Application method for sealant

A method applying a curable sealant composition comprising an oxyalkylene polymer having at least one silicon-containing group to the silicon atom of which a hydroxy group and/or a hydrolyzable group are bonded onto previously applied and cured sealant composition comprising an oxyalkylene polymer having at least one silicon-containing group to the silicon atom of which a hydroxy group and/or a hydrolyzable group are bonded, which method comprises applying a primer comprising a copolymer having at least one silicon-containing group to the silicon atom of which a hydroxy group and/or a hydrolyzable group are bonded,said copolymer having a molecular chain comprising substatially PA1 (1) a monomer unit of at least one of an alkyl acrylate and an alkyl methacrylate wherein the alkyl group has from 1 to 8 carbon atoms, and PA1 (2) a monomer unit of at least one of an alkyl acrylate and an alkyl methA method foracrylate wherein the alkyl group has not less than 10 carbon atoms, which method afford superior adhesiveness between previously applied sealant and newly applied sealant.

BACKGROUND OF THE INVENTION 
The present invention relates to an application method for sealant, and 
more particularly it relates to an re-application method for a curable 
oxyalkylene polymer sealant onto previously applied and cured oxyalkylene 
polymer sealant 
Oxyalkylene polymers containing a silicon-containing group comprising a 
silicon atom bonded to a terminal group selected from the groups 
consisting of a hydroxy group and a hydrolyzable group (hereinafter 
sometimes referred to as a reactive silicon group) and which are thereby 
capable of crosslinking through siloxane bond formation are disclosed, 
e.g., in U.S. Pat. No. 3,971,751. Representative of such oxyalkylene 
polymers is a polymer of the formula: 
EQU X'3 Si--(oxypropylene polymer)--SiX'3 
wherein X' represents a hydrolyzable group such as a methoxy group. 
Oxyalkylene polymers having a reactive silicon group are cured through 
formation of a siloxane bond (Si--O--Si) among polymer molecules by the 
action of moisture in the air and the like at room temperature similar to 
room temperature curable silicone rubbers to thereby provide a rubbery 
cured product. The cured product of the oxyalkylene polymer has excellent 
tensile characteristics, such as large elongation, low modulus and high 
breaking strength, excellent adhesive properties, and excellent 
paintability on the surface of the cured product and are therefore useful 
as sealants, adhesives and the like. 
With respect to the adhesiveness of oxyalkylene polymer having a reactive 
silicon group, it can be bonded to a fairly wide range of materials by 
utilizing various bonding methods and primers containing silane compounds, 
polyisocyanate resins, mixtures or reaction products of both, or mixtures 
with other resins. However, when bonding oxyalkylene polymer having a 
reactive silicon group onto previously applied oxyalkylene polymer having 
a reactive silicon group after some period has lapsed since application of 
the previously applied oxyalkylene polymer ("re-application"), a further 
improvement in the prior art primer compositions is desirable from the 
viewpoint of the adhesiveness. 
SUMMARY OF THE INVENTION 
The present invention has been realized in consideration of this kind of 
problem inherent in the prior art, and accordingly, an object of the 
present invention is to provide a method which is excellent for 
re-application purposes. 
In accomplishing the foregoing and related objects, the present invention 
provides a method for applying a curable sealant composition comprising: 
providing an applied and cured sealant composition comprising an 
oxyalkylene polymer having at least one silicon-containing group 
comprising a silicon atom bonded to a terminal group selected from the 
groups consisting of a hydroxy group and a hydrolyzable group; 
applying a primer to a surface of the applied and cured oxyalkylene 
polymer, the primer comprising a copolymer having at least one 
silicon-containing group comprising a silicon atom bonded to a terminal 
group selected from the group consisting of a hydroxy group and a 
hydrolyzable group, said copolymer having a molecular chain comprising 
substantially 
1. a monomer unit of at least one of an alkyl acrylate and an alkyl 
methacrylate wherein the alkyl group has from 1 to 8 carbon atoms, and 
2. a monomer unit of at least one of an alkyl acrylate and an alkyl 
methacrylate wherein the alkyl group has not less than 10 carbon atoms; 
and 
applying a sealant composition comprising an oxyalkylene polymer having at 
least one silicon-containing group comprising a silicon atom bonded to a 
terminal group selected from the groups consisting of a hydroxy group and 
a hydrolyzable group to the applied and cured oxyalkylene polymer having 
the primer thereon. 
The method of the present invention is particularly useful when a 
deteriorated sealant which has been used for many years in building 
construction is removed and a new sealant is re-applied since it is 
difficult to completely remove the deteriorated sealant from the substrate 
in the building construction and usually a small amount of sealant remains 
on the substrate. 
In the present invention, because the primer composition contains a 
reactive silicon group together with short and long chained alkyl acrylate 
groups, the primer composition gives superior adhesiveness in the 
re-application of oxyalkylene polymer sealant onto oxyalkylene polymer 
sealant compared to conventional primer compositions. 
Homma et al disclose in U.S. Pat. No. 4,981,728 that the primer composition 
comprising a copolymer having at least one silicon-containing group to the 
silicon atom of which a hydroxyl group and/or a hydrolyzable group are 
bonded, and having a molecular chain comprising substantially 
(1) a monomer unit of alkyl acrylate and/or alkyl methacrylate wherein the 
alkyl group has from 1 to 8 carbon atoms, and 
(2) a monomer unit of alkyl acrylate and/or alkyl methacrylate wherein the 
alkyl group has not less than 10 carbon atoms. 
However Homma et al do not describe the use of the primer for 
re-application of a sealant composition containing an oxyalkylene polymer 
having reactive silicon group.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The backbone of the oxyalkylene polymer used in the present invention 
essentially consists of repeating units of the formula: 
EQU --R--O-- (I) 
wherein R is a divalent organic group. Preferably, the most of the R groups 
in the backbone are hydrocarbon groups having 3 or 4 carbon atoms. 
Specific examples of R are --CH(CH.sub.3)CH.sub.2 --, --CH(C.sub.2 
H.sub.5)CH.sub.2 --, --C(CH.sub.3).sub.2 CH.sub.2 --, --CH.sub.2 CH.sub.2 
CH.sub.2 CH.sub.2 -- and the like. Among them, --CH(CH.sub.3)CH.sub.2 -- 
is preferable. The backbone of the oxyalkylene polymer may consist of a 
single kind of the repeating unit or two or more kinds of the repeating 
units. 
The silicon-containing group comprising a silicon atom bonded to a terminal 
group selected from the groups consisting of a hydroxy group and a 
hydrolyzable group (reactive silicon group) contained in the oxyalkylene 
polymer is the well known group and can be crosslinked even at room 
temperature. A typical example of such group may be represented by the 
formula: 
EQU --Si(R.sup.1.sub.2-b) (X.sub.b)--O--!.sub.m m--Si 
(R.sup.1.sub.3-a)X.sub.a(II) 
wherein X is the terminal group selected from the groups consisting of a 
hydroxyl group and a hydrolyzable group provided that when two or more X 
groups are present, they may be the same or different, R.sup.1 is 
monovalent hydrocarbon group having 1 to 20 carbon atoms or a 
triorganosiloxy group of the formula: 
EQU R.sup.2.sub.3 Si--O-- (III) 
in which R.sup.2 is a monovalent hydrocarbon group having 1 to 20 carbon 
atoms provided that three R.sup.2 groups may be the same or different and 
that when two or more R.sup.1 groups are present, they may be the same or 
different, "a" is 0,1,2 or 3, "b" is 0,1or 2 provided the sum of "a" and 
"b" is at least 1, preferably from 2 to 4, and "m" is 0 or an integer of 1 
to 19 provided that when "m" is not zreo, the bracketed groups may be the 
same or different. 
Among the reactive silicon group, a group of the formula: 
EQU --Si(R.sup.1.sub.3-n)Xn (IV) 
wherein X and R.sup.1 are the same as defined above and "n" is 1, 2 or 3 
preferably, 2 or 3, is preferable. 
The oxyalkylene polymer has at least one reactive silicon group, preferably 
at least 1.1 reactive silicon group, particularly 1.5 to 5 reactive 
silicon group in a molecule on the average. Preferably, the reactive 
silicon group is present at the molecular end of the oxyalkylene polymer. 
Specific examples of the hydrolyzable group are a hydrogen atom, a halogen 
atom, an alkoxy group, an acyloxy group, a ketoximate group, an amino 
group, an amide group, an aminoxy group, a mercapto group, an alkenyloxy 
group and the like. Among them, the alkoxy group having 1 to 8 carbon 
atoms such as methoxy or ethoxy is preferable since it is mildly 
hydrolyzed and easily handled. 
Specific examples of the group R.sup.1 are alkyl groups (e.g. methyl, 
ethyl, etc.), cycloalkyl groups (e.g. cyclohexyl, etc.), aryl groups (e.g. 
phenyl, etc.), aralkyl groups (e.g. benzyl, etc.), alkenyl groups (e.g. 
vinyl) and the like. 
The oxyalkylene polymer has a number average molecular weight of 500 to 
50,000, preferably 3000 to 30,000. The oxyalkylene polymer may be used 
independently or as admixture of two or more oxyalkylene polymers. 
The oxyalkylene polymer having reactive silicon group is usually admixed 
with various additives before curing. The examples of such additives are a 
silanol condensation catalyst (a curing accelerator), a plasticizer, a 
filler, an antisagging agent, a colorant, a stabilizer and the like. 
The alkyl (meth) acrylate (the term meaning both acrylate and methacrylate 
as used hereinafter) unit having an alkyl group with from 1 to 8 carbon 
atoms, which is a monomer unit of the monomer unit (1) in the alkyl (meth) 
acrylate copolymer (hereafter, referred to as Copolymer (A)) used in the 
present invention, is represented by the formula (V): 
EQU --CH.sub.2 --C(R.sup.4) (COOR.sup.3)-- (V) 
wherein R.sup.3 is an alkyl group having from 1 to 8 carbon atoms, and 
R.sup.4 is a hydrogen atom or a methyl group. 
The alkyl (meth)acrylate unit which has an alkyl group having not less than 
10 carbon atoms which is a monomer unit of the monomer unit (2) in the 
Copolymer (A) of the present invention is represented by the formula (VI): 
EQU --CH.sub.2 --C(R.sup.4) (COOR.sup.5)-- (VI) 
wherein R.sup.4 is the same as in the above-mentioned formula (V), and 
R.sup.5 is an alkyl group having not less than 10 carbon atoms. 
Examples of R.sup.3 in the above-mentioned formula (V) include alkyl groups 
having from 1 to 8, preferably from 1 to 4, and more preferably from 1 to 
2 carbon atoms, such as a methyl group, an ethyl group, a propyl group, 
n-butyl group, a tert-butyl group, a 2-ethyl hexyl group, and the like. 
The R.sup.3 alkyl group may be a single type of group, or it may be a 
mixture of two or more types of groups. 
Examples of R.sup.5 in the above-mentioned formula (VI) include alkyl 
groups having not less than 10, usually from 10 to 30, and preferably from 
10 to 20 carbon atoms, such as a lauryl group, a tridecyl group, cetyl 
group, a stearyl group, a docosanyl group, and the like. The R.sup.5 alkyl 
group may be, in a manner similar to the case of R.sup.3, a single type of 
group or it may be a mixture of two or more types of groups, such as a 
mixture of, for example, an alkyl group of 12 carbon atoms and an alkyl 
group of 13 carbon atoms. 
The molecular chain of the above-mentioned Copolymer (A) of the present 
invention is made substantially of monomer unit (1) and monomer unit (2). 
Herein, "made substantially of monomer unit (1) and monomer unit (2)" 
means that the total amount of monomer unit (1) and monomer unit (2) in 
the Copolymer (A) exceeds 50%, and is preferably not less than 70% of the 
total amount of the Copolymer (A). 
Furthermore, the ratio of monomer unit (1) to monomer unit (2) (monomer 
unit (1)/monomer unit (2)) is preferably in the range of from 95/5 to 
40/60, and more preferably from 90/10 to 60/40. 
In the Copolymer (A), in addition to monomer unit (1) and monomer unit (2), 
monomer units derived from monomers which are copolymerizable with these 
units may also be included. Specific examples of this kind of additional 
monomer unit include monomers containing --COOH groups, such as 
(meth)acrylic acid; amide groups, such as (meth)acrylamide and N-methylol 
(meth)acrylamide; epoxy groups, such as glycidyl (meth)acrylate; amino 
groups, such as diethyl amino ethyl (meth)acrylate and aminoethyl vinyl 
ether; and the like. Other examples include. monomer units derived from 
acrylonitrile, styrene, .alpha.-methyl styrene, alkyl vinyl ether, vinyl 
chloride, vinyl acetate, vinyl propionate, ethylene, and the like. 
From the viewpoint of easy handling, the Copolymer (A) has preferably a 
number average molecular weight of from 500 to 100,000, and more 
preferably from 1,000 to 30,000. 
The reactive silicon group in the Copolymer (A) are the same as already 
defined. Concerning the amount of reactive silicon groups in the Copolymer 
(A), it is preferable that there is an average of from 0.1 to 10 groups, 
desirably from 0.5 to 5.0 groups, and particularly from 0.5 to 2.5 groups 
per molecule of the Copolymer (A). 
The Copolymer (A) used in the present invention is obtained by vinyl 
polymerization, for example, by radical polymerization, using normal 
solution polymerization or block polymerization methods or the like, of 
monomers which contain monomers providing the units represented by the 
formulae (V) and (VI). 
The reaction is carried out by adding the normal above-mentioned monomers, 
radical initiator, chain transfer agent, solvent, and so forth, and 
reacting at a temperature of between 50.degree. C. and 150.degree. C. 
Specific examples of the above-mentioned radical initiator are 
azobisisobutyronitrile, benzoyl peroxide, and the like. Specific examples 
of the above-mentioned chain transfer agent are n-dodecyl mercaptan, 
tert-dodecyl mercaptan, and the like. For the solvent it is preferred that 
non-reactive solvents are used, such as ethers, hydrocarbons, acetates, 
and the like. 
There are various kinds of method to introduce the reactive silicon group 
into the Copolymer (A). Examples of suitable methods include the 
following: 
(i) A method in which a compound having a polymerizable unsaturated bond 
and a reactive silicon group (for example, CH.sub.2 
.dbd.CHSi(OCH.sub.3).sub.3) is copolymerized with monomers providing the 
units represented by the formulae (V) and (VI). 
(ii) A method in which a compound having a polymerizable unsaturated bond 
and a reactive functional group (below, referred to as Y group) (for 
example, acrylic acid) is copolymerized with monomers providing the units 
represented by the formulae (V) and (VI), and following this, the 
generated copolymer having a Y group is reacted with a compound having a 
functional group reactive with the Y group and a reactive silicon group 
(for example, a compound having an isocyanate group and a 
--Si(OCH.sub.3).sub.3 group such as OCNCH.sub.2 CH.sub.2 CH.sub.2 
Si(OCH.sub.3).sub.3). 
Compounds illustrating the above-mentioned compound having a polymerizable 
unsaturated bond and a reactive silicon group are represented by the 
following formula (VII): 
EQU R.sup.6 --Si(R.sup.1.sub.2-b) (X.sub.b)--O--!.sub.m 
--Si(R.sup.1.sub.3-a)X.sub.a (VIII) 
Wherein R.sup.1, X, a, b and m are the same as in the above-mentioned 
formulae. R.sup.6 is an organic residue having a polymerizable unsaturated 
bond. 
Among the compounds represented by the formula (VII), compounds represented 
by the following formula (VIII) are preferred: 
EQU CH.sub.2 .dbd.C (R.sup.4) Q Si (CH.sub.3).sub.3-n X.sub.n (VIII) 
wherein R.sup.4, Y and n are the same as in the above-mentioned formulae, Q 
is a divalent organic group, such as --COOR.sup.7 -- (wherein R.sup.7 is a 
divalent alkylene group having from 1 to 6 carbon atoms, such as 
--CH.sub.2 --, --CH.sub.2 CH.sub.2 --, and the like), --CH.sub.2 C.sub.6 
H.sub.5 CH.sub.2 CH.sub.2 --, --CH.sub.2 OCOC.sub.6 H.sub.4 
COO(CH.sub.2).sub.3 --, and the like, or a direct bond. 
Specific examples of compounds represented by the formulae (VII) or (VIII) 
include the following: 
EQU CH.sub.2 .dbd.CHSi (CH.sub.3) (OCH.sub.3).sub.2, 
EQU CH.sub.2 .dbd.CHSi (CH.sub.3) Cl.sub.2, 
EQU CH.sub.2 .dbd.CHSi (OCH.sub.3).sub.3, CH.sub.2 .dbd.CHSiCl.sub.3, 
EQU CH.sub.2 .dbd.CHCOO (CH.sub.2).sub.2 Si (CH.sub.3) (OCH.sub.3).sub.2, 
EQU CH.sub.2 .dbd.CHCOO (CH.sub.2).sub.2 Si (OCH.sub.3).sub.3, 
EQU CH.sub.2 .dbd.CHCOO (CH.sub.2).sub.2 Si (CH.sub.3) Cl.sub.2, 
EQU CH.sub.2 .dbd.CHCOO (CH.sub.2).sub.2 Si Cl.sub.3, 
EQU CH.sub.2 .dbd.C (CH.sub.3) COO (CH.sub.2).sub.2 Si (CH.sub.3) 
(OCH.sub.3).sub.2, 
EQU CH.sub.2 .dbd.C (CH.sub.3) COO (CH.sub.2).sub.2 Si (OCH.sub.3).sub.3, 
EQU CH.sub.2 .dbd.C (CH.sub.3) COO (CH.sub.2).sub.3 Si (CH.sub.3) 
(OCH.sub.3).sub.2, 
EQU CH.sub.2 .dbd.C (CH.sub.3) COO (CH.sub.2).sub.3 Si (OCH.sub.3).sub.3, 
EQU CH.sub.2 .dbd.C (CH.sub.3) COO (CH.sub.2).sub.2 Si (CH.sub.3) Cl.sub.2, 
EQU CH.sub.2 .dbd.C (CH.sub.3) COO (CH.sub.2).sub.2 SiCl.sub.3, 
EQU 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, 
EQU CH.sub.2 .dbd.CHCH.sub.2 OC (O)--Ph--COO (CH.sub.2).sub.3 Si 
(OCH.sub.3).sub.3, 
EQU CH.sub.2 .dbd.CHCH.sub.2 OC (O)--Ph--COO (CH.sub.2).sub.3 Si (CH.sub.3) 
Cl.sub.2, 
EQU CH.sub.2 .dbd.CHCH.sub.2 OC (O)--Ph--COO (CH.sub.2).sub.3 SiCl.sub.3, 
wherein, Ph is a phenyl group. 
As occasion demands, curing catalysts and other additive agents may be 
added and used in the primer compositions used in the present invention. 
As specific examples of this curing catalyst, there are no particular 
limitations, but normally used silanol condensation catalysts can be used. 
Specific examples of this kind of curing catalyst are organotin compounds, 
organotitanate compounds, organoaluminum compounds, organozirconium 
compounds, amine compounds, acidic phosphate esters, reaction products of 
acidic phosphate esters with amine compounds, saturated or unsaturated 
polyvalent carboxylic acids or their acid anhydrides, reaction products of 
carboxylic acid compounds and amine compounds and the like, lead octylate, 
and so forth. 
Specific examples of the above-mentioned organotin compounds include 
various types of tin carboxylic acid salt, such as dibutyl tin diacetate, 
dibutyl tin dilaurate, dibutyl tin maleate, dioctyl tin maleate, dibutyl 
tin phthalate, tin octylate and tin naphthenate; chelate compounds, such 
as dibutyl tin diacetylacetonate; reaction products of dibutyl tin 
methoxide or dibutyl tin oxide with phthalic acid ester; and the like. 
Specific examples of the above-mentioned organotitanate compounds include 
titanic acid ester compounds, such as tetrabutyl titanate, tetraisopropyl 
titanate, tetrapropyl titanate and triethanolamine titanate; chelate 
compounds, such as titanium tetraacetylacetonate; and the like. 
Specific examples of the above-mentioned organoaluminum compounds include 
aluminum tris acetylacetonate, aluminum tris ethylacetoacetate, 
diisopropoxy aluminum ethylacetoacetate, and the like. 
Specific examples of the above-mentioned organozirconium compounds include 
organozirconium compounds such as zirconium tetraisopropoxide and 
zirconium tetrabutoxide; chelate compounds, such as zirconium 
tetraacetylacetonate; and the like. 
Specific examples of the above-mentioned amine compounds include 
butylamine, monoethanol amine, triethylene triamine, guanidine, 
2-ethyl-4-methylimidazole, 1,8-diazabicyclo(5,4,0) undecene-7 (DBU), and 
the like. 
Furthermore, the above-mentioned acidic phosphate ester is a phosphate 
ester containing the part: 
EQU --O--P (.dbd.O) (OH)--, 
examples of which include acidic phosphate esters which are organic acid 
phosphate esters or the like, illustrated by 
EQU (RO).sub.d --P (.dbd.O)--(OH).sub.3-d 
(wherein d is 1 or 2, and R is an organic residue). Specific examples of 
the above-mentioned organic acid phosphate esters include the following: 
(CH.sub.3 O).sub.2 P (O) OH, (CH.sub.3 O) P (O) (OH).sub.2, 
(C.sub.2 H.sub.5 O).sub.2 P (O), (C.sub.2 H.sub.5 O) P (O) (OH).sub.2, 
(CH.sub.3).sub.2 CHO!.sub.2 P (O) OH, 
(CH.sub.3).sub.2 CHOP (O) (OH).sub.2, 
(C.sub.4 H.sub.9 O).sub.2 P (O) OH, (C.sub.4 H.sub.9 O) P(O)(OH).sub.2, 
(C.sub.8 H.sub.17 O).sub.2 P (O) OH, (C.sub.8 H.sub.17 O) P (O) (OH).sub.2, 
(C.sub.10 H.sub.21 O).sub.2 P (O) OH, (C.sub.10 H.sub.21 O) P (O) 
(OH).sub.2, 
(C.sub.l3 H.sub.27 O).sub.2 P (O) OH, (C.sub.13 H.sub.27 O) P (O) 
(OH).sub.2, 
(HOC.sub.8 H.sub.16 O).sub.2 P (O) OH, (HOC.sub.8 H.sub.16 O) P (O) 
(OH).sub.2, 
(HOC.sub.6 H.sub.12 O).sub.2 P (O) OH, (HOC.sub.6 H.sub.12 O) P (O) 
(OH).sub.2, 
(CH.sub.2 OH) (CHOH) O!.sub.2 P (O) OH, 
(CH.sub.2 OH) (CHOH) O!--P (O)--(OH).sub.2, 
(CH.sub.2 OH) (CHOH) C.sub.2 H.sub.4 O!.sub.2 P (O) OH, 
(CH.sub.2 OH) (CHOH) C.sub.2 H.sub.4 O!P (O) OH.sub.2. 
The amount of these curing catalysts used is from about 0 to about 20 parts 
by weight per 100 parts by weight of the above-mentioned Copolymer (A) 
having a reactive silicon group. 
Examples of additive agents other than those mentioned above, which can be 
used in the primer compositions of the present invention, include 
dehydrating agents, adhesion promoting agents, coloring agents, 
ultraviolet absorbers, antioxidants, solvents, and so forth. 
The primer composition used in the present invention is applied in advance 
to the surface of a substrate to form a dry coating, and can be used as a 
primer to give excellent adhesiveness between the resulting substrate and 
sealant when using a sealant containing the oxyalkylene polymer having 
reactive silicon group. In particular, it is useful as a reapplication 
primer for bonding oxyalkylene polymer sealant onto oxyalkylene polymer 
sealant at some period after the first application of the sealant. 
The present invention will now be more specifically described and explained 
by means of the following Examples, in which all parts are by weight. It 
is to be understood that the present invention is not limited to the 
Examples, and various changes and modifications may be made in the present 
invention without departing from the spirit and scope thereof. 
SYNTHESIS EXAMPLE 1 
Synthesis of a Copolymer (A) 
To 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.-methacryloxypropylmethyldimethoxy silane, 7.2 g of 
.gamma.-mercaptopropylmethyldimethoxy silane and 36 g of toluene was added 
3 g of azobisisobutyronitrile as the polymerization initiator. Then this 
solution was added dropwise to 30 g of toluene which was heated at 
110.degree. C., over a period of 6 hours. Following this, the 
polymerization reaction was carried out for a further 2 hours, to give a 
Copolymer (A) having a solids content of 60% and a number average 
molecular weight, by gel permeation chromatography (from a calibration 
curve obtained using polystyrene standards ), of 2,200. 
SYNTHESIS EXAMPLE 2 
Synthesis of a Copolymer (A) 
To a mixture of 5.7 g of butyl acrylate, 65.1 g of methyl methacrylate, 
13.3 g of stearyl methacrylate, 5.1 g of 
.gamma.-methacryloxypropyltrimehoxy silane, 8.0 g of 
.gamma.-mercaptopropyltrimethoxy silane and 22 g of xylene was added 3 g 
of azobisisobutyronitrile as the polymerization initiator. Then this 
solution was added dropwise to 20 g of xylene which was heated at 
110.degree. C., over a period of 6 hours. Following this, the 
polymerization reaction was carried out for a further 2 hours, to give a 
Copolymer (A) having a solids content of 70% and a number average 
molecular weight, by gel permeation chromatography (from a calibration 
curve obtained using polystyrene standards), of 2,100. 
EXAMPLE 1 
2 parts of dibutyl tin phthalate were added to 100 parts of the Copolymer 
(A) obtained in Synthesis Example 1, to give a primer (I). 
EXAMPLE 2 
2 parts of dibutyl tin phthalate were added to 100 parts of the Copolymer 
(A) obtained in Synthesis Example 2, to give a primer (II). 
COMATIVE EXAMPLE 1 
Synthesis of a Urethane Primer 
A reaction vessel equipped with a condenser and sealed under nitrogen was 
charged with weighed amounts of 37 g of .gamma.-mercaptopropyltrimethoxy 
silane (Trade Name: A189, made by Nippon Unicar) and 0.5 g of tin octylate 
(Trade Name: NEOSTAN U28, made by Nitto Kasei), and while agitating with a 
magnetic stirrer, 100 g of a polyisocyanate compound having a poiyalkylene 
oxide unit (Trade Name: TAKENATE M402, made by Takeda Pharmaceutical 
Industry CO., Ltd.) were added dropwise over a period of about 30 min. 
After completion of the dropwise addition, agitation was further carried 
out for about 1 hour, to give a silicon modified polyisocyanate compound. 
An agitator-equipped vessel, sealed under nitrogen, was charged with 
weighed amounts of 1.6 kg of methyl ethyl ketone and 40 g of molecular 
sieve 3A (made by Union Showa, Ltd.), and under agitation were added 60 g 
of diallyl phthalate prepolymer (Trade Name: DAISOTAP, made by Osaka Soda, 
Ltd.) and 15 g of vinylidine chloride resin (Trade Name: SALAN F310, made 
by Dow Chemical Co.) and these were allowed to dissolve. Following this, 
137 g of the above-mentioned silicon modified polyisocyanate compound and 
400 g of an aromatic polyisocyanate compound (Trade Name: SUMIJULE HL, 
made by Sumitomo-Beyer Urethane Co., Ltd.) were added and mixed by 
agitating, to give a urethane primer (III). 
EXAMPLE 3 
Test bodies were prepared using each of the primers obtained in Example 1 
(Primer I) and Example 2 (Primer II) and Comparative Example 1 (Primer 
III) , by using the following procedure as illustrated in FIGS. 1-4: A 50 
mm by 12 mm by 4 mm sample 10 was cut from a sealant containing 
oxyalkylene polymer having reactive silicon group after 5 years had 
elapsed from its application. The cut sample 10 was bonded onto an 
aluminum substrate 12 of dimensions 50 mm by 50 mm by 5mm, as shown in 
FIG. 1. Then the primer was applied to the face 14 of the sealant sample 
10 and also to a separately prepared aluminum substrate 16 treated with 
methy ethyl ketone, shown in FIG. 2. Using the thus-obtained substrate 12 
and 16 and two spacers 18, a No.2 type frame was made according to the 
regulations of JIS A5758 for tensile adhesiveness testing, and this frame 
was then filled with new sealant containing an oxyalkylene polymer having 
reactive silicon group 20, as shown in FIG. 3. The sealant was prepared as 
follows: 3 parts of tin octylate and 1 part of lauryl amine as a silanol 
condensation catalyst, 150 parts of colloidal calcium carbonate (Trade 
Name: CCR, made by Shiraishi Industry Co., Ltd.) as a filler, 65 parts of 
dioctyl phthalate as a plasticizer, and 1 part of hindered phenol 
anti-aging agent (Trade Name: NOCLAK NS-6, made by Ouchi Shinko Chemical 
Co., Ltd.) were added to 100 parts of propylene oxide polymer having a 
number average molecular weight of 9,600 and having two methyl dimethoxy 
groups represented by the formula --Si(CH.sub.3)(OCH.sub.3).sub.2 in the 
molecule on average. The test frame was left at room temperature for 7 
days and then at 50.degree. C. for 7 days to cure and after removal of 
spacers 18, yielded test body 22, as shown in FIG. 4. Following this, 
tensile adhesiveness testing was performed on test body 22 at a pulling 
speed of 50 mm/min, and the 50% modulus (abbreviated as "M50" in 
kgf/cm.sup.2), tensile strength at break (abbreviated as EB in kgf 
cm.sup.2) and degree of elongation at break (abbreviated as EB in %) were 
measured. The results are shown in Table 1. In Table 1, CF shows cohesive 
failure and AF shows adhesive failure and CF is preferable to AF. 
TABLE 1 
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Primer (I) Primer (II) 
Primer (III) 
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M50 1.4 1.4 1.6 
TB 3.9 3.65 3.0 
EB 400 370 230 
Failure sealant sealant between primer 
Position and old sealant 
CF CF AF 
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From these Examples, it can be seen that with the primer composition used 
in the present invention it is possible to improve the re-application of a 
sealant containing oxyalkylene polymer having reactive silicon group.