DE1595204A1 - Process for the production of low-formaldehyde, etherified aminotriazine resins - Google Patents

Description

Process for the preparation of low-formaldehyde, etherified aminotriazine resins Aminotriazine resins etherified with alcohols are used in combination with alkyd resins used extensively for stove enamelling. The manufacture of etherified Aminotriazine resins are generally carried out in such a way that initially in neutral or weakly alkaline aqueous, aqueous-alcoholic or alcoholic medium from an aminotriazine, possibly mixed with urea and / or urea derivatives and formaldehyde and / or formaldehyde-releasing agents such as Paraform a relative low molecular weight Eondensationsprodukt is produced, which is then in a acidic Eondansationsphase further condensed in aqueous-alcoholic or alcoholic solution and is at the same time partially etherified, or it is from the outset in weakly acidic aqueous-alcoholic or alcoholic medium condenses and etherifies. Examples of etherified aminotriasine resins and their preparation can be found e.g. B. in German patents 970 453, 1 055 811 and 1 127 085, as well as in J. Soheiber: "Chemistry and Technology of Artificial Resins" 1943, Pp. 386-39.

Examples of aminotriazines that may be mentioned are 2,4,6-triamino-1,3,5-triazine and liaminotriazines such as formoguanamine, acetoguanamine and benzoguanamine. As an ethereal agent butanols have found the most widespread use, but others are also found Alcohols such as methanol, ethanol, n- and i-propanol, allyl alcohol and the amyl alcohols, Use.

In etherified aminotriazine resins, which are usually 50 to 70% strength Solutions in organic solvents are on the market, always remains a certain one Correspondingly, the proportion of formaldehyde used, which can be up to 10% the equilibrium conditions of the law of mass action of the aminotriazine unboundX These aminotriazine resin solutions accordingly have the pungent odor of the free Formaldehyde. When using such resin solutions in paint shops This unbound formaldehyde becomes in the course of evaporation of the dissolving agent content free and leads to severe nuisance to the respiratory organs of those employed there People, apart from the fact that formaldehyde is a protein poison in higher concentrations is. For this reason, aminotriazine resin solutions are low-odor for the industry of great interest.

You could now use this to make low-formaldehyde, etherified aminotriazine resins win that one first prepares suitable Methglolwerbindungen the aminotriazine, these crystalline compounds by washing with water from the excess formaldehyde freed, dried and then condensed with suitable alcohols and catalysts and etherified. This procedure requires a considerable outlay in terms of equipment. Also, the technological properties of these aminotriazine resins would what which concerns hardness and elasticity, not the demands of the manufacturing industry suffice.

In U.S. Patent 2,603,623 a method of manufacturing of water-soluble aminotriazine resins described with alkali salts of the sulphurous Acid treated, whereby the free formaldehyde is bound and the reaction solution is then brought to dryness, eo that the treated water-soluble resin still contains bisulfite residues as an impurity. Evaporation of the reaction solution until drying is absolutely necessary in the known method, namely By adding the bisulfite, the formaldehyde is not completely bound, but Free formaldehyde is still present, which is then used in a second stage by which very expensive evaporation has to be removed (compare USA patent 2 603 623, column 5, lines 63-64).

Through the compounds of oxidizing peroxo compounds used according to the invention for the oxidation of the formaldehyde in water-insoluble etherified aminotriazine resin solutions, wherein the aminotriazine resins dissolved according to the invention are immiscible with water organic solvents are present in dissolved form, is a significant technical advance achieved as any excess oxidizing agent and oxidized formaldehyde tunsthars not treated ii remain. During the oxidation, the synthetic resin becomes itself not changed unfavorably, but the end product shows in not to be expected Show unpredictable improved properties, like here will still be executed.

The object of the present invention is to provide a method to etherify Aminotriazine resin solutions to practically eliminate the free formaldehyde are available to deliver.

The invention relates to a process for the production of water-insoluble Low-formaldehyde, etherified aminotriazine resins, characterized in that the formaldehyde-containing aminotriazine resin solutions with one for the oxidation of the formaldehyde sufficient amount of a peroxo compound, this peroxo compound being water substance peroxide, a peroxide, peroxide or sesquioxide of the alkali or alkaline earth metals, a peroxy acid or its salt, or peropydioic acid or its salts, of sulfur, Phosphorus, nitrogen, carbon or boron, or a feroxohydrate, treated.

For example, the following can be used: hydrogen peroxide, peroxy acids or their salts, or peroxydiacids or their salts of sulfur, phosphorus, Nitrogen, carbon and boron, peroxohydrates such. B. Sodium metaborate 3-hydrate-1-peroxide hydrate Sodium tetraborate 9-hydrate-1-peroxohydrate, sodium carbonate-1,5-peroxohydrate, sodium diphosphate-3-peroxohydrate and urea-1-peroxohydrate.

These are the solutions of the aminotreazin resins, for example in higher alcohols and / or aromatics sugesetzt, whereby one in neutral or weak alkaline medium at room temperature or elevated temperature to these resin solutions adding a sufficient amount of peroxo compounds based on the formaldehyde content.

The resulting formic acid is neutralized with soda or caustic soda, the sodium formate then washed out with water. The aminotriazine resin itself does not suffer any unfavorable changes in its properties as a result of this treatment, such as an oxidation of the free methylol groups to carboxyl groups, whereby a Increase in water solubility is associated with the use of aminotriazine resins is undesirable. According to A. Rieche and R. Meister, organic medium form formaldehyde peroxides from formaldehyde and H202 (see Ber.dtsch. chem. Ges. 68, 1465/73 (1935) and 66, 718/27 (1933). However, these reactions will occur in the process avoided the invention.

The oxidation of formaldehyde can occur in 50 to 70%, for example Solutions of the aminotriazine resins take place.

Hydrogen peroxide or concentrated hydrogen peroxide is used as the oxidizing agent Solutions preferred. 1 to 2 vales, preferably 1.1, are used of the peroxo compound up to 1.3 Vale, based on the formaldehyde: The oxidation is in the pH range from 5 to 9, preferably 6.5 to 7.5.

When working with the preferred hydrogen peroxide, use the Oxidation with 20 to 70, preferably 45 to 50, hydrogen peroxide solution. The oxidation is carried out at temperatures of about 10 to 100 ° G, preferably 65 to 75 ° C, through.

Apart from the benefits of eliminating the formaldehyde for the processing of these aminotriazine hard solutions, it was found in the technological test that stoving enamels based on these resin solutions a significantly greater hardness compared to the formaldehyde-containing Have resins, in which in particular the technical progress of this process compared to the multi-stage procedure already mentioned. This influence of the free formaldehyde on the hardness of the stoved films, as shown in the table Show summarized measurement results was previously unknown and also not to expect.

The process is explained in more detail in the following examples. As a base resin were two commercially available butanol-etherified melamine lye resins from Reichhold Chemie AG, Hamburg, used, namely 850 and 852, their content of free formaldehyde is between 2.5 and 5 wt.

The determination of the free formaldehyde in the aminotriazine resin solutions took place according to the hydroxylamine chlorohydrate method: 5 g of the resin solutions are in Dissolve 25 ml of isopropyl alcohol and apply n / 10 NaOH or HCl to the point of transition set of bromophenol blue.

50 ml of 0.5N hydroxylamine chlorohydrate solution (hydroxylamine chlorohydrate p.a., dissolved in 1 part H20 and 3 parts isopropyl alcohol). After 30 min reaction time, the released hydrochloric acid is back-titrated with 0.5 N NaOH.

Example 1: 1100 g of non-plasticized, butanol-etherite melamine resin 850 are added dropwise at 70 to 80 ° C with 55 g of 11202 (5X), while at the same time the pH by adding a total of 45 ml of NaOH (45, ') in the range from 6 to 7.5 is held. After the oxidation has ended, the mixture is left to stand for about 3 hours and separated the lower aqueous phase. The resin solution is washed twice with 100 ml water from, 110 g of isobutanol are added, drained by circulating distillation and concentrated finally a salt residue by vacuum distillation to a resin content of 52% are removed by piltration. The formaldehyde content falls from 2.7 to 0.5% by weight.

The technological test was carried out under practical conditions in the form of a white lacquer color.

Auo 80 parts TiO2 RJ 56 of the Titangesellechaft m.b.H., 178 parts of a commercially available ricine alkyd 234 from Reichhold Chemie AG., Hamburg, 6O% dissolved in xylene, 106 parts of the low-formaldehyde butanol-etherified melamine resin A paint is rubbed in with 850 and 20 parts of isopropyl glycol. The paint color is applied to two glass plates and baked for 90 minutes at 90 and 1200 C. After 24 hours, the König pendulum hardness is determined (the layer thickness of the baked Films should be between 25 and 35µ). For comparison, the same laok color is used manufactured and tested with formaldehyde-containing butanol-etherified melamine resin 850.

Table 1: Sinbrenn white lacquer color from temp. Time 850 with 850 with 2.7% by weight 0.5% by weight formaldehyde 90 ° C 30 min 29 - 30 38 - 39 12000 30 min 84 - 85 115-117 Example 2: 1100 g of non-plasticized butanol-etherified melamine resin 852 are added dropwise at 70 to 800C with 105 g H2O2 (50%), while at the same time the pH value iiroh addition of sodium carbonate in the range from 6.5 to 7.5 is held. After the oxidation has ended, the mixture is left to stand for about 3 hours and separated the lower aqueous phase. The resin solution is washed twice with 100 ml of water from, add 100 ml of isobutanol, drained by circulating distillation and concentrated by vacuum distillation to a resin content of 52%. Salt residue will be through Filtration removed. The formaldehyde content drops from originally 3.5 to 0.5% by weight.

The technological test was, as described under Example 1, performed.

Table 2: White paint from stoving temp. Time 852 with 852 with 3.5% by weight formaldehyde 0.5% by weight formaldehyde 90 ° C 30 min 28 - 29 44 - 45 120 ° C 30 min 80 - 81 100 - 101 The process according to the invention can also be carried out by the following Simplify the variant and make it cheaper. by putting some of the formaldehyde together with alcohol and water as an azeotropic mixture through an upstream and / or downstream steam distillation removed.

Example 3: 1000 g of non-plasticized butanol-etherified melamine resin 850 with a formaldehyde content of 2.7% by weight are heated to 90 to 950C. Man passes in steam for 1 1/2 h and separates 70 g of aqueous phase and 275 g of butanolic Phase off.

The free formaldehyde content has fallen to 1.7% by weight. Man cools to 70 to 80 ° C, adds 43 g of dry soda to the resin and leaves with stirring Add 28 g of H202 (50%) dropwise. When the oxidation is complete, the mixture is left to stand for 3 hours separates the lower aqueous phase. The resin solution is washed twice with 100 ml Water out. It is heated again to 950C and 100 g of solvent is distilled off, while at the same time 100 g of i-butanol flow into the resin solution. With a mixture from 1 part of xylene and 3 parts of i-butanol is diluted to a resin content of 52% by weight.

The precipitated salts are filtered off. The content of free formaldehyde has decreased to 0.1% by weight. It was according to example 1 paragraph 2 with the example 3 obtained resin produced a white lacquer color. The technological test was carried out in the same way as in example 1.

Table 3: Stoving white paint from Temp. Time 850 with 850 with 2.7% by weight formaldehyde 0.1% by weight formaldehyde 900C 30 min 29 - 30 40 - 42 1200C 30 min 84 - 85 117 - 119

Claims (7)

Patent claims 1.) Process for the production of water-insoluble Low-formaldehyde, etherified aminotriazine resins, characterized in that the formaldehyde-containing aminotriazine resin solutions with an oxidation of the formaldehyde sufficient amount of a peroxo compound, this peroxo compound being hydrogen peroxide, a peroxide, peroxide or sesquioxide of the alkali or alkaline earth metals, a peroxy acid or its salt, or peroxydioic acid or its salts, of sulfur, phosphorus, Nitrogen, carbon or boron, or a peroxohydrate can be treated. 2.) The method according to claim 1, characterized in that 1 to 2 moles, preferably 1.1 to 1, 3 vale of the peroxo compound based on the formaldehyde, used 3.) Process according to claim 1 and 2, characterized in that the Oxidation in the pH range from 5 to 9, preferably 6.5 to 7.5, carries out. 4.) The method according to one or more of claims 1 to 3, characterized characterized in that the oxidation with 20 to 70, preferably 45 to 50, percent Hydrogen peroxide solution. 5.) The method according to one or more of claims 1 to 4, characterized characterized in that oxidation at temperatures from 10 to 10,000 is preferred 65 to 75 ° c. 6.) Variant of the method according to one or more of the Expectations 1 to 5, characterized in that one is to be converted and / or converted Subjects aminotriazine resin solutions to steam distillation. 7.) Method fled claim 6, characterized in that -n the Steam distillation at temperatures of 70 to 1000C, preferably 90 to 100 ° C, performs.