JPH06271641A - One-packing curing type composition - Google Patents

Abstract

PURPOSE:To obtain the subject composition having excellent storage stability, high curing rate even at a low temperature, excellent heat resistance, even not foaming at a high temperature and high humidity by blending an NCO group-containing urethane prepolymer with specific two kinds of compounds. CONSTITUTION:The objective composition comprises (A) a compound containing two or more groups of the formula (R<1> to R<3> are 1-6 alkyl, phenyl or haloalkyl), having 700-10,000 average molecular weight, (B) a urethane prepolymer containing two or more NCO groups, having 800-20,000 average molecular weight an (C) a compound containing a group of the formula at the end, having <=600 average molecular weight in the ratio of 0.1-10 pts.wt. of the component C based on 100 pts.wt. of the total of the components A and B. The component A is preferably obtained by reacting a compound containing two or more thiols groups such as liquid polysulfide polymer with a silylating agent. The component C is preferably obtained by reacting a compound containing thiol at the end such as triethylenedimercaptan with a silylating agent.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a curable composition which is cured by a reaction between an isocyanate group and a thiol group, and in particular, a one-pack curable composition which can be used as a sealing material having excellent storage stability and curability. Regarding

[0002]

2. Description of the Related Art A polymer having two or more isocyanate groups in its molecule can be easily made into a high molecular weight by reacting it with a compound containing active hydrogen or water, and therefore, a sealing material, a caulking material, an adhesive agent. It is widely used in the fields of paints and paints. These isocyanate group-containing polymers are mixed with polyamines, amino alcohols, glycols, polyols, etc. and used as one-component or two-component curable compositions.

Of these, the one-pack type curable composition is generally cured by reacting with moisture in the air, and carbon dioxide gas generated during the curing causes expansion, foaming, and formation of a gasket. In particular, this phenomenon is remarkable in a one-component curable composition having a fast curability, and thus the curing speed has been a problem in the conventional one-component curable urethane sealant.

As a means for solving such a problem, there is a method of using a urethane prepolymer having a low isocyanate content. However, when the isocyanate content is low, there is a problem in storage stability because the reaction with residual water in the composition causes a high molecular weight even before use.

As a means for improving the storage stability of this urethane sealant, generally, a method is known in which a molecular sieve is blended with the sealant to adsorb residual water. 3-24109 describes a method of blending a molecular sieve which adsorbs a primary or secondary amine having two or more functional groups, and JP-A-52-32946 discloses a sealant. A method of adding a monoisocyanate compound is described.

[0006]

However, although the above method is effective in improving the storage stability, the curing rate is not the same as that of the conventional one-pack type urethane sealant and is not satisfactory.

The inventors of the present invention have already proposed in JP-A-63-145321 a one-part curable composition which is excellent in curability and heat resistance and does not cause foaming. However, the composition is sufficiently satisfactory in storage stability. Was not.

Therefore, an object of the present invention is to provide a one-pack curable composition having excellent storage stability, which has been a problem in conventional curable compositions containing an isocyanate group-containing polymer as a basic component.

[0009]

As a result of earnest research in view of the above objects, the present inventors have found that a compound containing two or more trialkyl (or phenyl) silylthio groups in one molecule,
A one-pack curable composition containing a urethane prepolymer having two or more isocyanate groups in the molecule and a compound having one or more trialkyl (or phenyl) silylthio groups at the terminals is excellent in storage stability. The inventors have found that the curing rate is high even at low temperatures and that they have excellent heat resistance, and have conceived the present invention.

That is, the one-part curable composition of the present invention is
(a) The following general formula (1):

[Chemical 2] (In the formula, R ¹ , R ² and R ³ are any one of an alkyl group having 1 to 6 carbon atoms, a phenyl group and a haloalkyl group.) Each molecule has two or more groups, and an average value. A compound having a molecular weight of 700 to 10,000, and (b) 2 per molecule
It has more than one isocyanate group and an average molecular weight of 800-
20,000 urethane prepolymers, and (c) the general formula
A compound having one or more (1) at the end and having an average molecular weight of 600 or less, and when the total amount of the compound (a) and the urethane prepolymer (b) is 100 parts by weight, The content of the compound (c) is 0.1 to 10 parts by weight.

The present invention is described in detail below. [1] Constituent component (a) Two or more trialkyl (or phenyl) compounds in one molecule.
Compounds containing a silylthio group, trialkyl (or phenyl) silylthio group is represented by the following general formula (1)

[Chemical 3] (In the formula, R ¹ , R ² , and R ³ are any of an alkyl group having 1 to 6 carbon atoms, a phenyl group, and a haloalkyl group.).

The structural group represented by the above general formula (1) is
When R ¹ , R ² and R ³ are all alkyl groups,
The alkyl group preferably has 1 or 2 carbon atoms.
In particular, the following general formula (2)

[Chemical 4] Is preferable because the reaction rate with water is fast. Also,
When any of R ¹ , R ² or R ³ is a haloalkyl group, the haloalkyl group is preferably a chloromethyl group.

The structural group represented by the general formula (1) is hydrolyzed by moisture in the air and converted into a thiol group containing active hydrogen.

The compound (a) containing the structural group of the general formula (1) is
Molecular weight is 700-10,000, preferably 800-5,000
Is. This is because if the molecular weight is less than 700, hydrolysis is extremely fast, handling becomes difficult, and the storage stability of the composition decreases, and if the molecular weight exceeds 10,000, the hydrolysis rate becomes slow.

Examples of the compound (a) having two or more structures represented by the general formula (1) as described above per molecule include compounds represented by the following general formula (3). ^{R 1 R 2 R 3 SiS (} CH 2 CH 2 OCH 2 OCH 2 CH 2 S 2) h - -CH 2 CH 2 OCH 2 OCH 2 CH 2 SSiR 1 R 2 R 3 ··· (3) ( in the formula, (h is an integer of 4 to 25.)

Compounds represented by the general formula (3) in which h exceeds 25 have poor compatibility with the isocyanate group-containing polyurethane prepolymer described below, particularly polyether and polyester skeleton polymers, and h Is 4
If less than, the hydrolysis rate is high and the storage stability is poor.

Among the above compounds, the following general formula (4): (CH ₃ ) ₃ SiS (CH ₂ CH ₂ OCH ₂ OCH ₂ CH ₂ S ₂ ) _i --CH ₂ CH ₂ OCH ₂ OCH ₂ CH ₂ S Si _{(CH 3) 3 ··· (4} ) ( wherein, i is a. integer of 4-15) preferably represented by.

Further, the following general formula (5): R ¹ R ² R ³ SiS (R ⁴ O) _j R ⁵ SSiR ¹ R ² R ³ (5) (wherein R ⁴ and R ⁵ are carbon atoms A compound represented by 2 or 3 alkylene groups and j is an integer of 0 to 50) is preferable since it has good compatibility with the urethane prepolymer.

In addition, as the compound (a), the following general formula
Those represented by (6) to (8) are preferable. ^{R 1 R 2 R 3 SiS (} CH 2) 6 SCH 2 CH 2 (OCHR 6 - -CH 2 SCH 2 CH 2) k (CH 2) 4 SSiR 1 R 2 R 3 ··· (6) ( in the formula, R ⁶ is hydrogen or a methyl group, and k is 4 to 25.
Is an integer. ^{) R 1 R 2 R 3 SiSCH} 2 COOCH 2 C- - (CH 2 OCOCH 2 SSiR 1 R 2 R 3) 3 ··· (7) (R 1 R 2 R 3 SiSCH 2 CH 2 COOCH 2) 3 CC 2 H ₅ ··· (8)

The compound (a) as described above may be used alone or in combination of two or more kinds.

The compound (a) has a thiol group of 1
It can be obtained by reacting a compound having two or more molecules per molecule with a commercially available silylating reagent or the like to convert a thiol group into a trialkyl (or phenyl) silylthio group.

Examples of the thiol group-containing compound used as a raw material include liquid polysulfide polymers. Among them, the following general formula (9): HS (CH ₂ CH ₂ OCH ₂ OCH ₂ CH ₂ S _{m ) n - -CH 2 CH 2 OCH} 2 OCH 2 CH 2 SH ··· (9) ( wherein, m is an integer from 1 to 4, the average value is 2 .n 4 to 25, preferably Is an integer of 4 to 10).

A small amount of a cross-linking agent may be introduced into the polysulfide compound represented by the general formula (9) from the synthetic stage thereof, and a cross-linking structure derived from this may be present in the skeleton. There is also a possibility. Further general formula (9)
There may be a small amount of monosulfide bond, trisulfide bond, tetrasulfide bond, etc. in addition to the disulfide bond shown in, but the average value of the number of atoms of these sulfur is 2, which is usually represented as a disulfide bond. It

As other known thiol group-containing compounds, for example, polyoxyalkylene polyol having a structure represented by the following general formula (10), polymercaptan having a structure represented by the general formula (11), On at least part of the skeleton

[Chemical 5] A mercaptan-terminated liquid polymer having, for example, a mercaptan-terminated liquid polymer having a urethane group-containing structure represented by the following general formula (12), a mercaptan-terminated liquid polymer having a structure represented by the general formula (13): And poly (oxyalkylene) -polyester-poly (monosulfide) -polythiol, butadiene mercaptan polymer, mercaptan-containing polymer and mercaptoorganopolysiloxane.

[0025]

[Chemical 6] (In the formula, p, q, r, s, and t are integers of 2 to 100,
R ⁷ is hydrogen or a methyl group. )

Still other thiol group-containing compounds include the following general formula (14): HS (CH ₂ CH ₂ OS _u ) _v CH ₂ CH ₂ SH
(14) (wherein u is an integer of 1 to 4 and v is an integer of 4 to 25) are known.

Examples of the method for converting the thiol group of the thiol group-containing compound as described above into a trialkyl (or phenyl) silylthio group include the following. A compound represented by a thiol group-containing compound and halosilanes (general formula: R ¹ R ² R ³ SiX) that are equimolar or more to the thiol group: provided that R ¹ , R ² and R ³ are the same as above. , X represents a halogen group. ) Are reacted with each other in the presence of a tertiary amine such as triethylamine to convert the thiol group of the thiol group-containing compound into a trialkyl (or phenyl) silylthio group.

Examples of the above-mentioned halosilanes include trimethylchlorosilane, trimethylbromosilane, trimethyliodosilane, dimethylphenylchlorosilane, chloromethyldimethylchlorosilane, and the like. Reactivity with thiol groups and easy removal of by-products Trimethylchlorosilane is particularly preferable from the standpoint of economy.

Further, as a means for converting the thiol group of the thiol group-containing compound into a trimethylsilylthio group, the thiol group-containing compound contains ½ or more moles of N,
A method of reacting O-bis (trimethylsilyl) acetamide or N, N'-bis (trimethylsilyl) urea with a thiol group-containing compound, in which the molar amount of the thiol group is 1/2 mol or more, preferably equimolar to 3 times Silazane
Examples include a method of reacting in the presence of a suitable reaction catalyst. As the above reaction catalyst, J. Org. Chem. 47 , 3966 (19
82) and the like can be used, but imidazole and saccharin are particularly preferable. The amount used is about 0.001 to 0.1 equivalent relative to the thiol group-containing compound.

In any of the above methods for converting a thiol group into a trialkyl (or phenyl) silylthio group, the starting thiol group-containing compound may be a thiol group, a hydroxyl group or an amino group. When it contains a functional group capable of reacting with another silylating agent (for example, when a compound having the structure of the general formulas (10) and (12) is used as a raw material), a large excess of the silylating agent is required. It is not preferable in terms of operation and economy.

(B) Two or more isocyanates per molecule
As the urethane prepolymer having two or more isocyanate groups per molecule of the urethane prepolymer having a group , commercially available polyester-based urethane prepolymer, polyether-based urethane prepolymer, and the like can be used. To 2
Those having one or more isocyanate groups are preferable. This urethane prepolymer (b) has a molecular weight of 800 to 20,000.
And preferably 1,000 to 8,000. Molecular weight 8
When it is less than 00, the reactivity of the isocyanate group is high, the storage stability of the composition is deteriorated, foaming is likely to occur, and even when the molecular weight exceeds 20,000, the storage stability is deteriorated.

The urethane prepolymer containing two or more isocyanate groups in one molecule can be obtained as a reaction product of an organic polyisocyanate and an active hydrogen-containing compound.

Examples of the above organic polyisocyanates include 2,4- or 2,6-tolylene diisocyanate (TD
I), diphenylmethane-4,4'-diisocyanate
(MDI), 4,4′-dicyclohexylmethane diisocyanate (hydrogenated MDI), isophorone diisocyanate (IPDI), 1,5-naphthalene diisocyanate (ND
I), tolidine diisocyanate (TODI), xylylene diisocyanate (XDI), hexamethylene diisocyanate (HDI), methylcyclohexylene diisocyanate (hydrogenated TDI), cyclohexylene diisocyanate (hydrogenated XDI) and the like. These may be used alone or in combination of two or more.

Examples of active hydrogen-containing compounds include high molecular weight polyols (eg, polyether polyols, polyester polyols, polybutadiene polyols, polyacrylate polyols, polyisoprene polyols).
And low molecular weight polyols.

(C) one or more trialkyl (or
Compounds containing a phenyl) silylthio group A trialkyl (or phenyl) silylthio group has the general formula
It is represented by (1) and is preferably the same as the compound (a). The structural group represented by the general formula (1) is
It is hydrolyzed by moisture in the air and converted into thiol groups containing active hydrogen.

The compound (c) has at least one structural group of the general formula (1) at the end and has a molecular weight of 600 or less. Molecular weight 60
This is because if it exceeds 0, the curing rate becomes slower along with the hydrolysis rate. Preferably, it has two or more structural groups of the general formula (1) at the terminal and a molecular weight of 100 to 600.

Such a compound (c) is prepared by reacting a compound having one or more thiol groups at the terminal with a commercially available silylating reagent or the like to convert the thiol group into a trialkyl (or phenyl) silylthio group. Obtainable.

The thiol group-containing compound used as a raw material here is a mercaptan-terminated oligomer or monomer having a molecular weight of 600 or less and having a structure represented by the general formulas (9) to (14), or the following general formula Formulas (15) to (19): HS (CH ₂ ) _w SH ... (15) HS (CH ₂ CH ₂ O) _x CH ₂ CH ₂ SH ... (16) HS (CH ₂ CHCH ₃ ) _y SH ・ ・ ・ (17) HS (CH ₂ CHCH ₃ O) _z CHCH ₃ CH ₂ SH ・ ・ ・ (18) HSCH ₂ C ₆ H ₄ CH ₂ SH ・ ・ ・ (19) (wherein w, x, y and z are integers of 1 to 15.) and the like.

Monomercaptan is also known as a thiol group-containing compound, but since it terminates at the end after curing, its physical properties are somewhat inferior to those of dimercaptan and the like. Further, the following general formulas (20) to (24): HSCH ₂ C (SH) HCH ₂ SH ... (20) (HSCH ₂ COOCH ₂ ) ₃ CC ₂ H ₅ ... (21) (HSCH ₂ CH ₂ COOCH ₂ ) ₃ CC ₂ H ₅ ... (22) HSCH ₂ COOCH ₂ C (CH ₂ OCOCH ₂ SH) ₃ ... (23) HSCH ₂ CH ₂ COOCH ₂ C (CH ₂ OCOCH ₂ SH) ₃ ... Although tri- or tetramercaptan represented by (24) is known, it is necessary to consider the physical properties of the cured product because it forms a crosslinked structure after curing.

[2] Blending Ratio The blending ratio of the compound (a) and the urethane prepolymer (b) described above is such that if the molar ratio of [structural group of general formula (1)] / isocyanate group is less than 0.3, the crosslinking point is Increase, the hardened product becomes hard and the elongation decreases, and the residual isocyanate group in the hardened product causes foaming. When the molar ratio of [structural group of general formula (1)] / isocyanate group exceeds 2.0, the general formula (1)
The compound having the above structural group acts as a terminal stopper of the reaction, and significantly hinders the increase in the molecular weight of the composition. for that reason,
The compounding ratio is preferably such that the molar ratio of [structural group of general formula (1)] / isocyanate group is 0.3 to 2.0, and particularly preferably 0.5 to 1.2.

The amount of the compound (c) added is preferably 0.5 to 5 times the molar amount of the water content mixed in the composition. For this, the compound (c) is added in an amount of 0.1 to 10 parts by weight, preferably 100 parts by weight of the compound (a) + the compound (b).
Add 0.2 to 3.0 parts by weight. The compound (c) is selectively hydrolyzed by the residual water in the composition and reacts with the compound (b) to form a thiourethane bond, but its molecular weight does not increase, so the composition does not thicken, It has excellent storage stability.

[3] Optional component The one-part curable composition of the present invention basically comprises (a) a compound containing two or more trialkylsilylthio groups in one molecule as described above, b) a urethane prepolymer containing two or more isocyanate groups in one molecule, and (c) one at the end.
It is composed of a compound containing three or more trialkylsilylthio groups, but in addition, for the purpose of improving economy, workability when applying the composition, and physical properties of the composition after curing, Fillers such as calcium, carbon black, titanium oxide, and butylbenzyl phthalate,
A plasticizer such as dioctyl phthalate can be added. However, in order to obtain a one-pack curable composition having excellent storage stability, the additive does not contain a functional group such as a hydroxyl group, an amino group, a carboxyl group, and a thiol group, or the functional group is capped. Those which do not show remarkable acidity or alkalinity are preferable. Further, it is preferable that the filler and the plasticizer are sufficiently dehydrated.

Further, a catalyst can be added to the one-part curable composition of the present invention in order to carry out curing after application quickly and reliably. These catalysts include tertiary ethylenediamine, triethylamine, tri-n-butylamine, pentamethyldiethylenetriamine, N, N-dimethylcyclohexylamine, N, N-dicyclohexylmethylamine, tetramethyl-1,3-diaminopropane and the like. Amine-based catalyst etc. can be used

The addition amount of these catalysts is preferably 0.001 to 1.0 part by weight to 100 parts by weight of the total amount of (a) + (b),
Particularly, 0.01 to 0.5 part by weight is preferable. If it is less than 0.001 part by weight, the curing rate of the composition, particularly at low temperature, is not sufficient, and if it exceeds 1.0 part by weight, the storage stability thereof is adversely affected.

In order to further enhance the effect of the compound (c), 2,4- or 2,6-tolylene diisocyanate is used.
(TDI), diphenylmethane-4,4'-diisocyanate (MDI), 4,4'-dicyclohexylmethane diisocyanate (hydrogenated MDI), isophorone diisocyanate (IPDI), 1,5-naphthalenediisocyanate
(NDI), tolidine diisocyanate (TODI),
Monomer polyisocyanates such as xylylene diisocyanate (XDI), hexamethylene diisocyanate (HDI), methylcyclohexylene diisocyanate (hydrogenated TDI), cyclohexylene diisocyanate (hydrogenated XDI), dimer polyisocyanate or trimer polyisocyanate Compound (a) + compound (b) such as isocyanate adduct
0.05 to 10 parts by weight may be added to the total amount of 100 parts by weight. The preferred addition amount is 0.1 to 5.0 parts by weight.

[0046]

The present invention will be described in more detail by the following examples. Synthetic following formula Synthesis Example 1 Compound _{(a): HS (CH 2} CH 2 OCH 2 OCH 2 CH 2 SS) 5 - liquid represented by _{-CH 2 CH 2 OCH 2 OCH 2} CH 2 SH polysulfide (E LP-3 manufactured by Rethiocol Co., Ltd. 500 g (0.5 mol), hexamethyldisilazane 151 g (1.0 mol), saccharin 0.5 g (0.0024 mol), dichloroethane 50 g (0.5 mol), 1 liter equipped with a condenser and a stirrer Was charged into the reactor. This was placed in a 120 ° C. bath and stirred for 5 hours.

After that, dichloroethane,
Remove excess hexamethyldisilazane and by-products,
A polymer represented by the following structural formula (hereinafter a thiol compound
(a)) was obtained. _{(CH 3) 3 SiS (CH} 2 CH 2 OCH 2 OCH 2 CH 2 SS) 5 - -CH 2 CH 2 OCH 2 OCH 2 CH 2 SSi (CH 3) 3

Synthesis Example 2 Synthesis of Compound (c) 500 g (2.7 mol) of triethylene dimercaptan represented by the following general formula: HSCH ₂ CH ₂ OCH ₂ CH ₂ OCH ₂ CH ₂ SH, 500 g of hexamethyldisilazane (3.1 mol) Mol), saccharin 0.5 g (0.0024 mol), dichloroethane 50 g (0.5
Mol) into a 1 liter reactor equipped with a condenser and stirrer. This was placed in a 120 ° C. bath and stirred for 5 hours.

Then, dichloroethane,
Remove excess hexamethyldisilazane and by-products,
A polymer represented by the following structural formula (hereinafter a thiol compound
(C) and obtained. _{(CH 3) 3 SiSCH 2 CH} 2 OCH 2 CH 2 - -OCH 2 CH 2 SSi (CH 3) 3

Example 1 A total of 100 parts by weight of polyoxypropylene triol having an average molecular weight of 5,000 and polyoxypropylene diol having an average molecular weight of 4,000 was reacted with 7.7 parts by weight of tolylene diisocyanate. Thus, a urethane prepolymer (isocyanate content 1.3% by weight, hereinafter referred to as urethane prepolymer (b)) was obtained.

To 100 parts by weight of this urethane prepolymer (b), 20 parts by weight of the thiol compound (a) was placed in a mixing container, and further dehydrated plasticizer (dioctyl phthalate) 30
Parts by weight and 150 parts by weight of dry calcium carbonate were added, thoroughly mixed and degassed under reduced pressure.

After mixing, 15 parts by weight of dehydrated xylene, N,
N, N ', N'-tetramethyl-1,3-diaminopropane
0.05 parts by weight was added and mixed well.

0.35 parts by weight of the thiol compound (c) was added to 315.05 parts by weight of the composition thus obtained, and the mixture was further kneaded to obtain a one-pack curable composition.

The obtained one-pack curable composition was evaluated for (1) storage stability, (2) curability, and (3) tack-free time by the following methods.

(1) Storage stability: The composition was sealed in an aluminum tube and stored in a thermostat at 80 ° C. and 70 ° C., and the composition was stored stable for a period of time until it was thickened or solidified in the tube and could not be extruded. It was used as a measure of sex.

(2) Curability: A single-sided bead having a width of 12 mm and a depth of 15 mm was prepared and exposed at 20 ° C., 55% humidity and 10 ° C., 40% humidity, and cured from the surface 3 and 7 days after exposure. The thickness of the part was measured and used as a measure of curability.

(3) Tack free time: 5 mm thick in composition
Make a sheet of this sheet, 20 ℃, 55% humidity and 10
It was exposed to 40 ° C and 40% humidity, and the tack-free time was measured.
The results are shown in Table 1 together with each composition.

Example 2 The same evaluation as in Example 1 was carried out on the composition of Example 1 containing 1.0 part by weight of the compound (c). The results are also shown in Table 1.

Comparative Example 1 The same evaluation as in Example 1 was carried out on the composition of Example 1 to which the compound (c) was not added. The results are shown in Table 1.
It is shown together with.

Table 1 Composition (parts by weight) Example 1 Example 2 Comparative Example 1 Thiol compound (a) 20 20 20 Urethane prepolymer (b) 100 100 100 Thiol compound (c) 0.3 1.0 − Physical property Storage stability (Day / 80 ℃) 12 13 6 (Day / 70 ℃) 17 25 14 Curability (mm / 20 ℃, RH55%: at 3 days) 5.0 5.8 4.5 (mm / 20 ℃, RH55%: at 7 days) 9.3 9.3 7.6 (Mm / 10 ℃, RH40%: at 3 days) 2.6 3.1 3.6 (mm / 10 ℃, RH40%: at 7 days) 5.0 5.2 5.8 Tack free time (hour / 20 ℃, RH55%) 6 5 7 (hour / 10 ℃ , RH40%) 10 10 10

As is clear from Table 1, the one-part curable composition of the present invention has excellent storage stability and no curability problem. On the other hand, the one-part curable composition of Comparative Example 1 is inferior in storage stability.

[0062]

As described in detail above, the one-part curable composition of the present invention comprises a compound containing two or more trialkyl (or phenyl) silylthio groups in one molecule and two or more compounds in one molecule. Since it contains the urethane prepolymer containing an isocyanate group and the compound containing one or more trialkyl (or phenyl) silylamino groups at the end, it has excellent storage stability. Further, the one-part curable composition of the present invention has a fast curing rate even at low temperatures, has excellent heat resistance, and does not foam even under conditions of high temperature and high humidity.

The one-part curable composition of the present invention as described above is
It is suitable as a sealing material for construction, an adhesive, and a coating agent.

Claims (1)

[Claims] 1. (a) The following general formula (1): (In the formula, R ¹ , R ² and R ³ are any one of an alkyl group having 1 to 6 carbon atoms, a phenyl group and a haloalkyl group.) Each molecule has two or more groups, and an average value. A compound having a molecular weight of 700 to 10,000, and (b) 2 per molecule
It has more than one isocyanate group and an average molecular weight of 800-
20,000 urethane prepolymers, and (c) the general formula
A compound having one or more (1) at the end and having an average molecular weight of 600 or less, and when the total amount of the compound (a) and the urethane prepolymer (b) is 100 parts by weight, A one-part curable composition, wherein the content of the compound (c) is 0.1 to 10 parts by weight.