Solvent-free adhesive for structure, cured product thereof, and structure

Abstract

Provided are: a solvent-free adhesive for a structure, which has excellent room-temperature rapid hardenability and long-term moist heat resistance; and a cured product and a structure, which have excellent long-term moist heat resistance. The problem is solved by a solvent-free adhesive for a structure, the solvent-free adhesive for a structure comprising a polyol main agent and a polyisocyanate curing agent, the polyol main agent comprising a polyol (A) and a phosphoric acid compound (B), the polyisocyanate hardener contains a reaction product (C) of an aromatic polyisocyanate and a polyol containing a polyol having 3 or more functional groups, and an epoxy compound (D) having 3 or more functional groups.

Description

Technical Field

[0001] The present disclosure relates to a solvent-free structural adhesive, a cured product thereof, and a structure. Background Art

[0002] In recent years, in the fields of automobiles or aircraft, the use ratio of lightweight raw materials such as light metals like aluminum or magnesium, or fiber reinforced plastic (hereinafter simply referred to as FRP) for vehicle body weight reduction has increased. However, for example, when bonding materials with different linear expansion coefficients such as aluminum and FRP, there is a problem that due to the difference in expansion rates between materials caused by temperature changes during the manufacturing process or in the use temperature environment, high stress is applied to the bonding layer, accelerating the damage or deterioration of the bonding layer. Therefore, as a stress relaxation design, methods of imparting flexibility to adhesives have been widely studied, and among them, urethane adhesives that balance high bonding strength and flexibility have attracted attention.

[0003] On the other hand, in the fields of automobiles and the like, from the viewpoints of productivity and energy conservation, a performance of exhibiting sufficient initial bonding strength at room temperature and in a short time (hereinafter referred to as room temperature rapid curing) is required. However, in existing urethane adhesives, there is a problem that the curing reaction of urethanization is slow and sufficient initial bonding strength cannot be obtained.

[0004] Regarding such a problem, in Patent Document 1, an adhesive is disclosed which exhibits initial strength in a short time while maintaining the pot life by including a main agent containing a urethane prepolymer containing polyether triol and polyether diol and an amine catalyst, and a curing agent containing an amine-based catalyst.

[0005] In addition, in Patent Document 2, a urethane adhesive is disclosed which exhibits high bonding strength, flexibility, and rapid curing properties by using a main agent containing a urethane polymer and a curing agent containing an amorphous polyol compound and a polyamine compound.

[0006] Prior Art Documents

[0007] Patent Documents

[0008] Patent Document 1: Japanese Patent Laid-Open No. 2012-207122

[0009] Patent Document 2: Japanese Patent Laid-Open No. 2020-055921 Summary of the Invention

[0010] Problems to be Solved by the Invention

[0011] However, in the adhesive described in Patent Document 1, since a large amount of polyether polyol is used, there are problems such as low strength after hardening and a decrease in long-term heat and humidity resistance.

[0012] Regarding the adhesive described in Patent Document 2, for the rapid hardening utilizing the ureation reaction of a large amount of amine compound and isocyanate, since the reaction is too fast, the pot life is short. Therefore, in the case of large-area applications, there are problems that it is difficult to exhibit adhesive strength after coating and the nozzle is easily clogged during coating. In addition, there is a problem that the crosslinking reaction is difficult to proceed due to the slow reaction rate between the non-crystalline polyol compound contained and isocyanate, and the initial adhesive strength at room temperature and in a short time cannot be sufficiently obtained.

[0013] Therefore, the subject of the present disclosure is to provide a solvent-free structural adhesive having excellent room-temperature rapid hardening property and long-term heat and humidity resistance. In addition, the subject of the present disclosure is to provide a hardened product and a structure of a solvent-free structural adhesive having excellent long-term heat and humidity resistance.

[0014] Technical means for solving the problem

[0015] The inventors of the present invention et al. made diligent studies and as a result, found that the above problems can be solved.

[0016] [1]: A solvent-free structural adhesive, comprising a polyol main agent and a polyisocyanate hardener, and in the solvent-free structural adhesive,

[0017] the polyol main agent contains a polyol (A) and a phosphoric acid-based compound (B), and the polyisocyanate hardener contains a reaction product (C) of a polyol containing a polyol having 3 or more functional groups and an aromatic polyisocyanate, and an epoxy compound (D) having 3 or more functional groups.

[0018] [2]: The solvent-free structural adhesive according to [1], wherein the aromatic polyisocyanate constituting the reaction product (C) is diphenylmethane diisocyanate.

[0019] [3]: The solvent-free structural adhesive according to [1] or [2], wherein the polyol (A) contains a polyol (A1) having a number average molecular weight of 2,000 or more and a polyol (A2) having a number average molecular weight of 100 or more and less than 2,000.

[0020] [4]: The solvent-free structural adhesive according to [3], wherein the polyol (A1) has a primary hydroxyl group at the terminal and has a urethane bond in the molecule.

[0021] [5]: The adhesive for solvent-free structures according to [3] or [4], wherein the proportion of the polyol (A1) relative to the total of the polyol (A1) and the polyol (A2) is 10% by mass to 70% by mass.

[0022] [6]: The adhesive for solvent-free structures according to any one of [1] to [5], wherein the content rate of the phosphoric acid compound (B) is 0.5% by mass to 5% by mass based on the mass of the polyol (A).

[0023] [7]: A cured product, which is a cured product of the adhesive for solvent-free structures according to any one of [1] to [6].

[0024] [8]: A structure body, which includes an adhesive layer between a first base material and a second base material, and in the structure body, the adhesive layer is the cured product according to [7].

[0025] Effects of the Invention

[0026] Through the present disclosure, a solvent-free structure adhesive having excellent room-temperature rapid curability and long-term damp heat resistance can be provided. In addition, through the present disclosure, a cured product and a structure body of a solvent-free structure adhesive having excellent long-term damp heat resistance can be provided. Detailed Embodiments

[0027] The solvent-free structure adhesive of the present disclosure includes a polyol main agent and a polyisocyanate curing agent. The polyol main agent includes a polyol (A) and a phosphoric acid compound (B), and the polyisocyanate curing agent includes a reaction product (C) of a polyol containing a polyol having 3 or more functional groups and an aromatic polyisocyanate, and an epoxy compound (D) having 3 or more functional groups.

[0028] By using the polyol main agent and the polyisocyanate curing agent in combination, with component (B) as the main agent and component (D) as the curing agent component, the reaction of component (B) can be suppressed until use, so that the adhesion can be ensured and a tough coating film can be obtained. Furthermore, the curing reaction at room temperature can be promoted by the phosphoric acid compound (B), sufficient strength can be exhibited even at the initial stage of curing, and the adhesion to the metal base material is improved. In addition, by including the reaction product (C) of a polyol containing a polyol having 3 or more functional groups and an aromatic polyisocyanate, sufficient strength can be exhibited even near room temperature, and flexibility and toughness can be imparted to the cured product. Furthermore, the long-term damp heat resistance is improved by the epoxy compound (D) having 3 or more functional groups.

[0029] Therefore, the adhesive of the present disclosure can be suitably used in the field of structural adhesives for automobiles, building materials, ships, aircraft, etc., and is solvent-free. Therefore, it is also excellent from the viewpoints of safety and environmental correspondence.

[0030] Hereinafter, the present disclosure will be described in detail. In addition, in this specification, the numerical range defined by "~" includes the range of the numerical values described before and after "~" as the lower limit value and the upper limit value.

[0031] <<Polyol main agent>>

[0032] The polyol main agent used in the present disclosure contains polyol (A) and a phosphoric acid-based compound (B). The polyol main agent preferably has fluidity at room temperature. In addition, the polyol main agent may contain an epoxy compound within the range that does not impair the effects of the present disclosure, but preferably does not contain an epoxy compound.

[0033] <Polyol (A)>

[0034] The polyol (A) used in the present disclosure may be any compound having two or more hydroxyl groups in the molecule, and there is no particular limitation. When the polyol (A) is a resin, the hydroxyl group may be located at any of the ends, side chains, or side groups of the resin.

[0035] As such a polyol (A), for example, polyester polyol, polyether polyol, polyurethane polyol, polyester amide polyol, acrylic polyol, polycarbonate polyol, polycaprolactone polyol, polyvalerolactone polyol, polybutadiene polyol, polyolefin polyol, polyhydroxyalkane, castor oil, or a mixture thereof can be used.

[0036] In addition, as the polyol (A), for example, ethylene glycol, propylene glycol, 1,3 - propanediol, 1,4 - butanediol, 1,5 - pentanediol, 3 - methyl - 5 - pentanediol, 1,6 - hexanediol, neopentyl glycol, methylpentanediol, triethylene glycol, tetraethylene glycol, dipropylene glycol, dihydroxyethoxybenzene, 1,4 - cyclohexanediol, 1,4 - cyclohexanedimethanol, triethylene glycol, etc. can be used; polyalkylene glycol having a number average molecular weight of 200 to 3,000; trifunctional or tetrafunctional aliphatic alcohols such as glycerol, trimethylolpropane, and pentaerythritol; and polyols obtained by adding the above - mentioned diol or polyol to the trifunctional or tetrafunctional aliphatic alcohol.

[0037] Among them, from the viewpoint of long - term heat and humidity resistance, polyether polyol, polyurethane polyol, acrylic polyol, polycarbonate polyol, and polybutadiene polyol are preferred. These polyols (A) can be used alone or in combination of two or more.

[0038] The polyol (A) is preferably one containing a polyol (A1) having a number-average molecular weight of 2,000 or more and a polyol (A2) having a molecular weight of 100 or more and less than 2,000. By using such polyol (A1) and polyol (A2) in combination, elongation of the cured product of the adhesive and adhesive strength can be balanced.

[0039] The proportion of polyol (A1) relative to the total of polyol (A1) and polyol (A2) is preferably 10% by mass to 70% by mass, more preferably 10% by mass to 50% by mass.

[0040] The polyol (A1) may also have a primary hydroxyl group at the terminal. If it has a primary hydroxyl group at the terminal, the initial adhesive strength at room temperature, foam suppression of the coating film, and strength after curing are excellent. In addition, the polyol (A1) may also be a polyol having a urethane bond in the molecule (hereinafter referred to as urethane polyol). By containing such a urethane polyol, suppression of sagging of the adhesive during vertical surface coating and stretchability of the cured coating film are excellent. That is, as the polyol (A1), a urethane polyol having a primary hydroxyl group at the terminal and a urethane bond in the molecule is preferred.

[0041] The method for producing the urethane polyol is not particularly limited. For example, a reaction product of a polyol and a polyisocyanate can be suitably used. As the polyol, for example, the compounds exemplified in the item <Polyol (A)> can be used.

[0042] Examples of the polyisocyanate include aromatic, aliphatic, or alicyclic diisocyanates (hereinafter also referred to as polyisocyanate monomers); dimers, trimers, biurets, and urethanes derived from polyisocyanate monomers; and polyisocyanates having a 2,4,6-oxadiazinetrione ring obtained from carbon dioxide and the polyisocyanate monomers. These can be used alone or in combination of two or more.

[0043] Examples of the aromatic diisocyanate include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4-diphenylmethane diisocyanate, 2,2'-diphenylmethane diisocyanate, 1,5-naphthalene diisocyanate, tolidine diisocyanate, xylylene diisocyanate, m-tetramethylxylylene diisocyanate, p-tetramethylxylylene diisocyanate, 3,3'-dimethyl-4,4'-biphenylene diisocyanate, 3,3'-dimethoxy-4,4'-biphenylene diisocyanate, 3,3'-dichloro-4,4'-biphenylene diisocyanate, and 1,5-tetrahydronaphthalene diisocyanate.

[0044] Examples of the aliphatic diisocyanate include trimethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, 1,2-propylene diisocyanate, 2,3-butylene diisocyanate, 1,3-butylene diisocyanate, dodecamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, lysine diisocyanate, lysine ester triisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate tetramethylene diisocyanate, pentamethylene diisocyanate, and trimethylhexamethylene diisocyanate.

[0045] Examples of the alicyclic diisocyanate include isophorone diisocyanate, 1,3-cyclopentane diisocyanate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, methyl-2,4-cyclohexane diisocyanate, methyl-2,6-cyclohexane diisocyanate, 4,4'-methylenebis(cyclohexyl isocyanate), 1,4-bis(isocyanatomethyl)cyclohexane, hydrogenated xylylene diisocyanate, dimer acid diisocyanate, and norbornene diisocyanate.

[0046] The number average molecular weight of the urethane polyol is not particularly limited, and is preferably 3,000 to 200,000. If the number average molecular weight is 3,000 or more, the elongation of the cured product is excellent. If the number average molecular weight is 200,000 or less, the adhesion at room temperature curing and the dispenser ejectability during adhesive coating are excellent.

[0047] The polyurethane polyol may further have a urea bond in the molecule. By having a urea bond in the molecule, the heat resistance durability or the bonding strength is improved. As such a urethane polyol having a urea bond, from the viewpoints of the viscosity and sagging property during ejection and the bonding strength, for example, a compound obtained by reacting the isocyanate group of a urethane polymer having an isocyanate group at the terminal with the amino group of a monoamine compound having a molecular weight of less than 200 and having a hydroxyl group in the molecule, which is a reaction product of a polyol and a polyisocyanate, is preferably used.

[0048] <Phosphoric acid compound (B)>

[0049] The polyol main agent of the present disclosure contains a phosphoric acid compound (B). The phosphoric acid compound (B) promotes the curing of the adhesive, and the initial strength and the adhesion to metal are improved by good room temperature curing. Thereby, excellent adhesion to aluminum can be exhibited without using a primer.

[0050] The phosphoric acid compound (B) only needs to have at least one free oxyacid, and examples thereof include: hypophosphorous acid, phosphorous acid, orthophosphoric acid, hypophosphoric acid, etc. phosphoric acids, metaphosphoric acid, pyrophosphoric acid, tripolyphosphoric acid, polyphosphoric acid, perphosphoric acid, etc. condensed phosphoric acids, phosphonic acids.

[0051] In addition, as the phosphoric acid compound (B), derivatives of the phosphoric acid compound can also be used. As such derivatives, for example, those partially esterified with an alcohol in a state where at least one free oxyacid in the oxyacid of phosphorus remains, and phosphonate esters can be cited. As the alcohol, for example, aliphatic alcohols such as methanol, ethanol, ethylene glycol, glycerol; aromatic alcohols such as phenol, xylenol, hydroquinone, catechol, phloroglucinol can be cited.

[0052] The phosphoric acid compound (B) can be used alone or in combination of two or more.

[0053] From the viewpoints of promoting hardening and adhesion to metals, based on the mass of the polyol (A), the blending amount of the phosphoric acid compound (B) is preferably 0.5% by mass or more, more preferably 0.6% by mass or more, and further preferably 0.7% by mass or more. In addition, from the viewpoint of the pot life after blending, it is preferably 5% by mass or less, more preferably 3% by mass or less, and further preferably 2% by mass or less.

[0054] <<Polyisocyanate hardener>>

[0055] The polyisocyanate hardener in the present disclosure includes a reaction product (C) of a polyol containing a polyol having a functional group number of 3 or more and an aromatic polyisocyanate, and an epoxy compound (D) having a functional group number of 3 or more. The polyisocyanate hardener preferably exhibits fluidity at room temperature.

[0056] <Reaction product (C) of a polyol containing a polyol having a functional group number of 3 or more and an aromatic polyisocyanate>

[0057] The reaction product (C) is an isocyanate compound which is a reaction product of a polyol containing a polyol having a functional group number of 3 or more and an aromatic polyisocyanate. For example, an adduct of an aromatic diisocyanate monomer and trimethylolpropane, a reaction product of an aromatic diisocyanate monomer and a trifunctional polypropylene glycol can be cited. These can be used alone or in combination of two or more.

[0058] Examples include dimers, trimers, biurets, urethanes, polyisocyanates having a 2,4,6-oxadiazinetrione ring obtained from carbon dioxide and the polyisocyanate monomer, and polyurethane prepolymers obtained by reacting a polyisocyanate with a polyol. These may be used individually or in combination of two or more.

[0059] As the aromatic polyisocyanate, from the viewpoint of the initial adhesion strength, diphenylmethane diisocyanate is preferably used. That is, as the reaction product (C), from the viewpoint of the initial adhesion strength, a reaction product of diphenylmethane diisocyanate and a polyol containing a polyol having 3 or more functional groups is preferred. The ratio of the number of isocyanate groups of diphenylmethane diisocyanate to the number of hydroxyl groups of the polyol (NCO / OH) in the reaction may be set to 1 or more, preferably 1.5 or more.

[0060] <Epoxy compound (D) having 3 or more functional groups>

[0061] The polyisocyanate hardener of the present disclosure contains an epoxy compound (D) having 3 or more functional groups. By containing a compound having three or more epoxy groups in one molecule, the adhesion strength after the damp heat resistance test of the adhesive can be maintained.

[0062] Examples of such an epoxy compound (D) include epoxy compounds derived from polyvinylphenol, polyisopropenylphenol, 1,1-bis-(4-hydroxyphenyl)-1-phenylethane, 1,1-bis-(4-hydroxyphenyl)-1,1-dimethylmethane, etc.; novolak resin series resins derived from phenol novolak, brominated phenol novolak, cresol novolak, brominated cresol novolak, resorcinol novolak, brominated resorcinol novolak, etc.; polyphenol series epoxy resins derived from resorcinol, hydroquinone, methylresorcinol, etc.; amine series epoxy resins derived from aniline, p-aminophenol, m-aminophenol, p-aminocresol, 4,4'-diaminodiphenylmethane, etc.; glycidyl ester series compounds derived from aromatic carboxylic acids such as p-oxybenzoic acid, m-oxybenzoic acid, terephthalic acid, isophthalic acid, etc.; hydantoin series epoxy resins derived from 5,5'-dimethylhydantoin, etc.; polymers of alicyclic epoxy such as vinylcyclohexene oxide; polyglycidyl ethers of polyfunctional polyols such as trimethylolpropane and sorbitol; in addition, for example, isocyanuric acid trisglycidyl ester, 2,4,6-triglycidyloxy-5-triazine, epoxidized polybutadiene, epoxidized vegetable oil, etc. Further, dimer acid-modified epoxy resins, urethane-modified epoxy resins, etc. as modified products thereof may also be used. These epoxy compounds (D) may be used individually or in combination of two or more.

[0063] From the perspective of the solution stability of the polyisocyanate hardener, the epoxy compound (D) is preferably a polymer of alicyclic epoxy such as epoxidized butadiene, epoxidized styrene ethylene butylene styrene (SEBS), epoxidized vegetable oil, or vinyl cyclohexene oxide, which is formed by adding oxygen to a double bond.

[0064] <Filler>

[0065] The adhesive of the present disclosure may contain known fillers. Examples of fillers include inorganic fillers and organic fillers.

[0066] Examples of inorganic fillers include talc, zeolite, silica, microballoons, clay, calcium carbonate, and carbon black. Examples of organic fillers include acrylic particles, carbon nanotubes, graphite, starch, natural organic fibers, and synthetic fibers. These fillers may be used alone or in combination of two or more.

[0067] <Additive>

[0068] The adhesive of the present disclosure may further contain known additives such as reaction promoters, silane coupling agents, leveling agents or defoaming agents, fillers, propellants, plasticizers, superplasticizers, wetting agents, flame retardants, viscosity modifiers, preservatives, stabilizers, and colorants. Such additives may be used alone or in combination of two or more.

[0069] Examples of reaction promoters include metal-based catalysts such as dibutyltin diacetate, dibutyltin dilaurate, dioctyltin dilaurate, and dibutyltin dimaleate. Based on the total mass of the polyol, the blending amount of the reaction promoter is preferably 0.005% by mass to 1% by mass.

[0070] Examples of silane coupling agents include trialkoxysilanes having a vinyl group such as vinyltrimethoxysilane and vinyltriethoxysilane; trialkoxysilanes having an amino group such as 3-aminopropyltriethoxysilane and N-(2-aminoethyl)-3-aminopropyltrimethoxysilane; trialkoxysilanes having a glycidyl group such as 3-glycidoxypropyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, and 3-glycidoxypropyltriethoxysilane; trialkoxysilanes having an isocyanate group such as 3-isocyanatopropyltriethoxysilane; and trialkoxysilanes having a mercapto group such as 3-mercaptopropylmethyldimethoxysilane and 3-mercaptopropyltrimethoxysilane. Based on the total mass of the adhesive, the blending amount of the silane coupling agent is preferably 0.05% by mass to 10% by mass.

[0071] As a leveling agent, examples include: polyether-modified polydimethylsiloxane, polyester-modified polydimethylsiloxane, aralkyl-modified polymethylalkylsiloxane, polyester-modified hydroxyl-containing polydimethylsiloxane, polyether ester-modified hydroxyl-containing polydimethylsiloxane, acrylic copolymer, methacrylic copolymer, polyether-modified polymethylalkylsiloxane, alkyl acrylate copolymer, alkyl methacrylate copolymer, lecithin.

[0072] As an antifoaming agent, examples include: known antifoaming agents such as silicone resin, silicone solution, copolymer of alkyl vinyl ether and alkyl acrylate and alkyl methacrylate.

[0073] <<Structures, cured products>>

[0074] The cured product of the present disclosure can be obtained by mixing a polyol main agent containing a polyol (A) and a phosphoric acid compound (B), a reaction product (C) of a polyol containing a polyol having 3 or more functional groups and an aromatic polyisocyanate, and an epoxy compound (D) having 3 or more functional groups with a polyisocyanate curing agent by a known method and curing it. The ratio [NCO / OH] of the number of hydroxyl groups in the polyol main agent to the number of isocyanate groups in the polyisocyanate curing agent is preferably 0.9 to 1.3, more preferably 1.0 to 1.2.

[0075] In addition, the structure of the present disclosure is characterized in that an adhesive layer is included between the first substrate and the second substrate, and the adhesive layer is the cured product. The manufacturing method of the structure is not particularly limited. For example, an adhesive is applied to one surface of the first substrate, and then the second substrate is overlapped on the uncured adhesive surface, and a curing reaction is carried out at about 20°C to 40°C to cure the adhesive, whereby a structure can be obtained. The thickness of the cured adhesive layer is preferably 0.1 μm to 300 mm.

[0076] <First substrate, second substrate>

[0077] The adhesive of the present disclosure can be used for bonding between various substrates. As substrates that can be used as suitable first substrates and second substrates, for example, metals such as aluminum, thermoplastic polymers such as polyethylene, polypropylene, polyurethane, polyacrylate, polycarbonate and copolymers thereof, thermosetting polymers such as vulcanized rubber, urea-formaldehyde foam, melamine resin, wood, carbon fiber reinforced plastic, glass fiber reinforced plastic and other fiber reinforced plastics can be cited. The first substrate and the second substrate can be the same substrate or different substrates.

[0078] The adhesive of the present disclosure has excellent room-temperature rapid curability, and further has excellent film strength, flexibility, heat resistance, and adhesive force. The structure using the adhesive is effectively used for structural members (such as panel parts, frame parts, and axle parts) of transportation equipment such as automobiles, building materials, ships, and aircraft.

[0079] Examples

[0080] Hereinafter, the present disclosure will be described in more detail by way of examples. However, the following examples do not limit the scope of the present disclosure in any way. In addition, unless otherwise specified, "parts" and "%" in the examples represent "parts by mass" and "mass %".

[0081] <Number-average molecular weight (Mn)>

[0082] The number-average molecular weight (Mn) and mass-average molecular weight (Mw) of the resin are determined as conversion values based on standard polystyrene by gel permeation chromatography (GPC). The measurement is carried out using GPC-8020 (manufactured by Tosoh Corporation) as the gel permeation chromatograph (GPC) device, tetrahydrofuran as the eluent, and three TSK gel Super HM-M (manufactured by Tosoh Corporation) columns connected in series. The measurement is carried out under the conditions of a flow rate of 0.6 mL / min, an injection volume of 10 μL, and a column temperature of 40°C.

[0083] The following shows the abbreviations of the compounds in this specification.

[0084] <Polyol>

[0085] ·P-400: Bifunctional polypropylene glycol, number-average molecular weight 400, hydroxyl value 280 mgKOH / g, manufactured by ADEKA Corporation

[0086] ·P-1000: Bifunctional polypropylene glycol, number-average molecular weight 1,000, hydroxyl value 112 mgKOH / g, manufactured by ADEKA Corporation

[0087] ·P-2000: Bifunctional polypropylene glycol, number-average molecular weight 2,000, hydroxyl value 56 mgKOH / g, manufactured by ADEKA Corporation

[0088] ·T-400: Trifunctional polypropylene glycol, number-average molecular weight 400, hydroxyl value 410 mgKOH / g, manufactured by Mitsui Chemicals, Inc.

[0089] · PTMG-650: difunctional polytetramethylene ether glycol, number average molecular weight 650, hydroxyl value 173 mg KOH / g, manufactured by Mitsubishi Chemical Corporation

[0090] · T5650E: difunctional polycarbonate polyol, number average molecular weight 500, hydroxyl value 220 mg KOH / g, trade name "DURANOL T5650E", manufactured by Asahi Kasei Corporation

[0091] · T5651: difunctional polycarbonate polyol, number average molecular weight 1000, hydroxyl value 110 mg KOH / g, trade name "DURANOL T5650E", manufactured by Asahi Kasei Corporation

[0092] · T5652: difunctional polycarbonate polyol, number average molecular weight 2000, hydroxyl value 56 mg KOH / g, trade name "DURANOL T5652", manufactured by Asahi Kasei Corporation

[0093] · TMP: trimethylolpropane

[0094] · GI-1000: polybutadiene polyol, number average molecular weight 1400, hydroxyl value 69 mg KOH / g, manufactured by Nippon Soda Co., Ltd.

[0095] <Polyisocyanate>

[0096] · IPDI: isophorone diisocyanate

[0097] · TDI: toluene diisocyanate

[0098] · 4,4'-MDI: 4,4'-diphenylmethane diisocyanate

[0099] · Liquid MDI: Millionate MN (manufactured by Tosoh Corporation, Monomeric MDI)

[0100] · Crude MDI: PM-200 (manufactured by Wanhua Chemical Group Co., Ltd., polymeric MDI)

[0101] · TDI-TMP adduct: toluene diisocyanate adduct of trimethylolpropane, manufactured by Mitsui Chemicals, Inc.

[0102] · HDI-urethanes: urethane bodies of hexamethylene diisocyanate, Basonat HI-100, manufactured by BASF SE

[0103] <Epoxy compound>

[0104] · JP-100: Epoxidized polybutadiene (manufactured by Nippon Soda Co., Ltd., number of functional groups 4 - 7)

[0105] · ED-505: Trimethylolpropane triglycidyl ether (manufactured by ADEKA Corporation, number of functional groups 3)

[0106] · jER-152: Phenol novolac type epoxy resin (number of functional groups 3 or more, polyfunctional)

[0107] · jER-828: Bisphenol A type epoxy resin (number of functional groups 2)

[0108] <Synthesis of polyol (A1) with number average molecular weight of 2,000 or more>

[0109] (Polyol (a1))

[0110] In a reaction vessel equipped with a nitrogen inlet tube, a stirring device, a thermometer, and a reflux condenser, 100 parts of T5651 as a polyol and 13.7 parts of toluene diisocyanate were charged. After stirring evenly, the reaction was carried out at 110 °C for 5 hours under a nitrogen atmosphere to obtain a urethane - modified polyol (a1) with a number average molecular weight of 5,000.

[0111] (Polyol (a2))

[0112] In the reaction vessel, 100 parts of T5651 as a polyol and 30.5 parts of isophorone diisocyanate were charged. After stirring evenly, the reaction was carried out at 90 °C for 5 hours under a nitrogen atmosphere to obtain a urethane - modified prepolymer. Then, it was cooled to 80 °C, 4.8 parts of ethanolamine was added, and the reaction was carried out at 75 °C for 2 hours to obtain a polyurethane - urea polyol (a2) with a number average molecular weight of 6,000.

[0113] (Polyol (a3))

[0114] In the reaction vessel, 100 parts of P - 1000 as a polyol and 13.9 parts of toluene diisocyanate were charged. After the reaction was carried out at 110 °C for 5 hours under a nitrogen atmosphere, a urethane - modified polyol (a3) with a number average molecular weight of 5,000 was obtained.

[0115] (Polyol (a4))

[0116] In the reaction vessel, 100 parts of P - 1000 as a polyol and 30.5 parts of isophorone diisocyanate were charged. After stirring evenly, the reaction was carried out at 90 °C for 5 hours under a nitrogen atmosphere to obtain a urethane - modified prepolymer. Then, it was cooled to 80 °C, 4.8 parts of ethanolamine was added, and the reaction was carried out at 75 °C for 2 hours to obtain a polyurethane - urea polyol (a4) with a number average molecular weight of 6,500.

[0117] [Table 1]

[0118] Table 1. Polyol (A1) with a number-average molecular weight of 2,000 or more

[0119]

[0120] <Synthesis of isocyanate compound>

[0121] (Isocyanate compound (c1))

[0122] Charge 12 parts of P-400, 12 parts of P-2000, and 1.6 parts of T-400 into a reaction vessel. After stirring evenly, charge 32.4 parts of 4,4'-MDI, and react at 90 °C for 3 hours under a nitrogen atmosphere to carry out a carbamate reaction. Then cool to 50 °C, add 12 parts of liquid MDI and 30 parts of crude MDI, and stir for 15 minutes to obtain isocyanate compound (c1).

[0123] (Isocyanate compound (c2))

[0124] Charge 85.6 parts of liquid MDI into a reaction vessel, and gradually add in small amounts the mixture prepared by previously mixing 6.9 parts of P-400 and 7.6 parts of TMP. After stirring evenly, react at 90 °C for 3 hours under a nitrogen atmosphere to carry out a carbamate reaction. Then cool to 50 °C, add 11.1 parts of crude MDI and stir to obtain isocyanate compound (c2).

[0125] (Isocyanate compound (c3))

[0126] Charge 80 parts of a 75% solution of TDI-TMP adduct into a reaction vessel. After distilling off the solvent by heating at 100 °C and reducing the pressure, add 40 parts of liquid MDI and stir to obtain isocyanate compound (c3).

[0127] (Isocyanate compound (c4))

[0128] Charge 31.2 parts of liquid MDI into a reaction vessel, and gradually add in small amounts the mixture prepared by previously mixing 43.4 parts of GI-1000 and 0.4 parts of TMP. After stirring evenly, react at 90 °C for 3 hours under a nitrogen atmosphere to carry out a carbamate reaction. Then cool to 50 °C, add 25 parts of liquid MDI and stir to obtain isocyanate compound (c4).

[0129] (Isocyanate compound (c5))

[0130] 20.2 parts of P-400 and 20.2 parts of 4,4-MDI were placed in a reaction container and reacted at 90° C. for 3 hours under a nitrogen atmosphere to perform a urethanization reaction. The mixture was then cooled to 50° C., 22.7 parts of crude MDI was added, and the mixture was stirred for 15 minutes to obtain an isocyanate compound (c5).

[0131] [Table 2]

[0132] Table 2. Isocyanate compounds

[0133]

[0134] <Manufacturing of polyol main agent>

[0135] (Polyol main agent 1)

[0136] 70 parts of T5650E and 1 part of polyphosphoric acid were added to 30 parts of the urethanized polyol (a1), and the mixture was stirred for 15 minutes to obtain a polyol main agent 1.

[0137] (Polyol main agent 2)

[0138] 70 parts of T5650E and 1 part of polyphosphoric acid were added to 30 parts of urethanized polyol (a2), and the mixture was stirred for 15 minutes. 0.5 parts of 3-glycidyloxypropyltrimethoxysilane was added, and the mixture was stirred for 15 minutes to obtain a polyol main agent 2.

[0139] (Polyol main agent 3)

[0140] 70 parts of P-400 and 1 part of phosphoric acid were added to 30 parts of urethanized polyol (a3), and the mixture was stirred for 15 minutes. 100 parts of calcium carbonate was added, and the mixture was stirred and degassed using an autogenous-revolution mixer (manufactured by Rentaro, Thinky Co., Ltd.) to obtain a polyol main agent 3.

[0141] (Polyol main agent 4)

[0142] Polyol base compound 4 was obtained in the same manner as polyol base compound 3 except that the blending composition of each component was changed to that shown in Table 3.

[0143] (Polyol main agent 5 to polyol main agent 14)

[0144] Polyol base compositions 5 to 14 were obtained in the same manner as the polyol base composition 1 or the polyol base composition 2 except that the blending compositions of the components were changed to those shown in Table 3.

[0145] (Polyol main agent 15)

[0146] To 30 parts of urethanated polyol (A1), 70 parts of T5650E and 1 part of polyphosphoric acid were added, and the mixture was stirred for 15 minutes. Then, 0.5 part of 3-glycidoxypropyltrimethoxysilane and 10 parts of JP-100 were added, and the mixture was stirred for 15 minutes to obtain 15 of the polyol main agent.

[0147] (Polyol main agent 16)

[0148] To 30 parts of urethanated polyol (A1), 70 parts of T5650E was added, and the mixture was stirred for 15 minutes to obtain 16 of the polyol main agent.

[0149]

[0150] <Manufacture of polyisocyanate hardener>

[0151] (Polyisocyanate hardener 1)

[0152] To 100 parts of isocyanate compound (c1), 10 parts of JP-100 was added, and the mixture was stirred for 15 minutes under a nitrogen atmosphere to obtain 1 of the polyisocyanate hardener.

[0153] (Polyisocyanate hardeners 2 to 11)

[0154] Polyisocyanate hardeners 2 to 11 were obtained in the same manner as polyisocyanate hardener 1, except that the blending composition of each component was changed to the content shown in Table 4.

[0155] [Table 4]

[0156] Table 4. Polyisocyanate hardener

[0157]

[0158] <Adjustment of solvent-free structural adhesive>

[0159] [Examples 1 to 16, Comparative Examples 1 to 6]

[0160] At room temperature, the polyol main agent and the polyisocyanate hardener were stirred and mixed with the blending composition shown in Table 5 to adjust solvent-free reactive adhesives respectively.

[0161] <Evaluation of solvent-free structural adhesive>

[0162] The obtained adhesives were evaluated as follows. The results are shown in Table 5.

[0163] [Room temperature rapid hardening property]

[0164] The obtained adhesive was coated on an aluminum substrate (100 mm in length, 25 mm in width, 2 mm in thickness) in a manner of 25 mm in width, 10 mm in length, and 0.3 mm in thickness, bonded to the same aluminum substrate, and cured was started in an environment at 23°C in a state of being crimped while maintaining a thickness of 0.3 mm.

[0165] After the start of curing, every 10 minutes under the condition of 23°C, a tensile testing machine was used to measure the shear bond strength at a tensile speed of 10 mm / minute. Based on the time when the shear strength reached 0.4 MPa or more, evaluation was carried out according to the following criteria.

[0166] A: Within 20 minutes (good).

[0167] B: More than 20 minutes and within 30 minutes (usable).

[0168] C: More than 30 minutes (not usable).

[0169] [Long-term damp heat resistance]

[0170] The test pieces made in the same way as the room temperature rapid hardening property were cured in an environment at 23°C for 3 days and then stored in an environment at 85°C and 85% relative humidity for 1000 hours. For the test pieces before storage and after storage, under the condition of 23°C, a tensile testing machine was used to measure the shear strength at a tensile speed of 10 mm / minute, and evaluation was carried out according to the following criteria.

[0171] A: The shear strength after storage is 75% or more of the shear strength before storage (good).

[0172] B: The shear strength after storage is 50% or more and less than 75% of the shear strength before storage (usable).

[0173] C: The shear strength after storage is less than 50% of the shear strength before storage (not usable).

[0174] [Pot life]

[0175] Immediately after the adhesive was coated on an aluminum substrate (100 mm in length, 25 mm in width, 2 mm in thickness), another identical aluminum substrate (100 mm in length, 25 mm in width, 2 mm in thickness) was bonded to obtain test pieces.

[0176] On the other hand, after the adhesive was coated on another aluminum substrate (100 mm in length, 25 mm in width, 2 mm in thickness), after 5 minutes, 10 minutes, or 15 minutes in an environment at 23°C, another identical aluminum substrate (100 mm in length, 25 mm in width, 2 mm in thickness) was bonded to obtain test pieces respectively.

[0177] After curing at 23°C for 1 day, under the condition of 23°C, use a tensile testing machine to measure the shear strength at a tensile speed of 10 mm / minute. Compare the shear strength of the test piece just after coating and lamination with the shear strength of the test piece with a time interval before laminating another aluminum substrate. For the shear strength of the test piece just after coating and lamination, based on the elapsed time representing 80% or less of the shear strength, make a judgment according to the following criteria.

[0178] A: In the test piece with an elapsed time of 15 minutes, it shows a shear strength within 80% of the test piece just after coating and lamination.

[0179] B: In the test piece with an elapsed time of 10 minutes, it shows a shear strength within 80% of the test piece just after coating and lamination.

[0180] C: In the test piece with an elapsed time of 5 minutes, it shows a shear strength within 80% of the test piece just after coating and lamination.

[0181] D: In the test piece with an elapsed time of 5 minutes, it does not show a shear strength within 80% of the test piece just after coating and lamination.

[0182] [Breaking stress and elongation at break of the cured coating film]

[0183] Fill the adhesive in a mold frame with a thickness of 1 mm, finish the surface, cure it for 1 day in an environment of 23°C, and punch it with a No. 3 dumbbell shape to produce a test piece. Use the test piece to conduct a tensile test at a tensile speed of 50 mm / minute in an environment of 23°C, measure the breaking stress (MPa) and elongation at break (%), and make a judgment according to the following criteria.

[0184] (Breaking stress)

[0185] A: The breaking stress is 30 MPa or more.

[0186] B: The breaking stress is 20 MPa or more and less than 30 MPa.

[0187] C: The breaking stress is 10 MPa or more and less than 20 MPa.

[0188] D: The breaking stress is 5 MPa or more and less than 10 MPa.

[0189] (Elongation at break)

[0190] A: The elongation at break is 200% or more.

[0191] B: The elongation at break is 150% or more and less than 200%.

[0192] C: The elongation at break is 100% or more and less than 150%.

[0193] D: Elongation at break is less than 100%.

[0194] [Table 5]

[0195] Table 5. Solventless Reactive Adhesive

[0196]

[0197] As shown in Table 5, it was confirmed that the polyol main agent of the solventless structural adhesive of the present disclosure containing polyol (A) and phosphoric acid compound (B), and the polyisocyanate curing agent containing the reaction product (C) of polyol having 3 or more functional groups and aromatic polyisocyanate and epoxide (D) having 3 or more functional groups exhibited good initial adhesion strength in a short time at room temperature and excellent long-term damp heat durability.

[0198] This application claims priority based on Japanese Patent Application No. 2022-208760 filed on December 26, 2022, and incorporates the entire contents disclosed therein into this application.

Claims

1. A solvent-free structural adhesive, comprising a polyol main agent and a polyisocyanate hardener, and in the solvent-free structural adhesive, the polyol main agent comprises a polyol (A) and a phosphoric acid-based compound (B), the polyisocyanate hardener comprises a reaction product (C) of a polyol containing a polyol having 3 or more functional groups and an aromatic polyisocyanate, and an epoxy compound (D) having 3 or more functional groups.

2. The solvent-free structural adhesive according to claim 1, wherein, The aromatic polyisocyanate constituting the reaction product (C) is diphenylmethane diisocyanate.

3. The solvent-free structural adhesive according to claim 1 or 2, wherein The polyol (A) comprises a polyol (A1) having a number average molecular weight of 2,000 or more, and a polyol (A2) having a number average molecular weight of 100 or more and less than 2,000.

4. The solvent-free structural adhesive according to claim 3, wherein The polyol (A1) has a primary hydroxyl group at the terminal and a urethane bond in the molecule.

5. The solvent-free structural adhesive according to claim 3, wherein, The proportion of the polyol (A1) relative to the total of the polyol (A1) and the polyol (A2) is 10% by mass to 70% by mass.

6. The solventless adhesive for structural use according to claim 1 or 2, wherein, Based on the mass of the polyol (A), the content rate of the phosphoric acid-based compound (B) is 0.5% by mass to 5% by mass.

7. A cured product, which is a cured product of the solvent-free structural adhesive according to any one of claims 1 to 6.

8. A structure, comprising an adhesive layer between a first substrate and a second substrate, and in the structure, the adhesive layer is the cured product according to claim 7.

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