JPH03281577A - Silica particle-containing plastic pigment and its production - Google Patents

Abstract

PURPOSE:To provide a white pigment composition through emulsion polymerization, excellent in opacifying power, heat resistance, polymerization stability and storage stability, thus to be used in paper, coatings, fibers, etc., consisting of fine particles with silica particle constituting the core and a vinyl resin around the core. CONSTITUTION:The objective pigment is composed of fine particles consisting of a silica particle constituting the core and a vinyl resin around the core. The periphery of each core has a hollow or porous structure. The present composition can be obtained by emulsion polymerization.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to providing a white pigment for use in paper, paints, fibers, etc.

[Conventional technology]

Japanese Patent Publication No. 52-13829 provides a porous plastic pigment with a particle size of about 30 microns containing a polyester resin component, but because the particle size is large, it is necessary to stabilize the dispersion of the particles with a high viscosity. However, there were drawbacks such as difficulty in handling. JP-A-56-32513 or JP-A-60-69103 proposes hollow particles consisting of a carboxylic acid resin core or amino resin core with a small particle size and a vinyl resin outer shell. , Japanese Patent Publication No. 6
No. 3-135409 proposes a hollow particle method in which a core particle of vinyl resin is swollen with a solvent and the outer shell is surrounded by another vinyl resin. However, these hollow particles are 1
When heated above 00°C or even above 150°C, the hollow particles melt and the hollow pores are lost, resulting in a decrease in hiding properties and further transparency, which causes the pigment to lose its original purpose as a pigment. It had Polymer Papers Vol.140
, N010, PP697-702 (Oct, 1983
In the year) issue.

A method has been proposed in which silica colloid is emulsified with hydroxypropyl cellulose and styrene monomer is used to obtain styrene resin encapsulated particles on the surface of the silica colloid, but this method does not function as a pigment with hiding properties. There wasn't. JP-A-59-71316 proposes a composition in which the surface of colloidal silica is coated with a vinyl resin using a silane coupling agent, but it has not yet achieved the function of a pigment having a hollow structure and hiding properties. [Problem to be solved by the invention] The present invention has a silica particle as a core, which is surrounded by at least one layer, preferably three layers, of a vinyl resin composed of different vinyl monomer compositions. (Encapsulated) microparticles can be obtained using an emulsion polymerization technique, and the silica core can be made hollow or porous. The obtained microparticles exhibit superior effects in the following points compared to conventionally known hollow resin particles.

(1) In addition to the hollow structure, the light-scattering effect of the silica core is added, further improving the concealing performance.

(2) It has excellent heat resistance, and even when heated to 100° C. or higher, the hollow layer hardly fuses and its concealing properties are not lost.

(3) Excellent dispersion stability in water even if the particle size is relatively large, and particles do not settle over time.

(4) It has excellent stability during polymerization and is easy to manufacture with little precipitation or adhesion of aggregates (gel substances).

(5) When obtained as a powder, it can withstand intense heat drying such as dry spraying, and the resulting powdery plastic pigment has less reduction in hiding power than that dispersed in water.

[Means to solve the problem]

The present invention involves dispersing silica particles in water, forming a swollen porous or hollow resin layer around the particles, and forming an enclosing resin layer in the outer shell by emulsion polymerization. The resin becomes a plastic pigment dispersed in water with a particle size of 0.1 to 10 microns, preferably 0.3 to 3 microns. If necessary, water is removed to form a powdered plastic pigment. When the particles are not colored, they are white pigments. Although silica powder may be used to disperse the silica core in water, a dispersion solution called colloidal silica is well known and is particularly preferred for the present invention. Although various attempts have been made to convert the
0. Nlll0゜PP697~7202) Oct, 19
As stated in No. 83, etc., except for special methods, ordinary emulsion polymerization methods do not cause the formation of micelles of monomers on the surface of colloidal silica, and as a result, colloidal silica cannot be encapsulated in vinyl resin. As a result of the inventor's research, it was found that polymerization with vinyl carboxylate monomers, copolymerization with vinyl carboxylate monomers and other vinyl monomers, or vinyl monomers using radical sulfate ions as emulsifiers. It has been found that when copolymerized with colloidal silica particles, the resulting resin forms inclusion particles with colloidal silica particles as the core. Next, at least one or more preferably two or more outer shell layers of a polymer are formed on the carboxylic acid resin-containing particles having colloidal silica as a core, and ammonia, an alkali metal, a polyvalent metal, or an amine is used to form the outer shell layer of a polymer. We discovered that a hollow particle structure or a porous pore structure can be obtained by neutralizing carboxylic acid. The thus obtained silica-based vinyl resin particles of the present invention are significantly superior to conventionally known hollow resin particles in terms of heat resistance and hiding properties. The theoretical basis for this is not fully elucidated, but it is presumed that heating to high temperatures activates the silica component, which has the effect of preventing the encapsulated resin from fusing. Furthermore, regarding the improvement of the hiding effect, it is presumed that light scattering or refraction occurs in the silica core in addition to the hollow structure, further increasing the hiding effect.

For the emulsion polymerization method of the present invention, conventionally known methods can be used except for the emulsifier. To deposit carboxylic acid vinyl resin or vinyl resin on the surface of colloidal silica, conventionally known nonionic activators and anionic activators may be used, but the critical micelle formation concentration (CMC)
) and is preferably zero. Preferred emulsifiers are radical sulfate ions, such as ammonium persulfate, sodium persulfate, etc., which are generated by decomposition of persulfates or ferrous sulfate.
These include potassium persulfate, ferrous sulfate, sodium hydrosulfite, and sodium formaldehyde hydrosulfite. Radical sulfate ions can be removed by heating or low-temperature ring-forming agents (e.g. ferrous sulfate, hydrosulfides,
ascorbic acid, etc.). A conventional activator is also used when forming an outer shell layer on the carboxylic acid resin particles containing the obtained colloidal silica core.

It is preferable to use an activator having a CMC or less and preferably a radical sulfate ion. Examples of activators that can be used below CMC include conventionally known activators such as nition oxide (EO) adducts of octyl (or nonyl) phenol, sodium lauryl sulfate, sodium dodecylbenzenesulfonate, lauryl ether sulfate salts, and sulfosuccinic acid alkyl ester salts. It is an activator.

Examples of vinyl carboxylic acid monomers deposited (contained) in the silica core are (abbreviations in parentheses), methacrylic acid (Maa), acrylic acid (Aa), itaconic acid, monoalkyl itaconic acid ester, male acid, fumaric acid, crotonic acid, 2-carboxyethyl acrylic acid ester, etc., and preferably methacrylic acid, acrylic acid, itaconic acid, etc. Copolymers of these vinyl carboxylic acid monomers and other monomers are also useful, and other monomers that can be used for copolymerization are α, β-ethylenically unsaturated monomers (
meth)acrylic esters (meaning methacrylic esters and acrylic esters): Methyl (11 (M
)A).

Ethyl, butyl (B(M)A), octyl (0(M)
A) Alkyl or allyl esters such as cyclohexyl and bezyl, vinyl acetate (VA), vinyl ethers: alkyl or haloalkyl ethers such as methyl, ethyl, 2-chloroethyl (CEVE), (meth)acrylonitrile ((M)AN) , styrene (ST), vinyltoluene.

α-methylstyrene, vinyl chloride, vinylidene chloride, (
meth)acrylamide, N-methylol(meth)acrylamide, N-butyrol(meth)acrylamide, hydroxyethyl(meth)acrylate, glycidyl(meth)acrylate (G(M)A), styrene sulfonic acid and its salts, ethylene glycol di (meth)acrylate, trimethylolpropane trimethacrylate (TMP)
, divinylbenzene (DVB), and the like.

As the monomer used to form the outer shell layer, the monomer of the resin deposited on the surface of the silica core mentioned above can be used. On the other hand, the amount of carboxylic acid monomer used in the outer shell layer must be within a range that does not dissolve in water upon alkali neutralization. Preferably, it is a relatively hydrophobic monomer, such as a polymer or copolymer selected from one or more monomers whose main components are methyl methacrylate, styrene, etc.

In order to form a hollow layer around a silica core, the first method is to form a carboxylic acid polymer layer on the silica core, and after forming an outer shell layer, add ammonia, alkali metals, amines, or polyvalent metals. This is achieved by adding an aqueous solution of to neutralize the carboxylic acid resin layer surrounding the silica core. Neutralization may be carried out at room temperature, but preferably at 50-95°C.
The carboxylic acid neutralization reaction proceeds more easily when the temperature is increased. Another second outer shell layer may be formed on the neutralized resin particle layer of the silica core, and preferably forming the second and third outer shells may be useful for improving performance. be. The second method is to form a copolymer layer of a carboxylic acid polymer and a crosslinked polymer on a silica core (selecting a monomer composition that swells upon neutralization), and then neutralize it with alkali to form an outer shell layer. It can be obtained by forming .

The polymerization reaction proceeds with a conventional radical catalyst.

It also serves as the radical sulfate ion activator mentioned above. For example, ammonium persulfate.

Persulfates such as sodium persulfate and potassium persulfate, peroxides such as hydrogen peroxide, t-butyl hydroperoxide, and benzoyl peroxide, and, if necessary, ferrous sulfate and sodium chloride as redox catalysts. Hydrosulfite, sodium formaldehyde hydrosulfite, ascorbic acid, etc. are also used. The polymerization temperature is the decomposition temperature of the catalyst, and is preferably 30 to
The temperature is 100°C.

Detailed explanations will be given below with examples, but the examples are not limited to the examples shown here. The abbreviations used in the examples are the same as those in parentheses described above or below. be.

Example 1. The colloidal silica particle R circumference is Maa-MP
Encapsulation polymer number, 0-180 with 4A copolymer In a 500 μl separable flask reactor with a cover,
Thermometer, stirrer, reflux condenser, water bath,
Equipped with a dropping funnel and nitrogen inlet.

475ml of deionized water in the reactor, Cataloid 5R-40
7.5 g of (colloidal silica, 40% solid content, product of Catalysts and Chemicals Industries) was charged, the atmosphere was replaced with nitrogen, and the mixture was heated to 85°C.

Add 4 g of 10% aqueous solution of sodium persulfate (NFS),
A mixture of Aaaflig and 9 g of HMA was continuously hand-dropped using a drop coat at 85° C.±1° C. over a period of 20 minutes, and the mixture was maintained at 85° C.±1° C. for an additional 45 minutes. ,30℃
The mixture was cooled down and filtered through a 300 mesh nylon cloth.

There is no aggregate of filter cloth residue and the residual monomer is 125p.
An emulsion polymer having a milky white appearance and a pm (polymerization rate of 99.5% or more), P) of 13.5 was obtained. Below, unless otherwise specified, the unit is duram (g).

Example 2. Maa-MH without colloidal silica particles
Copolymer A (reference $7) Polymer number: 0-77 The same procedure as in Example 1 was repeated except that the composition was changed to the following.

Deionized water 450 ml NPS (10%) 4 Maa/AMA 6/9 An emulsion polymer with a milky white appearance was obtained. The aggregate amount of filter cloth residue was 0.2 g.

The residual monomer was 100 ppm or less.

Example 3. Encapsulation of colloidal silica particles with H-A polymer Polymerization number: 0-181 The procedure was carried out in accordance with Example 1 using the following components.

Deionized water 475 Cataloid 5I-407,5 NFS (10%) 4 MMA Is Filter cloth residue aggregate o, os g, residual monomer 1100p
An emulsion polymer with a milky white appearance and a pH of 6.5 was obtained.

Example 4. Maa-MMA around colloidal silica particles
Double encapsulation of copolymer and Maa-HMA-BA copolymer Polymer number: 0-182 Emulsion polymer obtained in Example 1 (0-180)
Pour 486゜5 into a reaction tank and heat to 80℃, then NFS
(22% aqueous solution) 38.5 was added, and a mixed monomer solution of Aaa 2.8, MMA 106.5, and BA 25.8 was continuously dropped into the reaction tank over a period of 30 minutes.
It was maintained at 0±2°C. The mixture was further maintained at 80±2° C. for about 35 minutes to ripen.

8.5 g of ammonia water (25%) was added and heated to 90° C. over 15 minutes. The mixture was cooled to below 30°C and filtered using a 100 mesh nylon cloth. Aggregates of filter cloth residue 0.1, aggregates attached to blades 0.2, residual monomer 350p
An emulsion polymer with a milky appearance of pm, pH 7.9 was obtained.

Example 5. Confirmation of the phenomenon that colloidal silica particles are encapsulated by a polymer The emulsion polymers obtained in Examples 1 to 4 and Cataloid 5r-40 (colloidal silica) were measured using a dynamic light scattering photometer DLS-700 (manufactured by Union Giken). The particle size was measured by dynamic light scattering method (DLS method). The results are summarized in Table 1 and the attached distribution graph chart.

What can be considered from Table 1 and the distribution graph chart is that (1
) Most of the colloidal silica particles of 0-180 and 0-181 disappeared and were encapsulated in the polymer and grew into large particles. (2) The particle size of 0-182 was even larger than that of 0-180. It shows that it has grown, with colloidal silica as the core, containing Aaa-MAA, and then Aa
Table 1 n11=average particle diameter (nanometer, 10-9 meter unit) Distribution ratio in parentheses Example 6. Maa-ama around colloidal silica particles
Copolymer, Maa-HMA-BA copolymer and ST
Triple encapsulation with polymer (hollow plastic pigment) Polymer number: 0-183 Emulsion polymer obtained in Example 4 (0-182)
670, 1.5 ml of aqueous ammonia (25%) was added to the reaction tank and heated to 85°C. NFS (22% aqueous solution) 10
of deionized water 70 and sodium dodecymebenzenesulfonate (>99% purity) 0.15 and ST
A monomer emulsion consisting of 250 C. was continuously added dropwise over about 90 minutes using a dropping funnel, and the reaction temperature was maintained at 85.degree. C. during this period. After the dropwise addition was completed, the temperature was maintained at 85°C for about 15 minutes and cooled to 30°C or lower. It was filtered using a 100 mesh nylon cloth. Approximately 0.5° aggregate of filter cloth residue, residual monomer 420 ppm, pH 9.5, viscosity 240 cp
An emulsicon polymer having a milky white appearance and an average particle diameter of 0.9 micrometers (centivoids) and a non-volatile content of 40.2% was obtained.

Example 7. MMA copolymer, Maa-HMA-BA copolymer, and Maa-HMA copolymer surrounding the colloidal silica particles.
-Triple encapsulation with BA copolymer and ST polymer (non-hollow plastic pigment) Polymer number: 0-184 Emulsion polymer obtained in Example 3 (0-181)
545 was charged into a reaction vessel and heated to 70°C.

Add NFS (22% aqueous solution) 38, Maa 2,8
A mixed monomer of HMAl, 06.5, and B^25.8 was continuously added dropwise over about 50 minutes, and the reaction temperature was maintained at 70° C. during this period, and the mixture was aged for 10 minutes. Aqueous ammonia (25%) 8 was added and heated to 85°C. Then deionized water 80 and dodecylbenzenesulfone mO,15
A monomer emulsion consisting of ST 250 and ST 250 was continuously added dropwise over 90 minutes, and the reaction temperature was maintained at 85°C during this period for 15 minutes. The mixture was cooled to below 30° C. and filtered using a 100-mesh nylon cloth. Filter cloth residue 0.
5, residual monomer 150 ppm, pH 9.4, viscosity 9
An emulsion polymer having a milky white appearance with a mean particle size of 0.8 micrometers and a non-volatile content of 39.8% was obtained.

Example 8. Evaluation of ltl shielding property and heat resistance A coating liquid was obtained with the following formulation. A hollow plastic pigment emulsion polymer, which is already known and commercially available, was also included in the evaluation for comparison.

Water 20.6 Plastic pigment (35%) 57.1: Plastic pigment emulsion to be tested Adjust solid content to 35% with water A-20821, 3: Binder agent Acrylic emulsion polymer mainly composed of HMA-BA manufactured by Sansuisha Co., Ltd. , minimum film-forming temperature 3°C, 47% solids content Florard FC-149 (1% aqueous solution) l: Wetting agent, manufactured by Sumitomo 3M Co., Ltd. Tested plastic pigment emulsion polymer 〇-18
3: Example 6 0-184: Example 7 Primal 0P-42: manufactured by Rohm and Haas, hollow emulsion polymer without colloidal silica as a core,
40% non-volatile content Boncoat PP-1000: Manufactured by Dainippon Ink and Chemicals, a hollow plastic pigment emulsion polymer without colloidal silica as a core, 45% non-volatile content The resulting coating solution is applied to a 100-micron transparent polyester film by wire. It was applied using Rod Bar NQ8 (manufactured by Eto Kisho Co., Ltd.) and dried at room temperature. Half of the test piece was cut out and heated in a dryer at 180°C for 60 seconds to provide heat resistance. The hiding properties were measured using an absorbance measuring device (Shimabara LIV-160, manufactured by Shimabara Seisakusho Co., Ltd.) at a wavelength of 520 nm, and the results are summarized in Table 2.

Table 2 From the above results, it was shown that (1) the hollow colloidal silica core has high hiding properties, and 2) the colloidal silica core has little decrease in hiding properties (heat resistance) due to heating.

Example 9. Hollow Plastic Pigment Emulsion Polymer Using Crosslinkable Monomer The ST 250 of Example 6 was changed to the following composition, and the other conditions were the same, and the same work was carried out.

Polymer number 0-185 ST, 244 DνB6 Average particle size: 1.1 micron meter Polymer number 0-186 ST 225 GM^　　　　　25 Average particle size: 1.4 micron meter Polymer number 0-187 ST 244 Tap6 Average particle size: 1.1 micron meter Both have the same polymerization stability and hiding properties as 0-183.

Heat resistance was obtained.

Example 10. Hollow plastic pigment emulsion polymer copolymerized with other eastomers ST 250 in Example 6 was changed to the following composition, and the other compositions were the same and the same operations were carried out.

Polymer number - 199 Polymer number 8B ST 245 ST 225 CEVE 5 BMA 25 Polymer number - 189 Polymer number - 190 ST 245 ST 245 OA 5 AN
5, almost the same results as O-1 and 88 were obtained.

In Example 4, Maa 2.8. AMA 106.5,
When B^25.8 was changed to the following composition, 0-1
Almost the same results as 82 were obtained.

Polymer No. 0-1.91 Polymer No. 0-1.91 was obtained using the same monomer composition and the same operation as Example 6 except that the monomers of Example 4 were changed as follows.

Maa 2.8 AMA 106.5 VA 1.2. O BA I2.5 Example 11. Powderization and Application as Matte Paint 0-183 was powdered using a commercially available dry spray device under conditions of an inlet temperature of 150±5°C and an outlet temperature of 50±3°C. The obtained 0-183 powder, 0-183, and titanium oxide were used to form a paint in the following formulation.

The name in parentheses is the name of the manufacturing company.Blend number N11lBlend number Nα2Water 235
235 Triporin Stirrupuda (10% water soluble M)
IoT.

Poise 530 (Kao) 22 Noniball 120 (Sanyo Chemical Industries) Plaxel BD (ICI) Nopco 8034 (San Nopco) TiO□JRNC (Teikoku Kako) Taruri N5D (Nippon Taruri) CaCO, N5400 (Nitto Funka Industries) Kaolin Clay N022 0-183 powder-183 TjO□JRNC HECBG-15 (5%) (Fuji Chemical) 70=Iu') Ral PV85 (BASF) 25 water
78A-208 (Sansui) 133 C5-12 (Chisso) 16 Nopco 8
034 2.50 Combination number Na3 Water 35 Tribolin 1 Noda (10% aqueous solution) Poise 530 (Kao) Noniball 120 Plaxel BD (ICI) Nopco 8034 (San Nopco) TiO□JRNC (Teikoku Kako) Taruri N5D (Japan Taruri ) CaCO, N5400 (Nitto Funka Kogyo) Kaolin clay N022 0-183 powder-183 TiO□JRNC HECBG-15 (5%) (Fuji Chemical) Co-y')
Ral PV85 (BASF) Water A-208 (Sansui) C5-12 (Chisso) 10.0 2.0 2.5 1.0 3.0 138.0 45.0 155.0 60.0 Total 1000. 0 The obtained paint was evaluated for performance such as paint physical properties and hiding power based on JISK-5400, and the results are summarized in Table 3 below.

Table 3 From the above results, even if 0-183 is used as a partial substitute for titanium oxide, it is useful for improving whiteness without any loss in hiding performance.
On the other hand, the performance of 0-183 powder was almost the same as that of 0-183, and the deterioration in performance due to powderization was almost negligible.

〔Effect of the invention〕

The emulsion polymer or powdered polymer in which the silica particle core of the present invention is surrounded by a polymer at 5 peripheries is essentially different in structure from the conventionally known hollow emulsion polymer that does not contain silica particles. are doing. It has been found that the resulting performance is significantly superior to conventionally known hollow emulsion polymers in hiding properties, heat resistance, single polymerization stability, and provides a plastic pigment polymer with excellent storage stability.

[Brief explanation of drawings]

FIG. 1 is a particle distribution diagram of colloidal silica used as a core, FIG. 2 is a particle distribution diagram of polymerization numbers 0-180 in Example 1, and similarly, FIG. 3 is a particle distribution diagram of colloidal silica used as a core. Figure 4 is 0-1
82, FIG. 5 shows a particle distribution map of 0-77.

Claims (1)

[Claims] 1. A composition containing silica particles in the core and surrounded by a vinyl resin. 2. A composition containing silica particles in the core and having voids in the periphery with hollow or porous surfaces. Plastic pigment composition 3 characterized in that the outer shell is fine particles wrapped in a vinyl resin; Method 4 for producing the composition of claim 1 using an emulsion polymerization method; 4 Using an emulsion polymerization method A method for producing the composition according to claim 2