CS254186B1 - Thermal and thermo-oxidative stabilizer - Google Patents

Abstract

The solution relates to a thermal and thermo-oxidative stabilizer for polymers from the group comprising polyethylene, polypropylene, styrene polymers and copolymers consisting of one or more derivatives of 4-substituted-2,2,6,6-tetramethylpiperidine-N-oxyl. The solution can be used in the chemical industry.

Description

The invention relates to a thermal and thermo-oxidative stabilizer based on derivatives of 4-substituted-2,2,6,6-tetramethylpiperidine-N-oxyls, suitable for polymers from the group including polyethylene, polypropylene, styrene polymers and copolymers.

Polymers are subject to the influence of light and heat, thereby losing their originally advantageous mechanical, physical and chemical properties. For this reason, it is necessary to protect them during processing and long-term use, which is possible by adding stabilizers.

The use of some N-oxyl radicals of 4-substituted-2,2,6,6-tetramethylpiperidine as thermo-oxidative stabilizers in the processing of polypropylene is known from the literature [Scott, G.: British Polymer Journal, Vol. 15, 208 to 223 (1983); Herrman, T. J.: Developments in Polymer Stabilisation -1, Ed. Scott, G.: 39 (1979); Chakraborty, K. B., Scott, G.: Polymer, 21, 251 (1980)], and as light stabilizers of acrylic alkyd or polyester laminates (EP 16 723).

The use of N-oxyl radicals of 4-substituted-2,2,6,6-tetramethylpiperidine of the general formula II is known.

A ^Ch 3

X

O - n r

A n*C Ch ₃ in which

Y represents a group of the formula

in which

R represents alkyl, cycloalkyl or aryl, as heat stabilizers of polyolefin waxes (JP 53 040 005), but not of polyethylene, polypropylene or styrene polymers and copolymers.

The use of 2,2,6,6-tetramethylpiperidine-N-oxylbenzoate of formula III is also known.

to increase the heat and light resistance of styrene copolymers (SU 621697).

Furthermore, the use of N-oxyl radicals of 2,2,6,6-tetramethylpiperidine of the general formula IV in which m is an integer 1 or 2 is also known,

A represents O, NH and

R ¹ represents an aliphatic or aromatic acyl group as light stabilizers of polystyrene (JP 53 090 358).

Currently, either mononuclear phenols such as 2,6-ditert.butyl-4-methylphenol or tetranuclear non-volatile phenolic antioxidants such as pentaerythrityl tetrakis (3-(3,5-ditert.butyl-4-hydroxyphenyl)propionate, 3,5-ditert.butyl-4-hydroxyphenyl octadecylpropionate are used for thermal and thermo-oxidative stabilization of polyolefins.

Mononuclear phenolic antioxidants are highly volatile and cause significant technological problems when processed at high temperatures above 200 °C. Furthermore, they have minimal effect on the long-term thermal stability of polymers under in-use conditions at temperatures up to 120 °C.

Mononuclear phenolic antioxidants used in the processing of polymers at higher temperatures above 200°C are less effective than mononuclear ones and very often discolor the polymer, which is an undesirable phenomenon in practice.

Both types of phenolic antioxidants used so far are relatively resistant to washing out with water or other detergents and at the same time also provide minimal protection against the harmful effects of UV radiation. When they are applied with the newest and most effective group of light stabilizers — spherically hindered amines — their mutual undesirable interaction occurs.

The above-mentioned shortcomings are eliminated by the thermal and thermo-oxidative stabilizer for polymers from the group comprising polyethylene, polypropylene, styrene polymers and copolymers according to the invention, the essence of which lies in the fact that it consists of one or more derivatives of 4-substituted-2,2,6,6-tetramethylpiperidine-N-oxyl of the general formula I

in which

R represents a monoacyl radical derived from a normal saturated or unsaturated aliphatic carboxylic acid having 8 to 18 carbon atoms.

It has been found that it is advantageous if the stabilizer consists of 37 to 70% by weight of a compound of general formula I, where R is stearoyl, 20 to 52% by weight of a compound of general formula I, where R is palmitoyl, 0.2 to 6% by weight of a compound of general formula I, where R is heptadecanoyl, 0.1 to 5% by weight of a compound of general formula I, where R is myristoyl and 0.2 to 6.0% by weight of a compound of general formula I, where R is oleoyl.

The thermal and thermo-oxidative stabilizer according to the invention has, compared to currently used thermal and thermo-oxidative stabilizers for polyethylene, polypropylene, styrene polymers and copolymers, the advantages of extremely high efficiency in their processing at high temperatures and in ensuring long-term thermal protection of polymers in practical use. In addition, it has high resistance to water washing, even at higher temperatures, and at the same time ensures protection of the polymer against the action of UV radiation. Another advantage is the fact that the use of the stabilizer according to the invention in the processing of polymers prevents undesirable crosslinking in polyethylene.

The stabilizer according to the invention has low toxicity and can be combined with other stabilizing additives, such as antioxidants, light stabilizers, fillers, pigments, antistatics, flame retardants, etc. Stabilizing additives can be added to polymers by conventional methods directly during polymerization, or after polymerization by mixing into the melt. They can also be used in the form of polymer concentrates.

The polymers stabilized with the stabilizer according to the invention can be used in the form of films, tapes, plates, tubes, profiles or fibers.

The examples given illustrate, but do not limit, the subject matter of the invention.

Example 1

Powdered high-pressure polyethylene type RB 03 — 23 (n. p. SLOVNAFT), stabilized with 0.05 wt. % mixed stabilizer (AO-Zi) was stressed at a temperature of 165 °C under nitrogen on a Brabender plastograph until the relative viscosity decreased to half the value of τ/2. Unstabilized polyethylene and polyethylene stabilized with the currently used antioxidant 2,6-ditert.butyl-4-methylphenol (BHT) were evaluated in the same way. The results are shown in Table 1.

Table 1

PE (RB 03-23] stabilized τ/2 (min) 0.05% wt. AO-Zi 57 0.05% wt. BHT 38 unstabilized PE (control) 30

AO-Zi mixed stabilizer contains:

68.4% of 4-stearoyloxy-2,2,6,6-tetramethylpiperidine-N-oxyl,

24.1% 4-palmitoyloxy-2,2,6,6-tetramethylpiperidine-N-oxyl,

4.3% 4-heptadecanoyloxy-2,2,6,6-tetramethylpiperidine-N-oxyl,

1.9% of 4-myristoyloxy-2,2,6,6-tetramethylpiperidine-N-oxyl,

1.3% of 4-oleoyloxy-2,2,6,6-tetramethylpiperidine-N-oxyl.

Example 2

Powdered low-pressure high-density polyethylene with a melt index of 5.4 g/10 min, both stabilized and unstabilized, was repeatedly extruded through an extruder at temperatures of 235/250/ /265 °C. The melt index was measured at a temperature of 190 degrees Celsius. The results are shown in Table 2.

Table 2 PE (HDPE) stabilized

IT (g/10 min)

1st transition 5th transition

0.05 wt% PTDHP 6.8 6.3

0.05% wt. AO Z-l 7.3 6.9 unstabilized 6.2 5.6

PTDHP: pentaerythritol tetrakis [3-(3,5-di-tert.butyl-4-hydroxyphenyl)propionate].

Example 3

HPF type polypropylene powder (ex SLOVNAFT) with 11)230 = 10.4 g/10 min, stabilized and] unstabilized, was stressed at a temperature of 190 °C under nitrogen on a Brabender plastograph until the relative] viscosity decreased to half the value τ/2. The results are shown in Table 3.

Table 3

Polypropylene stabilized τ/2 (min)

0.05% by weight AO-Zi 200

0.05% by weight AO-Z2 183

0.05% by weight AO-Z3 158

0.05% by weight AO-1 76

0.05% by weight AO-2 92

0.05% by weight AO-3 165

0.05% by weight AO-4 47

0.05% by weight BHT 60

0.05 °/o wt. PTDHP 53 unstabilized PP (control) 35

AO-Z2 mixed stabilizer contains:

57.5% of 4-stearoyloxy-2,2,6,6-tetramethylpiperidine-N-oxyl,

36.4% 4-palmitoyloxy-2,2,6,6-tetramethylpiperidine-N-oxyl,

3.1% 4-heptadecanoyloxy-2,2,6,6-tetramethylpiperidine-N-oxyl,

1.8% of 4-myristoyloxy-2,2,6,6-tetramethylpiperidine-N-oxyl,

1.2% of 4-oleoyloxy-2,2,6,6-tetramethylpiperidine-N-oxyl.

AO-Z3 mixed stabilizer contains:

43.2% of 4-stearoyloxy-2,2,6,6-tetramethylpiperidine-N-oxyl,

51.9% 4-palmitoyloxy-2,2,6,6-tetramethylpiperidine-N-oxyl,

2.3% 4-heptadecanoyloxy-2,2,6,6-tetramethylpiperidine-N-oxyl,

1.6% of 4-myristoyloxy-2,2,6,6-tetramethylpiperidine-N-oxyl,

1.0% of 4-oleoyloxy-2,2,6,6-tetramethylpiperidine-N-oxyl,

AO-1:

4-octanoyloxy-2,2,6,6-tetramethylpiperidine-N-oxyl

AO-2:

4-undecanoyloxy-2,2,6,6-tetramethylpiperidine-N-oxyl

AO-3:

4-stearoyloxy-2,2,6,6-tetramethylpiperidine-N-oxyl

AO-4:

bis (2,2,6,6-tetramethyl-4-piperidyl)-N,N'-dioxyl sebacfit Example 4

HPF type polypropylene powder with IT230 = 6.8 g/10 min stabilized with different concentrations of AO-Zi was mixed in a laboratory mixer and processed multiple times through a CAMIL laboratory extruder at temperatures of 200/275/265 °C and speeds of 35 rpm. The change in IT230 (g/10 min) was monitored.

Polypropylene stabilized with the antioxidant BHT and unstabilized PP were evaluated in the same way. The results are shown in Table 4.

Polypropylene HPF Change IT230 (g/10 min) depending on the number of passes stabilized by a screw

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Table 4

0 1 3 5 7 10 0.01% AO-Zi 7.6 9.8 11.8 16.0 30.0 107.12 0.03% AO-Zl 7.0 7.5 9.9 13.0 16.3 21.8 0.05% AO-Zl 6.9 7.3 9.3 11.6 14.9 21.7 0.10% AO-Zl 6.9 7.3 8.7 11.2 14.5 19.6 1.00% AO-Zl 6.8 7.0 7.6 9.3 12.1 16.7 0.10% BHT 6.9 10.9 14.7 20.0 29.8 51.0 unstabilized 8.6 35.3 188.6 300.0

Example 8 rings with a diameter of 2 cm and exposed in a drying oven with air circulation at a temperature

Powdered polypropylene with IT230 = 10.4 g/10 min was stabilized with various concentrations of the stabilizer mixture AO-Z2 and 0.15% calcium stearate on a Brabender plastograph at 190 °C under nitrogen for 10 min. Films with a thickness of 0.5 mm were extruded under the following conditions: temperature 260 °C, pressure 19.6 MPa, 10 min. Die-cuts were made from the extruded films.

100 and 120 °C. From each concentration, 5 rings were used, which were visually evaluated until the initial degradation of the polymer. The results are shown in Table 5. At the same time, the resistance of polypropylene stabilized with AO-Z2 was monitored after washing with distilled water at a temperature of 90 °C for 50 h.

Table 5

Polypropylene stabilized flood film

100°C

0.05% AO-Z2 350 0.10% AO-Z2 530 0.20% AO-Z2 3,000 0.30% AO-Z2 4,200 0.10% BHT 380 unstabilized 250 Example 6

Thermal stability in the dryer fh) of washed foils

120°C 100°C 120°C 35 310 33 45 440 50 85 1,200 160 370 1,200 350 28 320 20 20 — temperature 190 °C under nitrogen for 10 minutes

Films with a thickness of 0.5 mm pressed at a temperature of 260 °C, a pressure of 19.6 MPa for 10 min were exposed in a drying oven at temperatures of 120 and 130 °C. The results are in Table 6.

Powdered polypropylene with IT230 = 8.4 g/10 minutes was stabilized with stabilizing additives at a concentration of 0.10% by weight and 0.15% Ca stearate on a Brabender plastograph at

Table 6

Polypropylene stabilized Thermo-oxidative stability in oven (h) 120 °C 130°C 0.1 0/0 AO-Zl 86 52 0.1% AO-Z2 78 50 0.1% AO-Z3 69 47 0.1% AO-1 58 36 0.1% AO-2 64 42 0.1% AO-3 128 96 0.1% BHT 28 16 unstabilized 16 8 Example 7 the cloth prepared as in the example

Films with a thickness of 0.5 mm were extruded from granule 4 under conditions of 260 °C, 19.6 MPa, 10 min. The testing was carried out under the conditions given in Example 5. The results are given in Table

7.

1.

5. 10.

Table 7

Polypropylene stabilized Thermo-oxidative stability at 120 °C depending on the number of passes (h)

0.01% by weight AO-Zi 54

0.03% by weight AO-Zl 112

0.05% by weight AO-Zi 262

0.10% by weight AO-Zi 330

0.25% by weight AO-Zi 2,800

0.10% wt. BHT 280 unstabilized 20

40 20 98 69 110 95 300 286 2,250 1,900 120 80 12 8

Example 8

Granulated standard polystyrene Krasten 27, both stabilized and unstabilized, was stressed at a temperature of 220 °C on a Brabender plastograph until the relative viscosity decreased to half the value of τ/2. The results are shown in Table 8.

Table 8

Polystyrene stabilized Thermal stability τ/2 (min)

0.05% by weight AO-Z3 158

0.10% wt. BHT 96 unstabilized PS 8

Table 9 Stabilized polyethylene

Mechanical properties of PE films film strength (MPa) lengthwise across film elongation impact (%) strength lengthwise across (g)

0.15% wt. 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene

0.15% wt. tris-(para-nonylphenyl)phosphite

0.15% wt. pentaerythritol tetrakis(3,5-di-t-butyl-4-hydroxyphenyl propionate)

0.15% wt. tris-(para-nonylphenyl)phosphite

0.15% wt. 2,6-di-t-butyl-4-methylphenol

0.15% wt. tris-(para-nonylphenyl)phosphite

AO-Zl

0.15% wt. tris-(para-nonylphenyl)phosphite

0.15% wt. ethylene glycol-bis(3,3-bis)-3-t-butyl-4-hydroxyphenyl (butyrate)

0.15% wt. distearylthiodipropionate

34.9 31.3 465 570 54.0 35.9 34.6 514 560 47.5 23.7 20.9 120 216 17.1 36.6 35.0 553 576 59.0

The foil cannot be produced.

5 4 1 8 B

SUBJECT

Claims (2)

SUBJECT Thermal and thermo-oxidizing stabilizer for polymers of the group consisting of polyethylene, polypropylene, styrene polymers and copolymers, characterized in that it consists of one or more 4-substituted-2,2,6,6-tetramethylpiperidine-N-oxyl derivatives of the general formula I OF THE INVENTION in which R represents a monoacyl radical derived from a normal saturated or unsaturated aliphatic carboxylic acid having 8 to 18 carbon atoms. 2. A thermal and thermo-oxidizing stabilizer according to claim 1, characterized in that it consists of 37 to 70 wt. % of a compound of formula I wherein R is stearoyl; % of a compound of formula I wherein R is palmitoyl, from 0.2 to 6 wt. % of a compound of formula I wherein R is heptadecanoyl, from 0.1 to 5 wt. % of a compound of formula I wherein R is myristoyl and from 0.3 to 1.5 wt. a compound of formula I wherein R is oleoyl based on the weight of the stabilizer.