Liquid PVC stabilizers and lubricants

Disclosed is a stabilizer composition effective to protect PVC resin against heat-mediated deterioration, comprising a mixture of barium and zinc salts of aliphatic C.sub.6 -C.sub.20 carboxylates and aromatic C.sub.7 -C.sub.12 carboxylates, organic triphosphites of the formula R.sub.1 OP(OR.sub.3)OR.sub.2 wherein each of R.sub.1, R.sub.2 and R.sub.3 is C.sub.6 -C.sub.12 alkyl or phenyl, and organic acid phosphites of the formula R.sub.4 OP(OH)OR.sub.5 wherein each of R.sub.4 and R.sub.5 is C.sub.6 -C.sub.12 alkyl or phenyl, or R.sub.4 can be hydrogen. PVC film compounded with this stabilizer composition also exhibits improved wettability and adherence to water-based inks applied to such films.

BACKGROUND OF THE INVENTION 
The present invention relates to printing onto PVC (i.e. polyvinyl 
chloride) materials, particularly flexible (i.e. plasticized) PVC film and 
sheeting. 
Successful processing of PVC plastic film and sheeting using metal 
equipment such as extruders, roll mills, or calendars requires 
lubrication, i.e. the maintenance of a thin (ideally monomolecular) film 
of material between the metal and the plastic to reduce friction and 
prevent sticking of the plastic to the metal. Consequently, there is 
usually some lubricant-derived foreign material present on the surface of 
the PVC film or sheet as a separate phase into which minor components of 
the plastic (components and impurities in plasticizers, stabilizers, etc) 
may migrate. At the same time, successful printing requires first wetting 
of the plastic surface by the ink and then bonding of the ink's binder to 
the plastic to ensure that the print does not rub off or wash off. Any 
foreign material present on the surface of the PVC may constitute a 
barrier to the required wetting and bonding of the printing ink. 
Successful lubrication and printing therefore require careful balancing of 
conflicting influences. 
A further complication is the likelihood of a time lag between the initial 
shaping of the plastic into e.g. film or sheet form, and printing, as 
quantities of unprinted PVC material may be shipped to off-site printing 
plants and warehoused for some time, possibly under warm and humid 
conditions, before being printed. In fact it has been observed that some 
PVC materials can be printed successfully when fresh but diminish in 
printability upon storage. 
DISCUSSION OF THE PRIOR ART 
Historically, problems with printing on PVC were dealt with beginning about 
40 years ago with the commercialization of liquid stabilizers, 
particularly blends of barium alkylphenates with certain cadmium 
carboxylates and organic phosphites (see Leistner et al. U.S. Pat. No. 
2,716,092) in hydrocarbon carriers such as mineral spirits. The recent 
recurrence of the problems referred to above coincides with the more or 
less simultaneous efforts to reformulate PVC stabilizers to exclude 
cadmium as well as hydrocarbons such as mineral spirits and to reformulate 
printing inks to water-based formulations minimizing the use of organic 
solvents. 
Historically, the commodity lubricant for PVC processing in the U.S. has 
been stearic acid. Oxidized polyethylene, or ester or amide waxes, or some 
metal soaps, have been used also. "Handbook of Plastics Additives and 
Modifiers" (J. Edenbaum editor, 1992, Van Nostrand Reinhold) at pages 
807-822 discloses illustrative PVC formulations including oxidized 
polyethylene. 
Liquid stabilizers having a low volatility (i.e. high flash point) 
combining a high concentration of active ingredients with low viscosity, 
are disclosed in Bae, U.S. Pat. No. 4,401,779 and Aza et al., U.S. Pat. 
No. 4,837,257. Both relate to barium-cadmium salt combinations in which 
the barium component is a liquid barium alkylphenate-barium carbonate 
composition, and teach nothing about a barium-zinc composition in which 
the barium component by itself is a high melting solid and cadmium is 
absent or present only as a trace impurity. 
Various stabilizers formulated without a cadmium component, without, 
however, any disclosure of low volatility (high flash point) and low 
viscosity liquid stabilizers, are disclosed in Minagawa et al., U.S. Pat. 
No. 4,348,308, Tadenuma et al., U.S. Pat. No. 5,004,776, Sugawara et al., 
U.S. Pat. No. 5,147,917, and Sander et al., U.S. Pat. No. 5,283,273. 
BRIEF SUMMARY OF THE INVENTION 
One aspect of the present invention is a liquid stabilizer composition 
which imparts heat stability to PVC and which is essentially free of 
cadmium, comprising 
(A) a salt mixture comprising cations of barium and zinc, one or more 
aliphatic carboxylates selected from the group consisting of straight and 
branched aliphatic saturated and unsaturated carboxylates containing 6 to 
20 carbon atoms, and one or more aromatic carboxylates containing 8 to 10 
carbon atoms, wherein the weight ratio of barium to zinc is about 2:1 to 
6:1; 
(B) one or more organic triphosphites of the formula R.sub.1 
OP(OR.sub.3)OR.sub.2 wherein R.sub.1, R.sub.2 and R.sub.3 are the same or 
different and each is alkyl containing 6 to 12 carbon atoms, or phenyl; 
and 
(C) one or more organic acid phosphites of the formula R.sub.4 
OP(OH)OR.sub.5 wherein R.sub.4 is alkyl containing. 6 to 12 carbon atoms, 
or phenyl, and R.sub.5 is alkyl containing 6 to 12 carbon atoms, phenyl or 
hydrogen. 
Another aspect of the present invention is a polyvinyl chloride resin 
composition having improved resistance to deterioration mediated by heat, 
comprising a polyvinyl chloride resin formed at least in part of the 
recurring group --CHCl--CX.sub.2 -- and having a chlorine content in 
excess of 40%, where each X is either hydrogen or chlorine, and an amount 
of the foregoing liquid stabilizer effective to enhance the resistance of 
the resin to heat-mediated deterioration. 
DETAILED DESCRIPTION OF THE INVENTION 
One useful aspect of the stabilizers of the present invention is that they 
permit the operator to avoid having to use components based on metals 
which have become environmentally objectionable, such as arsenic, 
beryllium, cadmium, lead, mercury and thallium. 
The stabilizers of the present invention are considered to be essentially 
free of cadmium, by which is meant that the total amount of cadmium is 
less than about 0.05 wt. % of the stabilizer, and less than 0.001 wt. % of 
PVC resin formulations. Preferably, the stabilizers of the present 
invention, and PVC formulations containing it, are essentially free of all 
six of the aforementioned metals, that is, the total amount of all six 
metals is less than about 0.05 wt. % of the stabilizer and less than about 
0.001 wt. % of PVC formulations containing the stabilizer. 
The stabilizer compositions of the present invention include a barium-zinc 
carboxylate component in combination with organic triphosphite and organic 
acid phosphite components. The are preferably used with an oxidized 
polyethylene component. It will be recognized that compositions effective 
as heat stabilizers comprise these components per se, and can comprise 
compositions containing these components in mixture with one or more 
additional components. 
One component of the stabilizer composition is characterized herein as a 
salt mixture. That term is intended to comprise mixtures formed by 
physically combining separate components each previously formed 
separately. The term "salt mixture" is also intended to include mixtures 
formed in situ by mixing and/or reacting together precursors containing 
the desired cations and/or anions. The latter type of salt mixture is 
preferred in the present invention. 
The salt mixture comprises cations of barium and zinc. The weight ratio of 
barium to zinc in the salt mixture should be in the range of about 2:1 to 
about 6:1, and is preferably about 3:1 to about 5:1 and more preferably 
about 4:1. 
The salt mixture comprises as well an anionic component. This anionic 
component comprises two types of anions. The anionic component comprises 
one or more anions selected from the group consisting of straight and 
branched aliphatic, saturated and unsaturated carboxylates, containing 6 
to 20 carbon atoms. The preferred carboxylates of this type are molecules 
containing 0 to 3 carbon--carbon double bonds. The most preferred 
carboxylates of this type are oleate and isomers of octanoate, such as 
2-ethyl hexanoate. 
The anionic component of the salt mixture also comprises one or more anions 
selected from the group consisting of aromatic carboxylates containing 8 
to 10 carbon atoms. By "aromatic carboxylate" is meant molecules 
containing a phenyl ring to which the carboxylate moiety is bonded 
directly, or indirectly through a saturated or unsaturated alkylene 
bridge. The phenyl ring can be additionally substituted, and in the 
preferred embodiments herein is substituted with one or more alkyl groups. 
Preferred examples of aromatic carboxylates useful in the present 
invention include meta-toluate. 
The weight ratio of the aliphatic carboxylate to the aromatic carboxylate 
will generally be in the range of about 1:3 to 3:1, and satisfactory 
results can be obtained wherein the weight ratio is about 1:1. 
The salt mixture can be prepared by combining separate salts previously 
separately prepared, such as by physically intimately admixing salts such 
as barium toluate and zinc oleate, in the desired relative respective 
amounts thereof. It is believed that a more intimate mixture of the 
desired salts is obtained by reaction in situ of precursor compounds, and 
this technique of preparing the salt mixture is preferred. This latter 
technique also affords the operator greater flexibility in adjusting 
relative amounts of barium, zinc, and the several carboxylate components. 
For instance, basic compounds of zinc and barium (that is, compounds 
capable of reacting with the aliphatic and aromatic carboxylic acids to 
form the desired salts), such as zinc oxide, barium hydroxide, and the 
like, are added to an intimate mixture of e.g. oleic acid and meta-toluic 
acid under conditions of agitation and heat effective to provide a through 
mixture of the salts which form upon reaction of the barium and zinc 
compounds with the organic acids. 
The stabilizers of the present invention also include an organic 
triphosphite component. The organic triphosphite is characterized by the 
formula R.sub.1 OP(OR.sub.3)OR.sub.2 wherein R.sub.1, R.sub.2 and R.sub.3 
are the same or different and each is an alkyl group containing 6 to 12 
carbon atoms, or phenyl. The alkyl group can be straight or branched, and 
is preferably branched. Examples of alkyl groups useful in this component 
include the one or more branched isomers of decyl known collectively in 
the art as "isodecyl", and any of the isomers of branched octyl groups 
such as 2-ethylhexyl. Preferably, a mixture of organic phosphites 
corresponding to the above-mentioned formula is employed. An example of 
one such preferred mixture contains about 18-24 wt. % triphenyl phosphite, 
about 58-60 wt. % diphenylisodecyl phosphite, about 18-20% 
phenyldi-isodecyl phosphite, and about 1-2 wt. % of tri-isodecyl 
phosphite. 
The stabilizer compositions of the present invention also include one or 
more organic acid phosphites of the formula R.sub.4 OP(OH)OR.sub.5 wherein 
R.sub.4 is a straight or branched alkyl group containing 6 to 12 carbon 
atoms, or phenyl; and R.sub.5 is a straight or branched alkyl group 
containing 6 to 12 carbon atoms, phenyl, or hydrogen. The R.sub.4 and 
R.sub.5 groups can be straight or branched alkyl, and are preferably 
branched alkyl, or phenyl. As is the case with the organic phosphites, it 
has been found useful to employ a mixture of organic acid phosphites of 
the foregoing formula, such as 19-21 wt. % of diphenylacid phosphite, 
58-60 wt. % of phenylisodecyl acid phosphite, and 18-22 wt. % of 
di-isodecyl acid phosphite. 
The salt mixture of barium and zinc aliphatic and aromatic carboxylates 
should comprise about 30 wt. % to about 50 wt. % of the total amount 
present of said salt mixture, said one or more organic triphosphites, and 
said one or more organic acid phosphites. Preferably, the amount of the 
salt mixture expressed on this basis is about 35 to about 45 wt. %, and 
preferably about 40 wt. %. 
The one or more organic triphosphites should be present in an amount of 
about 40 to about 60 wt. % of the total of the barium-zinc salt mixture, 
the one or more organic phosphates, and the one or more organic acid 
phosphites present. Preferably, the one or more organic triphosphites are 
present in amounts of about 45 wt. % to about 55 wt. % expressed on that 
basis, and more preferably about 50 wt. % to about 55 wt. %. 
The one or more organic acid phosphites are present in amounts of about 4 
to about 10 wt. % of the total amount of barium-zinc salt mixture, one or 
more organic triphosphites, and one or more organic acid phosphites 
present. Preferably, the one or more organic acid phosphites are present 
in amounts of about 4 wt. % to about 8 wt. %, and more preferably amounts 
of about 5 wt. % to about 7 wt. %, expressed on that basis. 
To make the stabilizer, it is most convenient to combine the components 
which are liquid or easily liquifiable with no more than moderate heating, 
adding a modest amount of solvent or diluent if necessary to keep this 
mixture from becoming excessively viscous, and then to stir in the other 
components which are solid at ambient conditions. For instance, as will be 
disclosed more fully in the examples below, it is convenient to form the 
barium-zinc-carboxylate salt mixture, the organic triphosphite or mixture 
of organic triphosphites which are liquid at ambient conditions, and the 
organic acid phosphite or mixture of organic acid phosphites which are 
liquid at ambient conditions, to stir these components together, and then 
to add addition solid components as desired such as additional barium 
and/or zinc carboxylates, and/or additional organic triphosphites and/or 
additional organic acid phosphites. The additional components thus added 
can be overbased barium and/or zinc compounds, such as barium 
carbonate/barium carboxylate wherein the molar ratio of barium to 
carboxylate exceeds 1:1. 
It is preferred to include in the stabilizer composition a diketone 
component which is one or more diketones of the formula D.sub.1 
C(O)--(CH.sub.2).sub.i --C(O)D.sub.2 wherein i is 1 or 2, preferably 1, 
and each of D.sub.1 and D.sub.2 is phenyl or C.sub.12 -C.sub.22 alkyl or 
alkylene, preferably phenyl. The preferred diketone is dibenzoyl methane. 
The diketone helps impart wettability (as defined herein) to the PVC resin 
and may assist in heat stabilization as well. The diketone, if used, will 
comprise about 1 wt. % to about 8 wt. % of the stabilizer composition, 
preferably about 5 wt. % thereof. 
It has been further determined that including in the stabilized PVC an 
effective amount of oxidized polyethylene (also known as oxidized 
polymeric wax) further enhances the advantageous properties of the 
aforementioned stabilizer composition in providing notable heat stability, 
processing ease, and in affording improved wettability, that is, an 
improved ability (compared to PVC products not containing the oxidized 
polyethylene) to receive and retain printing from water-based inks. 
Oxidized polyethylene is a commercially available polymer additive, known 
by that term, and is believed to comprise polyethylene (preferably 
homopolymeric) which has been subjected to oxidation so as to form a small 
proportion of oxidic substitution, such as hydroxyl, ketonic or 
carboxylic) at various sites along the polymer chain. The oxidized 
polyethylene useful in the present invention should have a molecular 
weight of at least about 750. The acid number of the oxidized polyethylene 
is not critical, and can range from about 2 to about 50. The oxidized 
polyethylene should be a solid material at the temperatures of use of the 
PVC film or sheeting. It is preferred that the oxidized polyethylene have 
a melting point of at least about 60.degree. C., up to about 150.degree. 
C. A preferred oxidized polyethylene useful in the stabilizer compositions 
of the present invention is known as "AC Polyethylene 629A", an oxidized 
polymer having a molecular weight of about 2000, a softening point of 
about 213.degree. of to about 221.degree. F., and an acid number of 14 to 
17 which is commercially available from Allied-Signal Corp. 
It is preferred to incorporate the oxidized polyethylene into the 
aforementioned stabilized composition after addition of the stabilizer to 
the PVC resin. The weight ratio of oxidized polyethylene to the total 
amount of barium-zinc carboxylate salt mixture, organic triphosphite, and 
organic acid phosphite, should generally be in the range of about 1:2 to 
about 1:6, preferably about 1:3 to 1:5 and more preferably about 1:4. 
The stabilized PVC composition comprising these ingredients can also 
contain conventional additional additives such as antioxidants, 
plasticizers, lubricity agents, flame retardants, fillers, pigments, and 
the like, in relative amounts affective to fulfill the desired functions 
of each such additional ingredient. These ingredients can be added, if 
desired, while the combination is being prepared of barium-zinc salt 
mixture, organic phosphite, and organic acid phosphite. 
The stabilizer systems of the present invention are effective in enhancing 
the resistance to heat-mediated deterioration of PVC resin. That is, 
"heat-mediated deterioration" includes deterioration which is due to 
exposure to excessive heat, as well as deterioration which is initiated or 
accelerated by exposure to heat. 
The terms "PVC" and "polyvinyl chloride" as used herein are inclusive of 
any polymer formed at least in part of the recurring group 
(--CHCl--CX.sub.2 --).sub.n and having a chlorine content in excess of 
40%. In this formula, each of the X groups can be either hydrogen or 
chlorine, and n is the number of units in the polymer chain. In PVC 
homopolymers, each of the X groups is hydrogen. Thus, the term includes 
not only polyvinyl chloride homopolymers but also after-chlorinated 
polyvinyl chlorides, as well as copolymers of vinyl chloride in a major 
proportion with other copolymerizable monomers in moderate proportion, 
such as copolymers of vinyl chloride and vinyl acetate, copolymers of 
vinyl chloride with maleic or fumaric acids or esters, and copolymers of 
vinyl chloride with styrene. The stabilizer compositions are effective 
also with mixtures of polyvinyl chloride in major proportion with a minor 
proportion of other synthetic resins such as chlorinated polyethylene or a 
copolymer of acrylonitrile, butadiene and styrene. 
The stabilizer compositions of the present invention can be used with 
plasticized polyvinyl resin compositions of conventional formulation. 
Conventional plasticizers well known to those skilled in the art can be 
employed such as, for example, dioctyl phthalate, octyl diphenylphosphate, 
and epoxidized soybean oil. Particularly useful plasticizers are the 
epoxidized esters having from 20 to 150 carbon atoms. 
The stabilizer compositions of the composition of the present invention are 
used in small but effective amounts to impart the desired stability to 
heat-mediated deterioration. Effective heat stability coupled with 
enhanced wettability by water-based ink formulations can be afforded 
generally by adding about 2 to about 5 phr (parts by weight per hundred 
parts by weight of resin) of the stabilizer composition of barium and zinc 
carboxylates, organic triphosphite(s) and organic acid phosphite(s) to the 
PVC resin to be compounded and formed into the desired film or sheeting. 
Preferred amounts of the stabilizer are in the range of about 3 to about 4 
phr. 
The oxidized polyethylene is believed to impart enhanced wettability, that 
is, an enhanced ability to allow a water-based ink applied to the surface 
to form a uniform, continuous or continuous-appearing film without the 
appearance of the formation of distinct micro beads or micro droplets of 
ink on the surface of the PVC film. The presence of the oxidized 
polyethylene with the stabilizer compositions of the present invention 
also imparts an enhanced ability for the water-based ink to adhere to the 
PVC film and to remain adherent thereto. By "water-based" ink formulations 
are included solutions, dispersions and emulsions wherein water is the 
continuous phase. Examples of such ink formulations abound in the printing 
field and are well known and ascertainable by those of ordinary skill in 
this art. Effective amounts of the oxidized polyethylene component are 
generally in the range of about 0.2 to 2 phr, and more preferably about 
0.5 to 1.25 phr. The oxidized polyethylene is also believed to contribute 
lubrication to the PVC film, thereby facilitating its formation into a 
sheet or film and facilitating removal of the film or sheet from the 
apparatus used to form that product. The presence of the oxidized 
polyethylene permits the formulator to reduce the amount of other 
lubricating additives used, or to eliminate them altogether. For instance, 
C.sub.12 -C.sub.22 carboxylic stearic acids such as stearic acid can be 
reduced or eliminated. 
PVC formulations compounded with PVC, a stabilizer composition according to 
the present invention, oxidized polyethylene, and other additives such as 
conventional fillers, processing aids, plasticizer, antioxidant, 
colorants, and the like, can be formed into film or sheeting useful in, 
for instance, the manufacture of wall coverings, by feeding the 
formulation between the heated rollers of a two-roll mill and forming and 
recovering the product in conventional manner. Thereafter, the film or 
sheet can be printed using customary techniques. 
The following examples will illustrate formulation and use of stabilizer 
compositions according to the present invention.

EXAMPLE 1 
In a heated, stirred reactor, 135.2 pounds of oleic acid and 199.2 pounds 
of meta-toluic acid were stirred together and heated to about 212.degree. 
F. To this mixture were added 139.6 pounds of barium hydroxide and 19.5 
pounds of zinc oxide which were stirred into the mixture and allowed to 
react at a temperature of about 275.degree. F. for about 1-2 hours. The 
resulting product was a 2:1 (wt.) mixture of barium meta-toluate and zinc 
oleate. 
To this material was added 467.6 pounds of a blend of phenyl-isodecyl 
phosphites composed of about 20 wt. % triphenyl phosphite, 59 wt. % 
diphenyl isodecyl phosphite, 19 wt. % phenyl-di-isodecyl phosphite and 1.5 
wt. % tri-isodecyl phosphite, and about 82.8 pounds of an organic acid 
phosphite which had been previously formed by hydrolyzing the 
aforementioned triorganic phosphite and stripping off one mole of phenol 
per mole of triorganic phosphite. This mixture was then stirred, at a 
temperature of about 220.degree. F. 
To this mixture were added 92.3 pounds of overbased barium oleate, 92.3 
pounds of zinc-2-ethyl hexanoate toluate (as an 8.5 wt. % solution in 
isodecyl alcohol and mineral spirits), 261.0 pounds of a 
phenyl-(2-ethylhexyl) phosphite product comprising a mixture of about 20 
wt. % triphenyl phosphite, about 59 wt. % of diphenyl (2-ethylhexyl 
phosphite), about 19 wt. % of phenyl-di(2-ethylhexyl) phosphite and about 
1.5 wt. % of tri(2-ethylhexyl) phosphite, and about 15.4 pounds of an 
antioxidant for PVC resin. 
About 77 pounds of diketone (dibenzoyl methane) was also added to this 
mixture. 
EXAMPLE 2 
Stabilizer compositions such as those prepared in accordance with Example 1 
have been incorporated into PVC films and sheeting in accordance with 
conventional formulation and processing techniques. For instance, the 
following components were mixed together in the amounts indicated: 
______________________________________ 
Amount, 
Component parts by weight 
______________________________________ 
medium weight PVC 96 
plasticizers 32 
other processing aids, flame retardants, 
5.5 
and antimicrobial agent 
inorganic fillers and opacifiers 
55 
and colorants 
______________________________________ 
To a thorough mixture of these components was added about 3.5 phr of the 
composition prepared in accordance with Example 1, and 0.75 phr of 
oxidized polyethylene ("A-C Polyethylene 629A", Allied-Signal Corp.). All 
these components were intimately stirred together and fed to a heated 
2-roll mill of conventional design whereon the mixture was formed into a 
thin, continuous, white sheet of PVC. The sheet was recovered off the 
mill. Application of a quantity of water-based ink using a conventional 
ink roller deposited a layer of color onto the PVC sheet which layer 
appeared uniform and continuous to the naked eye and which, upon drying, 
retained its uniform, continuous appearance free of the appearance of 
discrete micro drops and the like. 
It has been found that PVC films and sheets compounded with the stabilizers 
of the present invention exhibit notable heat stability, and also can be 
satisfactorily printed with water-based ink systems thereby forming 
attractive, continuous, adherent layers of ink which do not exhibit 
individual drop-like appearance, and which remain stable and adherent on 
the surface of the PVC even for prolonged periods of time. This 
observation has been confirmed for freshly compounded PVC film and 
sheeting, as well as for PVC film and sheeting which has been stored for 
several months between the compounding and the printing thereof.