JP4691894B2 - Acrylic polymer aqueous dispersion and production method - Google Patents

Description

  The present invention relates to an aqueous acrylic polymer dispersion that can be used as a coating agent that forms a film having excellent low-temperature characteristics and excellent hardness at room temperature, and a method for producing the same.

  Conventionally, an acrylic polymer aqueous dispersion obtained by polymerizing (meth) acrylate is used as an acrylic emulsion binder in applications such as paints, adhesives, paper processing, and fiber processing. Since these acrylic polymer aqueous dispersions usually exist as polymer particles, they are formed into a film through a film-forming process by fusion between the polymer particles at the time of film formation. When trying to obtain it, since the polymer particles themselves are hard, there is a drawback that the fusion between the polymer particles at the time of film formation is not sufficient, and only a hard and brittle film is formed. In general, an acrylic polymer has a high temperature sensitivity, and even under a temperature condition equal to or higher than the glass transition temperature (referred to as “Tg”) of the polymer, a temperature that is lower than the glass transition temperature even if the film is somewhat flexible. It is known that the film becomes extremely hard and brittle under conditions.

  On the other hand, when the polymer particles are soft and the fusion between the polymer particles is facilitated, the hardness of the resulting coating is insufficient.

  In order to remedy these drawbacks, (1) a plasticizer that plasticizes the polymer (referred to as “film-forming aid”) is added to the hard polymer particles to improve the fusion between the polymer particles. And (2) improving the fusing property between polymer particles by making the particle morphology of the polymer particles “multi-layer structure particles” composed of a hard polymer and a soft polymer. Methods have been proposed.

  However, in the method (1) in which the plasticizer (film-forming aid) is added, the fusion property between the polymer particles is improved, but the polymer itself is plasticized immediately after coating. However, since it has flexibility, it is difficult to develop hardness, and since the plasticizer flows out over time, the properties of the film (hardness, flexibility, etc.) change over time. However, the disadvantage that the film becomes extremely hard and brittle under temperature conditions lower than the glass transition temperature of the polymer is not improved.

  In addition, the method of making the particle shape of the polymer particles of the method (2) into a multilayer structure particle composed of a hard polymer and a soft polymer is known in the art, and for example, has excellent low-temperature characteristics. A coating agent that forms a film having excellent hardness at normal temperature is disclosed (for example, see Patent Document 1). However, although the hardness at room temperature is relatively high, the flexibility at a low temperature is still insufficient and there is a problem in practical use.

JP 2003-147150 A

  Accordingly, an object of the present invention is to form a film having flexibility at low temperatures (−30 ° C.) and excellent hardness at normal temperatures (25 ° C.) when used as a coating agent or an adhesive. It is an object to provide an aqueous acrylic polymer dispersion that can be used.

  As a result of intensive studies, the present inventors have obtained the following knowledge in order to solve the above problems.

(1) In an acrylic polymer aqueous dispersion, an ethylenic polymer [A] having a glass transition temperature (measured Tg) containing a carboxyl group of −50 to −15 ° C. and the ethylenic polymer [A] And an ethylenic polymer [B] having a glass transition temperature (measured Tg) of 30 to 150 ° C. obtained by batch charging and polymerizing the monomer component (b) in an aqueous medium containing An acrylic polymer aqueous dispersion characterized by containing polymer particles [X] forms a film that is flexible at low temperatures (−30 ° C.) and excellent in hardness at normal temperatures (25 ° C.). can do.

  (2) As a method for producing the water-dispersible acrylic polymer of the above (1), a monomer component (a) having an ethylenically unsaturated monomer (a-1) containing a carboxyl group as an essential component In a reaction vessel in which an aqueous medium is present and polymerized, the acid value is 10 to 300 mgKOH / g, the weight average molecular weight is 100,000 or more, and the gel fraction is 95% by weight or less. In addition, a polymer [A] having a measured Tg of the polymer of −50 to −15 ° C. is obtained, and the measured Tg of the polymer is 30 to 150 ° C. in an aqueous medium in which the polymer [A] is present. It has been found that a method for producing an acrylic polymer aqueous dispersion characterized in that the ethylenically unsaturated monomer component (b) as described above is charged all at once and polymerized is simple and useful.

That is, in the present invention, the monomer component (a) containing the ethylenically unsaturated monomer (a-1) containing a carboxyl group as an essential component is charged all at once into a reaction vessel in which an aqueous medium is present. In an aqueous medium containing the ethylenic polymer [A] having a glass transition temperature (measured Tg) of −50 to −15 ° C. and containing the carboxyl group obtained by polymerization in the above-mentioned ethylenic polymer [A] The monomer component (b) containing methyl (meth) acrylate and butyl (meth) acrylate is charged all at once and polymerized, and does not have a carboxyl group and has a glass transition temperature (measured Tg) of 30 to 30. An acrylic polymer aqueous dispersion comprising polymer particles [X] containing an ethylenic polymer [B] at 150 ° C. , wherein the outermost particles of the polymer particles [X] The structure located in the shell is Providing an acrylic polymer aqueous dispersion, characterized in that a layer consisting of serial ethylenic polymer [A].

In the present invention, the monomer component (a) having an ethylenically unsaturated monomer (a-1) containing a carboxyl group as an essential component is charged all at once into a reaction vessel in which an aqueous medium is present. A polymer having an acid value of 10 to 300 mgKOH / g, a weight average molecular weight of 100,000 or more, a gel fraction of 95% by weight or less, and an actual measured Tg of the polymer of -50 to -15 ° C. [A] is obtained, and the monomer component (b) containing methyl (meth) acrylate and butyl (meth) acrylate is collectively charged and polymerized in an aqueous medium in which the polymer [A] is present. Production of Acrylic Polymer Aqueous Dispersion Containing Polymer Particles [X] Containing Ethylenic Polymer [B] having No Carboxyl Group and Glass Transition Temperature (Measured Tg) of 30 to 150 ° C. A method, wherein the polymer particles [ The structure located in the outermost shell of X] is a layer made of the ethylenic polymer [A], and also provides a method for producing an acrylic polymer aqueous dispersion.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the coating agent which forms the film excellent in the hardness at normal temperature, and the acrylic polymer aqueous dispersion used for this can be provided.

  The polymer particle [X] used in the present invention is composed of at least two layers of an A layer composed of the polymer [A] and a B layer composed of the polymer [B]. In particular, the layer structure is specified. For example, the A layer is used as a matrix, and the B layer exists in the A layer of the matrix as one lump or dispersed in a large number and exists in the A layer serving as a matrix. can give. More specifically, the “core-shell structure” in which the B layer is the core and the A layer is the shell, or the B layer is dispersed in a large number in the A layer, and the A layer is completely or incomplete. Or an inhomogeneous structure such as an interpenetrating network in which the polymers of the A and B layers form a number of discontinuous domains, or the A layer is dissolved or non-dissolved in an aqueous medium. Examples include a state where the particles are dispersed in a particle state, and the layer B is dispersed in the form of particles using the layer A as a matrix.

  In addition, even if layers having properties other than the A layer and the B layer are present in the polymer particles [X] within the range that does not inhibit the low temperature characteristics of the film and the expression of hardness at room temperature, which is the object of the present invention. Good.

  In any of these dispersed states, a particle form in which the A layer composed of the polymer [A] is present in the outermost shell portion of the polymer particles is preferable.

  Also, in the above configuration, the so-called “core-shell structure” in which the A layer and the B layer are concentric, or the B layer is dispersed in a large number in the A layer, and the A layer encapsulates the B layer. And the structure in which the A layer is located at the outermost shell part of the particle is preferable because it has excellent low-temperature characteristics and excellent hardness at room temperature.

  This morphological particle structure can be observed by various methods known in the art, but the observation with a scanning transmission electron microscope using a staining method emphasizes the difference between the layers. Is suitable. In addition, the particle structure can be confirmed also in a method of observing a cross section of a particle prepared using a cryomicrotome using an atomic force microscope (AFM).

  Further, in the acrylic polymer aqueous dispersion obtained by the production method of the present invention described later, the polymer [B] of the B layer is present in the polymer [A] of the A layer by observation with an electron microscope. Can be confirmed.

  In the acrylic polymer aqueous dispersion of the present invention, the polymer particles [X] dispersed in an aqueous medium are composed of at least two layers of an A layer and a B layer, and the A layer has a carboxyl group. And a monomer component (b) in an aqueous medium comprising a polymer [A] having a measured Tg of −50 to −15 ° C. and having a B layer in which the ethylenic polymer [A] is present. The polymer T is a polymer [B] having a measured Tg of 30 to 150 ° C., which is obtained by polymerizing and polymerizing all of the above, and a film formed from the acrylic polymer aqueous dispersion has a measurement temperature of −30 ° C. The elongation in the tensile test is 50% or more, and the Young's modulus in the tensile test at a measurement temperature of 25 ° C. is 20 MPa or more.

  The A layer is present in the outermost shell of the polymer particle [X], and is composed of a flexible polymer [A] having a glass transition temperature (measured Tg) of −50 to −15 ° C. Flexibility at −30 ° C.).

  The flexibility of the coating at a low temperature (−30 ° C.) is greatly affected by the glass transition temperature of the polymer [A], but the glass transition temperature (measured Tg) of the polymer [A] is preferably −15 ° C. or less. Then, the film formed from the polymer particles [X] has an elongation rate of 50% or more in a tensile test at a measurement temperature of −30 ° C., and a film excellent in flexibility is obtained. Furthermore, the measured Tg of the polymer [A] is more preferably −20 ° C. or less, and particularly preferably −30 ° C. or less because of excellent flexibility.

  On the other hand, the measured Tg of the polymer [A] is preferably −50 ° C. or higher and more preferably −40 ° C. or higher from the viewpoint of maintaining the hardness at normal temperature (25 ° C.).

  Here, the glass transition temperature (actually measured Tg) of the polymer and the elongation percentage in the tensile test at the measurement temperature of −30 ° C. are values measured by the methods shown in Examples described later.

  In addition, the polymer [A] is an ethylenic polymer [A] that has the above-described conditions and is obtained by batch polymerization of the monomer component (a) in an aqueous medium. Is preferable because the flexibility at a low temperature (−30 ° C.) is remarkably improved.

  The polymer [A] is a polymer containing a carboxyl group, and the carboxyl group of the polymer [A] is used for the purpose of (1) stably dispersing the polymer particles [X] in an aqueous medium. (2) It also acts as a crosslinkable reactive group with a functional group in the polymer [B] described later.

  Further, from the balance between the flexibility at low temperature and the hardness at normal temperature of the resulting coating, the polymer [A] constituting the A layer of the polymer particle [X] and the polymer [B] constituting the B layer The weight ratio is preferably [A] / [B] = 7/3 to 4/6 in terms of solid content, and [A] / [B] = 6/4 to 4 from the viewpoint of excellent hardness at room temperature. More preferably, it is / 6.

  The content of the carboxyl group in the polymer [A] constituting the A layer of the polymer particle [X] used in the present invention is not particularly limited, but in the aqueous medium of the polymer particle [X]. The acid value is preferably in the range of 10 to 300 mgKOH / g from the viewpoint of imparting a good balance of dispersion stability and water resistance of the coating.

  Further, the polymer particle [X] is composed of at least two layers of the A layer and the B layer as described above, and is a particle stabilized with the polymer [A] containing a carboxyl group. The acid value of the entire polymer particle [X] is preferably in the range of 5 to 100 from the viewpoint of dispersion stability of the polymer particle [X] and water resistance of the resulting film.

  Here, the acid value is a numerical value representing the amount of carboxyl group contained in the polymer [A] or the polymer particle [X], and is a free content contained in 1 g of the polymer [A] or the polymer particle [X]. This is the number of mg of potassium hydroxide required to neutralize the carboxyl group, and the measurement is carried out under the conditions shown in the examples described later.

  The molecular weight of the polymer [A] constituting the A layer of the polymer particles [X] used in the present invention is not particularly limited, but is preferably 100,000 or more in terms of weight average molecular weight. . When the weight average molecular weight is within such a range, it is possible to obtain a film having excellent low-temperature flexibility and water resistance, low tackiness, and difficult to block.

  The weight average molecular weight is a weight in terms of polystyrene determined by dissolving the polymer constituting the polymer [A] in a solvent (tetrahydrofuran) and measuring it by gel permeation chromatography (GPC method). The average molecular weight is shown, and the measurement is carried out under the conditions shown in the examples described later.

  The polymer [A] preferably has a weight average molecular weight of 100,000 or more. For example, in order to increase the molecular weight, the polymer [A] may be crosslinked three-dimensionally. The gel fraction represented by the acetone insoluble content of the carboxyl group-containing polymer [A] is preferably 95% by weight or less, and the gel fraction is 0% by weight (the acetone insoluble content is 0% by weight). However, it is preferably 5 to 95% by weight.

  That is, by making the gel fraction of the polymer [A] 95% by weight or less, the polymer [A] can be easily present in the outermost shell part of the polymer particle [X], and further described later. Monomer component (b) stability during polymerization is also improved, and the low-temperature properties of the resulting coating are good.

  The polymer [A] constituting the A layer of the polymer particle [X] used in the present invention reacts with a reactive functional group in the polymer [B] constituting the B layer described later, in addition to the carboxyl group. It is preferable that the A layer and the B layer are bonded to each other by the reactive functional group and the hardness and water resistance of the film at room temperature are improved.

  Specific examples of the reactive functional group other than the carboxyl group that can be introduced into the A layer include, for example, glycidyl group, hydroxyl group, amino group, methylolamide group, hydrolyzable silyl group or silanol group, aziridinyl group, and isocyanate. Group, block isocyanate group, oxazoline group, amide group, carbonyl group, acetoacetyl group, allyl group, cyclopentenyl group and the like.

  The reactive functional group in the A layer and the reactive functional group in the B layer may react during the production of the acrylic polymer aqueous dispersion and may be crosslinked in the polymer particle [X]. From the viewpoint of film forming property and hardness, it is preferable that the polymer particles before film formation remain uncrosslinked, and crosslink by reacting reactive functional groups at the time of film formation or after film formation. Forming a film is more preferable because various physical properties are remarkably improved.

  Next, the polymer [B] constituting the B layer of the polymer particle [X] used in the present invention is present inside the A layer of the polymer particle [X], and the measured Tg is 30 to 150 ° C. The rigid polymer [B], and the presence of the rigid polymer [B] inside the polymer particle [X] improves the hardness at room temperature while maintaining the low temperature characteristics of the coating. ing.

  The hardness of the coating at room temperature is greatly affected by the glass transition temperature of the polymer [B]. When the measured Tg is 30 ° C. or higher, the coating formed from the polymer particles [X] has a measurement temperature of 25 ° C. The Young's modulus in the tensile test at is 20 MPa or more, and a film having excellent hardness can be obtained. Furthermore, the measured Tg of the polymer [B] is preferably 35 ° C. or higher because of excellent hardness.

  Here, the Young's modulus in the tensile test at a measurement temperature of 25 ° C. is a value determined by measurement by the method shown in the examples described later.

  On the other hand, in order to maintain the flexibility of the coating film at a low temperature (−30 ° C.), the measured Tg of the polymer [B] is preferably 150 ° C. or less.

  In addition, the polymer [B] is an ethylenic polymer [B] that has the above-described conditions and is obtained by polymerizing the monomer component (b) in an aqueous medium. Is preferable because it maintains flexibility at a low temperature (−30 ° C.) and remarkably improves the hardness at normal temperature.

  The molecular weight of the polymer [B] used in the present invention is not particularly limited, but from the viewpoint of improving the hardness of the coating at room temperature (25 ° C.), the molecular weight of the polymer [B] is The average molecular weight is preferably 100,000 or more.

  The polymer [B] constituting the B layer of the polymer particle [X] used in the present invention contains a group having reactivity with the carboxyl group and other reactive functional groups of the polymer [A] in the A layer. When it is contained, the A layer and the B layer are preferably bonded to each other by the reactive group, and the hardness and water resistance of the film at room temperature are improved, and in particular, from the viewpoint of improving the water resistance of the film. It is preferable that the compound [B] contains a functional group having reactivity with a carboxyl group.

  Examples of the functional group having reactivity with the carboxyl group in the polymer [B] constituting the B layer of the polymer particle [X] used in the present invention include, for example, a glycidyl group, a methylolamide group, an aziridinyl group, an isocyanate. Group, block isocyanate group, oxazoline group and the like are mentioned, and particularly when a glycidyl group is introduced, the effect of improving the water resistance of the film is high, which is preferable.

  Further, the polymer [B] constituting the B layer has reactivity with a reactive functional group other than the carboxyl group of the polymer [A] in the A layer, and has reactivity with the carboxyl group. Reactive functional groups (hereinafter abbreviated as “non-reactive functional groups with carboxyl groups”) may be introduced. Specifically, for example, hydroxyl groups, amino groups, amide groups, carbonyl groups, hydrolyzable groups Examples thereof include a silyl group or silanol group, an acetoacetyl group, an allyl group, and a cyclopentenyl group.

  As a combination with the reactive functional group present in the polymer [A] constituting the A layer and the polymer [B] constituting the B layer, for example, the following combinations are considered to be reactive with each other. It is preferable from an excellent point.

That is, a combination of a carboxyl group in the A layer and a glycidyl group, a methylolamide group, an aziridinyl group, an isocyanate group, a block isocyanate group, and an oxazoline group in the B layer; a glycidyl group in the A layer and a B layer A combination of amino group, methylolamide group, acetoacetyl group, hydrolyzable silyl group or silanol group; hydroxyl group in layer A, methylolamide group, isocyanate group, block isocyanate group in layer B, hydrolysis A combination of a functional silyl group or a silanol group; a combination of an amino group in the A layer and a glycidyl group or an acetoacetyl group in the B layer; a methylolamide group in the A layer, a methylolamide group or a hydroxyl group in the B layer , Glycidyl group, isocyanate group, block isocyanate group, amide group, acetoacetyl group Combination of hydrolyzable silyl group or silanol group; combination of hydrolyzable silyl group or silanol group in layer A and hydroxyl group, methylolamide group, glycidyl group, hydrolyzable silyl group or silanol group in layer B ;
Combination of isocyanate group in layer A and hydroxyl group, methylolamide group, glycidyl group, acetoacetyl group in layer B; amide group in layer A, methylolamide group, acetoacetyl group in layer B Combination: A combination of an acetoacetyl group in layer A and an amino group, methylolamide group, glycidyl group, isocyanate group in layer B; a cyclopentenyl group in layer A and a cyclopentenyl group in layer B Combination; combination of allyl group in layer A and allyl group in layer B; or a combination of two or more of these may be used.

  Among the above combinations, a combination of a carboxyl group in the A layer and a glycidyl group, a methylolamide group, an aziridinyl group, an isocyanate group, a block isocyanate group, and an oxazoline group in the B layer; A combination of a decomposable silyl group or silanol group and a hydroxyl group, methylolamide group, glycidyl group, hydrolyzable silyl group or silanol group in layer B, and various physical properties such as hardness and water resistance at room temperature of the resulting film Is significantly improved.

  The reactive functional group in the above-mentioned A layer and the reactive functional group in the B layer may react during the production of the acrylic polymer aqueous dispersion and may be crosslinked in the polymer particle [X]. From the viewpoint of film-forming properties and hardness of the film, it is preferable that the polymer particles before film formation remain uncrosslinked, by reacting reactive functional groups at the time of film formation or after film formation, It is more preferable to form a cross-linked film because various properties such as hardness at normal temperature and water resistance are further improved.

  The particle diameter of the polymer particles [X] constituting the acrylic polymer aqueous dispersion of the present invention is not particularly limited, but the particle diameter (50% median diameter on a volume basis) is 100 to 1500 nm. It is preferable that it is excellent in drying property at the time of film formation.

  Further, the solid content concentration of the acrylic polymer aqueous dispersion is not particularly limited, but it is preferable that the solid content concentration is 40% by weight or more from the viewpoint of excellent drying property during film formation.

  The acrylic polymer aqueous dispersion of the present invention itself forms a film having excellent low-temperature characteristics and excellent hardness and water resistance at room temperature by room temperature or heat drying. Water-soluble or water-dispersible cross-linking agents can be added and used. Examples of cross-linking agents include polyfunctional melamine compounds, polyfunctional polyamine compounds, polyfunctional polyethylenimine compounds, polyfunctional (block) An isocyanate compound, a polyfunctional hydrazine compound, a metal salt compound, etc. are mentioned, These can be used as 1 type, or 2 or more types of mixtures.

  In addition to the cross-linking agent, a water-soluble or water-dispersible thermosetting resin such as a phenol resin, a urea resin, a melamine resin, or a urethane resin can also be mixed and used.

  Furthermore, if necessary, the filler, pigment, pH adjuster, film forming aid, leveling agent, thickener, water repellent, antifoaming agent and the like are known as long as the desired effects of the present invention are not impaired. A thing can be appropriately added and used.

  In the method for producing an aqueous acrylic polymer dispersion of the present invention, it is preferable to increase the molecular weight of the polymer [A] and the polymer [B] in order to develop desired low-temperature characteristics and hardness of the coating film. For that purpose, it is preferably produced by the production method of the present invention described in detail below. Moreover, according to the method for producing an aqueous polymer dispersion of the present invention, it is effective in improving the storage stability and productivity of the aqueous acrylic polymer dispersion.

  That is, in the method for producing an aqueous acrylic polymer dispersion of the present invention, a monomer component (a) containing an ethylenically unsaturated monomer (a-1) containing a carboxyl group as an essential component is used as an aqueous solution. The reaction vessel containing the medium is charged in a batch and polymerized, the acid value is 10 to 300 mgKOH / g, the weight average molecular weight is 100,000 or more, the gel fraction is 95% by weight or less, and A polymer [A] having a measured Tg of the polymer of −50 to −15 ° C. is obtained, and an ethylenic polymer having a measured Tg of 30 to 150 ° C. in an aqueous medium in which the polymer [A] is present. A method for producing an aqueous dispersion of an acrylic polymer, wherein the unsaturated monomer component (b) is charged in a batch and polymerized.

  The properties of the polymer [A] in the aqueous medium when producing the polymer particles [X] in the method for producing an aqueous polymer dispersion of the present invention are not particularly limited, and the polymer [A] is an aqueous medium. In the case where it is completely dissolved, in the case of being semi-solubilized in an aqueous medium, or in the case of being dispersed as particles in an aqueous medium, etc. In order to improve hardness and further improve various physical properties such as water resistance, it is preferable to suppress the acid value of the polymer [A] as low as possible and to increase the molecular weight, specifically, the weight average molecular weight. Is preferably 100,000 or more. In order for the polymer [A] having such characteristics to exist stably in an aqueous medium, the polymer [A] is preferably dispersed as particles in the aqueous medium.

  In the present invention, the particle diameter (50% median diameter on a volume basis) of the polymer [A] dispersed as particles in the aqueous medium is not particularly limited, but an ethylenically unsaturated monomer described later is used. The particle diameter (50% median diameter on a volume basis) should be in the range of 10 to 1000 nm from the viewpoints of stability during polymerization of the body component (b) and film forming properties of the finally obtained film. preferable.

  In the present invention, as a method for producing the polymer [A] in an aqueous medium, the monomer component (a) having the carboxyl group-containing ethylenically unsaturated monomer component (a-1) as an essential component, A method in which a reaction vessel containing an aqueous medium is charged in a batch and polymerized is preferable because the resulting acrylic polymer aqueous dispersion is excellent in flexibility at low temperatures.

  Further, when the polymer [A] is produced in an aqueous medium, the step of dispersing the polymer [A] in the aqueous medium can be omitted, and the production process of the polymer [A] and the monomer component (b) Since a polymerization process can be performed continuously, it is preferable also from the point which can simplify a manufacturing process.

  In the present invention, the monomer component (a) used when polymerizing the polymer [A] in an aqueous medium contains the carboxyl group-containing ethylenically unsaturated monomer (a-1) as an essential component. The carboxyl group-containing ethylenically unsaturated monomer (a-1) is not particularly limited as long as it has a carboxyl group and an ethylenically unsaturated group in the molecule. For example, acrylic acid, methacrylic acid, β- Carboxyethyl (meth) acrylate, 2- (meth) acryloylpropionic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, itaconic acid half ester, maleic acid half ester, maleic anhydride, itaconic anhydride, β- (meta ) Acryloyloxyethyl hydrogen succinate, β- (meth) hydroxyethyl hydrogen phthalate and their salts Is, it is possible to use one kind of them or a mixture of two or more. Among these, methacrylic acid is particularly preferable as the carboxyl group-containing ethylenically unsaturated monomer because the monomer component (b) is excellent in stability during polymerization.

  As the monomer component (a) used in the present invention, in addition to the above-mentioned carboxyl group-containing ethylenically unsaturated monomer (a-1), other ethylenically unsaturated monomers (a-2) By polymerizing in combination, the polymer [A] in which the glass transition temperature (−50 to −15 ° C.) and the acid value of the polymer are adjusted to the above-described preferable ranges can be obtained.

  The other ethylenically unsaturated monomer (a-2) is not particularly limited as long as it is copolymerizable with the ethylenically unsaturated monomer (a-1). ) Acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, iso-butyl (meth) acrylate, t-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, hexyl (meth) acrylate, cyclohexyl (meth) ) Acrylate, octyl (meth) acrylate, nonyl (meth) acrylate, dodecyl (meth) acrylate, stearyl (meth) acrylate, isobornyl (meth) acrylate, dicyclopentanyl (meth) acrylate, phenyl (meth) acrylate, benzyl ( (Meth) acrylates such as (meth) acrylate 2,2,2-trifluoroethyl (meth) acrylate, 2,2,3,3-pentafluoropropyl (meth) acrylate, perfluorocyclohexyl (meth) acrylate, 2,2,3,3 , -Tetrafluoropropyl (meth) acrylate, β- (perfluorooctyl) ethyl (meth) acrylate and other fluorine-containing vinyl monomers; vinyl acetates such as vinyl acetate, vinyl propionate, vinyl butyrate and vinyl versatate Vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, butyl vinyl ether, amyl vinyl ether and hexyl vinyl ether; nitriles of unsaturated carboxylic acids such as (meth) acrylonitrile; styrene, α-methylstyrene, vinyl Vinyl compounds having an aromatic ring such as ene, vinylanisole, α-halostyrene, vinylnaphthalene, divinylstyrene; isoprene, chloroprene, butadiene, ethylene, tetrafluoroethylene, vinylidene fluoride, N-vinylpyrrolidone, and the like. One kind or a mixture of two kinds or more can be used. Among these, (meth) acrylic acid esters are preferred because polymerization is particularly easy and adjustment of the glass transition temperature of the polymer is easy.

  In the present invention, in order to obtain a polymer [A] having a desired glass transition temperature (that is, a measured Tg in the range of −50 to −15 ° C.), a long-chain alkyl having 4 to 12 carbon atoms in the alkyl group. It is preferable to use (meth) acrylic acid esters containing a group.

  In the present invention, as the other ethylenically unsaturated monomer in the monomer component (a), an ethylenically unsaturated monomer having a reactive functional group other than a carboxyl group together with the above-described monomer. Since the polymer (a-3) is used in combination with the reactive functional group in the ethylenic polymer [B] forming the B layer described later, various physical properties such as water resistance are improved. ,preferable.

  When the reactive functional group of the ethylenically unsaturated monomer (a-3) having a reactive functional group other than a carboxyl group is reactive with a carboxyl group, the molecular weight of the polymer [A] is increased. Although it has the effect of increasing various properties such as water resistance by increasing the condition, the polymer [A] has a gel fraction of 95% by weight or less as described above (reactive functional group type and amount selection, polymer [A] Adjustment of reaction temperature during polymerization, pH of system during polymerization, etc.).

  Although it does not specifically limit as an ethylenically unsaturated monomer (a-3) which has reactive functional groups other than the carboxyl group used by this invention, For example, glycidyl (meth) acrylate, allyl glycidyl ether Glycidyl group-containing polymerizable monomers such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, polyethylene glycol mono (meth) acrylate, glycerol mono (meth) acrylate, etc. Amino group-containing polymerizable monomers such as aminoethyl (meth) acrylate, N-monoalkylaminoalkyl (meth) acrylate, N, N-dialkylaminoalkyl (meth) acrylate; N-methylol (meth) acrylamide N-isopropoxymethyl (meth) act Methylolamide groups such as amide, N-butoxymethyl (meth) acrylamide and N-isobutoxymethyl (meth) acrylamide and polymerizable monomers containing alkoxylates thereof; vinyltrichlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane, Vinyltris (β-methoxyethoxy) silane, γ- (meth) acryloxypropyltrimethoxysilane, γ- (meth) acryloxypropyltriethoxysilane, γ- (meth) acryloxypropylmethyldimethoxysilane, γ- (meth) Contains silyl groups such as acryloxypropylmethyldiethoxysilane, γ- (meth) acryloxypropyltriisopropoxysilane, N-β- (N-vinylbenzylaminoethyl) -γ-aminopropyltrimethoxysilane and its hydrochloride Polymeric single Aziridinyl group-containing polymerizable monomers such as 2-aziridinylethyl (meth) acrylate; isocyanate groups such as (meth) acryloyl isocyanate, phenols of (meth) acryloyl isocyanate ethyl or methyl ethyl ketoxime adducts; // Blocked isocyanate group-containing polymerizable monomer; Oxazoline group-containing polymerizable monomer such as 2-isopropenyl-2-oxazoline, 2-vinyl-2-oxazoline; (meth) acrylamide, N-monoalkyl Amide group-containing polymerizable monomers such as (meth) acrylamide and N, N-dialkyl (meth) acrylamide; Cyclopentenyl group-containing polymerizable monomers such as dicyclopentenyl (meth) acrylate; Allyl (meth) acrylate and the like Allyl group-containing polymerizable monomer; acrolein Diacetone (meth) carbonyl group-containing polymerizable monomers such as acrylamide; acetoacetyl group-containing polymerizable monomers such as acetoacetoxyethyl (meth) acrylate. As an ethylenically unsaturated monomer (a-3), it can use as a 1 type, or 2 or more types of mixture of the monomer mentioned above.

  Among the ethylenically unsaturated monomers (a-3) having a reactive functional group other than the above carboxyl group, the reactivity with the reactive functional group in the polymer [B] described later is excellent, and the durability of the coating film In particular, glycidyl group-containing polymerizable monomer, hydroxyl group-containing polymerizable monomer, methylolamide group-containing polymerizable monomer, silyl group-containing polymerizable monomer, acetoacetyl It is preferable to use a group-containing polymerizable monomer, and among them, the use of a silyl group-containing polymerizable monomer is more preferable because various properties such as water resistance of the emulsion coating are remarkably improved.

  Further, as other ethylenically unsaturated monomers, in order to improve the stability during polymerization and the storage stability of the emulsion, sulfonic acid groups and / or Alternatively, an ethylenically unsaturated monomer containing a sulfate group (and / or a salt thereof), a phosphate group and / or a phosphate ester group (and / or a salt thereof) can be used in combination. Examples of such other ethylenically unsaturated monomers include vinyl sulfonic acids such as vinyl sulfonic acid and styrene sulfonic acid or salts thereof, and allyl group-containing sulfonic acids such as allyl sulfonic acid and 2-methylallyl sulfonic acid. Or a salt thereof, a (meth) acrylate group-containing sulfonic acid such as 2-sulfoethyl (meth) acrylate, 2-sulfopropyl (meth) acrylate or a salt thereof, (meth) acrylamide- (tert-butylsulfonic acid) ) Acrylamide group-containing sulfonic acids or salts thereof, “Adekaria soap PP-70, PPE-710” (manufactured by Asahi Denka Kogyo Co., Ltd.) having a phosphoric acid group, and the like, one or more of these Mixtures can be used.

  Furthermore, in the present invention, the gel fraction does not exceed 95% by weight for the purpose of increasing the molecular weight by crosslinking the polymer [A] as another ethylenically unsaturated monomer as necessary. It is also possible to use a polyfunctional ethylenically unsaturated monomer having two or more ethylenically unsaturated groups in combination. Examples of such polyfunctional ethylenically unsaturated monomers include ethylene glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, and trimethylolpropane. Examples include tri (meth) acrylate, polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, diallyl phthalate, divinylbenzene, and allyl (meth) acrylate.

  Other ethylenically unsaturated monomers can be used as one or a mixture of two or more of the above-described monomers.

  In the present invention, the proportion of the carboxyl group-containing ethylenically unsaturated monomer (a-1) and other ethylenically unsaturated monomers used is the glass transition temperature of the polymer [A] as described above. Is required to use the carboxyl group-containing ethylenically unsaturated monomer (a-1) at such a ratio that the acid value is from -50 to -15 ° C and the acid value is from 10 to 300, and the monomer component described later It is preferable to select the type and amount in consideration of compatibility with (b) and the resulting polymer component.

  The use ratio of the carboxyl group-containing ethylenically unsaturated monomer (a-1) and the other ethylenically unsaturated monomer is based on the weight, and the carboxyl group-containing ethylenically unsaturated monomer (a-1). ) / Other ethylenically unsaturated monomers = 1/99 to 40/60, more preferably the former / the latter = 2/98 to 20/80. By using the carboxyl group-containing ethylenically unsaturated monomer (a-1) and other ethylenically unsaturated monomers in such a range, the glass transition temperature (actually measured Tg) of the polymer [A] is in a desired range. The ethylenically unsaturated monomer component (b) is preferable because the stability during polymerization is improved and the water resistance of the resulting coating is improved.

  Moreover, when using the ethylenically unsaturated monomer (a-3) which has reactive functional groups other than a carboxyl group as another ethylenically unsaturated monomer, this monomer (a-3) Is reactive with the carboxyl group in the carboxyl group-containing ethylenically unsaturated monomer (a-1), the monomer component (b) from the viewpoint of stability during storage and storage stability, The amount used is preferably in the range of 0.01 to 0.5 mol of the monomer (a-3) with respect to 1 mol of the carboxyl group-containing ethylenically unsaturated monomer (a-1). . If the ethylenically unsaturated monomer (a-3) having a reactive functional group other than a carboxyl group is used in such a range, the gel fraction of the polymer [A] can be easily prepared to 95% by weight or less.

  Moreover, as another ethylenically unsaturated monomer, the ethylenically unsaturated monomer (a-3) having a reactive functional group other than a carboxyl group is a carboxyl group-containing ethylenically unsaturated monomer (a- 1) When not having reactivity with the carboxyl group in 1), the monomer (a-3) is 0.01% with respect to 1 mol of the carboxyl group-containing ethylenically unsaturated monomer (a-1). It is preferable to use in the range of -2.0 mol. If the ethylenically unsaturated monomer (a-3) having a reactive functional group other than a carboxyl group is used in such a range, the ethylenically unsaturated monomer component (b) has good stability during polymerization. ,preferable.

  In the present invention, when the polymer [A] is produced in an aqueous medium, it can be polymerized using an emulsifier or other dispersion stabilizer, and the emulsifier and other dispersion stabilizer at that time are obtained. It is preferable to use the coating film as needed as long as the water resistance of the coating film is not lowered.

  As the emulsifier used in the present invention, known anionic emulsifiers and nonionic emulsifiers can be used. However, the cationic emulsifier is a simple substance containing a carboxyl group-containing ethylenically unsaturated monomer (a-1). It is not preferable for the polymerization of the monomer component (a).

  Examples of the anionic emulsifier used in the present invention include sulfates of higher alcohols and salts thereof, alkylbenzene sulfonates, polyoxyethylene alkylphenyl sulfonates, polyoxyethylene alkyl diphenyl ether sulfonates, alkyl diphenyl ether disulfonic acids. And nonionic emulsifiers include polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene diphenyl ether, polyoxyethylene-polyoxypropylene block copolymer Etc., and one or a mixture of two or more of these can be used.

  Furthermore, an emulsifier having a polymerizable unsaturated group in the molecule generally called “reactive emulsifier” can also be used. As reactive emulsifiers that can be used in the present invention, for example, “Latemul S-180” (manufactured by Kao Corporation) having a sulfonic acid group and a salt thereof, “Eleminol JS-2, RS-30” (Sanyo Chemical Industries ( "Aqualon HS-10, HS-20, KH-05, KH-10" (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), "Adekaria soap SE-10, SE-20, SR-10N, SR-20N "(Asahi Denka Kogyo Co., Ltd.), etc .;" New Frontier A-229E "having a phosphate group (Daiichi Kogyo Seiyaku Co., Ltd.), etc .; nonionic “AQUALON RN-10, RN-20, RN-30, RN-50, ER-10, ER-20, ER-30, ER-40” (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) etc. having a hydrophilic group One or a mixture of two or more of these can be used.

  Other dispersion stabilizers other than the emulsifier that can be used in the present invention include, for example, polyvinyl alcohol, fiber ether, starch, maleated polybutadiene, maleated alkyd resin, polyacrylic acid (salt), polyacrylamide. Synthetic or natural water-soluble polymer substances such as water-based acrylic resins, water-based polyester resins, water-based polyamide resins, and water-based polyurethane resins can be used, and one or a mixture of two or more of these can be used.

  The emulsifier and the dispersion stabilizer are used for the purpose of improving the stability during storage and the storage stability, but it is preferable to reduce the amount of use as much as possible from the viewpoint of the water resistance of the emulsion coating, The content is preferably 2% by weight or less based on the solid content of the polymer [A].

  In the present invention, the aqueous medium for polymerizing the polymer [A] is not particularly limited, but only water may be used, or a mixed solution of water and a water-soluble solvent is used. May be. Examples of the water-soluble solvent used here include alcohols such as methyl alcohol, ethyl alcohol, isopropyl alcohol, ethyl carbitol, ethyl cellosolve, and butyl cellosolve, and polar solvents such as N-methylpyrrolidone. A mixture of two or more can be used.

  The amount of the water-soluble solvent used in the case of using a mixture of water and the water-soluble solvent can be arbitrarily selected from the viewpoint of stability during polymerization, but there is a risk of ignition of the resulting polymer aqueous dispersion. From the viewpoints of safety and health and safety, it is preferable to reduce the amount of water-soluble solvent as much as possible. For these reasons, it is particularly preferable to use water alone.

  In the method for producing an acrylic polymer aqueous dispersion of the present invention, the aqueous medium for polymerizing the monomer component is not particularly limited, but only water may be used, or A mixed solution of water and a water-soluble solvent may be used. Examples of the water-soluble solvent used here include alcohols such as methyl alcohol, ethyl alcohol, isopropyl alcohol, ethyl carbitol, ethyl cellosolve, and butyl cellosolve, and polar solvents such as N-methylpyrrolidone. A mixture of two or more can be used.

  The amount of the water-soluble solvent used in the case of using a mixture of water and the water-soluble solvent can be arbitrarily selected from the viewpoint of stability during polymerization. However, the resulting acrylic polymer aqueous dispersion is ignited. It is preferable to reduce the amount of the water-soluble solvent used as much as possible from the viewpoints of the risk and safety and health. For these reasons, it is particularly preferable to use water alone.

In the present invention, as described above, the monomer component (a) having the carboxyl group-containing ethylenically unsaturated monomer component (a-1) as an essential component is charged all at once into a reaction vessel containing an aqueous medium. Is preferable because an acrylic polymer aqueous dispersion capable of exhibiting the desired film performance can be easily obtained. On the other hand, in the production of an acrylic polymer by emulsion polymerization, the monomer component is Since the amount of heat generated during polymerization is large, it is difficult to control the polymerization heat generation particularly when monomer components are charged all at once. In particular, when emulsion polymerization is carried out by charging monomer components all at once without controlling the polymerization exotherm, the temperature in the polymerization system may become much higher than the boiling point of water as the polymerization medium. In the case of a reaction vessel attached to a condenser, which is used when producing an ordinary acrylic polymer by emulsion polymerization, there is a risk of the content being blown out from the reaction vessel, and a large amount of agglomerates due to boiling in the reaction vessel. Therefore, it is preferable to use a sealed pressure reaction vessel as the reaction vessel because the above risk can be avoided.
Here, the sealed pressure reaction vessel refers to a pressure-resistant sealed reaction vessel such as an autoclave, and is preferably provided with a stirrer, a pressure increasing / decreasing device, and an inert gas inlet.

  In the method for producing an acrylic polymer aqueous dispersion of the present invention, when a monomer component is polymerized using a sealed pressure reaction vessel, the pressure in the sealed pressure reaction vessel is changed between the aqueous medium and the polymerizable monomer. It is preferable to carry out the reaction while maintaining a vapor pressure exceeding the vapor pressure of the mixture of body components, since the disadvantage that a large amount of aggregates are generated due to boiling in the reaction vessel can be avoided. In this case, an inert gas may be pressurized and filled into the sealed pressure reaction vessel.

  The pressure in the reaction system is not particularly limited as long as the pressure in the sealed pressure reaction vessel at the start of the reaction is controlled to be equal to or higher than normal pressure, but the pressure in the reaction vessel is adjusted to the liquid in the reaction vessel (aqueous medium). It is preferable to maintain the pressure to be equal to or higher than the vapor pressure of the mixture of the monomer components) because boiling of the liquid in the reaction vessel can be suppressed, and as a result, generation of aggregates can be prevented. The degree of pressurization depends on the composition and concentration of the mixture of the aqueous medium and the monomer component, but is generally preferably in the range of 0 to 10 MPa, more preferably 0.1 to 1.5 MPa. In addition, a pressure does not mean an absolute pressure, but means the differential pressure | voltage which made normal pressure 0 MPa.

In the method for producing an aqueous acrylic polymer dispersion of the present invention, the monomer component is polymerized in a closed pressure reaction vessel, and therefore the temperature in the vessel at the time of polymerization is not particularly limited and is, for example, a medium. Emulsion polymerization can be safely performed even under conditions exceeding the boiling point of water. In the case of a reaction vessel attached to a condenser, which is used when an ordinary acrylic polymer is produced by emulsion polymerization, if the reaction vessel boils as described above, there is a risk that the contents will blow out from the reaction vessel, However, if a closed-type pressure reaction vessel is used, it is possible to control the contents so that they do not boil as necessary. Can be avoided. In particular, when polymerizing at a high temperature (temperature higher than the boiling point of the mixture of the aqueous medium and the monomer component), pressurizing the reaction vessel with an inert gas can suppress boiling in the reaction vessel. This is preferable because the generation of aggregates can be reduced.
In addition, when the dissolved oxygen concentration in the liquid in the closed pressure reaction vessel is polymerized under a condition where the oxygen concentration is 3 ppm or less, inhibition of radical polymerization by oxygen can be avoided, and the polymerization proceeds smoothly so that the acrylic polymer It is preferable because an aqueous dispersion can be produced efficiently. As a method of lowering the dissolved oxygen concentration in the liquid in the sealed reaction vessel, the aqueous medium (emulsifier if necessary), the monomer component, and the polymerization initiator are reduced in a separate vessel, respectively. , A method of mixing these, and a method of lowering dissolved oxygen after charging an aqueous medium, a monomer component, and a polymerization initiator into a sealed pressure reaction vessel, and a method is appropriately selected according to the apparatus to be used. In any method, it is preferable that the dissolved oxygen concentration in the liquid in the closed pressure reaction vessel at the start of the polymerization be 3 ppm or less. Specifically, the dissolved oxygen concentration in the liquid (a mixture of an aqueous medium or, in some cases, an aqueous medium containing polymer particles [A] or an emulsifier, a monomer component, and a polymerization initiator) is reduced. Specifically, (1) while stirring in the container, an inert gas is continuously blown or bubbled from one mouth of the container, and an inert gas and oxygen are blown out from the other mouth. (2) A method of lowering the dissolved oxygen concentration by boiling the liquid in the vessel once and then cooling it under an inert gas atmosphere. Examples of the method include reducing the dissolved oxygen concentration by lowering the partial pressure of oxygen in the container by lowering the pressure in the container after the inside of the container is stirred and pressurized with an inert gas. Among these, in order to reduce the dissolved oxygen in the liquid in the container, (3) the method of repeating the operation of lowering the pressure in the container after pressurizing and filling with an inert gas is efficient. Since dissolved oxygen can be reduced, it is preferable. The step of lowering the pressure in the container after pressurizing and filling with the inert gas is preferably repeated 2 to 10 times. The greater the number of repetitions of this step, the lower the dissolved oxygen concentration. Since the oxygen concentration is difficult to decrease, the dissolved oxygen removal efficiency is deteriorated.

  When an inert gas is pressure-filled in a sealed pressure reaction vessel, for example, the number of repetitions of the above-described pressure filling operation required to make the dissolved oxygen concentration 3 ppm or less is small. It is preferable to fill the inert gas at a pressure of 0 MPa, preferably 0.2 to 1.5 MPa. In the case of lowering the pressure in the reaction vessel, for example, the degree of decompression is −0.04 because the number of repetitions of the operation of lowering the pressure in the vessel required to make the dissolved oxygen concentration 3 ppm or less is small. The pressure is preferably reduced to -0.09 MPa. Furthermore, the pressure in the reaction vessel during the polymerization of the monomer component is particularly limited as long as the pressure in the closed pressure reaction vessel exceeds the vapor pressure of the mixture of the aqueous medium and the polymerizable monomer component. First, depending on the reaction temperature at the time of polymerization, which will be described later, the polymerization can be carried out at normal pressure or by pressurizing with an inert gas. The pressure referred to here does not mean an absolute pressure in the same manner as described above, but refers to a differential pressure obtained by setting the normal pressure to 0 MPa. Moreover, as inert gas, noble gases, such as nitrogen gas, helium, and argon, can be mentioned, These may be used in mixture of 1 or more types. As the type of inert gas, nitrogen gas is particularly preferable from the viewpoints of economy and versatility. The purity of the inert gas is usually 95% by volume or more, preferably 98% by volume or more.

  In the present invention, the polymerization temperature at the time of polymerization is not limited, but in particular, when the molecular weight of the obtained polymer [A] is to be increased and the flexibility of the resulting film at a low temperature is to be increased, the polymerization is started from a low temperature. It is preferable to start. Specifically, it is preferable to start the polymerization from a temperature of 10 ° C. or higher because the polymerization is likely to proceed smoothly and from 50 ° C. or lower because a high molecular weight polymer is easily obtained. In addition, when there is little heat_generation | fever at the time of reaction or superposition | polymerization does not advance smoothly, you may start reaction in the range higher than said temperature range.

  As the polymerization initiator used when polymerizing the polymer [A] in the present invention, a radical polymerization initiator is used. Examples of the radical polymerization initiator include persulfates, organic peroxides, hydrogen peroxide, and the like.

  In the polymerization of the monomer component, it can be obtained by radical polymerization using only these peroxides, or by a redox polymerization initiator in which a reducing agent is used in combination with the peroxide.

  Furthermore, azo initiators such as 4,4'-azobis (4-cyanovaleric acid) and 2,2'-azobis (2-amidinopropane) dihydrochloride can also be used as the polymerization initiator. Among the polymerization initiators, in particular, a redox polymerization initiator using a combination of persulfates and / or organic peroxides and a reducing agent can smoothly proceed the polymerization even at a low temperature. When it is desired to obtain an aqueous dispersion of a high molecular weight acrylic polymer, the polymerization can be started from a temperature within the range of 10 to 50 ° C., which is preferable.

  Specific examples of persulfates include potassium persulfate, sodium persulfate, and ammonium persulfate. Specific examples of organic peroxides include benzoyl peroxide, lauroyl peroxide, deca Diacyl peroxides such as noyl peroxide, dialkyl peroxides such as t-butylcumyl peroxide, dicumyl peroxide, peroxyesters such as t-butylperoxylaurate, t-butylperoxybenzoate, cumene And hydroperoxides such as hydroperoxide, paramentane hydroperoxide, and t-butyl hydroperoxide.

  Examples of the reducing agent used in the above redox polymerization initiator system include ascorbic acid and its salt, erythorbic acid and its salt, tartaric acid and its salt, citric acid and its salt, metal salt of formaldehyde sulfoxylate, Examples include sodium thiosulfate, sodium bisulfite, and ferric chloride.

  These polymerization initiators may be used in amounts that allow the polymerization to proceed smoothly. However, when water resistance is required for the resulting acrylic polymer aqueous dispersion film, the amount used is determined as follows. It is preferable to reduce the amount as much as possible, and the amount used is 0.3% by weight or less based on the weight of the monomer component (in the case of a redox polymerization initiator used in combination with a reducing agent, the total amount of an oxidizing agent and a reducing agent). It is preferable that

  In the present invention, when it is necessary to adjust the molecular weight of the acrylic polymer aqueous dispersion, a compound having a chain transfer ability as a molecular weight adjusting agent when polymerizing the monomer component, for example, lauryl mercaptan, octyl mercaptan, Mercaptans such as dodecyl mercaptan, 2-mercaptoethanol, octyl thioglycolate, 3-mercaptopropionic acid, thioglycerin, or α-methylstyrene dimer may be added.

  In the present invention, the proportion of the ethylenically unsaturated monomer component (b) used relative to the polymer [A] is determined based on the weight based on the balance between the low temperature characteristics of the resulting coating and the hardness at room temperature. It is preferable that the solid content weight of [A] / monomer component (b) = 7/3 to 4/6, and more preferably 6/4 to 4/6. If the use ratio is within such a range, a more excellent hardness at normal temperature can be obtained.

  In the present invention, the carboxyl group of the polymer [A] may be used as it is for the polymerization of the ethylenically unsaturated monomer component (b) without being neutralized. A method in which a part of the group is neutralized with a basic substance is preferred. The neutralization degree of the carboxyl group at that time is not particularly limited, but from the viewpoint of stability during polymerization, the amount of the basic substance used is 10 mol% or more based on the total carboxyl groups in the polymer [A]. It is preferable to do.

  As the basic substance used as the neutralizing agent, ordinary substances can be used, for example, alkali metal compounds such as sodium hydroxide and potassium hydroxide; alkaline earth metal compounds such as calcium hydroxide and calcium carbonate; Ammonia; water-soluble organic amines such as monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine, monopropylamine, dimethylpropylamine, monoethanolamine, diethanolamine, triethanolamine, ethylenediamine, diethylenetriamine, etc. One or a mixture of two or more of these can be used. In particular, when it is desired to further improve the water resistance of the resulting coating, it is preferable to use ammonia that scatters at room temperature or by heating.

  The polymer [A] obtained as described above forms an A layer present in the outermost shell part of the polymer particles [X] of the aqueous polymer dispersion of the present invention.

  In the method for producing an aqueous acrylic polymer dispersion of the present invention, ethylene having a glass transition temperature (measured Tg) of 30 to 150 ° C. in the presence of the polymer [A] obtained as described above is obtained. The polymerizable unsaturated monomer component (b) is charged all at once and polymerized.

  The ethylenically unsaturated monomer component (b) used in the present invention is not particularly limited as long as the measured Tg of the polymer is an ethylenically unsaturated monomer having a temperature of 30 to 150 ° C. For example, methyl ( (Meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, i-butyl (meth) acrylate, t-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, hexyl (meth) acrylate, cyclohexyl ( (Meth) acrylate, octyl (meth) acrylate, nonyl (meth) acrylate, dodecyl (meth) acrylate, stearyl (meth) acrylate, isobornyl (meth) acrylate, dicyclopentanyl (meth) acrylate, phenyl (meth) acrylate, benzyl Such as (meth) acrylate ( A) Acrylic acid esters; 2,2,2-trifluoroethyl (meth) acrylate, 2,2,3,3-pentafluoropropyl (meth) acrylate, perfluorocyclohexyl (meth) acrylate, 2,2,3 , 3, -tetrafluoropropyl (meth) acrylate, β- (perfluorooctyl) ethyl (meth) acrylate and other fluorine-containing vinyl monomers; vinyl acetate, vinyl propionate, vinyl butyrate, vinyl versatate, etc. Esters; vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, butyl vinyl ether, amyl vinyl ether, hexyl vinyl ether; nitriles of unsaturated carboxylic acids such as (meth) acrylonitrile; styrene, α-methylstyrene, Vinyl compounds having an aromatic ring such as nyltoluene, vinylanisole, α-halostyrene, vinylnaphthalene, divinylstyrene; isoprene, chloroprene, butadiene, ethylene, tetrafluoroethylene, vinylidene fluoride, N-vinylpyrrolidone, etc. One kind or a mixture of two kinds or more can be used. Among these, (meth) acrylic acid esters are preferred because polymerization is particularly easy and adjustment of the glass transition temperature of the polymer is easy.

  More specifically, in order to obtain a polymer [B] having a desired glass transition temperature (30 to 150 ° C.), an ethylene having a glass transition temperature of 30 ° C. or higher of the polymer obtained upon homopolymerization of the monomer is used. It is essential to use a polymerizable unsaturated monomer, for example, methacrylic acid esters such as methyl methacrylate, i-butyl methacrylate, t-butyl methacrylate, cyclohexyl methacrylate, dicyclopentanyl methacrylate, isobornyl methacrylate, Examples thereof include acrylic acid esters such as cyclohexyl acrylate, dicyclopentanyl acrylate, and isobornyl acrylate, styrene, α-methylstyrene, and the like, and one or more of these can be used in combination.

Moreover, the acrylic acid alkyl ester which has the said polymer whose glass transition temperature of the polymer obtained at the time of homopolymerization of said monomer is 30 degreeC or more, and the alkyl group whose carbon atom number of an alkyl group is 1-3 Alternatively, the glass transition temperature of the polymer [B] can be adjusted to 30 ° C. to 150 ° C. in combination with (meth) acrylic acid esters containing a long-chain alkyl group having 4 to 12 carbon atoms. .
In the present invention, ethylene containing a functional group having reactivity with the reactive functional group in the polymer [A] together with the above-described monomer in the ethylenically unsaturated monomer component (b). The polymer [B] obtained by polymerizing the polymerizable unsaturated monomer (b-1) in combination is combined with the polymer [A] constituting the A layer, and has various physical properties such as water resistance. Since it improves, it is preferable.

  Examples of the ethylenically unsaturated monomer (b-1) containing a functional group having reactivity with the reactive functional group in the polymer [A] as described above include glycidyl (meth) acrylate and allyl glycidyl. Glycidyl group-containing polymerizable monomers such as ether; hydroxyl group-containing polymerizable such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, polyethylene glycol mono (meth) acrylate, glycerol mono (meth) acrylate Monomer; Amino group-containing polymerizable monomer such as aminoethyl (meth) acrylate, N-monoalkylaminoalkyl (meth) acrylate, N, N-dialkylaminoalkyl (meth) acrylate; N-methylol (meth) Acrylamide, N-isopropoxymethyl (meth) acrylamide, N Methylolamide groups such as butoxymethyl (meth) acrylamide and N-isobutoxymethyl (meth) acrylamide and alkoxylated-containing polymerizable monomers thereof; vinyltrichlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (β- Methoxyethoxy) silane, γ- (meth) acryloxypropyltrimethoxysilane, γ- (meth) acryloxypropyltriethoxysilane, γ- (meth) acryloxypropylmethyldimethoxysilane, γ- (meth) acryloxypropylmethyl Silyl group-containing polymerizable monomers such as diethoxysilane, γ- (meth) acryloxypropyltriisopropoxysilane, N-β- (N-vinylbenzylaminoethyl) -γ-aminopropyltrimethoxysilane and its hydrochloride Body; 2-azi An aziridinyl group-containing polymerizable monomer such as dinylethyl (meth) acrylate; an isocyanate group such as (meth) acryloyl isocyanate, phenol of (meth) acryloyl isocyanate ethyl or an adduct of methyl ethyl ketoxime and / or a blocked isocyanate group -Containing polymerizable monomers; oxazoline group-containing polymerizable monomers such as 2-isopropenyl-2-oxazoline and 2-vinyl-2-oxazoline; (meth) acrylamide, N-monoalkyl (meth) acrylamide, N, Amide group-containing polymerizable monomers such as N-dialkyl (meth) acrylamide; Cyclopentenyl group-containing polymerizable monomers such as dicyclopentenyl (meth) acrylate; Allyl group-containing polymerizable monomers such as allyl methacrylate; Acrolein, diacetone (meta) Examples include carbonyl group-containing polymerizable monomers such as chloramide; acetoacetyl group-containing polymerizable monomers such as acetoacetoxyethyl (meth) acrylate and the like, and these monomers are used as one kind or a mixture of two or more kinds. can do.

  Among these, in particular, as the ethylenically unsaturated monomer (b-1) containing a functional group having reactivity with the reactive functional group in the polymer [A], a functional group having reactivity with a carboxyl group is used. When the ethylenically unsaturated monomer contained is used, the resulting polymer [B] reacts with the carboxyl group imparting hydrophilicity to the polymer [A] to form a crosslinked structure, thereby It is preferable because water resistance is remarkably improved.

  In the present invention, examples of the ethylenically unsaturated monomer containing a group reactive with a carboxyl group that can be used as the monomer (b-1) include glycidyl (meth) acrylate, allyl glycidyl ether, and the like. Glycidyl group-containing polymerizable monomers; methylolamides such as N-methylol (meth) acrylamide, N-isopropoxymethyl (meth) acrylamide, N-butoxymethyl (meth) acrylamide, N-isobutoxymethyl (meth) acrylamide Group and its alkoxylated product-containing polymerizable monomer; aziridinyl group-containing polymerizable monomer such as 2-aziridinylethyl (meth) acrylate; (meth) acryloyl isocyanate, phenol of (meth) acryloyl isocyanate ethyl or Methyl ethyl ketoxime adduct, etc. A cyanate group and / or a blocked isocyanate group-containing polymerizable monomer; and an oxazoline group-containing polymerizable monomer such as 2-isopropenyl-2-oxazoline and 2-vinyl-2-oxazoline. One or a mixture of two or more of these can be used. Among these, glycidyl group-containing polymerizable monomers, methylolamide groups, and alkoxylated products thereof are particularly included from the viewpoint of excellent reactivity with the carboxyl group in the polymer [A] and significantly improving various physical properties such as water resistance. It is preferable to use a polymerizable monomer.

  Furthermore, a polyfunctional ethylenic group having two or more ethylenically unsaturated groups for the purpose of increasing the molecular weight by crosslinking the polymer [B] as other ethylenically unsaturated monomers as necessary. An unsaturated monomer can be used in combination. Examples of the polyfunctional ethylenically unsaturated monomer include ethylene glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, Examples include neopentyl glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, diallyl phthalate, divinylbenzene, and allyl (meth) acrylate.

  In the method for producing an aqueous acrylic polymer dispersion of the present invention, the method of polymerizing the ethylenically unsaturated monomer component (b) in an aqueous medium in the presence of the polymer [A] In this case, the method of polymerizing without adding a new emulsifier, the polymer particle [X] in the desired form (that is, the polymer [A] is the outermost shell part of the particle) The particle morphology present in the

  That is, when the emulsion polymerization of the ethylenically unsaturated monomer component (b) is carried out without newly adding an emulsifier, the polymer [B] obtained by the ethylenically unsaturated monomer component (b) The polymer [A] is likely to be incorporated into the particle [A] and the polymer [B] in one particle, and the polymer [A] is formed in the outermost shell of the particle. ] Is more preferable.

  In the present invention, the method for batch-wise charging the ethylenically unsaturated monomer component (b) for polymerization is not particularly limited, but for the same reason as in the method for producing the polymer [A] described above. A closed pressure reaction vessel is used as the reaction vessel, and the pressure in the closed pressure reaction vessel at the start of the reaction is normal pressure or higher, more preferably the pressure in the reaction vessel is the liquid in the reaction vessel (aqueous medium and monomer). The polymerization is preferably carried out under the condition that the pressure is higher than the vapor pressure of the component mixture) and the dissolved oxygen concentration in the liquid in the closed pressure reaction vessel is set to 3 ppm or less.

  In the present invention, the polymerization temperature during the polymerization of the polymer [B] is not limited, but particularly when the molecular weight of the obtained polymer [B] is to be increased and the flexibility of the resulting coating at a low temperature is to be increased. Is preferably initiated from a low temperature. Specifically, it is preferable to start the polymerization from a temperature of 10 ° C. or higher because the polymerization is likely to proceed smoothly and from 50 ° C. or lower because a high molecular weight polymer is easily obtained. In addition, when there is little heat_generation | fever at the time of reaction or superposition | polymerization does not advance smoothly, you may start reaction in the range higher than said temperature range.

  As the polymerization initiator used in the polymerization of the ethylenically unsaturated monomer component (b) in the present invention, those described in detail in the method for producing the polymer [A] described above can be used.

  When it is necessary to adjust the molecular weight of the polymer [B] obtained by polymerization of the ethylenically unsaturated monomer component (b), those described in detail in the method for producing the polymer [A] described above are used. Can be used.

  The polymer [B] obtained as described above forms a B layer in the polymer particles [X] of the aqueous acrylic polymer dispersion of the present invention.

  In the present invention, the molecular weight of the polymer [B] constituting the B layer is not particularly limited, but it is usually preferably a weight average molecular weight of 100,000 or more, and if the weight average molecular weight is within such a range. In the obtained film, various physical properties such as excellent hardness at normal temperature and water resistance can be provided.

  If necessary, the measured Tg of the polymer is 30 in an aqueous medium in which the polymer [A] is present within the range that does not inhibit the low temperature characteristics of the film and the development of hardness at room temperature, which is the object of the present invention. The ethylenically unsaturated monomer component (b) having a temperature of ˜150 ° C. is charged all at once and polymerized to obtain a polymer [B], and in the presence thereof, other ethylenically unsaturated monomer components are polymerized. Alternatively, other ethylenically unsaturated monomer components can be repeatedly polymerized in multiple stages.

  The solid content concentration of the acrylic polymer aqueous dispersion including the acrylic polymer aqueous dispersion is not particularly limited, but the operability during production and transportation costs, and the acrylic polymer aqueous dispersion It is preferable that the solid concentration is 40 to 70% by weight from the viewpoint of excellent drying properties when the liquid is dried.

  A water-soluble or water-dispersible crosslinking agent can be added to the acrylic polymer aqueous dispersion as necessary. In this case, examples of the crosslinking agent include a polyfunctional melamine compound, a polyfunctional polyamine compound, a polyfunctional polyethyleneimine compound, a polyfunctional (block) isocyanate compound, a metal salt compound, and the like. In addition to being able to be used as a mixture of two or more kinds, a water-soluble or water-dispersible thermosetting resin, for example, a phenol resin, a urea resin, a melamine resin, a urethane resin, etc. can be mixed and used. .

  Further, if necessary, various agents such as fillers, pigments, pH adjusters, film forming aids, leveling agents, thickeners, water repellents, antifoaming agents and the like can be appropriately added and used. .

  When used as a coating agent or adhesive, the acrylic polymer aqueous dispersion has excellent hardness at room temperature, low temperature sensitivity, and flexibility even at a temperature lower than the glass transition temperature of the polymer. In order to form a film, its use is multi-functional, but paints, primer treatment agents, adhesives, film coating agents, fiber processing resins (woven fabrics and non-woven fabric binders / coating agents, flocking processing binders, etc.) It can be used as a resin for paper processing (impregnation, coating), a resin for glass fiber processing (glass fiber sizing agent, binder for glass paper, glass fiber coating agent, etc.), a resin for modifying mortar, and the like. In particular, in applications that are used in application fields such as paints, inks, varnishes, film coatings, adhesions, fiber processing resins, paper processing resins, etc., extremely excellent effects are exhibited as described.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further more concretely, the scope of the present invention is not limited to these Examples. In the following, unless otherwise specified, “%” represents “% by weight”, and “part” represents “part by weight”.

The evaluation method used in the present invention will be described below.
[Measurement method of acid value]
The acid value is a numerical value representing the amount of carboxyl groups contained in the polymer, and is the number of mg of potassium hydroxide required to neutralize free carboxyl groups contained in 1 g of the polymer. A sample was coated on a glass plate with a 3 mil applicator, dried at room temperature for 1 hour to form a semi-dry film, and the obtained film was peeled off from the glass plate, and 1 g of this film was precisely weighed and tetrahydrofuran (THF) A sample dissolved in 100 g was used as a measurement sample. The measuring method was a neutralization titration method using an aqueous potassium hydroxide solution.
For samples insoluble in THF, measurement by this method is impossible, so the calculated value calculated from the charged amount of the carboxyl group-containing monomer used in the production of the polymer was calculated as the acid value of the polymer. did.

[Method for measuring weight average molecular weight]
The weight average molecular weight was measured by gel permeation chromatograph (GPC method). A high performance liquid chromatograph HLC-8120GPC type manufactured by Toyo Soda Co., Ltd. was used as a measuring device, and a packed column TSK guard column and TSKgelGMH-HR column manufactured by Toyo Soda Co., Ltd. were used as columns. A calibration curve was prepared using standard polystyrenes manufactured by Showa Denko KK and Toyo Soda Co., Ltd. as standard samples. The weight average molecular weight was measured using an RI detector using THF as an eluent and a sample solution. The measurement sample was prepared by weighing 80 mg of the polymer aqueous dispersion containing the polymer [A] as a solid content, adding 20 ml of THF thereto, stirring and dissolving for 12 hours, and then filtering through a 1 μm membrane filter. A sample was used as a measurement sample.

[Measurement method of gel fraction]
The gel fraction was measured as an acetone insoluble fraction. A sample was coated on a glass plate so that the film thickness after drying was 0.5 mm, dried at 40 ° C. for 8 hours, then peeled off from the glass plate, and further dried at 140 ° C. for 5 minutes. A sample was cut out. Next, the weight (G1) before the acetone immersion of the sample is measured in advance, and the acetone insoluble matter of the sample after being immersed in an acetone solution at room temperature for 24 hours is separated by filtering with a 300 mesh wire net, The weight (G2) of the residue after drying at 110 degreeC for 1 hour was measured, and the gel fraction was calculated | required according to the following formula | equation.

Gel fraction (% by weight) = G2 / G1 × 100
[Measurement method of particle size]
The particle diameter was measured by a dynamic light scattering method, and the value of the particle diameter (50% median diameter) on a volume basis measured with a Microtrac UPA type particle size distribution measuring device manufactured by Nikkiso Co., Ltd. was obtained.

[Measurement method of glass transition temperature]
The acrylic polymer aqueous dispersion was coated on a glass plate so that the film thickness after drying was 0.5 mm, dried at 40 ° C. for 8 hours, then peeled off from the glass plate, and further dried at 140 ° C. for 5 minutes. 10 mg of the sample was weighed into an aluminum cylindrical cell having a diameter of 5 mm and a depth of 2 mm, and transferred in advance using a DSC-2920 modulated differential scanning calorimeter manufactured by TA Instruments. After maintaining the apparatus at a temperature about 100 ° C. lower than the temperature until it was stabilized, it was heated at a heating rate of 20 ° C. per minute to a temperature about 50 ° C. higher than the end of the transition temperature, and a DSC curve was drawn for measurement. The glass transition start temperature and the glass transition end temperature were determined according to the method described in Japanese Industrial Standard JIS “Plastic Transition Temperature Measurement Method” K7121.

[Measurement Method of Elongation Ratio in Tensile Test at Measurement Temperature-30 ° C.]
What was coated on a glass plate so that the film thickness of the acrylic polymer aqueous dispersion was 0.5 mm, dried at 40 ° C. for 8 hours, then peeled off from the glass plate, and further dried at 140 ° C. for 5 minutes. A sample was punched with a No. 2 dumbbell. Using this sample, the maximum elongation when a tensile test was carried out at a crosshead speed of 200 mm / min in an atmosphere of −30 ° C. using a Tensilon RTM-100 type tensile tester manufactured by Orientec Co., Ltd. Were determined.

[Measurement method of Young's modulus in tensile test at a measurement temperature of 25 ° C.]
The acrylic polymer aqueous dispersion was coated on a glass plate so that the film thickness after drying was 0.5 mm, dried at 40 ° C. for 8 hours, then peeled off from the glass plate, and further dried at 140 ° C. for 5 minutes. This was punched out with a No. 2 dumbbell and used as a sample. Using this sample, the origin of the chart and the elongation when the tensile test was conducted at a crosshead speed of 200 mm / min in an atmosphere of 25 ° C. in a Tensilon RTM-100 type tensile tester manufactured by Orientec Co., Ltd. It was determined by measuring the Young's modulus estimated from the stress at 2.5%.

[Measurement method of flexibility at measurement temperature -30 ° C]
The polymer aqueous dispersion was coated on a glass plate so that the film thickness after drying was 0.5 mm, dried at 40 ° C. for 8 hours, then peeled off from the glass plate, and further dried at 140 ° C. for 5 minutes. The sample was cut into 20 mm × 100 mm, and one end was fixed and bent 90 degrees in an atmosphere of −30 ° C., and the appearance change of the sample was observed and evaluated. The evaluation results are indicated by a symbol X when a fracture or crack occurs, a symbol Δ when stress whitening or wrinkles or other defects occur, and a symbol O when these defects do not occur.

[Measurement method of Shore D hardness at a measurement temperature of 25 ° C.]
The polymer aqueous dispersion was coated on a glass plate so that the film thickness after drying was 1.0 mm, dried at 40 ° C. for 8 hours, then peeled off from the glass plate, and further dried at 140 ° C. for 5 minutes. Samples were cut into 50 mm × 100 mm and 6 sheets were stacked, and the Shore D hardness was measured with a type D durometer (ASTM D2240) manufactured by Kobunshi Keiki Co., Ltd. in an atmosphere at 25 ° C.

Example 1
(1) Production of Polymer [A] (Aqueous Dispersion) Sealed pressure with internal volume of 2L equipped with stirrer, pressurizable nitrogen inlet tube, pressure reducing tube (pressure reducing pump), raw material charging port, thermometer In a reaction vessel (material in the vessel: made of glass lining), 320 parts of deionized water at 25 ° C. was charged, and under stirring, nitrogen gas was introduced into the reaction vessel through a nitrogen introduction tube, and the pressure in the reaction vessel was maintained over 1 minute. Pressurization was performed so that the pressure became 0.3 MPa. Thereafter, the pressure in the reaction vessel was reduced to −0.08 MPa over 5 minutes using a vacuum pump from the vacuum tube. After repeating this operation three times, the dissolved oxygen concentration in the deionized water in the reaction vessel was measured and found to be 0.5 ppm. While stirring the reaction vessel, 1 part of Aqualon KH-10 [Daiichi Kogyo Seiyaku Co., Ltd .: active ingredient 100%], 168 parts of butyl acrylate, 20 parts of methyl methacrylate and 12 parts of methacrylic acid were charged. Subsequently, 8.2 parts of a 2.4% aqueous solution of sodium bisulfite was charged, nitrogen gas was introduced into the reaction vessel from a nitrogen introduction tube, and the pressure in the reaction vessel was increased to 0.3 MPa over 1 minute. Thereafter, the pressure in the reaction vessel is reduced from the pressure reducing tube to −0.08 MPa over 5 minutes, and this operation is repeated three times, and then the reaction vessel pressure is increased to 0.05 MPa. Pressed. During this time, the temperature in the reaction vessel was adjusted to 30 ° C.

  Next, 8.4 parts of a 4.8% aqueous solution of ammonium persulfate was charged into another sealed pressure vessel having an internal volume of 0.2 L and pressurized so that the internal pressure of the vessel became 0.3 MPa over 10 seconds. did. Then, using a vacuum pump from the vacuum tube, the pressure in the container is reduced to -0.08 MPa over 20 seconds, this operation is repeated three times, and then the pressure in the container is increased to 0.15 MPa. did.

After confirming that the temperature in the sealed pressure reaction vessel was 30 ° C., a pressure vessel containing ammonium persulfate was placed in the raw material charging port, and an aqueous ammonium persulfate solution was pressed into the sealed pressure reaction vessel. Immediately after the injection of the ammonium persulfate aqueous solution, the temperature inside the reaction vessel started to rise, and it was confirmed that emulsion polymerization was started. After 20 minutes from the start of the emulsion polymerization, the temperature rise in the reaction vessel stopped at 93 ° C. During this time, the temperature adjustment operation of the reaction vessel was not performed. Thereafter, the temperature in the reaction vessel was adjusted to 85 ° C. and held for 60 minutes, and a sample was taken to measure the acid value, the weight average molecular weight, the gel fraction, and the particle size by the method described above. When the acid value, weight average molecular weight, and gel fraction of the polymer contained in this polymer aqueous dispersion were measured from the collected sample, the acid value was 39, the gel fraction was 38%, and the weight average molecular weight was that the polymer was GPC. The molecular weight as a whole could not be measured because it was not completely dissolved in the eluent and THF used as the sample solution and the gel content was large.
Thereafter, while maintaining the reaction vessel temperature at 85 ° C., 10 parts of ammonia water (active ingredient 5%) was charged into another sealed pressure vessel with an internal volume of 0.2 L, and the vessel internal pressure was increased to 0.40 MPa. The product was pressed into a reaction vessel to neutralize the carboxyl groups in the polymer. Thereafter, the temperature in the reaction vessel was kept at 85 ° C. for 30 minutes, the contents were cooled, the pressure in the reaction vessel was returned to normal pressure, and then filtered through a 200-mesh wire mesh to obtain the polymer [A] of the present invention. Obtained. The polymer [A] obtained here had a solid content concentration of 37.5%, a viscosity of 50 mPa · s, and an average particle size of 180 nm.

(2) Production of polymer [B] (Production of polymer particles [X])
A sealed pressure reaction vessel having a volume of 2 L equipped with a stirrer, a nitrogen inlet pipe capable of pressurization, a pressure reduction pipe (pressure reduction pump), a raw material charging port, and a thermometer (material in the container: made of glass lining), 25 548 parts of the aqueous dispersion of the polymer [A] at 0 ° C. was charged, and under stirring, nitrogen gas was introduced into the reaction vessel through a nitrogen introduction tube, and the pressure inside the reaction vessel was increased to 0.3 MPa over 1 minute. Pressed. Thereafter, the pressure in the reaction vessel was reduced to −0.08 MPa over 5 minutes using a vacuum pump from the vacuum tube. After repeating this operation three times, the dissolved oxygen concentration of the polymer [A] aqueous dispersion in the reaction vessel was measured and found to be 0.5 ppm. While stirring the reaction vessel, 60 parts of butyl acrylate, 132 parts of methyl methacrylate, and 8 parts of glycidyl methacrylate were charged. Subsequently, 8.2 parts of a 2.4% aqueous solution of sodium bisulfite was charged, nitrogen gas was introduced into the reaction vessel from the nitrogen introduction tube, and the pressure in the reaction vessel was increased to 0.3 MPa over 1 minute. . Thereafter, the pressure in the reaction vessel is reduced from the pressure reducing pipe to a pressure of -0.08 MPa over 5 minutes by using a pressure reduction pump, this operation is repeated three times, and then the pressure in the reaction vessel is reduced to 0.30 MPa. Pressurized. During this time, the temperature in the reaction vessel was adjusted to 40 ° C.

  Next, 8.4 parts of a 4.8% aqueous solution of ammonium persulfate was charged into another sealed pressure vessel having an internal volume of 0.2 L and pressurized so that the internal pressure of the vessel became 0.3 MPa over 10 seconds. did. After that, the pressure inside the container is reduced to -0.08 MPa over 20 seconds using a pressure reducing pump, and this operation is repeated three times, and then the pressure inside the container is increased to 0.40 MPa. did.

  After confirming that the temperature in the sealed pressure reaction vessel was 40 ° C., a pressure vessel containing ammonium persulfate was placed in the raw material charging port, and an aqueous ammonium persulfate solution was pressed into the sealed pressure reaction vessel. After 35 minutes from immediately after the injection of the ammonium persulfate aqueous solution, the temperature inside the reaction vessel started to increase, and it was confirmed that emulsion polymerization was started. After 105 minutes from the start of the emulsion polymerization, the temperature rise in the reaction vessel stopped at 83 ° C. During this time, the temperature adjustment operation of the reaction vessel was not performed. Thereafter, the temperature in the reaction vessel was adjusted to 85 ° C. and held for 120 minutes. Thereafter, the contents were cooled, adjusted with aqueous ammonia (active ingredient 5%) so that the pH was 7.5, and then filtered through a 200 mesh wire mesh to obtain an aqueous acrylic polymer dispersion of the present invention. . The aqueous acrylic polymer dispersion obtained here had a solid content concentration of 52.1%, a viscosity of 430 mPa · s, and an average particle size of 230 nm.

The evaluation results of the coating obtained using the acrylic polymer aqueous dispersion of the present invention are shown in Table 1, and the elongation rate in the tensile test at a measurement temperature of −30 ° C. is 320%. The Young's modulus in the tensile test at 25 ° C. was 70 MPa, and the glass transition temperatures (actually measured Tg) were −25 ° C. and 52 ° C. Moreover, as a low temperature characteristic of the coating obtained from this polymer aqueous dispersion, the flexibility at −30 ° C. is good without causing breakage and cracking, and the Shore D hardness of the coating at 25 ° C. is 87. there were.
Example 2 and Example 3
A polymer aqueous dispersion of the present invention was obtained in the same manner as in Example 1 except that the monomer mixture shown in Table 1 was used and the temperature at the start of polymerization was changed to the temperature shown in Table 1. It was. The acid value, weight average molecular weight, gel fraction, particle size, and particle size and solid content concentration of the polymer aqueous dispersion contained in this polymer aqueous dispersion are shown in Table 1. It was street. Moreover, the elongation rate in the tensile test at the measurement temperature of −30 ° C., the Young's modulus in the tensile test at the measurement temperature of 25 ° C., the glass transition temperature (measured Tg), The flexibility at −30 ° C. and the hardness at 25 ° C. were as described in Table 1.

Comparative Example 1
280 parts deionized water, Aqualon KH-10 [Daiichi Kogyo Seiyaku Co., Ltd .: active ingredient 100%] 0.5 in a reaction vessel equipped with a stirrer, reflux condenser, nitrogen inlet tube, thermometer, and dropping funnel The temperature was raised to 85 ° C. while blowing nitrogen. Under stirring, 0.02 part of ammonium persulfate was added, and then a monomer mixture composed of 168 parts of n-butyl acrylate, 20 parts of methyl methacrylate and 12 parts of methacrylic acid was added to Aqualon KH-10 [Daiichi Kogyo Seiyaku Co., Ltd. Product: 100% active ingredient] A part of a monomer pre-emulsion (referred to that the monomer is emulsified with the above-mentioned monomer, emulsifier and water) added with 1.5 parts and 60 parts of deionized water (5) Part) was added, and polymerization was carried out in 60 minutes while maintaining the temperature in the reaction vessel at 85 ° C. Subsequently, while maintaining the temperature in the reaction vessel at 85 ° C., the remaining monomer pre-emulsion (258 parts) and 20 parts of 1.0% aqueous solution of ammonium persulfate were separately added to the reaction vessel temperature using a separate dropping funnel. Was polymerized by dropping over 180 minutes while maintaining at 85 ° C. After completion of dropping, the mixture was stirred at the same temperature for 120 minutes, and then 20 parts of aqueous ammonia (active ingredient 5%) was added dropwise over 30 minutes while maintaining the temperature in the reaction vessel at 85 ° C.
Subsequently, while maintaining the temperature in the reaction vessel at 85 ° C., a monomer mixture consisting of 60 parts of n-butyl acrylate, 132 parts of methyl methacrylate and 8 parts of glycidyl methacrylate, and 20 parts of a 1.0% aqueous solution of ammonium persulfate, Using separate dropping funnels, polymerization was carried out by dropping over 180 minutes while maintaining the temperature in the reaction vessel at 85 ° C. After completion of the dropwise addition, the mixture is stirred for 120 minutes at the same temperature, the contents are cooled, adjusted to pH 7.5 with aqueous ammonia (active ingredient 5%), filtered through a 200 mesh wire net, An aqueous acrylic polymer dispersion of the invention was obtained. The aqueous acrylic polymer dispersion obtained here had a solid content concentration of 50.8%, a viscosity of 380 mPa · s, and an average particle size of 230 nm.

  The evaluation results of the coating obtained using the polymer aqueous dispersion obtained here are shown in Table 1, and the elongation rate in the tensile test at a measurement temperature of −30 ° C. is 20%, and the measurement temperature is 25 The Young's modulus in a tensile test at ° C was 53 MPa, and the glass transition temperatures (measured Tg) were -23 ° C and 45 ° C. Moreover, as a low temperature characteristic of the coating film obtained from this polymer aqueous dispersion, as for the flexibility at −30 ° C., stress whitening was observed at the bent portion, and cracks were partially formed. The Shore D hardness of the coating at 25 ° C. was 85.

Comparative Example 2
280 parts deionized water, Aqualon KH-10 [Daiichi Kogyo Seiyaku Co., Ltd .: active ingredient 100%] 0.5 in a reaction vessel equipped with a stirrer, reflux condenser, nitrogen inlet tube, thermometer, and dropping funnel The temperature was raised to 85 ° C. while blowing nitrogen. Under stirring, 0.02 part of ammonium persulfate was added, and then a monomer mixture consisting of 228 parts of n-butyl acrylate, 152 parts of methyl methacrylate, 8 parts of glycidyl methacrylate and 12 parts of methacrylic acid was added to Aqualon KH-10 [No. Ichi Kogyo Seiyaku Co., Ltd .: 100% active ingredient] A part (10 parts) of a monomer pre-emulsion emulsified by adding 1.5 parts and 80 parts of deionized water was added, and the temperature in the reaction vessel was 85 ° C. The polymerization was carried out for 60 minutes while maintaining the temperature. Subsequently, while maintaining the temperature in the reaction vessel at 85 ° C., the remaining monomer pre-emulsion (473 parts) and 40 parts of a 1.0% aqueous solution of ammonium persulfate were added to the reaction vessel temperature using separate dropping funnels. Was polymerized dropwise over 240 minutes while maintaining at 85 ° C. After completion of dropping, the mixture is stirred for 120 minutes at the same temperature, and the contents are cooled. Then, the pH is adjusted to 7.5 with aqueous ammonia (active ingredient 5%), and the mixture is filtered through a 200 mesh wire net. An aqueous polymer dispersion was obtained. The aqueous acrylic polymer dispersion obtained here had a solid content concentration of 48.8%, a viscosity of 200 mPa · s, and an average particle size of 280 nm.

The evaluation results of the coating obtained using the polymer aqueous dispersion obtained here are shown in Table 1. The elongation rate in the tensile test at a measurement temperature of −30 ° C. is 1%, and the measurement temperature is 25 The Young's modulus in the tensile test at 0 ° C. was 8 MPa, and the glass transition temperature (measured Tg) was 5 ° C. Moreover, as a low temperature characteristic of the film obtained from this polymer aqueous dispersion, the flexibility at −30 ° C. caused many cracks at the bent part. The Shore D hardness of the coating at 25 ° C. was 12. The official names of the abbreviations in Table 1 are shown below.
n-BA (n-butyl acrylate), MMA (methyl methacrylate), MAA (methacrylic acid), AA (acrylic acid), GMA (glycidyl methacrylate), MAPTMS (γ-methacryloxypropyltrimethoxysilane), L-SH ( Lauryl mercaptan), 2-EHA (2-ethylhexyl acrylate)

Claims (13)

A monomer component (a) having an ethylenically unsaturated monomer (a-1) containing a carboxyl group as an essential component is collectively charged into a reaction vessel in which an aqueous medium is present and polymerized. In an aqueous medium containing the ethylenic polymer [A] having a glass transition temperature (measured Tg) containing carboxy group of −50 to −15 ° C. and the ethylenic polymer [A], methyl (meth) Ethylene having no carboxyl group and glass transition temperature (measured Tg) of 30 to 150 ° C., obtained by batch charging and polymerizing monomer component (b) containing acrylate and butyl (meth) acrylate An acrylic polymer aqueous dispersion containing polymer particles [X] containing a polymer [B] , wherein the structure located in the outermost shell of the polymer particles [X] has the ethylenic structure. From the polymer [A] Acrylic polymer aqueous dispersion, characterized in that a layer. The polymer [A] has an acid value of 10 to 300 mgKOH / g, a weight average molecular weight of 100,000 or more, and a gel fraction (acetone insoluble fraction) of 95 wt% or less. Acrylic polymer aqueous dispersion. The acrylic polymer aqueous dispersion according to claim 1, wherein the polymer [A] and the polymer [B] have a reactive functional group capable of bonding to each other. The acrylic polymer aqueous dispersion according to claim 1, wherein the polymer [B] contains a group having reactivity with a carboxyl group.
The polymer and [A], the weight ratio of the polymer [B] is any one of claims 1-4 which is [A] / [B] = 7 / 3~4 / 6 in solid content ratio An acrylic polymer aqueous dispersion described in 1. The monomer component (a) having the ethylenically unsaturated monomer (a-1) containing a carboxyl group as an essential component is charged all at once into a reaction vessel in which an aqueous medium is present, and polymerized. 10 to 300 mgKOH / g, a weight average molecular weight of 100,000 or more, a gel fraction of 95% by weight or less, and a measured polymer Tg of −50 to −15 ° C. is obtained [A], In the aqueous medium in which the polymer [A] is present, the monomer component (b) containing methyl (meth) acrylate and butyl (meth) acrylate is charged all at once and has a carboxyl group obtained by polymerization. A method for producing an aqueous acrylic polymer dispersion containing polymer particles [X] containing an ethylenic polymer [B] having a glass transition temperature (measured Tg) of 30 to 150 ° C. In the outermost shell of polymer particle [X] A method for producing an aqueous acrylic polymer dispersion , wherein the structure located is a layer composed of the ethylenic polymer [A] . 7. The reaction according to claim 6 , wherein a closed pressure reaction vessel is used as the reaction vessel, and the reaction is carried out by controlling the pressure in the closed pressure reaction vessel at the start of the reaction of the monomer component (a) to a normal pressure or higher. A method for producing an aqueous acrylic polymer dispersion. The method for producing an acrylic polymer aqueous dispersion according to claim 7 , wherein the reaction is performed by pressurizing the pressure in the sealed pressure reaction vessel to a state exceeding the vapor pressure of the mixture of the aqueous medium and the polymerizable monomer component. . The method for producing an aqueous acrylic polymer dispersion according to claim 6 , wherein polymerization is performed using a redox polymerization initiator as a polymerization initiator. The method for producing an aqueous acrylic polymer dispersion according to claim 6 , wherein the temperature at the start of polymerization is in the range of 10 to 50 ° C. The method for producing an aqueous acrylic polymer dispersion according to claim 6 , wherein 10 mol% or more of the carboxyl groups in the polymer [A] are neutralized with a basic substance. The ethylenically unsaturated monomer component (b) is an essential component containing an ethylenically unsaturated monomer (b-1) containing a functional group having reactivity with the reactive functional group in the polymer [A]. The method for producing an aqueous acrylic polymer dispersion according to claim 6 . The ethylenically unsaturated monomer (b-1) containing a functional group having reactivity with the reactive functional group in the polymer [A] is an ethylenically unsaturated monomer having a functional group reactive with a carboxyl group. The method for producing an aqueous acrylic polymer dispersion according to claim 12, which is a saturated monomer.