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
1999-07-30
2001-08-07
Dawson, Robert (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C526S335000, C525S342000, C525S100000, C525S479000, C502S325000, C427S387000
Reexamination Certificate
active
06271309
ABSTRACT:
BACKGROUND
The invention relates to curable compositions resulting from the hydrosilation of olefin-containing polymers with organosiloxane hydrides. The curable compositions may be cured to provide low surface energy cured compositions which may be provided in the form of a coating on a substrate.
Coatings having low surface energy are well known for use as automotive waxes, marine waxes and antifouling coatings. These coatings are useful because the low surface energy inhibits attachment of marine organisms and causes water to bead and to run off the surface of the coating. Silicone containing materials are known to provide low surface energy when incorporated into coatings. However, when low molecular weight silicone containing additives are used as the means of incorporating silicone into a coating, leaching of the silicone containing additive may result. Over time, this leaching leads to an increase in the surface energy of the coating and, consequently, a reduction in the performance of the coating. Silicone based polymers themselves are of little use since they typically lack the mar and abrasion resistance needed for these applications.
Theoretically, an ideal material for durable low surface energy coatings would have a strong polymer backbone with multiple silicone containing substituents grafted onto the polymer backbone at various points along its length. Gabor et al. report the hydrosilation of styrene-butadiene block co-polymers with organosiloxane monohydrides such as pentamethyldisiloxane or 1,1,1,3,3,5,5-heptamethyl trisiloxane. The resulting polymers have linear silicon-containing pendant chains (see, Gabor et al., Polym. Prepr. (ACS Div. Poly. Chem.), 1992, 33 (2), pp. 136-137). The short chain organosiloxanes monohydrides provide only a low level of silicone in the resulting polymers.
U.S. Pat. No. 5,703,163 (Baum) reports loop polymers having a polymeric backbone and a plurality of olefinic groups which have been converted to closed loops by reaction with difunctional organic compounds reactive with the olefinic groups. Although Baum incorporates a higher level of silicone into the resulting polymers, the synthetic scheme used to form loop polymers is preferably carried out at low percent solids. This limitation complicates commercial use of the resulting loop polymers as they must be recovered from a large amount of solvent in order to be useful in high solids coating formulations.
In view of the foregoing, there is a need for curable compositions having a high level of silicone chemically grafted onto a polymer backbone that can be manufactured at high solids without the formation of an solid mass and/or insoluble gel. A synthetic route that eliminates gel formation resulting from excessive crosslinking and yields a high percent solids curable composition is highly desirablc.
SUMMARY
The present invention provides curable compositions and cured compositions comprising the hydrosilation product of olefin-containing polymers and organosiloxane hydrides. The curable compositions may be cured to provide cured compositions having a low surface energy (e.g., less than about 35 dynes/cm) which may be suitable for use as antifouling coatings on substrates such as boats, ship hulls or other at least partially submerged structures such as bridge pilings, docks, dams, an offshore oil rigs.
In one aspect of the present invention, a curable composition is provided comprising the hydrosilation product of:
(a) a polymer comprising a plurality of olefin groups and at least two organic functional groups; and
(b) an organosiloxane monohydride having the structure illustrated in formula (4):
wherein R
4
is a monovalent organosiloxane radical having the structure illustrated in formula (5):
wherein n is about 10 or greater;
R
5
is independently selected from organic radicals, for example, C
1-10
alkyl radicals and phenyl radicals; and
X is an oxygen atom or a divalent organic linking group;
In a preferred embodiment, R
4
has the structure illustrated below:
where n is about 10 or greater;
In another aspect of the present invention, a curable composition is provided comprising the hydrosilation product of:
(a) a polymer comprising a plurality of olefinic groups and at least two organic functional groups; and
(b) an organosiloxane dihydride having the structure illustrated in formula (6)
wherein the organosiloxane dihydride crosslinks the polymer and wherein the curable composition comprises about 45% weight or greater silicone.
In formula (6), n is about 200 or greater and R
6
is independently selected from the group consisting of C
1-10
alkyl radicals, phenyl radicals, organosiloxane radicals and hydrogen, with the proviso that two R
6
groups are hydrogen (i.e., a dihydride). Prior to the formation of the hydrosilation product, the ratio of the number of olefin groups in the polymer to the number of hydride groups in the organosiloxane dihydride is preferably about 20:1 or greater, more preferably about 50:1 or greater, and most prcferably about 100:1 or greater. The olefin to hydride ratio is selected to provide the desired balance of crosslinking and silicone content in the curable composition.
The olefin-containing polymer used to form the curable compositions of the present invention comprise a plurality of olefin groups and at least two organic functional groups. Functional groups include, for example, hydroxyl, carboxyl, epoxy, amino, silane, silanol, and mercapto groups. In one embodiment of the present invention, the olefin-containing polymer has the structure illustrated in formula (2) where n is about 20 or greater, preferably about 50 or greater:
The organic functional groups of the olefin-containing polymer may be reacted with a curative in order to form cured compositions of the present invention. Suitable curatives include, for example, water, polyftinctional isocyanates, polyols, polyamines, epoxies, olefins and acetylenes. In a preferred embodiment, a curable composition of the present invention is used as the polyol component of a silanol-terminated urethane dispersion, such as those described in U.S. Pat. No. 5,554,686 (Frisch et al.) and Ser. No. 08/978,331 (Roberts et al), filed Nov. 11, 1997.
Curable compositions of the present invention preferably have a Brookfield viscosity less than about 1,000,000 cP, more preferably less than about 500,000 cP and most preferably less than about 100,000 cP and preferably comprise about 45% weight or greater silicone, more preferably about 60% weight or greater silicone, more preferably about 70% weight or greater silicone and most preferably about 80% weight or greater silicone. As used herein, “% weight silicone” refers to the combined weight of silicon and oxygen present in the form of an alternating chain of covalently bonded silicon and oxygen atoms in a curable composition of the present invention expressed as a percentage of the total weight of the curable composition.
In another aspect of the present invention, a method of making a curable composition is provided comprising the steps of:
(a) providing a plurality of polymer molecules each molecule comprising a plurality of olefin groups and at least two organic functional groups;
(b) providing an plurality of organosiloxane monohydride molecules having the structure illustrated in formula (4):
wherein R
4
has the structure illustrated in formula (5):
wherein n is about 200 or greater;
R
5
is a monovalent organic radical; and
X is an oxygen atom or a divalent organic linking group; and
(c) reacting the plurality of olefin groups of the polymer with the organosiloxane monohydride to form the curable composition.
In another aspect of the present invention, a method of making a curable composition is provided comprising the steps of:
(a) providing a plurality of polymer molecules each polymer molecule comprising a plurality of olefin groups and at least two organic functional groups;
(b) providing a plurality of organosiloxane dihydride molecules having the structure illustrated in formula (6):
wherein n is about 200 or greater;
R
6
is independ
Roberts Gary P.
Vander Louw Steven J.
3M Innovative Properties Company
Dawson Robert
Peng Kuo-Liang
Pribnow Scott R.
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