NO302530B1 - Use of a polyolefin mass for permanent contact with extractive media - Google Patents

Abstract

A polyolefin moulding composition which has excellent chemical stability on long-term contact with extracting media contains, as stabilisers, a symmetrical triaryl phosphite and an ester of 3,3-bis(3'-t-butyl-4'-hydroxyphenyl)butanoic acid.

Description

The invention relates to the use of polyolefin molding compounds on

basis of polyolefins that have a special chemical stability,

in contact with extractive media.

It is known that polyolefins must be protected against oxidative damage during manufacture, processing and use by means of suitable stabilizer systems. Such stabilizer systems

temer consists, for example, of a phenolic antioxidant which is particularly intended to ensure the long-term use stability of the finished part and one or more co-stabilisers which regulate the processing stability and partially also synergistically enhance the effect of the phenolic components.

A known stabilizer combination of this type consists of a phenolic antioxidant with a symmetrical triaryl phosphate of formula

in which the residues R can be different aliphatic or aromatic residues, and R<2> and R^ can additionally be hydrogen (compare "US-4 187 212). In particular tris-(2,4-di-t-butylphenyl) is often used )-phosphite together with a phenolic antioxidant in practice. However, these commonly used stabilizers are not suitable for all applications

looking. In many cases, the molding compounds that are stabilized in the manner mentioned are in contact with liquid media during their use. To this end, it is necessary that the stabilizers added to the molding compounds also have sufficient chemical resistance to the respective contact media. Where this is not the case, the finished part fails in permanent use long before it

time that can be derived from laboratory tests conducted under dry conditions. For such parts as water pipes, submarine cables or tanks, there is therefore a considerable threat.

The task consisted in finding a polyolefin molding compound which, in long-term contact with extracting media, loses as little as possible of its chemical stability.

It was found that a polyolefin formulation containing a particular organic phosphite and a particular phenolic compound manages to solve the task.

According to the invention, the use of a polyolefin molding compound is thus provided comprehensively

90 to 99.98 weight # of olefin polymer,

0.01 to 5 wt-# of a triaryl phosphite having the formula:

in which—

R<1> represents a t-butyl, 1,1-dimethylpropyl, cyclohexyl or phenyl group, and

R<2> and r<3> are the same or different and mean a hydrogen atom, a methyl, t-butyl, 1,1-dimethylpropyl, cyclohexyl or phenyl group,

0.01 to 5 wt-# of a phenolic antioxidant which is an ester of 3^3-bis-(3'-t-butyl-4'-hydroxyphenyl)-butanoic acid of the formula

II

in which R<4> means a C₁-C₁₆ alkyl radical or a C₁-C₁ alkylene radical and n is 1 or 2, for the production of objects which are in permanent contact with extracting media.

The polyolefin in the molding compound used according to the invention can, for example, be one of the polymers mentioned below: 1. Polymers of mono- or diolefins, for example polyethylene (which may optionally be cross-linked), polypropylene, polyisobutylene, polybutene-1, polymethylpentene-1, polyisoprene or polybutadiene as well as polymers of cycloolefins such as e.g. of cyclopentene or norbornene. 2. Mixtures of the polymers mentioned under 1, e.g. mixtures of polypropylene with polyisobutylene. 3. Copolymers of mono- and diolefins with each other or with other vinyl monomers, such as e.g.

ethylene-propylene copolymers, propylene-butene-1 copolymers, propylene-isobutylene copolymers, ethylene-butene-1 copolymers, propylene-butadiene copolymers, isobutylene-isoprene copolymers, ethylene-alkyl acrylate copolymers, ethylene-alkyl- meiacrylate copolymers, ethylene-vinyl acetate copolymers or ethylene-acrylic acid copolymers and their salts (ionomers),

as well as terpolymers of ethylene with propylene and a diene, such as hexadiene, dicyclopentadiene or ethylidene norbornene.

The amount of the polyolefin in the molding compound amounts to 90 to 99.98, preferably 98 to 99.92, by weight.

As a stabilizer, the molding compound contains an organic phosphite and a phenolic antioxidant.

The organophosphite is a triaryl phosphite of formula

in which

R<1> denotes a t-butyl, 1,1-dimethylpropyl, cyclohexyl or phenyl group and

R<2> and R<3> are the same or different and mean a hydrogen atom, a methyl, t-butyl, 1,1-dimethylpropyl, cyclohexyl or phenyl group. Particularly preferred is tris-(2,4-di-t-butylphenyl)-phosphite.

The phenolic antioxidant is an ester of 3,3-bis-(3'-t-butyl-4'-hydroxyphenyl)-butanoic acid of formula II in which R<4>means a C 1 -C 3 -alkyl radical or a C 3 - C 1 -alkylene residue and n is 1 or 2. Preferably, R<4> means a C 2 -C 4 alkylene residue, especially a C 2 -alkylene residue.

The amount of phosphite and the phenolic antioxidant in the molding compound amounts to 0.01 to 5, preferably 0.04 to 1 wt-# for phosphite and 0.01 to 5, preferably 0.04 to 1 wt-# for the phenolic antioxidant.

Optionally, the molding compound according to the invention can also contain further additives, such as, for example:

1. Antioxidants

1.1 alkylated monophenols

2,6-di-tert-butyl-4-methylphenol, 2-tert-butyl-4,6-dimethyl-phenol, 2,6-di-tert-butyl-4-ethylphenol, 2 ,6-di -tert-butyl-4-n-butylphenol, 2,6-di-tert-butyl-4-i-butylphenol, 2,6-di-cyclopentyl-4-methylphenol, 2-(a-methylcyclohexyl)-4 ,6-dimethylphenol, 2,6-di-octadecyl-4-methylphenol, 2,4,6-tri-cyclohexylphenol, 2,6-di-tert-butyl-4-methoxymethylphenol.

1.2 alkylated hydroquinones

2,6-di-tert-butyl-4-methoxyphenol, 2,5-di-tert-butyl-hydroquinone, 2,5-di-tert-amyl-hydroquinone, 2,6-diphenyl-4-octadecylcyclooxyphenol .

1.3 Hydroxylated thiodiphenyl ethers

2,2'-thio-bis-(6-tert-butyl-4-methylphenol), 2,2'-thio-bis-(4-octylphenol), 4,4'-thio-bis-(6-tert .-butyl-3-methylphenol), 4,4'-thio-bis-(6-tert.-butyl-2-methylphenol).

1.4 alkylidene bisphenols

2,2'-methylene-bis-(6-tert.-butyl-4-methylphenol), 2,2'-methylene-bis-(-6-tert.-butyl-4-ethyl phenol), 2, 2'-methylene-bis-[4-methyl-6-(α-methylcyclohexyl)-phenol], 2,2'-methylene-bis-(4-methyl-6-cyclohexylphenol), 2,2'-methylene-bis -(6-nonyl-4-methylphenol),

2,2'-methylene-bis-(4,6-di-tert-butylphenol), 2,2'-ethylidene-bis-(4,6-di-tert-butylphenol), 2,2'-ethylidene -bis-(6-tert-butyl-4-isobutylphenol), 2,2'-methylene-bis-[6-^α-methylbenzyl )-4-nonylphenol], 2,2'-methylene-bis-[6 -(oc ,oc-dimethylbenzyl)-4-nonylphenol], 4,4'-methylene-bis-(2,6-di-tert.-butylphenol), 4,4'-methylene-bis-(6-tert. -butyl-2-methylphenol), 1,1-bis-(5-tert-butyl-4-hydroxy-2-methylphenyl)-butane, 2,6-di-(3-tert-butyl-5-methyl -2-hydroxybenyl)-4-methylphenol, 1,1,3-tris-(5-tert-butyl-4-hydroxy-2-methylphenyl)-butane, 1,1-bis-(5-tert-butyl -4-hydroxy-2-methylphenyl)-3-n-dodecyl mercaptobutane, di-(3-tert-butyl-4-hydroxy-5-methylphenyl)-dicyclopentadiene, di-[2-(3'-tert-butyl -2'-hydroxy-5'-methylbenzyl)-6-tert-butyl-4-methylphenyl]-terephthalate.

1.5 benzyl compounds 1,3,5-tri-(3,5-di-tert.-butyl-4-hydroxybenzyl)-2,4,6-tri-methylbenzene, di-(3,5-di-tert.- butyl-4-hydroxybenzyl)-sulfide, 3, 5-di-tert. -butyl -4 - hydroxybenzyl mercaptoacetic acid isooctyl ester, bis-(4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl )-dithiol terephthalate, 1,3,5-tris-(3,5 -di-tert-butyl-4-hydroxybenzyl)-isocyanurate, 1,3,5-tris-(4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl)-isocyanurate, 3,5-di- tert-butyl-4-hydroxybenzyl-phosphonic acid dioctadecyl ester, calcium salt of 3,5-di-tert-butyl-4-hydroxybenzyl-phosphonic acid monoethyl ester.

1.6 acylaminophenols

4-hydroxy-lauric acid anilide, 4-hydroxy-stearic acid anilide, 2, 4-free s-octylmercapto-6-(3,5-di-tert.-butyl-4-hydroxy-anilino)-s-triazine, N-(3,5-di-tert-butyl-4-hydroxyphenyl)-carbamic acid octyl ester.

1.7 Esters of p-(3,5-di-tert.-butyl-4-hydroxyphenyl)-propionic acid with monohydric or polyhydric alcohols such as e.g.

with

methanol diethylene glycol

octadecanol triethylene glycol

1,6-hexanediol pentaerythritol

neopentyl glycol tris-hydroxyethyl isocyanurate thiodiethylene glycol dihydroxyethyl oxalic acid diamide

1.8 Esters of p<->(5-tert-butyl-4-hydroxy-3-methylphenyl)-propionic acid with monohydric or polyhydric alcohols, such as e.g. with

methanol diethylene glycol

octadecanol triethylene glycol

1,6-hexanediol pentaerythrlt

neopentyl glycol tris-hydroxyethyl isocyanurate thiodiethylene glycol dihydroxyethyl oxalic acid diamide

1.9 amides of P-(3,5-di-tert.-hutyl-4-hydroxyphenyl)-propionic acid, such as e.g.

N,N'-di-(3,5-di-tert.-butyl-4-hydroxyphenylpropionyl)-hexamethylenediamine, N,N'-di-(3,5-di-tert.-butyl-4- hydroxyphenylpropionyl)-trimethylenediamine, N,N'-di-(3,5-di-tert-butyl-4-hydroxyphenylpropionyl)-hydrazine.

2. UV absorbers and light protection agents.

2.1 2-(2'-hydroxymethyl)-benztriazoles, such as e.g. 5'-methyl-, 3',5'-di-tert-butyl-, 5'-tert-butyl-, 5'-(1,1,3,3-tetramethylbutyl)-, 5-chloro-3 '-5'-di-tert-butyl-, 5-chloro-3'-tert-butyl-5'-methyl-, 3'-sec-butyl-5'-tert-butyl-, 4' -octoxy-, 3'-,5'-di-tert-amyl-, 3',5'-bis-(α,α-dimethyl-benzyl)-deriv.

2.2 2-Hydroxybenzophenones, such as e.g.

4-hydroxy-, 4-methoxy-, 4-octoxy-, 4-decyloxy-, 4-dedecyloxy-, 4-benzyloxy-, 4,2',4'-trihydroxy-, 2'-hydroxy-4,4' -dimethoxy derivative.

2.3 Esters of optionally substituted benzoic acids, such as e.g.

4-tert-butyl phenyl salicylate, phenyl salicylate, octyl phenyl salicylate, dibenzoyl resorcinol, bis-(4-tert-butylbenzoyl)-resorcinol, benzoyl resorcinol, 3,5-di-tert-butyl-4-hydroxy-

benzoic acid 2,4-di-tert-butyl phenyl ester, 3,5-di-tert-butyl 4-hydroxybenzoic acid hexadecyl ester.

2.4 Acrylates, such as e.g.

a-cyan-P,<p->diphenylacrylic acid ethyl ester resp. -isooctyl ester, α-carbomethoxy-cinnamic acid methyl ester, α-cyano-p<->methyl-p-methoxy-cinnamic acid methyl ester resp. -butyl ester, α-carbomethoxy-p-methoxy-cinnamic acid methyl ester, N-(p<->carbomethoxy-3-cyanovinyl )-2-methyl-indoline.

2.5 Nickel compounds, such as e.g.

nickel complexes of 2,2*-thio-bis-[4-(1,1,3,3-tetramethyl-butyl)-phenol], as 1:1- or 1:2-complex, optionally with additional ligands such as n- butylamine, triethanolamine or N-cyclohexyldiethanolamine, nickel alkyl dithiocarbamates, nickel salts of 4-hydroxy-3,5-di-tert.-butyl-benzylphosphonic acid monoalkyl esters such as of methyl or ethyl esters, nickel complexes of ketoximes such as of 2- hydroxy-4-methylphenyl-undecylketonoxime, nickel complexes of 1-phenyl-4-lauroyl-5-hydroxy-pyrazole, optionally with additional ligands. ;2.6 Sterically hindered amines, such as e.g. ;Bis-(2,2,6,6-tetramethylpiperidyl)-sebacate, bis-(1,2,2,6,6-pentamethylpiperidyl)-sebacate, n-butyl-3,5-di-tert-butyl- 4-Hydroxybenzyl-malonsy r e-b i s - (1 ,2 ,2 ,6,6-pentamethyl-piperidyl)-ester, condensation product of l-hydroxymethyl-2,2,6,6-tetramethyl-4-hydroxypiperidine and succinic acid, condensation product —of N,N'-(2,2,6,6-tetramethyl-4-piperidyl)-hexamethylenediamine and 4-tert-octylamino-2,6-dichloro-1,3, 5-s-triazine, tris-(2,2,6,6-1-tetramethyl-4-piperidyl)-nitrilotriacetate, tetrakis-(2,2,6,6-tetramethyl-4-piperidyl)-1,2, 3,4-Butanetricarboxylic acid, 1,1'-(1,2-ethanediyl)-bis-(3,3,5,5-tetramethyl-piperazinone). ;2.7 Oxalic acid diamides, such as e.g. ;4,4'-di-octyloxy-oxanilide, 2,2'-di-octyloxy-5,5'-di-tert .-butyl-oxanilide, 2,2'-didodecyloxy-5,5'-di-tert .-butyloxanilide, 2-ethoxy-2'-ethyloxanilide, N,N'-bis-(3-dimethylaminopropyl)-oxalamide, 2-ethoxy-5-tert.-butyl-2'-ethyloxanilide and mixtures of ortho- and para-methoxy as well as o- and p-ethoxy-di-substituted oxanilides. 3. Metal deactivators, such as ;N,N'-diphenyloxalic acid diamide, N-salicylal-N'-salicyloyl-hydrazine, N,N'-bis-salicyloyl-hydrazine, N,N'-bis-(3,5-di-tert.-butyl-4 -hydroxyphenylpropionyl)-hydrazine, 3-salicyloyl-amino-1,2,3-triazole, bis-benzylidene-oxalic acid dihydrazide. ; 4. Phosphites and phosphonites, such as ;triphenyl phosphite, diphenylalkyl phosphites, phenyl dialkyl phosphites, tri-(nonylphenyl) phosphite, trilauryl phosphite, trioctadecyl phosphite, distearyl pentaerythritol diphosphite, tris-(2,4-di-tert.-butyl-phenyl) phosphite, diisodecyl pentaerythritol diphosphite, di-(2 ,4-di-tert-butylphenyl)-pentaerythritol diphosphite, tristearyl sorbitol triphosphite, tetrakis-(2,4-di-tert-butylphenyl)-4,4*-biphenyl-ene-diphosphonite, 3,9-bis -(2,4-di-tert-butylphenoxy-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5,5]undecane.

5. Peroxide-destroying compounds, such as e.g.

Esters of p<->thio-dipropionic acid, for example of lauryl, stearyl, myristyl or tridecyl ester, the mercaptobenzimidazole zinc salt of 2-mercaptobenzimidazole, zinc alkyl dithiocarbamates, dioctadecyl sulphide, pentaerythritol tetrakis-(P-dodecyl mercapto)-propionate.

6. Basic cost stabilizers, such as e.g.

melamine, polyvinylpyrrolidone, dicyandiamide, triallyl cyanurate, urea derivatives, hydrazine derivatives, amines, polyamines, polyurethanes, alkali and alkaline earth salts of higher fatty acids, for example Ca stearate, Zn stearate, Mg stearate,

The mixing of the <14>C-marked antioxidants in the polyethylene powder took place in a laboratory rotary evaporator (Hei-dolph). The antioxidants were primarily dissolved in acetone, the solvent was slowly distilled off in a vacuum.

In this way it was mixed:

498.5 g ethylene copolymer (unstabilized),

density 0.95 g/cmJ , MFI 190/5 - 0.4 g/10 min.

1 g calcium stearate (= 0.256)

0.5g<14>C-labeled antioxidant (= 0.1#)

The production of the test specimen took place on a technical scale on an injection molding machine, type Arburg Allrounder, with a core progressive plasticizing screw with 20 steps and an electrically heated molding tool. Circular specimens, diameter 39 mm (in special cases also 12 mm) were punched out of the drop-shaped syringe parts (2.3 g, 1 mm thickness) with a wooden mandrel press.

The test bodies were held in a silver-plated wire spiral and with this device in a weighing glass covered on all sides with the test medium water. After certain times, samples were taken of the liquid and the radioactivity measured with a liquid scintillation counter. The migration was calculated from this. The results are listed in table 1.

Example 2

Samples were prepared as in example 1, however with the following recipe:

93.75 parts ethylene copolymer as in example 1

6.25 parts color concentrate (40 wt-# soot)

0.2 parts Ca stearate

0.05 parts phenolic antioxidant

0.05 part tris-(2,4-di-tert-butylphenyl)-phosphite.

The specimens were stored for different times in a water bath at 80° C. Small samples were then taken. In a DSC device (Differential Scanning Calorimetry) the time was determined at 200°C, where in an oxygen flow of 50 cm<3>/min. showed an exothermic reaction of the consumption of stabilizer. This time is also referred to as oxidation induction time ("OIT"). The results are listed in table 2. It can be seen that the reduction in OIT for the stabilizer combination used according to the invention of AO II with phosphite-(I) after contact with water is much smaller than for A0 I.

Example 3

Samples were prepared as described in example 1, however with the following recipe:

100 parts propylene homopolymer

(density 0.90 g/cm<J>(at 23°C), melt index 230.2.16:

2 g/10 min.

0.2 parts Ca stearate

0.1 part phenolic antioxidant (A0 II or AO I).

The results are listed in table 3.

Claims (2)

1. Use of a polyolefin composition comprising 90 to 99.98 wt.-S of an olefin polymer, 0.01 to 5 wt-56 of a triaryl phosphite having the formula: in which R<1> denotes a t-butyl, 1,1-dimethylpropyl, cyclohexyl or phenyl group and R<2> and R<3> are the same or different and mean a hydrogen atom, a methyl, t-butyl, 1,1-dimethylpropyl, cyclohexyl or phenyl group, and 0.01 to 5 wt-56 of a phenolic antioxidant which is an ester of 3,3-bis-(3'-t-butyl-4'-hydroxyphenyl)-butanoic acid with the formula: where R<4> means a C1-C4-alkyl residue or a C-L-C4-alkylene residue and n means 1 or 2, for the production of articles which are in permanent contact with extracting media. 2. Use according to claim 1, where the triaryl phosphite is tris-(2,4-di-t-butylphenyl)-phosphite and the phenolic antioxidant 3,3-bis-(3'-t-butyl-4'-hydroxyphenyl)-butanoic acid glycol ester.