Solventless reactive adhesive, hardened product thereof, and laminate

Abstract

To provide a solvent-free reactive adhesive, a hardened product thereof, and a laminate, which can maintain excellent film strength and softness even after heat resistance tests and oil resistance tests, and which has little influence on elongation at break even when the mixing ratio of a main agent and a hardener is changed. The object is solved by a solvent-free reactive adhesive comprising a polyisocyanate and a polyol, the polyisocyanate comprising a trimethylolpropane adduct of at least one of toluene diisocyanate and diphenylmethane diisocyanate, and an aromatic polyisocyanate other than the trimethylolpropane adduct, the trimethylolpropane adduct of the toluene diisocyanate and the trimethylolpropane adduct of the diphenylmethane diisocyanate being contained in a range of 40 to 80% by mass in total based on the total mass of the polyisocyanate.

Description

[0001] This application claims priority based on Japanese Patent Application No. 2020-193766 filed on November 20, 2020, Japanese Patent Application No. 2021-105556 filed on June 25, 2021, and Japanese Patent Application No. 2021-182699 filed on November 9, 2021, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This invention relates to a solvent-free reactive adhesive with high film strength and flexibility, heat resistance, oil resistance, adhesion and workability, as well as its cured form and laminate. Background Technology

[0003] In the automotive, building materials, shipbuilding, and aircraft industries, various structural adhesives are used to bond and fix metals such as iron, aluminum, and stainless steel, as well as resins, glass, and ceramics. In recent years, the automotive and aircraft industries have seen a surge in demand for adhesives that can firmly bond these materials, driven by trends towards lightweighting to improve fuel efficiency, increasing the use of materials containing plastics or fiber-reinforced plastics (FRP), and replacing iron with lighter aluminum. Furthermore, from the perspective of workability and reducing environmental impact, adhesives that do not contain volatile organic compounds are required.

[0004] However, for example, when bonding metals such as aluminum with materials such as FRP that have different coefficients of linear expansion, there is a problem that the difference in the coefficients of expansion between the materials due to temperature changes during the manufacturing process or in the operating environment can cause high stress on the adhesive layer, which can exacerbate the damage or deterioration of the adhesive layer.

[0005] Here, Patent Documents 1 to 3 disclose methods for adding long-chain polyamines or nano-dispersed rubber-like particles to epoxy compounds having high adhesion to metals or FRPs for the purpose of relieving stress. However, although these methods can impart a certain degree of flexibility, the resulting adhesive layer still tends to be hard and brittle, thus sometimes resulting in insufficient effectiveness.

[0006] Furthermore, Patent Document 4 discloses a solvent-free urethane-based adhesive composition with excellent elongation at break, comprising: a main agent containing a urethane prepolymer; and a curing agent containing a compound having an active hydrogen group. However, when the adhesive described in Patent Document 4 is applied using a two-component liquid mixing spraying device, there is a problem that the elongation at break may decrease significantly due to fluctuations in the mixing ratio or uneven mixing within the mixing nozzle.

[0007] To address this issue, Patent Document 5 discloses a urethane-based adhesive composition that, by using a base agent comprising a urethane polymer and a hardener comprising a non-crystalline polyol compound and a polyamine compound, suppresses the decrease in elongation at break even when the mixing ratio of the base agent and the hardener changes. However, the adhesive described in Patent Document 5 uses a large amount of amine compounds, making it sometimes difficult to adjust the curing speed. This can lead to nozzle clogging during application or uneven bonding in large-area or manual bonding operations. Furthermore, reducing the amount of amine compounds can slow down the curing speed, but this tends to reduce flexibility or coating strength. Moreover, in these methods, trace amounts of amines remain in the cured film, potentially reducing chemical resistance such as heat resistance or oil resistance.

[0008] Existing technical documents

[0009] Patent documents

[0010] Patent Document 1: Japanese Patent Publication No. 2018-506635

[0011] Patent Document 2: International Publication No. 2007 / 025007

[0012] Patent Document 3: Japanese Patent Application Publication No. 2015-182248

[0013] Patent Document 4: Japanese Patent Application Publication No. 2017-218539

[0014] Patent Document 5: Japanese Patent Application Publication No. 2020-055923 Summary of the Invention

[0015] The problem that the invention aims to solve

[0016] The purpose of this invention is to provide a solvent-free reactive adhesive that maintains excellent film strength and flexibility even after heat resistance and oil resistance tests, and has little effect on elongation at break even when the mixing ratio of the main agent (equivalent to polyol) and the hardener (equivalent to polyisocyanate) changes.

[0017] Technical means to solve the problem

[0018] The inventors have conducted intensive research and found that the aforementioned problem can be solved by using an adhesive that combines a polyol with a polyisocyanate comprising at least one of an aromatic polyisocyanate and a trimethylolpropane adduct of a toluene diisocyanate and a specific amount of a diphenylmethane diisocyanate.

[0019] That is, the present invention relates to a solvent-free reactive adhesive comprising a polyisocyanate and a polyol, wherein the polyisocyanate comprises a trimethylolpropane adduct of at least one of toluene diisocyanate and diphenylmethane diisocyanate, and an aromatic polyisocyanate other than the trimethylolpropane adduct, wherein the solvent-free reactive adhesive comprises, based on the total mass of the polyisocyanate, the trimethylolpropane adduct of toluene diisocyanate and the trimethylolpropane adduct of diphenylmethane diisocyanate in a total range of 40% to 80% by mass.

[0020] In addition, the present invention relates to a solvent-free reactive adhesive, wherein the aromatic polyisocyanate comprises at least one selected from the group consisting of diphenylmethane diisocyanate, polymethylene polyphenyl polyisocyanate, and carbodiimide-modified diphenylmethane diisocyanate.

[0021] In addition, the present invention relates to a solvent-free reactive adhesive, wherein the aromatic polyisocyanate is contained in a total range of 20% to 60% by mass, based on the total mass of the polyisocyanate.

[0022] In addition, the present invention relates to a solvent-free reactive adhesive, wherein the total mass of the polyisocyanate comprises, in a range of 45% to 75% by mass, the trimethylolpropane adduct of toluene diisocyanate and the trimethylolpropane adduct of diphenylmethane diisocyanate.

[0023] In addition, the present invention relates to a solvent-free reactive adhesive, wherein the polyol comprises a polycarbonate polyol that does not have urethane bonds.

[0024] In addition, the present invention relates to a solvent-free reactive adhesive, wherein the polyol comprises a polyol having a urethane bond.

[0025] In addition, the present invention relates to a solvent-free reactive adhesive, wherein the polyol having urethane bonds is contained in a total range of 30% to 70% by mass, based on the total mass of the polyol.

[0026] In addition, the present invention relates to a cured form of the solvent-free reactive adhesive.

[0027] In addition, the present invention relates to a laminate having an adhesive layer comprising the hardened material on a substrate.

[0028] The effects of the invention

[0029] The present invention provides a solvent-free reactive adhesive that maintains excellent film strength and flexibility even after heat resistance and oil resistance tests, and has little effect on elongation at break even when the mixing ratio of the main agent and the hardener changes. Detailed Implementation

[0030] Solvent-free reactive adhesives

[0031] The solvent-free reactive adhesive of the present invention comprises a specific polyisocyanate and a polyol. The polyisocyanate comprises at least (i) a trimethylolpropane adduct of at least one of toluene diisocyanate and diphenylmethane diisocyanate (hereinafter, sometimes referred to as adduct (i)); and (ii) an aromatic polyisocyanate (except for said adduct (i)).

[0032] Furthermore, adduct (i) may be only a trimethylolpropane adduct of toluene diisocyanate or only a trimethylolpropane adduct of diphenylmethane diisocyanate. That is, adduct (i) may be a trimethylolpropane adduct of either toluene diisocyanate or diphenylmethane diisocyanate. Alternatively, adduct (i) may be both a trimethylolpropane adduct of toluene diisocyanate and a trimethylolpropane adduct of diphenylmethane diisocyanate. Thus, adduct (i) may be used alone or in combination with multiple adducts.

[0033] In addition, based on the total mass of the polyisocyanates, the adduct(i) (trimethylolpropane adduct of toluene diisocyanate and trimethylolpropane adduct of diphenylmethane diisocyanate) are included in the range of 40% to 80% by mass.

[0034] Thus, by using a polyol and a specific polyisocyanate containing an aromatic polyisocyanate and an adduct (i) within a specified range, a hardened film with minimal change in elastic modulus can be obtained even when the mixing ratio of the main agent (polyol) and the hardener (polyisocyanate) varies, and excellent flexibility can be consistently maintained. Furthermore, the solvent-free reactive adhesive of the present invention exhibits high film strength and flexibility, as well as excellent heat resistance, oil resistance, adhesion, and a suitable cycle time.

[0035] Therefore, the solvent-free reactive adhesive of the present invention is suitable for use in the fields of automobiles, building materials, ships, and aircraft.

[0036] <Polyisocyanate>

[0037] The polyisocyanate of this invention comprises an aromatic polyisocyanate other than the adduct (i), and the adduct (i) is included in a total range of 40% to 80% by mass based on the total mass of the polyisocyanate. The adduct (i) is typically a viscous solid at room temperature (e.g., 25°C), making it difficult to handle and thus not previously used in solvent-free adhesives. However, by including the adduct (i) in a high proportion of 40% to 80% by mass in the total polyisocyanate, a unique crosslinking mechanism can be formed. Consequently, even when the mixing ratio of the main agent and the hardener varies, changes in the elastic modulus of the hardened film are suppressed, and the resulting hardened film exhibits high flexibility and excellent film strength, heat resistance, and oil resistance.

[0038] The total content of the admixture (i) is preferably in the range of 45% to 75% by mass, more preferably in the range of 50% to 75% by mass, based on the total mass of the polyisocyanate. If the content of the admixture (i) is 45% by mass or more, the breaking stress and elongation at break are superior, and therefore preferred. Furthermore, if the content of the admixture (i) is 75% by mass or less, the shear stress and elongation at break are superior, and therefore preferred.

[0039] Trimethylolpropane adducts of toluene diisocyanate can be used without particular restriction as long as they are reactants of 2,4-toluene diisocyanate and / or 2,6-toluene diisocyanate with trimethylolpropane. Examples of trimethylolpropane adducts of toluene diisocyanate include, for example, "Takenate D103H" manufactured by Mitsui Chemicals Co., Ltd., and "Desmodur L" manufactured by Sumitomo Chemical Bayer Urethane Co., Ltd.

[0040] Trimethylolpropane adducts of diphenylmethane diisocyanate can be used without particular restrictions as long as they are reactants of 4,4'-diphenylmethane diisocyanate and / or 2,4'-diphenylmethane diisocyanate with trimethylolpropane.

[0041] The polyisocyanate contains, in the range of 20% to 60% by mass, a polyisocyanate other than the adduct (i) (hereinafter, sometimes referred to as other polyisocyanates). Other polyisocyanates include at least aromatic polyisocyanates (including, also, modified aromatic polyisocyanates). There are no particular limitations on other polyisocyanates besides aromatic polyisocyanates; for example, aromatic aliphatic polyisocyanates, aliphatic polyisocyanates, and alicyclic polyisocyanates, as well as modified forms thereof, can be used.

[0042] Examples of aromatic polyisocyanates include: diphenylmethane diisocyanate, carbodiimide-modified diphenylmethane diisocyanate, phenyl diisocyanate, toluene diisocyanate, naphthalene diisocyanate, and other aromatic diisocyanates; polymethylene polyphenyl polyisocyanate and other aromatic polyisocyanates.

[0043] As described above, the aromatic polyisocyanates contained in the solvent-free reactive adhesive of the present invention include monomeric isocyanates such as diphenylmethane diisocyanate and polymeric isocyanates such as polymethylene polyphenyl polyisocyanate. Thus, the term "polyisocyanate" in this specification can refer to any compound having two or more isocyanate groups within its molecule, and the configuration of the isocyanate groups is not particularly limited.

[0044] Examples of aromatic aliphatic polyisocyanates include, for example, 1,3-phenylenedimethyl diisocyanate or 1,4-phenylenedimethyl diisocyanate or mixtures thereof, ω,ω'-diisocyanate-1,4-diethylbenzene, 1,3-bis(1-isocyanate-1-methylethyl)benzene or 1,4-bis(1-isocyanate-1-methylethyl)benzene or mixtures thereof.

[0045] Examples of aliphatic polyisocyanates include: trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, 1,2-propylene diisocyanate, 1,2-butylene diisocyanate, 2,3-butylene diisocyanate, 1,3-butylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate or 2,2,4-trimethylhexamethylene diisocyanate, 2,6-diisocyanate methylhexanoate, lysine diisocyanate, dimer acid diisocyanate, and other aliphatic diisocyanates.

[0046] Examples of alicyclic polyisocyanates include: 1,4-cyclohexane diisocyanate, 1,3-cyclohexane diisocyanate, isophorone diisocyanate, 4,4'-methylene bis(cyclohexyl isocyanate), methyl-2,4-cyclohexane diisocyanate, methyl-2,6-cyclohexane diisocyanate, 1,4-bis(isocyanate methyl)cyclohexane, 1,3-bis(isocyanate methyl)cyclohexane, norbornene diisocyanate, and other alicyclic diisocyanates.

[0047] Examples of modifiers for polyisocyanates include urethane-type modifiers, isocyanurate-type modifiers, biuret-type modifiers, and addition modifiers. Other examples include reaction products containing isocyanate groups and urethane bonds, obtained by reacting the polyisocyanate component with a polyol under conditions of excess isocyanate groups. The polyol used to form the polyisocyanate modifier is not particularly limited and can be selected from existing polyols, such as polyester polyols, polyester urethane polyols, polycarbonate polyols, polycaprolactone polyols, polyether polyols, polyether urethane polyols, polyolefin polyols, acrylic polyols, silicone polyols, castor oil-based polyols, and fluorinated polyols.

[0048] These other polyisocyanates can be used alone or in combination of two or more.

[0049] The solvent-free reactive adhesive of the present invention comprises an aromatic polyisocyanate as another polyisocyanate, wherein the aromatic polyisocyanate is preferably at least one selected from the group consisting of diphenylmethane diisocyanate, polymethylene polyphenyl polyisocyanate, and carbodiimide-modified diphenylmethane diisocyanate.

[0050] When the polyisocyanate includes aromatic polyisocyanate, the content of aromatic polyisocyanate is preferably 20% to 60% by mass, more preferably 20% to 50% by mass, and even more preferably 25% to 45% by mass, based on the total mass of the polyisocyanate. If it is within the range described above, the obtained hardened film has better flexibility, coating strength, and heat resistance, and is therefore preferred.

[0051] <Polyols>

[0052] The polyol in this invention forms a strong cross-linked structure through reaction with polyisocyanate, imparting appropriate softness and cohesiveness to the obtained hardened film, and playing a role in conferring excellent coating strength, softness, and heat resistance. The polyol can be any compound having two or more hydroxyl groups within its molecule. In the case of a resin, the hydroxyl groups can be located at the end of the resin, on a side chain, or as a side group.

[0053] Examples of such polyols include: polyether polyols, polyester polyols, polycarbonate polyols, polyolefin polyols, vegetable oil-based polyols, acrylic polyols, or other polyols, and complexes thereof. Additionally, low-molecular-weight polyols, as described later, may be used to adjust the urethane bond concentration in the cured film or to introduce various functional groups.

[0054] The solvent-free reactive adhesive of the present invention contains a polyol that can be an acid-modified product in which some of the hydroxyl groups are modified by acid, or a polyol in which a carboxyl group is introduced by reacting an anhydride, or a polyol in which a urethane bond is introduced by reacting a diisocyanate.

[0055] These polyols can be used alone or in combination of two or more.

[0056] (Polyether polyols)

[0057] Polyether polyols are compounds that have two or more hydroxyl groups and ether bonds within their molecules. Examples of polyether polyols include: polymers or copolymers of polyethylene glycol, polypropylene glycol, poly(ethylene / propylene) glycol, or polytetramethylene glycol, as well as methylene oxides, ethylene oxide, propylene oxide, tetrahydrofuran, etc.; polyether polyols obtained by condensation of hexanediol, methylhexanediol, heptanediol, octanediol, or mixtures thereof; and polyols obtained by adding compounds with at least two active hydrogen groups, such as low molecular weight polyols, aliphatic amines, aromatic amines, alkanolamines, or bisphenols, to methylene oxides, ethylene oxide, propylene oxide, butane oxide, tetrahydrofuran, or polyoxytetramethylene oxide, etc.

[0058] Examples of such low-molecular-weight polyols include: ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, pentylene glycol, hexanediol, octanediol, nonanediol, dipropylene glycol, diethylene glycol, triethylene glycol, 3-methyl-1,5-pentanediol, 2-butyl-2-ethyl-1,3-propanediol, 2-ethyl-1,3-hexanediol, 2-methyl-1,8-octanediol, polyoxyethylene glycol (addition molar number less than 10), polyoxypropylene glycol (addition molar number less than 10), cyclohexanediol, cyclohexanediethanol, tricyclodecanediethanol, cyclopentadienediethanol, and dimer. diol), bisphenol B, N,N-bis(2-hydroxypropyl)aniline, dihydroxymethylacetic acid, dihydroxymethylpropionic acid, dihydroxymethylbutyric acid, 2,2-dihydroxymethylbutyric acid, 2,2-dihydroxymethylvaleric acid, dihydroxysuccinic acid, dihydroxypropionic acid, dihydroxybenzoic acid and other difunctional low molecular weight polyols.

[0059] Trimethylolethane, Trimethylolpropane, 1,1,1-Trimethylolbutane, 1,2,3-Butanetriol, 1,2,4-Butanetriol, 1,2,6-Butanetriol, Trimethylolbutene, Trimethylolpentene, Trimethylolhexene, Trimethylolheptenene, Trimethyloloctene, Trimethylolnonene, Trimethyloldecene, Trimethylolundecene, Trimethyloldodecene, Trimethyloltridedecene, Trimethylolpentadene, Trimethylolhexadecene, Trimethylolheptadecene, Trimethyloloctadecaene, 1,1, 1-Tris(hydroxymethyl)-2-methylhexane, 1,1,1-tris(hydroxymethyl)-3-methylhexane, 1,1,1-tris(hydroxymethyl)-2-ethylhexane, 1,1,1-tris(hydroxymethyl)-3-ethylhexane, 1,2,3-octanetriol, 1,3,7-octanetriol, 3,7-dimethyl-1,2,3-octanetriol, 1,1,1-tris(hydroxymethyl)decane, 1,2,10-decanetriol, 1,1,1-tris(hydroxymethyl)isoheptadecane, 1,1,1-tris(hydroxymethyl)secbutane, 1,1,1-Tris(hydroxymethyl)-tert-pentane, 1,1,1-Tris(hydroxymethyl)-tert-nonane, 1,1,1-Tris(hydroxymethyl)-tert-tridecane, 1,1,1-Tris(hydroxymethyl)-tert-heptadecane, 1,1,1-Tris(hydroxymethyl)-2-methylhexane, 1,1,1-Tris(hydroxymethyl)-3-methylhexane, 1,1,1-Tris(hydroxymethyl)-2-ethylhexane, 1,1,1-Tris(hydroxymethyl)-3-ethylhexane, 1,1,1-Tris(hydroxymethyl)isoheptadecane, 1,2,3,4-Butanetetrol, Quaternary ammonium chloride Pentylenetetroxide, dipenta ...

[0060] Examples of aliphatic amine compounds include ethylenediamine, triethylenetetramine, diethylenetriamine, and triaminopropane. Examples of aromatic amine compounds include toluenediamine and diphenylmethane-4,4-diamine. Examples of alkanolamines include ethanolamine and diethanolamine. Examples of bisphenols include bisphenol B, bisphenol BP, bisphenol C, bisphenol A, bisphenol E, and bisphenol F.

[0061] (Polyester polyols)

[0062] Examples of polyester polyols include polyester polyols obtained by condensing the aforementioned low molecular weight polyols with diacid components, and lactone-based polyester polyols obtained by ring-opening polymerization of cyclic ester compounds such as lactones.

[0063] Examples of such dicarboxylic acid components include: terephthalic acid, adipic acid, azelaic acid, dimer acid, hydrogenated dimer acid, phthalic anhydride, isophthalic acid, trimellitic acid, glutaric acid, pimelic acid, octanoic acid, sebacic acid, and other aliphatic or aromatic dicarboxylic acids and their anhydrides.

[0064] Examples of lactones include ε-caprolactone, poly(β-methyl-γ-valerolactone), and polyvalerolactone.

[0065] (Polycarbonate polyols)

[0066] Examples of polycarbonate polyols include the reaction products of the aforementioned low molecular weight polyols with carbonate compounds such as dialkyl carbonate, alkylene carbonate, and diaryl carbonate.

[0067] Examples of dialkyl carbonates include dimethyl carbonate and diethyl carbonate. Examples of alkylene carbonates include ethylene carbonate. Examples of diaryl carbonates include diphenyl carbonate.

[0068] (Polyolefin polyols)

[0069] Examples of polyolefin polyols include: hydroxyl-containing polybutadiene, hydrogenated hydroxyl-containing polybutadiene, hydroxyl-containing polyisoprene, hydrogenated hydroxyl-containing polyisoprene, hydroxyl-containing chlorinated polypropylene, and hydroxyl-containing chlorinated polyethylene.

[0070] (Vegetable oil-based polyols)

[0071] Examples of plant-based polyols include those made from plant-derived castor oil, dimer acid, or soybean oil.

[0072] As mentioned above, these polyols can be acid-modified products in which some of the hydroxyl groups are modified by acid, or polyols in which carboxyl groups are introduced by reacting acid anhydrides, or polyols in which urethane bonds are introduced by reacting isocyanates.

[0073] Examples of such acid anhydrides include: pyromellitic anhydride, hexabenzoic anhydride, trimellitic anhydride, and trimellitic anhydride esters. Examples of trimellitic anhydride esters include ester compounds obtained by esterification of alkylene glycols or alkane triols with 2 to 30 carbon atoms using trimellitic anhydride. More specifically, examples of trimellitic anhydride esters include ethylene glycol dihydrotriphenyltriester and propylene glycol dihydrotriphenyltriester.

[0074] Examples of such diisocyanates include: 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, phenyl dimethyl diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate, 1,5-naphthalene diisocyanate, hexamethylene diisocyanate, and hydrogenated diphenylmethane diisocyanate.

[0075] Furthermore, the solvent-free reactive adhesive of the present invention preferably comprises a polyol having urethane bonds. Examples of such polyols having urethane bonds include those described above that have been introduced by reacting diisocyanates, as well as block polymers formed by linking different polymer types together.

[0076] The polyol having urethane bonds is preferably in which hydroxyl groups are locally present in the terminal region of the resin. The presence of hydroxyl groups in the terminal region of the resin results in excellent flexibility of the cured film, and is therefore preferred.

[0077] As a polyol having hydroxyl groups at the end of the resin and having urethane bonds, it can be obtained, for example, by reacting the polyisocyanate and the polyol in such a way that the molar equivalent ratio of isocyanate groups to hydroxyl groups (number of moles of NCO / number of moles of OH) is less than 1.

[0078] Among these, the polyol is preferably at least one selected from the group consisting of polyether polyols and polycarbonate polyols, more preferably polycarbonate polyols, and even more preferably polycarbonate polyols (wherein, they do not have urethane bonds) and polyols having urethane bonds.

[0079] When the polyol contains polycarbonate polyol, the content of polycarbonate polyol is preferably 30% by mass or more, more preferably 50% by mass or more, and preferably 100% by mass or less, more preferably 90% by mass or less, and even more preferably 70% by mass or less, based on the total mass of the polyol.

[0080] When the polyol contains polyols with urethane bonds, the content of polyols with urethane bonds is preferably 30% to 70% by mass, based on the total mass of the polyols. If the content of polyols with urethane bonds is 30% by mass or more, the foaming properties of the obtained cured film are superior. If the content of polyols with urethane bonds is 70% by mass or less, the usable time, described later, is superior.

[0081] The average molecular weight of the polycarbonate polyols without urethane bonds is preferably 500 or more but less than 5,000, more preferably 700 or more but less than 3,500.

[0082] The polyol having urethane bonds preferably has a weight average molecular weight of 3,000 to 200,000. If the weight average molecular weight is 3,000 or higher, the obtained hardened film has better flexibility; if the weight average molecular weight is 200,000 or lower, the viscosity is easier to adjust.

[0083] The hydroxyl value of the polyol containing the carbamate bond is preferably 50 mg KOH / g to 500 mg KOH / g, more preferably 100 mg KOH / g to 300 mg KOH / g. If it is 50 mg KOH / g to 500 mg KOH / g, the resulting hardened film has better adhesion, flexibility, and heat resistance, and is therefore preferred.

[0084] <Preparation of Solvent-Free Reactive Adhesives>

[0085] The solvent-free reactive adhesive of the present invention is a two-component liquid-curing urethane-based solvent-free adhesive obtained by blending the polyisocyanate and polyol. The preferred blending ratio of polyol to polyisocyanate is a molar equivalent ratio [NCO / OH] of all isocyanate groups contained in the isocyanate to all hydroxyl groups contained in the polyol in the range of 0.8 to 2.5, more preferably in the range of 1.0 to 2.0.

[0086] Furthermore, in the case of mass ratio, the ratio of polyisocyanate to the total mass of polyol is preferably 20% to 100% by mass.

[0087] The polyisocyanate content in the solvent-free reactive adhesive of the present invention is preferably in the range of 20% to 100% by mass, based on the total mass of the polyols. If it falls within this range, the resulting cured film exhibits superior coating strength, flexibility, and heat resistance, and is therefore preferred.

[0088] The viscosity of the solvent-free reactive adhesive of the present invention is preferably 10 Pa·s to 1,000 Pa·s at room temperature (25°C), and more preferably 50 Pa·s to 750 Pa·s.

[0089] If the viscosity is 10 Pa·s or higher, the adhesive exhibits excellent initial cohesiveness and is therefore preferred. If the viscosity is 1,000 Pa·s or lower, the adhesive exhibits excellent coatability and is therefore preferred.

[0090] [Other ingredients]

[0091] The solvent-free reactive adhesive of the present invention may further comprise existing additives such as reaction accelerators, silane coupling agents, phosphoric acid or phosphoric acid derivatives, leveling agents or defoamers, 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.

[0092] Examples of reaction promoters include: metal catalysts such as dibutyltin diacetate, dibutyltin dilaurate, dioctyltin dilaurate, and dibutyltin dimaleate; tertiary amines such as 1,8-diazabicyclo(5,4,0)undecene-7, 1,5-diazabicyclo(4,3,0)nonene-5, and 6-dibutylamino-1,8-diazabicyclo(5,4,0)undecene-7; and reactive tertiary amines such as triethanolamine.

[0093] The amount of reaction promoter prepared is based on the total mass of polyisocyanate, preferably 0.005% to 5% by mass.

[0094] Examples of silane coupling agents include: vinyltrimethoxysilane, vinyltriethoxysilane, and other vinyl-containing trialkoxysilanes; 3-aminopropyltriethoxysilane, N-(2-aminoethyl)3-aminopropyltrimethoxysilane, and other amino-containing trialkoxysilanes; 3-glycidoxypropyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, and other glycidyl groups; 3-isocyanate propyltriethoxysilane and other isocyanate groups; 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyltrimethoxysilane, and other mercapto groups.

[0095] The amount of silane coupling agent prepared is based on the total mass of polyisocyanate, and is preferably 0.05% to 10% by mass.

[0096] Phosphoric acid or its derivatives may contain at least one free oxyacid, such as hypophosphorous acid, phosphorous acid, orthophosphoric acid, hypophosphoric acid, etc.; and condensed phosphoric acid such as metaphosphoric acid, pyrophosphoric acid, tripolyphosphoric acid, polyphosphoric acid, and ultraphosphoric acid. Furthermore, phosphoric acid derivatives may include those obtained by partially esterifying the phosphoric acid with an alcohol while retaining at least one free oxyacid. Examples of such alcohols include aliphatic alcohols such as methanol, ethanol, ethylene glycol, and glycerol; and aromatic alcohols such as phenol, xylenol, hydroquinone, catechol, and phloroglucinol.

[0097] The amount of phosphoric acid and its derivatives is based on the total mass of polyisocyanate, and is preferably 0.005% to 5% by mass.

[0098] Examples of leveling agents include: polyether-modified polydimethylsiloxane, polyester-modified polydimethylsiloxane, aralkyl-modified polymethylalkylsiloxane, polyester-modified hydroxyl-containing polydimethylsiloxane, polyether ester-modified hydroxyl-containing polydimethylsiloxane, acrylic copolymers, methacrylic copolymers, polyether-modified polymethylalkylsiloxane, alkyl acrylate copolymers, alkyl methacrylate copolymers, and lecithin.

[0099] Existing defoamers include silicone resins, silicone solutions, copolymers of alkyl vinyl ethers with alkyl acrylates and alkyl methacrylates.

[0100] <Laminated bodies, hardened materials>

[0101] The cured product of the present invention is obtained by curing the solvent-free reactive adhesive of the present invention, which can be obtained by mixing the polyisocyanate, polyol and other components as needed using existing methods to carry out a urethane crosslinking reaction.

[0102] Furthermore, the laminate of the present invention has an adhesive layer comprising the cured material on a substrate. The manufacturing method of the laminate is not particularly limited; for example, a solvent-free reactive adhesive is applied to one side of a substrate, and then another substrate is overlapped on the uncured adhesive surface. The laminate is then heat-treated at approximately 20°C to 150°C to cure the solvent-free reactive adhesive, thereby obtaining the laminate. The thickness of the cured adhesive layer is preferably 0.1 μm to 300 mm.

[0103] The solvent-free reactive adhesive of the present invention can be used for bonding between a variety of substrates. Preferred substrates include, for example, metals such as aluminum, thermoplastic polymers such as polyethylene, polypropylene, polyurethane, polyacrylate, and polycarbonate and copolymers thereof, thermosetting polymers such as vulcanized rubber, urea-formaldehyde foam, melamine resin, wood, carbon fiber reinforced plastics, glass fiber reinforced plastics, and other fiber-reinforced plastics. The substrates bonded via the adhesive layer may be the same or different.

[0104] The solvent-free reactive adhesive of the present invention has excellent film strength, flexibility, heat resistance, oil resistance, adhesion, and moderate cycle time. Laminates using the adhesive are effectively used as structural components (panel parts, frame parts, wheel and axle parts, etc.) for transportation equipment such as automobiles, building materials, ships, and aircraft.

[0105] Example

[0106] The present invention will be described in more detail below through embodiments, but these embodiments do not limit the scope of the invention in any way. Furthermore, unless otherwise specified, "parts" in the embodiments refers to "parts by mass".

[0107] [Weight-average molecular weight (Mw)]

[0108] The weight-average molecular weight (Mw) of the resin was determined by gel permeation chromatography (GPC) as a conversion value based on standard polystyrene. The determination was performed using a GPC-8020 (product name, manufactured by Tosoh Corporation) as the GPC apparatus, tetrahydrofuran as the eluent, and three TSK gelSuper HM-M (trade name, manufactured by Tosoh Corporation) columns connected in series as a column. The determination was carried out at a flow rate of 0.6 ml / min, an injection volume of 10 μl, and a column temperature of 40°C.

[0109] The following are abbreviations for the compounds used in this specification.

[0110] <Polyisocyanate>

[0111] • TDI-TMP adduct: Obtained by removing ethyl acetate from the trimethylolpropane adduct of toluene diisocyanate (trade name "Takenate D103H", ethyl acetate solution (solid content concentration 75% by mass), manufactured by Mitsui Chemicals Co., Ltd.) under reduced pressure.

[0112] HDI: Hexamethylene diisocyanate

[0113] MDI: A mixture of 2,4'-diphenylmethane diisocyanate and 4,4'-diphenylmethane diisocyanate, traded under the name "Lupranate MI", manufactured by BASF Inoac Polyurethane.

[0114] • Carbodiimide-modified MDI: Trade name "Lupranate MM103", manufactured by BASF INOAC Polyurethane.

[0115] • Polymer MDI: Polymethylene polyphenyl polyisocyanate, trade name "Lupranate M5S", manufactured by BASF Inoac Polyurethane.

[0116] <Polyols>

[0117] • T5651: A difunctional polycarbonate polyol with a quantity average molecular weight of 1,000 and a hydroxyl value of 110 mg KOH / g. Trade name: "DURANOL T5651", manufactured by Asahi Kasei Corporation.

[0118] • T5650E: A difunctional polycarbonate polyol with a quantity average molecular weight of 500 and a hydroxyl value of 220 mgKOH / g. Trade name: "DURANOL T5650E", manufactured by Asahi Kasei Corporation.

[0119] P-1000: Difunctional polypropylene glycol, quantity average molecular weight 1,000, hydroxyl value 56.1 mgKOH / g, manufactured by Adeka.

[0120] P-400: Difunctional polypropylene glycol, quantity average molecular weight 400, hydroxyl value 280 mgKOH / g, manufactured by Adeka.

[0121] PTMG-1000SN: Difunctional polytetramethylene ether glycol, quantity average molecular weight 1,000, hydroxyl value 112 mgKOH / g, manufactured by Hodogaya Chemical Industry Co., Ltd.

[0122] GI-1000: Hydrogenated polybutadiene glycol, quantity average molecular weight 1,400, hydroxyl value 75 mg KOH / g, manufactured by Nippon Soda Co., Ltd.

[0123] ·URIC HF2009: A difunctional castor oil polyol with a quantity average molecular weight of 2,640 and a hydroxyl value of 41.5 mg KOH / g, manufactured by Ito Oil Co., Ltd.

[0124] NS-2400: A difunctional polyester polyol with a quantity average molecular weight of 2000 and a hydroxyl value of 56 mgKOH / g. It is manufactured by Adeka Newace under the trade name "Adeka Newace NS-2400".

[0125] <Low molecular weight polyols>

[0126] ·1,3-Propanediol (molecular weight: 76.1)

[0127] <Examples of Polyisocyanate Manufacturing>

[0128] [Preparation of the trimethylolpropane adduct of diphenylmethane diisocyanate (MDI-TMP adduct)]

[0129] In a reaction vessel including a nitrogen inlet tube, a stirrer, a thermometer, and a reflux condenser, 100.0 parts of MDI, 10.0 parts of trimethylolpropane, and 30.0 parts of ethyl acetate were charged. After uniform stirring, the mixture was reacted at 90°C for 3 hours under a nitrogen atmosphere. Subsequently, all ethyl acetate was removed under reduced pressure, and unreacted MDI was removed using a conventional thin-film distillation method, thereby obtaining the trimethylolpropane adduct of diphenylmethane diisocyanate (MDI-TMP adduct). The weight-average molecular weight of the obtained MDI-TMP adduct was 900.

[0130] [Manufacturing of Polyisocyanate A]

[0131] 100 parts of PTMG-1000SN and 150 parts of MDI were loaded into a reaction vessel including a nitrogen inlet pipe, a stirrer, a thermometer, and a reflux condenser. The reaction was carried out at 80°C for 4 hours under a nitrogen atmosphere to obtain aromatic polyisocyanate A.

[0132] <Example of manufacturing polyol B with carbamate bonds>

[0133] [Manufacturing of Polyol B1]

[0134] 100.0 parts of T5651, 19.9 parts of isophorone diisocyanate, and 0.02 parts of dibutyltin dilaurate as a catalyst were charged into a reaction vessel including a nitrogen inlet pipe, a stirrer, a thermometer, and a reflux condenser. After uniform stirring, the mixture was reacted at 100°C for 5 hours under a nitrogen atmosphere to obtain polyol B1 with urethane bonds. The weight average molecular weight of the obtained polyol B1 was 15,000.

[0135] [Manufacturing of polyol B2]

[0136] 100.0 parts of T5651 and 21.3 parts of MDI were charged into a reaction vessel including a nitrogen inlet pipe, a stirrer, a thermometer, and a reflux condenser. After uniform stirring, the mixture was reacted at 100°C for 5 hours under a nitrogen atmosphere to obtain polyol B2 with urethane bonds. The weight average molecular weight of the obtained polyol B2 was 11,000.

[0137] [Manufacturing of polyol B3]

[0138] A reaction vessel, including a nitrogen inlet pipe, a stirrer, a thermometer, and a reflux condenser, was loaded with 50.0 parts of P-1000, 50.0 parts of PTMG-1000SN, 19.9 parts of isophorone diisocyanate, and 0.02 parts of dibutyltin dilaurate as a catalyst. After uniform stirring, the mixture was reacted at 100°C for 5 hours under a nitrogen atmosphere to obtain polyol B3 with urethane bonds. The weight average molecular weight of the obtained polyol B3 was 15,000.

[0139] [Manufacturing of polyol B4]

[0140] A reaction vessel, including a nitrogen inlet pipe, a stirrer, a thermometer, and a reflux condenser, was loaded with 50.0 parts of GI-1000, 50.0 parts of PTMG-1000SN, 16.2 parts of isophorone diisocyanate, and 0.02 parts of dibutyltin dilaurate as a catalyst. After uniform stirring, the mixture was reacted at 100°C for 5 hours under a nitrogen atmosphere to obtain polyol B4 with urethane bonds. The weight average molecular weight of the obtained polyol B4 was 15,000.

[0141] [Manufacturing of polyol B5]

[0142] A reaction vessel, including a nitrogen inlet pipe, a stirrer, a thermometer, and a reflux condenser, was loaded with 50.0 parts of URICHF2009, 50.0 parts of PTMG-1000SN, 12.5 parts of isophorone diisocyanate, and 0.02 parts of dibutyltin dilaurate as a catalyst. After uniform stirring, the mixture was reacted at 100°C for 5 hours under a nitrogen atmosphere to obtain polyol B5 with urethane bonds. The weight average molecular weight of the obtained polyol B5 was 15,000.

[0143] [Manufacturing of polyol B6]

[0144] A reaction vessel, including a nitrogen inlet pipe, a stirrer, a thermometer, and a reflux condenser, was loaded with 50.0 parts of P-1000, 50.0 parts of NS-2400, 14.2 parts of isophorone diisocyanate, and 0.02 parts of dibutyltin dilaurate as a catalyst. After uniform stirring, the mixture was reacted at 100°C for 5 hours under a nitrogen atmosphere to obtain polyol B6 with urethane bonds. The weight average molecular weight of the obtained polyol B6 was 15,000.

[0145] <Preparation of Adhesives>

[0146] [Example 1]

[0147] 40.0 parts of TDI-TMP adduct and 60.0 parts of MDI were stirred and degassed at 100°C to obtain polyisocyanate. Separately, 194.4 parts of T5651 were added to 83.3 parts of polyol B1 containing urethane bonds, and the mixture was stirred and degassed at 100°C to obtain polyol. The obtained polyisocyanate and polyol were then mixed at room temperature (25°C) to prepare a solvent-free adhesive.

[0148] [Examples 2 to 48, Reference Examples 1 to 2, and Comparative Examples 1 to 12]

[0149] Except for changing the formulation to that shown in Tables 1 to 4, the adhesives of Examples 2 to 48, Reference Examples 1 to 2, and Comparative Examples 1 to 12 were prepared by performing the same operations as in Example 1.

[0150] <Evaluation of Adhesives>

[0151] The adhesives prepared in the Examples and Comparative Examples were evaluated as follows. The evaluation results are recorded in Tables 1 to 4. In addition, in Comparative Examples 3, 4, 11, and 12, the polyisocyanate had a high viscosity and was difficult to mix with polyols, so it could not be used as a solvent-free adhesive. Therefore, the following evaluation was not performed.

[0152] [Shear adhesion]

[0153] Each adhesive was applied to a stainless steel substrate (100mm long, 25mm wide, 2mm thick) with a width of 25mm, a length of 10mm, and a thickness of 0.1mm. This substrate was then bonded to a carbon fiber reinforced plastic substrate (100mm long, 25mm wide, 2mm thick). The substrate was cured at 80°C for one day while maintaining a thickness of 0.1mm to obtain test pieces. The shear bond strength of the obtained test pieces was measured using a tensile testing machine at a temperature of 25°C and a relative humidity of 50% at a tensile speed of 1mm / min. The evaluation criteria were as follows.

[0154] (Evaluation Criteria)

[0155] A: Shear bond strength is above 7 MPa (good)

[0156] B: Shear bond strength of 5 MPa or higher but less than 7 MPa (suitable for use)

[0157] C: Shear bond strength less than 5MPa (unusable)

[0158] [Break stress, elongation at break]

[0159] The adhesives were filled into a 2mm thick sheet mold frame, the surface was finished, and after curing at 80°C for 1 day, a dumbbell-shaped test piece for evaluation was produced by stamping using a No. 3 dumbbell mold. Tensile tests were performed using the dumbbell-shaped test piece at a tensile speed of 50mm / min, and the breaking stress (MPa) and elongation at break (%) were measured. Judgment was made according to the following criteria.

[0160] (Evaluation criteria for fracture stress)

[0161] A: Fracture stress is above 25 MPa (good)

[0162] B: Fracture stress is above 20MPa but less than 25MPa (suitable for use)

[0163] C: Fracture stress is less than 20 MPa (unusable)

[0164] (Evaluation criteria for elongation at break)

[0165] A: Elongation at break is above 250% (Good)

[0166] B: Elongation at break is 200% or more but less than 250% (suitable for use)

[0167] C: Elongation at break is less than 200% (unusable)

[0168] [Heat resistance at 100℃]

[0169] Dumbbell-shaped test pieces were prepared in the same manner as those described for [fracture stress and elongation at break]. After heat-treating the dumbbell pieces at 100°C for 500 hours, tensile tests were performed in the same manner as those for [fracture stress and elongation at break], and the fracture stress (MPa) and elongation at break (%) were measured. The rate of change of the test pieces before and after the test was calculated, and the results were judged according to the following criteria.

[0170] (Evaluation criteria for the rate of change of fracture stress)

[0171] A: The rate of change is less than 30% (good).

[0172] B: Change rate of 30% or more but less than 50% (can be used)

[0173] C: Change rate exceeding 50% (unusable)

[0174] (Evaluation criteria for the rate of change of elongation at break)

[0175] A: The rate of change is less than 30% (good).

[0176] B: Change rate of 30% or more but less than 50% (can be used)

[0177] C: Change rate exceeding 50% (unusable)

[0178] [Oil resistance at 100℃]

[0179] Dumbbell-shaped test pieces were prepared in the same manner as those described for [fracture stress and elongation at break]. After immersing the dumbbell-shaped pieces in automatic lubricating oil at 100°C for 100 hours, tensile tests were performed in the same manner as those for [fracture stress and elongation at break], and the fracture stress (MPa) and elongation at break (%) were measured. The rate of change of the test pieces before and after the test was calculated, and the results were judged according to the following criteria.

[0180] (Evaluation criteria for the rate of change of fracture stress)

[0181] A: The rate of change is less than 30% (good).

[0182] B: Change rate of 30% or more but less than 50% (can be used)

[0183] C: Change rate exceeding 50% (unusable)

[0184] (Evaluation criteria for the rate of change of elongation at break)

[0185] A: The rate of change is less than 30% (good).

[0186] B: Change rate of 30% or more but less than 50% (can be used)

[0187] C: Change rate exceeding 50% (unusable)

[0188] [Foaming property]

[0189] Prepare dumbbell-shaped test pieces in the same manner as described above for [fracture stress and elongation at break]. Visually observe the surface and interior of the test pieces for any signs of foaming, and make a judgment based on the following criteria.

[0190] A: No foaming observed (good)

[0191] B: One to two bubbles were observed (usable).

[0192] C: More than 3 bubbles were observed (unusable)

[0193] [Availability Time]

[0194] After mixing polyisocyanate with polyol, the time until the fluidity is significantly lost is observed, and the following criteria are used to determine the outcome.

[0195] A: Usable time is over 15 minutes (good)

[0196] B: Usable time is more than 10 minutes but less than 15 minutes (can be used)

[0197] C: Less than 10 minutes of usable time remaining (cannot be used)

[0198] [Evaluation Criteria for Decreased Elongation at Break]

[0199] For examples where only the ratio of polyisocyanate to polyol differs (e.g., Example 1 and Example 2), the evaluation results of the elongation at break are compared and determined according to the following criteria.

[0200] A: The evaluation results for elongation at break are the same (good).

[0201] C: The evaluation results for elongation at break are different (unusable)

[0202] [Table 1]

[0203]

[0204]

[0205]

[0206] [Table 4]

[0207] Table 4

[0208]

[0209] The solvent-free reactive adhesive of the present invention exhibits good adhesive strength and excellent film strength (tensile stress) and flexibility (elongation at break), maintaining excellent tensile stress and elongation at break even after heat and oil resistance tests. Furthermore, the elongation at break of the adhesive of the present invention remains stable even when the mixing ratio of the main agent and the hardener changes. In addition, foaming is suppressed in the adhesive of the present invention, resulting in a suitable cycle time and good pot life.

[0210] On the other hand, the comparative adhesive exhibited unstable elongation at break when the mixing ratio of the main agent and the hardener changed. Furthermore, the comparative adhesive failed to balance fracture stress and flexibility, and exhibited poor heat resistance and oil resistance.

Claims

1. A solvent-free reactive adhesive comprising a polyisocyanate and a polyol, wherein the polyisocyanate comprises a trimethylolpropane adduct of at least one of toluene diisocyanate and diphenylmethane diisocyanate, and an aromatic polyisocyanate other than the trimethylolpropane adduct, wherein the solvent-free reactive adhesive, Based on the total mass of the polyisocyanates, the range of 40% to 80% by mass includes the trimethylolpropane adduct of toluene diisocyanate and the trimethylolpropane adduct of diphenylmethane diisocyanate. The polyols mentioned therein are selected from polycarbonate polyols without urethane bonds, polycarbonate polyols without urethane bonds and polyols with urethane bonds, polyolefin polyols and polyols with urethane bonds, or vegetable oil-based polyols and polyols with urethane bonds.

2. The solvent-free reactive adhesive according to claim 1, wherein, The aromatic polyisocyanate comprises at least one selected from the group consisting of diphenylmethane diisocyanate, polymethylene polyphenyl polyisocyanate, and carbodiimide-modified diphenylmethane diisocyanate.

3. The solvent-free reactive adhesive according to claim 1 or 2, wherein, Based on the total mass of the polyisocyanate, the aromatic polyisocyanate is included in the range of 20% to 60% by mass.

4. The solvent-free reactive adhesive according to claim 1 or 2, wherein, Based on the total mass of the polyisocyanates, the range of 45% to 75% by mass includes the trimethylolpropane adduct of the toluene diisocyanate and the trimethylolpropane adduct of the diphenylmethane diisocyanate.

5. The solvent-free reactive adhesive according to claim 1, wherein, Based on the total mass of the polyols, the polyols having urethane bonds are included in the range of 30% to 70% by mass.

6. A cured product, which is a cured product of the solvent-free reactive adhesive as described in any one of claims 1 to 5.

7. A laminate having an adhesive layer comprising the hardened material as claimed in claim 6 on a substrate.

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