DD280772A1 - PROCESS FOR SURFACE FLUORATION OF POLYMERS - Google Patents

Abstract

The invention relates to a process for the surface fluorination of polymers. It is applicable in the plastic processing industry. According to the invention, fluorinated barrier layers are produced on polymers by exposing the polymer surface to a gas mixture of fluorine, oxygen and an inert gas. The fluorination is carried out as gas-phase off-line fluorination under static conditions until the fluorine content of the surface is at least 100 mg / cm 2.

Description

Field of application of the invention

The invention relates to a process for Oberflächenfiuorierung of polymers. The invention is applicable in the plastic processing industry.

Characteristic of the known state of the art

The use of plastic containers, in particular polyethylene, for non-polar liquids is only possible to a limited extent due to the relatively high permeation losses.

To eliminate this disadvantage, methods for the surface modification of the polymers are described, wherein the surface fluorination represents the technically most advantageous and most advantageous variant.

In DE-OS 3511743 a process for Oberflächenfluorieru ·. g of polymers described. The interior surfaces of plastic containers are fluorinated under static conditions in a gas phase off-line fluorinator. It is at Temperp 'ren from 20 to 80 ⁰ C and pressures of from 1 to 4 × 10 ⁴ Pa worked. The treatment gas consists of 3 to 10 vol .-% fluorine and 90 b 's 97Vol .-% inert gas. The exposure time is 1 to 15 minutes.

The essence of this process is the use of oxygen-free fluorine. As an upstream process stage is ¹ :

either the direct representation of oxygen-free fluorine or the separation of fluorine-oxygen mixtures necessary.

Both are technically complicated and expensive. In addition, in the implementation of fluorination air exclusion must be ensured, which makes the technology of the process complicated.

Substantial exclusion of oxygen from the flooding of polymer surfaces is considered necessary in US 4,491,653 because the oxygen on the surface of the polymer causes oxidation promoted by the presence of fluorine. This results in the formation of unstable fluorine-containing groups which have less resistance to external influences such as water or temperature changes.

Object of the invention

The object of the invention is to produce fluorinated surfaces on polymers by a simple and inexpensive process, which surfaces are to be used in particular as barrier layers against umolare liquids.

Explanation of the essence of the invention

The invention has for its object to develop a process for Oberflächenfluorierung of polymers, which is characterized by technological simplicity and waiver of technically complicated precursors and be produced by the usable as a barrier against non-polar liquids, resistant to acids and alkalis polymer surfaces. According to the invention, this object is achieved in that the surfaces to be treated are exposed to a fluorine and an inert gas-containing gas mixture having an oxygen content of up to 10 vol .-%. Nitrogen is preferably used as the inert gas. The Huorierung takes place up to a fluorine content on the Polymeroberflächo of at least lOOnmg / cm ² . The fluorination is carried out as gas-phase off-line fluorination under static conditions, preferably at room temperature.

The gas mixture has a total pressure of 10 ⁵ Pa. In addition to the oxygen, it contains about 40% by volume of fluorine and an inert gas, for example nitrogen. The oxygen content is preferably below 5% by volume. A fluorination up to a fluorine content on the polymer surface of 200 to 400 pg / cm ^{2 is} advantageous. With the method according to the invention, even in the presence of oxygen in the treatment gas, surfaces are obtained which, for example, can be used as barrier layers for non-polar liquids.

The process of the invention is particularly advantageous because it starts from oxygen-containing fluorine and thus eliminates the costly and expensive provision of oxygen-free fluorine and the exclusion of air during fluorination. Surprisingly, despite the presence of oxygen, no unstable fluorine-containing groups are formed on the polymer surface, so that the surfaces are resistant to acids and lyes.

Ausfühi ungsbelsplele

1. Inoinem Monel pressure reactor, which can be disassembled via a flange with PTFE seal for charging, a 30 pm thick high-pressure polyethylene film is inserted. Valves are used to regulate access to the vacuum or gas metering section. Before fluorination, the reactor is evacuated for 30 minutes. After separation of the vacuum section, a 2.5% by volume of oxygen-containing fluorine-nitrogen mixture (about 40% by volume of fluorine) is metered into the reactor in 10 minutes. A manometer is used to adjust the internal pressure of the reactor of about 10 ⁵ Pa. It is fluorinated at room temperature for another 50 minutes. After fluorination, the reactor is evacuated for 15 minutes and then vented with nitrogen.

The mass increase is 230pg / cm ² foil.

The permeation losses of n-pentane are reduced by a factor of 100 for the fluorinated film and also for the film pieces treated after the fluorination with 0.1 M NaOH or HCl.

2. The structure of the reactor proposed in DE-OS 3511743 was used for the fluorination of the inner surfaces of 100 ml high-pressure polyethylene containers.

The simultaneous evacuation (30 min) of container and reactor interior follows the parallel loading of the container interior with described in Example 1 fluorine-nitrogen-oxygen mixture and the reactor interior with nitrogen. At room temperature and about 10 ⁵ Pa gas pressure is fluorinated for 60min. After fluorination wc: evacuated the reactor and vessel simultaneously for 15 min and then vented with nitrogen. The mass increase is 240ug / cm ² container inner surface.

The permeation losses of n-pentane are for the fluorinated container and after the fluorination with 0.1 M NaOH or HC! treated container lowered by a factor of 100.

Claims (3)

1. A process for the surface fluorination of polymers, in which the surfaces of the polymers for fluorination are exposed to a gas mixture containing fluorine and an inert gas, for example nitrogen, and the fluorination is carried out under static conditions as gas-phase off-line fluorination, characterized by the gas mixture has an oxygen content of up to 10% by volume and the fluorination is carried out to a fluorine content of at least 10 (g / cm ²⁾ on the polymer surface. 2. The method according to claim 1, characterized in that the oxygen content in the gas mixture is less than 5%. 3. Process according to claims 1 and 2, characterized in that the fluorination is carried out to a fluorine content on the polymer surface of 200 to 400μg / cm ² .