Organic compounds -- part of the class 532-570 series – Organic compounds – Silicon containing
Reexamination Certificate
2001-10-17
2003-05-06
Moore, Margaret G. (Department: 1712)
Organic compounds -- part of the class 532-570 series
Organic compounds
Silicon containing
C556S130000, C556S441000, C556S446000, C556S479000
Reexamination Certificate
active
06559329
ABSTRACT:
BACKGROUND OF THE INVENTION
The structures of phenolic silanes are well known in the literature and are disclosed in U.S. Pat. No. 3,328,450. The utility of these phenolic silanes as coupling agents for polyester laminates were discussed in E. P. Plueddemann, H. A. Clark, L. E. Nelson and K. R. Hoffman,
The Society of Plastics Industry, Inc.,
17
th Annual Meeting of the Reinforced Plastics Divison
, Febuary 6-8, Section 14-A, 1 (1962). 3-(4-Hydroxy-3-methoxyphenyl)propyltrimethoxysilane was found to have excellent force transmission properties for glass fiber reinforced epoxy resins under evaluated temperatures or after exposure to boiling water by A. T. DeBenedetto, J. A. Gomez, C. L. Schilling, F. D. Osterholtz and G. Haddad,
Materials Research Society Symposium Proceeding,
170, 297 (1990).
A characteristic of these phenolic silanes is that they are unstable. The phenolic hydroxyl group undergoes a transesterification reaction with the alkoxysilyl or acyloxysilyl group to yield oligomers and polymers with high viscosity that may gel. In addition, the oligomers and polymers are very difficult to disperse in water because they are hydrophobic and are not water soluble. An essential end-use requirement is that the phenolic silanes need to be dispersible in water or in aqueous organic solvents, such as mixtures of water with alcohols, ketones, esters or ethers.
The influence of silane spacer groups on the hydrolytic stability of silica reinforced poly-(2,2-bis-[4-(methacryloxy)-2-(hydroxypropyl)phenyl]propane was investigated by N. Nishiyama, K. Horie and T. Asakura, from:
Interfaces in Polymer, Ceramic, and Metal Matrix Composites
, H. Ishida ed., Elsevier Science Publishing Co. Inc., 279 (1988). One silane studied was 4-methacryloyloxy-3-methoxy-1-(3-trimethoxysilylpropyl)benzene. R. H. Chung and W. D. Kray disclosed a series of silylated benzoate esters as an intermediate in making ultraviolet screening agents in U.S. Pat. Nos. 4,328,346 and 4,372,835. For example, they synthesized 2-methoxy-4-(3-methyldimethoxysilylpropyl)phenyl benzoate. When this silane was irradiated with ultraviolet light, it rearranged to make 2-methoxy-4-(3-methyldimethoxysilylpropyl)-6-benzoylphenol. These ester silanes are not suitable for use as coupling agents or as additives to waterborne coatings or primers because the by-products of hydrolysis, benzoic acid or methacrylic acid, are nonvolatile. The nonvolatility of these by-products prevents them from evaporating during the drying or curing process and they remain in the composite or dried coating.
The effects of hydroxyacetophenone structure on the ruthenium catalyzed alkylation using vinylsilanes was investigated by P. W. R. Harris and P. D. Woodgate,
Journal of Organometallic Chemistry,
530, 211 (1997). Two products that they made were 4-acetoxy-2-(3-triethoxysilylpropyl)acetophenone and 4-acetoxy-2,6-bis-(3-triethoxysilylpropyl)acetophenone. The acetophenone structural fragment may be undesirable because it decomposes when exposed to ultraviolet light. In addition, the acetophenone may react with other ingredients in the composite or coating.
2-(4-Acetoxyphenyl)-1-methyldiclorosilylpropane and 3-(4-acetoxyphenyl)propylmethyldichlorosilane were synthesized as intermediates in the preparation of a phenolic functional silicone fluids, as disclosed in V. A. Sergeev, V. K. Shitikov, G. U. Abbasov, M. R. Bairamov, A. A. Zhdanov, T. V. Astapova and S. M.
Aliev, Zhurnal Obshchel Khimii,
52, 1846 (1982). The acetyl groups were removed in the base-catalyzed hydrolysis and condensation of the chlorosilane intermediate. Chlorosilanes are not suitable for use in waterborne coatings because they are very corrosive and react very rapidly with water to generate hydrogen chloride.
Other blocking groups have been used to prevent the transesterification reaction of the phenolic hydroxyls with the alkoxysilyl groups. Several trimethylsilyl blocked phenolic chlorosilanes, such as [1-[4-[(trimethylsilyl)oxy]-3-methoxyphenyl]propyl]methyldichlorosilane, were prepared as intermediates in the synthesis of polysilanes, as disclosed by R. Horiguchi, Y. Onishi and S. Hayase,
Macromolecules,
21, 304 (1988). The trimethylsilyl group was removed by treatment of the polysilane with methanol. However, trimethyl silyl groups are unsuitable for composites, filler treatments and waterborne coating applications. When the blocked silane is added to water, the trimethyl silyl group forms trimethylsilanol, a silylating agent that will react with the inorganic surfaces. The silylation of the surface with trimethyl silyl groups would inhibit the chemical bonding of the silane coupling agent and reduce its efficacy. In addition, the trimethylsilanol can condense with itself to form hexamethyldisiloxane, a water insoluble oily material. Oily materials in the waterborne coating formulations result in poor coating uniformity and often form “fish-eyes” on the surface of applicators or coated substrates.
SUMMARY
The present acyl and carbonate blocked phenolic silanes are latent phenolic functional silanes that are useful as coupling agents for mineral filled composites, surface modifiers for inorganic materials and additives for coatings. These silanes can be used to treat particulate or fibrous inorganic fillers, prime inorganic surfaces, modify the surface properties of inorganic surfaces or modify end-use properties of coatings.
The general structural formula of these silanes is:
(R
I
C(═O)O)
y
C
6
R
II
6−y−z
[C
x
H
2x
Si(OR
III
)
3−a
(R
IV
)
a
]
z
where R
I
is H, CH
3
or R
V
O; R
II
is H or R
V
O; R
III
is alkyl, aryl, alkaryl or acyl from 1 to 8 carbon atoms; R
IV
is hydrogen, alkyl, aryl, or alkaryl from 1 to 8 carbon atoms; R
V
is a linear or branched alkyl group from 1 to 4 carbon atoms; y is an integer from 1 to 3; z is an integer from 1 to 3; x is an integer from 2 to 6 and a is an integer from 0 to 2.
DETAILED DESCRIPTION OF THE INVENTION
Structure of the Silanes
The general structural formula of the acyl and carbonate blocked phenolic silanes is set forth above. Additionally, the acyl or carbonate blocking group (R
I
C(═O)—) needs to generate by-products (R
I
C(═O)OH or CO
2
and R
V
OH) that evaporate readily. Therefore the by-products should have a boiling point of less than 120° C. and preferably less than 100° C., at atmospheric conditions. This boiling point requirement can be achieve if the by-products form azeotropes with water. For example, 1-butanol is a potential by-product if the blocking group is butyl carbonate. It forms an azeotrope with water that boils at 93° C. The formyl blocking group is preferred because it deblocks more rapidly when the silane is added to water. The formyl group is more hydrophilic and therefore the solubility of the silane in water is increased. The formyl group also hydrolyzes faster in water. For example, the hydrolysis of 4-nitrophenyl formate is 440 times faster than the corresponding 4-nitrophenyl acetate. See E. R. Pohl, D. Wu, D. J. Hupe,
Journal of the American Chemical Society,
102, 2759 (1980).
Examples of R
I
are hydrogen, methyl, ethoxy, butoxy, isopropoxy or propoxy. Preferred R
I
are hydrogen or methyl. Examples of R
II
are hydrogen, methyl or methoxy. Preferred R
II
are methoxy and hydrogen. The incorporation of R
II
that are methoxy increase the solubility of the silane in water. The increase in water solubility shortens the time necessary to hydrolyze the alkoxysilyl ester and remove the blocking group. These R
II
groups are not reactive with the resins during curing process nor do they increase the formation of undesirable color during the drying process and in-use.
Examples of R
III
are methyl, ethyl, acyl, formyl, propyl, phenyl, or n-butyl. It is preferred that the R
III
is methyl, formyl or acyl. The hydrolysis of the methoxysilyl, formyloxysilyl or acetoxysilyl groups are faster than the other R
III
groups. The replacement of the R
III
groups with hydrogen, the result of the hydrolysis, aids in dissolving
Pohl Eric R.
Turner Scot M
Crompton Corporation
Dilworth Michael P.
Moore Margaret G.
Zimmer Marc S
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