Antiskinning compound and compositions containing them

#The invention relates to anti-skinning agents containing mixtures of organic compounds (combinations of additives), coating compositions containing them and articles coated with them. The organic compounds are selected from the groups of (a) organic hydroxylamines and (b) amines including alkyl amines and/or alkyl alkanolamines. The invention further relates to compositions containing these anti-skinning agents, like coating compositions such as oxidatively drying alkyd resins.

#Colorless and pigmented oxidatively drying paints and coatings based on oxidatively drying oils, alkyd resins, epoxy esters and other oxidatively drying refined oils are known. These oils and binders crosslink oxidatively under the influence of oxygen (preferably atmospheric oxygen) by means of the addition of driers, such as metal carboxylates of transition metals. If this crosslinking takes place before the product is actually used, they can form a solid barrier film, a skin, on the surface when stored in open or closed containers. This is highly undesirable and should therefore be avoided since it makes the paint more difficult to work with and commonly interferes with the uniform distribution of the driers. The accumulation of the driers in the paint skin that forms can lead to considerable delays in the drying of the paint when it is applied.

#Skinning in the paint film after application is also disadvantageous. Excessively rapid drying of the surface of the paint prevents the lower film layers from drying evenly because they are shielded from oxygen, which is prevented from sufficiently penetrating into and dispersing within the paint film. This can lead among other things to flow problems in the paint film, adhesion problems, or insufficiently hard films.

#For the purposes of the invention mixtures of organic compounds of formulae (I) and (II) and/or (III) are used alone or as solutions or dispersions or emulsions in water and/or organic solvents. Suitable organic solvents include all conventional solvents, such as aromatics, white spirits, ketones, alcohols, ethers and fatty acid esters.

#For the use according to the invention the organic compounds of formulae (I) and (II) and/or (III) can be used in a broad range of mixtures with one another. They arc preferably used in the ratio (I):(II) or (III)=0:10 to 10:0.1 parts. In a mixture consisting of all three components each or the components can mutually independently preferably be used in the ratio 0.1 to 10 to each of the other components used. They can be used in pure form or in aqueous solution or aqueous dispersion or emulsion or in the form of solutions in organic solvents, whereby aqueous in this context is intended to mean that water is either the sole solvent or is added in a quantity of over 50 wt. % relative to the solvent blend together with conventional organic solvents (e.g. alcohols).

#The amount of anti-skinning agents primarily depends on the content of binder and drier used in the particular coating composition. As a general rule between 0.001 and 2.0 wt. % of mixtures of compounds according to formulae (I) and (II) and/or (III) should be added. Preferred amounts to be used are 0.01 to 0.5 wt. %, relative in each case to the overall recipe of the coating composition. The amounts can also depend on the type of binder and the pigments used. Thus in special systems the relative amount of additive to be used can also be greater than 2.0 wt. % (relative to the overall recipe).