DE2205450A1 - Objects with close-fitting coatings made from photolytically crosslinked ionomers and processes for their production - Google Patents

Description

HELMUT SCHROETER KLAUS LEHMANN

DIPL.-PHYS * D1PL.-INO. β MÖNCHEN 25 · LIPOWSKYSTR. IO

AMP Incorporated amp-Io

4.2.1972 S / tM / Bi.

"Items with close-fitting coatings from photolytic cross-linked ionomers and processes for their production "

From US patent specification 3,264,272 ionically crosslinked random copolymers of at least one 0 <-01efin, which contains 2 to 8 carbon atoms, and an, ß-ethylenically unsaturated monocarboxylic acid, which has a melting point of about 120 to 180 ° C ( 250 to 350 ⁰ P), have a melt index of about 0.5 to 40 g / 10 minutes and in which at least 10 % of the acid groups are neutralized by an ionizable metal salt, which are hereinafter referred to as zonomers. These ionomers combine the usual properties of crosslinked polymers with the ability to be deformed when hot, a property normally only possessed by non-crosslinked thermoplastic polymers.

These ionomers can also be crosslinked fotolytisoh in which exposing the ionomers to ultraviolet radiation.

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This photolytically crosslinked ionomer has the property to take on the original dimensions when exposed to heat. This means that an object from the ionomer, which is heated, changed in its dimensions and cooled while maintaining the changed dimensions, the original Reassumes dimensions when heated again. This property can be used to create an object to provide a tightly adhering coating of the ionomer. To do this, you bring a drill or another closed one Form from the ionomer in a dimensionally unstable form on the object and heats the ionomer, so that this with the formation of a tight »fitting coating in the dimensional stable form returns. The use of a tube or a closed shape limits the applicability of this Procedure. However, it has been found that a photolytically acidified ionomer of this type can be fused, whereby The restrictions that can be avoided by using tubular or closed fittings surrender.

One with a tight fitting coating of a photolytically crosslinked The article provided with ionomers is designed according to the invention in such a way that the coating is obtained by melting Has weld seam.

A method by which an object is provided with a tightly fitting coating of a photolytically crosslinked ionomer is carried out according to the invention in that one or more pieces of the ionomer, which is in a heat-sensitive, dimensionally unstable state, are loosely fitted Coating forms on the article, with a seam or seams between the edges of the piece or pieces, that the pieces of the ionomer are heated to weld the seam or seams and to return the ionomer to the dimensionally stable state, so that you get a tight fitting cover .

The cover can be attached on the outside or on the inside wall .

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If, for example, the lining of a tube, the heat-sensitive dimensionally unstable state is a state in which the material expands in the heat, so that when the pieces of ionomer are placed inside the object and heated, they are welded together and expand providing the pipe with a tight fitting liner. When the coating is applied to the outside and forms a shell, such as is the case with a pipe joint, the ionomer is used in a heat-shrinkable state. The envelope can be formed by wrapping a sheet of the heat-shrinkable photolytically crosslinked ionomers around the article so that the edges of the sheet overlap to form a seam, and then heating the overlapping edges to fuse them together and then heating the remainder of the sheet to shrink it onto the object. The envelope can also be formed by wrapping a tape of the photolytically crosslinked ionomers around the article so that the seam essentially screws! ¹ Strmig: runs around the object.

The welding by melting and the dimensional change can take place more or less simultaneously, or the welding can take place before or after the dimensional change.

Although the crosslinking of polymeric materials by irradiation with ultraviolet light has hitherto been carried out, the Irradiation of the polymeric material can be carried out at a time when this is in the deformed or elongated final shape exists because the irradiation destroys the melting properties of the polymeric material, making it impossible for this then to deform or extrude. The weldability of the photolytically crosslinked ionomers can also be used for production the photolytically crosslinked ionomers can be used. The presence of weldability means that the melting properties of the ionomer are not destroyed by the irradiation with ultraviolet light and that this irradiation

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_ 4 - amp-lo

can be done before deforming or extrusion. The invention "thus also relates to a process for the production of a piece from the 'ionomer, which is used for applying a closely adhering' tend coating is used on an object. According to the-.sem The process involves exposing an ionomer to ultraviolet radiation, deforming it into the piece, heating the piece while it is warm is subject to dimensional changes and with. changed Dimensions efcgskühl.t. The piece is preferably through Extrusion molded. An extruded sheet can be stretched so that it becomes heat-shrinkable.

The coatings of the invention have great value in use as protective coatings for pipes, pipelines, telephone and telegraph cables, high-pressure couplings, high-voltage cables and the like, as well as for applications in which the coating is continuously subjected to high abrasion, as is the case with welding cables, rollers is the case for drive belts and the like, and for the protection of good thermal insulators, such as fiberglass, glass foam, polyurethane foam, Calcium and magnesium silicates, asbestos and the like.

The heat sensitive piece of ionomer can conveniently be heated in place with the aid of a blowtorch take place. The heating of the ionomer leads to the formation of a shimmer or gloss on the surface of the material, indicating that the surface temperature of the material is high enough to cause welding. The heating also causes the coating to bond to the substrate in many cases.

The preferred ionomers are those in which the α-olefin is ethylene and the α, β-ethylenically unsaturated monocarboxylic acid is acrylic acid, methacrylic acid or ethacrylic acid. The ionomer should contain 20 to 30 mole percent acid, and preferably about 25 mole percent acid. Preferably at least 50 % of the acid groups are neutralized by the ionic crosslinking metal salt. The melt index of the polymeric material can be determined according to ASTM Method D-1238-57T

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and ionomers should be used before exposure to ultraviolet Light have a melt index between 1 and 10 g / 10 minutes.

The irradiation with the ultraviolet light to achieve the photolytic crosslinking of the present invention can be suitably carried out by using the ionomer in the form of disk-shaped pellets. These pellets are commercially available from EI du Pont de Nemours Incorporated under the trade name ¹¹ SUELIN ", these pellets having a diameter of about 2 to 4 mm and a thickness of about 1 to 3 mm.

After photolytic crosslinking, the pellets are quite hygroscopic and must be shielded from the atmosphere in order to avoid the absorption of atmospheric moisture, which would otherwise lead to difficult handling during extrusion. For this reason; weVden, in general, the pellets preferably directly prior to molding by extrusion or by another method to exposed _v Furthermore, makes the presence of already 1 wt -% water in the photolytically cross-linked material, the subsequent extrusion extremely difficult to do so. that when adding fillers, dyes or pigments, care must be taken that no moisture is introduced into the material. Fillers and the like can be added either as such or together with a suitable compatible carrier material. Euss is a preferred filler material because it gives the material resistance to degradation under ultraviolet radiation. Furthermore, a material that is mixed with soot has a darker color and absorbs heat more quickly than a lighter colored material «

The ultraviolet irradiation takes place vcn ^ ifspvel ψ- _x l-> xC ~ ^ ti η

the ionomer under lights hindurcliführt nnu cur 'L ι ¹ -'j »-

risat the light, a «? wavelength between 2100 and? ωΐ> A free sets. It is believed that this punishment "

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2205A50

Development leads to heterogeneous crosslinking, so that heating to a temperature of "for example about 110 ⁰ C leads to the fact that the material softens without it being hot enough to melt. The melt index of the photolytically crosslinked ionomer was increased and if so the materials are heated to melting temperatures, they change into a modified melting state. The photolytically crosslinked material shows a clear temperature difference between the point at which the fusion occurs through melting and the restoration of the original dimensional dimensions on the one hand and the melting point on the other hand not in the real sense if it changes its dimensions and is subject to welding.

The change in dimension preferably takes place when the material is extruded. The materials according to the invention are preferably extruded at temperatures of about 90 to 200.degree. The usual extrusion of ionomers has hitherto generally been carried out at elevated temperatures in the vicinity of ^ 00 ^° C. However, in the present case it is desirable to keep the thermal crosslinking that can occur when heating to the usual extrusion temperatures as low as possible . Preferably, the gap (land) of the extruder is given a minimum size so that some thickening of the material occurs after it has passed through. It has been found that pollen, with higher melting temperatures and better properties with regard to the recovery of the original dimension, can be obtained if one the thickened extruded material pulls or stretches and does not, as has been carried out so far, directly stretch the material exiting with the nozzle shape. If the stretching is carried out starting from the thickened material, one dimension is increased, preferably by 200 to 400 % . However, an object that expands in heat can also be obtained by compressing one dimension of the material loaf. 2, E-. in that in the case of an extruded pipe the ixirenir.esr * er is reduced by constricting the pipe. In this way one obtains after

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cutting and opening a foil or sheet that is expands in the heat and in the process regains the dimensions it had before the constriction.

The properties of the material according to the invention, through action from heat to change its dimensions, allow it to underlay a protective layer on a variety of substrates to apply unfavorable environmental conditions. . . Essentially, the only steps required are there in that one applies to the object a piece of the material which is oriented so that the dimensional change results in the appropriate direction and with the formation of a seam and one lets heat act on the piece, so that it regains its original dimensions and closes the seam by welding, in many cases a connection with the substrate is achieved. In general, the shrinkage force is proportional to the thickness of the piece and the degree of networking. A simple method, effectiveness to observe the dimensional change and the fusing of the leaves when heated is to observe when the surface changes from a dull appearance to a shiny appearance. This change suggests indicate that fusion has occurred.

The following examples are intended to explain the invention in more detail without, however, restricting it.

example 1

A random copolymer of ethylene and acrylic acid, which contains about 25 mol percent acid and a Has a melt index of about 2 (Surlyn A I650 from E.I. du Pont de Nemours, Inc.). Pellets or tablets of this material as were placed by vibration to form a flat layer with a layer thickness of a pellet on a silicone conveyor belt. The conveyor belt was passed under two mercury vapor lamps (Central Electric Corporation H 317), wherein

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220545O ₁

amp-lo

the tops of the pellets were 2.5 cm from the surface of the lamps. The lamps were operated at 160 volts instead of the standard 116 YoIt in order to develop ultraviolet light in the wavelength range from 2100 to 2200A. The lamps were mounted in highly polished aluminum reflectors and partition plates were placed between the lamps to ensure that each pellet received light from only one of the lamps. The lamps, lamp sockets, pellets and conveyor belt were cooled to prevent the pellets from fusing together. Movement of the conveyor belt at a speed of less than 3 * 6 m / minute (12 feet per minute) resulted in melting of the pellets, while speeds in excess of 12 m / minute ( ¹ K) feet per minute did not result in sufficient melting Ultraviolet radiation led. The speed at which the pellets are fed past the lamps is directly related to the melt index of the ionomer, with a higher speed corresponding to a higher melt index.

Immediately after the irradiation, the crosslinked ionomer pellets were introduced into an extrusion device which was kept at a temperature between 90 and 200.degree. The material was introduced through a transition piece from the round extrusion vessel into the gap of an extrusion head. Using a die head with an opening of 0.05 cm, a thick, ribbon-like sheet about 0.06 cm thick was obtained. The extruded material was stretched from the thickening on the die head to about 250 % of its original longitudinal dimensions and then cooled.

The tape was then wrapped helically around a steel tube to form a helical seam and ^{heated to 110 °} C., which resulted in the sheet resuming its dimensions before stretching and forming a tightly fitting envelope on the tube, the length of which welded while melting .wurde / i.

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Example 2

In this example an ionomer similar to that in Example 1 was used (Surlyn A 1557) but with a melt index of about 8, and in the same way as in Example 1 specified was treated. The extruded tape was used in the same manner with similarly good results.

Example 3

In this example, the procedure of Example 1 was repeated, but in this case the photolytically crosslinked ionomer with 25 % carbon black (Moneren 74X) was used, with a small amount of resin (Surlyn 1557) being used as the carrier material prior to extrusion. The furnace soot was before

^{heated to 410 °} C. for 20 hours in order to drive off any moisture contained. The mixture extruded well and showed the same handling properties as the material of Example 1.

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Claims (5)

2205A50 - ΊΟ - amp-lo claims 1. With a tight-fitting cover made of a photolytically cross-linked Article provided with ionomers, characterized in that the coating is obtained by melting Has weld seam. 2. Article according to claim 1, characterized in that that the coating is a shell with a seam welded by melt, which extends in a substantially axial direction extends along the object. 3. Article according to claim 1, characterized in that the coating has a shell welded to one by melting Is a seam that runs substantially helically around the object. A method for producing an article with a tightly fitting cover according to claim 1, characterized in that that one consists of one or more pieces of the ionomer, which is dimensionally sensitive to heat is unstable, forms a loosely fitting coating on the object, with a seam or seams present between the edges of the piece or pieces, that the pieces of the ionomer are heated to make the seam or to weld the seams by fusing and to return the ionomer to the dimensionally stable state, see above that you get a tight fitting cover. 5. A method for producing a piece to be used in the method according to claim 4 from a photolytically crosslinked Ionomers, characterized in that an ionomer is exposed to ultraviolet radiation, deformed into the piece which Piece warms while it is warm subject to dimensional change and cools it with changed dimensions. 209836/0743