JP2007031509A - Polyester resin aqueous dispersion and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyester resin aqueous dispersion excellent in shock-stable property even when organic solvent content is low, containing low acid value polyester resin forming a resin film excellent in adhesion to a substrate and producible in a high yield. <P>SOLUTION: The polyester resin aqueous dispersion is obtained by dispersing a polyester resin having 2-10 mgKOH/g acid value and ≥230,000 z-average molecular weight in an aqueous medium and has ≤3 mass% organic solvent content. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an aqueous polyester resin dispersion that can be applied to various substrates to form an excellent resin film.

  Polyester resin is a film-forming resin that is excellent in film processability, resistance to organic solvents (solvent resistance), weather resistance, adhesion to various substrates, paints, inks, adhesives, It is used in large quantities as a binder component in fields such as coating agents.

  In recent years, the use of organic solvents has tended to be restricted from the standpoints of environmental protection, resource saving, dangerous goods regulations by the Fire Service Act, and workplace environment improvement. A polyester resin aqueous dispersion finely dispersed in an aqueous medium has been actively developed.

  For example, an aqueous polyester resin dispersion in which a carboxyl group of a polyester resin is neutralized with a basic compound and dispersed in an aqueous medium has been proposed. When such an aqueous dispersion is used, processability, water resistance, solvent resistance are proposed. It is disclosed that a film excellent in performance such as property can be formed (Patent Documents 1 to 4).

  The polyester resin aqueous dispersions of Patent Documents 1 and 2 form a polyester resin film excellent in solvent resistance and can be used as a coating agent. From the standpoint of environmental protection and workplace environment improvement, Further reduction of the amount of organic solvent is desired, and Patent Document 3 is proposed. Further, the polyester resins used in Patent Documents 1 to 3 have a carboxyl end group corresponding to an acid value of 8 mgKOH / g or more, and as a result, the molecular weight of the polyester resin is limited, and workability and adhesion are insufficient. Therefore, Patent Document 4 has been proposed.

JP 2000-26709 A JP 2000-313793 A JP 2002-173582 A International Publication No. 2004/037924 Pamphlet

  However, since the polyester resin aqueous dispersions described in these documents use a polyester resin having a small acid value, the amount of carboxy anion produced by neutralization with a basic compound is small. Since the carboxy anion imparts stability to the polyester resin dispersed in the aqueous medium, if the amount of carboxy anion produced is small, the content of the organic solvent contained in the polyester resin aqueous dispersion is low. There is a problem that the polyester resin in the aqueous medium easily aggregates due to external impact.

  In addition, in the step of removing the organic solvent contained in the aqueous polyester resin dispersion under normal pressure, there is a problem that a large amount of polyester resin aggregates are generated and the yield decreases.

  Under such circumstances, the object of the present invention is to provide a low acid value polyester capable of forming a resin film having excellent impact stability and good adhesion to a substrate even when the organic solvent content is low. An object of the present invention is to provide an aqueous polyester resin dispersion containing a resin and capable of being produced in high yield, and a method for producing the same.

  As a result of diligent research to solve the above-mentioned problems, the present inventors have used a polyester resin having a specific molecular weight distribution, so that even when the content of the organic solvent is low, the polyester resin has excellent impact stability. The present invention has been completed by finding that an aqueous dispersion can be obtained in a high yield.

  That is, the gist of the present invention is as follows. First, a polyester resin having an acid value of 2 to 10 mgKOH / g and a Z average molecular weight of 230,000 or more is dispersed in an aqueous medium, and the content of the organic solvent is 3% by mass or less. The second is an aqueous polyester resin dispersion. Secondly, an organic solvent solution of a polyester resin having an acid value of 2 to 10 mg KOH / g and a Z average molecular weight of 230,000 or more is dispersed in water together with a basic compound to perform phase inversion. After emulsification, the organic solvent is removed under normal pressure. A method for producing an aqueous polyester resin dispersion.

  In the aqueous polyester resin dispersion of the present invention, a high molecular weight polyester resin is stably dispersed, and a resin film excellent in film performance such as processability, adhesion to various substrates, and water resistance can be formed. it can. Therefore, it can be suitably used alone or as a binder component by mixing other components as paints, coating agents, adhesives, polyester films, polyamide films, polyolefin films, and various kinds of films such as these deposited films. Anchor coat agent, adhesion imparting agent (easy adhesion), aluminum plate, steel plate, plated steel plate, and other metal plate anchor coat agent, adhesion imparting agent (easy adhesion), pre-coated metal paint, paper coating agent, fiber treatment It can be used for applications such as an adhesive for bonding substrates such as an agent, paper, a metal plate, and a resin sheet, and an ink binder.

  Furthermore, since the polyester resin aqueous dispersion of the present invention is excellent in impact stability, when mixed with other components using a stirrer, when coating on various substrates at high speed using a gravure coater, roll coater, etc. Even when the aqueous polyester resin dispersion is subjected to an impact during transportation, the aggregation of the polyester resin can be suppressed.

  Moreover, since the content rate of the organic solvent contained in the polyester resin aqueous dispersion is reduced, it can be suitably used for a wider range of substrates in the above applications as well as from the standpoint of environmental protection and workplace environment improvement.

  In addition, the aqueous polyester resin dispersion of the present invention is industrialized because it can be produced in high yield even when the organic solvent is removed under a practical normal pressure in terms of required time and workability. Preferred above. Thus, the industrial use value of the polyester resin aqueous dispersion of the present invention is extremely high.

  Hereinafter, the present invention will be described in detail.

  The aqueous polyester resin dispersion of the present invention is a liquid material in which a polyester resin having an acid value of 2 to 10 mg KOH / g and a Z average molecular weight of 230,000 or more is dispersed in an aqueous medium.

  First, the polyester resin will be described.

  In the present invention, the acid value of the polyester resin needs to be 2 to 10 mgKOH / g, preferably 4 to 9 mgKOH / g, and more preferably 5 to 8 mgKOH / g. When the acid value exceeds 10 mgKOH / g, the molecular weight of the polyester resin is lowered, the processability and adhesion of the resin film are lowered, and the water resistance is insufficient. Further, when the acid value is less than 2 mgKOH / g, it is difficult to obtain a uniform aqueous dispersion.

  In addition, the hydroxyl group may be contained in the range which does not impair the water resistance of a resin film, and the hydroxyl value is usually 30 mgKOH / g or less, and preferably 20 mgKOH / g or less.

  The Z-average molecular weight of the polyester resin needs to be 230,000 or more, preferably 250,000 or more, more preferably 270,000 or more. When the Z average molecular weight is less than 230,000, a large amount of a basic compound is used in order to improve the storage stability by reducing the volume average particle size of the aqueous dispersion in the production process described later. If it is necessary and the amount of the basic compound used is large, the polyester resin tends to aggregate while the organic solvent is removed by atmospheric distillation, which is not preferable. Moreover, since the impact stability of the polyester resin aqueous dispersion after removing the organic solvent tends to be inferior, it is not preferable.

The upper limit of the Z average molecular weight is not particularly limited, but the Z average molecular weight of the polyester resin is preferably 800,000 or less from the viewpoint of reducing undispersed polyester resin. Here, the Z average molecular weight is an average molecular weight Mz defined by the following formula (1) in the molecular weight distribution of the polyester resin.
^{_{Mz = Σn i M i 3 /}} Σn i M i 2 (1)
[In the formula (1), M _i represents the molecular weight of the component i in the resin, and n _i represents the molar fraction of the component i. ]

  The glass transition temperature of the polyester resin is preferably −50 to 120 ° C., more preferably 0 to 90 ° C., since the storage stability of the aqueous dispersion tends to be excellent.

  Next, the components of the polyester resin will be described.

  Examples of the polybasic acid component constituting the polyester resin include aromatic dicarboxylic acids, aliphatic dicarboxylic acids, alicyclic dicarboxylic acids, and trifunctional or higher polybasic acids. Aromatic dicarboxylic acids include terephthalic acid, isophthalic acid, phthalic acid, phthalic anhydride, naphthalene dicarboxylic acid, biphenyl dicarboxylic acid, etc., and aliphatic dicarboxylic acids include oxalic acid, succinic acid, succinic anhydride, adipine Saturated aliphatic dicarboxylic acids such as acid, azelaic acid, sebacic acid, dodecanedioic acid, eicosane diacid, hydrogenated dimer acid, fumaric acid, maleic acid, maleic anhydride, itaconic acid, itaconic anhydride, citraconic acid, anhydrous Examples thereof include unsaturated aliphatic dicarboxylic acids such as citraconic acid and dimer acid. Examples of the alicyclic dicarboxylic acid include 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 2,5-norbornenedicarboxylic acid and its anhydride, tetrahydrophthalic acid and its anhydride. Such as things. The tribasic or higher polybasic acid includes trimellitic acid, pyromellitic acid, benzophenone tetracarboxylic acid, trimellitic anhydride, pyromellitic anhydride, benzophenone tetracarboxylic acid anhydride, trimesic acid, ethylene glycol bis (an Hydrotrimellitate), glycerol tris (anhydrotrimellitate), 1,2,3,4-butanetetracarboxylic acid and the like.

  The polybasic acid is preferably an aromatic dicarboxylic acid, and the proportion of the aromatic dicarboxylic acid in the polybasic acid component of the polyester resin is preferably 50 mol% or more, more preferably 60 mol% or more. preferable. By increasing the ratio of the aromatic dicarboxylic acid, the hardness, water resistance, solvent resistance, workability, etc. of the resin film formed from the aqueous dispersion are improved. As the aromatic dicarboxylic acid, terephthalic acid and isophthalic acid are preferred because they are industrially produced in large quantities and are inexpensive.

  Polybasic acid having a hydrophilic group other than carboxyl group or hydroxyl group such as 5-sodium sulfoisophthalic acid can also be used as the polybasic acid, but the water resistance of the resin film formed from the aqueous dispersion is excellent. Use with caution as it tends to get worse.

  Examples of the polyhydric alcohol component constituting the polyester resin include an aliphatic glycol having 2 to 10 carbon atoms, an alicyclic glycol having 6 to 12 carbon atoms, an ether bond-containing glycol, and a trifunctional or higher polyhydric alcohol. Examples of the aliphatic glycol having 2 to 10 carbon atoms include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 2-methyl-1,3-propanediol, 1,5 -Pentanediol, neopentyl glycol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 1,9-nonanediol, 2-ethyl-2-butylpropanediol, etc. Examples of the alicyclic glycol of -12 include 1,4-cyclohexanedimethanol, and examples of the ether bond-containing glycol include diethylene glycol, triethylene glycol, dipropylene glycol, polytetramethylene glycol, polyethylene glycol, and polypropylene glycol. Can be mentioned. Examples of the trifunctional or higher polyhydric alcohol include glycerin, trimethylolethane, trimethylolpropane, pentaerythritol and the like.

  In addition, polyhydric alcohols such as ethylene oxide adducts of bisphenols (bisphenol A) such as 2,2-bis [4- (hydroxyethoxy) phenyl] propane and bis [4- (hydroxyethoxy) phenyl] sulfone Ethylene oxide adducts of bisphenols (bisphenol S) can also be used.

  As the polyhydric alcohol, ethylene glycol and neopentyl glycol are preferably used because they are industrially produced in large quantities and are inexpensive. Ethylene glycol and neopentyl glycol occupy the polyhydric alcohol component of the polyester resin. The total ratio of is preferably 50 mol% or more, more preferably 60 mol% or more. In particular, ethylene glycol has the advantage of improving the chemical resistance of the resin coating, and neopentyl glycol has the advantage of improving the weather resistance of the resin coating.

  The polyester resin may be copolymerized with monocarboxylic acid, monoalcohol, hydroxycarboxylic acid, such as lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, benzoic acid, Examples thereof include p-tert-butylbenzoic acid, cyclohexane acid, 4-hydroxyphenyl stearic acid, stearyl alcohol, 2-phenoxyethanol, ε-caprolactone, lactic acid, β-hydroxybutyric acid, and an ethylene oxide adduct of p-hydroxybenzoic acid.

  The polyester resin may be copolymerized with a trifunctional or higher polyvalent oxycarboxylic acid, and examples thereof include malic acid, glyceric acid, citric acid, and tartaric acid.

    Next, the polyester resin aqueous dispersion of the present invention will be described.

  The aqueous dispersion of the present invention is a liquid material in which the above-described polyester resin is dispersed in an aqueous medium. Here, the aqueous medium is a medium made of a liquid containing water, and may contain a basic compound or an organic solvent described later.

  5-50 mass% is preferable and, as for the content rate of the polyester resin in the aqueous dispersion of this invention, it is more preferable that it is 15-40 mass%. When the content of the polyester resin exceeds 50% by mass, the dispersed polyester resin tends to aggregate, and the storage stability tends to be impaired. If the content of the polyester resin is less than 5% by mass, it is not practical.

  Further, the volume average particle size of the aqueous polyester resin dispersion of the present invention, that is, the volume average particle size of the polyester resin dispersed in the aqueous medium containing water is usually 400 nm or less and 200 nm or less. Preferably, it is 150 nm or less. When the volume average particle diameter exceeds 400 nm, the dispersed polyester resin tends to aggregate and storage stability may be impaired.

  The water is not particularly limited, and distilled water, ion exchange water, city water, industrial water, and the like can be used, but it is preferable to use distilled water or ion exchange water.

  Next, the manufacturing method of the polyester resin aqueous dispersion of this invention is demonstrated.

  As will be described later, the aqueous dispersion of the present invention can be obtained by dispersing an organic solvent solution of a polyester resin in water together with a basic compound and performing phase inversion emulsification, and then removing the organic solvent under normal pressure. .

  First, a method for producing a polyester resin will be described.

  The polyester resin can be produced by polycondensation of one or more polybasic acids and one or more polyhydric alcohols by a known method. For example, all the monomer components and / or their low weight The coalescence is reacted at 180 to 260 ° C. for about 2.5 to 10 hours under an inert atmosphere to carry out an esterification reaction, and subsequently in the presence of a polycondensation catalyst at a temperature of 220 to 280 ° C. under a reduced pressure of 130 Pa or less. Examples thereof include a method of proceeding a polycondensation reaction until a desired molecular weight is reached to obtain a polyester resin.

  Examples of a method for imparting a desired acid value or hydroxyl value to a polyester resin include a method in which a polybasic acid or a polyhydric alcohol is further added following the polycondensation reaction and depolymerization is performed in an inert atmosphere. Can do.

  In addition, as a method for imparting a desired acid value to the polyester resin, a method in which a polybasic acid anhydride is further added following the polycondensation reaction and an addition reaction with a hydroxyl group of the polyester resin is performed in an inert atmosphere. You can also.

  In the present invention, a trifunctional or higher polyfunctional component is copolymerized at a ratio of 0.2 to 3.0 mol% with respect to the total dicarboxylic acid component, and then depolymerized and / or added using a polybasic acid. A method of reacting to produce a polyester resin is preferred in that the molecular weight and acid value of the polyester resin can be easily controlled.

  Examples of the trifunctional or higher polyfunctional component used for copolymerization include the trifunctional or higher polyhydric alcohol, the trifunctional or higher polybasic acid, the trifunctional or higher polyvalent oxycarboxylic acid, and the like.

  The polybasic acid used in the depolymerization reaction and / or addition reaction is preferably a tribasic or higher polybasic acid. By using a tribasic or higher polybasic acid, a desired acid value can be imparted while suppressing a decrease in the molecular weight of the polyester resin due to the depolymerization reaction. Moreover, although the reason is not fully clarified, an aqueous dispersion excellent in storage stability can be obtained by using a polybasic acid having three or more functional groups.

  Examples of the polybasic acid used in the depolymerization reaction and / or addition reaction include the polybasic acids described in the constituent components of the polyester resin. Among them, terephthalic acid, isophthalic acid, and phthalic anhydride which are aromatic dicarboxylic acids. And trimellitic acid and trimellitic anhydride which are trifunctional polybasic acids are preferable. In particular, when trimellitic anhydride is used, the depolymerization reaction and the addition reaction are considered to occur in parallel, which is more preferable.

    Next, the manufacturing method of an aqueous dispersion is demonstrated.

    A method for dispersing a polyester resin in an aqueous medium is exemplified. For example, an aqueous polyester resin dispersion in which a carboxyl group of a polyester resin is neutralized with a basic compound to generate a carboxyl anion, and fine particles of the polyester resin are stably dispersed without agglomeration between the anions. And so on.

  The aqueous polyester resin dispersion of the present invention is obtained by dispersing an organic solvent solution of a polyester resin in water together with a basic compound, phase-inversion emulsification, and then removing (desolving) the organic solvent under normal pressure. It is preferable for obtaining a polyester resin aqueous dispersion having a low content of.

  First, the organic solvent solution of the polyester resin will be described.

  The concentration of the polyester resin in the organic solvent solution of the polyester resin is preferably in the range of 10 to 70% by mass, and more preferably in the range of 20 to 50% by mass. When the concentration of the polyester resin in the solution exceeds 70% by mass, in the next phase inversion emulsification, the viscosity increases greatly when mixed with water, and the aqueous dispersion obtained from such a state has a volume. The average particle size tends to be large, and storage stability is impaired. Moreover, when the density | concentration of a polyester resin is less than 10 mass%, a large amount of organic solvents will be removed in the case of solvent removal, and it is economically unpreferable. An apparatus for dissolving the polyester resin in the organic solvent is not particularly limited as long as it includes a tank into which a liquid can be charged and can be appropriately stirred. Moreover, when the polyester resin is difficult to dissolve, heating may be performed.

  In addition, you may melt | dissolve a polyester resin individually or in mixture of 2 or more types.

  As the organic solvent, known ones can be used, for example, ketone organic solvents, aromatic hydrocarbon organic solvents, ether organic solvents, halogen-containing organic solvents, alcohol organic solvents, ester organics. A solvent, a glycol type organic solvent, etc. are mentioned. Examples of ketone organic solvents include methyl ethyl ketone (hereinafter referred to as MEK), acetone, diethyl ketone, methyl propyl ketone, methyl isobutyl ketone (hereinafter referred to as MIBK), 2-hexanone, 5-methyl-2-hexanone, and 2-heptanone. , 3-heptanone, 4-heptanone, cyclopentanone, cyclohexanone and the like. Aromatic hydrocarbon organic solvents such as toluene, xylene, benzene, ether organic solvents such as dioxane, tetrahydrofuran, and halogen-containing organic solvents such as carbon tetrachloride, trichloromethane, dichloromethane, etc. Examples of the organic solvent include methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, sec-butanol, tert-butanol, n-amyl alcohol, isoamyl alcohol, sec-amyl alcohol, tert-amyl alcohol, 1- Examples of ester organic solvents such as ethyl-1-propanol, 2-methyl-1-butanol, n-hexanol, and cyclohexanol include ethyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate, Acid-sec-butyl, 3-methoxybutyl acetate, methyl propionate, ethyl propionate, diethyl carbonate, dimethyl carbonate, etc., glycol organic solvents include ethylene glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene Glycol monopropyl ether, ethylene glycol monobutyl ether, ethylene glycol ethyl ether acetate, diethylene glycol, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, diethylene glycol ethyl ether acetate, propylene glycol, propylene glycol monomethyl ether, propylene glycol monobutyl ether, propylene Guri Examples thereof include coal methyl ether acetate. Moreover, organic solvents such as 3-methoxy-3-methylbutanol, 3-methoxybutanol, acetonitrile, dimethylformamide, dimethylacetamide, diacetone alcohol, ethyl acetoacetate, and the like. These organic solvents are used alone or in combination of two or more. Can be used in combination.

  In order to obtain the aqueous dispersion of the present invention, it is preferable to select an organic solvent that can dissolve 10% by mass or more of the polyester resin, and an organic solvent that can dissolve 20% by mass or more is more preferable. . Examples of such organic solvents include acetone, MEK, MIBK, dioxane, tetrahydrofuran, cyclohexanone alone, acetone / ethylene glycol monobutyl ether mixed solution, MEK / ethylene glycol monobutyl ether mixed solution, MIBK / ethylene glycol monobutyl ether mixed solution, dioxane. / Ethylene glycol monobutyl ether mixed solution, tetrahydrofuran / ethylene glycol monobutyl ether mixed solution, cyclohexanone / ethylene glycol monobutyl ether mixed solution, acetone / isopropanol mixed solution, MEK / isopropanol mixed solution, MIBK / isopropanol mixed solution, dioxane / isopropanol mixed solution, Tetrahydrofuran / isopropanol mixed solution, cyclohexane Etc. Non / isopropanol mixture solution can be suitably used.

  Next, phase inversion emulsification will be described.

  Phase inversion emulsification is performed by mixing water and a basic compound in an organic solvent solution of a polyester resin. In the present invention, it is preferable to carry out phase inversion emulsification by adding a basic compound to an organic solvent solution of a polyester resin and gradually adding water thereto. When the rate of water addition is high, a mass of polyester resin is formed, which mass may no longer disperse in the aqueous medium, resulting in a lower yield of the resulting aqueous dispersion, which is economical. Absent.

  In the present invention, “phase inversion emulsification” means that an amount (mass) of water exceeding the amount (mass) of organic solvent contained in this solution is added to an organic solvent solution of the polyester resin, so This means that the polyester resin is dispersed in a liquid phase containing a large amount of.

  The phase inversion emulsification is preferably performed at 30 ° C. or less, and more preferably at 20 ° C. or less. By carrying out phase inversion emulsification at 30 ° C. or less, the aqueous polyester resin dispersion obtained has a small volume average particle size, and an aqueous dispersion having excellent storage stability can be obtained. In addition, when the volume average particle size is small, it is possible to suppress aggregation and precipitation of the polyester resin fine particles in the solvent removal described later, and as a result, the yield is improved, which is preferable.

  An apparatus for performing phase inversion emulsification is not particularly limited as long as it includes a tank into which a liquid can be charged and can be appropriately stirred. Examples of such an apparatus include apparatuses widely known to those skilled in the art as a solid / liquid stirring apparatus and an emulsifier (for example, a homomixer). When using a high shearing emulsifier such as a homomixer, the liquid temperature may rise due to impact heat, so it is preferable to use it while cooling. The phase inversion emulsification may be performed under normal pressure, reduced pressure, or increased pressure.

  Next, the removal (desolvation) of the organic solvent will be described.

  The removal of the organic solvent can be performed by a method of distilling after phase inversion emulsification. Although distillation may be performed under normal pressure or reduced pressure, it is preferably performed under normal pressure from the viewpoint of required time and workability. By using the polyester resin within the scope of the present invention, aggregates are hardly generated even when distilled under normal pressure, and an aqueous dispersion can be obtained with good yield.

  The amount of the organic solvent in the aqueous dispersion must be 3% by mass or less from the viewpoints of environmental problems, improvement of the workplace environment, reduction of residual organic solvent that adversely affects the resin film physical properties, storage stability, and the like. % Or less is preferable, and 1% by mass or less is most preferable.

  As an apparatus for performing the distillation, any apparatus can be used as long as it has a tank into which a liquid can be introduced and can be appropriately stirred.

  According to the above production method, the aqueous polyester resin dispersion of the present invention has a uniform state in which the solid content concentration such as precipitation and phase separation in the aqueous medium is not found locally different from other parts. can get.

  In manufacturing the aqueous dispersion, a filtration step may be provided in the process for the purpose of removing foreign substances and the like. In such a case, for example, a stainless steel filter (wire diameter 0.035 mm, plain weave) of about 300 mesh may be installed and pressure filtration (air pressure 0.2 MPa) may be performed.

  Next, a method for using the aqueous dispersion of the present invention will be described.

  Since the aqueous dispersion of the present invention is excellent in film forming ability, it is uniformly coated on the surface of various substrates by known film forming methods such as dipping method, brush coating method, spray coating method, curtain flow coating method and the like. Then, after setting it at around room temperature as necessary, it is subjected to a heat treatment for drying and baking, whereby a uniform resin film can be formed in close contact with the surfaces of various substrates. As a heating device at this time, a normal hot air circulation type oven, an infrared heater, or the like may be used. In addition, the heating temperature and the heating time are appropriately selected depending on the type of substrate to be coated, etc., but considering the economy, the heating temperature is usually 60 to 250 ° C., 70-230 degreeC is preferable and 80-200 degreeC is optimal. The heating time is usually 1 second to 30 minutes, preferably 5 seconds to 20 minutes, and most preferably 10 seconds to 10 minutes.

  The thickness of the resin film formed using the aqueous dispersion of the present invention is appropriately selected depending on the purpose and application, but is usually 0.01 to 40 μm, and 0.1 to 30 μm. 0.5 to 20 μm is preferable.

  In addition, the aqueous dispersion of the present invention includes a curing agent, various additives, a surfactant, a compound having a protective colloid action, water, an organic solvent, a pigment such as titanium oxide, zinc white, and carbon black, if necessary. Dyes, other water-based polyester resins, water-based urethane resins, water-based olefin resins, water-based resins such as water-based acrylic resins, and the like can be blended and used.

  The curing agent is not particularly limited as long as it is a functional group possessed by a polyester resin, such as a carboxyl group or its anhydride and a hydroxyl group, and is not particularly limited. For example, a urea resin, a melamine resin, a benzoguanamine resin, etc. Examples include amino resins, polyfunctional epoxy compounds, polyfunctional isocyanate compounds and their various blocked isocyanate compounds, polyfunctional aziridine compounds, carbodiimide group-containing compounds, oxazoline group-containing polymers, and phenol resins. Use one of these. Or you may use 2 or more types together.

  Examples of additives include repellency inhibitors, leveling agents, antifoaming agents, anti-waxing agents, rheology control agents, pigment dispersants, ultraviolet absorbers, and lubricants.

  Examples of the surfactant include all surfactants such as an anionic surfactant, a cationic surfactant, an amphoteric surfactant, and a nonionic surfactant. Nonionic surfactants include alkylene oxide adducts of alkylphenols such as nonylphenol and octylphenol, and alkylene oxide adducts of higher alcohols. Examples of such nonionic surfactants include the Igepal series manufactured by Aldrich, NAROACTY N-100, NAROACTY N-120, NAROACTY N-140, etc. made by Sanyo Chemical Co., Ltd., NALOACTY series, SANNONIC SS-120, SANNONIC SS-90, SANNONIC SS-70, SANNONIC SS series, SANNONIC FD-140, Sannonic FD-100, Sannonic FD-80, etc., Sannonic FD series, Cedran FF-220, Cedran FF-210, Cedran FF-200, Cedran FF-180 However, Cedran FF series, Cedran SNP-112, Cedran SNP series, New Pole PE-64, New Pole PE-74, New Pole PE-75, New Pole PE series, and San Morin 11 are listed.

  In addition, as a compound having protective colloid action, polymerization of vinyl monomer containing polyvinyl alcohol, carboxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, modified starch, polyvinyl pyrrolidone, polyacrylic acid, acrylic acid and / or methacrylic acid as one component Products, polyitaconic acid, gelatin, gum arabic, casein, swellable mica and the like.

    The present invention will be specifically described below with reference to examples.

(1) Composition of polyester resin
^It calculated | required from < ¹ > H-NMR analysis (The product made by Varian, 300MHz). In addition, with respect to a resin containing a constituent monomer in which no assignable / quantifiable peak is observed on the ¹ H-NMR spectrum, it is subjected to methanol decomposition at 230 ° C. for 3 hours in a sealed tube, followed by gas chromatogram analysis for quantitative analysis. I did it.

(2) Acid value of polyester resin 0.5 g of polyester resin was dissolved in 50 ml of water / dioxane = 1/9 (volume ratio), titrated with KOH using cresol red as an indicator, and the amount of KOH consumed for neutralization. A value obtained by converting the number of mg per 1 g of the polyester resin was determined as an acid value.

(3) Hydroxyl value of polyester resin 3 g of polyester resin is precisely weighed, 0.6 ml of acetic anhydride and 50 ml of pyridine are added, and the reaction is stirred for 48 hours at room temperature, followed by addition of 5 ml of distilled water, By continuing stirring at room temperature for 6 hours, all acetic anhydride that was not used in the reaction was also changed to acetic acid. Adding dioxane 50ml of this solution titrated with KOH cresol red thymol blue as indicator, and the amount of KOH consumed in neutralization (W _1), acetic anhydride initially the charged amount and a polyester resin From the amount of KOH required for neutralization (calculated value: W ₀ ) when acetic acid is completely used without reaction, the difference (W ₀ -W ₁ ) is obtained in mg of KOH, and this is calculated. The value divided by the number of grams of the polyester resin was taken as the hydroxyl value.

(4) Molecular weight of polyester resin
The Z average molecular weight is determined by GPC analysis (using a liquid feeding unit LC-10ADvp type and an ultraviolet-visible spectrophotometer SPD-6AV type manufactured by Shimadzu Corp., detection wavelength: 254 nm, solvent: tetrahydrofuran, polystyrene conversion) The number average molecular weight was determined.

(5) Glass transition temperature of the polyester resin 10 mg of the polyester resin was used as a sample, and measurement was performed using a DSC (Differential Scanning Calorimetry) apparatus (DSC7 manufactured by PerkinElmer Co., Ltd.) at a temperature rising rate of 10 ° C./min. An intermediate value of two bending point temperatures derived from the glass transition in the temperature rising curve was determined, and this was taken as the glass transition temperature (Tg).

(6) Solid Content Concentration of Aqueous Dispersion About 1 g of the aqueous dispersion was weighed (Xg), and the mass of the residue (solid content) after drying at 150 ° C. for 2 hours was weighed (Yg) ), And the solid content concentration was determined by the following formula.

  Solid content concentration (% by mass) = Y / X × 100

(7) Organic solvent content in aqueous dispersion Shimadzu Corporation gas chromatograph GC-8A [using FID detector, carrier gas: nitrogen, column packing material (manufactured by GL Sciences): PEG-HT (5%) -UNIPORT HP (60/80 mesh), column size: diameter 3 mm × 3 m, sample charging temperature (injection temperature): 150 ° C., column temperature: 60 ° C., internal standard substance: n-butanol] The product diluted with water was directly put into the apparatus, and the content of the organic solvent was determined. The detection limit was 0.01% by mass.

(8) Storage Stability of Aqueous Dispersion 30 ml of the aqueous dispersion was placed in a 50 ml glass sample bottle, and the appearance change after storage at 25 ° C. for 60 days was visually observed to evaluate the storage stability.
○: Passed without change.
X: Precipitation is accumulated on the entire bottom surface, which is rejected.

(9) Volume average particle diameter of aqueous dispersion The aqueous dispersion was diluted to 0.1% with water, and the volume average particle diameter was measured using MICROTRAC UPA (model 9340-UPA) manufactured by Nikkiso Co., Ltd.

(10) Thickness of resin film After measuring the thickness of the base material in advance using a thickness meter (manufactured by Union Tool, MICROFINE), and forming the resin film on the base material using an aqueous dispersion, The thickness of the substrate having this resin coating was measured by the same method, and the difference was taken as the thickness of the resin coating.

(11) Resin film adhesion Using a tabletop coating device (manufactured by Yasuda Seiki Co., Ltd., film applicator No. 542-AB, equipped with a bar coater), an aqueous dispersion is coated on the base material and set to 130 ° C. By heating in an oven for 1 minute, a resin film having a thickness of about 1 μm was formed on the substrate, and then the end of the adhesive tape (width 18 mm) defined in JIS Z-1522 was formed on this resin film. The adhesive tape was left and pasted and rubbed with an eraser to sufficiently bond it, and then the end of the adhesive tape was made perpendicular to the film and then peeled off instantaneously. By analyzing the peeled adhesive tape surface with a surface infrared spectrometer (using a Perkin-Elmer SYSTEM2000, Ge60 ° 50 × 20 × 2 mm prism), it is determined whether or not a resin film is attached to the adhesive tape surface. And the adhesion of the resin film to the substrate was evaluated according to the following criteria. In addition, as a base material, the biaxially stretched PET film (Embret PET-12 by Unitika Ltd., thickness 12 micrometers) was used.
◯: A peak derived from the resin film was not recognized on the adhesive tape surface, and it passed.
X: There is a portion where a peak derived from the resin film is observed on the surface of the adhesive tape, which is rejected.

(12) Water resistance of resin film Using a tabletop coating apparatus, the above-mentioned biaxially stretched PET film is coated with an aqueous dispersion and heated in an oven set at 130 ° C. for 1 minute to obtain a thickness of about After forming a 1 μm resin film, the PET film on which this resin film was formed was immersed in hot water at 80 ° C., gently pulled up after 10 minutes and air-dried, and then the appearance of the resin film was visually observed. Observed and evaluated according to the following criteria.
○: No change in appearance is observed, and there is no practical problem.
(Triangle | delta): Whitening is partially seen and may become a problem in practical use.
X: Overall whitening is observed and there is a problem in practical use.

(13) Yield of aqueous dispersion In the production process of the aqueous polyester resin dispersion, distillation is performed to remove (desolvent) the organic solvent, but the solid content concentration before and after the solvent removal (previous: C ₁ mass) % After: C ₂ mass%) and the weight of the aqueous dispersion (front: W ₁ g after: W ₂ g).

Yield (mass%) = (W ₂ × C ₂ × 100) / (W ₁ × C ₁ )

The higher the yield, the better for practical use. If it is 95% by mass or more, there is no practical problem. If it is 96% by mass or more, it is preferable to reduce the filtration and washing operations of the precipitated resin, and if it is 97% by mass or more, it is more preferable from the viewpoint of cost. .

(14) Impact stability of aqueous dispersion About 400 g of an aqueous dispersion prepared by adding water to adjust the solid content concentration to 30% by mass is filled in a 500 ml polyethylene container, and a commercially available paint shaker (manufactured by Asada Iron Works, No. PC1290) was applied for 30 minutes in an atmosphere at 25 ° C. Then, the aqueous dispersion was filtered with a 250 mesh (mesh opening 0.071 mm) stainless steel filter, the solid content concentration of the filtrate was measured, and used as an index of impact stability. In addition, it is excellent in impact stability, so that the solid content density | concentration after giving an impact is high. A solid content concentration of 28% by mass or more after giving an impact is a practically acceptable range, and particularly a range of 29 to 30% by mass is a range in which the user can use comfortably without worrying about precipitation. .

  Moreover, the polyester resin used by the Example and the comparative example was obtained as follows.

[Production of polyester resin P-1]
2492 g (60 mol parts) of terephthalic acid, 623 g (15 mol parts) of isophthalic acid, 1263 g (25 mol parts) of sebacic acid, 1210 g (78 mol parts) of ethylene glycol, 1484 g (57 mol parts) of neopentyl glycol, 7 g of trimethylolpropane The mixture consisting of (0.2 mol part) was heated in an autoclave at 250 ° C. for 4 hours to carry out an esterification reaction. Subsequently, after adding 3.3 g of zinc acetate dihydrate as a catalyst, the temperature of the system was raised to 275 ° C., and the pressure of the system was gradually reduced to 13 Pa after a time. Under this condition, the polycondensation reaction was continued for another 2 hours, the system was brought to atmospheric pressure with nitrogen gas, the temperature of the system was lowered, and when the temperature reached 265 ° C., 38 g (0.8 mol parts) of trimellitic anhydride was added, The depolymerization reaction was performed by stirring at 265 ° C. for 2 hours. Thereafter, the system was put under pressure with nitrogen gas, and the resin was dispensed in a sheet form. After cooling at room temperature, a sheet-like polyester resin P-1 was obtained.

[Production of polyester resins P-2 to P-6]
Each polyester resin was obtained in substantially the same manner as in the production of P-1, except that the charged composition of each raw material was changed as shown in Table 1.

  Table 2 shows the results of analyzing the characteristics of the polyester resin thus obtained.

[Example 1]
400 g of polyester resin P-1 and 600 g of MEK are put into a jacketed glass container (contents 2 l), and stirred using a stirrer (Mazela 1000, manufactured by Tokyo Rika Co., Ltd.) while heating the jacket through warm water of 60 ° C. Thus, the polyester resin was completely dissolved to obtain 1000 g of a polyester resin solution having a solid concentration of 40% by mass. Next, 8.7 g of triethylamine is added as a basic compound while stirring at a rotational speed of 600 rpm while keeping the system temperature at 13 ° C. by passing cold water through the jacket, followed by 13 ° C. distilled water at a rate of 100 g / min. Phase-inversion emulsification was carried out until the total weight reached 2000 g. During the addition of the whole amount of distilled water, the system temperature was always kept below 15 ° C. After completion of the addition of distilled water, the mixture was stirred for 30 minutes to obtain an aqueous dispersion having a solid content concentration of 20% by mass.

  Next, 1600 g of the obtained aqueous dispersion was placed in a 2 l flask, and the organic solvent was removed by distillation under normal pressure. Distillation was terminated when the amount of distilled water reached about 600 g, and after cooling to room temperature, it was filtered through a 300 mesh stainless steel filter. 990 g of a polyester resin aqueous dispersion having a solid content concentration of 31.4% by mass was obtained. The yield was 97.1% by mass.

[Examples 2 to 4, Comparative Examples 1, 2, and 4]
A polyester resin aqueous dispersion described in Table 3 was obtained in the same manner as in Example 1 except that the type of polyester resin and the amount of triethylamine added were changed as shown in Table 3.

[Comparative Example 3]
Except for changing the polyester resin to P-6 and adding 5.8 g of triethylamine, the same operation as in Example 1 was performed. An aqueous dispersion could not be obtained.

Table 3 shows the results of examining the characteristic values and performance of the aqueous polyester resin dispersions obtained in Examples 1 to 4 and Comparative Examples 1 to 4.

  Since Examples 1 to 4 above are aqueous polyester resin dispersions of the present invention, they are excellent in impact stability even if they are aqueous polyester resin dispersions having a low organic solvent content, and solvent removal is performed under normal pressure. Even in high yields.

  On the other hand, since the polyester resin P-5 is below the range of the Z average molecular weight of the present invention, the volume average particle size is comparatively large in Comparative Example 1, and the yield is low when the solvent is removed under normal pressure. Moreover, it was inferior to the impact stability after solvent removal. In Comparative Example 2, since the amount of the basic compound used was increased to reduce the volume average particle size, the resin aggregated while the organic solvent was removed under normal pressure, resulting in a low yield. Moreover, it was inferior to the impact stability after solvent removal.

  Moreover, since the acid value of the used polyester resin P-6 was less than the scope of the present invention in Comparative Example 3, a uniform aqueous dispersion could not be obtained. In Comparative Example 4, since the acid value of the polyester resin P-7 used exceeds the range of the present invention, there is no problem with the yield when the solvent is removed under normal pressure and the impact stability after the solvent removal. However, the water resistance of the coating was poor.

Claims (6)

A polyester resin aqueous dispersion in which a polyester resin having an acid value of 2 to 10 mg KOH / g and a Z average molecular weight of 230,000 or more is dispersed in an aqueous medium, and the content of an organic solvent is 3% by mass or less. The polyester resin aqueous dispersion according to claim 1, wherein the polyester resin contains 50 mol% or more of an aromatic dicarboxylic acid as a polybasic acid component. The polyester resin aqueous dispersion according to claim 1 or 2, wherein the polyester resin contains a total of 50 mol% or more of ethylene glycol and neopentyl glycol as polyhydric alcohol components. After the polyester resin is copolymerized with a trifunctional or higher polyfunctional component in a proportion of 0.2 to 3.0 mol% with respect to the total dicarboxylic acid component, this is depolymerized using a polybasic acid and / or The aqueous polyester resin dispersion according to any one of claims 1 to 3, wherein the polyester resin aqueous dispersion is produced by performing an addition reaction. An organic solvent solution of a polyester resin having an acid value of 2 to 10 mg KOH / g and a Z average molecular weight of 230,000 or more is dispersed in water together with a basic compound, and after phase inversion emulsification, the organic solvent is removed under normal pressure. A method for producing an aqueous polyester resin dispersion. After the polyester resin is copolymerized with a trifunctional or higher polyfunctional component in a proportion of 0.2 to 3.0 mol% with respect to the total dicarboxylic acid component, this is depolymerized using a polybasic acid and / or 6. The method for producing an aqueous polyester resin dispersion according to claim 5, wherein the polyester resin aqueous dispersion is produced by an addition reaction.