DE2120955A1 - Thermally stable polymeric olefin preparation - Google Patents

Description

dr. W. Schalk dipl.-ing. P. Wirth · dipl.-inc.G. Dannenberc DR. V. SCHMIED-KOWARZIK · DR. P. WEI NHOLD · DR. D. GUDEL

6 FRANKFURT A'M MAIN

CR. ESCHENHEIMER STRASSE 39

Case C-8074-G
Wd / CW-500

UNION CARBIDE CORPORATION 270 Park Avenue, New York, State of New York 10017, USA .

Thermally stable polymeric olefin preparation.

The present invention relates to ethylene polymers and more particularly their thermal stabilization, being a combination of a hindered phenol and alkyl-substituted phenyl phosphite is mixed with it.

The thermal stability of ethylene polymers is an important property, both because of the elevated temperatures that on these polymers during their various stages of manufacture and those of these ethylene polymers with elevated temperatures. temperature-related processing methods, as well as because of the effect of aging and the effect of the Ambient temperature elements on the various plastic sales items made from them. Ethylene homopolymers and to an even greater extent ethylene copolymers containing polar groups such as carboxyl or carboxylate groups are adversely affected by thermal oxidative decomposition. These The phenomenon is first evident through short oxidation induction times (measured with a thermal analyzer), at the same time

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early due to the initiation of gel formation with subsequent generation of color bodies, which -a general deterioration of the mass properties, .z'.B-. Solution or melt viscosity. Gelation affects the appearance of the manufactured articles, with grains or speckled areas appearing in the press molded products and grains or streaks in the extruded products. In the case of ethylene / acrylic or methacrylic acid copolymers and their inorganic salts, materials such as -. ferrous metal alloys, their thermal decomposition. . »

It was found that known thermal stabilizers, such as hindered phenols, phenol phosphites, alkaryl phosphites, Phenol thioethers and the like, both in prevention of gel and color formation in low-density polyethylene and oxygen-containing ethylene copolymers are ineffective. Some of these additives inhibit color formation, but have no effect on inhibiting gel formation while others either do exactly the same thing, do the opposite, or at all have no stabilizing effect.

It has now been found that ethylene polymers, such as, for example , low-density polyethylene, ethylene · acrylic * or methacrylic acid mixed polymers with about 2 to 25% by weight of acrylic or methaeryl. acid therein mischpolymerj-Siert is, as well as their inorganic salts, with about 10-100 wt -% of the carboxyl groups are converted to carboxylate salt groups containing derived from alkali metals or alkaline earth cations, and ILthylen / Alkylaerylatmischpolymere, wherein-the alkyl.. groups about 1 to ·. May contain 4 carbon atoms, ther-. can be made mixed stable by adding about 0.005 to -5.09a, based on the weight of ethylene polymer em, of a mixture of a triply hindered η phenol, namely 2,6-bis (2'-hydroxy-3'-tert-butyl -5 ^l methylbenzyl) -4- ^ methylOhenol, and an alkylsubstituierteh-PheÄylmonophosphit with the formula:

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wherein η 1, 2 or 3 and R is an alkyl group having about 9 to 12 carbon atoms is, or an alkyl-substituted phenyl diphosphite, with the formula:

wherein R is as defined above, A is a divalent radical from the group

CH _{3 CH 3}

-0 (CH ₂ ) _x 0-, -OCH ₂ -CHO-, -Q (CH ₂ CH ₂ O-), -0 (CH ₂ -CHO-) or

-0 (CH ₂ ) _z S (CH ₂ ) _z 0-, where χ is an integer of

about 2 to 10 ,. y is an integer from about 2 to 6 and ζ is an integer from about 2 to 5 , the ratio of triply hindered phenol to alkyl substituted phenylphosphite can vary between about 1.5: 1 and 9: 1 will.

It is preferred to have a ratio of triply hindered phenol to alkyl substituted phenyl phosphite or diphosphite from about 3: 1 to 5: 1, with the ratio of about 4: 1 being most preferred.

The preferred concentration of the additive combination of triple hindered phenol and alkyl phenyl phosphite or diphosphite öubstituiertem is about 0.01 to 0.3 wt .-%, with the range of about 0.02 to 0.1 wt -.% Is particularly preferred.

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All ethereal polymers that are suitable for this invention, are commercially available. The polyethylene used here low density, have densities below about 0.93 g / ccm, a melt index of about 0.05 to 500 dg / min and a basal molar Viscosity number below 1.8 dl / g.

The ethylene / acrylic or methacrylic acid mixture polymers can contain from about 2 to 25% by weight of acrylic or methacrylic acid, which is copolymerized therein, with about 3 to 20% by weight , about 7 to 18% and 8 to 11%. represent the preferred ranges. The melt index (as determined by the method described in ASTM D1238-67T) of these ethylene / acrylic or methacrylic acid copolymers ("interpolymer") can be about 0.01 dg / min or up to about 350 dg / min, with the preferred ranges being between about 5 to 250 dg / min, 12 to 125 dg / min, and 5 to 50 dg / min.

In the invention. Ethylene / acrylic or methacrylic acid interpolymer salts are about 10 to 100% by weight of acrylic acid or methacrylic acid components of the ethylene / acrylic acid or methacrylic acid mixed polymers »As described above, converted to acrylate salt / with alkali metal or alkaline earth metal cations or neutralized. Alkali metal interpolymer salts are for example those containing sodium, potassium or lithium cations. Alkaline earth metal mixed polymer salts are, for example, those which contain calcium, barium or strontium.

The ethylene / acrylic acid or methacrylic acid Mischpoiyraeren can by free radical copolymerization with a random arrangement of components of ethylene with either acrylic or methacrylic acid using well known methods including bulk polymerization, solution polymerization, polymerization in aqueous suspension, polymerisation in non-aqueous dispersion or emulsion in either batch or continuous processes.

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The mixed polymer salts can be obtained by reacting ethylene / Acrylic acid or methacrylic acid mixed poles with metal salts, . such as carbonates or bicarbonates; Metal bases such as hydroxides or alkoxides; Metal alkyl compounds such as ethyl sodium or butyllithium; Metal aryls such as fhenyllithium or naphthalene potassium; Hydrides of sodium or potassium: oxides, such as sodium peroxide, barium peroxide or zinc oxide or, in the case of alkali metal salts, even with a free alkali metal itself.

The ethylene-allyl acrylate mixed according to the invention. . Polymers can be prepared by free radical copolymerization with a random arrangement of components of ethylene with an alkyl acrylate or methacrylate using well known methods including bulk polymerization, solution polymerization, Polymerization in aqueous suspension, polymerization in non-aqueous dispersion and emulsion in either batch or ongoing processes.

To typical ethylene / alkyl acrylate or methacrylate copolymer en include: ethylene / methyl acrylate, ethylene / methyl methacrylate, Ethylene / ethyl acrylate, ethylene / ethyl methacrylate, ethylene / propyl acrylate, ethylene / propyl methacrylate, ethylene / butyl acrylate and Ethylene / butyl methacrylate mixed polymers.

The triply hindered phenol component of the additional combination according to the invention, namely ZjS-BisCZ'-hydroxy - ^^ tert-butyl-5 ^l -methylbenzyl) -4-? Methylphenol is as Plastanox 80 (American Gyanamid Company) in the form of a white crystalline powder with a molecular weight of 460, a melting point of 171-172 ° C and a specific gravity of 1.04-0.03 are commercially available. The substituted phenyl monophosphites used in the additional combination according to the invention can be prepared by reacting 1, 2 or 3 mol of alkylphenol with phosphorus trichloride * -. ·

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The substituted phenol diphosphites can be prepared by first adding an alkylene glycol, a polyalkylene glycol or a thiodiglycol with a molar excess of phosphorus trichloride and then the product thus obtained with an alkyl substituted one Phenol in a molar ratio of 1:> 4 implemented will. . . '

Alkylene glycols that can be used include:

Ethylene glycol 1 j, 2-propylene glycol 1,3 propylene glycol

1,4-butylene glycol ■ - 1,5-pentylene glycol : 1,6-ßexylene glycol 1.7 ^ reptylene glycol 1,8 octylene glycol

1,9-nonylene glycol and -

1,1Q-deeylene glycol.

Typical polyalkylene glycols include:

Diethylene glycol, triethylene glycol, tetraethylene glycol, pentaethylene glycol, Hexaethylene glycol, dipropylene glycol, tripropylene glycol Tetrapropylene glycol, pentapropylene glycol and hexg: - propylene glycol.

Typical thiodiglycols include t

Thiodiethylene glycol ^: -

Thio-1,2 ^ dipropylene glycol and thio-1,3-dipropylene glycol.

The resistance of the ethylene polymer compositions according to the invention to thermal oxidative decomposition at elevated temperatures with or without the addition of stabilizers was determined with the aid of a "DuPont 900 Thermal Analyzer" and "Differential Scanning Calorimeter Cell ^11.

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measure up. This instrument is commercially available and recognized as a reliable device for measuring the effectiveness of oxidizing stabilizers or antioxidants. Test batches of ethylene polymer compositions were produced on a two-roll mill, on which 100 g batches of ethylene polymer and stabilizer additives were mixed. Minimum softening temperatures were used to avoid premature oxidation effects. The plasticized mixtures were then pressed into 25.4 χ 25.4 cm plates 0.25 mm thick on an electrically heated hydraulic press. Circular samples approximately 5 mm in diameter were cut from the 25.4 cm plates and then placed in the aluminum sample holder of the differential scanning calorimeter (DSC) cell. In each case, the sample holder plus sample was placed on the raised sample position, while an empty aluminum sample holder was placed in the appropriate position. Nitrogen was removed through the composite DSC- The cell was passed at a gas flow rate of 500 ml / min, the sample and reference cells being surrounded with an inert atmosphere. The samples and the reference cell were then heated to a preselected isothermal temperature ^{at a set rate of 80 ° C. per minute} When equilibrium was reached, a millivolt recorder ("L and N Speedomax H" began with a registr A sheet speed of 2.54 cm per minute and a recording range of 0 to 25 millivolts) to record the amplified differential thermocouple signal from the DSC cell. After 2.54 cm of movement of the recording sheet, the nitrogen flow was stopped quickly and air was passed through the DSC cell at a flow rate of 500 ml / min. The sharp deflection in the exothermic direction of the recorded curve indicated the end of the induction period. Since the induction time is that period of time in which no exothermic or thermal oxidative decomposition takes place, it is a measure of the effectiveness of thermal stabilization additives that have been mixed with the ethylene polymers. A

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direct comparison between comparison u. according to the invention. Compositions is therefore made possible by this induction time measurement.

The formation of color in the ethylene polymer compositions The present invention, which is another criterion for determining thermal stability, was confirmed by visual observation the color of a square section of 2.5.4 χ 2.54 cm of pressed foils of 0.25 mm after periods of either 15 or 60 minutes of exposure and aging to AIu-

o Minium foil sheets determined in a compressed air circulation oven at 200 ° C. This experiment is generally based on the work described on pages 138-9 PVC Technology "by ¥ .S. Penn, published by MacLaren and Sons Ltd., London, 1962. It is also described in this work that the degree of failure of a polymer composition is quantitative can be expressed in terms of numerical values such as the Gardner scale recorded below, where 0 is the highest and 10 is the ⁵ lowest rating:

Numerical evaluation • Observed color 0 No color change 1 1-5 ^ of the sample light yellow 2 5--10% of the sample is light yellow 3 11-50% of the sample is light yellow 4th 51-100% of the sample light yellow 5 yellow 6th light amber 7th amber colored 8th dark amber 9 light brown 10 Brown

The following examples serve to illustrate the invention without restricting it. Obtain all parts and percentages based on weight, unless otherwise stated.

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example 1

A batch of 100 g of low-density polyethylene (with a density of 0.917 g / ccm) and a melt index of 21.1 dg / min, the 0 * 05% by weight of a 3 ι 2 mixture of 2,6-bis (2 ^I- hydroxy-3'-tert-butyl-5'-methylbenzyl) -4-methylphenol and tetrakis (nonylphenyl) tetraethylene glycol diphosphite, the preparation of which is described below, was prepared by mixing the polyethylene and additives on a two-roll mill at 115 ° C was treated for 5 minutes. The plate obtained in this way was pressed in a heated press at 125 ° C. to give a 0.25 mm film. The Gardner color value of a 2.54

^{After treatment for 60 minutes at 200 °} C. in a compressed air oven, a 2.54 cm section of a 0.25 mm film of this mixture was 0 and the induction time at 200 ^° C. measured by the DSC oxidation test was 62 minutes.

The tetrakis (nonylphenyl) tetraethylene glycol diphosphite used above was made as follows.

0.025 mol of phosphorus trichloride is dissolved in 100 ml of toluene and heated in a 500 ml three-necked round bottom flask equipped with a thermometer, mechanical stirrer, gas inlet tube, reflux condenser and dropping funnel. The contents of the flask were heated with gentle stirring to 60 ⁰ C and 19.4 g (0.1 mol) of tetraethylene glycol, which was dissolved in 100 ml of toluene was then added dropwise through the dropping funnel over 1 hour. During this addition, dry nitrogen is passed through the flask through the gas inlet tube into a. Water trap where the pH of the water is monitored. A cold trap in the line from the flask to the water trap condenses everything except for the escaping HCl. The temperature is then increased to 100 ^° C. and held there for 2 to 3 hours, until no further evolution of HCl is noticed in the water trap. The reflux condenser is removed and the flask is equipped with a stripping head for distillation. The unreacted phosphorus trichloride and toluene is slowly

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Heat stripped to 120 ° C at which time a vacuum pump is attached to the system and the pressure is reduced to about 300 mm. The residual bubble is then cooled to 60 ° C and the pressure is brought to atmospheric by flowing nitrogen into the system. The still head is removed and replaced with a reflux condenser. A solution of 129 g (0.6 mol) of nonylphenyl in 100 ml of toluene is then added dropwise through the dropping funnel over 1 hour. The bubble temperature is gradually increased to 100 ° C. and held there until no further evidence of HGl evolution in the water trap is noticed. the RückfluBküh- ■ ler is again replaced by a, en output head, temperature to 150 ⁰ C increases u.der pressure to 2 mm reduced. After unreacted nonylphenol was stripped, the pot residue is cooled to give a straw-colored viscous product of tetrakis (nonylphenyl) tetraethylene glycol diphosphite obtained, which has the formula:

P- 0 h C ₂ H ₄ O

Example 2

Example 1 was repeated, with the exception that the stabilizing additive consists of a 4: 1 mixture of 2,6-bis- (2 ^f -hydroxy-3 ^l -tert-butyl ~ 5 ^T -methylbenzyl) -4-methylphenol and tetrakis ( nonylphenyl) tetraethyl en-glycol diphosphite. The Gardner color value of a square section (2.54 × 2.54 cm) of a 0.025 mm thick film was after 60 minutes in a compressed air oven at 200 ^° C.-1 and the DSC oxidation test, which was measured ^{at 210 ° C.} , brought an induction time of 13.5 minutes.

1098477 1,830

Comparison A.

Example 1 was repeated except that no stabilizing additive was added to the low density polyethylene. The Gardner color value after aging of a test sample section made of a 0.25 mm thick film after 60 minutes at 200 ^° C. in a compressed air oven was 5, and the induction time, which was ^{measured by the DSC oxidation test at 200 °} C., was 0.2 Minutes *

Comparison B

Example 1 was repeated with the exception that the stabilizing additive was 0.05% by weight 2,6-di-tert-butyl-4-methylphenol. After 60 minutes at 200 ⁰ C in a forced air oven, the Gardner color value was 5 and the process performed at 200 ⁰ C Oxydaticnstest showed an induction time of 0.2 minutes.

Comparison C ,

Example 1 was repeated with the exception that the stabilizing additive consisted of 0.05 wt .-% tetrahydroxyphenyl ester with the formula

Il

CH ₂ -O - C

CH ₂ CH ₂

After 60 minutes in a compressed air oven at 200 ° C., a had square sample (2.54 x 2.54 cm) from a 0.25 mm thick film has a Gardner color value of 3 and the DSC-Oxy-. Dation test carried out at 200 ° C showed an induction time of 13.7 minutes.

Comparison D

Example 1 was repeated, except that the verwen-

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finished stabilizing additive 0.05 wt -.% of a Bishydroxyphenylsulfids was of the formula

After aging a section (2.54 × 2.54 cm) of a 0.25 mm thick film in a compressed air oven at 200 ^° C. for 60 minutes, this composition had a Gardner color value of 6 and the measurement in a DSC oxidation test was 200 ⁰ C resulted in an induction time of 20.4 minutes. .

Comparison E

Example 1 was repeated with the exception that the stabilizing additive consisted only of 0.05% by weight of 2,6-bis- (2'-hydroxy-3'-tert-butyl-5 ^l -methylbenzyl) -4-methylphenol . The Gardner color value of a section (2.54 × 2.54 cm) of a 0.25 mm thick film was ^{7 after 60 minutes in a compressed air oven at 20O 0} C and the induction time measured in the DSC oxidation test at 20O ^{0 C was 42} Minutes.

Comparison F

Example 1 was repeated, with the exception that the stabilizing additive consists solely of that described in Example Λ -

, ^ (O, Q5 wt. -96)

Tetrakis (nonylphenyl) tetraethylene glycol diphosphate / consisted. The Gardner color value was after aging .one section (2.54 × 2.54 cm) of one. 0.25 mm thick film at 200 ^° C. for 60 minutes 1 and the ^{induction time measured in the DSC oxidation test at 200 °} C. was 0.02 minutes.

Example 5 .

Example 1 was repeated in that the low density polyethylene by an ethylene / acrylic acid interpolymer ^ was replaced, the 13 wt -.% Corresponds therein interpolymerized acrylic acid

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and had a melt index of 5.0 dg / min, 0.1% by weight, based on the total weight of the composition, of the 3: 2 mixture of hindered phenol and diphosphite described in Example 1 being used. The Gardner color value was after aging of a portion (2.54 χ 2.54 cm) from a 0.25 mm thick film after 60 minutes at 200 ° C = 1 and measured in the DSC Oxydationstest at 200 ⁰ C the induction time was 23 , 9 minutes. These results are compiled with those of comparative tests in Table I, which clearly shows the superiority of the compositions according to the invention.

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Table I.

Example no. • Stabilizing agents
at a concentrate
tion of 0.1% DSC oxidation test
at 190 ⁰ C .. induction
time in minutes Gardner color value according to
60 minutes at 200 ^° C methylbenzyl) -4-methylphenol. I.
■ P- 3 3: 2: (a) :( b) 23.9 1 t Comparison G (c) . '0.6 6th 'Compare H (d) 1.1 5 Comparison I. (e) 2.7 ' 5 ο Compare J (f) 2.0 5 co Comparison K (g): 7.0 7th 147/1 Compare L
Compare M (a)
(b) '12.1
0.6 8th
0 830 (a) 2,6-bis (2'-hydroxy-3'-tert-butyl-5 ^r

(b) Tetrakis -conylphenyl-tetraethylene glycol diphosphite.

(c) The same stabilizer as in comparison B.

^ -CH ₂ CH ₂ COC ₁₈ H ₃₇
t-butyl

(e) The same stabilizing agent as in comparison C. ^ ⁰

. · Cn

Table I continued

t-butyl

t-8utyl

HO

t-Butyl "^ ^CH 2 9 ^H 3 ^/ ^ έ-Butyl ^v C

CHß Y CH,

t-butyl ^ Y \ -butyl) H

(g) The same stabilizing agent as in comparison D.

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Example 4 '

Example 1 was repeated with the exception that replaces the low density polyethylene by an ethylene / acrylic acid copolymer * containing 13 wt - therein contained interpolymerized acrylic acid% and a melt index of 5 dg / min had, wherein 32%. its carboxyl groups were converted to the sodium salt. The additives or stabilizers were added in a concentration of 0.1% by weight, based on the total weight of the composition. The 3: 2 combination of the triply hindered phenol and diphosphite resulted in a polymer composition that had a Gardner Color Value of 5 and one measured in the DSC Oxidation Test. .Induction time at 190 ° C of 25.5 minutes and at 20O ⁰ C of 11.9 minutes. If only the hindered phenol is used in a concentration of 0.1%, and the Gardner color value 9 and the induction time in the DSC oxidation is 13.0 minutes at 190 ⁰ C and at 200 ° C 4.3 minutes (Comparative N ). If no stabilizing additive is added, the Gardner color value of the salt composition was 9 and the induction time, in the DSC oxidation test at 200 ° C., was 0.2 minutes (comparison 0). · "

Example 5

Example 1 was repeated, except that the low density polyethylene was replaced by an ethylene / ethyl acrylate copolymer containing 17 wt .-? 6 copolymerized therein ethyl acrylate and had a melt index of 6.0 dg / min, 2 was used combination of three times hindered phenol and the diphosphite:% that described in example 1 3 - wherein an additive concentration of 0.05 wt.. The Gardner color value of the composition was 0 and the induction time in the DSC oxidation test at 210 ^° C. was 19.8 minutes.

Example 6 '.

Example 5 was repeated with the exception that the additional coordination of triply hindered phenol and diphosphite was present in a ratio of 4: 1. The Gardner color value

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of the obtained composition was O and the induction time in the DSC Oxydationstest at 21O ⁰ C 23.3 minutes.

Example 7

Example 5 was repeated except that the combination of triply hindered phenol and diphosphite in a ratio of 9: 1 was used. The Gardner color value of the composition obtained was 0 and the induction time in the DSC oxidation test at 210 ^° C. was 13.0 minutes.

Example 8

Example 6 was repeated, with the exception that the diphosphite was tetrakis (nonylphenyl) hexanediol diphosphite instead of tetrakis (nonylphenyl) tetraethylene glycol diphosphite. The Gardner color value of the composition obtained was 0 and the Indu
Minutes.

the induction time in the DSC oxidation test at 210 ^° C. 22.7

Compare P

Example 5 was repeated with the exception that no stabilizing additive was used. The Gardner color value was 6 and the induction time in the DSC Oxydationstest both at 190 ° C and at 21O ⁰ C., 0.2 minutes.

Comparison Q

Example 5 was repeated with the exception that 2,6-di-tert-butyl-4-methylphenol was used as the stabilizing agent. The Gardner color value was 7 and the induction time in the DSC oxidation test at 190 ^° C. was 0.3 minutes. "'

Comparison R · ·

Example 5 was repeated with the exception that as a stabilizing agent that of Comparison E was used. The composition obtained had a Gardner color value of 4

ο and an induction time in the DSC oxidation test at 210 C of

1.0 minute.

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Comparison S -. '.

Example 5 was repeated except that stabilizing agent (d) in Table I was used. The Gardner color value of the composition obtained was 5 and the induction time measured at 210 ° C. in the DSC oxidation test
0.2 minutes.

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Claims (6)

Claims 1. Thermally stable polymeric olefin preparation, characterized in that it contains a larger amount of ethylene polymer from the group: 1) low-density polyethylene, 2) ethylene / acrylic acid copolymers with about 2 to 25 wt .-% acrylic acid copolymerized therein, 3) Ethylene / methacrylic acid copolymers with about 2 to 25 wt .-% methacrylic acid copolymerized therein, 4) alkali metal salts of ethylene /
• Acrylic acid copolymers of 2), 5) alkali metal salts of the ethylene / methacrylic acid copolymers of 3), 6) alkaline earth salts of the ethylene / acrylic acid copolymers of 2), 7) alkaline earth salts of the ethylene / methacrylic acid copolymers of 3) and 8) Ethylene / alkyl acrylate interpolymers having from about 1 to 18 carbon atoms in the alkyl group and from about 0.005 to 5
Weight .-? O, based on the total weight of the composition, of a mixture of about 1.5 to 9 parts of 2,6-bis (2 ^f -hydroxy-3 ^l -tert-butyl-5 ^! -Methylbenzyl) -4- methylphenol and about part of an alkyl-substituted phenylphosphite from the group: monophosphites with the formula: wherein η is 1 to 3 inclusive and R is an alkyl group
is about 9 to 12 carbon atoms, and diphosphites having the formula : 0 - - 0 - P L OHi 10 9847/1830 wherein R is as defined above, A is a divalent radical the group CH -z CH, ) -, -OCH ₂ CHO-, -0 (CH ₂ CH ₂ O-) _y , -0 (CH ₂ CHO-) and -0 (CH ₂ ) _Z S (CHg) ₂ O-, wherein χ is about 2 to 10, y is about 2 to 6, and ζ is about 2 to 5. '- 2. Preparation according to claim 1, characterized in that the . Alkyl substituted phenyl phosphite is a monophosphite, with the formula: where η and R are as defined above, or a diphosphite, with the formula: -O- (A) ■ · p where ■ "A and R are as defined above * 3. Preparation according to claim 1-2, characterized in that the ethylene polymer is a polyethylene with low density, an Ithyleh / acrylic acid misohpoly ^. or an ethylene / methacrylate 4. «preparation ^ next-claim - 1 -2 ^ characterized in that ' a ^y an <yrgÄisciieä - salt of ethylene / acrylic acid Copolymers or the ethylene / methacrylic acid copolymers is ". '■ 5. A preparation according to claim 4, characterized in that the inorganic Salt is derived from an alkali metal. 6. A preparation according to claim 1, characterized in that the ethylene polymer is an ethylene / alkyl acrylate copolymer , preferably an ethylene / ethyl acrylate copolymer. 1098 47/1830. OWGINAL INSPECTED