DE1504779B1 - Resettable composite bodies made of polymer material and process for their manufacture - Google Patents

Description

The invention relates to resilient composite bodies made of polymer material, that of a fusible part and one at the softening temperature of the fusible Part not yet melting part exist, as well as a process for their production.

It is well known that thermal springback or resilience is understood the endeavor of deformed plastics, both thermoplastics and certain elastomers to return to their original shape when reheated. According to a known method, articles with Theimo springback are manufactured as follows : A plastic material is first extruded or otherwise brought into the desired shape.

The polymer is then crosslinked or given its properties of a crosslinked material by the action of ultraviolet rays or high energy Rays, e.g. B. a high-energy electron beam, or rays of a Nuclear reactor, or by chemical means, e.g. B. with the help of peroxides or peroxide-like Substances in which polyolefins are used. The crosslinked polymer is then heated and deformed and then "frozen" by quenching in the deformed state.

The same process can also be carried out at room temperature, a higher force is applied to deform the polymer. The deformed one Material retains its shape almost indefinitely until it reaches a temperature above its own Crystal melting point is exposed, which in the case of polyethylene about 120 "C amounts to.

Composite bodies made of polymer material with restoring properties are already known from Austrian patent specification 221 795. It is about relatively thin composite films, in which the resilient part melts relatively more easily than the other part. However, such composite bodies have no sufficiently strong connection between the individual layers, rather they can be peeled off or separated by peeling them off. Even if the Adhesion of the individual layers of the composite body is sufficient under normal circumstances, However, there is a risk that during the heat shrinkage of the resilient Partly the connection between the resilient part and the other component of the composite body tears open what the use of such composite body as effective Insulating body against moisture impaired.

The object of the invention is to create a comparatively thick-walled hollow body-shaped composite material, the layers of which are so inseparably united with one another are that they are also during the heat recovery of the resilient part do not tear apart and thus for permanent insulation even from irregular shaped objects are suitable.

According to the invention this is achieved in that both parts as nested hollow bodies are formed. their opposite Surfaces firmly connected to one another to form a uniform structure are, and that the difficult to melt part is recoverable.

The process for producing the molded parts according to the invention is characterized in that two hollow-body-shaped plastic parts are plugged into one another and are connected to form a coherent inseparable composite body that then one part of the composite body by crosslinking Made difficult to melt while the other part is kept fusible, and that finally the Composite body the resilience is bestowed by it over the softening temperature of the crosslinked part is heated. deformed at this temperature and then quenched will.

The invention makes it possible to produce resilient composite bodies to apply to other objects or to combine them with other objects in such a way that that a reliable, intimate and impermeable connection due to the proportionate fusible part is formed, which is an inseparable part of the composite body forms. Welln the composite body is heated to an appropriate temperature, in which there is a tendency to return to the original shape the relatively fusible part of the composite is simultaneously melted or softened. If the composite body is brought into a suitable position for another object, so when it is reheated it is pressed against this other object, with the relatively fusible part creates an intimate and impermeable bond with this other Object forms.

The fusible and infusible parts of the molded parts according to FIG Invention are so combined that the article obtained is an inseparable Whole forms and without destroying the connection between the two parts in this Condition remains when the article is for the purpose of springing back or returning to the original Shape is heated.

Of course, in order to achieve such an intimate connection it is necessary that the materials of the parts to be united are highly compatible with one another are. They must be joined together in a method that allows the to achieve intimate connection in particular by fusing. This is for example possible through the combination of polyethylene and polypropylene, if these are in the liquid (molten) or semi-liquid state. Preferably the parts are through Composite extrusion combined at an elevated temperature at which the material melts.

It is essential that the two hollow body-shaped parts of the composite body be combined with each other before the one part is made difficult to melt. This is done, for example, by irradiation or by chemical means.

The composite body is preferably extruded as a tube, the then irradiated, stretched and quenched in the stretched state. Further it is possible to manufacture articles according to the invention by pressing. With another Embodiment of the invention, the relatively infusible material consists of a very high molecular material, which has gel strength and the property of elastic Has memory, e.g. B. polytetrafluoroethylene. The molded parts can also with a reinforced material, e.g. B. a braid or an active ingredient provided will.

The fusible part of the composite body according to the invention can be a Outside of the composite body or any large part of the entire outer surface form. In the case of tubular articles, the fusible part can be the inside or form the outside. The composite can then be used in any desired manner be used for coating, embedding or wrapping. He will do this in a such location brought to the object that coated with it or in other United wise should be that the composite body by heating changes its dimensions so that the relatively fusible part against the object is pressed to which it is to be connected. If necessary, the composite body then heated so much that the fusible part becomes liquid. That way will a reliable, intimate and impermeable connection between the invention Article and the object to which it is to be attached. The composite body can also have a shape that corresponds to the shape of the object with which he should be connected.

Two embodiments of the invention are given below as an example described on the basis of the drawings.

Fig. 1 illustrates an embodiment in which the composite body is made by composite extrusion in tubular form; F i g. 2 shows that Product which, according to the method shown in FIG. 1 method shown is produced; Fig. 3 illustrates schematically the embodiment of the invention in which the article extruded in tubular form, irradiated, stretched and quenched, with him the property of thermal springback is imparted.

In the case of the in FIG. 1 illustrated preferred embodiment of the Invention is a composite body 1 by composite extrusion of the polymers 2 and 3 made in tubular form. The extruder 4 is only indicated schematically and can be of any type.

F i g. FIG. 2 shows the product 1 obtained after the process shown in FIG. 1 shown Process is established. It forms an inseparable whole and consists of the Parts 5 and 6, which have different properties.

Part 5 is difficult to melt and part 6 is meltable. It however, it is also possible that the fusible part forms the outside.

In the preferred embodiment of the invention, part 5 made difficult to melt by crosslinking, preferably by irradiation.

Since the irradiation takes place after the production of the composite body 1, the difficult to melt part 5 must be crosslinkable by a radiation dose that not enough to mesh part 6 to a point where it is infusible will. This can be achieved in a number of ways. For example, it is possible adjust the initial molecular weight and / or the molecular weight distribution so that that the subsequent irradiation of part 6 is not so far crosslinked, that it becomes infusible.

For example, it is known that both molecular weight and also the molecular weight distribution have a great influence on the dose that is required to cross-link polyethylene until it is infusible. Using of polyethylene it is therefore possible to achieve the desired crosslinking properties of the Parts 5 and 6 by adjusting the molecular weight properties accordingly to achieve. The limits on molecular weight expressed as melt index of polyethylene are about 0.3 or less for the difficult-to-melt part and for the fusible part at about 20 or above.

To prevent the occurrence of infusibility, so-called »Antirads« can be used. When these substances are added to polymers will prevent they chemically crosslink the polymers, for example by radical reactions. Some heat stabilizers for olefin polymers also act as strong "anti-wheels". Thus, a heat stabilizer added to the fusible part 6 fulfills two Tasks: It prevents this part from reaching the point during the irradiation in which it becomes infusible, and at the same time serves to protect the polymer against thermal degradation. Of course, other substances that do not contain antioxidants can also be used act as »anti-wheels«. For polyolefins suitable substances that at the same time as a heat stabilizer and "anti-wheel" act, for example 4,4'-thiobis- (6-tert-butylm-cresol), 4,4'-methylene bis (2-tert-butylphenol), 2,6-di-tert. -butylphenol, 4, 4,4'-butylidene-bis- (6-tert-butyl-m-cresol) and 2,5-di- (tert-amyl) -hydroquinone.

As an example of "antirads" that do not contain antioxidants are, pentabromophenol, naphthylene and copper stearate may be mentioned.

A wide variety of polymers are suitable for the purposes of the invention, e.g. polyethylene, polypropylene, polyamide, fluorinated ethylene, propylene polymers, Polyvinyl chloride, polyvinylidene fluoride, and acrylic polymers. Generally speaking all polymers that can be crosslinked by irradiation or by chemical means and to which the reset property can be given, to produce the difficult fusible part 5 can be used.

In addition, very high molecular weight materials that have the Crystal melting point in addition to having strength, can be used.

Furthermore, combinations of materials for the production of the invention Articles are used. It is essential that the combined materials create one can form such intimate connection with one another that a unified, inseparable Structure is obtained. For example, polyethylene and polypropylene can be used together be used. Other materials are also resilient elastomers, z. Modified silicone rubber, modified neoprene rubbers.

For the difficult-to-melt part of the composite body according to the invention For example, one can use a material that has a higher molecular weight has as the fusible part, or a crosslinking agent can be added to the hard fusible part, z. B. polymerizable comonomers, add. Suitable crosslinking agents are, for example Divinylbenzene. Polybutadiene, allyl methacrylate, divinyl succinate, ethylene glycol diacrylate, Diallyl fumarate, triallyl phosphate, triallyl cyanurate. These crosslinking agents favor networking at low radiation doses in the difficult-to-melt part, especially when using polyolefins and polyvinyl halides.

So it is obvious that by using an "anti-wheel" and / or by adjusting the molecular weight in the fusible part and / or by Use of a crosslinking agent and / or by adjusting the molecular weight in the difficult-to-melt part is possible to produce composite bodies which, although a Form an inseparable whole, but different melting properties in different parts exhibit. The fusible part then fulfills the task of forming a reliable one impermeable and intimate connection with an object with which the inventive Composite body connected when heated to a sufficient temperature is, while the difficult to melt part as a strong and inseparably connected envelope or underlay. It is of course possible, depending on the intended use in the fusible part, the difficult to fusible part or fillers in both parts, incorporate flame retardants, etc.

Furthermore, it is possible to have additional thermal stability and / or chemical To achieve connection by mixing or coating the fusible part of the Composite body with a material that when the composite body is heated for attachment on another object chemically cross-linked or vulcanized the fusible part.

The preferred embodiment of the method according to the invention is in Fig. 3 shown schematically. The composite body 1 is made by extrusion produced with the composite extruder 4 and then passed into the chamber 7, in the an electron generator 8 is located. With the help of rollers 9 the strand is through guided the electron beam of the generator 8. A Van der Graafseher can act as a generator Electron accelerator used with an output of 2 million electron volts will.

When using polyethylene, the radiation doses are depending on the Properties of the material between about 5 and 15 megarads.

After the irradiation, the composite body is placed in the stretching apparatus introduced. Here it is guided by feed rollers 10 to two rollers 11.

The container 12 of this apparatus contains the heating medium 13. During of the passage between the rollers 10 and 11, the strand is under the action a pressure difference, e.g. from overpressure or underpressure, in order to stretch it. At the The extended strand exits the heating medium 13 through a cooling nozzle 14 quenched and then by a suitable device, e.g. B. a role added.

Example Using the methods shown in FIG. 1 composite extrusion press shown becomes a hard-to-melt outer part, consisting of 59.850 / 0 polyethylene high Density (melt index 0.6), 19.40 o / o polyethylene of medium density (melt index 1.0), 70% antimony oxide, 2.4% triallyl cyanurate, 0.4 01o PbO.

PbC2 wo (COO) 2 2H, O, 0.8 0 / o 4,4'-thiobis- (6-tert.-hutyl-m-cresol), 0.2 o / o petrolatum, 0.1 o / o finely divided silica and 9.85 tetrabromophthalic anhydride, together with a fusible inner part, consist of 17.56 kg of polyethylene low density (melt index 22), 3.84 kg low density polyethylene (melt index 200 = L 30), 1.13 kg of antimony oxide and 0.226 kg of 4,4'-thiobis- (6-tert-butyl-m-cres Dl), extruded into a one-piece, inseparable tube. This hose has an inner diameter of 1.04 mm, a fusible part with a wall thickness of 0.99 mm and a difficult-to-melt part with a wall thickness from 1.98 mm. The tube is then powered with an electron accelerator irradiated from 2 million electron volts up to a dose of 10 megarads. Of the The irradiated tube is then stretched in a bath at a temperature of 171C to such an extent that that the inside diameter was 8.4 mm. The hose is under a pressure of 0.7 kg / cmh on its inside and a pressure of 0.56 kg / cm2 on its outside at a speed of 1.5 m / min. passed through the device. The hose leaves the bath through an opening 6.4 mm in diameter and is passed through a cooling nozzle quenched from 10.7 mm inner diameter.

The 4,4'-thiobis- (6-tert-butyl-m-cresol) is difficult to melt Partly used as an antioxidant.

The composite body according to the invention can be in the most varied of forms manufactured and used in all forms in which objects are coated, to be coated or bonded.

The articles can be made to move when in use expand or contract from heat. For example, if you use the fusible Part as the outside of a hose and the hard-to-melt part as its Inside, the composite body can be used to line pipelines will.

From the numerous and diverse application possibilities of the composite body may be mentioned: connection of two or more metal pieces and / or Plastic parts, connection of two or more hoses or posts or theirs Combinations, attaching swivel castors to chair legs, sealing bottle closures or lids on other containers, formation of moisture-resistant a a coatings on one or more objects, formation of chemically resistant coatings on one or more objects and coating in general. Furthermore can the composite bodies are used for splicing, encasing, etc. electrical parts will.

Claims (15)

Claims: 1. Resilient composite bodies made of polymer material, consisting of a fusible part and one at the softening temperature of the fusible Part not yet melting part, characterized in that both parts as Hollow bodies lying one inside the other are formed, the opposite of which Surfaces firmly connected to one another to form a uniform structure and that the part that is difficult to melt is resilient. 2. Composite body according to claim l, characterized in that. let that both Parts are tubular. 3. Composite body according to claims 1 and 2, characterized in that that fusible and difficult to fusible parts are the same or different chemical ones Have composition. 4. composite body according to claims 1 to 3, thereby gekenllzeic'lllet, that the fusible part consists of a thermoplastic polymer. 5. Composite body according to claims 1 to 4, characterized in that there ! 3 the hard-to-melt part made of a cross-linked thermoplastic polymer consists. 6. Composite body according to claims 1 to 5, characterized in that that fusible and difficult to fusible part made of polyoleiins, preferably made of Polyethylene. 7. Composite body according to claims 1 to 6, characterized in that that fusible and difficult to fusible parts made of the same material are different Molecular weight and / or molecular weight distribution exist. 8. Composite body according to Claims 1 to 7, characterized in that that the fusible part contains a radiation protection agent, preferably at the same time Is heat stabilizer. 9. Composite body according to Claims 1 to 8, characterized in that that the difficult to melt part contains a crosslinking agent. 10. Composite body according to claims 1 to 9, characterized in that that the inner part is fusible. 11. Composite body according to claims 1 to 10, characterized in that that the fusible part consists of a material which is at or near the reset temperature of the resilient part softens. 12. Process for the production of resilient composite bodies made of polymer material according to claims 1 to 11, characterized in that two hollow body-shaped Plastic parts in one put together and become a cohesive inseparable Composite body are connected, that then one part of the composite body through Crosslinking is made difficult to melt while the other part is kept meltable is, and that finally the composite body is given the resilience, by heating above the softening temperature of the crosslinked part, in this case Temperature is deformed and then quenched. 13. The method according to claim 12, characterized in that the two fusible parts are united by composite extrusion. 14. The method according to claims 12 and 13, characterized in that that the difficult-to-melt part by the action of high-energy rays or ultraviolet rays is networked. 15. The method according to claims 12 and 13, characterized in that that the difficult to melt part is crosslinked chemically.