MXPA98008186A - A catalytic pasta free of acid, its production and the use of it in coatings of electroinmersion catod - Google Patents

Abstract

An aqueous free acid catallizing paste, characterized by having a solids content of 30 to 70 by weight and containing dialkyltin oxide and a cationic agglutinating vehicle adjagable with water, which is obtained: a) dialkyltin dispersing oxide in a free aqueous solution or dispersion Deacid of one or more salts of hydroxycarboxylic acid of bismuth (III) in a weight ratio of tin to bismuth, calculated as the metal, from 1: 3 to 3: 2. b) by grinding the obtained preparation with one or more cationic binder vehicles in a weight ratio of alkyltin oxide plus the salt of hydroxycarboxylic acid of bismuth (III) to cationic binder vehicle, from 0.5: 1 to 6

Description

A PASTA TASTING ÜAPPRA PRE PE ACIPQ. SM PRPPUCC ON AND THE L SP SP UA HIS A IN REVESTIGATIONS PE EUECTKPINHERSIPN CATPPICA FIELD OF THE INVENTION This invention relates to acid free catalyst pastes, to a process for producing them and to their use in processes for cathodic electrocoating (CEC) coating.

BACKGROUND PE A IN NTION It is customary to generally use metal catalysts for the interlacing of CEC coating layers to reduce the baking temperature. In this regard, organotin catalysts have generally been used. The use of dialqui oxide is convenient, and the use of dibutyltin oxide (DBTO) is particularly convenient due to its easy availability and favorable price. However, for it to be used successfully in CEC coatings, the DBTO requires conditioning. This conditioning may consist of a separate synthesis step, ie, in the chemical conversion of DBTO to a dibutyltin dicarboxate, for example. In this way, the CEC coating means that are entangled by blocked isocyanates are known from EP-A-0509437. These contain dialkyl carboxylic acids derived from aromatic carboxylic acids as entanglement catalysts, in addition to bismuth or zirconium compounds as additional catalysts. They can be used as the bismuth, hydroxide, trioxide, nitrate, benzoate, citrate, oxycarbonate and bismuth silicate compounds. DE-A-3940 7B1 describes a process for producing catalyst pastes containing dibutyltin oxide by preliminary dispersion of DBTO with organic solids and 0.05 to 5 moles, per mole of DBTO, of an organic acid which is customary for the neutralization of electrodemers cathodically deposited to a water content up to 5J4 by weight with respect to the sum of DBTO, solvent, acid and water, and the subsequent dispersion and grinding of the mixture obtained with vehicle binders and Water. The preliminary dispersion is preferably carried out on a temperature scale of 50 to 80 ° C. During the production of CEC coating media, the catalyst pastes entrain organic acid. However, low acid contents are convenient in the CEC coating medium, since they promote good wrapping behavior, and low current consumption during deposition of cathodic lacquer.

DESCRIPTION OF THE INVENTION The object of the present invention is to provide a catalyst paste containing tin which is introduced as dialkyl oxide, particularly as DBTO. The production of the catalyst paste should be simple, and the coating media produced using the catalyst paste should have a reduced acid content that is entrained by the paste. It has surprisingly been shown that this object is achieved by the acid-free aqueous catalyst paste with a solids content of 30 to 70 J / w and containing dialkis oxide and a cationic binder vehicle which can be thinned with water, to which the present invention, which is obtained by means of: a) dispersing dialkyl tin oxide in a dispersion or aqueous solution of the acid of one or more salts of bismuth hydroxycarboxylic acid (III) in a ratio of weight of tin to bismuth, calculated as the metal of: 3 to 3: 1, and b) trituration of the preparation obtained with one or more cationic binder vehicles in a weight ratio of dialkyl oxide plus hydroxycarboxylic acid salt bismuth (III), to a cationic binder vehicle, of 0.5: 1 as: 1. The present invention also relates to the process for producing the catalyst paste, which is characterized by steps a) and b) from the previous procedure. The process according to the invention is particularly suitable for producing catalyst pastes containing DBTO and / or dioctyltin oxide (DOTO) such as dialkis tin oxide., for example. The solutions used to produce the catalyst paste according to the invention, including colloidal solutions or dispersions, are hereinafter referred to as "aqueous preparations". Examples of aqueous preparations of bismuth (III) salts of hydroxycarboxylic acid which can be used include those which can be produced by the reaction of bismuth oxide and / or hydroxide (III) with a hydroxycarboxylic acid in a molar ratio of 1.0. to 3.0 carboxyl groups per mole of bismuth in the presence of water. Preferred hydroxy carboxylic acids for reaction with bismuth oxide and / or hydroxide (III) are the aliphatic hydroxycarboxylic acids, particularly aliphatic monocarboxylic hydroxyl acids containing from 3 to 8 carbon atoms are particularly preferred. lactic acid and dimpropi olpropionic acid. One or more hydroxycarboxylic acids can be used in admixture. Preference is given to using aqueous preparations of bismuth (III) hydroxycarboxylic acid salts having a bismuth content of 2 to 25% by weight, calculated as the metal, in particular aqueous preparations of dimethylol propionate and / or bismuth lactate ( III) which have a bismuth content of between 2 and 25% by weight. The dialkyl oxide, for example DBTO, is dispersed in the presence of the aqueous preparation of the hydroxycarboxylic acid salt of bismuth (III). In this respect, the weight ratio of tin to bismuth is between 1: 3 and 3-1 »calculated as the metal. The dispersing operation in step a) of the process can be carried out additionally and preferably in the presence of a partial amount of the cationic binder vehicle. If a binder vehicle containing a basic group is used as the cationic binder vehicle, the basic groups of which are neutralized by acid, it is preferable to use the partial amount used in step a) of the process in an unneutralized form. For example, up to 70% by weight of the binder vehicle amount of step b) of the process which is used as a whole can be used in step a) of the process. Customary binder vehicles which are suitable as CEC paste resins are preferably used for this purpose as cationic binder vehicles which are hereinafter referred to as "grinding resins" for simplicity purposes. However, these can also be other binders, such as those used in cathodic electrodeposition paints for the formation of coatings. These are described below as examples of binders for CEC coating media. For the most part they are characterized by good water solubility and good wettability. They are resins that contain basic groups and that are dispersible in water after neutralization with an acid. Examples of preferred paste binders such as these are described in EP-A-0 183025 or in EP-A-0469 497, for example. The dispersion operation in step a) is carried out with or without the addition of a grinding resin, so that an adequate viscosity of the mixture is obtained, that is, to produce a free-flowing liquid material that can be stirred in an agitator device such as a dissolutor. A suitable viscosity can be obtained according to the amount of water added. In general »dispersion times of 0.5 to 5 hours are sufficient» for example. During the dispersion operation, preferably the temperature is not higher than 40 ° C », preferably not higher than 30 ° C. The lower limit is preferably 20 ° C »but it may be below it. The dispersion obtained in step a) of the process is further dispersed and optionally crushed in step b of the process after the addition of milling resin, for example the residual amount of at least 30% by weight of the resin of grinding, of an amount of acid sufficient to ensure thinning with water for the grinding resin in general, and water. In the course of this procedure, the acid is added at most in the stoichiometric amount to neutralize all the neutral stable basic groups present in the binder vehicle, and is preferably added as a deficit, for example, as 40 to 9554 »Preferably 40 to 80%» of the maximum stoichiometric amount. The addition of acid is not necessary if the grinding resin contains only cationic groups and not basic groups. Organic acids such as formic acid »acetic acid» lactic acid and dimethylolpropionic acid are particularly suitable as acids for neutralizing the grinding resin. It is convenient to agglutinate the dispersion »the grinding resin» acid and water »directly after the dispersion operation of step a) of the process without an extended storage period. For example »the grinding resin can be added first» followed by the acid and water »or a mixture of the grinding resin which is neutralized with acid» and water can be added. In particular »water is used only in a de-ionized manner. The homogenized mixture can then be crushed to the desired fineness of grinding in a mill, for example, a ball mill or a multiple cage mill. The most favorable residence time for step b > The procedure can easily be determined by the person skilled in the art in only a few tests. It depends on the speed of production, the size of the cage, the dissipation of temperature and the amount and type of grinding media. A homogeneous turbid pigment paste is produced in this process. This catalyst paste is stable during storage in the free flowing form it wants. The catalyst paste according to the invention can be used in pigmented or pigment-free CEC coating media. If the catalyst paste is used in the production of pigmented CEC coating media, the catalyst paste is preferably pigmented in an appropriate manner to avoid the production of pigment pastes which are ground separately. For this purpose, the necessary pigments and / or diluents are added in step b) of the process as they are preferably dispersed in a mixture with the milling resin which is neutralized with acid and water and are comminuted together with the others. constituents of the catalyst paste. In the course of this process, the proportions of grinding resin, acid and water, additives and solids can optionally be increased. The catalyst pastes according to the invention have weight ratios / solids of grinding binder vehicle of 0.5: 1 to 6: 1. For catalyst pastes that are additionally pigmented, the ratio of pigment plus diluent to dialkyl oxide plus bismuth hydroxycarboxylic acid salt (III) is preferably 0.3: 1 to 60: i. The term "pigment" which is used herein denotes the sum of dialkis oxide and the hydroboxylic acid salt of bismuth (III) and the pigments and / or diluents that are optionally present. The solid content of the catalyst pads according to the invention is between 30 and 70% by weight. The customary inorganic and / or organic pigments suitable as pigment β and / or diluent β. The examples include black smoke, titanium dioxide »iron oxide» kaolin »French clay or silica» phthalocyanine pigments and quinacridone pigments »and also anti-corrosion pigments such as zinc phosphate and lead silicate. Steps a) and b) of the process can be carried out at low temperatures. Preferably »a temperature of 40 ° C is not exceeded. The lower limit is preferably about 20 ° C or less. The catalyst paste according to the invention may contain organic solvents. These can originate from the grinding binder vehicle or can be added separately in process a) and / or b) pages. Examples of β-solvent of this type include alcohol such as, for example, methanol, ethanol, cyclohexanol or 2-ethylene-1-glycol, such as, for example, ethylene glycol, propylene glycol, diethylene glycol or dipropylene glycol, glycol esters such as, for example, methoxypropanol, ethoxypropanol, butoxyethanol, or diethyl ether of diethylene glycol ketones, such as, for example, methyl-1-butyl-ketone, methyl-ethyl-ketone or cyclohexanone, or hydrocarbons. The amount of solvent is preferably 10 to 50% by weight with respect to the solids content of the catalyst paste. The catalyst paste according to the invention can contain the usual additives such as, for example, wetting agents and antifoaming agents. These may be added in the usual amounts familiar to the person skilled in the art during steps a) and / or b) of the process. A coating medium can then be produced CEC in the usual manner from the catalytic laß paßtaß according to the invention »as a single component material in admixture with the required CEC binder vehicle» optionally in admixture with crosslinking agents »if necessary» after neutralization with acid and dilution with water, or preferably as a two component material together with a dispersion of CEC binder vehicle. When the CEC coating medium is entangled by an external means, the Cß binder vehicle dißßssion generally contains an entanglement agent. The electrically conductive substrate can then be coated by customary methods with the CEC coating medium, and the coating of lacquer can be interlaced, for example, by means of baking. E: CEC coating medium which can be produced using the catalyst pastes according to the invention, medios aqueous coating media with a solids content of up to 50% by weight, for example 10 to 30% by weight. The content of solid and condensate of vehicleß binder, usually containing cationic ßubßti listeners or substituents, which can be converted into cationic groups, and which optionally contain chemical crosslinking groups as well as crosslinking agents which are optionally preβent and resin milling »of pigments and / or diluents that are optionally present» and of DBTO, bismuth hydroxycarboxylic acid salt (III) and other additives. The cationic groups are basic groups, for example groups derived from amino groups by neutralization with acid, for example ammonium groups or other cationic groups, for example quaternary ammonium groups. Examples of basic resins that can be used as a binder vehicle β include resins containing primary or secondary or tertiary amino groups and the number of amine of which is 20 to 250 mg KOH / g. for example. The weight average molecular weight (Mw) of the resins is preferably 300 to 10 * 000. Examples of resins such as these include aminomethacrylate resins »aminoepoxide resins» aminoepoxide resins containing terminal double bonds »aminoepoxide resins containing primary OH groups» polypropylene resin resins »polybutadiene resins containing groups amino "or reaction products of modified epoxy resin-carbon dioxide-amine. The basic groups may exist in a quaternary form or be converted into cationic groups with a usual neutralizing agent, for example with an organic monocarboxylic acid such as lactic acid, formic acid or acetic acid, as is familiar to the person skilled in the art. The resins may be entangle or ßß ußan in admixture with known crosslinking agents. Examples of entanglement agents such as these include aminoplastic resins, blocked polyisocyanates, crosslinking agents containing terminal double bonds, polyepoxide compounds, crosslinking agents containing cyclic carbonate groups or crosslinking agents containing groups susceptible to transesteriication, and / or transaction. Examples of the basic ß-reßinaß and crosslinking agents employed in cathodic electrocoating coating baths (CEC) that can be used are described in EP-A-0 082 291, EP-1-0 234 395, EP-A-0 208 857 , EP-A-0 227 975, EP-A-0 178 531, EP-A-0 333 327, EP-A-0 310971, EP-A-0456 270, US 3922253, EP-A-0261, EP- A-0245 786, EP-A-0414 199 and EP-A-0476 514. These refs can be used by themselves ßolaß or in admixture. In addition to the additives which are incorporated by means of the catalyst part according to the invention, the additive and also include the customary additives for CEC coating means. Examples thereof include wetting agents, flow improvers, antifoaming agents and solvents, for example the additives and solvents described in connection with the catalyzate pastee according to the invention. The catalyst pastes according to the invention are simple and can be produced at low temperatures. They do not entrain free acids into the CEC coating medium produced with them.

EXAMPLE Do you prepare a dispersion dt? ? g? 832 parts of an onocarbonate of an epoxy resin based on bisphenol A (the commercial product Epicote 828) were mixed with 830 parts of a polyol of commercially available polycaprolactone (the commercial product CAPA 205) and 712 parts of dimethyl ether of diglycol "and were reacted with approximately 0.3% BF3 stearate, from 70 to 140 ° C, until reaching an epoxide number of 0. 307 parts of the reaction product of 174 parts of toluene diisocyanate were added to this product ( 2 equivalents of NCO) with 137 parts of 2-ethylhexanol with the addition of 0.3% benzyltrimethylammonium hydroxide (Triton B), whose reaction product had an NCO content of about 12.8% »(solids content 70 %, 2 carbonate equivalents), from 40 to 80 ° C in the presence of 0.3% zinc acetylacetonate as a catalyst. The batch was reacted to an NCO value of about 0 and then adjusted to about 70% solid β with diglycol dimethyl ether. b) 618 parts of the reaction product of 348 parts of toluene di-ethanoate (80% of the 2.4-, 20% isomer of 2.6- isomer) were added slowly with 274 parts of 2-ethylenehexanol with the addition of 0.3% of benzyltrimethylammonium hydroxide as catalyst "whose reaction product had a residual NCO content of about 12.8%. to 1759 parts of a bicarbonate of an epoxy resin based on bisphenol A (the commercial product Epicote 1001") of 60 to 80 ° C. The reaction was allowed to continue until an NCO value of about 0. 622 parts of the product were added. of reaction of 137 parts of 2-ethylhexanol with 174 parts of toluene diisocyanate with catalysis by benzyltrimethylammonium hydroxide (0.3%) (NCO content of about 12.8%), to 860 parts of bis-hexamethyltin ina dissolved in 2315 parts of methoxypropanol at a temperature of 20 to 40 ° C. Then 4737 parts of reaction product b) and 3246 parts of reaction product a) were added (70% in diglycol dimethyl ether in each cation) and the batch was reacted from 60 to 90 ° C. The reaction was completed to an amine number of about 32 mg KOH / g The resulting product was subjected to vacuum distillation to a solids content of about 85% neutralized with 30 mmol of acid formic per 100 g of resin and it was converted into a dispersion with a solids content of approximately 40% in peel with desalinated water.

Production of a catalyst paste a) 100.0 g of the grinding resin were mixed according to EP-A-0469497 »Example 1 (55% by weight)» 16 g of a wetting agent based on polyethylene / propylene glycol » 24.0 g of a commercially available antifoam agent and 236.0 g of a 20% by weight aqueous preparation of a bismuth (II) hydroxycarboxylic acid salt (prepared from one mole of bismuth oxide (III) and one mole of acid) lpropionic dimet) "in a disulotor. Then 50.3 g of DBTO and 8.0 g of silica were added and the mixture was dispersed at 30 ° C for 1 hour after adding 41.0 g of deionized water. b) 94.5 g of the grinding resin were neutralized according to EP-A-0469497 »Example 1 (55% by weight) with 9.9 g of 5.3 N acetic acid and diluted with 180.0 g of deionized water. 3.8 g of carbon black and 436.5 g of titanium dioxide were added to it and the mixture dispersed. The dispersed mixtures obtained as in a) and b) 'were mixed and co-crushed in a ball mill at 30 ° C to produce a catalyst paste with a gray pigmentation. The catalyst paste thus produced contained no free acid.

Production of a CEC coating medium A CEC coating medium having a solids content of 20% by weight and a weight ratio of pigment / binder vehicle of 0.35: 1 »was produced by mixing the CEC dispersion» catalyst paste and deionized water (pigment = sum of the bismuth hydroxycarboxylic acid salt (III) »DBTO» silica »carbon black» titanium dioxide »binder vehicle = sum of the solids that originate from the dispersion of CEC and the solid grinding resin) .

Claims (8)

NOVELTY OF THE INVENTION CLAIMS

1. - An aqueous acid-free catalyst paste with a solids content of 30 to 70% by weight and containing dialkis oxide and a water-thinning cationic binder vehicle.

2. A process for producing an acid free acid catalyst catalyst vehicle with a content of-solid acids from 30 to 70% by weight and containing dialkis oxide and a water-thinning cationic binder, characterized in that it comprises the steps of (a) dissipating dialkaryl oxide in a dieperion or aqueous solution of the acid of one or more salts of bismuth (III) hydroxycarboxylic acid in a weight ratio of tin to bismuth calculated as the metal, of 1: 3 to 3: 1, and (b) grinding the preparation obtained with one or more cationic binder vehicles in a ratio of dialkis oxide oxide plus bismuth (III) hydroxy carboxylic acid salt to cationic binder vehicle, 0.5: 1 to 6: 1.

3. A process according to claim 2, further characterized in that step b) is carried out in the presence of one or more pigments and / or diluents, wherein the weight ratio of the pigment sum, diluent. Dialquilasin oxide and hydroxycarboxylic acid salt of bismuth (III) to cationic binder vehicle, is from 0.5: 1 to 6: 1, and the weight ratio of pigment plus diluent to dialqui oxide plus salt of bismuth hydroxycarboxylic acid (III), it is from 0.3: 1 to 60: 1.

4. A process according to claim 2 or 3 »further characterized in that steps a) and / or b) are carried out in the presence of organic solids and / or one or more of the usual lacquer additives.

5. A process according to any of the foregoing indications 2 to 4, characterized in that the dialkyl oxide is dibutyltin oxide.

6. A process according to any of the preceding claims 2 to 5 »further characterized in that the salt of hydroxycarboxylic acid of bismuth (III) is a salt of lactic acid or dimethyolpropionic acid.

7. A method according to any of the preceding indications to 6 »further characterized in that the cationic binder vehicle is a cationic paste resin or binder vehicle» customary for cathodic electrodeposition lacquers.

8. The use of the catalyst paste according to claim 1, in cathodically depositable electrodeposition lacquers.