Water-based primer and laminate

Abstract

This invention provides a water-based primer that exhibits excellent initial adhesion and water-resistant adhesion properties, and is used to form a primer layer between a polyester resin substrate and an inorganic layer. [Solution] The aqueous primer according to the embodiment is used to form a primer layer between a polyester resin substrate and an inorganic layer, and comprises an aqueous polyurethane dispersion in which a polyurethane resin (A) containing a polyester polyol as a constituent component is dispersed in an aqueous dispersion medium. The aqueous polyurethane dispersion contains a carbodiimide group-containing compound (B). The polyurethane resin (A) has a carboxyl group, and the acid value of the polyurethane resin (A) is 5 to 25 mgKOH / g.

Description

Technical Field

[0001] Embodiments of the present invention relate to an aqueous primer containing a polyurethane aqueous dispersion and a laminate using the same.

Background Art

[0002] A polyurethane aqueous dispersion obtained by dispersing a polyurethane resin in an aqueous dispersion medium is widely used in paints, inks, adhesives, etc. For example, Patent Document 1 discloses an aqueous polyurethane resin composition in which a urethane prepolymer composed of polyester glycol, organic diisocyanate, and a chain extender having a free carboxy group is crosslinked with water, and it is disclosed that a carbodiimide compound is added to the composition and used as a primer composition.

[0003] Patent Document 2 discloses using, as a primer, a polyurethane aqueous dispersion obtained by dispersing a polyester-based polyurethane resin having an acid value of 5 to 25 mgKOH / g in an aqueous dispersion medium and blending a predetermined amount of a carbodiimide group-containing compound.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] When a polyurethane aqueous dispersion is used as an aqueous primer for a polyester resin substrate, the aqueous primer is required to have good adhesion (adhesive property) to the polyester resin, and adhesion to the topcoat layer provided through the aqueous primer is also required.

[0006] Incidentally, in applications such as gas barrier films, an inorganic layer is sometimes laminated onto a polyester resin substrate, and a water-based primer may be used to improve the adhesion between the two. However, conventional water-based primers do not necessarily have high adhesion to both the polyester resin substrate and the inorganic layer, and their adhesion can decrease, especially when exposed to hot water. Therefore, a primer that has high adhesion to both the polyester resin substrate and the inorganic layer, including water-resistant adhesion, is required.

[0007] While Patent Document 2 discloses the incorporation of a carbodiimide group-containing compound into an aqueous dispersion of a polyester-based polyurethane resin having a relatively low acid value, as described above, it does not describe its use for forming a primer layer between a polyester resin substrate and an inorganic layer.

[0008] The embodiments of the present invention aim to provide a water-based primer with excellent initial adhesion and water-resistant adhesion, which is used to form a primer layer between a polyester resin substrate and an inorganic layer. [Means for solving the problem]

[0009] The present invention includes embodiments shown below. [1] A water-based primer used to form a primer layer between a polyester resin substrate and an inorganic layer, The present invention comprises a polyurethane aqueous dispersion in which a polyurethane resin (A) containing a polyester polyol as a constituent component is dispersed in an aqueous dispersion medium. The polyurethane aqueous dispersion comprises a carbodiimide group-containing compound (B), The polyurethane resin (A) has a carboxyl group, and the acid value of the polyurethane resin (A) is 5 to 25 mgKOH / g. Water-based primer.

[0010] [2] The aqueous primer according to [1], wherein the polyester polyol comprises an aromatic polyester polyol. [3] The aqueous primer according to [1] or [2], wherein the inorganic layer is an inorganic layer comprising at least one inorganic substance selected from the group consisting of silicon oxide, silicon nitride, silicon oxynitride, aluminum oxide, aluminum nitride, and aluminum. [4] A laminate comprising, in this order, a primer layer formed with an aqueous primer described in any one of [1] to [3], and an inorganic layer on a polyester resin substrate. [Effects of the Invention]

[0011] According to embodiments of the present invention, a water-based primer with excellent initial adhesion and water-resistant adhesion can be provided for forming a primer layer between a polyester resin substrate and an inorganic layer. [Modes for carrying out the invention]

[0012] The aqueous primer according to this embodiment comprises an aqueous polyurethane dispersion (hereinafter sometimes simply referred to as an aqueous dispersion), the aqueous dispersion comprising a polyurethane resin (A), a carbodiimide group-containing compound (B), and an aqueous dispersion medium (C). Here, an aqueous primer refers to a primer that uses an aqueous dispersion medium as the medium.

[0013] [Polyurethane resin (A)] Polyurethane resin (A) is obtained by reacting a polyol with a polyisocyanate and is a polymer having a urethane bond in its molecule. In this embodiment, polyurethane resin (A) containing polyester polyol as a constituent component is used. This improves adhesion to the polyester resin substrate. In this specification, "containing as a constituent component" means using it as a raw material (monomer) for synthesizing polyurethane resin (A), and having a structure derived from it in polyurethane resin (A).

[0014] A polyester polyol is a polyol having a plurality of ester bonds (-COO-) in the molecule, and is preferably obtained by a condensation reaction between a polyvalent carboxylic acid and a polyvalent hydroxy group-containing compound.

[0015] As the polyvalent carboxylic acid, a dicarboxylic acid is preferable, and examples thereof include aromatic dicarboxylic acids such as phthalic acid, terephthalic acid, isophthalic acid, and naphthalenedicarboxylic acid, and aliphatic dicarboxylic acids such as adipic acid, succinic acid, sebacic acid, azelaic acid, maleic acid, and fumaric acid. Any one of these may be used, or two or more thereof may be used in combination.

[0016] As the polyvalent hydroxy group-containing compound, a diol is preferable, and examples thereof include aliphatic diols such as ethylene glycol, diethylene glycol, propylene glycol, butylene glycol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, and 1,6-hexanediol, bisphenols such as bisphenol A and bisphenol F, and aromatic diols such as alkylene oxide adducts thereof. Any one of these may be used, or two or more thereof may be used in combination.

[0017] As the polyester polyol, an aromatic polyester polyol is preferable. That is, in a preferred embodiment, the polyester polyol contains an aromatic polyester polyol. By using an aromatic polyester polyol, the water-resistant adhesion can be improved. An aromatic polyester polyol is a polyester polyol having an aromatic ring in the molecule, and it is sufficient that at least one of the polyvalent carboxylic acid and the polyvalent hydroxy group-containing compound contains an aromatic ring. The amount of the aromatic polyester polyol with respect to 100% by mass of the polyester polyol is preferably 50% by mass or more, more preferably 70% by mass or more, still more preferably 90% by mass or more, and further preferably 100% by mass.

[0018] The molecular weight of the polyester polyol is not particularly limited. For example, the number average molecular weight (Mn) may be 500 to 5000, may be 800 to 4000, or may be 1000 to 3000.

[0019] In this specification, the number average molecular weight (Mn) is a value measured by the GPC method (gel permeation chromatography method) and calculated using a calibration curve with standard polystyrene. Specifically, as the conditions for GPC, the column: "TSKgel G4000HXL + TSKgel G3000HXL + TSKgel G2000HXL + TSKgel G1000HXL + TSKgel G1000HXL" manufactured by Tosoh Corporation, the mobile phase: THF (tetrahydrofuran), the mobile phase flow rate: 1.0 mL / min, the column temperature: 40 °C, the sample injection volume: 50 μL, and the sample concentration: 0.2 mass% can be used for measurement.

[0020] The amount of the polyester polyol in the polyol constituting the polyurethane resin (A) is not particularly limited. For example, it is preferably 60 to 99 mass% based on 100 mass% of the polyol, more preferably 70 to 97 mass%, still more preferably 75 to 95 mass%, and even more preferably 80 to 90 mass%.

[0021] In this specification, regarding the amount of each component constituting the polyol, the 100 mass% of the polyol as the reference is calculated with the carboxyl group in the acid form when the polyol contains a carboxyl group-containing polyol described later. Similarly, regarding the amount of the carboxyl group-containing polyol, the carboxyl group is calculated in the acid form.

[0022] In this embodiment, the polyurethane resin (A) has a carboxyl group, and thereby, it can react with the carbodiimide group-containing compound (B) to form a crosslinked structure during the heat drying of the aqueous dispersion. In this specification, the carboxyl group is a concept that includes not only the acid form (-COOH) but also the salt form, that is, the carboxylate group (-COOX, where X is a cation forming a salt with the carboxylic acid), and the acid form and the salt form may be mixed.

[0023] Examples of carboxylic acid base salts include alkali metal salts such as sodium salts and potassium salts, alkaline earth metal salts such as magnesium salts and calcium salts, ammonium salts, amine salts (primary amine salts, secondary amine salts, tertiary amine salts), and quaternary ammonium salts. Among these, salts of volatile bases such as ammonium salts and amine salts are preferred. When a volatile base is used, it vaporizes during heating and drying of the aqueous dispersion, causing the carboxyl group to easily become acidic, which improves reactivity with the carbodiimide group-containing compound (B) and enhances the adhesion effect.

[0024] In this embodiment, the acid value of polyurethane resin (A) is 5 to 25 mgKOH / g. An acid value of 5 mgKOH / g or higher facilitates emulsification of polyurethane resin (A) in an aqueous dispersion medium. An acid value of 25 mgKOH / g or lower improves initial adhesion. The acid value of polyurethane resin (A) is more preferably 7 to 20 mgKOH / g, and even more preferably 10 to 15 mgKOH / g.

[0025] In this specification, the acid value can be determined from the amount of KOH (mg) required to neutralize the carboxyl groups contained in 1 g of polyurethane resin (A), in accordance with JIS K0070-1992. Note that if polyurethane resin (A) is a salt of a volatile base, the volatile base vaporizes when measuring the mass of polyurethane resin (A), so the acid value is calculated based on the mass of the non-volatile acidic polyurethane resin. Thus, the mass of polyurethane resin (A) in this specification refers to the mass of the non-volatile content.

[0026] In order to introduce carboxyl groups into polyurethane resin (A), it is preferable to use a carboxyl group-containing polyol along with a polyester polyol in the polyol used to synthesize polyurethane resin (A). That is, it is preferable that polyurethane resin (A) contains a carboxyl group-containing polyol as a constituent component.

[0027] Examples of carboxyl group-containing polyols include carboxylic acid-containing compounds such as dimethylolpropionic acid, 2,2-dimethylolbutyric acid, 2,2-dimethylolvaleric acid, dihydroxymaleic acid, 2,6-dihydroxybenzoic acid, and tartaric acid, as well as their derivatives and salts. Any one of these may be used, or two or more may be used in combination.

[0028] The amount of carboxyl group-containing polyol in the polyol is not particularly limited, and may be, for example, 0.5 to 15% by mass, 1 to 10% by mass, 2 to 8% by mass, or 3 to 6% by mass, based on 100% by mass of the polyol.

[0029] Polyalkylene glycol may also be used as the polyol used to synthesize polyurethane resin (A). That is, it is preferable that polyurethane resin (A) further contains polyalkylene glycol as a constituent component. By including polyalkylene glycol, initial adhesion can be improved.

[0030] Examples of polyalkylene glycols include polyethylene glycol, polytrimethylene glycol, polypropylene glycol, polytetramethylene glycol, polybutylene glycol, and copolymers using two or more of these constituent monomers. The molecular weight of the polyalkylene glycol is not particularly limited; for example, the number average molecular weight (Mn) may be 500 to 5000, 800 to 4000, or 1000 to 3000.

[0031] The amount of polyalkylene glycol in the polyurethane resin (A) (i.e., the amount of structure derived from polyalkylene glycol) is preferably 5 to 15 parts by mass, more preferably 7 to 13 parts by mass, and even more preferably 8 to 10 parts by mass, per 100 parts by mass of the polyurethane resin (A). The amount of polyalkylene glycol in the polyol is not particularly limited and may be, for example, 3 to 25% by mass, 5 to 20% by mass, or 10 to 15% by mass, per 100% by mass of the polyol.

[0032] Polyols with three or more functional groups may be used as the polyol used to synthesize polyurethane resin (A). Examples of polyols with three or more functional groups include low molecular weight polyhydric alcohols (preferably trihydric alcohols) such as trimethylolpropane, glycerin, and pentaerythritol. The amount of such polyols with three or more functional groups is not particularly limited and may be 0.1 to 5% by mass, 0.2 to 3% by mass, or 0.3 to 1% by mass, based on 100% by mass of the polyol.

[0033] The polyol used to synthesize polyurethane resin (A) may include polyols other than those mentioned above. Examples of such other polyols include polymer polyols such as polycarbonate polyols, polyether polyols other than polyalkylene glycols, and polybutadiene polyols. Other polyols may also include low molecular weight diols such as ethylene glycol, propylene glycol, propanediol, butanediol, pentanediol, 3-methyl-1,5-pentanediol, hexanediol, neopentyl glycol, diethylene glycol, triethylene glycol, dipropylene glycol, tripropylene glycol, bisphenol A, bisphenol F, bisphenol S, and hydrogenated bisphenol A. Any one of these other polyols may be used, or two or more may be used in combination.

[0034] The amount of polyol constituting the polyurethane resin (A) (i.e., the amount of polyol-derived structure) is not particularly limited, and may be 70 to 90 parts by mass or 75 to 85 parts by mass per 100 parts by mass of polyurethane resin (A).

[0035] Examples of polyisocyanates used to synthesize polyurethane resin (A) include aromatic polyisocyanates, aromatic aliphatic polyisocyanates, aliphatic polyisocyanates, and alicyclic polyisocyanates.

[0036] Examples of aromatic polyisocyanates include diphenylmethane diisocyanate (MDI), polymeric MDI, tolylene diisocyanate (TDI), naphthalene diisocyanate, and modified forms thereof such as isocyanurates, adducts, biuret compounds, allophenates, and carbodiimides.

[0037] Examples of aromatic aliphatic polyisocyanates include xylylene diisocyanate (XDI), ω,ω'-diisocyanate-1,4-diethylbenzene, 1,3- or 1,4-bis(1-isocyanate-1-methylethyl)benzene, and modified forms thereof such as isocyanurates, adducts, biuret compounds, allophenates, and carbodiimides.

[0038] Examples of aliphatic polyisocyanates include tetramethylene diisocyanate, dodecamethylene diisocyanate, hexamethylene diisocyanate (HDI), 2,2,4-trimethylhexamethylene diisocyanate, lysine diisocyanate, and modified forms thereof such as isocyanurates, adducts, biuret compounds, allophenates, and carbodiimides.

[0039] Examples of alicyclic polyisocyanates include isophorone diisocyanate (IPDI), dicyclohexylmethane 4,4'-diisocyanate (hydrogenated MDI), hydrogenated xylylene diisocyanate, 1,4-cyclohexane diisocyanate, methylcyclohexylene diisocyanate, 1,3-bis(isocyanate-methyl)cyclohexane, and modified forms thereof such as isocyanurates, adducts, biuret compounds, allophenates, and carbodiimides.

[0040] These polyisocyanates may be used individually or in combination of two or more.

[0041] As the polyisocyanate, it is preferable to use aromatic ring-containing polyisocyanates such as aromatic polyisocyanates and aromatic aliphatic polyisocyanates, and more preferably aromatic aliphatic polyisocyanates. The amount of aromatic ring-containing polyisocyanate relative to 100% by mass of polyisocyanate is not particularly limited, and may be, for example, 50% by mass or more, 70% by mass or more, 90% by mass or more, or 100% by mass.

[0042] The amount of polyisocyanate constituting the polyurethane resin (A) (i.e., the amount of polyisocyanate-derived structure) is not particularly limited, and may be 10 to 30 parts by mass or 15 to 25 parts by mass per 100 parts by mass of polyurethane resin (A).

[0043] In one embodiment, the polyurethane resin (A) can be any of the following (A1) and (A2). (A1) An anionic polyurethane resin obtained by reacting a polyol containing a polyester polyol and a carboxyl group-containing polyol with a polyisocyanate to synthesize an isocyanate group-containing urethane prepolymer, and then extending the chains of the urethane prepolymer with a chain extender. (A2) A hydroxyl group-containing anionic polyurethane resin obtained by reacting a polyol containing a polyester polyol and a carboxyl group-containing polyol with a polyisocyanate.

[0044] [Carbodiimide group-containing compound (B)] The carbodiimide group-containing compound (B) is a compound that contains a carbodiimide group (-N=C=N-) in its molecule and reacts with the carboxyl group of the polyurethane resin (A).

[0045] Examples of carbodiimide group-containing compounds (B) include carbodiimide group-containing compounds used as aqueous crosslinking agents. Preferably, these are polycarbodiimides, which are polymers having carbodiimide groups in their molecules, and more preferably, aqueous polycarbodiimides obtained by introducing a hydrophilic segment into a polycarbodiimide having multiple carbodiimide groups in its molecule. Examples of such aqueous polycarbodiimides include the water-soluble types "Carbodilite V-02", "Carbodilite V-02-L2", "Carbodilite SV-02", "Carbodilite V-04", and "Carbodilite V-10", and the emulsion / dispersion types "Carbodilite E-02" and "Carbodilite E-05" (all manufactured by Nisshinbo Chemical Co., Ltd.).

[0046] The NCN equivalent of the carbodiimide group-containing compound (B) is not particularly limited and may be, for example, 300 to 600 or 350 to 500. Here, NCN equivalent represents the chemical formula weight per mole of carbodiimide group.

[0047] [Aqueous dispersion medium (C)] The aqueous dispersion medium (C) is a dispersion medium containing water, and includes water or a mixed medium of water and a hydrophilic organic solvent. From the viewpoint of dispersion stability of the aqueous dispersion, the aqueous dispersion medium (C) is preferably water, and although an organic solvent may be included, it is preferable that it be in small amounts. In one embodiment, the aqueous dispersion medium (C) preferably contains 70% by mass or more of water, more preferably 80% by mass or more of water, more preferably 90% by mass or more of water, and may even contain 100% by mass of water. That is, in the aqueous dispersion medium (C), the mass ratio of water / hydrophilic organic solvent is preferably 70 / 30 to 100 / 0, more preferably 80 / 20 to 100 / 0, and even more preferably 90 / 10 to 100 / 0.

[0048] As hydrophilic organic solvents, various organic solvents that dissolve in water can be used, such as lower monohydric alcohols like methanol, ethanol, and propanol; polyhydric alcohols like ethylene glycol and glycerin; and aprotic polar solvents like N-methylpyrrolidone, dimethyl sulfoxide, dimethylformamide, and acetonitrile.

[0049] [Polyurethane aqueous dispersion] The polyurethane aqueous dispersion is an aqueous dispersion in which polyurethane resin (A) is dispersed in an aqueous dispersion medium (C), and contains a carbodiimide group-containing compound (B). By incorporating the carbodiimide group-containing compound (B) into the aqueous dispersion of polyurethane resin (A) in this way, initial adhesion and water-resistant adhesion can be improved.

[0050] The content of the carbodiimide group-containing compound (B) in the polyurethane aqueous dispersion is preferably set as follows: Specifically, the aqueous dispersion preferably contains 80 to 350 moles of carbodiimide groups of the carbodiimide group-containing compound (B) per 100 moles of carboxyl groups of the polyurethane resin (A).

[0051] As described above, by making the acid value of the polyurethane resin (A) relatively low and setting the number of moles of carbodiimide groups to 80 moles or more per 100 moles of carboxyl groups, carbodiimide groups tend to remain in the cured coating film. These remaining carbodiimide groups can enhance the adhesion improvement effect. Furthermore, by having 350 moles or less of carbodiimide groups, the effect of improving the adhesion of the coating film to the polyester resin substrate can be enhanced. The amount of carbodiimide groups per 100 moles of carboxyl groups is more preferably 100 to 300 moles, more preferably 150 to 280 moles, and even more preferably 180 to 250 moles.

[0052] The content of polyurethane resin (A) in the aqueous polyurethane dispersion is not particularly limited and may be, for example, 5 to 50% by mass, 7 to 40% by mass, 10 to 30% by mass, or 15 to 25% by mass, relative to the total mass of the aqueous dispersion.

[0053] The particle size of the polyurethane resin (A) in the polyurethane aqueous dispersion is not particularly limited, and for example, the average particle diameter may be 0.001 to 0.5 μm. Here, the average particle diameter is the 50% cumulative particle diameter (d50) measured using "Microtrac UPA-UZ152" manufactured by Nikkiso Co., Ltd.

[0054] The polyurethane aqueous dispersion may contain other components as long as its effectiveness is not impaired. These other components may be contained in the resin particles as the dispersed phase, or they may be contained separately in the aqueous dispersion medium (C) in a dispersed or dissolved state. For example, in the polyurethane aqueous dispersion, the resin particles as the dispersed phase may consist only of polyurethane resin (A), or they may consist of polyurethane resin (A) along with other components. The polyurethane aqueous dispersion may also contain a surfactant for dispersing the polyurethane resin (A) in the aqueous dispersion medium (C). The carbodiimide group-containing compound (B) may be contained in the resin particles, but if they are hydrophilic or water-soluble, they may be contained separately in the aqueous dispersion medium (C) in a dispersed or dissolved state.

[0055] [Method for producing aqueous dispersions] The method for producing the polyurethane aqueous dispersion is not particularly limited. In one embodiment, the aqueous dispersion containing the anionic polyurethane resin described in (A1) above may be produced by the following steps (a1) to (a5). Step (a1): A step of synthesizing an isocyanate group-containing urethane prepolymer by reacting a polyol containing polyester polyol and carboxyl group-containing polyol with a polyisocyanate. Step (a2): A step to neutralize the carboxyl groups of the isocyanate group-containing urethane prepolymer. Step (a3): A step of dispersing an isocyanate group-containing urethane prepolymer in an aqueous dispersion medium (C). Step (a4): A step of extending the chains of an isocyanate group-containing urethane prepolymer with a chain extender. Step (a5): A step of mixing a carbodiimide group-containing compound (B) into an aqueous dispersion containing the anionic polyurethane resin after chain elongation.

[0056] In step (a1) described above, the polyisocyanate may be used such that the isocyanate groups are stoichiometrically in excess of the hydroxyl groups contained in the polyol, for example, the equivalent ratio of hydroxyl groups to isocyanate groups (NCO / OH) is 1.05 to 1.70 (more preferably 1.10 to 1.60).

[0057] Furthermore, in step (a1), the reaction between the polyol and the polyisocyanate may be carried out without an organic solvent, or in an organic solvent that does not have active hydrogen groups, such as methyl ethyl ketone or acetone.

[0058] In step (a2) above, examples of bases used to neutralize the carboxyl group 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.

[0059] In step (a3) ​​described above, the method for dispersing the urethane prepolymer in an aqueous dispersion medium is not particularly limited. Examples include (i) adding the urethane prepolymer or a solution thereof while stirring the aqueous dispersion medium with a homogenizer or homomixer, and (ii) adding the aqueous dispersion medium while stirring the urethane prepolymer or a solution thereof with a homogenizer or homomixer.

[0060] In step (a4) described above, the chain extender is not particularly limited and, for example, water can be used. Other examples include polyhydric amine compounds such as aliphatic polyamine compounds (e.g., ethylenediamine, trimethylenediamine, propylenediamine, diethylenetriamine, triethylenetetramine), aromatic polyamine compounds (e.g., metaxylenediamine, tolylenediamine, diaminodiphenylmethane), alicyclic polyamine compounds (e.g., piperazine, isophoronediamine), and polyhydrazide compounds (e.g., hydrazine, adipic acid dihydrazide).

[0061] The neutralization in step (a2), the dispersion in step (a3), and the chain extension in step (a4) may be carried out in this order, but two or more steps may be carried out simultaneously. For example, if aqueous ammonia is used to neutralize the carboxyl group, the dispersion in an aqueous dispersion medium may be carried out simultaneously with the neutralization, and then the chain extension with water may be carried out. If the reaction between the polyol and polyisocyanate in step (a1) is carried out in an organic solvent, the organic solvent may be removed after the dispersion in an aqueous dispersion medium in step (a4).

[0062] In one embodiment, the aqueous dispersion containing the anionic polyurethane resin described in (A2) above may be produced by the following steps (b1) to (b4). Step (b1): A step of synthesizing a hydroxyl group-containing polyurethane resin by reacting a polyol containing polyester polyol and carboxyl group-containing polyol with a polyisocyanate. Step (b2): A step to neutralize the anionic groups of the hydroxyl group-containing polyurethane resin. Step (b3): ​​A step of dispersing a hydroxyl group-containing polyurethane resin in an aqueous dispersion medium (C). Step (b4): A step of mixing a carbodiimide group-containing compound (B) into an aqueous dispersion containing a hydroxyl group-containing polyurethane resin.

[0063] In step (b1) described above, the polyol is used such that the amount of hydroxyl groups is stoichiometrically in excess of the amount of isocyanate groups contained in the polyisocyanate, for example, the equivalent ratio of hydroxyl groups to isocyanate groups (NCO / OH) is 0.70 to 0.95 (more preferably 0.75 to 0.90).

[0064] The neutralization in step (b2) and the dispersion in step (b3) may be carried out in this order, or they may be carried out simultaneously. For example, if aqueous ammonia is used to neutralize the carboxyl group, the dispersion in an aqueous dispersion medium may be carried out simultaneously with the neutralization. Furthermore, if the reaction between the polyol and polyisocyanate in step (b1) is carried out in an organic solvent, the organic solvent may be removed after the dispersion in the aqueous dispersion medium in step (b3).

[0065] [Water-based primer] The aqueous primer according to this embodiment includes the above-mentioned aqueous polyurethane dispersion, and therefore the aqueous primer comprises an aqueous dispersion medium (C), a polyurethane resin (A) dispersed in the aqueous dispersion medium, and a carbodiimide group-containing compound (B).

[0066] The aqueous primer may consist solely of the above-mentioned aqueous polyurethane dispersion, or it may contain other components as long as its effectiveness is not impaired. For example, the aqueous primer may or may not contain other aqueous resins used as film-forming components together with the polyurethane resin (A). Examples of other aqueous resins include 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. The aqueous primer may also contain additives such as wetting agents, pigments, UV absorbers, light stabilizers, surface modifiers, inorganic fillers, organic fillers, dispersion aids, preservatives, rust inhibitors, antioxidants, silane coupling agents, defoamers, viscosity modifiers, antistatic agents, crosslinking agents, and organic solvents.

[0067] The content of polyurethane resin (A) and carbodiimide group-containing compound (B) in the aqueous primer is not particularly limited. For example, the total content of both may be 20-100% by mass, 50-100% by mass, or 70-100% by mass, relative to 100% by mass of the total resin solids in the aqueous primer. The solids concentration of the aqueous primer is also not particularly limited. For example, it may be 5-50% by mass or 6-30% by mass. The content of polyurethane resin (A) in the aqueous primer may be 3-40% by mass, 4-30% by mass, or 5-20% by mass, relative to the total mass of the aqueous primer.

[0068] The aqueous primer according to this embodiment is used to form a primer layer between a polyester resin substrate and an inorganic layer. For example, the aqueous primer is used to fix an inorganic layer on a polyester resin substrate, and a laminate is obtained on the polyester resin substrate comprising the primer layer formed by the aqueous primer and the inorganic material in that order. More specifically, the laminate according to this embodiment can be obtained by applying the aqueous primer according to this embodiment to a polyester resin substrate, drying it to form a coating film which is the primer layer, and then forming an inorganic layer as a topcoat layer on the primer layer. The laminate may further comprise other layers on the inorganic layer.

[0069] As for the polyester resin substrate, it is sufficient that the surface to be coated on which the inorganic layer is provided is formed of polyester resin. Therefore, the entire substrate may be made of polyester resin, or it may have a polyester resin layer on the surface to be coated. Examples of polyester resins include polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), etc. In one embodiment, the polyester resin substrate may be a PET film, a PBT film, or a PEN film. Furthermore, the polyester resin substrate may be in the form of a film or a plate-shaped substrate, and its thickness and shape are not particularly limited.

[0070] The method for applying a water-based primer to a polyester resin substrate is not particularly limited and can be carried out using a coating machine such as a roll coater, bar coater, or spin coater. When applying a water-based primer, it is preferable to degrease the surface (surface to be coated) of the polyester resin substrate beforehand with an organic solvent such as isopropyl alcohol.

[0071] After applying a water-based primer using a coating machine, a primer layer can be formed on a polyester resin substrate by drying it at, for example, 80 to 250°C for 0.5 to 10 minutes. The thickness of the primer layer is not particularly limited and may be, for example, 0.01 to 3 μm or 0.05 to 1.0 μm.

[0072] After forming a primer layer on a polyester resin substrate, an inorganic layer is formed on top of the primer layer.

[0073] Examples of inorganic materials constituting the inorganic layer include silicon oxide, silicon nitride, silicon oxynitride, aluminum oxide, aluminum nitride, and aluminum. These may be used individually or in combination of two or more. Examples of silicon oxide include silicon dioxide, silicon monoxide, silicon suboxide, and combinations of two or more of these. Silicon nitride is Si x N y It is represented as, for example, Si3N4. Silicon oxynitride is, for example, Si x N y O z It is represented as follows. Examples of aluminum oxide include Al2O3 and AlO. Examples of aluminum nitride include AlN. The inorganic layer may be transparent if the constituent inorganic material is an oxide or nitride, or it may be a metallic color such as silver if the constituent inorganic material is a metal such as aluminum.

[0074] The method for forming the inorganic layer is not particularly limited. Examples include sputtering, vacuum deposition, ion plating, and plasma vapor deposition (CVD). Alternatively, the inorganic layer may be formed by applying an inorganic-containing liquid using a coating machine and drying it. The thickness of the inorganic layer is not particularly limited and may be, for example, 0.1 to 500 nm or 10 to 100 nm.

[0075] The applications of the laminate are not particularly limited; for example, it can be used as a gas barrier film. [Examples]

[0076] The present invention will be described in more detail below based on examples and comparative examples, but it is not limited thereto.

[0077] Details of each component used in the examples are as follows.

[0078] [Polyol] Aromatic polyester polyol 1: 2 functional groups, number average molecular weight 1000, solids content 70% by mass, diluent MEK. The synthesis method is as follows. In a reaction vessel equipped with a stirrer, thermometer, reflux condenser, dropping tank, and nitrogen gas inlet tube, 16.2 parts by mass of succinic anhydride and 83.8 parts by mass of bisphenol A ethylene oxide adduct ("Newpol BPE-20NK" manufactured by Sanyo Chemical Industries, Ltd.) were charged, and the mixture was heated to 250°C while stirring under a nitrogen atmosphere. The reaction was continued until the acid value was 5 mg KOH / g or less (2.92 parts by mass of distilled water was added), and after cooling to 70°C, 41.61 parts by mass of methyl ethyl ketone was added to obtain aromatic polyester polyol 1.

[0079] Aromatic polyester polyol 2: 2 functional groups, number average molecular weight 2000, solids content 70% by mass, diluent MEK. The synthesis method is as follows. In a reaction vessel equipped with a stirrer, thermometer, reflux condenser, dropping tank, and nitrogen gas inlet tube, 19.9 parts by mass of succinic anhydride and 80.1 parts by mass of bisphenol A ethylene oxide adduct ("Newpol BPE-20NK" manufactured by Sanyo Chemical Industries, Ltd.) were charged, and the temperature was raised to 250°C while stirring under a nitrogen stream. The reaction was continued until the acid value was 5 mg KOH / g or less (3.58 parts by mass of distilled water was added), and after cooling to 70°C, 41.32 parts by mass of methyl ethyl ketone was added to obtain aromatic polyester polyol 2.

[0080] Aromatic polyester polyol 3: 2 functional groups, number average molecular weight 1000, solids content 70% by mass, diluent MEK. The synthesis method is as follows. In a reaction vessel equipped with a stirrer, thermometer, reflux condenser, dropping tank, and nitrogen gas inlet tube, 40.9 parts by mass of isophthalic acid, 19.89 parts by mass of adipic acid, 25.14 parts by mass of neopentyl glycol, and 14.07 parts by mass of ethylene glycol were charged, and the mixture was heated to 250°C while stirring under a nitrogen atmosphere. The reaction was continued until the acid value was 5 mg KOH / g or less (13.76 parts by mass of water removed by distillation), and after cooling to 70°C, 36.96 parts by mass of methyl ethyl ketone was added to obtain aromatic polyester polyol 3.

[0081] Aliphatic polyester polyol: 2 functional groups, number average molecular weight 1000, solids content 70% by mass, diluent MEK. The synthesis method is as follows. In a reaction vessel equipped with a stirrer, thermometer, reflux condenser, dropping tank, and nitrogen gas inlet, 53.1 parts by mass of adipic acid and 46.9 parts by mass of neopentyl glycol were charged, and the mixture was heated to 250°C while stirring under a nitrogen stream. The reaction was continued until the acid value was 5 mg KOH / g or less (13.08 parts by mass of water removed by distillation), and after cooling to 70°C, 37.25 parts by mass of methyl ethyl ketone was added to obtain an aliphatic polyester polyol.

[0082] • PTMG1000: Polytetramethylene ether glycol, manufactured by Mitsubishi Chemical Corporation, 2 functional groups, number average molecular weight 1000 • PCD: Polycarbonate polyol, "ETERNACOLL UH-100" manufactured by UBE Corporation, 2 functional groups, number average molecular weight 1000

[0083] • Dimethylolpropionic acid: 2,2-bis(hydroxymethyl)propionic acid, 2 functional groups • 2,2-Dimethylolbutyric acid: 2,2-bis(hydroxymethyl)butyric acid, 2 functional groups Trimethylolpropane: 3 functional groups • PEG1000: Polyethylene glycol, 2 functional groups, number average molecular weight 1000, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.

[0084] [Polyisocyanate] • XDI: Xylylene diisocyanate (2 functional groups) • TDI: Tolylene diisocyanate (2 functional groups) • HDI: Hexamethylene diisocyanate (2 functional groups)

[0085] [Neutralizing agent] • Ammonia water: 25% by mass aqueous solution Triethylamine

[0086] [Carbodiimide group-containing compounds] • Water-soluble polycarbodiimide 1: "Carbodilite SV-02" manufactured by Nisshinbo Chemical Co., Ltd., solids content 40% by mass (solvent: water), NCN equivalent 430 • Water-soluble polycarbodiimide 2: "Carbodilite V-02-L2" manufactured by Nisshinbo Chemical Co., Ltd., solids content 40% by mass (solvent: water), NCN equivalent 385

[0087] The evaluation method for aqueous primers is as follows:

[0088] [Preparation of test specimens] A polyethylene terephthalate (PET) film (Toray Industries, Inc.'s "Lumirror T-60") was used as the substrate, and the substrate surface was degreased with isopropyl alcohol. Next, the aqueous primer of each example or comparative example was applied using a bar coater to a dry film thickness of 1 μm, and dried at 120°C for 1 minute to obtain a test piece X on which a primer layer was formed on the substrate.

[0089] On the primer layer of specimen X, a SiO2 film with a thickness of approximately 35 nm or an Al2O3 film with a thickness of approximately 40 nm was deposited using a magnetron sputtering apparatus to obtain specimens Y1 and Y2, respectively. For the SiO2 film, the deposition conditions were a deposition pressure of 0.5 Pa and a power density of 1.3 W / cm². 2 The target was SiO2. For the Al2O3 film, the deposition pressure was 0.5 Pa and the power density was 3.8 W / cm². 2 The target was Al2O3.

[0090] [Initial adhesion] Using test pieces X, Y1, and Y2 as samples, a 1mm grid test was conducted in accordance with JIS K5400-8.5:1990, and the initial adhesion in the state of two layers of PET film / primer layer, or three layers of PET film / primer layer / inorganic material layer, was calculated using the following formula. Initial adhesion (%) = 100 - (number of squares that peeled off)

[0091] [Water-resistant adhesion] Test specimens X, Y1, and Y2 were immersed in 100°C hot water for 48 hours. After cooling to room temperature, test specimens X, Y1, and Y2 were removed, and the condition of the coating surface when rubbed with a finger while wet was examined and evaluated according to the following criteria. A: No peeling B: Partial peeling where more than 60% of the paint film remains. C: Partial peeling where less than 60% of the paint film remains. D: Completely detached

[0092] [Example 1] In a four-necked flask equipped with a stirrer, reflux condenser, thermometer, and nitrogen gas inlet tube, 1 part by mass of aromatic polyester polyol (64.76 parts by mass as solids), 3.0 parts by mass of dimethylolpropionic acid, 0.5 parts by mass of trimethylolpropane, 9.82 parts by mass of PEG1000, and 100 parts by mass of methyl ethyl ketone were added and thoroughly mixed and dissolved. Next, 21.92 parts by mass of XDI as polyisocyanate was added, and the mixture was reacted at 70-75°C for 300 minutes to obtain a methyl ethyl ketone solution of isocyanate group-containing urethane prepolymer. In the obtained urethane prepolymer solution, the content of free isocyanate groups relative to the solids was 1.2% by mass. The obtained urethane prepolymer solution was cooled to 60°C, and while stirring with a homogenizer, an emulsified dispersion was carried out by gradually adding a solution of 3.46 parts by mass of 25% by mass of aqueous ammonia and 350 parts by mass of water. Subsequently, the emulsion was stirred at 40°C for 1 hour to complete the chain extension reaction with water. Methyl ethyl ketone was removed by distillation under heating and reduced pressure, and water was added to adjust the solid content to obtain an aqueous dispersion with a solid content of 25% by mass. 52.90 parts by mass (21.16 parts by mass as solid content) of water-soluble polycarbodiimide 1 was added to the obtained aqueous dispersion and stirred to obtain an aqueous polyurethane dispersion. In the obtained aqueous polyurethane dispersion, the acid value of the polyurethane resin was 12.5 mgKOH / g. Also, the amount of carbodiimide groups per 100 moles of carboxyl groups in the polyurethane resin was 220 moles.

[0093] The aqueous primer of Example 1 was prepared by adding water to the obtained polyurethane aqueous dispersion to obtain an aqueous dispersion with a solid content of 10% by mass, and then adding 0.1% by mass of a wetting agent ("NeoCall SW-C" manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) per 100% by mass of the aqueous dispersion.

[0094] [Examples 2-14 and Comparative Examples 1-7] The types and amounts (parts by mass) of the polyol, polyisocyanate, neutralizing agent, and carbodiimide group-containing compound were changed as shown in Tables 1 to 3 below, and the rest of the process was the same as in Example 1 to obtain aqueous polyurethane dispersions of Examples 2 to 14 and Comparative Examples 1 to 7. However, comparative example 5 could not be emulsified and dispersed, and therefore the carbodiimide group-containing compound was not added, and no aqueous primer was obtained.

[0095] The initial adhesion and water-resistant adhesion of the aqueous primers in Examples 1-14 and Comparative Examples 1-7 (excluding Comparative Example 5) were evaluated. The results are shown in Tables 1-3.

[0096] In Tables 1-3, the amount of polyester polyol represents the amount of solids, which are the active ingredient, and the number in parentheses represents the amount including the solvent. In Tables 1-3, the amount of carbodiimide group-containing compound represents the amount of each component including the solvent, and the number in parentheses represents the amount of solids, which are the active ingredient. "Solids of polyurethane resin" is the solids concentration (mass%) of the polyurethane resin in the aqueous dispersion before the addition of the carbodiimide group-containing compound. "(Carbodiimide group*100) / carboxyl group [mol]" is the amount (moles) of carbodiimide groups of the carbodiimide group-containing compound per 100 moles of carboxyl groups of the polyurethane resin.

[0097] [Table 1]

[0098] [Table 2]

[0099] [Table 3]

[0100] The results are shown in Tables 1-3. Comparative Examples 1 and 2 had poor water-resistant adhesion because they did not contain a carbodiimide group-containing compound. Comparative Examples 3 and 4 contained a carbodiimide group-containing compound, but had poor initial adhesion because the acid value of the polyurethane resin was too high.

[0101] Comparative Example 5 attempted to prepare the polyurethane resin so that its acid value was lower than the set value at 4.2 mg KOH / g. However, the amount of carboxyl group-containing polyol was too small, and the urethane prepolymer could not be emulsified. In Comparative Examples 6 and 7, polyether polyol or polycarbonate polyol was used instead of polyester polyol as a component of the polyurethane resin, resulting in poor initial adhesion.

[0102] In contrast, Examples 1 to 14 exhibited excellent initial adhesion between the polyester resin substrate and the primer layer, and between the primer layer and the inorganic layer, as well as excellent water-resistant adhesion. Thus, the water-based primer according to this embodiment has high adhesion, including water-resistant adhesion, to both the polyester resin substrate and the inorganic layer, and therefore has a remarkable effect as a water-based primer for immobilizing the inorganic layer on the polyester resin substrate. Furthermore, from a comparison between Example 1 and Example 14, aromatic polyester polyols showed superior water-resistant adhesion compared to aliphatic polyester polyols.

[0103] Furthermore, the various numerical ranges described in this specification can be any combination of their upper and lower limits, and all such combinations are described herein as preferred numerical ranges. Also, the description of a numerical range as "X~Y" means X or greater and Y or less.

[0104] 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, and modifications are included in the scope and spirit of the invention, as well as in the claims and their equivalents.

Claims

1. A water-based primer used to form a primer layer between a polyester resin substrate and an inorganic layer, The present invention comprises a polyurethane aqueous dispersion in which a polyurethane resin (A) containing a polyester polyol as a constituent component is dispersed in an aqueous dispersion medium. The polyurethane aqueous dispersion comprises a carbodiimide group-containing compound (B), The polyurethane resin (A) has a carboxyl group, and the acid value of the polyurethane resin (A) is 5 to 25 mg KOH / g. Water-based primer.

2. The aqueous primer according to claim 1, wherein the polyester polyol comprises an aromatic polyester polyol.

3. The aqueous primer according to claim 1, wherein the inorganic layer is an inorganic layer comprising at least one inorganic substance selected from the group consisting of silicon oxide, silicon nitride, silicon oxynitride, aluminum oxide, aluminum nitride, and aluminum.

4. A laminate comprising, in this order, a primer layer formed with an aqueous primer according to any one of claims 1 to 3, and an inorganic layer on a polyester resin substrate.

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