Aqueous dispersion of polyurethane resin and coating agent

Abstract

To provide a water dispersion of a polyurethane resin which improves self-repair property and solvent resistance, and can suppress tackiness.SOLUTION: A water dispersion of a polyurethane resin has a part derived from an isocyanate group-containing urethane prepolymer (A), and a part derived from a chain extender (B). The isocyanate group-containing urethane prepolymer (A) contains (A1) polycarbonate diol which contains a component of diol having 5 carbon atoms, and a component of diol having 6 carbon atoms, and has a number average molecular weight of 300 to 2,500, (A2) polyethylene glycol having a number average molecular weight of 500 to 2,500, (A3) carboxy group-containing polyol, and (A4) alicyclic polyisocyanate, as components. The amount of the polyethylene glycol with respect to 100 pts.mass of the polycarbonate diol is 5 to 30 pts.mass.SELECTED DRAWING: None

Description

[Technical Field]

[0001] An embodiment of the present invention relates to an aqueous dispersion of a polyurethane resin and a coating agent containing the same. [Background technology]

[0002] Aqueous dispersions of polyurethane resins are widely used as raw materials for various coating agents, for example, for the interior and exterior coating of aircraft and automobiles, and for the exterior wall and flooring surfaces of houses.

[0003] For example, Patent Document 1 discloses an aqueous dispersion of polyurethane resin obtained by reacting a urethane prepolymer with a chain extender, in which the weight average molecular weight of the urethane prepolymer is 2000 to 30000, the degree of crosslinking of the polyurethane resin is 0.03 to 0.15 mol / kg, and the amount of urea in the polyurethane resin is 0.5 mol / kg or less. Specifically, Patent Document 1 discloses an aqueous dispersion of polyurethane resin obtained by using polycarbonate diol, carboxy group-containing polyol, and alicyclic polyisocyanate as constituent components of the urethane prepolymer and reacting the urethane prepolymer with an amine chain extender. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2020 / 195964 Summary of the Invention [Problem to be solved by the invention]

[0005] According to Patent Document 1, an aqueous dispersion of a polyurethane resin can be obtained that can form a coating film having good self-repairing properties, reduced tackiness, and good solvent resistance. However, market demands for these properties are increasing, and further improvements are needed.

[0006] An object of an embodiment of the present invention is to provide an aqueous dispersion of a polyurethane resin that can improve self-repairing properties and solvent resistance and suppress tackiness. [Means for solving the problem]

[0007] The present invention includes the embodiments shown below. [1] A water dispersion of a polyurethane resin having a portion derived from an isocyanate group-containing urethane prepolymer (A) and a portion derived from a chain extender (B), wherein the isocyanate group-containing urethane prepolymer (A) comprises, as constituent components, (A1) a polycarbonate diol having a number average molecular weight of 300 to 2500, which contains a constituent component derived from a diol having 5 carbon atoms and a constituent component derived from a diol having 6 carbon atoms, (A2) a polyethylene glycol having a number average molecular weight of 500 to 2500, (A3) a carboxy group-containing polyol, and (A4) an alicyclic polyisocyanate, and the amount of the polyethylene glycol is 5 to 30 parts by mass per 100 parts by mass of the polycarbonate diol. [2] The aqueous dispersion of polyurethane resin according to [1], wherein the isocyanate group-containing urethane prepolymer (A) is a urethane prepolymer having a terminal isocyanate group obtained by reacting an isocyanate group with a hydroxyl group at an equivalent ratio NCO / OH of 1.02 to 1.50. [3] The aqueous dispersion of the polyurethane resin according to [1] or [2], which has an acid value of 15 to 40 mgKOH / g. [4] The aqueous dispersion of the polyurethane resin according to any one of [1] to [3], wherein the chain extender (B) contains a triamine. [5] The aqueous dispersion of the polyurethane resin according to any one of [1] to [4], wherein the alicyclic polyisocyanate contains hydrogenated diphenylmethane diisocyanate. [6] A coating agent comprising the aqueous dispersion of the polyurethane resin according to any one of [1] to [5]. [Effects of the Invention]

[0008] According to an embodiment of the present invention, it is possible to provide an aqueous dispersion of a polyurethane resin that is excellent in self-repairing property and solvent resistance, can suppress tackiness, and also has excellent stain resistance. DETAILED DESCRIPTION OF THE INVENTION

[0009] The aqueous dispersion of polyurethane resin according to this embodiment (hereinafter sometimes simply referred to as aqueous dispersion) is a dispersion in water of polyurethane resin obtained by reacting an isocyanate group-containing urethane prepolymer (A) with a chain extender (B). Therefore, the polyurethane resin has a portion derived from the isocyanate group-containing urethane prepolymer (A) and a portion derived from the chain extender (B).

[0010] [Isocyanate group-containing urethane prepolymer (A)] The isocyanate group-containing urethane prepolymer (A) is obtained by reacting a polyol component with a polyisocyanate component, and in this embodiment, its constituent components include (A1) a polycarbonate diol, (A2) a polyethylene glycol, (A3) a carboxy group-containing polyol, and (A4) an alicyclic polyisocyanate. Thus, the polyol component includes (A1) a polycarbonate diol, (A2) a polyethylene glycol, and (A3) a carboxy group-containing polyol, and the polyisocyanate component includes (A4) an alicyclic polyisocyanate.

[0011] [(A1) Polycarbonate diol] The polycarbonate diol is a polyol having a repeating unit containing a carbonate group (-O-(C=O)-O-) in the molecule and having hydroxy groups at both ends. In this embodiment, the polycarbonate diol used contains a constituent component derived from a diol having 5 carbon atoms and a constituent component derived from a diol having 6 carbon atoms.

[0012] The polycarbonate diol is obtained by reacting, for example, a carbonate ester and / or phosgene with a diol, and a copolymer in which a diol having 5 carbon atoms and a diol having 6 carbon atoms are used in combination as the diol is used.

[0013] The diol having 5 carbon atoms is preferably an alkanediol having 5 carbon atoms, and may be linear or branched. Specific examples include 1,5-pentanediol, 1,4-pentanediol, 2,4-pentanediol, 1,2-pentanediol, and 2-methyl-1,4-butanediol, and these may be used alone or in combination of two or more. 1,5-pentanediol is preferred.

[0014] The diol having 6 carbon atoms is preferably an alkanediol having 6 carbon atoms, and may be linear or branched. Specific examples include 1,6-hexanediol, 1,5-hexanediol, 2,5-hexanediol, 2,4-hexanediol, 1,2-hexanediol, and 3-methyl-1,5-pentanediol, and these may be used alone or in combination of two or more. 1,6-hexanediol is preferred.

[0015] Examples of the carbonate ester include dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, ethylene carbonate, propylene carbonate, butylene carbonate, diphenyl carbonate, dinaphthyl carbonate, and phenyl naphthyl carbonate, and any of these may be used alone or in combination of two or more.

[0016] The polycarbonate diol according to the embodiment may contain components other than the component derived from the diol having 5 carbon atoms and the component derived from the diol having 6 carbon atoms in its skeleton, as long as a person skilled in the art would generally recognize it as a polycarbonate diol.

[0017] In one embodiment, the polycarbonate diol may be represented by the following general formula (1). [ka] In the formula, R 1 represents a divalent hydrocarbon group having 5 carbon atoms (preferably an alkanediyl group, more preferably a pentamethylene group), and is a structural component derived from a diol having 5 carbon atoms. 2 represents a divalent hydrocarbon group having 6 carbon atoms (preferably an alkanediyl group, more preferably a hexamethylene group), and is a structural component derived from a diol having 6 carbon atoms. 3 is R 1 or R 2 Each of m and n represents an integer of 1 or more. The arrangement of the monomers in the copolymer is not particularly limited.

[0018] As the polycarbonate diol, a diol obtained by reacting 1,6-hexanediol and 1,5-pentanediol with a carbonate ester and / or phosgene, that is, poly(hexamethylene carbonate / pentamethylene carbonate) diol, is preferably used.

[0019] The molar ratio of the constituent component derived from a diol having 5 carbon atoms to the constituent component derived from a diol having 6 carbon atoms (m / n in the above formula (1)) is not particularly limited, and may be 75 / 25 to 25 / 75, or 65 / 35 to 35 / 65.

[0020] The number average molecular weight (Mn) of the polycarbonate diol is 300 to 2500, preferably 400 to 2200, more preferably 500 to 2000, and even more preferably 700 to 1500, from the viewpoints of self-repairing property, suppression of tackiness, and solvent resistance.

[0021] In this specification, the number average molecular weight (Mn) is a value measured by GPC (gel permeation chromatography) and calculated using a calibration curve of standard polystyrene. Specifically, the GPC conditions are as follows: columns: "TSKgel G4000HXL + TSKgel G3000HXL + TSKgel G2000HXL + TSKgel G1000HXL + TSKgel G1000HXL" manufactured by Tosoh Corporation; mobile phase: THF (tetrahydrofuran); mobile phase flow rate: 1.0 mL / min; column temperature: 40°C; sample injection volume: 50 μL; sample concentration: 0.2% by mass.

[0022] [(A2) Polyethylene glycol] In this embodiment, polyethylene glycol is used as the polyol component together with the polycarbonate diol. The use of polyethylene glycol can improve the stain resistance and solvent resistance.

[0023] From the viewpoints of self-repairing properties, suppression of tack, solvent resistance, and stain resistance, polyethylene glycol having a number average molecular weight of 500 to 2500 is used. The number average molecular weight of polyethylene glycol is preferably 600 to 2300, more preferably 700 to 2000, and even more preferably 800 to 1800.

[0024] [(A3) Carboxy group-containing polyol] In this embodiment, a carboxyl group-containing polyol is further used as the polyol component. By using the carboxyl group-containing polyol, it is possible to give the polyurethane resin an acid value.

[0025] The carboxyl group-containing polyol is a polyol having a carboxyl group in the molecule, and examples thereof include carboxylic acid-containing compounds such as dimethylolpropionic acid, 2,2-dimethylolbutyric acid, 2,2-dimethylolvaleric acid, dihydroxymaleic acid, 2,6-dihydroxybenzoic acid, and derivatives and salts thereof. Any of these may be used alone or in combination of two or more.

[0026] Here, the term "carboxy group" refers not only to the acid form (-COOH) but also to the salt form, i.e., carboxylate group (-COOX, where X is a cation that forms a salt with a carboxylic acid), and the acid form and the salt form may be mixed. By neutralizing the carboxy group to form a salt, the polyurethane resin finally obtained can be made water-dispersible. Therefore, in the aqueous dispersion of the polyurethane resin, the carboxy group exists in the salt form. The type of salt form varies depending on the type of neutralizing agent described below, and may be an alkali metal salt such as a sodium salt, a tertiary amine salt such as a triethylamine salt, or an ammonium salt.

[0027] [(A4) Alicyclic polyisocyanate] In this embodiment, an alicyclic polyisocyanate is used as the polyisocyanate component. The use of an alicyclic polyisocyanate can provide the polyurethane resin with appropriate rigidity, suppress tackiness, and improve self-repairing properties. In addition, yellowing of the polyurethane resin, which occurs when an aromatic polyisocyanate is used, can be suppressed.

[0028] Examples of alicyclic polyisocyanates include hydrogenated diphenylmethane diisocyanate (hydrogenated MDI), hydrogenated xylylene diisocyanate, isophorone diisocyanate, 1,4-cyclohexane diisocyanate, methylcyclohexylene diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane, and modified and polynuclear compounds thereof. Examples of modified compounds include isocyanurate modified compounds, allophanate modified compounds, biuret modified compounds, adduct modified compounds, and carbodiimide modified compounds. These alicyclic polyisocyanates may be used alone or in combination of two or more.

[0029] Among these, hydrogenated MDI is preferred as the alicyclic polyisocyanate. Hydrogenated MDI is obtained by hydrogenating diphenylmethane diisocyanate (MDI), and examples of hydrogenated MDI include dicyclohexylmethane 4,4'-diisocyanate.

[0030] [Polyol component] In the polyol component constituting the isocyanate group-containing urethane prepolymer (A), the amount of (A2) polyethylene glycol per 100 parts by mass of (A1) polycarbonate diol is 5 to 30 parts by mass. When the amount of (A2) polyethylene glycol is 5 parts by mass or more, it is possible to improve stain resistance and solvent resistance. Furthermore, when the amount of (A2) polyethylene glycol is 30 parts by mass or less, it is possible to suppress tackiness and improve solvent resistance and self-repairing ability. The amount of (A2) polyethylene glycol per 100 parts by mass of (A1) polycarbonate diol is preferably 6 to 28 parts by mass, more preferably 8 to 25 parts by mass, and even more preferably 10 to 20 parts by mass.

[0031] The amount of the (A1) polycarbonate diol in 100% by mass of the polyol component is not particularly limited, but is preferably 65 to 95% by mass, more preferably 70 to 93% by mass, and even more preferably 75 to 90% by mass.

[0032] The amount of (A2) polyethylene glycol in 100% by mass of the polyol component is not particularly limited, but is preferably 4.7 to 25% by mass, more preferably 5 to 20% by mass, and even more preferably 6 to 15% by mass.

[0033] The amount of the carboxyl group-containing polyol (A3) relative to 100% by mass of the polyol component is not particularly limited, and may be, for example, 0.3 to 20% by mass, 2 to 15% by mass, or 4 to 10% by mass.

[0034] Here, the amount of each component constituting the polyol component is calculated based on 100% by mass of the polyol component, assuming that the carboxyl groups of the carboxyl group-containing polyol (A3) are in the acid form. The amount of the carboxyl group-containing polyol (A3) is also the amount in the acid form.

[0035] The polyol component constituting the isocyanate group-containing urethane prepolymer (A) is basically composed only of the above-mentioned (A1) polycarbonate diol, (A2) polyethylene glycol, and (A3) carboxy group-containing polyol, but may contain other polyols as long as the effects of this embodiment are achieved. The total amount of the (A1) polycarbonate diol, (A2) polyethylene glycol, and (A3) carboxy group-containing polyol in 100% by mass of the above polyol component is preferably 85% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more.

[0036] Examples of other polyols include polyester polyols and polyether polyols other than polyethylene glycol. Other polyols include low molecular weight polyols such as ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,2-propanediol, 1,3-propanediol, dipropylene glycol, tripropylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,5-pentanediol, 1,5-hexanediol, 1,6-hexanediol, 2,5-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol, neopentyl glycol, glycerin, trimethylolpropane, ditrimethylolpropane, tritrimethylolpropane, pentaerythritol, 1,4-cyclohexanedimethanol, hydrogenated bisphenol A, and bisphenol A.

[0037] [Polyisocyanate component] The polyisocyanate component constituting the isocyanate group-containing urethane prepolymer (A) is basically composed only of the above-mentioned (A4) alicyclic polyisocyanate, but may contain other polyisocyanates as long as the effects of this embodiment are achieved. The amount of the (A4) alicyclic polyisocyanate in 100% by mass of the above-mentioned polyisocyanate component is preferably 85% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more.

[0038] Examples of other polyisocyanates include aliphatic polyisocyanates such as tetramethylene diisocyanate, dodecamethylene diisocyanate, hexamethylene diisocyanate, and lysine diisocyanate, and aromatic polyisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate (MDI), 1,5-naphthylene diisocyanate, and xylylene diisocyanate.

[0039] [NCO / OH] The isocyanate group-containing urethane prepolymer (A) is preferably a urethane prepolymer having terminal isocyanate groups obtained by reacting an isocyanate group with a hydroxy group at an equivalent ratio NCO / OH (index) of 1.02 to 1.50. NCO / OH is more preferably 1.05 to 1.35, even more preferably 1.08 to 1.25, and even more preferably 1.10 to 1.20.

[0040] Here, NCO / OH is the molar ratio of isocyanate groups contained in the polyisocyanate component to hydroxy groups contained in the polyol component. NCO / OH is calculated using the hydroxyl value of the polyol component and the isocyanate value of the polyisocyanate component. The isocyanate value is calculated using the isocyanate content measured in accordance with Method A of JIS K1603-1:2007, as follows: Isocyanate value = {(Isocyanate content) × 56110} / (42.02 × 100).

[0041] [Chain extender (B)] Examples of the chain extender (B) include diamines, triamines, and tetramines. Examples of diamines include ethylenediamine, trimethylenediamine, piperazine, and isophoronediamine. Examples of triamines include diethylenetriamine and dipropylenetriamine. Examples of tetramines include triethylenetetramine. These chain extenders may be used alone or in combination of two or more.

[0042] As the chain extender (B), it is preferable to use a trifunctional triamine, and more preferably diethylenetriamine, because this has a superior effect of improving the self-repairing property.

[0043] The amount of the chain extender (B) is not particularly limited, and may be, for example, 0.1 to 3.0 parts by mass, 0.2 to 2.5 parts by mass, 0.3 to 2.0 parts by mass, 0.4 to 1.5 parts by mass, or 0.5 to 1.2 parts by mass relative to 100 parts by mass of the isocyanate group-containing urethane prepolymer (A).

[0044] [Water dispersion of polyurethane resin] The aqueous dispersion of polyurethane resin is obtained by reacting an isocyanate group-containing urethane prepolymer (A), which is obtained by reacting a polyol component containing (A1) a polycarbonate diol, (A2) a polyethylene glycol, and (A3) a carboxy group-containing polyol with a polyisocyanate component containing (A4) an alicyclic polyisocyanate, with a chain extender (B).

[0045] The polyurethane resin preferably has an acid value of 15 to 40 mgKOH / g. An acid value of 15 mgKOH / g or more tends to improve tack suppression and solvent resistance. An acid value of 40 mgKOH / g or less tends to improve stain resistance and self-repairing properties. The acid value of the polyurethane resin is more preferably 17 to 30 mgKOH / g, and even more preferably 18 to 25 mgKOH / g. The acid value of the polyurethane resin can be adjusted, for example, by the type and amount of (A3) carboxyl group-containing polyol.

[0046] In this specification, the acid value can be determined in accordance with JIS K0070-1992 from the amount (mg) of KOH required to neutralize the free carboxyl groups contained in 1 g of the solid content of the aqueous dispersion of polyurethane resin (i.e., polyurethane resin).

[0047] The number average molecular weight (Mn) of the polyurethane resin is not particularly limited and may be, for example, 10,000 or more, or 50,000 or more. The average particle size of the aqueous dispersion of the polyurethane resin is not particularly limited and may be, for example, 0.0005 to 0.5 μm. Here, the average particle size is the 50% cumulative particle size (d50) measured using a "Microtrac UPA-UZ152" manufactured by Nikkiso Co., Ltd.

[0048] The method for producing the aqueous dispersion of polyurethane resin is not particularly limited, and examples thereof include a method in which a polyol component and a polyisocyanate component are reacted to obtain an isocyanate group-containing urethane prepolymer (A), the urethane prepolymer (A) is neutralized with a neutralizing agent, emulsified and dispersed in water, and then the urethane prepolymer (A) is reacted with a chain extender (B).

[0049] Specifically, the polyol component and the polyisocyanate component are reacted in the absence of a solvent or in an organic solvent lacking active hydrogen groups to synthesize an isocyanate group-containing urethane prepolymer (A). The NCO / OH ratio is set as described above. After synthesizing the isocyanate group-containing urethane prepolymer (A), the carboxy groups are neutralized with a neutralizing agent and then emulsified and dispersed in water. A chain extender (B) is then added in an equivalent amount less than the remaining isocyanate groups (e.g., an equivalent ratio of isocyanate groups to active hydrogen groups in the chain extender (B) of 1:0.50 to 0.95). The isocyanate groups in the emulsion micelles are then subjected to an interfacial polymerization reaction with the chain extender (B) to form urea bonds. The solvent used is then removed as necessary to obtain an aqueous dispersion of the polyurethane resin.

[0050] Examples of the neutralizing agent include non-volatile bases such as sodium hydroxide and potassium hydroxide, tertiary amines such as trimethylamine, triethylamine, dimethylethanolamine, methyldiethanolamine and triethanolamine, and volatile bases such as ammonia. Neutralization can be carried out before, during, or after the urethanization reaction.

[0051] The organic solvent optionally used in the synthesis of the isocyanate group-containing urethane prepolymer (A) is an organic solvent that is inert to the isocyanate group and can dissolve the resulting urethane prepolymer (A), such as dioxane, methyl ethyl ketone, acetone, dimethylformamide, tetrahydrofuran, N-methyl-2-pyrrolidone, toluene, and propylene glycol monomethyl ether acetate.

[0052] The aqueous dispersion of polyurethane resin contains water and polyurethane resin dispersed in water, but may contain other components, such as the organic solvents described above, as a dispersion medium, as long as the effects of the present embodiment are achieved. The concentration of polyurethane resin in the aqueous dispersion is not particularly limited and may be, for example, 10 to 50% by mass, or 20 to 45% by mass.

[0053] [Coating agent] The coating agent according to this embodiment contains the aqueous dispersion of the polyurethane resin, and therefore contains water and the polyurethane resin dispersed in the water.

[0054] The coating agent may contain other aqueous resins together with the polyurethane resin, such as water-soluble or water-dispersible acrylic resins, water-soluble or water-dispersible polyester resins, water-soluble or water-dispersible alkyd resins, and water-soluble or water-dispersible cellulose resins.

[0055] The coating agent may contain various commonly used additives as long as the effects of this embodiment are achieved. Examples of such additives include weathering agents, antibacterial agents, antifungal agents, fillers, rust inhibitors, pigments, dyes, film-forming aids, inorganic crosslinking agents, organic crosslinking agents (e.g., blocked isocyanate crosslinking agents, epoxy crosslinking agents, carbodiimide crosslinking agents, oxazoline crosslinking agents, and melamine crosslinking agents), silane coupling agents, antiblocking agents, viscosity modifiers, leveling agents, antifoaming agents, dispersion stabilizers, light stabilizers, antioxidants, ultraviolet absorbers, inorganic fillers, organic fillers, plasticizers, lubricants, and antistatic agents. [Example]

[0056] The present invention will be explained in more detail below based on examples and comparative examples, but the present invention is not limited thereto.

[0057] Details of each component used in the examples are as follows:

[0058] [(A1) Polycarbonate diol] Polycarbonate diol 1: Asahi Kasei Corporation's "DURANOL T5651" (number average molecular weight: 1000. Diol components are 1,5-pentanediol and 1,6-hexanediol. Repeating units: pentamethylene carbonate / hexamethylene carbonate = 1 / 1 (molar ratio))

[0059] Polycarbonate diol 2: UBE Corporation's "ETERNACOLL PH-50" (number average molecular weight 500. 1,5-pentanediol and 1,6-hexanediol are used as diol components.)

[0060] Polycarbonate diol 3: Asahi Kasei Corporation's "DURANOL T5652" (number average molecular weight: 2000. Diol components are 1,5-pentanediol and 1,6-hexanediol. Repeating units: pentamethylene carbonate / hexamethylene carbonate = 1 / 1 (molar ratio))

[0061] Polycarbonate diol C1: UBE Corporation's "ETERNACOLL UP-200" (number average molecular weight: 2000. Uses only 1,5-pentanediol as the diol component.)

[0062] Polycarbonate diol C2: UBE Corporation's "ETERNACOLL UH-200" (number average molecular weight: 2000. Uses only 1,6-hexanediol as the diol component.)

[0063] Polycarbonate diol C3: UBE Corporation's "ETERNACOLL PH-300" (number average molecular weight: 3000. Diol components are 1,5-pentanediol and 1,6-hexanediol.)

[0064] [(A2) Polyethylene glycol] Polyethylene glycol 1: "PEG-1000" (number average molecular weight: 1000) manufactured by Sanyo Chemical Industries, Ltd. Polyethylene glycol 2: "PEG-2000" (number average molecular weight: 2000) manufactured by Sanyo Chemical Industries, Ltd. Polyethylene glycol C1: "PEG-3000" (number average molecular weight: 3000) manufactured by Sanyo Chemical Industries, Ltd. Polyethylene glycol C2: "PEG-300" (number average molecular weight: 300) manufactured by Sanyo Chemical Industries, Ltd.

[0065] [(A3) Carboxy group-containing polyol] Dimethylolpropionic acid: Perstorp "Bis-MPA"

[0066] [Polyisocyanate component] Hydrogenated MDI: Dicyclohexylmethane 4,4'-diisocyanate MDI: 4,4'-diphenylmethane diisocyanate HDI: Hexamethylene diisocyanate

[0067] <Synthesis of aqueous dispersion of polyurethane resin> [Example 1] A four-neck flask equipped with a stirrer, reflux condenser, thermometer, and nitrogen inlet tube was charged with 57.0 parts by weight of polycarbonate diol 1, 8.0 parts by weight of polyethylene glycol 1, 5.0 parts by weight of dimethylolpropionic acid (DMPA), and 100 parts by weight of methyl ethyl ketone, thoroughly stirred and dissolved. Then, 30.0 parts by weight of hydrogenated MDI was added, and the reaction was continued at 75°C until the free isocyanate group content relative to the solids content reached 1.0% by weight, yielding a methyl ethyl ketone solution of an isocyanate group-containing urethane prepolymer. This prepolymer solution was cooled to 45°C and neutralized by adding 3.8 parts by weight of triethylamine as a neutralizing agent. Then, 300 parts by weight of distilled water was added while stirring using a homomixer to emulsify and disperse the mixture. Subsequently, 0.7 parts by weight of diethylenetriamine was added, and a chain extension reaction was carried out at 30°C for 30 minutes. The mixture was heated under reduced pressure to remove the methyl ethyl ketone, yielding an aqueous dispersion of polyurethane resin with a solids content of 25% by weight. The resulting polyurethane resin had an acid value of 21.0 mgKOH / g.

[0068] [Examples 2 to 13 and Comparative Examples 1 to 10] Aqueous dispersions of each polyurethane resin were obtained in the same manner as in Example 1, except that the type and amount of each raw material was changed as shown in Tables 1 and 2. In the tables, the "blending ratio (A2) / (A1)" indicates the parts by mass of (A2) polyethylene glycol relative to 100 parts by mass of (A1) polycarbonate diol.

[0069] <Evaluation of aqueous dispersion of polyurethane resin> [Creating the coating layer] A water dispersion of polyurethane resin was applied to a polyethylene terephthalate substrate (PET manufactured by Toray Industries, Inc., model number: #100 T60) to a film thickness of approximately 20 μm, and then dried at 80°C for 10 minutes to produce a coating layer.

[0070] [Anti-fouling] Fingerprint resistance test The index finger was pressed against the coating surface for 3 seconds, and then gently removed to leave a fingerprint. The fingerprint was then wiped off by wiping it back and forth in one direction with a nonwoven fabric (Asahi Kasei Corporation's "Bencotto M-311"). The condition after wiping was visually observed from a 45° angle above the coating under a three-band fluorescent lamp, and the number of times the fingerprint was wiped off until it could no longer be seen was evaluated on a three-point scale. ◯: Fingerprints were wiped off in less than 5 strokes. △: Fingerprints were wiped off with 5 or more strokes but less than 8 strokes. ×: Eight or more strokes were required to wipe off the fingerprint.

[0071] [Suppress tack] The coated surfaces were bonded together under a 1 kg load, and the condition of the coated surfaces was visually observed when peeled off to evaluate the tack suppression effect. If the coated surfaces did not adhere to each other, it was rated "Excellent", if less than 50% of the bonded area was bonded, it was rated "Good", and if 50% or more of the bonded area was bonded, it was rated "Poor".

[0072] [Solvent resistance] The coating layer was rubbed 10 times with a toluene-soaked felt pad at a load of 1 kg, and the condition of the coating surface was visually observed. If the coating surface remained unchanged, it was marked "Good", if it was eroded, it was marked "Good", and if the coating layer peeled off, it was marked "Poor".

[0073] [Self-repairability] The coating surface was rubbed back and forth 15 times with a 500g load brass wire brush (No. 9, manufactured by Fujiwara Sangyo Co., Ltd.), and the degree of scratches on the coating surface was visually observed. The evaluation was carried out at room temperature of 23°C, and scratches that recovered in less than 1 minute were marked "Good", scratches that took 1 to 30 minutes to recover were marked "Good", and scratches that did not recover after 30 minutes were marked "Poor".

[0074] [Table 1]

[0075] [Table 2]

[0076] The results are shown in Tables 1 and 2. Comparative Example 1 is an example in which a polycarbonate diol whose diol component is composed solely of a diol having 5 carbon atoms is used. Comparative Example 2 is an example in which a polycarbonate diol whose diol component is composed solely of a diol having 6 carbon atoms is used. Comparative Example 3 is an example in which a polycarbonate diol whose diol component is a combination of a 5-carbon diol and a 6-carbon diol, but whose Mn is larger than the specified value is used. In these comparative examples, one or more of antifouling property, tack suppression, solvent resistance, and self-repairing property were poor.

[0077] Comparative Example 4 is an example in which polyethylene glycol with a Mn greater than the specified value was used, and the coating layer was too soft, resulting in poor tack suppression and self-repairing properties, and insufficient solvent resistance.Comparative Example 5 is an example in which polyethylene glycol with a Mn smaller than the specified value was used, and the coating layer was hard, resulting in poor self-repairing properties, and insufficient stain resistance.

[0078] Comparative Examples 6 and 7 were examples in which polyethylene glycol was not used or the amount thereof was small, and were inferior in stain resistance and solvent resistance. Comparative Example 8 was an example in which the amount of polyethylene glycol was too large, and was inferior in tack suppression, solvent resistance, and self-repairing ability.

[0079] Comparative Example 9 was an example using an aromatic polyisocyanate, and the coating layer was too hard, resulting in poor self-repairing properties and poor stain resistance. Comparative Example 10 was an example using an aliphatic polyisocyanate, and the coating layer was too soft, resulting in poor tack suppression, and poor stain resistance, solvent resistance, and self-repairing properties.

[0080] In contrast, Examples 1 to 13 were excellent in self-repairing properties, tack suppression, and solvent resistance, and also in antifouling properties. Comparing Example 1 with Example 6, the use of trifunctional diethylenetriamine as the chain extender was more effective in suppressing tack and self-repairing properties than the use of difunctional isophoronediamine.

[0081] The various numerical ranges described in this specification can be arbitrarily combined with their upper and lower limits, and all such combinations are considered to be preferred numerical ranges described in this specification. Furthermore, a numerical range described as "X to Y" means from X to Y.

[0082] Although several embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their omissions, substitutions, modifications, etc. are included within the scope and spirit of the invention, as well as within the scope of the invention described in the claims and their equivalents.

Claims

1. An aqueous dispersion of a polyurethane resin having a portion derived from an isocyanate group-containing urethane prepolymer (A) and a portion derived from a chain extender (B), The isocyanate group-containing urethane prepolymer (A) is (A1) a polycarbonate diol having a number average molecular weight of 300 to 2500, which contains a constituent component derived from a diol having 5 carbon atoms and a constituent component derived from a diol having 6 carbon atoms; (A2) polyethylene glycol having a number average molecular weight of 500 to 2500; (A3) a carboxyl group-containing polyol, and (A4) Hydrogenated diphenylmethane diisocyanate as a constituent component, and the amount of the polyethylene glycol is 5 to 30 parts by mass relative to 100 parts by mass of the polycarbonate diol, The chain extender (B) comprises a triamine; A water dispersion of polyurethane resin.

2. The aqueous dispersion of polyurethane resin according to claim 1, wherein the isocyanate group-containing urethane prepolymer (A) is a urethane prepolymer having a terminal isocyanate group obtained by reacting an isocyanate group with a hydroxy group at an equivalent ratio NCO / OH of 1.02 to 1.

50.

3. 2. The aqueous dispersion of polyurethane resin according to claim 1, wherein the acid value is 15 to 40 mgKOH / g.

4. A coating agent comprising the aqueous dispersion of the polyurethane resin according to any one of claims 1 to 3.

Images