HU203124B - Process for producing ethylene-polymere- based laminated product of improved heat-stability and having felxible adhesive layer - Google Patents

Abstract

The present invention relates to a process for producing an ethylene polymer-based laminate product having a high temperature-resistant elastic layer. The product is suitable for the production of insulating, protective covers. The process according to the invention is characterized in that a heat stabilizer of 0.3 to 1.5 mm thickness and optionally a polyethylene or ethylene co-or terpolymer carrier strip or plate containing another additive is irradiated with an electron beam of 40120 kGy until a gel content of 30-50% by weight is reached. For the pre-cured strip or plate, an adhesive layer of 0.1-1.5 mm thick ethylene / acrylic acid co-or terpolymer containing 1-40% by weight comonomer is deposited, and the resulting two-layer product is crosslinked by 10-40 kGy electron beam in the adhesive layer to a gel content of 525% by weight. EN 203 124 A Scope of the description: 8 pages -1-

Description

FIELD OF THE INVENTION The present invention relates to a process for producing an ethylene polymer based laminate having an elastic adhesive with a high heat resistance. The product is suitable for the production of insulating, protective coverings.

It is known that plastics, including polyethylene and polyethylene derivatives, are widely used for corrosion protection and electrical insulation of metals. For example, plastic-based tapes and films are used to form protective sheaths for pipelines, usually by winding.

These tapes or films generally consist of at least two layers: a support layer and an adhesive layer. The carrier layer for strength properties is most often made of polyvinyl chloride, polyethylene, polypropylene or various copolymers thereof. Adhesive layers are generally thermoplastic polymers, blends of rubbers and various modifiers such as bitumen. It is a basic requirement for the adhesive layer to have sufficient adhesion to both the substrate and the surface to be protected. Another requirement is, in general, sufficient elasticity even at lower temperatures.

The most commonly used heat-melt - so-called. A common feature of hotmelt adhesives is that they are bonded to the substrate only by adhesion, i.e. secondary chemical bonds, and at temperatures above 60-100 ° C, their viscosity quickly decreases and practically loses their bonding freedom. These materials may not be used at higher operating temperatures, such as protecting district heating pipes, or only under special measures. Their cold resistance is also limited: at -20 'C they usually become brittle and brittle.

One of the state-of-the-art variants of tape-shaped protective coatings is a cross-linked polyethylene-based, heat-shrinkable substrate. However, the adhesive layers in the known products are almost exclusively heat-meltable adhesives which are soft at 90-150 ° C at the shrinkage temperature. Their resistance to solvents is generally poor.

Japanese Patent Application Laid-Open No. 86,264,079 discloses an adhesive tape in which a polyimide or polyamide supported polysiloxane layer is applied and the associated system is crosslinked by electron beam. This adhesive is not a heat-shrinkable type.

Heat-shrinkable tapes provide better protection than the above wrapping tapes.

One of the typical applications of heat-shrinkable tapes is the post-shielding of the welds in the pipelines. In this case, a suitably sized piece of shrinkable tape is applied to the tube portion to be protected by overlapping the ends and endlessly with a glass fiber reinforced bond sheet provided with a special adhesive. The special adhesives of the known products used as binding sheets are in all cases heat-meltable polymers, in particular expensive polyamides or polyesters. Although their softening temperature and melt viscosity are relatively high, special care must be taken when shrinking with heat so that the bond will withstand the sliding stress created by the shrinking tape.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method of forming a laminate of a substrate and an adhesive polymeric layer by combining them which exhibits excellent adhesion between the layers and adhesion of the adhesive to the surface.

The present invention is based on the discovery that certain ethylene copolymers and terpolymers containing polar chemical groups, such as carboxylic and / or acrylate ester groups, can be crosslinked by high-dose irradiation at a given dose so that their polar groups remain virtually intact, i.e. retain heat-activated, their properties, while losing their meltability and becoming rubber elastic at temperatures above their crystallization.

According to our experiments, such materials e.g. ethylene-acrylic acid copolymers and ethylene-butyl acrylate, acrylic acid-based copolymers containing from 10 to 40% by weight of comonomer in addition to ethylene. They have a melt index (MFI 190 / 2.16) of 5-30 g / min. range.

It has been found that when the carrier layer, which may be a polyethylene, ethylene copolymer or terpolymer, is pre-cured to a gel content of 30-50% by weight with a radiation dose of 40-120 kGy, it is combined with an ethylene acrylic or ethylene acrylic acrylate co irradiating the two layers together with a radiation dose of 10-40 kGy so that the top layer gel content is 5-25% by weight to provide an optimal coating system.

It is then achieved that the carrier and adhesive layer adhere so well that they cannot be separated even above their melting temperature, while still having excellent adhesion properties.

Namely, if the gel content of the adhesive layer increases to more than 25% - that is, a higher degree of crosslinking - the adhesion properties will deteriorate.

The carrier layer after the two crosslinking shows optimum physical properties at 40-70% by weight of the gel.

The essence of the process according to the invention is therefore to combine the two sheets or films of different chemical compositions, the advantageous properties of which are achieved by curing the two layers at different radiation doses to achieve different gel contents.

A 60-100% longitudinal stretch of polyethylene or ethylene copolymer or terpolymer strip containing a heat stabilizer of 0.3-1.5 mm thickness is applied per substrate layer.

The ethylene copolymer or terpolymer is preferably ethylene / vinyl acetate, ethylene / butyl acrylate copolymer or ethylene (propylene) norbomene terpolymer.

The adhesive layer is 0.3-1.5 mm thick. According to the invention, ethyl 21 containing 10-40% by weight of comonomer

The butylene acrylate polymer of len / acrylic acid or ethylene (acrylic acid) is used in the adhesive layer.

Thus, the present invention provides a process for the production of an ethylene polymer based laminate having a high heat resistance and an elastic adhesive layer.

The process is characterized in that a polyethylene or ethylene copolymer or terpolymer support strip or plate containing 0.3-1.5 mm thick stabilizer and optionally other additives is irradiated with 40-120 KGy electron beam to a gel content of 30-50 wt. an ethylene / acrylic acid co-polymer or terpolymer containing from 10 to 40% by weight of a pre-crosslinked tape or sheet with a thickness of 0.3 to 1.5 mm was deposited, and the resulting bilayer product was crosslinked by 10-40 kGy electron radiation, 5-25% by weight in the adhesive layer. until gel content is reached.

The carrier sheet is preferably made of polyethylene or polymer of ethylene / vinyl acetate, ethylene / butyl acrylate, ethylene / propylene / norborene. The combination of the carrier and the adhesive layer is preferably accomplished by calendaring.

The resulting product has excellent adhesion to metal or plastic surfaces and can be used over a wide temperature range.

For example, the product forms a high-strength, non-corrosive, stress-resistant, insulating casing for use on a steel tube preheated to 200-220'C, overlapping by about 10 mm, over a continuous operating temperature range of -55-1-120'C.

By selecting, combining, modifying polymeric starting materials from a particular range, and adding additives, reinforcing materials, the mechanical, chemical and electrical properties of the product can be substantially controlled according to the application.

Advantages of the laminate produced by the process of the invention are as follows:

Excellent adhesion to metal and plastic surfaces.

After cooling, the overlap on the coated surface is minimal. It behaves as a homogeneous material when used with a bilayer product.

The process of the present invention is illustrated by the following examples:

Example 1

A 0.8 mm thick core strip is made from a low temperature, heat stabilized polyethylene [density: 0.922 g / cm, according to ASTM D 1505, melt index (190 / 2.16): 0.3 g / 10 min, according to ASTM D 1238] having a longitudinal shrinkage of 65% after relaxation at 130 ° C.

The base tape was obtained from a linear electron accelerator

It was irradiated with an electron beam of 1.5 MeV at a dose of 45% gel. This corresponds to an absorbed dose of 80 kGy. The shrinkage of the strap is reduced to 28% after repeated relaxation.

The irradiated backing tape was laminated with the aid of the above sheet production line to a total of 20% by weight of a comonomer of ethylene (butyl acrylate acrylic acid terpolymer [density: 0.925 g / cm, ASTM D 1505, melt index (190 / 2.16): 19 g / 10min, ASTM) D 1238, softening point: 92 'C. The outlet temperature is 170' C, and the calender roll temperature is 70 ° C.

The double-layer tape is then irradiated again at a dose of 20 kGy with the above apparatus, resulting in a 22% shrinkage of the tape and a gel content of 12% by weight of the adhesive layer. The irradiated adhesive tape cannot be separated by physical methods even when hot.

The resulting bilayer tape is machine-wound onto a 200 ° C preheated, sandblasted steel tube with a 15 mm overlap. After complete cooling, overlaps in the overlaps average 1 mm. The peel strength measured on the pipe according to DIN 30 672 is 190 N / 25 mm on average at room temperature. The same value at 20 ° C is 20N / 25 mm, the adhesive layer breaks apart in the material.

A control experiment is also carried out by making a tube casing from the laminate without the need for a second irradiation. In this sample, an overlap of an average of 6 mm overlaps is observed after complete cooling. The measured peel strength at room temperature averaged 185 N / 25 mm, whereas at 100 ° C the same value was only 8 N / 25 mm. When peeled, it breaks in the material of the adhesive layer.

As a next control experiment, the original laminated tape is irradiated on the apparatus described above as a second irradiation at a dose of 60 kGy which results in a 28 wt% crosslinking of the adhesive layer while reducing the shrinkage of the tape to 18%.

Measured in the same way as pipe insulation, the peel strength at room temperature averages only 45 N / 25 mm and the adhesive layer separates from the target tube surface.

Example 2

An ethylene-acrylic acid copolymer containing 15% by weight of comonomer was extruded on a base strip extruded, irradiated and of the same material quality as described in Example 1 [density: 0.935 g / cm ^{3 according to} ASTM D 1505, melt index (190 / 2.16): 15 g / 10 min, according to ASTM D 1328, softening point: 99 ° C, outlet temperature 175 ° C, calender temperature 75 ° C, adhesive layer thickness 0.7 mm.

The bilayer is then irradiated a second time at a dose of 25 kGy, whereby the longitudinal shrinkage of the tape is 21% and the adhesive layer 13% by weight of gel.

The two-layer tape thus obtained cannot be separated by physical methods even when hot.

The double-layer tape is machine-wound onto a sandblasted steel tube preheated to 200 ° C with a 15 mm overlap. After complete cooling, the overlap of the overlaps does not exceed 1 mm on average.

The pipe has a peel strength according to DIN 30 672 of 175 N / 25 mm on average at room temperature. When peeled, the adhesive layer separates from the steel tube and does not break in its material. The peel strength is 32 N / 25 mm at 100 ° C, and the adhesive layer breaks in the material upon separation.

HU 203 124 A

As a control, a tube cover was prepared from a double-layered strip without a second irradiation, but in the same manner as above. In this sample, the average overlap slip after complete cooling is 5 mm. The peel strength is 170 N / 25 mm on average at room temperature and is not separated from the steel tube when the adhesive layer is separated. Measured at 100 ° C, the peel strength is an average of 15 N / 25 mm and breaks in the material of the adhesive upon separation.

Example 3

From a heat-stabilized 9% monomeric ethylene vinyl acetate copolymer [density: 0.926 g / cm ³ , ASTM D 1505 melt index (190 / 2.16): 3.0 g / 10 min, according to ASTM D 1238]. Sheet metal extruder line

A base band of 0.8 mm thickness is prepared which has a longitudinal shrinkage of 70% after relaxation at 130 ° C.

The base tape was obtained from a linear electron accelerator

It is irradiated with an electron beam of 1.5 MeV at a dose of 92 kGy, resulting in a gel content of 42% by weight. The shrinkage of the tape after irradiation is 30%.

The irradiated tape was coated with the aforesaid plate production line with a total of 20% by weight of a terpolymer of ethyl (butyl acrylate) acrylic acid (density: 0.925 gr / cm ³ , according to ATSM D 1605, melt index (190 / 2.16): 19 gr / 10 min, according to ASTM D 1238, softening point: 92 ° C]. Layer thickness: 0.7 mm.

At meal P., the outlet temperature is 170'C and the calender roll temperature is 70'C.

The bilayer tape is then irradiated at a dose of 20 kGy with the apparatus described above. At this time, the gel content of the adhesive layer was 12% by weight and the band shrinkage was 2% after relaxation. After the second irradiation, the two layers cannot be separated by physical methods, even when warm.

The resulting bilayer tape is machine-wound onto a 200 ° C preheated, sandblasted steel tube with a 15 mm overlap. After complete cooling, an average of 1 mm of overlap is observed at the overlaps.

The tube has an average peel strength of 215 N / 25 mm measured at room temperature in accordance with DIN 30 672. When peeled, it breaks in the material of the adhesive layer. The peel strength, measured at 100 ° C, is 22 N / 25 mm.

In a controlled manner, tubular insulation is made from the laminate base strip but without irradiation of the adhesive layer as described. After the tube has completely cooled, an overlap of 6-7 mm is observed on the overlaps. The peel strength is reduced to 195 N / 25 mm at room temperature, and to 8 N / 25 mm when measured at 100 ° C. In both cases, it is torn in the material of the adhesive layer upon separation.

As a second control sample, the original layered base tape was irradiated at a dose of 65 kGy, resulting in a gel content of 28% by weight in the adhesive layer and a 20% shrinkage of the tape.

In the same way as above, we make pipe insulation from the tape. After complete cooling, the overlaps do not slip, but the peel strength at room temperature is reduced to 42 N / 25 mm, and upon separation the adhesive layer is separated from the steel tube wall.

Example 4

From a low density polyethylene [density: 0.922 g / cm ³ , according to ASTM D 1505, melt index (190 / 2.16): 0.3 g / 10 mm, according to ASTM D 1238] After relaxation to 130 C, an average of 41%.

The core band is irradiated on a linear electron accelerator with 1.5 MeV energy at a dose of 105 kGy. This dose produces a gel content of 43% by weight of the base tape, and the longitudinal shrinkage of the base tape is reduced to an average of 8%.

The base strip thus obtained was laminated with the aid of the aforementioned sheet-making line to a ethylene butyl acrylic acrylic acid thermopolymer containing a total of 20% by weight of comonomer [density: 0.925 g / cm ³ , melt index according to ASTM D 1505 (190 / 2.16): 19 g / 10 min. D 1238, softening point 92 ° C]. The outlet temperature is 176 ° C, the calender temperature is 68 ° C, and the adhesive layer is 0.7 mm thick.

The bilayer tape is then irradiated with a dose of 32 kGy with the above electron accelerator which produces a gel content of 15% by weight in the adhesive layer. At the same dose, tape shrinkage is reduced to an average of 3%. After irradiation, the two layers cannot be separated by physical methods, even when warm.

The resulting bilayer tape is cut into a 100 * 50 mm sheet. A shrinkable corrosion protection tape is placed over a diameter 100 mm metal-clean tube 30 mm overlap, and a double-layer adhesive sheet of the above size is pre-heated and the adhesive surface is preheated to 60 ° C. After inserting the bonding sheet, a shrinking operation is performed along the tube rim. During shrinkage, the bonding sheet made by the process of the invention holds the two ends of the corrosion protection tape firmly together, without slipping, although the material temperature reaches 150 ° C during operation.

After complete cooling, the displacement of the bonding sheet does not exceed 2 mm on average. The peel strength measured on polyethylene at room temperature averaged 152 N / 25 mm.

As a control, a 100 x 50 mm binding sheet is made from a double-layer but unirradiated adhesive layer prepared as described in the example. Also, a metal tube with a 100 mm diameter metal surface is covered with a shrinkable corrosion protection tape overlap of 30 m. Then, a preheated binding sheet is placed overlapping on the adhesive side. During the shrinkage operation, the adhesive layer of the bonding sheet melts, the bonding member moves, the two ends of the band to be joined slip, and no infusion is achieved.

As another control, the double-layered strip prepared as described was irradiated at a dose of 70 kGy. As a result of the absorbed dose, 32 to 41 of the adhesive layer were applied

The gel content is%, and the shrinkage of the tape is only 1% on average. A sheet of 100 x 50 mm is also cut from the strip thus obtained. As before, a heat-shrinkable corrosion protection tape, 30 mm overlap, is applied to a steel tube with a 100 mm diameter metal surface. A pre-heated 100 * 50 mm double-layered control sheet is then placed on the adhesive side. Shrinkage! during operation, the bonding sheet does not move, holding the two ends of the tape firmly together. However, after complete cooling, the bonding sheet can be manually separated from the tape at room temperature, and there is no measurable peel strength.

Claims (3)

CLAIMS 1. A process for the production of a high temperature thermoplastic ethylene polymer based laminate having an elastic adhesive layer, characterized in that the polyethylene or ethylene copolymer or terpolymer support tape or sheet is 0.3 to 1.5 mm thick and contains a stabilizer and optionally other additives. It is irradiated with a 40-120 kGy electron beam to a gel content of 30-50% by weight, and a co-polymer or terpolymer of ethylene acrylic acid containing 0.3-1.5 mm thick is applied to the pre-cured tape or sheet in a thickness of 0.3-1.5 mm. The resulting bilayer product was cross-linked by 10-40 kGy electron irradiation to a gel content of 5-25% by weight in the adhesive layer. 2. A process according to claim 1 wherein the adhesive layer is an ethylene / acrylic acid copolymer. 3. The process according to claim 1, wherein the adhesive layer is an ethylene acrylic butyl acrylate terpolymer.