JP2606701B2 - Paint composition - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a coating composition comprising, as an essential component, an ultrafine aqueous emulsion obtained by emulsion polymerization of an unsaturated monomer.

(Prior art)

In recent years, from the viewpoints of air pollution, improvement of work environment on site, and effective use of resources, etc., as an alternative to organic solvent type paints, aqueous or water-dispersed water-based paints, powder paints, especially water-dispersed paints, that is, aqueous emulsions -Based paints are receiving attention.

However, for example, an aqueous emulsion paint obtained by emulsion polymerization of an unsaturated monomer in the presence of an emulsifier has a large particle size, and the formed film has higher transparency and transparency than an organic solvent type paint film. There is a drawback that the performance such as smoothness, water resistance and solvent resistance is poor.

In order to improve these drawbacks, a redox catalyst consisting of a persulfate and a reducing sulfoxy compound, a polymerization initiator added with a trace amount of a transition metal ion as an accelerator, and ultrafine particles of an aqueous emulsion were used. And a method of improving the film performance by forming an appropriate three-dimensional structure in an aqueous emulsion (JP-A-60-170604, JP-A-60-170604).
No. 60-170605, surface: vol 25, No 2.86, 1987).

However, in these methods, due to the effect of a small amount of transition metal ions used as a polymerization accelerator,
The particle size of the resulting aqueous emulsion is significantly different,
Even when ultrafine particles can be formed, the dispersing effect of the surfactant used after emulsion polymerization is small, and the viscosity of the resulting aqueous emulsion is significantly increased. There are problems such as the need to add.

Further, although the aqueous emulsion obtained by this method is cross-linked within and / or between particles, the film-forming property, transparency or mechanical strength of the film is poor due to the effect of the temperature at which the film is formed. When this aqueous emulsion is left standing for a long period of time due to the effect of an emulsifier having a high zeta potential and remaining, the particles coalesce and agglomerate to form coarse particles, causing a significant white turbidity phenomenon and causing phase separation. However, there is a problem that the viscosity increases and the viscosity is significantly increased, which is not an industrially advantageous method.

A method has also been proposed in which a certain type of polyoxyalkylene (meth) acrylic acid diester is used as a resin modifier to obtain an aqueous emulsion and improve the water resistance and the like of the formed film (Japanese Patent Publication No. 54-19905). However, in these methods, polyoxyalkylene (meth) acrylate diester has poor water-solubility and emulsifying power as well as not being able to form ultrafine particles, and the film performance such as water resistance is improved if not used in large amounts. This film is not sticky.
There was a problem that the tackiness was too strong.

〔Purpose〕

SUMMARY OF THE INVENTION An object of the present invention is to provide an ultrafine-particled cross-linked aqueous emulsion having excellent dispersion stability over a long period of time and a film-forming ability having excellent film-forming properties, transparency, smoothness, tackiness, water resistance and mechanical strength. An object of the present invention is to provide a paint composition.

〔Constitution〕

According to the present invention, the average particle size is 100 nm or less, having a cross-linked structure and having a higher glass transition temperature than the value calculated by the weight fraction method, the zeta potential is -30 mv or less, dispersion stability A coating composition characterized by comprising, as an essential component, an aqueous emulsion which is excellent over a long period of time.

First, the aqueous emulsion, which is an essential component of the coating composition of the present invention, is characterized in that its average particle size is 100 nm or less, preferably 80 nm or less.

Aqueous emulsions are essentially formed by filling and fusing particles, so that the average particle size is required to be small.In the present invention, the average particle size is 100 nm or less as described above. Since it is preferably limited to 80 nm or less, it becomes possible to greatly improve various properties such as heat fusion, transparency, smoothness, and glossiness of the film.

When the average particle size exceeds 100 nm, the adhesiveness (denseness) when a film is formed is inferior, and the gloss, transparency and smoothness of the film may be lacking. You cannot achieve your goals.

The second feature of the aqueous emulsion, which is an essential component of the coating composition of the present invention, is that it has a crosslinked structure within and / or between the particles.

That is, in the aqueous emulsion which is an essential component of the coating composition of the present invention, the inside of the particles and / or between the particles, for example, the functional groups of the raw material unsaturated monomers or the functional groups of the emulsifier and the Since it is cross-linked by bonding, hydrogen bonding, condensation reaction, polymerization reaction or the like, it is presumed that it forms a film having excellent transparency, tackiness, water resistance, solvent resistance and mechanical strength.

Further, a third feature of the aqueous emulsion, which is an essential component of the coating composition of the present invention, is that it has a high glass transition temperature higher than the value calculated by the weight fraction method, preferably 3 ° C. or higher. .

The glass transition temperature (Tg) is the temperature at which a polymer changes from a glassy hard state to a rubbery state when heated, and if the glass transition temperature of a component that is a structural factor of the polymer is known, the polymer has a glass transition temperature. The glass transition temperature can be determined from the following equation by the weight fraction method.

W _A ; Weight fraction of A component W _B ; Weight fraction of B component Tg _A ; Glass transition temperature of A component Tg _B ; Glass transition temperature of B component This glass transition temperature is affected by various structural factors, In general, it is known that the glass transition temperature of a polymer having a crosslinked structure increases, and that the glass transition temperature decreases when a plasticizer is added to the polymer.

On the other hand, for an aqueous emulsion, the lowest film formation temperature is known as the lowest temperature at which a film is formed by filling and fusing particles, and the minimum film formation temperature and the glass transition temperature are in a proportional relationship. It has been known.

The aqueous emulsion of the present invention has a film-forming ability exhibiting a glass transition temperature higher than the value calculated by the weight fraction method as described above, and has a dense cross-linked structure, so that it is transparent, tacky, and smooth. Excellent in water resistance and solvent resistance,
Further, it is possible to form a film that is hard and has good mechanical strength such as tensile strength and modulus strength.

A fourth feature of the aqueous emulsion which is an essential component of the coating composition of the present invention is that it has a zeta potential of -30 mv or less, preferably -50 mv or less.

Generally, dispersed colloidal particles such as an aqueous emulsion have an electrokinetic potential (zeta potential) in a system surrounding the particles at the interface between the particles and the solution. When the zeta potential is negatively charged, it is required that the zeta potential be lower.However, the aqueous emulsion of the present invention has a zeta potential of -30 mv or less, preferably-as described above. Since it has a value of 50 mv or less, the colloidal particles in the dispersion show extremely high stability.

A fifth feature of the aqueous emulsion, which is an essential component of the coating composition of the present invention, is that it has excellent dispersion stability over a long period of time.

That is, the aqueous emulsion of the present invention has an average particle diameter of 100 n.
m, but when subjected to a forced heating dispersion stability test at 45 ° C. for one week, there is substantially no change in the average particle diameter. Indicates a particle size distribution of a single peak distribution of a particle distribution having an average particle diameter of 150 nm or less, and even when the rate of change is large, the particle size distribution of the first peak having an average particle diameter of less than 150 nm is 97%.
As described above, the second peak due to agglomeration of particles shows a two-peak distribution in which 3% or less has a particle size distribution of 300 nm or more, and the particle size distribution of the average particle size is extremely small.

Furthermore, even when subjected to a long-term dispersion stability test at 25 ° C. for 6 months, the aqueous emulsion according to the present invention has a very high rate of change in the average particle diameter, as is clear from the Examples and Comparative Examples described later. small.

Therefore, the aqueous emulsion according to the present invention is substantially free of coalescence or aggregation of particles even with the lapse of time, and does not generate coarse particles, so that the particle size changes with time, the transmittance decreases, Since there is no change in viscosity and no change in appearance, it shows excellent dispersion stability over a long period of time, and when a film is formed, the mechanical strength does not decrease due to the formation of coarse particles. .

The reason why the aqueous emulsion according to the present invention exhibits excellent dispersion stability as described above is not necessarily clear,
Since the average particle size is 100 nm or less, Brownian motion between particles is relatively active, and undesired polymerization and cross-linking reactions caused by the polymerizable or reactive emulsifier remaining in the system are undesirable. In the present invention, since the sulfonate-type emulsifier and the reactive emulsifier are present in a well-ordered manner in the present invention, each particle is sufficiently dispersed for reasons such as suppression of a side reaction such as a polymerization reaction or a cross-linking reaction. It is presumed that the basic factor is that coalescence and agglomeration of the particles are prevented, and the formation of coarse particles is not promoted.

In the present invention, in order to improve the dispersion stability of the aqueous emulsion, for example, P-hydroxydiphenylamine, N, N'-diphenyldiamine, 2,5-
Conventionally known polymerization inhibitors and polymerization terminators such as di-tert-butylhydroquinone can also be added.

The average molecular weight of the aqueous emulsion, which is an essential component of the coating composition of the present invention, is generally one million or more, often about tens of millions to hundreds of millions. In some cases, the molecular weight may be as high as tens of millions to one billion.

 Hereinafter, the present invention will be described in more detail.

The aqueous emulsion used in the present invention can be obtained by emulsion polymerization of an unsaturated monomer in the presence of a specific emulsifier described below.

As the unsaturated monomer, (meth) acrylic esters represented by the following general formula (I) (Wherein R ₁ and R ₂ are hydrogen or a methyl group, and R ₃ is an alkyl group having 1 to 18 carbon atoms), as well as vinyl acetate, vinyl propionate, vinyl butyrate and other lower fatty acid vinyl esters, acrylonitrile,
Nitriles such as methacrylonitrile, styrene, α-
Styrenes such as methylstyrene and chlorostyrene, vinyls such as vinyl chloride and vinyl bromide, vinylidene chlorides such as vinylidene chloride and vinylidene bromide, butadiene,
Dienes such as chloroprene and isoprene and vinylpyridine are exemplified, but the use of (meth) acrylates, lower fatty acid vinyl esters, nitriles and styrenes is preferred.

In the present invention, the unsaturated monomer to be copolymerized with the unsaturated monomer is used to further strengthen the crosslinked structure in the particles of the aqueous emulsion to be formed and / or between the particles, and to form a film. Sometimes unsaturated monomers having a reactive functional group are preferably used to promote crosslinking, but even unsaturated monomers having no reactive functional group may be used.
In the emulsion polymerization system, it is also possible to use an unsaturated monomer which can be converted into a compound having active hydrogen.

Examples of such an unsaturated monomer having a reactive functional group include compounds represented by the following general formulas (II) to (VIII). These monomers can be used alone or in combination of two or more kinds, and if necessary, other copolymerizable unsaturated monomers can be used in combination.

(Wherein R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , R ₆ , R ₇ , R ₈ , R ₉ , B, D, E, t ₁ , t ₂ and
t ₃ is as follows.

R ₁ , R ₂ , a hydrogen atom or a methyl group R ₄ ; an alkylene group having 2 to ₄ carbon atoms R ₅ ; a direct bond, an alkylene group having 1 to 3 carbon atoms, a phenylene group or a substituted phenylene group R ₆ ; an oxygen atom or -NH- R _7; hydrogen, alkylol group or 1-5 C1-5 alkyl group having a carbon R _9;; hydrogen, alkylol groups R ₈ of C1-5 alkylene of 1 to 4 carbon atoms group a; methylene group or a carbonyl group B; -CH ₂ O- or a carboxyl group D; hydrogen atom, an alkyl group having 1 to 3 carbon atoms, carboxyl group, Or -CONHCONH ₂ E; hydrogen atom, an alkyl group having 1 to 3 carbon atoms or -CH ₂ COO
H t ₁ ; a real number of ₁ to 20 t ₂ ; an integer of 0 or 1 t ₃ ; an integer of 0 to 10) General formulas (II), (III), (IV), (V), (VI),
Examples of specific compounds of (VII) and (VIII) include:
The following can be mentioned.

Examples of general formula (II) Glycidyl acrylate Glycidyl methacrylate Glycidyl crotonate Glycidyl allyl ether Examples of general formula (III) Hydroxyethyl acrylate Hydroxyethyl methacrylate Hydroxyethyl crotonate Hydroxypropyl acrylate Hydroxypropyl methacrylate Hydroxypropyl crotonate Hydroxybutyl acrylate Hydroxybutyl methacrylate Polyoxyethylene monoacrylate Polyoxyethylene monomethacrylate Polyoxyethylene monotonate Polyoxypropylene monoacrylate Polyoxypropylene monomethacrylate Polyoxypropylene monotonate Polyoxybutylene monoacrylate Polyoxybutylene monotonate Hydroxy Tyl allyl ether hydroxypropyl allyl ether hydroxybutyl allyl ether polyoxyethylene allyl ether polyoxypropylene allyl ether polyoxybutylene allyl ether Examples of general formula (IV) allylamine acrylamine methacrylamine aminostyrene α-methylaminostyrene general formula (V ) Examples Acrylamide Methacrylamide Aminopropylmethacrylamide Monomethylacrylamide Monoethylacrylamide Diethylolaminopropylacrylamide Example of the general formula (VI) Acrylic acid Methacrylic acid Crotonic acid Itaconic acid Maleic acid and its monoester of alkyl group having 1 to 5 carbon atoms Or anhydride fumaric acid and its monoester or anhydride of an alkyl group having 1 to 5 carbon atoms De-fumaric acid alanide N-carbamoyl fumaric acid amide N-carbamoyl fumaric acid amide Example of general formula (VII) Methyl allyl thiol methyl mercaptostyrene Example of general formula (VIII) N-methylol acrylamide N-methylol methacrylamide N- Methylolcrotonamide N- (2-hydroxyethyl) acrylamide N- (2-hydroxyethyl) methacrylamide N- (2-hydroxypropyl) acrylamide N- (2-hydroxypropyl) methacrylamide The ratio of the unsaturated monomer having a reactive functional group to the saturated monomer is 99/1 to 60/40 (weight), preferably 99/1 to 99/10 (weight). This usage rate is 99/1
If it is larger than this, the degree of cross-linking within and between the particles of the resulting aqueous emulsion becomes smaller, and if it is smaller than 60/40, a large amount of agglomerates are formed due to lack of emulsion copolymerizability or poor film-forming properties. Cracks may occur in the film.

In the present invention, the following general formulas (IX), (X), (X)
At least one of the reactive emulsifiers represented by I), (XII), (XIII) and (XIV), a sulfonate type emulsifier represented by the general formula (XV), and a polyoxyalkylene ethylene represented by the general formula (XVI) It is necessary to use an anionic emulsifier composed of at least three components of the unsaturated carboxylic acid polyesters (hereinafter, abbreviated as poly (meth) acroyl type emulsifier).

(Wherein, R ₁₀ , R ₁₁ , R ₁₂ , R ₁₃ , R ₁₄ , R ₁₆ , a ₁ , a ₂ , a ₃ ,
a ₄ , M, m and G are as follows.

R ₁₀ ; an alkylene group having 2 to 4 carbon atoms R ₁₁ ; a hydrocarbon group which may have a substituent, a phenyl group, an amino group or a carboxylic acid group R ₁₂ , R ₁₆ ; a hydrogen or methyl group R ₁₃ ; a substituent May be a hydrocarbon group R ₁₄ , R ₁₅ ; hydrogen or an alkyl group having 1 to 20 carbon atoms, which may be linear or branched, and preferably one of R ₁₄ or R ₁₅ A ₁ , a ₂ , a ₃ , a ₄ ; the average number of moles of addition a ₁ , a ₂ , a ₃ ; 0 to 50 real numbers a ₄ ; 1 to 50 A preferable real number is 8 or more moles of the added alkylene oxide in the molecule M; monovalent or divalent cation m; ionic valence of M _{-O-CnH 2 n-g 2} (R 18) g 2 -O- R 16, R 17; hydrogen or carbon atoms 1-2 alkyl group R _18; hydrogen or R ₁₀ Oa ₅ H or g ₁ ; an integer of 0 to 5 g ₂ ; an integer of 0 to 10 n; an integer of 1 to 10 a ₅ ; a real number of 1 to 50 And y is a real number of 1 to 5 R ₁₉ , R ₂₀ ; hydrogen or an alkyl group of 1 to 20 carbon atoms Y ′; an alkylene group of 3 to 8 carbon atoms, oxygen or a carbonyl group) Ultrafine particles with a fine cross-linking structure inside and / or between particles, forming a film with a glass transition temperature higher than the value obtained from the calculation formula. In order to obtain an ultrafine cross-linked aqueous emulsion excellent in dispersion stability in which coalescence and aggregation of particles are suppressed over a long period of time, it is necessary to use (a) an emulsifier used for emulsion polymerization of the unsaturated monomer. The above general formulas (IX), (X), (XI), (XI
At least one of the reactive emulsifiers represented by I), (XIII) and (XIV), (b) a sulfonate type emulsifier represented by the general formula (XV), and (c) a compound represented by the above general formula (XVI) (A) / (c) = 9/1 to 1/9 weight ratio, preferably 4/1 to 1/4 weight ratio, (b) / (A) + (c) = 7 / 3-1
/ 9 weight ratio, preferably 3/2 to 1/4 weight ratio.

If the usage ratio of (a) / (c) is larger than 9/1,
The crosslinkability of the resulting aqueous emulsion and / or
Static stability may be deteriorated, and if it is smaller than 1/9, a large amount of aggregates may be formed during emulsion polymerization, or the average particle size of the resulting aqueous emulsion may be increased.

On the other hand, when the use ratio of (b) / (a) + (c) is more than 7/3, the inside of the resulting aqueous emulsion particles and / or
Alternatively, the degree of cross-linking between particles is small, and the formed film is inferior in transparency, water resistance and solvent resistance, and if it is smaller than 1/4, it lacks microemulsification or solubilization of unsaturated monomers, resulting in an aqueous emulsion formed Or the average particle size of
Even if the particles coalesce and agglomerate and become cloudy with the progress of emulsion polymerization, or even if an aqueous emulsion of transparent or translucent ultrafine particles is formed, the zeta potential is negatively small and stored for a long period of time. Then, coalescence and agglomeration of the particles easily occur, coarse particles are formed, the cloudiness becomes remarkable, further, the aqueous emulsion undergoes layer separation, or the viscosity is significantly increased.

By using these emulsifiers in the above ratio, they are ultrafine particles, have a crosslinked structure, exhibit a glass transition temperature higher than the value calculated by the weight fraction method, and have a high negative zeta potential, and furthermore, An aqueous emulsion excellent in dispersion stability in which coalescence and aggregation of particles are suppressed over a long period of time can be produced.

The amount of the emulsifier used is suitably about 0.1 to 15% by weight, and preferably 0.5 to 10% by weight, based on the unsaturated monomer to be subjected to emulsion polymerization.

In addition, known anionic, nonionic and cationic surfactants may be added as necessary. Specific examples thereof include higher alcohols, higher alcohol alkylene oxide adducts, alkylphenol alkylene oxide adducts and styrenated. A quaternary ammonium salt type of each of a phenol alkylene oxide adduct sulfate type, an olefin sulfonate type such as α-olefin, a long-chain alkylamine alkylene oxide adduct and a di-long chain alkylamine alkylene oxide adduct, N- (1, Sodium salt of 2-dicarboxyethyl) -N-octadecylsulfonic acid monoamide, dialkyl sulfosuccinate, bleached ceramic resin, 4-hydroxy-4,5-dicarboxylic pentadecanoic acid or 4,5-dicarboxy-pentadecanoloid Examples of organic and inorganic salts That.

In obtaining the aqueous emulsion according to the present invention, a conventionally known emulsion polymerization method can be used as it is in the presence of the unsaturated monomer and the emulsifier. For example, in the presence of a polymerization initiator corresponding to 0.1 to 5% by weight of the unsaturated monomer, the polymer of the unsaturated monomer is 20 to 60%.
What is necessary is just to emulsify and disperse in water at the concentration of weight%, and to carry out emulsion polymerization.

As the polymerization initiator, a water-soluble single initiator or a water-soluble redox initiator used for ordinary emulsion polymerization are used.For example, such as hydrogen peroxide alone or hydrogen peroxide and tartaric acid, citric acid, In addition to combinations with carboxylic acids such as ascorbic acid, and combinations of hydrogen peroxide with oxalic acid, sulfinic acid and salts or oxyaldehydes thereof, and water-soluble iron salts, etc., as well as persulfates, percarbonates, and peroxides Peroxides such as borates and 2,2'-azobis (2-amidinopropane) and its salts, 2,2'-azobis (N, N'-dimethylene-isobutylamidine) and its salts, 4,4'- Water-soluble azo initiators such as azobis (4-cyanovaleric acid) and salts thereof can be used.

In addition, a water-soluble nonionic polymer, an anionic polymer, a cationic polymer, or the like can be used in combination. Further, a plasticizer and a pH adjuster usually used in the conventional method can be used together if necessary.

Examples of the nonionic polymer substance include polyvinyl alcohol, dextrin, hydroxyethyl starch, starch derivatives such as hydroxyethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, and the like.

Examples of the anionic polymer include polymers such as anionized hydroxyethylcellulose, anionized starch, anionized guar gum, anionized chitosan, carboxymethylcellulose, and anionized polyvinyl alcohol.

Examples of the cationic polymer substance include cationized hydroxyethyl cellulose, cationized starch, cationized guar gum, cationized chitosan, and cationic (meth) acrylamide, cationic (meth) acrylamide, dimethyldiallylammonium chloride. And the like.

These nonionic polymer substances, cationic polymer substances and anionic polymer substances can be used singly or in combination of two or more, but the addition amount is 0.05 to the monomer to be subjected to emulsion polymerization. ~ 5% by weight, preferably 0.1 ~
It is appropriate to use 3% by weight.

Further, phthalic acid esters, phosphoric acid esters and the like can be used as the plasticizer. Further, salts such as sodium carbonate, sodium bicarbonate and sodium acetate are used as pH adjusters.
It can be used in the range of 01 to 3% by weight.

The coating composition of the present invention contains the above specific aqueous emulsion as an essential component.If necessary, various colored pigments, extender pigments, rust preventive pigments, antibacterial agents, fungicides, extenders, fillers Various auxiliary components usually used in this type of coating material, such as a dispersant, a viscosity modifier, an antifoaming agent, and a crosslinking agent such as a water-soluble melamine (resin) when it is necessary to crosslink the coating film. It can be arbitrarily added.

Preferred applications of the coating material include a wide range of applications from currently used aqueous coating materials to solvent-based coating materials. Specific examples include woodworking products, plastics products, metal products and civil and architectural structures, as well as vehicles for undercoats and topcoats for undercoats and topcoats for vehicles and railway vehicles, as well as water-soluble melamine. It can also be used as a baking coating material for baking and curing (crosslinking) by mixing with (resin) and the like, and also as a blending agent for improving the physical properties of coating films of water-soluble coatings, powder coatings, and high solid coatings.

Further, the coating composition of the present invention has remarkably good thixotropic properties and film-forming properties, is excellent in water resistance, and forms a tough film, so that it can be used as a multi-layer finish paint for civil engineering and building structures, ship bottom paint, and bridge paint. Also, by mixing with a metal powder, it can be used as a special paint such as a magnetic paint, a conductive paint, a radiation shielding paint such as an electromagnetic wave shielding material, or as a marker and a manicure.

〔effect〕

The coating composition of the present invention has an average particle size of 100 nm or less,
Since a water-based emulsion having a crosslinked structure, a glass transition temperature higher than the value calculated by the weight fraction method, and excellent dispersion stability over a long period of time was used as an essential component, a conventional coating composition was used. Unlike this, it has a film-forming ability with excellent film-forming properties, transparency, smoothness, tackiness, water resistance and mechanical strength.

For this reason, by applying to the surface of various base materials and products such as paints, woodworking products, plastic products, and metal products of the present invention, transparency, water resistance, weather resistance, and impact resistance Various excellent performances such as properties can be provided.

Further, since the coating composition of the present invention is a solvent-free coating composition, it also has the advantage of being excellent in safety and being pollution-free.

〔Example〕

Next, in order to explain the present invention in more detail, examples are shown below.

Example 1 [Preparation of Aqueous Emulsion] 8 parts by weight of the emulsifier shown in Table 1 and 150 parts by weight of water were dissolved in a glass reactor equipped with a thermometer, a stirrer, a reflux condenser, a nitrogen inlet tube and a dropping funnel. Then, the inside of the system was replaced with nitrogen gas. Separately, 90 parts by weight of ethyl acrylate, 60 parts by weight of methyl methacrylate, 156 parts by weight of an unsaturated monomer mixture consisting of 4.5 parts by weight of N-methylol acrylamide and 1.5 parts by weight of water, and 15 parts by weight of The mixture was added to the reaction vessel and emulsified at 40 ° C. for 30 minutes. Then, after the temperature was raised to 60 ° C., the polymerization initiator 2,2′-azobis (N, N′-dimethyleneisobutylamidine) hydrochloride was added to 9.0 × 10 ⁻³ mole /
It was dissolved in 48.5 parts by weight of water so as to become an aqueous phase, added to the above reaction vessel, and immediately the remaining unsaturated monomer was continuously dropped into the reaction vessel over 30 minutes, and the polymerization was carried out at 60 ° C. went. After completion of the dropwise addition of the unsaturated monomer, the mixture was aged at 60 ° C. for 60 minutes.

[Evaluation of properties and film properties of aqueous emulsion]

The average particle size, crosslinkability, zeta potential, film forming property, glass transition temperature, and film properties of the aqueous emulsion thus obtained were measured by the following methods.

Average particle size: Coulter submicron particle analyzer (Coulter Electronics, USA, Coulter
(Model N4 type).

Crosslinkability: 30 g of an aqueous emulsion adjusted to have a solid content of 40% by weight was cast uniformly on a 12 cm × 14 cm glass plate and air-dried at 25 ° C. The film thus obtained was cut into 2 cm × 4 cm, immersed in a petri dish filled with benzene at 20 ° C. for 48 hours, and evaluated based on the degree of swelling and solubility of the film as follows.

；: Equal to or slightly swelling with the film area (2 cm × 4 cm) before immersion in benzene.

Δ: The degree of swelling is large and the film shape is impaired.

X: The film was dissolved in benzene and turned into a uniform liquid.

Zeta potential; Laser rotating prism type colloid particle zeta potential measurement and measurement (LASER ZEETM M manufactured by PEN KEN INC, USA)
odel 500).

Film-forming property; air-dried at 25 ° C. to form a film, and the state of the formed film was visually evaluated.

；: A smooth and uniform film is formed.

Δ: A film having a network streak is formed.

X: No film is formed.

Glass transition temperature (Tg) Seiko Denshi Kogyo Co., Ltd. thermal diffraction analyzer (SSC5000
Tg was measured using DSC 200). The calculated Tg was calculated by the weight fraction method (described above).

[Evaluation of film properties]

The above aqueous emulsion 30 having a solid content adjusted to 20% by weight.
Weight part is evenly cast on a glass plate of 12cm x 14cm, 25 ℃
And air-dried to form a film, and the film characteristics were evaluated. The film characteristics were evaluated according to the following criteria.

Transparency: According to JIS K 6714, the haze value of the film was measured by an integral type light transmittance measuring device.

Water resistance: The film was cut into a size of 2 cm × 4 cm, immersed in a petri dish filled with water at 20 ° C., and the time until the film was whitened was visually determined.

;: 10 days or more Δ; 2 days or more, less than 10 days ×; less than 2 days Adhesion: The film surface was touched with fingers, and the solid feeling was evaluated according to the following criteria.

○: No stickiness △: Slightly sticky ×: Sticky Elongation and strength: Dumbbells were prepared in accordance with JIS K-6681, tensile strength at break, elongation and 50%, 100% and 200% modulus. Was measured.

[Performance evaluation as paint]

5.0cm x 5.0cm x 1.0cm mortar board, mackerel birch wood and 20cm x 10cm x 0.4cm steel plate (SS41) are cleaned with a polyoxyethylene nonyl phenyl ether (EOP = 9.7) aqueous solution to remove fouling components on the surface. After removal, washing with water and air drying at room temperature, the above-mentioned aqueous emulsion having a solid content of 40% by weight was uniformly applied to the surface so that the resin layer became 0.2 mm.

Then, after air-drying at 25 ° C, the appearance (glossiness), water resistance, salt water resistance and impact resistance of the mortar board, the raw birch wood and the clear coating film of the steel sheet are measured according to the following standards in accordance with JIS-5400. evaluated.

Appearance (glossiness) ；: The coating film is transparent and has the original gloss of the material to be coated.

Δ: The coating film was slightly translucent, the original gloss of the material to be coated was slightly inferior, and the coating film surface had some net-like streaks.

X: The coating film is translucent and does not have the original gloss of the material to be coated.

Water resistance and salt water resistance ；: There is no wrinkle, swelling, cracking or peeling on the coated surface.

Δ: There are some wrinkles, swelling, cracks and peeling on the coated surface.

X: There are wrinkles, swelling, cracks and peeling on the painted surface.

Impact resistance ；: There is no cracking or peeling in the film.

Δ: There is some cracking or peeling of the film.

X: The film has cracks or peeling.

By the above method, the properties of the aqueous emulsion, the film properties, and the performance as a paint were evaluated. Table 1 shows the results.
And Table-2. Samples Nos. 1 to 4 are examples of the present invention, and the aqueous emulsion according to the present invention is an ultrafine particle, has a cross-linked structure, and shows a coating film having a value higher than the glass transition temperature calculated by weight fraction. It is an aqueous emulsion that is highly negatively charged with a zeta potential and forms a film having excellent transparency, water resistance, and mechanical strength, and is a good coating composition.

 Samples Nos. 5 and 6 are comparative examples.

Example 2 (a) Sodium stearyl 2-hydroxy-3-allyloxy-1-propyl succinate sulfonate, (b) Sodium branched chain alkylbenzene sulfonate having 10 to 14 carbon atoms / xylene as shown in Table 3. Sodium sulfonate = 98/2 weight ratio, (c) polyoxypropylene polyoxyethylene P, P'-isopropylidene diphenyl ether diacrylate (PO = 2, EO =
Using 18) as an emulsifier, 156 parts by weight of an unsaturated monomer mixture consisting of 90 parts by weight of ethyl acrylate, 60 parts by weight of methyl methacrylate, 4.5 parts by weight of N-methylolacrylamide and 1.5 parts by weight of water. Emulsion polymerization was carried out in the same manner as in Example 1 to prepare an aqueous emulsion.

Properties of the aqueous emulsion thus obtained and
The film was air-dried at 30 ° C., and the properties of the formed film and the performance as a paint were measured and evaluated in the same manner as in Example 1. The results are shown in Tables 3 and 4.

Samples No. 8, 9, 12, and 13 are examples of the present invention,
7, 10, 11 and 14 are comparative examples.

Example 3 The following emulsifiers E-1 and E-2 shown in Table-5, and By adjusting the unsaturated monomer mixtures M-1 and M-2 shown above, Emulsion polymerization was carried out according to Example 1 to prepare an aqueous emulsion. The properties of the obtained aqueous emulsion, characteristics of a film formed by air drying at 30 ° C., and performance as a paint were measured and evaluated in accordance with Example 1. The results are shown in Table-5 and Table-6. Sample Nos. 15 and 16 are examples of the present invention.

Example 4 The solid content of the aqueous emulsions of Sample Nos. 8, 9, 12, and 13 obtained in Example 2 was adjusted to 40% by weight, and alumina (purity: 99.0% by weight, average particle size: 0.5 μm, manufactured by Showa Metal Co., Ltd.) Was used as a pigment, 200% by weight based on the solid content of the aqueous emulsion was added, and the mixture was stirred and mixed with a homomixer (1000 rpm × 10 minutes).

The pigment-mixed aqueous emulsion was washed with petroleum ether on a steel plate (SS41, 20.0 cm x 10.0 cm x 0.4 cm) with a thickness of 0.2 mm.
mm, air-dry at 20 ° C, JISK5400
The appearance (glossiness), water resistance, salt water resistance and impact resistance were measured according to the method described in Example 1.

The results were all good and showed an excellent effect as a coating film.

Example 5 The solid content of each of the aqueous emulsions of Samples Nos. 8, 9, 12, and 13 obtained in Example 2 was adjusted to 40% by weight, and a titanium white pigment (Titanium Kako Co., Ltd., titanium white RK) and an antifoaming agent ( Sannopco's Nopco 8034) was added to the solid content of the aqueous emulsion,
Add 150% by weight and 0.6% by weight and add a homomixer (1000
(rpm x 10 minutes) and mixed.

This pigment-mixed aqueous emulsion is applied by spraying to a zinc phosphate-treated steel sheet (22.0 cm × 10.0 cm × 0.4 cm) washed with petroleum ether, and heated at 130 ° C. for 30 minutes to form a film having a thickness of 50 μm.
A μm coating was formed. This coating film was measured for water resistance, salt water resistance and impact resistance according to JISK5400, and evaluated according to Example 1. The results were all good and showed an excellent effect as a coating film.

In addition, 5 g of the aqueous emulsion of Sample Nos. 8 to 11 adjusted to a solid content of 20% by weight was cast uniformly on a 5 cm × 6 cm glass plate and air-dried at 25 ° C. The film thus obtained was further heat-treated at 160 ° C. for 3 hours, and the yellowness of the film before and after the heat treatment was measured using an SM color computer manufactured by Suga Test Instruments Co., Ltd.
It was measured by SM-4-CH type (45 ° diffusion method). The results were 3 or less before heat treatment, 10 or less after heat treatment,
There was no yellowing problem.

From the above results, it can be seen that the coating composition of the present invention is also suitable as a baking coating.

Example 6 Using water and triethanolamine, adjusting the pH to 7 and the solid concentration to 40% by weight, preparing the aqueous emulsions of samples Nos. 15 and 16 of Example 3, calcium carbonate and glass fiber in a predetermined amount, and mixing. While adding predetermined amounts of sodium phosphate dibasic and water, the mixture is mixed uniformly. At this time, water is added so that the viscosity of the paint becomes about 350 as specified in the automotive standard (JASO-7006).

Aqueous emulsion; 85 parts by weight Calcium carbonate; 25 parts by weight Glass fiber; 8 parts by weight Sodium diphosphate; 0.5 part by weight Water: balance
The evaluation as an underbody coating paint having a grit of -7006 (Class B) was carried out for storage stability, workability, baking test, oil resistance, boiling water resistance, impact resistance, abrasion resistance and vibration isolation.

As a result, the specifications of JASO-7006 (Class B) were all satisfied. Therefore, it is understood that the coating composition of the present invention is also suitable as a vehicle coating.

Example 7 Sample No. 1 of Example 1 in which the solid content concentration was adjusted to 20% by weight
0.2 parts by weight of a fluorescent compound or dye of acridine, coumarin, rhodamine, rozamine or fluorescein was added to 99.8 parts by weight of the aqueous emulsion of (1) to (4) and uniformly mixed,
A marking ink was obtained.

This marking ink has a Shore hardness of 25 and a porosity of 57%.
Fill a felt-tip pen with a polyester nib of 10
It was written on a high-quality paper with a load of about 0 g. As a result, clear images and prints without any fog could be written. In addition, this written portion after drying was applied to 0.5 g of water droplets and benzene oil droplets.
After immersion for a minute, a clear image and print were maintained even when the finger was traced by applying a load pressure of about 300 g with the index fingertip.

From the above results, it can be seen that the coating composition of the present invention is suitable as a marking ink such as a marking pen and a brush pen and a nail varnish because it has excellent gloss, water resistance and solvent resistance.

Example 8 The dispersion stability of the aqueous emulsions of Samples Nos. 1 to 16 was evaluated in the following manner. The results are shown in Table-7. In addition, the dispersion stability test was based on the following.

(Dispersion stability)

Aqueous emulsion 15 with solid content adjusted to 40% by weight
After putting 0 g in a 220 ml glass bottle and sealing, leave it in a constant temperature room at 25 ° C. for 6 months and leave it in a constant temperature room at 45 ° C. for 1 week, then measure the appearance, transmittance, viscosity and average particle size. The dispersion stability of the emulsion was evaluated. The appearance, transmittance, viscosity and average particle size were measured by the following methods.

Appearance: Visually evaluated at 25 ° C. according to the following criteria.

○: Transparent or translucent liquid △: Cloudy liquid ×: Cloudy paste or cloudy, separated into two layers Transmittance: Wavelength 800 using spectrophotometer (Digital Double Beam Spectrophotometer UVIDEC-320 manufactured by JASCO Corporation)
The absorbance under light irradiation of nm was determined, and the light transmittance (%) was calculated.

Viscosity: The viscosity at 25 ° C. was measured using a Brookfield viscometer (B-type viscometer manufactured by Tokyo Keiki Co., Ltd.).

Average particle size: Coulter submicron particle analyzer (Coulte Electronics Co., USA, Coulte
r, Model N4 type).

Further, the aqueous emulsions of Samples 1-4, 8, 9, 12, 13, and 15-16 subjected to the forced heating dispersion stability test which was allowed to stand in a 45 ° C. constant temperature room for one week to form a film according to Example 1. It was formed and the film properties were measured according to Example 1. In all of the transparency, water resistance, pressure-sensitive adhesive, solvent resistance (crosslinkability) and mechanical strength, almost the same good effects as those of Examples 1, 2 and 3 were obtained.

Changes in the particle size distribution before and after the static stability test are shown in graphs in FIGS. 1 and 2. In addition, the sample No. 5 in Table-7 has a lot of super large particles after standing test at 45 ° C. for one week,
Since measurement was not possible due to poor dispersibility, the change in the particle size distribution of both Sample No. 1 and Sample No. 5 after standing at 25 ° C. for 6 months was compared.

[Brief description of the drawings]

1 and 2 are graphs showing changes in the particle size distribution of the aqueous emulsions of the product of the present invention (Sample No. 1) and the comparative product (Sample No. 5) after standing at 25 ° C. for 6 months.

Claims (1)

(57) [Claims] An average particle size of 100 nm or less, having a crosslinked structure, a glass transition temperature higher than a value calculated by a weight fraction method, a zeta potential of -30 mv or less, and dispersion stability. A coating composition comprising, as an essential component, an aqueous emulsion which is excellent over a long period of time.