DE1694223C3 - Stabilized polypropylene-asbestos mixture - Google Patents

Description

a) a common phenolic antioxidant,

b) an organic sulfur compound of the general formula

where R is an alkyl radical with 4 to 24 carbon atoms or a ji- propionic acid alkyl ester radical, the alkyl group of which contains 4 to 24 carbon atoms, and η = 1 to 4,

c) a condensation product of 3 moles of 4,4'-thio-bis (3-methyl-6-tert-butyl-phenol) and 1 mole of PCl ₃ and optionally

d) calcium stearate or calcium oxide.

2. Thermoplastic molding compositions according to claim 1, characterized in that they are the individual stabilizer components in concentrations of 0.02 to 2 percent by weight, based on the total mass.

3. Thermoplastic molding compositions according to claim 1 and 2, characterized in that they as stabilizer component a) condensation products from aldehydes, ketones. Contain ketocarboxylic acids or SCl ₂ with alkylphenols or esters of monophenolalkanoic acids.

4. Thermoplastic molding compositions according to claim 1 to 3, characterized in that they contain dithioether as stabilizer component b).

5. Thermoplastic molding compositions according to claim I to 4, characterized in that they as asbestos tremolite, anthophyllite. Contains hornblende or low-iron chrysotile.

It is known that hardness, rigidity and, above all, dimensional stability at elevated temperatures «On crystalline polypropylene can be significantly improved by adding asbestos. Table 1 shows the improvement of some important mechanical Properties when comparing polypropylene with a mixture containing 40 percent by weight tremolite-asbestos contains.

Table 1

Influence of tremolite asbestos on the mechanical properties of polypropylene

35

Poly Mix of propylene Polypropylene with 40% Tremolite asbestos Density, g / cm ³ 0.9 1.23 Ball indentation hardness, kp / cin ² 810 1075 DIN 57 302 fciege E module. 15,000 40 (KK) Flexural creep test (1-miin value), kp / cnr torsional stiffness 580 1230 at 120 "C, DIN 53447, kp / cm ^J Vicat temperature 95 117 DIN 53462, C. Mean linear heat 1.3 · K) " ⁴ 0.7 ■ IO ⁴ expansion coefficient according to the Leitz dilatometer, grd '

40

45

55

60

These good mechanical properties are known from DT-AS 11 65 254 that the resistance to heat aging of polypropylene-asbestos mixtures very much on the type of chosen Asbesls depends. It was shown there that anthophyllite asbestos the heat aging resistance of the propylene is least affected.

The task was therefore to improve the thermal aging stability of asbestos-reinforced polypropylene to be improved by special, synergistic stabilizer combinations.

It has now been found that thermoplastic molding compositions from 90 to 30 parts by weight, preferably 75 to 40 parts by weight, crystalline polypropylene and 10 to 70 parts by weight. preferably up to 60 parts by weight, asbestos and 0.5 to 5 percent by weight, preferably 1 to 2 percent by weight, based on the total mass of a stabilizer combination

a) a phenolic antioxidant,

b) an organic sulfur compound of the general formula

R - (S) ₁ , - R

wherein R is an alkyl radical having 4 to 24, preferably 8 to 18 carbon atoms or an /.'-propionic acid alkyl ester radical, whose alkyl group contains 4 to 24, preferably 8 to 18, carbon atoms and »i = 1 to 4,

c) a condensation product of 3 moles of 4,4'-thiobis (3-methyl-6-tert-bulylphenol) and 1 mole PCI, and optionally

d) Calcium stearal or calcium oxide have excellent properties.

The concentrations of the individual Stabilisalor-

but only partially utilize them, since a longer 65 components should be between 0.02 and 2, preferably

Application at higher temperatures the deterioration opposes the heat aging resistance of polypropylene due to the addition of asbestos.

wisely between 0.1 and 0.5 percent by weight. Mononuclear antioxidants are suitable as phenolic antioxidants and especially dinuclear or polynuclear alkyl

substituted phenols such as ζ. Β. Condensation products from aldehydes, ketones, ketocarboxylic acid esters or SCl ₂ with alkylphenols. for example 2.2-1 propylidene-bis-ip-nonylphenol), 4,4'-thio-bis- (3-methylene-6-tert-ethylphenol), 4,4'-butylidene-bis- (6-tert .-butyl-3-methyl-phenol), 3,3-bis- (4-oxy-3-tert-butylphenyl) -butanoic acid dodecyl ester, 4,4-bis- (4-oxy-3-tert-butylphenyl) octadecyl pentanoate. Esters of monophenol alkanoic acids, such as //-(4-oxy-3,5-di-tert.-butylphenyl- propionic acid octadecyl ester and tetra - [(4 - oxy - 3,5 - di - tert - butylphenyl) - / / - propionic acid] pentaerythril ester.

Suitable sulfur compounds are e.g. B. Didodecyl sulfide, Dioctadecyl sulfide, dioctyl disulfide, didodecyl disulfide, Dioctadecyl disulfide, dioctadecyl trisulfide, dioctadecyl tetrasulfide, lauryl thiodipropionate, Octyl dithio-dipropionate, lauryl dithio-dipropionate, octadecyl dithio-dipropionate or lauryl trithiodipropionate. The dithioethers have proven to be particularly effective.

Calcium oxide is preferably used as component d). By far the best aging resistance obtained with combinations of a) alkyl-substituted Mono- or diphenol alkanoic acid esters, b) dialkyl disulfides with 8 to 18 carbon atoms in the Alkyl group, the condensation product c) and d) calcium oxide.

Although this combination of stabilizers achieves a substantial improvement in the thermal resistance for all types of asbestos, the durability is also strongly influenced by the type of asbestos selected. Table 2 shows the influence of different types of asbestos on the heat aging resistance of polypropylene-asbestos mixtures stabilized according to the invention. The mixtures each contained 40 percent by weight of asbestos and had 0.1 percent by weight of 3,3-bis- (4-oxy-3-tert-butylphenyl) butanoic acid dodecyl ester, 0.5 percent by weight of dioctadecyl disulfide and 0.5 percent by weight of the condensation product of 1 mol of PCl ₃ and 3 moles of 4,4'-thio-bis (3-methyl-6-tert.-butylph "nol) stabilized.

Table 2

Influence of the different asbestos acids on the resistance to heat aging of stabilized polypropylene according to the invention

Polypropylene without asbestos Warmth- Hornblende aging ¹⁵ chrysotile besiändiukeit at IO Low iron chrysoiil 140 C Anthophyllite in days*) Tremolite 160 ²⁰ South African blue asbestos 65 Canadian white asbesl 18th 70 95 122 17th 17th

*) Time in days until discoloration or powdery disintegration of the sample surface.

The table shows that with all types of asbestos durability is achieved at 140 ⁰ C of at least 17 days. In addition to anthophyllite, hornblende and a low-iron chrysotile also give good values, while tremolite has an even less influence on the heat aging resistance of polypropylene than anthophyllite. Hornblende, low-iron chrysotile, anthophyllite and, above all, tremolite are therefore preferred for these mixtures.

The components can be mixed in any conventional way. Preferably mixes the polypropylene with the addition of the stabilizers with the asbestos and extruded and granulated the Mix afterwards.

Usual additives, such as. B. Pigments. Dyes.

Lubricants, auxiliaries or other stabilizers, such as z. B. UV absorbers can be added to the mixture.

Examples

In each case 6 kg of crystalline polypropylene with a melt index I ₅ = 30.5 g / K) min (measured according to DIN 53 735 E at 230 ° C. and 5 kp load) were intimately mixed with 4.0 kg of tremolite asbestos in a high-speed mixer after addition of the stabilizers and pigments listed in Table 3, it is extruded on a single-screw extruder to form a tape and granulated.

Made of 1 mm thick, on a screw injection molding machine at nozzle temperatures of 220 Plates sprayed up to 230 C were punched out and used for testing strips 10 mm wide and 100 mm long Determination of heat aging resistance in a circulating air drying cabinet freely suspended. the The test temperature was 110 "C. At an interval of 23 days, the test strips were switched to beginning Investigated embrittlement phenomena. The heat aging resistance for each of 2 samples was Time given in days after which the sample surface becomes discolored or embrittled was visibly changed. For comparison, the last column of Table 3 shows some values for appropriately stabilized asbestos-free polypropylene listed.

A comparison of the inventive experiments 3 and 4 with the comparative examples 7 and 8 shows that by adding the condensation product C, the stability of the asbestos-filled polypropylene is completely increased is increased significantly. This increase in stability is significantly greater than with unfilled polypropylene. The addition of trilauryl phosphite instead of the condensation product C becomes such Improvement not achieved. This is surprising since trilauryl phosphite is an effective door costabilizer Polypropylene is known and shows practically the same effectiveness as in asbestos-free polypropylene the condensation product C (compare the values of experiments 4 and 9).

There is therefore a very specific synergism of the stabilizer combination according to the invention for asbestos-reinforced polypropylene.

Experiments 4, 5 and 6 show that the stability is not influenced by adding a pigment Calcium oxide, however, is improved.

Table 3 Heat level lc 5 Yer- Slabilisalorkomhin.ilion V., Rmcal.cn ,,,, shcslaMu, Ver Siabilisatorkombinalion search
No wedge at 140
Poly (
l \ »h- search
No. TungsbejiUindiu- propylene
■ 411 ",,
1 pure, ilil
l'lauei prop \ Uli wedge at i4ü C
Pole) poly
propylene propylene
-t 411% (compare I.
Tremoli!

a) 0.1% A-I + b) 0.5% B-! -f- c) 0.5% C + d) 0.4% Ca-Siearal

a) 0.1% A-2 + b) 0.5% B-I + c) 0.5% C + d) 0.4% Ca-Stearal

a) 0.5% A-3 + b) 0.5% B-2 + c) 0.5% C 4- d) 0.03% CaO

a) 0.1% A-3 + b) 0.5% B-I + c) 0.5% C + d) 0.4% Ca stearate

like experiment 4, pigmented with 5% ZnS + 2% TiO ₂ + 0.05% Ullramarine blue

(Tuce I

65

X2

68

88/99

86/97

(mild)

75 85

140150

145/152

6 al 0.1% A-3 Hl 141 140 + b) 0.5% B-I + c) 0.5% C + d) 0.03% CaO

For comparison

7 al 0.5% A-3 25 25 50 + b) 0.5% B-2 4 d) 0.4% Ca stearate

8 a) 0.1% A-3 52 56 110 + b) 0.5% B-I + d) 0.4% Ca-Stearal

9 a) 0. '% A-3 62 66 140 + b! 0.5% B-I + 0 0.5% trilauryl-

phosphite -f d) 0.4% Ca stearate

Λ-Ι ----- condensation product of 2 mol p-Non \ lph.eno! mn! MnI acetone.
Λ-2 -,; - 14-ox \ -3.5-di-tert.-hui \ lplicn> 11-propionic acid octadec> iester.

Λ-3 = ■ 3.3-bis- (4-ox) -3-tcrl.-but \ lphon \ l) -buUiiis; iiiredodecylevtci. B-I - = di-octiidecyl disulfide. B-2 = lauryl thio-dipropionic acid

C - ■ Condensation product from 1 mole PCI, and 3 moles 4.4 -11110 ic bis-l.Vmcthjl-fi-lerl.-buiylphcno'.l.

Claims (1)

Patent claims: \. Thermoplastic dimensions. Consists of 90 to 30 parts by weight of crystalline polypropylene, 10 to 70 parts by weight of asbestos and 0.5 to 5 percent by weight, based on the total mass of a stabilizer combination