JPH0214222A - Flat emulsion particle having dent part and production thereof - Google Patents

Abstract

PURPOSE:To obtain the subject particle useful as a pigment for paint or paper- coating agent having excellent gloss, whiteness, etc., by emulsion-polymerizing a vinyl monomer to form seed particles, adding a water-insoluble organic solvent having a specific interfacial tension to the seed particles and carrying out emulsion-polymerization. CONSTITUTION:(A) A vinyl monomer such as styrene is subjected to emulsion- polymerization in the presence of a surfactant, a molecular weight modifier, a polymerization initiator, etc. The polymerization product is added with (B) a water-insoluble organic solvent having an interfacial tension of >=48dyne/cm at 20 deg.C between water (e.g., n-pentane) and (C) a vinyl monomer same to or different from the component A (e.g., alpha-methyl-styrene) and is subjected to emulsion polymerization to form the objective particle containing the component A and the component C at a weight ratio of preferably 0.5/99.5-50/50 and having a flat-face diameter D of 0.1-5.0mum and a ratio of the diameter to the thickness (d) (D/d) of 1.5-5.0.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to flat emulsion particles having concave portions useful as an additive for coating agents used in paints, coatings, information recording papers, etc., and a method for producing the same. .

[Conventional technology]

In recent years, various particulate polymers have been studied as additives for coating agents. The most commonly used particles are uniform, dense emulsion-polymerized polystyrene particles with a particle size of 0.2 to 0.5 microns. For example, JP-A-59-
59741, in which an unsaturated carboxylic acid and a vinyl monomer are copolymerized in the presence of an anionic surfactant and/or a nonionic surfactant, and 90% or more of the particles are 0.2 to 0.
．． An example of producing a 28μ copolymer emulsion and using it for applications such as paper coating or paint is exemplified.

The organic pigment produced by this method does not provide sufficient hiding power, whiteness and gloss, and has no practical advantage unless used in large amounts.

In recent years, for the purpose of further improving hiding properties, whiteness, and gloss, organic materials having uniform, dense, or small pores as described above have been proposed (US Pat. No. 3,152,280). That is, at least one type of monoethylenically unsaturated sheath monomer that forms the sheath polymer is added to a polymer dispersion in which at least 5% of an unsaturated carboxylic acid is copolymerized as a core material, and the emulsion polymerized is made into an aqueous emulsion. This is a method for producing an aqueous dispersion in which micropores are formed by neutralizing and swelling a core polymer with a volatile base.

When organic pigments prepared by this method are used in paint or paper coating compositions, hiding properties, whiteness, and gloss are improved compared to uniform, dense organic pigments, but pores may be impaired depending on the method of use. There is a drawback. The causes of small pores becoming T-shaped are destruction due to freezing, destruction due to certain solvents used in paint formulations, or destruction due to heating, and they can only be used in limited forms due to formulation or usage.

On the other hand, polyethylene flat particles as a pigment are produced by mechanically heating and compressing a polymer (Powder to Industry, (9), 1986, p. 33).
etc. are conventionally known, but only particles with a size variation of 1 μ or more can be obtained, and it is difficult to efficiently and accurately produce particles suitable for various uses.

[Problems to be Solved by the Invention] The present invention solves the problems of the prior art as described above, and when used in paints, coating agents, information recording paper, etc. , satisfies physical properties such as whiteness, and at the same time has few limitations when blending or using.
The purpose is to provide emulsion particles that can be stably used.

[Means for solving problems]

The present inventors have discovered that flat emulsion particles having concave portions have excellent suitability as organic pigments, and have arrived at the present invention.

That is, the present invention provides flat vinyl polymer emulsion particles, which have a recess on at least one of the flat surfaces, the diameter of the flat surface is 0.1 to 5.0 μ, and The ratio (D/d) to the thickness d is 1.5 to 5.0
A polymer obtained by emulsion polymerization of the vinyl monomer (a) and a polymer obtained by emulsion polymerization of the vinyl monomer (a) are used as seed particles, and the vinyl monomer (a)
vinyl monomer (b) with the same or different composition as 20
1. The method for producing emulsion particles according to claim 1, wherein emulsion polymerization is carried out in the presence of a water-insoluble organic solvent having an interfacial tension with water at C of 48 dyne/e- or more.

Emulsion particles having such a shape are produced by first emulsion polymerizing vinyl monomer (a) to produce a polymer emulsion, and then using 0.5 to 50 parts by weight of this emulsion as seed particles to form monomer (a). ) is obtained by adding 99.5 to 541 parts of vinyl monomer (b) having the same or different composition together with a water-insoluble organic solvent and carrying out emulsion polymerization.

Examples of the vinyl monomer (a) used for producing the seed particles include (f7..7, tyrene, α-methylstyrene,
Aromatic vinyl compounds such as vinyltoluene, (meth)acrylic acid esters such as methyl (meth)acrylate, ethyl (meth)acrylate, (meth)butyl acrylate, vinyl esters such as vinyl acetate, vinyl propionate, etc. (
Vinyl cyanide compounds such as meth)acrylonitrile, vinyl chloride, vinyl halide compounds such as vinylidene chloride, etc. can be used. In addition to the above monomers, unsaturated carboxylic acids such as (meth)acrylic acid, crotonic acid, and itaconic acid, unsaturated sulfonic acid salts such as sodium styrene sulfonate, and 2-hydroxyl are added to stabilize the emulsion. (Meth)acrylic acid esters such as ethyl (meth)acrylate and glycidyl (meth)acrylate, or functional monomers such as (meth)acrylamide and N-methylol (meth)acrylamide can be used. Moreover, a crosslinkable monomer can also be used if necessary. Such crosslinkable monomers include:
Examples include monomers having two or more polymerizable unsaturated bonds in one molecule, such as divinylbenzene, ethylene glycol di(meth)acrylate, and trimethylolpropane trimethacrylate. The crosslinkable monomer can be used in an amount of preferably 10 weight % or less, more preferably 5 weight % or less, based on the vinyl monomer.

Monomer (a) is a concept that includes all of the above monomers.

One type or two or more types of these vinyl monomers can be used, but it is preferable to use two or more types.

When producing seed particles, as a molecular weight regulator during polymerization,
Mercaptans such as t-dodecyl mercaptan and halogenated hydrocarbons such as carbon tetrachloride are added to the monomer in an amount of 0.
It may be added in an amount of 0.05 to 5.0% by weight, more preferably 0.4 to 3.0% by weight.

The seed particle emulsion is produced by a conventional emulsion polymerization method. Examples of the surfactants used include anionic surfactants such as sodium alkylbenzenesulfonate, sodium alkylsulfate, sodium dialkylsulfosuccinate, formalin condensate of naphthalenesulfonate, etc.
Nonionic surfactants such as polyoxyethylene alkyl ether, polyoxyethylene alkylphenol ether, ethylene oxide propylene oxide block copolymer, and sorbitan fatty acid ester are used alone or in combination. The amount of surfactant used is not particularly limited, but is usually about 0.1 to 10% by weight based on the total leather weight.

The polymerization initiator may be one that is used in ordinary emulsion polymerization, such as persulfates such as potassium persulfate, sodium persulfate, ammonium persulfate, and organic peroxides such as benzoyl hydroperoxide. and azo compounds such as azobisisobutyronitrile.

To produce a type 0 particle emulsion that can be used as a redox initiator in combination with a reducing agent if necessary, various monomers are usually added in the presence of the surfactant and polymerization initiator. Polymerization is carried out by adding the substance (a) in bulk, in portions, or continuously. The polymerization is carried out at a polymerization temperature of 20 DEG to 90 DEG C. under a nitrogen purge.

For 0.5 to 50 parts by weight of the seed particles thus produced, 99.5 parts of the vinyl monomer (b) containing a crosslinking monomer, if necessary, having the same or different composition than the monomer (a). ~50 parts by weight are subsequently added in one portion or in portions or continuously. At this time, the organic solvent may be added in a mixture with the vinyl monomer containing the crosslinking monomer, or may be added individually and all at once.

In this way, flat emulsion particles having concave portions made of monomer (a) and monomer (b) are obtained, but the weight ratio of monomer (a) and monomer (b) is 0. 5/99.5
Polymerization is carried out in the range of ~50,150. In a range other than the above, flat particles having concave portions cannot be obtained.

Examples of the vinyl monomer (b) include aromatic vinyl compounds such as styrene, α-methylstyrene, and vinyltoluene; Vinyl esters such as meth)acrylic acid esters, vinyl acetate and vinyl propionate, vinyl cyanide compounds such as (meth)acrylonitrile, and halogenated vinyl compounds such as vinyl chloride and vinylidene chloride are used.

In addition, unsaturated carboxylic acids such as (meth)acrylic acid, crotonic acid, and itaconic acid, unsaturated sulfonates such as sodium styrene sulfonate, and (meth)acrylates such as 2-hydroxyethyl (meth)acrylate and glycidyl (meth)acrylate. ) Acrylic acid esters, or functional monomers such as (meth)acrylamide and N-methylol (meth)acrylamide can also be used in combination with the above monomers, and in this case, stability is imparted to the emulsion. When a functional monomer is used, it is preferably at most 20% by weight, more preferably at most 1% by weight, based on the monomers mentioned above.

If the functional monomer is used in an amount of 1% or more, secondary particles are likely to be generated and water resistance is reduced.

Further, a crosslinkable monomer can be used if necessary. Such crosslinkable monomers include crosslinkable monomers that can be copolymerized with the above monomers, such as divinylbenzene, ethylene glycol di(meth)acrylate, trimethylolpropane trimecrylate, etc., which have a polymerizable unsaturated bond. Examples include two or more monomers present in one molecule. At this time, preferably 20% by weight or less, based on the vinyl monomer added,
More preferably, it is 10% by weight or less. By using a crosslinkable monomer, blocking resistance, heat resistance, solvent resistance, etc. are improved, but if more than 20% is used,
Polymerization does not proceed smoothly and a large amount of aggregates are generated.

The vinyl monomer (b) is a concept that includes all of the above monomers, and the combination thereof is free, but the glass transition temperature of the resulting polymer is preferably 50°C or higher, more preferably 70°C or higher. It is. From this point of view, it is preferable to use styrene and methyl methacrylate alone or in combination.

Further, as in the production of seed particles, the aforementioned chain transfer agent can be added as a molecular weight regulator.

Here, the organic solvent added at the same time must have an interfacial tension with water of 48 dyne/cm or more at 20°C, and from this point, n-penkun, n-hexane, n-
heptane, i-octane, n-octane, n-decane,
and at least one kind selected from (halogenated) aliphatic hydrocarbons such as 1-chlorodecane, etc., and the interfacial tension with water of the organic solvent to be added is less than 48 dyne/C11, flat particles having concave portions. spherical particles are more likely to be produced.

Vinyl monomer (b) containing the organic solvent selected as described above, seed particles and a crosslinking monomer added as necessary.
It is preferably added in an amount of 1 to 50% by weight, more preferably 5 to 20%, based on the total amount, during polymerization. If less than 1% by weight is added, spherical particles will be produced, while if more than 50% by weight, polymerization will be difficult to proceed.

The diameter of the oblique plane of the particles obtained in this way is 0.1~
5.0μ, and the ratio to the particle thickness d (D/d)
is in the range of 1.5 to 5.0. D and (D, /d) are determined by the particle size of the seed particles and the weight ratio of the monomer (b). For example, when the amount of monomer (b) is increased relative to the seed particles, D and (D/d) become larger.

Incidentally, if the particle size is less than 0.1 μm, sufficient hiding properties, whiteness, and gloss cannot be obtained. On the other hand, particles with a diameter of 5.0 μm or more have decreased stability and are difficult to manufacture.

In the process of removing the organic solvent from the emulsion particles thus obtained, flat emulsion particles having recesses of the present invention are produced. The aqueous solvent is removed together with water during the drying process of the emulsion, but it can also be easily removed in the emulsion state by steam distillation.

From the Examples and Comparative Examples described later, it is assumed that the reason why the flat particles of the present invention are produced is that the organic solvent is localized inside the particles and this is removed.

〔Example〕

Hereinafter, specific examples of the present invention will be described. Note that parts and % indicate parts by weight and % by weight in total.

Example 1 250 parts of water and 0.1 part of sodium lauryl sulfate are charged into a separable flask equipped with a stirrer, a thermometer, and a reflux condenser, and the temperature is raised to 70° C. while purging with nitrogen while stirring.

Keeping the internal temperature at 70°C, 1.0 part of potassium persulfate as a polymerization initiator and 0.05 part of t-dodecyl mercaptan as a molecular weight regulator were added, and after dissolving, 1.0 parts of methoxyfufu 10
1 part and 0.3 parts of acrylic acid were added, and the mixture was allowed to react for 2 hours. After the reaction is completed, 200 ml of water is added in advance.
parts, 1.5 parts of sodium lauryl sulfate and 270 parts of styrene.
parts, n-butyl methacrylate 30 parts, acrylic acid 9 parts
．． 0 parts, divinylbenzene 9.0 parts, n-hebutane 45
．． A mixed emulsion of a monomer and an organic solvent prepared by adding 0 part of the mixture with stirring is added continuously over a period of 4 hours to carry out the reaction. After the addition is completed, aging is further carried out for 3 hours.

The resulting emulsion has a nonvolatile property of approximately 40% and a viscosity of 40%.
cps (BM type viscometer rotor No. 1, number of revolutions 60 rp+w, temperature 25° C.) and pH 1.7. When the particles were measured using an electron microscope, the diameter of the oblique plane was 0.5μ, and the particle thickness d was 0.2μ, as shown in Figure 1.
, (D/d) was a flat particle having concave portions of 2.5.

Examples 2 to 7 Are you sure? Type and amount of 8 agents, monomer (a)/monomer (b)
Polymerization was carried out by the method of Example 1 with the composition shown in Table 1 while changing the weight ratio and monomer composition to obtain flat emulsion particles having concave portions as in Examples 2 to 7.

Comparative Example 1 Seed particles were prepared by polymerization with the same vinyl monomer composition as in Example 1, and then the monomers had the same composition as in Example 1, except that no organic solvent was mixed at all. Polymerization was carried out by adding the body emulsion in the same manner.

The resulting emulsion had a viscosity of about 42% and a viscosity of 10.
cps, ptl was 1.8. The particles were not flat with concave portions as seen in Example 1, but were spherical particles with an average particle diameter of 0.4 μm.

Comparative Examples 2 to 3 In Example 1, polymerization was performed using the same composition and the same method except that the organic solvent added was toluene, which has an interfacial tension with water of about 35 dyne/cm at 20 °C. In Comparative Example 2 and Example 1, the polymerization was completed without adding an organic solvent in the same manner as in Comparative Example I, and then an organic solvent was added and stirring was continued at 70°C for 2 hours. -1.

Application Example 1 Application for Paint Application The flat particles having concave portions of Examples 1 to 7 and the spherical particles of Comparative Examples 1 to 3 were used as organic pigments and a part of rutile titanium dioxide was substituted for paint formulation. In addition, at that time,
Almatex E-208, an acrylic emulsion with a resin solid content of 45%, was used as a paint vehicle. The paint formulation is shown in Table-2.

Table 2 25% Tamo-1 and 731 water solution [manufactured by Rohm & Haas] Ethylene glycol 2-amino-2-methyl propatool Nobuco 0F-122NS [manufactured by Sannopco] Rutile type titanium dioxide preparation emulsion (40%) Alma Tex E-208 [manufactured by Mitsui Toatsu Chemical] Butyl cellosolve/Texanol (1/2) mixed solvent Hydroxyethyl cellulose/propylene glycol (1/10) mixed m 12.2 parts 4060 parts 3.0 parts 0.8 parts 164.5 parts 102.8 parts 676.0 parts 40.0 parts 12.4 parts pwc (% by weight of pigment in solid content) 40.0
%Paint viscosity 70-80KU Paint adjustment includes water, Tamolure 31, ethylene glycol, 2-amino-2-methylpropertool, Nobuco DP-
After sufficiently dispersing 122Ns, rutile type titanium dioxide with a pigment dispersion machine, Emulsilane and Almatex E-208,7'Til Cellosolve/ prepared in Examples or Comparative Examples
Texanol, hydroxyethyl cellulose/propylene glycol were added under stirring, and the temperature reached 70 on the Stomer viscometer.
The paint was adjusted so that it was ~80KU.

The obtained coating material was applied to a slate plate so that the dry film thickness was about 40 μm, and the performance was evaluated after drying at room temperature for a week. Each evaluation method is shown below.

Gloss: Measured at a 60° angle using a gloss meter made by Suga Test Instruments.

Hiding rate: Measured according to JIS L5663.

Apply with an applicator using hiding power test paper manufactured by Nippon Test Panel Industries ■ so that the dry film thickness is 75μ, and calculate from the ratio of reflectance of 45° and 10° after drying at room temperature and after a week Water resistance: 25°C Items with no abnormalities such as blistering or whitening after being immersed in water for 2 days are judged as O.

Alkali resistance: Items with no abnormalities such as blistering or whitening after being immersed in a 2% caustic soda solution saturated with calcium hydroxide for 2 days are judged as ○.

Weather resistance: If there are no abnormalities such as blistering, whitening, or loss of gloss after 500 hours of irradiation using a weather meter, it is judged as O.

Washing resistance: Measured according to JIS K-5663.

No paint peeling after 2000 times or more 0 No paint peeling after 1000 to 2000 times Δ Adhesion:
Good adhesion in cross-cut peeling: O: Slight peeling at the cut part: 8 Evaluation results are shown in Table 3.

Application example 2 Application example 1 for paper coating
Performance evaluation was conducted when the emulsions obtained in Comparative Examples 1 to 7 and Comparative Examples 1 to 4 were used as a 8g pigment or an organic filler in a coating agent for Gion coating.

The formulation and evaluation method are shown below.

11W-90EMC 90 parts Pigment or filler 10 parts Aron T-40
0.09 parts [manufactured by Toagosei Kagaku Kogyo Co., Ltd.] Mon S-4600 [Nippon Shokuhin Kogyo Co., Ltd.] 33 parts Polyrank 755 12 parts [manufactured by Nii Toatsu Chemical Co., Ltd.] Coating liquid solid content 62% 8 of the coating liquid
11 is a dispersant in water with a solid content of 40% Aron T-
Add kaolin clay tl with a colorless mixer.
W-90 is sufficiently dispersed, and the emulsion prepared in Examples 1 to 7 or Comparative Examples 1 to 4 is added thereto as an organic pigment. For comparison, titanium dioxide paste with a solid content of 62% as an inorganic pigment [manufactured by Okuchi Seika ■], light calcium carbonate with a solid content of 60% as an inorganic filler, and Musurry TP-222.
H5 [manufactured by Okutama Kogyo ■1] was used. As a binder, phosphate esterified starch MS-4600 and Polylac 755 with a solid content of 50% were added to prepare a coating liquid.

The dry coating amount of the above coating liquid with an applicator is approximately 14~
15g/n (coated on high quality paper, drying condition 12
The dried material was dried at 0℃l2O seconds using a calender roll at a roll temperature of 60"C1 linear pressure of 70Kg/c and a speed of 10ni.
A coated paper was obtained by passing it twice under the conditions of /win, and its performance was evaluated.

Color viscosity Measured with a BM type viscometer (60 rpmN)
o, 40-ter).

Reflectance at 75@ was measured according to JIS P-8142.

Toyo Ink New Ply R1 printing test using 0.4cc of indigo Printed on a test machine, after drying JIS P According to 8142, 75@reflectance measurement.

Print Gloss White Paper Gloss Whiteness Opacity Dry Pink Wet Pick Measured using a bank whiteness meter in accordance with JIS P-8123.

Measured according to JIS P-8138.

Tested with R1 printing tester.

(10 point scale) Same as above The evaluation results are shown in Table-4.

[Effects of the Invention] Due to its morphological characteristics, the flattened emulsion particles of the present invention have excellent gloss, hiding power, whiteness, water resistance, etc. when used as pigments and fillers for paints and paper coating agents. Excellent. In addition, there are few restrictive conditions at the time of compounding or use, and it can be used stably. In such applications, part or all of titanium dioxide, kaolin clay, and calcium carbonate can be replaced. In addition, it has the effect of improving weight reduction, hardness, abrasion resistance, heat resistance, etc., and is used as an additive in various compounds, and is used for paper, metals, alkaline materials, plastics, fibers, cloth, etc. Figure 1 shows Example 1.
1 is a scanning electron micrograph showing the structure of flattened emulsion particles having concave portions obtained by the method.

Claims (4)

[Claims] (1) Flat vinyl polymer emulsion particles having a concave portion on at least one of the flat surfaces, the diameter D of the flat surface is 0.1 to 5.0μ, and the particle thickness is Flat emulsion particles having concave portions, characterized in that the ratio (D/d) to d is in the range of 1.5 to 5.0. (2) A polymer obtained by emulsion polymerization of the vinyl monomer (a) is used as a seed particle, and a vinyl monomer (b) having the same or different composition as the vinyl monomer (a) is added at 20°C. 2. The method for producing emulsion particles according to claim 1, wherein the emulsion polymerization is carried out in the presence of a water-insoluble organic solvent having an interfacial tension with water of 48 dyne/cm or more. (3) The weight ratio of monomer (a) and monomer (b) is 0.5
3. The manufacturing method according to claim 2, wherein the ratio is from /99.5 to 50/50. (4) The production method according to claim 2, wherein the amount of the water-insoluble organic solvent is 1 to 50% by weight based on the total amount of the seed particles and monomer (b).