DE102023132977A1 - Foamable pressure-sensitive adhesive formulation containing hydrogenated vinyl aromatic block copolymers - Google Patents

Abstract

The present invention relates to foamable pressure-sensitive adhesive formulations for self-adhesive tapes, a foamed pressure-sensitive adhesive layer comprising the pressure-sensitive adhesive formulation, a self-adhesive product comprising at least one layer of the pressure-sensitive adhesive formulation in foamed form, and to processes for producing the foamable pressure-sensitive adhesive formulation, the foamed pressure-sensitive adhesive layer, and the self-adhesive product, and to the use thereof.

Description

The present invention relates to foamable pressure-sensitive adhesive formulations for self-adhesive tapes, a foamed pressure-sensitive adhesive layer comprising the pressure-sensitive adhesive formulation, a self-adhesive product comprising at least one layer of the pressure-sensitive adhesive formulation in foamed form, and to processes for producing the foamable pressure-sensitive adhesive formulation, the foamed pressure-sensitive adhesive layer, and the self-adhesive product, and to the use thereof.

Adhesives and adhesive tapes are generally used to join two substrates together to create a temporary or permanent bond. Self-adhesive tapes containing at least one layer of a pressure-sensitive adhesive formulation are widely used. Tack is the property of a material or formulation to form a strong bond with a bonded surface at room temperature under light pressure, without undergoing any chemical or physical change. They are characterized by their permanent tack and thus differ from other adhesive systems, particularly liquid adhesives. This property leads to advantages in handling and use during the bonding process. Self-adhesive tapes have therefore found their way into a wide variety of industrial applications and in the consumer sector.

Lightweight construction is becoming an increasingly important design requirement, particularly but not exclusively in the automotive and transport sectors, as a vehicle's weight directly impacts its energy consumption. This applies not only to vehicles with fuel-burning engines, but also to electric vehicles. For the latter, the range increases with decreasing vehicle weight while maintaining the same battery capacity. Therefore, the demand for weight savings is not only present in the automotive sector, but also in all components, including self-adhesive tapes. This leads to adhesive tapes being used for applications for which previous adhesive tape products were not foreseen or developed. In addition to the mechanical stress and the critical substrates for adhesive applications, there are also constantly increasing requirements for UV and weathering stability, especially for permanent bonds.

A requirement for self-adhesive tapes often concerns not only the bonding performance on the components to be joined, but also a specific adhesive tape thickness in order to bridge or close design-specific gaps. Adhesive tape thicknesses can therefore be in the range of several hundred micrometers or even above 1 mm. To achieve these dimensions without adding excessively to the overall weight of the finished product, self-adhesive tapes with reduced density are suitable, which can be achieved by foaming individual or multiple layers. The self-adhesive tape should also meet other key requirements regarding bond strength and durability. Pressure-sensitive adhesives based on rubber are particularly suitable when components made of materials with low surface energy, such as polyolefins, are to be bonded.

Foamed pressure-sensitive adhesive layers can also provide mechanical and/or acoustic damping or contribute to resistance to shock. This is a common requirement in mobile (portable) electronic devices, for example, and tends to involve thinner layers, which can be less than 100 µm.

Formulations based on polyvinylaromatic block copolymers represent one of the classic pressure-sensitive adhesive families. In combination with adhesive resins and, if necessary, other admixtures, adhesives for self-adhesive tapes can be produced that exhibit very good adhesive properties, even on non-polar substrates, with good cohesion. Due to their characteristic physical crosslinking principle of reversible formation of a two-phase morphology with domains formed from polyvinylaromatic segments that soften at temperatures above room temperature, such formulations can be processed practically solvent-based or solvent-free in the melt ( FC Jagisch, JM Tancrede in Handbook of Pressure Sensitive Adhesive Technology, D. Satas (ed.), 3rd. ed., 1999, Satas & Associates, Warwick A disadvantage of the typically used polystyrene-polyisoprene-polystyrene block copolymer (SIS) and polystyrene-polybutadiene-polystyrene (SBS)-based pressure-sensitive adhesive formulations is their aging stability. Hydrogenated block copolymers have been proposed that exhibit increased aging stability.

Foamed pressure-sensitive adhesive systems have been known for some time and are described in the prior art. For example, they have lower densities than comparable non-foamed systems and are often characterized by non-destructive detachability and repositionability. Polymer foams can generally be produced in two ways. Firstly, through the action of a propellant gas, either added as such or resulting from a chemical reaction, and secondly, by incorporating hollow spheres into the material matrix. Foams produced in the latter way are referred to as syntactic foams. In a syntactic foam, hollow spheres such as glass spheres or ceramic hollow spheres (microspheres) or microballoons are embedded in a polymer matrix. As a result, the cavities in a syntactic foam are separated from one another, and the substances contained in the cavities (gas, air) are separated from the surrounding matrix by a membrane. Masses foamed with hollow microspheres are characterized by a defined cell structure with a uniform size distribution of the foam cells. Hollow microspheres are used to produce closed-cell foams without cavities, which, compared to open-cell versions, offer, among other things, better sealing against dust and liquid media. Furthermore, chemically or physically foamed materials are more susceptible to irreversible collapse under pressure and temperature and often exhibit lower cohesive strength. Particularly advantageous properties can be achieved when expandable microspheres (also known as "microballoons") are used as microspheres for foaming. Due to their flexible, thermoplastic polymer shell, such foams are more adaptable than those filled with non-expandable, non-polymeric hollow microspheres (e.g., hollow glass spheres). They are better suited to compensating for manufacturing tolerances, such as those commonly found in injection-molded parts, and, due to their foam nature, can also better compensate for thermal stresses.

Foamed self-adhesive layers based on styrene block copolymers are known.

DE 10 2008 004 388 A1 relates to a pressure-sensitive adhesive containing expanded microballoons, wherein the adhesive strength of the adhesive containing the expanded microballoons is reduced by at most 30%, preferably at most 20%, particularly preferably 10%, compared to the adhesive strength of an adhesive of identical basis weight and formulation, which is defoamed by the destruction of the cavities created by the expanded microballoons. Suitable elastomers include SBS and SIS; (partially) hydrogenated block copolymers are not mentioned.

DE 10 2008 004 388 A1 demonstrates, based on the degree of achievable density reduction at a given microballoon content, that the foaming of SIS-based formulations is not as effective as in those based on natural rubber. This indicates that the foamability of pressure-sensitive adhesives depends on the composition of the base formulation. It is reasonable to assume that the cohesion of the base formulation at the temperature at which foaming is carried out has a central influence on foaming efficiency. DE 10 2008 004 388 Differences in the foaming efficiency of pressure-sensitive adhesive formulations based on polydiene rubbers containing polystyrene segments (polystyrene-polydiene block copolymers using SIS as an example) can be seen compared to those based on pure polydiene rubbers (using natural rubber as an example) (see 1 ). Pressure-sensitive adhesives containing polystyrene-polydiene block copolymers exhibit lower foaming efficiency than those without polystyrene. The specific nature of the two-phase structure in polystyrene block copolymers appears to impede foaming behavior. Table 3 compares formulations based on SIS with those based on hydrogenated polystyrene-polydiene block copolymers. With the same amount of microballoons and a comparable foaming process, a significantly lower density is achieved for SIS than for those based on hydrogenated polystyrene-polydiene block copolymers. These explicitly mentioned formulations do not contain any plasticizers.

DE 10 2017 218 519 A1 teaches pressure-sensitive adhesive strips with an adhesive based on polydiene block copolymers, which can be coated with microballoons and irradiated with electrons. Hydrogenated block copolymers are not mentioned.

EP 2 832 779 A1 Describes a rubber-based pressure-sensitive foam with special adhesive resins and plasticizers. A number of different elastomers are listed that can form the basis for these foams. These include, very generally, natural rubbers, synthetic rubbers, thermoplastic elastomers, non-thermoplastic elastomers, thermoplastic hydrocarbon elastomers, and non-thermoplastic hydrocarbon elastomers. Among the block copolymers, only SIS is explicitly listed in the examples.

In terms of the longevity of bonded joints, pressure-sensitive adhesive formulations based on saturated elastomers such as polyacrylates are often preferred. However, these do not always offer the required bond strengths on the nonpolar materials mentioned above, for example, and some other materials. Hydrogenated vinyl aromatic block copolymers are offered in the rubber sector for applications requiring optimized durability. Although it is generally known that hydrogenated styrene block copolymers are very difficult to tackify (Jagisch and Tancrede in D. Satas, Handbook of Pressure Sensitive Adhesive Technology, 3rd ed., 1999, D. Satas & Associates, Warwick, p. 367, Table 16-5), there have been various approaches to formulating pressure-sensitive adhesives using such block copolymers.

DE 10 2007 021 504 A1 discloses, among other things, formulations containing polystyrene-poly(ethylene/butylene)-polystyrene (SEBS) block copolymer and a high proportion of liquid resin. Foaming of such formulations is not intended. Even though the description does not provide specific information on the polyvinyl aromatic content, DE 10 2007 021 504 However, the examples show that pressure-sensitive adhesives based on hydrogenated polystyrene-polydiene block copolymers are typically advantageously produced when block copolymers with a low polyvinyl aromatic content are selected.

DE 10 2006 037 627 A1 describes pressure-sensitive adhesives containing hydrogenated block copolymers, adhesive resin, and polyisobutylene. With regard to the hydrogenated block copolymers, no specific selection is made in the description; the examples only mention those with a polyvinyl aromatic content of 13 wt.%. Foaming of the pressure-sensitive adhesive is not intended.

Among hydrogenated polystyrene block copolymers, those with a low polystyrene content (< 15 wt.%) are frequently cited as base elastomers. Such block copolymers typically exhibit a higher melt flow index (MFI) compared to other hydrogenated polystyrene block copolymers with a polystyrene content of > 25 wt.%, which leads to improved processability in solvent-free processes. However, as a result of the low polystyrene content, the thermal shear strength of formulations based on these types of hydrogenated polystyrene block copolymers is not at the level required in many contemporary applications, particularly in the automotive sector.

The foaming of pressure-sensitive adhesives based on such hydrogenated block copolymers is WO 00/06637 A1 which, among other things, discloses a foamed layer composed of SEBS Kraton G1657 and adhesive resin Arkon P90 in equal proportions. According to the manufacturer, the polystyrene content of Kraton G1657 is 13% by weight.

Therefore, pressure-sensitive adhesives for self-adhesive tapes with reduced dead weight are still sought, which have sufficient adhesion to materials with different surface energies, have sufficient cohesion even at high temperatures and, above all, offer improved durability.

The object is achieved according to the invention by a foamable pressure-sensitive adhesive formulation as defined in claim 1. Preferred further developments of this pressure-sensitive adhesive formulation are set out in the subclaims.

1. a) mindestens eine Elastomerkomponente;
2. b) mindestens eine Klebharzkomponente;
3. c) mindestens 2,5 Gew.-% einer Weichmacherkomponente, bezogen auf das Gesamtgewicht der Haftklebeformulierung;
4. d) ein Schäumungsmittel, und
5. e) optional eine Verstärkungskomponente,

dadurch gekennzeichnet, dass die Elastomerkomponente zu mindestens 90 Gew.-%, bezogen auf das Gesamtgewicht der Elastomerkomponente, eines oder mehrerer Polyvinylaromaten-Polydien-Blockcopolymere, von denen zumindest eines mit mindestens zwei Polyvinylaromatenblöcken (A) enthalten ist, aufweist,
wobei

• • die Polydien-Blöcke (B) zu mindestens 90 Gew.-%, bezogen auf das Blockcopolymer, hydriert sind; und
• • der Anteil an Polyvinylaromatenblöcken (A) mindestens 18 Gew.-% beträgt, bezogen auf das Blockcopolymer.

Accordingly, a first subject matter of the present invention is a foamable pressure-sensitive adhesive formulation comprising:

1. a) at least one elastomer component;
2. b) at least one adhesive resin component;
3. c) at least 2.5% by weight of a plasticizer component, based on the total weight of the pressure-sensitive adhesive formulation;
4. d) a foaming agent, and
5. e) optionally a reinforcement component,

characterized in that the elastomer component comprises at least 90% by weight, based on the total weight of the elastomer component, of one or more polyvinylaromatic-polydiene block copolymers, at least one of which contains at least two polyvinylaromatic blocks (A),
where

• • the polydiene blocks (B) are hydrogenated to at least 90% by weight, based on the block copolymer; and
• • the proportion of polyvinyl aromatic blocks (A) is at least 18% by weight, based on the block copolymer.

From the DE 10 2008 004 388 Differences in the foaming efficiency of pressure-sensitive adhesive formulations based on polydiene rubbers containing polystyrene segments (polystyrene-polydiene block copolymers, exemplified by SIS) can be observed compared to those based on pure polydiene rubbers (example: natural rubber). Pressure-sensitive adhesives containing polystyrene-polydiene block copolymers exhibit lower foaming efficiency than those without polystyrene. The specific nature of the two-phase structure in polystyrene block copolymers appears to complicate foaming behavior.

Surprisingly, it was discovered within the scope of the present invention that even with pressure-sensitive adhesive formulations based on hydrogenated block copolymers with a high proportion of polyvinyl aromatics, a foaming efficiency comparable to that of non-hydrogenated block copolymers, such as SIS, can be achieved if the formulation additionally contains a plasticizer component. This offers the advantage that efficient weight reduction can be achieved even with a low foaming agent content. Thus, a suitable pressure-sensitive adhesive formulation can provide a satisfactory balance between good processability, high thermal shear strength, and low weight.

a) Elastomer component

Pressure-sensitive adhesive formulations according to the invention contain at least 90% by weight, based on the total weight of the elastomer component, of at least one type of a polyvinylaromatic-polydiene block copolymer in which the polydiene blocks are hydrogenated to at least 90% by weight, based on the block copolymer, which has at least two polyvinylaromatic blocks (A) and in which the proportion of polyvinylaromatic blocks, based on the total weight of all polyvinylaromatic-polydiene block copolymers in the elastomer component, is at least 18% by weight.

It is preferred if the block copolymer or block copolymers are hydrogenated to at least 95% by weight, preferably at least 99% by weight, of the polydiene blocks (B blocks), in each case based on the block copolymer. The ethylene content in the B blocks is preferably at least 50% by weight.

• • die Blöcke A unabhängig voneinander für ein Polymer, gebildet durch Polymerisation mindestens eines Vinylaromaten;
• • die Blöcke B unabhängig voneinander für ein Polymer, gebildet durch Polymerisation eines oder mehrerer konjugierter Diene mit 4 bis 18 C-Atomen, die anschließend hydriert wurden;
• • X für den Rest eines Kopplungsreagenzes oder multifunktionellen Initiators und
• • n für eine ganze Zahl ≥ 2 stehen.

In a preferred embodiment, the elastomer component is present to an extent of at least 50% by weight, preferably at least 70% by weight, in each case based on the elastomer component, in the form of hydrogenated polyvinylaromatic-polydiene block copolymers having a structure of the form ABA, (AB) _n , (AB) _n X or (ABA) _n X, wherein

• • the blocks A independently represent a polymer formed by polymerization of at least one vinyl aromatic compound;
• • the blocks B independently represent a polymer formed by polymerization of one or more conjugated dienes having 4 to 18 carbon atoms, which were subsequently hydrogenated;
• • X represents the residue of a coupling reagent or multifunctional initiator and
• • n stands for an integer ≥ 2.

The hydrogenated polyvinylaromatic-polydiene block copolymers preferably each comprise one or more rubbery blocks B (elastomer blocks, soft blocks) and at least two glassy blocks A (hard blocks). Particular preference in the embodiment described here is given to at least one hydrogenated polyvinylaromatic-polydiene block copolymer having a structure ABA, (AB) ₂ X, (AB) ₃ X, or (AB) ₄ X, where A, B, and X are as defined above. The elastomer component preferably contains at least one triblock copolymer or higher multiblock copolymer, which may be linear or multi-armed, such as radial or star-shaped.

Pressure-sensitive adhesive formulations with a high proportion of polyvinylaromatic blocks are generally characterized by good thermal shear strength. In the context of the present invention, it has surprisingly been found that this advantageous property can be combined with the advantage of low weight, as achieved through foaming. To achieve a property profile that meets the requirements, a minimum polyvinylaromatic content of 18 wt. % is selected in the at least one block copolymer of this type. However, this should not be too high, since too high a proportion reduces the adhesive strength. It is advantageous if the polyvinylaromatic content does not exceed 35 wt. %. A polyvinylaromatic content in a range between 22 wt. % and 33 wt. % is favorable. The proportion of polyvinylaromatics in the hydrogenated polyvinylaromatic-polydiene block copolymers can be determined, for example, by ¹ H or ¹³ C NMR (Test VI). The polyvinylaromatic content of commercially available hydrogenated polyvinylaromatic-polydiene block copolymers can also be obtained from the manufacturer's information.

Against this background, an embodiment of the pressure-sensitive adhesive formulation according to the invention is preferred in which the proportion of polyvinylaromatic blocks (A blocks) is at least 22 wt. %, based on the total amount of all hydrogenated polyvinylaromatic-polydiene block copolymers in the elastomer component. Furthermore, it has proven advantageous to limit the proportion of polyvinylaromatic blocks, based on the total amount of all hydrogenated polyvinylaromatic-polydiene block copolymers in the elastomer component, to a maximum of 35 wt. %. In this respect, an embodiment of the pressure-sensitive adhesive formulation according to the invention is particularly preferred in which the proportion of polyvinylaromatic blocks (A blocks) is at least 22 wt. % and a maximum of 33 wt. %, based on the total amount of all hydrogenated polyvinylaromatic-polydiene block copolymers in the elastomer component.

Vinylaromatics for constructing block A of the hydrogenated polyvinylaromatic-polydiene block copolymer used according to the invention preferably comprise styrene, α-methylstyrene, and/or other styrene derivatives. Block A can thus be present as a homopolymer or copolymer. Block A is particularly preferably a polystyrene.

The hydrogenated polyvinylaromatic-polydiene block copolymers used in the pressure-sensitive adhesive formulation according to the invention are preferably those obtained by anionic polymerization and sequential addition of the monomers for the respective polymer blocks, vinylaromatics for the A blocks and dienes for the B blocks. In many manufacturing processes, diblock intermediates AB ^- are coupled using a coupling agent Z' to form triblock copolymers (2 AB ^- + Z' → AB-Z-BA) or radial copolymers. Subsequently, the B blocks are selectively hydrogenated, resulting in preferred B blocks consisting of ethylene and butylene from a polybutadiene block, or ethylene and propylene from a polyisoprene block.

Block copolymers of this type form the backbone of the formulation. However, an excessive proportion or an unfavorable choice of molecular weight of these types can reduce the adhesive strength. To optimally balance these properties, it has been shown that block copolymers of this type should have a peak molecular weight of at least 70,000 g/mol and at most 400,000 g/mol. The higher the molecular weight, the more challenging the processability of the material becomes. Therefore, a peak molecular weight of at most 250,000 g/mol is preferred. Linear triblock copolymers or radial block copolymers with a peak molecular weight between 90,000 g/mol and 200,000 g/mol, especially between 100,000 g/mol and 180,000 g/mol, are very advantageous. The peak molecular weight can be determined, for example, using GPC, as described under Test Methods (Test 1a).

According to preferred embodiments of the invention, the elastomer component contained in the pressure-sensitive adhesive is not sulfonated in the vinyl aromatic blocks.

It is known that an increasing proportion of diblock copolymer in the elastomer component can result in a certain increase in peel strength. For example, as 16-18 As can be seen in D. Satas, Handbook of Pressure Sensitive Adhesive Technology, 3rd ed., 1999, D. Satas & Associates, Warwick, p. 370, a formulation containing 20% diblock copolymer (SIS) can achieve an approximately 12% increase in bond strength compared to a diblock-free formulation (bond strength for the diblock-free reference formulation corresponds to 0%). Surprisingly, it has been shown that the proportion of diblock copolymer in the elastomer component in formulations based on hydrogenated polyvinyl aromatic-polydiene block copolymers can result in a significantly greater increase in bond strength when foamed. Therefore, an embodiment is preferred in which the hydrogenated polyvinylaromatic-polydiene block copolymer used according to the invention has a diblock content AB of at least 10 wt.% and at most 50 wt.%, in each case based on the elastomer component, based on the total amount of all hydrogenated polyvinylaromatic-polydiene block copolymers in the elastomer component.

According to the invention, pressure-sensitive adhesive formulations are preferred in which the elastomer component accounts for a proportion of at least 35% by weight, based on the total weight of the pressure-sensitive adhesive formulation. Preferably, the proportion of the elastomer component should not exceed 60% by weight, so that an embodiment is preferred in which the proportion of elastomer component in the pressure-sensitive adhesive formulation is 35 to 60% by weight, preferably 40 to 55% by weight, in each case based on the total weight of the pressure-sensitive adhesive formulation.

b) Adhesive resin component

The pressure-sensitive adhesive formulation according to the invention further contains at least one adhesive resin component.

The adhesive resin component is in particular one or more adhesive resins.

The adhesive resin component used in the pressure-sensitive adhesive formulation according to the invention is preferably substantially incompatible with the polyvinylaromatic blocks of the hydrogenated polyvinylaromatic-polydiene block copolymer and thus differs from the optionally present reinforcing component. The at least one adhesive resin component is therefore preferably selected such that it is miscible (compatible) primarily with the regions of the pressure-sensitive adhesive dominated by the hydrogenated polydiene blocks.

The adhesive resin component is used in particular to adjust the adhesion in the desired manner. According to the general understanding of the person skilled in the art, an "adhesive resin" is understood to mean an oligomeric or polymeric resin that increases the adhesion, i.e., the inherent tackiness of the pressure-sensitive adhesive compared to a pressure-sensitive adhesive containing no adhesive resin but otherwise identical. Adhesive resins are special compounds with a low molecular weight compared to elastomers, usually with a weight-average molecular weight _Mw of less than 5,000 g/mol. Typically, the weight-average molecular weight of an adhesive resin component used in the present invention is from 400 to 5,000 g/mol, preferably from 500 to 2,000 g/mol, as determined by GPC (Test Ib). This preferably applies to each adhesive resin used in the adhesive resin component.

The proportion of adhesive resin component in the pressure-sensitive adhesive formulation has a positive effect on the bond strength. Therefore, the adhesive resin content should not be too low. However, it has been shown that an excessively high proportion of adhesive resin(s) can have a negative impact on the thermal shear strength.

The proportion of the adhesive resin component, based on the total weight of the pressure-sensitive adhesive formulation, is preferably at least 25% by weight to a maximum of 62.5% by weight, preferably at least 35% by weight to a maximum of 52% by weight.

At least one adhesive resin is further characterized by having a softening temperature according to the ring-and-ball method of greater than 95 °C, but not more than 135 °C. The softening temperature can be determined according to ASTM E28 (Test III) as described below. Preferably, all adhesive resins in the adhesive resin component have a softening temperature in this range.

Preferably, the adhesive resin component used comprises adhesive resins selected from the group consisting of partially or fully hydrogenated resin based on dicyclopentadiene, partially or fully hydrogenated hydrocarbon resins based on C5, C5/C9 or C9 monomer streams, partially or fully hydrogenated polyterpene resins based on α-pinene and/or β-pinene and δ-limonene and a hydrogenated polymer of pure C8 or C9 aromatics, wherein the resin is partially or in particular fully hydrogenated.

For the purposes of the present invention, “partially hydrogenated” means a degree of hydrogenation of at least 80%, preferably at least 85%.

The pressure-sensitive adhesive formulation according to the invention preferably comprises at least one tackifier resin in the tackifier resin component that has a DACP (diacetone alcohol cloud point) of at least 30°C, preferably of at least 40°C and at most 80°C. The DACP is determined according to Test IV, as described below. Preferably, all tackifier resins in the tackifier resin component have a DACP in this range.

In a further preferred embodiment, the pressure-sensitive adhesive formulation according to the invention comprises, in the adhesive resin component, at least one adhesive resin having an MMAP (mixed methylcyclohexane aniline point) of greater than 60°C, preferably greater than 70°C and at most 105°C. The MMAP is determined according to Test V as described below. Preferably, all adhesive resins in the adhesive resin component have an MMAP in this range.

In addition to the at least one adhesive resin described above, the adhesive resin component may also contain one or more additional adhesive resins that do not correspond to the specified definitions with regard to softening temperature and/or DACP and/or MMAP cloud point. Adhesive resins with a softening temperature below 95°C, such as 90°C or 85°C, can also be used in a proportion of up to 10% by weight or even up to 20% by weight, based on the composition of the adhesive resin component. Adhesive resins with a softening temperature above 135°C, such as 140°C, can also be used in a proportion of up to 10% by weight or even up to 20% by weight, based on the composition of the adhesive resin component.

Adhesive resins with an MMAP cloud point below 60°C or even below 45°C and/or a DACP cloud point below 30°C or even below 15°C can also be used, with a proportion of up to 20% by weight or even up to 40% by weight of the adhesive resin component. Examples of such adhesive resins are terpene-phenolic resins, particularly with an OH number of no more than 100 mg KOH/g, and rosin esters, which may be partially hydrogenated, fully hydrogenated, or disproportionated.

c) Plasticizer component

In addition to the elastomer component and the adhesive resin component, it is essential that the pressure-sensitive adhesive formulation according to the invention further contains at least 2.5 wt.% of a plasticizer component, based on the total weight of the pressure-sensitive adhesive formulation.

The plasticizer component is in particular one or more plasticizers.

The proportion of plasticizer component, based on the total weight of the pressure-sensitive adhesive, can be up to 20 wt.% and is preferably between 4 and 15 wt.%. Surprisingly, it has been found that even a small proportion of plasticizer component in the amounts mentioned is sufficient to obtain a pressure-sensitive adhesive formulation with sufficiently high bond strength and, above all, leads to increased foaming efficiency. This contrasts with what the prior art teaches, which sometimes assumes a plasticizer content of 60 to 95 wt.%.

The plasticizer component is preferably selected from the group consisting of ethylene/propylene copolymer, ethylene/butylene copolymer, butylene/isobutylene (co)polymer, butylene homopolymer and isobutylene homopolymer, with the amorphous representatives being preferred in each case.

In a further preferred embodiment, the plasticizer has a weight-average molecular mass, determined by GPC (Test Ib), of at least 100,000 g/mol and at most 1,000,000 g/mol. In these cases, the plasticizer is preferably an ethylene/propylene copolymer or ethylene/butylene copolymer with a linear or radial structure. These copolymers containing the plasticizer component are not block copolymers containing rigid blocks within the scope of the present invention.

In a more preferred embodiment, the plasticizer component has a weight-average molecular weight, determined by GPC (Test Ib), of at least 3,000 g/mol and at most 20,000 g/mol. In this case, the plasticizer is preferably a butylene/isobutylene (co)polymer.

Soft resins based on rosin are also suitable, especially methyl esters of rosin or partially or fully hydrogenated rosin.

It is also possible to use mineral oil as a plasticizer, especially naphthenic oil.

d) Foaming agent

An adhesive tape obtained from the pressure-sensitive adhesive formulation of the invention is characterized, among other things, by a low density, which is achieved by foaming the pressure-sensitive adhesive formulation. For this purpose, the pressure-sensitive adhesive formulation of the invention further comprises a foaming agent. The proportion of foaming agent in the pressure-sensitive adhesive formulation is preferably at least 0.5 wt.% and at most 10 wt.%, preferably at most 7.5 wt.% and more preferably at most 5 wt.%, particularly preferably at most 2.5 wt.%, in each case based on the total weight of the pressure-sensitive adhesive formulation.

A physical blowing agent, for example, can be used as a foaming agent. Such blowing agents can be used individually or as a mixture of different blowing agents. Blowing agents can be selected from a wide variety of materials, including hydrocarbons, ethers, esters, and the like. Typical physical blowing agents have a boiling point in the range from -50°C to +100°C, and preferably from -50°C to +50°C. Preferred physical blowing agents include hydrocarbons such as n-pentane, isopentane, and cyclopentane, methylene chloride, or any combination of the aforementioned compounds. Such blowing agents can preferably be used in amounts of from 5% to 50% by weight of the reaction mixture, in particular from 10% to 30% by weight of the reaction mixture.

Physical foaming is also possible by incorporating gases such as carbon dioxide or nitrogen.

It is also possible to use a chemical blowing agent in addition or as an alternative. Chemical blowing agents are substances that release gas during the processing due to a chemical reaction—usually initiated by the addition of heat—thus enabling the creation of a foam structure in the polymer. The cause of the gas release can be either the thermal decomposition of the blowing agent or a chemical reaction of various substances contained in the blowing agent. The resulting gas is usually _N2 , _CO2 , or CO.

The foaming agent particularly preferably comprises microballoons (also referred to as "µ-balloons" in the context of the present disclosure). Particularly when using such a foaming agent, it has surprisingly been found that, despite the comparatively high proportion of polyvinyl aromatic blocks in the pressure-sensitive adhesive formulation according to the invention, a foaming efficiency comparable to that of pressure-sensitive adhesive formulations that do not contain hydrogenated block copolymers is achieved by combining it with a plasticizer component. In this way, it is possible to advantageously reduce the weight of a corresponding adhesive tape even with only a small proportion of foaming agent, as required, for example, for applications in the automotive industry.

"Microballoons" are elastic, and thus expandable in their ground state, hollow microspheres with a thermoplastic polymer shell. These spheres are filled with low-boiling liquids or liquefied gas. Polyacrylonitrile, polyvinylidene chloride (PVDC), polyvinyl chloride (PVC), or polyacrylate are particularly used as shell materials. Low-boiling liquids, such as isobutane or isopentane, are particularly suitable, enclosed as liquefied gases in the polymer shell under pressure.

When exposed to external influences, particularly heat, the outer polymer shell softens. At the same time, the liquid propellant gas contained within the shell transforms into a gaseous state. The microballoons expand irreversibly and three-dimensionally. The expansion is complete when the internal and external pressures equalize. Since the polymer shell remains intact, a closed-cell foam is created.

A variety of microballoon types are commercially available, which differ primarily in their size, preferably 5 to 45 µm in diameter in the unexpanded state, and the starting temperatures required for expansion, preferably 75 to 220 °C. One example of commercially available microballoons is the Expancel® DU types (DU = dry unexpanded) from Nouryon, and another is Matsumoto Microsphere® F/FN from Matsumoto Yushi Seiyaku.

Unexpanded microballoon types are also available as aqueous dispersions with a solids or microballoon content of approximately 40 to 45 wt.%, and also as polymer-bound microballoons (masterbatches), for example in ethyl vinyl acetate with a microballoon concentration of approximately 50 wt.%.

According to the invention, the average diameter of the cavities formed by the microballoons in the foamed pressure-sensitive adhesive layer is preferably 10 to 200 µm, more preferably 15 to 200 µm. Since the diameters of the cavities formed by the microballoons in the foamed pressure-sensitive adhesive layer are measured here, the diameters are the diameters of the cavities formed by the expanded microballoons. The average diameter is the arithmetic mean of the diameters of the cavities formed by the microballoons in the foamed pressure-sensitive adhesive layer. The average diameter of the cavities formed by the microballoons can be determined using a scanning electron microscope (SEM). The diameters of the cavities visible in the images Microballoons are determined graphically in such a way that the maximum extension in any (two-dimensional) direction of each individual microballoon is taken from the SEM images and is regarded as its diameter.

In addition to expandable hollow microspheres, non-expandable hollow microspheres may also be present. Hollow microspheres may also be partially expanded, i.e., not fully expanded.

Also suitable - independently of other additives - are solid polymer spheres, hollow glass spheres, solid glass spheres, hollow ceramic spheres, solid ceramic spheres and/or solid carbon spheres ("Carbon Micro Balloons").

e) Reinforcement component

The pressure-sensitive adhesive formulation according to the invention may further contain a reinforcing component.

The reinforcement component differs from the adhesive resin component mainly in that it is essentially incompatible with the hydrogenated polydiene blocks of the elastomer component.

According to the invention, so-called end block amplifiers are used as amplification components.

Endblock reinforcing agents are materials that are essentially compatible with the polyvinyl aromatic blocks of the hydrogenated polyvinyl aromatic-polydiene block copolymers of the elastomer component.

The reinforcing component preferably comprises at least one resin based on at least one, in particular aromatic, hydrocarbon compound, which is preferably selected from the group consisting of styrene, alpha-methylstyrene, para-methylstyrene and copolymers thereof.

The at least one resin of the reinforcing component preferably has a weight-average molecular weight M _w of 1,000 g/mol to 15,000 g/mol, preferably 2,000 g/mol to 10,000 g/mol, determined by GPC (Test Ib).

The at least one resin of the reinforcing component preferably has an MMAP cloud point (Mixed Methylcyclohexane Aniline Cloud Point, Test V) of -10 °C to +30 °C, preferably of 0 °C to +20 °C.

The softening point of the at least one resin of the reinforcing component is preferably at least 140 °C, preferably at least 150 °C, determined according to Test III.

The proportion of the reinforcing component, based on the total weight of the pressure-sensitive adhesive formulation, is preferably at least 2.5% by weight and at most 22% by weight, preferably at least 4% by weight and at most 18% by weight.

The expression “essentially incompatible” or “essentially not compatible” is understood in the context of the present invention to mean in particular that the constituents or components mentioned are miscible with one another to a maximum of 10% by weight, preferably to a maximum of 5% by weight.

The expression “substantially compatible” in the context of the present invention is understood in particular to mean that the constituents or components mentioned are miscible with one another to at least 90% by weight, preferably to at least 95% by weight.

f) other additives

To further adapt the property profile of the pressure-sensitive adhesive formulation according to the invention, further additives can be added to the pressure-sensitive adhesive formulation. These are preferably those selected from the group consisting of primary antioxidants such as sterically hindered phenols, secondary antioxidants such as phosphites or thioethers, process stabilizers such as C radical scavengers, light stabilizers such as UV absorbers or sterically hindered amines, processing aids and Other elastomers, such as those based on pure hydrocarbons such as unsaturated polydienes, natural or synthetically produced polyisoprenes or polybutadienes, chemically essentially saturated elastomers such as saturated ethylene-propylene copolymers, α-olefin copolymers, polyisobutylene, butyl rubber, ethylene-propylene rubber, and functionalized hydrocarbons such as halogen-containing, acrylate-containing, or vinyl ether-containing polyolefins, can also be used. Furthermore, organic or inorganic fillers, as well as dyes and color pigments, can be used. The pressure-sensitive adhesive formulation can be black, gray, white, or colored.

The amount of further additives in the pressure-sensitive adhesive formulation is preferably not more than 18% by weight, more preferably not more than 10% by weight, based on the total weight of the pressure-sensitive adhesive formulation.

1. a) mindestens eine Elastomerkomponente;
2. b) mindestens eine Klebharzkomponente;
3. c) mindestens 2,5 Gew.-% einer Weichmacherkomponente, bezogen auf das Gesamtgewicht der Haftklebeformulierung;
4. d) ein Schäumungsmittel, und
5. e) optional eine Verstärkungskomponente,

dadurch gekennzeichnet, dass die Elastomerkomponente zu mindestens 90 Gew.-%, bezogen auf das Gesamtgewicht der Elastomerkomponente, eines oder mehrerer Polyvinylaromaten-Polydien-Blockcopolymere, von denen zumindest eines mit mindestens zwei Polyvinylaromatenblöcken (A) enthalten ist, aufweist,
wobei

• • die Polydien-Blöcke (B) zu mindestens 90 Gew.-%, bezogen auf das Blockcopolymer, hydriert sind;
• • der Anteil an Polyvinylaromatenblöcken (A) mindestens 18 Gew.-% beträgt, bezogen auf die Gesamtmenge aller Polyvinylaromaten-Polydien-Blockcopolymere in der Elastomerkomponente beträgt.

Pressure-sensitive adhesive formulations according to the invention are used in particular as pressure-sensitive adhesive layers in self-adhesive products. Therefore, the present invention further provides a foamed pressure-sensitive adhesive layer comprising a foamable pressure-sensitive adhesive formulation for self-adhesive tapes, wherein the pressure-sensitive adhesive formulation comprises:

1. a) at least one elastomer component;
2. b) at least one adhesive resin component;
3. c) at least 2.5% by weight of a plasticizer component, based on the total weight of the pressure-sensitive adhesive formulation;
4. d) a foaming agent, and
5. e) optionally a reinforcement component,

characterized in that the elastomer component comprises at least 90% by weight, based on the total weight of the elastomer component, of one or more polyvinylaromatic-polydiene block copolymers, at least one of which contains at least two polyvinylaromatic blocks (A),
where

• • the polydiene blocks (B) are hydrogenated to at least 90% by weight, based on the block copolymer;
• • the proportion of polyvinyl aromatic blocks (A) is at least 18% by weight, based on the total amount of all polyvinyl aromatic-polydiene block copolymers in the elastomer component.

The pressure-sensitive adhesive formulation contained is preferably a formulation according to the present invention.

The contained pressure-sensitive adhesive formulation can be applied in foamed or unfoamed form as a pressure-sensitive adhesive layer. Regardless of the application method, the foamed pressure-sensitive adhesive layer advantageously exhibits one or more criteria of the following performance profile: Table 1 Performance range Preferred performance area Peel (PE) ≥ 1.0 N/cm ≥ 3.0 N/cm Peel (steel) ≥ 2.0 N/cm ≥ 4.0 N/cm JUICE (200 g) ≥ 100 °C ≥ 140 °C density ≤ 850 kg/m ³ ≤ 750 kg/m ³

Accordingly, an embodiment is preferred in which the foamed pressure-sensitive adhesive layer (at 50 g/m ² ) has an adhesive strength, determined as peel strength, on steel of at least 2.0 N/cm, preferably at least 4 N/cm. The adhesive strength on steel can be determined according to Test II as described below.

The foamed pressure-sensitive adhesive layer according to the invention is particularly characterized by its thermal shear strength (SAFT). For a foamed sample with a 50 g/ ^m² coating, this is preferably at least 100°C, more preferably at least 140°C, and particularly preferably at least 170°C at a 200 g load. The thermal shear strength can be determined according to Test VII.

Furthermore, the pressure-sensitive adhesive composition of the invention is distinguished by its adhesive strength to polyethylene (PE), which for a foamed sample with a 50 g/ ^m² coating is preferably at least 1.0 N/cm, particularly preferably at least 3 N/cm. The adhesive strength to PE can be determined analogously to the adhesive strength to steel, as described under Test II. The adhesive strength to both materials, steel and PE, opens up a broad range of applications for the pressure-sensitive adhesive formulation of the invention.

A further subject matter of the present invention is a self-adhesive product, in particular an adhesive tape, which comprises at least one layer of a pressure-sensitive adhesive formulation according to the invention in foamed form.

The self-adhesive product according to the invention can be designed to be adhesive on one side or both sides, i.e. double-sided, wherein the adhesive layer is preferably formed from the pressure-sensitive adhesive formulation according to the invention.

Furthermore, the self-adhesive product according to the invention may further comprise at least one layer of a temporary carrier material (“release liner”).

This temporary carrier material is in particular a film-like material from which a layer of pressure-sensitive adhesive can be detached so that the remaining part of the self-adhesive tape can then be brought into contact with a substrate to be bonded or another material which is to form a composite with the remaining part of the self-adhesive tape.

The temporary carrier material is, in particular, a release paper or film, also called a release liner. It is a material that is not firmly bonded to the pressure-sensitive adhesive layer and, in particular, has an abhesive finish, allowing the pressure-sensitive adhesive layer to be removed from it. It therefore represents an aid for its production, storage, or further processing, for example, by die-cutting.

• - ein einschichtiges, beidseitig selbstklebendes Klebeband, bestehend aus einer einzigen Schicht der geschäumten erfindungsgemäßen Haftklebeformulierung und damit ein, sogenanntes „Transfertape“, oder
• - ein mehrschichtiges, beidseitig selbstklebendes Klebeband, bei denen die Schichten jeweils aus der geschäumten erfindungsgemäßen Haftklebeformulierung bestehen, oder
• - ein mehrschichtiges, beidseitig selbstklebendes Klebeband mit einem Permanentträger, der entweder in einer Schicht aus der geschäumten erfindungsgemäßen Haftklebeformulierung oder zwischen zwei Schichten aus der geschäumten erfindungsgemäßen Haftklebeformulierung angeordnet ist, oder
• - ein mehrschichtiges, einseitig selbstklebendes Klebeband mit einer Schicht aus der geschäumten erfindungsgemäßen Haftklebeformulierung und einem Permanentträger, oder
• - ein mehrschichtiges beidseitig selbstklebendes Klebeband mit einer Schicht aus der geschäumten erfindungsgemäßen Haftklebeformulierung und einer Schicht, die nicht geschäumt sein braucht und im Hinblick auf die Schicht aus der geschäumten erfindungsgemäßen Haftklebeformulierung von gleicher oder anderer Zusammensetzung ist.
• - jeweils in Kombination mit einem temporären Trägermaterial.

Using the at least one aforementioned pressure-sensitive adhesive formulation, the self-adhesive product according to the invention is, according to preferred embodiments of the invention,

• - a single-layer, double-sided self-adhesive tape consisting of a single layer of the foamed pressure-sensitive adhesive formulation according to the invention and thus a so-called “transfer tape”, or
• - a multi-layer, double-sided self-adhesive tape, in which the layers each consist of the foamed pressure-sensitive adhesive formulation according to the invention, or
• - a multilayer, double-sided self-adhesive tape with a permanent carrier arranged either in a layer of the foamed pressure-sensitive adhesive formulation according to the invention or between two layers of the foamed pressure-sensitive adhesive formulation according to the invention, or
• - a multi-layer, single-sided self-adhesive tape with a layer of the foamed pressure-sensitive adhesive formulation according to the invention and a permanent carrier, or
• - a multilayer, double-sided self-adhesive tape with a layer of the foamed pressure-sensitive adhesive formulation according to the invention and a layer which need not be foamed and is of the same or different composition with respect to the layer of the foamed pressure-sensitive adhesive formulation according to the invention.
• - each in combination with a temporary carrier material.

Permanent carriers are, in particular, intermediate carriers within the self-adhesive product. In particular, the intermediate carrier is stretchable, whereby the stretchability of the intermediate carrier must be sufficient for some applications to ensure detachment of the adhesive strip by stretching. Highly stretchable films, for example, can serve as intermediate carriers. A maximum stretchability of the film in at least one direction, preferably in both directions, of at least 200%, preferably of at least 400% (ISO 527-3) is advantageous. Examples of advantageously usable stretchable intermediate carriers are versions made of WO 2011/124782 A1 , DE 10 2012 223 670 A1 , WO 2009/114683 A1 , WO 2010/077541 A1 , WO 2010/078396 A1 .

Film-forming or extrudable polymers can be used to produce the stretchable intermediate carrier film, which can additionally be mono- or biaxially oriented.

In one embodiment, polyolefins are used. Preferred polyolefins are produced from ethylene, propylene, butylene, and/or hexylene, whereby the pure monomers can be polymerized or mixtures of the monomers mentioned can be copolymerized. The polymerization process and the selection of the monomers allow the physical and mechanical properties of the polymer film to be controlled, such as the softening temperature and/or the tear strength.

Polyurethanes are preferably used as starting materials for stretchable intermediate carrier layers. Polyurethanes are chemically and/or physically crosslinked polycondensates, which are typically composed of polyols and isocyanates. Depending on the type and ratio of the individual components, stretchable materials are available that can be used advantageously in the context of this invention. Raw materials available to the person skilled in the art for this purpose are described, for example, in EP 0 894 841 B1 and EP 1 308 492 B1 Other raw materials from which intermediate carrier layers according to the invention can be constructed are known to the person skilled in the art.

Furthermore, rubber-based materials can be used in intermediate carrier layers to achieve extensibility. As a starting material for extensible intermediate carrier layers, natural rubber or synthetic rubber, or blends thereof, can be selected from all available grades, such as crepe, RSS, ADS, TSR, or CV types, depending on the required purity and viscosity level. Synthetic rubber or synthetic rubbers can be selected from the group of randomly copolymerized styrene-butadiene rubbers (SBR), butadiene rubbers (BR), synthetic polyisoprenes (IR), butyl rubbers (IIR), halogenated butyl rubbers (XIIR), acrylate rubbers (ACM), ethylene-vinyl acetate copolymers (EVA), and polyurethanes and/or blends thereof.

Block copolymers are particularly advantageous for use as materials for stretchable intermediate carrier layers. Individual polymer blocks are covalently linked to one another. The block linkage can be linear, but also star-shaped or graft copolymer. An example of an advantageously usable block copolymer is a linear triblock copolymer whose two terminal blocks have a softening temperature of at least 40°C, preferably at least 70°C, and whose middle block has a softening temperature of at most 0°C, preferably at most -30°C. Higher block copolymers, such as tetrablock copolymers, can also be used. It is important that the block copolymer contains at least two polymer blocks of the same or different types, each having a softening temperature of at least 40°C, preferably at least 70°C, and which are separated from one another in the polymer chain by at least one polymer block with a softening temperature of at most 0°C, preferably at most -30°C. Examples of polymer blocks are polyethers such as polyethylene glycol, polypropylene glycol or polytetrahydrofuran, polydienes such as polybutadiene or polyisoprene, hydrogenated polydienes such as polyethylene butylene or polyethylene propylene, polyesters such as polyethylene terephthalate, polybutanediol adipate or polyhexanediol adipate, polycarbonate, polycaprolactone, polymer blocks of vinylaromatic monomers such as polystyrene or poly-[α]-methylstyrene, polyalkyl vinyl ethers, polyvinyl acetate, polymer blocks of [α],[β]-unsaturated esters such as in particular acrylates or methacrylates. The corresponding softening temperatures are known to those skilled in the art. Alternatively, they can look them up, for example, in the Polymer Handbook [J. Brandrup, E. H. Immergut, E. A. Grulke (eds.), Polymer Handbook, 4th ed. 1999, Wiley, New York]. Polymer blocks can be composed of copolymers.

To produce an intermediate carrier material, it may also be appropriate to add additives and other components that improve the film-forming properties, reduce the tendency to form crystalline segments and/or specifically improve or, if necessary, worsen the mechanical properties.

Furthermore, sheet-like foams (e.g. made of polyethylene, polyethylene vinyl acetate (EVA), polyacrylate copolymer and polyurethane) are suitable.

The intermediate supports can be designed in multiple layers.

Furthermore, the intermediate carriers can have cover layers, for example, barrier layers that prevent the penetration of components from the adhesive into the intermediate carrier or vice versa. These cover layers can also have barrier properties to prevent the diffusion of water vapor and/or oxygen.

To better anchor the pressure-sensitive adhesives to the intermediate carrier, the intermediate carriers can be pretreated using conventional methods such as corona, plasma, or flame treatment. The use of a primer is also possible. Ideally, however, pretreatment can be omitted.

The inventive concept also encompasses structures with an intermediate carrier of a high modulus of elasticity and low extensibility within the self-adhesive product, in particular in the middle of the single pressure-sensitive adhesive layer, wherein the modulus of elasticity of the intermediate carrier is advantageously at least 750 MPa, preferably at least 1 GPa ( ISO 527-3 ) and the maximum extensibility (after ISO 527-3 ) is particularly high, at a maximum of 200%. Such structures are particularly well-suited for die-cutting processes and facilitate handling during the application process. Permanent carriers designed in this way are also advantageous if the self-adhesive product needs to be peeled off.

For the production of such intermediate carrier films, film-forming or extrudable polymers are used, which can in particular also be mono- or biaxially oriented.

Polyester films, and particularly preferably films based on polyethylene terephthalate (PET), are particularly suitable as film materials for the at least one layer of a film for this design. Polyester films are preferably biaxially oriented. Films made of polyolefins, in particular polybutene, cycloolefin copolymer, polymethylpentene, polypropylene, or polyethylene, for example, monoaxially oriented polypropylene, biaxially oriented polypropylene, or biaxially oriented polyethylene, are also conceivable. This list is intended to illustrate examples; other systems corresponding to the concept of the present invention are known to those skilled in the art.

To produce an intermediate carrier material, it may also be appropriate to add additives and other components that improve the film-forming properties, reduce the tendency to form crystalline segments and/or specifically improve or, if necessary, worsen the mechanical properties.

The intermediate supports can be designed in multiple layers.

Furthermore, the intermediate carriers can have cover layers, for example, barrier layers that prevent the penetration of components from the adhesive into the intermediate carrier or vice versa. These cover layers can also have barrier properties to prevent the diffusion of water vapor and/or oxygen.

To better anchor the pressure-sensitive adhesives to the intermediate carrier, the intermediate carriers can be pretreated using conventional methods such as corona, plasma, or flame treatment. The use of a primer is also possible. Ideally, however, pretreatment can be omitted.

The general terms “self-adhesive product” and “self-adhesive tape” encompass, within the meaning of this invention, all flat structures such as films or film sections extended in two dimensions, tapes with an extended length and a limited width, tape sections and the like, and ultimately also die-cuts or labels.

The self-adhesive product thus has a longitudinal dimension and a lateral dimension. The adhesive tape also has a thickness perpendicular to both dimensions, whereby the lateral dimension and longitudinal dimension can be many times greater than the thickness. The thickness is as uniform as possible, preferably essentially the same, across the entire surface area of the self-adhesive product, determined by its length and width.

Typical packaging forms of the self-adhesive products according to the invention are adhesive tape rolls and self-adhesive strips, such as those obtained in the form of die-cuts.

Preferably, all layers are substantially cuboid-shaped. Further preferably, all layers are fully bonded to one another.

The self-adhesive product preferably has a thickness of 20 µm to 3000 µm, more preferably of 30 to 2000 µm, particularly preferably 50 to 1500 µm or 100 µm, 150 µm, 200 µm, 250 µm or 500 µm, not including the temporary carrier material.

A preferred embodiment of the self-adhesive product is one in which the permanent carrier has a thickness between 2 and 200 µm, preferably 5 µm to 100 µm, very preferably 10 µm to 80 µm. If the permanent carrier is a foam layer, the thickness can also be higher, for example, above 250 µm, above 500 µm, or even above 1000 µm.

Also preferred is an embodiment of the self-adhesive tape in which no permanent carrier is included and the pressure-sensitive adhesive is present as a single layer on a temporary carrier material. The pressure-sensitive adhesive layer has a thickness between 100 µm and 2000 µm, in particular between 200 µm and 1500 µm or between 400 µm and 1200 µm. However, thinner layers between approximately 25 µm and 100 µm are also possible.

The foamed pressure-sensitive adhesive formulation as used in the self-adhesive product according to the invention preferably has a density of at most 850 kg/m ³ , preferably at most 750 kg/m ³ , and particularly preferably at most 650 kg/m ³ . The density can be determined according to known methods.

The self-adhesive products according to the invention are ideally suited for long-term, stable permanent bonding, where high thermal shear strength and, depending on the design of the self-adhesive tape, separability of the bonded joint are required. Separability is particularly advantageous when the self-adhesive tape is a transfer tape or a double-sided self-adhesive tape with an extensible permanent carrier (maximum extensibility of at least 200%). In many cases, removal is then possible by stretching from the bonded joint.

The need for separability of a permanent bond may exist for reworking purposes (if a bond is to be corrected during the manufacturing process of an object), for repair purposes (if a defective component of the bonded joint is to be replaced) or for recycling purposes (if the bonded joint is to be disposed of separately after its useful life).

Self-adhesive products with the pressure-sensitive adhesive formulations described here have also proven particularly advantageous in conjunction with polar surfaces, such as steel, and also low-energy surfaces such as PP/EPDM, PP/EPM, and PP/EPR. Therefore, the present invention further provides for the use of the pressure-sensitive adhesive composition of the invention or the self-adhesive product of the invention for bonding plastics, glass, and/or metals.

The substrates to be bonded can contain a variety of materials. Thus, substrates containing ethylene (co)polymer, propylene (co)polymer, EPR, EPM, and/or EPDM, or another plastic, are preferred. In particular, the pressure-sensitive adhesive formulations or the adhesive tape according to the invention are used for bonding an attachment containing ethylene (co)polymer, propylene (co)polymer, EPR, EPM, and/or EPDM, or another plastic such as ABS or polycarbonate, in or on an automobile/vehicle. The durability of the pressure-sensitive adhesive formulations according to the invention also allows the bonding of other materials such as glass, ceramic, and metal.

The present invention further provides a process for producing the pressure-sensitive adhesive formulation and pressure-sensitive adhesive layer according to the invention. It has surprisingly been found that the use of solvents can be dispensed with in the production process, which not only reduces costs but also minimizes environmental pollution. Therefore, the process according to the invention is characterized in that the pressure-sensitive adhesive formulation is produced by solvent-free mixing. The coating is then also carried out solvent-free. In this way, layer thicknesses above and including 100 µm, in particular above 200 µm, can be produced particularly well. Processes which can be used very well in this context are those which are characterized by the DE 10 2008 004 388 A1 be taught.

Solvent-based mixing and coating processes are also ideally suited, especially if coatings in the range below 100 µm are desired.

The foaming of the pressure-sensitive adhesive formulation can be carried out using conventional methods. Preferably, the foaming is carried out by expanding the expandable microballoons by applying heat, either inline after coating or offline in a separate process step. This can again be carried out according to the teachings of DE 10 2008 004 388 A1 take place.

The pressure-sensitive adhesive for the self-adhesive product according to the invention is applied either to one side of a temporary carrier material or to one side of a permanent carrier. The pressure-sensitive adhesive can be applied to the carrier by methods known to those skilled in the art, for example by doctor blade methods, nozzle doctor blade methods, roller bar die methods, extrusion die methods, pouring die methods, and casting methods. Also within the scope of the invention are application methods such as roller application methods, printing methods, screen printing methods, anilox roll methods, inkjet methods, and spraying methods. A preferred coating variant is solvent-based. For this purpose, the components of the pressure-sensitive adhesive(s) are dissolved in a suitable solvent or solvent mixture and then coated from solution, and the coated material is dried. Suitable solvents, which can also be used in combination, are aliphatic (e.g., pentane, hexane, heptane, octane, and their structural isomers), cycloaliphatic (e.g., cyclohexane and methylcyclohexane), and aromatic hydrocarbons (e.g., toluene, xylene), particularly in combination with ketones (e.g., acetone, 2-butanone, isobutyl ketone) or esters (e.g., ethyl acetate, butyl acetate, propyl acetate, isopropyl acetate). A preferred procedure involves using a mixture of toluene and ethyl acetate. A mixture of methylcyclohexane and an ester, such as ethyl acetate or, in particular, butyl acetate, is very advantageous. A mixture of cyclohexane and an ester, in particular, butyl acetate, is also advantageous.

Another preferred manufacturing variant is hotmelt processes, in which the pressure-sensitive adhesive is mixed using a compounding unit and then applied directly (“inline”) to the carrier material by means of extrusion and/or nozzle and/or calender. However, the application process does not have to be direct coating. The pressure-sensitive adhesive can also be coated with another material first and then laminated to the carrier in a second step. If necessary, further layers or plies of material can then be laminated or coated inline or offline, so that multi-layer/multi-ply product structures can also be created. Such additional layers can introduce special additional properties into the adhesive tape, such as mechanical properties. They can also promote the anchoring between the adhesive and the carrier or suppress the migration of individual components from one layer to the other.

For product structures with an intermediate carrier layer, a pressure-sensitive adhesive layer can be applied by direct coating onto the permanent carrier material or by lamination, in particular hot lamination.

The present invention is explained in more detail with reference to the following examples and figures, which are in no way to be understood as a limitation of the inventive concept.

i) Test methods

Unless expressly stated otherwise, the measurements are carried out in a test climate of 23 ± 1 °C and 50 ± 5 % relative humidity.

Test I - Molar Mass (GPC)

(a) Peak molecular weight of individual block copolymer modes

Polymers are polymodal systems with respect to their molecular weight distribution. Mixtures of different polymers can be considered multimodal systems, with each polymer contributing its own molecular weight distribution. Mixtures of block copolymers with structures of different molecular weight distributions can also be considered multimodal systems. Each block copolymer then contributes its own molecular weight distribution. For simplicity, these are referred to here as block copolymer modes.

GPC is a suitable metrological method for determining the molar mass of individual polymer modes in mixtures of different polymers. For the block copolymers produced by living, anionic polymerization that can be used in this invention, the molar mass distributions are typically sufficiently narrow so that polymer modes that can be assigned to triblock copolymers, diblock copolymers, or multiblock copolymers appear sufficiently resolved from one another in the elugram. The peak molar mass for the individual polymer modes can then be read from the elugrams.

Peak molecular weights (MM) are determined by gel permeation chromatography (GPC). THF is used as the eluent. The measurement is carried out at 23 °C. The precolumn is PSS-SDV, 5 µ, 10 ³ Å, ID 8.0. mm x 50 mm. PSS-SDV columns with 5 µm, 10 ³ Å, 10 ⁴ Å, and 10 ⁶ Å, each with an ID of 8.0 mm x 300 mm, are used for separation. The sample concentration is 4 g/l, and the flow rate is 1.0 ml per minute. Calibration is performed using the commercially available ReadyCal Poly(styrene) high kit from PSS Polymer Standard Service GmbH, Mainz. (µ = µm; 1 Å = 10 ^-10 m).

(b) weight-average molecular weight, in particular of adhesive resins, reinforcing resins and plasticizers

The weight-average molecular weight (MW) is determined by gel permeation chromatography (GPC). THF is used as the eluent. The measurement is carried out at 23 °C. The precolumn used is PSS-SDV, 5 µ, 10 ³ Å, ID 8.0 mm x 50 mm. The columns used for separation are PSS-SDV, 5 µ, 10 ³ Å, 10 ⁴ Å, and 10 ⁶ Å, each with ID 8.0 mm x 300 mm. The sample concentration is 4 g/L, and the flow rate is 1.0 ml per minute. Calibration is performed using the commercially available ReadyCal Kit Poly(styrene) high from PSS Polymer Standard Service GmbH, Mainz.

Test II - Adhesive strength to steel (peel strength)

The adhesive strength is determined (according to AFERA 5001) as follows. A polished steel plate with a thickness of 2 mm is used as the defined adhesive substrate. The bondable surface element to be tested (50 g/ ^m² on 36 µm etched PET film or 500 µm pressure-sensitive adhesive layer as a transfer adhesive layer reinforced on the back with a 75 µm polyester film) is cut to a width of 20 mm and a length of approximately 25 cm, unless otherwise specified, provided with a handling section, and immediately pressed five times onto the selected adhesive substrate using a 4 kg steel roller at a feed rate of 10 m/min. Immediately afterwards, the bondable surface element is peeled off the adhesive substrate at an angle of 180° using a tensile testing device (Zwick) at a speed of v = 300 mm/min, and the force required for this is measured at room temperature. The measured value (in N/cm) is the average of three individual measurements.

The adhesive strength on PE (polyethylene) was determined analogously to the described method.

Test III - (Adhesive) Resin Softening Temperature

For individual substances: The (adhesive) resin softening temperature (softening point; expiration point) is determined according to the relevant methodology known as Ring & Ball and standardized according to ASTM E28.

Test IV - DACP

5.0 g of test substance (the adhesive resin sample to be tested) are weighed into a dry sample tube and mixed with 5.0 g of xylene (mixture of isomers, CAS [1330-20-7], ≥ 98.5%, Sigma-Aldrich #320579 or comparable). The test substance is dissolved at 130 °C and then cooled to 80 °C. Any escaped xylene is replaced with more xylene until the solution contains 5.0 g. Subsequently, 5.0 g of diacetone alcohol (4-hydroxy-4-methyl-2-pentanone, CAS [123-42-2], 99%, Aldrich #H41544 or comparable) are added. The sample tube is shaken until the test substance has completely dissolved. To do this, the solution is heated to 100 °C. The sample tube containing the resin solution is then placed in a Chemotronic Cool cloud point meter from Novomatics and heated to 110 °C. Cooling occurs at a rate of 1.0 K/min. The cloud point is detected optically. The temperature at which the solution reaches 70% turbidity is recorded. The result is expressed in °C. The lower the DACP value, the higher the polarity of the test substance.

Test V - MMAP

5.0 g of test substance (the adhesive resin sample to be tested) are weighed into a dry sample vial and mixed with 10 mL of dry aniline (CAS [62-53-3], ≥ 99.5%, Sigma-Aldrich #51788 or equivalent) and 5 mL of dry methylcyclohexane (CAS [108-87-2], ≥ 99%, Sigma-Aldrich #300306 or equivalent). The sample vial is shaken until the test substance has completely dissolved. To do this, the solution is heated to 100 °C. The sample vial containing the resin solution is then placed in a Chemotronic Cool cloud point meter from Novomatics and heated to 110 °C. Cooling is carried out at a cooling rate of 1.0 K/min. The cloud point is detected optically. For this purpose, the temperature at which the turbidity of the solution reaches 70% is recorded. The result is expressed in °C. The lower the MMAP value, the higher the aromaticity of the test substance.

Test VI - Polyvinyl aromatics content

The proportion of polyvinylaromatic blocks in hydrogenated polyvinylaromatic-polydiene block copolymers is determined by ¹³ C NMR, unless otherwise known. ¹³ C NMR is explained below using the example of determining the polystyrene content in hydrogenated polystyrene-polydiene block copolymers (SEBS). The average of two integrals is calculated from the ¹³ C spectrum, namely the styrene C signal at approximately 144 to 146 ppm and the styrene CH at approximately 125 to 127 ppm. This mean value is set for SEBS in relation to the butylene integral (hydrogenated 1,2-polybutadiene repeat units), namely the CH3 signal at approximately 10 ppm, and to the ethylene integral (hydrogenated 1,4-polybutadiene repeat units), which can be calculated from the total olefinic integral at approximately 20 to 50 ppm. The resulting mol% fractions are then converted to wt%.

Test VII - JUICE

This test is used to quickly determine the shear strength of adhesive formulations under thermal stress. A test specimen is bonded to a temperature-controlled steel plate, loaded with a 200 g weight, and the shear distance is recorded.

Sample preparation:

The test sample to be tested (50 g/m ² on 36 µm etched PET carrier or 500 µm backed with 75 µm PET film) is cut to a size of 10 mm * 50 mm.

The cut adhesive tape sample is placed with the other adhesive side on a polished test plate (material 1.4301, DIN EN 10088-2 , surface 2R, surface roughness _Ra = 30 to 60 nm, dimensions 50 mm * 13 mm * 1.5 mm) in such a way that the bonded area of the sample is height * width = 13 mm * 10 mm and protrudes 2 mm from the top edge of the test plate. The sample is then rolled over six times with a 2 kg steel roller at a speed of 10 m/min to secure it. The top of the sample is reinforced flush with a sturdy adhesive strip, which serves as a support for the displacement sensor. The sample is then suspended using the plate in such a way that the longer protruding end of the test specimen points vertically downwards.

Measurement:

The sample to be measured is loaded with a weight of 200 g at its lower end. The test plate with the bonded sample is heated from 25 °C at a rate of 9 K/min to a final temperature of 200 °C.

The sliding distance of the specimen is monitored using a displacement sensor as a function of temperature and time. The maximum sliding distance is set at 1000 µm (1 mm). If this value is exceeded, the test is aborted and the failure temperature is recorded. Test conditions: room temperature 23 +/- 3 °C, relative humidity 50 +/- 5%. The result is the average of two individual measurements and is expressed in °C.

ii) Figures

As reported by Jagisch and Tancrede in D. Satas, Handbook of Pressure Sensitive Adhesive Technology, 3rd edition, 1999, D. Satas Associates, Warwick, p. 367, 16-18 , an increasing proportion of diblock copolymer in the elastomer component can result in a certain increase in peel strength. For example, an increase in adhesive strength of approximately 12% was achieved when 20% diblock copolymer, in this case SIS, was added to a formulation. Within the scope of the present invention, it was surprisingly found that by adjusting the proportion of diblock copolymer in an elastomer component in formulations based on hydrogenated polyvinylaromatic-polydiene block copolymers, a significantly greater increase in adhesive strength could be achieved when these were foamed. For example, a proportion of 14 wt. % diblock in the elastomer component already led to an increase in adhesive strength of 67% (cf. Example E2, Table 5).

From the DE 10 2008 004 388 Differences in the foaming efficiency of pressure-sensitive adhesive formulations based on polydiene rubbers containing polystyrene segments (polystyrene-polydiene block copolymers, exemplified by SIS) compared to those based on pure polydiene rubbers (example: natural rubber) can be observed. Pressure-sensitive adhesives with polystyrene-polydiene block copolymers exhibit a lower foaming efficiency than those without polystyrene. The specific nature of the two-phase structure in polystyrene block copolymers appears to complicate the foaming behavior. The different foaming behavior is in 1 reproduced, where the density of the foamed formulation is given as a measure in relation to the content of microballoons in the formulation.

2 shows the foaming efficiency achieved with the inventive pressure-sensitive adhesive formulations based on hydrogenated polyvinylaromatic-polydiene block copolymers (SEBS). For comparison, an SIS-based formulation was chosen, as described in DE 10 2008 004 388 As described above, 2 As can be seen, the foaming efficiency of the pressure-sensitive adhesive formulations according to the invention is comparable to those based on SIS. This is particularly interesting at low microballoon contents, since even with a low microballoon content, a noticeable weight reduction can be achieved without compromising the adhesive properties. The compositions of the tested formulations are given in Table 9.

3 shows the influence of the diblock copolymer content relative to the elastomer component on the density of the pressure-sensitive adhesive formulations according to the invention. Contrary to expectations, the influence of the diblock copolymer content in the elastomer component on the foaming efficiency of the pressure-sensitive adhesive formulation is minimal. The compositions of the tested formulations are listed in Table 10.

iii) Examples

Method V1 (solvent method for samples with 50 g/m ² coating):

The components of the pressure-sensitive adhesive formulations were dissolved in 30% special-boiling-point spirit/toluene/acetone, mixed with the microballoons suspended in spirit and spread with a spreader bar onto an etched PET film with the desired basis weight. The solvent was then evaporated at 100°C for 15 minutes, thus drying the mass layer. This is possible in the examples presented because microballoons with an expansion temperature above 100°C were used. After drying, the pressure-sensitive adhesive layer was covered with a layer of a siliconized PET liner, free of any air pockets, and foamed for 30 seconds at 170°C between the etched PET film and the siliconized PET liner in a circulating air drying cabinet.

Process V2 (hot melt process for samples with 500 µm coating):

The solvent-free production of pressure-sensitive adhesive formulations was carried out using a planetary roller extruder (PWE), which comprised an infeed section and two process sections. The thrust rings had an increasing diameter in the process direction. Although various spindle configurations were suitable, configurations that amounted to at least ¾ of the maximum number of spindles in the first process section were preferred. The elastomer components were metered in the infeed section of the PWE. The resin components were melted and added in the first process section of the PWE. A resin split, in which part of the resin was added in zone 1 and the remainder downstream in the second process section, was particularly suitable for producing homogeneous mixtures. The addition of both components in solid form via side feed or thrust rings was particularly suitable, with the first component accounting for approximately 30 wt.% of the total resin quantity. Addition in liquid form would also be suitable. Plasticizer was added in zone 3, as was the stabilizer in molten form. Microballoons were also added in zone 3.

The coating was carried out by introducing the hot pressure-sensitive adhesive compound into a 2-roll calender between two siliconized PET liners and was in foamed form after calendering.

The following raw materials were used to produce the pressure-sensitive adhesive formulations according to the invention and the formulations used for comparison purposes. The raw materials are commercially available under the corresponding trade names. Table 2: Raw materials used Raw material Chemistry architecture Polystyrene content [wt.%] Molar mass (GPC) [g/mol] DiBlock content [wt.%] a) Elastomer component Kraton G1654 SEBS linear triblock 31 158,000 <1 Kraton G1652 SEBS linear triblock 30 71,000 <1 Kraton G1726 SEBS linear triblock 30 65,000 (Triblock) 70 Kraton G1657 SEBS linear triblock 13 120,000 (Triblock) 30 Europrene Sol T9113 SIS linear triblock 18 150,000 (Triblock) 8 Calprene C411 SBS radial multiblock 30 315,000 (radial block copolymer Not specified Calprene C7318 SBS linear triblock 32 158,000 (Triblock) ~75 b) Adhesive resin Regalite R1125 Fully hydrogenated C9 hydrocarbon resin Softening point 125 °C DACP = + 55 °C; MMAP = +85 °C Regalite R1100 Fully hydrogenated C9 hydrocarbon resin Softening point 100°C DACP = + 45 °C; MMAP = +76 °C Regalite R1090 Fully hydrogenated C9 hydrocarbon resin Softening point 88 °C DACP = + 37 °C; MMAP = +74 °C Dercolyte A115 Alpha-pinene resin Softening point 115 °C DACP = + 35 °C; MMAP = +76 °C c) Plasticizers Ter Pib 2600 Polyisobutylen M _W = 9,200 g/mol d) Foaming agent Expancel 920 DU20 Powder of unexpanded microballoons with an expansion range between 118 °C and 172 °C and a diameter in expanded form of approximately 20 µm. Matsumoto FN190SSD Powder of unexpanded microballoons with an expansion range between 155 °C and 220 °C and a diameter in expanded form of approximately 10 µm to 15 µm. e) Reinforcement component Endex 155 Aromatic hydrocarbon resin Softening point 153 °C DACP = -23 °C; MMAP = +16 °C f) Additive Irganox 1726 Primary anti-aging agent Sterically hindered phenol Irganox 1010 Primary anti-aging agent Sterically hindered phenol Irgafos 168 Secondary anti-aging agent Phosphoric acid esters

The following tables summarize the composition of the prepared and tested formulations, with comparative examples marked with C.

In Tables 1-7 and 9, the amounts of components (a), (b), (c) and (f) (and, if applicable, (e) of the base formulation add up to 100%. The stated proportions of this base formulation are then used, if applicable, in combination with the proportion of foaming agent (d), whereby the sum of the amounts of base formulation and foaming agent (d) then adds up to 100%.

Tables 8 and 10 directly show the proportions in % based on the total composition. Table 3: Comparative examples C1-C4 Raw materials Example C1 Example C2 Example C3 Example C4 (a) Elastomer [%] Europrene Sol T9113 49.5 49.5 Kraton G1654 40.0 40.0 Kraton G1726 9.5 9.5 (b) Adhesive resin K1 [%] Regalite R1100 50.0 I 50.0 50.0 50.0 (c) Plasticizer [%] -/- -/- -/- -/- (f) Additives [%] Irganox 1726 0.5 0.5 0.5 0.5 Basic formulation a+b+c+f 100.0% 100.0% 95.0% 95.0% (d) Foaming agent µ-balloons[%] Expancel 920 DU20 0.0 0.0 5.0 5.0 Density [kg/m ³ ] 1060 1040 546 861 Table 4 - Comparative examples C5-C10 (50 g/ ^m² pressure-sensitive adhesive layer). nb: not determined. Raw materials Example C5 Example C6 Example C7 Example C8 Example C9 Example C10 (a) Elastomer [%] Europrene Sol T9113 49.5 Kraton G1654 40.0 Kraton G1652 40.0 1 40.0 Kraton G1726 9.5 9.5 10.0 Kraton G1657 49.5 Calprene C411 20.0 Calprene C7318 30.0 (b) Adhesive resin K1 [%] Regalite R1100 50.0 50.0 50.0 49.5 Regalite R1090 50.0 Dercolyte A115 49.0 (c) Plasticizer [%] -/- -/- -/- -/- -/- -/- (f) Additives [%] Irganox 1726 0.5 0.5 0.5 0.5 0.5 Irganox 1010 0.5 Irgafos 168 0.5 Basic formulation a+b+c+f 99.0% 99.0% 99.0% 99.0% 99.0% 99.0% (d) Foaming agent µ-balloons [%] Expancel 920 DU20 1.0 1.0 1.0 1.0 1.0 1.0 Adhesive strength PE 180° [N/cm] nb nb nb 3.0 nb 0.5 Adhesive strength steel [N/cm] nb nb nb nb nb 5.0 JUICE 200 g [°C] nb nb nb 96 nb 117 Density [kg/m ³ ] 711 900 871 874 743 871 Table 5- Examples E1-E4 (50 g/m ² pressure-sensitive adhesive layer) Raw materials Example E1 Example E2 Example E3 Example E4 (a) Elastomer [%] Kraton G1654 45.0 40.0 35.0 25.0 Kraton G1726 5.0 10.0 15.0 25.0 (b) Adhesive resin K1 [%] Regalite R1100 44.5 44.5 44.5 44.5 (c) Plasticizer [%] terPib 2600 5.0 5.0 5.0 5.0 (f) Additives [%] Irganox 1726 0.5 0.5 0.5 0.5 Basic formulation a+b+c+f 99.0% 99.0% 99.0% 99.0% (d) Foaming agent µ-balloons [%] Expancel 920 DU20 1.0 1.0 1.0 1.0 Adhesive strength PE [N/cm] 1.4 2.0 2.2 3.4 Adhesive strength steel [N/cm] 2.6 4.2 5.3 4.5 JUICE 200 g [°C] 188 177 165 149 Density [kg/m ³ ] 817 775 833 Table 6: Examples E5-E9 (50 g/m ² pressure-sensitive adhesive layer) Raw materials Example E5 Example E6 Example E7 Example E8 Example E9 (a) Elastomer [%] Kraton G1654 30.0 40.0 Kraton G1652 35.0 35.0 35.0 Kraton G1726 20.0 10.0 15.0 15.0 15.0 (b) Adhesive resin K1 [%] Regalite R1100 34.5 34.5 44.5 44.5 44.5 (c) Plasticizer [%] terPib 2600 15.0 15.0 5.0 5.0 5.0 (f) Additives [%] Irganox 1726 0.5 0.5 0.5 0.5 0.5 Basic formulation a+b+c+f 99.0% 99.0% 99.0% 98.0% 97.0% (d) Foaming agent µ-balloons [%] Expancel 920 DU20 1.0 1.0 1.0 2.0 3.0 Adhesive strength PE [N/cm] 2.9 1.3 2.2 3.0 1.3 Adhesive strength steel [N/cm] 4.0 2.3 5.4 4.8 4.7 JUICE 200 g [°C] 122 183 116 115 119 Density [kg/m ³ ] 824 825 829 804 636 Table 7: Adhesive strength increase (50 g/m ² pressure-sensitive adhesive layer) Raw materials Example C11/E10 Example C12/E1 Example C13/E2 Example C14/E3 Example C15/E11 Example C16/E4 (a) Elastomer [%] Kraton G1654 50.0 45.0 40.0 35.0 30.0 25.0 Kraton G1726 0.0 5.0 10.0 15.0 20.0 25.0 (b) Adhesive resin K1 [%] Regalite R1100 44.5 44.5 44.5 44.5 44.5 44.5 (c) Plasticizer [%] TerPib 2600 5.0 5.0 5.0 5.0 5.0 5.0 (f) Additives [%] Irganox 1726 0.5 0.5 0.5 0.5 0.5 0.5 Basic formulation a+b+c+f 100%/ 99% 100%/ 99% 100%/ 99% 100%/ 99% 100%/ 99% 100%/ 99% (d) Foaming agent µ-balloons [%] Expancel 920 DU20 0.0/ 1.0 0.0/ 1.0 0.0/ 1.0 0.0/ 1.0 0.0/ 1.0 0.0/ 1.0 Diblock content in elastomer component 0.0% 7.0% 14.0% 21.0% 28.0% 35.0% Adhesive strength increase steel 180° [%] without µ-balloons 0% nb 0% nb 4% 18% Adhesive strength increase steel 180° [%] with 1% µ-balloons 0% 4% 67% 75% 88% 88% Density [kg/m ³ ] with 1% µ-balloons 789 817 775 (1023*) 809 845 833 nb: not determined; *) unfoamed reference sample, assumed to be representative Table 8: Examples E12-E15 (500 µm pressure-sensitive adhesive layer) Raw materials Example E12 Example E13 Example E14 Example E15 (a) Elastomer [%] Kraton G1654 25.5% 25.5% 25.5% 30.5% Kraton G1726 25.5% 25.5% ^- 25.5% 20.5% (b) Adhesive resin K1 [%] Regalite R1100 25.5% 25.5% 25.5% 25.5% Regalite R1125 11.5% 12.0% 12.5% 12.0% (c) Plasticizer [%] terPib 2600 5.0% 5.0% 5.0% 5.0% (f) Additives [%] Irganox 1726 0.5% 0.5% 0.5% 0.5% (e) Gain component Endex 155 5.0% 5.0% 5.0% 5.0% (d) Foaming agent µ-balloons [%] Matsumoto FN190SSD 1.5% 1.0% 0.5% 1.0% Adhesive strength steel 180° [N/cm] 18.0 24.4 24.9 16.1 JUICE 200 g [°C] 122 133 132 129 Density [kg/m ³ ] 730 810 790 810 Table 9: Compositions of the inventive examples of Figure 2 Raw materials Formulation 1 Formulation 2 Formulation 3 Formulation 4 Formulation 5 Formulation 6 Formulation 7 (a) Elastomer [%] Kraton G1654 40.0% 40.0% | 40.0% 40.0% 40.0% 40.0% 40.0% Kraton G1726 10.0% 10.0% 10.0% 10.0% 10.0% 10.0% 10.0% (b) Adhesive resin K1 [%] Regalit e R1100 44.5% 44.5% 44.5% 44.5% 44.5% 44.5% 44.5% (c) Plasticizer [%] terPib 2600 5.0% 5.0% 5.0% 5.0% 5.0% 5.0% 5.0% (f) Additives [%] Irganox 1726 0.5% 0.5% 0.5% 0.5% 0.5% 0.5% 0.5% Basic formulation a+b+c+f 100.0% 99.5% 99.0% 98.0% 97.0% 95.0% 92.5% (d) Foaming agent µ-balloons [%] Expanc el 920 DU20 0.0% 0.5% 1.0% 20% 3.0% 5.0% 7.5% Density [kg/m ³ ] 1024 892 775 667 575 486 388 Table 10 - Compositions of the examples according to the invention in Figure 3 Raw materials Formulation 8 Formulation 9 Formulation 10 Formulation 11 Formulation 12 Formulation 13 (a) Elastomers r [%] Kraton G1654 50.0% 45.0% 40.0% 35.0% 30.0% 25.0% Kraton G1726 0.0% 5.0% 10.0% 15.0% 20.0% 25.0% (b) Adhesive resin K1 [%] Regalite R1100 43.5% 43.5% 43.5% 43.5% 43.5% 43.5% (c) Plasticizer [%] terPib 2600 5.0% 5.0% 5.0% 5.0% 5.0% 5.0% (f) Additive Irganox 1726 0.5% 0.5% 0.5% 0.5% 0.5% 0.5% [%] (d) Foaming agent µ-balloons [%] Expancel 920 DU20 1.0% 1.0% 1.0% 1.0% 1.0% 1.0% Density [kg/m ³ ] 789 817 775 809 855 833

As can be seen from the examples summarized in the tables, a significant improvement in adhesive strength could be achieved by the pressure-sensitive adhesive formulations according to the invention, even in the foamed state, so that the requirements of low weight, high adhesive strength and satisfactory resistance to aging are advantageously combined in the pressure-sensitive adhesive formulations according to the invention.

QUOTES CONTAINED IN THE DESCRIPTION

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

Cited patent literature

• DE 10 2008 004 388 A1 [0009, 0010, 0123, 0125]
• DE 10 2008 004 388 [0010, 0021, 0147, 0148]
• DE 10 2017 218 519 A1 [0011]
• EP 2 832 779 A1 [0012]
• DE 10 2007 021 504 A1 [0014]
• DE 10 2007 021 504 [0014]
• DE 10 2006 037 627 A1 [0015]
• WO 00/06637 A1 [0017]
• WO 2011/124782 A1 [0093]
• DE 10 2012 223 670 A1 [0093]
• WO 2009/114683 A1 [0093]
• WO 2010/077541 A1 [0093]
• WO 2010/078396 A1 [0093]
• EP 0 894 841 B1 [0096]
• EP 1 308 492 B1 [0096]

Cited non-patent literature

• F.C. Jagisch, J.M. Tancrede in Handbook of Pressure Sensitive Adhesive Technology, D. Satas (ed.), 3rd. ed., 1999, Satas & Associates, Warwick [0006]
• ISO 527-3 [0104]
• DIN EN 10088-2 [0143]

Claims (15)

Foamable pressure-sensitive adhesive formulation for self-adhesive tapes, the pressure-sensitive adhesive formulation comprising: a) at least one elastomer component; b) at least one adhesive resin component; c) at least 2.5% by weight of a plasticizer component, based on the total weight of the pressure-sensitive adhesive formulation; d) a foaming agent, and e) optionally a reinforcing component, characterized in that the elastomer component comprises at least 90% by weight, based on the total weight of the elastomer component, of one or more polyvinylaromatic-polydiene block copolymers, at least one of which is present with at least two polyvinylaromatic blocks (A), where • the polydiene blocks (B) are hydrogenated to an extent of at least 90% by weight, based on the block copolymer; • the proportion of polyvinylaromatic blocks (A) is at least 18% by weight, based on the total amount of all polyvinylaromatic-polydiene block copolymers in the elastomer component. Foamable pressure-sensitive adhesive formulation according to Claim 1 , characterized in that the polyvinylaromatic-polydiene block copolymer has a di-block content AB of at least 10 wt.% and at most 50 wt.%, based on the total amount of all polyvinylaromatic-polydiene block copolymers in the elastomer component. Foamable pressure-sensitive adhesive formulation according to at least one of the preceding claims, characterized in that the proportion of elastomer component in the pressure-sensitive adhesive formulation is at least 35% by weight to a maximum of 60% by weight, preferably at least 40% by weight and a maximum of 55% by weight, based on the total weight of the pressure-sensitive adhesive formulation. Foamable pressure-sensitive adhesive formulation according to at least one of the preceding claims, characterized in that the proportion of adhesive resin components in the pressure-sensitive adhesive formulation is at least 25% by weight to a maximum of 62.5% by weight, preferably at least 35% by weight and a maximum of 52% by weight, based on the total weight of the pressure-sensitive adhesive formulation. Foamable pressure-sensitive adhesive formulation according to at least one of the preceding claims, characterized in that the proportion of foaming agent in the pressure-sensitive adhesive formulation is at least 0.5% by weight and at most 10% by weight, preferably at most 7.5% by weight and more preferably at most 5% by weight, particularly preferably at most 2.5% by weight, in each case based on the total weight of the pressure-sensitive adhesive formulation, and wherein the foaming agent is preferably microballoons. Foamable pressure-sensitive adhesive formulation according to at least one of the preceding claims, characterized in that the adhesive resin component is selected from the group consisting of partially or fully hydrogenated resin based on dicyclopentadiene, partially or fully hydrogenated hydrocarbon resins based on C5, C5/C9 or C9 monomer streams, partially or fully hydrogenated polyterpene resins based on α-pinene and/or β-pinene and δ-limonene and a hydrogenated polymer of pure C8 or C9 aromatics, wherein the resin is partially or in particular fully hydrogenated. Foamable pressure-sensitive adhesive formulation according to at least one of the preceding claims, characterized in that the plasticizer component is selected from the group consisting of ethylene/propylene copolymer, ethylene/butylene copolymer, butylene/isobutylene (co)polymer, butylene homopolymer and isobutylene homopolymer, the amorphous representatives being preferred in each case, the proportion of plasticizer component in the pressure-sensitive adhesive formulation preferably being at most 20% by weight, based on the total weight of the pressure-sensitive adhesive formulation. Foamable pressure-sensitive adhesive formulation according to at least one of the preceding claims, characterized in that the pressure-sensitive adhesive formulation contains further additives, preferably in an amount of not more than 18% by weight, particularly preferably not more than 10% by weight, based on the total weight of the pressure-sensitive adhesive. A foamed pressure-sensitive adhesive layer comprising a foamable pressure-sensitive adhesive formulation for self-adhesive tapes, the pressure-sensitive adhesive formulation comprising: a) at least one elastomer component; b) at least one adhesive resin component; c) at least 2.5% by weight of a plasticizer component, based on the total weight of the pressure-sensitive adhesive formulation; d) a foaming agent, and e) optionally a reinforcing component, characterized in that the elastomer component comprises at least 90% by weight, based on the total weight of the elastomer component, of one or more polyvinylaromatic-polydiene block copolymers, at least one of which is present with at least two polyvinylaromatic blocks (A), where • the polydiene blocks (B) are hydrogenated to an extent of at least 90% by weight, based on the block copolymer; • the proportion of polyvinylaromatic blocks (A) is at least 18% by weight, based on the total amount of all polyvinylaromatic-polydiene block copolymers in the elastomer component. Foamed pressure-sensitive adhesive layer according to Claim 9 , characterized in that the pressure-sensitive adhesive formulation has an adhesive strength expressed as peel strength (peel on steel) for a coating of 50 g/m ² of at least 2.0 N/cm. Foamed pressure-sensitive adhesive layer according to at least one of the Claims 9 and 10 Claims, characterized in that the pressure-sensitive adhesive formulation has a thermal shear strength (SAFT) at a coating of 50 g/m ² and a load of 200 g of at least 100 °C, preferably at least 140 °C and particularly preferably at least 170 °C. Self-adhesive product comprising at least one layer of a foamable pressure-sensitive adhesive formulation according to at least one of the Claims 1 until 8 or at least one foamed pressure-sensitive adhesive layer according to at least one of the Claims 9 until 11 . Self-adhesive product according to Claim 12 , characterized in that the foamed pressure-sensitive adhesive layer has a density of at most 850 kg/m ³ . Process for producing a pressure-sensitive adhesive formulation according to at least one of the Claims 1 until 10 , characterized in that the pressure-sensitive adhesive formulation is produced by solvent-free mixing. Use of a pressure-sensitive adhesive formulation according to at least one of the Claims 1 until 10 or a self-adhesive product according to Claim 11 for bonding plastics, glass and/or metals.

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