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
2001-11-09
2004-01-27
Egwim, Kelechi C. (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...
C524S225000, C524S262000, C524S265000, C524S267000, C524S269000, C524S282000, C524S285000, C524S305000, C524S392000, C525S342000, C525S350000
Reexamination Certificate
active
06683135
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to sulfur silane coupling agents which are latent, that is, they are in a state of reduced activity until such a time as one finds it useful to activate them. The invention also relates to the manufacture of rubbers including inorganic fillers and these silane coupling agents, as well as to the manufacture of the silanes.
BACKGROUND
The majority of art in the use of sulfur-containing coupling agents in rubber involves silanes containing one or more of the following chemical bond types:
S—H (mercapto), S—S (disulfide or polysulfide), or C═S (thiocarbonyl). Mercaptosilanes have offered superior coupling at substantially reduced loadings; however, their high chemical reactivity with organic polymers leads to unacceptably high viscosities during processing and premature curing (scorch). Their undesirability is aggravated by their odor. As a result, other, less reactive coupling agents have been found. Hence, a compromise must be found between coupling and the associated final properties, processability, and required loading levels, which invariably leads to the need to use substantially higher coupling agent loadings than would be required with mercaptosilanes, and often also to the need to deal with less than optimal processing conditions, both of which lead to higher costs.
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.). Takeshita and Sugawara disclosed in Japanese Patent JP 63270751 A2 the use of compounds represented by the general formula CH2═C(CH
3
)C(═O)S(CH
2
)
1-6
Si(OCH
3
)
3
in tire tread compositions; 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 or during storage.
Prior art by Yves Bomal and Olivier Durel in Australian Patent AU-A-10082/97 discloses the use in rubber 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. This prior art, however, stipulates that compositions of the structures of Formula (1P) must be used in conjunction with functionalized siloxanes. In addition, the prior art does not disclose or suggest the use of compounds of Formula (1P) as latent mercaptosilane coupling agents, nor does it disclose or suggest the use of these compounds in any way which would give rise to the advantages of using them as a source of latent mercaptosilane.
U.S. Pat. No. 4,519,430 to Ahmad 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 is a thermal mechanism. The purpose of this silane is to avoid the sulfur smell of the mercaptosilane, not to improve the processing of the tire. Moreover, the isocyanate used has toxicity issues when used to make the silane and when released during rubber processing.
U.S. Pat. No. 3,957,718 to Porchet et al. discloses compositions containing silica, phenoplasts or aminoplasts, and silanes, such as xanthates, thioxanthates, and dithiocarbamates; however, the prior art does not disclose or suggest the use of these silanes as latent mercaptosilane coupling agents, nor does it suggest or disclose the advantage of using them as a source of latent mercaptosilane. 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 silanes of the present invention are mercaptosilane derivatives in which the mercapto group is blocked (“blocked mercaptosilanes”), i.e., the mercapto hydrogen atom is replaced by another group (hereafter referred to as “blocking group”). Specifically, the silanes of the present invention are blocked mercaptosilanes in which the blocking group contains an unsaturated heteroatom or carbon chemically bound directly to sulfur via a single bond. This blocking group optionally may be substituted with one or more carboxylate ester or carboxylic acid functional groups. The use of these silanes in the manufacture of inorganic filled rubbers is taught wherein they are deblocked by the use of a deblocking agent during the manufacturing process. The manufacture of such silanes is taught as well.
DETAILED DESCRIPTION OF THE INVENTION
Silane Structures
The blocked mercaptosilanes can be represented by the Formulae (1-2):
[[(ROC(═O))
p
—(G)
j
]
k
—Y—S]
r
—G—(SiX
3
)
s
(1);
and
[(X
3
Si)
q
—G]
a
—[Y—[S—G—SiX
3
]
b
]
c
(2)
wherein
Y is a polyvalent species (Q)
z
A(═E), preferably selected from the group consisting of —C(═NR)—; —SC(═NR)—; —SC(═O)—; (—NR)C(═O)—; (—NR)C(═S)—; —OC(═O)—; —OC(═S)—; —C(═O)—; —SC(═S)—; —C(═S)—; —S(═O)—; —S(═O)
2
—; —OS(═O)
2
—; (—NR)S(═O)
2
—; —SS(═O)—; —OS(═O)—; (—NR)S(═O)—; —SS(═O)
2
—; (—S)
2
P(═O)—; —(—S)P(═O)—; —P(═O)(—)
2
; (—S)
2
P(═S)—; —(—S)P(═S)—; —P(═S)(—)
2
; (—NR)
2
P(═O)—; (—NR)(—S)P(═O)—; (—O)(—NR)P(—O)—; (—O)(—S)P(═O)—; (—O)
2
P(═O)—; —(—O)P(═O)—; —(—NR)P(═O)—; (—NR)
2
P(═S)—; (—NR)(—S)P(═S)—; (—O)(—NR)P(═S)—; (—O)(—S)P(═S)—; (—O)
2
P(═S)—; —(—O)P(═S)—; and —(—NR)P(═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 hydrogen, straight, cyclic, or branched alkyl that may or may not contain unsaturation, alkenyl groups, aryl groups, and aralkyl groups, with each R containing from 1 to 18 carbon atoms;
each G is independently a monovalent or polyvalent group derived by substitution of alkyl, alkenyl, aryl, or aralkyl wherein G can contain from 1 to 18 carbon atoms, with the proviso that if Y is —C(═O)—, G is not such that the blocked mercaptosilane would contain an &agr;,&bgr;-unsaturated carbonyl, and if G directly bonded to Y is univalent (i.e., if p=0), G can be a hydrogen atom;
X is independently selected from the group consisting of —Cl, —Br, RO—, RC(═O)O—, R
2
C═NO—, R
2
NO— or R
2
N—, —R, —(OSiR
2
)
t
(OSiR
3
) wherein each R and G is as above and at least one X is not —R;
Q is oxygen, sulfur, or (—NR—);
A is carbon, sulfur, phosphorus, or sulfonyl;
E is oxygen, sulfur, or NR;
p is 0 to 5; r is 1 to 3; z is 0 to 2; q is 0 to 6; a is 0 to 7; b is 1 to 3; j is 0 to 1, but it may be 0 only if p is 1; c is 1 to 6, preferably 1 to 4; t is 0 to 5; s is 1 to 3; k is 1 to 2; with the provisos that (A) if A is carbon, sulfur, or sulfonyl, then (i) a+b=2 and (ii) k=1; (B) if A is phosphorus, then a+b=3 unless both (i) c>1 and (ii) b=1, in which case a=c+1; and (C) if A is phosphorus, then k is 2.
As used herein, “alkyl” includes straight, branched, and cyclic alkyl groups, and “alkenyl” includes straight, branched, and cyclic alkenyl groups containing one or more carbon—carbon double bonds. Specific alkyls include methyl, ethyl, propyl, isobutyl, and specific aralkyls include phenyl, tolyl, and phenethyl. As used herein, “cyclic alkyl” or “cyclic alkenyl” also includes bicyclic and higher cyclic structures, as well as cyclic structures further substituted with alkyl groups. Representative examples include norbornyl, norbornenyl, ethylnorbornyl, ethylnorbornenyl, ethylcyclohexyl, ethylcyclohexenyl, and cyclohexylcy
Cruse Richard W.
Pickwell Robert J.
Pohl Eric R
Weller Keith J.
Dilworth Michael P.
Egwim Kelechi C.
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