CA1330846C

CA1330846C - Fast-cure polyurethane sealant composition containing titanium ester accelerators

Info

Publication number: CA1330846C
Application number: CA000607392A
Authority: CA
Inventors: Jamil Baghdachi
Original assignee: Adco Products Inc
Current assignee: Astor Corp
Priority date: 1988-08-03
Filing date: 1989-08-02
Publication date: 1994-07-19
Anticipated expiration: 2011-07-19
Also published as: EP0353551B1; KR900003298A; JPH0299579A; EP0353551A2; JP2539918B2; DE68913848T2; ATE102964T1; US4889903A; DE68913848D1; EP0353551A3

Abstract

Abstract One-component, moisture-curable sealant compositions having fast cure times comprise a mixture of a silane-capped polyurethane polymer, an aminosilane cross-linking agent, and a titanium ester accelerator.

Description

FAST-CUR~ POLYUREqHAN~ 5~ALANT
CO~POSITION CONTAINING TITaNIu~ ~ST~R
ACC~AT~R~
Fle~d of th~ Invantion This inv~ntion relate~ to roo~ te~perature curable . organic poly~er s~alant composition~. Mor~ particularly, thi~ invention conc~rn~ fast cur~ one-part room temperature curable organic polymer ~alant compositions containing titanium ester accelerating agents.
8ackground oP the In~ention Sealants are comprised o~ pigm~nted or unpigment~d synthetic ~lastom~ric polym~rs which, in th~ uncured state, constitut~ pourable or easily extrudable putty-lik~ mastics. When cured, the saalants are transformed into e~astomeric ~aterial~ which are abl~ to expand or contract with th~ relativ~ mot~on of the structural : ele~ents whlch the seal~nt connQcts and s~als. They also form a tight barrier against ~oisture, gase~ and ch~mic~l~. Such s~alants find a wide variety of ~ applications in the building trades industry and tho ¦ automoti~ industry wher~ they aro widely us~d to seal ~ix~d wlndow panals and taillight gla~ p~n~ls to coat~d:
auto, truck, and bus bodies.
Sueh sealants inelud~ eomposition~ ba~sd on polysiloxanc polymers as w~ll a5 others whieh ineludo ~: polyurethane or polyaerylat~ poly~2r~. Additionally, modern sealant compo~ition~ inelud~ one-part and two-part formul~tions which cur~ by a v~riety o~ eh~mical 35 meehanis~. One-p~rt s~alant eompositions gan~rally eontain an end-eappod base polymer together with a r~aetive eross-llnking agent and, typically, a curing " , ., . ~ ~ . .. ,., ~ , .

133~84~
catalyst which promote6 the cross-linking reaction either in the presencQ of h~t or atmosph~ric moi~ture. Upon application under normal conditions oP t~mperatur~ and moisture, one-part sealants r~act to form tough, pliable elastomeric seals.
Two-part sealant co~positions, on th~ other hand, comprise two re~ctive components which are ~eparately packaged and mixed ~U8t prior to or at the time of application and r~act upon ~ixing to form the semi-rigid s~alant bead.
Two-part sealant compo~ition~ are less convenient to use sinee it is necessary to ~ix th~ components prior to use or m~ter tho components during applieation to insure ~orr~ct proportlons if the two eomponents are appli~d together to form the s~alant bead. For this r~ason, one-part se~l~nts hav~ found wid~ accept~nc~ in th~ markst.
A number of sueh one-part ~oisture-curable se~l~nt compo~itions are known. ~ocau~ of their conveni~nce and ease of use, there has be~n increa~ing d~and for such s~alants, especia~ly if t~ey possass both good shelf li~e and rapid euring rat~s. To ~nhane~ th~ curing rates of moisture-cured s~alants, a variety o~ curing catalysts have b~n incorporated into such one-part compo~itions.
The following United St~tss pat~nts ~i~elose on~-part moistur~-cur~bla polyur~thane based sQal~nt co~positions and euring cat~lysts: 3,779,794 to D~ Santis (1,2,4-trimethylpiperazin~); 3,979,344 to Bryant (dibutyl tin d~aeetats); 4,038,239 to Coyn~r, at al. (metallie salts o~ tin, lead, ~ereury, or Group VIII sueh as iron, orqano-tin (IV) ~nd orqano-lead compounds, and organ$c amines such as trialkylamin~s, N-substituted pip~ridin~s, N,N' -subs~ituted piparazines, pyridin~: 4,469,831 to BuQlt~er, et al. ~aliph~tic or aro~atie carboxylic acids, toluene~ul~onic acid); and 4,707,515 to Gilch, Qt al.
~organic and inorganic acids, ~alts of org~nic aeids such , 13308~6 as tin naphthenate, tin octoate, tin butyrate, dibutyltln dioctoate, dibutyltin dilaurate, dibutyltin dlacetate, iron stearate, lead octoate, or organic amin~s).

- 5 SuJoary o~ the Invention It has been found, in accordanc~ wlth the przsent invention, tha~ one-componen~ polyurethane-based saalant co~po~itions having fast cure rates at room temperature in th~ presence of moisture comprise a mixture of a silicon-terminated polyure~hane polymer, from ~bout O.2 to about 1.0 part ~y weight o~ an aminosilan~ cross-linking agent, per 100 p~r~ by weight of the polyurethane polymer, and from about O.2 to about 1.O
part by weight of a titanium est~r accelerator per 100 parts of ~he polyurethane polymer.
The silano-capped polyur~thane polymer has the structure O H polyureth~na H O
1 11 1 containing at l 11 (RO) -Si-R -A-CN- - lea~t two - -N-C-A-R1-Si-(OR) 3 urethane link- 3 ages per mol~-cule wher~ R i8 lower alkyl of fro~ 1 ~o Ç carbon atoms and i8 a dival~nt bridging radical sel~cted ~rom th~ group consisting of divRl~nt hydrocarbon radic~ls, divalent hydroc2rbon Qther radicals, and dival~nt hydrocarbon amino radic~ls. The qroup A 18 selected ~rom -S- and -NR2- where R2 i8 hydrogen or alkyl of fro~ on~ to six carbon ato~s.
The aminosilan~ has the structur~
oR3 R6-NH-(CH2)X-Si-R5 OR

--~ 1330846 where x is an integer of from on~ to three, and R3 and R4 I may be the ~ame or different and are selected from alkylI of from one to four carbon atoms. The group ~5 i5 alkyl of from one to four carbon atoms or alkoxyl o~ fro~ on~
to four carbon atoms and R6 is hydrogen or ~(CH2)yNHR7 I where R 1B hydrogen or -(CH2)zNH2. The subscripts y and z may be the sam~ or di~ferent and ar~ ~nt~gers of ~rom one to three.
The titanium ~ster accelerator has the structure R -o-Ti-o-B-R
o-B-R3 where B is a direct bond or is -S02- and R8 is a hydrocarbyl group of fro~ thre~ to twenty carbon atoms.
R9 i~ -(R10-NH)m-RlO-NH~ wh~ro m i8 zero or an integer o~
from one to four and Rl i6 sel~cted from dival~nt hydrocarbyl radicals of ~rom two to ten carbon atoms, divalent hydrocarbaryl radic~ls of ~rom six to ten carbon atoms, and divalent cyclohydrocarbyl radic~ls of from six ;~ 20 three to t~n carbon atoms.
The co~position may also con~ain other ingredi~nts g~n~rally known to ~ormulators of polyceric se~lant composition6 such as pigm~nts, thixotropic agents, fillQr~, acidic or basic polymerization agent~, and th~
li~e.
.
:~ Detall d Doscripkion o~ tho I~vontion Th~ ~ealant co~positions of the present invention : co~priso a base silano-capped polyurothano polymer having a numb~r averag~ molecul~r woight in tho range of from about 10,000 to about 30,000. Such silane-capp~d polyur~thane polymers are prepared by convent~onal ~:
polymer~ation tochnigues by rQ~Cting a poly~th~r polyol having at lea~t two fr~e hydroxyl groups per mol~cul~
with an isocyanate compound having at l~ast two ~33084~
,~
isocyanate reactive groups per molecule. The polyether polyol and isocyanate compound are reacted in a weight ratio of about 8:1 to about 12:1, re~pectively. The startlng polyether polyol pre~erably has a number average molecular weight o~ between about 1,000 and 5,000. one such pref~rred starting material is polypropylene glycol available as Polypropyleno Glyco~2025 ~rom Union Carbids Co., 270 Park Avenue, New YorX, NY 10017.
The starting isocyanato compound ~ay be selected from a varisty o~ ~aterials known in the art for such purposes, but one such prefe~red material is toluene diisocycanate.
Th~ copoly~er for~sd by reaction of th~se two monomers is end-capped with a silane group having the structure -A-Rl-Si-(OR)3. Th~ group A is sulfur or an alkylamino group in which tho alkyl portion contain~ ~rom one to six carbon atoms. ~he bridging group Rl may be a divalent hydrocarbon radical, a divalent hydrocarbon radical containing one or more oxygen ether linkages, or a divalent hydrocar~on radical containing one or ~ore >NH
linkage~. The end-c~pping o~ the polyurethane polymer is achieved by including in the r~action mixture containing the polyether polyol and isocyanat~ compound an aminosilane compound such as g~mm~-aminopropyl trimethoxysilan~ (A lllO)~vailiable from Union Carbide Corp., 270 Park Av~., New York, NY 100~7).
The silane-capped polyuroth~ne polymer is mixed with Srom a~out 30 to about 40 p~rts by weight o~ a pigmenting agent such as carSon black per 100 parts by welght o~ the capped polyurethano polymer. Small amounts, ranging from abaut 0.25 to about 0.75 part~ by weiqht of a thixotropic agent p~r 100 parts by weight of ~olyurethane polymer may also b~ added to ad~ust the flow characteristics of the sealant composition. A typical thixotropic agent is Thixseal01085 available fro~ NL Chsmicals~ Inc., , .

.
~ , -- 133~846 Heightstown, NJ 08520.
Additional amino~ilane cross-linking agent is added to the fieal~nt composition in amounts ranging between about 0.2 to about 1.0 part~ by wsigh~ (pre~er~bly between about 0.4 to about 0.8 part~ by weight) per 100 parts by weight of th~ polyurethane polym~r. The aminosilane used i8 selected from co~pounds having the formula oR3 R6-NH-(CH2)X-Si-R5 oR4 where x i8 an integer of froD on~ to three and R3 and R4 may be the same or di~erent and ar~ selected fxom alkyl of from one to ~our carbon atom~. The group R5 i8 alkyl of from one to four carbon atoms or alkoxyl of from one to four carbon ato~s and R6 is hydrogen or -(CH2) ~ NR7.
R is hydrog~n or -(C~2)zNH2 wher~in y and z may be the same or diffexent and are integers of from one to three.
Suitable materials for this purpose ~re aminosilanes such as A 1110, A 1120, and ~ 1130, av~ilable from Union Carbide Corp., 270 Par~ Av~., NRW YOrk, NY 10017 ) .
As used throughout this sp~cification ~nd the appended claims, the torm "alkyl" ~eans a hydrocar~on r~siduQ derived from branchRd or unbranched alXane by re~oval o~ a single hydrog~n ato~. Th~ term "alkoxyl"
denotes alkyl groups at~ached through an oxygen eth~r linkage to the remainder of t~e parent molecula.
The sealant compositions of this invQntion ~urther contain fro~ about 0.2 to about 1.0 par~s by weight (pre~erably betwe~n about 0.2 to 0.8 parts by weight) p~r 100 parts by wQight of the polyureth~na polymer o~ a titanate ester acc~lera~or having th structure R8-0-Ti-O-B'-R9 5 6 :-1 3 3 ~ 6 wh~r~ B is a direct bond or is -S02-. The group R8 is a hydrocarbyl group o~ ~rom three to twenty carbon ato~, and R9 is -(Rl~-NH)m-~10-NH2 where ~ is zQro or an integer o~ ~rom one to ~our. R10 is ~elected ~rom a d~valont hydrocarbyl radical o~ ~ro~ two to ton carbon atoms, a dival~nt hydrocarbaryl radic~1 o~ ~rom slx to ten carbon atom~, and a div~l~nt cyclohydrocarbyl radlcal of from six three to ten carbon atoms.
A~s used throughout this specification and th~
appended claims, the term ~divalent hydrocarbyl" means a branched or unbranched hydrocarbon group der~ved by removal o~ two hydro~en ato~a ~rom a saturated or unsaturated acyclic hydrocarbon. ThQ term "divalent hydroc~rbaryl" denotes a group d~rived from th~ removal o~ two hydrogen stoms fro~ hydrocar~on~ containing one or more car~ocyclic arom~tic ring3 includ~ng phenyl, alkylphenyl, and phenylalkyl and the like. The term "divalent cyclohydrocarbyl~ ~oans a group ~erived by the removal o~ two hydrogen atomg ~rom a csr~ocyclic non-aromatic hydrocar~on ~ncluding cyclohexane, alkylcyc}ohexane, and the like.
Titanats esters of the typ~ suitable ~or use in sealant compo~itions o~ tha present in~ention are known in the art and have been disclosed in U.SO
Patent No. 4,623,738.
- It is preferr~d ~hat the t$tanate est~rs w~ich are employed as acc~lerators po~sess at least on~
primary or secondary amino group per motecule. Pre~erred ma~erials incl~dQ (4-amlnobenzene)sul~anato-0, bis-(dodecylb~nzene)sul~anato-o, 2-propanolato titan$um (IV):

2-propanolato, tr~s-(3~6-dia2a)hexanolato titanium (IV);
2, 2-bis- ( 2-propenolatomethyl)butanolato, tr~s-(2-ethylened$amino)ethylato titanium ~IV); and 2 , 2-~ls- ( 2-propenolatomethyl)butanol~to, tris-(3-amino)phenylato titanium ~IV), commercially ~ailable from Kenrich ~''' ' ' :.
,..
:~ , ~,. ;, 133~841~ -Pstrochemicals, Inc., 140 East 22d Street, Bayonne, NJ
07002).
It has been found in accordanco with the presant invention that the lncluslon of ~uch titanate ester accelerators in the sealant co~positlon~ signlficantly increases the cure rates over the cur~ rates ~or similar sealant compositions which lack th~ titanate ester accelerator compounds, as can be sesn from the data provided in thQ Exampl~s and in Table~ 1 and 2 below.
~0 En~anced cure rates provi~a an important advantage when the s~alants o~ thi~ inv~ntion are emp~oyed, ~or example, in sealing ~ixed window panel3 and taillight glass panels to motor vehicle bodies where slowly curing sealants may present problems in a continuous production assembly line lS operation.
Ths following examples are provided to enable one sXilled in the art to practice the present invention.
These examples are merely illustrative of the present invention and are not to read as limiting the scope of the invention which is defined by the appended claims.

Example 1 A silane-capped poly~rethane poly~er o~ the type described in Unit~d Statss Patent 3,632,557 was prepared as follows:

A. ~iax~PPG 2025 ONE 2001.00 g (2000 Molecular weigh~ polyether ~
polyol availabe ~ro~ Union Carbide ::
Corp., 270 Park Ave., New York, NY
10017) HyleneTM 204.00 g (80:20 Grade toluene diisocyanate availabl~ from E.I. duPont de Nemours ~ :~
& Co., Wil~ington, DE 1989B) Glacial acQtic acid 0.S5 g Dibutyltin diacetate 0.45 g ~' , . :: ~ , ' :, (~ 1330846 ( B. Anhydrous tolue~e 110.00 g C. Anhydrous toluene 81.00 g Silan~ A 1110 ~ 68.30 g (gamma-amlnopropyl)trimethoxy silane availiable from Union Ca~bide Corp., 270 Park Avo., New York, NY 10017 D. Anhydrous m~thanol 273.00 g ~ . . ..
The components of A abov~ wer~ ~ix~d and heated to 155-F ~68.3-C) under anhydrous conditions and maintained at that te~perature ~or ~sfty-~lve ~inutes. At the end of that timo, B was ~dd~d. Ov~r the next forty-~ive ~inut~s, the temperaturo o~ the mixtur~ was gradually reduced to 105^F (40.6-C) and h~ating was continued ~or two ~nd ono-quarter h~llr~. At th~ end ~f this time, C
was adde~ to tne ~ix~ure and the r~aultin~ ~ixture ~9 heated at 150-165-F (65.6-73.9-C~ for an addition~l two and ons-quarter hours. During this time, samples o~ the reactson mixture wer~ test~d for free isocyanate functional groups. When the tests indicated no residual free ~socyanate, D was add~d and th~ ~ixtur~ heated under reflux for a short time. Th~ ~ixturQ was degassed and cooled to room temperatur~.
Exa~ple 2 A mixer equipped with a sweep blade and a high speed disperser was charged with 1~1 lb (45.91 kg) of the poly~eric composition prepared as d~scribed in Example 1.
Under anhydrous conditions, 9 lb (4.09 kg) of anhydrous m~thanol was added to the mixer contents and the resultin~ mixtur~ wa~ st~rred for akout fi~e to t~n minut~. To thi~ mixtur~ was th~n ~dded O.5 lb (O.23 kg) of Silane A1120 (Union Carbide Company, 270 Park A~nue, J~ ,, .
;, .~
.

~'``

~3308~6 New York, NY 10017), 0.7 lb (0.32 kg) of Thixseal 1084 (NL Chemicals, Inc., Heightstown, NJ 08520) 0.6 lb (0.27 Xg) o~ DBTDA antioxidant (AO 2246, American Cyanamide Co., Bound 8rook, NJ 08805), o.5 lb to.23 kg) o~ 2,2-bis(2-propenalato~ethyl)butanalato, tris~3-amino)-phenylato titanium (IV) ~LICA~97, Renrlch Petrochemicals, Inc., 140 East 22d Street, Bayonne, NJ 07002), and 0.11 lb (0.05 kq) o~ dibutyltin diacetate. The resultinq mixture was stirred under anhydrous conditions for twenty minutes. Carbon black ~40 lb, 18.18 ~g) which had ~een previously drled to less than 0.05% by weight ~oisture content and the resulting mixture was heated to 140-150 F
(60-65.5-C) and stirred for one hour.
A~ter this time the mixture wa~ allowed to cool ~or ten to fifteen minutes, was degassed under reduced prQssure, and packaged under an~ydrous conditions. ~his material was found to possess good storage stability when tested under accelerated storage conditions (130 F
(54.4 C) ~or three days). The material was packaged under anhydrous conditions and its properties tested as described below and conpared with a similar material which lacked the titanium ester accelerator. The results of this testing appear in Table 1 below.

Example 3 A second batch of one-part fast curing sealant compositiion was pr~pared uaing the general methods o~
Example 1 and 2 with the following ingredients in the indicated proportions. In this example, 2,2(~is-2 pr~p~nal~tom~thyl)~utan~lato, tris (~-ethylenediamino)- 5 ethylato titanium (rY) (LICA~44, Xenrich Petrochemicals, Inc., 140 East 22d Street, Bayonne, NJ 07002) was substituted for the 2,2-~s(2-propenolatom~thyl)-butanalato, tris(3-amino)phenylato titaniu~ (IV) (LICA~
3s 97) used as the accelerator in Example 2.

:' -y: :

. 13308~6 Silane-Capped Polyurethane Base Polymer Composition Polypropylene glycol 2025 806.6 g Acetic acid 0.2 g Toluene dlis~cycnate 84.1 g Silane A 1110~ 28.8 g Dibutyl tin diacetate 0.2 g Toluene 80.0 g one-Part Sealant Composition Silane-capped polyurethane 658.4 polymer composition (above) Antioxidsnt A0 2246 4.5 g Thixseal~1085 tthixotropic a~ent) 3.2 g Dibutyl tin diacatetate 0.6 g Carbon blac~ 264.6 g Silane A-1120 3.9 g LICA344 titanate ester accelerator 2.9 g (availa~le from Xenrich Pet~o-chemicals, Inc., 140 East 22d Street, Bayonne, N~ ~7002) ~ethanol 61.9 g . .
This material was packaged under anhydrous conditions and it-~ properties tested as described below.
The results appear in Table 2.

Example 4 The general procedures of Example 1 and 2 were followed to prepare a polymeric sealant composition in which 2,2-~is-(2-propenolatomethyl)butanolato, t~is-(2-ethylenediamino)ethylato titanium (IV) (K~ 44, Kenrich Petrochemicals, Inc., 140 East 22d Street, Bayonne, NJ
07002) was used as the titanium ester accelerator compound in place of the 2, 2-bis ( 2-propenolatomethyl)-butanalato, tris(3-amino)-phenylato titanium (IV) used in Example 2.

i ~

-- 13308~6 This material was found to have a rapid curing rate, exhibiting a lap shear strength of 85 psi (76.1 kP) after 3 hours of curing at room tempsrature ~nd 50~ relative humidity.

Example 5 A moisture-curable one-part sealant composition was prepared using th~ general methods o~ Examples 1 and 2 but substituting (4-a~inobenzene)sulfanato-0, bis-~dodecyl~enzene)sul~anato-o~ 2-propanolato titanium (IV) (KR 26S, Kenrich Petrochemicals, Inc., 140 Ea~t 22d Street, B~yonne, NJ 07002) as the titanate ester accelerator compound in pl~ce of the 2, 2-bis ( 2-propenolatomethyl)-butanalato, ~r~s(3-amino)-phenylato titaniu~ ( IV) used there.
The resultant mat~rial was tested both on painted test pl~tes as described further below ~nd on ceramic glazed glass test plates. In the~e tests, the sealant composition was found to cure rapidly, developing a l~p shear strength of 68 psi ( kP) and 65 psi ( kP) on ~etal~
to-metal and glass-to-me~al test plates, respectiYaly after three hour~ at ~0% relative humidity. ~

Testing Proc~dures ::.
The lap shear strength of ths sealant material of Exa~ple 2 was te~ted and co~p~red with a similar material which did not contAin th~ tit~nate ester curing catalyst. ~--}n o~ch instance, pair~ o~ shoar strength test plates were pr~pared by bonding two prsviou~ly pri~ed and paint~d steel platos, each 1 inch by 0.32 inches (2.54 cm x 0.81 cm), with a sealant bead 1 inch long by 0.25 inche~ wide by 5/16 inches th~ck (2.54 c~ x 0.64 c~ x 0.~9 cm). The s~alant bead w~s applisd along one of the ~ ::
one-inch edges of the te~t plates by means of a sealant tube. The plates wer~ th~n pre~sed togother so that the ~2 s~alant bead was about 0.25 inches (0.64 cm) thick.
~ he sealant bead applied to the bonded tost plates was allowed to cure at room temperature and 50% relative humidity ~or periods which varied between three and seventy-two hours. After the appropriato cure time in each case, the shear strength of each s~alant bead was tested on an Instron testing machine by pulling in a direction parallel to the faco~ of th~ bond~d test plates. The results o~ these tests appear in Table 1.
Table 1 Shear Strength and Properties of Sealant Composition of Example 2 .
Property Titanium-Containing Titanium-Free Sealant Co~position Seal~nt Composition of This Invention 20Lap Shear Strength61 psi ll p8i After 3 Hours t54.6 kP) (9.84 kP) Lap Shear Strength 530 p8i 350 psi After 24 Hours (474.2 kP) (313.2 kP) Lap Shear Strength 681 psi 595 psi After 48 Hours (609.3 kP) ~532.4 kP3 Lap Shear Strength 975 psi 955 psi 30Aft~r 72 Hours (872.4 kP) (854.5 kP) Viscosity 37 sec 42 sec Tensile Str~ngth 1100 psi 1100 psi ~: 35 (984.2 kP) (984.2 kP) ~longation 250% 250%
Hardness (Shore A 60 60 40Durometer) Slump None None - - ,. -.
~,.. ~ , ..
,... .
, . . - . - -. . . .

~-"` 13308~
Table ~
Shear Strength and Properti~s of Sealant of Example 3 Propsrty Titaniu~-Containlng Titanium-Pree Sealant Composition Sealant Co~position of This Inv~ntion -10Lap Shear Strength 97 psi 10 p~i After 3 Hours (86.8 kP) (8-95 kP) Lap Shear Strength 580 psi 400 psi After 24 Hours (518.9 ~P~ (357.9 kP) 15Lap Shear Strength 610 psi 630 psi Aft~r 48 Hours (545.8 kP) (563.7 kP) Lap Shear Strength 1010 p~i 992 ~i 20After 7 Days t903.7 kP) (887.6 kP) Visc08ity 43 S~C 41 sec :~
T~nsile Strength 999 psi 1030 psi (893.9 kP) ~921.6 kP) Elongation 2~0% 241%
Hardness (Qhoro A 60 60 ~:
30Durometer) Slump None None ~ ;~

r~ ~z ;~ ~ :

Claims

1. A one-component, moisture-curable sealant composition comprising a mixture of (a) a silicon-terminated polyurethane polymer of the formula wherein R is lower alkyl of from 1 to 6 carbon atoms;
R1 is a divalent bridging radical selected from the group consisting of a divalent hydrocarbon radical, a divalent hydrocarbon ether radical, and a divalent hydrocarbon amino radical;
A is selected from the group consisting of -S- and -NR2-where R2 is hydrogen or alkyl of from one to six carbon atoms;
(b) from 0.2 to 1.0 parts by weight of an aminosilane per 100 parts by weight of said polyurethane polymer, said aminosilane having the structure wherein X is an integer of from one to three;

R3 and R4 may be the same or different and are selected from alkyl of from one to four carbon atoms;
R5 is alkyl of from one to four carbon atoms or alkoxyl of from one to four carbon atoms;
R6 is hydrogen or -(CH2)yNHR7 wherein R7 is hydrogen or -(CH2)zNH2 wherein y and z may be the same or different and are integers of from one to three;
(c) from 0.2 to 1.0 parts by weight of an accelerator per 100 parts by weight of said polyurethane polymer, wherein said accelerator has the structure wherein B is a direct bond or is -SO2-;
R8 is a hydrocarbyl group of from three to twenty carbon atoms, and R9 is -(R10-NH)m-R10-NH2 wherein m is zero or an integer of from one to four;
R10 is selected from a divalent hydrocarbyl radical of from two to ten carbon atoms, a divalent hydrocarbaryl radical of from six to ten carbon atoms, and a divalent cyclohydrocarbyl radical of from three to ten carbon atoms.

2. A one-component, moisture-curable sealant composition as defined in Claim 1 wherein said polyurethane polymer is the reaction product of a polyether polyol containing at least two hydroxyl groups per molecule and a number average molecular weight of about 1000 to about 3000 and an isocyanate having at least two isocyanate groups per molecule.

3. A one-component, moisture-curable sealant composition as defined in Claim 1 wherein said polyurethane polymer has a number average molecular weight of from about 10,000 to about 30,000.

4. A one-component, moisture-curable sealant composition as defined in Claim 3 wherein A is -NR2-where R2 is as defined therein.

5. A one-component, moisture-curable sealant composition as defined in Claim 1 wherein said composition comprises from 0.4 to 0.8 parts by weight of said aminosilane par 100 parts by weight of said polyurethane polymer.

6. A one-component, moisture-curable sealant composition as defined in Claim 5 wherein said aminosilane is N-(beta-aminoethyl)-gamma-aminopropyl trimethoxysilane.

7. A one-component, moisture-curable sealant composition as defined in Claim 1 wherein said composition comprises from 0.2 to 0.8 parts by weight of said accelerator per 100 parts by weight of said polyurethane polymer.

8. A one-component, moisture-curable sealant composition as defined in Claim 1 wherein said accelerator is selected from the group consisting of (a) (4-aminobenzene)sulfanato-O, bis-(dodecylbenzene)sulfanato-O, 2-propanolato titanium (IV):
(b) 2-propanolato, tris-(3,6-diaza)hexanolato titanium (IV);
(c) 2,2-bis-(2-propenolatomethyl)butanolato, tris-(2-ethylenediamino)ethylato titanium (IV); and (d) 2,2-bis-(2-propenolatomethyl)butanolato, tris-(3-amino)phenylato titanium (IV).

9. A one-component, moisture-curable sealant composition as defined in Claim 1 wherein said accelerator is (4-aminobenzene)sulfanato-O, bis-(dodecylbenzene)sulfanato-O, 2-propanolato titanium (IV).

10. A one-component, moisture-curable sealant composition as defined in Claim 1 wherein said accelerator is 2-propanolato, tris-(3,6-diaza)hexanolato titanium (IV).

11. A one-component, moisture-curable sealant composition as defined in Claim 1 wherein said accelerator is 2,2-bis-(2-propenolatomethyl)-butanolato, tris-(2-ethylenediamino)ethylato titanium (IV).

12. A one-component, moisture-curable sealant composition as defined in Claim 1 wherein said accelerator is 2,2-bis-(2-propenolato-methyl)butanolato, tris-(3-amino)phenylato titanium (IV).