Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
1999-02-05
2001-03-20
Wu, David W. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S342000, C524S262000, C524S265000, C524S305000
Reexamination Certificate
active
06204339
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to blocked mercapto silane coupling agents in coating, adhesive, sealant and elastomer applications (“CASE”).
BACKGROUND
Mercaptosilanes have been known for use in tire applications to couple fillers to the rubber; however their utility in CASE has been limited due to the reactivity of the mercaptan functionality with catalysts which are used in CASE, i.e., the catalysts react with the mercaptan group thus de-activating the catalyst.
Specifically, the prior art discloses acylthioalkyl silanes, such as CH
3
C(═O)S(CH
2
)
1-3
Si(OR)
3
[M. G. Voronkov et al. in
Inst. Org. Khim
., Irkutsk, Russia] and HOC(═O)CH
2
CH
2
C(═O)S(CH
2
)
3
Si(OC
2
H
5
)
3
[U.S. Pat. No. 3,922,436 to R. Bell et al.]. Japanese Patent 63270751A2 and DE 2508931 disclose the use of compounds represented by the general formula, CH
2
═C(CH
3
)C(═O)S(CH
2
)
1-6
Si(OCH
3
)
3
in tire tread compositions, and adhesive compositions, respectively, but these compounds are not desirable because the unsaturation &agr;,&bgr; to the carbonyl group of the thioester has the undesirable potential to polymerize during the compounding process, during storage or during the service life of the adhesive or coating.
Prior art by Yves Bomal and Olivier Durel, in Australian Patent AU-A-10082/97, discloses the use in rubber in conjunction with functionalized siloxanes of silanes of the structure represented by R
1
n
X
3-n
Si—(Alk)
m
(Ar)
p
—S(C═O)—R where R
1
is phenyl or alkyl; X is halogen, alkoxy, cycloalkoxy, acyloxy, or OH; Alk is alkyl; Ar is aryl; R is alkyl, alkenyl, or aryl; n is 0 to 2; and m and p are each 0 or 1, but not both zero.
U.S. Pat. No. 3,922,436 to Bell disclose a mercaptan/acid anhydride adduct as coupling agents for filled plastics, but there is no teaching to de-block the mercaptan group. U.S. Pat. No. 4,820,751 discloses certain blocked mercaptosilane for tires but again does not disclose any de-blocking of such silanes. U.S. Pat. No. 4,519,430 to Ahamd et al. and U.S. Pat. No. 4,184,998 to Shippy et al. disclose the blocking of a mercaptosilane with an isocyanate to form a solid which is added to a tire composition, which mercaptan reacts into the tire during heating, which could happen at any time during processing since this a thermal mechanism.
There remains a need for effective latent coupling agents which exhibit the advantages of mercaptosilanes without exhibiting the disadvantages such as described herein.
SUMMARY OF THE INVENTION
The present invention relates to compositions of an elastomer with an intrinsic or extrinsic crosslinker, a cure catalyst and a blocked mercaptosilane which are used as an adhesive, sealant or coating on a substrate. Methods of manufacturing such adhesive, sealants or coatings also are disclosed wherein the mercaptosilane is de-blocked during or after the curing of the composition.
DETAILED DESCRIPTION OF THE INVENTION
The latent mercaptosilanes have a blocking group on the mercaptan. This prevents the mercapto group from participating adversely in undesirable side reactions such as deactivation of cure catalysts, including organometallics, such as organotins. Undesired reactions of the mercapto group are slowed or prevented entirely until the blocking group is removed. As the blocking group is removed after application of a sealant or other system containing the mercaptosilanes, the desired reaction can occur or accelerate. If cure catalysts are affected at this point, it can be less critical since initial curing already has begun under the influences of the undisturbed catalyst. The deblocking mercapto group also can participate more readily in the curing reaction of the polymer system, in the normal mode of silane coupling agents.
COMPOSITION
The CASE compositions of the present invention are comprised of (a) an elastomer; (b) an intrinsic or extrinsic crosslinker; (c) a metallic or organometallic cure catalyst with a metal selected from the periodic groups VIIB, VIII, IB IIB, IIIA and IVA ; and (d) a blocked mercaptosilanes, which is deblocked with a (e) deblocking agent while the composition is on a (f) substrate. Standard excipients may also be included in the compositions.
Elastomer
The elastomer may be organic or inorganic polymers, such acrylates, methacrylates, vinyls, urethanes, polyester, polysiloxane, epoxides, polyolefins, polyureas, and polyols. Preferred for use herein are isocyanate or silane terminated urethanes and polyols.
Crosslinker
The crosslinker is a compound which has at least two functionalities which will react with the elastomer so that upon curing, the crosslinker will crosslink the elastomer. Examples of extrinsic (i.e., separate) crosslinkers are organofunctional silanes, vinyl functionalized siloxanes, isocyanates, or epoxides. Moreover, the crosslinking functionality may be part of the elastomer compound (i.e., intrinsic to the elastomer), e.g., an isocyanate end-capped polyol, an alkoxy silane terminated polyol or urethane or a silylated polyethylene (e.g., SI-LINK (Union Carbide) and MS Polymer (Kaneka)).
Examples of alkoxy silanes which may be used are &ggr;-aminopropyltrimethoxy silane, bis(trimethoxysilylpropyl)amine; N-phenyl-&ggr;-aminopropyltrimethoxysilane; &ggr;-glycidoxypropyl triethoxy silane; 3,4 epxoycyclohexylpropyl trimethoxysilane; &ggr;-isocyanatopropyl triethoxysilane; vinyltrimethoxysilane, methacryloxypropyl triethoxysilane,
The isocyanates or blocked isocyanates which may be used are methylene di-isocyanate (MDI), toluene di-isocyanate (TDI), 2,6-toluenediisocyanate, isophorone diisocyanate, dicyclohexylmethane-4,4′-diisocyanate, various liquid diphenyl methane-diisocyanates containing mixtures of 2,4- and 4,4′ isomers, DesmodurN® and the like and mixtures thereof.
The crosslinker should be present at 0.1 to 20 parts per hundred of elastomer, more preferably 1 to 10 parts per hundred.
Cure Catalyst
The cure catalyst is intended to cure the elastomer to the crosslinker and the crosslinkers to each other and the alkoxy functionality of the mercaptosilane. Examples of such cure catalysts are organotins, platinum, palladium and other catalysts from the periodic groups VIIB, VIII, IB, IIB IIIA and IVA. Organotins are preferred.
The catalyst should be present at 0.001 to 2 parts per hundred of the elastomer, preferably 0.01 to 1.0 parts per hundred elastomer.
Substrate
Inorganic substrates containing elements capable of complexation with the -SH group should be used. Such substrates might contain Zn, Cu, Pb, Bi and Sn as examples. The substrates may be glass, ceramics, galvanized metals, and plastics. Specific substrates include windscreens, aluminum, steel, and copper. Some specific applications include as an adhesive between a metalloceramic and a paint or coating and between copper wiring and a circuit board. More specifically an application of note is to bind the metalloceramic frit of a windscreen to the painted surface of the vehicle (e.g., boat, automobile, airplane, etc.).
Blocked Mercaptosilanes
The blocked mercaptosilanes are mercapto silanes wherein the hydrogen on the sulfur atom has been replaced by another labile group, but not by another sulfur atom. Polysulfide silanes, such as SILQUEST silanes A-1289 and A-1589 from Witco Corp., are not considered herein to be blocked mercaptosilanes. These blocked mercaptosilanes can be represented by the Formulae (1-2):
[[(ROC(═O))
p
—(G)
j
]
k
—Y—S]
r
—G—(SiX
3
)
s
(1)
[(X
3
Si)
q
—G]
a
—[Y—[S—G—SiX
3
]
b
]
c
(2)
wherein
Y is a polyvalent species (Q)
z
A(═E), wherein Q, A, E and z are as below. Y preferably is selected from the group consisting of —C(═NR)—; —SC(═O)—; (—NR)C(═O)—; (—NR)C(═S)—; —OC(═O)—; —OC(═S)—; —C(═O)—; —SC(═S)—; —C(═S)—; each wherein the atom (A) attached to the unsaturated heteroatom (E) is attached to the sulfur, which in turn is linked via a group G to the silicon atom;
each R is chosen independently from hydrog
Cruse Richard W.
Huang Misty Weiyu
Waldman Bruce A.
Crompton Corporation
Egwim K L
Ma Shirley S.
Wu David W.
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