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
2000-03-14
2001-09-25
Cameron, Erma (Department: 1762)
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
active
06294620
ABSTRACT:
BACKGROUND OF THE INVENTION
Conventional primer systems for use with sealants, adhesives and coatings generally comprise a large amount of organic solvent plus smaller amounts silane coupling agents and film formers. The solvent based primers provide good adhesion across the substrate-sealant interface and are convenient to use because they dry quickly. Organic solvents are the preferred carriers for such primers since silanes are generally not stable in waterbased systems. However, with the increased environmental concern over the emission of volatile organic compounds (VOC) it is appropriate to eliminate or lower such emissions whenever possible.
U.S. Pat. No. 4,309,326 discloses an aqueous polyester size emulsion for glass fiber comprising an unsaturated water-emulsifiable, silylated polyester resin, an EVA copolymer, and a copolymer of vinyl acetate and a prehydrolyzed, water soluble organosilane.
U.S. Pat. No. 4,394,418 discloses an aqueous sizing composition of a silylated polyvinyl acetate latex containing a low level of silane copolymerized with the vinyl acetate, a water soluble silane, non-ionic surfactants, a polyethylene-containing polymer, a glass fiber lubricant, a hydrocarbon acid and water. The monomeric silanes used in this patent are epoxysilanes and aminosilanes and can be mixed with acrylate containing water soluble silanes. The shelf life of these compositions, however, is generally less than 72 hours.
U.S. Pat. No. 5,393,330 describes emulsions of unsubstituted or halogenated alkyltrialkoxysilanes used as waterproofing agents.
U.S. Pat. No. 4,778,624 discloses a method for the preparation of a stable aqueous emulsion of a poly(silsesquioxane) from substituted and unsubstituted alkylsilanes.
Silane technology for aqueous primers has been developed in the last few years. Most of these developments are based on aminosilanes which uniquely are water soluble, forming water stable hydrolysates. Among these methods, U.S. Pat. No. 5,363,994 teaches the use of aminosilane up to 0.5 parts in combination with a hydrophobic silane in water as a primer. To inhibit condensation of the non-amino silane coupling agents the aqueous primer are required to have a pH from about 2.0 to about 5.5.
WO 9715700 describes a pre-hydrolyzed aminosilane in a concentrated phosphoric acid aqueous solution for use as a primer or conversion treatment on a metallic substrate. However, due to the inherent instability of silane in water, these aqueous primers have shelf lives less than 6 months.
U.S. Pat. No. 5,393,330 describes the use of silane emulsions for hydrophobizing concrete surfaces.
U.S. Pat. Nos. 5,686,523 and 5,714,532, incorporated herein by reference, describe a series of alkoxysilanes which can be formulated into stable emulsion for waterborne coating or sealant formulations as crosslinkers or adhesion promoters. In this technology the silanes are used as additives to a resin system or are incorporated into the resin during resin synthesis.
U.S. Pat. No. 4,689,085 describes the use of bis silyl alkanes in primer formulations but not in emulsions.
SUMMARY OF THE INVENTION
According to the present invention emulsions of water insoluble or semi-soluble silanes, described in detail below, may be employed as aqueous primers for promoting adhesion of polymeric sealant, adhesive and coating systems to a wide variety of substrates including glass, metal, concrete and plastics. These primers, when applied first to a substrate, will improve the adhesion of a variety of resin chemistries including acrylic or polyurethane dispersions, high solids polyurethanes, epoxies and RTV silicones. The resin systems being applied to the primer may or may not contain silane adhesive promoters.
These aqueous silane based primers have superior shelf stability when compared to other aqueous silane primers systems, they have good wetting properties and can be applied and cured at either room temperature or elevated temperatures. If a waterborne system is being applied over these primers it is not necessary to wait until the primer is dried before application.
The invention offers the distinct advantage of removing organic solvents (VOC's) from primer formulations while offering improved adhesion and excellent shelf stability.
Two-part primer/resin sealant, adhesive and coating systems employing the primer compositions as described herein constitute a further aspect of the invention.
DETAILED DESCRIPTION OF THE INVENTION
The adhesion promoting silanes used in the primer compositions are water insoluble or slightly soluble organosilanes with general structure of
R
1
a
R
2
b
Si(OR
3
)
4−a−b
where
R
1
is a hydrocarbon group having from three to thirty carbon atoms and substituted with an organic functional group, or is a two to thirty carbon alkenyl group;
R
2
is alkyl, alkoxy-substituted alkyl, aryl or aralkyl, and has from one to twelve carbon atoms;
R
3
is alkyl or alkoxy-substituted alkyl, aryl or aralkyl group, and has from two to ten carbon atoms; and
a is one to three, b is zero to two, and a+b is 1,2, or 3.
The R
1
, R
2
, and R
3
hydrocarbon groups may be cyclic, branched or linear.
The term water insoluble or slightly soluble silanes includes alkoxy silanes with solubilities between 0 and 8.0 weight percent in water at 25° C. Water insoluble alkoxy silanes with solubilities between 0 and 1 weight percent in water at 25° C. are preferred. Water soluble alkoxy silanes are not used because compositions made with such silanes are not stable for extended periods of time, i.e., more than two to three days at ambient conditions. Therefore, the R groups should be chosen to ensure low solubility of the silane in water.
R
1
may be an alkyl, aralkyl, alkaryl, or an aryl group, each further containing at least one organic-functional group substituent. Specific examples include substituted propyl, isopropyl, butyl, isobutyl, amyl, isoamyl, hexyl, heptyl, octyl, xylyl, benzyl, phenyl, cyclopentyl, cyclohexyl, phenylmethyl, phenylethyl, and the like. Specific examples of the substituent(s) on R
1
include mercapto, epoxy, methacryloxy, acryloxy, chloro, bromo, iodo, cyano, ketone, aldehyde, carboxylate, carboxylic acid, silyl ester (e.g., —SiR
2
b
(OR
3
)
3−b
where R
2
and R
3
are as previously defined), amine, alkylamine, dialkylamine, arylamine, diarylamine, ureide, amide, isocyanurate, and alkoxy groups substituted with any of the foregoing. R
1
may also be a 3-30 carbon alkenyl group such as vinyl, allyl, oleyl, linoleyl, linolenyl, etc. With regard to epoxy substituents, cycloaliphatic epoxies are preferred over glycidyl epoxies for their superior shelf-life stability.
R
2
is exemplified by methyl, ethyl, n-propyl, n-butyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decyl, lauryl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, isopropyl, isobutyl, sec-butyl, isoamyl, sec-amyl, 4-methyl-2-pentyl, 2-ethylhexyl and phenyl.
R
3
is exemplified by ethyl, n-propyl, n-butyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, isopropyl, isobutyl, sec-butyl, isoamyl, sec-amyl, 4-methyl-2-pentyl, 2-ethylhexyl and phenyl.
Examples of the above-mentioned silane compounds include &bgr;-(3,4-epoxycyclohexyl)-ethyltriethoxysilane, &bgr;-(3,4-epoxycyclohexyl)-ethyltriisopropoxysilane, &bgr;-(3,4-epoxycyclohexyl)-ethyltriisobutoxysilane, 3-glycidoxypropyltriisobutoxysilane, 3-methacryloxypropyltriethoxysilane, 3-methacryloxypropyltriisopropoxysilane, 3-methacryloxypropyltriisobutoxysilane, vinyltriisopropoxysilane, vinyltriisobutoxysilane, 3-acryloxypropyltriethoxysilane, 3-mercaptopropyltriethoxysilane, vinylmethylbis-(isopropoxy)silane, 3-methacryloxypropylmethyldibutoxysilane, and bis or tris silanes such as 1,2 bis-(alkoxy) silyl ethanes and tris(3-triethoxysilylpropyl)isocyanurate.
The emulsifiers for use herein include nonionic, anionic or cationic surfactants or mixtures of nonionic with anionic or cationic surfactants. Examples of the nonionic surfactants include polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, poly
Huang Misty Weiyu
Waldman Bruce A.
Cameron Erma
Crompton Corporation
Reitenbach Daniel
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