Cathodic electrocoating compositions
Disclosed herein are functionalized polymers comprising ethylene and substituted ethylene segments, which have been crosslinked using a multifunctional thiol to enhance their crosslinking ability. These functionalized polymers are useful as film forming resins in cathodic electrocoating compositions. Also disclosed herein are aqueous dispersion compositions comprising the functionalized polymers and a process for coating various electrically conductive substrates.
1. A composition comprising the reaction product formed by combining:
a) a polymer comprising:
i) at least one ethylene segment of structure 1
ii) at least one substituted ethylene segment of structure 2
iii) at least one substituted ethylene segment of structure 3
wherein:
x and y are independently integers from 10 to 30,000, and z is an integer from 1 to 10;
R is independently at least one member selected from the group consisting of: —(CH 2 ) m N(CH 3 ) 2 , —(CH 2 ) n —(CH═CH)—(CH 2 ) r CH 3 , —(CH 2 ) v CH 3 , —(CH 2 ) p OH, —(CH 2 ) s N(CH 2 CH 2 OH) 2 , and —(CH 2 ) t OPO 3 H 2 ;
R′ in structure 2 and R′ in structure 3 are independently H, —C q H 2q+1 , or —C q H 2q−k ;
R″ is H or CH 3 ; and
where q, r, s, t, m, n, v, and p are independently selected from the group of integers from 1 to 20, and k is the number of saturated hydrocarbon rings in —C q H 2q−k ;
with
b) a multifunctional thiol containing two or more thiol end groups.
2. The composition of claim 1 , wherein R′ in structure 2 and R′ in structure 3 are H, and R is —(CH 2 ) n —(CH═CH)—(CH 2 ) r CH 3 .
3. The composition of claim 2 , wherein n=8 and r=7.
4. The composition of claim 1 , wherein R′ in structure 2 and R′ in structure 3 are H, and R is —(CH 2 ) n —(CH═CH)—(CH 2 ) r CH 3 and —(CH 2 ) p OH.
5. The composition of claim 4 , wherein n=8, r=7, and p=2.
6. The composition of claim 1 , wherein the multifunctional thiol is selected from the group consisting of: pentaerythritol tetra-(3-mercaptopropionate), ethoxylated pentaerythritol tetra-(3-mercaptopropionate), trimethylpropane tri(3-mercapto-propionate), glycol 3-mercaptopropionate, poly propylene glycol 3-mercaptopropionate, ethoxylated trimethylpropane tri(3-mercapto-propionate), ethoxylated glycol dimercaptoacetate, trimethylolpropane trimercaptoacetate, glycol di-(3-mercaptopropionate), 1,4-bis(3-mercaptobutylyloxy) butane, pentaerithrytol tetrakis(3-mercaptobutylate), tris[2-(3-mercaptopropionyloxy)ethyl]isocyanurate, 1,3,5-Tris(3-melcaptobutyloxethyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, and mixtures thereof.
7. The composition of claim 6 , wherein the multifunctional thiol is tris[2-(3-mercaptopropionyloxy)ethyl]isocyanurate.
8. The composition of claim 1 , wherein the radical intiator is selected from the group consisting of peroxides and diazo compounds.
9. The composition of claim 1 wherein the combining of (a) and (b) is done in the presence of a radical initiator.
10. An aqueous dispersion composition comprising:
a) a composition of claim 1 ; and
b) water;
wherein said aqueous dispersion composition has a pH of 5.0 to 7.0.
11. The aqueous dispersion composition of claim 10 further comprising at least one crosslinking agent.
12. The aqueous dispersion composition of claim 11 , wherein the at least one crosslinking agent is a blocked isocyanate.
13. The aqueous dispersion composition of claim 11 , wherein the at least one crosslinking agent is an alkoxysilane.
14. The aqueous dispersion composition of claim 10 further comprising at least one additive selected from the group consisting of: surfactants, pigments, light stabilizers, anti-crater agents, flow aids, dispersion stabilizers, adhesion promoters, corrosion inhibitors, and fillers.
15. The aqueous dispersion composition of claim 10 having a pH of 6.0 to 7.0.
16. The aqueous dispersion composition of claim 10 having a pH of 6.5 to 7.0.
17. A process comprising the steps of:
a) providing an electrochemical cell comprising:
i) an aqueous dispersion composition of claim 8 ;
ii) a substrate to be coated, wherein the substrate is in contact with the aqueous dispersion composition and the substrate serves as a cathode of the electrochemical cell;
iii) an anode in contact with the aqueous dispersion composition; and
iv) a power supply in electrical contact with the anode and cathode; and
b) applying a voltage between the cathode and the anode to electrodeposit a polymer coating onto at least a portion of the substrate that is in contact with the aqueous dispersion.
18. The process of claim 17 further comprising the step of: heating the polymer coating.
19. The process of claim 17 wherein the aqueous dispersion further comprises a crosslinking agent.
20. The process of claim 17 wherein the aqueous dispersion further comprises at least one additive selected from the group consisting of: surfactants, pigments, light stabilizers, anti-crater agents, flow aids, dispersion stabilizers, adhesion promoters, corrosion inhibitors, and fillers.
21. A coated article produced by the process of claim 17 .