NL9302276A - Coagulants for painting or washing in wet separators. - Google Patents

Description

Coagulants for painting or washing in wet separators

The present invention relates to coagulants based on recent natural resins for the detachment and coagulation of coating materials such as lacquering and / or washing in wet separators of spray paint installations.

When coating metal, wood or plastic parts according to the injection molding method, it is not possible to apply the coating materials completely to the surfaces to be coated. Part of the coating material is sprayed along the object as so-called "overspray" and is removed from the air of the spray booths using wet separators. In order to prevent adhesion in the water-containing parts of the installations and to ensure a removal of the obtained coating material from the circulation water, coagulants are added to the water, which effect a detachment of the imported material and convert it into agglomeration. a coagulate that can be removed. A range of neutral, alkaline and also acidic products have hitherto been available as coagulants. These exhibit several drawbacks in coagulation and in any subsequent work-up of the obtained coagulate for the recovery of valuable substances such as binders and pigments contained therein.

It is known from DE-Cl.269.59 ^ to add alkaline substances up to a pH of about 9 "10> 5 to the circulation water, so that the binders for lacquer are saponified and therefore less sticky. The addition of an inorganic oil ensures an additional coating of the particles In this method, it is a drawback that alkaline products are objectionable because of the safety at work and the saponification reactions make it in many cases impossible to recover the binders from the coagulate.

It is known from DE-C3-2.758.873 to paints that contain little solvents, which cannot be satisfactorily removed by the previous method, instead of adding the inorganic oil a wax or paraffin wax, which contains the lacquer particles also envelops. The disadvantages of alkaline circulation solutions are therefore not eliminated.

Therefore, DE-Cl-3.42i.289 proposes to use amino alcohols or morpholine instead of alkali together with washing. With these agents, it is a drawback that the waxes and the binders for the lacquer are difficult to separate, which, when reusing recovered valuable substances from wax-containing coagulate, in the preparation of coating materials to a reduced adhesion and thus to coatings with defects, so that the resulting mixture must be removed and cannot be reused. Due to the presence of emulsifiers, coagulation components in the circulating water can partially emulsify and this prevents their removal. The thereby increasing concentration of these coagulant constituents necessitates an early change of the circulation water.

DE-C2-3,421,270 further discloses one-component wax-based coagulants containing marble lime hydrate, thickeners, lower aliphatic alcohols and naphthalenic acid condensation products as additives. These agents also react strongly alkaline.

Coagulants based on usually acidic metal salts can lead to strong corrosion of the plant by concentrating the salts in the circulation water and the reduced pH of the water promotes bacterial growth and the associated odor load.

The use of adsorptively acting clay minerals as coagulants leads to an increase in the obtained coagulate and to a high water content due to the pronounced swelling capacity of the clay minerals. Moreover, the rapid and uniform distribution of these products in the circulation water, which is necessary for coagulation, is often insufficient, because they are used in the form of powders or highly viscous pastes.

It was therefore the object of the present invention to provide coagulants for lacquers and other coating materials, which ensure a durable detachment and agglomeration and do not affect a possible recovery and reuse of valuable substances from the coagulate. The new products must be suitable for coagulating both solvent-containing and aqueous coating materials and have the thinnest possible liquid consistency in order to achieve simple dosing and a rapid and even distribution in the circulation water. Due to special additives in the formulation, the buoyancy of the coagulate that is created, i.e. sedimentation resp. flotation can be affected.

These objectives are achieved on the basis of the characteristics of the main claim and are supported by the characteristics of the sub-claims.

The present invention therefore relates to formulations which a) 1 to 50% by weight shellac, balsam resin or other recent natural resins, b) up to 10% by weight of an amine, alkanolamine or alkali metal hydroxide to adjust a pH of 6- 9.

c) the remainder contain up to 100% by weight water.

Recent natural resins are freshly obtained secretions of vegetable or - in the case of shellac - animal origin. Unlike the fossil natural resins extracted from geological deposits, they are distinguished by good solubility in organic solvents and they have been extensively displaced by synthetic materials for the preparation of printing inks, lacquers and other coating materials. used.

The use according to the invention thereof in coagulants, due to their high affinity with all kinds of binders, leads to an excellent debonding effect. Its properties, which resemble those of binders, also enable the coagulate to be recycled without affecting the quality of the recovered lacquer binders.

Chemically, recent natural resins consist of a mixture of very different substances, such as resin acids, resin alcohols, esters of resin acids and alcohols, phenols and unsaturated oxygen-containing compounds. Main components of the shellac are the aleuritic acid and the shellolic acid, balsam resin mainly contains abietic acid and its isomers. Wax contents which may interfere with the use of the invention are separated by dissolving in cold alcohol, in which the wax is insoluble, or by dissolving in toluene and precipitating with alcohol. The resin is recovered in pure form by evaporation of the solvent.

The resins used according to the invention can be converted into the soluble salts which have a pH of about 6-9, preferably 6-8, in a solution in water by neutralization with alkali (sodium or potassium hydroxide) or amines and alkanolamines. Any residual wax, which has not been dissolved, is filtered off at this step. This solution can therefore easily be added to the wet separator by-pass water, is non-aggressive and, unlike inorganic oils, waxes or solid flocculants, is not deposited in quiescent areas of the equipment.

The mode of action of the agents according to the invention resembles, as with the waxes, the detachment of the lacquer by adsorption on the resin flakes. The lacquer particles are partly enveloped and the fine flakes agglomerate into macro-flakes that can be removed.

The action according to the invention is further improved when the formulations contain tensides (surfactants) in a small amount, anionic, neutral or zwitterionic compounds being used to the same extent; cationic surfactants, which could form insoluble salts with the resin acids, are less advantageous. For example, the tensides are added to the mixture in an amount up to 5% by weight. To avoid excessive foaming by the tensides and the substances of the lacquer, it is preferable to add up to 5% by weight of a defoaming agent to the mixture. Polyalkylene glycols are preferably used for this purpose, but other known compounds can also be used for this.

It is often desirable to collect and remove the coagulates that arise, regardless of the specific weight of the components of the lacquer, on the bottom or on the surface of the circulation water. For this, up to 5% by weight of light, organic flocculants or up to 20% by weight of low-level silicates or silicas can be added, which settle in the coagulates, causing them to float or sediment.

The following examples further illustrate the invention. These standard formulations are added in an amount of 0.1-5% by weight to the circulation water of the wet separator and replenished accordingly after consumption. Based on the amount of the washed lacquer overspray, the coagulants should be present in an amount of 1-100, preferably 2-10% by weight.

Example I

10 wt. # Shellac (ammonium salt) 0.3 wt. # Polyalkylene glycol Residual up to 100 wt. # Water

Example II

10 wt. # Balsam resin 2 wt. # Potassium hydroxide 0.3 wt. # Polyalkylene glycol 0.5 wt. # Fatty acid polyglycol ester

Remain up to 100 wt. # Water

Example III

5 wt. # Shellac (ammonium salt) 5 wt. # Bentonite 0.3 wt.% Polyalkylene glycol 1 wt.% Fatty acid polyglycol ester Residual up to 100 wt.% Water

Example IV

5% by weight of balsam resin (pine resin) 1% by weight # potassium hydroxide 1% by weight bentonite 0.5% by weight silica 0.1% by weight # polyalkylene glycol Remaining to 100% by weight water

To prepare the mixtures, the resin is dissolved or suspended in the appropriate amount of water at 80 to 100 ° C. The other ingredients are then mixed under stirring.

For the coagulation tests, the following coating materials were used: (A) one-pack solvent top coat, burn-in paint (B) one-pack hydro top coat, UV drying (C) one-pack solvent base coat, air drying (D Preservative wax. 6 g of the coating materials were dropped with stirring into one liter of water, mixed with 3 g of the respective example mixture. In all tests, the coagulate was obtained in the form of fully detached, easily removable, floating upwards, respectively. sinking flakes. The following table provides information about the buoyancy behavior (flotation) or. sinking behavior (sedimentation).

(A) (B) (C) (D)

Example mixture I flot. flot. sed. flot.

Example mixture II flot. sed. sed. sed.

Example mixture III flot. sed. sed. sed.

Example mixture IV flot. sed. sed. sed.

Claims (6)

Coagulant for lacquering and / or washing in wet shells, containing an aqueous solution or suspension of shellac, balsam resin or other recent natural resins, characterized in that the resins are present as soluble salts with amines, alkanolamines or alkali metal hydroxides and the solution has a pH of 6-9. Coagulant according to claim 1, characterized in that defoaming agents, biocides and surfactants, as well as organic or inorganic auxiliaries, are present during flocculation as additional active substances. Coagulant according to claim 2, characterized in that organic polyelectrolytes or layered silicates and / or silicic acid are present as organic auxiliaries during flocking. 4. Method for coagulating coating materials such as lacquering and / or washing in the circulation water and / or the coagulation lake of lacquering installations, characterized in that a coagulant according to claims 1 to 3 is used. Method according to claim 4, characterized in that the concentration of the coagulant in the range of 0.01 to 5% by weight, preferably 0.1 to 0.5% by weight, based on the total amount of circulating water, lies. Process according to claim 4 or 5, characterized in that the coagulant is used in an amount of 1 to 100% by weight, preferably 2 to 10% by weight, based on the paint overspray.