CS224651B1 - Tuve made of plastic - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plastic pipe for hot pressurized water distribution.

Hitherto known hot water pressure pipes are made predominantly of metallic materials, and cased plastics such as polyethylene, polypropylene and their copolymers, polyvinylcliloride and its copolymers based on vinyl chloride, are thermoplastic and

224 651

Temperatures around 80-100 ° C soften and are unstable in shape. Increasing shape stability at elevated temperatures implies the introduction of precise bonds into thermoplastic materials. This can be accomplished according to the prior art by thermal decomposition of peroxides or their radical sources or irradiation with high energy radiation. But methods allowing the use of mass-produced thermoplastics to produce dimensionally stable hot water pressure pipes are costly and technologically demanding. This prevents the massive use of easy-to-process thermoplastic materials to produce high-quality and reliable hot water pressure pipes.

These drawbacks are eliminated by a plastic tube for hot, pressurized water distribution. It consists of a thermoplastic polymer, such as linear and branched polyethylene, polypropylene, copolymers and terpolymers of ethylene and mixtures thereof, chemically crosslinked by grafting organometallic compounds with at least one hydrolysable functional group or atom and at least one unsaturated functional group on chains polymers followed by crosslinking under the action of moisture of the hydrolyzable groups.

The invention makes it possible to obtain cross-linked thermoplastics on an existing apparatus for their conventional processing in the form of tubes whose shape stability at elevated temperatures is sufficient for the pressure distribution of hot water.

224 651

The chemically crosslinkable material can be processed on conventional types of plastic extrusion lines and the actual crosslinking occurs after the thermoplastic material has been formed into a final shape.

Chemical cross-linking preferably utilizes organometallic, for example organosilicon or organotitane, compounds containing at least one hydrolysable functional group or atom and at least one unsaturated functional group capable of reacting with free radicals on an organic thermoplastic polymer.

By utilizing radical reactions, these compounds are grafted onto polymer chains. For example, grafting occurs when the polymer is kneaded at elevated temperatures in a mechanochemical manner, optionally in the presence of free radical sources in the chain.

Unsaturated groups of organometallic compounds then react with these free polymer radicals. The hydrolyzable groups of the organometallic compounds, for example the alkoxy groups grafted on the polymer chain, then slowly react spontaneously in the presence of moisture or rapidly in the presence of hydrolysis catalysts to form cross-links between the linear polymer chains. This process can also be accelerated by exposing the material to a humid environment at elevated temperatures. The introduction of cross-links into the initially thermoplastic polymer results in a change in properties, particularly in the temperature range above the melting point of the thermoplastic materials.

- 4,224,651

In the crosslinked state, the originally thermoplastic polymer behaves like rubber and increases its shape stability. By suitable selection and dosing of raw materials and technology, a material with a high content of insoluble crosslinked material can be prepared which exhibits a considerably increased dimensional stability at temperatures in the vicinity of 100 ° C, i.e. in the upper temperature range required for contact with hot water.

In the described manner, transverse rates may advantageously be introduced into polyolefins such as linear polyethylene, branched polyethylene, linear and branched copolymers and terpolymers of ethylene, ethylene propylene rubbers and mixtures of said polymers, which can be used to prepare the tubes of the invention.

Example

The molten linear polyethylene is mixed with 4.5 wt.% Vinyltriethoxysilam and 0.15 wt.% Dicumyl peroxide in a heated kneader at 150 ° C and processed to a granulate. This material forms component A of the system. The second component B is prepared by homogenizing 0.1% by weight of dibutyltin dilaurate with molten linear polyethylene, also in the form of a granulate. After mixing the component A and the component B in a ratio of 2: 1 and homogenizing in an extruder screw, a tube of, for example, 25.4 mm (inner diameter) 33.3 mm (outer diameter) is formed. After cooling, the tube is allowed to spontaneously intensify by exposure to atmospheric humidity for 8 weeks. or accelerated in steam (e.g., 12 hours at 110 ° C).

After cross-linking, a material with an insoluble content of greater than 60% is obtained which ensures the dimensional stability of the pipe even at a temperature of 100 ° C.

Claims (1)

Plastic pipe for hot pressurized water distribution, consisting of a thermoplastic polymer such as linear and branched polyethylene, polypropylene, ethylene copolymers and terpolymers and mixtures thereof, chemically crosslinked by grafting organometallic compounds with at least one hydrolysable functional group, or atom and at least one unsaturated functional group on the polymer chains, followed by crosslinking under the action of moisture of the hydrolyzable groups.