WO1999041307A1

WO1999041307A1 - Hydrogenated aromatic polymer compositions containing stabilizers

Info

Publication number: WO1999041307A1
Application number: PCT/US1999/000189
Authority: WO
Inventors: John T. Blaha; Gary D. Parsons; Jerry L. Hahnfeld
Original assignee: The Dow Chemical Company
Priority date: 1998-02-17
Filing date: 1999-01-15
Publication date: 1999-08-19
Also published as: AU2310999A; CO4830473A1

Abstract

The present invention is a polymer compositions comprising: a) a hydrogenated aromatic polymer; b) a benzofuranone; and c) a hindered phenol. The composition of the present invention can be processed at high temperatures without losing significant Mw and thus can produce molded articles having excellent physical properties.

Description

HYDROGENATED AROMATIC POLYMER COMPOSITIONS CONTAINING

STABILIZERS This invention relates to hydrogenated aromatic polymer compositions. This invention particularly relates to molded products produced from hydrogenated aromatic polymer compositions.

Hydrogenated aromatic polymers such as polycyclohexylethylene (PCHE) have been used as a replacement for polycarbonates. PCHE has the advantage of good transparency, heat resistance and low moisture absorbency. In the production of PCHE and the formation of molded articles, the polymer is typically processed at temperatures of from 230 to 350°C. However, when PCHE is processed at such temperatures, the molecular weight of the polymer greatly decreases and the physical properties of the polymer and subsequently produced molded article severely declines. JP2586575 by Mitsubishi attempts to solve this problem by adding a hindered phenol and phosphorus type heat stabilizers. However, although this combination decreases the amount of polymer degradation which occurs, the polymer still loses significant Mw and thus physical properties.

Therefore, there remains a need to develop a hydrogenated aromatic polymer composition which will not lose significant Mw upon processing at 230 to 350°C and will produce an molded article having excellent physical properties. In one aspect, the present invention is a polymer composition comprising: a) a hydrogenated aromatic polymer and a heat stabilizer mixture consisting essentially of: b) a benzofuranone, and c) a hindered phenol. In another aspect, the present invention is a molded article produced from such a polymer composition .

The composition of the present invention can be processed at high temperatures without losing significant Mw and thus can produce molded articles having excellent physical properties. In one embodiment, the present invention is a polymer composition comprising a hydrogenated aromatic polymer and a stabilizer composition. The hydrogenated aromatic polymer used in the present invention includes any aromatic polymer which has been hydrogenated to a level of at least 60 percent aromatic hydrogenation, generally at least 80 percent, preferably at least 90 percent, more preferably at least 95 percent and most preferably at least 98 percent. Methods of hydrogenating aromatic polymers are well known in the art such as that described in US-A-5,612,422 by Hahn and Hucul, herein incorporated by reference, wherein aromatic polymers are hydrogenated by contacting an aromatic polymer with a hydrogenating agent in the presence of a silica supported metal hydrogenation catalyst having a narrow pore size distribution and large pores.

Aromatic polymers which are hydrogenated by such processes include any polymeric material containing pendant aromatic functionality. Pendant aromatic functionality refers to a structure wherein the aromatic group is a substituent on the polymer backbone and not embedded therein. Preferred aromatic groups are C₆-₂o aryl groups, especially phenyl. These polymers may also contain other olefinic groups in addition to the aromatic groups. Preferably, the polymer is derived from a monomer of the formula:

R'

I Ar— C— CH₂ wherein R is hydrogen or alkyl, Ar is phenyl, halophenyl, alkylphenyl, alkylhalophenyl, naphthyl, pyridinyl, or anthracenyl, wherein any alkyl group contains 1 to 6 carbon atoms which may be mono or multisubstituted with functional groups such as halo, nitro, amino, cyano, carbonyl and carboxyl. More preferably Ar is phenyl or alkyl phenyl with phenyl being most preferred. Typical vinyl aromatic monomers which can be used include styrene, alpha-methylstyrene, all isomers of vinyl toluene, especially paravinyltoluene, all isomers of ethyl styrene, propyl styrene, vinyl biphenyl, vinyl naphthalene, and vinyl anthracene, and mixtures thereof. Homopolymers may have any stereostructure including syndiotactic, isotactic or atactic; however, atactic polymers are preferred. In addition, hydrogenated copolymers containing these aromatic monomers including random, pseudo random, block and grafted copolymers may be used in accordance with the present invention. For example, copolymers of vinyl aromatic monomers and comonomers selected from nitriles, acrylates, acids, ethylene, propylene, maleic anhydride, maleimides, vinyl acetate, and vinyl chloride may also be used such as styrene-acrylonitrile, styrene-alpha- methylstyrene and styrene-ethylene. Hydrogenated block copolymers of vinyl aromatic monomers and conjugated dienes such as butadiene, isoprene may also be used. Examples include styrene-butadiene, styrene-isoprene, styrene-butadiene- styrene and styrene-isoprene-styrene copolymers. Further examples of block copolymers may be found in US-A-4,845,173, US-A-4,096.203, US-A-4,200,718, US-A-4,210,729, US-A-4,205,016, US-A-3,652,516, US-A-3,734,973,

-2- US-A-3,390,207, US-A-3,231 ,635, and US-A-3,030,346. Blends of such hydrogenated polymers with other polymers including impact modified, grafted rubber containing hydrogenated aromatic polymers may also be used. Preferably, the hydrogenated aromatic polymer is polycyclohexylethylene (PCHE) prepared by hydrogenating atactic polystyrene.

The weight average molecular weight (Mw)of the hydrogenated aromatic polymer is typically from 1 ,000, generally from 20,000, preferably from 50,000, more preferably from 100,000 and most preferably from 200,000 to 400,000, preferably to 375,000, more preferably to 350,000 and most preferably to 325,000.

To maintain the Mw and thus the excellent physical properties of the hydrogenated aromatic polymer, a stabilizer combination has been discovered which prevents polymer degradation during processing at high temperatures such as temperatures up to 350°C. The stabilizer combination consists of a benzofuranone and a hindered phenol. The benzofuranone can be produced by reacting an aminomethyl substituted phenol or a halomethyl substituted phenol with an ionic cyanide compound, hydrolyzing the product thereof, followed by ring closure condensation. Typical benzofuranones and methods of producing are described in US-A-4,325,863.

The benzofuranone used in the composition of the present invention is preferably of the formula:

in which either

R is hydrogen, and R₁ is hydrogen; C_{1 22} alkyl; C₅ or C₆ cycloalkyl; C_{1 5} alkyl, C₅ or C₆ cycloalkyl; phenyl; phenyl substituted by one to three substituents selected from the group consisting of C₁ _₁₂ alkyl, hydroxy, C₁ _₁₂ alkoxy, C._₁₈ acyloxy, chloro or nitro, with the provisos that: (1 ) when the phenyl ring contains more than one C alkyl group, said alkyl groups contain a maximum of 18 carbon atoms, (2) the maximum number of hydroxy substituents is two, and (3) the maximum number of each of the substituents selected from C_{1 12} alkoxy, C acyloxy, chloro and nitro is one; or a group of formula (a/4), (a/5) or (a/6)

-3- O

II (a/4)

-(CH₂- TΓC-OR₇

O R₈

II I (a/5)

1CH₂ TΓC— NR₈

or R and R together form a group (a/2)

,R

Rόai (a/2)

either each of R₂ to R₅, independently, is hydrogen; C_1-12 alkyl; C₅ or C₆ cycloalkyl; C alkyl-C₅ or C₆ cycloalkyl; C alkoxy; phenoxy; phenoxy substituted by one or two C alkyl groups, said alkyl groups having a maximum of 16 carbon atoms; C acyloxy; chloro; phenyl-C alkyl; phenylthio; phenyl-C alkyl or phenylthio substituted on the phenyl ring by one to three substituents selected from C alkyl, hydroxy and R₁₅CO — O — ; phenyl; phenyl substituted by one or two C_{1 ]2} alkyl groups, said alkyl groups having a maximum of 16 carbon atoms; nitro; 2-furanylcarbonyloxy; 2- thienylcarbonyloxy; a group of formula (b/2), (b/3) or (b/4)

O

II (b/2)

— C— H

(b/3)

— CH₂— S — R 12

-CH(C₆H₅)CO— 0-R₇ or; ^X a group of formula (a/4) or (a/5) as defined above; with the provisos that:

(a) a maximum of two of R₂ through R₅ is C₅ or C₆ cycloalkyl, C_{1 5} alkyl; C₅ or

C₆ cycloalkyl, C_{1 22} alkoxy, phenoxy, substituted phenoxy, C acyloxy or chloro; and

(b) a maximum of one of R₂ through R₅ is optionally substituted phenyl, phenyl-

C_{1 9} alkyl or phenylthio, nitro, 2-furanylcarbonyloxy, 2-thienylcarbonyloxy or a group of formula (b/2), (b/3), (b/4), (a/4) or (a/5), provided that only the R3 substituent can be a group of formula (b/3) or (b/4) and only the R₃ or R₅ substituent can be a group of formula (a/5); or R₂ and R₃, together, form a condensed benzene ring, or R₃ and R₄, together, form a furan(2) one ring in which the 3-position bears the substituents R and R₁ as defined above, or R₄ and R₅, together, form tetramethylene or a furan(2) one ring in which the 3-position bears the substituents R and R₁ as defined above, and one of the two remaining substituents is hydrogen and the other is any one of the significances given for R₂ to R₅ above; either

R₆ is C alkyl; C. or C₆ cycloalkyl; C_{1 5} alkyl; C₅ or C₆ cycloalkyl; benzyl; (CgH5)2CH; phenyl; phenyl mono- or disubstituted by C₁ _₁₂ alkyl, provided that when the phenyl ring contains more than one C. _₁₂ alkyl group, said alkyl groups contain a maximum of 16 carbon atoms; phenyl monosubstituted by hydroxy; phenyl mono- or disubstituted by methoxy; phenyl monosubstituted by chloro; phenyl monosubstituted by dimethylamino; 3,5-di-tertiary butyl-4-hydroxyphenyl; b -naphthyl; pyridinyl; 2-furyl; or a group of formula (c/1) or (c/2)

⁰ (c/l)

— C— OR₇

O R₈

II I — C-N-R_s, and ^^dl

R_6a is hydrogen; C_{1 18} alkyl; C₅ or C₆ cycloalkyl; C^ alkyl; C₅ or C₆ cycloalkyl; phenyl or benzyl; or

-5- R_g and R_6a, together with the carbon atom to which they are bound, form an unsubstituted 5- or 6-membered aliphatic ring or a 5- or 6-membered aliphatic ring monosubstituted by C_1-4 alkyl; each R₇, independently, is hydrogen; C alkyl; alkyl-O-alkylene having a maximum of 18 carbon atoms; alkyl-S-alkylene having a maximum of 18 carbon atoms; di- C alkylamino-C^ alkyl; C₅_₇ cycloalkyl; phenyl; or phenyl substituted by one to three C alkyl groups, said alkyl groups having a maximum of 18 carbon atoms; either each R , independently, is hydrogen; C^^ alkyl; C₅ or C₆ cycloalkyl; C alkyl-

C_£or C₆ cycloalkyl; phenyl; phenyl substituted by one or two C alkyl groups, said alkyl groups having a maximum of 16 carbon atoms; or a group of formula (d/1), (d/2) or (d/3)

— CH₂CH₂OH <^{d/1 )}

(d/2)

-CH₂CH₂OCι-ι₈aikyl

O II — CH₂CH₂— O-C— R„: (d/3) or both

R₈'s, together with the nitrogen atom, form an unsubstituted piperidine or morpholine ring;

R_g has one of the significances of R_g; R_9a is hydrogen; C_{1 18} alkyl; or a group of formula (d/1), (d/2) or (d/3) as defined above;

R_{1 t} is hydrogen; C_{1 22} alkyl; C^., cycloalkyl; phenyl; phenyl-C^ alkyl; or phenyl or phenyl-C^ alkyl substituted on the phenyl ring by one or two C_{1 12} alkyl groups, said alkyl groups having a maximum of 16 carbon atoms; R₁₂ is C_{1 18} alkyl; 2-hydroxyethyl; phenyl; or C_{1 9} alkylphenyl;

R₁₅ is C_{1 22} alkyl or phenyl; and n is 0, 1 or 2.

-6- R is preferably hydrogen.

R₁ is preferably R ^', where R is hydrogen; C_{1 18}alkyl; phenyl optionally substituted by one or two C^alkyl groups and/or a hydroxyl group; (a 4) or (a/5) or together with R is (a/2). More preferably R₁ is R, ", where R ^" is C_{1 18}alkyl, or phenyl optionally substituted by one or two C^alkyl groups and/or a hydroxyl group. Most preferably R₁ is phenyl optionally substituted by C alkyl.

When R₁ is optionally substituted phenyl, such phenyl preferably bears no chlorine atom. When R₁ as substituted phenyl bears a hydroxyl group said hydroxyl group is preferably adjacent to a branched alkyl group such as tert.-butyl, more preferably located between two such groups.

When R. is phenyl substituted by an acyloxy group preferably such group is in the 2- or 4-position and preferably a C^alkyl group is also present especially in para position to the acyloxy group.

When R₁ is optionally substituted phenyl, R₂ is preferably hydrogen or methyl, more preferably hydrogen.

When any two of R₂ to R₅ form a condensed benzene ring, tetramethylene or a condensed furan(2)one ring as defined above preferably both the other substituents are hydrogen or one is hydrogen and the other is C.^alkyl or COOH, most preferably both are hydrogen. When anyone of R₂ to R₅ is phenylalkyl or phenylthio in which the phenyl nucleus is substituted as defined above, preferably said phenylalkyl or phenylthio group is R3 or R5, more preferably R₅.

Furthermore, when such substituent is present as R₃ preferably R₂ and R₄ are hydrogen and R₅ is hydrogen or alkyl (pref. C._₅) and when such a substituent is present as R₅, preferably R₂ and R₄are hydrogen and R₃ is hydrogen or alkyl (pref.

C especially tert. octyl). Preferred phenylalkyl or phenylthio groups in the case of

R₅ are those in which the phenyl nucleus has a hydroxy or R₁₅ CO — O — substituent in ortho position to the alkyl or thio group. Preferred such groups are: (PA) (PT)

Rz

in which each R_x, independently, is hydrogen or (C )-alkyl,

Ry is hydrogen or CO-R₁₅, and each R_z, independently, is hydrogen, C_{1 g}-alkyl (linear or branched) and

R_z ^' is hydrogen or C_1-4 linear alkyl.

In the group (PA) preferably each R_x, independently, is hydrogen or C alkyl, more preferably hydrogen or methyl; each R_z independently, is preferably hydrogen or C^alkyl more preferably hydrogen, methyl or tert. butyl with hydrogen or methyl being most preferred. R_z ^' is preferably hydrogen or methyl, most preferably hydrogen. In the group (PT) each R_z. independently, is preferably hydrogen or (C,_ ₈)alkyl, more preferably, the R_z ortho to ORy is hydrogen and the other tert. octyl. R_z' is preferably hydrogen.

R₂ is preferably R₂ ^', wherein R₂ ^' is hydrogen, (C^alkyl or together with R ^' forms a condensed benzene ring. More preferably R₂ is R ^', where R₂ ^' is hydrogen or methyl, especially hydrogen.

R„ is preferably R ^', where RX is hydrogen, C, „alkyl, phenyl, C, _1Dalkoxy, phenoxy, C_{1 18}alkylcarbonyloxy, (a/4), (a/5), (b/2), (b/4) or together with R ^' forms a condensed benzene ring or together with R₄ ^' forms a furan(2)one nucleus in which R is hydrogen and R. is preferably R More preferably R₃ is R ^", where R₃ ^" is hydrogen, (C )alkyl, phenyl, (a/4) or together with R ^' forms a condensed benzene ring. Even more preferably R₃ is R₃ ^'", where R '" is hydrogen, (C_{1 9})alkyl or (a/4).

Most preferably R₃ is R₃ ^{" "}, where R₃ ^{" "} is hydrogen or alkyl C_{1 9}(preferably C_{1 5}), with methyl, tert.-butyl or tert.-amyl being most preferred. When R ^' forms a furanone ring together with R ^' the oxygen atom of said nucleus is preferably bound to the R ^' position. When R_ is (b/2) and R^ is other than hydrogen the adjacent hydroxyl group is preferably in the 6-position.

R₄ is preferably R₄\ where R₄ ^' is hydrogen, C_{1 12}alkyl, C_{1 1g}alkoxy, phenoxy or together with R ^' or R ^' forms a furan(2)one ring in which R is hydrogen and R is preferably R₁ or R₄ ^' together with R_g ^' forms tetramethylene. More preferably R₄" is R₄ ^", where R₄ is hydrogen, C_{1 12}alkyl, C_{1 18}alkoxy or phenoxy. Even more preferably R₄ is R₄ ^'", where R₄ ^'" is hydrogen or C. _₁₂alkyl, especially hydrogen. The preferred alkyl groups as R₄ are C-^alkyl, more preferably C_H, with methyl and tert.-butyl being the most preferred alkyl groups.

When R₄ ^' together with R₅ ^' forms a furan(2)one nucleus the oxygen atom of said nucleus is preferably bound to the 7-position.

R₅ is preferably R₅ ^', where R₅ ^' is hydrogen, C₁ _₁₂alkyl, phenyl, (a/4), (a/5), (PA), (PT) or together with R ^' forms tetramethylene or a furan(2)one ring. More preferably R_ is R₅ ^", where R_g ^" is hydrogen, C_{1 12}alkyl, (PA) or (PT). More preferably R, is R ^{' "}, where R ^'" is hydrogen or C^alkyl with alkyl, preferably C, .alkyl, being most preferred. The preferred C_{1 5}alkyl groups are methyl, tert.-butyl and tert.-amyl. When a furan(2)one nucleus is formed by any two of R₃' to R₅ ^' preferably the R ^'s are the same. Most preferably they are phenyl.

When R₆ is substituted phenyl, such phenyl is preferably hydroxyphenyl, phenyl substituted by up to two C._₁₂alkyl groups with max. 16 carbon atoms in the combined substituents or 3,5-di-tert.-butyl-4-hydroxyphenyl; more preferably any substituted phenyl as R₆ is mono substituted by one C_{1 12}-alkyl group or is 3,5-di-tert- butyl-4-hydroxyphenyl. Preferably any phenyl as R₆ is unsubstituted. Any alkyl as R preferably contains 1 to 12, more preferably 1 to 8, most preferably 1 to 4 carbon atoms.

R₆ is preferably R₆ ^', where R₆ ^' is C_{1 18}alkyl, phenyl, 3,5-di-tert.-butyl-4- hydroxyphenyl, (c/1) or together with R_6a is cyclohexylidene. More preferably R₆ is R₆ ^", where R₆ ^" is C-|_i2^a|kyl_> phenyl, 3,5-di-tert.-butyl-4-hydroxyphenyl or together with R_6a and the common C-atom form cyclohexylidene. Most preferably R₆ is R₆ ^{' "}, where R₆ ^{' "} is C_{1 12}alkyl or phenyl.

Any alkyl as R_6a preferably contains 1 to 12, more preferably 1 to 8, most preferably 1 to 4 carbon atoms, especially methyl. R_6a is preferably R_6a ^', where R_6a ^' is hydrogen, C₁ _₁₂-alkyl or together with R₆ and the common C-atom forms cyclohexylidene. Most preferably R_6a is hydrogen.

-9- When R₆ is substituted phenyl or CH(CβH5)2 or (c/1) R_6a is preferably hydrogen.

R₇ is preferably R-,^', where R-.^' is hydrogen, C_{1 18}alkyl, phenyl optionally substituted by up to two C₁ _₁₂alkyl groups with max. 16 carbon atoms in the combined substituents. More preferably R-, is R₇ ^", where R-,^" is C. _₁₈alkyl, phenyl or C ₁₂alkylphenyl. Most preferably R- is C_{1 18}alkyl, especially C_g_₁₈alkyl.

Each R₈, independently, is preferably R_g ^', where R₈' is hydrogen, C_{1 18}alkyl or both R₈ ^' together with the N-atom form piperidine. More preferably each R_g, independently is hydrogen or C₁ _₁₈alkyl. Preferred alkyl groups as R₈ are C_{1 12} — , preferably C — , most preferably C alkyl. R_g is preferably R_g ^', where R_g ^' is hydrogen, C_{1 g}alkyi or (d/1). More preferably

R_g is hydrogen or C^alkyl. Any alkyl as R_g preferably contains 1 to 8, more preferably 1 to 4 carbon atoms.

R_ga is preferably R_ga ^', where R_ga ^' is hydrogen, C_H — alkyl or (d/1). Any alkyl as R_ga preferably contains 1 to 8, more preferably 1 to 4 carbon atoms. R^ is preferably R^ ^', where R ' is hydrogen, C_{1 lg}alkyl or phenyl. R in (b/2) is preferably phenyl.

Any alkyl as R., preferably contain 4 to 17 carbon atoms.

R₁₂ is preferably R₁₂ ^', where R₁₂ ^' is C₁ _₁₂alkyl, phenyl or 4-(alkyl C^phenyl. n in (a/4) or (a/5) as R₁ is preferably 1. n in (a/4) or (a/5) as R_g is preferably 1. n in (a/4) or (a/5) as R₃ is preferably 2.

The preferred cycloalkyl groups are cyclohexyl and methylcyclohexyl, especially cyclohexyl.

Preferred compounds of formula l_c are those in which R₁ is R .R-, is R₂ ^', R₃ is R₃', R₄ is R₄ ^', and R₅ is R₅ ^' .More preferred compounds are those where R is hydrogen, R. is R. ^", R₂ is R₂ ^", especially hydrogen, R₃ is R₃ ^", preferably R₃ ^'", R₄ is R₄ ^" and R₅ is R ^". Especially preferred are those compounds where R is hydrogen, R₁ is C^alkyl substituted phenyl, or phenyl, especially phenyl, R₂ is hydrogen, R₃ is R,^{" "}, R. is hydrogen and R is R ^" especially C. alkyl. In preferred embodiment R₁ is C alkyl, phenyl or phenyl substituted by one to three substituents selected from C alkyl and hydroxy, with the proviso that the

-10- maximum number of C₁_₈ alkyl substituents is two and the maximum number of hydroxy substituents is one.

In a most preferred embodiment, the benzofuranone is 5,7-di-t-butyl-3-(3,4-di- methylphenyl)-3H-benzofuran-2-one(CAS No. 181314-48-7). The benzofuranone is advantageously present in amounts of from 10, generally from 20, typically from 30, preferably from 50, more preferably from 100 and most preferably from 200 ppm to 4000, generally to 2000, typically to 1000, preferably to 800, more preferably to 600 and most preferably to 400 ppm, based on the weight of the hydrogenated aromatic polymer. The hindered phenol used in the composition of the present invention can be any sterically hindered phenol which will act as a heat stabilizer for the hydrogenated aromatic polymer composition. Typical hindered phenols include: tetrakis[methylene(3,5-di-tert-butylhydroxyhydrocinnamate)]methane, β-(4-hydroxy- 3,5-ditert.-butylphenyl)-propionicacidstearylester, tetrakis[methylene-3(3',5'-ditert- butyl-4-hydroxyphenyl)-propionate]-methane, 1 ,3,3-tris(2-methyl-4-hydroxy-5-tert.- butylphenyl)-butane,1 ,3,5-tris(4-tert.-butyl-3-hydroxy-2,6-dimethylbenzyl)-1 ,3,5- triazine-2,4,6-(1 H,3H,5H)-trione, bis(4-tert.-butyl-3-hydroxy-2,6-dimethylbenzyl)- dithiolterephthalate, tris(3,5-ditert.-butyl-4-hydroxybenzylisocyanurate, triester of 3,5- di-tert.-butyl-4-hydroxyhydrocinnamic acid with 1 ,3,5-tris-(2-hydroxyethyl)-s-triazin- 2 ,4,6-(1 H,3H,5H)-trione, bis[3,3-bis-4'hydroxy-3-tert-butylphenyl)-butaneacid]- glycolester, 1 ,3,5-trimethyl-2,4,6-tris-(3,5-ditert-butyl-4-hydroxybenzyl)-benzene, 2,2'methylenebis(4-methyl-6-tert-butylphenyl)terephthalate, 4,4-methylene-bis-(2,6- ditert-butylphenol), 4,4'-butylidene-bis(6-tert-butyl-meta-cresol), 4,4-thio-bis(2-tert- butyl-5-methylphenol), 2,2'-methylene-bis(4-methyl-6-tert-butylphenol) and octadecyl- 3,5-di-tert-butyl-4-hydroxyhydrocinnamate.

Hindered phenols are advantageously present in the composition of the present invention in amounts of from 0.01 , generally from 0.03, typically from 0.05, preferably from 0.1 , more preferably from 0.15 and most preferably from 0.20 to 1 , generally to 0.8, typically to 0.6, preferably to 0.5, more preferably to 0.4 and most preferably to 0.3 wt. percent based on the weight of the hydrogenated aromatic polymer.

Generally, the ratio of the benzofuranone to the hindered phenol is 99:1 to 1 :99. Typically, the ratio is 75:25 to 25:75, preferably 50:50 to 25:75, more preferably 20:80 to 10:90, and most preferably 15:85.

-1 1 - The stabilizers can be combined with the hydrogenated aromatic polymer by any conventional method. The stabilizers can be pre-mixed prior to addition to the polymer or each component can be individually added to the polymer The stabilizers can be dry blended with pellets of hydrogenated aromatic polymer, but are preferably dissolved in the polymer and more preferably mixed with hydrogenated polymer prior to devolatilization and pelletization..

Other additives may be present in the composition of the invention as long as the heat stability is not further modified. Typical additives include viscosity modifiers such as mineral oil and low Mw hydrogenated vinyl aromatic polymers and hydrogenated copolymers of styrene, α-methyl styrene, vinyl toluene, and/or indene, mold release additives, and UV stabilizers.

The composition comprising the hydrogenated aromatic polymer and the stabilizers can be used to produce optical media such as optical media discs. Methods of molding discs are well known in the art as described in The Compact Disc Handbook, 2nd edition, by Pohlmann, and include compression and injection molding. Typically, the molding temperature is between 200 and 400°C, and is preferably between 260 and 350°C. Optical media discs are useful as optical high density information recording medium such as compact discs, video discs, DVD discs, CD-rewritable discs, memory discs for computers, optical magnetic discs or optical cards.

The molded articles produced have excellent physical properties including flexural strength, tensile strength, and impact properties.

The following examples are provided to illustrate the present invention. The examples are not intended to limit the scope of the present invention and they should not be so interpreted. Amounts are in weight parts or weight percentages unless otherwise indicated. EXAMPLE 1

A stabilizer composition containing 85 weight percent octadecyl-3,5-di-tert- butyl-4-hydroxyhydrocinnamate powder and 15 weight percent 5,7-di-t-butyl-3-(3,4- di-methylphenyl)-3H-benzofuran-2-one powder is prepared by mixing the two powders. The stabilizer mixture is then added to polycyclohexylethylene polymer pellets having a Mw of 249,000 in an amount of 0.2 parts per hundred resin (pph) based on the weight of the polymer. The polymer and stabilizer mixture is mixed by shake blending the components in a bag. The shake blended mixture is then emptied into a twin screw extruder hopper. The extruder temperature profile is

-12- configured such that zones 1-3 and the die heater are all at 260°C. The screw speed is set to 60 rpm. The polymer mixture is extruded into strands, cooled in a water bath, pelletized and collected in a bag. The collected pellets are then emptied into the hopper for another extruder pass and the process is repeated for a total of four passes. A sample of a strand is taken near the end of each pass prior to pelletization, from which molecular weight results are determined. Molecular weight determinations are made using gel permeation chromatography (GPC) analysis. Results are listed in Table I. COMPARATIVE EXAMPLE

The procedure of Example 1 is followed except that 0.5 pph of octadecyl-3,5-di-tert- butyl-4-hydroxyhydrocinnamate is added to the PCHE polymer. Results are listed in Table I.

TABLE I

Extruder Pass 0.2 pph Stabilizer mixture (Mw) 0.5 pph hindered phenol^* (Mw)

0 249,000 249,000

1 249,800 243,800

2 240,100 226,700

3 231 ,500 220,100

4 225,100 213,600

Comparative Example

The composition containing the combination of stabilizers of benzofuranone and hindered phenol prevents polymer degradation much more efficiently than when a hindered phenol is used alone.

-13- EXAMPLE 2

The procedure of Example 1 is repeated with the stabilizers as listed in Table

TABLE

Mw for Extruder Pass

Sample Stabilizer 0 1 2 3 4

1 0.17% Irganox^® 1076 + .03% 249.8 240.1 231.5 225.1 lrganox^®HP136

2^* None 249 152.9 130.4 1 12.1 101 .6

3^* 0.2% Irganox^® 31 14^a 192.8 159.7 142.1 126.8

4^* 0.2% Irganox^® 1330° 223.9 199.9 190 171 .7

5^* 0.2% Irganox^® 1076^c 235.8 201.7 192.4 175.7

6^* 0.2% lrganox^®1010^d 238.8 213.7 197.5 190

7^* 0.2% lrgafos^® 168^e 228.4 168.7 146.8 121 .3

8^* 0.2% lrganox^®HP 136¹ 228.9 203 189.1 174.8

9^* 0.1 % Irganox^® 1076 + .1 % 226.9 190.2 170.9 151.9 lrgafos^® 168

10^* .085% Irganox^® 1076 + .085% 241.9 228.4 217 208.5 lrgafos^® 168 + .03% lrganox^®HP136

1 1 ^* 0.5% Irganox^® 1076 243.8 226.7 220.1 213.6

Irganox^® 3114 is 1 ,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)-1 ,3,5-triazine-

2,4,6(1 H,3H,5H)-trione.

Vganox^® 1330 is 1 ,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene. ^clrganox^® 1076 is octadecyl 3,5-di-tert-butyl-4-hydroxyhydrocinnamate.

°lrganox^®1010 is tetrakis[methylene(3,5-di-tert- butylhydroxyhydrocinnamate)]methane. ^elrgafos^® 168 is tris(2,4-di-tert-butylphenyl)phosphite. ^flrganox^®HP 136 is 5,7-di-t-butyl-3-(3,4-di-methylphenyl)-3H-benzofuran-2-one.

Comparative Examples

The composition of the present invention is clearly superior in Mw when compared to compositions containing other heat stabilizers.

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Claims

CLAIMS:

1. A composition comprising: a) a hydrogenated aromatic polymer, b) a benzofuranone, and c) a hindered phenol.

2. The composition of Claim 1 wherein the hydrogenated aromatic polymer is polycyclohexylethylene.

3. The composition of Claim 1 wherein the benzofuranone is of the formula:

R₅

in which either

R is hydrogen, and R. is hydrogen; C_{1 22} alkyl; C. or C₆ cycloalkyl; C_{1 5} alkyl, C₅ or C₆ cycloalkyl; phenyl; phenyl substituted by one to three substituents selected from the group consisting of C₁ _₁₂ alkyl, hydroxy, C_{l 12} alkoxy, C_{1 18} acyloxy, chloro or nitro, with the provisos that: (1) when the phenyl ring contains more than one C alkyl group, said alkyl groups contain a maximum of 18 carbon atoms, (2) the maximum number of hydroxy substituents is two, and (3) the maximum number of each of the substituents selected from C₁ _₁₂ alkoxy, C acyloxy, chloro and nitro is one; or a group of formula (a/4), (a/5) or (a/6)

O

ΓÇö (CH₂-)J╬ôC-OR₇ ^(a/4)

O R$ ii r (a/5) CH₂VCΓÇö NR₈

(a 6)

-15- or R and R₁ together form a group (a/2)

R₆

'\

R╬╕ ╬╣;a╬╣ (a/2)

either each of R₂ to R₅, independently, is hydrogen; C_{1 12} alkyl; C₅ or C₆ cycloalkyl; C_{1 5} alkyl-C₅ or C₆ cycloalkyl; C_{1 22} alkoxy; phenoxy; phenoxy substituted by one or two C₁ _₁₂ alkyl groups, said alkyl groups having a maximum of 16 carbon atoms; C_{1 18} acyloxy; chloro; phenyl-C^ alkyl; phenylthio; phenyl-C_{1 9} alkyl or phenylthio substituted on the phenyl ring by one to three substituents selected from C_{1 12} alkyl, hydroxy and R₁₅CO ΓÇö O ΓÇö ; phenyl; phenyl substituted by one or two C_{1 12} alkyl groups, said alkyl groups having a maximum of 16 carbon atoms; nitro; 2-furanylcarbonyloxy; 2- thienylcarbonyloxy; a group of formula (b/2), (b/3) or (b/4)

O

I I (b/2) ΓÇö CΓÇö H

(b/3)

-CH₇ΓÇö -S ΓÇö R 12

ΓÇö CH(C₆╬ù₅)COΓÇö O-R₇ or; <^{b 4)} a group of formula (a/4) or (a/5) as defined above; with the provisos that:

(a) a maximum of two of R₂ through R₅ is C₅ or C₆ cycloalkyl, C_{1 5} alkyl; C_s or

C alkyl or phenylthio, nitro, 2-furanylcarbonyloxy, 2-thienylcarbonyloxy or a group of formula (b/2), (b/3), (b/4), (a/4) or (a/5), provided that only the R₃ substituent can be a group of formula (b/3) or (b/4) and only the R₃ or R₅ substituent can be a group of formula (a/5);

-16- or R₂ and R₃, together, form a condensed benzene ring, or R₃ and R₄, together, form a furan(2) one ring in which the 3-position bears the substituents R and R₁ as defined above, or R₄ and R₅, together, form tetramethylene or a furan(2) one ring in which the 3-position bears the substituents R and R₁ as defined above, and one of the two remaining substituents is hydrogen and the other is any one of the significances given for R_ to R₅ above; either

R₆ is C_{1 1g} alkyl; C₅ or C₆ cycloalkyl; C_{1 5} alkyl; C₅ or C_g cycloalkyl; benzyl; (C╬▓Hs^CH; phenyl; phenyl mono- or disubstituted by C_{1 12} alkyl, provided that when the phenyl ring contains more than one C alkyl group, said alkyl groups contain a maximum of 16 carbon atoms; phenyl monosubstituted by hydroxy; phenyl mono- or disubstituted by methoxy; phenyl monosubstituted by chloro; phenyl monosubstituted by dimethylamino; 3,5-di-tertiary butyl-4-hydroxyphenyl; b -naphthyl; pyridinyl; 2-furyl; or a group of formula (c/1) or (c/2) \ (c/i)

ΓÇö CΓÇö OR₇

O R₈

II I ΓÇö CΓÇö N-Rg, and <^{c 2)}

R_6a is hydrogen; C_t _₁₈ alkyl; C. or C₆ cycloalkyl; C_{1 5} alkyl; C_ or C₆ cycloalkyl; phenyl or benzyl; or R₆and R_6a, together with the carbon atom to which they are bound, form an unsubstituted 5- or 6-membered aliphatic ring or a 5- or 6-membered aliphatic ring monosubstituted by C_1-4 alkyl; each

R₇, independently, is hydrogen; C_{1 18} alkyl; alkyl-O-alkylene having a maximum of 18 carbon atoms; alkyl-S-alkylene having a maximum of 18 carbon atoms; di-

C_1-4 alkylamino-C^ alkyl; C_H cycloalkyl; phenyl; or phenyl substituted by one to three

C _ alkyl groups, said alkyl groups having a maximum of 18 carbon atoms; either

-17- each R₈, independently, is hydrogen; C_{1 18} alkyl, C₅ or C₆ cycloalkyl; C_{1 5} alkyl-

C₅or C₆ cycloalkyl; phenyl; phenyl substituted by one or two C alkyl groups, said alkyl groups having a maximum of 16 carbon atoms; or a group of formula (d/1), (d/2) or (d/3)

ΓÇö CH₂CH₂OH ^{(d 1})

(d/2)

-CH₂CH₂OC╬╣ isalkyl o

II CH₂CH₂ΓÇö OΓÇö C ΓÇö R_╧Ç, (d/3) or both

R₈'s, together with the nitrogen atom, form an unsubstituted pipendine or morphohne ring,

R_g has one of the significances of R₈, R_ga is hydrogen, C alkyl, or a group of formula (d/1 ), (d/2) or (d/3) as defined above,

R is hydrogen; C alkyl, C__₇ cycloalkyl, phenyl, phenyl-C^ alkyl; or phenyl or phenyl-C^ alkyl substituted on the phenyl ring by one or two C alkyl groups, said alkyl groups having a maximum of 16 carbon atoms, R₁₂ is C alkyl, 2-hydroxyethyl, phenyl; or C alkylphenyl,

^R╬╣s ^{╬╣s C}╬╣-22 ^alky' ^or P^nenvl- and n is 0, 1 or 2.

4. The composition of Claim 1 wherein the benzofuranone is 5,7-d╬╣-t- buty!-3-(3,4-d╬╣-methylphenyl)-3H-benzofuran-2-one).

5. The composition of Claim 1 wherein component b) is present in an amount of 10 to 4000 ppm based on the weight of the hydrogenated aromatic polymer.

6. The composition of Claim 1 wherein component b) is present in an amount of 20 to 2000 ppm based on the weight of the hydrogenated aromatic polymer.

7 The composition of Claim 1 wherein component c) is octadecyl- 3,5-d╬╣- tert-butyl-4-hydroxyhydroc╬╣nnamate or tetrak╬╣s[methylene(3,5-d╬╣-tert- butylhydroxyhydroc╬╣nnamate)]methane

-18-

8. The composition of Claim 1 wherein component c) is present in an amount of 0.01 to 1 wt. percent based on the hydrogenated aromatic polymer.

9. The composition of Claim 1 wherein component c) is present in an amount of 0.03 to 0.8 wt. percent based on the hydrogenated aromatic polymer.

10. The composition of Claim 1 wherein the ratio of component b) to component c) is from 10:90 to 20:80.

11. A molded article prepared from any of the compositions of Claim 1 through Claim 10.

-19-