DE3933874A1 - Modifying surface of polyolefin containers - by exposing container to low pressure plasma in fluorine-contg. gas atmos. - Google Patents

Abstract

Surface modification process for containers (I) made from polyolefin is claimed. One or more containers are exposed to a low pressure plasma in an atmosphere of a fluorine-contg. gas. (I) consist of polyethylene or polypropylene and are used e.g. for the storage of petrol. The fluorine-contg. gas is tetrafluorocarbon and/or sulphurhexafluoride opt. as a mixt. with one or more non-fluorine gases, e.g. noble gases e.g. helium, neon or argon, and/or oxygen. USE/ADVANTAGE - (I) are used for the storage of petrol. The permeability of (I) w.r.t. petrol is reduced.

Description

Polyolefin containers sometimes have the disadvantage that they are little for the storage of certain organic liquids suitable or unsuitable, provided they contain these liquids let through, for example, fuels, such as gasoline.

However, it is already known that the permeability of containers polyolefin over such organic liquids can be improved by giving it one Exposed to fluorine atmosphere. On the strong environmental impact of this State of the art need not be discussed in more detail.

According to the invention, a method for surface modification is now provided proposed by containers of polyolefin, in which one one or more such containers a low pressure plasma in exposing a fluorine-containing gas atmosphere. Fluorine itself is not meant by the term "fluorine-containing gas" be understood.

The skilled person is familiar with the production of a low-pressure plasma sufficiently familiar. To the relevant state technology was  by way of example only referred to rides & German, Plasma technology, Carl-Hanser-Verlag 1984. Thus, the process chamber made of a durable metal, such as aluminum or stainless steel. For the generation of low-pressure plasma becomes in the vacuum under Hochfrequenzeinwirkung for example worked in the frequency range from kHz to GHz, for example in the range of 30 kHz to 10 GHz.

Usually, the containers are made of polyethylene or polypropylene. The inventive method is particularly suitable for the surface modification of polyolefin containers used for Storage of fuels such as gasoline are provided.

Examples of fluorine-containing gases are carbon tetrafluoride and / or sulfur hexafluoride, which if necessary in each case in a mixture with one or more non-fluorine-containing gases can, for example, one or more noble gases, such as helium, Neon or argon, and / or oxygen.

When using, for example, a tetrafluorocarbon / Argon mixture will be assumed that the Polyolefinoberfläche fluorinated while using a Sulfur hexafluoride / oxygen mixture additionally sulfonated becomes. In both cases one achieves a partial polarization of Surface through which the permeability of the polyolefin container especially lower than gasoline.

The invention will be explained in more detail by an example.

example 1

The following process chamber was used:

process chamber

Chamber door at the front, with lever lock, seals automatically when closing, with isolating plug (safety shutdown of the high frequency), inspection window made of special glass, diameter approx. 150 mm. Chamber flood valve with particle filter in chamber rear wall. Solenoid valves and piping made of stainless steel.
Electropneumatic shut-off valve made of aluminum, NW 40 KF on underside of chamber.
Final pressure in the chamber: approx. 2-3 × 10 ^-2 mbar.
Typical working pressure: 0.2-0.5 mbar.
Vacuum measurement by means of a capacitance load cell, MKS type Baratron, gas type independent, measuring range 10 ^-3 -10 mbar.
All flange connections used in KF and Pneurop.

External dimensions chamber construction Width | 970 mm height 1800 mm depth 960 mm

pumping equipment

Leybold-Heraeus S 65 BC with oil filter, oil separator with oil return, pump filled with Fomblinöl, pumping capacity 65 m³ / h.

Other specifications

Process chamber: 3067-G
Material: Al
Inside dimensions (mm): width 800, height 840, depth 1080
Gas inlets: 12
Extraction: chamber floor
Available chamber volume: 787 l
Gas supply: 3 gas ducts with pressure gauge for pre-pressure indication.
Precision dosing by means of "mass flow controller" (calibrated for oxygen, freon 14 and air).
Ventilation: by solenoid valve in the back of the chamber
Process control: PC-5000
High frequency generator: Magnetron, operating frequency 2450 MHz, maximum output power up to 1200 W, infinitely adjustable from the controller PC-5000, coupling of the HF-capacity
Vacuum system: 100 m³ / h gate valve pump with oil filter and oil return, 500 m³ / h Rootsblower, Fomblinöl
Vacuum measurement: MKS Baratron, capacitance measuring tube
Vacuum connection: Pneurop NW 100 LF at the bottom of the chamber
Connection values: 220/380 V 3-phase three-phase with neutral and protective conductor 3 × 32 A.
Process gases and aeration: 1/4 '' Swagelok stainless steel connection, inlet pressure 2 bar
Compressed air: 1/4 '' Swagelok connection measurement, inlet pressure 4-5 bar
Ventilation 1 ''

There was an 80 liter polyethylene tank in the process chamber at a pressure of 50 pascals and a high frequency of 2.45 GHz in the presence of a mixture of 10% carbon tetrafluoride and 90% argon (volume basis) for 5 minutes in a plasma exposed. By the mentioned treatment became the permeability of the tank for Super (Aral) reduced by 85%.

Claims (3)

1. A method for surface modification of containers made of polyolefin, characterized in that exposing one or more containers to a low pressure plasma in a fluorine-containing gas having atmosphere. 2. The method according to claim 1, characterized in that one polyethylene or polypropylene containers used, for example, containers for storage of Fuels, such as gasoline. 3. The method according to claim 1 or 2, characterized that as fluorine-containing gas tetrafluorocarbon and / or Sulfur hexafluoride optionally in admixture with a or more non-fluorine-containing gases, such as noble gas, For example, helium, neon or argon, and / or oxygen used.