Acylcyanamide compounds and their production

Acylcyanamides are disclosed having the formula ##STR1## in which the symbol R represents a straight-chain or branched chain alkyl or alkenyl group having from about 5 to about 21 carbon atoms, which group may be substituted by OH--, O--CH.sub.2 --CH.sub.2 --OH-- and/or O--R'-- groups, where the symbol R' represents an alkyl group having from 1 to about 4 carbon atoms and wherein M is a manganese, iron, cobalt, nickel, zinc, cadmium, copper and/or lead. The compounds of the invention are useful as heat stabilizers for chlorine-containing polymers.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to new acylcyanamides of divalent metals and to 
their use as heat stabilizers for chlorine-containing polymers, 
particularly polyvinylchloride or polymers containing vinylchloride. It 
relates also to a process for producing the novel acylcyanamides. 
2. Description of Related Art 
In the molding of thermoplastic polymers to tubes, bottles, profiles, 
films, etc. by processes including extrusion, injection molding, 
blow-molding, deep-drawing and calendering, degradation of the plastic 
material involved can take place due to the high temperatures encountered. 
Degradation is manifested by undesirable discoloration of the plastic and 
in a deterioration in its mechanical properties. 
To prevent, or at least minimize this, stabilizers are added to the 
polymers before molding to counteract degradation. The heat stabilizers 
which are used for polyvinylchloride, and for copolymers essentially 
containing vinylchloride, are generally inorganic and organic lead salts, 
organic antimony compounds, organotin compounds as well as cadmium/barium 
carboxylates and phenolates. The foregoing metal compounds are normally 
designated as primary stabilizers, with secondary stabilizers or 
co-stabilizers often being added to the primary stabilizers to enhance 
their effectiveness. Additional information relating to the heat 
stabilizers normally used for vinylchloride polymers can be found in the 
technical literature, as, for example, Encyclopedia of Polymer Science and 
Technology, Vol. 12 Wiley-Interscience pub., New York, 1970, pages 737 to 
768. 
The stabilizers mentioned heretofore have, in general, been acceptable in 
actual use. However, certain polyvinylchloride mixtures yield products 
having undesirable properties, such as, unsatisfactory initial and/or 
long-term stability values. These values cannot be corrected or improved 
by modifying the presently known stabilizers or stabilizer mixtures or by 
increasing the quantities of stabilizers used. In addition, certain 
objections of a toxicological nature have been raised regarding the use of 
lead, antimony and cadmium compounds in certain fields. On the other hand, 
although many organotin compounds are toxicologically safe, their high 
price is an obstacle to their widespread use. For this reason, attempts 
have long been made to replace these compounds by safer, inexpensive 
compounds. 
For example, certain fatty acid salts, aromatic carboxylates and phenolates 
of the metals calcium, barium, zinc and aluminium have been advocated as 
primary stabilizers, optionally supported by co-stabilizers such as, for 
example, organic phosphites, imino compounds, epoxy compounds, polyhydric 
alcohols or 1,3-diketones. Unfortunately, however, these stabilizer 
systems do not impart adequate initial stability and/or adequate long-term 
stability to the molding compositions sought to be stabilized. In 
particular, undesirable premature termination of long-term stability, 
reflected by the sudden blackening of the polyvinylchloride molding 
compositions, is observed when stabilizer combinations which contain 
unduly large quantities of zinc soaps, are used to improve initial 
stability. This sudden blackening is known as zinc burning. Accordingly, 
there is a need for compounds which will provide an initial and/or long 
term effect to stabilizer systems for molding compositions based on 
polyvinylchloride. 
DESCRIPTION OF THE INVENTION 
Other than in the operating examples, or where otherwise indicated, all 
numbers expressing quantities of ingredients or reaction conditions used 
herein are to be understood as modified in all instances by the term 
"about." 
It has been found that new acylcyanamides, derived from C.sub.6 to C.sub.22 
fatty acids, of the metals manganese, iron, cobalt, nickel, zinc, cadmium, 
copper and lead are quite effective when used to stabilize 
polyvinylchloride molding compositions. These acylcyanamides may also be 
used for modifying stabilizer systems which are based on lead, antimony, 
cadmium/barium and organo-tin compounds, as well as stabilizer systems 
based on calcium, barium, zinc and aluminium compounds. In particular, it 
has been found that the acylcyanamides of toxicologically acceptable 
divalent metal cations are particularly suitable for the production of 
recently developed stabilizer systems insofar as they provide a means of 
avoiding the undesirable phenomenon of zinc burning and improving initial 
stability by replacing the zinc soaps which are normally used with 
corresponding acylcyanamides. 
Accordingly, the present invention relates to acylcyanamides having the 
formula 
##STR2## 
in which the symbol R represents a straight-chain or branched chain alkyl 
or alkenyl group having from about 5 to about 21 carbon atoms which may 
optionally be substituted by OH--, O--CH.sub.2 --CH.sub.2 --OH-- and/or 
O--R'-- groups; where the symbol R' represents an alkyl group having from 
1 to about 4 carbon atoms; and wherein M.sup.2.sym. is at least one 
manganese, iron, cobalt, nickel, iron, cadmium, copper or lead cation. 
The present invention also provides a process for producing the 
acylcyanamides corresponding to Formula I which process is characterized 
in that a acylcyanamide alkali metal salt corresponding to the following 
formula 
##STR3## 
in which the symbol R is as defined in Formula I; and M.sup.+ is an alkali 
metal cation, preferably a lithium, sodium or potassium cation, is reacted 
in aqueous or aqueous/methanolic solution with stoichiometric quantities 
of water-soluble manganese, iron, cobalt, nickel, zinc, cadmium, copper 
and/or lead salt. The acylcyanamide which is formed, corresponding to 
Formula I, is subsequently isolated from the reaction mixture. 
Sodium acylcyanamides corresponding to Formula II are preferably used as 
starting material for the preparation of the acylcyanamides of Formula I. 
The alkali metal cyanamides corresponding to Formula (II) can be obtained, 
for example, by reaction of cyanamide with carboxylic acid chlorides and 
subsequent neutralization with alkali metal hydroxides, carbonates and 
bicarbonates (cf. J. prakt. Chemie, N. F. Vol. 11 (1875), pp. 343-347; 
Vol. 17 (1878), pp. 9-13). On an industrial scale, the alkali metal 
acylcyanamides can be produced by reaction of cyanamide with alkali metal 
methylate and fatty acid methylester in stoichiometric quantities in 
methanol as solvent. A reaction time of from 1 to 5 hours at reflux 
temperature is generally sufficient to obtain a complete reaction. Since 
the reaction is quantitative, the product is worked up simply by the 
removal of the methanol by any appropriate method. 
The acylcyanamides corresponding to Formula I are prepared by double 
decomposition of alkali metal acylcyanamides with water-soluble salts of 
appropriate metals in aqueous or aqueous/alcoholic solutions. The 
chlorides, sulfates and acetates of the previously mentioned metals, 
providing they are readily soluble in water, are suitable for this 
reaction. The acylcyanamides of the divalent metals are poorly soluble in 
water. Accordingly, they accumulate during production as deposits which 
have to be filtered off and dried. 
The acyl groups R--CO-- of the compounds corresponding to Formula (I) are 
derived from straight-chain or branched, saturated or unsaturated C.sub.6 
to C.sub.22 fatty acids. Thus, for example, they are derived from fatty 
acids emanating from fats and oils of vegetable or animal orgin, such as 
caproic acid, caprylic acid, capric acid, lauric acid, myristic acid, 
palmitic acid, stearic acid, arachidic acid, behenic acid, palmitoleic 
acid, oleic acid, erucic acid, linoleic acid and linolenic acid. Such acyl 
groups may be derived from individual fatty acids or from fatty acid 
mixtures. In the latter case they are derived from fatty acid mixtures of 
the type accumulating in the lipolysis of natural fats and oils. In 
addition, the acyl groups of the acylcyanamides can also be derived from 
synthetic branched chain fatty acids containing from about 6 to 27 carbon 
atoms. The acyl groups can also be derived from fatty acids substituted by 
OH-groups, for example, from ricinoleic acid and hydrogenated ricinoleic 
acid. The acyl groups can also emanate from fatty acids substituted by 
O--CH.sub.2 --CH.sub.2 --OH-- groups and R'--O-- groups, wherein the 
symbol R' is a C.sub.1 to C.sub.4 alkyl group. Fatty acids such as these 
may be obtained from epoxy fatty acids, for example, epoxy stearic acid, 
by opening the oxirane ring with ethylene glycol, or from C.sub.1 to 
C.sub.4 alcohols. In a preferred embodiment of the invention, the acyl 
groups of the acylcyanamides corresponding to Formula (I) are derived from 
straight-chain, preferably unsubstituted fatty acids containing from about 
12 to about 18 carbon atoms, i.e. R in formula I represents a C.sub.11 to 
C.sub.17 alkyl group. 
In polyvinylchloride melting compositions, the acylcyanamides corresponding 
to Formula I manifest an above-average heat-stabilizing effect which, by 
suitable choice of the metal cations, may be directed both toward 
enhancing initial stability and also toward improving long-term stability. 
Use of the zinc acylcyanamides of this invention has a positive effect on 
the initial stability of PVC-molding compositions, without the undesirable 
zinc burning, even in relative high concentrations. In addition, 
PVC-molding compositions containing acylcyanamides instead of the usual 
stabilizers, such as metal soaps, are characterized by their improved 
transparency. 
The acylcyanamides corresponding to Formula (I) can be used as the sole 
primary stabilizers in the polyvinylchloride molding compositions. 
However, they can also be used in admixture with other known primary 
stabilizers, such as, inorganic and organic lead salts, organic antimony 
compounds, organotin compounds, cadmium/barium carboxylates and phenolates 
of calcium, barium, zinc and aluminium. 
In addition to the primary stabilizers mentioned, the stabilized 
polyvinylchloride molding compositions may contain known co-stabilizers, 
lubricants, plasticizers, antioxidants, additives for improving impact 
strength, fillers and other auxiliaries. 
The stabilized thermoplastic molding compositions are based on homopolymers 
or copolymers of vinylchloride. The copolymers contain at least 50 mole 
percent, and preferably at least 80 mole percent, of vinylchloride. The 
polymers may have been produced by any conventional method, for example, 
by suspension, emulsion or block polymerization. Their K-value may be in 
the range of from about 35 to 80. Molding compositions based on 
after-chlorinated polyvinylchloride and on resin mixtures predominantly 
containing homopolymers or copolymers of vinylchloride may also be 
stabilized with the acylcyanamide compounds of this invention. 
The use of the acylcyanamides of Formula I as heat stabilizers for 
chlorine-containing polymers is not being claimed in this application but 
instead is the subject of a separate patent application filed by 
Applicants on the same date.