DE102005029593A1 - Process for the preparation of acid-containing emulsion polymers for pressure-sensitive adhesives - Google Patents

Abstract

Process for the production of polymers by emulsion polymerization, with monomers being added at least partially during the polymerization (feed process), characterized in that the polymer also contains monomers with at least one carboxylic acid group (acid monomers for short) and at least 80% by weight of the acid monomers have been added if the polymerization mixture (mixture of monomers to be polymerized and possibly already formed polymer present in the polymerization vessel) contains less than 75% by weight of the total amount of monomers.

Description

The The invention relates to a process for the preparation of polymers Emulsion polymerization, wherein monomers are at least partially during the Polymerization are added (feed method), characterized in that that the polymer also monomers having at least one carboxylic acid group (short acid monomers) contains and at least 80% by weight of the acid monomers have been added when the polymerization mixture (present in the polymerization vessel Mixture of monomers to be polymerized and, if appropriate, already formed Polymer) contains less than 75% by weight of the total amount of the monomers.

Farther the invention relates to the use of the thus prepared or available Polymers as pressure-sensitive adhesives.

at Pressure-sensitive adhesives are both a good adhesion (adhesion) to Substrate desired as well as sufficient internal strength in the adhesive layer (Cohesion). For adhesion and cohesion these are opposite application properties. Activities, the improvement of the adhesion cause, lead in general at the same time as a deterioration of cohesion and vice versa.

PSAs based on aqueous Polymer dispersions obtainable by emulsion polymerization, have long been known. In particular, these are polyacrylates. An improvement in adhesion and cohesion has been used in such emulsion polymers so far by selection achieved suitable comonomers or additives. Exemplarily be on (PF 54601) DE-A-10323048, according to which by addition of silicon compounds to polymer dispersion positive effects can be achieved.

task The present invention has been a method which inhibits adhesion and / or cohesion improved without affecting the other property.

Accordingly, became Found the initially defined method. It was found too the use of the product manufactured or available by this process Polymers as or in pressure-sensitive adhesives.

The Preparation of the polymers is carried out by emulsion polymerization, it is therefore an emulsion polymer.

at the emulsion polymerization are ethylenically unsaturated compounds (Monomers) polymerized in water, with ionic and / or not ionic emulsifiers and / or protective colloids or stabilizers as surface-active Compounds for the stabilization of the momer droplets and later the monomer formed polymer particles are used.

A detailed description of suitable protective colloids can be found in Houben-Weyl, Methods of Organic Chemistry, Volume XIV / 1, Macromolecular substances, Georg-Thieme-Verlag, Stuttgart, 1961, pp 411 to 420. As emulsifiers are both anionic, cationic and nonionic emulsifiers into consideration. Emulsifiers whose molecular weight, unlike the protective colloids, are usually below 2000 g / mol, are preferably used as surface-active substances. Of course, in the case of the use of mixtures of surfactants, the individual components must be compatible with each other, which can be checked in case of doubt by hand on fewer preliminary tests. Anionic and nonionic emulsifiers are preferably used as surface-active substances. Common accompanying emulsifiers are, for example, ethoxylated fatty alcohols (EO degree: 3 to 50, alkyl radical: C ₈ - to C ₃₆ ), ethoxylated mono-, di- and tri-alkylphenols (EO degree: 3 to 50, alkyl radical: C ₄ - to C ₉ ), alkali metal salts of dialkyl esters of sulfosuccinic acid and alkali metal and ammonium salts of alkyl sulfates (alkyl radical: C ₈ - to C ₁₂ ), of ethoxylated alkanols (EO degree: 4 to 30, alkyl radical: C ₁₂ - to C ₁₈ ), of ethoxylated alkylphenols (EO degree: 3 to 50, alkyl radical: C ₄ - to C ₉ ), of alkylsulfonic acids (alkyl radical: C ₁₂ - to C ₁₈ ) and of alkylarylsulfonic acids (alkyl radical: C ₉ - to C ₁₈ ).

worin R₅ und R₆ Wasserstoff oder C4- bis C14-Alkyl bedeuten und nicht gleichzeitig Wasserstoff sind, und X und Y Alkalimetallionen und/oder Ammoniumionen sein können. Vorzugsweise bedeuten R5, R6 lineare oder verzweigte Alkylreste mit 6 bis 18 C-Atomen oder Wasserstoff und insbesondere mit 6, 12 und 16 C-Atomen, wobei R5 und R6 nicht beide gleichzeitig Wasserstoff sind. X und Y sind bevorzugt Natrium, Kalium oder Ammoniumionen, wobei Natrium besonders bevorzugt ist. Besonders vorteilhaft sind Verbindungen II in denen X und Y Natrium, R5 ein verzweigter Alkylrest mit 12 C-Atomen und R6 Wasserstoff oder R5 ist. Häufig werden technische Gemische verwendet, die einen Anteil von 50 bis 90 Gew.-% des monoalkylierten Produktes aufweisen, beispielsweise Dowfax☐ 2A1 (Warenzeichen der Dow Chemical Company).Further suitable emulsifiers are compounds of the general formula II

wherein R ₅ and R _{6 are} hydrogen or C _{4 to} C 14 alkyl and are not hydrogen at the same time, and X and Y may be alkali metal ions and / or ammonium ions. Preferably R5, R6 are linear or branched alkyl radicals having 6 to 18 C atoms or hydrogen and in particular having 6, 12 and 16 C atoms, wherein R5 and R6 are not both simultaneously hydrogen. X and Y are preferably sodium, potassium or ammonium ions, with sodium being particularly preferred. Particularly advantageous are compounds II in which X and Y are sodium, R5 is a branched alkyl radical having 12 C atoms and R6 is hydrogen or R5. Frequently, technical mixtures are used which have a proportion of 50 to 90% by weight of the monoalkylated product, for example Dowfax® 2A1 (trademark of the Dow Chemical Company).

suitable Emulsifiers are also found in Houben-Weyl, Methods of Organic Chemistry, Volume 14/1, Macromolecular Materials, Georg Thieme Verlag, Stuttgart, 1961, pages 192 to 208.

trade names of emulsifiers are e.g. Dowfax☐2 A1, Emulan☐ NP 50, Dextrol☐ OC 50, Emulsifier 825, Emulsifier 825 S, Emulan☐ OG, Texapon ☐ NSO, Nekanil ☐ 904 S, Lumiten ☐ I-RA, Lumiten E 3065, Disponil FES 77, Lutensol AT 18, Steinapol VSL, Emulphor NPS 25.

The surfactants Substance becomes common in amounts of 0.1 to 10 wt .-%, based on the polymerizable Monomers used.

at the emulsion polymerization are usually water-soluble initiators for the used radical polymerization of the monomers.

Water-soluble initiators for the Emulsion polymerization are e.g. Ammonium and alkali metal salts of peroxodisulfuric, e.g. Sodium peroxodisulfate, hydrogen peroxide or organic peroxides, e.g. tert-butyl hydroperoxide.

Suitable are also so-called reduction-oxidation (red-ox) initiator systems.

The Red Ox initiator systems consist of at least one mostly inorganic one Reducing agent and an inorganic or organic oxidizing agent.

at the oxidation component is e.g. already mentioned above mentioned initiators for the emulsion polymerization.

at the reduction components are e.g. to alkali metal salts sulphurous acid, such as. Sodium sulfite, Sodium hydrogen sulfite, Alkaline salts of Dischwefligen Acid like Sodium disulfite, bisulfite addition compounds of aliphatic aldehydes and ketones such as acetone bisulfite or reducing agents such as hydroxymethanesulfinic acid and their salts, or ascorbic acid. The red-ox initiator systems can with concomitant use of soluble Metal compounds whose metallic component in several valence states may occur.

Usual Red Ox initiator systems are e.g. Ascorbic acid / ferrous sulfate / sodium peroxydisulfate, tert-butyl hydroperoxide / sodium disulfite, tert-butyl hydroperoxide / Na hydroxymethanesulfinate. The individual components, e.g. the reduction component, too Mixtures, e.g. a mixture of the sodium salt of hydroxymethanesulfinic acid and Sodium metabisulfite.

The The compounds mentioned are usually used in the form of aqueous solutions, the lower concentration due to the amount of water acceptable in the dispersion and the upper concentration by the solubility of the respective Compound in water is determined. In general, the concentration is 0.1 to 30 wt .-%, preferably 0.5 to 20 wt .-%, particularly preferably 1.0 to 10 wt .-%, based on the solution.

The Amount of initiators is generally 0.1 to 10 wt .-%, preferably 0.5 to 5 wt .-%, based on the monomers to be polymerized. It can also be several, different Initiators in the emulsion polymerization find use.

According to the invention, the polymer contains Monomers having at least one acid group (short acid monomers, see below). The content of these acid monomers in the polymer is preferably 0.05 to 8 wt.%, Based on the polymer. Especially preferred the content is at least 0.1% by weight, very particularly preferably at least 0.2% by weight; the content is generally not higher than 4% by weight, more preferably not higher than 2% by weight, or not higher than 1% by weight.

The Acid monomers become prevalent added at the beginning of the polymerization, they can be submitted or their proportion in the continuously added monomer mixture is too Start according to size.

According to the invention are over 80 wt. % of the acid monomers has been added when the polymerization mixture (present in the polymerization vessel Mixture of monomers to be polymerized and, if appropriate, already formed Polymer) contains less than 75% by weight of the total amount of the monomers.

Preferably are about 90% by weight of the acid monomers has been added when the polymerization mixture (present in the polymerization vessel Mixture of monomers to be polymerized and, if appropriate, already formed Polymer) contains less than 75% by weight of the total amount of the monomers.

Especially 100% by weight of the acid monomers are preferred has been added when the polymerization mixture (present in the polymerization vessel Mixture of monomers to be polymerized and, if appropriate, already formed Polymer) contains less than 75% by weight of the total amount of the monomers.

at all statements which are based on the polymerization mixture are both not yet polymerized under the term monomer Monomers as well as monomer units of the polymer, i. the copolymerized Monomers, to be understood.

The Addition of the acid monomers is preferably carried out continuously during the polymerization, preferably via a Period of at least one hour, in particular at least 1.5 Hours.

Preferably in the polymerization polymerization regulator, short regulator, used. Regulators cause a chain termination reaction and decrease thus the molecular weight of the polymer. The regulators are connected to the Polymer bound, generally to the chain end.

The Amount of regulator is in particular 0.05 to 4 parts by weight, particularly preferably 0.05 to 0.8 parts by weight and most preferably 0.1 to 0.6 parts by weight, based on 100 parts by weight of the monomers to be polymerized. suitable Regulators are in particular compounds having a mercapto group such as tert-butylmercaptan, thioglycolate, Mercaptoethynol, mercaptopropyltrimethoxysilane or tert-dodecylmercaptan. The regulators are generally low-molecular compounds a molecular weight less than 2000, in particular less than 1000 g / mol.

Also the controller can be partially submitted, in whole or in part during the Polymerization or added towards the end of the polymerization.

More than 70% by weight of the total amount of regulator (total amount of in the later polymer containing regulator) are preferably added only when the Polymerization mixture (mixture present in the polymerization vessel) monomers to be polymerized and, if appropriate, already formed polymer) already contains at least 40 wt.% Of the total amount of monomers.

at all statements which are based on the polymerization mixture are both not yet polymerized under the term monomer Monomers as well as monomer units of the polymer, i. the copolymerized Monomers, to be understood.

Prefers be more than 70 wt.%, In particular more than 85 wt.%, Whole more preferably more than 90% by weight of the total regulator amount added only when the polymerization mixture already at least 60 wt.%, In particular at least 70 wt.% Of the total amount of Containing monomers.

Especially more than 70% by weight, in particular more than 85% by weight, are preferred. %, most preferably more than 90 wt.% Of the total amount of regulator added only when the polymerization mixture already at least Contains 80 wt.% Of the total amount of monomers.

All Particularly preferably, the entire amount of regulator (100% by weight) is only be added if the polymerization mixture already at least 60 wt., In particular at least 70, most preferably at least Contains 80 wt.% Of the total amount of monomers.

feature the invention is that monomers and optionally also polymerization at least partially during be added to the polymerization, so it is a feed process is.

One Subset of the monomers may, if desired, at the beginning of the polymerization submitted in the polymerization be the rest Monomers, or all monomers, if no monomers are presented, are added in the feed process during the course of the polymerization.

Also the controller can be partially submitted, in whole or in part during the Polymerization or added towards the end of the polymerization.

The Monomers become at least partially continuous during the polymerization added. In part you can Monomers also in the polymerization vessel before the start of the polymerization be submitted.

Preferably is at most 30 wt.% Of the total amount of monomers, especially preferably at most 20% by weight, very particularly preferably at most 10 % By weight of the monomers in the polymerization vessel. The remaining monomers, i.e. preferably at least 70% by weight, more preferably at least 80% by weight, most preferably at least 90% by weight while the polymerization continuously added. In a special embodiment no monomers are initially charged, i. the total amount of monomers is during fed to the polymerization.

The Temperature of the polymerization mixture is during the polymerization and accordingly during the addition of the monomers is preferably at least 50 ° C, especially preferably at least 70 ° C.

The Addition of the monomers to the polymerization vessel preferably takes place via a Period of at least two hours, more preferably at least 2.5 hours.

Otherwise, the following applies to the performance of the emulsion polymerization:
The emulsion polymerization is generally carried out at 30 to 130, preferably 50 to 90 ° C. The polymerization medium may consist of water only, as well as mixtures of water and water-miscible liquids such as methanol. Preferably, only water is used. The feed process can be carried out in a stepwise or gradient mode. Preferably, the feed process in which one submits a portion of the polymerization, heated to the polymerization, polymerized and then the rest of the polymerization, usually over several spatially separate feeds, one or more of which monomers in pure or in emulsified form, continuously , gradually or with the addition of a concentration gradient while maintaining the polymerization of the polymerization zone supplies. In the polymerization, it is also possible, for example for the purpose of better adjustment of the particle size, to introduce a polymer seed.

The Way in which the initiator in the course of radical aqueous Emulsion polymerization is added to the polymerization vessel is one of ordinary skill in the art known. It can be both complete presented in the polymerization vessel, as well as custom its consumption during the course of the free radical aqueous emulsion polymerization be used continuously or in stages. In detail depends on this from the chemical nature of the initiator system as well as the polymerization temperature. Preferably, a part is presented and the rest in accordance with the Consumption fed to the polymerization.

to Removal of the residual monomers is usually after the End of the actual emulsion polymerization, i. after a turnover the monomers of at least 95%, initiator added.

The individual components can the reactor in the feed process from above, in the side or of be added down through the reactor bottom.

at the emulsion polymerization are aqueous dispersions of the polymer usually with solids contents of 15 to 75 wt .-%, preferably from 40 to 75% by weight.

For a high space / time yield of the reactor, dispersions having the highest possible solids content are preferred. In order to achieve solids contents> 60 wt .-%, you should set a bimodal or polymodal particle size, otherwise the viscosity is too high, and the dispersion is no longer manageable. The generation of a new particle generation can be achieved, for example, by adding seed ( EP 81083 ), by adding excess emulsifier quantities or by adding miniemulsions. Another benefit associated with low viscosity at high solids content is improved coating behavior at high solids levels. The generation of a new / new particle generation (s) can take place at any time. It depends on the particle size distribution desired for a low viscosity.

The thus prepared polymer is preferably in the form of its aqueous Dispersion used.

The Emulsion polymer is preferably at least 40 wt .-%, preferably at least 60% by weight, more 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 one or two double bonds or mixtures of these monomers.

To call are e.g. (Meth) acrylates 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 include 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 ethylenically substituted with chlorine, fluorine or bromine unsaturated Compounds, preferably vinyl chloride and vinylidene chloride.

When Vinyl ethers are mentioned e.g. 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 ethylene, propylene, butadiene, isoprene and chloroprene called.

When Preferred main monomers are the C1 to C10 alkyl acrylates and methacrylates, in particular C1 to C8 alkyl acrylates and methacrylates and vinyl aromatics, in particular styrene and mixtures thereof.

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

Next the main monomer, the polymer may contain other monomers, e.g. Monomers with acid groups (Acid monomers, see above), e.g. Carboxylic acid, sulfonic acid or phosphonic acid groups. Prefers are carboxylic acid groups. Called e.g. Acrylic acid, methacrylic acid, Itaconic acid, maleic or fumaric acid.

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

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

When other monomers may also be mentioned as crosslinking monomers.

Especially Preferably, the polymer is at least 40 wt .-%, in particular at least 60% by weight, and most preferably at least 80 wt .-% of C1-C20, in particular C1-C10Alkyl (meth) acrylates.

The Glass transition temperature of the polymer preferably -60 up to 0 ° C, particularly preferred -60 to -10 ° C and whole particularly preferred -60 to -20 ° C.

The Glass transition temperature let yourself according to usual Methods such as differential thermal analysis or differential scanning Calorimetry (see, e.g., ASTM 3418/82, so-called midpoint temperature).

The Polymer is preferably used as or in pressure-sensitive adhesives.

Of the Contains pressure-sensitive adhesive the polymer vorzuhweise in the form of the aqueous polymer dispersion, as obtained or obtainable by the emulsion polymerization.

Of the Pressure sensitive adhesive can only from the polymer, or the aqueous Dispersion of the polymer exist.

Of the However, pressure-sensitive adhesive may also contain other additives.

In Consideration comes e.g. a tackifier, i. a tackifying resin. Tackifiers are e.g. from Adhesive Age, July 1987, pages 19-23 or Polym. Mater. Sci. Closely. 61 (1989), pages 588-592.

tackifiers are e.g. Natural resins, such as rosins and their disproportionation or isomerization, polymerization, dimerization, hydrogenation resulting derivatives. these can in their salt form (with, for example, monovalent 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.

Of others also find hydrocarbon resins, e.g. Coumarone-indene resins, Polyterpene resins, hydrocarbon resins based on unsaturated CH compounds, such as butadiene, pentene, methylbutene, isoprene, piperylene, Divinylmethane, pentadiene, cyclopentene, cyclopentadiene, cyclohexadiene, Styrene, a-methylstyrene, vinyltoluene use.

As tackifiers are increasingly also polyacrylates, which have a low molecular weight used. Preferably, these polyacrylates have a weight-average molecular weight M _w below 30,000. The polyacrylates are preferably at least 60, in particular at least 80 wt .-% of C ₁ -C ₈ alkyl (meth) acrylates.

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

The Tackifier can in a simple manner, the polymers according to the invention are preferred the aqueous Dispersions of the polymers can be added. Preferably lie the tackifiers themselves in the form of an aqueous dispersion.

The Weight of the tackifier is preferably 5 to 100 parts by weight. more preferably 10 to 50 Parts by weight. based on 100 parts by weight of polymer. (Solid / solid).

Next Tackifiern can e.g. still other additives e.g. Thickener, preferably Associative thickener, defoamer, Plasticizers, pigments, wetting agents or fillers in use find use as a pressure-sensitive adhesive.

The Pressure-sensitive adhesives according to the invention therefore contain in addition to the aqueous Polymer dispersion optionally tackifier and / or the above Additives.

For a better wetting of surfaces, the pressure-sensitive adhesives may, in particular, wetting assistants, for example fatty alcohol ethoxylates, alkylphenol ethoxylates, sulfosuccinic acid esters, nonylphenol ethoxyla te, polyoxyethylene / -propylenes or sodium dodecylsulfonates. The amount is generally 0.05 to 5 parts by weight, in particular 0.1 to 3 parts by weight per 100 parts by weight of polymer (solid).

The Pressure-sensitive adhesives are suitable for the production of self-adhesive articles like labels, foils or adhesive tapes. The pressure-sensitive adhesive can by usual Methods, e.g. by rolling, knife-coating, brushing etc. on supports, e.g. Paper or polymer films, preferably consisting of polyethylene, Polypropylene which may be biaxially or monoaxially stretched, polyethylene terephthalate, Polyvinyl chloride, polystyrene, polyamide or metal can be applied. In particular, carriers are also suitable with nonpolar surfaces, e.g. from polyolefins, in particular polyethylene or polypropylene, since the dispersions of the invention Stick well on it.

The Water may preferably be removed by drying at 50 to 150 ° C become. The carriers can before or after applying the adhesive to adhesive tapes, labels or slides are cut. For later use with the Pressure-sensitive adhesive coated side of the substrates, with a release paper, e.g. covered with a siliconised paper.

The Self-adhesive according to the invention Articles have very good adhesive properties, especially a good one adhesion to the substrates and high cohesion (internal strength in the adhesive layer). These good qualities are also achieved if the dispersions or pressure-sensitive adhesives wetting assistant contain. They also have good adhesion to nonpolar surfaces and Therefore, they are also particularly suitable for substrates with non-polar surfaces, e.g. polyolefin e.g. Polyethylene (HDPE or LDPE) or polypropylene.

Preparation of the polymer dispersions

In a 2-liter anchor stirred and heated / cooled polymerisation reactor, a mixture of 102.6 grams of deionized water and 8.33 grams of a 33 weight percent aqueous polymer latex (prepared by free radical initiated emulsion polymerization of styrene) with a weight average Particle diameter D _w50 of 30 nm under nitrogen atmosphere heated to 85 ° C. For this purpose, 4.71 g of a 7 wt .-% aqueous solution of sodium peroxodisulfate is added at the aforementioned temperature. After 2 minutes, feed 1 and feed 2 are started and are metered in uniformly over 3 h. Feed 1 was an aqueous emulsion prepared from 130.00 g deionized water 18.33 g a 30% strength by weight aqueous solution of Disponil FES 77 (ethoxylated C12-C14 sodium sulfate) 1.9 g a 58% by weight aqueous solution of Lumiten I-SC (succinic acid ester) 378.11 g ethylhexyl acrylate 122.38 g ethyl acrylate 11.0 g styrene 27.25 g Methyl acrylate.

Intake 2 was 47.14 g of a 7% by weight aqueous solution of sodium peroxodisulfate.

Intake 3 is added either simultaneously with feed 1 over 3 h (comparative experiment) or, after 0.5 hrs. after feed 1 has begun, it will be over 0.5 hrs dosed (according to the invention)

Intake 3 was 0.325 g of t-dodecylmercaptan.

Intake 4 is added either simultaneously with feed 1 over 3 h (comparative experiment) or will about the first 2.17 h of feed 1, metered in at the same time (according to the invention)

Intake 4 was 38.82 g of a 28.34% by weight aqueous solution of acrylic acid.

To End of the inlets 1, 2, 3 and 4 was 30 min. touched. After that, feed 5 and feed 6 were started and uniformly over 60 min. added.

Intake 5 was 5.5 g of a 10 wt% aqueous solution of t-butyl hydroperoxide.

Intake 6, 7.33 g was a 12% by weight aqueous solution of acetone bisulfite.

To End of the inlets 5 and 6, the internal reactor temperature was lowered to 25 ° C. The obtained aqueous polymer dispersion had a solids content of 53.5% by weight. The mean particle size was 220nm.

Composition of both polymers:

The two experiments differ as follows:

Application testing

To The polymer dispersions were further added Lumiten, so that the amount of Lumiten 1.2 parts by weight per 100 parts by weight of polymer (fixed) fraud.

The pressure-sensitive adhesives were coated on a polyethylene film as carrier (in the transfer process, first coating of silicone paper and transfer to polyethylene) at a rate of 19 g / m ² and dried at 90 ° C. for 3 minutes.

Subsequently was the peel strength (Adhesion) and shear strength (cohesion) certainly.

Of the pressure-sensitive adhesive coated carrier was in 25 mm wide test strips cut. The test strips were determined to determine the shear strength with a glued surface of 6.25 cm2 glued to steel, with a 1 kg roll 1 Rolled up, stored for 10 minutes (in normal climate, 50% relative humidity) 1 bar, 23 ° C) and subsequently hanging loaded with a 1 kg weight (in standard climate). The measure of the shear strength was the time in hours until the weight dropped; it was each calculated the average of 5 measurements.

at the determination of the peel strength (Adhesion) each was a 2.5 cm wide test strip on a test specimen Glued steel and rolled 1 time with a 1 kg roll. He was then with one end in the upper jaws of a tensile-strain tester clamped. The adhesive strip was at 300 mm / min under a 180 ° angle subtracted from the test area i.e. the adhesive strip was bent over and pulled off parallel to the test plate and the one needed Measured effort. The measure of the peel strength was the force in N / 2.5 cm, which is an average of five measurements revealed.

The peel strength was determined 24 hours after the bonding. After this time the adhesive power has fully developed.

The Test methods essentially correspond to the Finat test methods (FTM) No. 1 and No. 8.

Table 1

Claims (15)

Process for the preparation of polymers by emulsion polymerization, wherein monomers are added at least partly during the polymerization (feed process), characterized in that the polymer also contains monomers having at least one carboxylic acid group (short acid monomers) and at least 80% by weight of the acid monomers have been added are when the polymerization mixture (present in the polymerization vessel mixture of monomers to be polymerized and ggb. Already formed polymer) contains less than 75 wt.% Of the total amount of the monomers. Method according to claim 1, characterized in that a maximum of 30 wt.% Of the total amount of Monomers presented in the polymerization be and the rest Monomers during be added continuously to the polymerization. Method according to one the claims 1 or 2, characterized in that the polymerization temperature while the continuous addition of the monomers is at least 50 ° C. Method according to one the claims 1 to 3, characterized in that the continuous addition the monomers over a period of at least two hours. Method according to one the claims 1 to 4, characterized in that in emulsion polymerization Polymerization regulators are used and more than 70 wt.% the amount of regulator (total amount of the polymer contained in the later Regulator) are added only when the polymerization mixture already contains at least 40 wt.% Of the total amount of monomers. Method according to one the claims 1 to 5, characterized in that more than 70 wt.% Of the regulator amount be added only if the polymerization mixture already at least Contains 60 wt.% Of the total amount of monomers. Method according to one the claims 1 to 6, characterized in that the polymer is at least 60% by weight of so-called main monomers selected from C1 to C20 alkyl (meth) acrylates, Vinyl esters of up to 20 carbon atoms containing carboxylic acids, Vinylaromatics with up to 20 carbon atoms, ethylenically unsaturated Nitriles, vinyl halides, vinyl ethers of 1 to 10 C atoms Alcohols, aliphatic hydrocarbons having 2 to 8 atoms and one or two double bonds or mixtures of these monomers, is constructed. Method according to one the claims 1 to 7, characterized in that the polymer is at least 60 wt.% Made up of C1 to C20 alkyl (meth) acrylates. Method according to one the claims 1 to 8, characterized in that the polymer to 0.05 to 5 % By weight of acid monomers is constructed. Method according to one the claims 1 to 9, characterized in that as regulators those with mercapto groups be used. Method according to one the claims 1 to 10, characterized in that the total of the polymer is 0.05 to 4 parts by weight regulator per 100 parts by weight of monomers. Polymers, available by a method according to the claims 1 to 12. Pressure-sensitive adhesives containing a polymer according to claim 12th Method for producing self-adhesive articles, characterized in that first a polymer according to a the claims 1 to 11, and an adhesive sheet containing this polymer contains on a carrier is coated. Self-adhesive articles obtainable by a process according to claim 14th