CA2049824A1

CA2049824A1 - Process for producing binders for cathodic deposition coatings, and the use thereof

Info

Publication number: CA2049824A1
Application number: CA002049824A
Authority: CA
Inventors: Helmut Honig; Willibald Paar
Original assignee: Individual
Current assignee: Allnex Austria GmbH
Priority date: 1990-08-24
Filing date: 1991-08-26
Publication date: 1992-02-25
Also published as: KR930004414A; JPH04279680A; EP0473031A3; ATE117347T1; DE59104307D1; EP0473031A2; EP0473031B1; ES2067814T3; DE4026859A1

Abstract

ABSTRACT OF DISCLOSURE
Water-dilutable binders for cathodic deposition electro-dip coatings are disclosed wherein 5 to 60 mol percent of the epoxide groups of a resin-type compound having at least two 1,2-epoxide groups per molecule are reacted with a polyoxyalkylenepolyamine having secondary amino groups. The binders produced are especially suitable for the formulation of electro-dip coatings, whereby films of higher layer thickness can be obtained even under normal deposition conditions.

Description

-~` 2s95/ui3s70 ~ l324 FIELD OF INVENTION_ This invention relates tc binders for cathodic deposition electro-dip coatings. More particularly, the invention relates to binders for cathodic deposition electro-dip coatings which contain reaction products of polyoxyalkylenepolyamines having secondary amino groups with epoxide resins. The binders produced according to the invention are especially suitable for the formulation of electro-dip coatings, whereby films of higher layer thickness can be obtained under normal deposition condi-tions.

BACKGROUND OF INVENTION
In EP 0,070,550 Al, reaction products of poly-epoxide compounds with primary polyoxyalkylenepolyamines are described. Coatings formulated with such binders are reported to give cathodically applicable films havinq en-hanced cratering resistance. However, because of the poly-functionality o~ the reactant raw materials employed, the binders cannot be reproducibly prepared and tend to gelling during synthesis.
EP 0,193,635 81 relates to components for cationic electro-dip coatings based on reaction products of polyoxy-alkylenepolyamines with monoepoxides. These products have , . . ..

. .
. . : . :

- Z595/Us3570 2~ 824 pronounced hydrophilic properties and, in the hot damp test and/or salt spray tast, demonstrate a deterioration in the adhesion of the baked films on non-pretreated steel sheet.
It has now been found that cathodic deposition coatings which contain, as binders, polyepoxide resins which are modified partially with polyoxyalkylenepolyamines having secondary amino groups will provide films of higher layer thickness under normal deposition conditions. Moreover, the coating bath containing the binders have good stability and good deposition characteristics.

SUMMARY OF INVENTION
Accordingly, the present invention relates to a process for producing binders, which are based on amine-modified epoxide resins and are water-dilutable after com-plete or partial neutralization with inorganic and/or or-ganic acids. The process is characterized in that 5 to 60 mol percent, preferably 10 to 35 mol percent, of the epoxide groups of a resin-type compound having at least two 1,2-epoxide groups per molecule are reacted with a polyoxyalky-lenepolyamine having secondary amino groups and the remain-der of the epoxide groups is fully reacted at 60 to 120C
with amines and/or carboxylic acids and/or substituted phenols, the quantity of the basic components being selected in order that the end product has a theoretical amine number , ~

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-. Z595/Us3570 Z04~324 of at least 30 mg KOH/g, and preferably from 50 to 110 mg KOH/g.
The invention also embraces the binders produced and their use in the formulation of electro-dip coatings, with which films of higher layer thickness can be obtained even under normal deposition conditions.
The process of the invention provides products which can be used as a binder in combination with curing components or as the sole binder in the case of appropriate modification with curable groups, such as half-blocked diisocyanates, and also, due to their good pigment wetting, for the production of pigment pastes for later blending with other cathodic deposition electro-dip coating binders. The process is straight forward and economical.
The resin-type compounds used, having at least two 1,2-epoxide groups, which are reacted according to the invention with polyoxyalXylenepolyamines having secondary amino groups, are the commercially available epoxide resins which are obtained by reacting bisphenols, novolaks, glycols and the like with epichlorohydrin or methylepichlorohydrin.
A wide range of these products is commercially available.
The products based on bisphenol A or novolaks, which have an epoxide e~livalent weight between 170 and 1000, are par-ticularly preferred.

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The modifiers having curable groups which can be used according to the invention are obtained by reacting polyoxyalkylenepolyols with primary amines, for example, as disclosed in EP 0,369,752 A2. A large number of the other amines, carboxylic acids or substituted phenols, referred to as "residual modifiers'l in the examples, which are reacted with the epoxide groups remaining free in the epoxide resins after reaction with the polyoxalkylenepolyamines having secondary amine groups, are known to those skilled in the art.
The binders are produced by reacting the reactant components at 60 - 120C until free epoxide groups are no longer detectable.

PRESENTLY PREFERRED EMBODIMENTS
The examples which follow are to illustrate the invention, without re~triction of its scope. All the data in parts or percent relate to weight units, unless otherwise stated. All the data in the tables relate to 100 percent solids.
The following abbreviations are used in the exam-ples:

AM 1 secondary amine, prepared as follows: To a 200 ml high pressure autoclave, 5 g of Ni-Zn catalyst containing 50% by weight of Ni and 50~ by weight of ZnO, 100 g of polyoxypropylene triol obtained by addition polymeriæation of propylane oxide to 2595/Us357û
~ 4~24 glycerol and has a hydroxyl value of 33.4 mg KOH/g and an average molecular weight of 5040 (herein-after abbreviated as Polyol-P) and 15.2 g o~ iso-propylamine were successively charged. Nitrogen substitution was carried out 5 times at the pres-sure o~ 10 kg/cm2G and then hydrogen was charged at the initial pressure o~ 50 kg/cm2G. The mix-ture was heated to 220C with stirring and reacted `
for 8 hours. The pressure rose to 73 kg/cm2G.
After completing the reaction, the catalyst was removed by filtration. The filtrate was dried under reduced pressure to give polyoxyalkylene polyamine having secondary amino groups at the end of the polymer chain.
The product had a total amine value of 27.5mg KOH/g, primary amine value of 1.20 mg KOH/g, secondary amine value of 26.1 mg KOH/g, tertiary amine value of 0.09 mg KOH/g, and a residual hy-droxyl value oE 4.30 mg KOH/g. Thi~ preparation corresponds to Example 1 of EP 0,369,752 A2.
AM 2 secondary amine, prepared according to the pro-cedure of AM 1, except that polytetramethylene-ether glycol obtained by ring-opening polymeri-zation of tetrahydrofuran (hereinafter abbreviated as Polyol-R) was used in place of Polyal-P in AM
1. Polyol-R had a hydroxyl value of 112 mg KOH/g and an average molecular weight of 1000. The reaction pressure rose to 70 kg/cm2G. This prep aration corresponds to Example 6 of EP 0,369,752 ~2.
AM 3 secondary amine, prepared accordinq to the pro-cedure of AM 1, except that benzylamine was used in place of isopropylamine in ~M 1. The reaction ..

-` ZS'~S~US3570 pressure rose to 64 kg/cm2G, equivalent weight:
about 2240. This preparation corresponds to Example 9 of EP 0,369,752 A2.
AM 4 secondary amine Novamin~ N 10, which is an alky-lated polyetherdiamine, amine number: about 280 mg KOH/g; equivalent weight: about 200.
AM 5 secondary amine Novamin~ N 20, which is a polyoxy-propylenediamine: amine number: about 183 mg KOH/g: equivalent weight: about 300.
DEA diethylamine DEAPA 3-diethylamino-1-propylamine EPH I epoxide resin based on bisphenol A and epichloro-hydrin having an epoxide equivalent of About 200 EPH II epoxide resin based on bisphenol A and epichloro-hydrin having an epoxide equivalent of about 500 MP methoxypropanol EP ethoxypropanol NPH nonylphenol TDI toluylene diisocyanate (commercial isomer mixture with 80% of 2,4-TDI) SPH reaction product of one mol of phenol with 2 mol of DEAPA and 2 mol of formaldehyde and also w.ith 2 mol of a TDI half-blocked with 2-ethylhexanol (MW = 986) H 1 reaction product of one mol of trimethylolpropane with 3 mol of a TDI half-blocked with MP (urethane crosslinking agent~

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`2595/Us3570 2()g9~2~ ' H 2 transesterification curing agent which is the reaction product of 3 mol of dimethyl malonate and .
1 mol of trimethylolpropane (H 1 and H 2 are used if the initial binders do not have self-crosslinking properties) Sn tin catalyst (dibutyltin dilaurate), calculated as metal Pb lead catalyst (lead octoate), calculated as metal :

The starting materials for the binders produced according to the invention are summarized in Table 1.
In a suitable reaction vessel, all the components are mixed at 60C. The temperature is slowly raised to 80C
and, if necessary, up to 120C and held until free epoxide groups are no longer detectable.
Table 1 is as follows:

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4g8 Z ~~ a~ ~1 ~ ~D ~O O
N ~t) CO 10 t` ~ N ~o 3~

~ P. a z~ 5: ~ $ u~ ~ ei E~ r~ ~
.,1 _ _ __ ~ _ ~ _ ~ _ ~ ~ ~
~ ~ o c~ o In u~ ~ o o o ~ o o O N O~ N ~ ~ f~l ~ q~ ~ r~l ~ -- -- -- -- -- -- -- -- -- -- ~ -- --~,~ ~: O ~Or~ o ~ a~ u~ ~o o ~ o ~o u~ ~ ~ r~t~ ~ ~o ~o o~ ~r ~ ~ ~ ~
K :1 ~ ,1~ ,~ N a~ ~1 N N -~ ~1 ~1 N ~ rl N ~r m ~1 ~ E~~ ~ ~ ~ ~ ~ ~ ~
m ~ ~ ,~ ~ _ ,_ ~ _ ,~
tJ~ N O O co O O oo O
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~ O N N O O O . O
U~ ~ oO ~ ~ ~ ~O O ~ O
::~ O ~1 N U~ If ~ 'r U~ U~
O~

H H H H H H
H H H H H H H H H H
X ~ ~ :1: ~ 5 W ~ ~ ~ ~ W
_ a~ ~ o o u~ In o o o o o o ~ ~ ~1 ~ ~P 1 ~i ~ ~r ~r ~r ~o X _ _ _ ~, ~_ _ _ _ _ ~_ `._ O ~
O O Cl O O O O O O O
~J O O O. U~ O O O O O O
:~ N O G~ `t O ON

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X

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The binders produced according to Table 1 are mixed in the weight ratios indicated in Table 2 with the crosslinking agent and the catalyst. The quantity of the neutralizing agent Eor producing a stable aqueous cle~rcoat (in millimol of formic acid/100 g of solid resin) is indi-cated in the last column of the table.
Table 2 is as follows:

Table 2 Binder Parts of Solid Matter Catalyst NeutralizationCombination (BK) Binder Cross-(from linking Example)* agent 1 100(4)/ -- 1.0 Sn 40 . .
2 70(2)/30 H 1 1~0 Sn 35 __ . . ... ,, _ :
3 75(3)/25 H 2 1.2 Pb 40 4 70 (1)/ 30 H 1 0.8 Sn 35 100(5)/ 20 H 1 1.0 Sn 30 -6 75(6)/25 H 1 0.8 Sn 35 7 80(7)/~0 H 1 1.0 Sn 40 _ _ _ .
8 70(~)/30 H 1 0.8 Sn 35 .
* The data relate to the percentage content and to the solvent containing the binder.

' 2595/115357~
9~324 For producing pigmented coatings, the binder combinations 1 - 5 are processed in accordance with the following formulation:

100.0 parts of solid resin 0.5 part of carbon black pigment 3.3 parts of basic lead silicate pigment 35.5 parts of titanium dioxide 5.0 parts of monoethylene glycol monohexyl ether The pigmented coatings are tested by electro-deposition on non-phosphated, degreased steel sheet which is connected as the cathode. The films are then baked for 25 minutes at 180C, and they are tested for 360 hours for their resistance in the salt spray test according to ASTM.
Table 3 summarizes the respective data. A cath-odic deposition electro-dip coating according to Example 1 of EP 0,193,685 Bl was used as a comparison example (V).
Comparison example (V) is a resin mixture prepared by blending the following ingredients:
Inaredients Parts by Weight Pigment Paste L 210 Deionized water 1474 Cationic Resin A 1316 The cationic electrodeposition bath using thi~ mixture had a pH of 6.6 and a resistivity at 20C of 660 ohm cm 1.
Cationic Resin A was prepared from the following mixture of ingradients:

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2sss/us3s70 zq~382~

In~redientsParts by WeiqhtSolids EPON 8291 702.2 702.2 PCP-02002 263.4 263.4 Xylene 61.6 Bisphenol A 197.8 197.8 Benzyldimethylamine 3.8 Capped isocyanate crosslinker3 891 629.1 Diketimine derived from diethylenetriamine and methyl isobutyl ketone (73% solids in methyl isobutyl ketone)75.3 54.7 N-methylethanolamine 59.1 59.1 Phenoxypropanol 126.9 Acetic acid 29.5 Cationic surfactant429.3 Deionized water 2553.1 1 Epoxy resin made from reacting epichlorohydrin and bisphenol A having an epoxy equivalent of 188 commercially available from Shell Chemical Company.
2 Polycaprolactone diol available from Union Carbide Corporation.
3 Polyurethane crosslinker formed from half-capping toluene diisocyanate (80/20 2,4-/2,6-isomer mixture) with 2-ethylhexanol and reacting this product with trimethylol-propane in a 3:1 molar ratio. The crosslinker is present as a solution in 2-ethoxyethanol.
4Cationic surfactant prepared by blending 120 parts of an alkyl imidazoline commercially available from Geigy Industrial Chemicals as GEIGY AMINE C) 120 parts by weight of an acetylenic alcohol commercially available from Air Products and Chemicals as SURFYNOL 104, 120 parts of 2-butoxyethanol and 221 parts by weight of deioni~ed water and 19 parts of glacial acetic acid.

2595/Us357~
2al~9~ 4 The EPON 829, PCP-0200 and xylene were charged to a reaction vessel and heated under a nitrogen atmosphere to 210C. The reaction was held at reflux for about ~ hour to remove water. The reaction mixture was cooled to 150C and the bisphenol A and 1.6 parts of the benzyldimethylamine (catalyst) added. The reaction mixture was heated to 150-190C and held at this temperature for about 1~ hours and then cooled to 130C. The remaining portion of the benzyl-dimethylamine catalyst was added and the reaction mixture held at 130C for 2~ hours until a reduced Gardner-Holdt viscosity (50 percent resin solids solution in 2-ethoxy-ethanol) of P was obtained.
The polyurethane crosslinker, the diketimine derivative and the N-methylethanolamine were then added and the temperature of the reaction mixture brought to 110C and held at this temperature for 1 hour.
The phenoxypropanol was added and the reaction mixture was dispersed in water by adding the reaction mix-ture to a mixture of the acetic acld, deionized water and the cationic surfactant.
Pigment Paste L was prepared from the following mixture of ingredients:

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- 2595/Us3570 ZCl~l~3824 Ingredients Parts by Weiqht Titanium dioxide 44.42 Lead silicate 2.9 Carbon black 0.37 Pigment Grinding Vehicle of Example J 18.5 Deionized water 27.51 Catalyst Paste as described above 6.3 The above ingredients were ground in a mill to a Hegman No. 7 grind.
Table 3 is as follows:
Table 3 Coatinq Layer Thickness ~ml) Salt Spray Test mm 1 38 1.5 3 43 2.5 4 33 1.5 6 34 2.5 8 32 1.5 V 24 6.5 1) Maximum obtainable layer thickness at 32C bath temperature and 135 seconds.
2) Disbonding after a test period of 360 hours.

As will be apparent to one skilled in the art, various modi~ications can be made within the scope of the aforesaid description. Such modifications being within the ability of one skilled in the art form a part of the present invention and are embraced by the appended claims.

, . , .

Claims

1. Process for producing binders, which are based on amine-modified epoxide resins and are water-dilutable after complete or partial neutralization with an inorganic or organic acid, characterized in that from 5 to 60 mol percent of the epoxide groups of a resin-type compound having at least two 1,2-epoxide groups per molecule are reacted with a polyoxyalkylenepolyamine having secondary amino groups and the remainder of the epoxide groups is fully reacted at 60 to 120°C with an amine, a carboxylic acid, a substituted phenol, or mixtures thereof, the quan-tity of the basic components being selected such that the end product has a theoretical amine number of at least 30 mg KOH/g.

2. The process of claim 1, wherein from about 10 to 35 mol percent of the epoxide groups of the resin-type compound are reacted with said polyoxyalkylenepolyamine.

3. The process of claim 1, wherein said end product has a theoretical amine number of 50 to 110 mg KOH/g.

4. A cathodic deposition electro-dip bath for producing cathodic deposition electro-dip coatings contain-ing the binder made by the process of claim 1.

5. A cathodic deposition electro-dip bath for producing cathodic deposition electro-dip coatings contain-ing the binder made by the process of claim 2.

6. A cathodic deposition electro-dip bath for producing cathodic deposition electro-dip coatings contain-ing the binder made by the process of claim 3.

7. Binders, which are based on amine-modified epoxide resins and are water-dilutable after complete or partial neutralization with an inorganic or organic acid, wherein from 5 to 60 mol percent of the epoxide groups of a resin-type compound having at least two 1,2-epoxide groups per molecule are reacted with a polyoxyalkylenepolyamine having secondary amino groups and the remainder of the epoxide groups is fully reacted with an amine, a carboxylic acid, a substituted phenol, or mixtures thereof, the quan-tity of the basic components being selected such that said binder has a theoretical amine number of at least 30 mg KOH/g.

8. The binder of claim 7, wherein from about 10 to 35 mol percent of the epoxide groups of the resin-type compound are reacted with said polyoxyalkylenepolyamine.

9. The binder of claim 7, wherein said end prod-uct has a theoretical amine number of 50 to 110 mg KOH/g.

10. A cathodic deposition electro-dip bath for producing cathodic deposition electro-dip coatings contain-ing the binder of claim 7.

11. A cathodic deposition electro-dip bath for producing cathodic deposition electro-dip coatings contain-ing the binder of claim 8.

12. A cathodic deposition electro-dip bath for producing cathodic deposition electro-dip coatings contain-ing the binder of claim 9.