pressure-sensitive adhesive

Abstract

The aim was to provide a pressure-sensitive adhesive that exhibits good bond strength, particularly on polar substrates, as well as good shear strength, particularly at room temperature and elevated temperatures, and good peel adhesion, and that can be produced to a high proportion from bio-based raw materials. This can be achieved with a pressure-sensitive adhesive that is comprehensively - at least one copolymer A based on a monomer composition comprising a) one or more monomers selected from the group consisting of i-amyl acrylate, n-heptyl acrylate, and 2-octyl acrylate in a total amount of 45 to 85% by weight; b) one or more alkyl (meth)acrylates whose alcohol component has 1 to 4 C atoms, in a total of 24 to 50 wt.% and c) 0.5 to 10 wt.% acrylic acid; can be recycled; - at least one rosin resin KH with a softening temperature in the range of 80 to 150 °C; - at least one coordinative networker and - at least one covalent crosslinker. The invention further relates to an adhesive tape which comprises a carrier material and, on at least one of its two outer sides, a pressure-sensitive adhesive according to the invention, and to the use of a pressure-sensitive adhesive according to the invention or an adhesive tape according to the invention for producing bonds in electronic, optical and / or precision mechanical devices.

Description

The invention relates to the technical field of pressure-sensitive adhesives, as are frequently used for the temporary or permanent connection of joining parts. More specifically, the invention proposes a pressure-sensitive adhesive based on a specifically composed polyacrylate copolymer which enables good adhesive forces with good shear lives and peel adhesion, in particular on polar substrates for adhesives, a high proportion of the polyacrylate copolymer being based on renewable raw materials.The demands on the quality of pressure sensitive adhesives have increased dramatically in recent years. An example of this is the use of pressure sensitive adhesives in electronic products such as smartphones and tablet computers. The adhesives here are intended to have pronounced adhesion properties, for example high shock resistance, but must also be compatible with the electronic components, which are often highly sensitive. Ecological and social criteria have also increasingly come into the field of view, which concerns, for example, the origin of the raw materials. In this context, raw materials are particularly demanded, which are partly or even entirely derived from biological sources. This is part of the trend toward sustainable products, which is generally to be observed at present, and addresses in particular the finite crude oil reserves and the resulting requirement for an economical handling thereof; corresponding products are increasingly actively requested by the customers of the adhesive manufacturers.Poly(meth)acrylates have again and again proved to be readily usable starting materials from the stated aspects. Accordingly, suitable formulations for poly(meth)acrylate-based pressure-sensitive adhesives are being used continuously.An aqueous pressure-sensitive adhesive composition which is based essentially on an acrylate polymer dispersed in water is described, for example, in EP 2 062 955 A1.Typical of acrylate-based pressure-sensitive adhesives based on vegetable raw materials are adhesive compositions based on a copolymer which comprises the reaction product of 90 to 99.5% by weight of 2-octyl(meth)acrylate, 0.5 to 10% by weight of (meth)acrylic acid and less than 10% by weight of further monomers, as described in WO 2008 / 046000 A1.EP 3 013 767 A1 discloses the use of a polymer resulting from the polymerization of 2-octyl acrylate of renewable origin and optionally at least one other monomer as binder for the preparation of a coating composition, said polymer having a glass transition temperature of -30°C to 30°C.EP 2 626 397 A1 discloses a pressure-sensitive adhesive composition comprising an acrylate-based polymer component, wherein at least 50% by weight of the monomers used for producing the polymer component can be fully attributed to renewable raw materials.EP 4 196 509 A1 discloses a pressure sensitive adhesive comprising at least one copolymer which can be fed back to a monomer composition comprising 45-75% by weight of at least one monomer selected from the group consisting of i-amyl acrylate, n-heptyl acrylate and 2-octyl acrylate, 24-50% by weight of at least one alkyl (meth)acrylate whose alcohol component has 1 to 4 carbon atoms and 0.5 to 10% by weight of acrylic acid; and at least one adhesion enhancing resin.It is an object of the invention to provide a pressure-sensitive adhesive composition which has good adhesive forces, in particular on polar substrates, good shear lives, in particular at room temperature and elevated temperatures, and good peel adhesion and can be produced to a high extent from biobased raw materials.A first and general subject matter of the invention with which the object is achieved is a pressure-sensitive adhesive composition whichat least one copolymer A based on a monomer composition,a) one or more monomers selected from the group consisting of i-amyl acrylate, n-heptyl acrylate and 2-octyl acrylate in total from 45 to 85% by weight,b) one or more alkyl (meth)acrylates whose alcohol component has 1 to 4 carbon atoms of 24-50% by weight, andc) from 0.5 to 10% by weight of acrylic acid;including, being capable of being recycled;at least one rosin KH having a softening temperature in the range from 80 to 150° C.;at least one coordinative cross-linker, andat least one covalent cross-linking agent.Such a pressure-sensitive adhesive composition has the good adhesive properties according to the object, it being possible to formulate both the (co)polymer component and the resin fraction largely on the basis of renewable raw materials.According to the invention, a pressure-sensitive adhesive or a pressure-sensitive adhesive is understood as meaning, as is customary in general usage, a substance which is permanently tacky and tacky at least at room temperature. A characteristic of a pressure-sensitive adhesive is that it can be applied to a substrate by pressure and remains adhering there, the pressure to be applied and the duration of action of this pressure not being defined in any more detail. In general, but fundamentally depending on the exact type of pressure-sensitive adhesive and the substrate, the temperature and the air humidity, the action of a short-term minimum pressure, which does not go beyond a slight contact for a short moment, is sufficient to achieve the adhesion effect; in other cases, a longer-term action duration of a higher pressure may also be necessary.Pressure sensitive adhesives have particular, characteristic viscoelastic properties which lead to permanent tackiness and adhesiveness. It is characteristic of these that, if they are mechanically deformed, both viscous flow processes and the build-up of elastic restoring forces occur. With regard to their respective proportion, both processes are in a specific ratio to one another, depending both on the precise composition, the structure and the degree of crosslinking of the PSA and on the rate and duration of the deformation and on the temperature.The proportional viscous flow is necessary to achieve adhesion. Only the viscous components, frequently caused by macromolecules with relatively great mobility, permit good wetting and good flow onto the substrate to be bonded. A high proportion of viscous flow leads to a high pressure-sensitive adhesiveness (also referred to as tack or surface adhesiveness) and thus often also to a high adhesion. Highly crosslinked systems, crystalline or glassyally solidified polymers, are generally not tacky or at least only sparingly tacky, owing to the absence of flowable constituents.The proportional elastic restoring forces are necessary to achieve cohesion. They are caused, for example, by very long-chain and strongly entangled macromolecules and by physically or chemically crosslinked macromolecules and make it possible to transmit the forces acting on an adhesive bond. As a result, an adhesive connection can withstand a permanent load acting on it, for example in the form of a permanent shear load, to a sufficient extent over a relatively long period of time.For a more detailed description and quantification of the measure of elastic and viscous component as well as the ratio of the components to each other, the quantities storage modulus (G') and loss modulus (G") determinable by means of dynamic mechanical analysis (DMA) are used. G' is a measure of the elastic fraction, G" is a measure of the viscous fraction of a substance. Both variables are dependent on the deformation frequency and the temperature.The quantities can be determined with the aid of a rheometer. The material to be examined is exposed to a sinusoidal oscillating shear stress, for example in a plate-plate arrangement. In shear stress controlled devices, the deformation as a function of time and the time offset of this deformation with respect to the introduction of the shear stress are measured. This time offset is referred to as phase angle δ.The storage modulus G' is defined as follows: G' = (τ / γ)·cos(δ) (τ = shear stress, γ = deformation, δ = phase angle = phase shift between shear stress and deformation vector). The loss modulus G" is defined as: G" = (τ / γ) - sin(δ) (τ = shear stress, γ = deformation, δ = phase angle = phase shift between shear stress and deformation vector).A composition is especially considered to be a pressure-sensitive adhesive composition and is defined in the sense of the invention as such in particular when at 23° C. in the deformation frequency range of 10 0 to 10 1 rad / sec, both G' and G" are at least partly in the range of 10 3 to 10 7 Pa. "Partly" means that at least a portion of the G' curve lies within the window spanned by the deformation frequency range of 10 0 to 10 1 rad / sec (abscissa) inclusive and the range of the G' values of 10 3 to 10 7 Pa (ordinate) inclusive, and when at least a portion of the G" curve is also within the corresponding window.The pressure-sensitive adhesive composition of the invention comprises at least one copolymer A which can be fed back to a monomer composition comprising a) one or more monomers selected from the group consisting of i-amyl acrylate, n-heptyl acrylate and 2-octyl acrylate to a total of 45 to 85% by weight; b) one or more alkyl (meth)acrylates whose alcohol component has 1 to 4 carbon atoms to a total of 24 to 50% by weight and c) 0.5 to 10% by weight of acrylic acid.In particular, the monomers listed under a) can all be prepared from renewable raw materials.A process for preparing biobased acrylic acid, which can be used as monomer c) and as acid component for monomers a) and b), starts from glycerol, which is obtained, for example, in large amounts in the transesterification of vegetable oils with methanol for preparing biodiesel and is therefore available. The process comprises dehydration of the glycerol to acrolein; the acrolein is then oxidized to acrylic acid in a one-stage or two-stage process. Such a method is described, for example, in US 2007 / 0129570 A1.WO 2006 / 092272 A2 discloses a similar process in which glycerol is first converted into a dehydration product comprising acrolein and a gas phase oxidation of this dehydration product is then carried out, an acrylic acid-containing product being produced. Acrylic acid is obtained by contacting the oxidation product with a quenching agent and processing the quenching phase. This process enables the production of acrylic acid from renewable raw materials without the use of reactive compounds. The glycerol is preferably obtained from the saponification of animal or vegetable fats.Bio-based acrylic acid can also be obtained by a method in which lactic acid (2-hydroxypropionic acid) or 3-hydroxypropionic acid is produced from biological material as a fluid-in particular in the aqueous phase-the hydroxypropionic acid is dehydrated to obtain a fluid containing acrylic acid and the fluid containing acrylic acid is purified. The hydroxypropionic acid required can be prepared by fermentation. Fermentative reactions frequently proceed highly selectively, with high yields and virtually free of by-products owing to the high selectivity of the microorganisms used. Side reactions are also avoided in that the fermentation processes are carried out at low temperatures of 30-60° C. Industrial chemical processes of petrochemicals, on the other hand, are often carried out at very much higher temperatures of usually >200 °C to optimize the yields. However, high reaction temperatures always lead to side reactions and to the formation of cracking products.The process just described is described, for example, in DE 10 2006 039 203 A1, the purification of the fluid comprising acrylic acid being carried out by suspension crystallization or layer crystallization.Various processes are also available for the production of the alcohols from renewable raw materials.Butanol is thus obtainable by fermentation of plant biomass, usually prepared beforehand. Here, the starting material is, for example, sucrose, starch or cellulose, some of which are genetically modified microorganisms (so-called "white biotechnology"). In the so-called A.B.E. process (A.B.E. for acetone, butanol, ethanol), the bacterium Clostridium acetobutylicum is used for fermentation for the production of 1-butanol.2-octanol can be obtained and isolated as a byproduct in the oxidation of ricinoleic acid to sebacic acid. n-heptanol can be obtained from heptanal which is obtained in the thermal cleavage of ricinoleic acid (pyrolytic decomposition to heptanal and undecenoic acid).The monomers a) reduce the glass transition temperature of the copolymer A compared with the other monomers present. This is advantageous because it promotes the adhesive composition to be applied to the substrate. In addition, the composition can thus absorb more resin, which likewise has a positive effect on the adhesive performance.The monomer composition of the copolymer A of the pressure-sensitive adhesive composition of the invention comprises monomers a) in a total of 45 to 85% by weight according to the invention. The monomer composition of the copolymer A of the pressure-sensitive adhesive composition of the invention preferably comprises monomers a) in a total of 55 to 75% by weight, in particular in a total of 60 to 70% by weight. The monomer composition can in principle comprise one (single) or more monomers a).The monomer composition of the copolymer A of the pressure-sensitive adhesive composition of the invention preferably comprises at least 2-octyl acrylate as monomer a). This is particularly advantageous because this monomer further reduces the glass transition temperature of copolymer A to a greater extent. In addition, it does not introduce side chain crystallinity and thus contributes particularly strongly to the expression of pressure-sensitive adhesive properties. More specifically, the monomer composition of copolymer A comprises 2-octyl acrylate as monomer a). This means that only 2-octyl acrylate is included as monomer a).According to the invention, the monomer composition of the copolymer A of the pressure-sensitive adhesive composition of the invention further comprises one or more alkyl (meth)acrylates whose alcohol component has 1 to 4 carbon atoms, [monomers b)]. The monomer composition of the copolymer A of the pressure-sensitive adhesive composition of the invention comprises one or more monomers b), i.e. in total 24 to 50% by weight. The monomer composition of the copolymer A of the pressure-sensitive adhesive composition of the invention preferably comprises a total of 25 to 40% by weight, in particular a total of 27 to 37% by weight, of one or more monomers b). The monomer composition can in principle comprise one (single) or more monomers b).Preference is given to the one or more alkyl (meth)acrylates whose alcohol component has 1 to 4 carbon atoms selected from the group consisting of methyl acrylate, ethyl acrylate, n-butyl methacrylate and i-butyl acrylate. More preferably, the monomer composition of the copolymer A according to the invention comprises, as monomers b), i-butyl acrylate and methyl acrylate.The monomers b) bring about an increase in the glass transition temperature of the copolymer A-in particular in comparison with the monomers a)-because this is advantageous because the properties of the pressure-sensitive adhesive can be matched to the respective requirements by means of a shift in the proportions by weight of the monomers a) and b). Moreover, they are believed to introduce entanglements into the copolymer. This is advantageous because greater toughness and cohesion are thereby imparted to the pressure-sensitive adhesive.The monomer composition of the copolymer A of the pressure-sensitive adhesive composition of the invention comprises acrylic acid to an extent of from 0.5 to 10% by weight, preferably from 1 to 7% by weight, in particular from 2 to 4% by weight.The monomer composition of the copolymer A of the pressure-sensitive adhesive composition of the invention preferably consists of a) one or more monomers selected from the group consisting of i-amyl acrylate, n-heptyl acrylate and 2-octyl acrylate to a total of from 60 to 75% by weight, b) one or more alkyl (meth)acrylates whose alcohol component has from 1 to 4 carbon atoms to a total of from 27 to 37% by weight and c) from 1 to 4% by weight of acrylic acid; or of the monomers described above as preferred in the proportions specified therein.The copolymers A are preferably prepared by conventional free-radical polymerizations or controlled free-radical polymerizations. The copolymers A can be prepared by copolymerization of the monomers using customary polymerization initiators and, if appropriate, regulators, polymerization being carried out at the customary temperatures in bulk, in emulsion, for example in water or liquid hydrocarbons, or in solution.The copolymers A are preferably prepared by copolymerization of the monomers in solvents, more preferably in solvents having a boiling range from 50 to 150° C., in particular from 60 to 120° C., using from 0.01 to 5% by weight, in particular from 0.1 to 2% by weight, based in each case on the total weight of the monomers, of polymerization initiators.In principle, all conventional initiators are suitable. Examples of radical sources are peroxides, hydroperoxides and azo compounds, for example dibenzoyl peroxide, cumene hydroperoxide, cyclohexanone peroxide, di-t-butyl peroxide, cyclohexylsulfonyl acetyl peroxide, diisopropyl percarbonate, t-butyl peroctoate and benzopinacol. Preferred free-radical initiators are 2,2'-azobis(2-methylbutyronitrile) (Vazo® 67™ from DuPont) or 2,2'-azobis(2-methylpropionitrile) (2,2'-azobisisobutyronitrile; AIBN; Vazo® 64™ from DuPont).Preferred solvents for the preparation of the copolymers A are alcohols, such as methanol, ethanol, n- and isopropanol, n- and isobutanol, in particular isopropanol and / or isobutanol; hydrocarbons, such as toluene and in particular benzenes having a boiling range from 60 to 120° C.; ketones, in particular acetone, methyl ethyl ketone, methyl isobutyl ketone; esters, such as ethyl acetate, and mixtures of the abovementioned solvents. Particularly preferred solvents are mixtures which contain isopropanol in amounts of from 2 to 15% by weight, in particular from 3 to 10% by weight, based in each case on the solvent mixture used.The copolymer A of the pressure-sensitive adhesive composition of the invention preferably has a weight-average molecular weight M w of more than 750,000 g / mol. The polydispersity (M w / M n) of the copolymer is preferably 130 to 170.The pressure-sensitive adhesive composition of the invention can in principle comprise one (single) or more copolymers A of the type described above, preferably comprises exactly one such copolymer A.The pressure-sensitive adhesive composition of the invention preferably comprises copolymers A as described above to a total of from 50 to 90% by weight, more preferably to a total of from 55 to 85% by weight, in particular to a total of from 60 to 80% by weight, very particularly preferably to a total of from 65 to 75% by weight, based in each case on the total weight of the pressure-sensitive adhesive composition. The pressure-sensitive adhesive composition according to the invention particularly preferably comprises (precisely) a copolymer A as described above to the extent of 50 to 90% by weight, more preferably 55 to 85% by weight, in particular 60 to 80% by weight, very particularly preferably 65 to 75% by weight, based in each case on the total weight of the pressure-sensitive adhesive composition.The copolymer A or the copolymers A of the pressure-sensitive adhesive composition of the invention are preferably chemically crosslinked, in particular thermally crosslinked. "Thermally crosslinked" refers here to crosslinking by means of substances which make possible (initiate) and / or promote a crosslinking reaction under the influence of thermal energy. Preferred thermal crosslinkers are covalently reacting crosslinkers, in particular epoxides, isocyanates and / or aziridines, and coordinating crosslinkers, particularly preferably metal chelates, in particular aluminum, titanium, zirconium, zinc and / or iron chelates. Combinations of different cross-linkers, e.g., a combination of one or more epoxides with one or more metal chelates, may also be used.The pressure-sensitive adhesive of the invention comprises at least one coordinating and at least one covalent crosslinking agent.In a preferred embodiment of the invention, glycidylamines are used as covalent crosslinkers for the present invention. Representatives which are particularly preferred according to the invention which may be mentioned by way of example are N,N,N',N'-tetrakis(2,3-epoxypropyl)cyclohexane-1,3-dimethylamine and N,N,N',N'-tetrakis(2,3-epoxypropyl)-m-xylene-a,a'-diamine.Polyfunctional epoxides, in particular epoxycyclohexyl carboxylates, can furthermore advantageously be used as covalent crosslinkers. In particular, 2,2-bis(hydroxymethyl)-1,3-propanediol or (3,4 epoxycyclohexane)methyl 3,4-epoxycyclohexyl carboxylate is exemplified herein.Furthermore, multifunctional acridines can be used according to the invention. Trimethylolpropane tris(2-methyl-1-aziridine propionate) may be mentioned for example for this purpose.In a further preferred embodiment of the invention, isocyanates, in particular multifunctional isocyanate compounds, are used as covalent crosslinkers. As the multifunctional isocyanate compound, tolylene diisocyanate (TDI), 2,4-tolylene diisocyanate dimer, naphthylene-1,5-diisocyanate (NDI), o-tolylene diisocyanate (TODI), diphenylmethane diisocyanate (MDI), triphenylmethane triisocyanate, tris(p-isocyanatophenyl)thiophosphate, polymethylene polyphenyl isocyanate, for example, can be used. They may be used alone or in a combination of two or more kinds thereof.According to the invention, at least one covalent cross-linker is used, but it is also possible to use two or more covalent cross-linkers, for example the two aforementioned diamine compounds in combination with one another.As coordinative crosslinkers for the present invention, chelate compounds, in particular polyvalent metal chelate compounds, are particularly suitable. By the term "polyvalent metal chelate compound" is meant those compounds wherein a polyvalent metal is coordinated to one or more organic compounds. As the polyvalent metal atom, Al(III), Zr(IV), Co(II), Cu(I), Cu(II), Fe(II), Fe(III), Ni(II), V(II), V(III), V(IV), V(V), Zn(II), In(III), Ca(II), Mg(II), Mn(II), Y(III), Ce(II), Ce(IV), St(II), Ba(II), Mo(II), Mo(IV), Mo(VI), La(III), Sn(II), Sn(IV), Ti(IV) and the like can be used. Among them, Al(III), Fe(III), Zn(II), Zr(IV) and Ti(IV) are preferable, particularly Fe(III) and Al(III) are preferable.As ligands of the coordinative crosslinkers, in principle all known ligands can be used. The atoms used for the coordinative bond of the organic compound may, however, in particular be those atoms which have no electron pairs, such as, for example, oxygen atoms, sulfur atoms, nitrogen atoms and the like. As the organic compound, for example, alkyl esters, alcohol compounds, carboxylic acid compounds, ether compounds, ketone compounds and the like can be used. More specifically, iron(III) acetylacetonate (Fe chelate), titanium chelate compounds such as Titandipropoxidbis(acetylacetonat ), Titandibutoxidbis(octylenglycholat ), titanium dipropoxide bis(ethyl acetoacetate), Titandipropoxidbis(lactat ), Titandipropoxidbis(triethanolaminat ), titanium di-n-butoxide bis(triethanolamate), titanium tri-n-butoxide monostearate, butyl titanate dimer, poly(titanium acetylacetonate) and the like may be mentioned; Aluminum chelate compounds such as Aluminiumdiisopropoxidmonoethylacetat aluminum di-n-butoxide monomethyl acetoacetate, aluminum di-i-butoxide monomethyl acetoacetate, aluminum di-n-butoxide monoethyl acetoacetate, aluminum di-sec-butoxide monoethyl acetoacetate, aluminum triacetylacetonate, aluminum triethyl acetoacetate, Aluminiummonoacetylacetonatbis(ethylacetoacetonat ) and the like and zirconium chelate compounds such as zirconium tetraacetylacetonate and the like are exemplified. Of these, aluminum triacetylacetonate (Al chelate) and aluminum dipropoxide are preferred. They may be used alone or in a combination of two or more kinds thereof.Covalent crosslinkers are preferably used in a total amount of 0.02 to 0.04 parts by weight, preferably 0.025 to 0.035 parts by weight, based on 100 parts by weight of the entirety of the copolymers A.Coordinative crosslinkers are preferably used in an amount of 0.10 to 0.30 part by weight, preferably 0.12 to 0.23 part by weight, particularly preferably 0.13 to 0.17 part by weight, based on 100 parts by weight of the entirety of the copolymers A.It is further preferred to use covalent crosslinkers and coordinative crosslinkers in such a way that the coordinative crosslinkers are present in a molar excess, based on the covalent crosslinkers. The crosslinkers are preferably used such that the molar ratio of coordinating crosslinkers to covalent crosslinkers (n koord / n kov) is greater than 4.5 (4.5<n koord / n kov), preferably greater than 5.0 (5.0<n koord / n kov) and particularly preferably greater than 5.5 (5.5<n koord / n kov).The crosslinkers are preferably used in the abovementioned amounts in such a way that the molar ratio of covalent crosslinkers to coordinative crosslinkers (n koord / n kov) is greater than 4.5 (4.5<n koord / n kov), preferably greater than 5.0 (5.0<n koord / n kov) and particularly preferably greater than 5.5 (5.5<n koord / n kov).According to the general understanding of the person skilled in the art, a bond strength enhancing resin is understood to mean an oligomeric or polymeric resin which increases the autohesion (tack, inherent bond strength) of the PSA in comparison with the PSA which does not contain any bond strength enhancing resin but is otherwise identical. Adhesion-enhancing resins can furthermore advantageously also improve the wetting properties of the pressure-sensitive adhesive composition with respect to the substrate to be bonded, its release behavior and / or its adhesion.A bond strength-enhancing resin can in principle be any adhesive resin compatible with the pressure-sensitive adhesive and in particular with the copolymer A or the copolymers A of the pressure-sensitive adhesive.The pressure-sensitive adhesive composition of the invention comprises at least one colophmonium resin KH having a softening temperature in the range from 80-150° C. as adhesion-enhancing resin.Rosins are understood to mean a group of resins which comprise their disproportionated, hydrogenated, polymerized, modified derivatives and salts.Modified derivatives of the rosin include esterified derivatives and / or further substituted derivatives such as maleate resin (CAS: 68038-41-5).Rosin resins can be used advantageously because they can be produced or obtained to a large extent, in particular in their entirety, from renewable raw materials. These tackifier resins can be prepared from renewable raw materials and have proven particularly suitable for improving the technical adhesive properties of the pressure-sensitive adhesive composition of the invention to a particular extent.Most preferably, the adhesion-enhancing resin is a fully hydrogenated rosin. This is particularly advantageous because these resins have a comparatively low softening temperature and thus advantageously contribute to the formation of pressure-sensitively adhesive properties. Moreover, they have particularly good ageing stability.The pressure-sensitive adhesive composition of the invention may in principle comprise one (single) or more rosins KH.The pressure-sensitive adhesive composition of the invention may in principle comprise one (single) or more adhesion-enhancing resins.Further adhesion-enhancing resins are, for example, aliphatic, aromatic and alkylaromatic hydrocarbon resins; hydrocarbon resins based on pure monomers; hydrogenated hydrocarbon resins; functional hydrocarbon resins and, if appropriate, derivatized natural resins; the tackifier resin is preferably selected from the group consisting of pinene resins, indene resins and rosins, their disproportionated, hydrogenated, polymerized, esterified derivatives and salts; aliphatic and aromatic hydrocarbon resins; terpene resins and terpene-phenol resins, and also C 5-, C 9- and other hydrocarbon resins.The pressure-sensitive adhesive composition of the invention preferably comprises adhesion-enhancing resins to a total of 10 to 55% by weight, more preferably to a total of 15 to 50% by weight, in particular to a total of 20 to 40% by weight, very particularly preferably to a total of 25 to 35% by weight, based in each case on the total weight of the pressure-sensitive adhesive composition.The pressure-sensitive adhesive composition of the invention particularly preferably comprises at least one rosin KH in a total of from 10 to 55% by weight, more preferably in a total of from 15 to 50% by weight, in particular in a total of from 20 to 40% by weight, very particularly preferably in a total of from 25 to 35% by weight, based in each case on the total weight of the pressure-sensitive adhesive composition.The rosin resin KH according to the invention has a softening temperature of 80-150° C., preferably 85-130° C., very particularly preferably 90-110° C.The rosin resin KH according to the invention has a softening temperature of 80-150° C., preferably 85-130° C., very particularly preferably 90-110° C., the softening temperature being determined by the ring-ball method ("Ring & Ball") according to ASTM E28-18 (Standard issued 01. July 2018).The pressure-sensitive adhesive composition of the invention may additionally comprise further components, for example plasticizers (plasticizers); fillers, in particular fibers, carbon black, zinc oxide, titanium dioxide, spinels, dyes, pigments, chalk, solid glass balls or hollow glass balls, microspheres made of other materials, for example polymeric hollow microspheres, silica and / or silicates; nucleating agents; blowing agents; compounding agents; stabilizers and / or aging inhibitors, for example primary and / or secondary antioxidants and / or light stabilizers.The PSA of the invention is preferably prepared from solution, i.e. the components are dispersed or dissolved and mixed in a suitable solvent; the solvent is removed by conventional methods after completion of the mixing process.The pressure-sensitive adhesive composition of the invention can be used as such, for example in the form of a laminate or a carrier-free layer of the pressure-sensitive adhesive composition of the invention, which is also referred to as "transfer adhesive tape". Such a transfer adhesive tape is preferably applied only to a material which serves temporarily to protect the adhesive surface, to make it easier to handle and to make it easier to apply the pressure-sensitive adhesive composition. Such materials are also referred to as release liners or simply as "liners" and are generally easily removable again, in particular by suitable surface coatings. The second side of the adhesive transfer tape can also be provided with a liner.The release liners are in particular backing materials which have been provided with anti-adhesive properties on one or preferably on both sides (coated or treated). Suitable carrier material for release liners are, for example, various papers, optionally also in combination with a stabilizing extrusion coating. Further suitable liner carrier materials are films, in particular polyolefin films, for example based on ethylene, propylene, butylene and / or hexylene. Preferred support materials are papers, for example glassine papers. Papers are also preferred not least because the concept of the origin of the constituents from renewable raw materials can thus also be extended to auxiliary materials of the adhesive tape.Silicone systems are frequently used as anti-adhesive release coating. The liners usually used include, for example, siliconized papers and siliconized films.For the use of the transfer adhesive tape for bonding to a substrate surface, the liner or liners are then removed, so that the two adhesive sides each maintain direct contact with the substrate surfaces to be bonded to one another. The liner therefore does not represent a productive component and is accordingly also not counted as being part of the adhesive tape, but rather merely represents an aid for handling the same.The pressure-sensitive adhesive composition of the invention is preferably used in the construction or for producing multilayer adhesive tapes. Corresponding multilayer adhesive tapes usually comprise at least one backing layer and can have on one or both sides an outer layer of a pressure-sensitive adhesive composition according to the invention. In the case of adhesive tapes provided with double-sided adhesive properties, either one of the outer layers or both outer layers may be pressure-sensitive adhesives according to the invention. In the latter case, the pressure-sensitive adhesive layers may differ in terms of their chemical composition and / or their chemical and / or physical properties and / or their geometry (e.g. the layer thickness), but particularly preferably they are identical in terms of their chemical composition and / or their chemical and / or physical properties. In the case of multilayer adhesive tapes, too, one or both outer PSA layers may be covered with liners.The adhesive tapes can have further layers, for example further carrier layers, functional layers or the like.As carrier materials of the multilayer adhesive tape, preference is given to selecting biobased materials, for example those selected from the list consisting of papers; biobased wovens or nonwovens, for example of cotton or viscose; cellophane; cellulose acetate; biobased polyethylene films (PE) and polypropylene films (PP); films of thermoplastic starch; biobased polyester films, for example films of polylactide (PLA; polylactic acid), polyethylene terephthalate (PET), polyethylene tetrahydrofuranoate (PEF) or polyhydroxyalkanoate (PHA). The carrier material is particularly preferably a PET film. PET films are preferred, for example, because they can be used as recycled material and thus take into account the concept of sustainability in this way.In one embodiment, the pressure-sensitive adhesive is characterized in that at least 50% by weight, preferably at least 60% by weight, particularly preferably more than 70% by weight, of the monomers used for preparing the copolymer component A are based entirely on renewable raw materials.In one embodiment, the pressure-sensitive adhesive is characterized in that it is based to an extent of at least 50% by weight, preferably at least 60% by weight, particularly preferably more than 70% by weight, on renewable raw materials.In contrast to petrochemical-based products, those that are attributable to a considerable proportion, preferably completely, of renewable raw materials have a natural proportion of radioactive carbon atoms (14 C isotopes). The proportion of these isotopes can be determined and gives a conclusion as to the amount of natural raw material used. The proportion of renewable raw materials is determined here by means of the 14 C-radiocarbon method according to ASTM D6866-04. The method is based on the measurement of the isotope 14 C, which occurs naturally (i.e. in biomasses) with a frequency of 10 -10% in the carbon. The half-life of 5730 years is long enough, on the one hand, that no significant change in the 14 C content due to decomposition takes place in the periods of use of conventional adhesive products, such as pressure-sensitive adhesive tapes, for example (but short enough that historical articles produced from biological matter can be dated). The isotope 14 C is measured by liquid scintillation spectrometry or mass spectrometry. Due to the above-mentioned. Half-lives are no longer detectable in carbon samples older than 60 000 years, within the scope of the detection limit 14 C isotopes. The carbon in petroleum-based raw materials of petrochemicals, which is several million years old, therefore no longer contains 14 C isotopes. The same applies to natural gas- and coal-based raw materials.The invention therefore further provides an adhesive tape which comprises a carrier material and, at least on one of its two outer sides, preferably on both outer sides, a pressure-sensitive adhesive composition according to the invention. Preferably, the carrier material is a PET film. The PET film preferably has a thickness of 1 to 5 μm; the layer or the layers of the PSAs of the invention preferably each have a layer thickness of 20 to 30 μm. The preferred total thickness of the adhesive tape of the invention is thus from 41 to 65 μm.For anchoring the pressure-sensitive adhesive to the carrier or to another substrate, it may be advantageous if the composition and / or the substrate is treated with corona or plasma before the coating. Furthermore, for anchoring the pressure-sensitive adhesive layer to further layers, in particular to a carrier layer, it may be advantageous if chemical anchoring takes place, for example via a primer.The invention further provides for the use of a pressure-sensitive adhesive composition of the invention or of an adhesive tape of the invention for producing bonds in electronic, optical and / or precision-mechanical appliances.Electronic, optical and precision-mechanical devices in the sense of this application are in particular those devices as are to be classified in class 9 of the International Classification of Goods and Services for the Entry of Brands (Classification of Niza); 10th edition (NCL(10-2013)); if these are electronic, optical or precision-mechanical devices, furthermore clocks and time-measuring devices according to class 14 (NCL(10-2013)), such as in particular scientific, marine-trip, surveying, photographic, film, optical, weighing, measuring, signal, control, rescue and instruction apparatus and instruments; apparatuses and instruments for conducting, switching, converting, storing, regulating and controlling electricity; Image recording, processing, transmitting and reproducing apparatuses such as televisions and the like; acoustic recording, processing, transmitting and reproducing apparatuses such as radio terminals and the like; computers, arithmetic devices and data processing apparatuses, mathematical devices and instruments, computer accessories; office devices such as printers, facsimile machines, copying machines, typewriters; and data storage devices; remote communication and multifunction devices having remote communication function such as telephones and answering machines; chemical and physical measurement devices, control devices and instruments such as accumulator charging devices, multimeter, lamps, tachometers; nautia devices and instruments; optical devices and instruments; medical devices and instruments and those for sportsmen; watches and chronometers; Solar cell modules such as electrochemical dye solar cells, organic solar cells, thin film cells; and fire extinguishing devices.The focus of technical developments in the electronics sector has been on many occasions on devices which are made smaller and lighter so that they can be carried along by their owner at any time. This is usually done by realization of low weights and / or suitable size of such devices. Such devices are also referred to as mobile devices or portable devices. In this context, fine-mechanical and optical devices are also increasingly being provided with electronic components, which increases the options for minimization. Due to the entrainment of the mobile devices, these are exposed to increased mechanical loads, for example by abutting edges, by dropping, by contact with other hard objects in the pocket, but also already by the permanent movement due to entrainment per se. Mobile devices are also exposed to more severe loads due to moisture exposure, temperature influences and the like than "mobile" devices, which are usually installed in interior spaces and are not moved or are hardly moved. The pressure-sensitive adhesive composition according to the invention has proven to be particularly preferred for withstanding such disruptive influences and for attenuating or compensating them. The pressure-sensitive adhesive composition of the invention or the adhesive tape of the invention is therefore preferably used for producing bonds in portable electronic devices.Portable electronic devices are, for example:Still further, the invention relates to photographic apparatus for use in conjunction with photographic apparatus, such as photo-taking meters, flash lamps, diaphragms, photo-casings, lenses, film cameras, video cameras, and the like;Small computers (mobile computers, pocket computers, pocket computers), laptops, notebooks, netbooks, ultrabooks, tablet computers, handhelds, electronic schedulers and organizers (so-called "electronic organizers" or "personal digital assistants", PDAs, palmtops), modems;Computer accessory devices and control units for electronic devices such as mice, character pads, graphics tablets, microphones, speakers, game consoles, game pads, remote controls, remote controls, touch pads ("touch pads");monitors, displays, screens, touch-sensitive screens (touch screens, "touch screen devices"), beamers;Readers for Electronic Books ("E-Books");The invention relates to a small-scale television, pocket television, movie players, video players;Radios (also small and pocket radios), walkms, discs, music players for e.g. CD, DVD, Blueray, cartridges, USB, MP3; earphones;Cordless telephones, mobile telephones, smartphones, radio telephones, hands-free telephones, radio telephones (pagers, beepers);mobile defibrilators, blood glucose measuring devices, blood pressure measuring devices, pedometers, pulse meters;Flashlights, laser pointers;mobile detectors, optical magnifying devices, remote viewing devices, night viewing devices;GPS devices, navigation devices, portable interface devices of satellite communication;Data storage devices (USB sticks, external hard disks, memory cards); andWatches, digital watches, pocket watches, chain watches and stop watches.Measurement and test methods:Static Peel AdhesionThe PSA is laminated to a 125 μm polyimide backing, for example Kapton 500 HN from DuPont™. A 20 mm wide strip of the adhesive tape pattern was applied to steel plates which had been washed twice with acetone and once with isopropanol and then left to stand in the air for 5 minutes to allow the solvent to evaporate off. The pressure-sensitive adhesive strip was rolled onto the substrate ten times with a contact pressure corresponding to a weight of 4 kg and, after a pull-on time of two days, was subjected to a peeling load. A 100 g weight was hung on the one end of the adhesive tape and the adhesive bond was hung on top, so that a pull angle of 90° was produced. The test is carried out at 85° C. for 24 h. The peeled distance is then measured in mm. A static peel adhesion of less than or equal to 15 mm is evaluated as good.Determination of the Glass Transition Temperature Tg of the Pressure-Sensitive AdhesivesThe static glass transition temperature of the pressure sensitive adhesive compositions was determined by means of Dynamic Differential Calorimetry (DDK) or-synonymous-Dynamic Scanning Calorimetry (DSC). For this purpose, about 5 mg of an untreated sample of the pressure-sensitive adhesive were weighed into an aluminum crucible (volume 25 μl) and sealed with a perforated lid. For the measurement, a DSC 204 F1 from Netzsch was used. The reaction was carried out under nitrogen for inertization. The sample was first cooled to -150° C., then heated at a heating rate of 10 K / min to +150° C. and cooled again to -150° C. The subsequent second heating curve was again run at 10 K / min and the change in the heat capacity was recorded. Glass transitions are thereby recognized as steps in the thermogram (heat flux-temperature diagram). The glass transition temperature Tg is obtained as follows: the respective linearly running region of the measurement curve before and after the stage is extended in the direction of increasing (region before the stage) or decreasing (region after the stage) temperatures. In the region of the step, a compensation line is placed parallel to the ordinate in such a way that it intersects the two extension lines, namely in such a way that two surfaces (between the respective one extension line, the compensation line and the measurement curve) of the same content are produced. The intersection of the compensation straight line positioned in this way with the measurement curve yields the glass transition temperature.Determination of molecular weightThe data on the number-average molar mass M n and on the weight-average molar mass M w in this specification relate to the determination known per se by gel permeation chromatography (GPC). The determination is carried out on 100 μl of clear-filtered sample (sample concentration 4 g / l). Tetrahydrofuran with 0.1% by volume trifluoroacetic acid is used as the mobile phase. The measurement is carried out at 25° C.As the preliminary column, a column type PSS-SDV, 5 μm, 10 3 Å, 8.0 mm×50 mm (given here and below in the order: type, particle size, porosity, inner diameter×length; 1 Å=10 -10 m) is used. For separation, a combination of the columns of the type PSS-SDV, 5 μm, 10 3 Å and 10 5 Å and 10 6 Å with in each case 8.0 mm×300 mm is used (columns from Polymer Standards Service; detection by means of a differential refractometer Shodex RI71). The flow rate is 1.0 ml per minute. The calibration is carried out by means of the commercially available ReadyCal kit poly(styrene) high from PSS Polymer Standard Service GmbH, Mainz. This is universally converted into polymethyl methacrylate (PMMA) on the basis of the Mark-Houwink parameters K and.alpha., so that the data are specified in PMMA mass equivalents.Determination of K-ValueThe K value according to Fikentscher is a measure of the molecular weight and viscosity of polymers. The principle of the method is based on capillary viscosimetric determination of the relative solution viscosity. For this purpose, the test substance is dissolved in toluene by shaking for thirty minutes, so that a 1% solution is obtained. In a Vogel-Ossag viscometer, the outflow time is measured at 25° C. and the relative viscosity of the sample solution is determined therefrom with respect to the viscosity of the pure solvent. The K value can be read from tables according to Fikentscher [P. E. Hinkamp, Polymer, 1967, 8, 381] (K=1000 k).Determination of the StackIn this test, a steel ball weighing 5.6 g rolled from a ramp (inclination angle 21°) of 65 mm onto a horizontal strip of the adhesive to be tested. The distance until the ball stopped was measured (test climate 23° C., 50% relative humidity). A distance of at most 300 mm is considered a good result.The spheres were cleaned with cellulose and acetone before the measurement and conditioned open for 30 min under the test climate.The adhesive was conditioned under test climate for 1 day before measurement.Determination of Shear StrengthThe shear strength was determined under a test climate of 23 + / -1° C. temperature and 50% + / -5% rel. Humidity.The test specimens were cut to a width of 13±0.2 mm and stored in the climate for at least 16 h. For the test, 50×25 mm ASTM steel plates with a thickness of 2 mm and a marking line of 20 mm were used, which were cleaned repeatedly intensively with acetone before the bonding and then allowed to dry for 10 min. The bond area was 13×20±0.2 mm. The test strip was applied centrally to the adhesion base in the longitudinal direction, avoiding air inclusions, by sweeping over with a wiper, so that the upper edge of the test pattern was exactly in contact with the 20 mm marking line.The back side of the test sample was sealed with aluminum foil. The free end was sticked with paper. The adhesive strip was then rolled over twice to and fro with a 2 kg roll. After the rolling-on, a belt loop (weight 5-7 g) was attached to the protruding end of the adhesive tape.An adapter plate was then fastened to the front side of the shear test plate with screw and nut. To ensure that the adapter plate is firmly seated on the plate, the screw was tightened vigorously by hand.The plate prepared in this way was fastened via the adapter plate to a meter clock by means of a hook; a 1 kg weight was then suspended smoothly in the belt loop.The winding time between the coiling and the load was 12 min. The time in minutes until the bond failed was measured, and the measurement results are averaged from three measurements. A shear recovery time of at least 8,000 min is evaluated as a good result, and a shear recovery time of at least 10,000 min is evaluated as a very good result.The shear recovery time for other temperatures is determined analogously to the above methods, the prepared plate being equilibrated for 30 min under the test conditions, for example at 70° C., before the 1-kg weight is suspended. As a good result, a shear life at 70° C. of at least 100 min is evaluated.Bond force steelThe bond strength was determined under a test climate of 23° C.+ / - 1° C. temperature and 50% + / - 5% rel. Humidity. The samples were cut to 20 mm width and bonded to a steel plate (ASTM). The steel plate was cleaned and conditioned before adhesion. For this purpose, the plate was first wiped off with solvent and then left to stand in the air for 5 minutes in order that the solvent could evaporate off. The side of the adhesive tape facing away from the test substrate was then covered with etched PET film 25 μm thick, whereby the pattern was prevented from stretching during the measurement. The test pattern was then rolled onto the substrate. For this purpose, the tape was wound over five times back and forth with a 4 kg roll at a winding speed of 10 m / min. 1 min after the rolling-on, the plate was pushed into a special holder. The bond strength was measured using a Zwick tensile tester; the samples were drawn off at an angle of 180° at a speed of 300 mm / min. The measurement results are given in N / cm and are averaged from three individual measurements. Table 1: Commercially available chemicals used Table 1: Commercially available chemicals usedAcrylic acid (AA)various manufacturers79-10-72-Octylate (2-OA) (Octyl Residue Bio-Based)various manufacturers42928-85-8Isobornyl acrylate (BA)various manufacturers5888-33-52-Ethylhexyl acrylate (EHA)various manufacturers103-11-7i-Butyl acrylate (iBA) (butyl radical bio-based)various manufacturers106-63-8Methyl acrylate (MA)various manufacturers96-33-3Aluminum(III) acetylacetonateAl chelatevarious manufacturers13963-57-0Iron(III) acetylacetonateFe chelatevarious manufacturers14024-18-12,2-Azobis(2-methylbutyronitrile)Vazo® 67Akzo Nobel13475-08-7Bis-(4-tert-butylcyclohexyl) peroxydicarbonatePerkadox® 16Akzo Nobel15520-11-3Tetraglycidyl metaxylenediamine (crosslinking agent)ERISYS® GA-240CVC63738-22-7Hydrogenated Glycerol Ester of Rosin (Tackifier Resin)Foral® 85 (softening point 69-77° C., ring & ball)Les Derivatives Reesiniques et Terpéniques (DRT)65997-13-9Hydrogenated Glycerol Ester of Rosin (Tackifier Resin)Foral® 105 (softening point 95-103° C., ring & ball)DRT64365-17-9Terpene-phenol resin (tackifier resin; TP 95)Dertophene® T (softening point 95° C., ring & ball)DRT73597-48-5Terpene-phenol resin (tackifier resin; TP 110)Dertophene® T 110 (softening point 110° C., ring & ball)DRT25359-84-6Preparation of the Polyacrylates and of the PSAs:Polycarbonate P-IA 3 L vessel conventional for radical polymerizations was charged with 30 g of acrylic acid (AA), 650 g of 2-octyl acrylate (2-OA), 220 g of i-butyl acrylate (iBA) and 100 g of methyl acrylate (MA) and 724 g of benzine / acetone (70:30). After passing nitrogen gas through the reactor for 45 minutes while stirring, the reactor was heated to 58° C. and 0.5 g of Vazo® 67 was added. Then, the jacket temperature was set to 75 °C, and the reaction was constantly carried out at this external temperature. After a reaction time of 1 h, 0.5 g of Vazo® 67 was again added. After 3 hours, the mixture was diluted with 200 g of petrol / acetone (70:30) and after 6 hours with 100 g of petrol / acetone (70:30). To reduce the residual initiators, 1.5 g of Perkadox® 16 were added in each case after 5.5 and after 7 h. The reaction was stopped after a reaction time of 24 h and cooled to room temperature. The K value is 82.Polyarylate P-II (comparative example from EP 3 417 005 B1)A 300 L reactor conventional for radical polymerizations was charged with 2.0 kg of acrylic acid, 30.0 kg of isobornyl acrylate (BA), 68.0 kg of 2-ethylhexyl acrylate (EHA) and 72.4 kg of petroleum / acetone (70:30). After passing nitrogen gas through the reactor for 45 minutes while stirring, the reactor was heated up to 58° C. and 50 g of Vazo® 67 were added. Then, the jacket temperature was heated to 75°C, and the reaction was constantly carried out at this external temperature. After a reaction time of 1 h, 50 g of Vazo® 67 were again added. After 3 hours, dilution was carried out with 20 kg of petrol / acetone (70:30) and after 6 hours with 10.0 kg of petrol / acetone (70:30). To reduce the residual initiators, 0.15 kg of Perkadox® 16 were added in each case after 5.5 and after 7 hours. The reaction was stopped after a reaction time of 24 h and cooled to room temperature. Molar masses by means of GPC: Mn=12.800 g / mol; Mw=852.600 g / mol. K value: 62.5.PSAsThe polyacrylates were blended with the tackifier resin and the crosslinkers as shown in Table 2. The composition obtained in this way was coated from solution onto a siliconized release film (50 μm polyester) by means of a doctor blade and then dried (coating speed 2.5 m / min, drying channel 15 m, temperatures zone 1: 40° C., zone 2: 70° C., zone 3: 95° C., zone 4: 105° C.). The coatweight after drying was 50 g / m 2. Table 3: ResultsTable 3: Results18++++28+++3 (See)9-++-4 (See)8---5 (See)11.5---6 (See)7.5-+-7 (See)8---8 (See)8---9 (See)8---10 (See)8++-In Table 3, "+ +" means very good; "+" means good; "-" means not good"; "SSZ" means creep rupture time.References included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedEP 2 062 955 A1

[0004] WO 2008 / 046000 A1

[0005] EP 3 013 767 A1

[0006] EP 2 626 397 A1

[0007] EP 4 196 509 A1

[0008] US 2007 / 0129570 A1

[0022] WO 2006 / 092272 A2

[0023] Cited Non-Patent LiteratureRing & Ball") according to ASTM E28-18 (Standard issued 01. July 2018

[00770] P.E. Hinkamp, Polymer, 1967, 8, 381

[0093]

Claims

A pressure-sensitive adhesive composition comprising - at least one copolymer A which can be fed back to a monomer composition comprising a) one or more monomers selected from the group consisting of i-amyl acrylate, n-heptyl acrylate and 2-octyl acrylate to a total of 45 to 85% by weight; b) one or more alkyl (meth)acrylates whose alcohol component has 1 to 4 carbon atoms to a total of 24 to 50% by weight and c) 0.5 to 10% by weight acrylic acid; - at least one rosin KH having a softening temperature in the range from 80 to 150°C; - at least one coordinative crosslinker and - at least one covalent crosslinker.Pressure-sensitive adhesive composition according to Claim 1, characterized in that the softening temperature of the rosin KH is in the range from 90 to 110°C.Pressure-sensitive adhesive according to one of the preceding claims, characterized in that the molar ratio of the total amount of coordinating crosslinking agent to the total amount of covalent crosslinking agent is greater than 4.5; preferably greater than 5.0.Pressure-sensitive adhesive composition according to any of the preceding claims, characterized in that coordinating crosslinkers are present in a total amount of from 0.10 to 0.30 part by weight, preferably from 0.12 to 0.23 part by weight, more preferably from 0.13 to 0.17 part by weight, based on 100 parts by weight of the entirety of the copolymers A.Pressure-sensitive adhesive composition according to any of the preceding claims, characterized in that covalent crosslinkers are present in a total amount of 0.02 to 0.04 part by weight, preferably 0.025 to 0.035 part by weight, based on 100 parts by weight of the entirety of the copolymers A.Pressure-sensitive adhesive according to one of the preceding claims, characterized in that Al(III), Fe(II), Fe(III), Zn(II), Zr(IV) and / or Ti(IV) chelate compounds are selected as coordinating crosslinkers, in particular Al(III) acetylacetonate or Fe(III) acetylacetonate.Pressure-sensitive adhesive according to one of the preceding claims, characterized in that N,N,N',N'-tetrakis(2,3-epoxypropyl)cyclohexane-1,3-dimethylamine, N,N,N',N'-tetrakis(2,3-epoxypropyl)-m-xylene-a,a'-diamine, 2,2-bis(hydroxymethyl)-1,3-propanediol, (3,4-epoxycyclohexane)methyl-3,4-epoxycyclohexyl carboxylate, trimethylolpropane tris(2-methyl-1-aziridine propionate), tolylene diisocyanate (TDI), 2,4-tolylene diisocyanate dimer, naphthylene-1,5-diisocyanate (NDI), o-tolylene diisocyanate (TODI), diphenylmethane diisocyanate (MDI), triphenylmethane triisocyanate, tris(p-isocyanatophenyl)thiophos-phit, The preferred covalent cross-linking agent is N,N,N',N'-tetrakis(2,3-epoxypropyl)-m-xylene-a,a'-diamine.Pressure-sensitive adhesive according to one of the preceding claims, characterized in that the monomer composition comprises monomers a) in total from 60 to 75% by weight.Pressure-sensitive adhesive according to one of the preceding claims, characterized in that the monomer composition comprises 2-octyl acrylate as monomer a).Pressure-sensitive adhesive according to one of the preceding claims, characterized in that the monomer composition comprises monomers b) in total from 27 to 37% by weight.Pressure-sensitive adhesive according to any of the preceding claims, comprising copolymer A in total from 50 to 90% by weight, preferably from 65 to 75% by weight, based on the total weight of the pressure-sensitive adhesive.Pressure-sensitive adhesive according to any of the preceding claims, comprising one or more rosin KH in total from 20 to 50% by weight, preferably from 25 to 35% by weight, based on the total weight of the pressure-sensitive adhesive.Pressure-sensitive adhesive composition according to one of the preceding claims, characterized in that it is based to an extent of at least 50% by weight, preferably at least 60% by weight, particularly preferably more than 70% by weight, on renewable raw materials.Adhesive tape comprising a carrier material and, at least on one of its two outer sides, a pressure-sensitive adhesive composition according to any of Claims 1 to 13.Use of a pressure-sensitive adhesive composition according to any of Claims 1 to 13 or of an adhesive tape according to Claim 14 for producing bonds in electronic, optical and / or precision-mechanical appliances.