JP2023102148A - Two-liquid curing type adhesive composition - Google Patents

Abstract

To provide a two-liquid curing type adhesive composition excellent in tensile characteristics such as fracture strength and fracture elongation, and capable of obtaining a cured material small in temperature dependency of viscoelastic property.SOLUTION: A two-liquid curing type adhesive composition comprises a main agent (A) containing an urethane prepolymer (a1), and a curing agent (B) containing a polyol compound (b1) and a polyamine compound (b2), wherein the urethane prepolymer (a1) is obtained by reacting a raw material polyisocyanate and a polyol compound (a2) having a number average molecular weight of 500 or more having at least one hydroxyl group in one molecule with an equivalent ratio of the isocyanate group in the raw material polyisocyanate to the hydroxyl group in the polyol compound to be 2.05 to 14, and all of the polyol compounds (a2) to be monomer units of the urethane prepolymer (a1).SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to a two-part curable adhesive composition comprising a main agent and a curing agent.

2. Description of the Related Art In a structure such as an automobile body, parts made of different materials are sometimes joined together using an adhesive. Bonding via an adhesive can suppress the occurrence of distortion and warping even when there is a large difference in coefficient of thermal expansion between parts. On the other hand, adhesives used in such applications are required to have good tensile properties such as breaking strength and breaking elongation in a cured state as a measure of adhesive strength.

As an adhesive composition from which a cured product having excellent breaking elongation can be obtained, a two-component curing type polyurethane adhesive composition comprising a main component containing a urethane prepolymer and a curing agent containing a compound having an active hydrogen group is known. In a two-liquid curing type polyurethane adhesive composition, the compounding ratio of the main agent and the curing agent is generally adjusted so that the equivalent ratio between the isocyanate groups contained in the main agent and the hydroxyl groups in the polyol contained in the curing agent is around 1. However, when the isocyanate groups and hydroxyl groups are nearly equal, the curing speed of the urethane prepolymer is very slow. For this reason, attempts have been made to increase the curing speed by using catalysts such as organometallic compounds and tertiary amines (Patent Document 1). However, rapid curing of the adhesive composition using a catalyst may cause foaming, thereby degrading the tensile properties of the cured product.

JP 2017-218539 A

By the way, some of the cured products of conventional polyurethane-based adhesive compositions exhibit poor tensile properties at room temperature, but exhibit poor elongation, particularly in high-speed tensile tests, at low temperatures.

Accordingly, an object of the present invention is to provide a two-pack curing adhesive composition that uses two different polyols that are highly compatible with each other as constituent components, so that the hard segment and the soft segment spontaneously adopt a microphase-separated structure, and can form a cured product that is excellent in tensile properties at room temperature and has comparable tensile properties at low temperatures.

One aspect of the present invention is a two-component curable adhesive composition,
a main agent (A) containing a urethane prepolymer (a1);
and a curing agent (B) containing a polyol compound (b1) and a polyamine compound (b2),
The urethane prepolymer (a1) is obtained by reacting a raw material polyisocyanate and a polyol compound (a2) having a number average molecular weight of 500 or more and having at least one hydroxyl group in one molecule such that the equivalent ratio of the isocyanate group in the raw material polyisocyanate to the hydroxyl group in the polyol compound is 2.05 to 14 so that all of the polyol compound (a2) becomes the monomer unit of the urethane prepolymer (a1).
In addition to the urethane prepolymer (a1), the main component (A) further contains a residual polyisocyanate (a3) which is the remainder of the raw material polyisocyanate that has not reacted with the polyol compound (a2),
The equivalent ratio of the active hydrogen groups in the polyamine compound (b2) to the active hydrogen groups in the polyol compound (b1) is 1.5 to 6,
A two-component curing adhesive composition in which the equivalent ratio of the isocyanate groups in the main component (A) to the active hydrogen groups in the curing agent (B) is 0.25 to 2,
The solubility parameter (SP value) of the polyol compound (a2) and the polyol compound (b1) calculated by the Fedors method is different from each other and is 14.0 to 21.0 (J/cm ³ ) ^1/2 .

The polyol compound (a2) having a number average molecular weight of 500 or more is preferably at least one selected from the group consisting of polyethylene glycol, polypropylene glycol, polyester polyol, polytetramethylene ether glycol, polycarbonate polyol, and polycaprolactone polyol.

The polyol compound (b1) preferably has a number average molecular weight of 500 or more.

The polyol compound (b1) preferably contains at least one monomer unit selected from the group consisting of polyethylene glycol, polypropylene glycol, polytetramethylene ether glycol, and polycarbonate polyol in the molecule.

The polyamine compound (b2) preferably has a number average molecular weight of less than 500 and has at least two amino groups and at least one aromatic ring in the molecule.

The absolute value of the difference in solubility parameter (SP value) calculated by the Fedors method between the polyol compound (a2) and the polyol compound (b1) is preferably 0.1 to 4.0 (J/cm ³ ) ^1/2 .

The main agent (A) preferably contains at least one selected from the group consisting of fillers, antioxidants, colorants, viscosity modifiers, silane coupling agents, antifoaming agents, and plasticizers.

The curing agent (B) preferably contains at least one selected from the group consisting of fillers, antioxidants, colorants, viscosity modifiers, plasticizers, and polyhydric alcohols having a number average molecular weight of less than 500.

It is preferable that the mass ratio of the main agent (A) and the curing agent (B) is 3:7 to 7:3.

The cured product obtained by curing the two-liquid curing adhesive composition preferably has a breaking elongation at -40°C (tensile speed of 20 m/sec) of 100% or more.

The cured product obtained by curing the two-liquid curing adhesive composition preferably has a tensile strength of 15 MPa or more and a breaking elongation of 100% or more according to JIS K6251.

It is preferable that a cured product obtained by curing the two-liquid curing adhesive composition has a tensile modulus of 10 MPa or more.

Further, it is preferable that the pot life of the two-liquid curing adhesive composition is 30 seconds to 60 minutes.

The cured product of the two-component curing adhesive composition of the present invention has both good tensile properties at room temperature and good elongation in a low temperature high speed tensile test.

(a) to (c) are diagrams conceptually explaining the curing reaction of a two-liquid curing adhesive composition. It is a top view showing the shape of the test piece with which a low-temperature high-speed tensile test is presented.

The two-part curable adhesive composition of this embodiment will be described below. This embodiment includes various embodiments described later.

(Adhesive composition)
The two-part curable adhesive composition of the present embodiment (hereinafter also simply referred to as "adhesive composition") has a main agent (A) and a curing agent (B). As used herein, the term "composition" includes not only a mixture but also a so-called "combination" form in which multiple substances to be mixed at the time of use are included separately. Therefore, both a state in which the main agent (A) and the curing agent (B) are separately provided and a state in which the main agent (A) and the curing agent (B) are mixed are both referred to herein as an "adhesive composition".

(Main agent (A))
The main agent (A) contains a urethane prepolymer (a1).
The urethane prepolymer (a1) is obtained by reacting a raw polyisocyanate with a polyol compound (a2). The urethane prepolymer (a1) refers to a compound having a polyisocyanate (a3) monomer unit and a polyol compound (a2) monomer unit. Specifically, this reaction is carried out so that the equivalent ratio (hereinafter also referred to as index) of the isocyanate groups in the starting polyisocyanate to the hydroxyl groups in the polyol compound (a2) is 2.05 to 14, and all of the polyol compound (a2) becomes the monomer unit of the urethane prepolymer (a1).

By setting the index to 2.05 or more, it becomes easy to obtain a cured product having excellent breaking strength, specifically, a cured product having a breaking strength of 15 MPa or more. In addition, in this specification, breaking strength means the tensile strength based on JISK6251.
In addition, by setting the index to 2.05 or more and making the isocyanate groups excessively large relative to the hydroxyl groups, the isocyanate groups remaining after the reaction between the starting polyisocyanate and the polyol compound (a2) can be sufficiently reacted with the curing agent (B). This makes it easier to obtain a cured product having an excellent breaking elongation, specifically a cured product having a breaking elongation of 100% or more. In this specification, elongation at break means elongation at break in accordance with JIS K6251.

The index is preferably 3 or greater, more preferably 4 or greater. On the other hand, if the index is too large, the elongation at break may become too low. Therefore, the index is 14 or less, preferably 10 or less, more preferably 8 or less.

According to the adhesive composition of the present embodiment, after the polyisocyanate (a3) reacts with the polyol compound (a2), the active hydrogen groups of the polyol compound (b1) or the polyamine compound (b2) in the curing agent (B) described later are reacted, and after the polyisocyanate (a3) remains unreacted with the polyol compound (a2), the active hydrogen groups of the curing agent (B) are formed in the cured product. This forms a polymer blend in which polymer phases with different properties are mixed.

The starting polyisocyanate is not particularly limited as long as it has two or more isocyanate groups in the molecule. As the raw material polyisocyanate, conventionally known polyisocyanate compounds can be used.
原料ポリイソシアネートに使用されるポリイソシアネート化合物としては、具体的には、ＴＤＩ（例えば、２，４－トリレンジイソシアネート（２，４－ＴＤＩ）、２，６－トリレンジイソシアネート（２，６－ＴＤＩ））、ＭＤＩ（例えば、４，４'－ジフェニルメタンジイソシアネート（４，４'－ＭＤＩ）、２，４'－ジフェニルメタンジイソシアネート（２，４'－ＭＤＩ））、１，４－フェニレンジイソシアネート、ポリメチレンポリフェニレンポリイソシアネート、キシリレンジイソシアネート（ＸＤＩ）、テトラメチルキシリレンジイソシアネート（ＴＭＸＤＩ）、トリジンジイソシアネート（ＴＯＤＩ）、１，５－ナフタレンジイソシアネート（ＮＤＩ）、トリフェニルメタントリイソシアネートのような芳香族ポリイソシアネート；ペンタメチレンジイソシアネート（ＰＤＩ）、ヘキサメチレンジイソシアネート（ＨＤＩ）、トリメチルヘキサメチレンジイソシアネート（ＴＭＨＤＩ）、リジンジイソシアネート、ノルボルナンジイソシアネート（ＮＢＤＩ）のような脂肪族ポリイソシアネート；トランスシクロヘキサン－１，４－ジイソシアネート、イソホロンジイソシアネート（ＩＰＤＩ）、ビス（イソシアネートメチル）シクロヘキサン（Ｈ ₆ ＸＤＩ）、ジシクロヘキシルメタンジイソシアネート（Ｈ ₁₂ ＭＤＩ）のような脂環族ポリイソシアネート；これらのカルボジイミド変性ポリイソシアネート；これらのイソシアヌレート変性ポリイソシアネート；等が挙げられる。

Such polyisocyanate compounds can be used individually or in combination of two or more as the raw material polyisocyanate of the embodiment.
Among these, it is preferable to use aromatic polyisocyanate, and it is particularly preferable to use MDI because of its excellent curability.

According to one embodiment, the raw material polyisocyanate preferably contains at least one of diphenylmethane diisocyanate, polymeric methane diisocyanate, and an isocyanate compound containing an isocyanurate group, from the viewpoint of improving the reaction activity and developing good strength when cured.

The polyol compound (a2) has at least two hydroxyl groups in one molecule and a number average molecular weight of 500 or more.

If the number average molecular weight of the polyol compound (a2) is less than 500, the elongation at break of the cured product may be lowered and the cured product may become too hard. In addition, even if the equivalent ratio (active hydrogen groups of the polyamine compound (b2)/active hydrogen groups of the polyol compound (b1)), which will be described later, or the mixing ratio of the main agent (A) and the curing agent (B) is adjusted, it becomes difficult to adjust the tensile modulus of the cured product (hereinafter simply referred to as the elastic modulus). The upper limit of the number average molecular weight of the polyol compound (a2) is 3,000, for example.

From the viewpoint of effectively improving the breaking strength and breaking elongation of the cured product, the polyol compound (a2) is preferably at least one selected from the group consisting of polyethylene glycol, polypropylene glycol, polyester polyol, polytetramethylene ether glycol, polycarbonate polyol, and polycaprolactone polyol.

Polyester polyols include, for example, condensates (condensation polyester polyols) of low-molecular-weight polyhydric alcohols and polybasic carboxylic acids. Specific examples of low-molecular-weight polyhydric alcohols include ethylene glycol (EG), diethylene glycol, propylene glycol (PG), dipropylene glycol, 1,3-butanediol, 1,4-butanediol, pentanediol, neopentyl glycol, hexanediol, cyclohexanedimethanol, glycerin, 1,1,1-trimethylolpropane (TMP), 1,2,5-hexanetriol, pentaerythritol, and other low-molecular-weight polyols; sugars, such as sorbitol; etc. On the other hand, examples of polybasic carboxylic acids that form condensation polyester polyols include hydroxycarboxylic acids such as glutaric acid, adipic acid, azelaic acid, fumaric acid, maleic acid, pimelic acid, suberic acid, sebacic acid, phthalic acid, terephthalic acid, isophthalic acid, dimer acid, pyromellitic acid, other low-molecular-weight carboxylic acids, oligomeric acids, castor oil, and reaction products of castor oil and ethylene glycol (or propylene glycol).

Polycarbonate polyols are produced through reactions such as demethanol condensation reaction between polyol and dimethyl carbonate, dephenol condensation reaction between polyol and diphenyl carbonate, or deethylene glycol condensation reaction between polyol and ethylene carbonate. Polyols used in these reactions include various saturated or unsaturated glycols such as 1,6-hexanediol, diethylene glycol, triethylene glycol, propylene glycol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, pentanediol, 3-methyl-1,5-pentanediol, octanediol, 1,4-butynediol, dipropylene glycol, tripropylene glycol, and polytetramethylene ether glycol; - Alicyclic glycols such as cyclohexanedimethanol and the like.

Polycaprolactone polyols include, for example, lactones such as ε-caprolactone, α-methyl-ε-caprolactone and ε-methyl-ε-caprolactone which are ring-opening polymerized with a suitable polymerization initiator and have hydroxyl groups at both ends.

The number average molecular weight of the urethane prepolymer (a1) is preferably 1000 or more and 15000 or less, more preferably 1000 or more and 10000 or less.
Here, the number average molecular weight is the number average molecular weight (in terms of polystyrene) measured by gel permeation chromatography (GPC), and tetrahydrofuran (THF) and N,N-dimethylformamide (DMF) are preferably used as solvents for measurement.

The main agent (A) contains a residual polyisocyanate (a3) in addition to the urethane prepolymer (a1).
In this specification, the residual polyisocyanate (a3) refers to a polyisocyanate compound in which all the isocyanate groups in the molecule remain without reacting with the polyol compound (a2), i.e., the same compound as the starting polyisocyanate. Since the main agent (A) contains the residual polyisocyanate (a3), the reaction with the curing agent (B) can be carried out quickly. As a result, the curing time can be shortened, the residual polyisocyanate (a3) can be prevented from reacting with moisture and foaming, and the tensile properties such as breaking strength and breaking elongation of the cured product can be prevented from decreasing. As described above, the urethane prepolymer (a1) is obtained by reacting such that all of the polyol compound (a2) becomes the monomer unit of the urethane prepolymer (a1), with the index of the isocyanate groups in the raw material polyisocyanate to the hydroxyl groups in the polyol compound (a2) being 2.05 to 14. Therefore, in the main compound (A), the polyol compound (a2) is added to 1/14 to 1/2.05 of the total number of isocyanate groups present in the raw material polyisocyanate. It can be said that the urethane prepolymer (a1) and the residual polyisocyanate (a3) are mixed.

(Curing agent (B))
The curing agent (B) contains a polyamine compound (b2) and a polyol compound (b1).

Since the polyamine compound (b2) has a high reaction rate with polyisocyanate, the reaction with the residual polyisocyanate (a3) contained in the main component (A) proceeds rapidly. The polyamine (b2) also reacts with the urethane prepolymer (a1) to cure and grow the urethane prepolymer (a1). The adhesive composition in which the main agent (A) and the curing agent (B) are mixed generates heat with these reactions, so the reaction between the polyol compound (b1) and the residual polyisocyanate (a3) is further accelerated. As a result, the curing time is shortened, and the effect of shortening the pot life is obtained.

The polyamine compound (b2) is not particularly limited as long as it has a number average molecular weight of less than 500 and has at least two amino groups and at least one aromatic ring in the molecule, and conventionally known polyamine compounds can be used. It is preferable to use a polyamine compound having a number average molecular weight of less than 500 and having at least two amino groups and at least one aromatic group in one molecule as the polyamine compound (b2), because the rate of reaction with the residual polyisocyanate (a3) is increased.

Specific examples of the polyamine compound (b2) include metaphenylenediamine, orthophenylenediamine, paraphenylenediamine, m-xylylenediamine (MXDA), diaminodiphenylmethane, diaminodiphenylsulfone, diaminodiethyldiphenylmethane, diethylmethylbenzenediamine, 2-methyl-4,6-bis(methylthio)-1,3-benzenediamine, 4,4'-methylenebis(2-chloroaniline), 4,4'-methylenebis(3-chloro -2,6-diethylaniline), trimethylene bis(4-aminobenzoate), bis(4-amino-2,3-dichlorophenyl)methane and other aromatic polyamines, and these may be used alone or in combination of two or more.

The polyol compound (b1) is preferably a compound having at least two hydroxyl groups in one molecule and having a number average molecular weight of 500 or more. When the curing agent (B) contains the polyol compound (b1), the elongation at break of the cured product of the adhesive composition increases. When the number average molecular weight of the polyol compound (b1) is less than 500, the breaking elongation of the cured product of the adhesive composition may be lowered and the cured product may become too hard. The upper limit of the number average molecular weight of the polyol compound (b1) is 3,000, for example.

In addition, in the cured product of the adhesive composition, the starting polyisocyanate reacts with a plurality of types of compounds, that is, the polyol compound (a2), the polyol compound (b1), and the polyamine compound (b2). In this way, by introducing various compounds as the skeleton of the cured product, the temperature change in the tensile properties in the temperature range (for example, the range of -40 to 180 ° C.) assumed as the service temperature of the cured product is suppressed and stabilized.

In addition, since the polyol compound (b1) reacts with polyisocyanate more slowly than the polyamine compound (b2), the curing time is not too short, which contributes to the improvement of workability.

Moreover, by using different types of polyol compound (a2) and polyol compound (b1) as raw materials of the adhesive composition, the tensile modulus of the cured product can be adjusted.

According to one embodiment, the polyol compound (b1) is preferably a compound containing at least one monomer unit selected from the group consisting of polyethylene glycol, polypropylene glycol, polytetramethylene ether glycol, and polycarbonate polyol in the molecule, from the viewpoint of effectively improving the breaking strength and breaking elongation of the cured product. According to one embodiment, the polyol compound (b1) preferably contains at least one of polyethylene glycol and polypropylene glycol. Further, according to one embodiment, the terminal of the polyol compound (b1) preferably contains at least one selected from a primary hydroxyl group, a secondary hydroxyl group, an amino group, an acid anhydride-modified group, and a ring-opening group obtained by ring-opening the acid anhydride-modified group, from the viewpoint of improving the reaction activity. An acid anhydride-modified group is a group having an acid anhydride added to its end. Acid anhydrides may be those obtained by dehydration condensation of two molecules of carboxylic acid, and include acetic anhydride, propionic anhydride, oxalic anhydride, succinic anhydride, maleic anhydride, phthalic anhydride, and benzoic anhydride. A ring-opened group obtained by ring-opening an acid anhydride-modified group means a functional group produced by reacting an acid anhydride with water, a hydroxyl group, an amino group, an epoxy group, or the like. Cyclic acid anhydrides such as succinic anhydride, maleic anhydride, and phthalic anhydride are used as the acid anhydride of the acid anhydride-modifying group serving as the ring-opening group. According to one embodiment, the polyol compound (b1) is particularly preferably terminated with primary hydroxyl groups.

The equivalent ratio of the active hydrogen groups in the polyamine compound (b2) to the active hydrogen groups in the polyol compound (b1) (hereinafter referred to as "active hydrogen group (b2)/active hydrogen group (b1)") is 1.5 to 6. If the ratio of active hydrogen group (b2)/active hydrogen group (b1) is less than 1.5 or more than 6, the pot life of the adhesive composition is not within the appropriate range. The ratio of active hydrogen group (b2)/active hydrogen group (b1) is preferably 1.5-4.

In addition, the equivalent ratio of the assumed remaining isocyanate groups in the main agent (A) (after all of the polyol compound (a2) reacts with the raw material polyisocyanate to form the urethane prepolymer (a1), the total of the isocyanate groups remaining in (a1) and the remaining isocyanate groups in the remaining polyisocyanate (a3), that is, all unreacted isocyanate groups assumed residues in the main agent (A)) to the active hydrogen groups in the curing agent (B) (hereinafter referred to as "isocyanate groups (referred to as "residue (A)/active hydrogen group (B)") is 1-2. If the isocyanate group (A)/active hydrogen group (B) ratio is less than 1, even if the cured product of the adhesive composition contains the skeletons of the polyol compound (a2) and the polyol compound (b1), it becomes difficult to reduce the temperature dependence of the viscoelastic properties of the cured product. On the other hand, when the ratio of isocyanate group (A)/active hydrogen group (B) exceeds 2, the chances of reaction between the isocyanate group and the active hydrogen groups in the polyol (b1) and polyamine compound (b2) decrease, and the number of unreacted isocyanate groups becomes too large, which slows down the curing speed of the adhesive composition and increases the possibility of foaming.

The solubility parameters (SP values) of the polyol compound (a2) and the polyol compound (b1) calculated by the Fedors method are different from each other, and are very preferably 14.0 to 21.0 (J/cm ³ ) ^1/2 . Here, the Fedors method is the following formula:
[Number 1]

SP=[Σ(Ecoh)/Σ(Va)] ^1/2

(In the formula, Ecoh is the cohesive energy of one repeating polymer unit, and Va is the volume.)
is.

According to one embodiment, the solubility parameters (SP values) of the polyol compound (a2) and the polyol compound (b1) calculated by the Fedors method are preferably different from each other. By using two different polyols exhibiting high compatibility with each other, it is possible to form a cured adhesive composition in which the hard segment and the soft segment spontaneously adopt a microphase-separated structure. In particular, the absolute value of the difference in solubility parameter (SP value) calculated by the Fedors method between the polyol compound (a2) and the polyol compound (b1) is very preferably 0.1 to 4.0 (J/cm ³ ) ^1/2 .

According to one embodiment, the weight ratio of the main agent (A) and the curing agent (B) is preferably 3:7 to 7:3. According to the adhesive composition of the present embodiment, even if the mixing ratio of the main agent (A) and the curing agent (B) deviates within such a range, the impact on the breaking strength and breaking elongation of the cured product is extremely small. Specifically, the rate of change in the breaking strength and breaking elongation is suppressed within ±20% with respect to the breaking strength and breaking elongation when the mass ratio is 1:1. On the other hand, the maximum value of the tensile modulus can be adjusted to, for example, three times or more the minimum value within the range of the mass ratio.

Each of the main agent (A) and the curing agent (B) described above may further contain various additives such as fillers, curing catalysts, plasticizers, anti-aging agents, antioxidants, pigments (dyes), thixotropic agents, UV absorbers, flame retardants, surfactants (including leveling agents), dispersants, dehydrating agents, adhesion-imparting agents, and antistatic agents, if necessary, as long as they do not impair the object of the present invention. The main agent (A) desirably contains at least one selected from the group consisting of fillers, antioxidants, colorants, viscosity modifiers, silane coupling agents, antifoaming agents, and plasticizers. The curing agent (B) preferably contains at least one selected from the group consisting of fillers, antioxidants, colorants, viscosity modifiers, plasticizers, and polyhydric alcohols having a number average molecular weight of less than 500.

By changing the NCO group/total active hydrogen group ratio within the range of 0.5 to 4, the elastic modulus of the cured product can be adjusted, and the target elastic modulus can be obtained according to the application. Even if the NCO group/total active hydrogen group ratio is changed in this way, the breaking strength and breaking elongation of the cured product do not change significantly. Specifically, with respect to the breaking strength and breaking elongation when the mixing ratio (mass ratio) of the main agent (A) and curing agent (B) is 1:1, the rate of change in breaking strength and breaking elongation is suppressed within ±20%. Thus, even if the mixing ratio of the main agent (A) and the curing agent (B) deviates from 1:1, the breaking strength and breaking elongation of the cured product do not change significantly, so the elastic modulus can be adjusted while maintaining high breaking strength and breaking elongation. Therefore, according to one embodiment, the mixing ratio of the main agent (A) and the curing agent (B) can be 3:7 to 7:3.

It should be noted that the two-part curable adhesive composition of the embodiment does not need to include a catalyst such as an organometallic compound or a tertiary amine. When the main agent (A) and the curing agent (B) are mixed, the two-component curing adhesive composition of the embodiment starts a curing reaction at room temperature to form a cured product.

Here, the curing reaction of the adhesive composition will be conceptually described with reference to FIG. Typically, from the state shown in FIG. 1(a) at the time of mixing the two liquids, through the state in the middle of the curing reaction shown in FIG. 1(b), the final form shown in FIG. Depending on the mixing ratio of the main agent (A) and curing agent (B), the final form can be as shown in any one of FIGS. 1(a) to 1(c). Typically, the urethane prepolymer (a1) (symbol a1) and the residual polyisocyanate (a3) contained in the main agent (A) react with the polyamine compound (b2) contained in the curing agent (B) to form hard particles and grow (symbol 3). On the other hand, the polyol compound (b1) contained in the curing agent (B) reacts later than the reaction between the residual polyisocyanate (a3) and the polyamine compound (b2) contained in the main agent (A), forming a large amount of matrix (symbol 5). Depending on the mixing ratio of the main agent (A) and the curing agent (B), the number and size of the particles to be formed vary, and vary from spherulite level to micron level fine particles. It is considered that the change is reflected in the elastic modulus of the cured product. On the other hand, the breaking strength and breaking elongation of the cured product are adjusted by specifying the molecular weights of the polyol compound (a2) and the polyol compound (b1), and the equivalent ratio defined among these polyol compounds, polyisocyanate, and polyamine compound (b2) within the above-described range.

According to the adhesive composition of the present embodiment, it is possible to obtain a cured product having excellent tensile properties such as breaking strength and breaking elongation, and small temperature dependence of viscoelastic properties, and suppress foaming.
Tensile properties include breaking strength, breaking elongation, and tensile modulus. Specifically, as a cured product having excellent tensile properties, a cured product having a breaking strength of 15 MPa or more, a breaking elongation of 100% or more, and a tensile modulus of 10 MPa or more can be obtained. Tensile properties can be measured according to JIS K6251. Such tensile properties are such that the breaking elongation is equivalent to that of conventional polyurethane-based adhesives, while the breaking strength conforms to the breaking strength of epoxy resin-based adhesives. In addition, as a cured product with small temperature dependence of viscoelastic properties, a cured product having a breaking elongation at -40°C (tensile speed of 20 m/sec) of 100% or more can be obtained. In general, urethane-based adhesives have good tensile properties at room temperature, but few exhibit good elongation in tensile tests at low temperatures and high speeds. The cured product obtained from the adhesive composition of the present embodiment has improved tendency and extremely little temperature dependence. A cured product having such characteristics can be said to be suitable for joining structural parts such as automobile bodies.

The breaking strength is preferably 20 MPa or more, more preferably 25 MPa or more. Although the upper limit of the breaking strength is not particularly limited, it is, for example, about 100 MPa.
The breaking elongation is preferably 150% or more, more preferably 200% or more. Although the upper limit of the breaking elongation is not particularly limited, it is, for example, about 500%.
The tensile modulus is preferably 50 MPa or higher, more preferably 100 MPa or higher. Although the upper limit of the tensile modulus is not particularly limited, it is, for example, about 500 MPa.
The breaking elongation at −40° C. (tensile speed 20 m/sec) is preferably 150% or more, more preferably 200% or more.

According to this embodiment, the pot life of the adhesive composition is 30 seconds to 60 minutes. Here, the pot life means the time from when the main agent (A) and the curing agent (B) are mixed to when they can no longer be handled. Since the pot life of the adhesive composition of the embodiment can be adjusted in a relatively wide range, the workability is excellent and foaming can be suppressed. When the pot life is 30 seconds or more, the curing time is not too short and the workability is excellent. The usable time is preferably 40 minutes or less, more preferably 30 minutes or less, and even more particularly preferably 10 minutes or less.

The adhesive composition of the present embodiment is not limited to, for example, automobile bodies, but can be used for bonding parts of various structures. In addition to being used as an adhesive, the adhesive composition of the present embodiment can also be used as, for example, paints, waterproof materials, flooring materials, elastomers, artificial leather, spandex, and the like.

(Method for producing adhesive composition)
A method for producing an adhesive composition comprises a step of producing a main agent (A) and a step of producing a curing agent (B).

In the step of producing the main compound (A), the starting polyisocyanate and the polyol compound (a2) are reacted with an index of 2.05 to 14 so that all of the polyol compound (a2) becomes the monomer unit of the urethane prepolymer (a1) to produce the urethane prepolymer (a1). As a result, a main agent (A) containing the urethane prepolymer (a1) and residual polyisocyanate (a3) is produced. Here, the starting polyisocyanate, the polyol compound (a2), the urethane prepolymer (a1), and the residual polyisocyanate (a3) are configured in the same manner as the starting polyisocyanate, the polyol compound (a2), the urethane prepolymer (a1), and the residual polyisocyanate (a3), respectively.

In the step of producing the curing agent (B), the curing agent (B) containing the polyol compound (b1) and the polyamine compound (b2) is produced. Here, the polyol compound (b1) and polyamine compound (b2) are configured in the same manner as the polyol compound (b1) and polyamine compound (b2) described above.

The above-described adhesive composition can be produced using the production method described above.

In order to investigate the effects of the present invention, adhesive compositions were prepared according to the blending amounts shown in Tables 1 and 2, and the foamability, pot life, breaking strength of the cured product, breaking elongation, and storage elastic modulus were measured.

Urethane prepolymers 1 to 4 were prepared in the manner described below, and the additives shown in the table were added to prepare a base compound. A curing agent was prepared by mixing raw materials shown in the table.

<Synthesis of urethane prepolymer 1>
Urethane prepolymer 1 was synthesized by reacting 100 g of polytetramethylene ether glycol and 100 g of 4,4′-diphenylmethane diisocyanate (index 4.0) under a nitrogen atmosphere with stirring at 80° C. for 4 hours.

<Synthesis of urethane prepolymer 2>
Urethane prepolymer 2 was synthesized by reacting 100 g of polytetramethylene ether glycol and 150 g of 4,4′-diphenylmethane diisocyanate (index 6.0) under a nitrogen atmosphere with stirring at 80° C. for 4 hours.

<Synthesis of urethane prepolymer 3>
Urethane prepolymer 3 was synthesized by reacting 100 g of polycarbonate diol and 100 g of 4,4′-diphenylmethane diisocyanate (index 4.0) under a nitrogen atmosphere with stirring at 80° C. for 4 hours.

<Synthesis of urethane prepolymer 4>
Urethane prepolymer 4 was synthesized by reacting 100 g of polytetramethylene ether glycol and 50 g of 4,4′-diphenylmethane diisocyanate (index 2.0) under a nitrogen atmosphere with stirring at 80° C. for 4 hours.

The polytetramethylene ether glycol, polycarbonate diol, and 4,4′-diphenylmethane diisocyanate used in the production of the above urethane prepolymers 1 to 4 were as shown below.
・Polytetramethylene ether glycol:
PTMG1000 (weight average molecular weight 1000), manufactured by Mitsubishi Chemical Corporation, polycarbonate diol:
Duranol T6001 (weight average molecular weight 1000), manufactured by Asahi Kasei Co., Ltd. 4,4'-diphenylmethane diisocyanate:
Millionate MT (weight average molecular weight 250), manufactured by Tosoh Corporation

In the table, the values of urethane prepolymers 1 to 4 indicate the total amount of urethane prepolymer (a1) and residual polyisocyanate (a2). Raw materials other than the urethane prepolymers 1 to 4 shown in the table were those shown below. In the table, amounts of raw materials are shown in parts by mass.
・Carbon black: 200MP, manufactured by Shin Nikka Carbon ・Calcium carbonate 1: Heavy calcium carbonate, Super S, manufactured by Maruo Calcium ・Plasticizer: Diisononyl phthalate, manufactured by J-Plus ・Polyol 1: Polypropylene glycol, Sannix GL-3000, manufactured by Sanyo Kasei ・Polyol 2: Polybutadiene polyol, Poly bd R-45HT, manufactured by Idemitsu Kosan ・Polyol 3: Carbinol-modified silicone oil at both ends, K F-6002, manufactured by Shin-Etsu Chemical Co., Ltd. Polyamine: diethylmethylbenzenediamine, DETDA, manufactured by Mitsui Fine Chemicals Co., Ltd. Calcium carbonate 2: light calcium carbonate, Calfine 200, manufactured by Maruo Calcium Co., Ltd. Silica: Rheolosil QS-102S, manufactured by Tokuyama In the table, "main agent (A) / hardener (B) ratio" means the mass ratio of the main agent and the hardener.
Although not shown in the table, the amino group/hydroxyl group ratio was adjusted within the range of 1.5-6.

The prepared main agent and curing agent were mixed at the main agent (A)/curing agent (B) ratio shown in the table, and the pot life was evaluated in the following manner, and the breaking strength, breaking elongation, and low temperature and high speed breaking elongation were measured. Active hydrogen group (b2)/active hydrogen group (b1) and isocyanate-deemed residue (A)/active hydrogen group (B) are also shown in the table.

<SP value>
SP values were calculated by the following Fedors method:
[Number 2]

SP=[Σ(Ecoh)/Σ(Va)] ^1/2

(In the formula, Ecoh: cohesive energy of one repeating polymer unit, Va: volume.)

<Breaking strength, breaking elongation>
The cured product was used as a dumbbell-shaped No. 3 test piece, and a tensile test was performed in accordance with JIS K6251, and the tensile strength (breaking strength) and breaking elongation (elongation at break) were measured under the conditions of a temperature of 20 ° C. and a crosshead speed (tensile speed) of 200 mm / min. Marked lines for breaking elongation measurement were attached at intervals of 20 mm. As a result, when the breaking strength was 15 MPa or more, the breaking strength was evaluated as excellent, and when the breaking elongation was 100% or more, the breaking elongation was evaluated as excellent.

<Breaking elongation (low temperature and high speed)>
The cured product was used as a low-temperature high-speed tensile test piece as shown in FIG. 2, and a tensile test was performed in accordance with JIS K6251. Marked lines for breaking elongation measurement were attached at intervals of 5 mm. As a result, when the breaking elongation was 100% or more, it was evaluated as excellent in breaking elongation.

<Possible time>
The pot life was defined as the time after mixing the main agent and the curing agent until the mixture could no longer be handled, that is, the time until the fluidity as an adhesive was significantly lost. Those having pot life of 30 seconds to 60 minutes and suitable for use were evaluated as A, and those other than that were evaluated as B. Among these, A was evaluated as having an appropriate pot life.

(Discussion)
The two-component curing adhesive compositions of Examples satisfying the scope of the present invention had high breaking strength and breaking elongation (both at room temperature and at low temperature and high speed), and the pot life was within an appropriate range.
Comparative Example 1 is a composition having a small index and having a value of active hydrogen group (b2)/active hydrogen group (b1) and a value of isocyanate-deemed residue (A)/active hydrogen group (B) both outside the ranges of the present invention, and is slightly inferior in breaking strength and breaking elongation. Comparative Example 2 is a composition having a large difference in SP value between (a2) and (b1), and is significantly inferior in breaking strength and breaking elongation.

Although the two-part curable adhesive composition of the present invention has been described above, the present invention is not limited to the above embodiments and examples, and various improvements and modifications may be made without departing from the gist of the present invention.

1 Cured product 3 Particulate matter 5 Matrix

Claims (13)

a main agent (A) containing a urethane prepolymer (a1);
and a curing agent (B) containing a polyol compound (b1) and a polyamine compound (b2),
The urethane prepolymer (a1) is obtained by reacting a raw material polyisocyanate and a polyol compound (a2) having a number average molecular weight of 500 or more and having at least one hydroxyl group in one molecule such that the equivalent ratio of the isocyanate group in the raw material polyisocyanate to the hydroxyl group in the polyol compound is 2.05 to 14 so that all of the polyol compound (a2) becomes the monomer unit of the urethane prepolymer (a1).
In addition to the urethane prepolymer (a1), the main component (A) further contains a residual polyisocyanate (a3) which is the remainder of the raw material polyisocyanate that has not reacted with the polyol compound (a2),
The equivalent ratio of the active hydrogen groups in the polyamine compound (b2) to the active hydrogen groups in the polyol compound (b1) is 1.5 to 6,
A two-component curing adhesive composition in which the equivalent ratio of the isocyanate groups in the main component (A) to the active hydrogen groups in the curing agent (B) is 0.25 to 2,
The two-component curable adhesive composition, wherein the polyol compound (a2) and the polyol compound (b1) have different solubility parameters (SP values) calculated by the Fedors method and are 14.0 to 21.0 (J/cm ³ ) ^1/2 . The two-part curable adhesive composition according to claim 1, wherein the polyol compound (a2) having a number average molecular weight of 500 or more is at least one selected from the group consisting of polyethylene glycol, polypropylene glycol, polyester polyol, polytetramethylene ether glycol, polycarbonate polyol, and polycaprolactone polyol. The two-component curable adhesive composition according to claim 1 or 2, wherein the polyol compound (b1) has a number average molecular weight of 500 or more. The two-component curable adhesive composition according to any one of claims 1 to 3, wherein the polyol compound (b1) contains, in the molecule, at least one monomer unit selected from the group consisting of polyethylene glycol, polypropylene glycol, polytetramethylene ether glycol, and polycarbonate polyol. The two-component curable adhesive composition according to any one of claims 1 to 4, wherein the polyamine compound (b2) has a number average molecular weight of less than 500 and has at least two amino groups and at least one aromatic ring in the molecule. The absolute value of the difference in solubility parameter (SP value) calculated by the Fedors method between the polyol compound (a2) and the polyol compound (b1) is 0.1 to 4.0 (J/cm ³ ) ^1/2 . The two-component curable adhesive composition according to any one of claims 1 to 5. The two-part curable adhesive composition according to any one of claims 1 to 6, wherein the main agent (A) contains at least one selected from the group consisting of fillers, antioxidants, colorants, viscosity modifiers, silane coupling agents, antifoaming agents, and plasticizers. The curing agent (B) contains at least one selected from the group consisting of fillers, antioxidants, colorants, viscosity modifiers, plasticizers, and polyhydric alcohols having a number average molecular weight of less than 500. The two-part curable adhesive composition according to any one of claims 1 to 7. 9. The two-component curable adhesive composition according to any one of claims 1 to 8, wherein the mass ratio of the main agent (A) and the curing agent (B) is 3:7 to 7:3. The two-component curable adhesive composition according to any one of claims 1 to 9, wherein the cured product obtained by curing the two-component curable adhesive composition has a breaking elongation at -40 ° C. (tensile speed 20 m / sec) of 100% or more. The two-component curable adhesive composition according to any one of claims 1 to 10, wherein the cured product obtained by curing the two-component curable adhesive composition has a tensile strength of 15 MPa or more and a breaking elongation of 100% or more according to JIS K6251. The two-component curable adhesive composition according to any one of claims 1 to 11, wherein a cured product obtained by curing the two-component curable adhesive composition has a tensile modulus of 10 MPa or more. The two-part curable adhesive composition according to any one of claims 1 to 12, which has a pot life of 30 seconds to 60 minutes.

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