The addition of balanced mixtures of various types of stabilizers and/or lubricants to a polymer prior to molding is a well-known step for the stabilization of halogenated polymer compounds such as polyvinyl chloride (PVC) against the effects of light and heat. The processing of hard PVC, for example, requires the addition of a multicomponent mixture for stabilization and also for improvement of the lubrication behavior, which mixture consists of components that can be grouped in the following three or four classes: (1) lubricating stabilizers, (2) stabilizers with non-lubricating effect, (3) pure lubricants, as well as, optionally, (4) additives.
Components of the first-mentioned class combine a stabilizing effect with an improvement of the lubrication action. Examples of these include the well-known metallic soaps of higher carboxylic acids, such as fatty acid soaps of calcium, barium, cadmium, zinc, and/or lead. Especially important for practical applications are calcium and/or lead stearate. Non-lubricating stabilizers (2) generally comprise salts of organic acids and/or, especially, inorganic acids, mainly metallic sulfates, metallic phosphites, and/or metallic carbonates. Basic lead salts such as tribasic lead sulfate or dibasic lead phosphite are especially important among these. Useful lubricants (3) include numerous, purely organic non-metallic compounds which may be fatty acids, fatty acid esters, paraffins, wax esters, fatty alcohols, and/or partial esters of polyols or polycarboxylic acids. Finally, other conventional additives (4) include pigments, fillers, so-called modifiers, for example, resins that improve the toughness, and similar substances.
Dependent upon their chemical constitution, many members of these classes can enter into desirable or undesirable chemical reactions. For example, free fatty acids are desirable lubricants and flow promoters, but they react readily with basic parts of non-lubricating salts such as lead oxide. Important purely organic lubricants, such as fatty alcohols or partial esters of polyols, contain hydroxyl groups. Even these components are capable of reaction, that is, undesirable reaction, with free carboxyl groups.
As long as the individual compounds of such multicomponent mixtures are mixtures of solids, the danger of undesirable chemical reaction is practically non-existent. However, the problems of possible component separation as well as the known undesirable flying dust of powdered, especially toxic, mixing components and particularly powdered lead salts, must be taken into consideration.
For the elimination of these last-mentioned disadvantages, the suggestion has been made to melt one or several of the individual components at elevated temperatures and to add the other solid components, especially the dusting inorganic salts of heavy metals, to this melt to homogenize the mixture and finally to granulate it (see GB-PS No. 1 136 935, U.S. Pat. No. 3,461,081, and DE-PS No. 17 94 429, incorporated herein by reference, for pertinent information). The melts of the stabilizers with lubricating effect and/or purely organic lubricants that were heated to the temperature range from about 120.degree. to 130.degree. C. function as liquid phase for this purpose. However, this type of mixing with or addition to the melted phase creates an almost ideal condition for the uncontrolled reaction of active components, and the composition of the total mixture is thus influenced by considerations unrelated to the stabilization problem.