WO1998020065A1

WO1998020065A1 - Shaped polyolefin article stabilised by hals compounds

Info

Publication number: WO1998020065A1
Application number: PCT/NL1996/000434
Authority: WO
Inventors: Pieter Gijsman
Original assignee: Dsm N.V.
Priority date: 1996-11-06
Filing date: 1996-11-06
Publication date: 1998-05-14
Also published as: AU7343796A

Abstract

Shaped article made of a polyolefin composition comprising 100 parts of a polyolefin and 0.01-5 parts of a compound according to formula (1) (see formula sheet), wherein R' is hydrogen or a branched or non-branched alkyl group with 1-5 carbon atoms, R'' is a branched or non-branched alkylene, alkenylene or alkynylene group with 2-18 carbon atoms and A is hydrogen or a group according to formula (2) with R' being as defined above, and, when A is hydrogen, R'' is additionally methylene, at least one part of the shaped article having a wall thickness of at least 250 ν.

Description

SHAPED POLYOLEFIN ARTICLE STABILISED BY HALS COMPOUNDS

The invention relates to a shaped article made of a polyolefin composition comprising 100 parts by weight of a polyolefin and 0.01-5 parts by weight of a compound according to formula (1) (see formula sheet), where R' is hydrogen or a branched or non-branched alkyl group with 1- 5 carbon atoms, R'' is a branched or non-branched alkylene, alkenylene or alkynylene group with 2-18 carbon atoms and A is hydrogen or a group according to formula (2) (see formula sheet), with R' being as defined above, and when A is hydrogen, R" is additionally methylene. Compounds according to formula (1) belong to the group of the hindered amine compounds. Since the early seventies, hindered amine compounds have shown a strong rise and they are used as stabilizers against ultraviolet light (UV light) in thermoplas ic polymers. Used as such, the hindered amine compounds are also designated by the term 'HALS' (Hindered Amine Light Stabilizer).

By now a large number of hindered amines have been proposed for use as HALS in a wide variety of polymers. But only a small number of those have proved to be of practical and commercial value.

In recent years a trend has emerged towards development of hindered amines that are based on ever larger molecules, because it is claimed that these give the best results as regards the useful life of the polymer shaped articles in which the hindered amines are used as HALS.

In Ballardini Polymer Degradation and Stability 7, (1984), pp. 41-53 (Table 4) a comparison is presented of the UV light resistance of a number of 60μ-thick polypropene films which all contain a commercial or a noncommercial HALS. One of the non-commercial compounds is N,N-bis (1 , 1,6, 6-tetramethyl-4-piper idine-4-yl )hexane-l , 6- diamine (HMB-TAD) , indicated as A31 in Tables 3 and 4 in said publication by Ballardini. HMB-TAD shows less good results than most commercial HALS compounds, which in general give polypropene films with the best UV light resistance.

Surprisingly it has been found now that if at least one part of the shaped article made of a polyolefin composition comprising a polyolefin and 0.01-5 wt.% of a compound according to formula (1) has a wall thickness of at least 250μ, the shaped article possesses a very good UV light resistance. The resistance may even be better than the resistance achieved with a commercial HALS, in contrast to Ballardini 's results with polypropene films. The results achieved with the shaped articles according to the invention are all the more surprising when taking into account that the hindered amines of formula (1) remarkably enough consist of relatively small molecules, in contrast to most compounds that are used as commercial HALS.

EP-A-601745 describes shaped articles made of a polymer composition comprising (a) a polyolefin with carbon black,

(b) a phenolic compound according to formula (3) (see formula sheet) in which R¹ is an alkyl group with 1-4 carbon atoms,

(c) a sulphur compound of formula (4.1) or (4.2) (see formula sheet) in which R² is an alkyl group with 4- 20 carbon atoms,

(d) a hindered amine compound with at least one 2,2,6,6- tetramethylpiper idine ring in the molecule, and

(e) an epoxy compound on the basis of a glycidyl ether of the type bisphenol A.

The epoxy compound on the basis of a glycidyl ether of the type bisphenol A referred to is a compound which is usually produced by a condensation reaction of bisphenol A with epichlorohidr in, and which is an oligomeric compound having a residual end epoxy group, and has a structure of the formula (6) (see formula sheet) wherein q is a number of 0 or more. The composition is used for instance for injection moulding of 3.2 mm thick sheets. According to EP-A-601745 the shaped articles made of the above- mentioned composition offer a good heat resistance, but the document does not give any indication about the UV resistance of the shaped articles. Furthermore, EP-A- 601745 says nothing about the effect of the wall thickness of a shaped article on the UV resistance. Shaped articles made of a polymer composition comprising the phenolic compound according to formula (3) in which R¹ is an alkyl group, a sulfur compound of formula (4.1) or (4.2), in which R² is an alkyl group and an epoxy compound of bisphenol A type glycidylether are excluded from the invention. JP-A-Hei 3 290450 describes shaped articles of a polymer composition of:

(a) a polyolefin,

(b) a phosphite of formula (5) in which R ' is a tertiary butyl group or a tertiary amyl group, R'₂ is an alkyl group with 1-9 carbon atoms,

R'₃ is H or an alkyl group with 1-4 carbon atoms, and R'₄ is an alkyl group with 1-30 carbon atoms,

(c) a hindered amine compound with at least one 2,2,6,6- tetramethylpiper idine ring in the molecule. The composition is used for instance for injection moulding of 1.0 mm thick sheets.

According to JP-A-Hei 3 290450 the shaped articles made of the above-mentioned composition possess a good heat resistance and a good resistance against γ-radiation, but the document does not give any indication about the UV resistance of the shaped articles.

Further, J-A-Hei 3 290450 says nothing about the effect of the wall thickness of a shaped article on the UV resistance.

Shaped articles made of a polymer composition comprising a phosphite of formula (5) (formula sheet) wherein R'_lf R'₂ and R'₄ are an alkyl group and R'₃ is hydrogen or an alkyl group are excluded from the invention.

US-3904581 describes shaped articles made of a polymer composition of a polyolefin and a HALS. The HALS applied comprises one or more piperidine rings. But the N atom in the piperidine ring has to be substituted, while the hindered amine compound used in the composition for the shaped articles according to the invention by contrast is not substituted. Further, US-3904581 says nothing about the effect of the wall thickness of a shaped article on the UV resistance.

Preferably shaped articles made of a composition comprising a polyolefin and a) the combination of a sulfur compound of the formula (4.1) or (4.2) and an epoxy compound of bisphenol A type glycidyl ether or b) a cyclic organic phosphite having a group of the formula (7) (formula sheet) are excluded.

More preferably shaped articles made of a composition comprising a polyolefin and a) an epoxy compound of bisphenol A type glycidyl ether or b) a cyclic phosphite having a group of the formula (7) (formula sheet) are excluded. Still more preferably shaped articles comprising an epoxy compound, a phosphorous compound or a sulfur compound are excluded.

The invention also relates to the use of compounds of formula (1) for stabilising a shaped article made of a polyolefin composition against degradation induced by ultraviolet radiation, at least one part of the shaped article having a wall thickness of at least 250μ.

The invention relates to a method for stabilising a shaped article made of a polyolefin composition, at least one part of said article having a thickness of at least 250μ and the proviso of claim 1 being applied, which method comprises incorporating into the composition at 100 parts polyolefin 0.01-5 parts of a compound of the formula (1) as defined above.

The wall thickness of a shaped article may differ from place to place in the shaped article. The wall thickness may of course have the same value throughout the shaped article. A difference in the wall thickness of a shaped article may arise for instance owing to unwanted wall thickness fluctuations during the shaped article process. An example of this are differences in the thickness of an extruded sheet as a result of an inhomogeneous melting temperature during the extrusion.

The differences in wall thickness may also arise from the design of the shaped article, which implies that they have been made intentionally. An example of this is a garden table with a structured tabletop.

Preferably at least a part of the shaped article has a wall thickness of at least 500μ, more preferably 800μ, most preferably 1200μ.

It is possible that while a shaped article is being used in accordance with its function, only part of the shaped article is actually exposed to UV light. The wall thickness of the part of the shaped article that is not exposed to UV light is of course less relevant or not relevant at all to the UV resistance of the shaped article. Thus, those parts of a car bumper with which it is fixed to the body of the car will not be exposed to UV light. This also applies to any reinforcement ribs that may be present in the bumper. However, the part of a car bumper that forms part of the exterior contour of the car, especially the horizontal part at the top side of the bumper, is exposed intensively to UV light while the bumper is used in accordance with its function, assembled onto a car.

The wall thickness of that part of the shaped article which is exposed to UV light while the shaped article is used in accordance with its function, preferably is at least 250 μ, more preferably at least 500 μ, still more preferably at least 800 μ, most preferably at least 1200 μ.

In principle no value for the largest wall thickness of the shaped article according to the invention can be defined. In general however the shaped article will show wall _. thicknesses of 250μ up to 30 mm, the upper limit being determined by what is practical possible by the known techniques to produce the articles.

The polymer composition for the shaped articles according to the invention preferably comprises 0.03-3 parts by weight, more preferably 0.04-0.9 parts by weight of the compound of formula (1) per 100 parts by weight of polyolefin.

R'' in formula (1) preferably is an alkylene group with 2-10 carbon atoms, like ethylene, propylene, t- butylene, n-butylene, hexylene etc. Most preferably R'' is an alkylene group with 4-8 carbon atoms.

R' in formulas (1) and (2) preferably is a hydrogen atom. Particular preference is given to the use of the compounds N,N'-bis(2,2,6,6, -tetramethylpiper idine-4- yl)hexane-l, 6-diamine (HMB-TAD) and N-butyl-2 , 2 , 6 , 6 ,- tetramethylpiper idine-4-amine (N-butyl-TAD) .

Examples of polyolefins that are suitable for use in the shaped article according to the invention are:

- propene polymers, such as propene homopolymer , ethene- propene random copolymer, ethene-propene block copolymer and mixtures thereof. It is also possible to use mixtures of at least 50 wt.% of one of the above- mentioned propene polymers with for instance polyethene, ethene-propene-diene copolymers, etc.

- ethene polymers, such as low-density polyethene (LDPE) , high-density polyethene (HDPE) , very low-density polyethene (VLDPE) , linear low-density polyethene (LLDPE) , ultrahigh-molecular-weight polyethene (UHM PE), etc. and

- butene polymers, such as polybutene-1. Specially preferred is a propene polymer.

Most preferably, in a shaped article of propene polymers one of the compounds N, N '-bis (2 , 2 , 6 , 6 , - tetramethylpiper idine-4-yl )hexane-l , 6-diamine (HMB-TAD) and n-butyl-2 , 2 , 6 , 6 , -tetramethylpiper idine-4-amine (n- butyl-TAD) is used, because this gives shaped articles having a very high resistance to ultraviolet light.

The polymer composition for the shaped articles according to the invention with 0.05-5 parts by weight per 100 parts by weight of polyolefin of the above-defined compound according to formula (1) can be obtained by mixing the polymer in the melt or in powder form with said compound with the help of the customary equipment, such as mixers, kneaders and single- and twin-screw extruders. It is possible to produce the shaped article by means of the customary techniques, such as extrusion, injection shaped article and thermoforming.

Shaped articles according to the invention may further contain the usual additives such as stabilizers, antioxidants, lubricants, fillers, colorants, pigments, flame retarding agents, conductive fibres and reinforcing fibres, such as carbon fibres or glass fibres, making allowance for the above-mentioned shaped articles that are excluded from the invention. Examples of shaped articles according to the invention are exterior car parts, such as car bumpers, protective rims, etc., dashboards, garden furniture, such as garden tables, garden chairs, etc., building materials, such as facade cladding sheets, corrugated sheets, etc., packaging materials, for instance for fruit and vegetables.

The invention will be further elucidated by means of the following non-restrictive examples.

Examples

Examples I and II and comparative experiments C-E A high-impact ethene-propene block copolymer was compounded and granulated at 240°C on a single-screw extruder with

0.1 wt.% of calcium stearate, 0.125 wt.% of antioxidant, 0.6 wt.% of carbon black and 0.45 wt.% of the compound according to Table 2.

The granulate was injection-moulded at a temperature of 260°C to plaques measuring 3.2 x 65 x 65 mm and textured on one side.

These plaques were aged in a eather-Ometer ( OM) CI65A at the textured side.

This apparatus contains a xenon light source with borosilicate filters. The following values were set: - Black Panel Temperature: 63°C,

- Radiation intensity: 0.35 /(m .nm) at 340 nm,

102 minutes dry, 18 minutes' sprinkling, wit 55% humidity in the dry period. The ageing was measured by monitoring the degree of greying of the plaques by applying the grey scale assessment in accordance with DIN 54001. The ageing was stopped at a grey-scale value of 3. All plaques were tested in duplicate; the results are the average values for sets of two. Table 1 gives the times at which the exposed sides of the plaques reached grey scale rating 3.

TABLE 1

The examples clearly show that the compounds according to the invention are more effective as light stabilizer than the commercial HALS stabilizers of the comparative examples.

Example III and Comparative Experiment F

A black-coloured propene homopolymer (Stamylan P® PHC 22/20) was compounded with 0.2 wt.% of Tinuvin 770 (comparative experiment F) or 0.2 wt.% of HMB-TAD (example III), and granulated on a ZSK-30 twin-screw extruder at 240°C. The granulate was injection-moulded to plaques measuring 3.2 x 65 x 65 mm, textured on one side. These plaques were subjected to accelerated ageing in a Xenotest 1200 by continuously exposing the textured side to light. The Xenotest 1200 contains a xenon light source. The following values were set:

Black Panel Temperature: 80°C, Black Standard Temperature: 100°C, - relative humidity 20% The ageing was measured by monitoring the greying of the black plaques in time with application of the grey scale rating according to DIN 54001. At a grey scale value of 3 the ageing was stopped. All plaques were tested in duplicate; the results are the average values for sets of two. Table 2 gives the times at which the exposed sides of the plaques reached grey scale rating 3.

TABLE 2

The examples clearly show that the compound according to the invention (HMB-TAD) is more effective as light stabilizer than the commercial HALS stabilizer (Tinuvin 770) of the comparative example.

Claims

1. Shaped article made of a polyolefin composition comprising 100 parts by weight of a polyolefin and 0.01-5 parts by weight of a compound according to formula (1), wherein R' is hydrogen or a branched or non-branched alkyl group with 1-5 carbon atoms, R'' is a branched or non-branched alkylene, alkenylene or alkynylene group with 2-18 carbon atoms and A is hydrogen or a group according to formula (2) with R' being as defined above, and, when A is hydrogen, R'' is additionally methylene, at least one part of the shaped article having a wall thickness of at least 250μ, with the proviso that, shaped articles made of a composition comprising an polyolefin and a) the combination of a phenolic compound of the formule (3), wherein R_x is an alkyl group, a sulfur compound of the formula (4.1) or (4.2), wherein R₂ is an alkyl group, and an epoxy compound of bisfenol A type glycidyl ether, or b) a phosphite of formule (5), wherein R_lf R₂ and R₄ are an alkyl group and R₃ is hydrogen or an alkyl group, are excluded.

2. Shaped article according to claim 1, with the proviso that shaped articles made of a composition comprising a polyolefin and a) the combination of a sulfur compound of the formula (4.1) or (4.2) and an epoxy compound of bisphenol A type glycidyl ether or b) a cyclic organic phosphite having a group of the formula (7), are excluded

3. Shaped article according to claim 1, with the proviso that shaped articles made of a composition comprising a polyolefin and a) an epoxy compound of bisphenol A type glycidyl ether or b) a cyclic phosphite having a group of the formula (7) as defined in claim 2, are excluded.

4. Shaped article according to claim 1, with the proviso that shaped articles made of a composition comprising a polyolefin and an epoxy compound are excluded.

5. Shaped article according to claim 1 with the proviso that shaped articles made of a composition comprising a polyolefin and or a phosphorus compound or a sulfur compound are excluded.

6. Shaped article according to any one of Claims 1-5, characterized in that at least one part of the shaped article has a wall thickness of at least 500μ.

7. Shaped article according to any one of Claims 1-6, characterized in that the wall thickness of that part of the shaped article which is exposed to UV light while the shaped article is used in accordance with its function is at least 250 μ.

8. Shaped article according to any one of Claims 1-7, characterized in that the wall thickness of that part of the shaped article which is exposed to UV light while the shaped article is used in accordance with its function is at least 500 μ.

9. Shaped article according to any one of Claims 1-8, characterized in that the polymer composition of the shaped article comprises 0.03-3.0 parts by weight per 100 parts by weight of polyolefin of the compound according to formula (1).

10. Shaped article according to any one of Claims 1-9, characterized in that R'' in formula (1) is an alkyl group with 2-10 carbon atoms.

11. Shaped article according to any one of Claims 1-10, characterized in that R' in formulas (1) and (2) is a hydrogen atom.

12. Shaped article according to any one of Claims 1-11, characterized in that HMB-TAD is used as hindered amine compound.

13. Shaped article according to any one of Claims 1-12, characterized in that polypropene is used as polyolefin.

14. Shaped article according to any one of claims 1-13, made of a composition which additionally comprises carbon black.

15. Method for stabilising a shaped article made of a polyolefin composition, at least one part of said article having a thickness of at least 250μ and the proviso of claim 1 being applied, which method comprises incorporating into the composition at 100 parts polyolefin 0.01-5 parts of a compound of the formula 1 as defined in claim 1.

16. Use of compounds according to formula (1) in polyolefin shaped articles at least a part having a wall thickness of at least 250 μ for stabilising against degradation induced by ultraviolet radiation.