DE2404330B2 - POLYAETHYLENE MIXTURE FOR THE MANUFACTURING OF CONTAINERS FOR FLAMMABLE LIQUIDS - Google Patents

Description

It is known that on containers for highly flammable liquids such. B. petrol cans, certain minimum requirements are made that could not or only partially achieved with plastics. The surface resistance must not exceed 10 ⁹ Ω in order to definitely avoid static charging. In the drop test according to DIN 16904, the containers must withstand a drop height of at least 1.80 m and the diffusion loss according to DIN 16904 must not be greater than 5 g. In addition, the processability must be satisfactory, especially for larger containers.

With the 5-1 petrol cans that have been officially approved up to now, the surface resistance does not yet play such an important role, since the risk of fire is lower with the relatively small filling quantity. For larger containers, however, the surface resistance of polyethylene, which is more than 10 ¹³ Ω, must be reduced to ^{at least 10 9 Ω.}

Numerous methods for the antistatic treatment of plastics are known. So can surface-active Compounds applied to or incorporated into the surface, or the surface can be chemically modified, e.g. B. sulfonated (see. German Offenlegungsschrift 1953371).

All of these methods have the disadvantage that the effect depends on the air humidity and is through Abrasion is lost entirely or temporarily.

It is also known to reduce the surface resistance of plastics or rubber by adding carbon black. In order to achieve a value below 10 ^β Ω, however, amounts of around 20% are required for commercially available carbon blacks. So high soot

20th Table 1 Upper Diffu Height of fall product area- sions contrary- loss was standing (Ω) (G) (m) 25th 10 ¹³ 1 1.80 Polyethylene 10 ¹¹ 3 0.50 85% polyethylene 30th 15% soot *) 10 * 4th 0.50 80% polyethylene 20% soot *) 1O ¹² 17th 1.80 82.5% polyethylene 10% soot *) 35 7.5% styrene butadiene Block polymer 10 * 32 1.80 65% polyethylene 20% soot *) AQ 15% styrene butadiene Block polymer 10 ¹¹ 3 0.50 73% polyethylene 15% soot *) 12% acrylonitrile butadiene 45 Copolymer

*) Highly conductive carbon black with a BET surface area [determined after Brunauer, Emmet and Teller, J. Amer. Cbem. Soc. 60 (1938) p. 309] of 133 m '/ g, an oil absorption of about 5.1 ml / g, a volatile matter content of 1%, an ash content of 0.07% and a pH value of 8.

The table shows that with the previous mixtures, at least one of the requirements has always not been met was fulfilled.

It has now been found that the problem can be solved by using a special carbon black. With this soot, mixtures are obtained which meet all requirements and which are ideally suited for the production of containers for flammable liquids, especially for gasoline canisters over 51.

The subject of the invention is therefore a polyethylene mixture for the production of containers for easily flammable liquids, consisting of 94 to 85 percent by weight polyethylene with a density of 0.94 to 0.96 g / cm ^s and a melt index MFI 190/5 of 0.2 to 5 g / 10 min and 6 to 15 percent by weight of carbon black, each based on the polyethylene carbon black mixture

Schung, which is characterized in that the carbon black has a BET surface area of 300 to 1500, preferably 600 to 1000 Tn ¹ Jg, an oil absorption of 2.5 to 5.5, preferably 3.0 to 4.0 mi / g, a volatile content of 0.1 to 6.0, preferably 1 to 4 percent by weight, a pH of 7 to 9, preferably 8 to 8.5 and an ash content of 0.5 to 10.0, preferably 0, 5 to 1.0 percent by weight, as well as usual additives.

Such soot is a by-product of known gasification processes for the production of Gas mixtures of hydrocarbons containing carbon oxide and hydrogen, such as those used, for. Am "Advances in Petroleum Chemistry and Refining", Volume 10, Chapter 4, pp. 123 to 189 Q.nterscience Publishers ?, New York, 1965). This soot was already together with non-conductive Fillers used for the production of electrically conductive vulcanizates (German Offenlegungsschrift 20 47 333), but it is expressly pointed out that when this carbon black is used alone many disadvantages arise because the processability is difficult and the mechanical properties are poor are. From this information it could not be concluded that there were polyethylene blends with this carbon black without further fillers are particularly suitable for the production of petrol cans.

A particularly suitable polyethylene for the mixtures according to the invention is a linear polyethylene with a density of 9.4 to 9.6 g / cm ³ and a melt index MFI190 / 5 according to DIN 53735 of 0.2 to 5.0, preferably 0.5 to 1 , 6 g / 10 min. Copolymers of ethylene with up to 10 percent by weight of propylene and / or butene- (l) are also suitable.

Particularly suitable stabilizers are aromatic amines, ζ. B. octylated diphenylamine or derivatives of p-phenylenediamine, such as N-phenyl-N'-isopropyl-p-phenylenediamine or N, N'-di-2-naphthyl-p-phenylenediamine in amounts of 0.05 to 2.0, preferably 0.1 to 1.0 percent by weight, based on the mixture.

Metal stearates, e.g. B. calcium stearate or Zinc stearate is used in amounts of 0.1 to 1.0 percent by weight, based on the mixture.

Even small amounts of this soot, e.g. B. 4 to 5%, reduce the surface resistance of the polyethylene. The best results are obtained with blends of 93 to 90 percent by weight polyethylene and 7 to 10 weight percent carbon black obtained. With these mixtures, the surface resistance is at the desired level The value is lowered, while the mechanical properties are almost unaffected.

The mixtures can be prepared by customary processes. Premixing is particularly advantageous the powder in high-speed mixers with subsequent homogenization and granulation on twin screw extruders.

example 1

92 parts of a polyethylene with a density of 0.945 g / l and a melt index MFI 190/5, measured according to DIN 53735 of 0.5 g / 10 min, in powder form were mixed with 8 parts of a carbon black with a BET surface area of 950 in a high-speed mixer m ^: / g, a

ίο oil absorption of 3.2 ml / g, a content of volatile Ingredients of 1.0%, a pH of 8 and an ash content of 0.7%, and 0.2 parts Calcium stearate and 0.3 part of N-phenyl-N'-isopropyl-p-phenylenediamine mixed. Then the

The mixture is homogenized and granulated on a twin-screw extruder at temperatures between 180 and 250 ^{= C.} 10-1 canisters were extrusion blown from the granulate. The results of the testing of the canisters are shown in Table 2.

Example 2

A mixture of 90 parts of a polyethylene with a density of 0.946 g / 1 and a melt index MFI 190/5 of 0.8 g / 10 min, 10 parts of a carbon black with a BET surface area of 800 m ² / g, an oil absorption 'ion of 320 ml / g, a volatile matter content of 3.5%, a pH value of 8 and an ash content of 0.7%, 0.4 parts of zinc stearate and 0.6 parts of N, N'- Di-2-naphthyl-p-phenylenediamine were mixed, homogenized, granulated and processed into 10-1 canisters in the same manner as described in Example 1. The result of the test is also shown in Table 2.

., EXAMPLE 1 3

Example 1 was repeated with the modification

that 94 parts of polyethylene were mixed with 6 parts of carbon black. Mixing ingredients and stabilization were the same as in Example 1. The result of the test can be found in Table 2.

Table 2 example

Surface resistance

(Ω)

Diffusion height of fall
loss

(G)

(m)

1. 10 ⁵ 4th > 1.80 2 10 ⁴ 4th > 1.80 3 10 ⁸ 3 > 1.80

As can be seen from the table, 10-1 canisters can be produced from the mixtures according to the invention, which meet all requirements.

Claims (5)

Patent claims: 1. Polyethylene mixture for the production of containers for easily flammable liquids, consisting of 94 to 85 percent by weight of polyethylene with a density of 0.94 to 0.96 / cm ³ and a melt index MFI190 / 5 of 0.2 to 5 g / 10 min and 6 Up to 15 percent by weight of carbon black, based in each case on the polyethylene-carbon black mixture, characterized in that the carbon black has a BET surface area of 300 to 1500 m ² / g, an oil absorption of 2.5 to 5.5 ml / g of volatile constituents of 0.1 to 6.0 percent by weight, a pH value of 7 to 9 and an ash content of 0.5 to 10 percent by weight, as well as usual additives. 2. Polyethylene mixture according to claim 1, characterized in that the mixture with 0.1 to 1 percent by weight of aromatic amines is stabilized. 3. polyethylene mixture according to claim 2, characterized in that the polyethylene mixture is stabilized with a derivative of p-phenylenediamine. 4. Polyethylene mixture according to claim 1 to 3, characterized in that they are metal stearates as Processing aid contains. 5. Petrol cans made from polyethylene-carbon black mixtures according to claims 1 to 4. quantities worsen the mechanical properties, especially the impact resistance, so that the required height of fall is not even remotely reached. To improve the drop resistance one is therefore forced to use elasticizing agents, e.g. B. rubber to add. Elastifying rubbers swell however, strong in gasoline and therefore increase the diffusion loss. With all previous mixes at most two of the minimum requirements were met ίο meet. The following table 1 clearly shows the problem. The surface resistance was measured according to DIN 53482 with electrode arrangement A at a measuring voltage of 100 V. The diffusion loss in grams was determined in accordance with DIN 16904 on a 10-1 canister with a wall thickness of 3 mm at 75 ° C. for 4 hours. The height of fall was determined according to DIN 16904 on 10-1 canisters filled with cold brine at -2S ³ C.