Stock material or miscellaneous articles – Composite – Of epoxy ether
Reexamination Certificate
2002-09-05
2004-07-13
Tucker, Philip (Department: 1712)
Stock material or miscellaneous articles
Composite
Of epoxy ether
C204S504000, C204S505000, C204S506000, C523S403000, C523S409000, C523S420000, C523S423000, C528S045000
Reexamination Certificate
active
06761973
ABSTRACT:
The present invention relates to a cationic resin composition, more specifically to a cationic resin composition which comprises a cationic resin and polyisocyanate blocked with a blocking agent containing a specific diol and which can form a coating film excellent in a corrosion resistance and a curing property and particularly to a cationically electrodepositable coating material.
A coating material comprising a resinous vehicle having a cationic group such as an amino group, an ammonium group, a phosphonium group and a sulfonium group or a neutralized cationic group thereof and blocked polyisocyanate which is a blocking agent has so far been available as a cationic resin composition comprising blocked polyisocyanate. To be typical, capable of being given is a cationically electrodepositable coating material comprising a resinous vehicle having a neutralized cationic group and blocked polyisocyanate.
In a cationically electrodepositable coating material, ether alcohol base compounds have so far been used as a blocked polyisocyanate compound in many cases in terms of a corrosion resistance of a coating film and a coating material stability. However, a coating film of a cationic coating material comprising polyisocyanate blocked with an ether alcohol base compound has the defects that it has a lot of a heat loss (a loss proportion in baking and curing a coating film) and that tar and soot are produced in large quantities in a drying oven of a coating line. Further, a curing property of a coating material at a low temperature has been desired in order to lower a baking temperature at a drying step in a coating line from a viewpoint of energy saving. In recent years, a cationic coating material comprising polyisocyanate blocked with an oxime base compound is used in many cases as a composition satisfying these requirements. However, a cationic coating material comprising polyisocyanate blocked with an oxime base compound as a blocking agent has problems on stability with the passage of time and a corrosion resistance of a coating film.
An object of the present invention is to provide a cationic resin composition which has a good coating material stability and corrosion resistance and which is excellent in a low heat loss and a curing property at a low temperature.
Intensive investigations made by the present inventors have resulted in finding that the object described above can be achieved by using polyisocyanate blocked with a specific blocking agent as a cross-linking agent for a cationic resin composition, and they have come to complete the present invention.
Thus, according to the present invention, provided is a cationic resin composition comprising:
(A) a cationic resin
and
(B) a blocked polyisocyanate obtained by reacting an active hydrogen-containing component comprising a diol (a) which has two hydroxyl groups having different reactivities from each other and which has a molecular weight of 76 to 150 and a carboxyl group-containing diol (b) having a molecular weight of 106 to 500 with a polyisocyanate compound (c).
Further, according to the present invention, provided is a cationically electrodepositable coating method characterized by using the cationic resin composition described above.
The present invention shall be explained below in further details.
The cationic resin composition of the present invention comprises the cationic resin (A) and the blocked polyisocyanate (B) obtained by reacting the active hydrogen-containing component comprising the specific diol components with the polyisocyanate compound as the essential components.
Cationic Resin (A)
In the resin composition of the present invention, the cationic resin (A) used as a resinous vehicle is a resin having a cationic group which can be ionized when dispersed in water to make the above resin water-soluble or water-dispersible and a functional group (for example, a hydroxyl group, a primary amino group and the like) which reacts with an isocyanato group. To be specific, included are, for example, resins having a cationic group such as an amino group, an ammonium salt group, a sulfonium salt group and a phosphonium salt group and a hydroxyl group. The resin kind of such cationic resin (A) includes, for example, resins of an epoxy base, an acryl base, a polybutadiene base, an alkyd base and a polyester base. In particular, an amine-added epoxy resin obtained by subjecting a polyepoxide compound to addition reaction with amine is suited as the cationic resin (A).
Capable of being given as the amine-added epoxy resin described above are, for example, (1) an adduct of a polyepoxide compound to primary mono- or polyamine, secondary mono- or polyamine or primary and secondary mixed polyamine (refer to, for example, U.S. Pat. No. 3,984,299); (2) an adduct of a polyepoxide compound to secondary mono- or polyamine having a primary amino group which is reduced to ketimine (refer to, for example, U.S. Pat. No. 4,017,438); and (3) a reaction product obtained by etherifying a polyepoxide compound with a hydroxy compound having a primary amino group which is reduced to ketimine (refer to, for example, Japanese Patent Application Laid-Open No. 43013/1984).
The polyepoxide compound used for producing the amine-added epoxy resin described above is a compound having 1.5 or more, preferably 2 or more epoxy groups on average in a molecule and is suitably a compound having a number average molecular weight falling in a range of usually at least 200, preferably 400 to 4000 and more preferably 800 to 2500 and an epoxy equivalent falling in a range of at least 160, preferably 180 to 2500 and more preferably 400 to 1500. In particular, preferred is a compound obtained by reacting a polyphenol compound with epichlorohydrin. Capable of being given as the polyphenol compound which can be used for forming the above polyepoxide compound are, for example, bis(4-hydroxyphenyl)-2,2-propane, 4,4′-dihydroxybenzophenone, bis(4-hydroxyphenyl)-1,1-ethane, bis(4-hydroxyphenyl)-1,1-isobutane, bis(4-hydroxy-tert-butyl-phenyl)-2,2-propane, bis(2-hydroxynaphthyl)methane, tetra(4-hydroxyphenyl)-1,1,2,2-ethane, 4,4′-dihydroxydiphenylsulfone, phenol novolak and cresol novolak.
The above polyepoxide compound may be those reacted partly with polyols, polyetherpolyols, polyesterpolyols, polyamideamines, polycarboxylic acids and polyisocyanate compounds. Further, it may be those which are graft-polymerized with caprolactones such as &egr;-caprolactone and acryl monomers.
Capable of being given as the primary mono- or polyamine, secondary mono- or polyamine or primary and secondary mixed polyamine used for producing the amine-added epoxy resin of (1) described above are, for example, mono- or di-alkylamines such as monomethylamine, dimethylamine, monoethylamine, diethylamine, monoisopropylamine, diisopropylamine, monobutylamine and dibutylamine; alkanolamines such as monoethanolamine, diethanolamine, mono(2-hydroxypropyl)amine and monomethylaminoethanol; and alkylenepolyamines such as ethylenediamine, propylenediamine, butylenediamine, hexamethylenediamine, diethylenetrimine and triethyleneteteramine.
Among the primary mono- or polyamines, secondary mono- or polyamines or primary and secondary mixed polyamines used for producing the amine-added epoxy resin of (1) described above, ketimine compounds obtained by reacting ketone compounds with compounds having a primary amino group (for example, monomethylamine, monomethanolamine, ethylenediamine and diethylenetriamine) can be given as the secondary mono- or polyamine having a primary amino group reduced to ketimine which is used for producing the amine-added epoxy resin of (2) described above.
Among the primary mono- or polyamines, secondary mono- or polyamines or primary and secondary mixed polyamines used for producing the amine-added epoxy resin of (1) described above, hydroxyl group-containing ketimine compounds obtained by reacting ketone compounds with compounds having a primary amino group and a hydroxyl group (for example, monoethanolamine, mono(2-hydroxypropyl)amine and the like) can be
Iijima Hideki
Ikejiri Souichi
Kamikado Koji
Nishiguchi Shigeo
Aylward D.
Kansai Paint Co. Ltd.
Tucker Philip
Wenderoth Lind & Ponack LLP
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