Adhesive set, structure, and method for manufacturing the same.

Abstract

To provide an adhesive set capable of forming a cured product of an adhesive composition that has sufficient shear strength and is less prone to surface fracture of the substrate in a high-temperature environment. [Solution] An adhesive set comprising a main component and a curing agent is disclosed. The main component contains a urethane prepolymer. The curing agent contains a polyol having a glass transition temperature of 0°C or lower. At least one of the main component and the curing agent contains a filler containing calcium carbonate. The average hydroxyl value of the polyol is 50 mgKOH / g or less. The average number of hydroxyl groups of the polyol is 2.5 or less. The content of the polyol having a glass transition temperature of 0°C or lower is 20% by mass or more based on the total amount of the main component and curing agent. The content of calcium carbonate is 10% by mass or more based on the total amount of the main component and curing agent.

Description

Technical Field

[0001] The present disclosure relates to an adhesive set, a structure, and a method for producing the same.

Background Art

[0002] Steel sheets are generally used for interior and exterior components such as automobile bodies, front doors, rear doors, back doors, front bumpers, rear bumpers, and rocker moldings. In order to meet the recent demand for improved fuel efficiency, weight reduction is required. For this reason, plastic materials such as polypropylene are increasingly used in place of steel sheets as interior and exterior components for automobiles. Since plastic materials such as polypropylene have lower strength than steel sheets, it is common to add talc, glass filler, etc. to improve strength.

[0003] Urethane-based adhesive compositions have been proposed as adhesives for bonding plastic automotive components such as polypropylene to each other. Urethane-based adhesive compositions include a one-component curable adhesive called a moisture-curable type that cures by moisture in the air, and an adhesive set composed of a main agent and a curing agent. Two-component curable adhesives obtained by mixing a main agent and a curing agent are known. A two-component curable urethane-based adhesive composition cures as a crosslinking reaction proceeds between an isocyanate group (NCO group) component contained in the main agent and a hydroxyl group (OH group) contained in the curing agent. Among these, from the viewpoint of workability in the bonding process, two-component curable adhesives that can sufficiently secure pot life (the time until the paint starts to cure due to a chemical reaction or the like in multi-component paints) and enable fast curing tend to be preferred.

[0004] Generally, polypropylene substrates have low surface polarity and are difficult to bond. Therefore, surface treatments are performed to introduce polar groups to the substrate surface to facilitate bonding. Examples of surface treatments include corona treatment, flame treatment, and plasma treatment. Furthermore, since it is difficult to directly apply urethane adhesive compositions to bond surface-treated polypropylene substrates to each other, it is common practice to apply a primer treatment to each polypropylene substrate as a pretreatment before applying the urethane adhesive composition. However, in recent years, from the viewpoint of simplifying processes and improving the working environment, there has been a demand for improved adhesion of urethane adhesive compositions even without primer treatment (i.e., non-primer adhesion).

[0005] For example, Patent Document 1 discloses a two-component curing urethane adhesive composition in which a main component containing a urethane prepolymer and an isocyanate silane compound is mixed with a curing agent containing polybutadiene diol during the work process. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2014-077094 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] Incidentally, our inventors have found that when a structure in which substrates are bonded together via an adhesive layer containing a cured product of a conventional adhesive composition is subjected to shear stress in a high-temperature environment (e.g., 090°C), surface fracture of the substrate (substrate cohesive failure) may occur. When surface fracture of the substrate occurs, problems such as unstable structural strength and inability to reuse the substrate arise.

[0008] Therefore, the main objective of this disclosure is to provide an adhesive set capable of forming a cured product of an adhesive composition that has sufficient shear strength and is less prone to surface fracture of the substrate in a high-temperature environment. [Means for solving the problem]

[0009] It is presumed that surface fracture of a substrate occurs when shear stress is applied to the substrate, causing stress to concentrate on the substrate surface. From the viewpoint of mitigating stress concentration on the substrate surface, the inventors investigated how to lower the storage modulus of a cured adhesive composition in a high-temperature environment (for example, to 1.0 MPa or less). They found that by using a predetermined amount of a predetermined polyol as the polyol in the curing agent, it is possible to lower the storage modulus of a substrate in a high-temperature environment. Further investigation by the inventors revealed that by using a predetermined amount of calcium carbonate as a filler in such an adhesive composition, it is possible to lower the storage modulus of a substrate while improving the shear strength in a high-temperature environment, thus completing the present invention.

[0010] One aspect of this disclosure relates to an adhesive set. The adhesive set comprises a main component and a curing agent. The main component contains a urethane prepolymer, and the curing agent contains a polyol having a glass transition temperature of 0°C or lower. At least one of the main component and the curing agent contains a filler containing calcium carbonate. The average hydroxyl value of the polyol is 50 mgKOH / g or less. The average number of hydroxyl groups of the polyol is 2.5 or less. The content of the polyol having a glass transition temperature of 0°C or lower is 20% by mass or more based on the total amount of the main component and curing agent. The content of calcium carbonate is 10% by mass or more based on the total amount of the main component and curing agent. The cured product of an adhesive composition prepared using such an adhesive set may have sufficient shear strength and be less prone to substrate surface fracture.

[0011] By using a predetermined amount of a predetermined polyol as the polyol in the curing agent, it is possible to lower the storage modulus of the cured adhesive composition in a high-temperature environment. Furthermore, by including a filler containing a predetermined amount of calcium carbonate in at least one of the main component and the curing agent, it is possible to improve the shear strength while lowering the storage modulus of the cured adhesive composition. The reason for the improvement in shear strength is not entirely clear, but the inventors believe that when calcium carbonate is used compared to other mineral-based fillers, the increase in elastic modulus is suppressed, and stress concentration on the substrate surface is mitigated, making it less likely for substrate surface fracture to occur at low strength.

[0012] The storage modulus of the cured product at 90°C after curing the adhesive composition containing the main component and the curing agent at 23°C for 72 hours may be 1.0 MPa or less.

[0013] The calcium carbonate may be surface-treated calcium carbonate, which has been treated with fatty acids or the like. Surface-treated calcium carbonate tends to have an even greater shear strength in high-temperature environments.

[0014] Another aspect of this disclosure relates to a structure comprising a first substrate, a second substrate, and an adhesive layer that bonds the first and second substrates together. The adhesive layer contains a cured product of an adhesive composition comprising the main agent and curing agent in the adhesive set described above.

[0015] Another aspect of this disclosure relates to a method for manufacturing a structure. The method for manufacturing the structure comprises the step of bonding a first substrate and a second substrate via an adhesive composition comprising a main agent and a curing agent.

[0016] This disclosure includes the following: [1] An adhesive set comprising a main component and a hardener, The main component contains a urethane prepolymer, The curing agent contains a polyol having a glass transition temperature of 0°C or lower, At least one of the main agent and the curing agent contains a filler including calcium carbonate, the average hydroxyl value of the polyol is 50 mgKOH / g or less, the average number of hydroxyl groups of the polyol is 2.5 or less, the content of the polyol having a glass transition temperature of 0°C or lower is 20 mass% or more based on the total amount of the main agent and the curing agent, the content of the calcium carbonate is 10 mass% or more based on the total amount of the main agent and the curing agent, An adhesive set. [2] When an adhesive composition containing the main agent and the curing agent is cured under conditions of 23°C for 72 hours, the storage modulus of the cured product at 90°C is 1.0 MPa or less, The adhesive set according to [1]. [3] The calcium carbonate is surface-treated calcium carbonate, The adhesive set according to [1] or [2]. [4] A first base material, a second base material, an adhesive layer that bonds the first base material and the second base material to each other, comprising, wherein the adhesive layer contains a cured product of an adhesive composition including the main agent and the curing agent in the adhesive set according to any one of [1] to [3], A structure. [5] A method for producing the structure according to [4], comprising a step of laminating the first base material and the second base material together via an adhesive composition containing the main agent and the curing agent, A method for producing a structure. Effects of the Invention

[0017] According to the present disclosure, there is provided an adhesive set capable of forming a cured product of an adhesive composition that has sufficient shear strength in a high-temperature environment and is less likely to cause surface layer fracture of a base material. Further, according to the present disclosure, there are provided a structure obtained by using such an adhesive set and a method for producing the same. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] [Figure 1] FIG. 1 is a schematic diagram showing the fracture state of a test specimen after an adhesion test. FIG. 1(a) is a schematic cross-sectional view showing the test specimen before the adhesion test. FIG. 1(b) is a schematic cross-sectional view showing that the fracture state of the test specimen is cohesive failure. FIG. 1(c) is a schematic cross-sectional view showing that the fracture state of the test specimen is interfacial fracture. FIG. 1(d) is a schematic cross-sectional view showing that the fracture state of the test specimen is substrate surface layer fracture. MODES FOR CARRYING OUT THE INVENTION

[0019] Hereinafter, embodiments of the present disclosure will be described. However, the present disclosure is not limited to the following embodiments. In the present specification, a numerical range indicated using "~" means a range that includes the numerical values described before and after "~" as the minimum value and the maximum value, respectively. Further, in the numerical ranges described stepwise in the present specification, the upper limit or lower limit of the numerical range in a certain step may be replaced with the upper limit or lower limit of the numerical range in another step. In addition, in the numerical ranges described in the present specification, the upper limit or lower limit of the numerical range may be replaced with the values shown in the examples.

[0020] As used herein, the term "polyol" means a compound having an average of more than one hydroxyl group in the molecule.

[0021] As used herein, the term "polyisocyanate" means a compound having an average of more than one isocyanate group in the molecule.

[0022] Unless otherwise specified, the materials exemplified below may be used alone or in combination of two or more. When a plurality of substances corresponding to each component are present in the main agent or the curing agent, the content of each component in the main agent or the curing agent means the total amount of the plurality of substances present in the main agent or the curing agent, unless otherwise specified.

[0023] (A) The main component contains (a) a urethane prepolymer. (A) The main component may further contain (b) a polyisocyanate oligomer with a molecular weight of 1000 or less. (B) The curing agent contains (c) a polyol. (A) The main component and (B) the curing agent contain (d) a filler. (A) The main component and (B) the curing agent may further contain (e) a curing catalyst, (f) carbon black, or (g) a plasticizer. The following describes each component.

[0024] (a) Urethane prepolymer Component (a) is a reaction product of a compound having two or more active hydrogen groups (a-1) and a polyisocyanate compound having two or more isocyanate groups (a-2). Component (a) is preferably a urethane prepolymer having isocyanate groups (as terminal groups). Such a urethane prepolymer having isocyanate groups as terminal groups can be obtained by reacting such a compound (a) in such a way that there is an excess of isocyanate groups. Note that by using two or more types of components (a-1) and / or (a-2), multiple reaction products of component (a) may exist. Examples of active hydrogen groups include hydroxyl groups (OH groups), carboxyl groups (COOH groups), amino groups (NH2 groups), mercapto groups (SH groups), etc. The active hydrogen group may be a hydroxyl group (OH group). Component (a) may be used by isolating the reaction product of component (a-1) and component (a-2), or it may be used as is after the reaction in the reaction system without isolation.

[0025] (a-1) Component may be a polyol which is a compound having two or more hydroxyl groups (OH groups), for example, a polyether polyol. There are no particular limitations on the polyether polyol, but examples include polyethylene glycol (PEG), polypropylene glycol (PPG), ethylene oxide / propylene oxide copolymer, polytetramethylene ether glycol (PTMEG), sorbitol-based polyols, etc. Among these, the polyether polyol may be, for example, polypropylene glycol (PPG).

[0026] The number-average molecular weight of component (a-1) may be 20,000 or less, and may be 18,000 or less, 15,000 or less, or 12,000 or less. When the number-average molecular weight of component (a-1) is 20,000 or less, the number of crosslinking points increases, and the mechanical properties during curing tend to improve. The number-average molecular weight of component (a-1) is not particularly limited, but may be, for example, 1,000 or more.

[0027] In this specification, "number-average molecular weight" refers to the value calculated using gel permeation chromatography (GPC) and a calibration curve for standard polystyrene. The GPC measurement conditions are as follows, for example: Measuring instrument: ACQUITY UPLC APC system (manufactured by Waters) Columns: APC XT-900, APC XT-200, APC XT-125, APC XT-45 (manufactured by Waters) Carrier: Tetrahydrofuran (THF) Detector: Differential refractive index detector Sample: 0.5% by mass THF solution Calibration curve: Polystyrene

[0028] Examples of component (a-2) include aromatic polyisocyanates in which the isocyanate group is bonded to an aromatic hydrocarbon, alicyclic polyisocyanates in which the isocyanate group is bonded to an alicyclic hydrocarbon, and aliphatic polyisocyanates in which the isocyanate group is bonded to an aliphatic hydrocarbon. Among these, component (a-2) may be an aromatic polyisocyanate, for example, diphenylmethane diisocyanate. Examples of diphenylmethane diisocyanates include 4,4'-diphenylmethane diisocyanate (4,4'-MDI) and 2,4'-diphenylmethane diisocyanate (2,4'-MDI).

[0029] When component (a) is obtained by reacting component (a-1) and component (a-2), a catalyst for forming a urethane prepolymer (a-3) may be used as needed. Component (a-3) can be any known catalyst that promotes the urethaneization reaction or ureaization reaction, as exemplified by component (d) (curing catalyst) described later.

[0030] The content of component (a-3) can be appropriately adjusted according to the types of components (a-1) and (a-2). The content of component (a-3) may be, for example, 0.001 to 5% by mass, 0.005 to 1% by mass, or 0.01 to 0.1% by mass relative to the total amount of components (a-1) and (a-2).

[0031] The content of component (a) (the sum of component (a-1), component (a-2), and component (a-3)) may be 20-55% by mass, 25-50% by mass, or 30-45% by mass, based on the total amount of main component (A). When the content of component (a) is 20% by mass or more, based on the total amount of main component (A), it tends to prevent a decrease in elongation rate during curing, and when it is 55% by mass or less, it tends to prevent a decrease in adhesive properties after curing (after hardening).

[0032] (b) Polyisocyanate oligomers with a molecular weight of 1000 or less (A) By including component (b) in the main component, it is possible to prepare an adhesive composition that exhibits excellent non-primer adhesion. The reason for this effect is not entirely clear, but for example, it is thought that by changing some of the isocyanate group (NCO group) components in the main component involved in crosslinking to low molecular weight components, the adhesive composition becomes more able to conform to the irregularities of the substrate surface. On the other hand, for example, by using a low molecular weight component as part of the NCO group component of the main component, the polarity of the adhesive composition and the substrate surface become closer, the wettability of the adhesive composition is improved, and the NCO group components that have the potential to form covalent bonds with the substrate surface become closer to the substrate surface.

[0033] (b) Component (b) may be, for example, a polyisocyanate polymer having two or more isocyanate groups with a molecular weight of 1000 or less, or a diisocyanate polymer having two isocyanate groups with a molecular weight of 1000 or less. Examples of such polymers include aliphatic diisocyanate polymers such as hexamethylene diisocyanate (HDI); and aromatic diisocyanate polymers such as diphenylmethane diisocyanate (MDI). The aliphatic diisocyanate polymer may be, for example, a trimer of aliphatic diisocyanate (isocyanurate, biuret, or adduct of trimethylolpropane (TMP)). The aliphatic diisocyanate polymer may be a trimer of HDI. The aromatic diisocyanate polymer may be a polymer of MDI. (b) Component may contain at least one of an aliphatic diisocyanate polymer with a molecular weight of 1000 or less and an aromatic diisocyanate polymer with a molecular weight of 1000 or less, but it is preferable to contain both an aliphatic diisocyanate polymer with a molecular weight of 1000 or less and an aromatic diisocyanate polymer with a molecular weight of 1000 or less, as this provides even better non-primer adhesion.

[0034] Examples of commercially available aliphatic diisocyanate polymers (HDI trimers) with a molecular weight of 1000 or less include Sumidur N3300 (trade name, manufactured by Sumika Bayer Urethane Co., Ltd.), Duranate 24A-100 (trade name, manufactured by Asahi Kasei Corporation), and Duranate E402-100 (trade name, manufactured by Asahi Kasei Corporation). Examples of aromatic diisocyanate polymers (MDI polymers) with a molecular weight of 1000 or less include Myrionate MR-100 (trade name, manufactured by Tosoh Corporation) and Desmodule VKS20 (trade name, manufactured by Sumika Covestro Urethane Co., Ltd.).

[0035] (b) The molecular weight of component (b) may be the average molecular weight. The molecular weight or average molecular weight of component (b) is 1000 or less, and may be 900 or less, 800 or less, 700 or less, or 600 or less, and may be 100 or more, 200 or more, 300 or more, or 400 or more.

[0036] (b) The content of component (b) may be 1 to 15% by mass, 3 to 12% by mass, or 5 to 10% by mass, based on the total amount of main component (A). When the content of component (b) is 1% by mass or more, based on the total amount of main component (A), non-primer adhesion tends to be improved, and a decrease in adhesive durability between the substrate surface and the adhesive composition can be prevented. When the content of component (b) is 15% by mass or less, based on the total amount of main component (A), more sufficient flexibility tends to be imparted during curing.

[0037] (c) Polyol Component (c) comprises a polyol having a glass transition temperature (Tg) of 0°C or lower. Component (c-1) is not particularly limited as long as it has a Tg of 0°C or lower, but may be, for example, a polyether polyol. Examples of polyether polyols are not particularly limited, but include polyethylene glycol (PEG), polypropylene glycol (PPG), ethylene oxide / propylene oxide copolymer, etc. Among these, the polyether polyol may be, for example, polypropylene glycol (PPG). Polypropylene glycol usually has a glass transition temperature of about -50°C. In this specification, Tg refers to the intermediate glass transition temperature calculated by measuring the calorific value change by differential scanning calorimetry (DSC) and using a method in accordance with JIS K7121:2012. The number-average molecular weight of component (c-1) may be the same as that of component (a-1). The number of hydroxyl groups in component (c-1) may be 2 to 6, or 2 to 4.

[0038] The Tg of component (c-1) may be below -10°C, below -20°C, below -30°C, or below -40°C, and may be above -100°C, above -80°C, or above -60°C.

[0039] Component (c) may, in addition to component (c-1), include a polyol having a glass transition temperature (Tg) greater than (c-2)0°C, to the extent that it does not impair the effects of the present disclosure. It is preferable that component (c) does not contain component (c-2). That is, component (c) may consist of component (c-1).

[0040] The content of component (c-1) may be 60-100% by mass, 80-100% by mass, 90-100% by mass, or 95-100% by mass, or 100% by mass, based on the total amount of component (c). The content of component (c-2) may be 0-40% by mass, 0-20% by mass, 0-10% by mass, or 0-5% by mass, based on the total amount of component (c), or 0% by mass.

[0041] The average hydroxyl value of component (c) is 50 mgKOH / g or less, and may be 48 mgKOH / g or less, 45 mgKOH / g or less, 42 mgKOH / g or less, or 40 mgKOH / g or less. When the average hydroxyl value of component (c) is 50 mgKOH / g or less, it is possible to lower the storage modulus of the cured product of the resulting adhesive composition in a high-temperature environment. The average hydroxyl value of component (c) may be, for example, 20 mgKOH / g or more, 25 mgKOH / g or more, or 30 mgKOH / g or more.

[0042] The average hydroxyl value refers to the hydroxyl value of component (c) when there is only one type of component (c). When two or more types of component (c) are used, the average hydroxyl value is the weighted average of the hydroxyl values ​​of the component (c) according to the blending ratio of the two or more components (c). For example, when two types of component (c), (c1) polyol and (c2) polyol, are used, and the hydroxyl value of component (c1) is X1, the blending ratio is m1, the hydroxyl value of component (c2) is X2, and the blending ratio is m2, the average hydroxyl value can be expressed by the following formula. Note that the blending ratio refers to the ratio on a mass basis. Also, the hydroxyl value refers to the value measured in accordance with JIS K1557-1:2007. Average hydroxyl value (mgKOH / g)=X1×(m1 / (m1+m2))+X2×(m2 / (m1+m2))

[0043] The average number of hydroxyl groups in component (c) is 2.5 or less, and may be 2.4 or less, 2.3 or less, or 2.2 or less. When the average number of hydroxyl groups in component (c) is 2.5 or less, it becomes possible to lower the storage modulus of the cured adhesive composition in a high-temperature environment. The average number of hydroxyl groups in component (c) may be 2.0 or more, or greater than 2.0.

[0044] The average number of hydroxyl groups refers to the number of hydroxyl groups in a single component (c) when that component is of one type. When two or more components (c) are used, the average number of hydroxyl groups is the weighted average of the number of hydroxyl groups of the components (c) according to the mole fractions of those two or more components (c). For example, when two types of polyols, (c1) polyol and (c2) polyol, are used as components (c), and when the number of hydroxyl groups of component (c1) is Y1, the number of moles is n1, the hydroxyl value of component (c2) is Y2, and the number of moles is n2, the average number of hydroxyl groups can be expressed by the following formula. Note that the number of moles refers to the value obtained by dividing the combined mass (mass-based ratio) by the number-average molecular weight. Average number of hydroxyl groups (number) = Y1×(n1 / (n1+n2))+Y2×(n2 / (n1+n2))

[0045] The content of component (c-1) (or component (c)) is 20% by mass or more, based on the total amount of (A) main agent and (B) curing agent. When the content of component (c-1) (or component (c)) is 20% by mass or more, based on the total amount of (A) main agent and (B) curing agent, it is possible to lower the storage modulus of the cured adhesive composition in a high-temperature environment. The content of component (c-1) (or component (c)) may be 22% by mass or more, 24% by mass or more, or 25% by mass or more, based on the total amount of (A) main agent and (B) curing agent. The content of component (c-1) may be 50% by mass or less, 40% by mass or less, or 35% by mass or less, based on the total amount of (A) main agent and (B) curing agent.

[0046] The content of component (c-1) (or component (c)) may be 20-60% by mass, 25-55% by mass, or 30-50% by mass, based on the total amount of curing agent (B). When the content of component (c-1) (or component (c)) is 20% by mass or more, based on the total amount of curing agent (B), it is possible to lower the storage modulus of the cured adhesive composition in a high-temperature environment, and it tends to prevent a decrease in the flexibility of the adhesive composition during curing. When the content of component (c-1) (or component (c)) is 60% by mass or less, based on the total amount of curing agent (B), it tends to prevent a decrease in strength during curing.

[0047] (d) Filler Component (d) contains (d-1) calcium carbonate. By including (d-1) calcium carbonate in component (d), it is possible to improve the shear strength while lowering the storage modulus of the cured adhesive composition. Examples of component (d-1) include heavy calcium carbonate and precipitated calcium carbonate. The surfaces of these may be surface-treated with fatty acids or the like. Component (d) may be surface-treated calcium carbonate, whose surface is surface-treated with fatty acids or the like, from the viewpoint of further improving the shear strength of the cured product at 90°C.

[0048] Examples of commercially available untreated calcium carbonate include SS#30, NN#500, NN#200, NS#100, NS#400, NS#2300, NITOREX30P, NITOREX#80 (product name, manufactured by Nitto Funka Kogyo Co., Ltd.), Whiteon P-10, Whiteon P-30, Whiteon P-50, Whiteon P-70, and Whiteon H (product name, manufactured by Shiraishi Calcium Co., Ltd.).

[0049] Examples of commercially available surface-treated calcium carbonate products include Shiratsuka CC, Shiratsuka CC-R, Shiratsuka CCR-B, Shiratsuka CCR-S, Shiratsuka CCR-S10 (product names, manufactured by Shiraishi Calcium Co., Ltd.), ASK-5, SST-40, UST-50, BSR-5, and Suncut-160 (product names, manufactured by Calfine Co., Ltd.).

[0050] Component (d) may include, in addition to component (d-1), fillers other than calcium carbonate (d-2). Examples of component (d-2) include kaolin, talc, silica, titanium dioxide, bentonite, mica, sericite, glass flakes, glass fibers, graphite, magnesium hydroxide, aluminum hydroxide, antimony trioxide, barium sulfate, zinc borate, alumina, magnesia, wollastonite, xonotlite, whiskers, and resin fillers. Note that component (f), described later, is not included in component (d-2).

[0051] The content of component (d-1) may be 50-95% by mass, 60-92% by mass, or 70-90% by mass, based on the total amount of component (d) contained in (A) the main agent and (B) the hardener. The content of component (d-2) may be 5-50% by mass, 8-40% by mass, or 10-30% by mass, based on the total amount of component (d).

[0052] The content of component (d-1) is 10% by mass or more, based on the total amount of (A) main agent and (B) curing agent. When the content of component (d-1) is 10% by mass or more, based on the total amount of (A) main agent and (B) curing agent, it is possible to improve the shear strength while achieving a lower storage modulus in the cured product of the resulting adhesive composition. The content of component (d-1) may be 12% by mass or more, 14% by mass or more, or 16% by mass or more, based on the total amount of (A) main agent and (B) curing agent. The content of component (d-1) may be 40% by mass or less, 30% by mass or less, or 25% by mass or less, based on the total amount of (A) main agent and (B) curing agent.

[0053] (d) The content of component (d) may be 15% by mass or more, 18% by mass or more, or 20% by mass or more, based on the total amount of (A) main agent and (B) hardener. The content of component (d) may be 45% by mass or less, 40% by mass or less, or 35% by mass or less, based on the total amount of (A) main agent and (B) hardener.

[0054] (e) Curing catalyst (e) Component can be, for example, a known catalyst that promotes the urethane reaction or the urea reaction. Examples of component (e) include tin-based catalysts and amine-based catalysts. Examples of tin-based catalysts include dibutyltin dilaurate, dioctyltin dilaurate, dibutyltin didecanate, dioctyltin didecanate, and tin 2-ethylhexanoate. Examples of amine catalysts include triethylenediamine, bis(dimethylaminoethyl) ether, di(N,N-dimethylaminoethyl)amine, and 1-isobutyl-2-methylimidazole. Component (e) can be appropriately selected according to the desired curing rate.

[0055] (e) The content of component (e) may be 0.01 to 5% by mass, 0.1 to 3% by mass, or 0.2 to 1% by mass, based on the total amount of (A) main agent and (B) curing agent. When the content of component (e) is 0.01% by mass or more, based on the total amount of (A) main agent and (B) curing agent, the curing reaction of the adhesive composition tends to be more sufficiently promoted. When the content of component (e) is 5% by mass or less, based on the total amount of (A) main agent and (B) curing agent, the pot life of the adhesive composition tends to be more sufficiently ensured.

[0056] (f) Carbon Black Component (f) may have an average particle size (D50: particle size at the 50th percentile of the volume particle size distribution curve) of 20-40 nm or 25-35 nm. When the average particle size of component (f) is within the above range, the viscosity of the adhesive composition and the dispersibility of component (f) are adjusted to a more appropriate range, and the workability and strength of the adhesive composition tend to improve. The average particle size (D50) of carbon black can be measured by laser diffraction scattering using, for example, a Beckman Coulter "Model LS-230".

[0057] (f) Examples of commercially available components include Monarch 460 (manufactured by Cabot Corporation), Asahi Carbon 70 (manufactured by Asahi Carbon Co., Ltd.), Seast 3 (manufactured by Tokai Carbon Co., Ltd.), Mitsubishi Carbon 32 (manufactured by Mitsubishi Chemical Corporation), and Nitelon 200 (manufactured by Shin-Nippon Chemical Carbon Co., Ltd.).

[0058] (f) The content of component (f) may be 5 to 40% by mass or 10 to 30% by mass, based on the total amount of (A) main agent and (B) hardener. When the content of component (f) is 5% by mass or more, based on the total amount of (A) main agent and (B) hardener, the strength during curing tends to improve. When the content of component (f) is 40% by mass or less, based on the total amount of (A) main agent and (B) hardener, the dispersibility is further improved, and the strength during curing tends to be maintained.

[0059] (g) Plasticizer (g) Examples of components include phthalate ester compounds, alkyl sulfonic acid ester compounds, and adipic acid ester compounds. Specific examples of phthalate ester compounds include dioctyl phthalate (DOP), dibutyl phthalate (DBP), diisononyl phthalate (DINP), diisodecyl phthalate (DIDP), and butyl benzyl phthalate (cBP).

[0060] (g) The content of component (g) may be 5 to 40% by mass or 10 to 30% by mass, based on the total amount of (A) main agent and (B) hardener.

[0061] (A) The main component and (B) the curing agent may further contain, in addition to the components (e) to (g) above, UV absorbers, dehydrating agents, pigments, dyes, antioxidants, antioxidants, antistatic agents, flame retardants, adhesion promoters, dispersants, solvents, etc.

[0062] When mixing (A) the main component and (B) the curing agent, the equivalent ratio (molar ratio) (NCO group / OH group) of isocyanate groups (NCO group) in the main component (A) to the hydroxyl groups (OH) in the curing agent (B) may be, for example, 1.0 to 5.0. If the equivalent ratio (NCO group / OH group) is 1.0 or higher, the proportion of unreacted polyol present when the main component and curing agent are mixed is reduced, and sufficient non-primer adhesion tends to be obtained. If the equivalent ratio (NCO group / OH group) is 5.0 or lower, the proportion of isocyanate and prepolymer present when the main component and curing agent are mixed is within an appropriate range, the reaction rate with moisture in the air can be suppressed, and sufficient curing tends to be obtained. Note that the isocyanate groups in the main component (A) mainly originate from component (a), and the hydroxyl groups in the curing agent (B) mainly originate from component (c).

[0063] The adhesive set of this embodiment allows for the preparation of an adhesive composition (a two-component curing type urethane adhesive composition) by mixing (A) the main component and (B) the curing agent. The temperature and time when mixing (A) the main component and (B) the curing agent may be, for example, 10 to 35°C and 1 to 60 minutes.

[0064] The method of mixing (A) the main component and (B) the hardener is not particularly limited. For example, it may be mixed by hand using a regular caulking gun, or it may be mixed using a mechanical rotary mixer, static mixer, etc., with a quantitative pump (e.g., gear pump, plunger pump, etc.) and a throttle valve in combination for supplying the raw materials.

[0065] The prepared adhesive composition (a two-component curing type urethane adhesive composition) can form a cured product by curing (hardening) and can act as an adhesive layer that bonds substrates together. The conditions for curing the adhesive composition (curing conditions) may be, for example, 10 to 35°C, 30 to 60% RH (relative humidity), and 2 to 7 days.

[0066] The storage modulus at 90°C of the cured product when the adhesive composition containing the main agent and the curing agent is cured at 23°C for 72 hours may be 1.0 MPa or less, 0.9 MPa or less, or 0.8 MPa or less. A storage modulus at 90°C of 1.0 MPa or less further reduces stress concentration on the surface of the substrate. The storage modulus at 90°C of the cured product may be 0.1 MPa or more, 0.3 MPa or more, or 0.5 MPa or more. In this specification, this refers to values ​​measured in accordance with JIS K6251:2017, and more specifically, to values ​​obtained by the method described in the examples.

[0067] One embodiment of the structure comprises a first substrate, a second substrate, and an adhesive layer that bonds the first and second substrates together. The adhesive layer contains a cured product of an adhesive composition that includes the main agent and curing agent in the adhesive set described above. Examples of the structure include a vehicle back door, trunk lid, windshield, spoiler, etc.

[0068] At least one of the first and second substrates may be a polypropylene (PP) substrate, or both the first and second substrates may be polypropylene (PP) substrates. Examples of substrates other than polypropylene (PP) substrates include plastic substrates such as polyvinyl chloride, acrylonitrile / butadiene / styrene copolymer (ABS), polycarbonate (PC), polyamide (PA), poly(methyl methacrylate (PMMA), polyester, epoxy resin, polyurethane (PUR), polyoxymethylene (POM), polyethylene (PE), ethylene / propylene copolymer (EPM), and ethylene / propylene / diene polymer (EPDM); fiber-reinforced plastic substrates such as carbon fiber reinforced plastic (CFRP) and glass fiber reinforced plastic (GFRP); and resin compound substrates such as sheet molding compound (SMC). When the structure is a vehicle back door, the first substrate may be an inner panel made of a polypropylene substrate, and the second substrate may be an outer panel made of a substrate other than a propylene substrate.

[0069] A method for manufacturing a structure according to one embodiment comprises the step of bonding a first substrate and a second substrate via an adhesive composition containing a main component and a curing agent. A known method can be applied to the method of placing the adhesive composition containing the main component and the curing agent on at least one of the first substrate or the second substrate. The temperature and time when mixing (A) the main component and (B) the curing agent in the adhesive set, the conditions for curing the adhesive composition, etc., are the same as described above. [Examples]

[0070] The present disclosure will be described in more detail below with reference to examples. However, the present disclosure is not limited to these examples.

[0071] [Preparation of the main ingredient intermediate] In a mixing vessel equipped with a stirrer, nitrogen inlet tube, vacuum pump, and heating / cooling device, 36.9 parts by mass of Preminol 3012 (polyether polyol (polymer of propylene glycol initiated with glycerin), manufactured by Asahi Glass Co., Ltd., number average molecular weight: 12000, number of hydroxyl groups: 3, symbol: a-1-(1)) as component (a-1) of component (a), 12.4 parts by mass of Monarch 460 (carbon black, manufactured by Cabot Corporation, symbol: f-(1)) as component (f), 18.4 parts by mass of Iceberg (calcined kaolin, manufactured by Shiraishi Calcium Co., Ltd., symbol: d-2-(1)) as component (d-2) of component (d), and 20.0 parts by mass of DINP (diisononyl phthalate, symbol: g-(1)) as component (g), were charged and stirred at room temperature (25°C) for 60 minutes until no lumps of carbon black remained. Next, the kneading container was heated until the contents reached 100°C, and the pressure inside the kneading container was reduced to 2.7 kPa (20 mmHg) using a vacuum pump, and the contents were stirred for 1 hour. Then, the contents were cooled to 40°C, and 3.7 parts by mass of myrionate MT (4,4'-diphenylmethane diisocyanate, manufactured by Tosoh Corporation, NCO content: 33.6%, symbol: a-2-(1)) as component (a-2) of component (a) and 0.008 parts by mass of KS-1260 (tin-based catalyst, dibutyltin dilaurate, manufactured by Sakai Chemical Industry Co., Ltd., symbol: a-3-(1)) as component (a-3) of component (a) were added to the kneading container. After that, nitrogen was introduced, and the kneading container was heated until the contents reached 70°C, and the contents were stirred for 1 hour. The contents were cooled to 40°C, and 3.7 parts by mass of Sumijool N3300 (isocyanurate of hexamethylene diisocyanate (HDI), manufactured by Sumika Bayer Urethane Co., Ltd., molecular weight: 504.6, symbol: b-(1)) was added as component (b), and the mixture was stirred for 30 minutes. The viscosity obtained from the above steps was used as the main component intermediate. The viscosity is presumed to contain a urethane prepolymer, which is a reaction product of Preminol 3012 and Myrionate MT.

[0072] [Preparation of the main ingredient] To the above main component intermediate, 4.9 parts by mass of Myrionate MR-100 (aromatic polyfunctional isocyanate (polymethylene polyphenyl polyisocyanate (polymeric MDI)), manufactured by Tosoh Corporation, NCO content: 31.0%, average molecular weight: 450), symbol: b-(2)) was added as component (b), and the mixture was stirred for 10 minutes to obtain main component A. Table 1 shows the composition of main component A.

[0073] [Table 1]

[0074] [Preparation of hardener B-1] In a mixing vessel equipped with a stirrer, nitrogen inlet tube, vacuum pump, and heating / cooling device, the following were added as component (c-1) of component (c): 63.4 parts by mass of Preminol 5005 (polypropylene glycol, manufactured by Asahi Glass Co., Ltd., number average molecular weight: 5000, number of hydroxyl groups: 2, hydroxyl value: 28 mg KOH / g, glass transition temperature: approximately -50°C, symbol: c-1-(1)), 15.9 parts by mass of Excenol 2020 (polypropylene glycol, manufactured by Asahi Glass Co., Ltd., number average molecular weight: 2000, number of hydroxyl groups: 2, hydroxyl value: 56 mg KOH / g, glass transition temperature: approximately -50°C, symbol: c-1-(3)), and EDP-110 1.6 parts by mass of 0 (ethylenediaminepropylene oxide modified, manufactured by ADEKA Corporation, hydroxyl group count: 4, hydroxyl value: 215 mg KOH / g, glass transition temperature: approximately -50°C, symbol: c-1-(5)), 47.5 parts by mass of NS#2300 (calcium carbonate (surface treatment: none), manufactured by Nitto Funka Kogyo Co., Ltd., symbol: d-1-(1)) as component (d-1) of component (d), 32.8 parts by mass of Monarch 460 (same as above) as component (f), and 36.3 parts by mass of DINP (same as above) as component (g) were added, and the mixture was stirred at room temperature (25°C) for 30 minutes until there were no more lumps of carbon black. Next, the kneading container was heated until the contents reached 100°C, and the pressure inside the kneading container was reduced to 2.7 kPa (20 mmHg) using a vacuum pump, and the contents were stirred for 1 hour. The contents were cooled to 40°C, and 0.2 parts by mass of BHT (dibutylhydroxytoluene, symbol: h-(1)) as component (h) (ultraviolet absorber), 0.8 parts by mass of dehydrated molecular sieve 4A (symbol: i-(1)) as component (dehydrating agent), and 1.6 parts by mass of TEDA (triethylenediamine, amine catalyst, manufactured by Tosoh Corporation, symbol: e-(1)) as component (e) were added and the mixture was stirred for 30 minutes. The viscosity obtained from the above steps was designated as curing agent B-1. Table 2 shows the composition of curing agent B-1.

[0075] [Preparation of hardener B-2] Hardener B-2 was prepared in the same manner as hardener B-1, except that 47.5 parts by mass of Shiratsuka CC-R (calcium carbonate (surface treated), manufactured by Shiraishi Calcium Co., Ltd., symbol: d-1-(2)) was used as component (d-1) in component (d). Table 2 shows the composition of hardener B-2.

[0076] [Preparation of hardener B-3] (c) component (c-1) consists of 65.1 parts by mass of Preminol 5005 (same as above), 16.3 parts by mass of Excenol 2020 (same as above), and 1.6 parts by mass of EDP-1100 (same as above), (d) component consists of 48.8 parts by mass of Shirotsuya CC-R (same as above), (f) component consists of 29.6 parts by mass of Monarch 460 (same as above), (g) component consists of 35.9 parts by mass of DINP (same as above), as an ultraviolet absorber, 0.2 parts by mass of BHT (same as above), and (j) component (antioxidant) consists of 4.3 parts by mass of AO-412S (thioether-based antioxidant, manufactured by ADEKA Corporation, symbol: j-1-(1)) and SONGNOX1010 (phenol-based antioxidant, Songwon Curing agent B-3 was prepared in the same manner as curing agent B-1, except that 10.7 parts by mass of Industrial Co., Ltd., symbol: j-1-(2)) was used. Table 2 shows the composition of curing agent B-3.

[0077] [Preparation of hardener b-1] Curing agent b-1 was prepared in the same manner as curing agent B-1, except that component (c-1) in component (c) consisted of 65.1 parts by mass of Preminol 5005 (same as above), 12.2 parts by mass of Excenol 2020 (same as above), 4.5 parts by mass of Excenol 430 (polypropylene glycol, manufactured by Asahi Glass Co., Ltd., number average molecular weight: 430, number of hydroxyl groups: 3, hydroxyl value: 400 mg KOH / g, glass transition temperature: approximately -50°C, symbol: c-1-(4)), and 1.2 parts by mass of EDP-1100 (same as above), component (d-2) in component (d) consisted of 47.5 parts by mass of Iceberg (same as above), component (f) consisted of 29.6 parts by mass of Monarch 460 (same as above), and component (g) consisted of 35.9 parts by mass of DINP (same as above). Table 2 shows the composition of curing agent b-1.

[0078] [Preparation of hardener b-2] Curing agent b-2 was prepared in the same manner as curing agent B-1, except that component (c-1) in component (c) was 63.4 parts by mass of exenol 837 (polypropylene glycol, manufactured by Asahi Glass Co., Ltd., number average molecular weight: 6000, number of hydroxyl groups: 3, hydroxyl value: 27 mg KOH / g, glass transition temperature: approximately -50°C, symbol: c-1-(2)), 15.9 parts by mass of exenol 2020 (same as above), and 1.6 parts by mass of EDP-1100 (same as above), component (d-2) in component (d) was 47.5 parts by mass of Iceberg (same as above), component (f) was 32.8 parts by mass of Monarch 460 (same as above), and component (g) was 36.3 parts by mass of DINP (same as above). Table 2 shows the composition of curing agent b-2.

[0079] [Preparation of hardener b-3] Curing agent b-3 was prepared in the same manner as curing agent B-1, except that component (d-2) of component (d) consisted of 23.8 parts by mass of Iceberg (same as above) and 33.8 parts by mass of LA-2330 (acrylic block copolymer, manufactured by Kuraray Co., Ltd., symbol: d-2-(2)), and component (f) consisted of 22.8 parts by mass of Monarch 460 (same as above). Table 2 shows the composition of curing agent b-3.

[0080] [Table 2]

[0081] [Making an adhesive set] (Example 1) The above-mentioned main component A was used as the main component in Example 1. The above-mentioned curing agent B-1 was used as the curing agent in Example 1.

[0082] (Example 2) The above main component A was used as the main component in Example 2. The above curing agent B-2 was used as the curing agent in Example 2.

[0083] (Example 3) The above main component A was used as the main component in Example 3. The above curing agent B-3 was used as the curing agent in Example 3.

[0084] (Comparative Example 1) The above main component A was used as the main component in Comparative Example 1. The above curing agent b-1 was used as the curing agent in Comparative Example 1.

[0085] (Comparative Example 2) The above main component A was used as the main component in Comparative Example 2. The above curing agent b-2 was used as the curing agent in Comparative Example 2.

[0086] (Comparative Example 3) The above main component A was used as the main component in Comparative Example 3. The above curing agent b-3 was used as the curing agent in Comparative Example 3.

[0087] [Measurement of Storage Modulus] A 2.0 mm spacer was placed on a release sheet (size: 150 mm x 150 mm, thickness: 0.1 mm, material: polytetrafluoroethylene) so that the adhesive layer thickness was 2.0 mm. The main agent and curing agent of Examples 1-3 and Comparative Examples 1-3 were mixed in the mass ratio shown in Table 3 so that the molar ratio of NCO groups of the main agent to OH groups of the curing agent was (NCO groups / OH groups) = 1.10 to 1.42. After applying the obtained adhesive composition onto the release sheet, another release sheet was laminated on top and pressed with a flat plate (size: 150 mm x 150 mm, thickness: 1.0 mm, material: glass, etc.). After being left at 23°C for 72 hours, a laminated sheet of the release sheet and the cured adhesive composition was obtained. In accordance with JIS K6251:2017, the laminated sheet was punched out into a dumbbell shape (Type 3), and the release sheet was peeled off to prepare test specimens for Examples 1-3 and Comparative Examples 1-3. Using an Autograph with a constant temperature bath (Shimadzu Corporation, Model: AGS-1kNX, Load cell: 50kN), the storage modulus of the test specimens at a 90°C environment was measured with a chuck distance of 70mm and a tensile speed of 200mm / min. The results are shown in Table 3.

[0088] [Measurement of shear strength] Two substrates, primarily composed of frame-treated polypropylene (PP), were prepared. The main components and curing agents of Examples 1-3 and Comparative Examples 1-3 were mixed in the mass ratios shown in Table 3, such that the molar ratio of NCO groups in the main component to OH groups in the curing agent was (NCO groups / OH groups) = 1.10-1.42. The resulting adhesive compositions were applied to one of the substrates to create an adhesive layer with a thickness of 3 mm, and the bonding area was 250 mm². 2 A laminate was obtained by bonding the surface of one substrate to the surface of the other substrate (25 mm x 10 mm) and pressing them together. By curing the obtained laminate at 23°C for 72 hours, multiple test specimens of Examples 1 to 3 and Comparative Examples 1 to 3 were obtained, in which the substrates were bonded to each other via an adhesive layer containing the cured product of the adhesive composition. In the following adhesion tests, a different test specimen was used for each condition.

[0089] (initial conditions) The obtained test specimens were subjected to tensile tests at 23°C in accordance with JIS K6850:1999, and their shear strength (breaking strength) was determined. The results are shown in Table 3.

[0090] (High temperature (90°C) conditions) The obtained specimens were heated at 90°C for 1 hour, and tensile tests were performed in a 90°C environment under the same conditions as the initial tests to determine the shear strength (breaking strength). Furthermore, the specimens were observed after the tests (after fracture in the tensile tests), and their fracture state was evaluated based on the evaluation criteria described below. The results are shown in Table 3.

[0091] Figure 1 is a schematic diagram showing the failure state of a test specimen after an adhesion test. Figure 1(a) is a schematic cross-sectional view showing a test specimen before the adhesion test. The test specimen 10 shown in Figure 1(a) comprises substrates 2a and 2b and an adhesive layer 1 that adheres these substrates to each other before the adhesion test. Figure 1(b) is a schematic cross-sectional view showing that the failure state of the test specimen is cohesive failure (hereinafter sometimes referred to as "CF"). When CF occurs, the test specimen 10 is separated inside the adhesive layer 1, as shown in Figure 1(b). Figure 1(c) is a schematic cross-sectional view showing that the failure state of the test specimen is interfacial failure (hereinafter sometimes referred to as "AF"). When AF occurs, the test specimen 10 is separated at the interface between substrate 2a and adhesive layer 1 (or the interface between substrate 2b and adhesive layer 1), as shown in Figure 1(c). Figure 1(d) is a schematic cross-sectional view showing that the failure state of the test specimen is substrate surface failure (substrate cohesive failure) (hereinafter sometimes referred to as "CSF"). When CSF occurs, as shown in Figure 1(d), the test specimen 10 is fractured inside the substrate 2a (or inside the substrate 2b), and the surface layer of substrate 2a (or the surface layer of substrate 2b) is destroyed. The failure of the test specimen 10 usually occurs as a combination of these failures (CF, AF, CSF, etc.). In this test, the failure area caused by each failure was observed, and the evaluation was performed by determining the area percentage derived from CF. For example, in Table 3, "100%" means that the entire area of ​​failure (100%) is derived from CF, and "60%" means that 60% of the failure area is derived from CF, and the remainder is derived from AF or CSF. In this test, the larger the ratio of the failure area derived from CF to the total failure area, the more the failure of the substrate can be suppressed, and therefore, surface failure of the substrate is less likely to occur.

[0092] [Table 3]

[0093] As shown in Table 3, the cured products of the adhesive compositions prepared from the adhesive sets of Examples 1 to 3, which contain a predetermined main component and a predetermined curing agent, exhibited a lower storage modulus of elasticity in high-temperature environments. Furthermore, the cured products of the adhesive compositions prepared from the adhesive sets of Examples 1 to 3 showed higher shear strength in high-temperature environments and a larger ratio of fracture area due to CF to fracture area compared with the cured products of the adhesive sets of Comparative Examples 1 to 3. These results confirm that the adhesive sets of this disclosure can form cured products of adhesive compositions that have sufficient shear strength and are less prone to substrate surface fracture in high-temperature environments. [Explanation of Symbols]

[0094] 1...Adhesive layer, 2a, 2b...Substrate, 10...Test specimen.

Claims

1. An adhesive set comprising a main component and a hardener, The main component contains a urethane prepolymer, The curing agent contains a polyol having a glass transition temperature of 0°C or lower, At least one of the main component and the hardening agent contains a filler containing calcium carbonate, The average hydroxyl value of the polyol is 50 mg KOH / g or less. The average number of hydroxyl groups in the polyol is 2.5 or less. The content of the polyol having a glass transition temperature of 0°C or lower is 20% by mass or more, based on the total amount of the main component and the curing agent. The calcium carbonate content is 10% by mass or more, based on the total amount of the main component and the hardening agent. Adhesive set.

2. The storage modulus of the cured product at 90°C is 1.0 MPa or less when the adhesive composition containing the main component and the curing agent is cured at 23°C for 72 hours. The adhesive set according to claim 1.

3. The aforementioned calcium carbonate is surface-treated calcium carbonate. The adhesive set according to claim 1.

4. The first substrate and A second substrate and An adhesive layer that bonds the first substrate and the second substrate together, Equipped with, The adhesive layer contains a cured product of an adhesive composition comprising the main component and the curing agent in the adhesive set according to any one of claims 1 to 3. structure.

5. A method for manufacturing the structure described in claim 4, The process includes bonding the first substrate and the second substrate via an adhesive composition containing the main component and the curing agent. A method for manufacturing a structure.

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