DE102020205048A1 - Polyacrylate and pressure sensitive adhesive based thereon - Google Patents

Abstract

The aim was to provide a polymer which can serve as a basis for pressure-sensitive adhesives, which in turn are suitable for bonds in vehicle batteries and exhibit high shear strengths at elevated temperatures and good redetachability even after storage for several days. This is achieved with a polyacrylate which can be attributed to the following monomer composition: a) 65 to 80% by weight of at least one acrylic acid ester according to the formula (I) CH2 = CH-C (O) OR1 (I) where R1 is a linear or branched, unfunctionalized alkyl group with 1 to 10 carbon atoms; b) 10 to 20% by weight of at least one acrylic acid ester according to the formula (II) CH2 = CH-C (O) OR2 (II) where R2 is a phenoxyalkyl radical; c) 10 up to 15% by weight of at least one acrylic monomer according to the formula (III) CH2 = CH-C (O) OR3 (III) in which R3 stands for an H atom or a hydroxyalkyl radical with 1 to 4 C atoms. The invention also relates to a pressure-sensitive adhesive which contains a total of at least 50% by weight of at least one such polymer; an adhesive tape which comprises such a pressure-sensitive adhesive and the use of the pressure-sensitive adhesive for producing bonds in accumulators.

Description

The invention relates to the technical field of polyacrylates, such as are often used, inter alia, as a base component in adhesives, in particular in pressure-sensitive adhesives. More specifically, the invention relates to a polyacrylate with a special monomer composition and a heat-shear-resistant pressure-sensitive adhesive with a comparatively low bond strength, which contains such a polyacrylate and which can advantageously be used for the production of bonds in vehicle batteries.

Global climate change is now omnipresent and clearly noticeable in many parts of the world. The prevention of profound climate change is now widely accepted as a task for society as a whole. This makes extensive changes necessary in many areas of technology. A significant proportion of the emissions of climate-damaging exhaust gases can be traced back to mobility. Great efforts are therefore being made to continue to enable diverse individual mobility, but to reduce the resulting emissions of climate-damaging exhaust gases to an acceptable level. In this context, electromobility and the use of batteries as an energy supplier for the operation of vehicles play a key role.

• Prismatische Zellen basieren auf tiefgezogenem Aluminium; sie haben ein vergleichsweise hohes Gewicht. Da das Gewicht der Batterie einen erheblichen Nachteil für den Wirkungsgrad von Elektrofahrzeugen darstellt, bestehen Vorbehalte gegen die Nutzung prismatischer Zellen.

Accumulators - or batteries - for vehicles usually contain a number of interconnected modules (so-called stacks). These modules in turn consist of several individual battery cells. There are three different types of cells:

• Prismatic cells are based on deep-drawn aluminum; they are comparatively heavy. Since the weight of the battery is a significant disadvantage for the efficiency of electric vehicles, there are reservations about the use of prismatic cells.

A second group is made up of cylindrical cells. Due to their cylindrical shape, these cells can only be packed with little efficiency, so that batteries on this basis have a very high volume requirement.

The third group are the so-called pouch cells. These are polymer-aluminum laminates into which the actual battery cell is welded. Pouch cells are characterized in particular by their low weight, with them a comparatively high energy density can be achieved in the battery. They are widely regarded as the most beneficial battery cells.

The individual pouch cells are glued together within a battery module, sometimes with the aid of a foamed spacer. The cells can thus be arranged in the manner of “cell-adhesive-cell” or “cell-adhesive-spacer-cell”. Adhesive tapes are increasingly being used as "adhesives", and their property profile is subject to high requirements.

A central challenge in the operation of electric vehicles is still the thermal management, since the batteries heat up during operation. Temperatures of around 40 to 60 ° C arise, which the adhesive tapes with which the pouch cells are bonded must withstand.

Another requirement results from the manufacturing process for the battery modules. The pouch cells are largely automatically glued to one another. If errors occur here, e.g. folds or incorrect placement of the cells in relation to one another, the relevant modules are sorted out and stored in order to be corrected in a concerted step. The relevant storage times can be one to two weeks. After this time, it must be possible to loosen the bonds between the pouch cells again without great effort so that the bond can be corrected. If the adhesive bonds offer too much resistance to their dissolution, the cell packaging may tear open, as a result of which, for example, electrolyte can escape from the battery cells. In this respect, the redetachability of the bonds is also very important.

Pressure-sensitive adhesives based on poly (meth) acrylates with aromatic constituents are known in the prior art.

• - 40 bis 80 Gew.-% eines Phenoxyalkyl(meth)acrylats, dessen Phenylgruppe Mono- oder Dialkylsubstituiert sein kann;
• - 19 bis 40 Gew.-% eines Alkyl(meth)acrylats, dessen Alkylgruppe 2 bis 14 Kohlenstoffatome aufweist; und
• - 1 bis 20 Gew.-% eines copolymerisierbaren monoethylenisch ungeättigten Monomers. EP 2 233 546 A2 beschreibt eine haftklebende Zusammensetzung, die
• - ein vernetzbares Acrylat-Copolymer A, das ein Monomer mit einer vernetzenden funktionellen Gruppe enthält; und
• - ein nicht vernetzbares Copolymer B

in einem Mischverhältnis von 1:9 bis 5:5 umfasst, wobei jedes der Copolymere A und B 75 bis 97 Gew.-% eines (Meth)acrylsäureester-Monomers und 3 bis 25 Gew.-% eines Monomers, das eine aromatische Gruppe aufweist, enthält.So had US 6,312,799 B1 an acrylate pressure-sensitive adhesive which contains a copolymer made from the following monomer mixture:

• - 40 to 80% by weight of a phenoxyalkyl (meth) acrylate, the phenyl group of which can be mono- or dialkyl-substituted;
• 19 to 40% by weight of an alkyl (meth) acrylate, the alkyl group of which has 2 to 14 carbon atoms; and
• - 1 to 20% by weight of a copolymerizable monoethylenically unsaturated monomer. EP 2 233 546 A2 describes a pressure sensitive adhesive composition that
• a crosslinkable acrylate copolymer A containing a monomer having a crosslinking functional group; and
• - a non-crosslinkable copolymer B

in a mixing ratio of 1: 9 to 5: 5, wherein each of the copolymers A and B comprises 75 to 97% by weight of a (meth) acrylic acid ester monomer and 3 to 25% by weight of a monomer having an aromatic group , contains.

EP 1 275 706 A1 discloses a pressure-sensitive adhesive which comprises an acrylate copolymer which comprises, as copolymerizable components, an acrylic alkyl ester which does not contain an aromatic ring and a monomer which contains an aromatic ring and is contained in the monomer mixture at 40 to 90% by weight.

• - 30 bis 75 Gew.-% eines Acrylsäurealkylesters;
• - 20 bis 65 Gew-% eines Acrylsäurephenoxyalkylesters;
• - 0 bis 40 Gew.-% eines Acrylsäurealkyldiglykolesters und/oder eines Acrylsäurealkoxyalkylesters; und
• - 0,5 bis 10 Gew.-% Acrylsäure und/oder eines Acrylsäurehydroxyalkylesters.

Gegenstand der Schrift ist auch eine Haftklebmasse, die auf einem solchen Polyacrylat basiert. WO 2019/106194 A1 deals with a polyacrylate that can be traced back to the following monomer composition:

• - 30 to 75 wt .-% of an acrylic acid alkyl ester;
• - 20 to 65% by weight of an acrylic acid phenoxyalkyl ester;
• - 0 to 40 wt .-% of an acrylic acid alkyl diglycol ester and / or an acrylic acid alkoxyalkyl ester; and
• - 0.5 to 10 wt .-% acrylic acid and / or an acrylic acid hydroxyalkyl ester.

The document also relates to a pressure-sensitive adhesive based on such a polyacrylate.

There is a continuing need for polymers which can serve as the basis for pressure-sensitive adhesives, which in turn are suitable for bonds in vehicle batteries. It was an object of the invention to provide such a polymer, the pressure-sensitive adhesives based thereon exhibiting high shear strengths at elevated temperatures and good redetachability even after storage for several days.

1. a) 65 bis 80 Gew.-% mindestens eines Acrylsäureesters gemäß der Formel (I) CH₂=CH-C(O)OR¹ (I) worin R¹ für eine lineare oder verzweigte, unfunktionalisierte Alkylgruppe mit 1 bis 10 C-Atomen steht;
2. b) 10 bis 20 Gew.-% mindestens eines Acrylsäureesters gemäß der Formel (II) CH₂=CH-C(O)OR² (II) worin R² für einen Phenoxyalkylrest steht;
3. c) 10 bis 15 Gew.-% mindestens eines Acrylmonomers gemäß der Formel (III) CH₂=CH-C(O)OR³ (III) worin R³ für ein H-Atom oder einen Hydroxyalkylrest mit 1 bis 4 C-Atomen steht.

A first and general object of the invention, with which the above object is achieved, is a polyacrylate, which is characterized in that the polyacrylate is based on the following monomer composition:

1. a) 65 to 80% by weight of at least one acrylic acid ester according to the formula (I) CH ₂ = CH-C (O) OR ¹ (I) wherein R ^{1 is} a linear or branched, unfunctionalized alkyl group having 1 to 10 carbon atoms;
2. b) 10 to 20% by weight of at least one acrylic acid ester according to the formula (II) CH ₂ = CH-C (O) OR ² (II) wherein R ^{2 is} a phenoxyalkyl radical;
3. c) 10 to 15% by weight of at least one acrylic monomer according to the formula (III) CH ₂ = CH-C (O) OR ³ (III) wherein R ^{3 represents} an H atom or a hydroxyalkyl radical having 1 to 4 carbon atoms.

As has been shown, such polymers meet the requirements outlined above and are therefore very suitable as base material for pressure-sensitive adhesives for bonding in battery cells.

R ¹ in the formula (I) preferably represents an alkyl group having 1 to 8 carbon atoms, particularly preferably a linear alkyl group having 1 to 4 carbon atoms. In particular, R ^{1 represents} a radical selected from the group consisting of methyl, n-butyl and 2-ethylhexyl radicals, very particularly preferably an n-butyl or methyl radical. Most preferably, R ¹ in the formula (I) is an n-butyl radical. Monomers a) are contained in the monomer composition of the polyacrylate according to the invention preferably in a total of 68 to 78% by weight, in particular n-butyl acrylate being contained in this proportion

R ² in the formula (II) preferably represents a phenoxyethyl radical, in particular a 2-phenoxyethyl radical. Monomers b) are contained in the monomer composition of the polyacrylate according to the invention preferably in a total of 12 to 18% by weight, in particular 2-phenoxyethyl acrylate being contained in this proportion.

R ³ in the formula (III) preferably represents a hydrogen atom.

In one embodiment, the polyacrylate according to the invention is due to the following monomer composition: n-butyl acrylate at 65 to 80% by weight, 2-phenoxyethyl acrylate at 10 to 20% by weight and acrylic acid at 10 to 15% by weight.

The polyacrylate according to the invention is particularly preferably attributable to the following monomer composition: n-butyl acrylate from 70 to 76% by weight, 2-phenoxyethyl acrylate from 12 to 18% by weight and acrylic acid from 10 to 14% by weight.

The polyacrylate according to the invention is preferably crosslinked. The polyacrylate is particularly preferably thermally crosslinked. Thermal crosslinking can be carried out under considerably milder conditions than, for example, radiation-induced crosslinking, which can occasionally also have a destructive effect. In principle, however, it is also possible to effect crosslinking of the polyacrylate exclusively or additionally by actinic radiation, it being possible to add necessary or promoting crosslinking substances, e.g. UV crosslinking agents.

The polyacrylate according to the invention is therefore preferably thermally crosslinked, i.e. by means of substances which enable (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 coordinative crosslinkers, particularly preferably metal chelates, in particular aluminum, titanium, zirconium and / or iron chelates. Combinations of different crosslinkers, e.g. a combination of one or more epoxides with one or more metal chelates, can also be used.

The polyacrylate according to the invention is particularly preferably crosslinked with at least one covalent crosslinker.

Very particularly preferred metal chelates are aluminum chelates, for example aluminum (III) acetylacetonate. These crosslinkers are preferably used in an amount of 0.1 to 0.8 part by weight, particularly preferably 0.2 to 0.7 part by weight, based in each case on 100 parts by weight of the polyacrylate (solvent-free) .

Very particularly preferred covalent crosslinkers are epoxides, especially those with tertiary amine functions such as tetraglycidyl meta-xylenediamine (N, N, N ', N'-tetrakis (oxiranylmethyl) -1,3-benzene dimethanamine) or cycloaliphatic epoxy resins such as 3,4-epoxycyclohexylmethyl -3,4-epoxycyclohexane carboxylate. These compounds are preferably used in an amount of 0.03 to 0.1 part by weight, particularly preferably 0.04 to 0.07 part by weight, in each case based on 100 parts by weight of the polyacrylate (solvent-free) .

In principle, all free-radical or free-radical-controlled polymerizations, as well as combinations of different polymerization processes, can be used to prepare polyacrylates according to the invention. In addition to the conventional, free radical polymerization, these are z. B. also the ATRP, the nitroxide / TEMPO-controlled polymerization or the RAFT process.

The polyacrylate according to the invention preferably has a weight-average molecular weight of 600,000 to 1,200,000 g / mol.

The invention further provides a pressure-sensitive adhesive which contains at least 50% by weight of at least one polyacrylate according to the invention. A pressure-sensitive adhesive according to the invention is characterized are characterized by high shear strength even at elevated temperatures and by comparatively easy removal.

According to the invention, a pressure-sensitive adhesive or a pressure-sensitive adhesive is understood, as is customary in common parlance, to be a substance which is permanently tacky and also tacky at least at room temperature. It is characteristic of a pressure-sensitive adhesive that it can be applied to a substrate by pressure and remains adhered there, the pressure to be applied and the duration of this pressure not being defined in more detail. In general, but basically depending on the exact type of pressure-sensitive adhesive as well as the substrate, the temperature and the air humidity, the application of a short-term, minimal pressure, which does not go beyond a light touch for a short moment, is sufficient to achieve the adhesive effect in other cases a longer period of exposure to a higher pressure may be necessary.

Pressure-sensitive adhesives have special, characteristic viscoelastic properties which lead to permanent tack and adhesiveness. They are characterized by the fact that when they are mechanically deformed, both viscous flow processes and the build-up of elastic restoring forces occur. With regard to their respective proportions, the two processes are in a certain relationship to one another, depending both on the precise composition, the structure and the degree of crosslinking of the PSA and on the speed and duration of the deformation and on the temperature.

The proportionate viscous flow is necessary to achieve adhesion. Only the viscous components, often caused by macromolecules with relatively high mobility, enable good wetting and flow onto the substrate to be bonded. A high proportion of viscous flow leads to high pressure-sensitive tack (also referred to as tack or surface tack) and thus often also to high adhesion. Strongly cross-linked systems, crystalline or glass-like solidified polymers are generally not or at least only slightly tacky due to the lack of flowable components.

The proportional elastic restoring forces are necessary to achieve cohesion. They are caused, for example, by very long-chain and strongly tangled macromolecules as well as by physically or chemically cross-linked macromolecules and enable the forces acting on an adhesive bond to be transmitted. They lead to the fact that an adhesive connection can withstand a permanent load acting on it, for example in the form of permanent shear stress, to a sufficient extent over a longer period of time.

The polyacrylate according to the invention is preferably pressure-sensitively adhesive. In the simplest case, the pressure-sensitive adhesive of the invention therefore consists of one or more polyacrylates of the invention, in particular of a thermally crosslinked polyacrylate. Manufacturing-related impurities such as solvent residues or unreacted monomers are irrelevant here.

The pressure-sensitive adhesive of the invention can contain additives such as adhesive resin and / or plasticizer.

Tackifying resins, also referred to as tackifying resins, are often admixed with pressure-sensitive adhesives in order to fine-tune the pressure-sensitive adhesive properties.

According to the invention, “resins” are understood to mean in particular those oligo- and (low) polymeric compounds whose number-average molar mass M _{n is} not more than 5,000 g / mol. Of course, short-chain polymerization products that arise during the polymerization of the polyacrylate according to the invention are not subsumed under the term “resins”. Adhesive resins generally increase the bond strength, in particular also the “tack”, the so-called tack of a pressure-sensitive adhesive.

Tackifying resins often have softening points in the range from 80 to 150 ° C. The information on the softening point T _E of oligomeric and polymeric compounds, such as resins, relate to the ring-ball method in accordance with DIN EN 1427: 2007 when the provisions are applied accordingly (examination of the oligomer or polymer sample instead of bitumen if otherwise retained procedure). The measurements are carried out in a glycerol bath.

If contained at all, the pressure-sensitive adhesive of the invention comprises at least one adhesive resin selected from the group consisting of pinene and indene resins; Rosin and rosin derivatives such as rosin esters, also by z. B. disproportionation or hydrogenation stabilized rosin derivatives; Polyterpene resins; Terpene phenolic resins; Alkylphenol resins; and aliphatic, aromatic and aliphatic-aromatic hydrocarbon resins. The tackifier resins are optionally in the PSA according to the invention preferably contain a maximum of 30% by weight in total. It can contain one or more tackifier resins.

In addition, a pressure-sensitive adhesive of the invention can also contain reactive resins. Reactive resins are understood as meaning those resins which have functional groups such that they can react chemically with further constituents of the pressure-sensitive adhesive, in particular the polyacrylate or the polyacrylates, with suitable activation.

The pressure-sensitive adhesive of the invention is preferably free from tackifier resins.

Plasticizers are - if present at all - preferably selected from the group consisting of (meth) acrylate oligomers, phthalates, hydrocarbon oils, cyclohexanedicarboxylic acid esters, benzoic acid esters, water-soluble plasticizers, soft resins, phosphates and polyphosphates. Plasticizers are optionally present in the pressure-sensitive adhesive of the invention to a total of at most 30% by weight, particularly preferably at most 20% by weight, in particular at maximum 15% by weight.

The pressure-sensitive adhesive of the invention is preferably free from plasticizers.

With regard to the feature “free of adhesive resins” as well as the feature “free of plasticizers”, proportions in the range of ubiquitous concentrations as well as production-related residues - for example resulting from the manufacture of the polyacrylate or crosslinker used - are irrelevant.

To optimize the properties of the pressure-sensitive adhesive of the invention, it can also contain other common additives such as fillers, for example electrically conductive fillers, thermally conductive fillers and the like, or flame retardants, for example ammonium polyphosphate and / or its derivatives.

The pressure-sensitive adhesive of the invention can also be foamed. A “foamed pressure-sensitive adhesive” is understood to mean a pressure-sensitive adhesive which comprises a pressure-sensitive adhesive matrix material and a plurality of gas-filled cavities, so that the density of this pressure-sensitive adhesive is reduced compared to the mere matrix material without cavities. The foaming of the matrix material of the foamed PSA can - if the PSA is actually foamed - have in principle been brought about in any desired manner. For example, the pressure-sensitive adhesive can be foamed by means of a propellant gas introduced or released in it, or it contains expanded hollow microspheres.

The pressure-sensitive adhesive of the invention is preferably not foamed.

A pressure-sensitive adhesive according to the invention is preferably produced in such a way that the polyacrylate or polyacrylates are first produced from the correspondingly underlying monomer mixtures by free-radical polymerizations. In the case of several polyacrylates, these are then intimately mixed. If provided, crosslinkers are added during or preferably after the polymerization. If further additives are to be added, these are also added.

A pressure-sensitive adhesive according to the invention is preferably coated onto a carrier or a release liner as a solution - if necessary after setting a specific solids content. The coating is preferably carried out by means of conventional coating processes such as anilox roller application, comma blade coating, multi-roller coating or in a printing process. The solvent can then be removed in a drying tunnel or oven.

When thermal crosslinkers are used, crosslinking generally takes place to a lesser extent at room temperature and to a greater extent when heat is supplied, in particular during the removal of the solvent. Coordinative crosslinkers usually crosslink the polyacrylate independently of the temperature; For this reason, substances are occasionally added which initially block the crosslinker. These are then removed with the solvent, so that crosslinking starts immediately at this point in time.

Alternatively, the coating can also be carried out in a solvent-free process. For this purpose, the polyacrylate is heated and melted in an extruder. Further process steps such as mixing with additives, filtration or degassing can take place in the extruder. The melt is then applied as a layer to a carrier or a release liner by means of a calender.

The invention further provides an adhesive tape which comprises a pressure-sensitive adhesive of the invention.

In the simplest case, an adhesive tape according to the invention consists only of a pressure-sensitive adhesive according to the invention. In order to be able to apply the adhesive tape rolled up into a cup roll or cross-wound into a spool without it sticking to itself, the pressure-sensitive adhesive is preferably covered with at least one release liner.

In addition to a pressure-sensitive adhesive according to the invention, an adhesive tape according to the invention can also comprise at least one carrier and optionally also further layers, for example further pressure-sensitive adhesive layers, barrier layers, further reinforcing carrier layers, etc. In principle, there are no restrictions with regard to the design of the carrier and the further layers. Usual carrier materials are, for example, woven fabrics, scrims and plastic films, for example PET films and polyolefin films. Foamed carrier materials can also be used. In such embodiments, too, at least one pressure-sensitive adhesive of the adhesive tape is preferably covered with a release liner in order to enable problem-free unwinding and to protect the pressure-sensitive adhesive (s) from soiling. Release liners usually consist of a plastic film siliconized on one or both sides (e.g. PET or PP) or a siliconized paper carrier. They are not included in the adhesive tape, but are only temporarily connected to it as an aid.

The invention further provides the use of a polyacrylate according to the invention or a pressure-sensitive adhesive according to the invention for producing bonds in accumulators, preferably in vehicle batteries. The pressure-sensitive adhesive of the invention or an adhesive tape containing this pressure-sensitive adhesive is particularly preferably used for bonding pouch cells in vehicle batteries.

Examples:

Manufacture of polyacrylates

A 300 L reactor conventional for free radical polymerizations was filled with a total of 100 kg of the monomers given in Table 1, corresponding to the composition also given there, and 72.4 kg of gasoline / acetone (70:30). After nitrogen gas had been passed through it for 45 minutes with stirring, the reactor was heated to 58 ° C. and 50 g of Vazo® 67 were added. The jacket temperature was then heated to 75 ° C. and the reaction was carried out constantly at this external temperature. After a reaction time of 1 hour, another 50 g of Vazo® 67 were added. After 3 h, the mixture was diluted with 20 kg petrol / acetone (70:30) and after 6 h with 10.0 kg petrol / acetone (70:30). To reduce the residual initiators, 0.15 kg of Perkadox® 16 were added after 5.5 and after 7 hours. The reaction was terminated after a reaction time of 24 hours and the mixture was cooled to room temperature. The solution was adjusted to a solids content of 38% by weight. Finally, 0.075% by weight, based on the polymer, of Erysis GA240 (epoxy crosslinker) was stirred in as a crosslinker.

The composition obtained was coated in solution onto a siliconized PET film using a comma blade. The solvent was removed in a drying tunnel (20 min, 80 ° C.); the final application weight was 50 g / cm ² . In the tests described below, the adhesives obtained in this way were used as adhesive transfer tape.

Static shear test

The shear strength was determined in a test climate of 80 ° C +/- 1 ° C temperature and 50% +/- 5% rel. Humidity.

The test samples were cut to a width of 25 mm and stored for 24 hours at room temperature. 25 × 100 mm PET-coated aluminum pouch foils were used for the test. The bond area was 25 × 25 mm. The test strip was applied to the center of the primer in the longitudinal direction, avoiding air inclusions, by wiping it over with a squeegee.

Since the samples tested were double-sided, the back was also masked with a PET-coated aluminum pouch film. The adhesive strip was rolled back and forth twice with a 2 kg roller. After rolling, two belt loops (weight 5-7 g) were attached to the protruding end of the test specimen.

The samples prepared in this way were attached to a counter clock by means of a hook; A 1 kg weight was then hung into the belt loop without jerking.

The time between rolling and loading was 24 hours. The time in minutes until the bond failed was then measured; the measurement results are averaged from three measurements.

T-peel test

Two PET coated aluminum foils were cut to 25.4 mm x 250 mm. The pressure-sensitive adhesive was cut to 25.4 mm × 127 mm. The two aluminum foils were then glued to one another by means of the pressure-sensitive adhesive and rolled over back and forth twice with a 2 kg roller. The test specimen produced was then stored for 24 or 48 hours at 23 ° C. and 50% relative humidity. The test specimen was then clamped in a tensile testing machine from ZWICK, whereupon the protruding aluminum foils were pulled apart at a speed of 254 mm / min. The maximum force required for this was measured, and the result given in Table 2 is the mean value from two individual measurements in N / cm. Table 1: Composition of the polyacrylates No. Acrylic acid (wt .-%) 2-phenoxyethyl acrylate (% by weight) n-butyl acrylate (% by weight) Methyl acrylate (wt .-% 1 (V) 12th 0 88 0 2 (V) 3 30th 47 20th 3 (V) 7th 0 73 20th 4 (V) 8th 14th 78 0 5 (V) 15th 8th 77 0 6 (V) 8th 8th 76 0 7th 10 10 80 0 8th 12th 15th 63 0 9 15th 18th 67 0 10 15th 10 75 0 V = comparative example Table 2: Test results No. Static shear test T-peel 24 h T-peel 48 h T-peel residue 1 (V) 0.5 h 2 2.3 Yes 2 (V) > 24 h 3.7 4.1 Yes 3 (V) > 0.5 h 4.3 4.6 Yes 4 (V) > 24 h 3.8 4.4 Yes 5 (V) 15 h 2 2.4 no 6 (V) 3 h 3.1 3.6 Yes 7th > 24 h 2.4 2.6 no 8th > 24 h 1.8 1.7 no 9 > 24 h 1.9 1.8 no 10 > 24 h 2.2 2.1 no

QUOTES INCLUDED IN THE DESCRIPTION

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

Patent literature cited

• US 6312799 B1 [0010]
• EP 2233546 A2 [0010]
• EP 1275706 A1 [0011]
• WO 2019/106194 A1 [0012]

Claims (8)

Polyacrylate, characterized in that the polyacrylate is due to the following monomer composition: a) 65 to 80% by weight of at least one acrylic acid ester according to the formula (I) CH ₂ = CH-C (O) OR ¹ (I) wherein R ^{1 is} a linear or branched, unfunctionalized alkyl group having 1 to 10 carbon atoms; b) 10 to 20% by weight of at least one acrylic acid ester according to the formula (II) CH ₂ = CH-C (O) OR ² (II) wherein R ^{2 is} a phenoxyalkyl radical; c) 10 to 15% by weight of at least one acrylic monomer according to the formula (III) CH ₂ = CH-C (O) OR ³ (III) wherein R ^{3 represents} an H atom or a hydroxyalkyl radical having 1 to 4 carbon atoms. Polyacrylate according to Claim 1 , characterized in that R ^{1 stands} for a radical selected from the group consisting of methyl, n-butyl and 2-ethylhexyl radicals. Polyacrylate according to one of the preceding claims, characterized in that R ^{2 stands} for a phenoxyethyl radical. Polyacrylate according to one of the preceding claims, characterized in that R ^{3 stands} for a hydrogen atom. Pressure-sensitive adhesive comprising a total of at least 50% by weight of at least one polyacrylate according to one of the Claims 1 until 4th . An adhesive tape comprising a pressure-sensitive adhesive according to Claim 5 . Use of a pressure-sensitive adhesive according to Claim 5 for the production of bonds in accumulators. Use according to Claim 7 for bonding pouch cells in vehicle batteries.