Polyurethane aqueous dispersions, adhesives, synthetic leather and coatings

Abstract

Provided is an aqueous polyurethane dispersion capable of producing an adhesive, coating, or the like that forms a cured film (i.e., an adhesive layer) whose physical properties, such as strength, are less susceptible to change even with temperature fluctuations, and has excellent storage stability. The aqueous polyurethane dispersion comprises resin particles formed from a polyurethane having terminal hydroxyl groups and water as a dispersion medium. The polyurethane has a structure derived from a urethane prepolymer, the urethane prepolymer comprising structural units derived from a polyol including a polyether polyol; structural units derived from a polyisocyanate including an aliphatic polyisocyanate and an alicyclic polyisocyanate; and structural units derived from a polyol containing an acidic group. The polyurethane has an acid value of 30 mgKOH / g or less, and the polyol further comprises a polycarbonate polyol. The mass ratio of the polyether polyol (C) to the polycarbonate polyol (D) is (C):(D) = 20:80 to 95:5.

Description

Technical Field

[0001] The present invention relates to a polyurethane aqueous dispersion, an adhesive, synthetic leather and a coating. Background Art

[0002] Polyurethane resins are excellent in various physical properties, including wear resistance, bendability, flexibility, softness, processability, adhesion, and chemical resistance, and are also highly adaptable to various processing methods. Therefore, polyurethane resins have been widely used as materials for synthetic leather (a general term for both artificial leather and synthetic leather), as binders for various coatings, inks, and paints, and as materials for films, sheets, and various molded articles. These resins are suitable for a wide range of applications.

[0003] Among them, aqueous dispersions of hydrophilic polyurethane resins that can be emulsified and dispersed in water are dried after coating to form a coating with excellent mechanical properties, durability, chemical resistance, and abrasion resistance. Therefore, such aqueous dispersions of hydrophilic polyurethane resins (polyurethane aqueous dispersions) are widely used in coatings, adhesives, fiber processing agents, paper treatment agents, and inks. For a long time, solvent-based liquid compositions obtained by dissolving polyurethane resins in organic solvents have been used in these coatings and other applications. However, in recent years, in order to address environmental issues, etc., there has been a continuous switch from solvent-based compositions to aqueous dispersions.

[0004] Various aqueous polyurethane resin dispersions are known, depending on the required properties. For example, a dispersion of an aqueous polyurethane resin containing a structure derived from a hydroxyl-containing polyamine or a hydroxyl-containing monoamine, and a coating composition using the same, have been proposed (Patent Document 1). Furthermore, a hydroxyl-functional polyurethane obtained by reacting an NCO-functional prepolymer with an amino alcohol component, and a coating and coating material using the same have been proposed (Patent Document 2). Furthermore, an aqueous coating composition containing an anionic urethane resin emulsion having an acid value of 20 to 50 mgKOH / g has been proposed (Patent Document 3).

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 2020-83902

[0008] Patent Document 2: Japanese Patent Application No. 2011-518899

[0009] Patent Document 3: Japanese Patent Application Laid-Open No. 2005-330339 Summary of the Invention

[0010] Problems to be solved by the invention

[0011] However, the viscosity of the polyurethane resin dispersions proposed in Patent Documents 1 to 3 tends to increase over time, and it is not necessarily said that they have good storage stability. It should be noted that these polyurethane resin dispersions can be used as adhesives by combining them with a curing agent. However, the cured film (adhesive layer) formed using such an adhesive has a large difference in physical properties such as strength under normal temperature conditions and low temperature conditions, and it is not necessarily suitable as a material for articles exposed to temperature changes (such as synthetic leather used in cold regions).

[0012] The present invention has been made in view of the problems existing in the prior art. An object of the present invention is to provide an aqueous polyurethane dispersion having excellent storage stability, which can be used to prepare an adhesive, coating, or the like that forms a cured film, i.e., an adhesive layer, whose physical properties, such as strength, are not easily altered even with temperature fluctuations. Another object of the present invention is to provide an adhesive, synthetic leather, and coating using the aqueous polyurethane dispersion.

[0013] Solutions for solving problems

[0014] That is, the present invention provides the following polyurethane aqueous dispersion.

[0015] [1] A polyurethane aqueous dispersion comprising: resin particles formed from a polyurethane having a hydroxyl group at its terminal and water as a dispersion medium, wherein the polyurethane has a structure derived from a urethane prepolymer, wherein the urethane prepolymer has: a structural unit derived from a polyol including a polyether polyol; a structural unit derived from a polyisocyanate including an aliphatic polyisocyanate and an alicyclic polyisocyanate; and a structural unit derived from a polyol containing an acidic group, wherein the polyurethane has an acid value of 30 mgKOH / g or less, and the polyol further comprises a polycarbonate polyol, wherein the mass ratio of the polyether polyol (C) to the polycarbonate polyol (D) is (C):(D) = 20:80 to 95:5.

[0016] [2] The polyurethane aqueous dispersion according to the above [1], wherein the urethane prepolymer is a reactant having an isocyanate group at its terminal, obtained by reacting the polyisocyanate with the polyol in a ratio of [NCO group] in the polyisocyanate to the hydroxyl group (OH group) in the polyol such that [NCO group / OH group (molar ratio)]>1, and the polyurethane is a reactant obtained by reacting the urethane prepolymer with an alkanolamine.

[0017] [3] The polyurethane aqueous dispersion according to [2], wherein the polyurethane is a reaction product obtained by reacting 10 mol % or more of the alkanolamine relative to the isocyanate groups in the urethane prepolymer.

[0018] [4] The aqueous polyurethane dispersion according to [2] or [3], wherein the alkanolamine is an alkanolmonoamine.

[0019] [5] The polyurethane aqueous dispersion according to any one of [2] to [4] above, wherein the urethane prepolymer is a reactant obtained by reacting the polyisocyanate with the polyol so that the ratio of the isocyanate group (NCO group) in the polyisocyanate to the hydroxyl group (OH group) in the polyol is 1 < [NCO group / OH group (molar ratio)] ≤ 1.7.

[0020] [6] The polyurethane aqueous dispersion according to any one of [1] to [5] above, wherein the molar ratio of the aliphatic polyisocyanate (A) to the alicyclic polyisocyanate (B) is (A):(B) = 10:90 to 90:10.

[0021] [7] The polyurethane aqueous dispersion according to any one of [1] to [6], wherein the mass ratio of the polyether polyol (C) to the polycarbonate polyol (D) is (C):(D) = 25:75 to 90:10.

[0022] [8] The polyurethane aqueous dispersion according to any one of [1] to [7], wherein the cumulative 50% particle size (D 50 ) is 5~500nm.

[0023] Furthermore, according to the present invention, there are provided the following adhesives, synthetic leathers, and coating materials.

[0024] [9] An adhesive comprising the polyurethane aqueous dispersion according to any one of [1] to [8] and an isocyanate curing agent.

[0025]

[10] A synthetic artificial leather comprising an adhesive layer formed from the adhesive according to [9] above.

[0026]

[11] A coating comprising the polyurethane aqueous dispersion according to any one of [1] to [8].

[0027] Effects of the Invention

[0028] The present invention provides an aqueous polyurethane dispersion capable of producing an adhesive, coating, or the like that forms a cured film, i.e., an adhesive layer, whose physical properties, such as strength, are not easily altered even by temperature fluctuations, and that exhibits excellent storage stability. Furthermore, the present invention provides an adhesive, synthetic leather, and coating using the aqueous polyurethane dispersion. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1This is a schematic diagram illustrating the form of a sample used for evaluation in Examples.

[0030] Figure 2 This is a schematic diagram illustrating the configuration of a Girard oven used for evaluation in Examples. DETAILED DESCRIPTION

[0031] <Polyurethane aqueous dispersion>

[0032] The following describes embodiments of the present invention, but the present invention is not limited to the following embodiments. One embodiment of the polyurethane aqueous dispersion of the present invention contains resin particles formed from a polyurethane having terminal hydroxyl groups and water as a dispersion medium. The polyurethane has a structure derived from a urethane prepolymer. The urethane prepolymer has: structural units derived from a polyol including a polyether polyol; structural units derived from a polyisocyanate including an aliphatic polyisocyanate and an alicyclic polyisocyanate; and structural units derived from a polyol containing an acidic group. Furthermore, the acid value of the polyurethane is 30 mgKOH / g or less. The following describes the details of the polyurethane aqueous dispersion of this embodiment.

[0033] (Polyurethane)

[0034] The polyurethane aqueous dispersion of this embodiment contains resin particles (polyurethane resin particles) formed of polyurethane having a structure derived from a urethane prepolymer. That is, the polyurethane aqueous dispersion of this embodiment is an aqueous dispersion in which polyurethane resin particles are dispersed in an aqueous dispersion medium containing water.

[0035] [Polyol]

[0036] Urethane prepolymers have structural units derived from polyols. Polyols are compounds having two or more hydroxyl groups (OH groups) per molecule. Considering environmental impact, polyols derived from biomass may also be used.

[0037] Polyols (excluding "acidic group-containing polyols" described below) include polyether polyols. Polyether polyols are polyols having ether bonds in the molecule. Examples of polyether polyols include polyethylene glycol, polypropylene glycol, polyethylene glycol-polytetramethylene ether glycol (block or random), polytetramethylene ether glycol, and polyhexamethylene ether glycol. Among them, polytetramethylene ether glycol (poly(oxytetramethylene) glycol) is preferred. These polyethers can be used alone or in combination of two or more.

[0038] The number average molecular weight of the polyether polyol is more preferably 500 to 3000, and even more preferably 900 to 2100. If the number average molecular weight of the polyether polyol is too low, flexibility may be slightly insufficient and cold resistance may be insufficient. On the other hand, if the number average molecular weight of the polyether polyol is too high, solvent resistance and long-term heat resistance may be reduced.

[0039] The polyol may also contain other polyols other than polyether polyol. Examples of other polyols include polycarbonate polyols and polyester polyols. Among these, the use of polycarbonate polyols, i.e., the polyol further containing polycarbonate polyols, is preferred because it can form an adhesive layer having improved solvent resistance and long-term thermal durability.

[0040] When the polyol comprises a polyether polyol and a polycarbonate polyol, the mass ratio of the polyether polyol (C) to the polycarbonate polyol (D) is preferably (C):(D) = 20:80 to 95:5, more preferably 25:75 to 90:10, and particularly preferably 35:65 to 80:20. By using the polyether polyol and the polycarbonate polyol in the above mass ratio, a polyurethane aqueous dispersion can be prepared that can form a coating material that forms a cured film having excellent abrasion resistance and cold-resistant flexural properties.

[0041] The polycarbonate polyol is preferably a polycarbonate polyol having a structure derived from at least one of a diol represented by the following general formula (1) and a diol represented by the following general formula (2) and a carbonate bond.

[0042] HO-A1-OH (1)

[0043] HO-A2-OH (2)

[0044] In the general formula (1), A1 represents a divalent aliphatic hydrocarbon group having 2 to 12 carbon atoms. The divalent aliphatic hydrocarbon group having 2 to 12 carbon atoms is preferably a tetramethylene group, a pentamethylene group, or a hexamethylene group. Furthermore, in the general formula (2), A2 represents a divalent cyclic aliphatic hydrocarbon group having 6 to 18 carbon atoms. The divalent cyclic aliphatic hydrocarbon group having 6 to 18 carbon atoms is preferably a 1,4-cyclohexanedimethylene group.

[0045] The diol represented by general formula (1) is preferably ethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, heptanediol, octanediol, nonanediol, decanediol, undecanediol, and dodecanediol, and more preferably 2-methyl-1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, and 1,6-hexanediol. These diols may be used alone or in combination of two or more.

[0046] The diol represented by general formula (2) is preferably 1,3-cyclohexanediol, 1,4-cyclohexanediol, and 1,4-cyclohexanedimethanol, and more preferably 1,4-cyclohexanedimethanol. These diols may be used alone or in combination of two or more.

[0047] Examples of the polyester polyol include polyethylene adipate diol, polybutylene adipate diol, polyethylene butylene adipate diol, polyhexamethyleneisophthalate adipate diol, polyethylene succinate diol, polybutylene succinate diol, polyethylene sebacate diol, polybutylene sebacate diol, poly-ε-caprolactone diol, poly(3-methyl-1,5-pentanediol adipate) diol, and condensation products of 1,6-hexanediol and dimer acid.

[0048] Polyisocyanate

[0049] Urethane prepolymers have structural units derived from polyisocyanates. Polyisocyanates are compounds having two or more isocyanate groups (NCO groups) in one molecule. Polyisocyanates include aliphatic polyisocyanates and alicyclic polyisocyanates. That is, urethane prepolymers have both structural units derived from aliphatic polyisocyanates and structural units derived from alicyclic polyisocyanates.

[0050] By using alicyclic polyisocyanates, the cohesive force of the obtained polyurethane can be reduced. Thus, the aggregation between the resin particles (emulsion particles) becomes difficult to occur, the thickening of the polyurethane aqueous dispersion over time can be suppressed, and the storage stability can be improved. However, if an aliphatic polyisocyanate is not used in combination and only an alicyclic polyisocyanate is used, the physical property changes of the cured film (adhesive layer) based on temperature become easy to occur, and the cold resistance is reduced. In contrast, by using an aliphatic polyisocyanate and an alicyclic polyisocyanate in combination, the storage stability of the polyurethane aqueous dispersion can be improved, and the physical property changes of the cured film (adhesive layer) formed by the adhesive using the polyurethane aqueous dispersion can be difficult to occur based on temperature.

[0051] Aliphatic polyisocyanates (excluding alicyclic polyisocyanates) are isocyanate compounds having a linear or branched alkyl group. Examples of aliphatic polyisocyanates include ethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate (HDI), decamethylene diisocyanate, 1,6,11-undecane triisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, lysine diisocyanate, 2,6-diisocyanatomethylhexanoate, bis(2-isocyanatoethyl)fumarate, bis(2-isocyanatoethyl)carbonate, and 2-isocyanatoethyl-2,6-diisocyanatohexanoate.

[0052] Alicyclic polyisocyanates are isocyanate compounds having a cyclic alkyl group. Examples of alicyclic polyisocyanates include isophorone diisocyanate (IPDI), 4,4'-dicyclohexylmethane diisocyanate (H12-MDI), cyclohexylene diisocyanate, methylcyclohexylene diisocyanate (hydrogenated TDI), bis(2-isocyanatoethyl)-4-cyclohexene-1,2-dicarboxylate, 2,5-norbornane diisocyanate, and 2,6-norbornane diisocyanate.

[0053] In the polyisocyanate, the molar ratio of the aliphatic polyisocyanate (A) to the alicyclic polyisocyanate (B) is preferably (A):(B) = 10:90 to 90:10, and more preferably 30:70 to 70:30. If the proportion of the aliphatic polyisocyanate in the polyisocyanate is excessive, the resulting cured film (adhesive layer) is less susceptible to temperature-related property changes. Meanwhile, the storage stability of the aqueous polyurethane dispersion may be slightly reduced.

[0054] [Polyol containing acidic group]

[0055] Urethane prepolymers have structural units derived from polyols containing acidic groups. A polyol containing an acidic group is a polyol having one or more acidic groups per molecule. Therefore, polyurethane is a resin having an acidic group in its molecule and an acid value within a specified range. Examples of acidic groups include carboxylic acid groups, sulfonic acid groups, phosphoric acid groups, and phenolic hydroxyl groups. Examples of polyols containing acidic groups include dimethylolalkanoic acids such as 2,2-dimethylolpropionic acid and 2,2-dimethylolbutanoic acid, as well as N,N-bishydroxyethylglycine, N,N-bishydroxyethylalanine, 3,4-dihydroxybutanesulfonic acid, and 3,6-dihydroxy-2-toluenesulfonic acid. Among these, from the perspective of ease of use, alkanoic acids having 4 to 12 carbon atoms and containing two hydroxymethyl groups (dimethylolalkanoic acids) are preferred, and 2,2-dimethylolpropionic acid (2,2-bis(hydroxymethyl)propionic acid) is more preferred.

[0056] [Urethane prepolymer]

[0057] Urethane prepolymers are reactants obtained by reacting raw materials containing polyisocyanates and polyols according to conventional methods. More specifically, urethane prepolymers are reactants containing terminal isocyanate groups, obtained by reacting polyisocyanates with polyols so that the ratio of isocyanate groups (NCO groups) in the polyisocyanate to hydroxyl groups (OH groups) in the polyol is [NCO groups / OH groups (molar ratio)]>1, preferably 1<[NCO groups / OH groups (molar ratio)]≤1.7, and more preferably 1.1<[NCO groups / OH groups (molar ratio)]≤1.5. When the [NCO groups / OH groups (molar ratio)] value during the reaction of polyisocyanates and polyols is excessively high, the amount of isocyanate groups present at the terminals of the resulting urethane prepolymer (terminal isocyanate group (NCO group) content) and the amount of urea, etc., become excessive. Therefore, an adhesive layer obtained by curing a polyurethane produced using the urethane prepolymer with a curing agent tends to be susceptible to temperature-dependent changes in physical properties and to have a slightly reduced adhesive strength.

[0058] The amount of isocyanate groups present at the terminals of the urethane prepolymer (terminal isocyanate group (NCO group) content) is preferably 1.0 to 10.0% by mass, more preferably 1.5 to 6.0% by mass, relative to the resin solid content. If the terminal NCO group content of the urethane prepolymer is too high, the adhesive layer obtained by curing the polyurethane produced using the urethane prepolymer with a curing agent tends to be more susceptible to temperature-dependent changes in physical properties, and the adhesive strength tends to be slightly reduced.

[0059] [Polyurethane]

[0060] The acid value of the polyurethane is 30 mgKOH / g or less, preferably 3 to 27 mgKOH / g, more preferably 5 to 25 mgKOH / g, and particularly preferably 15 to 25 mgKOH / g. It should be noted that the urethane prepolymer constituting the polyurethane has a structural unit derived from a polyol containing an acidic group, so the acid value of the polyurethane is usually greater than 0 mgKOH / g. When the acid value of the polyurethane is too high, the proportion of the hard segment becomes excessive. Therefore, the temperature-based physical property changes of the adhesive layer obtained by curing the polyurethane with a curing agent become easy to occur, and the flexibility and adhesion are reduced. On the other hand, when the acid value of the polyurethane is too low, the storage stability of the polyurethane aqueous dispersion becomes insufficient. It should be noted that the "acid value of the polyurethane" in this specification is a physical property value (calculated value) calculated by the following formula (1).

[0061] Acid value of polyurethane (mgKOH / g)

[0062] ={(W / M)×56110} / Y···(1)

[0063] W: Amount of polyol containing acidic groups used (g)

[0064] M: molecular weight of the polyol containing the acidic group

[0065] Y: Total usage of polyurethane constituent materials (g)

[0066] Polyurethanes have hydroxyl groups at the ends of their molecular chains. The hydroxyl value of polyurethanes is typically 0.5 to 60 mgKOH / g, preferably 2 to 45 mgKOH / g, and more preferably 10 to 35 mgKOH / g. It should be noted that the "hydroxyl value of polyurethane" in this specification is a physical property value (calculated value) calculated using the following formula.

[0067] Hydroxyl value of polyurethane (mgKOH / g)

[0068] ={(A / B)×C×56110} / Y

[0069] A: Amount of alkanolamine used (g)

[0070] B: molecular weight of alkanolamine

[0071] C: Number of hydroxyl groups in one molecule of alkanolamine

[0072] Y: Total usage of polyurethane constituent materials (g)

[0073] The polyurethane is preferably a product obtained by reacting the urethane prepolymer having an isocyanate group at its terminal with an alkanolamine. The alkanolamine reacts with the terminal isocyanate group of the urethane prepolymer to form a urea bond. Thus, a polyurethane containing a urea bond and having a hydroxyl group at its terminal is formed.

[0074] Examples of the alkanolamine include monoethanolamine, mono-n-butylethanolamine, N-methylethanolamine, N-ethylaminoethanol, N-tert-butylethanolamine, epinephrine, 2-(4-aminophenyl)ethyl alcohol, trishydroxymethylaminomethane, 2-amino-2-methyl-1-propanol, 1-amino-2-propanol, 3-amino-1,2-propanediol, 2-amino-1-butanol, 1-amino-2-butanol, and 5-amino-1-pentanol; and alkanoldiamines such as N-(β-aminoethyl)ethanolamine, 3,5-diaminobenzyl alcohol, 1,3-diamino-2-propanol, and 2,2'-(ethylenebisimino)bisethanol. Among these, alkanolmonoamines are preferred, and monoethanolamine is more preferred from the perspective of availability. By using alkanol monoamines, a polyurethane aqueous dispersion can be produced that has a better balance between storage stability and the cold resistance of the resulting adhesive layer (the property that physical properties such as strength are less susceptible to changes even with temperature fluctuations). In contrast, the use of alkanol diamines tends to slightly reduce the storage stability of the resulting polyurethane aqueous dispersion.

[0075] Polyurethane is a reactant obtained by reacting an alkanolamine in an amount of preferably 1 to 100 mol%, more preferably 5 to 95 mol%, particularly preferably 25 to 70 mol%, and most preferably 40 to 60 mol%, relative to the isocyanate groups in a urethane prepolymer. By adjusting the amount of the reacted alkanolamine within the above range, a polyurethane aqueous dispersion can be obtained that has further improved storage stability and can be used to prepare an adhesive layer capable of forming an adhesive layer with excellent solvent resistance and heat resistance. If the amount of reacted alkanolamine is too small, the degree of crosslinking may be slightly reduced, the resulting network structure may be insufficient, and the amount of hydroxyl groups introduced into the terminal polyurethane may be slightly insufficient. On the other hand, if the amount of reacted alkanolamine is too large, unreacted alkanolamine may cause adverse effects, or the physical properties may be susceptible to changes in temperature.

[0076] The cumulative 50% particle size (D 50 ) is preferably 5 to 500 nm, more preferably 10 to 450 nm, and particularly preferably 50 to 350 nm. 50 When the median particle size is less than 5 nm, the viscosity of the aqueous dispersion increases excessively. 50 Resin particles having a (median particle size) greater than 500 nm may be prone to sedimentation.

[0077] The content of the resin particles in the polyurethane aqueous dispersion is preferably 5 to 70% by mass, more preferably 10 to 60% by mass, based on the entire aqueous dispersion.

[0078] (Dispersion Medium)

[0079] The polyurethane aqueous dispersion of the present embodiment is an aqueous dispersion in which polyurethane resin particles are dispersed in an aqueous dispersion medium containing water. As water, ion-exchanged water, distilled water, pure water, and ultrapure water can be used. Among them, ion-exchanged water is preferred from the perspective of the dispersion stability of the resin particles. The aqueous dispersion medium may further contain an organic solvent to the extent that the dispersibility and stability of the resin particles are not reduced. Examples of the organic solvent include acetone, methyl ethyl ketone, methyl isobutyl ketone, tetrahydrofuran, dioxane, dimethylformamide, dimethyl sulfoxide, N-methylpyrrolidone, N-ethylpyrrolidone, β-alkoxypropionamide, dipropylene glycol dimethyl ether, and ethyl acetate.

[0080] (Method for producing aqueous polyurethane dispersion)

[0081] The polyurethane aqueous dispersion of this embodiment can be produced by the same method as the conventionally known method for producing an aqueous dispersion of resin particles formed from polyurethane. Specifically, the target polyurethane aqueous dispersion can be obtained by a prepolymer method, for example, in which a urethane prepolymer having terminal isocyanate groups is prepared and then reacted with an alkanolamine that functions as a chain extender.

[0082] The method for producing a polyurethane aqueous dispersion based on the prepolymer method includes, for example, step (1): reacting a polyol, a polyisocyanate, and a polyol containing an acidic group to obtain a urethane prepolymer; step (2): neutralizing the acidic groups in the obtained urethane prepolymer with a neutralizing agent, and then reacting the obtained urethane prepolymer with an alkanolamine to form a polyurethane; and step (3): dispersing resin particles of the formed polyurethane in a dispersion medium containing water.

[0083] The neutralizing agent used to neutralize the acidic groups in the urethane prepolymer can be appropriately selected depending on the type of acidic groups. Examples of the neutralizing agent include organic amines such as trimethylamine, triethylamine, triisopropylamine, and tributylamine; inorganic bases such as sodium hydroxide and potassium hydroxide; and ammonia. Among these, organic amines are preferred, and triethylamine is more preferred.

[0084] Adhesive

[0085] One embodiment of the adhesive of the present invention comprises the aforementioned aqueous polyurethane dispersion and an isocyanate-based curing agent. Because the adhesive of this embodiment contains the aforementioned aqueous polyurethane dispersion, it can form an adhesive layer as a cured film whose physical properties, such as strength, are not easily altered even with temperature fluctuations. Therefore, the adhesive of this embodiment is suitable as an adhesive for the production of synthetic artificial leather and various laminates.

[0086] As the isocyanate curing agent, a conventionally known isocyanate curing agent can be used. Commercially available isocyanate curing agents include the following trade names: DURANATE WT30-100, DURANATE WB40-100, DURANATE WL70-100, DURANATE WR80-70P (all manufactured by Asahi Kasei Corporation); Aquanate 105, Aquanate 130, Aquanate 140, Aquanate 200, Aquanate 210 (all manufactured by Tosoh Corporation); TAKENATE WD-725, TAKENATE WD-730, TAKENATE WD-726 (all manufactured by Mitsui Chemicals, Inc.); and the like.

[0087] The content of the isocyanate curing agent in the adhesive can be appropriately set according to the purpose. Specifically, the content of the isocyanate curing agent in the adhesive is preferably 1 to 50 parts by mass, more preferably 10 to 40 parts by mass, per 100 parts by mass of the polyurethane (solid content).

[0088] The adhesive of the present embodiment may contain various additives such as a thermoplastic resin, a tackifying resin, a catalyst, a pigment, an antioxidant, an ultraviolet absorber, a surfactant, a flame retardant, a filler, and a foaming agent in appropriate amounts as needed.

[0089] The adhesive of this embodiment can be applied to the surface of an adherend to facilitate bonding of adherends. Examples of adherends other than the above-mentioned base material layer for synthetic leather include metal and non-metal (polycarbonate, glass, etc.) base materials.

[0090] Synthetic leather

[0091] One embodiment of the synthetic artificial leather of the present invention includes an adhesive layer formed from the aforementioned adhesive. Because the adhesive forming the adhesive layer contains the aforementioned aqueous polyurethane dispersion, its physical properties, such as strength, are not easily altered even with temperature fluctuations. Therefore, the synthetic artificial leather of this embodiment including this adhesive layer exhibits physical properties, such as strength, that are not easily altered even with temperature fluctuations, and exhibits excellent cold resistance.

[0092] Synthetic artificial leather comprises, for example, a skin layer, an adhesive layer disposed on the skin layer, and a base layer such as a base fabric disposed on the adhesive layer. Examples of the base fabric constituting the base layer include fabrics formed from twill or plain weaves, raised fabrics obtained by mechanically raising the cotton texture of such fabrics, rayon fabrics, nylon fabrics, polyester fabrics, Kevlar (registered trademark) fabrics, non-woven fabrics (polyester, nylon, various latexes), various films, and sheets. Furthermore, examples of the skin layer include those formed from skin-forming coatings such as solvent-based polyurethanes, water-based polyurethanes, and TPU.

[0093] Synthetic artificial leather can be manufactured, for example, as follows. First, by known methods such as comma coating, knife coating, roller coating, gravure coating, die coating, spraying, the coating for forming the epidermis layer is applied on release paper. The applied coating is suitably dried to form the epidermis layer, and then the aforementioned adhesive is applied on the formed epidermis layer by known methods such as comma coating, knife coating, roller coating. After the applied adhesive is pressed against the substrate layer, aging (aging) etc. is carried out under specified conditions. Then, the synthetic artificial leather as the purpose is obtained by peeling off with release paper. The synthetic artificial leather of the present embodiment is suitable as a material constituting shoes, clothing, bags, furniture, vehicle interior materials (such as dashboards, doors, consoles, seats) etc.

[0094] <Paint>

[0095] One embodiment of the coating of the present invention contains the aforementioned aqueous polyurethane dispersion. The coating of this embodiment contains the aforementioned aqueous polyurethane dispersion. Therefore, after application to a coated surface and, if necessary, aging, the coating can form a cured film (film) with excellent cold resistance, whose physical properties, such as strength, are not easily altered even with temperature fluctuations. Therefore, the coating of this embodiment is useful as a coating agent for coating the surfaces of various substrates.

[0096] The coating preferably further contains a curing agent (hereinafter also referred to as a "crosslinking agent") in order to improve the mechanical properties, durability and other physical properties of the formed cured film (film). Examples of the crosslinking agent include, in addition to isocyanate crosslinking agents, carbodiimide crosslinking agents, oxazoline crosslinking agents, and epoxy crosslinking agents.

[0097] If the content of the crosslinking agent in the coating is too high, problems such as plasticization or embrittlement of the coating film may occur due to unreacted crosslinking agent. Therefore, the content of the crosslinking agent in the coating (based on solid content) is preferably 40 parts by mass or less, and more preferably 0.5 to 35 parts by mass, per 100 parts by mass of the polyurethane resin.

[0098] The coating may also contain various additives as needed. Examples of these additives include matting agents; antioxidants such as hindered phenol-based, phosphite-based, and thioether-based antioxidants; light stabilizers such as hindered amine-based; UV absorbers such as benzophenone-based and benzotriazole-based; gas discoloration stabilizers such as hydrazine-based; and metal deactivators.

[0099] Examples of matting agents include resin particles, silica particles, talc, aluminum hydroxide, calcium sulfate, calcium silicate, calcium carbonate, magnesium carbonate, barium carbonate, aluminum silicate, molecular sieves, kaolin, mica, and mica. By using a coating containing a matting agent, a coating film of a surface material or the like with a matte tone can be formed.

[0100] Example

[0101] The present invention will be described in detail below based on examples, but the present invention is not limited to the following examples. It should be noted that "parts" and "%" in the examples and comparative examples are based on mass unless otherwise specified.

[0102] <Material Preparation>

[0103] Prepare the following materials.

[0104] Polyether polyol (1): poly(oxytetramethylene) glycol, number average molecular weight 2000

[0105] Polyether polyol (2): poly(oxytetramethylene) glycol, number average molecular weight 1000

[0106] Polyether polyol (3): poly(oxytetramethylene) glycol, number average molecular weight 3500

[0107] Polyether polyol (4): poly(oxytetramethylene) glycol, number average molecular weight 250

[0108] Polycarbonate polyol: polyhexamethylene carbonate diol, trade name "ETERNACOLL UH-100", manufactured by Ube Industries, Ltd., number average molecular weight 1000

[0109] HDI: Hexamethylene diisocyanate

[0110] IPDI: Isophorone diisocyanate

[0111] BisMPA: 2,2-bis(hydroxymethyl)propionic acid

[0112] MEA: Monoethanolamine

[0113] MBM: Mono-n-butylethanolamine

[0114] EA: N-(β-aminoethyl)ethanolamine

[0115] ·TEA: triethylamine

[0116] MEK: methyl ethyl ketone

[0117] <Production of Polyurethane Aqueous Dispersion>

[0118] (Example 1)

[0119] 150 parts of polyether polyol (2), 150 parts of polycarbonate polyol, 22.1 parts of BisMPA, 28.2 parts of HDI and 86.8 parts of IPDI were added to a reaction vessel equipped with a stirrer, a thermometer, a gas inlet pipe and a reflux cooler. MEK was added so as to make the solid content 30%, and after being uniformly dissolved, it was reacted at 60°C for 7 hours. After confirming that the isocyanate group (NCO group) reached the specified content, the reaction liquid was cooled to room temperature. 16.7 parts of TEA was added and stirred to obtain a liquid containing a carbamate prepolymer. The terminal NCO group content of the carbamate prepolymer in the obtained liquid was 0.54% (1.8% relative to the resin solid content). It should be noted that the terminal NCO group content of the carbamate prepolymer was calculated as follows: after reacting the NCO group at the terminal of the carbamate prepolymer with an excess amount of dibutylamine, the amount of the remaining dibutylamine was titrated with hydrochloric acid.

[0120] 5.7 parts of MEA were added to the obtained liquid and stirred to react. After adding an appropriate amount of water for emulsification, vacuum degassing was performed to remove MEK to obtain a polyurethane aqueous dispersion containing polyurethane resin particles (solid content 30%). The acid value of the polyurethane forming the polyurethane resin particles was 20.0 mgKOH / g and the hydroxyl value was 11.4 mgKOH / g. In addition, the average particle size (D 50 ) is 200nm.

[0121] (Examples 2, 3, 5 to 18, Reference Example 4, Comparative Examples 1 to 7)

[0122] A polyurethane aqueous dispersion (30% solids) containing polyurethane resin particles was obtained in the same manner as in Example 1, except that the formulations shown in Tables 1-1 to 1-3 were used. In Comparative Example 4, a surfactant (nonionic polyoxyalkylene ether, trade name "Pionin D-1110DIR," manufactured by Takemoto Oil & Fat Co., Ltd.) was added in an amount of 10% relative to the resin solids content, instead of the acidic group-containing polyol (BisMPA) for emulsification. Various physical properties are shown in Tables 1-1 to 1-3.

[0123] Table 1-1

[0124]

[0125] Table 1--

[0126]

[0127] Table 1-3

[0128]

[0129] <Evaluation of polyurethane aqueous dispersion>

[0130] (Storage stability)

[0131] The polyurethane aqueous dispersion was stored at 10°C for one month. The viscosity of the polyurethane aqueous dispersion after storage at 25°C was measured using a Brookfield viscometer (spindle #2, 30 rpm). Storage stability was evaluated according to the following evaluation criteria. The results are shown in Tables 2-1 and 2-2.

[0132] 1 (very good): 150 mPa·s or less.

[0133] 2 (good): greater than 150 mPa·s and less than 300 mPa·s

[0134] 3 (normal): greater than 300 mPa·s and less than 800 mPa·s

[0135] 4 (allowed): greater than 800 mPa·s and less than 1000 mPa·s

[0136] 5 (Unqualified): Greater than 1000mPa·s or sedimentation / separation

[0137] <Adhesive Manufacturing and Film Production>

[0138] To 100 parts of the polyurethane aqueous dispersion was added 10 parts of an isocyanate curing agent (trade name "DURANATE WT30-100," manufactured by Asahi Kasei Corporation) (i.e., 33.3 parts per 100 parts of the polyurethane resin (solids content)). The mixture was mixed and degassed to produce an adhesive. The resulting adhesive was applied onto release paper and then dried at 70°C for 3 minutes and at 100°C for 1 minute. It was then aged at 50°C for 24 hours to cure, resulting in a 30 μm thick film.

[0139] <Evaluation of adhesive>

[0140] (Rate of change of physical properties)

[0141] The film was cut into pieces with a width of 15 mm and a length of 60 mm to prepare test pieces. The strength (100% M) of the test piece was measured using a tensile testing machine (trade name "Autograph AGS-500NS", manufactured by Shimadzu Corporation) at a tensile speed of 200 mm / min. The temperature conditions were set to 25°C, -10°C, and -30°C. Next, the property change rate A and property change rate B were calculated using the following calculation formula, and the property change rate was evaluated according to the evaluation criteria shown below. The results are shown in Tables 2-1 and 2-2.

[0142] ·Physical property change rate A(%)

[0143] ={(100% M at -10°C) / (100% M at 25°C)}×100

[0144] ·Physical property change rate B (%)

[0145] ={(100% M at -30°C) / (100% M at 25°C)}×100

[0146] [Evaluation Criteria for Property Change Rate A]

[0147] 1 (very good): less than 155%

[0148] 2 (Good): More than 155% and less than 165%

[0149] 3 (normal): greater than 165% and less than 180%

[0150] 4 (Allowed): Greater than 180% and less than 200%

[0151] 5 (Unqualified): More than 200%

[0152] [Evaluation Criteria for Physical Property Change Rate B]

[0153] 1 (very good): less than 170%

[0154] 2 (good): more than 170% and less than 200%

[0155] 3 (normal): greater than 200% and less than 230%

[0156] 4 (Allowed): Greater than 230% and less than 250%

[0157] 5 (Unqualified): More than 250%

[0158] (Solvent resistance)

[0159] The prepared film was cut into test pieces with a width of 15 mm and a length of 60 mm. The test pieces were immersed in acetone for 10 minutes, and the lengths of the test pieces before and after immersion were measured. The linear swelling ratio was then calculated using the following formula, and solvent resistance was evaluated according to the following evaluation criteria. The results are shown in Tables 2-1 and 2-2.

[0160] Linear swelling ratio (%) = {(length of the test piece after immersion) / (length of the test piece before immersion)}×100

[0161] 1 (very good): less than 120%

[0162] 2 (Good): More than 120% and less than 125%

[0163] 3 (normal): greater than 125% and less than 130%

[0164] 4 (Allowed): Greater than 130% and less than 140%

[0165] 5 (Unqualified): More than 140%

[0166] (Long-term heat resistance)

[0167] The film was cut into 10 cm wide and 10 cm long test pieces. After the test pieces were kept at 120°C for 400 hours, the strength (100% M) was measured using a tensile testing machine (trade name "Autograph AGS-500NS", manufactured by Shimadzu Corporation) at a tensile speed of 200 mm / min. The temperature was set to 25°C. The rate of change was then calculated using the following formula, and the long-term heat resistance was evaluated according to the evaluation criteria shown below. The results are shown in Tables 2-1 and 2-2.

[0168] Change rate (%) = {(100% M after holding) / (100% M before holding)} × 100

[0169] 1 (very good): more than 90%

[0170] 2 (Good): 80% or more and less than 90%

[0171] 3 (normal): 70% or more and less than 80%

[0172] 4 (allowed): 60% or more and less than 70%

[0173] 5 (Unqualified): Less than 60%

[0174] (Heat resistance)

[0175] The prepared film was cut into pieces with a width of 15 mm and a length of 60 mm as test pieces. Figure 1As shown, the film 10 is mounted on the upper and lower clamps 12, and the clamps 12 are further fixed with glass tape. When suspended on a clamp 12, the film is mounted with a pressure of 450g / cm 2 A weight 14 such as a load of 100 was placed to prepare a sample 16. It should be noted that the central portion (2 cm) of the film 10 was not covered with the glass ribbon.

[0176] Then, if Figure 2 As shown, the jig 12 of sample 16, without weight 14, was mounted on the rotating plate 22 of a Girrel oven 20. The temperature inside the Girrel oven 20 was then raised from room temperature at a rate of 3°C / minute while rotating the rotating plate 22 at 5 rpm. The temperature (softening point (°C)) at the time of film 10 being cut or stretched to 2 times its original length was measured, and heat resistance was evaluated according to the following evaluation criteria. The results are shown in Tables 2-1 and 2-2.

[0177] 1 (very good): above 220℃

[0178] 2 (good): 200°C or higher and less than 220°C

[0179] 3 (normal): 180°C or higher and less than 200°C

[0180] 4 (allowed): 160°C or higher and less than 180°C

[0181] 5 (unqualified): less than 160℃

[0182] (Adhesion)

[0183] A urethane resin for synthetic leather (trade name "RESAMINE NE-8875-30M", manufactured by Dainichi Seika Industries) was applied on release paper and dried at 120°C to form a surface layer with a thickness of 50 μm. After applying an adhesive on the formed surface layer, it was dried at 70°C for 3 minutes and at 100°C for 1 minute to form an adhesive layer with a thickness of 100 μm. A base fabric of polyester mesh material was attached to the surface of the formed adhesive layer. After aging for 24 hours at 50°C, the release paper was peeled off to obtain the synthetic leather for the test. The obtained synthetic leather was cut into 2 cm wide pieces as test pieces. Then, a T-peel test of the surface layer / base fabric was carried out at 25°C and a tensile speed of 200 mm / min using a tensile testing machine (trade name "Autograph AGS-500NS", manufactured by Shimadzu Corporation), and the adhesion was evaluated according to the evaluation criteria shown below. The results are shown in Tables 2-1 and 2-2.

[0184] 1 (very good): 1.0 kgf / cm or more or the material is broken

[0185] 2 (good): 0.7 kgf / cm3 or higher and less than 1.0 kgf / cm3

[0186] 3 (normal): 0.5kgf / cm3 or more and less than 0.7kgf / cm3

[0187] 4 (allowable): 0.2kgf / cm3 or more and less than 0.5kgf / cm3

[0188] 5 (unqualified): less than 0.2kgf / cm

[0189] <Manufacturing of paint and preparation of test pieces>

[0190] To 20 parts of the polyurethane aqueous dispersion, 1.8 parts of a matting agent (trade name "ACEMATT TS-100", manufactured by Evonik Industries, volume average particle size 9.5 μm) and ion-exchanged water were added to obtain an aqueous surface treatment agent (20% solids content). To 100 parts of the resulting surface treatment agent, 2.0 parts of an isocyanate curing agent (trade name "DURANATE WT30-100", manufactured by Asahi Kasei Corporation) were added (i.e., 33.3 parts per 100 parts of the polyurethane resin (solids content)) to prepare a coating. The prepared coating was applied to a PVC sheet using a bar coater. The coating was dried in a dryer at 120°C for 1 minute to obtain a test piece with a 10 μm thick coating.

[0191] <Evaluation of paint>

[0192] (Abrasion resistance)

[0193] A test piece with a width of 70 mm and a length of 300 mm was cut out from the test piece. The test piece was placed on the cushioning material of the flat wear table of the flat wear tester for surface cloth materials of JASO M403 / 88 / piece (B method, manufactured by Daiei Kagaku Seiki Manufacturing Co., Ltd.), and fixed with pliers in a way that no cracking occurs. A friction piece provided with No. 6 cotton canvas of JIS L 3102 (cotton canvas) was brought into contact with the test piece. The following wear test was carried out: the pressing load containing the friction piece was set to 9.81 N (1 kgf), and the test piece was reciprocated 10,000 times under the conditions of a stroke of 140 mm and a speed of 60±10 reciprocations / minute. The results of the evaluation of wear resistance according to the evaluation criteria shown below are shown in Tables 2-1 and 2-2.

[0194] 1 (Excellent): No change in appearance

[0195] 2 (Good): No scratches, slight changes in appearance

[0196] 3 (usually): no scratches, no noticeable changes in appearance

[0197] 4 (Permitted): There are at least 1 and less than 5 visible scratches

[0198] 5 (Unacceptable): 5 or more scratches can be confirmed

[0199] (Dispersibility)

[0200] The appearance of the test piece was visually observed and the touch of the surface was confirmed, and the dispersibility was evaluated according to the following evaluation criteria. The results are shown in Tables 2-1 and 2-2.

[0201] 1 (very good): No white spots due to aggregation of the matting agent are observed in appearance, and no coarse particles are felt to the touch.

[0202] 2 (Good): 1 to 5 white spots are found in an area of ​​5 cm x 5 cm. No coarse particles can be felt.

[0203] 3 (Normal): 1 to 5 white spots are found in an area of ​​5 cm x 5 cm. Slightly coarse particles are felt to the touch.

[0204] 4 (Acceptable): 5 to 10 white spots are found in an area of ​​5 cm x 5 cm. Coarse particles are clearly felt to the touch.

[0205] 5 (Unqualified): The coating film is white and lacks transparency.

[0206] (Cold resistance and bending)

[0207] Specimens 50 mm wide and 150 mm long were cut from the test pieces. Bend tests were conducted using a DE MATTIA testing machine with a bending stroke of 100 mm and a temperature of -10°C. Cold-resistant flexural properties were evaluated according to the following evaluation criteria. The results are shown in Tables 2-1 and 2-2.

[0208] 1 (very good): No whitening or cracking at 30,000 times

[0209] 2 (Good): Whitening or cracking occurred between 20,000 and 30,000 cycles.

[0210] 3 (normal): Whitening or cracking occurs between 10,000 and 20,000 cycles.

[0211] 4 (Allowable): Whitening or cracking occurs between 5,000 and 10,000 cycles.

[0212] 5 (Unqualified): Whitening or cracking occurred after less than 5000 cycles

[0213] Table 2-1

[0214]

[0215] Table 2-2

[0216]

[0217] Industrial applicability

[0218] The polyurethane aqueous dispersion of the present invention is useful as a material for forming adhesive layers of various products such as synthetic leather, and is also useful as various coating agents and paints capable of forming cured films having excellent abrasion resistance and cold-resistant flexural properties.

[0219] Description of Reference Numerals

[0220] 10: Film

[0221] 12: Fixture

[0222] 14: Heavy Objects

[0223] 16: Sample

[0224] 20: Gill oven

[0225] 22: Rotating disk

Claims

1. A polyurethane aqueous dispersion comprising: resin particles formed of polyurethane having hydroxyl groups at their terminals and water as a dispersion medium, The polyurethane has a structure derived from a urethane prepolymer, The urethane prepolymer has a structural unit derived from a polyol including a polyether polyol, a structural unit derived from a polyisocyanate including an aliphatic polyisocyanate (A) and an alicyclic polyisocyanate (B), and a structural unit derived from a polyol containing an acidic group. The acid value of the polyurethane is less than 30 mgKOH / g, The polyol further comprises a polycarbonate polyol, The mass ratio of the polyether polyol (C) to the polycarbonate polyol (D) is (C): (D) = 20:80 to 95:5, The polyurethane is a reaction product obtained by reacting the urethane prepolymer with an alkanolamine.

2. The polyurethane aqueous dispersion according to claim 1, wherein The urethane prepolymer is a reactant having an isocyanate group at its terminal, obtained by reacting the polyisocyanate with the polyol so that the isocyanate group (NCO group) in the polyisocyanate and the hydroxyl group (OH group) in the polyol are in a ratio of [NCO group / OH group]>1. The ratio of [NCO group / OH group] is calculated as a molar ratio.

3. The polyurethane aqueous dispersion according to claim 2, wherein The polyurethane is a reaction product obtained by reacting 10 mol % or more of the alkanolamine relative to the isocyanate groups in the urethane prepolymer.

4. The polyurethane aqueous dispersion according to claim 2 or 3, wherein The alkanolamine is an alkanolmonoamine.

5. The polyurethane aqueous dispersion according to claim 2, wherein The urethane prepolymer is a reactant obtained by reacting the polyisocyanate and the polyol so that the ratio of isocyanate groups (NCO groups) in the polyisocyanate to hydroxyl groups (OH groups) in the polyol is 1<[NCO groups / OH groups]≤1.7, and the ratio of [NCO groups / OH groups] is calculated as a molar ratio.

6. The polyurethane aqueous dispersion according to claim 1 or 2, wherein The molar ratio of the aliphatic polyisocyanate (A) to the alicyclic polyisocyanate (B) is (A):(B)=10:90 to 90:

10.

7. The polyurethane aqueous dispersion according to claim 1 or 2, wherein The mass ratio of the polyether polyol (C) to the polycarbonate polyol (D) is (C):(D)=25:75 to 90:

10.

8. The polyurethane aqueous dispersion according to claim 1 or 2, wherein The cumulative 50% particle size (D 50 ) is 5~500nm. 9 . An adhesive comprising the polyurethane aqueous dispersion according to claim 1 and an isocyanate curing agent. 10 . A synthetic artificial leather comprising an adhesive layer formed from the adhesive according to claim 9 .

11. A coating comprising the polyurethane aqueous dispersion according to any one of claims 1 to 8.

Images