Curable composition

A curable resin composition is disclosed which is composed of (a) an oxyalkylene polymer containing at least one reactive silicon group per molecule and having a number average molecular weight of not less than 3000 and an Mw/Mn ratio of not higher than 1.6, (b) a copolymer having a molecular chain which comprises (A) an alkyl acrylate monomer unit and/or an alkyl methacrylate monomer unit each having 1 to 8 carbon atoms in the alkyl moiety thereof and (B) an alkyl acrylate monomer unit and/or an alkyl methacrylate monomer unit each having 10 or more carbon atoms wherein the total number of monomer units (A) and monomer units (B) constitutes more than 50% of the monomer units in the copolymer (b), and (c) a curing catalyst.

FIELD OF THE INVENTION 
The present invention relates to a curable composition useful as a contact 
adhesive. A contact adhesive is an adhesive which is allowed to stand for 
a prescribed time after being applied to one or more adherend and being 
assembled thereto. 
BACKGROUND OF THE INVENTION 
Conventionally widespread contact adhesives are of a solvent type 
comprising an organic solvent having uniformly dissolved therein 20 to 35% 
of solid matter, comprising natural rubber or a diene compound polymer 
such as a synthetic rubber and additives such as a tackifying resin, a 
plasticizer, and an antioxidant. However, adhesives of the solvent type 
are costly due to a use of large amounts of an organic solvent. Besides, 
the organic solvent must be evaporated, which involves deterioration of 
the working environment, danger of fire, and air pollution. 
In order to provide an adhesive which is free from the above problems while 
exhibiting adhesion performance comparable to the conventional solvent 
type adhesives, a contact adhesive of a solventless type comprising a 
modified silicone polymer has been proposed as disclosed in JP-A-3-263478 
(the term "JP-A" as used herein means an "unexamined published Japanese 
patent application"). 
However, the contact adhesive using a modified silicone polymer as 
disclosed in JP-A-3-263478 is disadvantageous in that it requires a long 
time for developing sufficient tackiness for making assembly possible 
(hereinafter referred to as a tack developing time) and that it has 
insufficient tack strength and poor workability due to its high viscosity. 
An object of the present invention is to provide a curable composition 
which develops tackiness rapidly, retains the developed tackiness for a 
long time (the time during which the tackiness is exhibited will 
hereinafter be referred to as a tack range), exhibits sufficient tack 
strength, satisfactory initial and final adhesive strength, and is 
excellent in workability. In particular, the present invention is to 
provide a curable composition which develops sufficient tackiness rapidly 
and forms excellent cured products. 
SUMMARY OF THE INVENTION 
The above object of the present invention is to provide a curable 
composition comprising (a) an oxyalkylene polymer containing at least one 
reactive silicon group per molecule and having a number average molecular 
weight of not less than 3000 and an Mw/Mn ratio of not higher than 1.6, 
(b) a copolymer whose molecular chain substantially comprises (A) an alkyl 
acrylate monomer unit and/or an alkyl methacrylate monomer unit each 
having 1 to 8 carbon atoms in the alkyl moiety thereof and (B) an alkyl 
acrylate monomer unit and/or an alkyl methacrylate monomer unit each 
having 10 or more carbon atoms, and (c) a curing catalyst.

DETAILED DESCRIPTION OF THE INVENTION 
The oxyalkylene polymer which can be used in the present invention as 
component (a) includes polymers having a molecular chain represented by 
formula (1): 
EQU --(R--O).sub.n -- (1) 
wherein R represents a divalent alkylene group having 2 to 4 carbon atoms; 
and n represents the number of repeating units. 
From the viewpoint of availability of the formula (R--O) in formula (1), an 
oxyalkylene polymer having a repeating unit represented by formula (2) 
shown below is preferred: 
EQU --CH(CH.sub.3)CH.sub.2 O-- (2) 
The above oxyalkylene polymer may have a straight-chain or a branched 
structure, or a mixed structure thereof. The polymer may contain other 
monomer units but preferably comprises the monomer unit of formula (1) in 
a proportion of at least 50% by weight, particularly 80% by weight or 
more. 
Oxyalkylene polymers having a number average molecular weight (Mn) of 3,000 
or more are effectively usable. Those having an Mn of 3,000 to 50,000, 
particularly 3,000 to 30,000, are preferred. The ratio (Mw/Mn) of weight 
average molecular weight (Mw) to number average molecular weight (Mn) is 
not higher than 1.6, which indicates that the polymer has an extremely 
narrow molecular weight distribution (i.e., it is highly monodisperse). 
The Mw/Mn ratio is preferably not higher than 1.5, still preferably not 
higher than 1.4. While molecular weight distribution is measurable by 
various methods, it is generally measured by gel-permeation chromatography 
(GPC). Since the oxyalkylene polymer has such a narrow molecular weight 
distribution in spite of a great number average molecular weight, the 
composition of the present invention has a low viscosity and is easy to 
handle before curing while showing satisfactory rubbery elastic behavior 
after curing. 
The oxyalkylene polymer (a) is an organic polymer having at least one 
reactive silicon group per molecule and having an Mw/Mn ratio of not more 
than 1.6. The terminology "reactive silicon group" in the polymer denotes 
a silicon-containing group in which a hydrolyzable group or a hydroxyl 
group is bonded to the silicon atom and which is crosslinkable through 
silanol condensation reaction. While not limited thereto, typical reactive 
silicon groups are represented by formula (3) 
##STR1## 
wherein R.sup.1 and R.sup.2 each represents an alkyl group having 1 to 20 
carbon atoms, an aryl group having 6 to 20 carbon atoms, an aralkyl group 
having 7 to 20 carbon atoms or a triorganosiloxy group represented by 
(R').sub.3 SiO--, wherein each of the three R' groups, which may be the 
same or different, represents a monovalent hydrocarbon group having 1 to 
20 carbon atoms; when there are two or more of each of the R.sup.1 or 
R.sup.2 groups, each of the R.sup.1 and R.sup.2 groups may be the same or 
different, and the R.sup.1 can be the same or different from R.sup.2 ; X 
represents a hydroxyl group or a hydrolyzable group; when there are two or 
more X groups, they may be the same or different; a represents 0, 1, 2 or 
3; b represents 0, 1 or 2; b for R.sup.1 and b for X in different units of 
formula: 
##STR2## 
may be the same or different; and m represents 0 or an integer of from 1 
to 19 satisfying the relationship a+.SIGMA.b.gtoreq.1. 
The hydrolyzable group represented by X is not particularly limited and is 
selected from conventional hydrolyzable groups. Specific examples are a 
hydrogen atom, a halogen atom, an alkoxy group, an acyloxy group, a 
ketoximate group, an amino group, an amido group, an acid amido group, an 
amino-oxy group, a mercapto group, and an alkenyloxy group. Preferred 
among them are a hydrogen atom, an alkoxy group, an acyloxy group, a 
ketoximate group, an amino group, an amido group, an amino-oxy group, a 
mercapto group, and an alkenyloxy group. An alkoxy group, e.g., a methoxy 
group, is particularly preferred for ease in handling due to its mild 
hydrolyzability. 
One to three hydroxyl groups or hydrolyzable groups may be bonded to one 
silicon atom, and (a+.SIGMA.b) is preferably 1 to 5. Where two or more 
hydroxyl groups or hydrolyzable groups are present per reactive silicon 
group, they may be the same or different. 
The reactive silicon group may have one or more silicon atoms. A reactive 
silicon group in which silicon atoms are linked to form siloxane bondings 
may have as much as 20 silicon atoms. 
From the standpoint of availability, reactive silicon groups represented by 
formula (4) shown below are preferred: 
##STR3## 
wherein R.sup.1, X, and a are as defined above 
R.sup.1 and R.sup.2 in formula (3) specifically include an alkyl group, 
e.g., methyl or ethyl; a cycloalkyl group, e.g., cyclohexyl; an aryl 
group, e.g., phenyl; an aralkyl group, e.g., benzyl; and a triorganosiloxy 
group of formula (R').sub.3 SiO-- in which R' is methyl or phenyl R.sup.1, 
R.sup.2, and R' each preferably represents a methyl group. 
The oxyalkylene polymer contains at least one, preferably 1.1 to 5, 
reactive silicon groups per molecule. If the number of the reactive 
silicon group per molecule is less than 1, the polymer has insufficient 
curability, failing to achieve satisfactory rubbery elasticity. 
The reactive silicon group may be placed either at the terminal or in the 
inside of the molecular chain of the oxyalkylene polymer. An oxyalkylene 
polymer having the reactive silicon group at the molecular terminal 
thereof tends to provide a rubbery cured product having high tensile 
strength and high elongation. 
The oxyalkylene polymer having a reactive silicon group is preferably 
obtained by introducing a reactive silicon group into the above-mentioned 
oxyalkylene polymer having a functional group. 
Introduction of a reactive silicon group may be carried out in a 
conventional manner, for example, as follows. (I) An oxyalkylene polymer 
having a functional group, such as a hydroxyl group, in the molecule 
thereof is reacted with an organic compound having a group reactive with 
the functional group and an unsaturated group to obtain an oxyalkylene 
polymer having unsaturated group. Alternatively, the oxyalkylene polymer 
is copolymerized with an unsaturated group-containing epoxy compound to 
obtain an unsaturated group-containing oxyalkylene polymer. The resulting 
reaction product is then hydrosilylated with a hydrosilane having a 
reactive silicon group. (II) An unsaturated group-containing oxyalkylene 
polymer, obtained in the same manner as in (I) above, is reacted with a 
compound having a mercapto group and a reactive silicon group. (III) An 
oxyalkylene polymer having a functional group, such as a hydroxyl group, 
an epoxy group or an isocyanate group (hereinafter referred to as a Y 
functional group), in the molecule thereof is reacted with a compound 
having a group reactive with the Y functional group (hereinafter referred 
to as a Y' functional group) and a reactive silicon group. 
The silicon compound having a Y' functional group includes an 
amino-containing silane, such as 
.gamma.-(2-aminoethyl)aminopropyltrimethoxysilane, 
.gamma.-(2-aminoethyl)aminopropylmethyldimethoxysilane or 
.gamma.-aminopropyltriethoxysilane; a mercapto-containing silane, such as 
.gamma.-mercaptopropyltrimethoxysilane or 
.gamma.-mercaptopropylmethyldimethoxysilane; an epoxysilane, such as 
.gamma.-glycidoxypropyltrimethoxysilane or 
.beta.-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; a vinyl type 
unsaturated group-containing silane, such as vinyltriethoxysilane, 
.gamma.-methacryloyloxypropyltrimethoxysilane or 
.gamma.-acryloyloxypropylmethyldimethoxysilane; a chlorine-containing 
silane, such as .gamma.-chloropropyltrimethoxysilane; an 
isocyanate-containing silane, such as 
.gamma.-isocyanatopropyltriethoxysilane or 
.gamma.-isocyanatopropylmethyldimethoxysilane; and a hydrosilane, such as 
methyldimethoxysilane, trimethoxysilane or methyldiethoxysilane. The 
silicon compounds containing a Y' functional group are by no means limited 
to these examples. 
Among the above-mentioned methods, the method (I) and the method (III), in 
which a polymer having a hydroxyl group at the terminal thereof is reacted 
with a compound having an isocyanate group and a reactive silicon group, 
are preferred. 
While not limited thereto, the above-described reactive silicon 
group-containing oxyalkylene polymers typically include those disclosed in 
JP-A-50-156599, JP-A-54-6069, JP-A-57-126823, JP-A-59-78223, 
JP-A-55-82123, JP-A-55-131022, JP-A-55-47825, JP-A-62-230822, 
JP-A-63-83131, JP-A-3-47825, JP-A-3-72527, JP-A-3-122152, U.S. Pat. Nos. 
3,632,557, 4,345,053, 4,366,307, and 4,960,844. 
The alkyl (meth)acrylate copolymer which can be used in the present 
invention as component (b) (hereinafter referred to as copolymer (b)), 
comprises as monomer units (A) alkyl (meth)acrylate unit having 1 to 8 
carbon atoms in the alkyl moiety and represented by formula (5): 
EQU --[CH.sub.2 --C(R.sup.4)(COOR.sup.3)--]-- (5) 
wherein R.sup.3 represents an alkyl group having 1 to 8 carbon atoms; 
R.sup.4 represents a hydrogen atom or a methyl group. 
The alkyl (meth)acrylate copolymer (b) also comprises as monomer units (B) 
alkyl (meth)acrylate units having 10 or more carbon atoms in the alkyl 
moiety and represented by formula (6): 
EQU --[CH.sub.2 --C(R.sup.4)(COOR.sup.5)--]-- (6) 
wherein R.sup.4 is as defined above; and R.sup.5 represents an alkyl group 
having 10 or more carbon atoms. 
R.sup.3 in formula (5) includes alkyl groups having 1 to 8 carbon atoms, 
such as methyl, ethyl, propyl, t-butyl and 2-ethylhexyl, preferably those 
having 1 to 4 carbon atoms, still preferably those having 1 to 2 carbon 
atoms. The alkyl groups represented by R.sup.3 in copolymer (b) may be the 
same or of plural species throughout the repeating units of the polymer. 
R.sup.5 in formula (6) includes alkyl groups having 10 or more, usually 10 
to 30, and preferably 10 to 20 carbon atoms, such as lauryl, tridecyl, 
cetyl, stearyl, and behenyl (C.sub.22). Containing a monomer unit having 
such a long-chain alkyl group, the copolymer (b) exhibits compatibility 
with oxyalkylene polymer (a). The alkyl group represented by R.sup.5 in 
copolymer (b) may be the same or may be of two or more species throughout 
the repeating units of the polymer, e.g., Rs being a C.sub.12 alkyl group 
and a C.sub.13 alkyl group. 
The molecular chain of copolymer (b) substantially comprises monomer units 
(A) and (B). The term "substantially" as used herein means that the 
proportion of monomer units (A) and (B) in copolymer (b) exceeds 50%, 
preferably 70% or more. Where the proportion of monomer units (A) and (B) 
is less than 50%, the copolymer (b) is less compatible with oxyalkylene 
copolymer (a), tending to cause white turbidity and to exhibit reduced 
adhesion characteristics. 
The ratio of monomer unit (A) to monomer unit (B) preferably ranges from 
95/5 to 40/60, still preferably from 90/10 to 60/40. If the ratio exceeds 
95/5, the compatibility tends to be reduced. If it is lower than 40/60, an 
economical disadvantage may result. 
Copolymer (b) may further contain, in addition of monomer units (A) and 
(B), monomer units derived from monomers copolymerizable with monomer 
units (A) and (B). Such monomer units include those derived from monomers 
having a --COOH group, e.g., acrylic acid and methacrylic acid; those 
derived from monomers having an amido group, e.g., acrylamide, 
methacrylamide, N-methylolacrylamide, and N-methylolmethacrylamide; those 
derived from monomers having an epoxy group, e.g., glycidyl acrylate and 
glycidyl methacrylate; those derived from monomers having an amino group, 
e.g., diethylaminoethyl acrylate, diethylaminoethyl methacrylate, and 
aminoethyl vinyl ether; and those derived from acrylonitrile, iminol 
methacrylate, styrene, .alpha.-methylstyrene, alkyl vinyl ethers, vinyl 
chloride, vinyl acetate, vinyl propionate, ethylene, etc. 
From the standpoint of ease in handling, copolymer (b) preferably has a 
number average molecular weight of 500 to 100,000, still preferably 1,000 
to 30,000. 
Copolymer (b) may contain a reactive silicon group. Copolymer (b) having a 
reactive silicon group has improved compatibility with copolymer (a) which 
leads to high adhesive strength. 
Where copolymer (b) contains a reactive silicon group, it preferably 
contains, on the average, 0.1 to 10.0, still preferably 0.5 to 5.0, 
particularly 0.5 to 2.5, reactive silicon groups per molecule. 
Copolymer (b) used in the present invention is obtained by vinyl 
polymerization, for example, vinyl polymerization through radical 
reaction, of monomers providing units represented by formulae (5) and (6) 
and other copolymerizable monomers and, if desired, a compound having a 
polymerizable unsaturated bond and a reactive silicon group in accordance 
with conventional solution polymerization or bulk polymerization 
techniques. 
The reaction may usually be carried out using a reaction system comprising 
the above-mentioned monomers, a radical initiator, a chain transfer agent, 
a solvent, etc., at 50.degree. to 150.degree. C. 
Examples of suitable radical initiators are azobisisobutyronitrile and 
benzoyl peroxide. Examples of suitable chain transfer agents are 
n-dodecylmercaptan and t-dodecylmercaptan. Suitable solvents include inert 
solvents, such as ethers and hydrocarbons. 
Introduction of a reactive silicon group into the copolymer (b) can be 
effected through various methods including, for example: (i) a method of 
copolymerizing a compound having a polymerizable unsaturated bond and a 
reactive silicon group (e.g., CH.sub.2 .dbd.CHSi(OCH.sub.3).sub.3) and 
monomers providing units of formulae (5) and (6), and (ii) a method 
comprising copolymerizing a compound having a polymerizable unsaturated 
bond and a reactive functional group (hereinafter referred to as a Y" 
group) (e.g., acrylic acid) with monomers providing units of formulae (5) 
and (6) and reacting the resulting copolymer with a compound having a 
reactive silicon group and a functional group capable of reacting with the 
Y" group (e.g., a compound having an isocyanate group and an 
--Si(OCH.sub.3).sub.3 group). 
The above-mentioned compound having a polymerizable unsaturated bond and a 
reactive silicon group includes compounds represented by formula (7): 
##STR4## 
wherein R.sup.6 represents an organic residue having a polymerizable 
unsaturated bond; and R.sup.1, R.sup.2, X, a, b, and m are as defined 
above. 
The compounds represented by formula (7) preferably include those 
represented by formula (8): 
EQU CH.sub.2 .dbd.C(R.sup.4)QSi(CH.sub.3).sub.3-c X.sub.c (8) 
wherein R.sup.4 and X are as defined above; c represents 1, 2 or 3; and Q 
represents a divalent organic group, such as --COOR.sup.8 (wherein R.sup.8 
represents a divalent alkylene group having 1 to 6 carbon atoms, e.g., 
--CH.sub.2 -- or --CH.sub.2 CH.sub.2 --), --CH.sub.2 C.sub.6 H.sub.4 
CH.sub.2 CH.sub.2 -- or --CH.sub.2 OCOC.sub.6 H.sub.4 COO(CH.sub.2).sub.3 
--, or a direct bond. 
Specific examples of the compounds represented by formula (7) or (8) 
include: 
CH.sub.2 .dbd.CHSi(CH.sub.3)(OCH.sub.3).sub.2, 
CH.sub.2 .dbd.CHSi(CH.sub.3)Cl.sub.2, 
CH.sub.2 .dbd.CHSi(OCH.sub.3).sub.3, 
CH.sub.2 .dbd.CHSiCl.sub.3, 
CH.sub.2 .dbd.CHCOO(CH.sub.2).sub.2 Si(CH.sub.3)(OCH.sub.3).sub.2, 
CH.sub.2 .dbd.CHCOO(CH.sub.2).sub.2 Si(OCH.sub.3).sub.3, 
CH.sub.2 .dbd.CHCOO(CH.sub.2).sub.2 Si(CH.sub.3)Cl.sub.2, 
CH.sub.2 .dbd.CHCOO(CH.sub.2).sub.2 SiCl.sub.2, 
CH.sub.2 .dbd.C(CH.sub.3)COO(CH.sub.2).sub.2 Si(CH.sub.3)(OCH.sub.3).sub.2, 
CH.sub.2 .dbd.C(CH.sub.3)COO(CH.sub.2).sub.2 Si(OCH.sub.3).sub.3, 
CH.sub.2 .dbd.C(CH.sub.3)COO(CH.sub.2).sub.3 Si(CH.sub.3) 
(OCH.sub.3).sub.2, 
CH.sub.2 .dbd.C(CH.sub.3)COO(CH.sub.2).sub.3 Si(OCH.sub.3).sub.3, 
CH.sub.2 .dbd.C(CH.sub.3)COO(CH.sub.2).sub.2 Si(CH.sub.3)Cl.sub.2, 
CH.sub.2 .dbd.C(CH.sub.3)COO(CH.sub.2).sub.2 SiCl.sub.3, 
CH.sub.2 .dbd.CHCH.sub.2 OC(O)--Ph--COO(CH.sub.2).sub.3 Si(CH.sub.3) 
(OCH.sub.3).sub.2, 
CH.sub.2 .dbd.CHCH.sub.2 OC(O)--Ph--COO(CH.sub.2).sub.3 
Si(OCH.sub.3).sub.3, 
CH.sub.2 .dbd.CHCH.sub.2 OC(O)--Ph--COO(CH.sub.2).sub.3 
Si(CH.sub.3)Cl.sub.2, and 
CH.sub.2 .dbd.CHCH.sub.2 OC(O)--Ph--COO(CH.sub.2).sub.3 SiCl.sub.3 (wherein 
Ph represents a phenyl group.) 
Copolymer (b) is preferably used in an amount of from 20 to 200 parts by 
weight, still preferably from 30 to 160 parts by weight, per 100 parts by 
weight of oxyalkylene polymer (a); for, in this range, both polymers (a) 
and (b) exhibit remarkable improving effects on the characteristics of the 
adhesive. The specific ratio of copolymer (b) to oxyalkylene polymer (a) 
is usually selected from the above range according to the end use and 
intended performance. 
The catalyst which may be used in the present invention as component (c) is 
a catalyst for making the above-described polymers form a 
three-dimensional network structure and be cured to obtain a solid with 
rubbery elasticity. A broad range of known silanol condensation catalysts 
(curing catalysts) can be employed as component (c). Suitable examples of 
silanol condensation catalysts include titanic esters, such as tetrabutyl 
titanate and tetrapropyl titanate; tin carboxylates, such as dibutyltin 
dilaurate, dibutyltin maleate, dibutyltin diacetate, tin octylate, tin 
naphthenate, tin laurate, and tin ferzalate; a reaction product of 
dibutyltin oxide and a phthalic ester; dibutyltin diacetylacetonate; 
organoaluminum compounds, such as trisacetylacetonatoaluminum, 
tris(ethylacetoacetato)aluminum, and 
ethylacetoacetatodiisopropoxyaluminum; chelate compounds, such as 
tetraacetylacetonatozirconium and tetraacetylacetonatotitanium; lead 
octylate; iron naphthenate; bismuth compounds, such as bismuth 
tris(neodecanoate) and bismuth tris(2-ethylhexoate); amine compounds, such 
as butylamine, octylamine, dibutylamine, monoethanolamine, diethanolamine, 
triethanolamine, diethylenetriamine, triethylenetetramine, oleylamine, 
cyclohexylamine, benzylamine, diethylaminopropylamine, xylylenediamine, 
triethylenediamine, guanidine, diphenylguanidine, 
2,4,6-tris(dimethylaminomethyl)phenol, morpholine, N-methylmorpholine, 
2-ethyl-4-methylimidazole, and 1,8-diazabicyclo(5,4,0)undecene-7 (DBU); 
salts of these amine compounds with a carboxylic acid, etc.; low-molecular 
polyamide resins obtained from an excess polyamine and a polybasic acid; a 
reaction product of an excess polyamine and an epoxy compound; silane 
coupling agents having an amino group, such as 
.gamma.-aminopropyltrimethoxysilane and 
N-(.beta.-aminoethyl)aminopropylmethyldimethoxysilane; and other acidic 
catalysts and basic catalysts. These catalysts may be used either 
individually or as a combination of two or more thereof. 
The silanol condensation catalyst is used in an amount preferably of from 
0.01 to 20 parts by weight, still preferably of from 0.1 to 10 parts by 
weight, per 100 parts by weight of the oxyalkylene polymer. If the amount 
of the silanol condensation catalyst is too small with respect to the 
oxyalkylene polymer, the curing rate becomes low, and the curing reaction 
does not proceed sufficiently. On the other hand, when the amount of the 
silanol condensation catalyst is too large with respect to the oxyalkylene 
polymer, there is a tendency that curing is excessively accelerated, 
causing adverse influences on workability. 
If desired, the tacky adhesive using the curable composition according to 
the present invention may further contain adhesive resins, fillers, 
plasticizers, pigments, silicon compounds, ultraviolet absorbents, 
antioxidants, solvents, and the like in addition to the effective 
components (a), (b), and (c). 
Methods for preparing the contact adhesive using the curable composition of 
the present invention are not particularly restricted. For example, the 
contact adhesive can be prepared by compounding the above-described 
components and kneading the mixture at room temperature or under heating 
by means of a mixer, a roll, a kneader, etc. or dissolving the mixture 
with a small amount of an appropriate solvent. Further, the contact 
adhesive may be formulated into either a one-pack type or a two-pack type 
adhesive by appropriately combining the components. 
The method for applying the adhesive is not limited also. For example, the 
adhesive may be applied in a usual manner with a spatula, a roller, a 
spray gun, etc. 
In carrying out adhesion, the adhesive is allowed to stand in open air for 
a given period of time after being applied to one or more adherend whereby 
curing proceeds by action of moisture in the air to develop tackiness. 
Development of tackiness may be accelerated by heating or humidifying. 
While tackiness is still present, the adherends are bonded together. 
The contact adhesive using the curable composition of the present invention 
is characterized by using an oxyalkylene polymer having a number average 
molecular weight of not less than 3000 and an Mw/Mn ratio of not higher 
than 1.6, as a result of which the adhesive has remarkably improved 
workability and develops tackiness more rapidly as compared with 
conventional solventless type tacky adhesives. Further, the adhesive is 
excellent in weather resistance and storage stability on account of 
copolymer (b) containing a long-chain alkyl group. Hence, the curable 
composition of the present invention is expected to find broader 
application than ever as a solventless type contact adhesive. 
The present invention provides a curable composition which develops tack 
more rapidly and has a longer tack range as compared with conventional 
compositions comprising an oxyalkylene polymer and a copolymer comprising 
alkyl (meth)acrylate monomer units. Further, the composition exhibits 
satisfactory initial and final adhesion as well as excellent workability 
and is therefore useful as a contact adhesive. 
The curable composition of the present invention will now be illustrated 
with reference to Examples. 
The present invention will be described in greater detail by way of 
Synthesis Examples and Examples, but it should be understood that the 
present invention is not limited thereto. 
SYNTHESIS EXAMPLE 1 
One mole of polypropylenetriol having a number average molecular weight of 
15,000 (Mw/Mn=l.38; viscosity: 89 poise) and 3 moles of 
.gamma.-isocyanatopropylmethyldimethoxysilane were reacted in the presence 
of dibutyltin dilaurate to obtain a colorless transparent polymer. The IR 
spectrum was obtained before and after the reaction. As a result, 
disappearance of the absorption due to NCO at around 2280 cm.sup.-1 and 
appearance of absorption due to C.dbd.O at about 1730 cm.sup.-1 lent 
confirmation to the production of an oxyalkylene polymer having a 
methyldimethoxysilyl group at the molecular terminal thereof. 
SYNTHESIS EXAMPLE 2 
Polypropylene glycol having a number average molecular weight of 15,000 
(Mw/Mn=l.26; viscosity: 110 poise) was treated with sodium methoxide and 
then reacted with allyl chloride to convert the terminal hydroxyl group to 
an unsaturated group. 
One mole of the resulting unsaturated group-terminated polyoxyalkylene was 
reacted with 2 moles of dimethoxymethylsilane in the presence of 
chloroplatinic acid to obtain a yellow transparent oxyalkylene polymer 
having a methyldimethoxysilyl group at the molecular terminal thereof. 
SYNTHESIS EXAMPLE 3 
Polypropylenetriol having a number average molecular weight of 20,000 
(Mw/Mn=l.267; viscosity: 195 poise) was treated with sodium methoxide and 
then reacted with allyl chloride to convert a terminal hydroxyl group to 
an unsaturated group. 
One mole of the resulting unsaturated group-terminated polyoxyalkylene was 
reacted with 3 moles of dimethoxymethylsilane in the presence of 
chloroplatinic acid to obtain a yellow transparent oxyalkylene polymer 
having a methyldimethoxysilyl group at the molecular terminal thereof. 
COMATIVE SYNTHESIS EXAMPLE 1 
A mixture of polypropylene glycol (number average molecular weight: 2,500) 
and polypropylenetriol (number average molecular weight: 3,000) was used 
as a starting material. The mixture was treated with sodium methoxide, 
subjected to chain extending reaction using methylene chloride, and 
subsequently reacted with allyl chloride to convert the terminal hydroxyl 
group to an unsaturated group. 
One mole of the resulting unsaturated group-terminated polyoxyalkylene was 
reacted with 2.5 moles of dimethoxymethylsilane in the presence of 
chloroplatinic acid to obtain a yellow transparent polymer. The amount of 
hydrogenated silicon in the reaction solution was determined by IR 
spectroscopic analysis and, as a result, production of an oxyalkylene 
polymer having a methyldimethoxysilyl group at the molecular terminal 
thereof was confirmed. 
The viscosity of the polymers obtained in Synthesis Examples 1, 2, and 3 
and Comparative Synthesis Example 1 was measured with a Brookfield 
viscometer (BM type rotor No. 4; 12 rpm) at 23.degree. C. The number 
average molecular weight (Mn) and the molecular weight distribution 
(Mw/Mn) of each polymer were analyzed by gel-permeation chromatography 
(GPC). GPC was carried out by using a column packed with polystyrene gel 
(produced by Tosoh Corp.) and tetrahydrofuran as an eluent at an oven 
temperature of 40.degree. C. The results obtained are shown in Table 1. 
TABLE 1 
______________________________________ 
Number Molecular 
Average Weight 
Viscosity Molecular Distribution 
Polymer (poise) Weight (Mn) 
(Mw/Mn) 
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Synthesis 150 1.7 .times. 10.sup.4 
1.4 
Example 1 
Synthesis 160 1.8 .times. 10.sup.4 
1.3 
Example 2 
Synthesis 220 2.3 .times. 10.sup.4 
1.4 
Example 3 
Comparative 
240 1.5 .times. 10.sup.4 
2.3 
Example 1 
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SYNTHESIS EXAMPLE 4 
Synthesis of Copolymer (b) 
A mixture of 5.9 g of butyl acrylate, 66 g of methyl methacrylate, 13.2 g 
of stearyl methacrylate, 5.4 g of 
.gamma.-methacryloxypropylmethyldimethoxysilane, 7.2 g of 
.gamma.-mercaptopropylmethyldimethoxysilane, and 36 g of toluene was 
prepared. In the mixture was dissolved 3 g of azobisisobutyronitrile as a 
polymerization initiator. The resulting solution was added dropwise to 30 
g of toluene heated at 110.degree. C. over 6 hours. The mixture was 
allowed to polymerize for 2 hours to obtain copolymer (b) having a solid 
content concentration of 60% and a number average molecular weight (Mn) of 
2,200 as measured by GPC (on polystyrene conversion). 
EXAMPLE 1 
The reactive silicon group-containing oxyalkylene polymer (a) obtained in 
Synthesis Example 1 and the copolymer (b) obtained in Synthesis Example 4 
were blended in a weight ratio of 60/40 on a solid basis. The blend was 
evaporated in an evaporator by heating at 110.degree. C. under reduced 
pressure to obtain a clear viscous liquid having a solid content of 99% or 
more. To the liquid were added 2 parts by weight of vinyltrimethoxysilane 
(A-171, produced by Nippon Unicar Co., Ltd.) and 1 part by weight of 
N-.beta.(aminoethyl)-.gamma.-aminopropylmethyldimethoxysilane as silane 
compounds and 2 parts by weight of a dibutyltin compound (#918, produced 
by Sankyo Yuki Gosei K.K.) as a curing catalyst for an oxyalkylene 
polymer, and the mixture was uniformly mixed to prepare a one-pack type 
curable composition of the present invention. 
EXAMPLE 2 
A curable composition of the present invention was prepared in the same 
manner as in Example 1, except for using the reactive silicon 
group-containing oxyalkylene polymer (a) obtained in Synthesis Example 2. 
EXAMPLE 3 
A curable composition of the present invention was prepared in the same 
manner as in Example 1, except for using the reactive silicon 
group-containing oxyalkylene polymer (a) obtained in Synthesis Example 3. 
COMATIVE EXAMPLE 1 
A curable composition of the present invention was prepared in the same 
manner as in Example 1, except for using the reactive silicon 
group-containing oxyalkylene polymer (a) obtained in Comparative Synthesis 
Example 1. 
Evaluation of Physical Properties 
Tack Range and Tack Strength 
Each of the contact adhesives prepared in Examples 1 to 3 and Comparative 
Example 1 was spread thin on a soft steel plate and allowed to stand at 
23.degree. C. and under 50% RH. A tack development time (time required for 
developing tackiness), tack strength, and tack range (the time from tack 
development to tack disappearance) were evaluated by finger touch. The 
tack strength was evaluated in comparison with the curable composition of 
Comparative Example 1 and rated according to the following standard: 
.circleincircle. . . . Considerably stronger 
.largecircle. . . . Substantially equal 
.DELTA. . . . Weaker 
Adhesive Strength Under Shear 
A test specimen for tensile shear strength measurement in accordance with 
JIS K6850 was prepared by applying each curable composition to one of two 
JIS H4000 aluminum plates A-1050P (100.times.25.times.2 mm) with a spatula 
and, after 5 minutes from the application, adhering the plates by manually 
pressing. After curing the specimen at 23.degree. C. for 2 hours, a 
tensile shear test was conducted to evaluate initial adhesion. Further, 
the specimen was cured at 23.degree. C. for 2 days and then at 50.degree. 
C. for 3 days, and then a tensile test was conducted to evaluate final 
adhesion. 
Peel Strength 
Peel strength was evaluated by a T-peel test in accordance with JIS K6854. 
Each curable composition was applied with a spatula to one of a pair of 
JISH4000 aluminum plates A-2050P (200.times.25.times.0.1 mm) with a 
thickness of about 0.5 mm. After 5 minutes from the application, the 
aluminum plates were bonded together by giving 5 one-way rollings with a 5 
kg hand roller in the longitudinal direction. The thus prepared specimen 
was cured at 23.degree. C. for 2 hours and subjected to a tensile test at 
a pulling speed of 200 mm/min to evaluate initial adhesion. Further, the 
specimen was cured at 23.degree. C. for 2 days and then at 50.degree. C. 
for 3 days and tested similarly to evaluate final adhesion. 
Workability 
Each curable composition was stirred with a spatula at 23.degree. C. and 
under 50% RH, and the stirring workability was evaluated in comparison 
with the curable composition of Comparative Example 1 and rated according 
to the following standard: 
.circleincircle. . . . Considerably easier to stir 
.largecircle. . . . Easier to stir 
.DELTA. . . . Substantially equal in ease of stirring 
x . . . Considerably hard to stir 
TABLE 2 
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Compara. 
Example Example Example 
Example 
1 2 3 1 
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Tack: 
Tack developing time 
12 10 9 18 
(min) 
Tack strength 
.circleincircle. 
.circleincircle. 
.circleincircle. 
control 
Tack range (min) 
50 40 50 15 
Shear: 
Initial adhesion 
25 9 28 17 
(kgf/cm.sup.2) 
Final adhesion 
76 42 80 42 
(kgf/cm.sup.2) 
Peel: 
Initial adhesion 
8.5 5.2 11.3 5.5 
(kgf/25 mm) 
Final adhesion 
7.5 6.3 10.1 6.7 
(kgf/25 mm) 
Workability .circleincircle. 
.circleincircle. 
.DELTA. 
control 
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As is apparent from Table 2, it can be seen that use of the oxyalkylene 
polymer having an Mw/Mn ratio of not more than 1.6 provides a curable 
composition which develops tack rapidly, high tackiness, and has a long 
tack range as well as excellent workability and, on curing, exhibits 
reasonable initial and final strength. 
In particular, it should be noted that the curable composition of the 
present invention develops high tackiness rapidly and sufficiently. 
While the invention has been described in detail and with reference to 
specific embodiments thereof, it will be apparent to one skilled in the 
art that various changes and modifications can be made therein without 
departing from the spirits and scope thereof.