CA1136152A

CA1136152A - Process for preparing aromatic polyphosphites

Info

Publication number: CA1136152A
Application number: CA000343754A
Authority: CA
Inventors: Ingenuin Hechenbleikner; Leo L. Valdiserri
Original assignee: Borg Warner Chemicals Inc
Current assignee: GE Chemicals Inc
Priority date: 1979-02-05
Filing date: 1980-01-16
Publication date: 1982-11-23
Also published as: GB2041938A; GB2041938B; JPS55104321A; FR2447927A1; DE3003984A1; FR2447927B1

Abstract

PROCESS FOR PREPARING AROMATIC POLYPHOSPHITES

Abstract:

A process for preparing aromatic polyphosphites wherein a pentaerythritol diphosphite compound having "leaving" groups is reacted with a bis-(hindered phenolic) compound. The resulting aromatic polyphosphite is free of phenol which fact enlarges its sphere of utility as a polymer additive.

Description

Z

07800~

PROChSS FOR PREPA~ING AROMATIC
POLYPHOSPHITES
.

Description The invention of this application r~lates to aromatic polyphosphites and, in particular, to a process for their preparation. More particularly, it relates to a process for preparing phenol-free aromatic poly-phosphites.
The aromatic polyphosphites which are prepared by the process of this invention are useful as polymer stabilizers. They are especially useful for such purpose in olefin polymer compositions, which require a high degree of thermal stability. One of the advantages of polypro-pylene, for example, is the fact that it is readily processed and fabricated in all of the conveutional systems; these include solid foam molding, solid and composite extrusion, spinning and orienting, rotocasting, powder coating, thermoforming and pressure forming, stamping and laminating. Moreover, post-fabrication operations which are commonly applied include machining, weldi~g, turning, sawing, drilling, butt and spin welding, and hot stamping. ~any of these operations are carried out at relatively high temperatures, however, and it is necessary to protect the polypropylene from thermal degradation at these temperatures.
Polypropylene is especially vulnerable to degradation under conditions which favor oxidation, for example, because of the recurring pres~nce in the molecular chain of tertiary carbon atoms. These are notoriously susceptible to oxidative attack.

113~ilS~
078004~ 2 -The problem of oxidative degration generally is met by incorporation into the olefin polymer composition of a small proportion of a high molecular ueight anti-oxidant. Phenolic phosphite antioxidants are well known and, in most instances are quite suitable for this purpose.
They frequently suffer one disadvantage, hcwever, because of the invariable contamination of the antioxidant with a small proportion of phenol. Such contamination tends to render the polypropylene unsuitable for uses involving probable contact with food, medicines and ~he like.
The contamination arises from the fact that the high molecular weight phenolic phosphite compounds are prepared by a transesteri~ication reaction involvin~ triphenyl phosphite and a bis-phenol. The product which results from such a reaction contains phenol as a by-product, and it is not practical to remove all of this phenol from the desired product.
U.S. 3,053,878 (~riedman et al.) shows the reaction of diphenyl pentaerythritol diphosphite with bisphenol A
in the presence of a diphenyl phosphite catalyst to form a polymeric phosphite.
~ .S. 3,305,608 (Baranauckas et al.) sho~s the reaction of stoichiometric quantities of triphenyl phosphite, penta-erythritol and 4,4-isopropylidenediphenol (bisphenol A) in the presence of a sodium catalyst.
Japanese Patent Publication No. 1975-35097 shows the reaction of triphenyl phosphite and pentaerythritol to form an intermediate product whiGh then is reacted with a mixture of more pentaerythrltol and bisphenol A.
Stoichiometric quantities are used. The resulting product is said to be effective as a polymer sta~ilizer.
The process of the present invention does not utilize triphenyl phosphite at any stage~ nor any other reactant that can, upon hydrolysis, yield phenol. The resulting product thus is not contaminated wlth phenol and, ln this 1~3tj~5~
07~0~ 3 -respect, is entirely suitable for use in olefin polymer compositions which are intended for uses which may bring them in contact with food or medicines. The process involves preparing a phenolic antioxidant composition by reacting a pentaerythritol diphosphite compound having the structure: OCH2 CH O
/\ / ~
X p / C j p y

2 CH20 where X and Y are the same or different groups selected from the class consisting of halo, amino, di-(lower alkyl) amino, anilino, morpholino and methylanilino, with a stoichiometrically excessive amount, up to about 5 mols per mol, of a bis-(hindered phenolic) compound having the structure:
p. R' R ~ A _ ~ OH

where the HO groups are on the 2- or 4- positions of the benzene rings, R is the same or different alkyl group and is ortho to the HO group, R' and R" are lo~Ner alkyl or hydrogen, and A is alkylidene or sulfur. The term "lower alkyl" denotes alkyl of 1-6 carbon atoms.
The X and Y groups on the pentaerythritol diphosphite reactant are, in the circumstances here, known as "leaving"
groups. That is, they "leave" the pentaerythritol di-phosphite nucleus and are replaced in each case by the phenolic group of a bis-(hindered phenolic) compound.
The reaction is illustrated below:

078004-~ - 4 -C~ CH~ CH3 CH~

~CH2 \ / 2HO~/~3H7~0H

~ bc~ ` ' `_~ C ~oTH

where R is a tertiary alkyl group and n is at~least 1.
When X and Y are halo they may be either chloro or bromo.
As indicated, the bis-(hindered phenolic) compound is characterized by the presence of at least one alkyl group which is ortho to a phenolic group. This alkyl group may contain 4-10 carbon atoms and preferably is tertiary butyl.
Other suitable groups include amyl, 1,1,2-trimethylpropyl, l-methyl-2-ethylpropyl, l,l-diethylpropyl, l-methyl-l-ethylpentyl, n-octyl and the like.
Moreover, when A in the bis-(hindered phenolic) compound is alkylidene, the alkylidene may contain 1-10 carbon atoms. Methylene and butylidene are pre~erred because o~ the ready availability of bis-(hindered phenolic) compounds containing such alkylidene groups, but others are suitable and include isopropylidene, ethylidene, hexylidene, etc.
With respect to the pentaerythritol diphosphite compound, the X and Y groups may, as indicated, be halo, amino, di-(lower alkyl)amino, anilino, morpholino or methylanilino. Lower alkyl groups include those containing 1-6 carbon atoms, such as methyl, ethyl, propyl, isopropyl, butyl, etc.

078004~ 5 -The process may be carried out in a solvent although a solvent is ordinarily unnecessary. Suitable solvents include toluene, benzene, chloroform, carbon tetrachloride, dioxane, etc. Ordinarily, it is necessary merely to mix the reactants and heat the mixture with suitable agitation.
~ Vhen the leaving groups, i.e., X and Y in the pentaerythritol diphosphite, are chloro the process can be carried out as above, or a hydrogen chloride acceptor may be used. In such case~ it is advisable to use a solvent also. The hydrogen chloride acceptor may be any basic amine, and low molecular weight tertiary amines are preferred. These include trimethyl amine, triethyl amine, tripropyl amine, i.e., those having up to 10 carbon atoms.
The product which results from the above process has the structure:

._ R R R R
~ A - ~ OCH2 CH2O ~\ A ~ ¦
HO~ OP \, ~ , I I I r t R' R" R' R' R' R~ R~ R' _ n where the oxygen atoms linking phosphorus to the benzene rings are in the 2- or 4- positions, R is the same or different alkyl group and is ortho to the hydroxy or aryloxy group, R' and R" are lower alkyl or hydrogen, n is at least 1 and A is alkylidene or sulfur. Preferably n is 1-10, and still more preferably, n is 2-10.
The process of the invention is illustrated by the following examples.

078004-~ - 6 -Example 1 A mixture of 36.90 g. tO.l mol) of bis-(2-hydroxy-3-tertiarybutyl-5-methylphenyl)methane and 8.75 g. (0.033 mol) of dichloro pentaerythritol di-phosphite is heated with agitation at 170C under reducedpressure (water aspirator) for two hours. The cooled, glassy residue weighs 43.5 g.~ has an acid number of 1.24, melts at 75-160C and is soluble in benzene, hot cyclo-hexane and (partially) in hot pentane.
Example 2 A mixture of 31.0 g. (0.083 mol) of bis-(2-hydroxy-

3-tertiarybutyl-5-methylphenyl)methane and 8.75 mg. (0.033 mol) of dichloro pentaerythritol diphosphite is heated with agitation at 170C for two hours under reduced pressure (water aspirator). The residual product has an acid number of 0.62 and melts at 55-60C.
3xample 3 To a solution of 221.6 g. (0.58 mol) of 4,4'-butylidene-bis-(6-tertiarybutyl-m-cresol) and 117.2 g.
(1.11 mol) of triethylamine in 800 g. of toluene is added, over a period of one hour, a solution of 145.8 g. (0.55 mol) of dichloro pentaerythritol diphosphite in 500 g.
of toluene. The resulting solution is heated at reflux temperature for 13 hours, then permitted to cool to room temperature and filtered. The solid triethyl amine hydro-chloride is removed by filtration and the filtrate is con-centrated by heating to a final temperature of 165C/5mm.
The solid residual product (81% of the theroet~cal yield) is shown to have an acid number of 1.7 and an average molecular ~eight of 1670 (corresponding to three bis-phenolic residues and two pentaerythritol residues).

5~

078004~ 7 ~

Example 4 A stirred mixture of 35.8 g. (0.094 mol) of

4,4'-butylidene-bis-(6-tertiarybutyl-m-cresol) a~d 8.75 g.
(0.033 mol) of dichloro pentaerythritol diphosphite is heated at 170C (under reduced pressure) for two hours, then cooled to room temperature. The solid residue weights 42.1 g., has an acid number of 1.35 and melts at 130-170C.
Example 5 A stirred mixture of 38.2 g. (0.10 mol) of 4,4'-butylidene-bis-(6-tertiarybutyl-m-cr~soi) and 15.6 g.
(0.058 mol) of dichloro pentaerythritol diphosphite is heated under reduced pressure at 170C for two hours, then allowed to cool to room temperature. The solid residue weights 47 g., melts at 130-155C and has an acid number of 1.32. Its average molecular weight is 920, indicating a molecule containing two bis-phenolic residues and one pentaerythritol residue.
Example 6 A stirred mixture o~ 35.8 g. (0.10 mol) of bis-(4-hydroxy-2-methyl-5-tertiarybutylphenyl) sulfide and 17.5 g. (0.066 mol) of dichloro pentaerythritol di-phosphite is heated under reduced pressure at 170C
for two hours, then allowed to cool to room temperature.
2~ The residue weights 48 g. and has an acid number of 0.37.
The aromatic polyphosphites which are prepared by the process of this invention are useful as polymer additi~es. They provide thermal stability to polymer compositions, especially to olefin polymer compositions.
For such use, preferred concentrations are from about 0.01 to about 1.0 percent, based on the ~eight of polymer. Ordinarily, the aromatic polyphosphites are 11361S'~

07800~-~l - 8 -used in such concentrations in combination with polyvalent metal salts of fatty a~ids or polyvalent metal oxides in the stabilization of polypropylene;
the poly~ralent metal salt preferably is an alkaline earth metal stearate and is used in concentrations o~
from about 0.02 to about 1.0 percent based on the weight of polypropylene.
The efficacy of the phenolic antioxidants herein as polymer stabilizers is shown by the data co~tained in Table I, where there is shown the time required for a polypropylene film to develop a crazed or embrittled surface, in an oven at 150C. In each case the poly-propylene film test sample contains 0.10 phr (parts per hundred parts of resin) of calcium stearate, Q.25 phr of distear~lthiodipropionate and 0.20 phr of a phenolic antioxidant.
The test samples are prepared by dry blending the polypropylene and additives, as above, in a Waring blender for one minute. The mixture then is extruded into a two-inch (wide) by 25-~il (thick) tape from which test samples are cut. The samples are placed in a circulating oven at 150C and chec~ed twice daily for signs of crazing and/or embrittlement.
TABLE I
_enolic Antioxidant Hours to Fail 1. Product of Example 1 1009 2. Product of Example 2 1000 3. Bis-~2-hydroxy-3-tertiarybutyl-

5-methylphenyl)methane 814 4. Bis-(4-hydroxy-2-methyl-5-tertiarybutylphenyl)sulfide 828 ~13~5~
0780~4~ 9 -The data in Table II also shows the stabilizing properties of the antioxidants herein. Like the data in Table I, it is based on oven stability tests. The test samples each contain polypropylene, 0.25 phr of distearylthiodipropionate and 0.20 phr of a phenolic antioxidant.
The test samples are prepared by blending the dry ingredients in a twin shell blender for 15 minutes, then extruding the mixture. The extrudate is cut into pellets whi~h are injection molded into 25-mil and 100-mil plaques. Three plaques of each size are mounted on a biaxial rotator and placed in a circulating air oven at 150C and the time required for development of crazing and/or embrittlement is noted.
TABLE II
Hours to Fail Phenolic Antioxidan~ 25-mil 100-mil 1. Product of Example 4621 1317 2. Product of Example 5677 1485 3. 4,4'-butylidene-bis-(6-tertiarybutyl-m-cresol) 501 1045 It will be noted from the data above, both in Tables I and II, that addition of the pentaerythritol diphosphite residue to the bis-(hindered phenolic) compound results in a polymer additive having improved stabilizing properties.
Those aromatic polyphosphites herein having at least two pentaerythritol residues and three bis-(hindered phenolic) residues are especially effective polymer additives, and for this reason, are preferred. Their effectiveness is shown by the data in Table III wherein the test samples are subjected to thermal gravimetric bl~
078004~ 10 -analysis. In this test a carefully weighed sample is heated at gradually increasing temperatures while the loss in weight of the sample is noted. The temperature required to produce a given percent weight loss, e.g., 10%, 20%
and 50%, is taken as a measure of the relative thermal stability or volatility of the sample. Thus, if a sample has suffered a 50% weight loss by the time the temperature has reached 350C, it is regarded as more stable or less volatile, for example, than a sample which has lost that much weight at 300C.
In the tests here, the samples are heated under ordinary atmospheric conditions.
TABLE III
Product of Product of 15 % Weight Loss DPD* Ex. 5 Ex. 3 onset 110-120C 130C 190C
10% 222C 250C 295C
20% 270C 285C 340C
50% 311C 360C 400C
*DPD: distearyl pentaerythritol diphosphite The data above shows the clearly superior thermal stability or lesser volatility of the higher molecular weight aromatic polyphosphite, i.e., the product of Example 3, which has at least two pentaerythritol residues and three bis-(hindered phenolic) residues.
Another method o~ testing the stabilizing influenceof a test sample involves subjecting a polymer composition to repeated extrusions and determining the melt index after each such extrusion. A rapid increase in the meltindex with repeated extrusions indicates a deterioration of the polymer.

113~i152 078004-~ - 11 -The data of Table IV is taken after 1, 3 and 5 extrusions of four test samples. Each sample contains 100 parts of polypropylene, 0.05 phr of calcium stearate, 0.08 phr of Irganox 1010** and 0.07 phr, if any, of stabilizer.
~ ~ao~ ~nark-**f pentaerythritol tetrakis-3-(3,5-ditertiarybutyl-4-hydroxyphenylpropionate) TABLE IV

Melt Index After Extrusion No.
Stabilizer 1 3 5 AMI*
1. None 8.7 23.3 42.9 40 2. BHT (butylated (hydroxytoluene) 4.5 7.1 13.4 10.5 3. Tris)nonylphenyl) phosphite 3.5 5.0 8.9 6.0 4. Product of Example 3 3.3 4.8 5.9 3.0 *AMI: Melt Index a~ter 5th Extrusion minus 2.9 (MeltIndex before 1st Extrusion).
All parts and percentages herein are by weight unless otherwise expressly stated.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A process for preparing a phenolic antioxidant composition having the structure:

where the oxygen atoms linking phosphorus to the benzene rings are in the 2- or 4- positions, R is the same or different alkyl group and is ortho to the hydroxy or aryloxy group, R' and R" are lower alkyl or hydrogen, n is at least 1 and A is alkylidene or sulfur comprising reacting a pentaerythritol diphosphite compound having the structure:

where X and Y are the same or different group selected from the class consisting of halo, amino, di-(lower alkyl) amino, anilino, morpholino and methylanilino, with a stoichiometrically excessive amount, up to about 5 mols per mol, of a bis-(hindered phenolic) compound having the structure:

where the HO groups are on the 2- or 4- positions of the benzene rings, R is the same or different alkyl group and is ortho to the HO group, R' and R" are lower alkyl or hydrogen, and A is alkylidene or sulfur.

2. The process of Claim 1 wherein X and Y are each chloro.

3. The process of Claim 1 wherein A is sulfur.

4. The process of Claim 1 wherein A is alkylidene.

5. The process of Claim 1 wherein A is butylidene.

6. The process of Claim 1 wherein A is methylene.

7. The process of Claim 1 wherein R is tertiary butyl.