Two-component, separately-applied adhesive, adhesion method, and two-component, separately-applied adhesive kit

Abstract

The present invention pertains to a two-component, separately-applied adhesive containing a component (I) and a component (II), wherein: component (I) contains a polyvinyl alcohol-based resin (A); component (II) contains an inorganic salt (B) and a water-soluble polymer (C); and the polyvinyl alcohol-based resin (A) contains a polyvinyl alcohol-based resin including a carboxyl group or a salt thereof, and the viscosity of a 4 mass% aqueous solution of the water-soluble polymer (C) at 23°C is 1.9-90 mPa·s.

Description

Two-component separately applied adhesive, bonding method, and two-component separately applied adhesive kit

[0001] The present invention relates to a two-component separately applied adhesive, a bonding method, and a two-component separately applied adhesive kit.

[0002] In wood products used for housing construction materials and furniture, a certain level of adhesive strength is required immediately after bonding for efficient production. In addition, since wood products are often used in environments exposed to moisture and water, water resistance is required after a certain period of time has passed since bonding. As such an adhesive resin, an adhesive using carboxylic acid-modified PVA is known (Patent Documents 1 and 2).

[0003] Generally, one-component adhesives and two-component adhesives are known. From the viewpoints of coating properties and adhesive strength that allow the adhesive to be applied evenly on the wood surface, the use of two-component adhesives has been considered. A two-component adhesive is an adhesive that cures and bonds by mixing a main agent and a curing agent. Among two-component adhesives, there are types in which the main agent and the curing agent are separately applied to two substrates to be bonded, and then the two substrates are bonded together to cause the main agent and the curing agent to react, such as two-component separately applied adhesives and honeymoon adhesives.

[0004] Japanese Patent Application Laid-Open No. 11-001595, Japanese Patent Application Laid-Open No. 11-148061

[0005] The carboxylic acid-modified PVA-based adhesives described in Patent Documents 1 and 2 utilize the high reactivity between carboxylic acid-modified PVA and aluminum sulfate. Due to this reactivity, they tend to thicken, making stable storage and uniform application difficult. In addition, due to poor coating properties, adhesion to the adhesive interface is likely to be insufficient, and the initial adhesiveness, that is, the property of exhibiting a certain adhesive strength instantaneously, is inferior.

[0006] Therefore, from the viewpoints of improving initial adhesiveness and storage stability, the inventors of the present invention considered using a two-component separately applied adhesive. A two-component separately applied adhesive is an adhesive that has a mechanism in which the main agent and the curing agent are separately applied to two substrates to be bonded, and then the two substrates are bonded together to cause the main agent and the curing agent to react, thereby expressing adhesiveness.

[0007] Conventional two-component adhesives containing polyvinyl alcohol-based resins (hereinafter also referred to as "PVA-based resins") have problems such as requiring a long time for initial bonding and insufficient initial adhesion. They also have issues with coatability.

[0008] Therefore, the object of the present invention is to provide a two-component, separate-coating adhesive containing a PVA-based resin that adheres in a short time, has excellent initial adhesion, and also possesses coating properties.

[0009] As a result of diligent research, the present inventors have found that a two-component, fractional application adhesive comprising agent (I) and agent (II), wherein agent (I) contains a predetermined polyvinyl alcohol-based resin (A), and agent (II) contains a predetermined inorganic salt (B) and a predetermined water-soluble polymer (C), solves the above problems, and have completed the present invention.

[0010] Embodiment 1A of the present invention is a two-component fractional coating adhesive comprising agent (I) and agent (II), wherein agent (I) comprises a polyvinyl alcohol-based resin (A), the polyvinyl alcohol-based resin (A) comprises a polyvinyl alcohol-based resin having a carboxyl group or a salt thereof, and agent (II) comprises aluminum sulfate and polyamide-epichlorohydrin.

[0011] Embodiment 1B of the present invention is a two-component fractional coating adhesive according to Embodiment 1A, wherein the content ratio of aluminum sulfate in the solid content of agent (II) is 20 to 99.95% by mass.

[0012] Embodiment 1C of the present invention is a two-component fractional coating adhesive according to Embodiment 1A or 1B, wherein the content ratio of aluminum sulfate in the solid content of the two-component fractional coating adhesive is 0.1 to 99% by mass.

[0013] Embodiment 1D of the present invention is a two-component fractional coating adhesive according to any one of embodiments 1A to 1C, wherein the content ratio of the polyvinyl alcohol-based resin (A) to the aluminum sulfate in the two-component fractional coating adhesive (polyvinyl alcohol-based resin / aluminum sulfate) is 100 / 2 to 100 / 10000 in parts by mass.

[0014] Embodiment 1E of the present invention is a two-component fractional coating adhesive according to any one of Embodiments 1A to 1D, wherein the content ratio of the polyamide-epichlorohydrin in the solid content of agent (II) is 1 to 80% by mass.

[0015] Embodiment 1F of the present invention is a two-component fractional coating adhesive according to any one of embodiments 1A to 1E, wherein the content ratio of the polyamide-epichlorohydrin in the solid content of the two-component fractional coating adhesive is 0.5 to 85% by mass.

[0016] Embodiment 1G of the present invention is a two-component fractional coating adhesive according to any one of embodiments 1A to 1F, wherein the content ratio of aluminum sulfate to polyamide-epichlorohydrin (aluminum sulfate / polyamide-epichlorohydrin) in the two-component fractional coating adhesive is 100 / 1 to 100 / 500 in parts by mass.

[0017] Embodiment 2A of the present invention is a two-component, fractional application adhesive comprising agent (I) and agent (II), wherein agent (I) comprises a polyvinyl alcohol-based resin (A), the polyvinyl alcohol-based resin (A) comprises a polyvinyl alcohol-based resin having a carboxyl group or a salt thereof, and agent (II) comprises aluminum sulfate and polyethyleneimine.

[0018] Embodiment 2B of the present invention is a two-component fractional coating adhesive of Embodiment 2A, wherein the content ratio of aluminum sulfate in the solid content of agent (II) is 20 to 99.95% by mass.

[0019] Embodiment 2C of the present invention is a two-component fractional coating adhesive according to Embodiment 2A or 2B, wherein the content ratio of aluminum sulfate in the solid content of the two-component fractional coating adhesive is 0.1 to 99% by mass.

[0020] Embodiment 2D of the present invention is a two-component fractional coating adhesive according to any one of embodiments 2A to 2C, wherein the content ratio of the polyvinyl alcohol-based resin (A) to the aluminum sulfate in the two-component fractional coating adhesive (polyvinyl alcohol-based resin / aluminum sulfate) is 100 / 2 to 100 / 10000 in parts by mass.

[0021] Embodiment 2E of the present invention is a two-component fractional coating adhesive according to any one of embodiments 2A to 2D, wherein the content ratio of polyethyleneimine in the solid content of agent (II) is 1 to 80% by mass.

[0022] Embodiment 2F of the present invention is a two-component fractional coating adhesive according to any one of embodiments 2A to 2E, wherein the content ratio of polyethyleneimine in the solid content of the two-component fractional coating adhesive is 0.5 to 85% by mass.

[0023] Embodiment 2G of the present invention is a two-component fractional coating adhesive according to any one of embodiments 2A to 2F, wherein the content ratio of aluminum sulfate to polyethyleneimine (aluminum sulfate / polyethyleneimine) in the two-component fractional coating adhesive is 100 / 1 to 100 / 500 in parts by mass.

[0024] Embodiment 3A of the present invention is a two-component, fractional application adhesive comprising agent (I) and agent (II), wherein agent (I) comprises a polyvinyl alcohol-based resin (A), the polyvinyl alcohol-based resin (A) comprises a polyvinyl alcohol-based resin having a carboxyl group or a salt thereof, and agent (II) comprises aluminum sulfate and an oxazoline group-containing polymer.

[0025] Embodiment 3B of the present invention is a two-component fractional coating adhesive according to Embodiment 3A, wherein the content ratio of aluminum sulfate in the solid content of agent (II) is 20 to 99.95% by mass.

[0026] Embodiment 3C of the present invention is a two-component fractional coating adhesive according to Embodiment 3A or 3B, wherein the content ratio of aluminum sulfate in the solid content of the two-component fractional coating adhesive is 0.1 to 99% by mass.

[0027] Embodiment 3D of the present invention is a two-component fractional coating adhesive according to any one of embodiments 3A to 3C, wherein the content ratio of the polyvinyl alcohol-based resin (A) to the aluminum sulfate in the two-component fractional coating adhesive (polyvinyl alcohol-based resin / aluminum sulfate) is 100 / 2 to 100 / 10000 in parts by mass.

[0028] Embodiment 3E of the present invention is a two-component fractional coating adhesive according to any one of embodiments 3A to 3D, wherein the content ratio of the oxazoline group-containing polymer in the solid content of agent (II) is 1 to 80% by mass.

[0029] Embodiment 3F of the present invention is a two-component fractional coating adhesive according to any one of embodiments 3A to 3E, wherein the content ratio of the oxazoline group-containing polymer in the solid content of the two-component fractional coating adhesive is 0.5 to 85% by mass.

[0030] Embodiment 3G of the present invention is a two-component fractional coating adhesive according to any one of embodiments 3A to 3F, wherein the content ratio of aluminum sulfate to the oxazoline group-containing polymer (aluminum sulfate / oxazoline group-containing polymer) in the two-component fractional coating adhesive is 100 / 1 to 100 / 500 in parts by mass.

[0031] Aspect 4 of the present invention is a two-component, fractional application adhesive comprising agent (I) and agent (II), wherein agent (I) comprises a polyvinyl alcohol-based resin (A), agent (II) comprises an inorganic salt (B) and a water-soluble polymer (C), the polyvinyl alcohol-based resin (A) comprises a polyvinyl alcohol-based resin having a carboxyl group or a salt thereof, and the viscosity of a 4% by mass aqueous solution of the water-soluble polymer (C) at 23°C is 1.9 to 90 mPa·s.

[0032] Embodiment 5 of the present invention is a two-component fractional coating adhesive according to any one of embodiments 1A to 1G, 2A to 2G, 3A to 3G, and 4, wherein the polyvinyl alcohol-based resin (A) is a polyvinyl alcohol-based resin having a carboxyl group or a salt thereof in its side chain.

[0033] Embodiment 6 of the present invention is a two-component fractional coating adhesive according to any one of embodiments 1A to 1G, 2A to 2G, 3A to 3G, and 4 to 5, wherein the content ratio of the polyvinyl alcohol-based resin (A) in the solid content of agent (I) is 50 to 100% by mass.

[0034] Embodiment 7 of the present invention is a two-component fractional coating adhesive according to any one of embodiments 1A to 1G, 2A to 2G, 3A to 3G, and 4 to 6, wherein the content ratio of the polyvinyl alcohol-based resin (A) in the solid content of the two-component fractional coating adhesive is 0.5 to 95% by mass.

[0035] Embodiment 8 of the present invention is a two-component fractional coating adhesive according to any one of embodiments 4 to 7, wherein the inorganic salt (B) is an inorganic salt consisting of a divalent or higher metal cation, or an ammonium ion and an anion derived from an inorganic acid.

[0036] Embodiment 9 of the present invention is a two-component fractional coating adhesive according to any one of embodiments 4 to 8, wherein the inorganic salt (B) is a sulfate.

[0037] Embodiment 10 of the present invention is a two-component fractional coating adhesive according to any one of embodiments 4 to 9, wherein the inorganic salt (B) is aluminum sulfate or ammonium sulfate.

[0038] Embodiment 11 of the present invention is a two-component fractional application adhesive according to any one of embodiments 4 to 10, wherein the content ratio of the inorganic salt (B) in the solid content of agent (II) is 20 to 99.95% by mass.

[0039] Embodiment 12 of the present invention is a two-component fractional coating adhesive according to any one of embodiments 4 to 11, wherein the content ratio of the inorganic salt (B) in the solid content of the two-component fractional coating adhesive is 0.1 to 99% by mass.

[0040] Embodiment 13 of the present invention is a two-component fractional coating adhesive according to any one of embodiments 4 to 12, wherein the content ratio (A / B) of the polyvinyl alcohol-based resin (A) to the inorganic salt (B) in the two-component fractional coating adhesive is 100 / 2 to 100 / 10000 in parts by mass.

[0041] Embodiment 14 of the present invention is a two-component fractional coating adhesive according to any one of embodiments 4 to 13, wherein the water-soluble polymer (C) is one or more selected from the group consisting of polyamide-epichlorohydrin, polyethyleneimine, and oxazoline group-containing polymers.

[0042] Aspect 15 of the present invention is a two-component fractional coating adhesive according to any one of aspects 4 to 13, wherein the water-soluble polymer (C) is one or more selected from the group consisting of unmodified polyvinyl alcohol, polyamide-epichlorohydrin, polyethylene glycol, polyvinylpyrrolidone, and carboxymethylcellulose.

[0043] Embodiment 16 of the present invention is a two-component fractional coating adhesive according to any one of embodiments 4 to 15, wherein the content ratio of the water-soluble polymer (C) in the solid content of agent (II) is 1 to 80% by mass.

[0044] Embodiment 17 of the present invention is a two-component fractional coating adhesive according to any one of embodiments 4 to 16, wherein the content ratio of the water-soluble polymer (C) in the solid content of the two-component fractional coating adhesive is 0.5 to 85% by mass.

[0045] Embodiment 18 of the present invention is a two-component fractional coating adhesive according to any one of embodiments 4 to 17, wherein the content ratio (B / C) of the inorganic salt (B) to the water-soluble polymer (C) in the two-component fractional coating adhesive is 100 / 1 to 100 / 500 in parts by mass.

[0046] Embodiment α of the present invention is a two-component fractional coating adhesive according to any one of embodiments 4 to 18, wherein the polyvinyl alcohol-based resin (A) comprises a polyvinyl alcohol-based resin having a carboxyl group or a salt thereof in its side chain, and the (II) agent comprises aluminum sulfate and polyamide-epichlorohydrin.

[0047] Embodiment β of the present invention is a two-component fractional coating adhesive according to any one of embodiments 4 to 14 and 16 to 18, wherein the (I) agent comprises a polyvinyl alcohol-based resin (A), the polyvinyl alcohol-based resin (A) comprises a polyvinyl alcohol-based resin having a carboxyl group or a salt thereof in its side chain, and the (II) agent comprises aluminum sulfate and polyethyleneimine.

[0048] Embodiment γ of the present invention is a two-component fractional coating adhesive according to any one of embodiments 4 to 14 and 16 to 18, wherein the (I) agent comprises a polyvinyl alcohol-based resin (A), the polyvinyl alcohol-based resin (A) comprises a polyvinyl alcohol-based resin having a carboxyl group or a salt thereof in its side chain, and the (II) agent comprises aluminum sulfate and an oxazoline group-containing polymer.

[0049] Aspect 19 of the present invention is an adhesion method comprising the step of contacting an agent (I) containing a polyvinyl alcohol-based resin (A) with an agent (II) containing an inorganic salt (B) and a water-soluble polymer (C), wherein the polyvinyl alcohol-based resin (A) contains a polyvinyl alcohol-based resin having a carboxyl group or a salt thereof, and the viscosity of a 4% by mass aqueous solution of the water-soluble polymer (C) at 23°C is 1.9 to 90 mPa·s.

[0050] Aspect 20 of the present invention is an adhesive method described in aspect 19, wherein the polyvinyl alcohol-based resin (A) is a polyvinyl alcohol-based resin having a carboxyl group or a salt thereof in its side chain.

[0051] Aspect 21 of the present invention is an adhesive method according to aspect 19 or 20, wherein an aqueous solution containing the polyvinyl alcohol-based resin (A) at a solid content concentration of 0.5 to 40% by mass is used as agent (I).

[0052] Aspect 22 of the present invention is an adhesive method according to any one of aspects 19 to 21, wherein the inorganic salt (B) and an aqueous solution of the water-soluble polymer (C) with a concentration of 0.3 to 30% by mass are used as the (II) agent.

[0053] Embodiment 23 of the present invention is an adhesive method according to any one of embodiments 19 to 22, comprising the following steps 1 and 2 in this order: 1) Applying agent (I) to surface a and applying agent (II) to surface b; 2) Bringing agent (I) and agent (II) into contact to bond surface a and surface b.

[0054] Embodiment 24 of the present invention is an adhesive method described in Embodiment 23, wherein step 2 is performed after step 3 below: 3) A step of drying at least one of the agent (I) applied to surface a and the agent (II) applied to surface b.

[0055] Aspect 25 of the present invention is a two-component, fractional application adhesive kit comprising agent (I) and agent (II), wherein agent (I) comprises a polyvinyl alcohol-based resin (A), agent (II) comprises an inorganic salt (B) and a water-soluble polymer (C), the polyvinyl alcohol-based resin (A) comprises a polyvinyl alcohol-based resin having a carboxyl group or a salt thereof, and the viscosity of the water-soluble polymer (C) in a 4% by mass aqueous solution at 23°C is 1.9 to 90 mPa·s.

[0056] Aspect 26 of the present invention is a two-component fractional coating adhesive kit as described in aspect 25, wherein the polyvinyl alcohol-based resin (A) is a polyvinyl alcohol-based resin having a carboxyl group or a salt thereof in its side chain.

[0057] The two-component, separate-coating adhesive of the present invention adheres in a short time and exhibits excellent initial adhesive strength. Furthermore, the two-component, separate-coating adhesive of the present invention also possesses excellent water resistance and coating properties.

[0058] Figure 1 is a schematic diagram of the state in Example 1 where the surface coated with agent (I) and the surface coated with agent (II) are in contact. The photograph shows the state in Example 1 where weights were attached to the bonded wood and it was suspended from a rod using a string for initial adhesion evaluation.

[0059] The present invention will be described in detail below, but these are merely examples of preferred embodiments and are not limited to these. The "~" in a numerical range indicates a range that includes the numbers before and after it. For example, "0 mass% to 100 mass%" means a range that is 0 mass% or more and 100 mass% or less.

[0060] [Two-component fractional coating adhesive] The two-component fractional coating adhesive of this embodiment is a two-component fractional coating adhesive comprising agent (I) and agent (II), wherein agent (I) comprises a PVA-based resin (A), agent (II) comprises an inorganic salt (B) and a water-soluble polymer (C), the PVA-based resin (A) comprises a PVA-based resin having a carboxyl group or a salt thereof, and the viscosity of the water-soluble polymer (C) in a 4% by mass aqueous solution at 23°C is 1.9 to 90 mPa·s.

[0061] In this embodiment of the two-component fractional coating adhesive, since it contains a PVA-based resin (A) and an inorganic salt (B), the carboxyl groups of the PVA-based resin (A) or their salts rapidly interact with the inorganic salt (B), resulting in good initial adhesion. Furthermore, the strong bond between the PVA-based resin (A) and the inorganic salt (B) is considered to provide excellent water resistance. In addition, while mixing the inorganic salt (B) and the PVA-based resin (A) in a two-component fractional coating adhesive results in instability due to high reactivity and poor coating performance, using the water-soluble polymer (C) with a specific viscosity together with the inorganic salt (B) as the (II) agent improves the dispersibility of the inorganic salt (B), enabling uniform coating. This allows for an appropriate reaction rate and a uniform reaction. Furthermore, by using the water-soluble polymer (C) with a specific viscosity as the (II) agent, the viscosity of the (II) agent can be suitably controlled, which is considered to improve coating performance.

[0062] (PVA-based resin (A)) The two-component, separate-coating adhesive of this embodiment includes agent (I), and agent (I) includes PVA-based resin (A). PVA-based resin (A) includes a PVA-based resin having a carboxyl group or a salt thereof.

[0063] The PVA-based resin (A) has vinyl alcohol structural units and, if necessary, also has unsaponified vinyl ester structural units.

[0064] Examples of monomers having the above-mentioned vinyl ester structural units include structural units derived from vinyl formate, vinyl acetate, vinyl propionate, vinyl valerate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl benzoate, vinyl versatate, etc., but vinyl acetate structural units are preferred from an economic standpoint.

[0065] Furthermore, the PVA resin (A) used in this embodiment includes a PVA resin having a carboxyl group or a salt thereof, from the viewpoint of reactivity with the inorganic salt (B). Examples of functional groups containing a carboxyl group include maleic acid group, fumaric acid group, itaconic acid group, etc. Examples of salts of the carboxyl group include sodium salt, calcium salt, magnesium salt, aluminum salt, etc. The PVA resin (A) used in this embodiment may also further contain a cyclic ester. Examples of cyclic esters include a lactone ring, etc.

[0066] The carboxyl groups described above are mainly introduced to hydrophilic and reactive hydroxyl groups on the polymer chain of PVA, or to the polymerization ends. However, in the PVA-based resin (A) of this embodiment, the location of introduction is not limited. The main candidate locations for introduction are the hydroxyl groups of the polymer side chains of PVA, the ends of the polymer main chain of PVA, or direct introduction into the polymer main chain of PVA by random copolymerization, with introduction to the hydroxyl groups of the side chains being preferable.

[0067] In other words, the PVA resin (A) is preferably a PVA resin having a carboxyl group or a salt thereof in its side chain. Examples of such PVA resins include those having a structure represented by the following formula (1).

[0068]

[0069] In formula (1) above, X represents a carboxyl group or a salt thereof, l+m is preferably 50 to 2500, l / (l+m) is preferably 70 to 99.9%, and n is preferably 1 to 30. "l+m" indicates the degree of polymerization, and "l / (l+m)" indicates the degree of saponification. The order of arrangement of the l, m, and n units is not restricted and may be random or in blocks, indicating that the total number of l, m, and n units present in one molecule is l, m, and n, respectively.

[0070] Examples of methods for producing the PVA resin in this embodiment include (1) obtaining a copolymer from an unsaturated monomer having a carboxyl group or a salt thereof and a vinyl ester compound, and then saponifying the copolymer; and (2) polymerizing a vinyl ester compound in the presence of an alcohol having at least one of a carboxyl group or a salt thereof, or a compound having a carboxyl group or a salt thereof and a functional group such as an aldehyde or thiol, as a chain transfer agent, and then saponifying with a catalyst such as an alkali metal hydroxide. However, method (1) is practical in terms of resin production and performance.

[0071] The method described in (1) will be explained in detail below. Examples of unsaturated monomers having a carboxyl group or a salt thereof include ethylenically unsaturated dicarboxylic acids (maleic acid, fumaric acid, itaconic acid, etc.), or ethylenically unsaturated carboxylic acid monoesters (maleic acid monoalkyl ester, fumaric acid monoalkyl ester, itaconic acid monoalkyl ester, etc.), or ethylenically unsaturated dicarboxylic acid diesters (maleic acid dialkyl ester, fumaric acid dialkyl ester, itaconic acid dialkyl ester, etc.), or ethylenically unsaturated carboxylic acid anhydrides (maleic anhydride, itaconic acid anhydride, etc.), or monomers such as (meth)acrylic acid, and salts thereof, with ethylenically unsaturated carboxylic acid monoesters or salts thereof being preferred. Among these, ethylenically unsaturated carboxylic acid monoesters are preferred in terms of reactivity with vinyl ester monomers, and maleic acid monoalkyl esters and itaconic acid monoalkyl esters are even more preferred, with maleic acid monoalkyl esters being particularly preferred. In other words, as the PVA resin (A) having a carboxyl group or a salt thereof, a PVA resin having a maleic acid group or a salt thereof is preferred.

[0072] Furthermore, in addition to unsaturated monomers having a carboxyl group or a salt thereof and monomers having vinyl ester structural units, monomers having structural units derived from compounds copolymerizable with vinyl ester compounds may also be included. Examples of such copolymerizable compounds include olefins such as ethylene, propylene, isobutylene, α-octene, α-dodecene, and α-octadecene; hydroxyl group-containing α-olefins such as 3-buten-1-ol, 4-penten-1-ol, 5-hexen-1-ol, and 3,4-dihydroxy-1-butene, and their acylated derivatives; unsaturated acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, maleic anhydride, itaconic acid, and undecylenic acid, their salts, monoesters, and others. Examples include dialkyl esters; nitriles such as acrylonitrile and methacrylonitrile; amides such as diacetone acrylamide, acrylamide, and methacrylamide; olefin sulfonic acids such as ethylene sulfonic acid, allyl sulfonic acid, and methallyl sulfonic acid, or their salts; vinyl compounds such as alkyl vinyl ethers, dimethylallyl vinyl ketone, N-vinylpyrrolidone, vinyl chloride, vinylethylene carbonate, 2,2-dialkyl-4-vinyl-1,3-dioxolane, and glycerin monoallyl ether; substituted vinyl acetates such as isopropenyl acetate and 1-methoxyvinyl acetate; vinylidene chloride, 1,4-diacetoxy-2-butene, 1,4-dihydroxy-2-butene, and vinylene carbonate. Polymerization may be carried out with the copolymerizable compound present in an amount of 50 mol% or less, preferably 30 mol% or less. There are no particular restrictions on copolymerization, and any known polymerization method can be used; however, solution polymerization using a lower alcohol such as methanol or ethanol as a solvent is usually carried out.

[0073] In this method, the monomers are first charged with the entire amount of the vinyl ester compound and a portion of the unsaturated monomer having a carboxyl group or a salt thereof to initiate polymerization, and the remaining unsaturated monomers may be added by any means, such as (1) continuously or in installments during the polymerization period, or (2) all at once. The copolymerization reaction is carried out using known radical polymerization catalysts such as azobisisobutyronitrile, acetyl peroxide, benzoyl peroxide, or lauroyl peroxide. The reaction temperature is selected from a range of 50°C to the boiling point.

[0074] The copolymer obtained as described above is then saponified to become a PVA-based resin containing carboxyl groups or salts thereof. Saponification is carried out by dissolving the copolymer in an alcohol, an acetate ester, or a mixture thereof in the presence of an alkaline catalyst. Examples of alcohols include methanol, ethanol, and butanol, and examples of acetate esters include methyl acetate and ethyl acetate. The concentration of the copolymer in the alcohol is usually selected from the range of 20 to 50% by mass. As the alkaline catalyst, an alkali metal hydroxide or alkali catalyst such as sodium hydroxide, potassium hydroxide, sodium methylate, sodium ethylate, and potassium methylate is used. The amount of such catalyst used is usually 1 to 100 mmol equivalents relative to the vinyl ester compound.

[0075] The average degree of polymerization of the above PVA-based resin (A) can be appropriately selected depending on its application, but is preferably 100 to 5000, more preferably 300 to 3000, and even more preferably 500 to 2500. An average degree of polymerization of 100 or higher tends to enhance its function as a binder. In this specification, "binder" refers to a function that allows for uniform application to a substrate and binds the substrate to agent (II). When the degree of polymerization is within the above range, it has the advantage of high binder function and ease of handling. The above average degree of polymerization is measured in accordance with JIS K6726 3.7.

[0076] The viscosity of the above-mentioned PVA-based resin (A) in a 4% by mass aqueous solution at 20°C is preferably 5 to 50 mPa·s, more preferably 13 to 45 mPa·s, and particularly preferably 17 to 40 mPa·s. When the viscosity is within this range, the PVA-based resin (A) has the advantage of having high binder functionality and being easy to handle. The viscosity of the above-mentioned 4% by mass aqueous solution is measured in accordance with JIS K 6726 3.11.2.

[0077] The degree of saponification of the above PVA resin (A) is preferably 70 to 99.9, more preferably 80 to 99.7, and even more preferably 83 to 99.5. When the degree of saponification is 70 or higher, the hydrophilicity of the PVA resin (A) tends to increase and its solubility in water tends to improve, while when it is 99.9 or lower, the crystallinity of the PVA resin (A) tends to decrease and its solubility in water tends to improve. The above degree of saponification is measured in accordance with JIS K6726.

[0078] The content of carboxyl groups or their salts in the PVA resin (A) is preferably 0.2 to 10 mol%, more preferably 0.3 to 7 mol%, and even more preferably 0.5 to 5 mol%. When the above modification amount is 0.2 mol% or more, the reaction between the PVA resin (A) and the inorganic salt (B) tends to be good, and when it is 10 mol% or less, the coating properties of the aqueous solution of the PVA resin (A) alone tend to be good.

[0079] In the two-component fractional coating adhesive of this embodiment, it is preferable that all of the PVA-based resin (A) used is a PVA-based resin having a carboxyl group or a salt thereof. However, PVA-based resins other than those having a carboxyl group or a salt thereof may also be used in combination. The content of such other resins is preferably 20 parts by mass or less, more preferably 10 parts by mass or less, even more preferably 5 parts by mass or less, and particularly preferably 0 parts, i.e., PVA-based resin (A) consists only of a PVA-based resin having a carboxyl group or a salt thereof, based on 100 parts by mass of the PVA-based resin having a carboxyl group or a salt thereof.

[0080] In the PVA-based resin such as the PVA-based resin having a carboxyl group or a salt thereof, even if a part of an alkali metal acetate such as sodium acetate used or by-produced in the production process (mainly derived from a reaction product of an alkali metal hydroxide used as a saponification catalyst and acetic acid generated by saponification of polyvinyl acetate), an organic acid such as acetic acid, or an organic solvent such as methanol or methyl acetate (derived from a reaction solvent of the PVA-based resin or a cleaning solvent during production of the PVA-based resin having a carboxyl group or a salt thereof) remains, it does not matter.

[0081] (Inorganic salt (B)) The two-component separate coating type adhesive of the present embodiment contains the agent (II), and the agent (II) contains an inorganic salt (B).

[0082] The inorganic salt (B) contained in the two-component separate coating type adhesive of the present embodiment contains ions of divalent or higher, and the ions may be either anions or cations, preferably contains metal cations of divalent or higher, and more preferably contains metal cations of trivalent or higher.

[0083] The anion constituting the inorganic salt (B), that is, the acid component, is preferably derived from an inorganic acid or an inorganic salt, more preferably derived from sulfuric acid or bisulfate, sulfurous acid, dithionous acid, or a halogen-based salt, and even more preferably derived from sulfuric acid.

[0084] Specifically, as the inorganic salt (B), magnesium (Mg ２＋ ), calcium (Ca ２＋ ), strontium (Sr ２＋ ), manganese (Mn ２＋ ), iron (Fe ２＋ ), cobalt (Co ２＋ ), nickel (Ni ２＋ ), copper (Cu ２＋ ), zinc (Zn ２＋ ), yttrium (Y ３＋ ), lanthanum (La ３＋ ), cerium (Ce ３＋ ), praseodymium (Pr ３＋ ), neodymium (Nd ３＋ ), iron (Fe ３＋ ), aluminum (Al ３＋ ), cerium (Ce ４＋), Titanium (Ti ４＋ ), zirconium (Zr ４＋ ), molybdenum (Mo ６＋ ), tungsten (W ６＋ Examples include sulfates, bisulfites, sulfites, bisulfites, disulfites, bisulfites, iodates, iodides, bromates, or double salts thereof of divalent or higher metal cations such as (SO4). Furthermore, sulfate ions (SO4) ４ ２－ ), carbonate ions (CO ３ ２－ ), chromate ion (CrO ４ ２－ ), oxalate ion (C ２ O ４ ２－ ), thiosulfate ion (S ２ O ３ ２－ ), sulfite ions (SO ３ ２－ ), silicate ions (SiO ４ ４－ and SiO ３ ２－ At least one of the following), molybdate ion (MoO ４ ２－ ), selenite ion (SeO ４ ２－ ), dichromate ion (Cr ２ O ７ ２－ ), tetraborate ion (B ４ O ７ ２－ ), phosphate ion (PO ４ ３－ Examples include ammonium salts, metal salts, or double salts thereof of divalent or greater anions.

[0085] More specifically, the inorganic salt (B) is aluminum sulfate (Al ２ (SO ４ ) ３ ), ammonium sulfate ((NH ４ ) ２ SO ４ ), sodium aluminum sulfate (AlNa(SO) ４ ) ２ Na ＋ and Al３＋ (double salt of sulfate), potassium aluminum sulfate (AlK(SO)) ４ ) ２ ;K ＋ and Al ３＋ (double salt of sulfate), ammonium aluminum sulfate (Al(NH) ４ ) (SO ４ ) ２ NH ４ ＋ and Al ３＋ (double salt of sulfate), zinc sulfate (ZnSO4) ４ ), calcium sulfate (CaSO4) ４ ), copper sulfate (CuSO ４ ), ferrous sulfate (FeSO ４ ), ferric sulfate (Fe ２ (SO ４ ) ３ ), magnesium sulfate (MgSO ４ ), manganese sulfate (MnSO ４ ), calcium iodate (Ca(IO ３ ) ２ ), copper(I) iodide (CuI) is preferred. From the viewpoint of initial adhesion and water resistance, the inorganic salt (B) is preferably a sulfate of a metal cation with a valence of 2 or higher, and aluminum sulfate is more preferred.

[0086] (Water-soluble polymer (C)) The two-component adhesive of this embodiment contains agent (II), and agent (II) contains a water-soluble polymer (C). Note that the water-soluble polymer (C) does not contain polyvinyl alcohol-based resin (A).

[0087] The viscosity of a 4% by mass aqueous solution of the water-soluble polymer (C) at 23°C is 1.9 to 90 mPa·s, preferably 2.0 to 70 mPa·s, more preferably 2.1 to 60 mPa·s, and even more preferably 2.2 to 50 mPa·s. A viscosity of 1.9 mPa·s or higher tends to result in good binder strength of the water-soluble polymer (C), while a viscosity of 90 mPa·s or lower tends to result in good handling during coating.

[0088] In this specification, the viscosity of a 4% by mass aqueous solution of water-soluble polymer (C) at 23°C is the value measured using a B-type viscometer (Eiko Seiki Co., Ltd.). For viscosities of 10 mPa·s or higher, model number "DV2T RV" (spindle, No. 1, rotation speed 50 rpm) is used, and for viscosities less than 10 mPa·s, model number "DV3T LV" (spindle, ULA-DIN-85, rotation speed 100 rpm) is used.

[0089] In this specification, a water-soluble polymer means one that dissolves in 1 g or more of water at 20°C. Examples of water-soluble polymers include starch-based polymers (e.g., carboxymethyl starch, methylhydroxypropyl starch, etc.); cellulose-based polymers (methylcellulose, ethylcellulose, methylhydroxypropylcellulose, hydroxyethylcellulose, sodium cellulose sulfate, hydroxypropylcellulose, carboxymethylcellulose sodium, etc.); alginate-based polymers (e.g., sodium alginate, propylene glycol alginate, etc.); vinyl-based polymers (e.g., polyvinyl methyl ether, polyvinylpyrrolidone, unmodified polyvinyl alcohol, carboxyvinyl polymer, etc.); polyoxyethylene-based polymers (e.g., polyethylene glycol, etc.); acrylic-based polymers (e.g., sodium polyacrylate, polyethyl acrylate, polyacrylamide, etc.); polyethyleneimine; cationic polymers; polyamide-based polymers (e.g., polyamide polyamine epichlorohydrin, polyamide-epichlorohydrin, etc.); and oxazoline group-containing polymers. (I) When a PVA-based resin having at least one of a carboxyl group or a salt thereof is used as the agent, it is preferable that the agent be one or more selected from the group consisting of polyamide-epichlorohydrin, polyethyleneimine, and oxazoline group-containing polymers, from the viewpoint of improving reactivity. Also, from the same viewpoint, it is preferable that the agent be one or more selected from the group consisting of unmodified polyvinyl alcohol, polyamide-epichlorohydrin, polyethylene glycol, polyvinylpyrrolidone, and carboxymethylcellulose. Furthermore, polyamide-polyamine epichlorohydrin and polyamide-epichlorohydrin are preferred.

[0090] [Characteristics of two-component dispensing adhesive] In the two-component dispensing adhesive of this embodiment, agent (I) is preferably a solution containing a PVA-based resin (A) and a solvent.

[0091] The concentration of the PVA-based resin (A) in agent (I) is preferably 0.1 to 30% by mass, more preferably 0.3 to 25% by mass, and even more preferably 0.5 to 20% by mass. A concentration of 0.1% by mass or more tends to result in good reactivity with the inorganic salt (B), while a concentration of 30% by mass or less tends to result in low viscosity and good handling.

[0092] (I) The content ratio of PVA-based resin (A) in the solid content of the agent is preferably 50 to 100% by mass, more preferably 60 to 100% by mass, and even more preferably 70 to 100% by mass, from the viewpoint of adhesive strength.

[0093] In the two-component fractional coating adhesive of this embodiment, agent (II) is preferably a solution containing an inorganic salt (B), a water-soluble polymer (C), and a solvent.

[0094] The concentration of inorganic salt (B) in agent (II) is preferably 0.1 to 50% by mass, more preferably 0.2 to 40% by mass, and even more preferably 0.4 to 30% by mass. A concentration of 0.1% by mass or more tends to result in good initial adhesion, while a concentration of 50% by mass or less tends to result in good water resistance after a certain period of time has elapsed since adhesion.

[0095] (II) The content ratio of inorganic salt (B) in the solid content of agent (II) is preferably 20 to 99.95% by mass, more preferably 25 to 99% by mass, and even more preferably 28 to 95% by mass, from the viewpoint of adhesive strength. When inorganic salt (B) is aluminum sulfate, the content ratio of aluminum sulfate in the solid content of agent (II) is preferably 20 to 99.95% by mass, more preferably 25 to 99% by mass, and even more preferably 28 to 95% by mass, from the viewpoint of adhesive strength.

[0096] The concentration of the water-soluble polymer (C) in agent (II) is preferably 0.1 to 50% by mass, more preferably 0.5 to 40% by mass, and even more preferably 1 to 30% by mass. A concentration of 0.1% by mass or more tends to result in good binder strength, while a concentration of 50% by mass or less tends to result in good handling during coating.

[0097] (II) The content ratio of the water-soluble polymer (C) in the solid content of the agent is preferably 1 to 80% by mass, more preferably 3 to 77% by mass, and even more preferably 5 to 75% by mass, from the viewpoint of binder strength. When the water-soluble polymer (C) is polyamide-epichlorohydrin, the content ratio of polyamide-epichlorohydrin in the solid content of the agent (II) is preferably 1 to 80% by mass, more preferably 3 to 77% by mass, and even more preferably 5 to 75% by mass, from the viewpoint of binder strength. When the water-soluble polymer (C) is polyethyleneimine, the content ratio of polyethyleneimine in the solid content of the agent (II) is preferably 1 to 80% by mass, more preferably 3 to 77% by mass, and even more preferably 5 to 75% by mass, from the viewpoint of binder strength. When the water-soluble polymer (C) is an oxazoline group-containing polymer, the content ratio of the oxazoline group-containing polymer in the solid content of agent (II) is preferably 1 to 80% by mass, more preferably 3 to 77% by mass, and even more preferably 5 to 75% by mass, from the viewpoint of binder strength.

[0098] Examples of solvents included in agents (I) and (II) are water and volatile solvents such as hexane, toluene, xylene, ethyl acetate, butyl acetate, methanol, ethanol, isopropanol, and acetone. Water is preferred from the viewpoint of high solubility of the PVA resin (A), inorganic salt (B), and water-soluble polymer (C), as well as worker safety. Note that the solvents included in agents (I) and (II) may be the same or different.

[0099] Agents (I) and (II) may contain other additives to the extent that they do not impair the physical properties. Examples of additives include various emulsions such as acrylic emulsions, styrene-butadiene emulsions, vinyl acetate resin emulsions (e.g., polyvinyl acetate emulsions), compounds having oxazoline groups (excluding oxazoline group-containing polymers), epoxy compounds such as glyoxal derivatives, methylol derivatives, and epichlorohydrin derivatives, aziridine compounds, hydrazine, hydrazide derivatives, and carbodiimide derivatives. The emulsion used in the two-component fractional coating adhesive of this embodiment includes all substances that are commonly referred to as latex or emulsion.

[0100] The content of the PVA-based resin (A) in the two-component fractional coating adhesive of this embodiment is preferably 0.5 to 95 parts by mass, more preferably 0.7 to 90 parts by mass, and even more preferably 0.8 to 70 parts by mass, per 100 parts by mass of solid content. A content of 0.5 parts by mass or more tends to result in good initial adhesion, and a content of 95 parts by mass or less tends to result in good water resistance after a certain period of time has elapsed since adhesion.

[0101] The inorganic salt (B) content per 100 parts by mass of solids in the two-component fractional coating adhesive of this embodiment is preferably 0.1 to 99 parts by mass, more preferably 1 to 95 parts by mass, and even more preferably 3 to 95 parts by mass. When the inorganic salt (B) is aluminum sulfate, the aluminum sulfate content per 100 parts by mass of solids in the two-component fractional coating adhesive of this embodiment is preferably 0.1 to 99 parts by mass, more preferably 1 to 95 parts by mass, and even more preferably 3 to 95 parts by mass. A content of 0.1 parts by mass or more tends to result in good initial adhesion, and a content of 99 parts by mass or less tends to result in good water resistance after a certain period of time has elapsed since adhesion.

[0102] In the two-component fractional coating adhesive of this embodiment, the content of water-soluble polymer (C) is preferably 0.1 to 85 parts by mass, more preferably 0.5 to 80 parts by mass, and even more preferably 1 to 75 parts by mass per 100 parts by mass of solid content. When water-soluble polymer (C) is polyamide-epichlorohydrin, the content of polyamide-epichlorohydrin is preferably 0.1 to 85 parts by mass, more preferably 0.5 to 80 parts by mass, and even more preferably 1 to 75 parts by mass per 100 parts by mass of solid content of the two-component fractional coating adhesive of this embodiment. When water-soluble polymer (C) is polyethyleneimine, the content of polyethyleneimine is preferably 0.1 to 85 parts by mass, more preferably 0.5 to 80 parts by mass, and even more preferably 1 to 75 parts by mass per 100 parts by mass of solid content of the two-component fractional coating adhesive of this embodiment. When the water-soluble polymer (C) is an oxazoline group-containing polymer, the content of the oxazoline group-containing polymer per 100 parts by mass of solids in the two-component fractional coating adhesive of this embodiment is preferably 0.1 to 85 parts by mass, more preferably 0.5 to 80 parts by mass, and even more preferably 1 to 75 parts by mass. A content of 0.1 parts by mass or more tends to result in good binder strength, and a content of 85 parts by mass or less tends to result in good migration between the inorganic salt (B) and agent (I), leading to good initial adhesion.

[0103] In the two-component fractional coating adhesive of this embodiment, the content ratio (A / B) of PVA-based resin (A) to inorganic salt (B) is preferably 100 / 2 to 100 / 10000, more preferably 100 / 3 to 100 / 1000, and even more preferably 100 / 4 to 100 / 500, in parts by mass. When the inorganic salt (B) is aluminum sulfate, the content ratio (PVA-based resin / aluminum sulfate) of PVA-based resin (A) to aluminum sulfate in the two-component fractional coating adhesive of this embodiment is preferably 100 / 2 to 100 / 10000, more preferably 100 / 3 to 100 / 1000, and even more preferably 100 / 4 to 100 / 500, in parts by mass. When the ratio of A / B is less than 100 / 2, the migration of inorganic salts to other layers is improved, resulting in better initial adhesive strength. When the ratio of A / B is more than 100 / 10000, the binder strength is improved.

[0104] In the two-component fractional coating adhesive of this embodiment, the content ratio of inorganic salt (B) to water-soluble polymer (C) (B / C) is preferably 100 / 1 to 100 / 500, more preferably 100 / 2 to 100 / 300, and even more preferably 100 / 5 to 100 / 250 in parts by mass. When the inorganic salt (B) is aluminum sulfate and the water-soluble polymer (C) is polyamide-epichlorohydrin, the content ratio of aluminum sulfate to polyamide-epichlorohydrin (aluminum sulfate / polyamide-epichlorohydrin) in the two-component fractional coating adhesive of this embodiment is preferably 100 / 1 to 100 / 500, more preferably 100 / 2 to 100 / 300, and even more preferably 100 / 5 to 100 / 250 in parts by mass. When the inorganic salt (B) is aluminum sulfate and the water-soluble polymer (C) is polyethyleneimine, the content ratio of aluminum sulfate to polyethyleneimine (aluminum sulfate / polyethyleneimine) in the two-component fractional coating adhesive of this embodiment is preferably 100 / 1 to 100 / 500, more preferably 100 / 2 to 100 / 300, and even more preferably 100 / 5 to 100 / 250 in parts by mass. When the inorganic salt (B) is aluminum sulfate and the water-soluble polymer (C) is an oxazoline group-containing polymer, the content ratio of aluminum sulfate to the oxazoline group-containing polymer (aluminum sulfate / oxazoline group-containing polymer) in the two-component fractional coating adhesive of this embodiment is preferably 100 / 1 to 100 / 500, more preferably 100 / 2 to 100 / 300, and even more preferably 100 / 5 to 100 / 250 in parts by mass. When the B / C ratio is lower than 100 / 1, the binder strength tends to be better. When the B / C ratio is higher than 100 / 500, the migration between the inorganic salt (B) and agent (I) is better, and the initial adhesion tends to be better.

[0105] In the two-component fractional coating adhesive of this embodiment, the content ratio (A / C) of PVA-based resin (A) to water-soluble polymer (C) is preferably 100 / 1 to 100 / 10000, more preferably 100 / 2 to 100 / 5000, and even more preferably 100 / 3 to 100 / 2000, in parts by mass. When the amount of PVA-based resin (A) is less than when A / C is 100 / 1, and more than when A / C is 100 / 10000, agent (I) and agent (II) come into good contact.

[0106] In the two-component fractional application adhesive of this embodiment, the ratio of agent (I) to agent (II) (I / II) is preferably 1 / 99 to 90 / 10, more preferably 2 / 98 to 80 / 20, and even more preferably 5 / 95 to 70 / 30, based on parts by mass. Being within this range tends to result in good initial adhesive strength.

[0107] In the two-component, separately dispensed adhesive of this embodiment, agent (I) and agent (II) exist separately and are not mixed before being used for bonding. For example, agent (I) may be contained in container 1 and agent (II) may be contained in container 2.

[0108] The two-component adhesive of this embodiment may further contain additives such as surfactants, preservatives, thickeners, colorants, and plasticizers.

[0109] [Two-component separate-coating adhesive kit] The two-component separate-coating adhesive kit of this embodiment is a two-component separate-coating adhesive kit comprising agent (I) and agent (II), wherein agent (I) comprises a polyvinyl alcohol-based resin (A), agent (II) comprises an inorganic salt (B) and a water-soluble polymer (C), the polyvinyl alcohol-based resin (A) comprises a polyvinyl alcohol-based resin having a carboxyl group or a salt thereof, and the viscosity of the water-soluble polymer (C) in a 4% by mass aqueous solution at 23°C is 1.9 to 90 mPa·s.

[0110] The two-component separate-dispensing adhesive kit of this embodiment may comprise a container 1 containing agent (I) and a container 2 containing agent (II). At least one of containers 1 and 2 may be tube-type, cartridge-type, pouch-type, or syringe-type.

[0111] The polyvinyl alcohol-based resin (A), inorganic salt (B), and water-soluble polymer (C), as well as agents (I) and (II), are as described above in this specification.

[0112] [Bonding Method] The bonding method of this embodiment includes the step of bringing into contact an agent (I) containing a polyvinyl alcohol-based resin (A) with an agent (II) containing an inorganic salt (B) and a water-soluble polymer (C), wherein the polyvinyl alcohol-based resin (A) contains a polyvinyl alcohol-based resin having a carboxyl group or a salt thereof, and the viscosity of the water-soluble polymer (C) in a 4% by mass aqueous solution at 23°C is 1.9 to 90 mPa·s.

[0113] The polyvinyl alcohol-based resin (A), inorganic salt (B), and water-soluble polymer (C), as well as agents (I) and (II), are as described above in this specification.

[0114] The bonding method of this embodiment preferably includes the following steps 1 and 2 in this order: 1) Applying agent (I) to surface a and agent (II) to surface b; 2) Bringing agent (I) and agent (II) into contact to bond surface a and surface b.

[0115] In step 1 described above, the order in which agent (I) is applied to surface a and agent (II) is applied to surface b does not matter.

[0116] In the bonding method of this embodiment, when surfaces a and b are bonded together in step 2, the curing of the adhesive containing agent (I) and agent (II) begins.

[0117] After bringing agent (I) and agent (II) into contact, it is preferable to dry them. The drying method is not particularly limited, but examples include heating with hot air or an oven, or natural drying. The drying time is preferably 0.1 to 200 minutes, more preferably 0.5 to 60 minutes, and even more preferably 1 to 30 minutes.

[0118] In the bonding method of this embodiment, step 2 may be performed after step 3 below. 3) A step of drying at least one of the agent (I) applied to surface a and the agent (II) applied to surface b.

[0119] By performing step 3 described above, the drying time after bonding can be shortened. When performing step 3 described above, the drying method is not particularly limited, but examples include heating and drying with hot air or an oven, or natural drying. The drying time is preferably 0.1 to 200 minutes, more preferably 0.5 to 60 minutes, and even more preferably 1 to 30 minutes.

[0120] Alternatively, after step 3, water may be applied to or sprayed onto at least one of the dried (I) agent on surface a and the dried (II) agent on surface b, and then step 2 may be performed.

[0121] Thus, by applying or spraying water after the drying of agents (I) and (II), the time until adhesive strength is achieved can be shortened. At this time, the amount of water applied or sprayed can be appropriately adjusted depending on the composition of the resin composition and the content of various components.

[0122] In the bonding method of this embodiment, from the viewpoint of bonding strength, drying time, and handling, it is preferable to use an aqueous solution of PVA-based resin (A) with a solid content concentration of 0.2 to 40% by mass as the (I) agent. The solid content concentration of the aqueous solution of PVA-based resin (A) used as the (I) agent is more preferably 0.2 to 38% by mass, and even more preferably 0.5 to 35% by mass.

[0123] In the bonding method of this embodiment, the concentrations of various aqueous solutions can be appropriately adjusted depending on the solubility of the inorganic salt (B) used. However, for the sake of miscibility with the water-soluble polymer, it is preferable to use an aqueous solution of the inorganic salt (B) and the water-soluble polymer (C) with a concentration of 0.3 to 30% by mass as the (II) agent. At this time, the concentration of the aqueous solution of the inorganic salt (B) before mixing with the water-soluble polymer (C) is preferably 0.1 to 50% by mass, more preferably 1 to 30% by mass, and even more preferably 3 to 15% by mass. Furthermore, the concentration of the aqueous solution of the water-soluble polymer (C) before mixing with the inorganic salt (B) is more preferably 0.3% to 30% by mass, and even more preferably 0.5% to 20% by mass.

[0124] In the bonding method of this embodiment, examples of adherends having at least one of the above-mentioned surfaces a and b include the following: • Wood such as cedar, beech, cypress, and walnut, and bamboo (such as compressed molded bodies made of veneers and chips); • Fibrous structures such as banana fibers, bamboo fibers, kenaf fibers, ginger lily fibers, bagasse fibers, wood fibers, bark fibers, paper, and cellulose nanofibers; • Resins such as polyamide 66, polyamide 6, cellulose acetate, and PVA, and compounds thereof; • Compounds made of wood powder and resins such as polypropylene; • Resins such as polyethylene, polypropylene, polyethylene terephthalate, polybutylene terephthalate, polycarbonate, polyvinyl chloride, nylon 610 (PA610), nylon 6T (PA6T), and polyphenylene sulfide; • Metals such as iron, stainless steel, copper, and aluminum; • Inorganic materials such as concrete, stone slabs, and ceramics; • Fiber-reinforced plastics such as glass fiber reinforced plastics (GFRP) and carbon fiber reinforced plastics (CFRP).

[0125] In the bonding method of this embodiment, the method of applying agent (I) and agent (II) to the adherend may be, for example, by applying with a brush or spatula, by applying in stripes using a pump or flow coater, by applying in spots using a coating robot, or by using a tubular extruder used for sealants.

[0126] In the bonding method of this embodiment, adhesion of the adherends is performed by bonding surfaces to which at least one of agent (I) and agent (II) has been applied, for example, surface a and surface b. In the bonding method of this embodiment, bonding may be performed simply by overlapping surfaces to which at least one of agent (I) and agent (II) has been applied, but it is preferable to apply pressure to the surfaces, taking into consideration the shape, material, and bonding area of ​​the surfaces.

[0127] In the bonding method of this embodiment, a PVA-based resin (A) is preferably applied to surface a at a rate of 1 to 500 g / m². ２ More preferably 5 to 200 g / m² ２ Apply in the following manner. Preferably, the total amount of inorganic salt (B) and water-soluble polymer (C) applied to surface b should be 1 to 500 g / m². ２ More preferably 5 to 200 g / m² ２ Apply it so that it looks like this.

[0128] The present invention will be specifically described below with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist of the invention. In the examples, "parts" and "%" refer to weight basis.

[0129] In the examples and comparative examples described later, the following components were used. <PVA-based resin (A)> [Preparation of polyvinyl alcohol-based resin C-PVA1 having carboxyl groups in the side chains] 100 parts vinyl acetate, 26 parts methanol, and 0.1 parts monomethyl maleate (0.09 mol% relative to the total amount of vinyl acetate) were charged into a reaction vessel equipped with a reflux condenser, a dropping funnel, and a stirrer. The mixture was heated to 60°C under a nitrogen stream while stirring, and then 0.001 mol% (relative to the total amount of vinyl acetate) of t-butyl peroxyneodecanoate (with a half-life of 1 hour at a temperature of 65°C) was added as a polymerization catalyst, and polymerization was started. Immediately after the start of polymerization, 2.2 parts of monomethyl maleate (2 mol% of the total amount of vinyl acetate) and 0.008 mol% of t-butyl peroxyneodecanoate (relative to the total amount of vinyl acetate) were continuously added in accordance with the polymerization rate. When the polymerization rate of vinyl acetate reached 73%, 0.01 parts of 4-methoxyphenol and 58 parts of methanol for dilution and cooling were added to terminate the polymerization. The amount of residual active catalyst at the end of polymerization was 2 ppm relative to the total amount of reaction solution. Subsequently, unreacted vinyl acetate monomer was removed from the system by blowing methanol vapor to obtain a methanol solution of the copolymer. Next, this solution was diluted with methanol to a concentration of 40%, and a 4% methanol solution of sodium hydroxide was mixed in at a ratio of 30 mmol per mole of vinyl acetate structural units in the copolymer, and a saponification reaction was carried out at a temperature of 40-50°C. The resin solidified by the saponification reaction was cut and dried at 70°C to obtain C-PVA1. The vinyl acetate component of the PVA in question had a degree of saponification of 93 mol%, a degree of polymerization of 1800, and a carboxyl group content of 2 mol%.

[0130] [Preparation of C-PVA2] C-PVA2 was obtained by adjusting C-PVA1 to have a degree of saponification of 88 mol%, a degree of polymerization of 1800, and a carboxyl group content of 2 mol%.

[0131] <Inorganic Salt (B)> The following compounds were used as inorganic salt (B): • Aluminum sulfate (also referred to as "Sulfate Al" in this specification): Manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. • Ammonium sulfate (also referred to as "Sulfate (NH4)" in this specification) ４ ) ２It is also written as: ) Manufactured by Fujifilm Wako Pure Chemical Corporation

[0132] <Water-soluble polymer (C)> The following compounds were used as water-soluble polymer (C): ・PVA1: Unmodified polyvinyl alcohol (4% by mass aqueous solution viscosity 56.9 mPa·s, degree of saponification 99 mol%) ・PVA2: Unmodified polyvinyl alcohol (4% by mass aqueous solution viscosity 52.5 mPa·s, degree of saponification 88 mol%) ・PEG1: Polyethylene glycol PEG200 (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) (4% by mass aqueous solution viscosity 2.3 mPa·s) ・PEG2: Polyethylene glycol PEG600 (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) (4% by mass aqueous solution viscosity 2.4 mPa·s) ・PAE1: Polyamide-epichlorohydrin Polycup 172 (manufactured by Solenis) (4% by mass aqueous solution viscosity 31.6 mPa·s) • PAE2: Polyamide polyamine-epichlorohydrin EPA-SK01 (manufactured by Yokkaichi Gosei Co., Ltd.) (viscosity of 4% by mass aqueous solution: 5.0 mPa·s) • PEI1: Polyethyleneimine 1800 (manufactured by Fujifilm Wako Pure Chemical Industries Ltd.) (viscosity of 4% by mass aqueous solution: 5.5 mPa·s) • PEI2: Polyethyleneimine 600 (manufactured by Fujifilm Wako Pure Chemical Industries Ltd.) (viscosity of 4% by mass aqueous solution: 4.6 mPa·s) • OXZ1: Oxazoline group-containing polymer, Epocross WS-700 (manufactured by Nippon Shokubai Co., Ltd.) (viscosity of 4% by mass aqueous solution: 4.8 mPa·s)

[0133] <Other> The following compounds were used as other components: • A-PVA: Acetoacetyl group-containing polyvinyl alcohol (4% viscosity 21 mPa·s, degree of saponification 93 mol%, acetoacetyl modification amount 4 mol%) • ADH: Adipic acid dihydrazide (manufactured by Otsuka Chemical Co., Ltd.) • CMC: Carboxymethylcellulose (manufactured by Fujifilm Wako Pure Chemical Corporation) (4% viscosity 11,800 mPa·s) • PVP: Polyvinylpyrrolidone (manufactured by Fujifilm Wako Pure Chemical Corporation) (viscosity measurement not possible: outside the measurable range of the B-type viscometer DV-2T RV type (high viscosity), measurement limit ~40,000,000 mPa·s) • PVA3: Unmodified polyvinyl alcohol (4% by mass aqueous solution viscosity 91.4 mPa·s, degree of saponification 98 mol%)

[0134] [Example 1] An aqueous solution containing 10% by mass of carboxylic acid-modified PVA1 (C-PVA1) resin was used as agent (I), and was applied to a 15 cm × 7 cm piece of wood in a range of 13 cm × 7 cm at 55 g / m ２ such that the application amount was as specified. Separately, an aqueous solution containing 10% by mass of aluminum sulfate and an aqueous solution containing 10% by mass of PVA1 were mixed at a mass ratio of 1:1, and the resulting mixture was used as agent (II). This agent (II) was applied to another 15 cm × 7 cm piece of wood in a range of 13 cm × 7 cm at 55 g / m ２ such that the application amount was as specified. Then, the surface coated with agent (I) and the surface coated with agent (II) were brought into contact. A schematic diagram of this state is shown in Fig. 1.

[0135] [Example 2] In Example 1, after applying agent (II) to the wood and drying it at 105°C for 10 minutes, the procedure was the same as in Example 1 except that the non-dried surface coated with agent (I) was brought into contact with the dried surface coated with agent (II).

[0136] [Examples 3 to 29, and Comparative Examples 1 to 4] The surface coated with agent (I) and the surface coated with agent (II) were brought into contact in the same manner as in Example 1, except that various components were changed as shown in Tables 1 to 4. In Tables 1 to 4, the values described in the "g / m ２ " column mean the amount of the aqueous solution containing the component of that item in the total amount of agent (I) and agent (II).

[0137] [Comparative Examples 5, 6] The surface coated with agent (I) and the surface coated with agent (II) were brought into contact in the same manner as in Example 1, except that various components were formulated as shown in Tables 1 to 4 and water-soluble polymer (C) was not used as agent (II).

[0138] [Comparative Example 7] An aqueous solution containing 10% by mass of carboxylic acid-modified PVA1 (C-PVA1) resin was used as agent (I), and was applied to a 15 cm × 7 cm piece of wood in a range of 13 cm × 7 cm at 55 g / m ２ such that the application amount was as specified, and it was brought into contact with another 15 cm × 7 cm piece of wood that had not been coated with anything. [[ID=二十二]]

[0139] [Comparative Example 8] A mixture of an aqueous solution containing 10% by mass of carboxylic acid-modified PVA1 (C-PVA1) resin, an aqueous solution containing 10% by mass of aluminum sulfate, and an aqueous solution containing 10% by mass of PVA1, mixed in a mass ratio of 2:1:1, was applied to a 15cm x 7cm piece of wood in a 13cm x 7cm area at a rate of 55g / m². ２ The coating was applied in this manner, and then it was brought into contact with another 15cm x 7cm piece of wood that had not been coated.

[0140] [Comparative Examples 9-13] In Comparative Example 9, agent (I) and agent (II) of Example 3 were mixed and applied at a rate of 55 g / m² to a 13 cm x 7 cm area on a 15 cm x 7 cm piece of wood. ２ The mixture was applied in this manner and brought into contact with another 15 cm x 7 cm piece of wood. In Comparative Example 10, agent (I) and agent (II) of Example 9 were mixed; in Comparative Example 11, agent (I) and agent (II) of Example 16 were mixed; in Comparative Example 12, agent (I) and agent (II) of Example 17 were mixed; and in Comparative Example 13, agent (I) and agent (II) of Example 18 were mixed. Comparative Examples 10 to 13 were the same as Comparative Example 9 except for this point.

[0141] <Initial Adhesion Evaluation> A 500g weight was placed on the wood after contact, and it was left undisturbed for 30 seconds. Then, the unbonded ends were clipped together, and a 200g weight was attached and the wood was suspended. Figure 2 is a photograph of this state. After suspending the wood in this manner, the time it took for the two pieces of wood to separate and fall was measured. For samples that fell in 2 minutes or less, the time in seconds at which they fell was recorded in the initial adhesion evaluation column of Tables 5 to 7. For samples that fell in more than 2 minutes to 3 minutes, more than 3 minutes to 4 minutes, or more than 4 minutes to 5 minutes, the initial adhesion evaluation column of Tables 5 to 7 was recorded as more than 2 minutes (>2 minutes), more than 3 minutes (>3 minutes), and more than 4 minutes (>4 minutes), respectively. For samples that did not fall in more than 5 minutes, the initial adhesion evaluation column of Tables 5 to 7 was recorded as more than 5 minutes (>5 minutes). Note that if the viscosity of at least one of the agents (I), (II), or their mixture was too high, and uniform application to the wood was not possible, the measurement was deemed impossible.

[0142] <Later Water Resistance Evaluation> Samples that performed well in the initial adhesion evaluation (no falling for more than 2 minutes) were bonded in the same manner as in the initial adhesion test, then stored at 23°C for 24 hours, and immersed in 23°C water for 24 hours. After that, the unbonded ends were clipped together again, and a 200g weight was attached and the sample was suspended. After suspending the wood in this manner, the time it took for the two pieces of wood to separate and fall was measured. For samples that fell in 2 minutes or less, the time in seconds at which they fell was recorded in the later water resistance evaluation column of Tables 5 to 7. For samples that fell in more than 2 minutes to 3 minutes, more than 3 minutes to 4 minutes, or more than 4 minutes to 5 minutes, the later water resistance evaluation column of Tables 5 to 7 was recorded as more than 2 minutes (>2 minutes), more than 3 minutes (>3 minutes), and more than 4 minutes (>4 minutes), respectively. For samples that did not fall for more than 5 minutes, the later water resistance evaluation column of Tables 5 to 7 was recorded as more than 5 minutes (>5 minutes). For samples with an initial adhesion time of 2 minutes or less, a later water resistance evaluation was not conducted.

[0143] <Storage Stability> The storage stability of the adhesive was evaluated by visually checking the state of the coating solution. In the case of two-component application, the result was marked as ○ if both agent (I) and agent (II) were in the ○ state, and as × if at least one of them was in the × state. In the case of one-component application, the state of the mixed solution after 15 minutes was evaluated. ○: The coating solution had not gelled. ×: The coating solution had gelled.

[0144] <Evaluation of Coatability> The coatability of the coating solution when applied to wood was evaluated visually. In the case of two-component application, the result was marked as ○ if both agent (I) and agent (II) were in the ○ state, and as × if at least one of them was in the × state. In the case of one-component application, the state of the mixed solution was evaluated. ○: The coating solution could be applied uniformly, and the coatability was good. ×: The coating solution gelled, etc., and uniform application was not possible, resulting in poor coating.

[0145]

[0146]

[0147]

[0148]

[0149]

[0150]

[0151]

[0152] The two-component fractional application adhesives of Examples 1 to 29, which used a PVA-based resin (A) as agent (I) and an inorganic salt (B) and a water-soluble polymer (C) as agent (II), exhibited excellent initial adhesion and late-stage water resistance, as well as good storage stability and coating properties. On the other hand, in Comparative Examples 1 to 4, which used water-soluble polymers with a 4% by mass aqueous solution viscosity outside the range of 1.9 to 90 mPa·s, the coating properties of agent (II) were poor, resulting in insufficient adhesion with agent (I), and thus poor initial adhesion and late-stage water resistance. Furthermore, Comparative Examples 5 and 6, which used acetoacetyl group-containing PVA as agent (I) and adipic acid dihydrazide as agent (II), and Comparative Example 7, which did not include agent (II), exhibited poor initial adhesion and late-stage water resistance. Furthermore, in Comparative Examples 8 to 13, which were one-component adhesives made by mixing a PVA-based resin (A), an inorganic salt (B), and a water-soluble polymer (C), the high reactivity of the PVA-based resin (A) and the inorganic salt (B) caused the adhesive to thicken, resulting in poor initial adhesion, later water resistance, storage stability, and coating properties.

[0153] [Reference Prescriptions] Tables 8-9 show preferred specific prescription examples. <Emulsion (Em)> Emulsions listed in Tables 8-9 (also referred to as "Em" in this specification): ・Em1: 138N (manufactured by Japan Coating Resin Co., Ltd.) ・Em2: Woodworking Adhesive (manufactured by Konishi Co., Ltd.) ・Em3: 128N (manufactured by Japan Coating Resin Co., Ltd.) ・Em4: 135N (manufactured by Japan Coating Resin Co., Ltd.) ・Em5: A-QR (manufactured by Aica Kogyo Co., Ltd.) ・Em6: A-Q1 (manufactured by Aica Kogyo Co., Ltd.) ・Em7: A-Q2 (manufactured by Aica Kogyo Co., Ltd.) ・Em8: A-Q3 (manufactured by Aica Kogyo Co., Ltd.) ・Em9: Movinyl (registered trademark) 172 (manufactured by Japan Coating Resin Co., Ltd.) ・Em10: Luxstar 1181F (manufactured by DIC Corporation) ・Em11: Nipol LX421 (manufactured by Nippon Zeon Co., Ltd.)

[0154]

[0155]

[0156] It is clear to those skilled in the art that various modifications or alterations can be conceived within the scope of the claims, and these will naturally fall within the technical scope of the present invention. Furthermore, the components of the above embodiments may be combined in any way without departing from the spirit of the invention.

[0157] This application is based on Japanese Patent Application No. 2025-130066 filed on August 4, 2025, and its contents are incorporated herein by reference.

[0158] 1. Wood 2. Agent (I) 3. Agent (II)

Claims

1. A two-component, fractional application adhesive comprising agent (I) and agent (II), wherein agent (I) comprises a polyvinyl alcohol-based resin (A), the polyvinyl alcohol-based resin (A) comprises a polyvinyl alcohol-based resin having a carboxyl group or a salt thereof, and agent (II) comprises aluminum sulfate and polyamide-epichlorohydrin.

2. A two-component, fractional application adhesive comprising agent (I) and agent (II), wherein agent (I) comprises a polyvinyl alcohol-based resin (A), the polyvinyl alcohol-based resin (A) comprises a polyvinyl alcohol-based resin having a carboxyl group or a salt thereof, and agent (II) comprises aluminum sulfate and polyethyleneimine.

3. A two-component, fractional application adhesive comprising agent (I) and agent (II), wherein agent (I) comprises a polyvinyl alcohol-based resin (A), the polyvinyl alcohol-based resin (A) comprises a polyvinyl alcohol-based resin having a carboxyl group or a salt thereof, and agent (II) comprises aluminum sulfate and an oxazoline group-containing polymer.

4. A two-component, fractional application adhesive comprising agent (I) and agent (II), wherein agent (I) comprises a polyvinyl alcohol-based resin (A), agent (II) comprises an inorganic salt (B) and a water-soluble polymer (C), the polyvinyl alcohol-based resin (A) comprises a polyvinyl alcohol-based resin having a carboxyl group or a salt thereof, and the viscosity of the water-soluble polymer (C) in a 4% by mass aqueous solution at 23°C is 1.9 to 90 mPa·s.

5. The two-component fractional application adhesive according to claim 4, wherein the polyvinyl alcohol-based resin (A) is a polyvinyl alcohol-based resin having a carboxyl group or a salt thereof in its side chain.

6. The two-component fractional application adhesive according to any one of claims 1 to 5, wherein the content ratio of the polyvinyl alcohol-based resin (A) in the solid content of agent (I) is 50 to 100% by mass.

7. The two-component fractional coating adhesive according to any one of claims 1 to 5, wherein the content ratio of the polyvinyl alcohol-based resin (A) in the solid content of the two-component fractional coating adhesive is 0.5 to 95% by mass.

8. The two-component fractional application adhesive according to claim 4 or 5, wherein the inorganic salt (B) is an inorganic salt consisting of a divalent or higher metal cation or ammonium ion and an anion derived from an inorganic acid.

9. The two-component fractional application adhesive according to claim 4 or 5, wherein the inorganic salt (B) is a sulfate.

10. The two-component fractional application adhesive according to claim 4 or 5, wherein the inorganic salt (B) is aluminum sulfate or ammonium sulfate.

11. The two-component fractional application adhesive according to claim 4 or 5, wherein the content ratio of the inorganic salt (B) in the solid content of the agent (II) is 20 to 99.95% by mass.

12. The two-component fractional coating adhesive according to claim 4 or 5, wherein the content ratio of the inorganic salt (B) in the solid content of the two-component fractional coating adhesive is 0.1 to 99% by mass.

13. The two-component fractional coating adhesive according to claim 4 or 5, wherein the content ratio (A / B) of the polyvinyl alcohol-based resin (A) to the inorganic salt (B) in the two-component fractional coating adhesive is 100 / 2 to 100 / 10000 in parts by mass.

14. The two-component fractional application adhesive according to claim 4 or 5, wherein the water-soluble polymer (C) is one or more selected from the group consisting of polyamide-epichlorohydrin, polyethyleneimine, and oxazoline group-containing polymers.

15. The two-component fractional application adhesive according to claim 4 or 5, wherein the water-soluble polymer (C) is one or more selected from the group consisting of unmodified polyvinyl alcohol, polyamide-epichlorohydrin, polyethylene glycol, polyvinylpyrrolidone, and carboxymethylcellulose.

16. The two-component fractional application adhesive according to claim 4 or 5, wherein the content ratio of the water-soluble polymer (C) in the solid content of agent (II) is 1 to 80% by mass.

17. The two-component fractional coating adhesive according to claim 4 or 5, wherein the content ratio of the water-soluble polymer (C) in the solid content of the two-component fractional coating adhesive is 0.5 to 85% by mass.

18. The two-component fractional coating adhesive according to claim 4 or 5, wherein the content ratio (B / C) of the inorganic salt (B) to the water-soluble polymer (C) in the two-component fractional coating adhesive is 100 / 1 to 100 / 500 in parts by mass.

19. A bonding method comprising the step of contacting an agent (I) containing a polyvinyl alcohol-based resin (A) with an agent (II) containing an inorganic salt (B) and a water-soluble polymer (C), wherein the polyvinyl alcohol-based resin (A) contains a polyvinyl alcohol-based resin having a carboxyl group or a salt thereof, and the viscosity of a 4% by mass aqueous solution of the water-soluble polymer (C) at 23°C is 1.9 to 90 mPa·s.

20. The bonding method according to claim 19, wherein the polyvinyl alcohol-based resin (A) is a polyvinyl alcohol-based resin having a carboxyl group or a salt thereof in its side chain.

21. The bonding method according to claim 19 or 20, wherein an aqueous solution containing the polyvinyl alcohol-based resin (A) at a solid content concentration of 0.5 to 40% by mass is used as agent (I).

22. The bonding method according to claim 19 or 20, wherein the inorganic salt (B) and an aqueous solution of the water-soluble polymer (C) with a concentration of 0.3 to 30% by mass are used as the (II) agent.

23. The bonding method according to claim 19 or 20, comprising the following steps 1 and 2 in this order: 1) Applying agent (I) to surface a and agent (II) to surface b; 2) Bringing agent (I) and agent (II) into contact to bond surface a and surface b.

24. The bonding method according to claim 23, wherein step 2 is performed after step 3 below. 3) A step of drying at least one of the agent (I) applied to surface a and the agent (II) applied to surface b.

25. A two-component, fractional application adhesive kit comprising agent (I) and agent (II), wherein agent (I) comprises a polyvinyl alcohol-based resin (A), agent (II) comprises an inorganic salt (B) and a water-soluble polymer (C), the polyvinyl alcohol-based resin (A) comprises a polyvinyl alcohol-based resin having a carboxyl group or a salt thereof, and the viscosity of the water-soluble polymer (C) in a 4% by mass aqueous solution at 23°C is 1.9 to 90 mPa·s.

26. The two-component fractional application adhesive kit according to claim 25, wherein the polyvinyl alcohol-based resin (A) is a polyvinyl alcohol-based resin having a carboxyl group or a salt thereof in its side chain.

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