Silane functional oligomer

Details Silane functional oligomer Silane functional oligomer

1999-10-15

2001-07-10

Dawson, Robert (Department: 1712)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

From silicon reactant having at least one...

C528S025000, C528S026000, C528S028000, C528S031000, C528S032000, C528S033000, C528S034000, C528S035000, C556S431000, C556S434000, C556S435000, C556S443000, C556S450000, C556S478000, C556S479000, C525S100000, C525S101000, C525S106000, C525S474000, C525S478000, C525S479000

Reexamination Certificate

active

06258914

ABSTRACT:

Silanes are known as cross-linking agents which are useful in coatings and adhesives. One such type of coating is “clearcoats” for automobiles, which provide a clear protective layer over pigmented basecoats. Such coatings have been disclosed in U.S. Pat. Nos. 5,250,605, 5,162,426 and 5,244,959 to Hazin et al.; U.S. Pat. Nos. 4,499,150 and 4,499,151 to Dowbenko et al.; and PCT Publication No. WO 95/19982.
Some of this art teaches the utility of silane oligomers or interpolymers for such coatings. For example, U.S. Pat. Nos. 4,499,150 and 4,499,151 teach a copolymer of an ethylenically unsaturated alkoxysilane with another ethylenically unsaturated group made by free radical polymerization. Because of the formulation chemistry, these interpolymers are limited in structure and functionalities.
Moreover, U.S. Pat. No. 5,432,246 to Fenn et al. discloses a silane oligomer made from a 2° amino-alkoxy silane, a polyisocyanate and optionally a single isocyanate group. Such oligomers are based on the reaction of the amine with the isocyanate to form a substituted urea. In these oligomers all the isocyanate groups have reacted with the amine groups, so no isocyanate functionalities are present. Further, urea structures may increased viscosity to an unwanted degree.
It is desirable to have coatings which incorporate alkoxy silane functionalities because siloxane bonds formed during curing provide good chemical resistance; however, appearance (gloss and DOI (distinctiveness of image)), mar resistance and lack of cracking all are other properties required for coatings, which properties are deficient in one respect or another in the known prior art.
SUMMARY OF THE INVENTION
The present invention teaches the formation and use of siloxane oligomers having a plurality of alkoxy groups, which oligomers have attached thereto, by other than an Si—O bond, further silyl functionalities. These oligomers may be of the formula
[R
3
SiO
1/2
]
m
[O
1/2
Si(R
2
)O
1/2
]
n
[SiO
3/2
R]
o
[SiO
4/2
]
p
  (I)
wherein
Each R is selected individually from the group consisting of B, R
1
, —OR
1
and W;
wherein
B is a silyl functionality group bridged by other than an Si—O bond to the Si atom of the siloxane oligomer backbone;
each R
1
is individually a saturated or aromatic hydrocarbon group of 1 to 12 carbon atoms;
each W individually is a monovalent radical;
with the provisos that at least one R is a B and at least one quarter of all R groups are —OR
1
;
m=2 to 20;
n=0 to 50;
o=0 to 20; and
p=0 to 5.
DETAILED DESCRIPTION OF THE INVENTION
Structure
In structure I above, B is a silyl functionality group which is attached to the siloxane oligomer by other than an Si—O bond. There must be at least one B per siloxane oligomer, which preferably is internal to (pendant on) the oligomer. More preferably there are at least two B groups per oligomer. Usually, if a B group is attached to a silicon atom of the siloxane backbone, the other R group(s) on that silicon atom is an alkoxy group.
The divalent linking group between the silicon atom of the silyl functionality group and the silicon atom of the siloxane oligomer may not contain an Si—O bond, but otherwise may include any heteroatoms, e.g., it may be alkylene, arylene, alkarylene, polyalkylene oxide, polyurethane, carbamate, an ester or isocyanurate. The linking group may be branched and may be olefinically or aromatically unsaturated. Preferably the bridging group is an alkylene of 2 to 12 carbon atoms, e.g., cyclo aliphatic (e.g., 1,4 diethylene-cyclohexane or 1,3,5 triethylene cyclohexyl) or linear (e.g., butylene, propylene).
Alternatively, the bridging group is one that includes heteroatoms, such as a sulfide bridge (—(CH
2
)
n
—Sx—(CH
2
)
n
— wherein n=1 to 6 and x=1 to 8), a polyurethane (i.e., contains —NC(═O)— bonds), a urea (—NC(═O)N—), a carbonate (—NHC(═O)O—), an ester —C(═O)O— a polyether (which may contain ethylene oxide, propylene oxide or butylene oxide units), or an isocyanurate bond (in which case the third valency of the ring should have a silane or siloxy functionality). Moreover, the bridging group may contain side chains, such a hydroxyl or amine functionality.
The divalent linking group may be substituted with silyl or siloxy functions, as well as unsaturated groups. Indeed, the divalent linking group may form part of a backbone with relatively linear siloxane chains attached to either end of the group. An exemplary bridging group is 2,4 ethylene, 1-vinyl cyclohexane.
The silyl functionality at the end of the divalent bridging group may be an alkoxysilane, halo silane, a siloxane or may have further functionalities. Preferably, the silane is an alkoxy silane, more preferably a dialkoxy silane and most preferably a trialkoxy silane.
A preferred B group may be represented as —C
f
H
2f
—SiR
2
g
(X)
3−g
wherein f=2 to 12, g=0 to 2, X is a halogen or —OR
2
, and each R
2
is selected from W and R
1
. More preferably f=2 to 6, g=3 and X is —OR
2
, and most preferably wherein R
2
is preferably R
1
and is most preferably methyl. Preferable B's are —(CH
2
)
2
Si(OCH
3
)
3
; —(CH
2
)
2
Si(OC
2
H
5
)
3
—(CH
2
)
2
Si(OCH
3
)
2
(CH
3
); —(CH
2
)
2
Si(OCH
3
)
2
Cl; —C
2
H
4
(C
6
H
9
)(C
2
H
4
Si(OCH
3
)
3
)
2
; —C
2
H
4
(C
5
H
8
)C
2
H
4
Si(OC
2
H
5
)
3
; and —C
2
H
4
Si(OCH
3
)
2
(OSi(OCH
3
)
3
). When X is OR
2
, each R
2
may be the same or different in the OR
2
groups on any one silicon atom.
W is a monovalent radical and may be an unsaturated non-aromatic hydrocarbon, hydroxy, an amine, an ester, a polyalkylene oxide, a thioester, an amide, a carbamate, an epoxy, cyano, polysulfide, or isocyanurate. Specific examples of W include gamma propyl amino, gamma propyl glycidoxy, acetoxy ethyl, propylene glycol, gamma propyl carbamate, dimethoxy phenyl propyl, n-octenyl, 2-ethyl, 3,4 epoxy cyclohexane, or cyano ethyl or an alkyl radical substituted with such groups. Usually if a W group is attached to a silicon atom, the other R group(s) on that silicon atom is a hydrocarboxy group (—OR
1
), preferably an alkoxy. In one embodiment of the present invention, there is at least one W on the oligomer.
R
1
is a saturated or aromatic hydrocarbon of 1 to 12 carbon atoms, e.g., alkyl (linear or branched) cycloalkyl, aryl or alkaryl. Exemplary R
1
are i-propyl, i-butyl, t-butyl, n-pentyl, cyclohexyl, phenyl, benzyl or napthyl. Specifically, methyl or ethyl are preferred for R
1
. If there is an R
1
on a silicon atom, it is preferred that that the other R group(s) on the silicon atom be other than R
1
, most preferably, they are —OR
1
. Since the R
1
groups, and particularly methyl groups as R
1
groups, may affect the compatibility of the oligomer in some embodiments (especially as compared to —OR
1
functionalities), R
1
should be such that less than five percent of the [O
1/2
Si(R
2
)O
1/2
]
n
groups have two R
1
on them. More preferably in the [R
3
SiO
1/2]
groups, only one of the R groups is R
1
, more preferably none are R
1
. In a preferred embodiment there are less than five percent by weight of the oligomer is dimethylsiloxy units and more preferably, there are no dimethyl siloxy units in the oligomer.
Preferably m+n+o+p<50, more preferably <30 and most preferably <15. Preferably m is 2 to 4, n is to 1 to 15, o is 0 to 2 and p is 0 to 1, though it is understood there may be distributions of the number of siloxy units within a given oligomer batch.
Preferably there are multiple alkoxy groups available on the oligomer so that upon curing these oligomers may cross-link, i.e., form Si—O—Si bonds with each other or with a silylated polymer or inorganic material. Thus, R is —OR
1
, more preferably ethoxy or methoxy, in at least one quarter of the R groups, more preferably in at least half of the R groups, while the remainder of the R groups are B or W groups, more preferably, trialkoxysilylethyl groups, most preferably trimethoxysilylethyl. In such embodiments p&

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