JP7740338B2 - 2-cyanoacrylate adhesive composition - Google Patents

Description

The present disclosure relates to a 2-cyanoacrylate adhesive composition.

Adhesive compositions containing 2-cyanoacrylate compounds, due to the unique anionic polymerization properties of 2-cyanoacrylate compounds, initiate polymerization with weak anions, such as traces of moisture, adhering to the surface of the substrate, enabling them to firmly bond various materials in a short period of time. For this reason, they are used as so-called instant adhesives in a wide range of fields, including industrial, medical, and household applications.

For example, Japanese Patent No. 5267571 proposes an adhesive composition containing a 2-cyanoacrylic acid ester and a polyfunctional cyanoacrylic acid ester having two or more 2-cyanoacryloyl groups, in which the number average molecular weight of the (b) polyfunctional cyanoacrylic acid ester is 1,000 to 50,000, and the amount of the (b) polyfunctional cyanoacrylic acid ester is 1 to 400 parts by mass per 100 parts by mass of the 2-cyanoacrylic acid ester.

Adhesive compositions containing 2-cyanoacrylate compounds have the problem that the cured product is hard and brittle and does not have a crosslinked structure, so while they have excellent shear adhesive strength, they have low peel adhesive strength. In recent years, adhesive compositions are required to have excellent peel adhesive strength when cured against a variety of materials, for example, excellent peel adhesive strength against rubbers such as ethylene propylene diene rubber (EPDM).

The inventors have discovered that the adhesive composition disclosed in Japanese Patent No. 5267571 leaves room for improvement in terms of peel adhesion strength of the cured product to rubber.

The present inventors have now discovered that a 2-cyanoacrylate adhesive composition containing a 2-cyanoacrylate compound and a polyfunctional cyanoacrylate compound, wherein the 2-cyanoacrylate compound is homopolymerized to produce a cured product with a storage modulus of 1.0 x ¹⁰ Pa or less at 25°C, results in improved peel adhesion strength to rubber and a superior rate of increase in peel adhesion strength, compared to adhesive compositions that do not contain the polyfunctional cyanoacrylate compound.

Therefore, the problem to be solved by this disclosure is to provide a 2-cyanoacrylate adhesive composition that has an excellent rate of increase in peel adhesion strength of the cured product to rubbers such as EPDM.

The specific means for achieving the objectives are as follows:
<1> A 2-cyanoacrylate adhesive composition containing a 2-cyanoacrylate compound and a polyfunctional cyanoacrylate compound, wherein the 2-cyanoacrylate compound is homopolymerized to produce a cured product having a storage modulus at 25°C of 1.0 x 10 ⁷ Pa or less.
<2> The 2-cyanoacrylate adhesive composition according to <1> above, wherein a cured product obtained by curing the 2-cyanoacrylate adhesive composition and having a width of 5 mm, a length of 50 mm and a thickness of 1 mm is fixed to a tensile tester with a jig distance of 20 mm (L0), a mark is made at the jig fixing position, and the product is pulled at a pulling rate of 20 mm/min until the jig distance reaches 40 mm (L1), after which the jig is released from fixation and the length (L2) between the marks is measured after 1 minute has elapsed, and the elongation recovery rate (%) calculated using the following formula is 70% or more.
Elongation recovery rate (%): {(L1-L2)/(L1-L0)}×100
<3> The 2-cyanoacrylate adhesive composition according to <1> or <2> above, wherein a cured product obtained by curing the 2-cyanoacrylate adhesive composition and having a width of 5 mm, a length of 50 mm and a thickness of 1 mm is fixed to a tensile tester with a jig distance of 20 mm (L0), a mark is made at the jig fixing position, and the product is pulled at a pulling rate of 20 mm/min until the jig distance reaches 40 mm (L1), after which the jig is released from fixation and the length (L3) between the marks is measured after 5 minutes have passed, and the elongation recovery rate (%) calculated using the following formula is 80% or more.
Elongation recovery rate (%): {(L1-L3)/(L1-L0)}×100
<4> The 2-cyanoacrylate adhesive composition according to any one of the above <1> to <3>, wherein a cured product obtained by curing the 2-cyanoacrylate adhesive composition and having a width of 5 mm, a length of 50 mm and a thickness of 1 mm is fixed to a tensile tester with a jig distance of 20 mm (L0), a mark is made at the jig fixing position, and the product is pulled at a pulling rate of 20 mm/min until the jig distance reaches 40 mm (L1), after which the jig is released from fixing and the length (L4) between the marks is measured after 30 minutes have passed, and the elongation recovery rate (%) calculated using the following formula is 95% or more.
Elongation recovery rate (%): {(L1-L4)/(L1-L0)}×100
<5> The peel adhesive strength (N/cm) of the 2-cyanoacrylate adhesive composition to an ethylene propylene diene rubber (EPDM) substrate, measured in accordance with JIS K 6854-3:1999, is defined as As1,
The 2-cyanoacrylate adhesive composition according to any one of <1> to <4> above, wherein the peel adhesion strength (N/cm) of a 2-cyanoacrylate adhesive composition obtained by excluding the polyfunctional cyanoacrylate compound from the 2-cyanoacrylate adhesive composition from which the peel adhesion strength As1 has been measured is defined as As2, and the following formula is satisfied:
(As1-As2/As2)×100≧150%
<6> The 2-cyanoacrylate adhesive composition according to any one of <1> to <5>, containing 0.01 to 50 parts by mass of the polyfunctional cyanoacrylate compound per 100 parts by mass of the 2-cyanoacrylate compound.
<7> The 2-cyanoacrylate adhesive composition according to any one of <1> to <6>, wherein the 2-cyanoacrylate compound has an ether bond.
<8> The 2-cyanoacrylate adhesive composition according to <7>, wherein the 2-cyanoacrylate compound has two or more of the ether bonds.
<9> The 2-cyanoacrylate adhesive composition according to any one of <1> to <8> above, wherein the 2-cyanoacrylate compound includes a compound represented by the following formula (1):

In formula (1),
L ¹ 's each independently represent -CH ₂ CH ₂ -, -CH ₂ CH ₂ CH ₂ -, -CH(R ¹ )CH ₂ - or -CH ₂ CH(R ¹ )-;
R ¹ represents a linear or branched alkyl group having 1 to 6 carbon atoms which may have a substituent;
^R2 represents a linear or branched alkyl group having 1 to 8 carbon atoms which may have a substituent;
p represents an integer of 1 to 5;
<10> The 2-cyanoacrylate adhesive composition according to any one of <1> to <9>, wherein the temperature at which the 2-cyanoacrylate compound exhibits a maximum value of loss tangent (tan δ(max)) is 65°C or lower.
<11> The 2-cyanoacrylate adhesive composition according to any one of <1> to <10>, wherein the polyfunctional cyanoacrylate compound includes at least one of a biscyanoacrylate compound and a triscyanoacrylate compound.
<12> The 2-cyanoacrylate adhesive composition according to any one of <1> to <11> above, wherein the polyfunctional cyanoacrylate compound has a molecular weight or number average molecular weight of 200 to 50,000.

According to the present disclosure, a 2-cyanoacrylate adhesive composition can be provided that exhibits an excellent increase in peel adhesion strength of the cured product against rubbers such as EPDM.

The following describes in detail the forms for implementing the present disclosure. However, the present disclosure is not limited to the following embodiments. In the following embodiments, the components (including element steps, etc.) are not essential unless otherwise specified. The same applies to numerical values and their ranges, and do not limit the present disclosure.

In the present disclosure, numerical ranges indicated using "to" include the numerical values before and after "to" as the minimum and maximum values, respectively.
In the numerical ranges described in stages in the present disclosure, the upper or lower limit value described in one numerical range may be replaced with the upper or lower limit value of another numerical range described in stages. Furthermore, in the numerical ranges described in the present disclosure, the upper or lower limit value of the numerical range may be replaced with the value shown in the synthesis examples.
In addition, in the present disclosure, a combination of two or more preferred aspects is a more preferred aspect.

(2-Cyanoacrylate Adhesive Composition)
The 2-cyanoacrylate adhesive composition of the present disclosure contains a 2-cyanoacrylate compound and a polyfunctional cyanoacrylate compound, and the cured product obtained by homopolymerizing the 2-cyanoacrylate compound has a storage modulus at 25°C of 1.0 x ¹⁰ Pa or less.

As a result of extensive research, the present inventors have found that by adopting the above-described configuration, it is possible to provide a 2-cyanoacrylate adhesive composition that exhibits an excellent rate of increase in peel adhesive strength of the cured product to rubbers such as EPDM.
The mechanism of action of this excellent effect is not clear, but is presumed as follows.
The 2-cyanoacrylate adhesive composition contains a 2-cyanoacrylate compound (hereinafter, a cured product obtained by homopolymerizing a 2-cyanoacrylate compound will also be referred to as a homopolymer) having a storage modulus of 1.0 x ¹⁰ Pa or less at 25°C, and a polyfunctional cyanoacrylate compound. This improves the entropy elasticity of the cured product of the 2-cyanoacrylate adhesive composition of the present disclosure (hereinafter, simply referred to as the cured product), improving its ability to follow deformations of the adherend. This is presumably why the peel strength and rate of increase of the cured product against rubbers such as EPDM are improved.

<2-Cyanoacrylate Compound>
The 2-cyanoacrylate adhesive composition of the present disclosure contains a 2-cyanoacrylate compound (hereinafter also referred to as a specific 2-cyanoacrylate compound) that is homopolymerized and has a cured product with a storage modulus at 25°C of 1.0 x ¹⁰ Pa or less. The 2-cyanoacrylate adhesive composition of the present disclosure may contain two or more types of the specific 2-cyanoacrylate compounds.
When a 2-cyanoacrylate adhesive composition contains a 2-cyanoacrylate compound that has a storage modulus of 1.0 x ¹⁰ Pa or less at 25°C when homopolymerized and cured (hereinafter, a cured product obtained by homopolymerizing a 2-cyanoacrylate compound is also referred to as a homopolymer), and a polyfunctional cyanoacrylate compound, the elongation recovery rate of the cured product tends to be improved. This is presumably because the entropy elasticity of the cured product of the 2-cyanoacrylate adhesive composition of the present disclosure (hereinafter, simply referred to as the cured product) is improved, which promotes deformation of the cured product back to its pre-elongation state and improves the elongation recovery rate of the cured product.

From the viewpoint of the increase rate of peel adhesive strength of the cured product to rubbers such as EPDM and the elongation recovery rate of the cured product, the storage modulus of the homopolymer at 25°C is preferably 9.0 x ¹⁰⁶ Pa or less.
The lower limit of the storage modulus of the homopolymer at 25° C. is not particularly limited, but can be, for example, 1.0×10 ⁴ Pa or more.

In the present disclosure, the storage modulus of a cured product obtained by homopolymerizing a specific 2-cyanoacrylate compound is measured as follows.
The 2-cyanoacrylate compound is injected between the jig of a dynamic viscoelasticity measuring device coated with triethanolamine, and then the storage modulus is measured using the dynamic viscoelasticity measuring device under conditions of a frequency of 1 Hz, a temperature of 25°C, and a thickness of 300 μm.
Once it has been confirmed that there is no longer any change in the storage modulus of the 2-cyanoacrylate compound, this is taken as a cured product of the 2-cyanoacrylate compound.
Next, using the above cured product, the storage modulus of the cured product is measured by shear in the range of -50°C to 150°C under conditions of a frequency of 1 Hz, a temperature increase rate of 2°C/min, and a relative humidity of 50%, and the storage modulus of the cured product at 25°C is determined.
As the dynamic viscoelasticity measuring device, an MCR301 manufactured by Anton Paar or a device of the same level can be used.

From the viewpoint of the rate of increase in peel adhesive strength of the cured product against rubber such as EPDM and the elongation recovery rate of the cured product, the temperature at which the maximum value of the loss tangent (tan δ(max)) of the cured product obtained by homopolymerizing the specific 2-cyanoacrylate compound is exhibited is preferably 65°C or lower, more preferably 55°C or lower, even more preferably 45°C or lower, and particularly preferably 40°C or lower.
The lower limit of the temperature is not particularly limited, but can be, for example, −20° C. or higher.

In the present disclosure, the temperature at which the loss tangent of a specific 2-cyanoacrylate compound exhibits a maximum value is measured as follows.
The specific 2-cyanoacrylate compound is injected between the jig of a dynamic viscoelasticity measuring device coated with triethanolamine, and then the storage modulus is measured using the dynamic viscoelasticity measuring device under the conditions of a frequency of 1 Hz, a temperature of 25°C, and a thickness of 300 μm.
After confirming that there is no longer any change in the storage modulus of the specific 2-cyanoacrylate compound, this is designated as a cured product of the specific 2-cyanoacrylate compound. Using the cured product, a dynamic viscoelasticity spectrum is obtained in the range of -50°C to 150°C under conditions of a frequency of 1 Hz and a temperature rise rate of 2°C/min, and the temperature at which the loss tangent (tan δ) reaches its maximum is measured. If two or more peaks are observed, the loss tangent (tan δ) corresponding to the largest peak is designated as the maximum value.
The dynamic viscoelasticity measuring device that can be used is as described above.

From the viewpoints of the increase rate of peel adhesive strength of the cured product against rubbers such as EPDM and the elongation recovery rate of the cured product, the specific 2-cyanoacrylate compound preferably has an ether bond. From the same viewpoints, the specific 2-cyanoacrylate compound preferably has two or more ether bonds, more preferably two to five ether bonds, even more preferably two to four ether bonds, and particularly preferably two or three ether bonds.
The 2-cyanoacrylate adhesive composition of the present disclosure may contain two or more specific 2-cyanoacrylate compounds having different numbers of ether bonds.

From the viewpoint of the increase rate of peel adhesion strength of the cured product to rubbers such as EPDM and the elongation recovery rate of the cured product, it is preferable that the specific 2-cyanoacrylate compound contains a compound represented by the following formula (1):

In formula (1), L ^1s each independently represent -CH ₂ CH ₂ -, -CH ₂ CH ₂ CH ₂ -, -CH(R ¹ )CH ₂ - or -CH ₂ CH(R ¹ )-, and from the viewpoint of the increase in peel adhesive strength of the cured product to rubbers such as EPDM and the elongation recovery rate of the cured product, they preferably represent -CH ₂ CH ₂ -, -CH(R ¹ )CH ₂ - or -CH ₂ CH(R ¹ )-, and more preferably represent -CH(R ¹ )CH ₂ - or -CH ₂ CH(R ¹ )-.

In formula (1), ^R1 represents an alkyl group having 1 to 6 carbon atoms, preferably 1 to 3 carbon atoms, which may have a substituent, and may be a linear or branched alkyl group. Examples of the substituent include an aryl group, a halogen atom, an alkoxy group, an aryloxy group, a cyano group, an alkoxycarbonyl group, an aryloxycarbonyl group, an acyl group, and an acyloxy group. Examples of ^R1 include a methyl group, an ethyl group, a propyl group, and a butyl group. From the viewpoints of the increase rate of peel adhesive strength of the cured product to rubbers such as EPDM and the elongation recovery rate of the cured product, a methyl group or an ethyl group is preferred, and a methyl group is more preferred.

In formula (1), ^R2 represents an alkyl group having 1 to 8 carbon atoms, preferably 1 to 4 carbon atoms, which may have a substituent, and may be a linear or branched alkyl group. Examples of the substituent include the substituents described above for ^R1 .
From the viewpoint of the rate of increase in peel adhesive strength of the cured product relative to rubber such as EPDM and the elongation recovery rate of the cured product, ^R2 in formula (1) is more preferably an alkyl group having 1 to 3 carbon atoms, more preferably a methyl group, an ethyl group, an n-propyl group or an isopropyl group, even more preferably a methyl group or an ethyl group, and particularly preferably a methyl group.

In formula (1), p represents an integer of 1 to 5, and from the standpoint of the rate of increase in peel adhesion strength of the cured product to rubbers such as EPDM and the elongation recovery rate of the cured product, it is preferably an integer of 1 to 4, more preferably an integer of 1 to 3, and even more preferably 2 or 3.

Specific examples of the compound represented by formula (1) include 2-(2-methoxyethoxy)ethyl, 2-(2-ethoxyethoxy)ethyl, 2-(2-propoxyethoxy)ethyl, 2-[2-(1-methylethoxy)ethoxy]ethyl, 2-[2-(2-methylpropoxy)ethoxy]ethyl, 2-[2-(1-methylpropoxy)ethoxy]ethyl, 2-[2-(1-ethylpropoxy)ethoxy]ethyl, 2-(2-methoxy-1-methylethoxy)ethyl, 2-(2-methoxy-2-methylethoxy)ethyl, 2-(2-ethoxy-1-methylethoxy)ethyl, 2-(2-ethoxy-2-methylethoxy)ethyl, 1-(2-methoxyethoxy)propyl-2-yl, 2-(2-methoxyethoxy)propyl-1-yl, 1-(2-ethoxyethoxy)propyl-2-yl, 2 -(2-ethoxyethoxy)propyl-1-yl, 1-(2-methoxy-1-methylethoxy)propyl-2-yl, 1-(2-methoxy-2-methylethoxy)propyl-2-yl, 2-(2-methoxy-1-methylethoxy)propyl-1-yl, 2-(2-methoxy-2-methylethoxy)propyl-1-yl, 1-(2-ethoxy-1-methylethoxy)propyl-2-yl, 1 -(2-ethoxy-2-methylethoxy)propyl-2-yl, 2-(2-ethoxy-1-methylethoxy)propyl-1-yl, 2-(2-ethoxy-2-methylethoxy)propyl-1-yl, 1-(2-propoxy-1-methylethoxy)propyl-2-yl, 1-(2-propoxy-2-methylethoxy)propyl-2-yl, 2-(2-propoxy-1-methylethoxy)propyl propyl-1-yl, 2-(2-propoxy-2-methylethoxy)propyl-1-yl, 1-(2-butoxy-1-methylethoxy)propyl-2-yl, 1-(2-butoxy-2-methylethoxy)propyl-2-yl, 2-(2-butoxy-1-methylethoxy)propyl-1-yl, 2-(2-butoxy-2-methylethoxy)propyl-1-yl, 2-(2-butoxy-2-methylethoxy)propyl-1-yl, 1-(2-hexyloxy-1-methylethoxy)propyl-2-yl, 1-(2-hexyloxy-2-methylethoxy)propyl-2-yl, 2-(2-hexyloxy-1-methylethoxy)propyl-1-yl, 2-(2-hexyloxy-2-methylethoxy)propyl-1-yl, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monopropyl 2-cyanoacrylates such as ethylene glycol monobutyl ether, triethylene glycol monohexyl ether, triethylene glycol mono-2-ethylhexyl ether, tripropylene glycol monomethyl ether, tripropylene glycol monoethyl ether, tripropylene glycol monopropyl ether, tripropylene glycol monobutyl ether, tripropylene glycol monopentyl ether, tripropylene glycol monohexyl ether, tetrapropylene glycol monomethyl ether, tetrapropylene glycol monoethyl ether, tetrapropylene glycol monopropyl ether, tetrapropylene glycol monobutyl ether, and tetrapropylene glycol monohexyl ether.
Among the above, from the viewpoint of the increase rate of peel adhesive strength of the cured product against rubber such as EPDM and the elongation recovery rate of the cured product, 2-(2-methoxyethoxy)ethyl 1-(2-methoxy-1-methylethoxy)propyl-2-yl, 1-(2-methoxy-2-methylethoxy)propyl-2-yl, 2-(2-methoxy-1-methylethoxy)propyl-1-yl, or 2-(2-methoxy-2-methylethoxy)propyl-1-yl 2-cyanoacrylate is preferred, and 1-(2-methoxy-1-methylethoxy)propyl-2-yl, 1-(2-methoxy-2-methylethoxy)propyl-2-yl, 2-(2-methoxy-1-methylethoxy)propyl-1-yl, or 2-(2-methoxy-2-methylethoxy)propyl-1-yl 2-cyanoacrylate is more preferred.

From the viewpoint of the rate of increase in peel adhesive strength of the cured product against rubbers such as EPDM and the elongation recovery rate of the cured product, the content of the specific 2-cyanoacrylate compound relative to the total mass of the 2-cyanoacrylate adhesive composition is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, and most preferably 80% by mass or more.
The upper limit of the content of the specific 2-cyanoacrylate compound is not particularly limited, but can be, for example, 99.9% by mass or less.

When the specific 2-cyanoacrylate compound contains a compound represented by formula (1), from the viewpoint of the increase in peel adhesion strength of the cured product to rubbers such as EPDM and the elongation recovery rate of the cured product, the content of the compound represented by formula (1) relative to the total mass of the specific 2-cyanoacrylate compound contained in the 2-cyanoacrylate adhesive composition is preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, particularly preferably 95% by mass or more, and may even be 100% by mass.

<Polyfunctional cyanoacrylate compound>
The 2-cyanoacrylate adhesive composition of the present disclosure contains a multifunctional cyanoacrylate compound. The 2-cyanoacrylate adhesive composition of the present disclosure may contain two or more types of multifunctional cyanoacrylate compounds.
Furthermore, from the viewpoint of the increase rate of peel adhesive strength of the cured product relative to rubber such as EPDM and the elongation recovery rate of the cured product, the polyfunctional cyanoacrylate compound is preferably a polyfunctional 2-cyanoacrylate compound.
In the present disclosure, a polyfunctional cyanoacrylate compound refers to a compound having two or more cyanoacryloyl groups.

Examples of polyfunctional cyanoacrylate compounds include 2-cyanoacrylate esters such as polyoxyalkylene polyols, polyester polyols, polycarbonate polyols, polyurethane polyols, polyamide polyols, polyester polyamide polyols, acrylic polyols, polybutadiene polyols, hydrogenated polybutadiene polyols, ethylene-butylene copolymer polyols, polyisoprene polyols, hydrogenated polyisoprene polyols, polyvinyl butyral, polyvinyl formal, polyvinyl alcohol, phenolic resins, silane compounds having hydroxyl groups at both ends, and siloxane compounds having hydroxyl groups at both ends.
From the viewpoint of flexibility and toughness of the cured product, the polyfunctional cyanoacrylate compound preferably contains at least one selected from the group consisting of polyoxyalkylene polyol, polyester polyol, polycarbonate polyol, polyurethane polyol, polyamide polyol, polyester polyamide polyol, acrylic polyol, polybutadiene polyol, hydrogenated polybutadiene polyol, polyisoprene polyol, and hydrogenated polyisoprene polyol, and more preferably contains at least one 2-cyanoacrylate ester of a compound selected from the group consisting of polyoxyalkylene polyol, polyester polyol, polycarbonate polyol, polybutadiene polyol, hydrogenated polybutadiene polyol, polyisoprene polyol, and hydrogenated polyisoprene polyol.
Among the above, the polyfunctional cyanoacrylate compound preferably contains polyoxyalkylene polyol, and more preferably contains polyoxypropylene glycol.
The polyfunctional cyanoacrylate compound may also contain glycerin ether.

The polyoxyalkylene polyol is not particularly limited, but examples thereof include polyethylene glycol, polyethylene triol, polyethylene tetraol, polypropylene glycol, polypropylene triol, polypropylene tetraol, polytetramethylene glycol, and copolymers with polyols or other glycols.
The polyester polyol is not particularly limited, but examples thereof include general polyester polyols produced by the reaction of a dibasic acid such as adipic acid with a glycol, triol, or the like, and polycaprolactone polyols obtained by ring-opening polymerization of caprolactone.
The polycarbonate diol is not particularly limited, but may be a general polycarbonate diol derived from ethylene carbonate or a copolymer of carbonate and glycol.
Furthermore, 2-cyanoacrylate esters of polybutadiene polyol, hydrogenated polybutadiene polyol, polyisoprene polyol, and hydrogenated polyisoprene polyol are preferred from the viewpoint of warm water resistance as well as flexibility and toughness of the cured product.

The polyfunctional cyanoacrylate preferably contains at least one of a biscyanoacrylate compound and a triscyanoacrylate compound.
From the viewpoint of the increase rate of peel adhesive strength of the cured product to rubbers such as EPDM and the elongation recovery rate of the cured product, biscyanoacrylate compounds are preferred to triscyanoacrylate compounds.
From the viewpoint of the increase rate of peel adhesive strength of the cured product against rubbers such as EPDM and the elongation recovery rate of the cured product, the biscyanoacrylate compound is preferably an alkanediol biscyanoacrylate compound or a polyoxyalkylene polyol biscyanoacrylate compound.
From the viewpoint of the increase rate of peel adhesive strength of the cured product to rubbers such as EPDM and the elongation recovery rate of the cured product, the triscyanoacrylate compound is preferably a polyoxyalkylene polyol tricyanoacrylate compound.
The aliphatic group of the alkanediol biscyanoacrylate compound preferably has 2 to 18 carbon atoms, and more preferably has 4 to 12 carbon atoms.
The aliphatic group may be linear, branched, or cyclic.
Examples of the alkanediol biscyanoacrylate compound include 1,6-hexanediol biscyanoacrylate, 1,4-butanediol biscyanoacrylate, 1,8-octanediol biscyanoacrylate, 1,9-nonanediol biscyanoacrylate, 1,10-decanediol biscyanoacrylate, 1,12-dodecanediol biscyanoacrylate, 1,5-pentanediol biscyanoacrylate, 1,16-hexadecanediol biscyanoacrylate, and 1,18-octadecanediol biscyanoacrylate. Of the above, from the viewpoints of the rate of increase in peel adhesive strength of the cured product relative to rubber such as EPDM and the elongation recovery rate of the cured product, 1,6-hexanediol-biscyanoacrylate, 1,8-octanediol-biscyanoacrylate, 1,9-nonanediol-biscyanoacrylate, 1,10-decanediol-biscyanoacrylate, 1,12-dodecanediol-biscyanoacrylate, 1,16-hexadecanediol-biscyanoacrylate, and 1,18-octadecanediol-biscyanoacrylate are preferred, with 1,6-hexanediol-biscyanoacrylate and 1,10-decanediol-biscyanoacrylate being more preferred.
Examples of the polyoxyalkylene polyol that constitutes the polyoxyalkylene polyol biscyanoacrylate compound or the polyoxyalkylene polyol tricyanoacrylate compound include polyoxypropylene glycol (PPG), polyoxyethylene glycol, polyoxytetramethylene glycol, polyoxyethylene polyoxypropylene glycol, polyoxyethylene polyoxytetramethylene glycol, and polyoxypropylene polyoxytetramethylene glycol.
Among the above, polyoxypropylene glycol (PPG)-biscyanoacrylate and polyoxypropylene glycol (PPG)-triscyanoacrylate are preferred from the viewpoints of the increase rate of peel adhesive strength of the cured product to rubbers such as EPDM and the elongation recovery rate of the cured product.

From the viewpoint of the rate of increase in peel adhesive strength of the cured product against rubber such as EPDM and the elongation recovery rate of the cured product, the molecular weight or number average molecular weight (Mn) of the polyfunctional cyanoacrylate compound is preferably 200 to 50,000, more preferably 200 to 25,000, and even more preferably 200 to 23,000.
In the present disclosure, Mn is a value calculated in terms of standard polystyrene obtained using gel permeation chromatography (GPC).

From the viewpoint of the rate of increase in peel adhesion strength of the cured product against rubbers such as EPDM and the elongation recovery rate of the cured product, the content of the polyfunctional cyanoacrylate compound per 100 mass parts of 2-cyanoacrylate compound contained in the 2-cyanoacrylate adhesive composition of the present disclosure is preferably 0.01 to 50 mass parts, more preferably 0.1 to 30 mass parts, even more preferably 0.5 to 20 mass parts, and particularly preferably 0.7 to 10 mass parts.

When the polyfunctional cyanoacrylate contains at least one of a biscyanoacrylate compound and a triscyanoacrylate compound, from the viewpoint of the increase in peel adhesion strength of the cured product against rubbers such as EPDM and the elongation recovery rate of the cured product, the sum of the contents of the biscyanoacrylate compound and the triscyanoacrylate compound relative to the total mass of the polyfunctional cyanoacrylate contained in the 2-cyanoacrylate adhesive composition is preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, particularly preferably 95% by mass or more, and may even be 100% by mass.

<Other ingredients>
The 2-cyanoacrylate adhesive composition of the present disclosure may contain components other than the specific 2-cyanoacrylate compound and the polyfunctional cyanoacrylate compound, provided that the properties of the adhesive composition are not impaired.
Examples of other components include 2-cyanoacrylate compounds other than the specific 2-cyanoacrylate compound, stabilizers, curing accelerators, plasticizers, thickeners, particles, colorants, fragrances, solvents, and strength improvers.

Examples of 2-cyanoacrylate compounds other than specific 2-cyanoacrylate compounds include esters of 2-cyanoacrylic acid such as methyl, ethyl, chloroethyl, n-propyl, i-propyl, allyl, propargyl, n-butyl, i-butyl, n-pentyl, n-hexyl, cyclohexyl, phenyl, tetrahydrofurfuryl, heptyl, 2-ethylhexyl, n-octyl, 2-octyl, n-nonyl, oxononyl, n-decyl, n-dodecyl, methoxyethyl, methoxypropyl, methoxyisopropyl, methoxybutyl, ethoxyethyl, ethoxypropyl, ethoxyisopropyl, propoxymethyl, propoxyethyl, isopropoxyethyl, propoxypropyl, butoxymethyl, butoxyethyl, butoxypropyl, butoxyisopropyl, butoxybutyl, 2,2,2-trifluoroethyl, and hexafluoroisopropyl. These 2-cyanoacrylate compounds may be used alone or in combination of two or more.

Examples of stabilizers include (1) sulfur dioxide and aliphatic sulfonic acids such as methanesulfonic acid, aromatic sulfonic acids such as p-toluenesulfonic acid, boron trifluoride complexes such as boron trifluoride methanol and boron trifluoride diethyl ether, anionic polymerization inhibitors such as HBF ₄ and trialkyl borates, and (2) radical polymerization inhibitors such as hydroquinone, hydroquinone monomethyl ether, t-butylcatechol, catechol, pyrogallol, etc. These stabilizers may be used alone or in combination of two or more.

Any curing accelerator that accelerates the anionic polymerization of the 2-cyanoacrylate adhesive composition can be used. Examples of curing accelerators include polyether compounds, calixarenes, thiacalixarenes, pyrogallolarenes, onium salts, etc. These curing accelerators may be used alone or in combination of two or more.

Further examples of plasticizers include triethyl acetyl citrate, tributyl acetyl citrate, dimethyl adipate, diethyl adipate, dimethyl sebacate, dimethyl phthalate, diethyl phthalate, dibutyl phthalate, diisodecyl phthalate, dihexyl phthalate, diheptyl phthalate, dioctyl phthalate, bis(2-ethylhexyl) phthalate, diisononyl phthalate, diisotridecyl phthalate, dipentadecyl phthalate, dioctyl terephthalate, diisononyl isophthalate, decyl toluate, bis(2-ethylhexyl) camphorate, 2-ethylhexyl cyclohexyl carboxylate, diisobutyl fumarate, diisobutyl maleate, triglyceride caproate, 2-ethylhexyl benzoate, and dipropylene glycol dibenzoate. Among these, acetyl tributyl citrate, dimethyl adipate, dimethyl phthalate, 2-ethylhexyl benzoate, and dipropylene glycol dibenzoate are preferred because they have good compatibility with 2-cyanoacrylate compounds and high plasticizing efficiency. These plasticizers may be used alone or in combination of two or more.

Examples of thickeners include polymethyl methacrylate, copolymers of methyl methacrylate and acrylic esters, copolymers of methyl methacrylate and other methacrylic esters, acrylic rubber, polyvinyl acetate, polyvinyl chloride, polyurethane resins, polyamide resins, polystyrene, cellulose esters, polyalkyl-2-cyanoacrylate esters, and ethylene-vinyl acetate copolymers. These thickeners may be used alone or in combination of two or more.

The 2-cyanoacrylate adhesive composition of the present disclosure may contain particles to the extent that the properties of the composition are not impaired, and this makes it possible to adjust the thickness of the adhesive layer formed by using the 2-cyanoacrylate adhesive composition.
The average particle size of the particles is preferably 10 μm to 200 μm, more preferably 15 μm to 200 μm, and even more preferably 15 μm to 150 μm.
The material of the particles is not particularly limited as long as it is insoluble in the 2-cyanoacrylate compound used and does not cause deterioration such as polymerization. Examples of the particles include thermoplastic resins such as polyethylene, polypropylene, polymethylpentene, acrylic resin, polyvinyl chloride, polytetrafluoroethylene, polyethylene terephthalate, polybutylene terephthalate, polysulfone, and polyphenylene oxide; crosslinked resins such as unsaturated polyester, divinylbenzene polymer, divinylbenzene-styrene copolymer, divinylbenzene-(meth)acrylic acid ester copolymer, and diallyl phthalate polymer; inorganic compounds such as spherical silica, glass beads, and glass fiber; silicone compounds; and organic-inorganic composite particles comprising an organic polymer skeleton and a polysiloxane skeleton.
Furthermore, the particle content is not particularly limited, but from the standpoint of curing speed, adhesive strength, and the like, the particle content relative to 100 parts by mass of the 2-cyanoacrylate compound contained in the 2-cyanoacrylate adhesive composition of the present disclosure is preferably 0.1 parts by mass to 10 parts by mass, more preferably 1 part by mass to 5 parts by mass, and even more preferably 1 part by mass to 3 parts by mass.
In the present disclosure, the average particle size of particles is a volume-based average value measured by a laser diffraction particle size distribution analyzer.

<Elongation Recovery Rate of the 2-Cyanoacrylate Adhesive Composition of the Present Disclosure>
A cured product having a width of 5 mm, a length of 50 mm, and a thickness of 1 mm obtained by curing the above-described 2-cyanoacrylate adhesive composition of the present disclosure is fixed to a tensile tester with a jig distance of 20 mm (L0), a mark is made at the jig fixing position, and the product is pulled at a pulling rate of 20 mm/min until the jig distance reaches 40 mm (L1). After that, the jig is released and the length between the marks (L2) is measured after 1 minute has passed. The elongation recovery rate (%) calculated using the following formula is preferably 70% or more, more preferably 80% or more, even more preferably 90% or more, and particularly preferably 95% or more.
The elongation recovery rate is measured in an environment of a temperature of 25° C. and a relative humidity of 50%.
Elongation recovery rate (%): {(L1-L2)/(L1-L0)}×100

A cured product having a width of 5 mm, a length of 50 mm, and a thickness of 1 mm obtained by curing the above-described 2-cyanoacrylate adhesive composition of the present disclosure is fixed to a tensile tester with a jig distance of 20 mm (L0), a mark is made at the jig fixing position, and the product is pulled at a pulling rate of 20 mm/min until the jig distance reaches 40 mm (L1). After that, the jig is released and the length between the marks (L3) is measured after 5 minutes have passed. The elongation recovery rate (%) calculated using the following formula is preferably 80% or more, more preferably 90% or more, even more preferably 95% or more, and particularly preferably 97% or more.
The elongation recovery rate is measured in an environment of a temperature of 25° C. and a relative humidity of 50%.
Elongation recovery rate (%): {(L1-L3)/(L1-L0)}×100

A cured product having a width of 5 mm, a length of 50 mm, and a thickness of 1 mm obtained by curing the above-described 2-cyanoacrylate adhesive composition of the present disclosure is fixed to a tensile tester with a jig distance of 20 mm (L0), a mark is made at the jig fixing position, and the product is pulled at a pulling rate of 20 mm/min until the jig distance reaches 40 mm (L1). After that, the jig is released from fixation, and the length between the marks (L4) is measured after 30 minutes have passed. The elongation recovery rate (%) calculated using the following formula is preferably 95% or more, more preferably 97% or more, and even more preferably 99% or more.
The elongation recovery rate is measured in an environment of a temperature of 25° C. and a relative humidity of 50%.
Elongation recovery rate (%): {(L1-L4)/(L1-L0)}×100

The tensile tester used to measure the elongation recovery rate may be a Strograph V20-C manufactured by Toyo Seiki Seisakusho Co., Ltd. or a device of the same level.
The cured product used in measuring the elongation recovery rate is produced as follows.
First, a silicone rubber mold having a thickness of 1 mm is placed on a release polyethylene terephthalate (PET) film.
Next, 1 μL of triethanolamine is added to 1 g of the 2-cyanoacrylate adhesive composition of the present disclosure, and after stirring, the mixture is poured into the mold.
After pouring the 2-cyanoacrylate adhesive composition, the above-mentioned separately prepared release PET film is placed over the mold and the adhesive composition, and the mold and the adhesive composition are sandwiched between glass plates. The mixture is then left to stand at 25°C and a relative humidity of 50% for 24 hours to allow the composition to completely cure.
After curing, the mold and release PET film are removed to obtain a cured product having a width of 5 mm, a length of 50 mm and a thickness of 1 mm.

<Peel Adhesion Strength of the 2-Cyanoacrylate Adhesive Composition of the Present Disclosure>
The peel adhesion strength (N/cm) of the 2-cyanoacrylate adhesive composition of the present disclosure to an ethylene propylene diene rubber (EPDM) substrate, measured in accordance with JIS K 6854-3:1999, is designated As1,
When the peel adhesion strength (N/cm) of a 2-cyanoacrylate adhesive composition obtained by excluding the polyfunctional cyanoacrylate compound from the above 2-cyanoacrylate adhesive composition from which the peel adhesion strength As1 was measured is designated as As2, it is preferable that the following formula (A) is satisfied, it is more preferable that the following formula (B) is satisfied, and it is even more preferable that the following formula (C) is satisfied.
The increase rate of peel adhesive strength can be determined by the following formulas (A) to (C).
(As1-As2/As2)×100≧150% (A)
(As1-As2/As2)×100≧200% (B)
(As1-As2/As2)×100≧250% (C)

More specifically, the peel adhesion strength is measured as follows.
First, 1 g of the 2-cyanoacrylate adhesive composition of the present disclosure is applied to an EPDM substrate, and the composition is left to stand at a temperature of 23° C. and a relative humidity of 50% for 7 days to allow it to cure completely.
After curing, the T-peel adhesive strength (N/cm) is measured using a tensile tester in accordance with JIS K 6854-3: 1999. The pulling speed is 100 mm/min.
The T-peel adhesive strength is measured in an environment of a temperature of 25° C. and a relative humidity of 50%.
The tensile tester may be the same as that used to measure the elongation recovery rate.

<Uses of the 2-cyanoacrylate adhesive composition of the present disclosure>
The 2-cyanoacrylate adhesive composition of the present disclosure can be used in a variety of applications, including construction applications, automotive applications, and electrical and electronic material applications.
Examples of construction applications include elastic adhesives for construction, adhesives for double-glazing, adhesives for artificial marble, etc. Examples of electrical and electronic material applications include resins for sealing semiconductors, insulating materials for printed wiring boards, insulating coating materials for electric wires and cables, coating agents for electronic components, potting agents for electronic components, and sealers for electrical equipment. The 2-cyanoacrylate adhesive composition of the present disclosure can also be used for packings, O-rings, etc. Specific examples include waterproof packings, insect-proof packings, vibration-proof, sound-absorbing and air-sealing materials for cleaners, drip-proof covers for electric water heaters, waterproof packings, heater packings, electrode packings, safety valve diaphragms, solenoid valves, waterproof packings for steam oven ranges and jar rice cookers, water tank packings, water intake valves, water receiver packings, heat-retaining heater packings, oil packings for combustion equipment such as steam outlet seals, O-rings, drain packings, air supply and intake packings, vibration-proof rubber, oil filler port packings, oil gauge packings, diaphragm valves, speaker gaskets and speaker edges for audio equipment.
In addition, in automotive-related applications, the adhesive composition can be used for body parts such as adhesive sealants for maintaining airtightness, vibration-proofing materials for glass, and vibration-damping materials for vehicle body parts, particularly wind seal gaskets and door glass gaskets. As engine parts, the adhesive composition can be used for adhesive sealants for engine oil, etc. Furthermore, the adhesive composition of the present invention can also be used in gasket methods [Mold-In-Place Gasket (MIPG), Formed-In-Place Gasket (FIPG), Cured-In-Place Gasket (CIPG)] in which a liquid sealant is automatically applied by a robot or the like on an assembly line for electric/electronic parts and automobile parts to form an adhesive seal.

In addition, the 2-cyanoacrylate adhesive composition disclosed herein can be suitably used on resins or metals as the adherend, more suitably used on rubber, and particularly suitably used on EPDM.

The above embodiment will be explained in more detail below using examples, but the above embodiment is not limited to these examples. Furthermore, in the following, "parts" means "parts by mass" unless otherwise specified.

Various physical properties were measured as follows.

<Storage Modulus at 25°C of Cured Material Obtained by Homopolymerization of 2-Cyanoacrylate Compound>
The 2-cyanoacrylate compound was injected between the tools of a dynamic viscoelasticity measuring device coated with triethanolamine, and then the storage modulus was measured using a dynamic viscoelasticity measuring device (manufactured by Anton Paar, product name "MCR301") under conditions of a frequency of 1 Hz, a temperature of 25°C, and a thickness of 300 μm.
After confirming that there was no change in the storage modulus of the 2-cyanoacrylate compound, this was designated as a cured product of the 2-cyanoacrylate compound. Using the cured product, the storage modulus of the cured product was measured by shearing in the range of -50°C to 150°C under conditions of a frequency of 1 Hz, a temperature rise rate of 2°C/min, and a relative humidity of 50%, and the storage modulus of the cured product at 25°C was determined.
Table 1 shows the storage moduli at 25°C of the cured products obtained by homopolymerizing the 2-cyanoacrylate compounds used in each of the Examples and Comparative Examples (referred to as "storage moduli of 2-cyanoacrylate compounds" in the table).

<Temperature at which the loss tangent of the 2-cyanoacrylate compound exhibits a maximum value (tan δ(max))>
The 2-cyanoacrylate compound was injected between the tools of a dynamic viscoelasticity measuring device coated with triethanolamine, and then the storage modulus was measured using a dynamic viscoelasticity measuring device (manufactured by Anton Paar, product name "MCR301") under conditions of a frequency of 1 Hz, a temperature of 25°C, and a thickness of 300 μm.
After confirming that there was no change in the storage modulus of the 2-cyanoacrylate compound, this was designated as a cured product of the 2-cyanoacrylate compound. Using the cured product, a dynamic viscoelastic spectrum was obtained over a temperature range of -50°C to 150°C at a frequency of 1 Hz and a temperature increase rate of 2°C/min, and the temperature at which the loss tangent (tan δ) reached its maximum value was measured. When two or more peaks were observed, the loss tangent (tan δ) with the largest peak was designated as the maximum value.

(Examples 1 to 14)
A 2-cyanoacrylate adhesive composition was produced by blending 100 parts of a 2-cyanoacrylate compound shown in Table 1 with a polyfunctional cyanoacrylate compound shown in Table 1 in an amount shown in Table 1, and stirring until homogenous.

(Comparative Example 1)
The 2-cyanoacrylate compounds listed in Table 1 were used as adhesive compositions.

(Comparative Examples 2 to 5)
An adhesive composition was produced by blending 100 parts of a 2-cyanoacrylate compound shown in Table 1 with a polyfunctional cyanoacrylate compound shown in Table 1 in an amount shown in Table 1, and stirring until homogenous.

(Comparative Example 6)
The 2-cyanoacrylate compounds listed in Table 1 were used as adhesive compositions.

(Comparative Examples 7 to 10)
An adhesive composition was produced by blending 100 parts of a 2-cyanoacrylate compound shown in Table 1 with a polyfunctional cyanoacrylate compound shown in Table 1 in an amount shown in Table 1, and stirring until homogenous.

(Comparative Examples 11 and 12)
The 2-cyanoacrylate compounds listed in Table 1 were used as adhesive compositions.

Details of the abbreviations for the polyfunctional cyanoacrylates in Table 1 are as follows:
HBCA: bifunctional 2-cyanoacrylate compound (1,6-hexanediol-biscyanoacrylate), molecular weight: 276.29
DBCA: bifunctional 2-cyanoacrylate compound (1,10-decanediol-biscyanoacrylate), molecular weight: 332.40
PPG4000TCA: Trifunctional 2-cyanoacrylate compound (PPG (Mn4000)-triscyanoacrylate), Mn 4,640
PPG10000BCA: bifunctional 2-cyanoacrylate compound (PPG (Mn 10000)-biscyanoacrylate), Mn 19,700

HBCA was synthesized by the following method.
A 500 mL flask equipped with a stirrer, a thermometer, a Liebig condenser, a nitrogen inlet tube, and a dropping funnel was charged with 4.80 g (41.6 mmol) of cyanoacrylic acid chloride and 270 mL of benzene. Thereafter, the reaction system was heated to 60°C, and a solution of 5.22 g of 1,6-hexanediol (reagent) dissolved in 5 mL of benzene was added while blowing nitrogen gas through the nitrogen inlet tube.
The temperature was then maintained at 60° C. and the mixture was stirred for 30 minutes. After that, the mixture was cooled to 25° C., the benzene was distilled off under reduced pressure, and the mixture was recrystallized twice by cooling to −20° C. in a 7/4 pentane/hexane mixed solution, to obtain 5.02 g of a solid polyfunctional cyanoacrylate (HBCA).
In addition, dry benzene was used as the benzene, and glassware was thoroughly dried by heating. The same applies to the following synthesis examples.

DBCA was synthesized by the following method.
A 500 mL flask equipped with a stirrer, a thermometer, a Liebig condenser, a nitrogen inlet tube, and a dropping funnel was charged with 4.80 g (41.6 mmol) of cyanoacrylic acid chloride and 270 mL of benzene. Thereafter, the reaction system was heated to 60°C, and a solution prepared by dissolving 10.2 g of 1,10-decanediol (reagent) in 10 mL of benzene was added while blowing nitrogen gas through the nitrogen inlet tube.
The temperature was then maintained at 60° C. and the mixture was stirred for 30 minutes. After that, the mixture was cooled to 25° C., and the benzene was distilled off under reduced pressure. Recrystallization by cooling to −20° C. in a 7/4 pentane/hexane mixed solution was repeated twice, yielding 8.00 g of a solid polyfunctional cyanoacrylate (DBCA).

PPG4000TCA was synthesized by the following method.
A 500 mL flask equipped with a stirrer, a thermometer, a Liebig condenser, a nitrogen inlet tube, and a dropping funnel was charged with 2.40 g (20.8 mmol) of cyanoacrylic acid chloride and 135 mL of benzene. Thereafter, the reaction system was heated to 60°C, and a solution of 25.2 g of polyoxypropylene glycol [number average molecular weight: 4000 (catalog value), polyether triol type, manufactured by ADEKA Corporation, trade name "ADEKA Polyether G-4000"] dissolved in 16 mL of benzene was added while blowing nitrogen gas through the nitrogen inlet tube.
The mixture was then stirred for 30 minutes while maintaining the temperature at 60° C. After that, the mixture was cooled to 25° C., and the benzene was distilled off under reduced pressure to obtain 28.1 g of a colorless, viscous oily polyfunctional cyanoacrylate (PPG4000TCA).

PPG10000BCA was synthesized by the following method.
A 500 mL flask equipped with a stirrer, a thermometer, a Liebig condenser, a nitrogen inlet tube, and a dropping funnel was charged with 2.40 g (20.8 mmol) of cyanoacrylic acid chloride and 135 mL of benzene. Thereafter, the reaction system was heated to 60°C, and while blowing nitrogen gas through the nitrogen inlet tube, a solution of 94.5 g of polyoxypropylene glycol [number average molecular weight: 10,000 (catalog value), both-terminal hydroxyl group type, manufactured by AGC, trade name "Preminol S-4011"] dissolved in 60 mL of benzene was added.
The mixture was then stirred for 30 minutes while maintaining the temperature at 60° C. After that, the mixture was cooled to 25° C., and the benzene was distilled off under reduced pressure to obtain 97.8 g of a colorless, viscous, oily polyfunctional cyanoacrylate (PPG10000BCA).

<Evaluation of peel adhesion strength>
1 g of the adhesive composition produced in the above Examples and Comparative Examples was applied to an ethylene propylene diene rubber (EPDM) substrate (EPDM-5065 manufactured by Irumagawa Rubber Co., Ltd.), and left to stand at 23°C and a relative humidity of 50% for 7 days to allow it to completely cure.
After curing, the T-peel adhesive strength (N/cm) was measured using the tensile tester in accordance with JIS K 6854-3:1999. The T-peel adhesive strength was measured in an environment of 25°C and 50% relative humidity, with a pulling speed of 100 mm/min. The measurement results are shown in Table 1.

The increase in peel adhesive strength (As1a) to an EPDM substrate of the 2-cyanoacrylate adhesive composition produced in Example 1 and the increase in peel adhesive strength (As2a) to an EPDM substrate of the adhesive composition produced in Comparative Example 11 ((As1a - As2a/As2a) x 100) was calculated to be 270%.
The increase in peel strength was calculated in the same manner as above from the peel strength of the 2-cyanoacrylate adhesive compositions produced in Examples 2 to 7 to an EPDM substrate and the peel strength of the adhesive composition produced in Comparative Example 11 to an EPDM substrate, and the results were 242%, 247%, 201%, 278%, 163%, and 156%, respectively.

Furthermore, the increase rate in peel adhesion strength ((As1b-As2b/As2b) x 100) was calculated from the peel adhesion strength (As1b) of the 2-cyanoacrylate adhesive composition produced in Example 8 to an EPDM substrate and the peel adhesion strength (As2b) of the adhesive composition produced in Comparative Example 12 to an EPDM substrate, and was found to be 372%.
The increase in peel strength was calculated in the same manner as above from the peel strength of the 2-cyanoacrylate adhesive compositions produced in Examples 9 to 14 to an EPDM substrate and the peel strength of the adhesive composition produced in Comparative Example 12 to an EPDM substrate, and the results were 432%, 440%, 410%, 521%, 270%, and 206%, respectively.
Furthermore, the increase rate of peel adhesion strength ((As1c-As2c/As2c) x 100) was calculated from the peel adhesion strength (As1c) of the adhesive composition produced in Comparative Example 1 to an EPDM substrate and the peel adhesion strength (As2c) of the adhesive composition produced in Comparative Example 2 to an EPDM substrate, and was found to be 2%.
The increase in peel adhesion strength was calculated in the same manner as above from the peel adhesion strength to an EPDM substrate of the adhesive composition produced in Comparative Example 3 and the peel adhesion strength to an EPDM substrate of the adhesive composition produced in Comparative Example 1, and was found to be 8%.
Furthermore, the increase rate in peel adhesion strength ((As1d-As2d/As2d) x 100) was calculated from the peel adhesion strength (As1d) to an EPDM substrate of the adhesive composition produced in Comparative Example 7 and the peel adhesion strength (As2d) to an EPDM substrate of the adhesive composition produced in Comparative Example 6, and was found to be 137%.
The increase in peel adhesive strength was calculated in the same manner as above from the peel adhesive strength to an EPDM substrate of the adhesive compositions produced in Comparative Examples 8 to 10 and the peel adhesive strength to an EPDM substrate of the adhesive composition produced in Comparative Example 6, and the results were 144%, 94%, and 81%, respectively.

From the above, it can be seen that the 2-cyanoacrylate adhesive compositions produced in the examples have an excellent increase in peel adhesive strength to rubbers such as EPDM.
The increase rate of peel adhesive strength for each of the examples and comparative examples is summarized in Table 1.
In addition, Comparative Examples 1, 6, 11, and 12, which are the standards for peel adhesive strength, are all recorded in Table 1 as "1."
In addition, for Comparative Examples 4 and 5, no increase in peel adhesive strength was observed, and therefore, they are recorded as "-" in Table 1.

<Evaluation of elongation recovery rate>
A silicone rubber mold frame having a thickness of 1 mm was placed on a release polyethylene terephthalate (PET) film (manufactured by Teijin Film Solutions Co., Ltd., product name "Purex (registered trademark) A31").
1 μL of triethanolamine was added to 1 g of the adhesive composition produced in the above Examples and Comparative Examples, and after stirring, the mixture was poured into the above mold.
After the adhesive composition was poured, the mold and the adhesive composition were covered with the above-mentioned release PET film that had been separately prepared, and the mold and the adhesive composition were sandwiched between glass plates. The mixture was then left to stand at 25°C and a relative humidity of 50% for 24 hours to allow it to completely harden.
After curing, the mold and release PET film were removed to obtain a cured product having a width of 5 mm, a length of 50 mm and a thickness of 1 mm.

Using a tensile testing machine (manufactured by Toyo Seiki Seisaku-sho, product name "Strograph V20-C"), the cured product was fixed at a jig distance of 20 mm (L ₀ ) and marked at the jig fixing position, and pulled at a tensile speed of 20 mm/min until the jig distance reached 40 mm (L ₁ ).
After the jig was released, the length (L ₂ ) between the marks was measured 1 minute, 5 minutes, and 30 minutes later, and the elongation recovery rate (%) was calculated using the following formula. The calculation results are shown in Table 1.
Elongation recovery rate (%): {(L ₁ - _{L 2} )/(L ₁ - _{L 0} )}×100

Table 1 shows that the 2-cyanoacrylate adhesive compositions produced in the examples have superior peel adhesion strength and peel adhesion strength increase rate to rubbers such as EPDM compared to the adhesive compositions produced in the comparative examples. It also shows that the 2-cyanoacrylate adhesive compositions produced in the examples have superior elongation recovery rates of the cured products compared to the adhesive compositions produced in the comparative examples.

The disclosure of Japanese Patent Application No. 2021-115346, filed on July 12, 2021, is incorporated herein by reference in its entirety. All documents, patent applications, and technical standards described herein are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard was specifically and individually indicated to be incorporated by reference.

Claims (12)

Contains a 2-cyanoacrylate compound and a polyfunctional cyanoacrylate compound,
the storage modulus at 25°C of a cured product obtained by homopolymerizing the 2-cyanoacrylate compound is 1.0 × 10 ⁷ Pa or less ;
the polyfunctional cyanoacrylate compound includes at least one selected from the group consisting of an alkanediol biscyanoacrylate compound and a 2-cyanoacrylic acid ester of a polyoxyalkylene polyol;
2-Cyanoacrylate adhesive compositions. 2. The 2-cyanoacrylate adhesive composition according to claim 1, wherein a cured product of the 2-cyanoacrylate adhesive composition having a width of 5 mm, a length of 50 mm and a thickness of 1 mm is fixed to a tensile testing machine with a jig distance of 20 mm (L0), a mark is made at the jig fixing position, and the product is pulled at a pulling rate of 20 mm/min until the jig distance reaches 40 mm (L1), after which the jig is released from fixation and the length (L2) between the marks is measured after 1 minute has elapsed, and the elongation recovery rate (%) calculated using the following formula is 70% or more.
Elongation recovery rate (%): {(L1-L2)/(L1-L0)}×100 3. The 2-cyanoacrylate adhesive composition according to claim 1, wherein a cured product of the 2-cyanoacrylate adhesive composition having a width of 5 mm, a length of 50 mm and a thickness of 1 mm is fixed to a tensile tester with a jig distance of 20 mm (L0), a mark is made at the jig fixing position, and the product is pulled at a pulling rate of 20 mm/min until the jig distance reaches 40 mm (L1), after which the jig is released from fixation and the length (L3) between the marks is measured after 5 minutes have passed, and the elongation recovery rate (%) calculated using the following formula is 80% or more.
Elongation recovery rate (%): {(L1-L3)/(L1-L0)}×100 2. The 2-cyanoacrylate adhesive composition according to claim 1, wherein a cured product of the 2-cyanoacrylate adhesive composition having a width of 5 mm, a length of 50 mm and a thickness of 1 mm is fixed to a tensile tester with a jig distance of 20 mm (L0), a mark is made at the jig fixing position, and the product is pulled at a pulling rate of 20 mm/min until the jig distance reaches 40 mm (L1), after which the jig is released from fixation and the length (L4) between the marks is measured after 30 minutes have passed, and the elongation recovery rate (%) calculated using the following formula is 95% or more.
Elongation recovery rate (%): {(L1-L4)/(L1-L0)}×100 The peel adhesive strength (N/cm) of the 2-cyanoacrylate adhesive composition to an ethylene propylene diene rubber substrate measured in accordance with JIS K 6854-3:1999 is designated as As1,
2. The 2-cyanoacrylate adhesive composition according to claim 1, wherein the following formula is satisfied when the peel adhesion strength (N/cm) of a 2-cyanoacrylate adhesive composition obtained by excluding the polyfunctional cyanoacrylate compound from the 2-cyanoacrylate adhesive composition from which the peel adhesion strength As1 has been measured is defined as As2:
(As1-As2/As2)×100≧150% 2. The 2-cyanoacrylate adhesive composition according to claim 1 , wherein the polyfunctional cyanoacrylate compound is contained in an amount of 0.01 to 50 parts by mass per 100 parts by mass of the 2-cyanoacrylate compound. 2. The 2-cyanoacrylate adhesive composition according to claim 1 , wherein the 2-cyanoacrylate compound has an ether bond. The 2-cyanoacrylate adhesive composition according to claim 7, wherein the 2-cyanoacrylate compound has two or more ether bonds. 2. The 2-cyanoacrylate adhesive composition according to claim 1 , wherein the 2-cyanoacrylate compound comprises a compound represented by the following formula (1):


In formula (1),
L ¹ 's each independently represent -CH ₂ CH ₂ -, -CH ₂ CH ₂ CH ₂ -, -CH(R ¹ )CH ₂ - or -CH ₂ CH(R ¹ )-;
R ¹ represents a linear or branched alkyl group having 1 to 6 carbon atoms which may have a substituent;
^R2 represents a linear or branched alkyl group having 1 to 8 carbon atoms which may have a substituent;
p represents an integer of 1 to 5; 2. The 2-cyanoacrylate adhesive composition according to claim 1 , wherein the temperature at which the maximum value of the loss tangent (tan δ(max)) of a cured product obtained by homopolymerizing the 2-cyanoacrylate compound is 65°C or lower. 2. The 2-cyanoacrylate adhesive composition according to claim 1 , wherein the multifunctional cyanoacrylate compound comprises at least one of a biscyanoacrylate compound and a triscyanoacrylate compound. 2. The 2-cyanoacrylate adhesive composition according to claim 1 , wherein the polyfunctional cyanoacrylate compound has a molecular weight or number average molecular weight of 200 to 50,000.