In the manufacture of automobiles, the automobile body is initially primed with a coating composition to prevent corrosion of the metal. This can be done in a number of ways although generally it is performed by cationic electrodeposition using the auto body as the cathode. Once the automobile body has been primed in this manner, subsequent steps in the assembly are carried out. These steps typically include the use of sealants over the primed automobile body. The sealants are subsequently topcoated along with the remainder of the body during the final stages of the painting process.
Polyvinyl chloride plastisols offer several advantages for use as sealant compositions: a good balance of strength, elongation and toughness, minimal to no volatile organic component and low cost. However, despite these advantageous properties, when used in conjunction with cationically electrodepositable primer compositions in automotive applications, adhesion is poor and yellowing of the topcoat composition results.
Historically, polyaminoamides which are art recognized adhesion promoters, have been utilized in an attempt to deal with the above adhesion problems. These, however, can adversely affect the stability of the plastisol based sealant composition, the cure of the topcoat and in addition, cause more yellowing.
There is a need, therefore, for a polyvinyl chloride plastisol based composition which exhibits excellent adhesion to primed metal and is capable of being topcoated with a variety of coating compositions without yellowing of the topcoat.
SUMMARY OF THE INVENTION
In accordance with the present invention, there is provided a plastisol based composition comprising:
(a) a copolymer of an aliphatic olefinically unsaturated material and an anhydride containing material; and
(b) a polyvinyl chloride plastisol.
DETAILED DESCRIPTION OF THE...