DE202014101183U1 - Adhesive coated thermally sensitive polymer substrate - Google Patents

Abstract

An adhesive-coated polymeric substrate comprising (a) a polymeric substrate which contains or consists of a thermoplastic polymer with a Vicat A50 softening point according to DIN EN ISO 306 of up to 220 ° C, and (b) an adhesive composition which is directly applied at least one side of the polymer substrate is coated, wherein the adhesive composition (b) is a UV-curable or UV-cured pressure sensitive hot melt adhesive (PSA).

Description

The invention relates to an adhesive-coated thermally sensitive polymer substrate. In particular, the invention relates to an adhesive-coated, thermally-sensitive polymeric substrate wherein the thermally-sensitive polymeric substrate is a thermoplastic polymer having a VICAT A50 softening point DIN EN ISO 306 contains up to 220 ° C or consists of this.

Thermally sensitive film, generally consisting of a thermoplastic polymer, has so far not been directly coated with a UV-curable hot melt pressure-sensitive adhesive (PSA) and crosslinked. Already during the coating of the substrate with a non-UV-curable hot-melt adhesive, the films are often thermally damaged at the temperatures usually applied of about 160-180 ° C. More importantly, at the latest in the curing or crosslinking step, when the UV-curable hotmelt adhesive is crosslinked upon exposure to UV light from a conventional UV source, the films are very thermally damaged or even burned. In particular, films which have been pigmented with carbon black will burn because of the absorption of infrared radiation by the carbon black and the intense evolution of heat when cross-linked with a commonly used medium pressure UV mercury lamp. As a result, it has been impossible to manufacture, for example, black PVC insulating tapes coated with a UV-cured hotmelt adhesive.

Various attempts have therefore been made so far to deal with these heat-related problems when using thermally sensitive substrates such as soft PVV.

The EP 1 693 428 B1 refers to a reinforcing film for a hot melt type adhesive tape based on a bisoriented polypropylene (BOPP) comprising in sequence at least one layer comprising polypropylene or a blend of polypropylene resins, an opaque layer, and a polyamide resin based paint layer. This invention addresses the problem that the relatively high temperatures required by the hot melt technique require the use of a corresponding heat resistant reinforcing film, such as bis-oriented polypropylene, thus making the use of the most so far for this purpose used material, polyvinyl chloride (PVC), is excluded.

The EP 1 528 091 B1 describes a pressure-sensitive adhesive tape comprising a backing and an adhesive layer or adhesive layers formed from an adhesive comprising a base polymer and crosslinking agent on a single surface of the backing or on the surface and the other surface thereof, wherein the backing comprises a soft polyvinyl chloride a plasticizer, and at least the single surface adhesive as a base polymer comprises an acrylic copolymer having a carboxyl group, and further, as the crosslinking agents, a mixture of crosslinking agents comprising an isocyanate type crosslinking agent, a glycidylamine type crosslinking agent, and a melamine-type crosslinking agent.

It is therefore an object of the present invention to provide an adhesive-coated thermally-sensitive polymeric substrate wherein the adhesive is a UV-cured or UV-curable hot melt PSA.

• (a) ein Polymersubstrat, das ein thermoplastisches Polymer mit einem Vicat A50-Erweichungspunkt gemäß DIN EN ISO 306 von bis zu 220°C enthält oder aus diesem besteht, und
• (b) eine Klebstoffzusammensetzung, welche direkt auf mindestens einer Oberfläche des Polymersubstrates beschichtet ist,

worin die Klebstoffzusammensetzung (b) ein UV-härtbarer oder UV-gehärteter Schmelzhaftklebstoff ist. Accordingly, the present invention relates to an adhesive-coated polymeric substrate comprising

• (a) a polymer substrate comprising a thermoplastic polymer having a Vicat A50 softening point according to DIN EN ISO 306 contains up to 220 ° C or consists of this, and
• (b) an adhesive composition coated directly on at least one surface of the polymer substrate,

wherein the adhesive composition (b) is a UV-curable or UV-cured hot-melt pressure sensitive adhesive.

In the adhesive-coated polymer substrate of the present invention, the polymer substrate contains or consists of the aforementioned thermoplastic polymer. Even if the polymer substrate consists of the aforementioned thermoplastic polymer, the presence of additives to obtain desired properties of the polymer substrate, for example, a monomeric or polymeric plasticizer, is not excluded.

The thermoplastic polymer having a Vicat A50 softening point according to DIN EN ISO 306 of up to 220 ° C, preferably up to 200 ° C and even more preferably up to 170 ° C of the polymer substrate is preferably selected from the group of thermoplastic polymers consisting of polypropylene, in particular bisoriented polypropylene (BOPP), polyvinyl chloride (PVC), in particular soft PVC (short name according to DIN 7728 : PVC-P), polyethylene (PE), ethylene-1-alkene copolymers, regenerated cellulose ( cellophane ^®) and polylactic acid (PLA). Accordingly, the Vicat A50 softening point is used herein to indicate the temperature-sensitive behavior of a substrate.

Among these are BOPP and soft PVC (short name according to DIN 7728 : PVC-P) more preferred.

The melting temperature of a UV-cured adhesive composition corresponding to a UV-curable adhesive composition that has been cured is generally substantially higher because UV curing, and therefore crosslinking, to larger molecular weight polymers after coating of the UV-curable adhesive composition is performed on the substrate.

In the adhesive-coated substrate of the present invention, the substrate shows little thermal damage. This means, in particular, that the composition of the substrate in the interior does not differ substantially from the composition at the surface.

The substrate may be a compact film or a web consisting of fibers of one or more thermoplastic polymers. The substrate may also be a laminate of a compact film with a fabric. Additionally, the substrate may include multiple films and / or tissue.

The substrate may comprise various additives including, but not limited to, plasticizers, dyes and / or pigments, e.g. Soot.

For the adhesive coated substrate of the present invention, the most preferred thermoplastic polymer for the substrate is PVC, especially soft PVC plasticized with a monomeric and / or polymeric plasticizer.

Suitable monomeric plasticizers are, for example, di-n-butyl adipate, dioctyl adipate (DOA), diisononyl phthalate (DINP), benzyl (2-ethylhexyl) adipate, mixtures of alkylsulfone phenyl esters and mixtures of glycerol acetates. Suitable polymeric plasticizers for PVC are especially adipic acid polyesters. The latter are under the trade names Ultramoll ^® (Lanxess) or Palamoll ^® (BASF).

Preferably, in the UV-curable hot-melt pressure-sensitive adhesive, the content of the UV-curable copolymer, e.g. UV-curable polyacrylate or UV-curable synthetic rubber copolymer at least 30 wt .-%, more preferably at least 70 wt .-%, based on the total weight of the UV-curable hotmelt PSA. The remainder in the UV-curable hot melt pressure sensitive adhesive would be additives including tackifiers to provide the hot melt pressure sensitive adhesive with desired properties.

The UV-curable hot-melt adhesive used for the adhesive-coated substrate of the present invention, especially such an adhesive containing a UV-curable acrylic copolymer, preferably has a viscosity measured at 140 ° C with the Rheometer MCR 300 made by Anton Pair at D = 92.7 s ^-1 , in the range from 10,000 to 50,000 mPa · s, preferably in the range from 20,000 to 35,000 mPa · s.

In a preferred embodiment of the adhesive coated polymeric substrate, the hot melt pressure sensitive adhesive is a UV cured PSA obtainable from the corresponding UV curable PSA by irradiation with a UV light source in such a manner that the temperature is at a distance of 15 to 50 mm in the vicinity of the surface of the coating of the UV-curable hotmelt adhesive does not exceed an upper temperature T _max of 120 ° C. More preferably, the temperature T _max does not exceed an upper limit temperature of 100 ° C in the range of 15 to 50 mm adjacent to the surface of the coating of the ultraviolet curable hot melt adhesive on the substrate.

Herein, the "corresponding UV curable hot melt pressure sensitive adhesive" generally differs from the "UV cured hot melt pressure sensitive adhesive" in that the latter is the result of UV curing of the preceding one.

The chemical type of the UV-curable or UV-cured hot-melt adhesive of the adhesive composition (b) is not particularly limited. However, particularly suitable UV curable or UV cured hot melt adhesives are UV curable polyacrylates, especially acrylic copolymers or synthetic rubber copolymers, optionally in combination with suitable resins as tackifiers and / or other additives commonly used in hot melt adhesives.

A preferred acrylic copolymer comprises a mixture of alkyl (meth) acrylates. Preferably, the mixture of alkyl (meth) acrylates from 0.1 to 30 wt .-%, based on the mixture, methyl (meth) acrylate.

In a preferred embodiment, the mixture of alkyl (meth) acrylates 70 to 99.9 wt .-%, based on the mixture, of C ₂ to C ₁₈ alkyl (meth) acrylates. Among these are C ₂ -C ₁₀ - Alkyl (meth) acrylates, ie n-butyl acrylate, ethyl acrylate and / or 2-ethylhexyl acrylate preferred.

The acrylic copolymer may additionally contain other ethylenically unsaturated monomers. Suitable further ethylenically unsaturated monomers may be e.g. Vinyl esters of carboxylic acids containing up to 20 carbon atoms, vinyl aromatics containing up to 20 carbon atoms, ethylenically unsaturated nitriles, vinyl halides, vinyl ethers of alcohols containing 1 to 10 carbons, aliphatic hydrocarbons having 2 to 8 carbon atoms and 1 or 2 double bonds, or mixtures of these monomers.

Examples of vinyl esters of carboxylic acids having 1 to 20 carbon atoms are vinyl laurate, vinyl stearate, vinyl propionate, Versatic ^® acid vinyl ester and vinyl acetate. Suitable vinyl aromatic compounds are styrene, vinyl toluene, α- and p-methylstyrene, α-butylstyrene, 4-n-butylstyrene. Examples of nitriles are acrylonitrile and methacrylonitrile. The vinyl halides are chlorine, fluorine or bromine substituted ethylenically unsaturated compounds, preferably vinyl chloride and vinylidene chloride. Examples of vinyl ethers are vinyl methyl ether and vinyl isobutyl ether. Suitable hydrocarbons have in particular 2 to 8 carbon atoms and two olefinic double bonds, and are for example butadiene, isoprene and chloroprene.

The acrylic copolymer may also contain ethylenically unsaturated monomers having carboxylic acid, sulfonic acid or phosphonic acid groups. Among these, preferred are monomers having carboxyl groups. Suitable examples include acrylic acid, methacrylic acid, itaconic acid, maleic acid and fumaric acid. The copolymer may also contain other monomers, for example hydroxyl-containing monomers.

Preferred synthetic rubber copolymers are based on modified SBS (styrene-butadiene-styrene) or SIS (styrene-isoprene-styrene) block copolymers.

In order to enable crosslinking by UV light, the adhesive composition (b) generally contains a photoinitiator. It should be noted that the terms "curable" and "crosslinkable" are used herein to mean the same thing. The photoinitiator may be present in the adhesive composition as an added low molecular weight compound and / or as a copolymerized photoinitiator.

Typical photoinitiators which can be used together with the acrylate copolymer or the synthetic rubber copolymer are, for example, acetophenone, benzoin ethers, benzyl dialkyl ketals or derivatives thereof. The amount of the mixed photoinitiator is preferably 0.05 to 10 parts by weight, more preferably 0.1 to 2 parts by weight, per 100 parts by weight of the copolymer.

In the present invention, the use of a copolymerized photoinitiator is preferred. In the case of the copolymerized photoinitiator, for example, the acrylate copolymer or the synthetic rubber copolymer additionally contains, based on the weight of the copolymer, 0.05 to 10 wt%, preferably 0.1 to 2 wt%, and more preferably 0 , 1 to 1 wt .-% of ethylenically unsaturated compounds having a photoinitiator group. The ethylenically unsaturated compound having a photoinitiator group is preferably an acetophenone derivative or, more preferably, a benzophenone derivative. Suitable compounds are acetophenone or benzophenone derivatives which contain at least one, preferably one, ethylenically unsaturated group. The ethylenically unsaturated group is preferably an acrylic or methacrylic group. The ethylenically unsaturated group can be arranged directly on the phenyl ring of the acetophenone or benzophenone derivative. In general, a spacer group of up to 100 carbon atoms is between the phenyl ring and an ethylenically unsaturated group.

The photoinitiator causes crosslinking of the copolymer upon exposure to UV light, generally by a chemical grafting reaction of the photoinitiator group with a spatially adjacent polymer chain. The crosslinking can be effected, in particular, by inserting a carbonyl group of the photoinitiator into an adjacent C-H bond to form a -C-C-O-H group.

In a preferred embodiment, the adhesive coated polymeric substrate of the present invention is obtainable by irradiating and thereby crosslinking the UV curable hot melt pressure sensitive adhesive by a UV-C radiation source selected from the group consisting of a medium pressure or low pressure mercury lamp Excimer lamp and at least one LED is made. Preferably, the UV-C radiation source is a low-pressure mercury lamp. More preferably, the low pressure mercury (amalgam) lamp emits only light having a peak maximum at about 254 nm. Infrared radiation can be avoided, which would result in thermal damage to the thermally sensitive film. Herein sometimes the term "mercury (amalgam) lamp" is used because both terms "mercury" and "amalgam" are used with respect to such lamps.

In the adhesive-coated polymer substrate of the present invention, the thermoplastic polymer is preferably selected from the group consisting of polypropylene, especially bis-oriented polypropylene (BOPP), polyvinyl chloride (PVC), especially soft PVC, polyethylene (PE), ethylene-1-alkene copolymers, regenerated cellulose (cellophane ^®) and polylactic acid (PLA). More preferably, the thermoplastic polymer is soft PVC and the substrate contains a plasticizer. The plasticizer is preferably selected from di-n-butyl adipate, dioctyl adipate (DOA), diisononyl phthalate (DINP), benzyl (2-ethylhexyl) adipate, mixtures of alkylsulfonylphenyl esters, mixtures of glycerol acetates and adipic acid polyesters.

In a preferred embodiment, the soft PVC used as the preferred substrate of the present invention (abbreviated to DIN 7728 : PVC-P) has a Vicat A50 value in the range of 50 to 80 ° C. In addition, the preferably used PVC-P shows generally in a tensile test, using a tensile stress of 10 N / cm, an elongation value of 5 to 100%, preferably from 10 to 50%.

In a preferred embodiment of the present invention, the UV-curable or UV-cured hotmelt adhesive in the adhesive-coated substrate contains an acrylic copolymer or a synthetic rubber copolymer. Here, the acrylic copolymer preferably comprises a mixture of alkyl (meth) acrylates, which has from 0.1 to 30 wt .-%, based on the mixture, of methyl (meth) acrylate.

In a preferred embodiment, the mixture of alkyl (meth) acrylates 70 to 99.9 wt .-%, based on the mixture, of C ₂ to C ₁₈ alkyl (meth) acrylates. Among them, preferred are C ₂ -C ₁₀ alkyl (meth) acrylates, ie, n-butyl acrylate, ethyl acrylate, and / or 2-ethylhexyl acrylate.

The acrylic copolymer is obtainable by free radical copolymerization starting from ethylenically unsaturated monomers. In the preferred case where the photoinitiator is attached to the polymer, an ethylenically unsaturated compound having a photoinitiator group is preferably incorporated by copolymerization. The UV-crosslinkable copolymers can be prepared by the copolymerization of the monomer components, using the usual polymerization initiators and, if desired, using regulators. The copolymerization can be carried out at the usual temperatures in bulk, in emulsion, for example in water or liquid hydrocarbons, or else in solution. The copolymers are preferably prepared by polymerizing the monomers in solvents having a boiling range of from 50 to 150 ° C. using the customary amounts of polymerization initiators, the amounts of which are generally in the range from 0.01 to 10% by weight, in particular from 0.1 to 4 wt .-%, based on the total weight of the monomers are. Suitable solvents include alcohols, e.g. Methanol, ethanol, n- and isopropanol, n- and isobutanol, preferably isopropanol and / or isobutanol, hydrocarbons, e.g. Toluene, and especially petroleum ethers having a boiling range of from 60 to 120 ° C, ketones such as e.g. Acetone and methyl ethyl ketone, preferably methyl ethyl ketone, and esters such as e.g. Ethyl acetate, and also mixtures of such solvents.

In the case of solution polymerization, suitable polymerization initiators include, for example, azo compounds or ketone peroxides.

Following the polymerization in solution, the solvents are generally dried under reduced pressure and at elevated temperatures in the range of e.g. 100 to 150 ° C away. In this way, the acrylic copolymers can be in the solvent-free state, i. as melts. In many cases, it is also advantageous to coat the UV-crosslinkable acrylic copolymers by bulk polymerization, i. without the use of a solvent.

The adhesive composition containing the acrylic copolymer is preferably in the form of a melt, i. used in substantially solvent-free form for the preparation of the adhesive-coated thermally sensitive polymer substrate. As used herein, "substantially solvent-free" means that the content of solvent is preferably less than 2% by weight, more preferably less than 1% by weight, based on the weight of the acrylic copolymer.

To obtain the coated substrate of the present invention, the adhesive composition containing the acrylic copolymer can be melt-applied to the substrate by conventional techniques such as brushing, rolling, flow coating, die coating or knife coating. Hot melt adhesives are generally melted by block smelters or drum unloaders. The coating is usually carried out at 150 to 180 ° C, depending on the specific application, on standardized roller or slot die coating machines.

In order to have sufficient flowability of a hotmelt adhesive copolymer therein, the known PSA composition generally becomes at a temperature of up to 180 ° C coated the substrate. However, this temperature could cause damage to the film surface. In contrast, the UV-curable or UV-curable acrylic copolymers or synthetic rubber copolymers used in embodiments of the present invention allow prepolymers or low molecular weight polymers having a high viscosity at room temperature to be used for coating the substrate. The UV-curable or UV-curable acrylic copolymer can therefore be applied at a very low temperature, usually in the range of 90-120 ° C, with excellent flowability.

The film thickness of the coated adhesive composition, i. the thickness of the adhesive layer on the partially or completely coated at least one side of the substrate, measured at 25 ° C, is preferably in the range of 1 to 100 μm, more preferably in the range of 1 to 30 μm, and most preferably in the range of 1 to 25 μm.

The thickness of the polymer substrate is generally in the range of 30 to 1000 μm, preferably in the range of 30 to 300 μm (0.03-0.3 mm). It has surprisingly been found that with the present invention the thickness of the substrate can be very small, in particular from 30 to 130 μm (0.03-0.13 mm) in the case of soft PVC.

• (a) ein Polymersubstrat, das ein thermoplastisches Polymer mit einem Vicat A50-Erweichungspunkt nach DIN EN ISO 306 von bis zu 220°C enthält oder aus diesem besteht, und
• (b) eine Klebstoffzusammensetzung, welche direkt auf mindestens einer Seite des Polymersubstrates beschichtet ist,

worin die Klebstoffzusammensetzung (b) ein UV-härtbarer oder UV-gehärteter Haftschmelzklebstoff ist,
umfasst die Schritte

• (i) Bereitstellen eines Polymersubstrates, das ein thermoplastisches Polymer mit einem Vicat A50-Erweichungspunkt gemäß DIN EN ISO 306 von bis zu 220°C enthält oder aus diesem besteht;
• (ii) direktes Beschichten eines UV-härtbaren Haftschmelzklebstoffes (PSA) auf zumindest einer Seite des Substrates;
• (iii) und, falls die Klebstoffzusammensetzung (b) ein UV-gehärteter Haftschmelzklebstoff ist, Härten der Klebstoffzusammensetzung (b) durch Bestrahlung mit UV-Licht.

A preferred method of making the adhesive-coated polymeric substrate comprising

• (a) a polymer substrate containing a thermoplastic polymer having a Vicat A50 softening point DIN EN ISO 306 contains up to 220 ° C or consists of this, and
• (b) an adhesive composition coated directly on at least one side of the polymeric substrate,

wherein the adhesive composition (b) is a UV-curable or UV-cured hot-melt adhesive,
includes the steps

• (i) providing a polymer substrate comprising a thermoplastic polymer having a Vicat A50 softening point according to DIN EN ISO 306 contains up to 220 ° C or consists of this;
• (ii) directly coating a UV-curable hot melt pressure sensitive adhesive (PSA) on at least one side of the substrate;
• (iii) and, if the adhesive composition (b) is a UV-cured pressure sensitive hot melt adhesive, curing of the adhesive composition (b) by irradiation with UV light.

In a more preferred method, the UV curable hot melt pressure sensitive adhesive (PSA) is irradiated and cured with a UV light source such that the temperature is at a distance of 15 to 50 mm adjacent the surface of the coating of the UV curable hot melt pressure sensitive adhesive on the substrate does not exceed an upper temperature T _max of 120 ° C.

In a preferred embodiment of the present invention, the polymeric substrate is made of soft PVC and the UV curable hot melt pressure sensitive adhesive (PSA) contains an acrylic copolymer containing as monomer from 0.1 to 30% by weight of methyl (meth) acrylate.

In a preferred embodiment of the process, the UV-curable or UV-cured PSA contains an acrylate copolymer which is a mixture of alkyl (meth) acrylates containing from 70 to 99.9% by weight, based on the mixture, of C ₂ to C ₁₈ alkyl (meth) acrylates. Among them, preferred are C ₂ -C ₁₀ alkyl (meth) acrylates, ie, n-butyl acrylate, ethyl acrylate, and / or 2-ethylhexyl acrylate.

In the method preferably used for the invention, the coating of the substrate is preferably carried out using a slot die coating machine. The coating speed can be as high as 60 m / min, for example.

After the substrate has been coated with adhesive composition (b) on at least a portion of at least one of its two surfaces, the UV-crosslinkable copolymers in the UV-curable hot melt adhesive are generally cured by UV light from a suitable UV source. The wavelength range of the UV light to be used is preferably in the range of 200 to 450 nm, more preferably in the range of 200 to 350 nm. The ultraviolet light used is most preferably in the UV-C region of 200 to 280 nm. However, it may be advantageous to supplement this UV light with longer-wavelength monochromatic light. As a UV source, various lamps can be used. Suitable lamps are, for example, mercury (amalgam) lamps, excimer lamps or LEDs. Suitable mercury (amalgam) lamps are, for example, medium-pressure and low-pressure lamps. With regard to their use, it is important that their surface temperatures are different. The surface temperature of a medium pressure mercury lamp is quite high; For example, the surface temperature of the medium pressure mercury lamps available from Heraeus is about 900 ° C. In such circumstances, the distance between the lamp and the surface of the adhesive coating on the substrate need not only be large. In addition, adequate cooling of the substrate must also be ensured. However, in low pressure lamps, the temperature at the surface of the low pressure mercury lamp is in the range of about 90 to 120 ° C. Moreover, the energy consumption of medium pressure mercury lamps is about 180-240 W / cm and that of low pressure mercury lamps is about 4 W / cm.

Accordingly, in the method preferably used here, the use of low-pressure mercury lamps is preferred. Therefore, the adhesive-coated substrate of the present invention is preferably obtainable by a method in which crosslinking of the UV-curable hot-melt adhesive is performed by using a low-pressure mercury lamp.

The UV lamps of various types can be used alone or in combination. In a preferred embodiment, the UV-C light of a medium pressure and / or a low pressure mercury lamp is combined with longer wavelength light from UV LEDs to obtain an improved curing result.

Moreover, the UV light can be provided as a broad spectrum, for example over the full range of 200 to 300 nm (medium pressure mercury lamp) or at a particular wavelength, for example at a peak wavelength of about 254 nm (low pressure mercury lamp).

An additional suitable UV source is an excimer lamp. Excimer lamps are mercury-free UV lamps that provide UV radiation with a monochromatic characteristic, produced by the spontaneous emission of excimer (exciplex) molecules. The maximum of a radiation wavelength of an excimer lamp is defined by a working excimer molecule, eg KrCl * at 222 nm, KrF * at 248 nm, XeI * at 253 nm, Cl ₂ * at 259 nm or XeBr * at 282 nm. Moreover, no heat is generated because excimer UV lamps do not produce infrared radiation.

It is also possible to use LEDs as a UV source in the UV-C region.

In order to obtain the adhesive coated substrates of the present invention, the use of low pressure mercury lamps is preferred. A particularly suitable UV light source is the low-pressure mercury lamp with the label Soluva ^® UVC-Cure Module from Heraeus Noblelight GmbH. This module emits extremely intense shortwave light with high efficiency. A specific reflector integrated into the module also contributes to the high efficiency of the module. The temperature at the surface of the UV light source is 90 to 120 ° C.

It has been found that UV-curable hotmelt adhesives can be crosslinked particularly advantageously on soft PVC with this low-pressure mercury lamp (abbreviated to DIN 7728 : PVC-P). This is particularly true when the Vicat A50 value for PVC-P is in the range of 50 to 80 ° C. The PVC-P used generally shows in a tensile test, using a tensile stress of 10 N / cm, an elongation value of 5 to 100%, preferably from 10 to 50%.

The required UV dose of low pressure mercury (amalgam) lamps depends on the adhesive composition and must be determined for each UV curable or UV cured hot melt pressure sensitive adhesive (PSA). The PSA properties depend on the applied UV dose (mJ / cm ² ). However, it has been found that suitable power consumption is in the range of 2.5 W to 16 W / cm at a working width of 1300 mm when 4 lamps are used. These UV lamps are commonly used as cassette modules with multiple UV lamps. The required cure is often achieved at a working distance of 15 to 50 mm between the surface of the adhesive composition on the substrate and the surface of the UV lamp. Using these lamps, it has been found that there is little thermal stress on the substrate, namely a surface temperature which is often 35 ° C at a distance of 30 mm from the lamps.

Depending on the UV curable hot melt adhesive to be used for a specific substrate and the intended use and / or characteristics of such an adhesive coated substrate, the characteristics of UV light, particularly its dose and wavelength, may vary. Accordingly, different sources of UV light can be used as long as the adhesive-coated substrate of the present invention can be obtained. For example, mercury lamps (low pressure and medium pressure) and LED lamps can be used. In the case of mercury lamps, low pressure lamps are preferred because they do not require carefully controlled crosslinking as in medium pressure lamps to avoid serious damage or even burning of temperature sensitive substrates.

The characteristic of the coated and preferably cured adhesive composition will depend in particular on the substrate. Namely, depending on the properties of the substrate, it may be useful to provide the coated adhesive composition with specific properties. For example, if the substrate is a soft PVC substrate containing plasticizer, it is desirable to use a plasticizer To produce adhesive coating, which reduces the migration of the plasticizer from the soft PVC to the coated adhesive.

Suitable plasticizers have already been mentioned with regard to soft PVC. It has surprisingly been found that a particularly advantageous tacky UV-cured pressure sensitive hot melt adhesive coating for soft PVC containing 30 wt .-% adipic acid polyester can be obtained as a plasticizer, if at least one Soluva ^® UV-C lamp is used. The use of two or more lamps is preferred. Most preferably, 6 lamps are used. In addition, the coating amount is preferably in the range of 10 to 30 g / m ² , more preferably in the range of 15 to 25 g / m ^2, and most preferably in the range of 18 to 22 g / m ^{2 of} UV-curable hot melt pressure sensitive adhesive (PSA) on acrylic copolymers.

In this regard, it is preferred that a slot die coating machine be used at a coating speed in the range of 5 to 15 m / min.

For the crosslinking step, the substrate coated with the adhesive composition, ie, a pressure-sensitive hot melt adhesive (PSA), is generally placed on a conveyor belt and the conveyor belt is passed by a suitable UV lamp. The extent of crosslinking of the copolymers depends on the intensity and duration of the irradiation. The UV-C radiation dose is generally in the range of 20 to 150 mJ / cm ² of irradiated area measured with a UV-C Power Puck II (EIT). It is preferable that the applied UV-C dose is in the range of 30 to 50 mJ / cm ² .

The adhesively coated substrates according to the invention are suitable for the production of a pressure-sensitive adhesive tape or a self-adhesive poster or banner.

The invention has numerous advantages. The present invention provides adhesive coated substrates wherein temperature sensitive substrates are coated with hot melt pressure sensitive adhesives (PSAs). Accordingly, the advantages of hot melt adhesives can be obtained even if thermally sensitive substrates are used. Namely, the applied adhesive composition contains practically no water or an organic solvent. It is therefore neither a recycling of the solvent nor a burning of residual solvent required. This also allows a more compact manufacture of adhesive coated substrates, since long drying chambers are not required. In addition, transportation costs may be lower because neither water nor organic solvents need to be transported.

It is also possible to obtain adhesive-coated substrates in which an adhesive layer having a high internal cohesion can be produced. In particular, it is also possible to set a desired level of internal cohesion by controlling the extent of UV crosslinking. As a result of increasing cross-linking, the polymer weight of the pressure-sensitive hotmelt adhesive (PSA) increases. When the molecular weight of the PSA after crosslinking is high, the adhesive layer is generally more resistant to heat. In addition, cross-linking creates a very high level of permanent internal cohesion and therefore makes the adhesive layer more resistant to plasticizers which may be present in the substrate and which may migrate into the adhesive layer, which may result in cohesive failure and damage to the adhesive. This is of particular importance in the case of soft PVC, which usually contains significant amounts of a plasticizer. By appropriate individual selection of a UV dose to be used for crosslinking, the adhesive properties of the adhesive coated substrate can be adjusted as desired.

In addition, the formation of a primer layer, i. a primer coating, which is often required when using an adhesive composition based on an aqueous or organic solvent, can be avoided. Even without such a primer coating, the present invention can achieve a reduction in the migration of plasticizers since quite high molecular weights of the polymer in the adhesive composition, and thus higher cohesion in the adhesive layer, can be achieved when UV-curable hot melt adhesives are used.

example

A soft PVC black film 0.12 mm thick containing 30% by weight, based on the PVC film, of a polymeric plasticizer (adipic acid, polymer of 1,3-butanediol and 1,4-butanediol of 2 Ethylhexyl ester) was measured using a slot die coater at a machine speed of 10 m / min with 220 g / m of a UV curable hot melt pressure sensitive adhesive containing 98% by weight of a UV curable polyacrylate containing 94% by weight of n-butyl acrylate, 5% by weight .-% acrylic acid and 1 wt .-% Visiomer ^® 6976 (solution of Methacryloylbenzophenon derivative in a methyl methacrylate / methacrylic acid mixture) of 2 wt .-% and Evonics a plasticizer (Palamoll ^® 654 from BASF SE; of aliphatic dicarboxylic acids, polyester) coated. The coated UV-curable hot-melt adhesive was then using Soluva ^® UV-C modules (6) lamps from Heraeus cured. The UV crosslinking dose was 40 mJ / cm ² measured with a UV-C Power Puck II (EIT).

The peel strength with respect to steel was measured according to the FINAT method FTM 1 (peel strength (180 °) at a speed of 300 mm / min) at room temperature. As a result, the adhesion to steel failed at 12.7 N / inch (5 N / cm).

The soft PVC substrate coated with the UV-cured hotmelt adhesive was wound into a coil. The coil was then stored for 5 hours at a temperature of 70 ° C in an oven to simulate aging. Subsequently, possible damage to the cohesion was assessed by possible migration of the plasticizer present in the substrate into the adhesive composition, here into an adhesive layer which is accelerated at elevated temperatures, during unrolling of the coil. As a result, no cohesive failure of the adhesive layer occurred when the roll was unrolled. Moreover, the measurement of steel adhesion at 180 ° according to FINAT method FTM 1 at room temperature gave the result of 4.8 N / inch (1.89 N / cm), also without cohesive failure.

Accordingly, such an adhesive-coated substrate could be used, for example, as a soft PVC adhesive tape for electrical insulation.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 1693428 B1 [0004]
• EP 1528091 B1 [0005]

Cited non-patent literature

• DIN EN ISO 306 [0001]
• DIN EN ISO 306 [0007]
• DIN EN ISO 306 [0009]
• DIN 7728 [0009]
• DIN 7728 [0010]
• DIN 7728 [0034]
• DIN EN ISO 306 [0045]
• DIN EN ISO 306 [0045]
• DIN 7728 [0057]

Claims (12)

An adhesive coated polymeric substrate comprising (A) a polymer substrate containing or consisting of a thermoplastic polymer having a Vicat A50 softening point according to DIN EN ISO 306 of up to 220 ° C, and (b) an adhesive composition coated directly on at least one side of the polymeric substrate, wherein the adhesive composition (b) is a UV-curable or UV-cured hot-melt pressure sensitive adhesive (PSA). The adhesive coated polymeric substrate of claim 1 wherein the hot melt pressure sensitive adhesive is a UV cured hot melt pressure sensitive adhesive (PSA) obtainable from the corresponding UV curable hot melt pressure sensitive adhesive (PSA) by irradiation with a UV light source such that the temperature is at a distance from 15 to 50 mm adjacent to the surface of the coating of the UV-curable hotmelt adhesive on the substrate does not exceed an upper temperature T _max of 120 ° C. The adhesive coated polymeric substrate of claim 2, wherein the temperature at a distance of 15 to 50 mm adjacent to the surface of the coating of the UV curable hot melt adhesive on the substrate does not exceed an upper limit temperature T _max of 100 ° C. An adhesive coated polymeric substrate according to any one of claims 1 to 3 obtainable by irradiation and thus crosslinking of the UV curable hotmelt adhesive by a UV-C radiation source selected from the group consisting of a medium pressure or low pressure mercury lamp, an excimer lamp and at least one LED. The adhesive coated polymeric substrate of claim 4, wherein the UV-C radiation source is a low pressure mercury (amalgam) lamp. The adhesive coated polymeric substrate of claim 5, wherein the low pressure mercury lamp emits substantially only light at a peak maximum at about 254 nm. An adhesive coated polymeric substrate according to any one of claims 1 to 6, wherein the thermoplastic polymer is selected from the group consisting of polypropylene, especially bisoriented polypropylene (BOPP), polyvinyl chloride (PVC), especially soft PVC, polyethylene (PE), ethylene 1-alkene copolymers, regenerated cellulose (cellophane ^®) and polylactic acid (PLA). The adhesive coated polymeric substrate of claim 7 wherein the thermoplastic polymer is soft PVC and the substrate contains a plasticizer. The adhesive coated polymeric substrate of claim 8, wherein the plasticizer is selected from di-n-butyl adipate, dioctyl adipate (DOA), diisononyl phthalate (DINP), benzyl (2-ethylhexyl) adipate, mixtures of alkylsulfonephenyl esters, mixtures of glycerol acetates and adipic acid polyesters. The adhesive coated polymeric substrate of any of claims 1 to 9, wherein the UV curable or UV cured hot melt pressure-sensitive adhesive comprises an acrylic copolymer or a synthetic rubber copolymer. The adhesive coated polymeric substrate of claim 10, wherein the acrylic copolymer comprises a mixture of alkyl (meth) acrylates comprising from 0.1 to 30% by weight, based on the mixture, of methyl (meth) acrylate. An adhesive coated polymeric substrate according to claim 10 or 11, wherein the acrylic copolymer comprises a mixture of alkyl (meth) acrylates containing from 70 to 99.9% by weight, based on the mixture, of C ₂ to C ₁₈ alkyl (meth) acrylates , preferably C ₂ -C ₁₀ alkyl (meth) acrylates, more preferably n-butyl acrylate, ethyl acrylate and / or 2-ethylhexyl acrylate.