2,6-Di-Tertiary Butyl Phenyl Phosphites and Synthetic Resin Compositions Having Enhanced Stability to Heat and Light

Polypropylene and other polyolefins such as polyethylene, polybutylene and polyisopentylene show a strong tendency to deteriorate in physical properties at elevated temperatures and when exposed to ultraviolet light. The deterioration is evidenced by, among other things, a decrease in viscosity, a tendency to become brittle, and a discoloration which is particularly pronounced at the exposed edge of the material. This deterioration can be accompanied by distortion, cracking, and powdering of the material. The deterioration is accentuated in the presence of oxygen.

To overcome these difficulties, many stabilizer systems have been proposed for combination with polyolefins, with varying degrees of success. No single stabilizer has proved adequate, and combinations of stabilizers are consequently used almost exclusively. Most stabilized polyolefins on the market contain one or more of such stabilizer combinations. The deterioration appears to be due to a combination of factors, and a combination of stabilizers is therefore more capable of coping with the various types of deterioration. However, the retention of good physical properties over long periods of time remains rather difficult to achieve.

Of the many stabilizer systems that have been proposed, one particularly satisfactory stabilizer system is described in U.S. Pat. No. 3,255,136, patented June 7, 1966 to Arthur Hecker, Otto S. Kauder and Norman Perry. This stabilizer system comprises three stabilizers: an organic mono- or polyhydric phenol, an organic phosphite, and a thiodipropionic acid ester. An additional fourth ingredient, which is preferred but not essential, is a polyvalent metal salt of an organic acid. These three and four stabilizers together give an enhanced stabilization which is not obtainable from any of them alone, or in combinations of two.

In these combinations, the phenol alone gives an improved resistance to embrittlement and reduction in melt viscosity of polypropylene at elevated temperatures, but little assistance as to maintenance of color. The phosphite alone is a rather poor stabilizer in preventing deterioration in the first two properties, but it does assist in resisting discoloration. The two together are worse than the phenol alone in every respect except color, which is intermediate.

The thiodipropionic acid ester by itself only improves resistance to embrittlement. The polyvalent metal salt of an organic acid by itself only prevents discoloration. In combinations with the phenol, the color is worse than with the salt alone, and combinations with phosphite only, discoloration is prevented. The effectiveness of all three or four ingredients taken together against all of these types of deterioration is therefore particularly surprising.

The organic phosphite can be any organic phosphite having the formula (RA).sub.3 -P, in which A can be oxygen or sulfur or a mixture of the same, and R is aryl, cycloalkyl, aralkyl or aralkaryl in any combination. A variety of tris-alkaryl phosphites are disclosed, such as tris-(tertiary-octyl-phenyl)phosphite and tris-(tertiary-nonyl-phenyl)phosphite, but no tri-(alkaryl)phosphites having more than one alkyl group per phenyl group.

Organic phosphites have been widely used as stabilizers for polyolefins and similar polymeric materials, and many different types of phosphites, some of rather complex structure, have been proposed. U.S. Pat. Nos. 3,255,136 and 3,655,832 have suggested organic phosphite-phenol transesterification products, the preferred phenol being a bis-phenol. Other types of tris-(alkaryl)phosphite esters have been disclosed in U.S. Pat. Nos. 2,220,113; 2,220,845; 2,246,059; 2,419,354; 2,612,488; 2,732,365; 2,733,226; and 2,877,259. Additional tris-(alkaryl)phosphites are disclosed in U.S. Pat. No. 3,167,526 to Nicholson, patented Jan. 26, 1965; U.S. Pat. No. 3,061,583 to Huhn and Sheets, patented Oct. 30, 1962; U.S. Pat. No. 3,829,396 to Oakes and Cross, patented August 13, 1974; French Pat. Nos. 1,496,563 to U.S. Rubber Company, delivre Aug. 21, 1967, and French Pat. No. 1,497,390 to Ethyl Corporation, delivre Aug. 28, 1967; and British Pat. Nos. 1,058,977, published Feb. 15, 1967, to Hooker Chemical Corporation and 1,143,375, published Feb. 19, 1969, to Uniroyal Inc.

Oakes et al disclose bis-(2,4-di-tertiary-butyl-phenyl)cyclohexyl phosphite and 2,4-di-(tertiary butyl)phenyl dicyclohexyl phosphite, which are liquids.

French Pat. No. 1,496,563 described phosphites derived from 2,6-di-tertiary-butyl-hydroxyquinone and 2,5-di-tertiary-butylhydroquinone, and it is suggested that they can be used with thiodipropionic acid esters of olefin polymers.

British Pat. No. 1,143,375 has a similar disclosure; tris-(2,5-di-tertiary-butyl-4-hydroxy-phenyl)phosphite is disclosed.

British Pat. No. 1,058,977 discloses 2,4,6-tri-substituted aryl phosphites, the substituents including tertiary-butyl groups.

French Pat. No. 1,497,390 discloses tris-(3,5-di-alkyl-4-hydroxy-phenyl)phosphites, as well as tris-(3-isopropyl-5-tertiary-butyl-phenyl)phosphite.

Kuriyama et al U.S. Pat. No. 3,558,554 patented Jan. 26, 1971, provides olefin polymer compositions containing as a stabilizer an organophosphite having the general formula: ##STR2## wherein:

R.sub.1 and R.sub.2 each represents a member selected from the group consisting of substituted and unsubstituted alkyl, cycloalkyl, aryl, alkaryl, aralkyl, and aliphatic thio ether groups and R.sub.3, R.sub.4 and R.sub.5 each represents a member selected from the group consisting of hydrogen and alkyl, cycloalkyl, aryl, alkaryl, and aralkyl groups, at least one of said R.sub.3 and R.sub.4 being a tertiary butyl group.

Suitable organo phosphites include, for example, di-n-butyl (2-t-butyl-cresyl)phosphite, di-n-hexyl(2-t-butyl-m-cresyl)phosphite, di-n-hexyl(2-t-butyl-p-cresyl)phosphite, di-n-octyl(2t-butyl-p-cresyl)phosphite, di-n-butyl-3,4-di-t-butyl-phenyl)phosphite, di-n-butyl-(2,6-di-t-butyl-p-cresyl)phosphite, di-phenyl(2-t-butyl-p-cresyl)phosphite, tri-(2-t-butyl-p-cresyl)phosphite, di(ethylthioethyl)-(2-t-butyl-p-cresyl)phosphite, di(octylthioethyl)(2-t-butyl-p-cresyl)phosphite, and tri(2,4-di-butyl-phenyl)phosphite.

Many organic phosphites have been proposed as stabilizers for polyvinyl chloride resins, and are employed either alone or in conjunction with other stabilizing compounds, such as polyvalent metal salts of fatty acids and alkyl phenols. Such phosphite stabilizers normally contain alkyl or aryl radicals in sufficient number to satisfy the three valences of the phosphite, and typical phosphites are described in the patent literature, for example, W. Leistner et al., U.S. Pat. No. 2,564,646 of Aug. 14, 1951, U.S. Pat. No. 2,716,092 of Aug. 23, 1955, and U.S. Pat. No. 2,997,454 of Aug. 2, 1961.

Organic phosphites have also been added as stabilizers in amounts of 0.01 to 1%, preferably 0.05% to 0.2% by weight, to high molecular weight polycarbonate plastics, for example the polycarbonate of 2,2'-bis(4-hydroxyphenyl)propane of molecular weight 10,000 and up to over 50,000 as disclosed by G. Fritz in U.S. Pat. No. 3,305,520 of Feb. 21, 1967.

A. Hecker in U.S. Pat. No. 2,860,115 of Nov. 11, 1958 discloses compositions of organic phosphites with metal salts of carboxylic acids used in olefin polymers.

Phosphites are also employed in conjunction with other stabilizers such as a polyhydric phenol in the stabilization of polypropylene and other synthetic resins against degradation upon heating or ageing under atmospheric conditions. The polyhydric phenol is thought to function as an antioxidant in such combinations. Disclosures by R. Werkheiser, U.S. Pat. Nos. 2,726,226 of Dec. 6, 1975; I. Salyer et al, U.S. Pat. No. 2,985,617 of May 23, 1961; L. Friedman, U.S. Pat. No. 3,039,993 of June 19, 1962; W, Nudenberg, U.S. Pat. No. 3,080,338 of Mar. 5, 1963; C. Fuchsman, U.S. Pat. No. 3,082,187 of Mar. 19, 1963; H. Orloff et al, U.S. Pat. No. 3,115,465 of Dec. 24, 1963; A. Nicholson, U.S. Pat. No. 3,167,526 of Jan. 26, 1965; A. Hecker et al, U.S. Pat. No. 3,149,093 of Sept. 15, 1964, U.S. Pat. No. 3,244,650 of Apr. 5, 1966 and U.S. Pat. Nos. 3,225,136 and 3,255,151 of June 7, 1966; C. Bawn, U.S. Pat. No. 3,352,820 of Nov. 14, 1967; D. Miller, U.S. Pat. No. 3,535,277 of Oct. 20, 1970;J. Casey, U.S. Pat. No. 3,586,657 of June 22, 1971; C. Abramoff U.S. Pat. No. 3,856,728 of Dec. 24, 1974; M. Minagawa, U.S. Pat. No. 3,869,423 of Mar. 4, 1975 and U.S. Pat. No. 3,907,517 of Sept. 23, 1975; and British Pat. Nos. 846,684, 851,670, and 866,883 are representative of stabilizer combinations including organic phosphites, polyhydric phenols, and other active ingredients.

The importance of organic phosphites as stabilizers for synthetic resins has led to the development of a large variety of special phosphites intended to provide improved stabilizing effectiveness and compatability and ease of compounding with the resin and with other stabilizers commonly used. However, the phosphites which have been proposed have not been entirely successful, partly because of their complicated structure, which makes them costly to prepare, and partly because of their difficulty of preparation.

Among these special phosphites, L. Friedman, U.S. Pat. No. 3,047,608 of July 31, 1962 discloses a class of biphosphites having the formula: ##STR3## in which R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are alkyl or aryl and Z is --CH.sub.2 CH.sub.2 SCH.sub.2 CH.sub.2 O--, --C.sub.2 CH.sub.2 SO.sub.2 C.sub.2 CH.sub.2 --(--CH.sub.2 CH.sub.2 O--).sub.x or (CHCH.sub.3 CH.sub.2).sub.x where x is at least two, and in U.S. Pat. No. 3,053,878 of Sept. 11, 1962 a class of linear phosphite polymers having the formula: ##STR4## in which Q is the alkylene or arylene portion of a dihydric alcohol or dihydric phenol.

R. Morris et al in U.S. Pat. No. 3,112,286 of Nov. 26, 1963 discloses phosphites having the formula: ##STR5## in which:

R represents a bulky hydrocarbon group such as t-butyl, t-amyl, t-hexyl, cyclohexyl, t-pentyl, t-octyl, phenyl and the like;

R.sub.1 represents hydrogen and R;

R.sub.3 represents an alkyl group from six to twenty carbon atoms which is preferably in the meta or para position;

x represents a number of from 1 to 3 inclusive;

y represents a number of from 0 to 2 inclusive and the sum of the numerical value of x+y is always exactly 3.

D. Brown, U.S. Pat. No. 3,297,631 of January 10, 1967 discloses condensation products of phosphorus compounds with bisphenols and trisphenols which may be represented by the structures: ##STR6## where X is selected from the following: >P--OR'; >P--R'; ##STR7## and Y is selected from the following: --P(OR').sub.2 ; ##STR8## R is hydrogen, alkyl of one to sixteen carbon atoms or aryl or a combination of these; R' is alkyl of one to sixteen carbon atoms or aryl, and R" is alkylidene of one to sixteen carbon atoms or an aryl-substituted alkylidene.

C. Baranauckas, U.S. Pat. No. 3,305,608 of Feb. 21, 1967, discloses phenolic phosphites useful as polymer stabilizers prepared by reacting a triorganophosphite, a polyol, and an aromatic material having two to six phenolic hydroxyl groups at 60.degree. to 180.degree. C. in specified proportions.

C. Brindell, U.S. Pat. No. 3,412,064 of Nov. 19, 1968 discloses phenolic phosphites represented by the general formula: ##STR9## where x is from 1 to 3, y and z each from 0 to 2, x+y+z=3, R is hydrogen or alkyl and Y is hydroxyl or a group of the formula: ##STR10## where R is hydrogen or alkyl.

M. Larrison, U.S. Pat. No. 3,419,524 of Dec. 31, 1968, discloses phosphites useful as polymer stabilizers having the formula: ##STR11## where R.sub.1, R.sub.2, R.sub.4, R.sub.6 and R.sub.7 are aryl or haloaryl, and R.sub.3 and R.sub.5 are a polyalkylidene glycol or an alkylidene bisphenol or a hydrogenated alkylidene bisphenol or a ring-halogenated alkylidene bisphenol from which the two terminal hydrogens have been removed.

O. Kauder et al, U.S. Pat. No. 3,476,699 of Nov. 4, 1969 and U.S. Pat. No. 3,655,832 of Apr. 11, 1972 discloses organic phosphites containing a free phenolic hydroxyl group and defined by the formula: ##STR12## wherein Z is selected from the group consisting of hydrogen and aliphatic, cycloaliphatic, aromatic, heterocyclic and (Ar).sub.p --Y--Ar groups, taken in sufficient number to satisfy the valences of the two phosphite oxygen atoms; Y is a polyvalent linking group selected from the group consisting of oxygen; aliphatic, cycloaliphatic and aromatic hydrocarbon groups attached to each Ar group through a carbon atom not a member of an aromatic ring; oxyaliphatic; thioaliphatic, oxycycloaliphatic, thiocycloaliphatic; heterocyclic, oxyheterocyclic, thioheterocyclic, carbonyl, sulfinyl; and sulfonyl groups; Ar is a phenolic nucleus which can be phenyl or a polycarbocyclic group having condensed or separate phenyl rings; each Ar group is either connected through an oxygen atom to a phosphite group or contains a free phenolic hydroxyl group, or both; and p is a number, one or greater, and preferably from one to four, which defines the number of Ar groups linked to Y.

L. Friedman, U.S. Pat. No. 3,516,963 of June 23, 1970 discloses phosphites having the formula: ##STR13## where R is alkyl, alkenyl, aryl, aralkyl, haloaryl, haloalkyl or ##STR14## and n is an integer of at least 1. n can be 2,3,4,5,6,7,8,10,50, 100 or even more.

D. Bown et al in U.S. Pat. No. 3,510,507 of May 5, 1970 and U.S. Pat. No. 3,691,132 of Sept. 12, 1972 discloses polyolefins stabilized with polyphosphites, polyphosphates, polyphosphonites, polyphosphonates, polyborates, polycarbonates, and polysilanes which are condensation products of a 4,4'-bisphenol with a condensing or linking agent which may be of the ester type, such as the esters of triaryl or mixed aryl-alkyl compounds, or the acid halide type. Bown's condensation product stabilizers have molecular weights between 600 and 8000 or higher and are described by the structural formula: ##STR15## where X is selected from the group consisting of: ##STR16## --C--C, and C--A--C-- where A is a C.sub.1 to C.sub.16 alkylene or an arylene; R', R", R'", and R"" are selected from the group consisting of hydrogen, C.sub.1 to C.sub.18 alkyls, and an aryl group; Y is selected from the group of: ##STR17## where R is hydrogen, a C.sub.1 to C.sub.18 alkyl or aryl; ##STR18## where m is 0 to 10, preferably 4 to 8, ##STR19## where A' is (CH.sub.2).sub.n --S--(CH.sub.2).sub.n or --(CH.sub.2).sub.n --S--(CH.sub.2).sub.m --S--(CH.sub.2).sub.n where n is 0 to 10, preferably 2 and m is 0 to 10, preferably 5; ##STR20## where R is an alkyl, preferably methyl, and Z is ##STR21## where R', R", R'", R"", and X correspond respectively to the R', R", R'", R"", and X previously selected when n has a value from 1 to 15, or may be derived from the compound used to introduce Y into the product when n has a value from 2 to 15, for example, --R or --OR where R is hydrogen, an alkyl, or aryl. When Y is the formula of Bown's stabilizer is: ##STR22## the stabilizer is a type of hydroxyaryl phosphite. Similarly, when Y in the formula is: ##STR23## the stabilizer is a hydroxyaryl carbonate.

Bown's condensation products are described as especially effective in high molecular weight solid polyolefins when used together with a dialkyl sulfide costabilizer such as dilauryl thiodipropionate, distearyl thiodipropionate, ditridecyl thiodipropionate, dicetyl sulfide, bis(tetradecylmercapto)paraxylylene, and 10,24-dithiotetracontane.

J. Floyd et al in German Published application No. 2505071 of Aug. 14, 1975 abstracted in Chemical Abstracts 1976, Volume 84, abstract No. 5945f, discloses low molecular weight polycarbonate esters of bisphenols such as 2,2-bis(3-t-butyl-4-hydroxyphenylpropane) and 4,4'-butylidene bis(6-t-butyl-3-methylphenol) prepared in such a way as to contain few or no free phenolic hydroxyl groups as being highly effective heat and light stabilizers for polyolefins and giving a synergistic effect with distearyl thiodipropionate, tris (nonylphenyl)phosphite, and distearyl pentaerythritol diphosphite.

In accordance with the present invention, there is provided a new class of 2,6-di-tertiary-butyl phenyl phosphites having the general structure: ##STR24## wherein:

R.sub.1 is selected from the group consisting of hydrogen, methyl, ethyl, and (CH.sub.2).sub.m COOR, where R is selected from the group consisting of alkyl having from one up to about ten carbon atoms; cycloalkyl having from three up to about twelve carbon atoms; alkaryl and aryl having from six to about twelve carbon atoms; and m is a number within the range from 0 to 5;

R.sub.2 is selected from the group consisting of hydrogen, alkyl having from one to about twenty-two carbon atoms; cycloalkyl having from three up to about twelve carbon atoms; alkaryl and aryl having from six to about eighteen carbon atoms; the residue of a polyhydric alcohol having from two to about eighteen carbon atoms, and from two to three hydroxyl groups; and the residue of a polyphenol having from six to about eighteen carbon atoms and from two to about ten phenolic hydroxyl groups;

R.sub.3 is selected from the group consisting of hydrogen and P(OR.sub.2).sub.2 ;

Z is the bivalent to tetravalent residue of a polyhydric alcohol having from two to about eighteen carbon atoms, and from two to five hydroxyl groups; or of a polyphenol having from six to about eighteen carbon atoms and from two to about ten phenolic hydroxyl groups;

n.sub.1 is 0 or 1; and

n.sub.2 is a number from 1 to 5.

Synthetic resin compositions are also provided having an enhanced resistance to deterioration by heat and/or light due to the presence therein of an organic phosphite of this class.

These phosphites are capable of enhancing the resistance to deterioration due to heat and/or light of synthetic resins as a class, when combined therewith in small amounts within the range from about 0.01 to about 5% by weight of the synthetic resin.

Exemplary R and R.sub.2 groups include alkyl groups having from one to about twenty-two carbon atoms, for example, methyl, ethyl, propyl, isopropyl, butyl, secondary butyl, tertiary butyl, isobutyl, amyl, isoamyl, secondary amyl, tertiary amyl, hexyl, isohexyl, heptyl, octyl, 2-ethyl hexyl, isooctyl, nonyl, isononyl, decyl, isodecyl, lauryl, myristyl, palmityl, stearyl, eicosyl and behenyl.

R and R.sub.2 may also be cycloalkyl having about three to about twelve carbon atoms, including, for example, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclododecyl and alkyl-substituted cycloalkyl such as 4-methyl cyclohexyl, 4-methyl cyclopentyl, and p-dimethyl cyclohexyl.

R and R.sub.2 alkaryl and aryl groups include phenyl, diphenyl, naphthyl, tolyl, xylyl, ethylphenyl, butylphenyl, tertiary butylphenyl, octylphenyl, 2,6-di-t-butyl-4-methylphenyl, 2,6-di-t-butyl-4-methoxycarbonyl, ethylphenyl, isooctylphenyl, t-octylphenyl, nonylphenyl, 2,4-di-t-butylphenyl, cyclohexylphenyl, cyclooctylphenyl, 4-methoxyphenyl, 4-ethoxyphenyl, 3-lauroxyphenyl, 2-methoxy-4-methylphenyl, 2-t-butyl-4-methoxyphenyl, 4-benzyloxyphenyl, and 3,4-methylenedioxyphenyl.

R and R.sub.2 can also be the residue of a polyhydric alcohol or polyphenol having at least two up to three alcoholic or about ten phenolic hydroxyl groups capable of being esterified with trivalent phosphorus of a phosphite, of which at least one such group is taken up by phosphorus and the remaining group or groups may be taken up with phosphorus or may be free, such as, for example, ethylene glycol, glycerol, trimethyl ethane trimethylol propane, trimethylol butane, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,4-butanediol, neopentylglycol, thiodiethyleneglycol, 1,6-hexanediol, 1,10-decanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, 1,4-phenylenedimethanol, hydrogenated Bisphenol A, and tris(2-hydroxyethyl)isocyanurate.

Also included are the polyoxyalkylene polyols containing one or more oxyalkylene groups with terminal hydroxyls free or etherified with alkyl, cycloalkyl or phenyl groups having from one to about ten carbon atoms. Exemplifying this class are methyl Cellosolve, ethyl Cellosolve, isopropyl Cellosolve, butyl Cellosolve, hexyl Cellosolve, cyclohexyl Cellosolve, and phenyl Cellosolve; methyl Carbitol, ethyl Carbitol, isopropyl Carbitol, butyl Carbitol and isobutyl Carbitol; dipropylene glycol, diethylene glycol, triethylene glycol, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether, glyceryl 1,2-dimethyl ether, glyceryl 1,3-dimethyl ether, glyceryl 1,3-diethyl ether and glyceryl 1-ethyl-2-propyl ether; nonyl phenoxy; polyethoxy ethyl, and lauroxy polyethoxyethyl.

In the case where the Z radical is a polyhydric alcohol residue, the Z substituent is alkylene, and the compounds take the form: ##STR25## where:

n.sub.3 is a number from 2 to 20; and

R.sub.1, R.sub.2 and n.sub.2 are as in Formula I.

When the Z radical is a polyphenol residue, Z is arylene, and the compounds take the form: ##STR26## where:

R.sub.0 is alkyl having from one to about twenty carbon atoms;

p is a number selected from zero to 4;

n.sub.3 is zero or 1; and

Y is a bivalent or trivalent linking radical and is selected from the group consisting of alkylene groups having from one to about twenty carbon atoms; oxygen; sulfur, cycloalkylene having from about five to about seven carbon atoms; and arylene having from six to about thirty atoms.

R.sub.0 and OH can be in any position or positions of the ring. OH is preferred in the para position to Y.

When Z is derived from a tetrahydric polyol, and taken together with OR.sub.2, the compounds take the form: ##STR27## where:

R.sub.1 and R.sub.2 are as above; and

Z.sub.1 is selected from the group consisting of: ##STR28##

Other variations will be apparent from consideration of Formula I.

Exemplary Y groups are alkylene, alkylidene, and alkenylene; arylene, alkyl arylene, arylalkylene; cycloalkylene, cycloalkylidene, and oxa- and thia-substituted such groups; carbonyl groups, tetrahydrofuranes, esters and triazino groups. The Y groups are usually bi, tri, or tetravalent, connecting two, three or four ##STR29## groups. However, higher valence Y groups, connecting more than four ##STR30## groups, can also be used. According to their constitution, the Y groups can be assigned to subgenera as follows:

(1) Y groups where at least one carbon in a chain or cyclic arrangement connect the aromatic groups, such as: ##STR31##

(2) Y groups where only atoms other than carbon link the aromatic rings, such as: ##STR32## where x is a number from one to ten;

(3) Y groups made up of more than a single atom including both carbon and other atoms linking the aromatic nuclei, such as: ##STR33##

Exemplary polyhydric phenol residues include hydroquinone, 2,5-di-t-butylhydroquinone, 2,3,6-trimethylhydroquinone, 2-methylresorcinol, 2,6-di-t-butylresorcinol, 2,2'-methylenebis(4-methyl-6-t-butylphenol), 2,2'-methylenebis(4-ethyl-6-t-butylphenol), 2,2'-methylenebis[4-methyl-6-(.alpha.-methylcyclohexyl)phenol], 2,2'-n-butylidenebis(4,6-dimethylphenyl), 1,1-bis-(2'-hydroxy-3',5'-dimethylphenyl)-3,5,5-trimethylhexane, 2,2'-cyclohexylidenebis(4-ethyl-6-t-butylphenol), 2,2'-thiobis(4-t-butyl-6-methylphenol), 2,2'-isopropylidene bis(4-t-butyl-6-methylphenol), 1,4-benzylidenebis(4-ethyl-6-t-butylphenol), 2,2'-thiobis(4-methyl-6-t-but ylphenol), 2,2'-thiobis(4,6-di-t-butylphenol), 4,4'-methylene bis(2-methyl-6-t-butylphenol), Bisphenol A, 4,4'-isopropylidenebis(2-phenylethylphenol), 4,4'-n-butylidenebis(3-methyl-6-t-butylphenol), 4,4'-cyclohexylidenebisphenol, 4,4'-cyclohexylidenebis(2-t-butylphenol), 4,4'-cyclohexylidenebis(2-cyclohexylphenol), 4,4'-benzylidenebis(2-t-butyl-5-methylphenol), 4,4'-oxabis(3-methyl-6-isopropylphenol), 4,4'-thiobis(3-methyl-6-t-butylphenyl), 4,4'-sulfobis(3-methyl-6-t-butylphenol), bis(2-methyl-4-hydroxy-5-t-butylbenzyl)sulfide, and 1,1,3-tris(2'-methyl-4'-hydroxy-5'-t-butylphenyl)butane.

Exemplary 2,6-di-t-butylphenyl phosphites in accordance with the invention include tetra(2,6-di-t-butylphenyl)hydroquinone diphosphite, tetra(2,6-di-t-butyl-4-methylphenyl)-2,5-di-t-butylhydroquinone diphosphite, tetra(2,6-di-t-butyl-4-methylphenyl)Bisphenol A diphosphite, tetra(2,6-di-t-butyl-4-ethylphenyl)Bisphenol A diphosphite, tetra(2,6-di-t-butyl-4-methoxycarbonyl ethylphenyl)-4,4'-butylidenebis(2-t-butyl-5-methylphenol)diphosphite, tetra(2,6-di-t-butyl-4-methylphenyl)-4,4'-thiobis(2-t-butyl-5-methylphenol )diphosphite, tetra(2,6-di-t-butyl-4-methylphenyl)4,4'-thiobis(2,6-dimethylphenol)diphos phite, tetra(2,6-di-t-butyl-4-methylphenyl-4,4'-thiobis(2-t-butyl-6-methylphenol) diphosphite, tetra(2,6-di-t-butyl-4-methylphenyl)-4,4'-cyclohexylidenediphenyl diphosphite, tetra(2,6-di-t-butyl-4-methylphenyl)-1,1,3-tris(2-methyl-4-hydroxy-5-t-but ylphenyl)butane diphosphite, tetra(2,6-di-t-butyl-4-methylphenyl)diethyleneglycol diphosphite, tetra(2,6-di-t-butyl-4-stearyloxycarbonylethylphenyl)1,6-hexanediol diphosphite, tetra(2,6-di-t-butyl-4-methylphenyl)hydrogenated Bisphenol A diphosphite, tetra(2,6-di-t-butyl-4-methylphenyl)1,4-cyclohexanedimethanol diphosphite, bis(2,6-di-t-butyl-4-methylphenyl)diphenyl hydroquinone diphosphite, bis(2,6-di-t-butylphenyl)-di(isodecyl)-2,5-di-t-butylhydroquinone diphosphite, bis(2,6-di-t-butyl-4-methylphenyl)-di(isooctyl)-Bisphenol A diphosphite, 2,6-di-t-butyl-4-ethylphenyl-tri(2-ethylhexyl)Bisphenol A diphosphite, bis(2,6-di-t-butyl-4-methylphenyl)-di(tridecyl)-4,4'-butylidenebis(2-t-but yl-5-methylphenyl)diphosphite, bis(2,6-di-t-butyl-4-methoxycarbonylethylphenyl)-di(tridecyl)-4,4'-butylid enebis(2-t-butyl-5-methylphenyl)-diphosphite, bis(2,6-di-t-butyl-4-methylphenyl)-dicyclohexyl-4,4'-thiobis(2-t-butyl-5-m ethylphenyl)diphosphite, bis(2,6-di-t-butyl-4-methylphenyl)dibenzyl-4,4'-thiobis(2,6-dimethylphenyl )diphosphite, bis(2,6-di-t-butyl-4-methylphenyl)-bis(2,6-di-t-butylphenyl)-4,4'-thiobis (2-t-butyl-6-methylphenyl)diphosphite, bis(2,6-di-t-butyl-4-methylphenyl)-bis(butoxyethyl)-cyclohexylidenebisphen yl diphosphite, bis(2,6-di-t-butyl-4-methylphenyl)-bis(tridecyl)-1,1,3-tris(2-methyl-4-hyd roxy-5-t-butylphenyl)butane diphosphite, tris(2,6-di-t-butyl-4-methylphenyl)-tris(decyl)-1,1,3-tris(2-methyl-4-hydr oxy-5-t-butylphenyl)butane triphosphite, bis(2,6-di-t-butyl-4-ethylphenyl)distearyl triethyleneglycol diphosphite, bis(2,6-di-t-butyl-4-methylphenyl)-bis(2-cyclohexylphenyl)neopentylglycol diphosphite, bis(2,6-di-t-butyl-4-methoxycarbonylphenyl)dilauryl neopentylglycol diphosphite, bis(2,6-di-t-butyl-4-methylphenyl)bis(C.sub.12-15 mixed alkyl)-1,6-hexanediol diphosphite, bis(2,6-di-t-butyl-4-methylphenyl)-di(Bisphenol A)diphosphite, bis(2,6-di-t-butyl-4-methylphenyl)-bis(nonylphenyl-1,10-decanediol diphosphite, bis(2,6-di-t-butyl-4-methylphenyl)-bis(nonylphenoxypolyethoxyethyl)thiodie thanol diphosphite, bis(2,6-di-t-butylphenyl)diisodecyl hydrogenated Bisphenol A diphosphite, bis(2,6-di-t-butylphenyl)tetraisodecyl tri(Bisphenol A)tetraphosphite, bis(2,6-di-t-butylphenyl)-bis(4-t-butylphenyl)-1,4-cyclohexanedimethanol diphosphite, tris(2,6-di-t-butyl-4-methylphenyl)-tri(tridecyl-tris(hydroxyethyl)isocyan urate triphosphite, bis[2,6-di-t-butyl-4-(2',4'-di-t-butylphenoxycarbonyl)phenyl]diphenyl hydrogenated Bisphenol A diphosphite.

These phosphites are readily prepared by conventional procedures. Thus, for example, the corresponding 2,6-di-t-butylphenol can be reacted with phosphorus dichloride in the presence of a base, such as an amine catalyst, to form the phosphite derivative, and then the compound having the corresponding Z radical that is to be introduced reacted therewith, again in the presence of a base. Conventional transesterification procedures can also be used.

The following Examples serve to illustrate the procedure:

Synthesis of bis(2,6-di-t-butyl-4-methylphenyl)-diisodecyl Bisphenol A-diphosphite.

2,6-Di-t-butyl-4-methylphenol 22.0 g (0.1 mole) and triethylamine 11.1 g (0.11 mole) were dissolved in 100 ml of toluene, PCl.sub.3 13.8 g (0.1 mole) was then added to the reaction mixture dropwise at room temperature, and the mixture was then refluxed for three hours.

Then, Bisphenol A 11.4 g (0.05 mole) and triethylamine 10.1 g (0.1 mole) were added, and the mixture refluxed for two hours.

Then, isodecanol 14.8 g (0.1 mole) and triethylamine 10.1 g (0.1 mole) were added, and the mixture refluxed for two hours.

Triethylamine hydrochloride which precipitated was filtered, and the filtrate was evaporated. The product obtained was a pale yellow viscous liquid.

Synthesis of 2,6-di-t-butyl-4-methylphenyl tri(tridecyl)hydroquinone-diphosphite.

1,4-Bis(dichlorophosphinoxy)benzene 31.3 g (0.1 mole), 2,6-di-t-butyl-4-methylphenol 22.0 g (0.1 mole) and tridecylalcohol 60 g (0.3 mole) were dissolved in 200 ml of toluene, and triethylamine 42.4 g (0.42) mole was added dropwise at room temperature.

The reaction mixture was refluxed for five hours, and the triethylamine hydrochloride which precipitated was filtered. The filtrate was evaporated. The product obtained was a pale yellow viscous liquid.

The phosphites of the invention are especially effective in enhancing the resistance to deterioration by heat and light of polyvinyl chloride resins. The term "polyvinyl chloride" as used herein is inclusive of any polymer formed at least in part of the recurring group: ##STR34## and having chlorine content in excess of 40%. In this group, the X groups can each be either hydrogen or chlorine, and n is the number of such units in the polymer chain. 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 chlorides as a class, for example, those disclosed in British Pat. No. 893,288 and also copolymers of vinyl chloride in a major proportion and other copolymerizable monomers in a minor 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 phosphites are effective also with mixtures of polyvinyl chloride in a major proportion with a minor proportion of other synthetic resins such as chlorinated polyethylene or a copolymer of acrylonitrile, butadiene and styrene.

The phosphites are applicable to the stabilization of rigid polyvinyl chloride resin compositions, that is, resin compositions which are formulated to withstand high processing temperatures, of the order of 375.degree. F. and higher, as well as plasticized polyvinyl chloride resin compositions of conventional formulation, even though resistance to heat distortion is not a requisite. Conventional plasticizers well known to those skilled in the art can be employed such as, for example, dioctyl phthalate, octyl diphenyl phosphate and epoxidized soybean oil.

Particularly useful plasticizers are the epoxy higher esters having from 20 to 150 carbon atoms. Such esters will initially have had unsaturation in the alcohol or acid portion of the molecule, which is taken up by the formation of the epoxy group.

Typical unsaturated acids are acrylic, oleic, linoleic, linolenic, erucic, ricinoleic, and brassidic acids, and these may be esterified with organic monohydric or polyhydric alcohols, the total number of carbon atoms of the acid and the alcohol being within the range state. Typical monohydric alcohols include butyl alcohol, 2-ethyl hexyl alcohol, lauryl alcohol, isooctyl alcohol, stearyl alcohol, and oleyl alcohol. The octyl alcohols are preferred. Typical polyhydric alcohols include pentaerythritol, glycerol, ethylene glycol, 1,2-propylene glycol, 1,4-butylene glycol, neopentyl glycol, ricinoleyl alcohol, erythritol, mannitol and sorbitol. Glycerol is preferred. These alcohols may be fully or partially esterified with the epoxidized acid. Also useful are the epoxidized mixtures of higher fatty acid esters found in naturally-occurring oils such as epoxidized soybean oil, epoxidized olive oil, epoxidized coconut oil, epoxidized cottonseed oil, epoxidized tall oil fatty acid esters and epoxidized tallow. Of these, epoxidized soybean oil is preferred.

The alcohol can contain the epoxy group and have a long or short chain, and the acid can have a short or long chain, such as epoxystearyl acetate, epoxystearyl stearate, glycidyl stearate, and polymerized glycidyl methacrylate.

The polyvinyl chloride resin can be in any physical form, including, for example, powders, films, sheets, molded articles, foams, filaments, and yarns.

A sufficient amount of the phosphite is used to enhance the resistance of the polyvinyl chloride to deterioration in physical properties, including, for example, discoloration and embrittlement, under the heat and/or light conditions to which the polymer will be subjected. Very small amounts are usually adequate. Amounts within the range from about 0.01 to about 5% by weight of the polyvinyl chloride resin are satisfactory. Preferably, an amount within the range from about 0.05 to about 2%, is employed for optimum stabilizing effectiveness.

The phosphites of the invention can be employed as the sole stabilizer. They can also be used in combination with other conventional heat and light stabilizers for polyvinyl chloride resins, such as, for example, polyvalent metal salts, alkaline earth metal phenolates, and phenolic antioxidants, as well as epoxy compounds.

A particularly useful stabilizer system contains the following amounts of ingredients:

(a) phosphite in an amount within the range from about 25 to about 45 parts by weight;

(b) polyvalent metal salt of an aliphatic carboxylic acid or of an alkyl phenol in an amount within the range from about 25 to about 45 parts by weight; plus any one or more of the following optional ingredients:

(c) phenolic antioxidant in an amount within the range from about 0.01 to about 1 part by weight;

(d) free aliphatic carboxylic acid in an amount within the range from about 0.5 to about 5 parts by weight, but in no case more than 15% by weight of the cadmium carboxylate; and

(e) acid phosphite in an amount within the range from about 0.5 to about 5 parts by weight.

In addition, any of the conventional polyvinyl chloride resin additives, such as lubricants, emulsifiers, antistatic agents, flame-proofing agents, pigments and fillers, can be employed.

Preferably, the stabilizer system is added to the polyvinyl chloride resin in an amount to provide in the resin from about 0.1 to about 2% of polyvalent metal salt or phenolate; from about 0.2 to about 1% of the phosphite; and from about 0 to about 1% total of one or more of the additional ingredients, as noted above.

The stabilizer system is incorporated in the polymer in suitable mixing equipment, such as a mill or a Banbury mixer. If the polymer has a melt viscosity which is too high for the desired use, the polymer can be worked until its melt viscosity has been reduced to the desired range before addition of the stabilizer. Mixing is continued until the mixture is substantially uniform. The resulting composition is then removed from the mixing equipment and brought to the size and shape desired for marketing or use.

The stabilized polyvinyl chloride resin can be worked into the desired shape, such as by milling, calendering, extrusion or injection molding, or fiber-forming. In such operations, it will be found to have a considerably improved resistance to discoloration and embrittlement on exposure to heat and light.

The phosphites of the invention are especially effective heat stabilizers for olefin polymers such as polyethylene, polypropylene, polybutylene, polypentylene, polyisopentylene, and higher polyolefins.

Olefin polymers on exposure to elevated temperatures undergo degradation, resulting in embrittlement and discoloration.

The stabilizer systems can be employed with any olefin polymer, including low-density polyethylene, high density polyethylene, polyethylenes prepared by the Ziegler-Natta process, polypropylenes prepared by the Ziegler-Natta process, and by other polymerization methods from propylene, poly(butene-1)poly(pentene-1)poly(3-methylbutene-1)poly(4-methyl-pentene-1 ), polystyrene, and mixtures of polyethylene and polypropylene with other compatible polymers, such as mixtures of polyethylene and polypropylene, and copolymers of such olefins, such as copolymers of ethylene, propylene, and butene, with each other and with other copolymerizable monomers. The term "olefin polymer" encompasses both homopolymers and copolymers.

Polypropylene solid polymer can be defined in a manner to differentiate it from other polyolefins as having a density within the range from 0.86 to 0.91, and a melting point above 150.degree. C. The phosphites of the invention are applicable to all such polypropylenes, as distinguished from polypropylenes in the liquid form or in semiliquid of gel-like forms, such as are used as greases and waxes.

The phosphites of the invention are applicable to polypropylenes prepared by any of the various procedures, for the molecular weight and tacticity are not factors affecting this stabilizer system. Isotactic polypropylene, available commercially under the trade name PRO-FAX, and having a softening or hotworking temperature of about 350.degree. F., is an example of a sterically regular polypropylene polymer.

Mixtures of polypropylene with other compatible polymers and copolymers of propylene with copolymerizable monomers not reactive with the phosphite or stabilizer combination can also be stabilized, for example, mixtures of polyethylene and polypropylene, and copolymers of propylene and ethylene.

The phosphites are also effective to enhance the resistance to heat degradation of polystyrene; polydienes, such as polybutadiene and polyisoprene; and copolymers of olefins and dienes with other ethylenically and acetylenically unsaturated monomers, such as ethylene-vinyl acetate copolymers, styrene-butadiene copolymers, acrylonitrile-styrene-butadiene copolymers, synthetic rubbers of all types, such as polychloroprene; polyvinylidene chloride; and copolymers of vinyl chloride and vinylidene chloride; vinylidene chloride and vinyl acetate; and other ethylenically unsaturated monomers; polyacetals such as polyoxymethylene and polyoxyethylene; polycarbonates; polyphenylene oxides; polyesters such as polyethylene glycol-terephthalic acid ester polymers; polyamides such as poly-epsilon-caprolactam; polyhexamethylene adipamide and polydecamethylene adipamide; polyurethanes; and epoxy resins.

The synthetic polymer can be in any physical form, including (for example) filaments, yarns, films, sheets, molded articles, latex and foam.

A sufficient amount of the phosphite and any stabilizer combination including the phosphite is used to improve the resistance of the synthetic polymer to deterioration in physical properties, including, for example, discoloration, reduction in melt viscosity and embrittlement, under the conditions to which the polymer will be subjected. Very small amounts are usually adequate. Amounts within the range from about 0.001 to about 5% total stabilizers by weight of the polymer are satisfactory. Preferably, from 0.01 to 3% is employed, for optimum stabilization.

The phosphites of the invention can be employed as the sole stabilizer or in combination with phenolic antioxidants and/or other conventional heat and light stabilizers for the particular olefin polymer.

Thus, for example, there can be employed fatty acid salts of polyvalent metals, phenolic antioxidants, and the higher fatty acid esters of thiodipropionic acids, such as, for example, dilauryl thiodipropionate.

With polyamide resin compositions, polyamide stabilizers such as copper salts in combination with iodides and/or other phosphorus compounds and salt of divalent manganese can be used.

With synthetic rubbers and acrylonitrile-butadiene-styrene terpolymers, phenolic antioxidants and polyvalent metal salts of the higher fatty acids can be used.

In addition, other conventional additives for synthetic polymers, such as plasticizers, lubricants, emulsifiers, antistatic agents, flame-proofing agents, pigments and fillers, can be employed.

The stabilizer combination is incorporated in the polymer in suitable mixing equipment, such as a mill or a Banbury mixer. If the polymer has a melt viscosity which is too high for the desired use, the polymer can be worked until its melt viscosity has been reduced to the desired range before addition of the stabilizer. Mixing is continued until the mixture is substantially uniform. The resulting composition is then removed from the mixing equipment and brought to the size and shape desired for marketing or use.

The stabilized polymer can be worked into the desired shape, such as by milling, calendering, extruding or injection molding or fiber-forming. In such operations, it will be found to have a considerably improved resistance to reduction in melt viscosity during the heating, as well as a better resistance to discoloration and embrittlement on ageing and heating.

The following Examples illustrate preferred phosphite stabilizer systems and resin compositions of the invention:

A group of polyvinyl chloride resin compositions was prepared having the following formulation:

This formulation was blended and sheeted off on a two-roll mill to form sheets 1 mm thick.

The sheets were heated in air in a Geer oven at 190.degree. C. to evaluate heat stability, and the time in minutes noted for the sheet to develop a noticeable discoloration and/or embrittlement. Initial color also was measured, using a Hunter color difference meter to determine the amount of yellowness on a scale where the higher the numerical value, the more yellow the sample is, and the clarity of the sheet was also observed.

The results are shown in Table I.

It is apparent that the phosphites in accordance with the invention are far superior to the Controls.

A group of polyvinyl chloride resin compositions was prepared having the following formulation:

This formulation was blended and sheeted off on a two-roll mill to form sheets 1 mm thick.

The sheets were heated in air in a Geer oven at 190.degree. C. to evaluate heat stability, and the time in minutes noted for the sheet to develop a noticeable discoloration and/or embrittlement. Initial color was measured in a Hunter color difference meter, to determine degree of yellowness, and plate-out was also measured on a scale where the higher the numerical value the more the plate-out.

The results are shown in Table II:

It is apparent that the phosphites in accordance with the invention are far superior to the Controls.

A group of polyvinyl chloride resin compositions was prepared having the following formulation:

This formulation was blended and sheeted off on a two-roll mill to form sheets 1 mm thick.

The sheets were heated in a Geer oven at 175.degree. C. to evaluate heat stability, and the time in minutes noted for the sheet to develop a noticeable discoloration and/or embrittlement.

The results obtained are given in Table III:

It is apparent that the phosphites in accordance with the invention are far superior to the Controls.

A group of polyvinyl chloride resin compositions was prepared having the following formulation:

This formulation was blended and sheeted off on a two-roll mill to form sheets 1 mm thick.

The sheets were heated in air in a Geer oven at 190.degree. C. to evaluate heat stability, and the time in minutes noted for the sheet to develop a noticeable discoloration and/or embrittlement. Initial color was measured for yellowness using a Hunter color difference meter and resistance to sun and weather (ultraviolet light) was measured using a Weather-O-Meter.

The results obtained are given in Table IV:

It is apparent that the phosphites in accordance with the invention are far superior to the Controls.

A group of polyvinyl chloride resin compositions was prepared having the following formulation:

This formulation was blended and sheeted off on a two-roll mill to form sheets 1 m thick.

The sheets were heated in air in a Geer oven at 190.degree. C. to evaluate heat stability, and the time in minutes noted for the sheet to develop a noticeable discoloration and/or embrittlement. Initial color also was measured, using a Hunter color difference meter to determine the amount of yellowness on a scale where the higher the numerical value, the more yellow the sample is, and the clarity of the sheet was also observed.

The results obtained are given in Table V:

It is apparent that the effectiveness of the phosphite in accordance with the invention is improved by combination with epoxy compounds.

Acrylonitrile-styrene copolymer resin compositions were prepared using phosphites of the invention and having the following formulation:

The stabilizers were blended with the resin on a two-roll mill, and extruded at 230.degree. C. Samples were prepared by injection molding of the resulting blend, and yellowness measured in a Hunter color difference meter.

Samples were heated at 230.degree. C. for ten minutes, and yellowness again measured in a Hunter color difference meter. Samples were also heated at 230.degree. C. for twenty minutes, and yellowness measured in the same way.

The results are shown in Table VI:

It is apparent from the data that the phosphites of the invention are far superior to the Control.

Acrylonitrile-butadiene-styrene terpolymer resin compositions were prepared using phosphites of the invention and having the following formulation:

The stabilizers were blended with the resin on a two-roll mill and extruded at 200.degree. C., followed by injection molding at 230.degree. C. of the resulting blend to prepare samples.

Heat stability was evaluated by heating the specimen samples at 135.degree. C. in a Geer Oven for thirty hours. The whiteness of the specimens was evaluated using a Hunter color difference meter. Izod impact strength of the specimens was determined before and after immersion in hot water at 100.degree. C. for seventy-two hours.

The results are shown in Table VII:

It is apparent from the data that the phosphites of the invention are far superior to the Controls.

Polypropylene compositions were prepared using phosphites of the invention and having the following formulation:

The composition was thoroughly blended for five minutes in a Brabender Plastograph.

One part of the mixture was then extruded at 20 rpm, cylinder temperature 230.degree. to 240.degree. C. and head die temperature 250.degree. C. Another part was injection-molded at 475 kg/cm.sup.2, cylinder temperature 240.degree. C., nozzle temperature 250.degree. C., to form sheets 95.times.40.times.1 mm.

Pieces 2.5 cm.sup.2 were cut off from the sheets and heated at 160.degree. C. in a Geer oven to evaluate heat stability.

The time in hours required for the sheet to develop a noticeable discoloration and/or embrittlement was noted as the hours to failure.

The yellowness of the sheet after exposure to ultraviolet light for 72 hours was measured in a Hunter color difference meter.

The results obtained are shown in Table VIII.

It is apparent from the above results that the phosphites of the invention are superior to the control in enhancing resistance of the polypropylene polymer composition to deterioration when heated and when exposed to ultraviolet light.

High density polyethylene compositions were prepared using phosphites of the invention, and having the following formulation:

The stabilizers were blended with the polymer on a two-roll mill at 150.degree. C. for five minutes, and sheets 1 mm thick were prepared by compression molding of the blend at 150.degree. C. and 180 kg/cm.sup.2 pressure.

Pieces 10.times.20 mm were cut off from the sheets, and heated at 150.degree. C. in a Geer oven on aluminum foil.

The time in hours when degradation set in, as determined by a significant discoloration and/or embrittlement, was noted as hours to failure.

The results are reported in Table IX.

It is apparent from the above results that the phosphites of the invention are superior stabilizers in enhancing the resistance of the polyethylene polymer composition to deterioration when exposed to heat.

Resin compositions having the following composition were prepared:

The ingredients were mixed and then extruded at 60 rpm, 260.degree. C., followed by injection molding at 290.degree. C. to prepare the test pieces. The heat stability was evaluated by heating the test pieces in a Geer oven at 125.degree. C. for 100 hours. Elongation and Izod impact strength were measured before and after the heating, and the percent elongation and percent Izod impact strength retained were calculated.

The results are shown in Table X.

The phosphites of the invention are clearly more effective heat stabilizers than the Controls.

Polycarbonate resin compositions were prepared having the following formulation:

The ingredients were mixed and compression-molded at 260.degree. C. to prepare a sheet 1 mm thick. Heat stability was evaluated by heating the sheets in a Geer oven at 230.degree. C. for thirty minutes, and then observing the color of the sheets.

The results are shown in Table XI.

The phosphites of the invention are clearly more effective heat stabilizers than the Control.