DE102007010093A1 - Preparation of adhesive layers with a defined surface structure, useful e.g. as a self adhesive particle, comprises coating of the adhesive on a substrate that is equipped with an anti-adhesive coating exhibiting contact points - Google Patents

Abstract

Preparation of adhesive layers with a defined surface structure comprises coating of the adhesive on a substrate that is equipped with an anti-adhesive coating, which exhibits holes and the coated adhesive has direct contact with the substrate at these holes (therefore called contact points). An independent claim is included for a multi-layered laminate obtained by the above process.

Description

The The invention relates to a method for producing adhesive layers with defined surface structure by coating adhesive on one with an anti-adhesive layer equipped Carrier, by characterized in that the non-stick layer has holes and the coated one Glue on these holes direct contact with the carrier has (hereinafter referred to as contact points).

It It is known that microstructured surfaces by van der Waals forces a increased adhesion exhibit. In nature, this increased adhesion is observed in gecko feet. There are a variety of attempts such surface structures synthetically produce.

WHERE 01/49776 describes z. B. the modification of artificial surfaces with the natural gecko feet structures.

DE-A 102 23 234 lists a variety of possible methods, called be z. As the micro or nanolithography or treatment of the surface with high-energy radiation.

Are desired preferably simple process for producing such microstructures.

at Adhesives, especially in pressure-sensitive adhesives, is both a good adhesion to the substrate to be bonded (good adhesion) as also a sufficient internal strength in the adhesive layer (Cohesion) desired. For adhesion and cohesion these are opposite application properties. Activities, the improvement of the adhesion cause, lead in general, a deterioration of cohesion.

Is desired Therefore, a simple process for improving the application technology Properties of adhesives.

task Therefore, the present invention was as simple as possible for the production of microstructured surfaces to improve the application technology Characteristics more usual Adhesives.

Accordingly, became Found the initially defined method. Were also found the ones available by this method multilayer laminates, or their use for self-adhesive Items.

At the inventive method can be a carrier be used from any material. In particular, carriers are customary Paper or polymer films. The polymer films are z. B. microns Polyacetate films, polyester films, polyolefin films, such as polyethylene, Polypropylene or polyvinylchloride films.

Of the carrier is coated with a non-stick coating.

Non-stick coatings usually consist of Silicone, it is therefore preferably a silicone layer.

The Thickness of the non-stick layer is preferably greater than 0.5 μm, in general, it is smaller than 2, or 1 mm.

The Non-stick layer has holes on, i. the later Adhesive coated adhesive has direct contact with these holes Contact with the wearer. The holes are therefore referred to below as contact points.

The size of the holes, ie the area of the contact points is preferably 5 μm ² to 3 mm ² , in particular up to 1 mm ² .

The number of contact points is preferably at least> 10 per cm ² .

The Non-stick coating can be customary Procedure on the carrier be coated.

The Contact points can z. B. be prepared by the fact that the coated, preferably weblike carrier is passed over a roller in a continuous production process, which has a correspondingly opposite surface structure. surveys lead on the roller upon contact with the release layer to a corresponding depression (Contact point in the non-stick layer).

at the adhesive is preferably one at room temperature permanently sticky adhesive, d. H. a pressure-sensitive adhesive.

essential Feature of a pressure-sensitive adhesive is sufficient adhesion (stickiness) associated with a necessary cohesion (internal strength in the adhesive layer).

Of the Adhesive has at 21 ° C preferably a peel strength (as a measure of the adhesion) of at least 1 N / 2.5 cm according to the following Measurement method. Preferably the peel strength 1 to 15, more preferably 2 to 12, most preferably 3 to 10 N / 2.5 cm.

The shear strength as a measure of the cohesion is preferably greater than 10 minutes according to standing measuring method. The shear strength is preferably 10 to 1440 minutes, more preferably 100 to 1000 minutes, most preferably 200 to 500 minutes.

To the test methods

The adhesive is coated with 20 g / m ² (solid) on polyethylene film and dried at 90 ° C for 3 minutes.

to the determination of the peel strength (Adhesion) becomes a 2.5 cm wide test strip on a chromed V2A test sheet glued and rolled 1 time with a 1 kg roll. He will then with one end into the upper jaws of a tensile-strain tester clamped. The adhesive strip is at 300 mm / min at a 180 ° angle from the Test surface (V2A steel) subtracted i. the adhesive strip was bent over and parallel to the test sheet deducted and needed it Measured effort. The measure of the peel strength is the force in N / 2 cm, which is an average of five measurements resulted (corresponds to AFERA standard method). The peel strength is determined 24 hours after the bonding.

To determine the shear strength, the test strips are glued with a glued surface of 25 mm ² on a chromed V2A test sheet, rolled with a 1 kg roll 1 time, 10 min stored (in standard atmosphere, 1 bar, 21 ° C) and then hanging loaded with a 0.5 kg weight (in standard climate, 1 bar, 21 ° C). The measure of shear strength was the time to weight drop in minutes; in each case the average of 5 measurements is calculated (corresponds to PSTC standard method).

adhesives, or pressure sensitive adhesives generally consist of at least one Binders and possibly other additives.

at the binder may in particular be a synthetic polymer act (hereinafter called adhesive polymer). Under the Term adhesive polymer should also be mixtures of different Be understood polymers, in particular, it may be Mixtures of non-tacky polymers with sticky polymers or with other polymers that have a stickiness of the mixture cause, act.

When Adhesive polymer are radically polymerized polymers, polyesters or polyadducts. Unless it is non-sticky polymers is the above stickiness (peel strength) by addition of tackifying resins or plasticizers.

Called be z. B. styrene copolymers, in particular styrene-butadiene copolymers, Ethylene-vinyl acetate copolymers, polyurethanes, polyisobutylenes and non-crystalline polyolefins which have a corresponding content of plasticizers or tackifying resins.

Especially Block copolymers are also suitable.

in the Case of styrene block copolymers may, for. B. radically polymerized Styrene-butadiene Copolymers can be used which have a butadiene content of greater than or equal 50 wt .-%, preferably greater than or equal 60 wt .-%, more preferably greater than or equal to 80 wt .-% have.

Styrene-butadiene Copolymers can z. B. di-, tri- or multiblock copolymers whose soft phase content preferably greater than or equal 60% by weight.

Especially is the adhesive polymer composed of radically polymerizable Compounds (monomers). Preferably, it is at least 40 % By weight, more preferably at least 60% by weight, most especially preferably at least 80 wt .-% of so-called main monomers.

The Main monomers are selected from C1-C20-alkyl (meth) acrylates, vinyl esters of up to 20 C atoms containing carboxylic acids, Vinylaromatics with up to 20 C atoms, ethylenically unsaturated Nitriles, vinyl halides, vinyl ethers containing from 1 to 10 carbon atoms Alcohols, aliphatic hydrocarbons having 2 to 8 carbon atoms and 1 or 2 double bonds or mixtures of these monomers.

To are called z. B. (meth) acrylic acid alkyl ester with a C 1 -C 10 -alkyl radical, such as methyl methacrylate, methyl acrylate, n-butyl acrylate, ethyl acrylate and 2-ethylhexyl acrylate.

Especially also mixtures of (meth) acrylic acid alkyl esters are suitable.

Vinylester of carboxylic acids with 1 to 20 carbon atoms are e.g. Vinyl laurate, stearate, vinyl propionate, Versatic and vinyl acetate.

When vinylaromatic compounds contain vinyltoluene a- and p-methylstyrene, a-butylstyrene, 4-n-butylstyrene, 4-n-decylstyrene and preferably styrene into consideration. examples for Nitriles are acrylonitrile and methacrylonitrile.

The vinyl halides are chloro, fluoro or bromo substituted ethylenically unsaturated Ver compounds, preferably vinyl chloride and vinylidene chloride.

When To name vinyl ethers are, for. As vinyl methyl ether or vinyl isobutyl ether. Vinyl ether is preferably from 1 to 4 C-containing alcohols.

When Hydrocarbons having 2 to 8 carbon atoms and one or two olefinic Double bonds are butadiene, isoprene and chloroprene, ethylene or called propylene. Polymers obtained from butadiene or isoprene or copolymers can also later be hydrogenated.

When Preferred main monomers are vinyl esters, preferably vinyl acetate, especially in combination with ethylene (short vinyl acetate / ethylene copolymers), Butadiene, especially in combination with styrene (short butadiene / styrene copolymers) and the C1 to C10 alkyl acrylates and methacrylates, in particular C1 to C8 alkyl acrylates and methacrylates (polyacrylates for short) where Polyacrylates are each particularly preferred.

All particularly preferred are methyl acrylate, ethyl acrylate, n-butyl acrylate, n-hexyl acrylate, octyl acrylate and 2-ethylhexyl acrylate and mixtures of these monomers.

Next the main monomer, the polymer may contain other monomers, z. B. monomers with carboxylic acid, sulfonic acid or phosphonic acid groups. Preferred are carboxylic acid groups. Called z. For example, acrylic acid, methacrylic acid, itaconic, maleic or fumaric acid.

Further Monomers are e.g. also hydroxyl-containing monomers, in particular C 1 -C 10 -hydroxyalkyl (meth) acrylates, (Meth) acrylamide and ureido-containing monomers such as ureido (meth) acrylates.

When more monomers are above it phenyloxyethylglycol mono (meth) acrylate, glydidyl acrylate, Glycidyl methacrylate, amino (meth) acrylates such as 2-aminoethyl (meth) acrylate called.

monomers the except the double bond still carry other functional groups, for. B. Isocyanate, amino, hydroxy, amide or glycidyl, for. B. improve adhesion to substrates. In particular, be considered also cyclic lactams such as N-vinylpyrrolidone or N-vinylcaprolactam.

In Adhesives are also considered, whose adhesive properties by photochemical crosslinking, e.g. B. by irradiation with electron beams or UV light can be adjusted (acResin © from BASF)

photochemical crosslinkable, the polymer is e.g. when hydrogen protons from the Polymer backbone photochemically, especially using a photo initiator or separated by electron beams can, so that a radical is formed, which further chemical reactions can go down.

Of the Adhesive may contain a photoinitiator.

At the Photoinitiator may be z. B. act so-called α-splitter, these are photoinitiators, in where a chemical bond is cleaved, leaving 2 radicals arise, the further crosslinking or polymerization reactions initiate.

Called z. B. Acylphosphinoxide (Lucirin ^® brands of BASF), hydroxyalkylphenones (eg Irgacure ^® 184), benzoin derivatives, benzil derivatives, dialkyloxyacetophenones.

Especially they may be so-called H-abstractors which are a hydrogen atom detach from the polymer chain, z. For example, these are photoinitiators with a carbonyl group. This carbonyl group slides into a C-H bond with formation a C-C-O-H grouping.

Called here are in particular acetophenone, benzophenone and their derivatives.

It can both classes of photoinitiators used alone or in admixture become. Preferably, it is H-abstractors as a photoinitiator.

Of the Photoinitiator or at least one of the photoinitiators, if any Mixture used may be bound to the adhesive polymer.

Especially it is preferably a photoinitiator, which by radical copolymerization is incorporated into the polymer chain. Preferably contains the photoinitiator to an acrylic or (meth) acrylic group.

suitable copolymerizable photoinitiators are acetophenone or benzophenone derivatives which at least one, preferably one, ethylenically unsaturated group contain. The ethylenically unsaturated group is preferably an acrylic or methacrylic group.

The ethylenically unsaturated group may be bonded directly to the phenyl ring of the acetophenone or benzophenone derivative. In general, there is a spacer group between the phenyl ring and the ethylenically unsaturated group (distance holder).

The Spacer group can z. B. contain up to 100 carbon atoms.

worin R¹ für einen organischen Rest mit bis zu 30 C-Atomen, R² für ein H-Atom oder eine Methylgruppe und R³ für eine gegebenenfalls substituierte Phenylgruppe oder eine C₁-C₄-Alkylgruppe steht.Suitable acetophenone or Benzophenonderivate are z. For example, in EP-A-346 734, EP-A 377 199 (claim 1), DE-A 40 37 079 (claim 1) and DE-A-38 44 444 (claim 1) and are described by this Reference also disclosed in the present application. Preferred acetophenone and benzophenone derivatives are those of the formula

wherein R ^{1 is} an organic radical having up to 30 C atoms, R ^{2 is} an H atom or a methyl group and R ^{3 is} an optionally substituted phenyl group or a C ₁ -C ₄ alkyl group.

R ¹ particularly preferably represents an alkylene group, in particular a C ₂ -C ₈ -alkylene group.

R ³ particularly preferably represents a methyl group or a phenyl group.

suitable UV-crosslinkable adhesives generally contain from 0.0001 to 0.5 mol, more preferably 0.0002 to 0.1, most preferably 0.003 to 0.01 mol of the photoinitiator or photoinitiator, bonded to the polymer molecule group, per 100 g of adhesive polymer.

suitable UV-crosslinkable polymers are available under the trade name acResin® from BASF available.

at the adhesive used in the invention it may be a hot melt adhesive, i. H. one essentially solvents and anhydrous, melt-to-process adhesive.

Preferably it is an aqueous Adhesive.

Of the aqueous Contains adhesive the adhesive polymer, in particular in the form of an aqueous dispersion, in particular obtainable by emulsion polymerization.

The Glass transition temperature (Tg) of the adhesive polymer is preferably -65 to +10 ° C, especially preferably -65 up to 0 ° C, most preferably -65 to -10 ° C, or -65 to -20 ° C, in one very particularly preferred embodiment is the glass transition temperature -55 to -30 ° C, or -50 to -40 ° C.

The Glass transition temperature of the polymer yourself after usual Methods such as differential thermal analysis or differential scanning Calorimetry (see, e.g., ASTM 3418/82, so called "midpoint temperature").

Adhesive- Polymers can by copolymerization of the monomers using the usual Polymerization initiators and optionally produced by regulators be, taking the usual Temperatures in mass, in emulsion, z. In water or liquid hydrocarbons, or in solution polymerized. The polymerization, z. B. bulk polymerization can also performed in an extruder become.

Of the Adhesive can consist solely of the binder (adhesive polymer) or also contain other additives. Be considered z. B. so-called tackifying resins (Tackifier).

tackifiers are z. As natural resins such as rosins and their disproportionation or isomerization, polymerization, dimerization, hydrogenation Derivatives. these can in their salt form (with, for example, mono- or polyvalent counterions (cations) or preferably in their esterified form. Alcohols that used for esterification may be mono- or polyvalent. Examples are methanol, ethanediol, diethylene glycol, triethylene glycol, 1,2,3-propanethiol, Pentaerythritol.

preferred Tackifiers are natural or chemically modified rosin resins. Rosin resins exist for the most part Part of abietic acid or abietic acid derivatives.

Further Additives which can be added to the adhesive are e.g. Antioxidants, fillers, Dyes, leveling agents.

Of the Adhesive or pressure-sensitive adhesive is, apart from water or other solvents, in particular to more than 40% by weight, more preferably to more than 60% by weight and most preferably more than 80% by weight of the adhesive polymer, among which also mixtures of different polymers are to be understood (see above)

Of the Adhesive can according to usual Method to be coated on the non-stick layer.

The adhesive can be coated directly on the release layer or first coated on another carrier (secondary carrier); in the latter case, then this second carrier must be laminated on the non-stick layer.

Preferably the adhesive is coated as a free falling film curtain; at the coating process is therefore a curtain coating process.

Preferably the coating is applied directly to the non-stick layer of the the non-stick coated carrier.

Especially In a continuous process, first on one with a non-stick coating equipped web-like carrier Contact points, z. B. with a roller, and then the Coating with the adhesive, preferably as a free-falling Film curtain, made.

On The adhesive layer can then also in a continuous Process filed a second carrier so that results in a multilayer laminate.

• – 2. Träger
• – Klebstoffschicht
• – Antihaftschicht
• – Träger

Laminates having at least the following layers are therefore obtainable by the process according to the invention, the following sequence corresponding to the spatial arrangement:

• - 2nd carrier
• - adhesive layer
• - non-stick coating
• - Carrier

To peel off the coated with the release layer carrier the adhesive layers the desired Surface structure. The removal takes place in particular at or shortly before the later use.

The according to the inventive method available Adhesive layers with a defined surface structure, in particular the above laminates are suitable as self-adhesive articles or for the production of self-adhesive articles.

When Self-adhesive articles can be labels, adhesive tapes or adhesive foils.

By the surface structure the adhesive layers have increased adhesion.

Examples

Used material:
Support coated with a non-stick layer: commercially available silicone paper from Laufenberg, type NSA 1370 white (140 g / m ² , total thickness 130 μm).

Adhesive: 75 TI. Acronal® V 215, a commercial one Polymer dispersion for Pressure-sensitive adhesives, mixed with 25 TI. a rosin resin dispersion (tackifier).

manufacturing the contact points in the non-stick layer

With a Nadelrad contact points were generated in the non-stick layer. The wheel points to the surface at intervals of 3mm protrusions (spikes) and was pressed by hand on the non-stick layer and rolled at a distance of 3 mm several times in parallel, so in all three spatial directions contact stems were generated at intervals of 3 mm

coating with the glue and peel strength

Subsequently was Glue the adhesive and dry. The resulting application weight was 40 g / m2 (solid). The adhesive layer was covered with a paper. When the paper is peeled off, the adhesive layer is on the paper (transfer coating).

The peel strength was determined as indicated above. For comparison, the experiment was also performed with an untreated non-stick layer without contact points.

The peel strength was determined as indicated above in N / 2.5 cm:
With contact points (ie surface-structured adhesive): 32.6
Without contact points (ie adhesive without surface structure): 27.0

Claims (15)

A method for producing adhesive layers having a defined surface structure by coating adhesive on a carrier provided with an anti-adhesive layer, characterized in that the anti-adhesive layer has holes and the coated adhesive has direct contact with the carrier at these holes (hereinafter referred to as contact points). Method according to claim 1, characterized in that the carrier is paper or Polymer film is. Method according to claim 1 or 2, characterized in that it is the non-stick layer to a silicone layer is. Method according to one the claims 1 to 3, characterized in that the thickness of the non-stick layer is> 0.5 microns. Method according to one of claims 1 to 4, characterized in that the surface of the contact points is 5 microns ² to 1 mm ² . Method according to one of claims 1 to 5, characterized in that the number of contact points> 10 per cm ² . Method according to one the claims 1 to 6, characterized in that it is in the adhesive is a pressure sensitive adhesive. Method according to one the claims 1 to 7, characterized in that the pressure-sensitive adhesive at 21 ° C a peel strength (as a measure of the adhesion) of has at least 1 N / 2.5 cm. Method according to one the claims 1 to 8, characterized in that the adhesive at 21 ° C a shear strength (as a measure of the cohesion) of has at least 10 minutes. Method according to one the claims 1 to 9, characterized in that it is an aqueous Adhesive that is an aqueous Polymer dispersion contains as a binder. Method according to one the claims 1 to 10, characterized in that the coating of the adhesive with a free falling curtain (curtain coating). Method according to one the claims 1 to 11, characterized in that in a continuous Process on a provided with an anti-adhesive layer web-shaped carrier contact points, eg. B. with a roller, and then the Coating with the adhesive, preferably as a free-falling Movie curtain, done. Method according to one the claims 1 to 12, characterized in that on the adhesive layer a second carrier is deposited, so that is a multi-layer laminate with at least following layers results (sequence corresponds to the spatial Arrangement): - 2. carrier - adhesive layer - non-stick coating - Carrier Multilayer laminates obtainable by a process according to one the claims 1 to 13. Use of the laminates according to claim 14 as self-adhesive Articles or for the production of self-adhesive articles.