CA1109245A - Antimony mercaptocarboxylic acid or ester-ortho dihydric phenol stabilizers for rigid polyvinyl chloride resin compositions - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

Stabilizer compositions are provided, capable of enhancing the resistance to the development of early discoloration in the first five to twenty minutes of heating at 375°F of rigid polyvinyl chloride resin compositions, comprising an antimony mercaptocarboxylic acid or ester having an arsenic content of less than 0.1% by weight and an ortho-dihydric phenol. There may also be present, as an optional component, an alkaline earth metal salt of a carboxylic acid having from about 8 to about 24 carbon atoms, or an epoxidized triglyceride ester of a carboxylic acid having from about 3 to about 24 carbon atoms.

Description

SPECI~C~TION
PolyYinyl chloride resin compositions used for the manu-facture of rigid articles such as pipe and profiles are processed nowadays by extrusion in multi-screw extruders. Multi-screw extruders differ from the older single-screw extruders, calenders and blow-molding ma~hines in retain-ing the polyvinyl chloride resin composition being processed fo~ a much shorter period of time. Such polyvinyl chloride resin compositions are usually pig-mented, and they are also highly lubricated, by virtue of the addition of substantial amounts of lubricants such as wa~es, mineral oilj and calcium stearate, so that under the positive displacement pumping action of the multi-screw extruder they~ can be processed at any desired rate.
Thus, the polyvinyl chloride resin compositions may not be subjected to the rather elevated temperatures, of the order of 3~5F and higher, required to bring the composition to an extrudable, softened condition, for much longer than thirty minutes, and frequently only for as 5ittle as fi~e to ten minutes.
Conventional heat stabilizer compositions are not suited for use with such rigid polyvinyl chloride resin compositions. The highly lubricated compositions that are especially formulated for extrusion in such machines do not require stabilization against long heating times at 375~F.
What is required,especially for light colored compositions, is resistance to the developrnent of any significant discoloration during the first five to ten or twenty minutes of heating, so as to avoid change in the color. Such discoloration is referred to as "early yellowing".
This discoloration conventional heat stabilizers are not gener-ally formulated to prevent. While long term heat stability has been a pre-requisite an early discoloration could be tolerated, if it did not deepen 3~
significantly with continued heating, since the art tolera~ed some discoloration, but in order to avoid degradation inphysical properties duringl~ng term heating The highly lubricated formulations that have been de-veloped for extrusion in these machines contain substantial quantities 5 of lubricants, such as calcium stearate, frequently more lubricant than stabilizer. Typically frorn 0. 6 to 1 part per hundred, and sometimes as much as two parts per hundred of lubricant,are used with from 0.3 to 0. 5 part per hundred of an organotin stabilizer containing 12% tin or less. Such proportions are to be contrasted with the proportions used in con~entional 10 e~trudable compositions for use with single-screw extruders, where from 1 to 1. 6 parts per hundred of stabilizers containing 18% tin or 21 to 26% tin is used with a maximum of about 0. 5 part per hundred of the lubricant. Since the most popular lubricant has been calcium stea~ate, the change in relative proportions has meant a considerable change in the tin/calcium ratio..
Moreover, since calcium stearate has a tendency to impart a yellow discoloration of its own, the prevention cf early yellowing in such highly lubricated extrudable formulations has become correspondingly more difficult.
The organotin mercaptocarboxylic acid esters are widely 20 recognized as the most effective organotin stabilizers, having a tin content of about 18% Sn. The position o~ the organotin mercaptocarboxylic acid es~ers has been challenged in recent years by the provision of stabilizers containing a higher proportion of tin, from about 21 to about 26% ~n, referred to as "high efficiency" organotins. The latter are exemplified by 25 the organotin mercaptocarboxylic acid ester sulfides of U.S. patents Nos. ,39 565, 930, 3, 565, 931, 3~ 63~, 538 and 3, 817, 915. However, a high tin content is n~t a determinative factor in preventing the development of s early discoloration, as exemplified by the organotin sulfides, which off~r the highest tin and sulfur content per organotin group, and yet are not the most effective in this respect, affording a poor initial color, particularly.
While there are organotin stabilizers which are capable of lessening or inhibiting early discoloration, in recent years the organotins have become ex tremely expensive, and in short supply, with the result that the low cost products such as pipe and profiles have not been able to bear the cost of such stabilizers, and the art has had to turn to substitute systems, which are less expen~ive.
Stabilizer systems based on antimony compounds are less e~pensive,but, however f~rmulated, have not been capable of inhibiting the development of a yellow discoloration during the first five or ten minutes of heating. The yellow discolora-tion has been sufficiently intense, after only ten minutes of heating, that suchstabilizer systems despite their lower cost ha~e not been competitive with organot~n systems. Antimony-based stabilizers have also been characterized by poor storage life, with the formation of red, orange or black precipitates (presumably antimony sulfides and metallic antimony,respectiYely) known to occur.
Moreover, polyvinyl chloride compositions stabilized with antimon~based stabiliæe~s have had a greater tendency to discolor on exposure to sunlight than~imilar compositions with stabilizeræ not based on antimony.
A humber of patents have suggested the use of antimony compounds, particularly sulfur-containing compounds such as the antimony mercaptides.
These include U.S. patents Nos. 2,680,7269 2,684,956, 3,340,285, 3,g99,220, 3,466,261 and 3~530J158~ These patents disclose various types of organic sulfur-containing antimony compounds, but none have been adequate in inhibiting the development of an early yellow discoloration, in the processing of rigid pol~inyl chloride resin compositions.
Weinberg, Johnson and Banks U. S. patent No. 2, 680, 726 patented June 8, 1954 suggested the use of antimony mercaptoc~rboxylic ?t ~ ~ 5 acid esters of the formu3a Sb(~CO2~'33, where R is a~ylene, ax~ylene or aralkylene and R1 is a substituted or unsu~stituted alkyl or mixed .
alkyl-aryl ~;roup. Among the compounds named are Sb(SCH2CO2C9H~,~3 a mobile slightly yellow liquid; Sb-S, S', S"-tris(octadecyl thiomalate);
5 Sb(SCH2CO2CloH2l)3; Sb-S, S', S~-tris(glyceryl monoricinoleate-monomer captoacatate) and Sb-S, S', S"-tris(dihydroabietyl mercaptoacetate).
German patent No. 1,114, 808 to Deutsche Advance proposed antimony compounds of the formula (XS)2SbS(CH2)XCOO-A-COO(CH2)"SSb(SX)2, where x is an integer from 10 1 to 4, A an a.U~ylene residue of up to ten carbon atoms, ~ith or without OH groups, or merely a bond, and SX is the residue (having from eight to eighteen carbon atoms) of an aliphatic or aromatic mercaptan, or of an ester of a thioalcohol or thio acid, as stabilizers for polyvinyl halide resins.
Chemische Werke Barlocher British patent No 1,194, 414, published June 10, 1970, suggested antimony compounds of the formu~:
~,1 S-~3 ., \ ~
Sn-~-CH2 COO-CH2-CH2-OOC-CE2-S-~

(~2 )2 ~ -R4 20 wherein 1~ is an organic group (which may contain tin and/or antimony atoms) which is linked to the tin atom via a carbo~ylic group or a thio group and is the radical of an aliphatic carbo~ylic acid having at least 4 carbon atoms or of a mercaptan;
R2 is an alkyl radical;
R3 and R4 are organic groups linked to the sulphur atom via a carbon atom and are together with the sulphur atom radical~ oE

mercapto compounds; and s-~3 R5-S-Sn-OCO-CH2-S-Sb (R2)z S-R4 (III) wherein Rs is an organic group (which may contain tin and/or antimony atoms) which is linked to the sulphur atom via a carbon atom;
R2, R3 and ~4 have the designations assigned to them in formula II.
These are mixed compounds con~aining botli antimony and tin 10 in the molecule.
E:ast German patent No. 71, 380 patented February 20, 1970 suggested antlmony mercaptocarboxylate esters such as ~b-tris(2-ethylhexyl thioglycolate), used together with the corresponding organotin mercapto carboxylic ester.
~5 Dieckmann9 U.S. patent No. 3, 887, 508, patented June ~, 1975 has suggested that the stabilizing effectiveness of such antimony compuunds can be improved by combining them with a metal carboxylate. Dieckmann proposed that antimony sulfur-containing compounds of the general formula Sb (SR)3 (where R is a hydrocarbon or substituted hydrocarbon radical;
20 SR the residue 0~ a mercaptan or mercapto alcohol or a mercapto carboxylic acid ester) be improved by combining therewith an a~ali metal or alkaline earth metal salt of monocarboxylic and dicarboxylic acids of the type (RCXX) D M wherein the group RC~X is the carboxylate and/or thlocarboxylate group of an aliphatic or aromatic mono or polyfunctional acid containing, for 25 example, about C2-C54 carbon atoms; R is a hydrocarbon or substituted hydrocarbon radical; X is o~ygen and/or sulfur; n is an integral number from 1-2 and M is an a~kali or all~aline earth metal, ïor e~ample, sodium, potassium, lithium, magnesium, calcium, strontium and barium. This cLass of course includes calcium stearate. According 5 to Dieckmaml, such combinations exhibit a synergism in long term heat stability, in comparison with a standard resin formuLation containing neither antimony organic compound nor metal carbo2~ylate. The results in the working Examples9 for instance, Table II, column 7, are reported in terms o~ the length of time required for the resin composition to 10 develop the same degree of discoloration-as a control composition without either stabilizer aftel ten minutes of heating. There i~ no con-sideration given nor any report of the effectiveness of the stabilizer combina~ions in pre~renting the development of early discoloration, including the yellow discoloration imparted by the metal carboxyl~te.
~ fact, these compositions are not capable of preventing the deYelopment of eariy discoloration. The metal carbo~ylate continues to contribute to early di~coloration, just as it does in the absence of the antimony compound Not only doe~ it not enhance the effectiveness oE
the antimony compound in this respect; it worsen~ it. Compositions 20 containi~g the antimony compound and the metal c~rboxyLa;te develop a more intense yellow discoloration after the îirst five or ten minutes of heating than the antimony compo~md taken alone, although the long term stability may be extended.

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3~S

Phenolic antioxidants, especially hindered phenols, have long ~een known as stabilizers for polyvinyl chloride resin compositions, particul~r~
when used in combinations with other stabilizers. One of the first dis-closures of the use of hindered phenols for this purpose is in U.S. patent .

.

, .~,. .

:~ 6a , ; !

.;:

s NtJ. 2,564,646, patented August 14, 1~51 to William E. Leistner, Arthur C.
Hecker and Olga H. Knoepke. The effectiveness of phenols is discussed in the Encyclope_ia of Polymer Science and Technolo~ Volume 12 (1970), pag~ t752.
A problem with phenols is their tendency to impar$ a yellow discoloration to the 5 compound on their own, which puts them in the category of calcium stearate;
the result is an initial yellow discoloration which remains during the initial stages of heating, and then worsens. This of course disqualifies them; they are incapable of preventing the development of an early discoloration.
DieckmannU.S. patentNo. 4,0~9,618, patentedJunel4, 1977claims 10 that the early color heat performance of antimony organic sulfur containing compounds is significantly improved if they are combined with ortho-dihydric phenols. Improvements in long term heat stability also are achievable, according to the patent7 and in addition, the compositions are asserted to be liquids which are shelf-stable at ambient temperatures. Dieckmann points out 5 that liquid antimony stabilizer compositions tend to deteriorate on standing, as observed by the formation and/or precipitation of solids in the liquid compounds, formin~ heterogeneous liquids, which increase the problems of measuring and mixing the antimony compounds into vinyl halide resins for stabilization. This problem, it is asserted, is overcome by incorporating the ortho-dihydric phenol 20 with the liquid antimony stabilizer. In these combinations, metal carboxylates, and particularly calcium stearate, can also be incorporated to achieve ~he advantages of the previously issued Diecl~mann patent No. 3, 887, 508.
While Dieckmann claims improvements in long term heat stability are achieved with these combinations, this has not been comirmed, at least 25 for combinations utilizing antimony mercaptocarboxylic acids, esters and ~ t,~

~ixed acid esters. ~ttempts to duplicate Dieckmann's resu'lts h~ve sho1wn that while the ortho-dihydric phenol increases the resistance to the development of early discoloration during the first twenty minutes of heating at 375F7 the ortho-dihydric phenol reduces the resistance to the development of long term 5 discoloration. After Eorty minutes of heating, the composition containing the ortho-dihydric phenol and antimony mercaptocarboxylic acid or ester is invariably much more intensely discolored than the composition containing the antimony mercaptocarboxylic acid or ester alone. The effect appears to be due to the phenol, and may involve some interaction with the antimony 10 compound. The effect may not simply be an effect arising from instability of the polyvinyl halide resin, but may also in~olve instability of the phenol, or some delayed interaction at such elevated temperatures between the phenol and the antimony compound, which destroys the effectiveness of both as stabilizers for the polyvinyl halide resin.
Neither has it been possible to confirm the assertions of long-term shelf stability for the combinations of ortho-dihydric phenols and liguid antimony compounds, at least in the case of the antirnony mercaptocarboxylic acids ar esters. Such blends also develop precipitates on standing, in the same manner as the liquid antimony compounds described by Dieclmlann which do not contain 20 the ortho-dihydric phenols.
In accordallce with the instant invention, it has been determined that difficulties attendant on the use o-f antimony mercaptocarboxylic acids7' ester~, and mixed acid esters appear to arise from the presence of arsenic as an impurity. Antimony compounds frequently contain arsenic as an impurity, 25 in relatively large amounts. It has been determined that arsenic interferes with the stabilizing effectiveness of the antirnon~ mercaptocarbo~ylic acids and esters, and that the arsenic content thereof must be less ~an lûO0 mg/kg (0.10%) and preferably is less than 100 mg/kg (O.Ol~c~.
Arsenic can be removed from the starting antimony compound used in 5 the preparation of the antimony mercaptocarboxylic acid or ester by known procedures.
Accordingly, in accordance with the present invention, there are provided stabilizer composit~ns capable of enhancing the re-sistance to the development of early discoloration in the first five to 10 twenty minutes of heating at 375F of rigid polyvinyl chloride resin compositions, comprising an antimony mercaptocar~oxylic acid or ester having an arsenic content of less than 0.1% by weight and an ortho-dihydric phenol.
It has also been determined in accordance with this invention 15 that epoxidized triglyceride esters are highly effective in improving the resistance to discoloration on exposure to light of polyvinyl chloride compositions stabilized with antimony mercaptocarboxylic acids and esters containing less than 1000 mg/kg of arsenic impurLty.
Further7 it has been determined in accordance wLth the 20 invention that precipitatîon problems arising in blends of antimony mercaptocarbo}~ylic acid or ester or mixed acid ester and ortho-dihydric phenols can be avoided by heating the blend of the ortho-dihydric phenol and antimony mercaptocarbox~Tlic acid or ester at an elevated tem~erature within the range from about 50 to about 150C
25 and preferably from about 80 to about 150C. Heating7 especially at temperatures in excess of 80C, appears to effect a reaction of Uil-lmown nature, which either delays or entirely prevents the develop-ment of precipitates on standing. Only a short heating time is required, from about fifteen minutes to about foux hours~ The resulting blend is homogeneous, and remains so in storage for six 5 months or longer.
It has been noted that during blending of antimony mercapto-carboxylic acid or ester or mixed acid ester and ortho-dihydric phenol, heat is liberated, suggesting that there is a reaction between the ortho-dihydric phenol and the antimony mercaptocarbox~lic 10 as~id or ester. VVhatever reaction this may be, however, it furthex ap ?ears that heating at a temperature in excess of about 9a .

~0C, and preferably in excess of 80C, ef-fects a differentreaction, not obtained at lower temperatures, which results in the formation of a reactiGn product that remains homogeneous at atmospheric temperatures.
While the combinatLons of the ~nvention include as essential ingredients 5 antimony mercaptocarboxylic acid or ester or mixed acid ester and an ortho-dihydric phenol with, optionally, an epoxidized triglyceride ester, a further improvement in resistance to the developrnent of early discoloration is obtained if with such stabilizer compositions there is combined a third ingredient, an aLkaline earth metal carboxylate. The aLkaline earth metal carboxylate in 10 small amounts further increases the resistance to the development of early - discoloration of these blends. Such compositions fail to develop noticeable or significant yellow discoloration when heated at 375 F for up to approximately thirty minutes.
The invention further provides rigid polyvinyl chloride resin compo-15 sitions suitable for extrusion in multiscrew extruders and having ~n enhancedresistance to the development of early discoloration when heated at 375F7 comprising a polyvinyl chloride resin, an antimony mercaptocarboxylic acid or ester having an arsenic content of less than 1000 mg/kg, an ortho-dihydric phenol, and optionally, an alkaline earth metal carbo~ylate, epoxidized tri-20 glyceride ester or both. Preferredfor use in such polyvinyl chloride resin com-positions are blends of antimony mercaptocarbocyclic acid or ester and ortho-dihydric phenol which have been heated at an elevated temperature of at least about 50C for at least fifteen minutes. To such reaction products there can also be added an aLkaline earth metal carboxylate and/or epoxidized triglyceride 25 ester.
The stabilizer compositions of the invention contain as the principal stabilizing component antimony mercaptocarboxylic acids or esters having the general formula:

/~ 2~5 ~ Z ~C~ I n 3 ~ Y o ~ n _ . .
~, 2 ~ --Sb--S--Z~COO-- --Sb L[~(coo~,] ~ ~[s,~ ~coo~z]~z in which (1) Rl is selected from the group consisting of organic groups of the formula--SR30H and--OR3SE, where R3 is a~lylene having from tw~ to about eight carbon atoms; and S--Z--(COOR2~m g~oups;

(2) R2 iS selected from the group consisting of hydrogen9 alkyl, : ' alkylene, alkenyl, aryl, arylene, mixed al~ aryl, mia~ed aryl-all~yl, 10 cycloaliphatic, and hetexocyclic containing one ormore sulfur, oxygen or nitrogen ring atoms, having from about one to about twelve carbon -atoms~ and such groups containing ester groups, alko~y groups, hydro~yl groups, and halogen atoms7

(3) S--Z--COOR2 is a mercaptocarboxylic acid or ester group, ! 15 (4~ nl, n2 and n4 are the number of S--Z--CO0~2 groups, and are integers from O Ito 2; but at least one of nl and n2 is 1 or 2;
(5) n3 i~ the number of - .
- S -Z-~~- 1 Z ~c oo R2) ~

20 groups, and is a number from O to 10, and preferablyfrom O to 1;
(6) ml7 m2 and m3 are the num~er of C~OR2 groups, and are integers from 1 to 6;

~, (7~ Z is selected from the group consisting of bi~alent al~ylene radicals ha~ring from one to about five ca:rbon atoms, carrying the S
group in a position ~ or ~ to a COORz group; and such radicals containingfree carboxylic acid9 carboyxlic ester, and carboa~ylic 5 acid salt groups and mercapto groups.
The--S--Z -(COOR2)m and--S--Z--COO--groups are derived from mono - or poly - c~ and ~ - mercapto carboxylic acids and esters by removal of the hydrogen atom of the mercapto group.
The S--Z--(COOR2~ and--S--Z--C~O--groups can be the same or 10 different in the antimony compound, and the fnrmer if different can be all.acid (R2 = H), all ester (R2 ~ other than H~, or mixed acid and ester groups. The groups include the aliphatic acids and esters which contain at least one mercapto group, such as, for example, mercapto-acetic acid, - and ~- rnercaptopropionic acid, - and ~-., lla ,, s mercaptobutyric acid, c~ - and ~- mercaptovaleric acid, ~ - and ~-mercaptohexanoic acid, thiomalic acid, cy - and ~- mercaptoadipic acid, and ~ - and ~3- mercaptopimelic acid, and the Rz esters of each of these.
Preferably, R2 is either hydrogen or is derived from a mono-hydric alcohol containing from one to about fifteen carbon atoms, such as methyl, ethyl, propyl, s-butyl, n-butyl, t-butyl, isobutyl, octyl, isooctyl, 2-ethylhexyl, 2-octyl, decyl, lauryl, and myristyl; cyclic monohydric aIcohols, such as cyclopropanol, 2, 2,-dimethyl-1-cyclo-10 propanol, cyclobutanol, 2-phenyl-1-cyclobutanol, cyclopentanol, cyclo-hexanol, 2-methyl-, 3-methyl-, and 4-methyl-cyclopentanol and 2-methyl, 3-methyl-and 4-methyl-cyclohexanol, 2-phenyl-cyclohe~nol, 3, 3, 5-tri-methyl cyclohe~anol, cycloheptanol, 2-methyl-3-methyl-and 4-methyl-cycloheptanol, cyclooct~nol, cyclononanol, cyclodecanol, 15 cyclododecanol, or from a dihydric alcohol, such as glycols containing from two to about fifteen carbon atoms, including ethylene glycol;
propylene glycol; diethylene glycol; di-propylene glycol; tetramethylene glycol; neopentyl glycol and decamethylene glycol; 2, 2, 4-tri-methyl-pentane-diol; 2, 2, 4, 4-tetramethyl cyclobutane-diol; cyclohe:~ane-1, 4-20 dimethanol; and polyols such as glycerine, trimethylolethane, mannitol,sorbitol, erythritol, dipentaerythritol, pentaerythritol, and trimethylol propane.

~,, , ?~
The other essential ingredient of the stabilizer compo~ition of the invention is the ortho dihydric phenol. The effectiveness of this class of the ortho dihydric phenols is unique, and not displayed by its isomers, the meta and para dihydric phenols, such as hydroquinone and resorcinol.
The class of ortho dihydric phenols ernployed in the compositions of the invention has the following general formula:
OH

where:
R is selected from the group consisting of hydroxyl, aLkyl, cycloaLkyl, aryl7 alkoxy, aryloxy, a~enyl, carboxylalkyl, carboxyaryl, acyl, aryl, a~enyloxy, hydroxyaL~yl, hydroxyaryl, all~oxyaryl, and aLkoxyalkyl haYing ~rom one to about twelve carbon atoms; and n is an integer from zero to four.
E~emplary ortho dihydric phenols include catechol (which is preferred because of its cost and eEfectiveness), alkyl catechols such as p-t-butyl~catechol, p-methyi-catechol, m-ethyl-catechol, alkoxy catechols such as p-methoxy catechol, p-propoxy-catechol, p-hexoxy-catechol, cycloalkyl catechols such as p-cyclohexyl-catecholg ha1ogenated catechols such as m-chloro-catechol, p-chloro-catechol, p-bromo-catechol, polynuclear catechols sush as p-phenyl catechol, o~"B -dihydroxy naphthyl catechol, 2,2-di(4, 5-dihydroxyphenyl~ propane and bis-(4, 5-dihydroxy phenyl~ methane.
The antimony merca~tocarboxylic acid est~rs in accordance with the invention are mostly known compounds, and can be prepared by known reaction , procedures. One procedure employs antimony oxicle having less than 2000 mcDrtkg arsenic (0. 2'~),which is reacted with the corresponding mercaptocarb~xylic acid or ester or mixture thereof. Another procedure employs antimony tri-chlori~e having less than 1500 mg/kg arsenic (0.15~c), and alkali, which nre 5 reacted with the corresponding mercaptocarboxylic acid or es-ter or mixture thereof. If the acid is used, polymers containing the repeating unit --[Ib -S-Z -~ ]D3 ~S--Z ~(COOR~)m ]~4 can be and probably are formed. These procedures are illustrated in 10 Examples I to V.
The stabilizer system in accordance with the invention containing the antimony mercaptocarboxylic acid or ester or mixed acid ester and ortho-dihydric phenol can be prepared by simple blending of the ortho-dihydric phenol and antimony mercaptocarboxylic acid or ester.
If desired, the ortho-dihydric phenol ca~ be added to the reaction mixture in the course of preparation of the antimony mercaptocarboxylic acid or ester. The acid ~r ester can be obtained by reacting low arsenic antimony oxide (or antimony trichloride and alkali) with the corresponding mercaptocarboxs71ic acid or ester. When ortho-dihydric phenol is present, 20 - the final reaction product is the stabilizer system of the invention, containing the ortho-dihydric phenol already reacted with the low arsenic antimony mercaptocar~xylic acid or ester.
It is also possible to react low arserlic antimony trio~ide with the ortho-dihydric phenol in preparing the arltimony phenolate of the type 2 5 HO Sb--O~O

The antimony phenolate is then dissolved in either mercaptocarbo~,rlic acid o~
ester, prior to reaction thereof with low arsenic antimony trioxide or antimony trichloride and alkali, to form the antimony mercaptocarboxylic acid or ester, or the antimony phenolate can be dissolved directly in the low arsenic antimony 5 m~rcaptocarboxylic acid or ester, to prepare the stabilizer system.
The proportion of antimony mercaptocarboxylic acid or ester or mixed acid ester to ortho-dihydric phenol in the blends of the invention can be within the range from aboutlOQ:1 to about 2:1, alld preferably from about 50 :1 to about g:1.

As the al~aline earth metal carboxylate7 there can be used alkaline earth metal salts of an aliphatic monocarboxylic acid having from about eight to about twenty~four carbon atoms. Such metal salts are wid~ly used in the processing of polyvinyl chloride resins, particularly by extrusion, because of their lubricating characteristics. Exemplary ahkaline earth metals are calcium, strontium and barium, and exemplary organic acids are lauric acid,2-ethyl hexoic acid, undecylenrc acid, capric acid, caproic acid, myristic acid9 palmitic acid, stearic acid, oleic acid, linoleic acid, ricinoleic acid, linolenic acid, behenic acid and eicosanic acid.
These acid salts are particularly advantageously prepared from the mixed fatty acids obtained by saponification of natural fat~ d waxes, such as coconut oil fatty acids, tallow fatty acids, montan wax fatty acids3 castor oil fatty acids, corn oil fatty acids, fish oil fatty acids, sesame seed oil fatty acids, soya oil fatty acids, and tung oil fatty acids. Also useful are the partially saponified ester waxes, such as esters of montan wax partially saponified with lime, and the synthetic aliphatic monocarboxylic acids. r '' Exemplary alkaline earth metal carboxylates that can be errl~oyed include calcium stearate, barium stearate, strontium stearate, calcium 2-ethylhexoate, calcium oleate, barium oleate, calcium laurate, barium laurate, strontium caprylate, calcium palmitate, calcium caproate, and calcium eicosanoate, 5 barium neodecanoate, barium octoate, strontium octoate, calcium decanoate and calcium undecanoate.
Mixtures of alkaline earth metal carboxylates can also be used, such as mixtures of barium and calcium stearate, barium and calcium octoate, barium and calcium oleate, barium and calcium myristate, and barium and 10 calcium palmitate, as well as the calcium salts of coconut fatty acids, barium salts of coconut fatty acids, and strontium salts of tallow fatty acids.
Any of the metal c~boxylates disclosed in U.S. patents No.
3, 88q, 508 and No. 4, 029, 618 to Dieckmann can also be used~
The proportion of alkaline earth metal carboxylate to the blend of the invention can be within the range from about 10:1 to about 1:10, ~d preferably from about 3 :1 to about 1: 3 .
Epoxidized triglyceride esters that can be used together with the low level arsenic antimony compound and ortho-dihydric phenol blend, and homogeneously blended therewith, include any epoxidized previously ethylenisally unsaturated fatty oils and fatty acid esters. Such oils and esters may have had one or more ethylenicallyunsaturated groups per molecule. Fatty oils, as is well known, are usually composed of varying proportions of glycerides of organic fatty acids including both saturated and unsaturated fatty acids, of which only the unsaturated groups have been epoxidized, the fatty acids having from about eight to about twenty-fnur carbon atoms.
Exemplary are the epoxidized soyabean oil, epoxidized cottonseed oil, epoxidized beef tallow, epoxidized sheep tallow, epoxidized fish oils of various types, such as epoxidized menhaden oil, epoxidized cod liver oil, epaxidized , .

shark oil, epoxidized sperm oil, epoxidized whale oil, epoxidized herring oil, epoxidi~ed peanut oil, epoxidized linseed oil, epoxidized sunflower seed oil, epoxidized safflower seed oil, eps)xidized coconut oil, epoxidized palm oil, epoxidized lard oil, epoxidi~ed perilla oil, epoxidized kernel oil, epoxidized 5 poppyseed oil, epoxidized rapeseed oil, epoxidized sesame seed oil, epoxidized hempseed oil, epoxidized cocoa oil, epoxidized acorn s)il, epoxidized apricot kernel oil, epoxidized beechnut oil, epoxidized cherry kernel oil, and epoxidized corn oil, as well as epoxidized triglyceride esters mixed with epoxidized esters of the unsaturated fatty acids and. mon~hydric and other polyhydric alcohols 10 including epoxidized esters of oleic acid, linoleic acid, liIlolenic acid, ricinoleic acid, crotonic acid, and isocrotonic acid, with ethylene glycol, ethyl alcohol, pentaerythritol, butyl alcohol, mannitol, sorbitol, Lauryl alcohol and stearyl alcohol.
The weight ratio of epoxidized triglyceride ester:blend of low level 15 arsenic antimony compound and ortho-dihydric phenol blend can be within the range from about 10:1 to about 1:10 and preferably from about 3:1 to about 1:3.
The stabilizer systems in accordance with the invention can be used as stabilizers with any rigid polyvinyl chloride resin formulation~ The ~0 term "polyvinyl chloride" as used herein is inclwsive of any polymer .formed at least in part of the recurring group -, I
--CH--C--11 ~
~5 and having a chlorine content in excess of 40~c. In this group, the X group can each be either hydrogen or chlorine. In polyvinyl chloride homopolymers each of the X groups is hydrogen. Thus, the term includes not only polyvinyl chloride homopolymers but also after-chlorinated polyvinyl chloride such as those disclosed in British Patent NG. B93, 288 and also copolyrners of vinyl chloride in a major proportion and other copolymerizable monomers in a minor proportion, such as copolymers of vinyl chloride and vinyl acetate, co-polymers of vinyl chloride with maleic or fumaric acids or esters, and copolymers of vinyl chloride with styrene, propylene, and ethylene. The in-vention also is applicable to mixtures of polyvinyl chloride in a major pro-portion with other synthetic resins such as chlorinated polyethylene or a co-polymer of acrylonitrile, butadiene and styrene. Among the polyvinyl chlorides which can be stabilized are the uniaxially-stretch oriented polyvinyl chlorides described in U.S. patent No. 2,984, 593 to Isaksem et al, that is, syndiotactic polyvinyl chloride as well as atactic and isotactic polyvinyl chlorides.
The stabilizer systems of the invention are particularly use-ul with rigid polyvinyl chloride resin formulations. These are defined as containing no or only up to 10~c plasticizer. Plasticizers which can be employed to impart an improved processability without impairing the rigidity of the formulation include dioctyl phthalate~ dioctyl sebacate, and tricresyl phosphate.
Where a plasticizer is employed, it can be used in ~n amount within the range from about 0. 5 to about 10 parts per one hundred parts by weight of the resin.
Also useful plasticizers are the epoxy higher fatty acid esters having from about tw-snty to about one hundred fifty carbon atoms.
Impact modifiers, for improving the toughness or impact-resistance of unplasticized resins, can also be added to the res~n compositions stabilized by the present invention in minor amounts of usually not more than 10~C.
~; ! .
25 Examples of such impact modifiers include chlorinated polyethylene, ABS
polymers, and polyacrylate-butadiene graft copolymers.
, ~ 18 The total amount of stabilizer system in accord~nce with the invention is sufficient to impart the desired resistance to the devel~pment of early discoloration at working temperatures of 375 F and above for at least ten minutes up to but not necessarily exceeding the first twenty to thirty minutes of heating. The more onerous the conditions to which the resin will be sub-jected during working, the greater will be the amount of stabili~er system required. ~;enerally, as little as 0.1~ total stabilizer by weight of the resin will improve the resistance of the developmen~ of early discoloration. There is no critical upper limit on the amount, but amounts a~ove about 1O~G by weight of the re~in do not give an increase in stabilizing ef~ectiveness com~
mensurate with the additional stabilizer employed. Preferably, the amount is within the range from about 0. 20 to about 2% by weight ~ the resin.
Of this amount, from about 0. 007 to about 9. 8~G by weight, pref~rably from about 0.18 to 1. 95~; by weight, is antim~ny mercaptocarboxylic acid or e~ter; from about 0. 001 to about l'yc by weight~ preferably from about 0. 01 to-about 0. 5~ by weight, is ortho-dihydric phensl; and from about 0.1 to about 1. 5% by weight is alkaline earth metal carboxyl~te, if present, and from about 1. 5~, by weight is epoxidized triglyceride ester~ if present. ~-.. . . . ....... . . .............. .. . ..... .
The stabilLzer of the invention is extremely effective when used 20 alone, but it can be employed together with other polyvinyl chloride resin stabiliz~rs, including organotin compounds, if special effects are desired.
The stabilizer of the invention in this event will be the major stabilizer~
and the additional stabilizer will supplement the stabilizing action of the former, the amount of the antimony mercapto ester and catechol stabilizer 25 being within the range from about 0.1 to about 10 parts by weight per 100 parts of the resin, and the additional stabilizer being in the amount of from :.

.

about Q. 05 to about 5 parts per 100 parts of the resin.
Among the additional metallic stabilizers are included polyvalent metal salts of medium and of high molecular weight phencLs, with metals such as calcium, tin, barium, zinc, magnesium, and strontium. The nor.metallic stabilizers include organic phosphites, epoxy compounds (other than the tri-glycerides referred to above), polyhydric alcohols, and the like Epoxy compounds are especially useful, and typical c~mpounds are described in U. S. patent No. 2, 997, 454.
The stabilizer systems of this invention can be formulated for market-ing by mixing the ortho-dihydric phenol antimony mercaptocarbo~ylic acid t)r ester or a previ~usly prepared blend thereof, desirably after heating at a elevated temperature, with an inert diluent or with any liquid lubricant or plasticizer in suita~le concentrations ready to be added to the resin composition to give an appropriate stabilizer a~d lubricant or plasticizer concentration in the resin. Other stabilizers and stabilizer adjuncts can be incorporated as well.
The preparation of the polynnyl chloride resin composition is easily accomplished by conventional procedures. The selected stabilizer combination is formed as described above, and then is blended with the polyvinyl chloride resin~ or alternatively, the components are blended individually in the resin, using, for instance, a two or three roll mill, at a temperature at which the mix is fluid and thorough blending f~cilitated, milling the resin composition including any plasticizer at from 250 to 375 F
for a time ~ufficient to form a homogeneous mass, five minutes, usually.
After the mass is uniform, it is extruded in the usual way.
For the commercial processing of rigid polyvinyl chloride, the ~tabilizer is eonveniently mixed with all or a portion s)f the polymer to ~e stabilized with vi~orous agitation under such conditions o~ tinle and temperature that the stabilizer is sufficiently imbibed by the polymer to ~roduce a dry, free-flowing powd~r. The well-~own ~enschel mixer is well suited to this procedure.
The following Examples illustrate the preparation of the antimony compounds and blends thereof with ortho dihydric phenols of the invention:
Example I
Preparation of antimony tris(isooctyl thioglycoLate) from antimony oxide:
Into a five liter three-nec~ flask was put 1173. 8 g (5. 4 moles) o~
isooctyl thioglycolate, 93 . 85'~ . The isoocty l thioglycolate was heated to 40C, and then there was ~radually added 0.9 mole, 262.35 g, of antimony trioxide, arsenic content 0~o5q7c. Vacuum was applied, -and heating continued to 70C at 29 mm of mercury 0. 5~c ''suPer~el~was added, and the reaction mixture was then filtered. The product assayed 16:4~c antimony by atomic absorption spectroscopy, as compared to a theoretical of 16. 6 Example II
Preparation of antimony tris(isooctyl thioglycolate) from antimony trichloride: ;
44.2 g purified antimony trichloride containing 0.0005~ arsenic was m~d with 62.4 g isooctyl thioglycolate and 120 g of a 10~ sodium hydroxide solution. The addition of sodium hydroxide was controlled to keep the temperature of the mixture ~ithin the range from 40-5~C, and the pH not exceeding 6. After the addition, the mi2~ture was stirred for one hour at 50C, ` ~ and allowed to separate. The upper antimony tris(isooctyl thioglycolate~ ester was collected, dried by heating and stirring at 50C under 20 mm of vacuum, and filtered. The dried product analyzed 15.9~c antimony by atomic absorption spectroscopy, and contained 3 mg per kg of arsenic.
' .

~1 .

* Trademark for diatomaceous earth; i' is used as a ril~eri~g and clari.ying ~edium.

,,t, ,,~

Examples ITI and IV
. .
Direct preparation of blends of catechol with antimony tris-(isooctyl thioglycolate) startintr with antimony oxide:
111. Into a one liter three neckecl fla~k was weighed 1. 8 mole (367. 2 g) of5 isooctyl thioglycolate, and this was then heated to 5ûC. The addition o-f ant-mony trioxide, arsenic content 0.05~c, was begun, at a xate to maint~in the tempera-ture oE the reaction mixture betveen 70 and 75C. The reaction was continued at a temperature in the range for ohe-half hour af~er all the antimony trioxide had been added, and the reaction mi~ture was then vacuum-stripped at 75C and 25 mm o~ mercuryO ( atechol, 22. 5 g, was then added, and the mixture heated for three hours at 70 to 75C. Tonoll 30 g (2, 6-di-tert-butyl p-cresol), was added, and dissolved by mixing for ten to fifteen minutes at 75 C. 114. 0 g of epoxidized soya bean oil was then added, and the reaction mixture filtered.
I~T. This procedure was repeated, with the difePence that after the add~tion of the catechol, th0 blend was heated for three hours at 110 to 115 ~C.
After three months storage at room temperature, the product of E}~ample lll, obtained by heating with catechol at 70 to 75C, showed a precipitate, but the product of Example IV, which had been heated at 110 to 115C after addition of catechol, showed no precipitate. Thus, the use of the higher temperature gives abetter product, since the productremains hornogeneous at r oom temperature.
Example V

Preparation of diantimony tet:rakis (isooctyl thioglycolate~-3-mercaptopropionate frorn antimony oxide: _ Into a fi~e liter three~neck flask was put 163 . 2 g (Q. 8 mole) of isocctyl thioglycolate, g3.85~c~ and 21.2 g (0.2 mole) 3-~ercaptopropionic acid.
The mixture was heated to 40 C, and then there ~vas ~adually added 58. 3 g (0. 2 mole) of antimony trioxide, arsenic content 0. 05~C~ 500 mg/kg. Vacuun~ was 1 T rademark 22 .~ 7, ., ~, , applied and heating continued to 75 C at 25 mm of mercury. The liyuid was free of suspended matter and did not need to bé ~iltered.
The reaction product was di-(antimony bis~(isooctyl thioglycolate))-3-mercaptopropionate, presumably having the formula:

(CaH,~O~CH2S)2--Sb--ol~--CH2CH2--S--Sb--(SCHz~;OC,H")z Example VI

Direct preparation of blend of catechol with antimony tris-(isooctyl thioglycolate) 10 startin~ with antimonv oxide:
.. . . _ . . . ........................ . _ . . ........... .
Into a one liter three-necked flask was weighed 1. 8 mole (367. 2 g) of isooctyl thioglycolate, and this was then heated to 50C. The addition of antimony tL ioxide, arsenic content 0. 05~C, was begun, at a rate to maintain the temperature of the reaction mixture between 70 and 75C. The reaction was 15 continued at a temperature in the range for one-half hour after all the antimony `` trioxide had been added, and the reaction mixture was then vacuum-stripped `~ at 75C and 25 mm of mercury. Catechol, 22.5 g, was then added, and the mixture beated for three hours at 70 to 75C.
The following are further Examples of blends in accordance with the 20 invention of antimony mercaptocarboxylic acids or esters and ortho-dihydric phenols. In all cases, the arsenic content of the antimony carboxylic acid or ester, while not precisely known, was less than 0. l~c by weight.
Pa~t by Weight Example ~ntimony tris-(isooc~l thioglycolate) 34~ 2 2, 6-di-tert-butyl-p-cresol 1. 8 Catechol 4 0 Parts by Weight Example Antimony tr is - (isooetyl thioglycolate~3 6. û
Catechol 4 0 ~3 s Pa:rts By Wei~ht Examples C
Antimony tris(isooctyl thioglycolate) 18 18 Propyl gallate (propyl-3, 4, 5-trihydroxg - 2 benzoate) 2, 4, 5-trihydroxy but~Txophenone 2 Parts By Weight Examples E F_ Antimony tris(isooctyl thioglycolate)28.5 29.25 Catechol 1. 5 O. 75 Parts By Weight Examples G H
Antimony tris(isooctyl thioglycolate) 45 46.25 Catechol 2 . 5 1. 25 2, 6-di-tert-butyl-p-cresol 2 . 5 2 . 5 ;. .
,~, .
"., .
. Parts By Weight Examples 2û J K_. L . ~ N
Blend of Exa~nple Vl Antimony t}is(isooctyl thioglycolate) heatedwith 5~c catechol` 25.5 25.5 25.5 25.525.5 Flus 5~c 2, 6-ditert-butyl-p-cresol) E~poxidized soya bean oil 4. 5 - - - -Isooctyl ~poxy stearate - 4.5 - Epoxidized linseed oil - - 4,5 Di(tridecyl thiodipropionate) - - 4. 5 Dinonyl phenol - - - _ - 4. 5 ~4 Parts By Wei Examples O P Q ~ S
Blend o~ ExampleVI
(Antimony t~s(isooctyl thioglycolate) 21 18 15 24 23.25 with 5~c catechol) 2, 6-ditert-butyl-p-cresol 1.5 1.5 1.5 - 1.5 :E:poxidi~ed soya bean oil 7 . 5 10 . 5 13 . 5 4. 5 4. 5 Topanol CA1(1, 1, 3 -tris(3-tert-butyl-4- - - - 1. 5 hydroxy-6-methylphellyl) butane 2-mercaptobenzothiazole - - - - . 75 Parts By Weight E:xamples T U V
Blend of Exan~ple Vi (Antimony tris(isooctyl thioglycolate) 24 24 24 heated with 5~ catechol) 2, 6-ditert-butyl-p-cresol 1. 5 1. 5 1. 5 :Epoxidized soya bean oil 3 1. 5 Soyabean oil 1. 5 3. 0 4. 5 ~:~
Parts By Weight Example ~ - W
Blend of Example -Vl (Antimony tris(isooctyl thioglycolate) 23 . 4 2 5 heated with 5~ catechol) - 2, 6-ditert-butyl-p-cresol 1. 5 Cinnamic acid O . 6 Epoxidized soya bean oil 4 . 5 1 Trademark 25 Parts By Weight Example Blend of Example Vl (Antimony tris(isooctyl thiog]ycolate) 22.5 heated with 5~c catechol) Epoxidi~ ed soya bean oil 4 . 5 2, 6-ditert-butyl-p-cresol 21. 5 Bis(nonylphenyl) di(t-butyl)Bisphenol A phosphite 1. 5 Parts By Wei~ht Examples ~Y Z
Antimony tris(isooc~l thioglycolate) 22 . 822. 8 2, 4, 5-trihydroxy butyrophenone 1.2 2 . 4 . 15 Epoxidized soyabean oil 4,5 4 5 .. . .
~' (1,1, 3-h is-(3-t~buty1-4-hydroxy-6- 1. 5 1. 5 methyl-phenyl) butane .
Parts By Weight Exam~les A~ :313 CC DD
Blend of Example Vt (Antimony tris(isooctyl thioglycolate) 21 18 24 24 ; heated with 5~ catechol) 2, 6-dite~-butyl-p-cresol 1. 5 1. 5 1. 5 1. 5 . 25 Epoxidized soyabeanoil . 4.5 4.5 1.5 (Bis (nonylphenyl) di-(t-butyl-) Bisphenol 3 6 3 4.5 A phosphite) .

~6 Parts ~3y Wei~ht Examples EE FF
E~lend of Example Vl (Antimony tris(isooctyl thioglycolate) 22.5 22.5 heated with 5~ catechol) 2 ~nercaptobenzothiazole I . 5 3 . O
2, 6-ditert-butyl-p-cresol 1. 5 1. 5 Epoxidized soya bean oil 4 . 5 3 . 0 ` 10 Parts By Weight Examples GG HH I~
_ ~ _ _ _ _ Antimony tris~isooctyl thioglycolate~ 21.7 Catechol - 15Blend of Example VI
(Antimony tris(isooctyl thioglycolate) - 20;1 20.1 - ~heated with 5~ catechol) 2, 6-ditert-butyl-p-cresol 1. 5 1. 5 1. 5 . . .
Epoxidiz.ed soya bean oil 5.7 8.4 8.4 - . ' - ` .
~- .

Parts By Wei~ht Examples J~ KK
Antimony tris(isooctyl thioglycolate) 72.25 1661.8 2 5 Catechol 3, 7586 . 3 2, 6-~itert-butyl-p-cresol 5. Oû 115. 0 Epoxidized soya bean oil 19 . 00437 . 0 .

Parts By Weight 3~:xam ples LL MM NN
Antimony tris-(isooctyl thioglycolate) 85 70 45 5LD 210~ (Calcium carbonate -calcium alkylthiobisphenoLate~ 10 25 50 Catechol 5 5 5 ~ the preparation of blends LL, MM and NN, catechol was first di~solved in the antimony tris~(isooctyl thioglycolate), then the 10 LD 2105 was added and the whole heated and stored for one hour at 120~.
Parts By Weight `: ¦ E~amples 15 Antimony tris (isooctyl 21.q 19.5 17.4 13.0 8.7 21.7 21.7 ~¦ thioglycoL~te3 Catechol 1.1 1.1 1.1 1.1 1.1 1.1 1.1 2, 6-ditert-butyl-p-cresol 1.5 1.5 1.5 1.5 1.5 1.5 1.5 Epoxidized soya bean oil 5.7 5.7 5.7 5~7 5.7 5.7 5.7 20 Isooctyl thioglycolate - 2. 2 4. 3 8. 7 13 . O - -Triphenyl phosphite - - - - - 5.7 Trid~cyl :E~isphenol A
. phosph~te - - _ _ _ _ 5, 7 Trademark The following Examples in the opinion of the inventors represent preferred embodiments of rigid polyvinyl chloride resin compositions incorpor~t-ing the stabilizer systems in accordance with the invention.
Example 1 ~ rigid, i. e., nonplasticized, polyvinyl chloride resin formulation was preparecl having the following composition:

Parts by Wei"ht Component Control ExampIe Polyvinyl chloride resin polymer (Diamond 40l) 100 100 Titanium dioxide (pigment) 2 2 Wax 160 (160F m.p. paraffin) ~ Stabilizer -~ (1) Sb (sc~2cO2cs Hl? )3 OEXample ~

(2) Blend of Sb (SCH2COOC8Hl7)3, catechol, . - 1 ' Ionol and epoxidized soyabean oil (Exarnple III) The stabilizer was mixed in the resin in the proportion indicated in the Table above on a two-roll mill to form a homogeneous sheet and sheeted off. Strips were cut from the sheet and heated in an oven at 375~C for up to forty minutes. Pieces of each strip were removed at five minute intervals, 20 and a~i2~ed to cards, to show the progressive development of the discoloration.
During the first fifteen to twenty minutes of heating early discoloration manifests itself. A~ter twenty to thirty minutes of heating, long term heat stability can be observed.
The Control composition contained only antimony tris (isooctyl 25 thioglycolate). Example 1 contained antimony tris-(isooctyl thioglycola$e~, catechol, lonol and epoxidized soyabean oil, in the amounts given.
The development of early discoloration is evaluated by the intensity of yellow tint formed, relative to the Control.

~ .

l Trademark 29 Table I
Time (minutes? Control E~rample 1 Initial No discoloration No discoloration No discoloration No discoloration , Very slight yellow discoloration No discoloration , 15 Significant yellow discoloration No discoloration Yellow discoloration Buff discoloration, ~, 10 - and staining Yellow with dark Dark tan stains Yellow with dark Dark tan ' ~tains 15 35 Dark tan Grey-~lack : -:~' 40 Dark tan Grey-black It is apparent from the above results that the catechol greatly enhanced the resistance of the resin composition to the deYelopment ' of yellow di~coloration during the first fifteen minutes of heating. However, 20 the deterioration a~ter that accelerates, and after twenty minutes ~f heating the color is much darker than the Control, which i~ clearly super.ivr. Th~s~
the catechol worsens long term heat stability.
E~amples 2 to 4 .. . _ A rigid, i.e. nonplasticized, poly~inyl chloride resin 25 formulationwas prepared hav~ing the following compositic~n: -. 'omponent Parts by Weight (: ontrols A, B, C Examples 2 to 4 Polyvinyl chloride resin homopolymer [Diamond 40) 100 100 Titanium dioxide (pigment) 2 2 Calcium stearate 0. 25 to 0. 75 ' 0. 25 to 0. 75 Wax 160 (16~F m.p. paraffin) Stabilizer (1) Sb(SCH2CO2C~H,7)3 (Example II) (2) Blend of Sb (SCH2COOC8 Hl7-iso~3, Qatechol9 Ionol and epoxidized soyabean oil _ 1 `~ OExample IV) l See Table II.
The stabilizer was mixed in the resin in the proportion indicated in Table II below on a two roll mill to form a homogeneous sheet, and sheeted off. Strips were cut ~om the sheet and heated in an oven ~t 375F to determine the on~et of early discoloration during the first stages of heating. Pieces of each strip were removed at five-minute 20 intervals, and affixed to cards, to show the progressive development of the discoloration for the first twenty to thirty minutes. The effect on long term - heat stability was determined by continuiTIg the test for seventy-five minutes.
TheControl compositions A, B and C contained antimony tris~
(isooctyl thioglycolate) and calcium stearate 0. 25, 0. 5 and 0. 75 part, 2~ re~pectively, by weight. E~amples 2 to 4 contained antimony tris-(isooctyl thioglycolate), and calcium stearate in the same amounts, plu~ catechol, ~onol and ~poxidized soyabean oil, in the amount given.
The development of early discoloration is evaluated by the intensity of yellow tint formed, relative to the Control.

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32a ~,r,~f~,~5 The calcium stearate clearly introduces a yellow discoloratlon that manifests itself in the first five mimltes of heating, and continues to intensify as heating continues. The yellow color is more intense than when calcium stearate is not present; compare the C~ntrol of Example I, Table I. Its 5 intensity is proportional to the ~mount of calcium stearate present.
The catechol overcomes this yellow discoloration during the first twenty minutes of he~ting. However, after that the deterioration accelerates, an~ the col~r is much worse during ~he peri~d from thirty to forty minutes of heating than when catechol is not there, and this tendency is not overcome 10 by the calcium stearate or the antimony compound.
It is apparent from the results in Table II that the effect of the calcium stearate (compare to Control in ~:xample 1, Table I) is to impart a si~nificant yellow discoloration, immediately after heating begins, and this intensifies as hea~ing continues, so tha~ the ~ffect is always worse than without 15 the calcium stearate through thé first 30 minutes of heating. Examples 2 to

4, on the other hand, show an increased resistance of the development of yellow discolor~tion, particularly when compared to Example 1. In the presence of the calcium st~arate, the phenol: clearly increases the resistance to the development of early discolorati~n. This effect is quite surprising, inasmuch 20 as in the absence of the phen~ the effect of the ~alcium stearate is t~ intensify the yellow discoloration, n~ lessen it.
' ?~3~
Examples 5 and 6 A rigid, i.e. nonplasticized, polyvinyl chloride resin formulation was prepared having the following composition:

Parts By Weight ; 5 Component Example 5 xample 6 Polyvinyl chloride resin polymer 100 100 (Diamond 40) Titanium dio~{ide (pigment) 2 2 Wax 160 (160F. m.p. pa~fin) Stabilizer (~ ) Sb (SCF~CO2C8H~7)3 blend with catechol and 2, 6-ditert-butyl-p-cresol of Example A
(2)~ 13lend-of Example J ~ ~ 1 The stabilizer was mixed in the resin in the propo~tion indicated on a two-roll mill to form a homogeneous sheet and sheeted off. Strips were cut from the sheet and heated in an oven at 375Ffor up to 4~ minutes. Pieces of each strip were removed at five minute intervals, and affixed to cards, to show the progressive development of the discoloration. During the first fifteen 20 to twent~7 minutes of heating early discoloration manifests itself. Aiter twenty to thirty minutes of heating, long term heat stability can be observed.
The development of early discoloration was evaluated by the intensi~7 of yellow tint formed.
It was apparent from the results that the stabilizers greatly enhanced 25 the resistance of the resin composition to the development of yellow discoloration during the first fifteen minutes of heating.

.
Examples 7 and 8 A rigid, i. e . nonplasticized, polyvinyl chloride resin formulation was prepared having the following composition:

Component Parts By Weight Example 7 Example 8 Polyvinyl chloride resin homopolymer (Diamond 40) 100 100 Titanium dioxide (pigment) 2 2 Calcium stearate ` o. 5 o. 5 Wax 160 (160F m.p. paraffin) Stabilizer (1) Blend of Example R
~2~ Blend of Example X - 1 The stabilizer was mixed in the resin in the proportion indicated 15 on a two-roll mill to ~orm a homogeneous sheet, and sheeted off. Strips were cut from the sheet and heated in an oven at 375F ~o determine the onset of early discoloration during the first stages of heating. Pieces of each strip - -~
were removed at five-minute intervals, and affixed to cards, to show the progressive development of the discoloration for the firslt twenty to thirty 20 minutes. The effect on long term heat stability was determined by continuing the test for seventy-five minutes.
The development of early discoloration was evaluated by the intensil~
o~ yellow tint formed.
The calcium stearate clearly introduced a yellow discoloration that - 25 manifested itself in the first five minutes of heating, and continued to intensify as heating continued. The yellow color was more intense than when calcium 3SC~ S
cearate was not present.
The catechol overcomes this yellow discoloration during the first twenty minutes of heating. However, after that the deterioration accelerates, and the color is much worse during the period from thirty to for~ minutes of

5 heating than when catechol is not there, and this tendency is not overcome by the calcium stearate or the antimony compound.
Examples 9 and 10 A rigid, i.e. nonplasticized, polyvinyl chloride resinformulation was prepared having the following composition:

Parts By Wei~ht Component Example 9 Example 10 Polyvinyl chloride resin polymer (I~iamond 40) 1ûO 100 Titanium dioxide (pigment) 2 2 Wax 160 (160F. m.p. paraffin~

Stabilizer (1~ Blend of Example HH
(2) Blend oE Examplé M~ - - 1 The stabilizer was mixed in the r esin in the proportion indicated 20 on atwo-roll mill to form a homogeneous shee~ and sheete~l off. Strips were sut from the sheet and heated in an oven at 375F for up to 40 minutes. Pieces of each strip were removed at five minute intervals, and affixed to ca~ds, to show the progressive development of the discoloration. During the first fifteen to twenty minutes of heating early discoloration manifests itself. After 25 twenty to thirt~ minutes of heating, long term heat stability can be observed.
The development of early discoloration was evaluated by the intensity of yellow tint formed.

It was apparent from the results that the catechol greatly enhanced the resistance of the resin composition to the development of yellow discoloxation during the first fifteen minutes of heating. However, the deterioration a~ter that accelerated, and the catechol cl~arly worsened long term heat stability.
Examples 11 and 12 A rigid, i.e. nonplasticized, polyvinyl chloride resin formulation was prepared having the following composition:

Parts By Weight Component Contxols A, B, C E~amples 2 to 4 Polyvinyl chloride resin homopolymer (Diamond 40) 100 100 Titanium dioxide (pigment) 2 100 Calcium stearate 0. 50 ~. 50 Wax 160 (160F m.p. paraffin) Stabilizer (1) Blend of Example TT
(2) Blend of Example UU - 1 The stabilizer was mi~ed in the resin in the proportion indicated on a two-roll mill to form a homogeneous sheet, and sheeted off. Strips were 20 cut rQm the sheet and heated in an oven at 375F to determine the onset of early discoloration during the first stages of heating. Pieces of çach strip were removed at five-minute intervals, and affi~ed to cards, to show the progressive development of the discoloration for the fixst twenty to thirty minutes. The effect on long term heat stabili~y was determined by continuing 25 the test for seventy-five minutes.
The development of early discoloration was evaluated by the intensity of yellow tint formed.

The calcium stearate clearly introduced a yellow discoloration ~at manifested itself in the first five minutes of heating, and continued to intensify as heating continued. The yellow color was more intense than when calcium stearate was not present.
The catechol o~ercomes this yellow discoloration during the first twenty minutes of heating~ However, after that the deterioration accelerates, and the color is much worse during the period from thirty to forty minutes of heating than when catechol is not there, and this tendency is not overcome by the calcium stearate or the antimony compound.

In order to show the effect of arsenic on the stabilizing eff~ctiveness of the antimony tris-(isooctyl thioglycolate) rigid i. e., nonplasticized polyvinyl chloride resin formulations were prepared containing blends in accordance with the invention of antimony ~is-(isooctyl thioglycolate) with catechol, the only difference being the amount of arsenic contained in the antimony tris-(isooctyl t~ioglycolate). The resin formulations had the following composition:
Parts by Weight Component ControlExample 1 Polyvinyl chloride resin polymer (Diamond 40) 100 100 Titanium dioxide (pigment) 2 2 Wax 160 (160F m.p. pa~affin) Stabilizer (1) Sb (SCH2CO2C8 Hl7 ~3 containing 0- 5 ~c arsenic in a blend of 95 parts to 5 parts catechol (2) Sb (SCH2C02C8 Hl7 )3 containing 0. 05~C arsenic - in a blend of 95 parts with 5 parts catechol - l The stabilizer was mixed in the resin in the proportion indicated in the Table above on a two-roll mill to form a homogeneous sheet and sheeted off. Strips we~e cut f~om the sheet and heated in an oven at 375F for up to forty minutes. Pieces of each strip were removed at five minute intervals, 5 and affixed to cards, to show the progressive development of the discoloration.
During the first fifteen to twenty minutes of heating early discoloration manifests itself. After twenty to thirty minutes of heating, long term heat stability can be observed.
The development of early discoloration is evaluated by the intensity 10 of yellow tint formed, relati~re to the control, and is shown in Table 111:

. - .
- Time (minutes) Control Example 1 Initial No discoloration No disculoration No discoloration No discoloration Very sli~Jht yellow discoloration No discol~ration Significant yellow discoloration No discolsxration Yellow discoloration Bu~f discoloration 2~ and staining Yellow with dark Dark tan - stains ~ellow with clark Dark tan stains Dark tan Grey-black Dark tan Grey-black ~L~r~ S

It is appa~ent from the above results that in the absence of arsenic in the antimony tris-(isooctyl thioglycolate), the stabilizer blend greatly enhanced the resistance of the resin composition to the development of yellow discoloration during the Eirst Eifteen minutes of heating.

Claims (23)

Having regard to the foregoing disclosure, the following is claimed as inventive and patentable embodiments thereof:

1. A stabilizer composition capable of enhancing the resistance to the development of early discoloration in the first five to twenty minutes of heating at 375°F of rigid polyvinyl chloride resin compositions, comprising an antimony mercaptocarboxylic acid or ester having an arsenic content of less than 0.1% by weight and an ortho-dihydric phenol.

2. A stabilizer according to claim 1, comprising, in addition, an alkaline earth metal carboxylate of a carboxylic acid having from about eight to about twenty-four carbon atoms.

3. A stabilizer according to claim 1, comprising, in addition, an epoxidized triglyceride ester of a carboxylic acid having from about eight to about twenty-four carbon atoms.

4. A stabilizer composition according to claim 1, in which the antimony mercaptocarboxylic acid or ester has the formula:

in which (1) R1 is selected from the group consisting of organic groups of the formula -SR3OH and -OR3SH, where R3 is alkylene having from two to about eight carbon atoms; and S-Z-(COOR2)m groups;

(2) R2 is selected from the group consisting of hydrogen, alkyl, alkylene, alkenyl, aryl, arylene, mixed alkyl-aryl, mixed aryl-alkyl, cycloaliphatic, and heterocyclic containing one or more sulfur, oxygen or nitrogen ring atoms, having from about one to about twelve carbon atoms, and such groups containing ester groups, alkoxy groups, hydroxyl groups, and halogen atoms;
(3) S-Z-COOR2 is a mercaptocarboxylic acid or ester group;
(4) n1, n2 and n4 are the number of S-Z-COOR2 groups, and are integers from 0 to 2; but at least one of n1 and n2 is 1 or 2;
(5) n3 is the number of groups, and is a number from 0 to 10, (6) m1, m2 and m3 are the number of COOR2 groups, and are integers from 1 to 6; and (7) Z is selected from the group consisting of bivalent alkylene radicals having from one to about five carbon atoms, carrying the S group in a position .alpha. or .beta. to a COOR2 group; and such radicals containing free carboxylic acid carboxylic ester, and carboxylic acid salt groups and mercapto groups.

5 A stabilizer composition according to claim 4, in which Z is CH2.

6. A stabilizer composition according to claim 4, in which R2 is a C8H17, group.

7. A stabilizer composition according to claim 4, in which m1 is 1; n1 is 3, and n2 and n3 are zero.

8. A stabilizer composition according to claim 4, in which the ortho dihydric phenol has the formula:

in which R is selected from the group consisting of hydroxyl, alkyl, cycloalkyl, aryl, alkoxy, aryloxy, alkenyl, carboxyalkyl, carboxyaryl, acyl, aryl, alkenyloxy, hydroxyalkyl, hydroxyaryl, alkoxyaryl, and alkoxyalkyl having from one to about twelve carbon atoms; and n is an integer from zero to four.

9. A stabilizer composition according to claim 1, in which the alkaline earth metal carboxylate is calcium stearate.

10. A stabilizer composition according to claim 1, in which the antimony mercaptocarboxylic acid or ester has an arsenic content of less than 0.01% by weight.

11. A stabilizer composition according to claim 1, comprising the reaction product of the antimony mercaptocarboxylic acid or ester and orthodihydric phenol after heating at a temperature of at least 50°C for at least fifteen minutes.

12. A stabilizer composition according to claim 1, comprising the reaction product of the antimony mercaptocarboxylic acid or ester and ortho-dihydric phenol after heating at a temperature of at least 80°C for at least fifteen minutes.

13. A rigid polyvinyl chloride resin composition comprising polyvinyl chloride and a stabilizing amount of a stabilizer composition according to claim 1.

14. A rigid polyvinyl chloride resin composition comprising polyvinyl chloride and a stabilizing amount of a stabilizer composition according to claim 2.

15. A rigid polyvinyl chloride resin composition comprising polyvinyl chloride and a stabilizing amount of a stabilizer composition according to claim 3.

16. A rigid polyvinyl chloride resin composition comprising polyvinyl chloride and stabilizing amount of a stabilizer composition according to claim 9.

17. A rigid polyvinyl chloride resin composition comprising polyvinyl chloride and a stabilizing amount of a stabilizer composition according to claim 10.

18. A rigid polyvinyl chloride resin composition comprising polyvinyl chloride and a stabilizing amount of a stabilizer composition according to claim 11.

19. A rigid polyvinyl chloride resin composition comprising polyvinyl chloride and a stabilizing amount of a stabilizer composition according to claim 12.

20. A rigid polyvinyl chloride resin composition in accordance with claim 13 in which the amount of stabilizer composition is within the range from about 0.25% to about 10% by weight of the composition.

21. A rigid polyvinyl chloride resin composition in accordance with claim 14, in which the amount of stabilizer composition is within the range from about 0.25% to about 10% by weight of the composition.

22. A rigid polyvinyl chloride resin composition in accordance with claim 13, including in addition a plasticizer for the resin in an amount up to about 10% by weight of the composition.

23. A rigid polyvinyl chloride resin composition in accordance with claim 14, including in addition a plasticizer for the resin in an amount up to about 10% by weight of the composition.