DE10212899A1 - Production of polyacrylate adhesive material for use on adhesive tape involves emulsion or dispersion polymerisation of acrylate monomers in presence of a cyclodextrin, preferably methylated beta-cyclodextrin - Google Patents

Abstract

A method for the production of polyacrylate adhesive material by polymerisation of acrylate-based monomer compositions in aqueous emulsion or dispersion involves carrying out the polymerisation in presence of cyclodextrin in amounts (in aqueous solution) such that the polyacrylate precipitates from the dispersion.

Description

The invention relates to a method for producing polyacrylate compositions, in particular those that can be used as PSAs and for coating substrates in the Hot melt processes are suitable, and the use of the polyacrylate obtained PSAs for the production of PSA tapes.

There are technological advances in the field of PSAs in the coating process an ongoing need for new developments. In the Industry are hot melt processes (hot melt processes) with solvent-free Coating technology for the production of Hafikklebemassen of increasing importance, because the Environmental regulations are getting bigger and the price of solvents is increasing. Therefore should remove solvents as much as possible from the manufacturing process PSA tapes are eliminated. The polymerization of acrylates is mostly in Solvents or carried out in aqueous medium. From ecological and For economic reasons, polymerization in the aqueous medium is preferred. On The disadvantage of the acrylate dispersions is that the emulsifiers remain in the PSA. These adversely affect the adhesive properties. The hot melt technology offers a variety of procedural advantages, such as. B. high Coating speeds, a very clean line, and it also allows the production of pressure sensitive adhesive tapes with high adhesive mass application.

For the production of pressure sensitive adhesive coatings with hot melt pressure sensitive adhesives Polymerizations made from water-based dispersions are examples DE 24 55 133, US 4 906 421 and US 5 716 669 to name. In these patents Procedure for removing the water phase and then extruding it described by a slot die. In this regard, the patents US 4,906,421 and US 5,716,669 show a special extrusion technique. to Production of the acrylate dispersions only use common chemicals. In the patent specification DE 24 55 133 the production of the acrylate dispersions is somewhat described in more detail. Quality improvement is achieved through the networking of Pressure-sensitive adhesive layer achieved with high-energy radiation.

For polymer dispersions used for pressure sensitive adhesive coatings from the melt should be, but are z. B. the polymer composition, the average Polymer chain length, the number of polymer chain branches and the selection of one functional and thermally highly resilient stabilizer system of crucial Importance for workability. Many of the commercially available PSA dispersions cannot therefore be processed from the melt.

The acrylate dispersions described in patent DE 24 55 133, which are controlled by means of a regulator Degree of polymerization are reduced and therefore better for the melt application are suitable, cause difficulties in processing because z. B. the as Dispersion stabilizer used polyvinyl alcohol gel formation during the high promotes thermal stress on the polymer and thus through the process Speck formation is negatively affected. Furthermore, in DE 24 55 133 the 20-50% by weight Filtered polyacrylate from the dispersion. The amount of contaminated waste water is considerable. In addition, emulsifier residues remain in the PSA, which the adversely affect adhesive properties.

The aim of the present invention is a production process for polyacrylate compositions, in particular acrylic PSAs in dispersion, in which the stabilizers slightly from the PSA can be separated and the aqueous phase with the Stabilizer can be reused.

This task was surprising and could not have been foreseen by a person skilled in the art Realized method as shown in the main claim. The subclaims relate to advantageous developments of the invention.

According to the invention it is provided that in a generic method for Production of a polyacrylate mass by polymerization of Acrylate-based monomer compositions in aqueous emulsion or dispersion, the emulsion or dispersion polymerization in the presence of cyclodextrin, the Concentration of the cyclodextrin in the aqueous solution is adjusted so that the Polyacrylate precipitates from the aqueous dispersion, or from this in its own Phase separates and can be easily separated. The severed Acrylic PSA can then melt from the melt without thermal gelling be coated.

Polyacrylates, here polyacrylate PSAs, are usually replaced by radical ones Polymerization of the monomers or monomer mixtures - the use of Prepolymers or prepolymer mixtures should not be excluded - optionally with the addition of conventional additives. The polymerization can take place in Solution, emulsion or dispersion. The invention relates to a method for Production and further processing of acrylic dispersions, in which an initial one aqueous emulsion or dispersion of the monomers or comonomers and then the polymerization is initiated in a suitable manner. Such methods are in State of the art as described above is basically known.

According to the invention, the polymerization is now carried out in the presence of cyclodextrin, that acts as a protective colloid and stabilizer. The cyclodextrin is preferably added to Start of the process added to the aqueous phase and remains in the aqueous phase Phase, while the polyacrylate formed practically fails and its own Forms phase that only needs to be dried a little.

A mixture of water, cyclodextrin and monomer is preferred first or monomer mixture, which is treated with ultrasound to a to achieve a more even and finer distribution of the components.

The polymerization is preferably carried out in the presence of linearly polymerizing, radical initiators soluble in particular in organic media, the particular are suitable for suppressing microgel formation. An example of an advantageous in The initiator to be used in this sense is AIBN. With the addition of controllers, too conventional initiators soluble in aqueous phase, such as. B. 2,2'-azobis (2- amidopropane) or potassium peroxosulfate. examples for Free radical initiators are peroxides, hydroperoxides and azo compounds than some are not exclusive examples of typical radical initiators are mentioned here Potassium peroxodisulfate, dibenzoyl peroxide, cumene hydroperoxide, cyclohexanone peroxide, di-t- butyl peroxide, azodiisoic acid butyronitrile, cyclohexylsulfonylacetyl peroxide, Diisopropyl percarbonate, t-butyl peroctoate, benzpinacol. In a preferred embodiment as a radical initiator 1,1'-azo-bis- (cyclohexanecarbonitrile) (Vazo 88 ™ from DuPont) is used.

The degree of polymerization can be limited by the addition of polymerization regulators are, as known in the art, z. B. for dispersions alkylthiols, such as Dodecanethiol, or tetrabromomethane are suitable. The proportion of the controller is between 0.1 and 5% by weight, more preferably between 0.5 and 1% by weight.

Controlled radical polymerization methods are also suitable for the production of polyacrylate PSAs with a narrow molecular weight distribution. A control reagent of the general formula is then preferably used for the polymerization:

• - verzweigte und unverzweigte C₁- bis C₁₈-Alkylreste; C₃- bis C₁₈-Alkenylreste; C₃- bis C₁₈-Alkinylreste;
• - C₁- bis C₁₈-Alkxoyreste
• - durch zumindest eine OH-Gruppe oder ein Halogenatom oder einen Silylether substituierte C₁- bis C₁₈-Alkylreste; C₃- bis C₁₈-Alkenylreste; C₃- bis C₁₈- Alkinylreste;
• - C₂-C₁₈-Hetero-Alkylreste mit mindestens einem O-Atom und/oder einer NR*- Gruppe in der Kohlenstoffkette, wobei R* ein beliebiger (insbesondere organischer) Rest sein kann,
• - mit zumindest einer Estergruppe, Amingruppe, Carbonatgruppe, Cyanogruppe, Isocyanogruppe und/oder Epoxidgruppe und/oder mit Schwefel substituierte C₁- C₁₈-Alkylreste, C₃-C₁₈-Alkenylreste, C₃-C₁₈-Alkinylreste;
• - C₃-C₁₂-Cycloalkylreste
• - C₆-C₁₈-Aryl- oder Benzylreste
• - Wasserstoff

darstellen. wherein R and R ^{1 are} independently selected or the same

• - branched and unbranched C ₁ - to C ₁₈ -alkyl radicals; C ₃ to C ₁₈ alkenyl radicals; C ₃ to C ₁₈ alkynyl radicals;
• C ₁ to C ₁₈ alkoxy residues
• - C ₁ - to C ₁₈ -alkyl radicals substituted by at least one OH group or a halogen atom or a silyl ether; C ₃ to C ₁₈ alkenyl radicals; C ₃ to C ₁₈ alkynyl radicals;
• C ₂ -C ₁₈ heteroalkyl radicals having at least one O atom and / or one NR * group in the carbon chain, where R * can be any (in particular organic) radical,
• - with at least one Estergruppe, amine group, carbonate group, cyano group, isocyano group and / or epoxide group and / or sulfur-substituted C ₁ - C ₁₈ alkyl radicals, C ₃ -C ₁₈ alkenyl radicals, C ₃ -C ₁₈ -alkynyl;
• - C ₃ -C ₁₂ cycloalkyl radicals
• - C ₆ -C ₁₈ aryl or benzyl radicals
• - hydrogen

represent.

Control reagents of type (I) preferably consist of the following further restricted compounds:
Halogen atoms here are preferably P, Cl, Br or I, more preferably Cl and Br. Both linear and branched chains are outstandingly suitable as alkyl, alkenyl and alkynyl radicals in the various substituents.

Examples of alkyl radicals which contain 1 to 18 carbon atoms are methyl, ethyl, Propyl, isopropyl, butyl, isobutyl, t-butyl, pentyl, 2-pentyl, hexyl, heptyl, octyl, 2- Ethylhexyl, t-octyl, nonyl, decyl, undecyl, tridecyl, tetradecyl, hexadecyl and Octadecyl.

Examples of alkenyl radicals with 3 to 18 carbon atoms are propenyl, 2-butenyl, 3- Butenyl, isobutenyl, n-2,4-pentadienyl, 3-methyl-2-butenyl, n-2-octenyl, n-2-dodecenyl, Isododecenyl and oleyl.

Examples of alkynyl having 3 to 18 carbon atoms are propynyl, 2-butynyl, 3-butynyl, n-2-octynyl and n-2-octadecynyl.

Examples of hydroxy-substituted alkyl radicals are hydroxypropyl, hydroxybutyl or Hydroxyhexyl.

Examples of halogen-substituted alkyl radicals are dichlorobutyl, monobromobutyl or Trichlorohexyl.

A suitable C ₂ -C ₁₈ heteroalkyl radical with at least one O atom in the carbon chain is, for example, -CH ₂ CH ₂ -O-CH ₂ -CH ₃ .

Cyclopropyl, cyclopentyl, cyclohexyl or trimethylcyclohexyl are used, for example, as C ₃ -C ₁₂ cycloalkyl radicals.

As C ₆ -C ₁₈ aryl radicals are used, for example, phenyl, naphthyl, benzyl, 4-tert-butylbenzyl or other substituted phenyl, such as, for. As ethyl, toluene, xylene, mesitylene, isopropylbenzene, dichlorobenzene or bromotoluene.

The above listings are only examples of each Connection groups and have no claim to completeness.

Compounds of the following types can also be used as control reagents


where R ^{2 can} also be selected independently of R and R ¹ from the group listed above for these radicals.

As a further controlled radical polymerization method, nitroxide-controlled polymerizations can be carried out. For radical stabilization, nitroxides of type (Va) or (Vb) are used in a favorable procedure:

• a) Halogenide, wie z. B. Chlor, Brom oder Iod
• b) lineare, verzweigte, cyclische und heterocyclische Kohlenwasserstoffe mit 1 bis 20 Kohlenstoffatomen, die gesättigt, ungesättigt oder aromatisch sein können,
• c) Ester -COOR¹¹, Alkoxide -OR¹² und/oder Phosphonate -PO(OR¹³)₂,

wobei R¹¹, R¹² oder R¹³ für Reste aus der Gruppe ii) stehen. where R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ , R ⁸ , R ⁹ , R ¹⁰ independently of one another denote the following compounds or atoms:

• a) halides, such as. B. chlorine, bromine or iodine
• b) linear, branched, cyclic and heterocyclic hydrocarbons with 1 to 20 carbon atoms, which can be saturated, unsaturated or aromatic,
• c) esters -COOR ¹¹ , alkoxides -OR ¹² and / or phosphonates -PO (OR ¹³ ) ₂ ,

where R ¹¹ , R ¹² or R ^{13 are} radicals from group ii).

Compounds of (Va) or (Vb) can also be bound to polymer chains of any kind (primarily in the sense that at least one of the radicals mentioned above is a represents such a polymer chain) and thus for the construction of polyacrylate PSAs be used.

• - 2,2,5,5-Tetramethyl-1-pyrrolidinyloxyl (PROXYL), 3-Carbamoyl-PROXYL, 2,2-dimethyl-4,5-cyclohexyl-PROXYL, 3-oxo-PROXYL, 3-Hydroxylimine-PROXYL, 3-Aminomethyl-PROXYL, 3-Methoxy-PROXYL, 3-t-Butyl-PROXYL, 3,4-Di-t-butyl- PROXYL
• - 2,2,6,6-Tetramethyl-1-piperidinyloxy pyrrolidinyloxyl (TEMPO), 4-Benzoyloxy-TEMPO, 4-Methoxy-TEMPO, 4-Chioro-TEMPO, 4-Hydroxy-TEMPO, 4-Oxo-TEMPO, 4-Amino-TEMPO, 2,2,6,6,-Tetraethyl-1-piperidinyloxyl, 2,2,6-Trimethyl-6-ethyl-1- piperidinyloxyl
• - N-tert.-Butyl-1-phenyl-2-methyl propyl Nitroxid
• - N-tert.-Butyl-1-(2-naphtyl)-2-methyl propyl Nitroxid
• - N-tert.-Butyl-1-diethylphosphono-2,2-dimethyl propyl Nitroxid
• - N-tert.-Butyl-1-dibenzylphosphono-2,2-dimethyl propyl Nitroxid
• - N-(1-Phenyl-2-methyl propyl)-1-diethylphosphono-1-methyl ethyl Nitroxid
• - Di-t-Butylnitroxid
• - Diphenylnitroxid
• - t-Butyl-t-amyl Nitroxid

Controlled regulators for the polymerization of compounds of the type:

• - 2,2,5,5-tetramethyl-1-pyrrolidinyloxyl (PROXYL), 3-carbamoyl-PROXYL, 2,2-dimethyl-4,5-cyclohexyl-PROXYL, 3-oxo-PROXYL, 3-hydroxylimine-PROXYL, 3-aminomethyl-PROXYL, 3-methoxy-PROXYL, 3-t-butyl-PROXYL, 3,4-di-t-butyl-PROXYL
• - 2,2,6,6-tetramethyl-1-piperidinyloxy pyrrolidinyloxyl (TEMPO), 4-benzoyloxy-TEMPO, 4-methoxy-TEMPO, 4-chloro-TEMPO, 4-hydroxy-TEMPO, 4-oxo-TEMPO, 4 -Amino-TEMPO, 2,2,6,6, -Tetraethyl-1-piperidinyloxyl, 2,2,6-trimethyl-6-ethyl-1-piperidinyloxyl
• - N-tert-butyl-1-phenyl-2-methyl propyl nitroxide
• - N-tert-Butyl-1- (2-naphthyl) -2-methyl propyl nitroxide
• - N-tert-Butyl-1-diethylphosphono-2,2-dimethyl propyl nitroxide
• - N-tert-butyl-1-dibenzylphosphono-2,2-dimethyl propyl nitroxide
• - N- (1-phenyl-2-methyl propyl) -1-diethylphosphono-1-methyl ethyl nitroxide
• - Di-t-butyl nitroxide
• - Diphenyl nitroxide
• - t-butyl-t-amyl nitroxide

A number of other polymerization methods, by means of which the Hafikklebemassen can be produced in an alternative procedure, can be selected from the prior art:
No. 4,581,429 A discloses a controlled radical polymerization process which uses an initiator of a compound of the formula R'R "NOY, in which Y is a free radical species which can polymerize unsaturated monomers. However, the reactions generally have low conversions. Particularly problematic the polymerization of acrylates, which takes place only in very low yields and molecular weights. WO 98/13392 A1 describes open-chain alkoxyamine compounds which have a symmetrical substitution pattern. EP 735 052 A1 discloses a process for producing thermoplastic elastomers with narrow molecular weight distributions. WO 96/24620 A1 describes a polymerization process in which very special radical compounds such as, for example, phosphorus-containing nitroxides based on imidazolidine are used WO 98/44008 A1 discloses special nitroxyls based on morpholines, piperazinones and piperazine dions DE 199 49 352 A1 describes heterocyclic Alko xyamine as regulators in controlled radical polymerizations. Corresponding further developments of the alkoxyamines or the corresponding free nitroxides improve the efficiency for the production of polyacrylates (Hawker, contribution to the General Meeting of the American Chemical Society, spring 1997; Husemann, contribution to the IUPAC World-Polymer Meeting 1998, Gold Coast).

As a further controlled polymerization method can be used in an advantageous manner Synthesis of the polyacrylate PSAs, the Atom Transfer Radical Polymerization Use (ATRP), the initiator preferably being monofunctional or difunctional secondary or tertiary halides and for the abstraction of the halide (s) Cu, Ni, Fe, Pd, Pt, Ru, Os, Rh, Co, Ir, Ag or Au complexes (EP 0 824 111 A1; EP 826 698 A1; EP 824 110 A1; EP 841 346 A1; EP 850 957 A1) can be used. The different possibilities of the ATRP are furthermore described in US 5,945,491 A, US 5,854,364 A and US 5,789,487 A.

The preferred stabilizer is methylated cyclodextrin, in particular methylated β- Cyclodextrin used. In the examples, methylated β-cyclodextrin from. Wacker-Chemie GmbH (Cavasol W7 M ™) is used. The weight percentage in the aqueous solution should be between 20 and 50%, preferably between 30 and 45% by weight can be used.

The polymerization is carried out in a reactor suitable for acrylic dispersions carried out. The polymerization time is about 1-6 h, the conversion being about 20-95% lies. The polymer precipitated from the clatrate is generally filtered off and then dried in a vacuum. The filtrate, namely the cyclodextrin-containing aqueous Phase that also contains residual monomers and possibly other additives can be recycled and is then used for the next polymerization. For example, it can by gas chromatography (GC) the missing portion of the monomer or Monomer mixture determined and added for the subsequent polymerization become.

In a development of the invention it is provided that the polyacrylate composition obtained in transferred a concentration extruder and freed of residual water there, d. H. is dried. The residual water can with the filtrate or after the polymerization obtained polyacrylate supernatant, are combined The polyacrylate composition obtained can be processed further in any manner. There hardly using stabilizers and Is contaminated, it is excellent for processing in Suitable hot melt process and can, for example, after passing through the Extruder from which the melt is coated on one or both sides of the carrier. By the process can therefore be based on dispersion-based acrylic PSA tapes Make melt.

The invention itself is not limited with respect to the acrylate compositions. However, comonomer compositions which contain 70 to 100% by weight = acrylic acid and methacrylic acid derivatives according to formula (I) are preferred for the production of PSAs and in particular hot melt processable PSAs

CH ₂ = C (R ₁ ) (COOR ₂ ) (I)

where R ₁ = H or CH ₃ and R ₂ = an alkyl chain with 2-20 C atoms.

The acrylic and methacrylic acid esters of the formula (I) used as acrylic monomers include in particular those with alkyl groups consisting of 4 to 14 carbon atoms, preferably 4 to 9 carbon atoms. Specific examples without going through this list want to restrict are n-butyl acrylate, n-pentyl acrylate, n-hexyl acrylate, n- Heptyl acrylate, n-octyl acrylate, n-nonyl acrylate, laury acrylate, stearyl acrylate, behenyl acrylate, and their branched isomers, such as. B. 2-ethylhexyl acrylate. More usable Compound classes are methyl methacrylates, cyclohexyl methacrylates and Isobornyl methacrylates.

In a preferred embodiment, the comonomer composition can continue to 30% by weight, based on the components of the formula (I), of copolymerizable contain olefinically unsaturated monomers with functional groups.

As vinyl compounds or olefinically unsaturated monomers with functional groups can be used in particular: vinyl esters, vinyl ethers, vinyl halides, Vinylidene halides, vinyl compounds with aromatic cycles and heterocycles in α position, for example vinyl acetate, vinyl formamide, vinyl pyridine, ethyl vinyl ether, Vinyl chloride, vinylidene chloride and acrylonitrile. It is further preferred to use monomers use the following functional groups: hydroxyl, carboxy, acid amide, Isocyanato or amino groups.

Particularly preferred examples of those to be used in the context of the invention Vinyl compounds with functional groups are hydroxyethyl acrylate, Hydroxypropyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, allyl alcohol, Maleic anhydride, itaconic anhydride, itaconic acid, acrylamide, benzyl acrylate, Benzyl methacrylate, phenyl acrylate, phenyl methacrylate, t-butylphenyl acrylate, t- Butylaphenyl methacrylate, phenoxyethyl acrylate, phenoxyethyl methacrylate, 2- Butoxyethyl methacrylate, 2-butoxyethyl acrylate, dimethylaminoethyl methacrylate, Dimethylaminoethyl acrylate, diethylaminoethyl methacrylate, diethylaminoethyl acrylate, Cyanoethyl methacrylate, cyanoethyl acrylate, 6-hydroxyhexyl methacrylate, N-tert.- Butylacrylamide, N-methylol methacrylamide, N- (buthoxymethyl) methacrylamide, N- Methylolacrylamide, N- (ethoxymethyl) acrylamide, N-isopropylacrylamide, vinyl acetic acid, Tetrahydrofurfuryl acrylate, β-acryloyloxypropionic acid, trichloracrylic acid, fumaric acid, Crotonic acid, aconitic acid, dimethylacrylic acid, but this list is not is final.

Aromatic vinyl compounds can also be used, the aromatic nuclei preferably consisting of C ₄ to C ₁₈ and also containing heteroatoms. Particularly preferred examples are styrene, 4-vinylpyridine, N-vinylphthalimide, methylstyrene, 3,4-dimethoxystyrene, 4-vinylbenzoic acid, although this list is not exhaustive.

These compounds are used in PSAs to control the adhesive technology Properties used.

In an advantageous further development, fumaric acid esters or vinyl ethers, in particular cyclohexenyl ether, added in small amounts for the polymerization.

In a particularly advantageous further development, small amounts of resins, such as B. Rosin resin acids added that do not destabilize the dispersion.

The composition of the corresponding comonomers is chosen so that the resulting PSAs according to D. Satas [Handbook of Pressure Sensitive Adhesive Technology, 1989, published by VAN NOSTRAND REINHOLD, New York] have adhesive properties and that the polymer is not in the aqueous Phase resolves.

In order to achieve a preferred glass transition temperature T _{G of} the polymers of T _G 25 25 ° C., the monomers are very preferably selected in accordance with what has been said above and the quantitative composition of the monomer mixture is advantageously chosen such that the Fox equation (G1) (cf. TG Fox, Bull. Am. Phys. Soc. 1 (1956) 123) gives the desired T _G value for the polymer.

Herein n represents the running number of the monomers used, w _n the mass fraction of the respective monomer n (% by weight) and T _{G, n} the respective glass transition temperature of the homopolymer from the respective monomers n in K.

To optimize the pressure sensitive adhesive properties of an acrylate hot melt, the polyacrylate pressure sensitive adhesive can be mixed with resins after concentration. Terpene, terpene-phenol resins, C ₅ - and C ₉ -hydrocarbon resins, pinene, indene and rosin resins, for example, can be used alone and also in combination with one another as resins. In principle, however, all resins soluble in the corresponding polyacrylate can be used, in particular reference is made to all aliphatic, aromatic, alkylaromatic hydrocarbon resins, hydrocarbon resins based on pure monomers, hydrogenated hydrocarbon resins, functional hydrocarbon resins and natural resins.

In a further advantageous further development, one or several plasticizers, such as B. low molecular weight polyacrylates, phthalates, or Soft resins added. Be in a preferred advancement Phosphates / polyphosphates used.

Furthermore, crosslinking substances such as. B. multifunctional Acrylates or urethane acrylates are metered in and mixed into the acrylic melt.

The polyacrylate PSAs can be used for optional crosslinking with UV light UV-absorbing photoinitiators can be added. Useful photoinitiators, which are very good to use, are benzoin ethers such. B. benzoin methyl ether and Benzoin isopropyl ether, substituted acetophenones, such as. B. 2,2-Diethoxyacetophenone (available as Irgacure 651® from Ciba Geigy®), 2,2-dimethoxy-2-phenyl-1- phenylethanone, dimethoxyhydroxyacetophenone, substituted α-ketols, such as. B. 2-methoxy-2-hydroxypropiophenone, aromatic sulfonyl chlorides such as e.g. B. 2-naphthyl sulfonyl chloride, and photoactive oximes such. B. 1-phenyl-1,2-propanedione-2- (O- ethoxycarbonyl) oxime.

The above-mentioned and other usable photoinitiators and others of the type Norrish I or Norrish II may contain the following residues: benzophenone, Acetophenone, benzil, benzoin, hydroxyalkylphenone, phenylcyclohexyl ketone, Anthraquinone, trimethylbenzoylphosphine oxide, methylthiophenylmorpholine ketone, Aminoketone, azobenzoin, thioxanthone, hexarylbisimidazole, triazine, or fluorenone, each of these radicals additionally having one or more halogen atoms and / or one or more alkyloxy groups and / or one or more amino groups or Hydroxy groups can be substituted. A representative overview is provided by Fouassier: "Photoinititation, Photopolymerization and Photocuring: Fundamentals and Applications", Hanser-Verlag, Munich 1995. In addition, Carroy et al. in "Chemistry and Technology of UV and EB Formulation for Coatings, Inks and Paints ", Oldring ed.), 1994, SITA, London.

Furthermore, various fillers such as carbon black, TiO ₂ , solid or hollow spheres made of glass or other materials, nucleating agents, blowing agents, compounding agents and / or anti-aging agents can be added.

The acrylate hot melt is made from solution or in a particularly advantageous way Further development from the melt applied to a carrier material. As Backing material, for example for adhesive tapes, can be used by those skilled in the art common and usual materials, such as foils (polyester, PET, PE, PP, BOPP, PVC), Nonwovens, foams, fabrics and fabric films as well as release paper (glassine, HDPE, Use LDPE). This list is not intended to be exhaustive.

A further development that the method according to the invention is particularly favorable for Manufacture of adhesive tapes, for example, is characterized in that the PSA thermally, by UV radiation or by ionizing radiation, such as z. B. electron radiation is networked.

The invention further includes the use of the according to the invention Process obtained PSA for an adhesive tape, the Acrylic PSA as a single or double-sided coating (film) on a carrier is present.

The pressure sensitive adhesive tapes produced by this process face each other conventional acrylic dispersion PSAs have better resistance against moisture and water, because the inventive method on the The use of emulsifiers remaining in the polymer could be dispensed with.

Examples

The invention will be explained in more detail below by means of a few examples, without want to limit unnecessarily.

test methods

The following test methods were used to determine the properties of the acrylate hotmelts to evaluate.

Determination of the gel fraction (test A)

The carefully dried solvent-free adhesive samples were put in one Fleece bags made of polyethylene (Tyvek fleece) welded in. From the difference of Sample weights before extraction and after extraction with toluene was the Gel value determined.

180 ° adhesive strength test (test B)

A 20 mm wide strip of an acrylic PSA coated on a polyester was applied to steel plates. The pressure sensitive adhesive strip was washed twice with a 2 kg Weight pressed onto the substrate. The tape was then immediately with 300 mm / min and subtracted from the substrate at a 180 ° angle. The steel plates were made twice washed with acetone and once with isopropanol. The measurement results are in N / cm and are averaged from three measurements. All measurements were taken at Room temperature carried out under air-conditioned conditions.

Shear strength (test C)

A 13 mm wide strip of the adhesive tape was placed on a smooth steel surface was cleaned three times with acetone and once with isopropanol. The Application area was 20.13 mm (length.width). Then with a 2 kg Weight the tape pressed four times on the steel support. At room temperature a 2 kg weight was attached to the adhesive tape (test C1), at 70 ° C. a 1 kg weight (Test C2). The measured shear life times are given in minutes and correspond to the mean of three measurements.

Examined samples

The samples used for the experiments were prepared as follows:
The polymers were conventionally made via free radical polymerization.

example 1

266.3 g of methylated β-cyclodextrin (Cavasol W7 M ™) were dissolved in 642 g of water and 35 g of 2-ethylhexyl acrylate with vigorous stirring and then the dispersion was treated with ultrasound for 10 minutes. The resulting clear solution was mixed with vigorous stirring with 0.105 g BPO (benzoyl peroxide) and then heated to 70 ° C. After about 30 minutes, a white sticky precipitate formed, which was filtered off after a reaction time of 6 hours. To dry the sticky precipitate, the remaining water was removed under low pressure, the PSA was dissolved in toluene and coated with 50 g / m ² on a primed PET film. After the solvent had been evaporated off in a drying cabinet at 120 ° C. for 15 minutes, the PSA tape was irradiated with a 60 kGy Es dose at an acceleration voltage of 230 kV and then tested according to test methods A, B and C.

Example 2

The filtrate from Example 1 was made up with 7 g of 2-ethylhexyl acrylate and 10 g of water and then proceeded analogously to Example 1.

Example 3

266.3 g of methylated β-cyclodextrin (Cavasol W7 M ™) were dissolved in 642 g of water, 175 mg of dodecanethiol, 17.5 g of 2-ethylhexyl acrylate and 17.5 g of n-butyl acrylate with vigorous stirring and then the dispersion was treated with ultrasound for 10 minutes. 0.105 g of Vazo 67 ™ (from DuPont) was added to the clear solution with vigorous stirring and the mixture was then heated to 70.degree. After about 30 minutes, a white sticky precipitate formed, which was filtered off after a reaction time of 6 hours. After the sticky precipitate had dried, the remaining water was removed under low pressure, the PSA from the melt was coated with 50 g / m ² onto a primed PET film through a slot nozzle, and the PSA tape was irradiated with a 60 kGy Es dose at an acceleration voltage of 230 kV and then tested according to test methods A, B and C.

Example 4

266.3 g of methylated β-cyclodextrin (Cavasol W7 M ™) were dissolved in 642 g of water, 125 mg of dodecanethiol, 25 g of 2-ethylhexyl acrylate and 7 g of styrene with vigorous stirring and then the dispersion was treated with ultrasound for 10 minutes. The clear solution was reacted with vigorous stirring with 0.105 g of azoisobutyronitrile and then heated to 70 ° C. After about 30 minutes, a white sticky precipitate formed, which was filtered off after a reaction time of 6 hours. After the sticky precipitate had dried, the remaining water was removed under low pressure, the PSA from the melt was coated with 50 g / m ² onto a primed PET film through a slot nozzle, and the PSA tape was irradiated with a 60 kGy Es dose at an acceleration voltage of 230 kV and then tested according to test methods A, B and C.

Example 5

266.3 g of methylated β-cyclodextrin (Cavasol W7 M ™) were dissolved in 642 g of water, 150 mg, dodecanethiol, 25 g of 2-ethylhexyl acrylate, 4 g of styrene and 2 g of methacrylic acid with vigorous stirring and then the dispersion was treated with ultrasound for 10 minutes , The clear solution was reacted with vigorous stirring with 0.105 g AIBN and then heated to 70 ° C. After about 30 minutes, a white sticky precipitate formed, which was filtered off after a reaction time of 6 hours. After the sticky precipitate had dried, the remaining water was removed under low pressure, the PSA from the melt was coated with 50 g / m ² onto a primed PET film through a slot nozzle, and the PSA tape was irradiated with a 60 kGy Es dose at an acceleration voltage of 230 kV and then tested according to test methods A, B and C.

The results of the tests are shown below. Example 1 and Example 2 demonstrate the universal applicability of the method. The monomer dissolves in the β-cyclodextrin-water phase. After the polymerization, the polymer precipitates and thus separates from this phase. The polymer can simply be filtered off and, after the appropriate drying and coating from solution and crosslinking, can be tested using adhesive technology. Example 2 in particular shows that after the polymer has been separated off, the filtrate can be used again for the next polymerization after appropriate filling, and the process can thus be carried out continuously. The results of the adhesive tests are listed in Table 1: Table 1

The comparison provides for Examples 1 and 2 and very small differences in the adhesive properties. The recycling concept is therefore very good for production of acrylic PSAs.

In order to demonstrate the universal applicability of the method according to the invention, various comonomer compositions were prepared and coated in an analogous manner. The results of these technical adhesive tests are listed in Table 2: Table 2

The higher polar proportions increase the cohesion of the polyacrylate PSAs clearly. The coating from the melt also demonstrates that methylated β- Cyclodextrin, even if it should only be present in traces in the polyacrylate, not that Concentration process and the hot melt coating negatively affected. The good Coatability was achieved by initiation with a linear polymerizing initiator, such as AIBN or Vazo 67 ™ (Du Pont) reached. During the coating from the In the melt, no specks have occurred due to gelling.

Claims (12)

1. A method for producing a polyacrylate PSA by polymerizing monomer compositions based on acrylate in aqueous emulsion or dispersion, characterized in that the emulsion or dispersion polymerization is carried out in the presence of cyclodextrin, the concentration of the cyclodextrin in the aqueous solution being adjusted so that Polyacrylate precipitates out of the aqueous dispersion. 2. The method according to claim 1, characterized in that first a mixture is prepared from water, cyclodextrin and monomer composition with Ultrasound is being treated. 3. The method according to claim 1 or 2, characterized in that the polymerization by radical, linear polymerizing, preferably in organic media soluble initiators is started. 4. The method according to any one of claims 1 to 3, characterized in that the aqueous, cyclodextrin-containing phase is recycled. 5. The method according to any one of claims 1 to 4, characterized in that the Polyacrylate PSA is transferred to a concentration extruder and from there Residual water is freed. 6. The method according to any one of claims 1 to 5, characterized in that the Polyacrylate mass processed in a melt and especially on carrier is coated. 7. The method according to any one of claims 1 to 6, characterized in that as Cyclodextrin methylated cyclodextrin, especially methylated □ -cyclodextrin is used. 8. The method according to any one of claims 1 to 7, characterized in that the Cyclodextrin in parts by weight between 20 and 50% by weight, preferably between 30 and 45% by weight, based on the aqueous phase, is used. 9. The method according to any one of claims 1 to 8, characterized in that the polyacrylate PSA is obtained from a comonomer composition which contains 70-100 wt .-% acrylic acid and methacrylic acid derivatives according to formula (I),

CH ₂ = C (R ₁ ) (COOR ₂ ) (I)

where R ₁ = H or CH ₃ and R _{2 is} an alkyl chain with 2-20 C atoms. 10. The method according to claim 9, characterized in that the Comonomer composition further 0-30 wt .-%, based on the components according to the formula (I), on copolymerizable olefinically unsaturated monomers with functional Contains groups. 11. The method according to any one of claims 1 to 10, characterized in that the Resins or plasticizers obtained polyacrylate PSA are added. 12. Use of a polyacrylate PSA obtained according to one of claims 1 to 11, for the production of adhesive tapes in which the polyacrylate PSA is present as a coating on one or both sides on a carrier.