants, polymeric surfactants, etc. Among these, anionic surfactants such as sodium dodecylbenzenesulfonate and sodium lauryl sulfate are preferred in terms of being able to prepare a fine and stable monomer emulsion. The amount of surfactant to be blended may be about 0.01 to 10 parts by weight based on 100 parts by weight of the total amount of monomers.

[0023] Examples of dispersion stabilizers include water-soluble polymers such as gelatin, methylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, carboxymethylcellulose, polyethylene glycol, polyoxyethylene-polyoxypropylene block copolymer, polyacrylamide, polyacrylic acid, polyacrylate, sodium alginate, polyvinyl alcohol, and polyvinylpyrrolidone, which can be used alone or in combination of two or more. The amount of dispersion stabilizer to be blended may be about 0.01 to 30 parts by weight based on 100 parts by weight of the total amount of monomers.

[0024] The aforementioned monomer emulsion is mixed with the aqueous dispersion of the aforementioned inorganic powder, and a radical polymerization initiator is further added to cause a radical polymerization reaction to proceed, thereby forming a polymer coating. The temperature during the radical polymerization reaction may be constant from the initial stage to the middle stage to the final stage of the reaction, or may be changed over time. As the temperature range for carrying out the radical polymerization reaction, 40 to 95 °C can be exemplified. There is no particular limitation on the radical polymerization reaction time, and it may be appropriately set according to the progress of the reaction. For example, 2 to 10 hours from the start to the end of polymerization can be exemplified. Also, in order to enhance the efficiency of the radical polymerization initiator, it is common to carry out the radical polymerization reaction under an inert gas atmosphere such as nitrogen.

[0025] Since the polymer-coated particles adjusted by the radical polymerization reaction are a suspension dispersed in an aqueous layer, the polymer-coated particles can be obtained by removing the aqueous layer. The removal of moisture is carried out by known methods such as filtration, centrifugal dehydration, heat drying, vacuum drying, spray drying, etc. Since the polymer-coated particles thus obtained may contain secondary aggregates or coarse particles, if necessary, grinding using a cutter mill, hammer mill, jet mill, etc., and purification by sieving, air classification, etc. may be performed.

[0026] The polymer-coated particles thus obtained are powder with a particle size of about 0.2 to 500 μm, and can be used for applications such as fillers for improving the properties of paints and coating films.

[0027] Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but these are merely specific examples and are not particularly limited thereto. The measurement of the particle size was carried out using a laser diffraction / scattering particle size distribution measuring device (MT3300, manufactured by Microtrac Bell Corporation). In addition, the constant temperature and humidity environment described hereinafter refers to an environment maintained at a temperature of 23 °C and a humidity of 50%.

Examples

[0028] Example 1 80 g of titanium oxide (CR-50, average particle size: 0.25 μm, manufactured by Ishihara Sangyo Co., Ltd., trade name) and 300 g of ion-exchanged water were put into a separable flask equipped with a stirrer and stirred to prepare a titanium oxide dispersion. A monomer solution was prepared by mixing 19.8 g of methyl methacrylate (MMA), 2.2 g of ethylene glycol dimethacrylate (EGDMA), and 1.6 g of a wetting dispersant (DISPERBYK-106, acid value: 132 mg KOH / g, amine value: 74 mg KOH / g, manufactured by Altana AG, trade name) uniformly. 0.3 g of sodium dodecylbenzenesulfonate (Neopelex G-15, manufactured by Kao Corporation, trade name) and 0.3 g of polyvinyl alcohol (Poval 5-88, manufactured by Kuraray Co., Ltd., trade name) were dissolved in 100 g of ion-exchanged water, and the monomer solution was added and dispersed with a disperser (Homomixer MARKII 2.5 type, manufactured by Primix Corporation) to prepare a monomer emulsion. After mixing the monomer emulsion with the titanium oxide dispersion, the temperature was raised to 60 °C under a nitrogen stream, and 0.1 g of a radical polymerization initiator 2,2'-azobis(2-methylpropionamidine) dihydrochloride (V-50, manufactured by Fujifilm Wako Pure Chemical Corporation, trade name) was added and polymerized for 6 hours. The reaction product was filtered, washed with ion-exchanged water, and dried to recover polymer-coated titanium oxide. As a result of measuring the particle size, the average particle size was 2.91 μm.

[0029] Examples 2 to 8 In the production method of Example 1, except that the amounts used were changed as described in Table 1 using DISPERBYK-106 (acid value: 132 mg KOH / g, amine value: 74 mg KOH / g, manufactured by ALTANA, trade name), DISPERBYK-118 (acid value: 36 mg KOH / g, manufactured by ALTANA, trade name), DISPERBYK-180 (acid value: 94 mg KOH / g, amine value: 94 mg KOH / g, manufactured by ALTANA, trade name), DISPERBYK-2000 (acid value: 4 mg KOH / g, manufactured by ALTANA, trade name), DISPERBYK-2023 (acid value: 4 mg KOH / g, amine value: 7 mg KOH / g, manufactured by ALTANA, trade name), DISPERBYK-9077 (amine value: 48 mg KOH / g, manufactured by ALTANA, trade name) as wetting dispersants, the procedure was the same as in Example 1, and polymer-coated titanium oxides of Examples 2 to 8 were obtained.

[0030] Example 9 80 g of silica (NIPGELAY-603, manufactured by Tosoh Corporation, average particle size 10.8 μm, trade name) and 300 g of ion-exchanged water were charged into a separable flask equipped with a stirrer and stirred to prepare a silica dispersion. A monomer solution was prepared by mixing and homogenizing 10.8 g of MMA, 2.2 g of EGDMA, and 1.6 g of DISPERBYK-106. 0.3 g of Neoperex G-15 and 0.3 g of Poval 5-88 were dissolved in 100 g of ion-exchanged water, monomers were added, and the mixture was dispersed with a disperser to prepare a monomer emulsion. After mixing the monomer emulsion with the silica dispersion, the temperature was raised to 60 °C under a nitrogen stream, 0.1 g of V-50 was added, and a polymerization reaction was carried out for 6 hours. The reaction product was filtered, washed with ion-exchanged water, and dried to recover polymer-coated silica. As a result of measuring the particle size, the average particle size was 13.21 μm.

[0031] Examples 10 to 16 In the production method of Example 9, except that the wetting dispersant was changed as described in Table 2, the procedure was the same as in Example 9, and polymer-coated silicas of Examples 10 to 16 were obtained.

[0032] Comparative Example 1 In Example 1, polymer-coated titanium oxide was prepared in the same procedure except that no wetting dispersant was added. The obtained reaction product had extremely poor filterability and was difficult to recover as a powder.

[0033] Comparative Example 2 In Example 9, polymer-coated silica was prepared in the same procedure except that no wetting dispersant was added. The obtained reaction product had extremely poor filterability and was difficult to recover as a powder.

[0034]

Table 1

[0035]

Table 2

[0036] To 100 parts by weight of an acrylic paint base (Acrylic A-801-P, manufactured by DIC Corporation, trade name), 10 parts by weight of the polymer-coated particles, titanium oxide, and silica prepared in each Example and Comparative Example were blended as fillers, and the paint was adjusted by mixing with a revolving mixer. A 100-μm-thick spacer was placed on a cold-rolled steel sheet (200 mm × 100 mm × 0.6 mm thick, manufactured by TP Giken Co., Ltd.), and each adjusted paint was applied by blade coating and dried in a constant temperature and humidity environment for 24 hours to prepare a coated film plate. To evaluate the lubricity of the coated film, a weight (weight: 150 g, coated film contact area: 40 mm × 40 mm) was placed on a fixed point of the coated film plate, and the inclination in the long axis direction of the coated film plate was increased from 0° to 90° at a rate of 5° / min. The angle (sliding-off angle) at which the weight slid on the coated film and moved outside the fixed point was measured, and it was evaluated that the smaller the sliding-off angle, the better the lubricity. When measured without blending the polymer-coated particles, it was 37.9°, when measured by blending uncoated titanium oxide, it was 36.4°, and when measured by blending uncoated silica, it was 32.8°.

[0037] As shown in Tables 1 and 2, the coating films using the polymer-coated particles of Examples 1 to 8 as fillers had a smaller slip-off angle and improved coating film lubricity than the blank without adding fillers. Furthermore, since the slip-off angles of Examples 1 to 6 were smaller than those when titanium oxide without polymer coating was used as a filler, it was shown that the polymer-coated particles were effective in improving the coating film lubricity. Also, in Examples 7 and 8, the amount of the wetting dispersant in Example 6 was reduced to 1 part by weight and 0.5 part by weight with respect to titanium oxide, respectively, but the slip-off angle similar to that of Example 6 was maintained, indicating that it is effective to apply 0.5 part by weight or more of the wetting dispersant with respect to titanium oxide. Similarly, in Examples 9 to 16, Example 17, and Example 18, the slip-off angle was smaller than that of the blank without adding fillers or silica without polymer coating, and the coating film lubricity was improved. It was shown that by applying 0.5 part by weight or more of the wetting dispersant with respect to silica, the polymer-coated particles were effective in improving the coating film lubricity. In Comparative Examples 1 and 2, an attempt was made to produce polymer-coated titanium oxide and silica without adding a wetting dispersant, but the powder was difficult to recover and could not be evaluated.

[0038] With respect to 100 parts by weight of an acrylic emulsion (Ultrazol A-50, manufactured by Aika Kogyo Co., Ltd., trade name), 5 parts by weight of each of the polymer-coated particles prepared in Examples 1 and 9, titanium oxide as Reference Example 1, and silica as Reference Example 2 were added as fillers and mixed with a disper mixer to adjust the compound. The adjusted compound was degassed, put into a mold, and then dried in a constant temperature and humidity environment for 48 hours to prepare a film. The film taken out from the mold was punched out with a cutter (Super dumbbell cutter SDK-400, manufactured by Dumbbell Co., Ltd.) to form a test piece for a tensile test and cured in a constant temperature and humidity environment for 24 hours. Using a high-speed peeling tester (manufactured by Intesco Co., Ltd.), a tensile test was carried out in a constant temperature and humidity environment with a chuck distance of 6 cm and a tensile speed of 300 mm / min.

[0039] As shown in Table 3, the films using the polymer-coated particles of Examples 1 and 9 as fillers had a greater maximum stress than Reference Examples 1 and 2 using uncoated titanium oxide and silica as fillers, indicating an improvement in the adhesion between the acrylic emulsion and the fillers. Although the elongation values of the films containing the polymer-coated particles prepared in Examples 1 and 9 as fillers decreased compared to the blank without added fillers as Reference Example 3, the decrease in elongation was reduced compared to the case where titanium oxide and silica alone were used as fillers, indicating an improvement in the toughness of the thin film.

[0040]

Table 3

Claims

1. A method for producing polymer-coated particles, characterized by polymerizing a radically polymerizable monomer (a) in the presence of an inorganic powder (b), a wetting dispersant (c) and a radical polymerization initiator (d).

2. The method for producing polymer-coated particles according to claim 1, wherein the acid value of the wetting dispersant (c) is 132 mgKOH / g or less and / or the amine value is 94 mgKOH / g or less.

3. The method for producing polymer-coated particles according to claim 1, wherein the amount of the wetting dispersant (c) relative to 100 parts by weight of the inorganic powder (b) is 0.5 to 30 parts by weight.

4. The method for producing polymer-coated particles according to claim 1, wherein the radically polymerizable monomer (a) and the wetting dispersant (c) are premixed.

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