Cathodic electrocoating composition containing morpholine dione blocked polyisocyanate crosslinking agent

a technology of morpholine dione and crosslinking agent, which is applied in the direction of electrolysis applications, coatings, polyurea/polyurethane coatings, etc., can solve the problems of high reactive isocyanate groups on the curing agent that must be blocked, block polyisocyanates, and require high temperatures to unblock and begin the curing reaction. , to achieve the effect of reducing bake-off loss

Inactive Publication Date: 2005-08-25
ANDERSON ALBERT G +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0009] The invention is directed to an improved aqueous cathodic electrocoating composition having a film forming binder of an epoxy-amine adduct, a crosslinking agent for the epoxy-amine adduct and an organic or inorganic acid as the neutralizing agent for the epoxy-amine adduct; wherein the improvement is the use of a blocked polyisocyanate crosslinking agent that has, on an average basis, at least one isocyanate group blocked with a morpholine dione compound for reduced bake-off loss on cure. A standard blocking agent is also preferably used to provide a highly crosslinked final film network.

Problems solved by technology

One disadvantage associated with conventional electrocoating compositions containing polyisocyanate crosslinking agents is that in order to prevent premature gelation of the electrocoating composition, the highly reactive isocyanate groups on the curing agent must be blocked, for example, with an alcohol.
Blocked polyisocyanates, however, require high temperatures to unblock and begin the curing reaction.
This curing mechanism also releases a substantial amount of volatile blocking agents during curing, which generates unwanted film weight losses, also known as bake-off loss, and makes it necessary to purify the exhaust air discharged from the oven and constitutes an unwanted loss in resin solids.
In addition, the volatile blocking agents released during cure can cause other deleterious effects on various coating properties, e.g., producing a rough film surface.
Such blocking agents, however, can produce undesirable film defects.
Cyclic carbonates, however, are oftentimes difficult to incorporate into the principal emulsion.

Method used

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  • Cathodic electrocoating composition containing morpholine dione blocked polyisocyanate crosslinking agent
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  • Cathodic electrocoating composition containing morpholine dione blocked polyisocyanate crosslinking agent

Examples

Experimental program
Comparison scheme
Effect test

example 1

Preparation of 4(2-hydroxyethyl)morpholine-2,3-dione monomer

[0062] A 4(2-hydroxyethyl)morpholine-2,3-dione was prepared by charging 125 g diethyl oxalate and 80 g n-butanol into a suitable reaction vessel and heated to 22° C. under nitrogen blanket. A mixture of 89.9 g diethanolamine and 72 g n-butanol was slowly charged into the reaction vessel while maintaining the reaction mixture below 50° C. After stirring for 30 minutes, the reaction mixture was refluxed for one hour and then allowed to stand at room temperature for 16 hours. The product was collected by filtration and the solid was washed twice with diethyl ether and dried under nitrogen to give 100 g (73.4% yield) of white crystals with 83.3° C.-84.4° C. melting point. IR (Nujol mull) 1759 (ester carbonyl), 1684 (amide carbonyl) cm−1. 1H NMR (500 MHz, acetone-d6) δ 4.592 (approx. triplet, 2H, J=5.0 Hz, ring CH2O), 3.903 (approx. triplet, 2H, J=5.0 Hz, ring CH2N), 3.767 (t, 2H, J=5.5 Hz, CH2OH), 3.597 (t, 2H, J=5.5 Hz, chain...

example 2

Preparation of 4(2-hydroxyethyl)morpholine-2,3-dione Monomer at Lower Temperature and Higher Yield

[0063] A 4(2-hydroxyethyl)morpholine-2,3-dione was prepared at low temperatures by the following procedure. Into a five-necked 22 liter round bottomed flask equipped with a reflux condenser, nitrogen bubbler, addition funnel, thermocouple well, and mechanical stirrer was charged 3000 g (20.53 mol) of diethyl oxalate and 2000 ml of isopropyl alcohol. The solution was cooled to 0 to 5° C. using a cold bath of ice and methanol. A solution of 2160 g (20.53 mol) of diethanolamine dissolved in 2000 ml of isopropyl alcohol was added through the addition funnel during a period of 5 to 6 hours. The reaction is exothermic. After addition was complete, the mixture was allowed to stand at room temperature overnight. The product is collected by filtration. After air drying, 2923 g (89.5% yield) of white crystals were obtained with identical spectral properties to the compound prepared in Example 1....

example 3

Preparation of Blocked Polyisocyanate Resin with 4(2-hydroxyethyl) morpholine-2,3-dione and diethylene glycol monobutyl ether

[0064] A new blocked polyisocyanate crosslinking resin solution was prepared by charging 338 parts Mondur® MR (methylene diphenyl diisocyanate, from Bayer Corp.), 113 parts methyl isobutyl ketone and 0.07 parts dibutyl tin dilaurate into a suitable reaction vessel and heated to 37° C. under a dry nitrogen blanket. 269 parts diethylene glycol monobutyl ether was slowly charged into the reaction vessel while maintaining the reaction mixture below 93° C. 142 parts 4(2-hydroxyethyl)morpholine-2,3-dione (prepared in Example 1) was then charged into the reaction vessel and kept the reaction temperature below 93° C . The resulting mixture was held at 110° C. until all of the isocyanate was reacted as indicated by infrared scan. 5 parts butanol and 133 parts methyl isobutyl ketone were added to the reaction mixture. The resulting resin solution had a nonvolatile cont...

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Abstract

An improved aqueous cathodic electrocoating composition having a binder of an epoxy-amine adduct and a polyisocyanate crosslinking agent; wherein the improvement is the use of a polyisocyanate crosslinking agent having at least one crosslinkable morpholine dione group per molecule. Electrodeposited finishes are formed that have reduced volatile emissions and film weight loss when heated to cure.

Description

BACKGROUND OF THE INVENTION [0001] This invention is directed to a cathodic electrocoating composition and in particular to a cathodic electrocoating composition containing a morpholine dione crosslinking agent which significantly reduces volatile emissions and bake-off loss that occur from the coating film during curing. [0002] The coating of electrically conductive substrates by an electrodeposition process, also called an electrocoating process, is a well known and important industrial process. Electrodeposition of primers on metal automotive substrates is widely used in the automotive industry. In this process, a conductive article, such as an autobody or an auto part, is immersed in a bath of a coating composition of an aqueous emulsion of film forming polymer and the article acts as an electrode in the electrodeposition process. An electric current is passed between the article and a counter-electrode in electrical contact with the coating composition until a coating of a desi...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): C08G18/28C08G18/58C08G18/80C09D5/44C09D163/00C09D175/04C09D201/02
CPCC08G18/2875C09D5/4453C08G18/807C08G18/581
Inventor ANDERSON, ALBERT G.GAM, ALLISA
Owner ANDERSON ALBERT G
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