Sprayable pressure sensitive adhesive compositions with improved flame retardant properties

Abstract

The invention relates to a pressure-sensitive adhesive composition comprising a) at least one styrene block copolymer SC, b) at least one tackifying resin TR, c) a flame retardant system FR comprising c1) at least one first organophosphorus compound FR1 having a melting temperature of 100 DEG C or below, c2) at least one second organophosphorus compound FR2 having a melting temperature of at least 150 DEG C, and d) optionally, at least one compatibilizer CO.

Description

Technical Field

[0001] The present invention relates to pressure-sensitive adhesive compositions, particularly pressure-sensitive adhesive compositions suitable for spray applications, and to the use of these compositions for bonding electrical components, especially batteries for electric vehicles. Background Art

[0002] Pressure-sensitive adhesives (PSAs) are viscoelastic materials that adhere instantly to almost any type of substrate by applying slight pressure and are permanently tacky. Pressure-sensitive adhesives applied in the form of a melt, also known as hot-melt pressure-sensitive adhesives (HM-PSAs), have the advantage of having an infinitely long open time, which makes them suitable for bonding large surfaces with thin adhesive films. These types of adhesives are also suitable for use in lamination application processes involving long waiting times without the need for reactivating the applied adhesive layer by heating. Due to the permanent tack of the adhesive material, the pre-applied pressure-sensitive adhesive layer is usually covered with a release liner to avoid unwanted bonding and protect the adhesive layer from contamination.

[0003] Pressure sensitive adhesives are polymeric materials that typically have a limiting oxygen index (LOI) of less than 25%, which makes them flammable or combustible. Flame retardant additives can be added to adhesive compositions to improve their fire resistance / flame retardant properties. Common flame retardants for polymeric materials include inorganic flame retardants such as metal oxides, metal hydroxides, and clays such as alumina trihydrate (ATH), precipitated aluminum hydroxide, and magnesium hydroxide. The flame retardant properties of adhesive compositions are particularly critical in the bonding of electric vehicle batteries, where mitigation of thermal runaway events is extremely important.

[0004] Inorganic flame retardants are typically not well compatible with the polymer matrix of the adhesive, and their use, especially under high loads, may cause adverse effects on the adhesive's performance. In addition, flame retardants that remain solid at the application temperature are generally less suitable for use in adhesive compositions applied by spraying. Some inorganic flame retardants (FRs), particularly ATHs, are provided in particle sizes that make spray application impossible.

[0005] Halogenated flame retardants, particularly brominated flame retardants (BRFs), are highly effective in achieving desired fire rating requirements, but their use is generally not preferred due to environmental and safety concerns. In fact, the use of BRFs has been banned in some applications.

[0006] The use of halogen-free organic and metal organic flame retardants has become increasingly common, primarily due to regulatory restrictions on the use of halogenated compounds. Typical halogen-free flame retardants used for polymeric materials include organophosphorus compounds such as polyphosphates, phosphonates, phosphinates, phosphoramidates, and phosphonamidites, as well as 1,3,5-triazine compounds such as melamine and melamine salts and adducts, oligomeric and polymeric 1,3,5-triazine compounds, and polyphosphates of 1,3,5-triazine compounds.

[0007] There is a need for new pressure sensitive adhesives that can be used in spray applications and that exhibit improved flame retardant properties compared to prior art pressure sensitive adhesives. Summary of the Invention

[0008] Summary of the Invention

[0009] The present invention aims to provide pressure-sensitive adhesive compositions for use in spray applications that have improved flame retardant properties, in particular meeting the requirements of the UL94V test V-0 rating. Such adhesive compositions are particularly suitable for use in automotive applications, in particular as assembly adhesives for electric vehicle batteries.

[0010] Surprisingly, it has been found that this object can be achieved by the features of claim 1 .

[0011] In particular, organophosphorus flame retardants with low melting points (e.g., below the application temperature) have been found to be particularly suitable for use in spray applications, primarily due to their good incorporation into the polymer matrix of the adhesive formulation. Compatibilizers can further be used to compensate for a certain degree of incompatibility between the organophosphorus compound and the base adhesive formulation to maintain high adhesive performance.

[0012] The subject of the present invention is a pressure-sensitive adhesive composition as defined in claim 1 .

[0013] Further aspects of the invention are presented in the other independent claims. Preferred embodiments of the invention are presented in the dependent claims.

[0014] Detailed description of the invention

[0015] The subject of the present invention is a pressure-sensitive adhesive composition comprising:

[0016] a) at least one styrene block copolymer SC,

[0017] b) at least one tackifying resin TR,

[0018] c) a flame retardant system FR comprising:

[0019] c1) at least one first organophosphorus compound FR1 having a melting temperature of 125° C. or below,

[0020] c2) at least one second organophosphorus compound FR2 having a melting temperature of at least 150° C., and

[0021] d) Optionally, at least one compatibilizer CO.

[0022] The prefix "poly" in substance names such as "polyol" or "polyisocyanate" refers to substances that formally contain two or more of the functional groups indicated in the name per molecule. For example, a polyol is a compound having two or more hydroxyl groups, while a polyisocyanate is a compound having two or more isocyanate groups.

[0023] The term "polymer" refers to a collection of chemically homogeneous macromolecules produced by a polymerization reaction (polymerization, polyaddition, polycondensation), wherein the macromolecules differ in their degree of polymerization, molecular weight and chain length. The term also includes derivatives of the collection of macromolecules resulting from the polymerization reaction, i.e. compounds obtained by reaction (e.g. addition or substitution) of functional groups in the predetermined macromolecule and which may be chemically homogeneous or chemically heterogeneous.

[0024] The term "molecular weight" refers to the molar mass (g / mol) of a molecule or a portion of a molecule (also referred to as a "moiety"). The term "average molecular weight" refers to the number average molecular weight (M) of an oligomer or polymer mixture of a molecule or moiety. n ) or weight average molecular weight (M w The molecular weight can be determined by conventional methods, preferably by gel permeation chromatography (GPC) as follows: using polystyrene as a standard, using styrene-divinylbenzene gels with porosities of 100 angstroms, 1000 angstroms and 10,000 angstroms as a column, and using tetrahydrofuran as a solvent at 35° C. or using 1,2,4-trichlorobenzene as a solvent at 160° C., depending on the molecule.

[0025] The term "softening point" or "softening temperature" refers to the temperature at which a compound softens in a rubbery state, or the temperature at which a crystalline portion of a compound melts. The softening point can be measured by the ring and ball method according to DIN EN 1238:2011.

[0026] The term "glass transition temperature" (T g ) refers to the temperature above which the polymer component becomes soft and flexible, and below which the polymer component becomes hard and glassy. g) is preferably determined by dynamic mechanical analysis (DMA) as the peak value of the loss modulus (G") curve measured using an applied frequency of 1 Hz and a strain level of 0.1%.

[0027] The "amount or content of at least one component X" in a composition, such as the "amount of the at least one styrene block copolymer," refers to the sum of the individual amounts of all styrene block copolymers contained in the composition. For example, where the composition contains 20% by weight of at least one styrene block copolymer, the sum of the amounts of all styrene block copolymers contained in the composition is equal to 20% by weight.

[0028] The pressure-sensitive adhesive composition comprises as a first essential component at least one styrene block copolymer SC.

[0029] Suitable styrene block copolymers include, in particular, block copolymers comprising polystyrene and polybutadiene blocks and / or polyisoprene blocks. These materials are generally available as pure triblock copolymers, also known as SIS and SBS block copolymers, and as diblock copolymers (SI and SB block copolymers). In addition, styrene block copolymers are also commercially available as mixtures of diblock and triblock copolymers. Suitable styrene block copolymers may have a linear, radial or star-shaped structure, with linear structures being particularly preferred.

[0030] According to one or more embodiments, the at least one styrene block copolymer SC comprises at least one styrene isoprene diblock (SI) and / or triblock (SIS) copolymer and / or at least one styrene-butadiene diblock (SB) and / or triblock (SBS) copolymer.

[0031] Suitable SI, SIS, SB and SBS block copolymers are commercially available, for example, from TSRC / Dexco under the trade name like 4000 series and from Kraton Polymers under the trade name D series obtained.

[0032] Preferably, the at least one styrene block copolymer SC has:

[0033] - a polystyrene content of not more than 45% by weight, more preferably not more than 40% by weight, and / or

[0034] - a melt flow rate measured according to ASTM D1238 (200°C / 5kg) of not more than 75 g / 10 min, more preferably not more than 50 g / 10 min, and / or

[0035] - The solution viscosity measured according to ASTM D2196 does not exceed 1000 MPa·s, preferably does not exceed 850 MPa·s.

[0036] The term "polystyrene content of a block copolymer" as used herein refers to the weight percent of styrene or polystyrene in the block copolymer and is based on the total weight of the block copolymer.

[0037] The pressure sensitive adhesive further comprises a flame retardant system FR comprising:

[0038] c1) at least one first organophosphorus compound FR1 having a melting temperature of 125° C. or below, preferably 115° C. or below, more preferably 105° C. or below, and

[0039] c2) at least one second organophosphorus compound FR2 having a melting temperature of at least 150°C, preferably at least 175°C, more preferably at least 195°C.

[0040] The melting point of the organophosphorus compound can be determined, for example, by differential scanning calorimetry (DSC).

[0041] According to one or more embodiments, the at least one first organophosphorus compound FR1 is represented by formula (I):

[0042]

[0043] wherein R1 and R2 each independently represent an alkyl group having 1 to 5 carbon atoms;

[0044] R3 and R4 each independently represent a hydrogen atom or an alkyl group having 1 to 5 carbon atoms;

[0045] Y represents a bond or a group -CH2-, -C(CH3)2-, -S-, -SO2-, -O-, -CO- or -N=N-;

[0046] k represents 0 or 1; and

[0047] m represents an integer from 0 to 4.

[0048] The alkyl group having 1 to 5 carbon atoms represented by R1 and R2 in the general formula (I) is preferably a linear or branched alkyl group having 1 to 5 carbon atoms, preferably selected from methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl and neopentyl, among which methyl and ethyl are particularly preferred.

[0049] As for the alkyl group having 1 to 5 carbon atoms represented by R3 and R4 in the general formula (I), linear or branched alkyl groups having 1 to 5 carbon atoms are preferred, such as methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl and neopentyl. Preferably, R3 and R4 in the general formula (I) represent hydrogen atoms or methyl groups.

[0050] Suitable organophosphorus compounds of formula (I) are commercially available, for example from Daihachi Chemical Industry Co., Ltd. under the trade name PX-200.

[0051] According to one or more embodiments, the at least one first organophosphorus compound FR1 is selected from tetrakis(2,6-dimethylphenyl)-m-phenylene bisphosphate, tetrakis(2,6-dimethylphenyl)-p-phenylene bisphosphate and tetrakis(2,6-dimethylphenyl)-4,4′-diphenylene bisphosphate.

[0052] Preferably, the amount of the at least one first organophosphorus compound FR1 constitutes no more than 30 wt %, in particular no more than 25 wt %, of the total weight of the pressure-sensitive adhesive. The upper limit of the first organophosphorus compound FR1 is based on the finding that the use of too large a amount of a low-melting flame retardant can lead to crystallization of the flame retardant from the polymer matrix of the adhesive composition, thereby significantly adversely affecting the adhesive properties.

[0053] According to one or more preferred embodiments, the pressure-sensitive adhesive composition comprises 2.5-20 wt. %, preferably 5-15 wt. %, more preferably 7.5-12.5 wt. % of the at least one first organophosphorus compound FR1.

[0054] The flame retardant system FR further comprises the at least one second organophosphorus compound FR2.

[0055] According to one or more embodiments, the at least one second organophosphorus compound FR2 is a phosphonate of formula (II):

[0056]

[0057] wherein R5 and R6 independently of one another represent a substituted or unsubstituted linear or branched alkyl group having 1 to 10 carbon atoms or a substituted or unsubstituted cycloalkyl group or an aryl group.

[0058] Suitable organophosphorus compounds of the general formula (II) are commercially available, for example from THOR GmbH under the trade name Afflammit Series obtained.

[0059] According to one or more embodiments, R5 and R6 independently represent a substituted or unsubstituted linear or branched alkyl group having 1 to 4 carbon atoms, a substituted or unsubstituted benzyl group, a substituted or unsubstituted phenyl group, or a substituted or unsubstituted naphthyl group.

[0060] R5 and R6 may also independently represent a haloalkyl group substituted by one, two or three halogen atoms selected from chlorine and bromine, or a phenyl group or a halogen-substituted phenyl group, for example 4-chlorophenyl, 2,4-dichlorophenyl, 2,4,6-trichlorophenyl, 4-bromophenyl, 2,4-dibromophenyl or 2,4,6-tribromophenyl. However, preferably, R5 and R6 do not contain halogen atoms.

[0061] According to one or more further embodiments, R5 and R6 independently of one another represent a phenylalkyl group having 7 to 9 carbon atoms or a phenylalkenyl group having 8 to 10 carbon atoms, which may be substituted in the alkyl group.

[0062] Phosphonates that are particularly suitable for use as the second organophosphorus compound FR2 include compounds of the formula (II) in which R5 and R6 independently of one another represent methyl, ethyl or propyl, in particular methyl or ethyl.

[0063] According to one or more preferred embodiments, the at least one second organophosphorus compound FR2 is pentaerythritol spirobis(methylphosphonate), wherein R5 and R6 in formula (I) represent methyl groups.

[0064] Preferably, the amount of the at least one second organophosphorus compound FR2 constitutes not more than 25% by weight, in particular not more than 20% by weight, of the total weight of the pressure-sensitive adhesive.

[0065] According to one or more embodiments, the pressure-sensitive adhesive composition comprises 0.5-15 wt. %, preferably 2.5-10 wt. % of the at least one second organophosphorus compound FR2.

[0066] It has also been found that compatibilizers can be used to compensate for a certain degree of incompatibility that may arise between the flame retardant system FR and the base adhesive formulation in order to maintain high adhesive properties.

[0067] Advantageously, the pressure-sensitive adhesive composition further comprises at least one compatibilizer CO chosen from ethylene vinyl acetate copolymers and polyester polyols.

[0068] Ethylene vinyl acetate copolymers suitable for use as compatibilizer CO may have:

[0069] - a content of structural units derived from vinyl acetate of at least 5% by weight, preferably at least 10% by weight, more preferably at least 15% by weight, based on the weight of the ethylene vinyl acetate copolymer, and / or

[0070] - a melt flow index (190°C / 2.16 kg) of at least 50 g / 10 min, preferably at least 100 g / 10 min, more preferably at least 150 g / 10 min, determined according to ISO 1133, and / or

[0071] - The melting point measured according to ISO 11357-3 is not more than 100°C, preferably not more than 90°C, more preferably not more than 80°C.

[0072] Suitable ethylene vinyl acetate copolymers are commercially available, for example under the trade name (from Exxon Mobil), trade name (from Repsol Quimica SA), trade name (from Arkema Functional Polyolefins), trade name (from Eniversalis SpA), trade name (from Arlanxeo GmbH) and trade names (from Dupont).

[0073] Polyester polyols suitable for use as compatibilizer CO can be obtained by reacting dihydric and trihydric alcohols, preferably dihydric alcohols, such as 1,2-ethanediol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, dipropylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, 1,10-decanediol, 1,12-dodecanediol, di-fatty alcohols, neopentyl glycol, glycerol, 1 Suitable are 1,1-trimethylolpropane or mixtures of the aforementioned alcohols with organic dicarboxylic or tricarboxylic acids, preferably dicarboxylic acids, or anhydrides or esters thereof, such as succinic acid, glutaric acid, 3,3-dimethylglutaric acid, adipic acid, suberic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, azelaic acid, maleic acid, fumaric acid, phthalic acid, dimerized fatty acids, isophthalic acid, terephthalic acid and hexahydrophthalic acid, or mixtures of the aforementioned acids. Polyester polyols made from lactones such as ε-caprolactone (also known as polycaprolactone) are also suitable.

[0074] Particularly suitable polyester polyols include those obtained by reacting adipic acid, sebacic acid or dodecane dicarboxylic acid as dicarboxylic acids with hexanediol or neopentyl glycol as diols. Other examples of suitable polyester polyols include polyester polyols of oleochemical origin. This type of polyester polyol can be prepared, for example, by complete ring opening of an epoxidized triglyceride of a fat mixture containing at least partially ethylenically unsaturated fatty acids with one or more alcohols having 1 to 12 carbon atoms, followed by partial transesterification of the triglyceride derivative to obtain an alkyl ester polyol having 1 to 12 carbon atoms in the alkyl group. Particularly suitable crystalline and partially crystalline polyester polyols include adipic acid / hexanediol polyesters and dodecane dicarboxylic acid / hexanediol polyesters.

[0075] According to one or more embodiments, the at least one compatibilizer CO is a polyester polyol, preferably an amorphous polyester polyol, more preferably an amorphous linear polyester polyol, preferably having a glass transition temperature of 5°C or above, preferably 15°C or above.

[0076] Suitable amorphous polyester polyols are commercially available, for example under the trade name 7100 series (from Evonik Industries) and under the trade name 1800 series (from DIC Performance Resins).

[0077] The at least one compatibilizer CO, if used, is preferably present in the pressure-sensitive adhesive composition in an amount not exceeding 25 wt.-%, more preferably not exceeding 20 wt.-%. According to one or more embodiments, the at least one compatibilizer CO constitutes 0.5-10 wt.-%, preferably 1.5-7.5 wt.-%, of the total weight of the pressure-sensitive adhesive composition.

[0078] The pressure-sensitive adhesive further comprises at least one tackifying resin TR.

[0079] The term "tackifying resin" as used herein refers to a resin that generally enhances the adhesive and / or tack of an adhesive composition. The term "tackiness" as used herein refers to the property of a substance to exhibit tack or adhesive properties upon simple contact. Tack can be measured, for example, as loop tack. Preferred tackifying resins are tackifying at a temperature of 25°C.

[0080] Examples of suitable tackifying resins include natural resins, synthetic resins, and chemically modified natural resins.

[0081] Examples of suitable natural resins and chemically modified natural resins include rosin, rosin esters, phenolic modified rosin esters and terpene resins. The term "rosin" is understood to include gum rosin, wood rosin, tall oil rosin, distilled rosin and modified rosins, such as dimerized, hydrogenated, maleated and / or polymerized forms of any of these rosins.

[0082] Suitable terpene resins include copolymers and terpolymers of natural terpenes, such as styrene / terpene and α-methylstyrene / terpene resins; polyterpene resins, which are typically produced by the polymerization of terpene hydrocarbons (such as the bicyclic monoterpene known as pinene) in the presence of a Friedel-Crafts catalyst at moderately low temperatures; hydrogenated polyterpene resins; and phenolic-modified terpene resins (including hydrogenated derivatives thereof).

[0083] The term "synthetic resin" refers to a compound obtained by a controlled chemical reaction such as polyaddition or polycondensation between well-defined reactants that do not themselves have resin properties. The monomers that can be polymerized to synthesize the synthetic resin may include aliphatic monomers, alicyclic monomers, aromatic monomers, or mixtures thereof. Aliphatic monomers may include C4, C5, and C6 alkanes, olefins, and conjugated dienes. Examples of aliphatic or alicyclic monomers include butadiene, isobutylene, 1,3-pentadiene, 1,4-pentadiene, cyclopentane, 1-pentene, 2-pentene, 2-methyl-1-pentene, 2-methyl-2-butene, 2-methyl-2-pentene, isoprene, cyclohexane, 1,3-hexadiene, 1,4-hexadiene, cyclopentadiene, dicyclopentadiene, and terpenes. Aromatic monomers may include C8, C9, and C 10 Aromatic Monomers. Examples of aromatic monomers include styrene, indene, styrene derivatives, indene derivatives, coumarone, and combinations thereof.

[0084] Particularly suitable synthetic resins include those obtained by polymerization of mixtures of unsaturated monomers obtained as by-products of cracking of natural gas liquids, gas oils or naphthas. Such synthetic resins obtained from petroleum-based feedstocks are also characterized as "petroleum resins" or "hydrocarbon resins." These also include pure monomer aromatic resins, which are made by polymerization of aromatic monomer feedstocks that have been purified to eliminate color-causing contaminants and accurately control product composition. Tackifying hydrocarbon resins typically have a relatively low average molecular weight (M n ), for example in the range of 250-5000 g / mol, and a glass transition temperature above 0°C, preferably equal to or higher than 15°C, more preferably equal to or higher than 30°C.

[0085] Examples of hydrocarbon resins suitable for use as tackifying resins (TR) include C5 aliphatic hydrocarbon resins, mixed C5 / C9 aliphatic / aromatic hydrocarbon resins, aromatic-modified C5 aliphatic hydrocarbon resins, cycloaliphatic hydrocarbon resins, mixed C5 aliphatic / cycloaliphatic hydrocarbon resins, mixed C9 aromatic / cycloaliphatic hydrocarbon resins, mixed C5 aliphatic / cycloaliphatic / C9 aromatic hydrocarbon resins, aromatic-modified cycloaliphatic hydrocarbon resins, C9 aromatic hydrocarbon resins, polyterpene resins, and copolymers and terpolymers of natural terpenes, as well as hydrogenated versions of the aforementioned hydrocarbon resins. The designations "C5" and "C9" indicate that the monomers comprising the resins are primarily hydrocarbons having 4-6 and 8-10 carbon atoms, respectively. The term "hydrogenated" encompasses fully, substantially, and at least partially hydrogenated resins. Partially hydrogenated resins may have, for example, a hydrogenation level of 50%, 70%, or 90%.

[0086] Preferably, the at least one tackifying resin TR is a non-functionalized tackifying resin.The term "non-functionalized tackifying resin" refers to a tackifying resin that has not been chemically modified to contain functional groups such as epoxy, silane, sulfonate, amide or anhydride groups.

[0087] According to one or more embodiments, the at least one tackifying resin TR has:

[0088] - a softening point determined by the ring and ball method according to DIN EN 1238:2011 standard in the range of 65-175°C, preferably 70-145°C, more preferably 75-115°C, even more preferably 80-125°C; and / or

[0089] - a number average molecular weight (M) in the range of 150-5000 g / mol, preferably 250-3500 g / mol, more preferably 250-3000 g / mol, even more preferably 250-2500 g / mol n ); and / or

[0090] - Glass transition temperature (T) determined by dynamic mechanical analysis (DMA) as the peak of the loss modulus (G") curve measured using an applied frequency of 1 Hz and a strain level of 0.1% g ) is at 0°C or above, preferably at 10°C or above, more preferably at 15°C or above, even more preferably at 20°C or above.

[0091] Suitable hydrocarbon resins are commercially available, for example under the trade name series,

[0092] Plus, Extra and STS (both from Cray Valley); under the trade name 1000 series, 2000 series and 5000 series (all from Exxon MobileChemical); under the trade name T series, TT series, TD series, TL series, TN series, TK series and TV series (all from Novares GmbH); and under the trade name and (all from Eastman Chemicals).

[0093] According to one or more embodiments, the pressure-sensitive adhesive composition comprises:

[0094] a) 15 to 45% by weight, preferably 20 to 40% by weight, of at least one styrene block copolymer SC,

[0095] b) 15-55% by weight, preferably 20-50% by weight, of the at least one tackifying resin TR,

[0096] c) 2.5-25 wt. %, preferably 5-20 wt. % of the at least one first organophosphorus compound FR1, and

[0097] d) 0.5-15% by weight, preferably 2.5-10% by weight, of the at least one second organophosphorus compound FR2.

[0098] According to one or more further embodiments, the pressure-sensitive adhesive composition comprises:

[0099] a) 15 to 45% by weight, preferably 20 to 40% by weight, of at least one styrene block copolymer SC,

[0100] b) 15-55% by weight, preferably 20-50% by weight, of the at least one tackifying resin TR,

[0101] c) 2.5-25% by weight, preferably 5-20% by weight, of the at least one first organophosphorus compound FR1,

[0102] d) 0.5-15 wt. %, preferably 2.5-10 wt. % of the at least one second organophosphorus compound FR2, and

[0103] e) 0.1-10% by weight, preferably 0.5-10% by weight, of the at least one compatibilizer CO, all proportions being based on the total weight of the adhesive composition.

[0104] The pressure-sensitive adhesive composition may further comprise:

[0105] e) at least one plasticizer PL selected from process oils and liquid polyolefin resins, and / or

[0106] f) At least one thermoplastic resin TP.

[0107] Processing oils suitable for use as plasticizers PL include at least mineral oils, synthetic oils and vegetable oils.

[0108] The term "mineral oil" as used in this disclosure refers to a hydrocarbon liquid having a lubricating viscosity (i.e., a kinematic viscosity at 100° C. of 1 cSt or greater) that is derived from petroleum crude oil and has undergone one or more refining and / or hydroprocessing steps, such as fractionation, hydrocracking, dewaxing, isomerization, and hydrorefining, to purify and chemically modify the components to achieve a final set of properties. In other words, the term "mineral" as used in this disclosure refers to refined mineral oils, which may also be characterized as Group I-III base oils according to the American Petroleum Institute (API) classification.

[0109] Mineral oils suitable for use as the at least one plasticizer PL include paraffinic, cycloalkyl and aromatic mineral oils. Particularly suitable mineral oils include paraffinic and cycloalkyl oils containing relatively low amounts of aromatic moieties (e.g., not more than 25 wt. %, preferably not more than 15 wt. %, based on the total weight of the mineral oil).

[0110] The term "synthetic oil" in this disclosure refers to fully synthetic (polyalphaolefin) oils, which are also referred to as Group IV base oils according to the classification of the American Petroleum Institute (API). Suitable synthetic oils are produced from liquid polyalphaolefins (PAOs), which are obtained by polymerizing alpha-olefins in the presence of a polymerization catalyst (e.g., Friedel-Crafts catalyst). Typically, liquid PAOs are high-purity hydrocarbons having a paraffinic structure and a high degree of side chain branching. Particularly suitable synthetic oils include those obtained by the so-called Gas-To-Liquids process.

[0111] The term "liquid polyolefin resin" in the present disclosure refers to a polyolefin resin that flows at normal room temperature, ie, has a pour point below 20°C.

[0112] Liquid polyolefin resins suitable for use as the at least one plasticizer PL include, for example, liquid polybutene and liquid polyisobutylene (PIB). The term "liquid polybutene" refers to a low molecular weight olefin oligomer comprising isobutylene and / or 1-butene and / or 2-butene in the present disclosure. The ratio of C4-olefin isomers may vary due to manufacturer and grade. When the C4-olefin is solely 1-butene, the material is referred to as "poly-n-butene" or "PNB." The term "liquid polyisobutylene" refers to a low molecular weight olefin oligomer of isobutylene in this document, preferably comprising at least 75 wt %, more preferably at least 85 wt % of repeating units derived from isobutylene. The number average molecular weight (M) of suitable liquid polybutene and polyisobutylene is preferably 0.05 wt %. n ) is less than 5000 g / mol, preferably less than 3500 g / mol, more preferably less than 3000 g / mol, even more preferably less than 2500 g / mol.

[0113] Suitable liquid polybutenes and polyisobutenes are commercially available, for example under the trade names like H-300 and H-1200 (from Ineos); under the trade name like V230, V500 and V700 (from BASF); under the trade name like poly230 (from Univar GmbH); and like PB950 (from Daelim Industrial) was obtained.

[0114] Particularly suitable liquid polybutenes and liquid polyisobutenes have:

[0115] - Average molecular weight (M) of 150-3500 g / mol, preferably 250-3000 g / mol, more preferably 350-2500 g / mol n ); and / or

[0116] - a pour point in the range of -10 to +15°C, preferably -10 to +10°C, determined according to ISO 3016; and / or

[0117] - Polydispersity index (M) determined by GPC w / M n ) is not more than 5, preferably 0.5-5.0, more preferably 1.0-4.5, even more preferably 1.0-3.5.

[0118] The at least one plasticizer PL, if used, preferably constitutes 0.5-15 wt.-%, more preferably 1.5-12.5 wt.-%, even more preferably 2.5-10 wt.-%, based on the total weight of the pressure-sensitive adhesive composition.

[0119] The pressure-sensitive adhesive composition may further comprise at least one thermoplastic resin TP different from the at least one tackifying resin TR.

[0120] Thermoplastic resins TP that are particularly suitable for use in pressure-sensitive adhesives have:

[0121] - a softening point of 125-250° C., preferably 130-225° C., more preferably 135-200° C., even more preferably 140-185° C., determined by the ring and ball method according to DIN EN 1238:2011, and / or

[0122] -Number average molecular weight (M n ) is 150-5000 g / mol, preferably 500-4500 g / mol, more preferably 1000-3500 g / mol, even more preferably 1500-3500 g / mol, and / or

[0123] - Glass transition temperature (T) determined by dynamic mechanical analysis (DMA) as the peak of the loss modulus (G") curve measured using an applied frequency of 1 Hz and a strain level of 0.1% g ) is 35°C or above, preferably 50°C or above, more preferably 65°C or above, even more preferably 75°C or above.

[0124] In addition, the pressure-sensitive adhesive composition may contain additional auxiliary substances and additives, such as those selected from the group consisting of UV absorbers, UV and heat stabilizers, fluorescent whitening agents, antioxidants, pigments, dyes and desiccants. Exemplary UV stabilizers that may be included in the hot melt adhesive composition include, for example, sterically hindered phenols. However, the total amount of such additional auxiliary substances and additives preferably constitutes no more than 15 wt %, more preferably no more than 10 wt %, and even more preferably no more than 5 wt % of the total weight of the pressure-sensitive adhesive composition.

[0125] According to one or more embodiments, the pressure-sensitive adhesive composition has a loop tack adhesion to a steel plate of at least 5 N / 25 mm, preferably at least 7.5 N / 25 mm, more preferably at least 10 N / 25 mm, and even more preferably at least 15 N / 25 mm, measured at a temperature of 23° C. The loop tack adhesion can be measured using “FINAT Test Method No. 9 (FTM9)” defined in the FINAT Technical Handbook, 9th edition, published in 2014.

[0126] The pressure-sensitive adhesive composition of the present invention can be prepared by mixing its components at a temperature of 140-220° C., preferably 160-200° C., until a uniformly mixed mixture is obtained. Any conventional mixing technique known to those skilled in the art can be used. Preferably, the mixing is carried out using a kneading process. Components a) to d) and optional components d) and e) (if used) can be added to the mixer in any order. Preferably, the styrene block copolymer SC is first mixed with the tackifying resin TR until a uniformly mixed mixture is obtained. The remaining ingredients can be added to the uniformly mixed mixture of a) and b) in any order.

[0127] Another aspect of the present invention is a method for bonding two substrates to each other, the method comprising the steps of:

[0128] i) applying the pressure-sensitive adhesive composition of the present invention in the form of a melt onto the surface of a first substrate,

[0129] ii) allowing the applied adhesive composition to cool and solidify,

[0130] iii) contacting the set adhesive with a surface of a second substrate and pressing the substrates together without reheating the set adhesive.

[0131] Preferably, in step iii), the substrates are pressed together for a period of at least 1 minute and using a pressure of at least 1 kg / cm 2 pressure.

[0132] The first and second substrates can be sheet-like articles having first and second major surfaces defined by peripheral edges and defining a thickness therebetween, or three-dimensionally shaped articles having any type of shape.

[0133] In the method for bonding two substrates to each other, the pressure-sensitive adhesive composition is first heated to a temperature above the softening point of the adhesive composition and applied in a molten state to the surface of the first substrate using any conventional technique (preferably by spray coating or extrusion using a slot die). The pressure-sensitive adhesive composition can be applied at a rate of, for example, 20-500 g / m 2 , such as 40-350g / m 2 , especially 50-150g / m 2 A coating weight of 1000 Nm is applied to the surface of the first substrate.

[0134] The first and second substrates can be composed of any conventional material, including polymeric materials, metals, painted metals, glass, mineral materials such as silicate minerals such as mica (muscovite), wood, wood-derived materials such as natural fiber polypropylene (NFPP), and fibrous materials. Suitable polymeric materials include, for example, polyethylene (PE), particularly high-density polyethylene (HDPE), polypropylene (PP), glass fiber reinforced polypropylene (GFPP), polyvinyl chloride (PVC), polyethylene terephthalate (PET), polystyrene (PS), polycarbonate (PC), polymethyl methacrylate (PMMA), acrylonitrile butadiene styrene (ABS), polyamide (PA), polyurethane, and combinations thereof.

[0135] The first and second substrates may consist of a single layer or of multiple layers of different types of materials. The layer consisting of polymeric material may further contain additives such as fillers, plasticizers, flame retardants, heat stabilizers, antioxidants, pigments, dyes and biocides.

[0136] According to one or more embodiments, at least one of the first and second substrates or, in the case where the first and / or second substrate consists of multiple layers, at least one outer layer of the first and second substrates that is in contact with the adhesive composition in step II) or step III) of the process consists of a metal preferably chosen from stainless steel, galvanized steel, aluminum and aluminum alloys, or of a mineral material, preferably a silicate mineral such as mica.

[0137] According to one or more further embodiments, at least one of the first and second substrates, or at least one outer layer of the first and second substrates that comes into contact with the adhesive composition in step II) or step III) of the method, when the first and / or second substrates consist of multiple layers, consists of electroplated steel or an aluminum alloy, preferably electroplated nickel steel or aluminum 3003 alloy. These types of materials are commonly used in automotive battery housings, which are designed to carry and protect battery modules, in particular battery modules for electric vehicles.

[0138] According to one or more embodiments, at least one of the first and second substrates, or, if the first and / or second substrates are composed of multiple layers, at least one outer layer of the first or second substrate that comes into contact with the adhesive composition in step II) or step III) of the method, is composed of a mineral material, preferably a silicate mineral such as mica. These types of materials are commonly used as fire-resistant protective plates for battery module covers.

[0139] According to one or more further embodiments, at least one of the first and second substrates or, in the case where the first and / or second substrate consists of multiple layers, at least one outer layer of the first and second substrates that is in contact with the adhesive composition in step II) or step III) of the method consists of a thermal interface material, a thermal insulation material, an electrically insulating material or a coating for an electrically insulating material.

[0140] The term "thermal interface material (TIM)" herein refers to a material that conducts heat between two or more solid mating surfaces. These types of materials can be used as gap fillers to improve heat transfer between two surfaces, such as between the surfaces of an electronic device and a heat sink.

[0141] Examples of commonly used TIM materials include pyrolytic graphite-based materials, dielectric pads, thermally conductive adhesives such as epoxy-based, silicone-based, and polyurethane-based adhesives, and phase change materials.

[0142] The term "thermal insulation" refers to materials designed to inhibit the transfer of heat between objects in thermal contact by conduction or convection, or within the influence of radiation. Materials used for thermal and electrical insulation in automotive batteries include, for example, carbon fiber, ceramic fiber, meta-aramid fiber-based materials, silica aerogel, polypropylene, polyester, polyimide, and mica flakes, typically mixed with a binder.

[0143] Materials useful as coatings for electrically insulating materials include, for example, reactive and non-reactive compositions such as adhesives and sealants, particularly including acrylics, epoxies, polyurethanes, silane-functionalized polyurethanes, and butyl rubber.

[0144] A further aspect of the present invention is a composite element obtainable by using the method of the invention for bonding two substrates to one another.

[0145] The composite elements of the present invention can be used, for example, to produce battery packs and / or modules for electric vehicles or interior lining components for motor vehicles. Examples of interior lining components include door panels, switch panels, rear cargo area, headliners, sliding roofs, center consoles, glove boxes, sun visors, pillars, door handles, armrests, floor panels, cargo and trunk floors, and sleeper compartments and tailgates for trucks.

[0146] Another aspect of the present invention is an adhesive tape comprising a carrier layer and an adhesive layer composed of the pressure-sensitive adhesive composition of the present invention.

[0147] The carrier layer preferably has a top surface and a bottom surface, ie an upper major surface and a lower major surface, defining a thickness therebetween.The adhesive layer covers at least a portion of the top surface or the bottom surface of the carrier layer.

[0148] The adhesive layer may be present on the carrier layer in the form of a continuous or discontinuous adhesive layer. The term "continuous adhesive layer" in the present disclosure refers to a layer consisting of a single area coated with an adhesive composition, while the term "discontinuous adhesive layer" refers to a layer consisting of two or more areas coated with an adhesive composition, which areas are not connected to each other to form a continuous layer.

[0149] According to one or more embodiments, the adhesive tape further comprises a release liner covering the outwardly facing surface of the adhesive layer opposite to the surface of the carrier layer.

[0150] The release liner can be used to prevent premature, undesirable adhesion and protect the adhesive layer from moisture, dirt, and other environmental factors. In cases where the adhesive tape is provided in roll form, the release liner allows for easy unwinding without the adhesive sticking to the back of the tape. The release liner can be cut into multiple sections to allow the liner to be partially peeled from the adhesive layer.

[0151] Suitable materials for the release liner include kraft paper, polyethylene coated paper, silicone coated paper, and polymeric films such as polyethylene, polypropylene, and polyester films coated with a polymeric release agent selected from silicone, silicone urea, urethane, wax, and long chain alkyl acrylate release agents.

[0152] According to one or more embodiments, the adhesive tape is a double-sided tape comprising a first adhesive layer composed of the pressure-sensitive adhesive composition of the present invention covering at least a portion of the top surface of the carrier layer and a second adhesive layer composed of the pressure-sensitive adhesive composition of the present invention covering at least a portion of the bottom surface of the carrier layer.

[0153] The preferred dimensions of the carrier layer depend primarily on the application of the adhesive tape. The adhesive tape can be provided, for example, in the form of relatively narrow strips, wherein the carrier layer has a width of, for example, 10-750 mm, in particular 25-650 mm, for example 50-500 mm; or in the form of wide sheets, wherein the carrier layer has a width of, for example, 0.85-3.5 m, in particular 1-3 m, for example 1-2.5 m.

[0154] Single-sided and double-sided adhesive tapes can be prepared by a process comprising the following steps:

[0155] I) applying the pressure-sensitive adhesive composition of the present invention in the form of a melt to the surface of a carrier layer, II) allowing the applied adhesive composition to cool and solidify, and

[0156] iii) Optionally, applying a release liner on the side opposite to the carrier layer to cover at least a portion of the outer surface of the set adhesive.

[0157] The pressure-sensitive adhesive composition can be applied to the surface of the carrier layer using any conventional coating technique, preferably by spraying or extrusion using a slot die.

[0158] A further aspect of the present invention is the use of the pressure-sensitive adhesive composition of the invention as assembly adhesive, preferably for electric vehicle batteries.

[0159] When used as an assembly adhesive, the pressure-sensitive adhesive composition can be applied directly to the surface of the substrate (preferably by spraying or extrusion using a slot die), or provided in the form of a single-sided or double-sided adhesive tape and then used to bond the substrates to each other after removing the release liner (if present).

[0160] Uses of the pressure sensitive adhesive may include bonding battery pouches or cells, such as prismatic or cylindrical battery cells, to each other, bonding a fire-resistant protective plate to a battery module cover, bonding a thermal interface material or thermal insulation material or electrical insulating material or a coating for an electrical insulating material to a battery pouch, battery cell or module, or bonding a compressible layer ("liner") to a battery pouch or battery cell.

[0161] A further aspect of the present invention is the use of a pressure-sensitive adhesive as an assembly adhesive for electric vehicle batteries, wherein the pressure-sensitive adhesive comprises at least one styrene block copolymer SC and a flame retardant system FR and has a flame resistance of at least class V2, preferably at least class V1, measured according to the UL 94 test for the flammability of plastics.

[0162] When used as an assembly adhesive, the pressure-sensitive adhesive can be applied directly to the surface of the substrate (preferably by spraying or extrusion using a slot die), or provided in the form of a single-sided or double-sided adhesive tape and then used to bond the substrates to each other after removing the release liner (if present).

[0163] In some embodiments, the styrene block copolymer SC comprises at least one styrene isoprene diblock (SI) and / or triblock (SIS) copolymer and / or at least one styrene-butadiene diblock (SB) and / or triblock (SBS) copolymer.

[0164] Preferably, the styrene block copolymer SC has:

[0165] - a polystyrene content of not more than 45% by weight, more preferably not more than 40% by weight, and / or

[0166] - a melt flow rate of not more than 75 g / 10 min, more preferably not more than 50 g / 10 min, as measured according to ASTM D1238 (200°C / 5 kg), and / or

[0167] - The solution viscosity measured according to ASTM D2196 is not more than 1000 MPa·s, preferably not more than 850 MPa·s.

[0168] In some embodiments, the pressure sensitive adhesive further comprises a flame retardant system FR comprising at least one first organophosphorus compound FR1 having a melting temperature of 125°C or below and / or at least one second organophosphorus compound FR2 having a melting temperature of at least 150°C.

[0169] In other embodiments, the pressure-sensitive adhesive comprises at least one tackifying resin TR.

[0170] In one or more preferred embodiments, the pressure-sensitive adhesive comprises the at least one first organophosphorus compound FR1 and the at least one second organophosphorus compound FR2 as described above.

[0171] The pressure-sensitive adhesive may be composed of the pressure-sensitive adhesive composition described above.

[0172] Uses of the pressure sensitive adhesive may include bonding soft pack batteries or battery cells such as prismatic or cylindrical battery cells to each other, bonding a fire resistant protective plate to a battery module cover, bonding a thermal interface material or thermal insulation material or electrical insulating material or a coating for an electrical insulating material to a soft pack battery, battery cell or module, or bonding a compressible layer ("liner") to a soft pack battery or battery cell. DETAILED DESCRIPTION

[0173] Example

[0174] The following compounds and products shown in Table 1 were used in the Examples.

[0175] Table 1

[0176]

[0177] Preparation of adhesive composition

[0178] For each adhesive composition, the ingredients shown in Table 2 were mixed in a Sigma kneader at 180°C. The preparation process began by mixing the styrene block copolymer, a small portion of the resin, and the additives. The first mixing step was carried out under a CO2 atmosphere and lasted for 45 minutes, after which the remaining resin was added and mixing continued under vacuum for 30 minutes.

[0179] Liquid polyisobutylene was then added to the mixture and mixing continued for an additional 30 minutes under vacuum.The adhesive composition was stored in a siliconizing box for one day before being used for performance characterization.

[0180] Measurement method

[0181] The pressure sensitive adhesive compositions were characterized using the following measurement methods.

[0182] Viscosity at 190°C

[0183] The sample adhesive composition provided in the sealed tube was preheated in an oven at a temperature of 190° C. for a period of 20 minutes. After heating, a sample of the adhesive composition of 9.5 g was weighed and placed in a disposable cannula into a viscometer. Viscosity was measured at 190° C. at 5 rev / min using a Brookfield DV-2 Thermosel viscometer and a No. 27 spindle. The values ​​obtained by tempering for 20 minutes and measuring for 5 minutes at the measurement temperature were recorded as representative viscosities.

[0184] Peel strength 180°

[0185] A polyester foil with a width of approximately 25 mm was first melt-coated with the adhesive composition to be tested to a thickness of 100 μm. A test strip of approximately 200 mm in length was cut from the self-adhesive material, and the adhesive layer was placed in contact with a stainless steel test plate measuring 200 x 50 x 2 mm (length, width, thickness), with an overlap of approximately 70 mm. The adhesive strip was rolled four times using a standard roller at a speed of approximately 10 mm / s.

[0186] The peel adhesion was then measured immediately after the adhesive strips were rolled using a conventional Zwick material testing machine at a test speed of 300 mm / min. The average pull value obtained during the peeling of the test strips from the stainless steel plate at an angle of 180° over a length of 5 cm was recorded as the peel strength value of the tested adhesive.

[0187] The adhesive peel strength values ​​presented in Table 3 are the average of two measurements made using the same adhesive composition.

[0188] Initial adhesion of ring

[0189] The loop tack of the adhesive composition is tested according to the "FTM 9-Loop Tack measurement" method at a temperature of 23°C. For the measurement of loop tack, a sample strip of 25 mm in width and approximately 200 mm in length is first coated with the adhesive composition to be tested, with a coating thickness of 100 μm. The sample strip is then formed into a ring and contacted with a steel plate at a constant speed of 300 mm / minute. Once a contact area of ​​25 mm x 25 mm is generated, the ring is withdrawn, and the force required to separate the ring from the test plate is recorded as the loop tack value.

[0190] The loop tack values ​​presented in Table 2 are the average of two measurements made using the same adhesive composition.

[0191] Shear Adhesion Failure Temperature (SAFT)

[0192] The adhesive composition tested was applied to the surface of Sicol paper in the form of a melt with a coating thickness of 100 μm. An adhesive strip of approximately 70 mm in length and 25 mm in width was then cut from the self-adhesive material and the adhesive layer was contacted with a stainless steel test plate having a size of 60 x 40 mm (length, width) with an overlap of approximately 25 mm. The self-adhesive strip was rolled four times using a standard roller at a speed of approximately 10 mm / s.

[0193] The SAFT value is measured immediately after the adhesive strip has been rolled. At the start of the SAFT measurement, the free end of the test adhesive strip is folded over itself to form a loop. The test sample, consisting of a stainless steel test plate and adhesive strip, is suspended vertically from the free end of the stainless steel plate on a metal hook and placed in an oven preheated to 40°C. A metal weight corresponding to a static load of 500g or 1000g is attached to another metal hook, which is fixed to a fixture attached to the loop formed on the free end of the adhesive strip.

[0194] The test samples were first kept in an oven at 40°C for 30 minutes. Three test samples were placed in the oven at a time for the SAFT measurement. The oven temperature was then increased at a constant rate of 0.37% per minute. The temperature continued to rise until the adhesive bonds of all test samples in the oven failed. The temperature of the last measurement before the bond failure occurred was recorded as the representative thermal stability temperature. For each adhesive composition tested, two measurements were taken. If the difference between the two SAFT values ​​obtained using the same adhesive composition was greater than 10°C, a third measurement was taken.

[0195] The SAFT values ​​presented in the table for the tested adhesive compositions are the average of two measurements made using the same adhesive composition.

[0196] Table 3

[0197]

[0198]

Claims

1. A pressure-sensitive adhesive composition comprising: a) at least one styrene block copolymer SC, b) at least one tackifying resin TR, c) a flame retardant system FR comprising: c1) at least one first organophosphorus compound FR1 having a melting temperature of 125° C. or below, c2) at least one second organophosphorus compound FR2 having a melting temperature of at least 150° C., and d) Optionally, at least one compatibilizer CO.

2. The pressure-sensitive adhesive composition according to claim 1 , wherein the at least one styrene block copolymer SC comprises at least one styrene isoprene diblock (SI) and / or triblock (SIS) copolymer and / or at least one styrene-butadiene diblock (SB) and / or triblock (SBS) copolymer.

3. The pressure-sensitive adhesive composition according to any one of the preceding claims, wherein the at least one first organophosphorus compound FR1 is represented by formula (I): wherein R1 and R2 each independently represent an alkyl group having 1 to 5 carbon atoms; R3 and R4 each independently represent a hydrogen atom or an alkyl group having 1 to 5 carbon atoms; Y represents a bond or a group -CH2-, -C(CH3)2-, -S-, -SO2-, -O-, -CO- or -N=N-; k represents 0 or 1; and m represents an integer from 0 to 4.

4. The pressure-sensitive adhesive composition according to claim 1 , wherein the at least one first organophosphorus compound FR1 is selected from tetrakis(2,6-dimethylphenyl)-m-phenylene bisphosphate, tetrakis(2,6-dimethylphenyl)-p-phenylene bisphosphate and tetrakis(2,6-dimethylphenyl)-4,4′-diphenylene bisphosphate.

5. The pressure-sensitive adhesive composition according to any one of the preceding claims, comprising 2.5-25% by weight, preferably 5-20% by weight, of the at least one first organophosphorus compound FR1.

6. The pressure-sensitive adhesive composition according to any one of the preceding claims, wherein the at least one second organophosphorus compound FR2 is a phosphonate of formula (II): wherein R5 and R6 independently of one another represent a substituted or unsubstituted linear or branched alkyl group having 1 to 10 carbon atoms or a substituted or unsubstituted cycloalkyl group or an aryl group. 7 . The pressure-sensitive adhesive composition according to claim 6 , wherein R 5 and R 6 independently of each other represent a methyl group, an ethyl group or a propyl group, preferably a methyl group or an ethyl group.

8. The pressure-sensitive adhesive composition according to any one of the preceding claims, comprising 0.5-15 wt.-%, preferably 2.5-10 wt.-% of the at least one second organophosphorus compound FR2.

9. The pressure-sensitive adhesive composition according to any one of the preceding claims, further comprising at least one compatibilizer CO selected from ethylene vinyl acetate copolymers and polyester polyols.

10. The pressure-sensitive adhesive composition according to claim 9, wherein the at least one compatibilizer CO is a polyester polyol, preferably an amorphous polyester polyol, preferably having a glass transition temperature of 5°C or above, preferably 15°C or above.

11. The pressure-sensitive adhesive composition according to any one of the preceding claims, comprising 0.5-10 wt. %, preferably 1.5-7.5 wt. %, of the at least one compatibilizer CO, based on the total weight of the adhesive composition.

12. The pressure-sensitive adhesive composition of any preceding claim, comprising: a) 15 to 45% by weight, preferably 20 to 40% by weight, of at least one styrene block copolymer SC, b) 15-55% by weight, preferably 20-50% by weight, of the at least one tackifying resin TR, c) 2.5-25% by weight, preferably 5-20% by weight, of the at least one first organophosphorus compound FR1, d) 0.5-15 wt. %, preferably 2.5-10 wt. % of the at least one second organophosphorus compound FR2, and e) 0-10 wt. %, preferably 0.5-10 wt. % of the at least one compatibilizer CO, All proportions are based on the total weight of the adhesive composition.

13. A method for bonding two substrates to each other, the method comprising the steps of: i) applying the pressure-sensitive adhesive composition according to any one of claims 1 to 12 in the form of a melt onto the surface of a first substrate, ii) allowing the applied adhesive to cool and solidify, iii) contacting the set adhesive with a surface of a second substrate and pressing the substrates together without reheating the set adhesive.

14. An adhesive tape comprising a carrier layer and an adhesive layer composed of the pressure-sensitive adhesive composition according to any one of claims 1 to 12.

15. Use of the pressure-sensitive adhesive composition according to any one of claims 1 to 12 as an assembly adhesive, preferably for electric vehicle batteries.

16. Use of a pressure-sensitive adhesive as an assembly adhesive for electric vehicle batteries, wherein the pressure-sensitive adhesive comprises at least one styrene block copolymer SC and a flame retardant system FR and has a flame resistance of at least class V2, preferably at least class V1, measured according to the UL 94 test for the flammability of plastics.

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