Addition-crosslinkable epoxy-functional organopolysiloxane polymer and coating composition

A high weather and chemical resistant, 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 2 2 ( D ⁢ ⁢ units ) E a ⁢ R b 1 ⁢ R c 2 ⁢ SiO 3 2 ( T ⁢ ⁢ units )
• wherein
• R1 and R2 are independently a C1-20 hydrocarbon, optionally interspersed with
• a heteroatom linking group;
• a is an integer of 0, 1, or 2;
• b is an integer of 0, 1, 2 or 3;
• c is an integer of 0, 1, 2 or 3;
• and
• in D units, a+b+c=2,
• in T units, a+b+c=1,
• wherein
• the D units are present in about 30 mole percent;
• the T units are present in about 70 mole percent;
• the molecule, on average, contains at least two E components;
• and
• wherein the epoxy-functional organopolysiloxane resin has an epoxy equivalent weight in the range of about 200-600, the epoxy-functional organopolysiloxane resin has a viscosity in the range of about 200-70,000 cps at 25° C. and the E is glycidoxypropyl

An epoxy-functional organopolysiloxane coating composition comprising:

• a hardener;
• an acrylic resin;
• and
• an 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 2 2 ( D ⁢ ⁢ units ) E a ⁢ R b 1 ⁢ R c 2 ⁢ SiO 3 2 ( T ⁢ ⁢ units )
• wherein
• E is an epoxy-functional C1-18 hydrocarbon group containing one or more oxygen atoms, provided that no oxygen atom is directly bonded to a Si— atom;
• and
• R1 and R2 are independently a C1-20 hydrocarbon, optionally interspersed with
• a heteroatom linking group;
• a is an integer of 0, 1, or 2;
• b is an integer of 0, 1, 2 or 3;
• c is an integer of 0, 1, 2 or 3;
• and
• in D units, a+b+c=2,
• in T units, a+b+c=1,
• wherein
• the D units are present in about 30 mole percent;
• the T units are present in about 70 mole percent;
• and
• the molecule, on average, contains at least two E components.