CA1291289C

CA1291289C - Process for producing water dilutable phosphoric acid modified binders for stoving enamels

Info

Publication number: CA1291289C
Application number: CA 545585
Authority: CA
Inventors: Lukas Klaus Behmel; Gert Dworak; Werner Staritzbichler
Original assignee: Vianova Resins AG
Current assignee: Allnex Austria GmbH
Priority date: 1986-09-01
Filing date: 1987-08-28
Publication date: 1991-10-22
Anticipated expiration: 2008-10-22
Also published as: JPS6368673A; ATA234986A; AT385764B; EP0259681A3; EP0259681B1; DE3772494D1; EP0259681A2; JPH07765B2

Abstract

ABSTRACT OF DISCLOSURE

Water dilutable phosphoric acid modified binders for stoving paints, particularly suited for the formulation of anti-corrosive single coats with excellent decorative properties and a process for their preparation are described.
A water insoluble film-forming polyhydroxy component, op-tionaliy containing phosphoric acid groups, is combined with a water-soluble component, the salt forming groups of which are, in part, phosphoric acid groups to provide the coating compositions.

Description

)3~

This invention relates to water-dilutable pho~-phoric acid modified binders for stoving enamels particular-ly useful in the formulation of anti-corrosive single coats with excellent decorative properties and to a process for producing the binders. More particularly, the binders of the invention are water-dilutable upon their partial or total salt formation with inorganic or organic bases to pro-vide a continuous reduction of the binder viscosity on dilu-tion with water. This property affords favorable applica~
tional properties of the stoving enamels formulated with these binders.

AT-PS 328 587, corresponding to U.S. Patent No.
3,960,789, describes binder systems which overcome the ano-malic changes in viscosity on dilution with water through the combination of a polymer salt solution with a water insoluble film-forming polyhydroxy compound. The stoving paints formulated with such binder systems have excellent application properties due to the viscosity reduction upon dilution to provide coatings with flawless decorative fea-tures. However, corrosion protection is not achieved to theincreasing degree that paint consumers now desireO

2049/uS2930 æ~3 ~ ome improvement in corrosion protection can be achieved through the use of hardening catalysts containing phosphoric acid groups. However, even with the addition of minor amounts of low molecular phosphoric acid compounds or s free phosphoric acid, the surfaces of the film, particularly the radiance, deteriorates.

The possibility of introducing phosphoric acid groups into binder molecules of products which are processed with organic solvents is recognized in the literature. For example, AT~PS 356 782, corresponding to EU-PS 0 012 205, discloses the introduction of phosphoric acid groups into a binder for stoving enamels, whereby a hydroxy group contain-ing phosphoric acid compound is reacted with an amino resin.
AT-PS 379 402, corresponding to U.S. Patent No. 4,450,257, sets forth a process for the substantially complete intro-duction of phosphoric acid into polyester resins. The poly-condensation is carried out in solution.

It has now been found that it is possible to pro-duce water-dilutable binders for the formulation of paints which provide coatings which combine anti-corrosive proper-ties with decorative features, if a film-forming polyhydroxy compound is combined with a water-soluble component, the salt-forming groups of which, in part, are phosphoric acid groups. Optionally, the film-forming polyhydroxy compound can contain phosphoric acid groups. Surprisingly, it has been found that with relatively high portions of phosphorous in the water-soluble component obtained according to U.S.
Patent No. 4,450,257, combinations with excellent compati-bility are obtained. The phosphoric acid group containing products producsd according to the present invention, in comparison to analogous products containing carboxy groups only, show improved stability on storage at elevated temper-ature. Furthermore, the phosphoric acid groups catalyze the crosslinking reaction with the crosslinking components of the amino resin type.

The present invention is, therefore, concerned with the production of water-dilutable phosphoric acid modified binders for crosslinking stoving paints, based on polyester resins, characterized in that -(A) 15 to 80% by weight, preferably 35 to 65% by weight, of a water-insoluble film-forming poly-hydroxy compound with an acid value of below about 10 mg KOH/g and a hydroxyl value of from about 50 to 650 mg KOH/g, preferably 80 to 400 mg KOH/g, are mixed with . ~ ... ...

` 2049/US2930 (B) 85 to 20~ by weight, preferably 65 to 35% by weight, of a polyester component, rendered water-soluble through at least partial neutralization of the present acid functional groups, with an acid value of 20 to 150 mg ~OH/g, preferably 35 to 120 mg KOH/g, containing at least 0.1 mole, preferably 0.2 to 2.0 moles, of phosphorous per 1000 g of com-ponent in the form of ester-like linked phosphoric acids, the molar portion of phosphorous not ex-tractable with water in unneutralized state being at least 50%, preferably at least 70%, and/or the conversion (p~ on the esterification of all acid groups being in excess of 50%, preferably in excess of 70%.

Preferably after partial condensation of the components and the addition of a crosslinking component, the thus obtained resin combination is rendered water-dilutable through par-tia] neutralization of the acid functional groups.

The invention is further concerned with a process for preparing the binders and to the use of the binders obtained from components tA) and tB) in combination with a crosslinking component in the formulation of stoving paints.

.. ... . ..
. : , ... ~............. .

20~9/US2930 Suitable crosslinking components are the amino resins, phe-nol resins, blocked polyisocyanates, or epoxy resins.

Component (A) used according to the present inven-tion is a water-insoluble film-forming polyhydroxy compound with an acid value of below 10 mg KOH/g and a hydroxyl value of 50 to 650 mg KOH/g, preferably 80 to 400 mg KOH/g. Com-ponent (A) is, therefore, a polycondensation product ob-tained from polyols, polycarboxylic acids and, optionally, monocarboxylic acids or diisocyanates in accordance with known procedures. Raw materials and methods of production are disclosed, for example, in "Makromolekule, n by Elias, Edition Huthig & Wepf, Basel-Heidelberg, 1971. Optionally, componen' (A) may contain phosphoric acid units. In such case, the phosphoric acid units should be chemically linked.
Furthermore, such component must not be soluble in water, even after addition of bases.

Component (B), functioning as a macromolecular emulsifier in the binder combinations of the invention, af-ter crosslinking, is an integrating ingredient of the paint film. It is soluble in water through partial neutralization of its acid groups according to an acid value of 20 to 150, preferably 35 to 120 mg KOH/g.

"Water-soluble" in the sense of the present inven-tion means that the binders or binder combinations are ren-dered water-dilutable through salt formation of the acid groups of the resin with bases. The molecular disperse systems are either clear in water, or opaque or turbid in water.

The acid functional groups are, in part, phosphoric acid groups, component (B) having a portion of ester-like linked phosphoric acid groups corresponding to at least 0.1 mole, preferably 0~2 to 2.0 moles, of phosphorous per 1000 g of component. The phosphoric acids have to be incorporated into the molecule composite in order that the molar portion not extractable with water in the unneutralized state is at least 50~ and preferably at least 70~, and/or the conversion (p) at the esterification of all acid groups is over 50%, preferably over 70%.

The batches are formulated according to the same general principles for the preparation of phosphoric acid-free polyesters as are known in the art such as in "Makro-molekule" by Elias noted above. Preferably they are pre-pared through polyesterification of the raw materials used in polyester production, such as polyols, polycarboxylic ~049/US2930 ~ 9~

acids and, optionally, monocarboxyllc acids, in the presence of phosphoric acid esters and/or phosphoric acids.

It is essential that the phosphoric acids are che-mically linked as part of the condensate, since low molecu-lar water-soluble phosphoric acid compounds do not have an emulsifying capacity and cause problems in pigmented stoving paints, such as loss of radiance and flexibility. Thus, the resins are preferably produced according to the m~thod dis-closed in U.S. Paten~ No~ 4,450,257 which provides a chemi-cal linking of the phosphoric acids into the polyesterresins.

Polyphosphoric acids are preferred for the intro-duction of phosphoric acid groups. Acids having the general formula Hn+2PnO3n+l with 3 or more phosphorous atoms in the molecule and P-O-P linkages are preferred. Normally, these acids are contained in technical blends with a P4Olo-content of between 70 and 90%. For reasons of compatibility, the available blends of mono- and diesters are preferred, such as are obtained through the reaction of polyphosphoric acid (84% P2Os) or phosphor pentoxide with mono- or polyvalent alcohols. Such ester blends can contain portions of free phosphoric acids. Ester blends of this type may also be obtained in the production of component (B) in situ through alcoholysis of polyphosphoric acids.

The components are combined through mixing in the ratios as above set forthO Preferably, however, components (A) and (B) are subjected to a partial condensation in the unneutralized or neutralized state. Water-dilutability, as is evident, upon neutralization of the combination must not be substantially reduced.

In order to render the resins water-soluble as salts, the acid groups are partially neutralized with inor-ganic or organic bases. Preferably organic nitrogen bases are used such as the secondary or tertiary aliphatic amines o~ alkanol amines. Suitable examples are triethylamine, diethylamine N,N-dimethylethanolamine, diethanolamine, and the like.

In the formulation of stoving paints, organic sol-vents may be coemployed. However, the level should be kept as low as possible. The preferred solvents are alcohols and glycolmono- or glycoldiethers.

Crosslinking of the coatin~ compositions prepared according to the present invention is carried out at an ele-_g_ 20~9/US2930 3 ~

vated temperature in the presence of the crosslinking com-ponents of the type conventionally used for stoving paints.
It is advantageous for the crosslinking agents to have an at least limited tolerance to water to enable a reduced portion of auxiliary solvents. Suitable crosslinking agents are the available amino resins, i.e., condensation products of for-maldehyde with urea, melamine, benzoguanamine, and the like, in most cases etherified with alcohols. Also! phenol-aldehyde condensates, blocked polyisocyanates, or epoxy resins can be used. The criteria for the selection of suit-able products are recognized by one skilled in the art.

As a result of their improved corrosion resistance in comparison to the known products, the products of the present invention are particularly suited for industrial single coats, affording excellent decorative properties such as radiance, flow-out, weather resistance, and high flexi-bility. It is evident that primers, fillers, and finishes can be formulated with the products of the invention.

The coating compositions can be applied as unpig-mented clear varnish or as a pigmented paint. The selectionof pigments, extenders, additives, and auxiliary solvents i5 conventional and needs no further explanation.

~ 3~ 3 The following examples illustrate the invention without limiting its scope. Parts and percentages refer to weight unless otherwise stated.

1. Preparation of the Water-Insoluble Polyhydroxy Component (PH-Components) PH-Component A and Bs These components are prepared in a conventional resin reactor such as disclosed in Winnacker-KUchler, Chem-ische Technologie, Edition, C. Hansert Municht 1972, using toluol as an entraining agent in an azeotropic distillation.
.

PH-Component A B
Batch (parts) Hexanediol-1,6............................. 37 Cyclohexanedimethanol.................... 14.5 Pentaerythritol................... ~. 4.5 136 Tall oil fatty acids........................ - 168 Dehydrated castor oil atty acids. 5.5 Isononanoic acid.......................... 1.0 32 Isophthalic acid......................... 12.5 126 Trimellitic acid anhydride............... 25.5 Reaction Temperature, C + 5C.............. 205 230 Acid Value mg KOH/g........................... 4 4 Intrinsic Viscosity~ ml/g, DMF/20C. 10.3 10.3 Efflux Time DIN 53211, 50% in Butylglycol, Seconds....................... 90 100 Hydroxyl Value DIN 53240, mg KOH/g.......... 219 223 3~

2. Preparation of Phosphoric Acid Group Containing Pol~ester Components The phosphoric acid polyesters (PP-Components) used according to the present invention are prepared in a resin reactor as described under Preparation 1 according to the following:

PP-Component 1:
11 parts trimethylol propane (TMP), 60 parts neo-pentylglycol (NPG), 10 parts adipic a,c~d anhydride (ADI) and A ~1y~Pr A lo 48 parts tetrahydrophthalic acid~(THPSA) are melted at 120 to 140C and blended with 18 parts phosphoric acid (PS 84) (84% P4Olo-content). The temperature is raised to 200C and the batch is esterified with azeotropic distillation to an acid value of 100 mg KOH/g and an intrinsic viscosity of 9.2 ml/g. When the final values are attained, the batch is diluted to a solids content of 85% with diethylene-glycoldi-methylether (DGDM).

Cp,m/Cp,total = 71% (not extractable portion) p (polymerization conversion) = 83%

PP-Com onents 2 - 5:
p Analogous to PP-l, PP-components are prepared ac-cording to the following:

_ PP 2 3 4 5 PC(3) Batch, Parts TMP...... ,...... 11 11 11 35 40 NPG............. 60 71 59 62 38 ADI............. 10 10 13 -- 10 CON 50(1)....... ~ 50 -~
THPSA~ o 36 72 84 -- 113 PSA(2).......... -- -- - 109 ~~
PS 84........... 18 13.5 3 9 --Phosphoric acid MOL/Kg 1.80 0.99 0.22 0.43 --Acid Value mg KOH/g..... 87.3 72.2 85.6 83 99~3 Intrinsic Viscosity ml/g........ O................ 9.2 7.2 8.0 4.6 7.4 Cp,m/Cp,total (%)....... 74 67 52 36 --p,%... ~..... ....,............ 85 87 83 80 79 _ (1) technical conjugated linoleic acid (2) o-Phthalic acid anhydride

(3) Polycarboxy component (comparison example) Examples 1-5 Of The Invention The components are combined according to the follow-ing table:

Example 1 2 3 4 5 VB(1) Batch (parts resin solids) PP~ o~ -- 88 -~
PP-2......... -- -- 50 -- -- --PP-3......... 89 -- -- --PP-4......... -- - -- 50 -~ --PP-5......... ~ 40 --PC........... ---- ---- ---- ---- ---- 5o _________.________________________________.____________ ___ PH-A............... 89 88 50 50 -- 50 PH-B .............. -- -- -- -- 60 --__________________________________________ _______________ DGDM......... .... 15 15 9 9 7 --Condensation(l) Temperature~C120 110- 110- 110- 110- 110-_____________ _________-__________________________________ Intrinsic Viscosity ml/g DMF/20C.............. 12.3 15 15 8 7.5 11.0 _____._____________________________________________________ Dilution and Neutralization Temperature,C.......... 85 85 85 85 85 85 _____________________________________________________ Water, parts........... 391 300 169 - -- 108 Solvent, parts.... -- -- -- 39BUGL 41BUGL 14DGMD
____________________________________.__,_______________~___ Dimethylethanol-amine, Parts...... 10 14 8.4 _ 5 5 _5.6 _ 6 Solids Content,%.............._30 35 _ 35 65 _ 65 43 pH-value(10~).................8.0 _8.1 8.2 8.2 8.1 8.6 DGMD... ..Diethyleneglycoldimethylether BUGL... ..Monethyleneglycolmonobutylether VB~l).. ..Comparison Example (l).... c. The condensation is carried to the point when a 5% solution of the reaction blend is soluble in water to provide a clear or opaque solution, after neutralization with dimethylethanolamine.

A white enamel is selected as an example of a typi-cal and exemplary use of the synthetic resins o the inven-tion as binders for anti-corrosive single coats and finishes.

Paint Example A (Using a Resin of the Present Invention) 128 parts resin of Example 2 / 35%, 33 parts deion-ized water, 100 parts titanium dioxide pigment, Rutile type, and a sufficient quantity of glass beads or quartz sand, as is conven~ional, are milled in a pearl mill for 20 minutes.
The disperse paste is mixed with 114 parts resin of Example 2 / 35%, lS parts of a melamine resin, 98-100%, hexamethoxy-methylmelamine type, 6 parts water, 1 part of a leveling and A anti-cratering aid, such as Additol XL 204, and 3 parts diethanolamine/ and adjusted to a solids content of about 50~. Efflux time according to DIN 53 211/20C is about 100 seconds. The pH-value (glass electrode) is about 8.5. For air spray gun application, the paint is diluted with deion-ized water to provide an efflux time of about 30 seconds, the resulting solids content being about 48%.

Paint Example B (Comearison Examele) As described in Paint Example A, a pearl mill grinding paste is prepared from 104.2 parts resin, 43%, as set forth in comparison example VB above, 52.5 parts deion-~ T~a~-~k ,. ~ , . ~ , ized water and 100 parts titanium dioxide, Rutile type. The paste is dispersed for 20 minutes. The dispersed paste i9 mixed with 92.8 parts resin, 43~, according to comparison example VB, 15 parts of hexamethoxymethylmelamine, 98-100%, 31.2 parts water, 1 part of a leveling and an~i-cratering aid, such as Additol XL 204, and 3 parts diethanolamine to give a paint with a solids content of about 50%. Efflux time according to DIN 53 211/20C is about 30 seconds. The pH-value (glass electrode) is about 8.9.

The paint properties are listed in the following table:

T A B L E
Important Paint Film Propertiesl) Paint Example A Paint Example B
15Stoving Conditions Stoving Conditions 20min.140C/20min.160C 20min.140C/20min.160C

Pendulum hardness K~nig (seconds) 130 160 10 - 20 150 Erichsen Indentation (mm) 8 ~ 9 6 - 7 9 6 - 7 Salt spray2) ASTM B 117/643 - 6 2 - 4 >20 8 - 12 mm-total peel-off 1) dry film thickness 30 ~m 252) time of exposure, 144 hours;
substrate: untreated steel panels "~

Test for stability of the 30% aqueous solutions:
The diluted binder of Example 2 is in good order after storage for two weeks at 60C, while the diluted solution of the comparison example has separated into two phases.

As will be apparent to one skilled in the art, various modifications 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

IT IS CLAIMED:

1. Water-dilutable phosphoric acid modified bin-ders for use in crosslinking stoving paints, based on poly-ester resins, comprising the reaction product of components (A) and (B), component (A) being 15 to 80% by weight of a water-insoluble film-forming polyhydroxy compound having an acid value of below 10 mg KOH/g and a hydroxyl value of 50 to 650 mg KOH/g; and component (B) being 85 to 20% by weight of a polyester component which is rendered water-soluble through at least partial neutralization of the acid func-tional groups, having an acid value of 20 to 150 mg KOH/g and containing at least 0.1 mole of phosphorous per 1000 g in the form of ester-like linked phosphoric acids, with the molar portion of phosphorous not extractable with water in the unneutralized state being at least 50%, and/or the con-version (p) on the esterification of all acid groups being in excess of about 50%.

2. The binders of claim 1 wherein component (A) contains phosphoric acid units.

3. The binders of claim 1 wherein component (A) is present in an amount of from 35 to 65% by weight and component (B) is present in an amount of 65 to 35% by weight.

4. The binders of claim 3 wherein the acid value of component (B) is from about 35 to 120 mg KOH/g and con-tains 0.2 to 2.0 moles of phosphorous per 1000 g.

5. The binders of claim 4 wherein the molar por-tion of phosphorous not extractable with water in the unneutralized state is at least about 70%.

6. The binders of claim 1 wherein the conversion (p) on the esterification of all acid groups is in excess of about 70%.

7. Process for the production of water-dilutable phosphoric acid modified binders for crosslinking stoving paints, based on polyester resins, wherein (A) 15 to 80% by weight of a water-insoluble film-forming polyhydroxy com-pound with an acid value of below 10 mg KOH/g and a hydroxyl value of 50 to 650 mg KOH/g (component A) are mixed with (B) 85 to 20% by weight of a polyester component which is ren-dered water-soluble through at least partial neutralization of the acid functional groups, with an acid value of 20 to 150 mg KOH/g containing at least 0.1 mole of phosphorous per 1000 g in the form of ester-like linked phosphoric acids, with the molar portion of phosphorous not extractable with water in unneutralized state being at least 50%, and/or the conversion (p) on the esterification of all acid groups being in excess of about 50% (component B).

8. The process of claim 7 wherein after partial condensation of the components (A) and (B) a crosslinking component is added and the thus obtained resin combination is rendered water-dilutable through partial neutralization of the acid functional groups.

9. The process of claim 7 wherein component (A) contains phosphoric acid units.

10. The process of claim 7 wherein component (A) is present in an amount of from 35 to 65% by weight and component (B) is present in an amount of 65 to 35% by weight.

11. The process of claim 10 wherein the acid value of component (8) is from about 35 to 120 mg KOH/g and con-tains 0.2 to 2.0 moles of phosphorous per 1000 g.

120 The process of claim 11 wherein the molar portion of phosphorous not extractable with water in the unneutralized state is at least about 70%.

13. The process of claim 7 wherein the conversion (p) on the esterification of all acid groups is in excess of about 70%.

14. Stoving paints comprising the binders of claim 1 in combination with a crosslinking component selected from the group consisting of amino resins, phenolic resins, blocked polyisocyanates, and epoxy resins.

15. Stoving paints comprising the binders of claim 2 in combination with a crosslinking component selected from the group consisting of amino resins, phenolic resins, blocked polyisocyanates, and epoxy resins.

16. Stoving paints comprising the binders of claim 4 in combination with a crosslinking component selected from the group consisting of amino resins, phenolic resins, blocked polyisocyanates, and epoxy resins.