NO301021B1 - Process for stabilizing olefin polymers polymerized on support catalysts - Google Patents

Description

The present invention relates to a method for stabilizing olefin polymers polymerized on carrier catalysts with an average particle diameter of 1-5 mm.

JP-Å-84/150 719 describes a method for stabilizing polypropylene powders whereby the polypropylene powder, the stabilizers and a carrier material are homogenised in a mixer while heating.

EP-A-281 189 describes a method for producing a hydrolysis-resistant stabilizer mixture of a phosphite and a phenolic antioxidant, as well as the use of this stabilizer mixture for stabilizing polypropylene powder. Powdered polyolefin must be granulated in an extruder before shaping. During this granulation, stabilizers and other processing aids are added to the polymer.

Unstabilized, granule-like polyolefins which have been produced by polymerization of olefins on solid carrier catalysts have already been available in the market for some time. Since these polyolefins are already formed in granule-like form during production, they no longer have to be extruded in a subsequent processing step; it would then have to be whether the incorporation of the stabilizers and processing aids requires a remelting to ensure an adequate distribution of the additive in the polymers.

The addition of stabilizers during the olefin polymerization in many cases causes disruption of the polymerization, as well as a discoloration of the polymers.

The present invention relates to a method for stabilizing olefin polymers polymerized on carrier catalysts with an average particle diameter of 1-5 mm, which is characterized by the fact that these polyolefins are treated with a stabilizer mixture which is produced by heating a mixture containing components a), b) and c) or containing components b) and c), to 120-260°C and subsequent cooling to solidification, whereby components b) and c) are different and where the components mean the following: component a) is at least one carrier material,

component b) is at least one stabilizer melting at 20-120°C, and

component c) is at least one stabilizer melting at 120-260°C,

and whereby the treatment of the polyolefins is carried out below the melting point of the polyolefin particles.

The component b) can possibly take over the function of component

a) as carrier material.

The weight ratio a:c is preferably 0.1:1 to 4:1, in particular

0.5:1 to 2:1 and the weight ratio b:c is e.g. 4:1 to 0.1:1 or 2:1 to 0.1:1, preferably 1:1 to 0.1:1.

Preferred is a method where the stabilizer mixture used contains components a), b) and c).

The carrier material is preferably a wax, paraffin oil or a glyceryl monocarboxylic acid ester. As examples of suitable carrier materials can be mentioned: polyethylene, polypropylene (e.g. atactic), olefinic copolymers (e.g. copolymers of propylene, such as propylene-ethylene copolymer or propylene-butene-1 copolymer), ethylene-vinyl- acetate copolymers, ethylene-(unsaturated carboxylic acid ester) copolymers (e.g. ethylene-methyl methacrylate copolymer), ethylene-(unsaturated carboxylic acid metal salt) copolymers (e.g. ethylene-magnesium acrylate copolymer or ethylene-zinc acrylate copolymer), with unsaturated carboxylic acids, such as maleic anhydride, modified polyethylene or modified polypropylene, petroleum, paraffin oil, polyalkylene glycol, such as e.g. polyethylene glycol, polypropylene glycol, etc., or glyceryl monocarboxylic acid ester, preferably glyceryl monostearate.

Depending on the nature, the carrier material melts, e.g. at 0-120°C, 10-120°C or 20-100°C. Preferably, a carrier material is used which either melts at 0-79°C (e.g. paraffin oil) or 80-105°C (e.g. wax).

The component b) is preferably a sterically hindered phenolic antioxidant, a phosphorus-containing stabilizer, a sterically hindered amine, a benztriazole, a benzophenone, a thiodicarboxylic acid diester and/or a dialkyl disulphide.

The following stabilizers are examples of component b):

Sterically hindered phenolic antioxidants:

A) 2,2-bis[3'-5'-di-tert-butyl-4*-hydroxyphenylpropionyl-oxyethoxyphenyl]propane

Melting point: 100-102°C

B) tetrakis[3, 5-di-tert-butyl-4-hydroxyphenylpropionyl-oxymethyl]methane

Melting point: 110-120°C

C) n-octadecyl-3-(3',5'-di-tert-butyl-4'-hydroxyphenyl)-propionate

Melting point: 50-55"C

D) triethylene glycol bis[3-(3'-tert-butyl-4' hydroxy-5'-methylphenyl]propionate

Melting point: 67-79°C

E) 1,5-bis[3',5'-di-tert-butylol-4'-hydroxyphenyl prop i onyl-oxy]-3'-thiapentane

Melting point: 63-68°C

Phosphorus-containing stabilizers:

F) tetrakis[2,4-di-tert-butylphenyl]-diphenylenediphosphonite

Melting point: 75-95°C

G) distearyl pentaerythritol diphosphite

Melting point: 40-60°C

Sterically hindered amines:

H) bis[2,2,6,6-tetramethyl-4-piperidinyl]sebacate

Melting point: 82-86°C

I) bis[1,2,2,6,6-pentamethyl-4-piperidinyl]sebacate

Melting point 20°C

J) bis[2,2,6,6-tetramethyl-4-piperidinyl]succinate

Melting point: 120°C

K) condensation product of 1-(2'-hydroxyethyl)-2,2,6,6-tetramethyl-4-piperidinol and succinic acid

Melting point: 55-70°C

Benztrazoles:

L) 2-(2'-Hydroxy-5'-tert-octylJbenztriazole<1>).

Melting point: 103-104°C

M) 2-(2'-hydroxy-3',5'-di-tert-pentyl)benztriazole<2>

Melting point: 79-87°C

<1> tert-octyl = 1,1,3,3-tetramethyl-l-butyl <2> tert-pentyl = 1,1-dimethyl-l-propyl

Benzophenone:

N) 2-hydroxy-4-octyloxybenzophenone

Melting point: 47°C

Thiodicarboxvls<y>redlester:

0) dilauryl thiodipropionate

H2gC2200CCH2CH2_S-CH2CH2C00C22225

Melting point: 40-45°C

P) dimyristylthiodlproplonate

H29C14OOCCH2CH2—S—CH2CH2COOC ^41129

Melting point: 44-48°C

Q) distearylthiodipropionate

H3'7C2g00CCH2CH2-S-CH2CH2C00 0^8^37

Melting point: 57-67°C

Dialkyldisulfides:

R) distearyl disulfide

<H>37<C>18"<SS>_<C>18<E>37

Melting point: ~ 66°C

A sterically hindered phenolic antioxidant is particularly preferably used as component b).

Component c) is preferably a sterically hindered phenolic antioxidant, a metal deactivator, a sterically hindered amine, a benztriazole, a phosphorus-containing stabilizer, a nickel-containing UV absorber and/or a metal salt of a C16-C22" fatty acid.

The following stabilizers are examples of component c):

Sterically hindered phenolic antioxidants:

a) 1,3,5-trimethyl-2,4,6-tris(3',5'-di-tert-butyl-4'-hydroxy-benzyl)benzene

Melting point: 242-245'C

e) 1,3,5-tris(3',5'-di-tert-butyl-4'-hydroxybenzyl)-isocyamirate

Melting point: 218-223°C

T) 1,3,5-tris(2,6'-dlmethyl-4'-tert-butyl-5'-hydroxy-benzyl)isocyanurate

Melting point: 145-155°C

S) 1,2,bls[3',3'-bis(4"-hydroxy-5"-tert-butylphenyl)butanoyl-oxy]ethane

Melting point: 170°C

c) bis(tert-butyl-4-hydroxy-6-methylphenyl)sulfide

Melting point: 161°C

z) 2-(2'-hydroxy-3'-tert-butyl-5'-methylbenzyl)-4-methyl-tert-butyl-phenylacrylate

Melting point: 130-132°C

H) 1,1,3-tris[3'-tert-butyl-4'-hydroxy-6'-methylphenyljbutane

Melting point: 182.5-190°C e ) 2,4,-di-tert-butylphenyl-3',5»-di-tert-butyl-4'-hydroxy-benzoate

Melting point: 190°C

Wetall deactivators:

i) N,N-bis[3,5-di-tert-butyl-4-hydroxyphenylpropionyl]-hydrazine

Melting point: 224-229°C

k) N,N,-bis[3, 5 - di -1 er t - butyl-4-hydroxyf enylpropiony 1-oxyethyl]oxalic acid diamide

Melting point: 173°C

Sterically hindered amines:

X) poly[2-(N,N-bis(2 ' ,2' ,6' , 6 • -tetramethyl-4'-piperidinyl )-hexamethylene-diamino-4-morpholino-1, 3,5- triazin-6-yl]

Melting point: 110-130°C

jj) poly[2-(N,N-bis(2',2',6',6'-tetramethyl-4'-piperidinyl)-hexamethylene-diamino-4-tert-octyl-1,3,5-triazine -6-yl]

Melting point: 120-150°C

v ) 1,5 ,8,12-tetrakis[2* ,4 '-Ms(1" ,2" ,2" ,6" ,6 "-pentamethyl-4 "-piperidinyl (butyl )amino-1' ,3 ',5'-triazin-6'-yl]-1,5,8,12-

tetraazadodecane

Melting point 150°C

E) bisCl',2',2',6',6'-pentamethyl-4'-piperidinyl]-2-butyl-2-(3,5"-di-tert-butyl-4"-hydroxybenzyl) malonate

Melting point: 146-150°C

o) 1,2-bis[3',3',5',5*-tetramethyl-2'-oxo-1',4'-diazinan-1'-yl]ethane

Melting point: 136°C IT)

Melting point: 270°C

Benztriazoles:

p) 2-(2'-hydroxy-3,5-di-tert-butylphenyl)benztriazole

Melting point: 150-155°C

a) 2-(2'-hydroxy-3'-tert-butyl-5'-methyl phenyl)-5'-chloro-benztriazole

Melting point: 137-140"C

■r) 2-(2'-hydroxy-3',5'-di-tert-butylphenyl)-5'-chlorobenz-triazole

Melting point: 154-158"C

Phosphorus-containing stabilizers:

• J ) tris[2,4-di-tert-butylphenyl]phosphite

Melting point: 180-185'C $) bis[2,4-di-tert-butylphenyl]pentaerythrididiphosphite

Melting point: 160-175°C

X) bls[2,6-di-tert-butyl-4-methylphenyl]pentaerythrididiphosphite

Melting point: 235'C

Melting point: 200-201<6>C

two) calcium salt of 3,5-di-tert-butyl-4-hydroxybenzylphosphonic acid monoethyl esters

melting point: > 150°C

A) nickel salt of 3,5-di-tert-butyl-4-hydroxybenzylphosphonic acid monoethyl esters

Melting point: > 180 °C

Nickel-containing UV absorption. ionic agent:

B) 2,2'-thio-bis[4-tert-octylphenolate]-butyl-amino-nickel (II)

Melting point: 258°C

Metal salts of C±b- C22~ fatty acids: T) Ca-palminate, melting point: 150-155°C (decomposition)

a) Mg-palminate, melting point: 121 °C

E) Zn palmitate. melting point: ~ 125 °C

Z) Ca stearate, melting point: 180°C

H) Mg stearate, melting point: 145°C

8) Zn stearate, melting point: 130°C

I) Ca-behenate, melting point: ~ 150°C

K) Mg-behenate, melting point: ~ 150°C

A) Zn behenate, melting point: ~ 125°C

As components c), a phosphorus-containing stabilizer, especially a phosphite, is of interest.

A particularly preferred object of the invention is a method where the used stabilizer system contains components a), b) and c), and component b) is a sterically hindered phenolic antioxidant and component c) is a phosphite.

It is further preferred that component b) is n-octadecyl-3-(3',5'-di-tert-butyl-4'-hydroxyphenyl)propionate or/and tetrakis[3,5-di-tert-butyl-4 -hydroxyphenylpropionyl-oxymethyljmethane and component c) is tris[2,4-di-tert-butylphenyl]phosphite.

Also preferred is a method where component b) is a stabilizer melting at 50-120°C and component c) is a stabilizer melting at 180-200°C and the stabilizer mixture is heated to 180-200°C.

Components a), b) and c) are known, mainly commercially available products.

Olefins that can be polymerized on supported catalysts are e.g. ethylene or α-olefins, especially propylene, 1-butene, 4-methylpentene-1 or 5-methylhexene-1, as well as mixtures of olefins such as e.g. ethylene-propylene or propylene in mixture with smaller amounts of higher α-olefins.

Of interest are supported catalysts applied to polyethylene, polypropylene, copolymers of ethylene and copolymers of propylene, especially polyethylene and polypropylene.

The polymerization catalysts used, which are often referred to as catalysts of the third generation, are suitably solid catalysts of a specific particle size, such as e.g. described in DE-A-29 33 997 and DE-A-26 41 960. They consist, e.g. of an anhydrous magnesium dihalide in active form and a titanium compound. Magnesium halide in active form is understood as such where the lines of the strongest reflection in the X-ray spectrum are extended compared to the corresponding line in the spectrum for the inactive magnesium halide.

Magnesium dichloride or magnesium dibromide is preferably used as magnesium dihalide. The titanium compound preferably contains at least one titanium-halogen bond, the use of titanium tetrachloride being particularly preferred.

The titanium compound can be used in combination with an electron donor, for example a carboxylic acid ester, which e.g. described in EP-A-45 977.

After the reaction of the magnesium halide component with the titanium compound and optionally with the electron donor, the excess titanium compound and the excess electron donor are suitably washed out in an inert solvent, for example with hexane or heptane.

The catalyst produced in this way is activated by reaction with an aluminum alkyl, which is preferably used as a solution in an alkane. Examples of suitable aluminum alkyls are Al (02115)3 or Al (0419)3. Here, as a coactivator, an electron donor such as e.g. an organosilicon compound containing at least one Si-O-C bond, such as described in EP-A-45 977. Examples of such silicon compounds are phenyltriethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane or ethyltrimethoxysilane.

The polymerization with these catalysts can be carried out by known methods in the liquid or gaseous phase. The liquid phase can e.g. be an aliphatic hydrocarbon or the liquid monomer itself.

Spherical polymerized polyolefins are described e.g. also in P. Galli, P.C. Barbé and L. Noristi; "High Yield Catalysts in Olefin Polymerization", Die Angewandte Markomolekulare Chemie 120 (1984), pp. 73-90 (No. 1935).

The diameter of the olefin polymer polymerized on the carrier catalyst is preferably 2-5 mm, especially 2-3 mm.

The melting point for this granular polyolefin is e.g. 140-165°C.

The stabilizer mixtures are preferably present in a concentration of 0.01 to 5% by weight, especially 0.05 to 1% by weight, in the polyolefin to be stabilized.

It is advantageous to heat the stabilizer system before incorporating it into the polyolefin until a milky solution is present. This milky solution is a suspension of component c) in a) and/or b). For stabilization, the polyolefin is stirred with the stabilizer system, which has a temperature of e.g. 60-120°C, preferably 100-120°C, especially 100-110°C, in a suitable device (preferably a mixer), e.g. 2-10 minutes and then cool. Appropriately, the polyolefin is heated before stabilization to e.g. ~60-120°C.

The temperature of the polyolefin can e.g. amount to 60-79°C when the stabilizer system as carrier material contains a substance melting at ~0-79°C, such as e.g. paraffin oil, or which has been subsequently treated with paraffin oil. In the latter case, the weight ratio between stabilizer system and paraffin oil amounts to e.g. 1:1 to 3:1. In the subsequent treatment of the stabilizer system with paraffin oil, the stabilizer system is suitably stirred into hot paraffin oil (100-120°C) and then stirred (e.g. 15-30 minutes) until a homogeneous mixture is formed which can be used for the stabilization of the polyolefin.

If a substance melting at ~80-110°C is used as carrier material, such as e.g. a wax, it is advantageous when the temperature of the polyolefin e.g. is 80-120°C, preferably 80-110°C.

The preparation of the stabilizer system conveniently takes place by mixing the components a) or/and b) and c). The mixture is preferably heated with stirring until e.g. 120-260°C. The obtained melt is stirred, e.g. 2-15 minutes, preferably 8-12 minutes and then cooled to solidification, which e.g. occurs at a temperature of 0-30°C. The cooling can e.g. carried out with cold water or another inert liquid, with nitrogen or another inert gas. It is also possible to cool the forge, e.g. with a cold metal plate.

The production of the stabilizer system can e.g. also take place in a knee device. The stabilizer mixture is then formed as granules.

The following examples illustrate the invention in more detail.

Example 1: Preparation of the stabilizer mixtures.

Stabilizer mixture I:

20 g n-octadecyl-3-(3',5'-di-tert-butyl-4'-hydroxyphenyl)-propionate, 50 g tetrakis[3,5-di-tert-butyl-4-hydroxyphenyl-propionyloxymethyl]methane and 100 g of tris[2,4-di-tert-butylphenyl]phosphite and 200 g of polyethylene wax (melting point according to ASTM D-3104: 102°C, hardness according to ASTM D-5: 7.0 dmm, density according to ASTM D-1505 : 0.91 g/cm<5> , viscosity according to Brookfield at 140°C: 180 cp) are mixed and heated to 200°C. The molten material is stirred for 10 minutes at this temperature. The mixture is then cooled, also with stirring, whereby it solidifies.

Stabilizer mixture II:

II is prepared analogously to I, whereby glyceryl monostearate is used instead of wax.

Stabilizer mixture III:

III is prepared analogously to I, whereby distearylthiodipropionate is used instead of polyethylene wax.

Stabilizer mixture IV:

IV is prepared analogously to I, whereby 50 g of polyethylene wax is used instead of 200 g of polyethylene wax.

Stabilizer mixture V:

V is produced analogously to IV, whereby the mixing and heating take place in an extruder ("BUSS-KO-KNETER") and the additive mixture is produced as granules.

Examples 2a-2c: Stabilization of spherical polypropylene balls.

a) 1000 g of spherical polypropylene ("Moplen SPL 12") is heated in a Henschel mixer (capacity: 5000 ml) for 7 minutes more

104°C. 3.7 g of the stabilizer mixture specified in table 1a, which had previously been melted at 104°C, are added. The mixture is stirred for 2 minutes and then cooled. The stabilized polypropylene balls are exposed for 30 hours to an oven curing at 149°C. The test results are given in table la. Discoloration of the polypropylene balls means insufficient stabilization.

b) 100 g of spherical polypropylene ("Moplen SPL 12") is heated in a Henschel mixer (capacity: 5000 ml) for 3 minutes at 65°C. 3.7 g of the stabilizer mixture indicated in table 1b which had previously been heated to 104°C is added. The further processing and examination took place as under a). The test results are listed in table lb. c) 1000 g of spherical polypropylene ("Moplen SPL 12") is heated in a Henschel mixer (capacity: 5000 ml) for 13 minutes to 65°C. 2.2 g of the stabilizer mixture indicated in table 1c are added to 1 g of hot paraffin oil (110° C) and the resulting mixture is stirred for 20 minutes at this temperature. This mixture is then added to the polypropylene (65°C), the mixture is stirred for 2 minutes and then cooled. The examination of the polypropylene balls takes place as under a). The test results are given in table 1c.

Claims (13)

1. Process for the stabilization of olefin polymers polymerized on carrier catalysts with an average particle diameter of 1-5 mm, characterized in that these polyolefins are treated with a stabilizer mixture which is prepared by heating a mixture containing components a), b) and c) or containing components b) and c), to 120-260°C and subsequent cooling to solidification, whereby the components b) and c) are different and where the components mean the following: component a) is at least one carrier material, component b) is at least one at 20- 120°C melting stabilizer, and component c) is at least one 120-260°C melting stabilizer, whereby the treatment of the polyolefins is carried out below the melting point of the polyolefin particles. 2. Method according to claim 1, characterized in that the stabilizer mixture used contains the components a), b) and c). 3. Method according to claim 1, characterized in that component a) consists of a wax, paraffin oil or a glyceryl monocarboxylic acid ester. 4. Method according to claim 3, characterized in that a polyethylene, a polypropylene, an olefinic copolymer, an ethylene-vinyl acetate copolymer, an ethylene (unsaturated carboxylic acid ester) copolymer, an ethylene (unsaturated carboxylic acid metal salt) copolymer is used as component a) , a polyethylene modified with unsaturated carboxylic acids, or polypropylene modified, petroleum, paraffin oil, a polyalkylene glycol or a glyceryl monocarboxylic acid ester. 5. Method according to claim 1, characterized in that a sterically hindered phenolic antioxidant, a phosphorus-containing stabilizer, a sterically hindered amine, a benztriazole, a benzophenone, a thiodicarboxylic acid diester and/or a dialkyl disulfide are used as component b). 6. Method according to claim 1, characterized in that a sterically hindered phenolic antioxidant is used as component b). 7 . Process according to claim 1, characterized in that a sterically hindered phenolic antioxidant, a metal deactivator, a sterically hindered amine, a benztriazole, a phosphorus-containing stabilizer, a nickel-containing UV absorber and/or a metal salt of a C^( ,-C22_fe't't'acid• 8. Method according to claim 1, characterized in that a phosphorus-containing stabilizer is used as component c). 9. Method according to claim 1, characterized in that a phosphite is used as component c). 10. Method according to claim 2, characterized in that as component b) a sterically hindered phenolic antioxidant is used and as component c) a phosphite. 11. Method according to claim 10, characterized in that n-octadecyl-3-(3',5'-di-tert-butyl-4'-hydroxyphenyl)propionate or/and tetrakis[3,5-di- tert-butyl-4-hydroxyphenylpropionyl-oxymethyl]methane and as component c) tris[2,4-di-tert-butylphenyl]phosphite. 12. Method according to claim 1, characterized in that component b) is a stabilizer melting at 50-120°C and component c) is a stabilizer melting at 180-200°C and that the stabilizer mixture is heated to 180-200°C. 13. Method according to claim 1, characterized in that the polyolefins have an average diameter of 2-5 mm.