DE1084175B - Process for combining polyolefins with macromolecular substances - Google Patents

Description

GERMAN

A firmly adhering printing, gluing or other type of coating of polyethylene and its homologues is not easily possible due to the special molecular structure of these high polymers. As is well known, these polyolefins are made up of linear or branched carbon chains, the macromolecules of which do not contain any chemically bonded polarizable atoms or groups of atoms which, due to strong electrical (intermolecular) forces, close to related or dissimilar plastics, such as those contained in paints or adhesives, to the waxy surface to bind. In addition, all technical articles made from these high molecular weight hydrocarbons have a very smooth, practically pore-free surface, which also makes it difficult to anchor prints, adhesives and other Kuhststoffschichten. To improve the surface adhesion, a number of processes have been developed for these macromolecular substances, with the aim of applying a physical, physico-chemical or chemical pretreatment (flame, electron bombardment / radiation, electrical gas discharge, oxidation, halogenation) to the surface to be coated modify. In all of the methods used so far, this modification is brought about by the addition of palarizable atoms or groups of atoms (or ⁼ radicals with permanent dipole moment) to the hydrocarbon chains of the material surface. The essential feature of the better adhesion achieved in this way, however, is that it is achieved through the polarity of the pretreated surface, i.e. only through secondary valence forces. However, this pretreatment mostly affects the weldability and heat sealability to a greater or lesser extent. A number of processes are also known (British patents 659 958, 619 905, 597 833, USA patents 2,528,523, 2,455,910) in which the macromolecules of the high polymer are crosslinked by adding radical formers to the thermoplastics to be crosslinked is achieved by chemical means. All of these processes use the property-changing crosslinking within the high polymer body in order to favorably influence the heat resistance and solubility of the polyolefins.

It has now been found that you can combine polyolefins with macromolecular substances by the polyolefins coated with the macromolecular substances in the presence of known ones Radical formers subjected to a known radical-inducing treatment.

The polyolefins to be coated according to the invention can be made from high pressure or low pressure polyolefins Process for combining polyolefins with macromolecular substances

Applicant:

Farbwerke Hoechst Aktiengesellschaft

formerly master Lucius Sd Brüning,

Frankfurt / M., Brüningstr. 45

Dipl.-Ing. Dr. Alfred Hermann Grimminger,

Frankfurt / M.-Hachst,
has been named as the inventor

exist that were manufactured by processes such as those in Raff - Allison, "Polyethylene", 1956 (P. 72ff.). Such low pressure polyolefins are z. B. referred to as Ziegler polyolefins and can be made from ethylene, propylene, butylene, or mixtures of these olefins.

The macromolecular substances with which the above-mentioned polyolefins are coated can the same polyolefins mentioned above or other macromolecular substances, such as. B. polyvinyl chloride or polyvinyl acetate.

Radical formers known per se which can be used in the process according to the invention are, for. B. peroxides, perazides, hydrazine or its derivatives. The radical formers mentioned are either applied to the polyolefin together with the macromolecular substance, ζ. B. by brushing or spraying a solution or dispersion of the radical formers. They can also be applied to the polyolefin prior to coating. If necessary, however, the radical formers can also be applied subsequently by using the coated polyolefins ζ. B. immersed in a solution or suspension of the radical generator. The radical formers then migrate into the interior of the composite body and, in the subsequent treatment that triggers radicals, lead to a firm bond between the two layers through main valence forces.

In all of the above-mentioned embodiments, the treatment which triggers free radicals is carried out, which is known per se (e.g. by heating or irradiation) after the coating has been carried out.

In this way it is ensured that the radicals, some of which are quite short-lived, also form the main valence can operate between the layers to be connected.

009 547/241

As a result of the known measures, the macromolecules inside the macromolecular network were indeed networked To reach the substance, however, the radicals occurring on the surface could not main valence bonds press more as they are converted after about 1 minute due to saturation and a possibly applied layer can no longer be bound by main valence forces. One The prerequisite for the method according to the invention is that the layer application and the base material are as intimate as possible Contact (molecular distance) with each other. Since the inventive method without can be designed continuously, its technical application is economically feasible. Even the weldability and heat sealability of the treated plastic is not impaired.

The inventive method can be z. B. when printing or gluing polyolefins carry out.

The drawing shows the technical implementation of the method according to the invention during printing of plastic films. The film wound onto the roll 1 is printed on by the roller 2 and passed through it then a bath 3 to fix the print, which contains the radical generator, for example a peroxide. Drying can take place between printing and bathing z. B. be done by means of an infrared heating section, which is not shown in the drawing. The the chemical The heat treatment that triggers the reaction takes place at 4. The printed film is then placed on the roll 5 wound up.

example

A low pressure polyethylene sheet is built up with a known polyvinyl chloride based one Printed pigment varnish and then dried. After a subsequent one-time immersion treatment in a 2 to 5 mol% solution of benzoyl peroxide in benzene, the duration of which depends on the thickness depends on the paint layer, and varied between 0.5 and 10 minutes in these tests, the film printed in this way was placed in a drying cabinet at temperatures between 100 and 115 ° C Thermally post-treated for 15 to 30 minutes. It was found here that the paint adhesion achieved depends on the duration and temperature of the post-treatment. The optimal one that can be achieved in this way Adhesion is so great that the printing ink neither with the fingernail (fingernail test) nor through a commercially available adhesive strip pressed onto the colored lacquer must be pulled off. Also by wrinkling and the print cannot be removed from the film by rubbing.

Claims (3)

Patent claims: 1. A method for connecting polyolefins with macromolecular substances, characterized in that that the coated with the macromolecular substances polyolefins in the presence of known radical formers of a known radical-inducing treatment subject. 2. The method according to claim 1, characterized in that the radical formation by heating is triggered. 3. The method according to claim 1, characterized in that the radical formation by irradiation is triggered. 1 sheet of drawings © 009 547/241 6.