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
1999-06-24
2002-02-05
Moore, Margaret (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...
C525S476000, C528S034000, C528S039000, C524S588000
Reexamination Certificate
active
06344520
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an addition-crosslinkable epoxy-functional organopolysiloxane polymer useable to make a coating composition having high weather and chemical resistance, and more particularly, to a weather and chemical resistant coating composition comprising an addition-crosslinkable epoxy-functional organopolysiloxane polymer.
BACKGROUND ART
Protective coatings used for industrial equipment, manufacturing facilities, oil-drilling platforms and above water marine applications face exposure to corrosive and ultraviolet (U.V.) light environments. These environments often cause harm to these coatings which may require frequent repainting of the underlying substrate. These protective coatings typically include a crosslinkable resin system, which acts as a binder, a hardener (i.e., a crosslinking agent), flow additives and optional pigments. The crosslinkable resin system typically comprises one resin, but may also comprise two or more resins. The resins which have been typically used for these applications are based on epoxy resins (aromatic and aliphatic), condensation curable polysiloxanes, silicone alkyds, urethanes and silicone polyesters.
Coatings based on aromatic epoxy resins provide acceptable results when resistance to chemical and corrosive environments are necessary. However these coatings often fail when exposed to U.V. light, such as that found in sunlight, and tend to chalk when used as a topcoat on exterior applications. Coatings based on aliphatic epoxy resin react relatively slowly, but are somewhat less susceptible to damage from U.V. light then their aromatic counterparts.
Coatings based on urethanes have been used when the application requires corrosion resistance and weather resistance with an ambient cure response. However, these materials are considered to be toxic due to the possibility of minute amounts of free isocyanate present. Moreover, they are generally high in volatile organic components (VOC's).
Coatings based on silicone alkyds have been used for applications requiring an ambient cure schedule and high temperature resistance. The silicone alkyds provide good U.V. light resistance and since it contains between 20-30% (by wt.) silicone it also useful for high temperature resistance. However, in the presence of water and heat, the silicone-alkyd polymer may break down into its starting components. Once this occurs the alkyd will continue to oxidize and form water-soluble polymers. Coatings based on silicone polyesters are used for baking enamels in which high temperature and weather resistance is important, however they also contain the same reversible reaction as silicone-alkyds, which results in the formation of polyester and silicone polymers.
Recently, coatings formed of interpenetrating networks (IPN) containing polysiloxanes have been used. These polysiloxanes utilize the alkoxy functionality on the silicone to crosslink, and often require a moisture curing mechanism and a high energy pre-hydrolysis step. These compositions may also require a high degree of alkoxy functionality on the silanes and polysiloxane components, which, after curing, will have a high VOC due to the evolution of alcohol as a byproduct. In addition, these coatings will tend to wrinkle if a good cure is not achieved throughout the film, due to a continuation of the cure after exposed to moisture and heat (sunlight). The byproducts are normally methanol, however in some cases butanol or propanol can be present.
It would be desirable to provide a coating composition which is resistant to corrosion and exhibits U.V. light and heat resistance as well. It would also be desirable to provide a coating composition which can be used in low VOC formulations and can be formulated using solvents which are considered non-hazardous air pollutants. It would be further desirable to provide a coating composition which the crosslinking mechanism is primarily an addition reaction, and which renders no or fewer by-products as would be found in the cold blended silicone polymers.
DISCLOSURE OF INVENTION
The present invention pertains to an epoxy-functional organopolysiloxane polymer, and a method of making the same. The present invention also pertains to an epoxy-functional organopolysiloxane coating composition comprising the epoxy-functional organopolysiloxane polymer, and a method of making the same.
The epoxy-functional organopolysiloxane polymer is preferably a mildly crosslinked epoxy-functional organopolysiloxane resin and contains at least one or more of the repeating units having the formulae:
E
a
R
b
1
R
c
2
SiO
½
(M units)
E
a
R
b
1
R
c
2
SiO
{fraction (2/2)}
(D units)
E
a
R
b
1
R
c
2
SiO
{fraction (3/2)}
(T units)
SiO
{fraction (4/2)}
(Q units)
wherein
E is an epoxy-functional C
1-18
hydrocarbon group containing one or more oxygen atoms, provided that no oxygen atom is directly bonded to a S- atom; and
R
1
and R
2
are independently a C
1-20
hydrocarbon, optionally interspersed with a heteroatom linking group such as, but not limited to,
a is an integer of 0, 1, or 2, preferably 0 or 1;
b is an integer of 0, 1, 2 or 3, preferably 0, 1, or 2;
c is an integer of 0, 1, 2 or 3, preferably 0, 1, or 2; and
in M units, a+b+c=3,
in D units, a+b+c=2,
in T units, a+b+c=1,
with the proviso that the molecule, on average, contain at least two E components.
E is preferably an epoxy-functional C
2-15
hydrocarbon group, more preferably a C
3-12
hydrocarbon group, and even more preferably a C
3-6
hydrocarbon group. E is most preferably glycidoxypropyl
Preferably, the R
1
and R
2
are individually C
1-18
alkyl, C
6-20
aryl, C
7-18
alkylaryl, C
7-18
arylalkyl, C
5-12
cycloalkyl, C
2-18
alkenyl, glycol, epoxy (provided that the oxygen atom is not bonded directly to a Si- atom), C
1-18
alkoxy, C
2-20
unsaturated hydrocarbons such as vinyl, allyl, propenyl, isopropenyl and terminal C
4-18
alkenyl, alkynyl, vinyl ether, and allyl ether groups.
More preferably, R
1
and R
2
are independently methyl, ethyl, vinyl, allyl, methoxy, ethoxy, and phenyl groups.
If T units are present, the molecule may contain or form silsesquisiloxanes, and polysilsesquioxanes from the T units.
The coating composition cures through the crosslinking of the epoxy groups in the E group of the resin to provide a coating which is weather and chemical resistant. The polysiloxane moieties in the resin render the cured coating resistant to U.V. light and heat.
BEST MODE FOR CARRYING OUT THE INVENTION
The coating composition of the present invention comprises a binder and a hardener. The coating composition may also comprise flow additives, a crosslinking reaction catalyst to increase the rate of reaction, pigment to impart color to the coating, wetting agents, surface modifiers, extenders and inerts, and other commonly used coating composition ingredients.
Preferably, the coating composition comprises about 10 to about 90 weight percent binder, based on the total weight of the coating composition. More preferably, the coating composition comprises about 25 to about 50 weight percent binder, based on the total weight of the coating composition.
The binder preferably comprises at least about 80 weight percent solids, based on the weight of the binder, and more preferably, at least about 90 weight percent solids.
The binder preferably comprises a mildly crosslinked, addition-crosslinkable epoxy-functional organopolysiloxane resin which contains at least one or more of the repeating units having the formulae:
E
a
R
b
1
R
c
2
SiO
½
(M units)
E
a
R
b
1
R
c
2
SiO
{fraction (2/2)}
(D units)
E
a
R
b
1
R
c
2
SiO
{fraction (3/2)}
(T units)
SiO
{fraction (4/2)}
(Q units)
wherein
E is an epoxy-functional C
1-8
hydrocarbon group containing one or more oxygen atoms, provided that no oxygen atom is directly bonded to a S-atom; and
a is an integer of 0, 1 or 2, preferably 0 or 1;
b is an integer of 0, 1, 2 or 3, preferably 0, 1, or 2;
Brooks & Kushman P.C.
Moore Margaret
Wacker Silicones Corporation
LandOfFree
Addition-crosslinkable epoxy-functional organopolysiloxane... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Addition-crosslinkable epoxy-functional organopolysiloxane..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Addition-crosslinkable epoxy-functional organopolysiloxane... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2985181