JP4721695B2 - Aqueous coating composition - Google Patents

Description

  The present invention relates to an aqueous resin dispersion, and more specifically, protects a sheet metal working member from scratches caused by flying stones on an outdoor sheet metal working member such as a vehicle, particularly an automobile floor, a tire house, a gasoline tank, etc., so-called “chipping”. In addition to chipping resistance, the composition for water-based coatings that also has vibration control over a wide temperature range to prevent noise and vibration from the engine and road surface. It has a good balance of properties as a chipping-resistant coating, such as uniform film formation, adhesion to substrates such as sheet metal parts, water resistance, gasoline resistance, impact resistance, and soundproofing. It has excellent low-temperature characteristics such as chipping resistance at extremely low temperatures such as −30 ° C., and also has vibration damping properties over a wide temperature range. Useful Te for the manufacturing aqueous coating composition capable of reducing the thickness of the vibration damping coating film provided in the vehicle of the automobile, an aqueous resin dispersion.

  More specifically, it is an aqueous resin dispersion containing copolymer fine particles (A) dispersed in an aqueous medium, wherein the copolymer fine particles (A) are made of an acrylic-styrene copolymer core. The present invention relates to an aqueous resin dispersion characterized by being composite particles comprising a part (A-1) and a shell part (A-2) made of a conjugated diene copolymer.

  Conventionally, as an aqueous chipping-resistant coating agent used for outdoor sheet metal processing members of vehicles such as automobiles, an aqueous resin dispersion of an acrylic (co) polymer emulsion is used as a vehicle, and inorganic fillers such as calcium carbonate and talc are filled. The thing which mix | blended the agent is known and the thing based on the acrylic type (co) polymer aqueous resin dispersion liquid is disclosed by patent documents 1-4 etc., for example.

  However, these chipping-resistant water-based coatings described in these publications have chipping resistance, excellent adhesion to a sheet metal working member, and impact resistance, in particular, impact resistance at an extremely low temperature of, for example, −30 ° C. or less (hereinafter, Satisfy both characteristics as a chipping-resistant coating agent (sometimes referred to as “low-temperature impact resistance”) and anti-dandruff property in the drying process when forming a thick coating such as 600 μm or more. In order to improve chipping resistance and low-temperature impact resistance, if the amount of the inorganic filler in the coating material is reduced, blistering is likely to occur in the baking process, and the filler is used to prevent blistering. When the amount is increased, there is a problem that the chipping resistance and the low temperature impact resistance are remarkably lowered.

  Further, for example, Patent Documents 5 to 7 disclose a chipping-resistant aqueous coating agent using a rubber latex as a vehicle. However, the water-resistant coating materials for chipping described in these publications have a problem that they are not necessarily sufficient in terms of chipping resistance, adhesion and low-temperature impact resistance.

  Also known is a chipping-resistant aqueous coating agent using a mixture of two or more acrylic (co) polymer emulsions having different glass transition temperatures (hereinafter sometimes referred to as Tg). 8 is disclosed. The aqueous coating material for chipping resistance disclosed in this publication is a mixture of at least two resin emulsions having a Tg difference of 10 ° C. or more, one Tg of 0 ° C. or less, and the other Tg of 0 ° C. or more. It is.

  However, in the example of Patent Document 8, an acrylic resin emulsion having a Tg of −35 ° C. and an acrylic resin emulsion having a Tg of 9 ° C. are used. It was found that an aqueous coating agent is not necessarily sufficient in terms of its chipping resistance and adhesion.

  Furthermore, in order to eliminate these problems, Patent Document 9 describes that acrylic polymer particles dispersed in an aqueous medium contain a carboxyl group having a glass transition temperature in the range of −30 ° C. to 10 ° C. A core part mainly composed of the acrylic polymer (A), and an acrylic polymer having a glass transition temperature covering the core part of -10 ° C. or lower and lower than the glass transition temperature of the acrylic polymer forming the core part. It has also been proposed to use an aqueous dispersion of an acrylic polymer, which is a composite particle having a specific ratio with the shell portion mainly composed of the polymer (B), in a chipping-resistant aqueous coating composition.

  Furthermore, Patent Document 10 discloses an aqueous coating composition comprising polymer fine particles dispersed in an aqueous medium and an inorganic filler, which is used for a chipping-resistant coating, and the like. There has been proposed an aqueous coating composition comprising synthetic rubber-based emulsion polymer particles (A) having a glass transition temperature of 0 ° C. or lower and specific emulsion polymer particles (B) having a glass transition temperature of at least 20 ° C.

  However, these aqueous coating compositions described in Patent Documents 9 and 10 can surely form an excellent chipping-resistant coating film, but until the coating film has vibration damping properties over a wide temperature range. Did not come.

  Furthermore, Patent Document 11 proposes a cold-resistant chipping-resistant coating composition using a specific emulsion copolymer based on styrene, butadiene and acrylic monomers as a base resin, and according to the examples, The “base resin” is prepared by emulsion copolymerization of an acrylic monomer in the presence of a styrene-butadiene rubber latex.

  However, according to the additional test by the present inventors, in such a polymerization method, acrylic monomers are graft-polymerized with respect to residual double bonds in the rubber-based polymer of the latex, and the rubber elasticity is lost and hardened. In many cases, it becomes a brittle copolymer, and the chipping-resistant coating composition using such a copolymer is insufficient not only in low-temperature chipping resistance but also in room temperature chipping resistance. found.

  On the other hand, in order to prevent vibrations on the surface of structural members such as vehicles, ships, various machines / equipment, and building materials to prevent noise, to increase the thickness of the members themselves and to reduce the occurrence of vibrations Measures have been taken to prevent vibration and noise by trying to improve the device itself, by sticking a sheet-like damping material on the surface of the member, or by applying or spraying a damping paint.

  However, increasing the thickness of the member itself causes problems such as an increase in the cost of the member and a decrease in workability, and further leads to an increase in fuel consumption in the case of an automobile vehicle or the like. Further, in the pasting of the sheet-shaped damping material, it is indispensable to perform a cutting process in accordance with the shape of the member, and there is a problem that the process is complicated.

  Furthermore, various anti-vibration coatings have been proposed in the past, such as those based on materials having viscoelastic properties such as rubber, asphalt, various synthetic resin emulsions, etc., and graphite. In addition, inorganic powders such as mica, leechite, calcium carbonate, talc, and clay are blended to impart mechanical hysteresis, internal friction, and the like.

  However, many of these conventionally proposed vibration-damping coatings have a high temperature-damping performance, but have a narrow temperature range for exhibiting the vibration-damping performance, and the formed coating film is hard and brittle. There are drawbacks such as poor chipping.

  In addition, water-based vibration-damping paints are attracting attention because they are excellent in terms of easy handling and safety in the working environment, but there is a problem that formation of a thick coating film is generally not easy.

  From the standpoint of developing its performance, the vibration-damping paint must be formed with a thick coating of usually 1000 μm (1 mm) or more, and from the viewpoint of productivity, it should be quickly dried at high temperatures (high-temperature baking) However, when a thick coating is dried rapidly, the surface of the coating dries first to form a skin, and then the water remaining inside evaporates to remove the skin formed earlier. Problems such as lifting and causing blisters (thermal blisters) or cracking of the epidermis are likely to occur. When a thick coating is dried at room temperature to avoid the occurrence of such blisters and cracks, it takes a long time to dry and the productivity is lowered. Problems such as occurrence are likely to occur.

  Patent Document 12 discloses an emulsion styrene-acrylic acid ester copolymer, a polyamide epoxy compound and / or a melamine-formaldehyde compound as an aqueous vibration-damping coating material that exhibits excellent vibration damping performance in a wide temperature range from low temperature to high temperature. And a water-based vibration-damping coating material obtained by dispersing flaky inorganic powder in water. Patent Document 13 discloses an emulsion styrene-acrylate copolymer, an emulsion vinyl acetate polymer, and a crosslinking agent. In addition, water-based vibration-damping paints obtained by dispersing flaky inorganic powders in water are disclosed, but the coating films formed from these paints are insufficiently flexible and have chipping resistance and low-temperature resistance. It is not satisfactory in terms of low-temperature physical properties such as impact properties.

  The present inventors have solved the problems of the above-mentioned conventional water-based vibration-damping paints, show excellent vibration-damping performance in a wide temperature range, and are flexible and water-resistant with excellent chipping resistance and low-temperature impact resistance. Research has been conducted to provide paints. As a result, two or more types of specific composite particles are used as vehicle components in specific amounts, or specific composite particles and specific polymer particles of specific Tg are used in specific amounts to achieve these objects. As a result, a patent application was filed as an aqueous resin dispersion (Patent Document 14).

  The water-based paint based on the above-mentioned proposals by the present inventors showed excellent vibration damping performance in a wide temperature range, and showed excellent physical properties in terms of flexibility and chipping resistance. It was found that the high-temperature bakeability of the paint is not always sufficient.

  Furthermore, recently, there has been a strong demand for improvement of automobile fuel consumption in connection with environmental problems, particularly reducing the amount of carbon dioxide emitted. Reducing the weight is also an extremely important factor.

Usually, as mentioned above, automobiles have a chipping-resistant coating film for protecting outdoor sheet metal parts such as the floor of a vehicle body, tire houses, gasoline tanks, etc. A vibration-damping coating film is formed to prevent noise and vibration, and in particular, the vibration-damping coating film usually has a thickness of about 4 mm and is applied to a considerably wide area inside the vehicle body. Therefore, the weight of the coating film in the body weight is not negligible.
JP 58-187468 A (the whole specification) JP-A-62-230868 (full text) JP-A 63-10678 (the full specification) Japanese Unexamined Patent Publication No. 63-172777 (full description) JP 59-75954 A (the full description) JP 59-129213 A (the whole specification) JP 59-180617 A (the whole specification) JP-A-53-64287 (page 3, upper right column, line 8 to lower right column, seventh line, Example 1) JP-A-5-148446 (full description) JP-A-5-194906 (the whole specification) Japanese Patent Laid-Open No. 2-28269 (the full description) JP-A-57-167360 (Claims) Japanese Patent Laid-Open No. 58-141251 (Claims) JP-A-9-111132 (the full description)

  In order to reduce the weight of the chipping-resistant coating film and the vibration-damping coating film, which have contributed to the increase in the weight of the automobile body, the present inventors have improved the vibration-damping property of the chipping-resistant coating film itself. If improved, the thickness of the vibration-damping coating can be reduced, and the possibility of reducing the weight of these coatings as a whole can be reduced. Development research has been conducted to obtain an aqueous resin dispersion useful for the production of an aqueous coating composition having vibration properties.

As a result, the copolymer fine particles (A) dispersed in the aqueous medium are converted into the core-shell structure composite particles, that is, the core (A-1) in the range of 0 to 50 ° C., for example, 20 ° C. Conjugated with an acrylic-styrene copolymer having a glass transition temperature (Tg _A1 ) and a shell (A-2) having a glass transition temperature (Tg _A2 ) of 20 ° C. or lower such as −27 ° C. It was found that by forming with a diene copolymer, an aqueous resin dispersion capable of solving all of the above problems can be provided, and the present invention has been completed.

  Thus, according to the present invention, there is provided an aqueous resin dispersion containing copolymer fine particles (A) dispersed in an aqueous medium, wherein the copolymer fine particles (A) are acrylic-styrene copolymers. There is provided an aqueous resin dispersion characterized in that it is a composite particle composed of a core part (A-1) constituted by (1) and a shell part (A-2) constituted by a conjugated diene copolymer.

  The aqueous coating composition prepared using the aqueous resin dispersion of the present invention is excellent in various stability as a paint, flat and uniform coating film forming property, adhesion to a substrate such as a sheet metal part, water resistance In addition to being balanced with various properties as a chipping-resistant coating material such as gasoline resistance, impact resistance, soundproofing, and low-temperature characteristics, it also has vibration damping properties over a wide temperature range. By reducing the thickness of the vibration-damping coating film provided in the vehicle, the weight of the automobile body can be reduced.

  Hereinafter, the aqueous resin dispersion of the present invention and the aqueous coating resin composition using the same will be described in more detail.

[Copolymer fine particles (A)]
The copolymer fine particles (A) contained in the aqueous resin dispersion of the present invention comprise a core (A-1) composed of an acrylic-styrene copolymer that occupies a relatively large portion of the particles, and the core. It is a composite particle consisting of a shell part (A-2) composed of a conjugated diene copolymer, comprising at least one layer outside the part (A-1) and occupying a relatively small part than the core part. The shell part (A-2) may cover the core part (A-1) in a substantially uniform layer shape. In some cases, the shell part (A-2) may be partially covered with, for example, a mesh shape or an island shape. Good. Furthermore, such a multilayer particle does not necessarily have a two-layer structure, and may have a three-layer structure or more having two or more shell portions as necessary.

In such copolymer fine particles (A) in the present invention, the glass transition temperature (Tg _A1 ) of the core (A-1) is 0 to 50 ° C., more preferably 0 to 30 ° C., particularly 5 to 25 ° C. It is preferable that it is the range of these. If the glass transition temperature (Tg _A1 ) of the copolymer forming the core (A-1) of the composite particles is equal to or lower than the upper limit, the coating composition using the aqueous resin dispersion obtained is baked at high temperature. It is preferable because the coating film obtained has excellent flexibility and has sufficient flexibility and excellent vibration damping characteristics on the low temperature side such as around 20 ° C. On the other hand, if the glass transition temperature (Tg _A1 ) is equal to or higher than the lower limit value, it has excellent damping characteristics in a wide temperature range including damping characteristics on the high temperature side such as around 60 ° C. of the coating film, Moreover, since it is excellent also in chipping resistance, it is preferable.

Further, the (average) glass transition temperature (Tg _A2 ) of the shell (A-2) of the copolymer constituting the copolymer fine particles (A) is 20 ° C. or less, particularly in the range of −50 to 0 ° C. It is preferable. When the glass transition temperature (Tg _A2 ) is within this temperature range, a coating composition having sufficient high-temperature bakeability can be obtained, and a coating film based on the coating composition has excellent vibration damping in a wide temperature range. It is preferable because of its characteristics.

The glass transition temperature (Tg _A1 ) of the copolymer forming the core (A-1) and the (average) glass transition temperature (Tg _A2 ) of the copolymer forming the shell (A-2) are: Based on the combination of repeating units (derived from monomers) constituting the core (A-1) and the shell (A-2), that is, the core (A-1) and the shell (A- Based on the monomer composition of the copolymer forming 2), it can be obtained by the following calculation formula (1). However, when the shell part (A-2) has two or more layers, the shell part (A-2) as a whole has the weighted average value of the monomer composition of each copolymer forming each layer. The average glass transition temperature (Tg _A2 ) is obtained based on this.
Calculation of glass transition temperature (Tg):

Here _{Tg 1,} Tg 2 ...... and Tg _n Component 1 has a glass transition temperature of component 2 ...... and component n respectively homopolymers and converted to the absolute temperature calculation . m ₁ , m ₂ ... and _mn are molar fractions of the respective components.

  The “glass transition temperature of the homopolymer” referred to in the present specification includes “L. E. The glass transition point of the monomer described in Nielsen, translated by Nojiharu Onoki, “Mechanical properties of polymers”, pages 11 to 35, is applied.

  In the present invention, the proportion of the shell part (A-2) in the copolymer fine particles (A) is not necessarily limited, but based on 100% by weight of the polymer fine particles (A), In general, it is preferably in the range of 5 to 40% by weight, preferably 10 to 50% by weight, and more preferably 15 to 40% by weight. If the ratio of the shell part (A-2) is less than or equal to the upper limit value, the production is easy, and the coating film based on the obtained coating composition is preferable because it can exhibit excellent vibration damping characteristics in a wide temperature range. If it is more than a lower limit, it will work effectively as composite particles, and the coating composition has sufficient high-temperature bakeability, which is preferable.

[Core (A-1)]
In the aqueous resin dispersion of the present invention, the acrylic-styrene copolymer constituting the core (A-1) of the copolymer fine particles (A) is not necessarily limited, but the following monomer (a ₁₎ it is preferably a copolymer of ~ _{(a 4).}

(A ₁₁ ) The following general formula (1),
H ₂ C = CHCOOR ¹ (1)
(However, in the formula, R ¹ represents a linear or branched alkyl group having 4 to 12 carbon atoms.)
An acrylic ester whose homopolymer has a glass transition point of −40 ° C. or lower,
_{(A 12)} styrene,
_{(A 13)} of 3 to 5 carbon atoms alpha, beta-unsaturated mono- - or di - carboxylic acid,
_{(A 14)} the following general formula (2),
H ₂ C = CR ² COOR ³ (2)
(In the formula, R ² represents hydrogen or a methyl group, R ³ represents a linear or branched alkyl group having 1 to 20 carbon atoms, an alkenyl group, a cycloalkyl group, an aryl group, or an aralkyl group)
A monomer other than the above (a ₁₁ ) represented by:

Examples of the acrylic acid ester having a homopolymer having a glass transition temperature of −40 ° C. or lower as the monomer (a ₁₁ ) include n-butyl acrylate, n-pentyl acrylate, i-pentyl acrylate, and n- Examples include hexyl acrylate, n-octyl acrylate, i-octyl acrylate, 2-ethylhexyl acrylate, n-nonyl acrylate, i-nonyl acrylate, and n-decyl acrylate.

The proportion of the monomer (a ₁₁ ) in the total 100% by weight of the monomers (a ₁₁ ) to (a ₁₄ ) is preferably 20 to 60% by weight, more preferably 25 to 55% by weight. It is good to be in the range. If the ratio is equal to or higher than the lower limit value, a coating film based on the resulting coating composition is preferable because it has sufficient flexibility. If the ratio is equal to or lower than the upper limit value, the coating film has sufficient vibration damping characteristics. This is preferable.

The proportion of the styrene as the monomer (a ₁₂ ) in the total 100% by weight of the monomers (a ₁₁ ) to (a ₁₄ ) is preferably 5 to 45% by weight, more preferably 10%. It should be in the range of ~ 35% by weight. If the ratio is equal to or higher than the lower limit, the resulting coating composition has sufficient high-temperature seizure properties, and if it is equal to or lower than the upper limit, a coating film based on the coating composition is wide. It is preferable because excellent damping characteristics can be expressed in the temperature range.

Examples of the monomer (a ₁₃ ), which is an α, β-unsaturated mono- or dicarboxylic acid having 3 to 5 carbon atoms (hereinafter sometimes referred to as ethylene-based carboxylic acid), include acrylic acid. Methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, citraconic acid, etc., but in addition to these, anhydrides of these ethylene-based carboxylic acids such as maleic anhydride; -Monoesters of divalent ethylene carboxylic acids such as butyl malate, mono-n-butyl fumarate, monoethyl itaconate; for example, these ethylene carboxylic acids or ethylene carboxylic acid mono esters such as sodium acrylate and ammonium methacrylate Examples include alkali metal salts or ammonium salts of esters, among which acrylic acid, Acrylic acid, the use of itaconic acid are preferred.

The proportion of the monomer (a ₁₃ ) in the total 100% by weight of the monomers (a ₁₁ ) to (a ₁₄ ) is preferably 0.3 to 5% by weight, more preferably 0.5%. It should be in the range of ˜3% by weight. If the ratio is equal to or higher than the lower limit value, it is preferable because the stability of the composite particles during the emulsion polymerization and the aqueous dispersion of the composite particles and the mechanical stability of the coating composition are good, If it is below an upper limit, since the coating stability at the time of coating of this coating composition is good, it is preferable.

Monomeric _{(a 14)} of the, as the monomer represented by monomer _{(a 11)} than in the general formula (2), such as methyl acrylate, ethyl acrylate, i- butyl acrylate, t - butyl acrylate, cyclohexyl acrylate, the monomer (a ₁₁₎ other than the acrylic acid ester monomers such as benzyl acrylate; for example, methyl methacrylate, ethyl methacrylate, n- butyl methacrylate, i- butyl methacrylate, t- butyl methacrylate , N-pentyl methacrylate, n-hexyl methacrylate, n-heptyl methacrylate, n-octyl methacrylate, i-octyl methacrylate, 2-ethylhexyl methacrylate, n-nonyl methacrylate, i-nonyl methacrylate, n-decyl methacrylate Can be mentioned (meth) acrylic acid esters and the like; Relate, n- dodecyl methacrylate, t-dodecyl methacrylate, cyclohexyl methacrylate, methacrylic acid ester monomers such as benzyl methacrylate.

The monomer _{(a 14),} the percentage of total of 100 wt% of the monomers _{(a 11) ~ (a 14} ) is preferably 5 to 65 wt%, more preferably 10 to 50 wt% It is good to be in the range. If the ratio is equal to or higher than the lower limit value, a coating film based on the coating composition obtained is preferable because it has sufficient vibration damping properties. If the ratio is equal to or lower than the upper limit value, the coating film has sufficient flexibility. Since it has, it is preferable.

[Shell (A-2)]
The copolymer fine particles (A) in the present invention include a core part (A-1) constituted by the acrylic-styrene copolymer described above and a shell part (A-2) constituted by a conjugated diene copolymer. It is a composite particle consisting of

As described above, the shell (A-2) is preferably composed of a conjugated diene copolymer having a glass transition temperature (Tg _A2 ) in the range of −50 to 0 ° C. The coalescence is the following monomers (a ₂₁ ) to (a ₂₃ ),
_{(A 21)} conjugated diene monomer,
(A ₂₂ ) Methacrylic acid ester monomer having a glass transition point of 40 ° C. or higher, vinyl cyanide monomer and / or aromatic vinyl monomer, and if necessary,
_{(A 23)} the monomers _{(a 21)} and _{(a 22)} and copolymerizable a, the monomer _{(a 21)} and _{(a 22)} other than the monomers,
More preferably, it is a copolymer of

Examples of the conjugated diene monomer (a ₂₁ ) include one or more monomers selected from butadiene, imprene, chloroprene, and the like, and butadiene is particularly preferable.

The proportion of the monomer (a ₂₁ ) in the total 100% by weight of the monomers (a ₂₁ ) to (a ₂₃ ) is preferably 20 to 70% by weight, more preferably 25 to 60% by weight. More preferably, it is in the range of 30 to 50% by weight. If the copolymerization amount is less than or equal to the upper limit value, a coating film having sufficient rubber elasticity is obtained, which is preferable. On the other hand, if the copolymerization amount is greater than or equal to the lower limit value, the adhesion force of the coating film to the substrate is sufficient. This is preferable.

In the essential monomer (a ₂₂ ), examples of the methacrylic acid ester monomer having a homopolymer having a glass transition point of 40 ° C. or higher include methyl methacrylate and the like. Examples thereof include acrylonitrile and methacrylonitrile, and examples of the aromatic vinyl monomer include styrene, α-methylstyrene, vinyltoluene, ethylvinylbenzene and the like. Of these monomers (a ₂₂ ), use of styrene and / or methyl methacrylate is preferred.

The monomer (a ₂₂ ) can be used alone or in combination of two or more. From the viewpoints of adhesion of the resulting coating film to the substrate and excellent rubber elasticity, there are two types. It is preferable to use in combination, and it is particularly preferable to use styrene and methyl methacrylate in combination. The ratio of styrene and methyl methacrylate used in combination is usually in the range of styrene / methyl methacrylate = 30/70 to 70/30, preferably 40/60 to 60/40.

The copolymerization amount of the monomer (a ₂₂ ) is generally 30 to 80% by weight, more preferably 40 to 75%, based on the total 100% by weight of the monomers (a ₂₁ ) to (a ₂₃ ). It is preferably in the range of wt%, particularly 50 to 70 wt%. If the copolymerization amount is less than or equal to the upper limit value, a coating film having sufficient rubber elasticity is obtained, which is preferable. Therefore, it is preferable.

The conjugated diene copolymer constituting the shell (A-2) of the composite particle in the present invention includes the conjugated diene monomer (a ₂₁ ), the methacrylic acid ester monomer, and the vinyl cyanide monomer described above. And / or an aromatic vinyl monomer (a ₂₂ ) as an essential monomer component, which can be further copolymerized with the monomers (a ₂₁ ) and (a ₂₂ ) as necessary. Monomers (a ₂₃ ) other than the monomers (a ₂₁ ) and (a ₂₂ ) [hereinafter sometimes referred to as optional monomer (a ₂₃ )] can be used in combination for copolymerization.

Examples of such an optional monomer (a ₂₃ ) include the following.
(1) Acrylic acid ester and methacrylic acid ester other than the monomer (a ₂₂ ): for example, methyl acrylate, ethyl acrylate, n-butyl acrylate, i-butyl acrylate, n-octyl acrylate, i-octyl acrylate, 2 -Carbon number of acrylic acid or methacrylic acid such as ethylhexyl acrylate, i-nonyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, n-hexyl methacrylate, n-octyl methacrylate, n-dodecyl methacrylate, etc. ~ 18 alkyl esters.

(2) In addition to one radical polymerizable unsaturated group, an unsaturated monomer containing at least one functional group: the same ethylenic carboxylic acid as exemplified in the monomer (a ₁₃ ); Amides such as acrylamide, methacrylamide, diacetone acrylamide, N-methylol acrylamide, N-methylol methacrylamide, Nn-butoxymethyl acrylamide, Ni-butoxymethyl acrylamide, N, N-dimethyl acrylamide, N-methyl acrylamide Group or substituted amide group-containing monomer; for example, aminoethyl acrylate, N, N-dimethylaminoethyl acrylate, N, N-diethylaminoethyl acrylate, N, N-dimethylaminoethyl methacrylate, N, N-diethylaminoethyl methacrylate, etc. Amino Or substituted amino group-containing monomer;

For example, hydroxyl group-containing monomers such as 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, allyl alcohol, methallyl alcohol, polyethylene glycol monoacrylate, polyethylene glycol monomethacrylate For example, 2-methoxyethyl acrylate, 2-ethoxyethyl acrylate, 2-n-butoxyethyl acrylate, 2-methoxyethoxyethyl acrylate, 2-ethoxyethoxyethyl acrylate, 2-n-butoxyethoxyethyl acrylate, 2-methoxyethyl Methacrylate, 2-ethoxyethyl methacrylate, 2-n-butoxyethyl methacrylate, 2-methoxyethoxyethyl methacrylate Acrylate, 2-ethoxyethoxy ethyl methacrylate, 2-n-butoxyethoxy ethyl methacrylate, methoxy polyethylene glycol monoacrylate, lower alkoxyl group-containing monomers such as methoxy polyethylene glycol monomethacrylate;

For example, epoxy group-containing monomers such as glycidyl acrylate, glycidyl methacrylate, glycidyl allyl ether, and glycidyl methallyl ether; mercapto group-containing monomers such as allyl mercaptan; , Vinyltriethoxysilane, vinyltri-n-propoxysilane, vinyltri-i-propoxysilane, vinyltri-n-butoxysilane, vinyltris (2-methoxyethoxy) silane, vinyltris (2-hydroxymethoxyethoxy) silane, vinyltriacetoxysilane , Vinyldiethoxysilanol, vinylethoxysiladiol, vinylmethyldiethoxysilane, vinyldimethylethoxysilane, vinylmethyldiacetoxysilane, Rutrimethoxysilane, allyltriethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-acryloxypropyltriethoxysilane, 3-methacryloxypropyltris (2-methoxyethoxy) silane, 3-methacryloxypropylmethyldiethoxysilane Monomers having silicon-containing groups such as 3-methacryloxypropyldimethylethoxysilane, 3-acryloxypropyldimethylmethoxysilane, 2-acrylamidoethyltriethoxysilane;

For example, divinylbenzene, diallyl phthalate, triallyl cyanurate, triallyl isocyanurate, ethylene glycol di (meth) acrylate, 1,2-propylene glycol di (meth) acrylate, 1,3-propylene glycol di (meth) acrylate, 2 such as 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, allyl (meth) acrylate, etc. A monomer having one or more radically polymerizable unsaturated groups;

The copolymerization amount of the comonomer (a ₂₃ ) described above is generally 0 to 20% by weight, more preferably 0 to 0% based on the total 100% by weight of the monomers (a ₂₁ ) to (a ₂₃ ). It is preferably 15% by weight, particularly in the range of 0 to 10% by weight. If the amount of copolymerization is less than or equal to the upper limit, it is preferable because the resulting coating has excellent rubber elasticity and substrate adhesion.

The method for producing the aqueous resin dispersion containing the copolymer fine particles (A) in the present invention described above is not particularly limited. For example, first, in the presence of a surfactant and / or a protective colloid. The core (A-1) -forming monomers (a ₁₁ ) to (a ₁₄ ) are emulsion-polymerized in an aqueous medium to obtain the core (A-1) of the copolymer fine particles (A). (First step polymerization), and then in the presence of the aqueous dispersion, if necessary, under a predetermined pressure, and further for forming the shell (A-2). A method in which the monomers (a ₂₁ ) to (a ₂₃ ) are added and further copolymerized (second stage polymerization) can be suitably employed.

The reaction temperature is usually about 30 to 100 ° C., preferably about 40 to 90 ° C. When the shell part is composed of two or more layers, the shell part first layer forming monomers (a ₂₁₁ ) to (a ₂₁₃ ) are added and (co) polymerized. The layer-forming monomers (a ₂₂₁ ) to (a ₂₂₃ ) are added and (co) polymerized, and composite particles having two or more shell parts can be produced by repeating this operation. In this case, values obtained by weighted averages of these shell-forming monomers (a ₂₁₁ ) to (a _2n1 ), (a ₂₁₂ ) to (a _2n2 ), and (a ₂₁₃ ) to (a _2n3 ) (A ₂₁₁ ) to (a ₂₁₃ ) are regarded as shell-forming monomers as a whole, assuming a copolymer based on this monomer composition (a ₂₁₁ ) to (a ₂₁₃ ), It is regarded as a copolymer that forms the shell (A-2).

  As the above surfactant, any type of surfactants of nonionic type, anionic type, cationic type or amphoteric type can be used.

  Examples of nonionic surfactants include polyoxyalkylene alkyl ethers such as polyoxyethylene lauryl ether and polyoxyethylene stearyl ether; for example, polyoxyalkylene alkyl such as polyoxyethylene octyl phenol ether and polyoxyethylene nonyl phenol ether Phenol ethers; for example, sorbitan fatty acid esters such as sorbitan monolaurate, sorbitan monostearate, sorbitan trioleate; for example, polyoxyalkylene sorbitan fatty acid esters such as polyoxyethylene sorbitan monolaurate; for example, polyoxyethylene Polyoxyalkylene fatty acid esters such as monolaurate and polyoxyethylene monostearate; for example, monoglyceride oleate Id, glycerin fatty acid esters such as monoglyceride stearate, polyoxyethylene distyrenated phenols, polyoxyethylene-polyoxypropylene block copolymers; and the like.

  Examples of the anionic surfactant include fatty acid salts such as sodium stearate, sodium oleate, and sodium laurate; alkyl aryl sulfone hydrochlorides such as sodium dodecylbenzene sulfonate; and alkyl sulfates such as sodium lauryl sulfate. Ester salts: alkyl sulfosuccinic acid ester salts such as sodium monooctyl sulfosuccinate, sodium dioctyl sulfosuccinate, sodium polyoxyethylene lauryl sulfosuccinate and derivatives thereof; for example, polyoxyalkylene alkyl such as sodium polyoxyethylene lauryl ether sulfate Ether sulfate ester salts; for example, polyoxyalkylene alkyl aryl ethers such as sodium polyoxyethylene nonylphenol ether sulfate It can be exemplified alkyl sulfate ester salts of diphenyl such like; le sulfate ester salts, polyoxyethylene distyrenated sulfates of phenol.

  Examples of the cationic surfactant include alkylamine salts such as laurylamine acetate; quaternary ammonium salts such as lauryltrimethylammonium chloride and alkylbenzyldimethylammonium chloride; polyoxyethylalkylamine; and the like. Furthermore, examples of amphoteric surfactants include alkyl betaines such as lauryl betaine.

  Further, a part of hydrogen of the alkyl group of these surfactants is substituted with fluorine; a so-called reactive surfactant having a radical copolymerizable unsaturated bond in the molecular structure of these surfactants; Can be used.

  Among these surfactants, non-ionic surfactants include polyoxyalkylene alkyl ethers, polyoxyalkylene alkyl phenol ethers; and anionic interfaces from the viewpoint of less aggregate formation during emulsion polymerization. As the activator, alkyl aryl sulfonates, alkyl sulfates, alkyl sulfosuccinate esters and derivatives thereof, polyoxyalkylene alkyl ether sulfate salts, polyoxyalkylene alkyl phenol ether sulfate salts; and the like can be used. preferable. These surfactants can be used alone or in appropriate combination.

  The amount of these surfactants used may vary depending on the type of surfactant used, etc., but is generally within the range of about 0.5 to about 10 parts by weight with respect to 100 parts by weight of the resulting polymer composite fine particles. The stability of aqueous emulsion polymerization, the storage stability of aqueous dispersions of the resulting copolymer fine particles (A), and the bases of metalworking members when used in aqueous coating compositions. From the viewpoint of excellent adhesion to the material, etc., it is preferably used in the range of about 1 to 6 parts by weight, particularly about 1 to 4 parts by weight.

  Examples of the protective colloid that can be used in the production of the aqueous dispersion of the copolymer fine particles (A) include polyvinyl alcohols such as partially saponified polyvinyl alcohol, fully saponified polyvinyl alcohol, and modified polyvinyl alcohol; , Cellulose derivatives such as hydroxyethylcellulose, hydroxypropylcellulose, carboxymethylcellulose salts; natural polysaccharides such as guar gum; and the like.

  The amount of these protective colloids to be used is not particularly limited, and can be changed depending on the type thereof. Usually, 0 to 3 parts by weight per 100 parts by weight of the obtained copolymer fine particles (A). The amount of degree can be illustrated.

  The emulsion polymerization of the monomer component is performed using a polymerization initiator. Examples of the polymerization initiator that can be used include persulfates such as ammonium persulfate, sodium persulfate, and potassium persulfate; organic peroxides such as t-butyl hydroperoxide, cumene hydroperoxide, and p-menthane hydroperoxide. Hydrogen peroxide: and the like, and these may be used alone or in combination of two or more.

  The amount of the polymerization initiator used is not strictly limited and can be varied in a wide range depending on the type, reaction conditions, and the like, but generally 100 parts by weight of the obtained copolymer fine particles (A) Examples of the amount used are about 0.05 to 1 part by weight, more preferably about 0.1 to 0.7 part by weight, and particularly preferably about 0.1 to 0.5 part by weight.

  In the emulsion polymerization, a reducing agent can be used in combination as desired. Examples of the reducing agent that can be used include reducing organic compounds such as ascorbic acid, tartaric acid, citric acid, and glucose; for example, reducing inorganic compounds such as sodium thiosulfate, sodium sulfite, sodium bisulfite, and sodium metabisulfite. It can be illustrated. The amount of these reducing agents to be used is not particularly limited, but generally, the amount within about 0.05 to 1 part by weight is exemplified with respect to 100 parts by weight of the obtained copolymer fine particles (A). Can do.

  Furthermore, a chain transfer agent can be used as desired in the emulsion polymerization. Examples of such chain transfer agents include cyanoacetic acid; alkyl esters having 1 to 8 carbon atoms of cyanoacetic acid; bromoacetic acid; alkyl esters having 1 to 8 carbon atoms of bromoacetic acid; anthracene, phenanthrene, fluorene, 9 -Polycyclic aromatic compounds such as phenylfluorene; aromatic nitro compounds such as p-nitroaniline, nitrobenzene, dinitrobenzene, p-nitrobenzoic acid, p-nitrophenol, p-nitrotoluene; benzoquinone, 2, Benzoquinone derivatives such as 3,5,6-tetramethyl-p-benzoquinone; borane derivatives such as tributylborane; carbon tetrabromide, carbon tetrachloride, 1,1,2,2-tetrabromoethane, tribromoethylene, Trichloroethylene, bromotrichloromethane, tribromomethane, 3-chloro-1-propyl Halogenated hydrocarbons such as pens; Aldehydes such as chloral and furaldehyde; For example, alkyl mercaptans having 1 to 18 carbon atoms such as n-dodecyl mercaptan; Aromatic mercaptans such as thiophenol and toluene mercaptan; Mercaptoacetic acid; Mercapto Examples thereof include alkyl esters having 1 to 10 carbon atoms of acetic acid; hydroxyalkyl mercaptans having 1 to 12 carbon atoms such as 2-mercaptoethanol; terpenes such as binene and terpinolene.

  The amount of the chain transfer agent used is preferably in the range of about 0.005 to 3 parts by weight with respect to 100 parts by weight of the resulting copolymer fine particles (A).

  The aqueous resin dispersion in which the copolymer fine particles (A) formed by emulsion polymerization described above are dispersed is generally 10 to 70% by weight, preferably 30 to 60% by weight, and more preferably 40 to 60% by weight. %, And the viscosity is usually 10,000 mPa · s or less, particularly about 50 to 5,000 mPa · s (B-type rotational viscometer, 25 ° C., 20 rpm; the same applies hereinafter) ) Is desirable.

  Further, the average particle size of the copolymer fine particles (A) is such that the polymerization reactivity is good, the mechanical stability and storage stability of the resulting aqueous resin dispersion liquid, and the coating film formation when a coating composition is formed. From the viewpoint of good drying properties and good adhesion to the substrate of the resulting coating film, it is preferably 50 to 1000 nm, more preferably 100 to 800 nm, and particularly preferably 150 to 400 nm. preferable. The particle size of the copolymer fine particles (A) in the aqueous resin dispersion can be controlled by appropriately selecting, for example, the type and amount of the surfactant to be used and the polymerization temperature.

  In the present specification, the average particle diameter of the copolymer fine particles (A) is a value measured by a laser diffraction type particle size distribution measuring device, specifically “Master Sizer 2000” [manufactured by Sysmex Corporation]. ] Is a weight average diameter measured using

  The aqueous resin dispersion preferably has a pH of usually 2 to 10, particularly 5 to 9, and the pH can be adjusted using, for example, aqueous ammonia, an aqueous amine solution, or an aqueous alkali hydroxide solution.

(Aqueous coating composition)
As described above, the aqueous resin dispersion of the present invention described in detail above is used for, for example, an automotive sheet metal member such as the back of an automobile, a tire house, a gasoline tank, and the like. It is suitably used as an aqueous coating composition having both properties.

  Such an aqueous coating composition contains an inorganic filler (B) together with copolymer fine particles (A) which are composite particles dispersed in the aqueous resin dispersion.

  Examples of the inorganic filler (B) include inorganic solid powders that are substantially insoluble or hardly soluble in water, needle-like powders, fibrous powders, scaly and true spherical inorganic substances such as calcium carbonate, silica, alumina, and kaolin. Clay, talc, diatomaceous earth, pearlite, aluminum hydroxide, glass powder, barium sulfate, magnesium carbonate, sepiolite, mica, wollastonite, zeolite and the like can be used. Moreover, what carried out the surface treatment of the said filler can also be used as needed. The blending amount of these inorganic fillers (B) can be varied in a wide range depending on the type and physical properties desired for the coating film, but the copolymer fine particles contained in the aqueous resin dispersion liquid Generally, it can be in the range of 100 to 390 parts by weight, preferably 110 to 350 parts by weight, and more preferably 120 to 300 parts by weight with respect to the total of 100 parts by weight of (A).

  The aqueous coating composition of the present invention may contain a rust preventive pigment and a color pigment as necessary.

  Examples of the anticorrosive pigment include red lead; for example, chromate metal salts such as zinc chromate, barium chromate, strontium chromate; for example, zinc phosphate, calcium phosphate, aluminum phosphate, titanium phosphate, silicon phosphate. Or metal phosphates such as ortho or condensed phosphates of these metals; for example, zinc molybdate, calcium molybdate, calcium calcium molybdate, potassium potassium molybdate, zinc potassium phosphomolybdate, calcium potassium phosphomolybdate Examples thereof include metal molybdates such as calcium borate, zinc borate, barium borate, barium metaborate, calcium metaborate and the like. Of these rust preventive pigments, non-toxic or low-toxic rust preventive pigments such as metal phosphates, metal molybdates and metal borates are preferred.

  As a compounding quantity of a rust preventive pigment, it is 0-50 weight part with respect to a total of 100 weight part of copolymer fine particles (A) contained in aqueous resin dispersion liquid, Preferably it is the range of 5-30 weight part. It can be illustrated.

  Examples of the color pigment include organic or inorganic color pigments such as titanium oxide, carbon black, dial, Hansa Yellow, Benzidine Yellow, phthalocyanine blue, and quinacridone red. The blending amount of these color pigments is, for example, 0 to 10 parts by weight, preferably 0.5 to 5 parts by weight with respect to 100 parts by weight of the total copolymer fine particles (A) contained in the aqueous resin dispersion. A range can be illustrated.

  The particle diameters of these inorganic fillers, rust preventive pigments and color pigments are preferably in the range of 10 to 50,000 nm from the viewpoint of the smoothness of the formed coating film of the resulting aqueous coating composition. .

  The aqueous coating composition of the present invention may further contain various additives used in ordinary aqueous paints as necessary. Such additives include lightening agents, viscosity or viscosity modifiers, organic solvents such as dispersants, antifoaming agents, fusion aids, anti-aging agents, preservatives / antifungal agents, UV absorbers, antistatic agents. An agent or the like can be added and mixed.

  Examples of the further additive include lightening agents such as shirasu balloon, glass balloon, and resin balloon; viscosity or viscosity modifiers such as bentonite, polyvinyl alcohol, cellulose derivatives, polycarboxylic acid resins, and surfactants. For example, inorganic dispersants such as sodium hexametaphosphate and sodium tripolyphosphate; organic dispersants such as “NOBCOSPERS 44C” [trade name, polycarboxylic acid-based dispersant, manufactured by San Nobco Co., Ltd.]; ethylene glycol, butyl cellosolve, Organic solvents such as butyl carbitol and butyl carbitol acetate; antifoaming agents; anti-aging agents; antiseptics / antifungal agents; ultraviolet absorbers; antistatic agents;

  The aqueous coating composition of the present invention may be abbreviated as PWC (hereinafter referred to as PWC) of the total pigment (total amount of the inorganic filler, coloring pigment, rust preventive pigment, etc.) in the coating film formed thereby. However, it is preferably 50 to 80% by weight, more preferably 55 to 77% by weight, and still more preferably 60 to 75% by weight. If the value of the PWC is not less than the lower limit value, the resulting coating composition has excellent high-temperature seizure properties, and is preferable because the coating film based on the coating composition has excellent strength and chipping resistance. If it is below the upper limit, the coating composition has excellent high-temperature bakeability, and the resulting coating film has excellent cold resistance, flexibility and chipping resistance, which is preferable.

  The aqueous coating composition of the present invention is not particularly limited, but is generally in the range of about 40 to 90% by weight, preferably about 50 to 85% by weight, particularly preferably about 60 to 80% by weight. The pH is usually in the range of 7-11, preferably 8-10, and in the range of about 3,000-100,000 mPa · s, preferably about 5,000-50,000 mPa · s. Can have viscosity.

  The substrate to which the aqueous coating composition of the present invention can be applied is not particularly limited, for example, a steel plate; for example, a lead-tin alloy plated steel plate (tan sheet steel plate), a tin plated steel plate, an aluminum plated steel plate , Various plated steel sheets such as lead-plated steel sheets, chrome-plated steel sheets, nickel-plated steel sheets; coated steel sheets (ED steel sheets) such as electrodeposition-coated steel sheets; and the like.

  The aqueous coating composition of the present invention can be applied by a coating method known per se, for example, brush coating, spray coating, roller coating, etc., but airless coating is generally preferred. The coating film thickness at that time varies depending on the use of the substrate, but is usually about 500 μm or more, and particularly within the range of about 1000 to 5000 μm. The coating film can be dried by natural drying, heat drying or the like.

Hereinafter, the present invention will be described more specifically with reference to Examples, Comparative Examples, and Production Examples.
In addition, preparation of the test piece used in an Example and a comparative example, and its test method are as follows.

(1) Preparation of test piece Steel plate (ED steel plate) electroplated with a cationic electrodeposition paint “U-600” manufactured by Nippon Paint Co., Ltd. on a steel plate for automobiles specified in JIS G-3141 (dimension 0. 8 mm × 100 mm × 200 mm) as a base material, and each of the aqueous coating compositions obtained by the following Examples and Comparative Examples is used by an airless spray coating method so that the dry coating film has a thickness of 500 μm. The sample was left to stand at room temperature for 10 minutes, dried at 80 ° C. for 20 minutes, and then dried at 120 ° C. for 60 minutes to prepare a test piece.

(2) Before reaching the adhesion test, the test piece produced in the item (1) is a depth that reaches the substrate at intervals of 2 mm from the coating surface in the vertical and horizontal directions using a gobang eye tester (manufactured by Suga Test Instruments Co., Ltd.). Including the cut line, 25 gobangs were made in 1 cm ² . A cellophane tape having a width of 24 mm (manufactured by Nichiban Co., Ltd.) was affixed to this goblin, and it was quickly peeled by 180 ° by hand. The remaining number of eyes is preferably 20 or more.

(3) Before the chipping resistance test The test piece prepared in (1) is allowed to stand for 16 hours under a constant temperature condition of about 25 ° C., and then at a depth reaching the substrate from the coating film surface using an office cutter. A cut of 10 mm length × 5 mm width was put in 4 cm ² . The test piece is fixed at an angle of 60 ° with respect to the horizontal surface, and the nut (M-4) is vertically oriented through a polyvinyl chloride pipe from 2m height to 25mmφ, facing the cut part of the coated surface. The nuts were continuously dropped, and the total weight of the nuts dropped when the base material substrate was exposed was evaluated.
The total weight of the nut showing chipping resistance is preferably 30 kg or more, more preferably 50 kg or more.

(4) Before the vibration damping test (1) In place of the ED steel plate, a beam (metal plate for measurement sample preparation attached to the damping material property evaluation system) is used so that the dry film thickness becomes 500 μm. A sample was prepared in the same manner as in the previous section (1) except that the sample was made to be 2000 μm, and in accordance with ASTM E756-83, a vibration damping material property evaluation system “DAMP TEST” was prepared. ”[Manufactured by Toyo Technica Co., Ltd.] was used to measure the loss factor (loss factor) at each temperature of 0 ° C., 20 ° C., 40 ° C. and 60 ° C. In addition, the measurement is processed by the 3 dB method, and the obtained data is converted into a frequency of 140 Hz.
The loss coefficient at each temperature is preferably 0.05 or more, more preferably 0.07 or more, and particularly preferably 0.10 or more.

(5) High-temperature seizure test (bullet limit film thickness)
In spray coating in the previous (1), change the thickness of the dry coating, apply for 10 minutes at room temperature, then immediately dry at 140 ° C. for 60 minutes, the maximum The film thickness was determined and used as the blister limit film thickness.
The swelling limit film thickness is preferably 1300 μm or more, and more preferably 1500 μm or more.

(6) Low-temperature flexibility Before the test piece prepared in (1) was allowed to stand at a constant temperature of about 25 ° C. for 16 hours and then left in a freezer at −30 ° C. for at least 2 hours. Subsequently, using a 25 mmφ metal pipe at an ambient temperature of −30 ° C., the state of the bent portion when the test piece was bent was visually confirmed and evaluated according to the following criteria.
◎ ・ ・ ・ No cracks at all.
○ ・ ・ ・ A very small crack.
Δ: A crack having a crack width of less than 1 mm enters.
X: A large crack having a crack width of 1 mm or more is formed.

(7) Comprehensive evaluation of chipping-resistant coating film and vibration-damping coating film Coating composition for forming chipping-resistant coating film on one side of the beam, which is a metal plate for measurement sample preparation attached to the damping material property evaluation system The object is coated by airless spray coating method so that the dry coating thickness is 1 mm, and dried in accordance with a conventional method so as not to cause a coating film defect to form a chipping-resistant coating film. On the other side, a coating composition for forming a vibration-damping coating film is similarly formed by changing the dry film thickness by an airless spray coating method to form a vibration-damping coating film to obtain a test piece. Using the obtained test piece, the loss factor at each temperature is measured by the method according to the vibration damping test in the previous section (4), and the vibration damping when the loss factor at each temperature is 0.10 or more. The thickness of the protective coating was determined, and the total weight of the chipping-resistant coating and the vibration-damping coating at that time was determined.

[Preparation of aqueous resin dispersion containing copolymer fine particles]
Example 1
In an autoclave equipped with a stirrer, a plurality of liquid and gas raw material supply devices, and a thermometer, 90 parts by weight of deionized water, 1 part by weight of sodium alkyldiphenyl ether disulfonate as a surfactant and polyoxyethylene lauryl ether (HLB about 16) 1 part by weight was charged and the temperature was raised to 70 ° C. while flowing nitrogen. Next, as a monomer for forming the core (core-forming monomer), 30.8 parts by weight of 2-ethylhexyl acrylate (EHA), which is the monomer (a ₁₁ ) (single core forming monomer) 44% by weight, based on the total 100% by weight of the body), styrene monomeric _{(a 12)} (St) 16.8 parts by weight (same 24 wt%), acrylic acid is a monomer _{(a 13)} (AA) A monomer mixed solution in which 1.4 parts by weight (2% by weight) and 21 parts by weight (30% by weight) of methyl methacrylate (MMA) as the monomer (a ₁₄ ) were uniformly mixed. From the first liquid raw material supply device, 6 parts by weight of a 5 wt% aqueous solution of ammonium persulfate (APS) as a polymerization initiator aqueous solution was continuously added from the second liquid raw material supply device over 3 hours, respectively, and then the same. Hold for 2 hours at temperature to form the core of composite fine particles Glass transition temperature (Tg _A1) an aqueous dispersion of an acrylic-styrenic copolymer of from about 20 ° C. to obtain a.

Subsequently, styrene (St) as a monomer (a ₂₂ ) 9 wt.% As a monomer (shell-forming monomer) for forming a shell in the acrylic-styrene copolymer aqueous dispersion. A monomer mixture obtained by uniformly mixing parts (30% by weight based on a total of 100% by weight of shell-forming monomers) and 9 parts by weight (30% by weight) of methyl methacrylate (MMA) as a first liquid From the raw material supply device, 12 parts by weight (40% by weight) of gaseous butadiene (Bd) as the monomer (a ₂₁ ) is supplied from the gas raw material supply device, and 2 parts by weight of 5% by weight aqueous solution of APS is added to the second material. From the liquid raw material supply apparatus, each is continuously added over 1 hour to form a shell portion having a glass transition temperature (Tg _A2 ) of about −27 ° C., and then aging at the same temperature for 4 hours. Adjust the pH to 7-8 and steam steam Unreacted monomer was removed to obtain an aqueous dispersion of a copolymer particles are composite particles by adding an appropriate amount water by. The obtained aqueous dispersion of copolymer fine particles had a solid content of 50.2% by weight, a pH of 7.5, a viscosity of 140 mPa · s, and an average particle size of 210 nm.

Examples 2-7
In Example 1, instead of using 44 parts by weight of EHA and 30 parts by weight of MMA as the core-forming monomer, the use ratio of these monomers is changed as shown in Table 1, or the monomer (a ₁₁ ) The polymerization is carried out in the same manner as in Example 1 except that butyl acrylate (BA) is used instead of EHA and the amount used is changed, and the glass transition temperature (Tg _A1 ) for forming the core of the copolymer fine particles is different. Except for obtaining an aqueous dispersion of an acrylic / styrene copolymer, an aqueous dispersion of copolymer fine particles as composite particles was obtained in the same manner as in Example 1.

  Table 1 shows the composition of each core and shell of the obtained copolymer fine particles, the Tg, and the ratio of the shell to the copolymer fine particles, and the solid content of the aqueous dispersion of the obtained copolymer fine particles Table 2 shows the pH, viscosity, and average particle size.

Examples 8-11
In Example 1, instead of using 40 parts by weight of Bd, 30 parts by weight of St, and 30 parts by weight of MMA as the shell-forming monomer, it was produced except that the monomers shown in Table 1 were used in the amounts shown in Table 1. Polymerization was carried out in the same manner as in Example 1 to obtain aqueous dispersions of copolymer fine particles having different glass transition temperatures (Tg _A2 ) forming shells of the copolymer fine particles.

  Table 1 shows the composition of each core and shell of the obtained copolymer fine particles, the Tg, and the ratio of the shell to the copolymer fine particles, and the solid content of the aqueous dispersion of the obtained copolymer fine particles Table 2 shows the pH, viscosity, and average particle size.

Examples 12-15
In Example 1, instead of using the core-forming monomer and shell-forming monomer having the same composition as in Example 1 and setting the proportion of the core in the copolymer fine particles to 70% by weight, Table 1 Accordingly, the addition time of the 5 wt.% APS aqueous solution of the mixed solution of the core-forming monomer and 4 wt. Parts of the 5 wt.% APS aqueous solution and the mixed solution of the shell-forming monomer is changed accordingly. An aqueous dispersion of copolymer fine particles as composite particles is obtained in the same manner as in Example 1 except that the copolymer for forming the core and the copolymer for forming the shell are respectively polymerized by appropriately changing. It was.

  Table 1 shows the composition of each core and shell of the obtained copolymer fine particles, the Tg, and the ratio of the shell to the copolymer fine particles, and the solid content of the aqueous dispersion of the obtained copolymer fine particles Table 2 shows the pH, viscosity, and average particle size.

Comparative Example 1
A reaction vessel equipped with a stirrer, reflux condenser and thermometer was charged with 90 parts by weight of deionized water, 1 part by weight of sodium alkyldiphenyl ether disulfonate as a surfactant and 1 part by weight of polyoxyethylene lauryl ether (HLB about 16). The temperature was raised to 70 ° C. while flowing nitrogen. Next, as a monomer for forming the core (core forming monomer), 30.8 parts by weight of EHA as the monomer (a ₁₁ ) (total 100% by weight of the core forming monomer) 44 wt%), St 16.8 parts by weight of monomer (a ₁₂ ) (24 wt%), AA 1.4 parts by weight of monomer (a ₁₃ ) (2 wt%), and A monomer mixed solution in which 21 parts by weight (30% by weight) of MMA as a monomer (a ₁₄ ) was uniformly mixed and 6 parts by weight of a 5% by weight aqueous solution of APS as a polymerization initiator aqueous solution continuously over 3 hours. Then, an aqueous dispersion of an acrylic / styrene copolymer having a glass transition temperature (Tg _A1 ) of about 20 ° C., which forms the core of the composite fine particles, was maintained at the same temperature for 2 hours.

Next, in the aqueous dispersion of the acrylic / styrene copolymer, as a monomer (shell forming monomer) for forming the shell, 3.6 parts by weight of the monomer (a ₂₂ ) St ( 12 parts by weight based on a total of 100% by weight of the shell-forming monomer) and 3.6 parts by weight (12% by weight) of MMA, and 22.8 parts by weight of BA (76% by weight) as the monomer (a ₂₃ ). %)) And a 2% by weight aqueous solution of APS in an amount of 2 parts by weight are continuously added over 1 hour to form a shell having a glass transition temperature (Tg _A2 ) of about −28 ° C. Then, after aging for 4 hours at the same temperature, the pH is adjusted to 7-8 with an aqueous caustic soda solution, unreacted monomers are removed by steam distillation, and an appropriate amount of water is added to form composite particles. An aqueous dispersion of certain copolymer fine particles was obtained. The obtained aqueous dispersion of copolymer fine particles had a solid content of 50.1% by weight, a pH of 7.3, a viscosity of 160 mPa · s, and an average particle size of 220 nm.

Reference example 1
A reaction vessel similar to that used in Comparative Example 1 was charged with 90 parts by weight of deionized water, 1 part by weight of sodium alkyldiphenyl ether disulfonate and 1 part by weight of polyoxyethylene lauryl ether (HLB about 16) as a surfactant, and a nitrogen flow. The temperature was raised to 70 ° C. Next, a monomer mixed solution in which 44 parts by weight of EHA, 24 parts by weight of St, 2 parts by weight of AA and 30 parts by weight of MMA were uniformly mixed as a monomer, and 8 parts by weight of a 5% by weight aqueous solution of APS as a polymerization initiator aqueous solution. Was continuously added over 4 hours, and then kept at the same temperature for 2 hours to obtain an aqueous dispersion of acrylic / styrene copolymer fine particles having a glass transition temperature of about 20 ° C., which is homogeneous particles. The obtained aqueous dispersion of copolymer fine particles had a solid content of 50.1% by weight, a pH of 7.3, a viscosity of 160 mPa · s, and an average particle size of 220 nm.

Reference example 2
In Reference Example 1, an aqueous dispersion of an acrylic copolymer having a glass transition temperature of about −28 ° C., which is a homogeneous particle, in the same manner as in Reference Example 1 except that the composition of the monomer was changed as shown in Table 1. Fine particles were obtained. The obtained aqueous dispersion of copolymer fine particles had a solid content of 50.2% by weight, a pH of 7.2, a viscosity of 120 mPa · s, and an average particle size of 250 nm.

In addition, the symbol of the monomer used in Table 1 is as follows.
EHA: 2-ethyl hexyl acrylate BA: n-butyl acrylate MMA: methyl methacrylate St: Styrene AA: acrylic acid Bd: butadiene

[Production of aqueous coating composition]

Example 21
199.2 parts by weight (about 100 parts by weight in solid content) of the copolymer fine particle aqueous dispersion of Example 1 which is a composite particle obtained by copolymerizing Bd in the shell, and “NOBCOSPERS 44C” [San Nopco ( Co., Ltd., polycarboxylic acid-based dispersant] 2.0 parts by weight (approximately 0.88 parts by weight of solid content), “Nopco 8034L” (manufactured by San Nopco) 0.2 parts by weight as an antifoaming agent, inorganic filling 100 parts by weight of heavy calcium carbonate as an agent and 50 parts by weight of light calcium carbonate, 3 parts by weight of carbon black as a color pigment, and 7 parts by weight of barium metaborate as a rust preventive pigment are uniformly dispersed using a tisper, and then the interface Add 0.5 part by weight of “Adecanol UH-472” (manufactured by Asahi Denka Co., Ltd.) and 0.2 part by weight of “Nopco 8034L” as an activator-based thickener and further stir in the coating. The proportion of total pigment (total amount of calcium carbonate, carbon black and barium metaborate) occupied (hereinafter sometimes abbreviated as PWC) is about 62% by weight, the solid content is 71.6% by weight, and the viscosity is 8.9. Produced an aqueous coating composition having a viscosity of 24000 mPa · s.

  Using the obtained aqueous coating composition, various coating film physical properties tests were performed according to the above (1) to (6). Table 4 shows the measurement results of various coating film properties of the composition.

Examples 22 and 23
In Example 21, the amount of use of the inorganic filler, the color pigment and the rust preventive pigment was changed, and the amount of use of the dispersant, antifoaming agent and thickener was changed as necessary. Then, an aqueous coating composition was prepared and various coating film physical properties were tested. Table 3 shows the composition of the obtained aqueous coating composition and its characteristic values (PWC, solid content, pH and viscosity), and Table 4 shows the measurement results of various coating film properties.

Examples 24-28
In Example 21, instead of using the aqueous copolymer fine particle dispersion of Example 1, the glass transition temperature (Tg _A2 ) of the composite particle shell of Examples 2 to 7 is the same, and the glass transition of the composite particle core An aqueous coating composition was prepared and various coating properties were tested in the same manner as in Example 21, except that an aqueous dispersion of copolymer fine particles having different temperatures (Tg _A1 ) was used. Table 3 shows the composition and characteristic values of the coating composition, and Table 4 shows the measurement results of various coating film properties.

Examples 29-32
In Example 21, instead of using the aqueous dispersion of copolymer fine particles of Example 1, the glass transition temperature (Tg _A1 ) of the copolymer fine particle cores of Examples 8 to 11 is the same, and the copolymer fine particle shell is used. An aqueous coating composition was prepared and various coating film physical properties tests were conducted in the same manner as in Example 21 except that an aqueous dispersion of copolymer fine particles having different glass transition temperatures (Tg _A2 ) was used. Table 3 shows the composition and characteristic values of the coating composition, and Table 4 shows the measurement results of various coating film properties.

Examples 33-36
In Example 21, instead of using the aqueous copolymer fine particle dispersion of Example 1, the aqueous copolymer fine particle dispersions of Examples 12 to 15 prepared by changing the ratio of the core part and the shell part of the composite particles were used. An aqueous coating composition was prepared in the same manner as in Example 21 except that it was used, and various coating film physical properties tests were performed. Table 3 shows the composition and characteristic values of the coating composition, and Table 4 shows the measurement results of various coating film properties.

Comparative Example 21 and Reference Examples 21-22
In Example 21, instead of using the aqueous copolymer fine particle dispersion of Example 1, it is the aqueous copolymer fine particle dispersion of Comparative Example 1 or a homogeneous particle that is a composite particle that does not copolymerize Bd in the shell. An aqueous coating composition was prepared and various coating film physical properties tests were conducted in the same manner as in Example 21 except that the copolymer fine particle aqueous dispersion of Reference Example 1 or 2 was used. Table 3 shows the composition and characteristic values of the coating composition, and Table 4 shows the measurement results of various coating film properties.

[Comprehensive evaluation of anti-chipping coating and anti-vibration coating]
Example 41
According to the test methods (7), it was performed a comprehensive evaluation of the coating film and the vibration damping coating film for chipping. The composition prepared in Example 21 was used as both a coating composition for forming a chipping-resistant coating film and a coating composition for forming a vibration-damping coating film. The evaluation results are shown in Table 5.

Example 42
In Example 41, comprehensive evaluation was performed in the same manner as in Example 41 except that the film thickness of the vibration-damping coating film was made slightly thicker than Example 41. The evaluation results are shown in Table 5.

Example 43
In Example 41, overall evaluation was performed in the same manner as in Example 41 except that the composition prepared in Reference Example 21 was used only for the coating composition for forming the vibration-damping coating film. The evaluation results are shown in Table 5.

Comparative Example 41
In Example 41, 50 parts by weight of a polyvinyl chloride paste resin {manufactured by Kaneka Chemical Co., Ltd.} and 50 parts by weight of a blend resin {manufactured by Nippon Zeon Co., Ltd.} are used as coating compositions for forming a chipping-resistant coating film. Using a mixture of 100 parts by weight of dioctyl phthalate (DOP) as a plasticizer and 150 parts by weight of calcium carbonate (average particle size 10 μm) as a filler, baking is performed at 140 ° C. for 30 minutes, and a vibration-damping coating is applied. The overall evaluation was performed in the same manner as in Example 41 except that the coating composition for film formation was the composition prepared in Reference Example 21. The evaluation results are shown in Table 5.

Comparative Example 42
In Example 41, as the coating composition for forming a chipping-resistant coating film, the composition prepared in Reference Example 22 was used, and the coating composition for forming a vibration-damping coating film was prepared in Reference Example 21. The overall evaluation was performed in the same manner as in Example 41 except that was used. The evaluation results are shown in Table 5.

Claims (13)

An aqueous resin dispersion containing copolymer fine particles (A) dispersed in an aqueous medium, wherein the copolymer fine particles (A) are composed of an acrylic-styrene copolymer ( a-1) and Ri Oh composite particles consisting configured shell (a-2) by the conjugated diene copolymer,
The acrylic-styrene copolymer constituting the core (A-1) is the following monomers (a ₁₁ ) to (a ₁₄ ) [however, the total of the monomers (a ₁₁ ) to (a ₁₄ ) 100% by weight]
(A ₁₁ ) The following general formula (1),
H ₂ C = CHCOOR ¹ (1)
(In the formula, R ¹ represents a linear or branched alkyl group having 4 to 12 carbon atoms)
20 to 60% by weight of an acrylate ester represented by
_{(A 12)} styrene 5 to 45 wt%,
(A ₁₃ ) 0.3 to 5% by weight of an α, β-unsaturated mono- or di-carboxylic acid having 3 to 5 carbon atoms,
_{(A 14)} the following general formula (2),
H ₂ C = CR ² COOR ³ (2)
(In the formula, R ² represents hydrogen or a methyl group, R ³ represents a linear or branched alkyl group having 1 to 20 carbon atoms, an alkenyl group, a cycloalkyl group, an aryl group, or an aralkyl group)
In represented by the above _{(a 11)} a monomer 5-65% by weight of the non,
A copolymer of
Furthermore, the conjugated diene copolymer constituting the shell (A-2) is the following monomers (a ₂₁ ) to (a ₂₂ ),
_{(A 21)} a butadiene,
_{(A 22)} styrene and / or methyl methacrylate,
The aqueous resin dispersion, wherein the copolymer der Rukoto consisting. The shell portion conjugated diene copolymer constituting the (A-2) is, in claim 1, copolymer der wherein Rukoto consisting of those further containing a monomer (a ₂₃₎ n-Butyl acrylate The aqueous resin dispersion described . The aqueous resin dispersion according to claim 1 or 2 , wherein the glass-transition temperature (Tg _A1 ) of the acrylic-styrene copolymer constituting the core (A-1) is in the range of 0 to 50 ° C. The aqueous resin dispersion according to any one of claims 1 to 3, wherein the (average) glass transition temperature (Tg _A2 ) of the copolymer constituting the shell (A-2) is 20 ° C or lower. The aqueous resin dispersion according to any one of claims 1 to 3, wherein the (average) glass transition temperature (Tg _A2 ) of the copolymer constituting the shell (A-2) is in the range of -50 to 0 ° C. liquid. The weight ratio of the core portion constituting the copolymer particles (A) (A-1) / shell (A-2) is one of the 50 / 50-90 / 10 claims 1-5 is in the range of 1 The aqueous resin dispersion according to Item . The aqueous resin dispersion according to any one of claims 1 to 6, wherein the average particle size of the copolymer fine particles (A) is in the range of 150 to 400 nm. The aqueous resin dispersion according to any one of claims 1 to 7, wherein the copolymer fine particles (A) are formed by emulsion polymerization. An aqueous coating composition comprising the aqueous resin dispersion according to any one of claims 1 to 8 , which comprises copolymer fine particles (A) dispersed in an aqueous medium, and an inorganic filler (B). object. The inorganic filler (B) is made of calcium carbonate, silica, alumina, kaolin, clay, talc, diatomaceous earth, perlite, aluminum hydroxide, glass powder, barium sulfate, magnesium carbonate, sepiolite, mica, wollastonite, and zeolite. The aqueous coating composition according to claim 9, which is selected from: Aqueous coating composition further comprises red lead; metal chromate of zinc chromate, barium chromate, strontium chromate; zinc phosphate, calcium phosphate, aluminum phosphate, titanium phosphate, silicon phosphate metal phosphate Zinc molybdate, calcium molybdate, zinc molybdate, potassium potassium molybdate, zinc molybdate phosphate, calcium potassium molybdate phosphate; calcium borate, zinc borate, barium borate, barium metaborate, meta anticorrosive pigment and titanium oxide selected from the group consisting of boric acid metal salts of calcium borate, carbon black, red iron, Hansa Yellow, benzidine Yellow, phthalocyanine Blue, a coloring pigment selected from the group consisting of quinacridone red claim 9 or to 10 The aqueous coating composition of the mounting. The aqueous coating composition according to claim 11 , wherein the rust preventive pigment is selected from a metal phosphate, a metal molybdate and a metal borate. The proportion of the total pigment occupying in the coating film formed by the aqueous coating composition (anticorrosive pigment, inorganic filler and the total amount of the coloring pigment) (PWC) is claim is in the range of 50 to 80 wt% 9 The aqueous coating composition according to any one of -12 .