Pressure-sensitive adhesive composition based on acrylonitrile butadiene rubber

Abstract

The present invention relates to a nitrile rubber-based pressure-sensitive adhesive composition, a self-adhesive tape comprising the pressure-sensitive adhesive composition, and the use thereof. The pressure-sensitive adhesive composition according to the present invention comprises: (a) a nitrile rubber component; and (b) a tackifying resin component; wherein the nitrile rubber component (a) comprises at least one first nitrile rubber N1 having an acrylonitrile content of at least 14% by weight and at most 22% by weight and at least one second nitrile rubber N2 having an acrylonitrile content of at least 25% by weight and at most 32% by weight, and the fraction of nitrile rubbers N1 and N2 is at least 90% by weight based on nitrile rubber component (a); and the tackifying resin component (b) comprises at least one tackifying resin having aromatic structural units, said tackifying resin having an MMAP of at most 40 DEG C and a softening point of at least 85 DEG C and at most 135 DEG C.

Description

Technical Field

[0001] The present invention relates to a pressure-sensitive adhesive composition based on nitrile rubber, a self-adhesive tape comprising the pressure-sensitive adhesive composition and use thereof. Background Art

[0002] Pressure-sensitive adhesive composition has been known for a long time.Even if pressure-sensitive adhesive composition refers to relatively weak applied pressure, also allow to be connected with adhesion substrate permanently and after use can be peeled off again from adhesion substrate substantially without residue.At room temperature, pressure-sensitive adhesive composition plays permanent pressure-sensitive adhesive effect, therefore has enough low viscosity and high contact viscosity (or initial viscosity), thereby it has just wetted the surface of corresponding bonding substrate under low applied pressure.In this respect, they are different from heat-activated adhesive, but heat-activated adhesive only sets up final connection with adhesion substrate by the effect of heat.The bondability of pressure-sensitive adhesive composition and re-peelability are based on its adhesive properties and based on its cohesive properties.Usually, adhesive properties and cohesive properties contradict each other, thereby usually a kind of character can reduce when another kind of character for example improves by revising formula.In addition, also often other requirement is proposed to pressure-sensitive adhesive composition, and some of them require to be very specific to application.

[0003] The adhesive tape (so-called self-adhesive tape) that is equipped with pressure-sensitive adhesive composition is widely used in industry and family field now.Self-adhesive tape usually includes the carrier film that is equipped with pressure-sensitive adhesive composition on one side or both sides.Also there is the self-adhesive tape that only consists of pressure-sensitive adhesive composition layer and does not have carrier film, and these are called transfer tape.The composition of self-adhesive tape may be very different, and is subject to the guidance of the special requirements of various applications.Carrier usually includes plastic film, as for example formed by polypropylene, polyethylene, polyester, or the plastic film formed by paper, fabric (woven fabric) or non-woven fabric.

[0004] Various compounds can be used as the basis for pressure-sensitive adhesive compositions. Pressure-sensitive adhesive compositions or self-adhesives typically include acrylate copolymers, silicones, natural rubber, synthetic rubber, styrene block copolymers, or polyurethanes, often in combination with further mixture components. Pressure-sensitive adhesive compositions based on acrylonitrile-butadiene rubber have been proposed for applications requiring particularly good chemical resistance.

[0005] Acrylonitrile-butadiene rubber (also referred to as acrylonitrile-butadiene rubber, it is abbreviated as NBR, derived from nitrile butadiene rubber) refers to the synthetic rubber obtained by copolymerizing acrylonitrile and butadiene-1,3-diene with a mass ratio of about 52:48 to 10:90. Its manufacture is carried out almost completely in aqueous emulsion. The emulsion obtained here is used as it is (NBR latex) or processed to obtain solid rubber. The character of acrylonitrile-butadiene rubber depends on the ratio and molar mass thereof of the starting monomers. The vulcanized product that can be obtained by acrylonitrile-butadiene rubber (that is, the formulation of chemically crosslinked rubber) has high tolerance to fuel, oil, fat and hydrocarbon, and is characterized in that more favourable aging behavior, lower wear and tear and the breathability of reduction are compared with those made of natural rubber.

[0006] Nitrile-butadiene rubber can be obtained in a wide range of types. Except for the acrylonitrile content, the difference of different types also lies in the viscosity of the rubber in particular. This viscosity is typically described by the Mooney viscosity. This is then determined on the one hand by the number of branches in the polymer, and on the other hand by the molecular weight. In principle, between so-called cold polymerization and thermal polymerization, polymerization is distinguished. Cold polymerization is typically carried out at a temperature of 5 to 15 ℃, and compared with the thermal polymerization typically carried out at 30 to 40 ℃, causes lower number of branches.

[0007] Nitrile rubber is commercially available from a number of manufacturers such as Nitriflex, Zeon, LG Chemicals, Kumho Petrochemicals, and Arlanxeo, among others.

[0008] Except the copolymer formed by acrylonitrile and butadiene, other, more specific NBR grade, such as carboxylated NBR grade, is also commercially available.This carboxylated NBR grade is produced by the terpolymerization of acrylonitrile and butadiene with a small portion of (meth) acrylic acid in emulsion.They are known with high strength.The selective hydrogenation of the CC double bond of NBR causes the temperature (up to 150 ℃ in hot air or ozone) of raising or to the hydrogenated nitrile rubber (H-NBR) of the tolerance of swelling agent (for example sulphurous crude oil, brake fluid or hydraulic fluid) of further improvement.Except the above-mentioned acrylonitrile-butadiene rubber with elastomeric properties and carboxylated or hydrogenated NBR rubber, also has liquid NBR rubber.This liquid NBR rubber is limited on its molecular weight due to the interpolation of polymerization regulator in polymerization process, and therefore obtains with the form of liquid rubber.

[0009] For many applications, additional cohesion is required. To this end, nitrile rubber formulations can be chemically crosslinked, which is called vulcanization. Vulcanization can be carried out with common sulfur crosslinking agents, peroxides or by high-energy radiation.

[0010] Pressure-sensitive adhesive compositions based on nitrile rubber are known.

[0011] US 2601016 A describes a formulation with an acrylonitrile-butadiene copolymer, a tackifying resin and, in an advantageous embodiment, a plasticizer (0 to 50% by weight of the total formulation). Specifically, a nitrile rubber (Hycar OR-25) with an acrylonitrile content of 30% by weight can be mentioned.

[0012] US 3374134 A proposes a formulation with nitrile rubber (Hycar 1022; acrylonitrile content 33%, Mooney grade 48) and an alkylphenol resin.

[0013] EP 0 381 349 A2 has described the formulation that contains acrylonitrile-butadiene rubber.At this, also mention the mixture of various acrylonitrile-butadiene rubbers.Clearly listed is the combination of 60 % by weight Therban 1707 (hydrogenated acrylonitrile-butadiene rubber, acrylonitrile content 34%) and 40 % by weight Perbunan 3312 (acrylonitrile-butadiene rubber, acrylonitrile content 34%).This specification sheet mentions other acrylonitrile-butadiene rubber types that can be used in the meaning of EP 0 381 349 A2.Even if acrylonitrile content can be 10-45 % by weight according to instruction, the type that clearly mentions as an example has an acrylonitrile content of at least 30 % by weight.It does not propose to combine elastomer with tackifying resin.

[0014] WO 2012 / 092129 A1 discloses a formulation with, for example, 30.7 to 34.0% by weight of nitrile rubber, a hydrocarbon resin, and two different plasticizers. The materials explicitly listed are a nitrile rubber with an acrylonitrile content of 33% and an aromatic hydrocarbon resin with a softening point of 80°C.

[0015] EP 3 334 797 B1 discloses a pressure-sensitive adhesive composition based on acrylonitrile-butadiene rubber and a tackifying resin, wherein the acrylonitrile content is between 10 and 25 wt % and there is 30 to 130 phr of tackifying resin. Although a variety of acrylonitrile-butadiene rubber types can be combined, the selection or amount ratios in such a combination are not clearly stated.

[0016] DE 10 2018 222 679 A1 teaches a pressure-sensitive adhesive composition layer having a nitrile rubber and a tackifying resin crosslinked by electron irradiation. The acrylonitrile content is preferably at least 20% by weight. Advantageously, liquid nitrile rubber is added. There is no explicit mention of mixtures of different elastomer nitrile rubber types.

[0017] WO 2007 / 012656A1 has described the heat-activated adhesive formulation of the mixture that comprises three kinds of different specific acrylonitrile-butadiene rubber types.Disclosed formulation is designed for by hot pressing processing, and at room temperature is not pressure-sensitive adhesive or at least is hardly pressure-sensitive adhesive.A kind of acrylonitrile-butadiene rubber of use has an acrylonitrile content of at most 25 weight %.For this kind, preferred usage amount requires to be no more than 50 weight %, based on the amount of all acrylonitrile-butadiene rubbers.In clear and definite example, usage amount is 32.0 weight % or 54.5 weight %.In addition, there is the second acrylonitrile-butadiene rubber with the acrylonitrile content between 25 weight % and 35 weight % (clear and definite mark is 34 weight % or 27.3 weight % in an embodiment).

[0018] Furthermore, according to an embodiment, the third nitrile rubber having an acrylonitrile content of 35 wt % or more is contained at a fraction of 18 wt % or 34 wt % based on the total amount of the nitrile rubber.

[0019] This results in the formulations having no appreciable pressure-sensitive adhesive properties at room temperature, which is also unnecessary for the systems emphasized in WO 2007 / 012656 A1, since they are intended for bonding in hot pressing processes.

[0020] Along with electronic equipment is more and more general, their application field is also increasing.This also causes the demand to the growth of installed assembly.For example, owing to develop wearable electronic equipment (so-called wearable thing) for example smart watch, it becomes more and more important as follows: the bonding wherein used has high tolerance to various chemicals, and even after long-term storage in various media, does not lose too much adhesion.The self-adhesive tape with the pressure-sensitive adhesive composition based on acrylonitrile-butadiene rubber has been proved to be very suitable for this type of application.For different electronic equipment for example smart phone (mobile phone), flat board (tablet computer), notebook (notebook computer), camera, camcorder, keyboard, touchpad etc. also are day by day producing similar demand.

[0021] Although self-adhesive tapes having pressure-sensitive adhesive compositions based on nitrile rubber have already been proposed and provided, further improvements in the adhesive properties are always desired, wherein the aforementioned conflicting goals of simultaneously improving the mutually contradictory properties, namely adhesion and cohesion, are a constant challenge during development. Summary of the Invention

[0022] It was therefore an object of the present invention to provide chemically resistant pressure-sensitive adhesive compositions for technical applications which have both improved adhesion and improved cohesion compared to the pressure-sensitive adhesive compositions of the prior art.

[0023] The object is achieved by the pressure-sensitive adhesive composition according to the present invention.

[0024] Therefore, the present invention relates to a pressure-sensitive adhesive composition comprising

[0025] (a) a nitrile rubber component; and

[0026] (b) a tackifying resin component;

[0027] wherein the nitrile rubber component (a) comprises at least one first nitrile rubber N1 having an acrylonitrile content of at least 14 wt % and at most 22 wt % and at least one second nitrile rubber N2 having an acrylonitrile content of at least 25 wt % and at most 32 wt %, and the fraction of the nitrile rubbers N1 and N2 is at least 90 wt %, based on the nitrile rubber component (a); and

[0028] The tackifying resin component (b) comprises at least one tackifying resin having aromatic structural units, said tackifying resin having an MMAP of at most 40° C. (according to test VI) and a softening point of at least 85° C. and at most 135° C. (according to test IV).

[0029] Therefore, the pressure-sensitive adhesive composition according to the present invention is a pressure-sensitive adhesive composition based on nitrile rubber.

[0030] The preferred technical solution of the present invention is an advantageous further development of the subject matter of the present invention. In addition, the present invention comprises a self-adhesive tape comprising at least one pressure-sensitive adhesive composition according to the present invention and the use thereof.

[0031] All embodiments of this description apply to the pressure-sensitive adhesive composition according to the invention, the self-adhesive tape according to the invention, the method for producing a pressure-sensitive adhesive composition according to the invention, and the use of the pressure-sensitive adhesive composition or the self-adhesive tape according to the invention.

[0032] The present invention also includes all features as any preferred solution. Furthermore, the present invention includes combinations of individual features, and in these cases, also includes different levels of preference. Thus, for example, the combination of a first feature designated as "preferred" with a second feature designated as "particularly preferred" is included in the present invention. The subject matter specified within the "embodiment" also includes different levels of preference.

[0033] The application technical performance profile of the pressure-sensitive adhesive composition according to the present invention preferably meets the following requirements:

[0034] Table 1: Preferred performance profile

[0035]

[0036] (a) Nitrile rubber component

[0037] The pressure-sensitive adhesive composition comprises (a) a nitrile rubber component, wherein the nitrile rubber component (a) comprises at least one first nitrile rubber N1 having an acrylonitrile content of at least 14 wt. % and at most 22 wt. % and at least one second nitrile rubber N2 having an acrylonitrile content of at least 25 wt. % and at most 32 wt. %, and the fraction of the nitrile rubbers N1 and N2 is at least 90 wt. %, based on the nitrile rubber component (a).

[0038] It is also conceivable here that two or more nitrile rubbers N1 and / or two or more nitrile rubbers N2 are contained.

[0039] In this case, the characteristics of the rubbers N1 and N2, such as the indicated acrylonitrile content, relate to each nitrile rubber N1 or N2 contained.

[0040] Preferably, each nitrile rubber N1 has an acrylonitrile content of 16 to 21% by weight.

[0041] Preferably, each nitrile rubber N2 has an acrylonitrile content of 26% to 30% by weight.

[0042] Preferably, each nitrile rubber N1 has an acrylonitrile content of 16 to 21% by weight and each nitrile rubber N2 has an acrylonitrile content of 26 to 30% by weight.

[0043] Preferably, each nitrile rubber N1 has a Mooney viscosity (ML (1+4) 100° C.) of 45 to 80 MU.

[0044] The data on Mooney viscosity within the scope of the present disclosure relates to the determination according to ISO 289-1:2015.

[0045] Preferably, each nitrile rubber N2 has a Mooney viscosity (ML (1+4) 100° C.) of 35 to 65 MU.

[0046] Preferably, each nitrile rubber N1 has a Mooney viscosity (ML (1+4) 100° C.) of 45 to 80 MU and each nitrile rubber N2 has a Mooney viscosity (ML (1+4) 100° C.) of 35 to 65 MU.

[0047] It is essential for the present invention that the total fraction of the nitrile rubbers N1 and N2, based on the nitrile rubber component (a), is at least 90% by weight in order to provide the pressure-sensitive adhesive composition according to the object of the present invention.

[0048] The nitrile rubber component (a) therefore comprises in particular only a maximum of 10% by weight of nitrile rubber having an acrylonitrile content of more than 32% by weight.

[0049] Preferably, the fraction of nitrile rubbers N1 and N2 is at least 95% by weight, particularly preferably 100% by weight, based on the nitrile rubber component (a). Thus, the object of the present invention is achieved particularly well.

[0050] Preferably, the pressure-sensitive adhesive composition according to the present invention comprises at least 38.0 wt % and at most 60.0 wt %, preferably at least 42.0 wt % and at most 55.0 wt % of the nitrile rubber component (a), based on the total weight of the pressure-sensitive adhesive composition.

[0051] The nitrile rubber component (a) preferably contains at least 35% by weight and at most 70% by weight, particularly preferably 40% to 60% by weight, very particularly preferably at least 45% by weight and at most 55% by weight of nitrile rubber N1.

[0052] Nitrile rubber can be polymerized cold or hot independently of one another.

[0053] During the polymerization of butadiene, different monomer bonding possibilities are available, which, depending on the production method, appear in different fractions (or ratios, proportions) in the polymer.

[0054] The 1% to 2% cis- and 1% to 4% trans-of the nitrile rubber N1 and N2 are preferably connected to acrylonitrile-butadiene rubbers N1 and N2 by a 1% to 2% cis-connection fraction, a 1% to 2% trans-connection fraction, and a 10% to 18% vinyl-connection fraction, i.e., a so-called microstructure. The microstructure can be determined, for example, by nuclear resonance spectroscopy (NMR).

[0055] According to the present invention, what is particularly advantageous to acrylonitrile-butadiene rubber N1 is 8% to 15% cis-linked fraction, 65% to 80% trans-linked fraction and 10% to 18% vinyl-linked fraction.Certainly, this also applies to the situation of the acrylonitrile-butadiene rubber that only comprises a kind of N1 type.

[0056] Therefore, each nitrile rubber N1 preferably has a cis-linkage fraction of 8% to 15%, a trans-linkage fraction of 65% to 80%, and a vinyl-linkage fraction of 10% to 18%.

[0057] The same applies to NBR N2.

[0058] Each nitrile rubber N2 preferably has a cis-linkage fraction of 8% to 15%, a trans-linkage fraction of 65% to 80%, and a vinyl-linkage fraction of 10% to 18%.

[0059] Nitrile rubbers which can be used are in particular amorphous elastomers.

[0060] For the nitrile rubber N1, the glass transition temperature (determined by DSC (dynamic differential calorimetry (or differential scanning calorimetry)) is preferably in the range between -60°C (minus 60 degrees Celsius) and -45°C (minus 45 degrees Celsius), and for the nitrile rubber N2, it is preferably in the range between -40°C (minus 40 degrees Celsius) and -25°C (minus 25 degrees Celsius).

[0061] The dispersibility index Mw / Mn of acrylonitrile-butadiene rubber is generally >10 and <100.According to the present invention, this acrylonitrile-butadiene rubber can be used for N1 and N2.According to the present invention, advantageously, select one of acrylonitrile-butadiene rubber grade N1 and N2 so that dispersibility index is between 10 and 30, and the dispersibility index of another grade is between 40 and 70.Yet two kinds of acrylonitrile-butadiene rubber grade N1 and N2 also can have the dispersibility index between 10 and 30 or between 40 and 70.Very advantageously, acrylonitrile-butadiene rubber N1 has the dispersibility index between 10 and 30, and acrylonitrile-butadiene rubber N2 has the dispersibility index between 40 and 70.Dispersibility index is measured (test 1a) by GPC.

[0062] (b) Tackifying resin component (adhesive resin component)

[0063] The pressure-sensitive adhesive composition according to the present invention further comprises a tackifying resin component (b), wherein the tackifying resin component (b) comprises at least one tackifying resin having aromatic structural units, the tackifying resin having an MMAP of at most 40°C (according to test VI) and a softening point of at least 85°C and at most 135°C (according to test IV).

[0064] The tackifying resin component is in particular one or more tackifying resins.

[0065] The tackifying resins are selected so that they are miscible (compatible, compatible) with the nitrile rubber component (a) of the pressure-sensitive adhesive composition.

[0066] Tackifying resin component is especially used for regulating adhesion in a required manner.According to the general understanding of those skilled in the art, " tackifying resin " should be interpreted as referring to and not containing any tackifying resin but compared with otherwise identical pressure-sensitive adhesive composition, increases the tackiness of pressure-sensitive adhesive composition, i.e. oligomer or polymer resin of inherent viscosity.Tackifying resin is the specific compound with lower molar mass compared with elastomer, usually has the weight-average molecular weight Mw less than 5000 g / mol.Usually, the weight-average molecular weight of the tackifying resin component used within the scope of the present invention is 400 to 5000 g / mol, preferably 500 to 2000 g / mol, measures (test 1b) by GPC.

[0067] The fraction of the tackifying resin component (b) in the pressure-sensitive adhesive composition has a positive effect on the bond strength. Therefore, the tackifying resin fraction should not be too low. However, it has been shown that too high a fraction of the tackifying resin can have a negative impact on cohesion and hot shear strength.

[0068] Therefore, the pressure-sensitive adhesive composition according to the present invention preferably contains 40.0 to 62.0 wt %, preferably 40.0 to 55.0 wt % of the tackifying resin (b), based on the total weight of the pressure-sensitive adhesive composition.

[0069] According to the invention, the tackifying resin component (b) comprises at least one tackifying resin having aromatic structural units, said tackifying resin having an MMAP (mixed methylcyclohexane aniline point) of at most 40° C. (according to Test VI) and a softening temperature according to the Ring and Ball method of more than 85° C. but not more than 135° C.

[0070] The softening temperature is preferably a minimum of 95° C. and preferably a maximum of 115° C. The softening temperature is determined according to Test IV as described below. Preferably, in the case of more than one tackifying resin, all tackifying resins in the tackifying resin component (b) have a softening temperature within the stated range.

[0071] The MMAP (mixed methylcyclohexane aniline point) is preferably at most 25°C.

[0072] The MMAP is determined according to Test VI as described below. Preferably, the at least one tackifying resin of the tackifying resin component (b) also has a DACP (Diacetone Alcohol Cloud Point) of at most 0° C., preferably at most −15° C. The DACP is determined here according to Test V as described below.

[0073] Preferably, the at least one tackifying resin of the tackifying resin component (b) is chosen from tackifying resins having aromatic structural units, in particular polymers based on C9 monomer streams and pure C8 or C9 aromatic compounds, aliphatically modified aromatic hydrocarbon resins, so-called C9 / C5 resins and oxygen-containing tackifying resins having aromatic structural units, such as in particular terpene-phenol resins.

[0074] Examples of such tackifying resins are terpene-phenolic resins, in particular terpene-phenolic resins having an OH value of not more than 100 mg KOH / g.

[0075] Very preferably, at least one hydrocarbon resin having aromatic structural units is used.

[0076] Particularly preferably, the at least one tackifying resin of the tackifying resin component (b) is selected from tackifying resins having aromatic structural units, in particular based on C9 monomer streams, and polymers of pure C8 or C9 aromatic compounds, aliphatically modified aromatic resins, so-called C9 / C5 resins.

[0077] Advantageously, the tackifying resin component comprises at least 50% by weight, or even at least 70% by weight (in each case based on the tackifying resin component), particularly preferably also 90 to 100% by weight, of at least one hydrocarbon resin having aromatic structural units.

[0078] Hydrocarbon resins having aromatic structural units are obtainable, for example, from Synthomer under the name Picco, from Raincarbon under the name Novares or from Neville under the name Nevchem or Cumar.

[0079] In the tackifying resin component (b), more than or less than 50% by weight of the oxygen-containing tackifying resin may be used, based on the composition of the tackifying resin component (b).

[0080] Terpene-aldehyde resins used with particular preference are those sold, for example, under the trade name Dertophene by the company DRT or under the trade name Sylvares by the company Kraton.

[0081] In addition to at least one of the above-mentioned tackifying resins, the tackifying resin component may also contain one or more additional tackifying resins that do not meet the prescribed definitions of softening temperature and / or DACP and / or MMAP cloud point. For example, tackifying resins having a softening temperature below 85°C may also be used in a proportion of up to 10% by weight or even up to 20% by weight relative to the composition of the tackifying resin component (b). For example, tackifying resins having a softening temperature above 135°C, such as about 140°C, may also be used in a proportion of up to 10% by weight or even up to 20% by weight relative to the composition of the tackifying resin component.

[0082] Tackifying resins having an MMAP cloud point below 40° C. and / or a DACP cloud point below 0° C. may also be used in proportions of up to 20% by weight or even up to 40% by weight, relative to the composition of the tackifying resin component (b). Examples of such tackifying resins are rosin esters, which may be partially hydrogenated, fully hydrogenated or disproportionated.

[0083] In order to adjust the properties to suit the application, the pressure-sensitive adhesive composition can be modified by mixing plasticizers, crosslinking agents or fillers.

[0084] Therefore, the pressure-sensitive adhesive composition according to the present invention optionally further comprises one or more additional components selected from the group consisting of a plasticizer component (c), a filler component (d) and an additive component (e).

[0085] (c) Plasticizer component

[0086] Except nitrile rubber component (a) and tackifying resin component (b), pressure-sensitive adhesive composition according to the present invention also can comprise plasticizer component (c).Optional plasticizer component is one or more plasticizers.Compare with tackifying resin, the feature of plasticizer is that they have<25 ℃, particularly<0 ℃ glass transition temperature (DSC).

[0087] The fraction of the plasticizer component (c) here is at most 10% by weight, particularly preferably at most 7% by weight, very particularly preferably at most 5% by weight, in particular when present in a minimum amount of 0.1% by weight.

[0088] In some embodiments, the present invention provides the elastomeric acrylonitrile-butadiene rubber of the present invention.Preferably, plasticizer is liquid acrylonitrile-butadiene rubber.The viscosity of liquid acrylonitrile-butadiene rubber is different from the elastomer acrylonitrile-butadiene rubber as the part of acrylonitrile-butadiene rubber component.For liquid acrylonitrile-butadiene rubber, measuring Mooney viscosity is unusual or even impossible, because these raw materials are too rare (although even thickness) at 100 ℃, and do not have elastomeric properties.Instead, indicated melt viscosity, according to the present invention, melt viscosity is advantageously 30 Pa s at the most, more preferably 20 Pa s at the most or even 10 Pa s at the most at 70 ℃, but preferably 1 Pa s at least.

[0089] The acrylonitrile content in the liquid acrylonitrile-butadiene rubber is advantageously between 10 and 35% by weight.

[0090] During the polymerization process, the liquid NBR rubber is restricted in its molecular weight by adding a polymerization regulator and is thus available as a liquid rubber.

[0091] However, this preference does not exclude the use of other chemical plasticizers, such as esters.

[0092] (d) Filler components

[0093] Fillers are used, for example, to increase the cohesion of pressure-sensitive adhesive compositions. In this context, a combination of filler / filler interactions and filler / polymer interactions generally leads to the desired reinforcement of the polymer matrix.

[0094] Fillers are also added to paper, plastics, adhesives, coatings, and other products to increase weight or bulk. Fillers are often added to improve the product's technical usability and affect its qualities, such as strength and hardness. Natural, inorganic, and organic fillers, such as calcium carbonate, kaolin, and dolomite, are produced mechanically.

[0095] The pressure-sensitive adhesive composition optionally comprises one or more fillers, wherein these fillers can be distinguished in particular as being reinforcing or non-reinforcing. Of particular note are silica (spherical, needle-shaped or irregular pyrogenic silica), phyllosilicates, calcium carbonate, zinc oxide, titanium dioxide, aluminum oxide or aluminum hydroxide. Fillers of this type are preferably used in an amount of up to 10.0 wt %, based on the total weight of the pressure-sensitive adhesive composition.

[0096] It is very preferred to use fillers of organic nature. In this case, elastomers or viscoelastic fillers are particularly noteworthy because they have a positive effect on cohesion. Fillers based on polyurethane, so-called polyurethane beads (polyurethane beads) have proven to be very advantageous. Beads should be understood to mean particles that are largely spherical. Particularly preferably, aliphatic polyurethane beads are used, which can also be combined with other polymers. In particular, those with a glass transition temperature (DSC) of up to -20 ° C are advantageous. In one embodiment, the beads have an average particle size d(50) of 1 to 80 μm, preferably 1 to 30 μm, more preferably 1 to 25 or 10 to 30 μm or 10 to 20 μm, measured according to DIN 66111:1989-02 or according to ISO 13320:2020-01 by laser diffraction. In one embodiment, the beads, in particular polyurethane beads, have a bulk density of 300 to 800 g / L, preferably 500 to 800 g / L, measured according to DIN EN 1097-3:1998-06. Suitable polyurethane-based fillers are commercially available, for example, from Lamberti SpA under the trade name Decosphaera®, in particular Decosphaera® 15F. Also very suitable are polymer beads (polymer beads) from Sunjin Beauty Science, in particular EPU 40, which consists of a crosslinked HDI (hexamethylene diisocyanate) / trimethylol hexyl lactone polymer and polymethyl methacrylate.

[0097] These fillers are also preferably used in an amount of not more than 10.0% by weight. A range of use between 2.0% and 8.0% by weight, based on the total weight of the pressure-sensitive adhesive composition, is very advantageous.

[0098] According to a preferred embodiment, the pressure-sensitive adhesive composition according to the invention comprises one or more fillers, preferably organic elastomers or viscoelastic fillers, particularly preferably polyurethane beads and / or polymer beads composed of crosslinked HDI (hexamethylene diisocyanate) / trimethylolhexyllactone polymers and polymethyl methacrylate.

[0099] (e) Additive components

[0100] In order to further adapt the properties overview of the pressure-sensitive adhesive composition of the present invention, other additives can be added to the pressure-sensitive adhesive composition.Here, the other additives are preferably selected from following those: primary antioxidants such as hindered phenols, secondary antioxidants such as phosphites or thioethers, process stabilizers such as C free radical scavengers, sunscreens such as UV absorbers or hindered amines, processing aids, crosslinking agents (also in combination with accelerators), crosslinking accelerators, and other elastomers, for example those elastomers based on pure hydrocarbons, such as unsaturated polydiene, natural or synthetically produced polyisoprene or polybutadiene, and functionalized hydrocarbons, such as halogenated, containing acrylate or containing the polyolefin of vinyl ether.In addition, dyes and pigments can also be used.

[0101] The pressure-sensitive adhesive composition may be black, grey, white or colored accordingly.

[0102] According to the invention, the fraction of all additives added, such as further elastomers and / or dyes and / or anti-aging agents, should preferably not exceed 10.0% by weight, particularly preferably 5.0% by weight, based on the total weight of the pressure-sensitive adhesive composition.

[0103] The substances listed in additive component (e) are not mandatory. The pressure-sensitive adhesive composition according to the invention also functions without the addition of said additive components, either alone or in any combination, ie without the addition of further elastomers and / or dyes and / or anti-aging agents.

[0104] Foaming

[0105] The pressure-sensitive adhesive composition according to the present invention can also be designed to be foamable, and the corresponding pressure-sensitive adhesive composition layer in the self-adhesive tape also exists in foamed form accordingly. For this reason, at least one suitable blowing agent can be added to the pressure-sensitive adhesive composition.

[0106] The pressure-sensitive adhesive composition according to the present invention is foamed according to a preferred embodiment.

[0107] The advantages of foaming are evident in some applications where weight reduction is desired, in others where increased impact resistance is required, such as in particular in mobile electronics.

[0108] Foaming is preferably performed by introduction and subsequent expansion of microspheres.

[0109] "Microspheres" are understood to mean hollow microspheres that are elastic and therefore expandable in their basic state and have a thermoplastic polymer shell. These spheres are filled with a low-boiling liquid or liquefied gas. The shell materials used are, in particular, polyacrylonitrile, PVDC, PVC, or polyacrylates. Suitable low-boiling liquids or gases are, in particular, lower alkane hydrocarbons, such as isobutane or isopentane, which are encapsulated as liquefied gases under pressure in the polymer shell.

[0110] The action on the microspheres, particularly heat, causes the polymer shell to soften. Simultaneously, the liquid propellant present in the shell transitions to its gaseous state. This causes the microspheres to expand irreversibly and three-dimensionally. Expansion ends when the internal and external pressures are balanced. Since the polymer shell remains, a closed-cell foam is obtained.

[0111] Many types of microspheres are commercially available, which differ essentially in their size (diameter in the unexpanded state: 6 to 45 μm) and the onset temperature required for their expansion (75 to 220° C.). Examples of commercially available microspheres are the Expancel® DU types from Nuryon (DU = dry unexpanded).

[0112] Unexpanded microsphere types are also available as aqueous (aqueous) dispersions with a solids content or microsphere content of about 40 to 45% by weight, and also as polymer-bound microspheres (masterbatches), for example in ethylene vinyl acetate with a microsphere concentration of about 65% by weight. Like the DU type, both the microsphere dispersions and the masterbatches are suitable for preparing the foamed pressure-sensitive adhesive compositions according to the invention.

[0113] It is also possible to use so-called pre-expanded microspheres to produce the foamed pressure-sensitive adhesive composition according to the invention. In the case of pre-expanded microspheres, expansion occurs before introduction into the polymer matrix. For example, pre-expanded microspheres are commercially available from Nuryon under the name Dualite® or as Expancel xxx DE yy (dry expanded).

[0114] According to the present invention, preferably at least 90% of all cavities formed by the microspheres have a maximum diameter of 10 to 200 μm, more preferably 15 to 200 μm. “Maximum diameter” refers to the maximum extent of the microspheres in any direction in space.

[0115] The diameter was determined based on cryo-fracture edges in a scanning electron microscope (SEM) at a magnification of 500. The diameter of each individual microsphere was determined graphically.

[0116] If microspheres are used for foaming, they can then be provided to the formulation in the form of a batch, a paste, or an unblended or blended powder. They can also be present in a suspended form in a solvent.

[0117] According to a preferred embodiment of the present invention, the fraction of microspheres in the pressure-sensitive adhesive composition is greater than 0% by weight to 3.0% by weight, particularly between 0.2% by weight and 2.0% by weight, very particularly between 0.4% by weight and 1.5% by weight, in each case based on the overall composition of the pressure-sensitive adhesive composition. The figures relate to unexpanded microspheres.

[0118] Pressure-sensitive adhesive compositions containing expandable hollow microspheres according to the invention may also contain non-expandable hollow microspheres. The only decisive factor is that nearly all gas-containing cavities are closed by a permanently dense membrane, whether this membrane consists of an elastic and thermoplastic stretchable polymer mixture or of an elastic and—within the temperature range possible in plastics processing—non-thermoplastic glass.

[0119] Furthermore, suitable for the pressure-sensitive adhesive composition according to the invention are—independently of the choice of further additives—polymer solid spheres, glass hollow spheres, glass solid spheres, ceramic hollow spheres, ceramic solid spheres and / or carbon solid spheres (“carbon microspheres”).

[0120] The absolute density of the foamed pressure-sensitive adhesive composition according to the present invention is preferably from 500 to 990 kg / m 3 , extremely preferably 600 to 970 kg / m 3 , especially 700 to 900 kg / m 3 The relative density describes the ratio of the density of the foamed pressure-sensitive adhesive composition according to the invention to the density of the corresponding unfoamed pressure-sensitive adhesive composition according to the invention of the same formulation. The relative density of the pressure-sensitive adhesive composition according to the invention is preferably 0.50 to 0.99, more preferably 0.60 to 0.97, in particular 0.70 to 0.90.

[0121] Cross-linking

[0122] Furthermore, the pressure-sensitive adhesive composition according to the invention or the layer formed from the pressure-sensitive adhesive composition according to the invention may be crosslinked, in particular chemically or radiation-chemically crosslinked.

[0123] For this purpose, at least one suitable crosslinking system can be added to the pressure-sensitive adhesive composition or radiation-chemical crosslinking can be carried out, in particular by irradiation with electron beams.

[0124] In order to increase the cohesive properties of the pressure-sensitive adhesive composition, the pressure-sensitive adhesive composition can be crosslinked thermally using established vulcanization systems or, in particular, by adding peroxides.

[0125] However, within the scope of the present invention, preference is given to radiation-chemical crosslinking using high-energy radiation, in particular by irradiation with electron beams.

[0126] This has a particularly positive impact on properties such as cohesion. Based on current expertise, a simultaneous decrease in adhesion would be expected. However, it has been shown that, surprisingly, the pressure-sensitive adhesive compositions according to the present invention exhibit a significantly lower than expected decrease in adhesion after crosslinking, particularly after radiation-chemical crosslinking. With regard to suitable parameters for electron beam crosslinking, reference is explicitly made to the teachings of DE 10 2018 226 679 A1.

[0127] In the context of the present invention, doses of at least 20 kGy and at most 60 kGy are preferred. The accelerating voltage depends on the layer thickness of the material to be crosslinked. Within the scope of the present invention, it is advantageously between 1.8 kV and 2.4 kV per 1 μm layer thickness.

[0128] To support the crosslinking process or increase the crosslinking efficiency, crosslinking accelerators such as polyfunctional acrylates or polyfunctional methacrylates can be used. Up to 2% by weight of such accelerators, based on the total weight of the pressure-sensitive adhesive composition, are advantageous.

[0129] Pressure-sensitive adhesive composition layer

[0130] A further aspect of the present invention is a pressure-sensitive adhesive composition according to the invention forming a layer, and therefore a pressure-sensitive adhesive composition layer of a pressure-sensitive adhesive composition according to the invention.

[0131] In particular, the pressure-sensitive adhesive composition according to the invention can be formed into a layer of the pressure-sensitive adhesive composition according to the invention and only then crosslinked, in particular with electron beams.

[0132] Therefore, the pressure-sensitive adhesive composition according to the present invention may be cross-linked or non-cross-linked.

[0133] The terms "pressure-sensitive adhesive composition layer" and "pressure-sensitive adhesive layer" are used synonymously herein.

[0134] Self-adhesive tape

[0135] Preferably, the pressure-sensitive adhesive composition is used in a self-adhesive tape.

[0136] The present invention therefore provides a self-adhesive tape comprising at least one pressure-sensitive adhesive composition according to the invention.

[0137] Self-adhesive tapes in the sense of the present invention are understood here to mean all sheet-like or web-like carrier structures coated on one or both sides with a pressure-sensitive adhesive composition. This includes, in addition to classic tapes, labels, segments, die-cut parts (punched sheet-like carrier structures coated with a pressure-sensitive adhesive composition), two-dimensionally extending structures (e.g. foils), etc., as well as multilayer arrangements.

[0138] The term "self-adhesive tape" also includes so-called "transfer tapes," i.e., self-adhesive tapes without a carrier. In the case of transfer tapes, the pressure-sensitive adhesive composition is applied before application between flexible liners that are provided with a release layer and / or have anti-stick properties. For application, the liner is usually removed first, the pressure-sensitive adhesive composition is applied, and then the second liner is removed. Instead of using two liners, it is also possible to process with liners that can be separated on both sides.

[0139] The self-adhesive tape can be provided in fixed lengths, for example as a product by the meter or as a continuous product in a roll (Archimedes screw).

[0140] The application amount (coating thickness) of the pressure-sensitive adhesive composition is preferably between 20 and 500 g / m 2 between 30 and 250 g / m 2 between 40 and 150 g / m 2 between.

[0141] The layer thickness of the at least one layer of the pressure-sensitive adhesive composition according to the invention is generally preferably at least 20 μm and at most 500 μm, typically at least 30 μm and at most 250 μm, or even at least 40 μm and at most 150 μm.

[0142] As carrier materials for the self-adhesive tape, carrier materials commonly used and known to those skilled in the art are used, such as paper, woven fabrics, nonwoven fabrics, or foils made of, for example, polyesters such as polyethylene terephthalate (PET), polyethylene, polypropylene, oriented polypropylene, or polyvinyl chloride. Carrier materials made from renewable raw materials, such as paper, woven fabrics made from, for example, cotton, hemp, jute, or nettle fibers, or foils made from, for example, polylactic acid, cellulose, modified starch, or polyhydroxyalkanoates, can also be used. This list is not exhaustive, and other foils can be used within the scope of the present invention.

[0143] Particularly preferably, the foil is made of PET.

[0144] The carrier material can preferably be provided with a pressure-sensitive adhesive substance on one or both sides.

[0145] Self-adhesive tape is formed by being applied to the carrier partly or on the whole area by pressure-sensitive adhesive composition.Coating also can be carried out with the form of one or more strips on the longitudinal direction (machine direction), optionally carries out in transverse direction, but it is on the whole area especially.In addition, pressure-sensitive adhesive composition can be applied in a lattice mode by screen printing (wherein adhesive point also can have different sizes and / or different distributions), by the gravure printing of the bridge (Stegen) of the continuous (connection) in the longitudinal and transverse direction, by grid printing or flexographic printing.Adhesive composition can exist in spherical form (manufacturing by screen printing), or also can exist in the form of other patterns such as grid, bar, zigzag line.In addition, it also can for example be sprayed, and this causes more or less irregular applying figure.

[0146] Advantageously, between carrier and the pressure-sensitive adhesive composition, use tackifier, i.e. so-called primer layer, or carrier surface is carried out physical pre-treatment, to improve the adhesion of the pressure-sensitive adhesive composition to the carrier.Known dispersion and solvent system can be used as primer, for example based on rubber, acrylate rubber, polyethylene, polyvinylidene fluoride and / or cyclic rubber containing isoprene or butadiene.Isocyanate or epoxy resin can improve adhesion as additive, and partly also can improve the shear strength of pressure-sensitive adhesive.Adhesion promoter also can be applied on a side of carrier foil by coextruded layer.For example, flame retardant, corona or plasma or coextruded layer are suitable as physical surface treatment.

[0147] Furthermore, in the case of single-sided self-adhesive tapes, the carrier material can be physically treated or coated on the back or top side (ie opposite the side with the pressure-sensitive adhesive composition) to provide an anti-adhesive property, in particular with a release agent or mold release agent (optionally mixed with other polymers).

[0148] Examples are stearyl compounds (e.g. polyvinyl stearyl carbamate, stearyl compounds of transition metals such as Cr or Zr, ureas of polyethyleneimines and stearyl isocyanates or polysiloxanes. The term stearyl is a synonym for all straight-chain or branched alkyl or alkenyl groups having at least 10 carbon atoms, such as octadecyl.

[0149] Suitable release agents also include surfactant release systems based on long chain alkyl groups, such as stearyl sulfosuccinate or stearyl sulfosuccinamates, but also include polymers that can be selected from the group consisting of polyvinyl stearyl carbamates such as Escoat 20 from Mayzo, polyethylene imine stearyl urea, C 14 to C 28 Chromium complexes of fatty acids and stearyl copolymers, as described, for example, in DE 28 45 541 A. Also suitable are mold release agents based on acrylic polymers with perfluoroalkyl groups, for example silicones based on poly(dimethylsiloxane), or fluorosilicone compounds.

[0150] In addition, the carrier material can be pre-treated or post-treated. Common pre-treatments are hydrophobization, corona pre-treatment such as N2 corona or plasma pre-treatment, and common post-treatments are calendering, tempering, lamination, punching (die cutting) and covering.

[0151] The self-adhesive tape can also be laminated with commercially available release films or papers which are usually formed from a base material consisting of polyethylene, polypropylene, polyester or paper coated on one or both sides with silicone.

[0152] Manufacturing method

[0153] The manufacture of the self-adhesive tape according to the present invention can be carried out by conventional coating methods known to those skilled in the art. Here, the adhesive composition including the additive can be dissolved in a suitable solvent and applied to a carrier film or release film by, for example, anilox roller coating, comma roller coating, multi-roll coating, or during a printing process, and then the solvent can be removed in a drying pipe or an oven. Alternatively, the coating of the carrier film or release film can also be carried out in a solvent-free process. To this end, acrylonitrile-butadiene rubber is heated and melted in an extruder. In the extruder, further process steps can be carried out, such as mixing with a tackifying resin and with the additive, filtering, or degassing. The melt is then applied to the carrier film or release film by a calender.

[0154] Possible processes for producing pressure-sensitive adhesive compositions based on acrylonitrile-butadiene rubber, such as those according to the invention, can be found in DE 198 06 609 A1 and in patents WO 94 / 11175 A1, WO 95 / 25774 A1, WO 97 / 07963 A1.

[0155] Ideally, a production method in which the use of solvents is substantially and in particular completely omitted is also suitable. Advantageously, this is carried out according to WO 2019 / 101938 A1.

[0156] A suitable production method begins with the preparation of the formulation of the pressure-sensitive adhesive composition in solution, followed by coating, drying and optionally crosslinking, in particular radiation-chemical crosslinking, and optionally subsequent foaming.

[0157] Another suitable production method begins with the preparation of the formulation of the pressure-sensitive adhesive composition in solution, followed by coating, drying and, if appropriate, foaming, and optionally subsequent crosslinking, in particular radiation-chemical crosslinking.

[0158] Another suitable production method begins with the solvent-free preparation of the pressure-sensitive adhesive composition formulation in an extruder, followed by coating and optionally foaming, optionally followed by, in particular, radiation-chemical crosslinking.

[0159] Another suitable production process begins with the solvent-free preparation of the pressure-sensitive adhesive composition formulation in an extruder, followed by coating and, optionally, in particular radiation-chemical crosslinking, and optionally subsequent foaming.

[0160] use

[0161] The present invention further provides the use of the pressure-sensitive adhesive composition according to the invention or the self-adhesive tape according to the invention for bonding electronic, optical or precision mechanical devices and for bonding therein and for bonding labels or markings, in particular for bonding in mobile devices.

[0162] Electronic, optical and precision mechanical devices within the meaning of this application are, in particular:

[0163] Scientific, nautical, surveying, photographic, cinematographic, optical, weighing, measuring, signalling, monitoring, life-saving and teaching apparatus and instruments;

[0164] Apparatus and instruments for conducting, switching, converting, storing, regulating and monitoring electricity;

[0165] Image recording, processing, transmission, and reproduction equipment, such as televisions;

[0166] Acoustic recording, processing, transmission, and reproduction equipment, such as broadcasting equipment;

[0167] Computers, calculators and data processing equipment, mathematical equipment and instruments, computer accessories, office equipment such as printers, fax machines, copiers, typewriters; and data storage devices;

[0168] telecommunications equipment and multi-function devices with telecommunications capabilities, such as telephones and answering machines;

[0169] Chemical and physical measuring equipment, control equipment, and instruments, such as battery chargers, multimeters, lamps, and tachometers;

[0170] Navigational equipment and instruments;

[0171] optical equipment and instruments;

[0172] medical equipment and instruments and those used by athletes;

[0173] clocks and chronometers;

[0174] Solar cell modules, such as electrochemical dye-sensitized solar cells, organic solar cells, and thin-film batteries;

[0175] Fire-fighting equipment.

[0176] Technological developments often focus on devices that are increasingly smaller and lighter in design so that they can be carried by their owners at all times and often on a regular basis. This is usually achieved by achieving a low weight or suitable dimensions for such devices. Such devices are also referred to as mobile devices or portable devices within the scope of this specification. In this context, precision mechanical and optical devices are (also) increasingly equipped with electronic components, which increases the potential for miniaturization. Because mobile devices are carried, they are subject to increased, in particular mechanical and chemical loads, for example through impacts with edges, through being dropped, through contact with other hard objects in a bag, and also through the long-term movement caused by carrying them. However, compared to "non-mobile (stationary)" devices, which are usually installed indoors and rarely or not moved at all, mobile devices are also subject to stronger loads due to moisture exposure, temperature influences, etc.

[0177] Therefore, the present invention particularly preferably relates to mobile devices, since the adhesive composition used according to the invention has particular advantages here due to its unexpectedly good properties. Some portable devices are listed below, without wishing to be unnecessarily restricted to the specific representatives of the subject matter of the present invention in this list.

[0178] Cameras, digital cameras, camera accessories (such as light meters, flash units, apertures, camera housings, lenses, etc.), film cameras, camcorders, minicomputers (mobile computers, handheld computers, handheld calculators), laptops, notebooks, netbooks, ultrabooks, tablet computers, handheld devices, electronic organizers and organizers (so-called "electronic organizers" or "personal digital assistants", PDAs, handheld computers), modems;

[0179] Computer accessories and operating units for electronic devices, such as mice, drawing pads, drawing tablets, microphones, speakers, game consoles, joysticks, remote controllers, remote controls, touchpads ("touchpads");

[0180] Monitors, displays, screens, touch-sensitive screens (sensor screens, “touchscreen devices”), projectors;

[0181] electronic book reading devices ("e-books");

[0182] Mini televisions, pocket televisions, movie playing devices, video players, radios (including mini radios and pocket radios), walkmans, disc players (Discmans), music players for, e.g., CD, DVD, Blu-ray, cassette, USB, MP3, headphones, cordless telephones, mobile phones, smartphones, walkie-talkies (two-way radios), hands-free telephones, pagers (pagers, beepers);

[0183] mobile defibrillators, blood glucose meters, blood pressure monitors, pedometers, and pulse monitors;

[0184] Flashlight, laser pointer;

[0185] Motion detectors, optical amplifiers, binoculars, night vision equipment, GPS equipment, navigation equipment, portable interface (interface) equipment for satellite communications;

[0186] Data storage devices (USB sticks, external hard drives, memory cards);

[0187] Wristwatches, digital watches, pocket watches, bracelet watches and stopwatches.

[0188] Another area in which chemically resistant bonding is important is the bonding of labels or tags, for example in environments where there may be contact with chemicals, such as engine compartments, or where tamper resistance of the label must also be guaranteed in the application of various chemicals. BRIEF DESCRIPTION OF THE DRAWINGS

[0189] Further details, objects, features and advantages of the present invention are explained below with reference to several preferred embodiments depicted in the accompanying drawings. The drawings show:

[0190] Figure 1 Single-sided self-adhesive tape,

[0191] Figure 2 Double-sided self-adhesive tape,

[0192] Figure 3 Self-adhesive tape without carrier (transfer tape). DETAILED DESCRIPTION

[0193] Figure 1 A single-sided self-adhesive tape 1 is shown. The self-adhesive tape 1 has a pressure-sensitive adhesive layer 2, which is produced by applying one of the aforementioned pressure-sensitive adhesive compositions to a carrier 3. The pressure-sensitive adhesive is preferably applied in an amount of between 20 and 250 g / m².

[0194] Furthermore (not shown), a particularly siliconized release film can still be provided, which covers and protects the pressure-sensitive adhesive layer 2 before use of the self-adhesive tape 1. The release film is then removed from the pressure-sensitive adhesive layer 2 before use.

[0195] Figure 2 The product construction shown in shows a self-adhesive tape 1 with a carrier 3 which is coated on both sides with a pressure-sensitive adhesive composition and thus has two pressure-sensitive adhesive layers 2. The amount of pressure-sensitive adhesive applied per side is preferably between 20 and 250 g / m².

[0196] In this embodiment as well, at least one pressure-sensitive adhesive layer 2 is preferably covered by a particularly siliconized release film. In a self-adhesive tape roll, this can be covered with a particularly siliconized release film and optionally also with a second pressure-sensitive adhesive layer 2. However, a plurality of particularly siliconized release films can also be provided.

[0197] It is further possible that the carrier film is provided with one or more coatings. Furthermore, it is also possible to provide the self-adhesive tape with the pressure-sensitive adhesive composition of the invention on only one side and to use a further pressure-sensitive adhesive composition on the other side.

[0198] Figure 3 The product structure shown in FIG shows a self-adhesive tape 1 in the form of a transfer tape, i.e., a self-adhesive tape 1 without a carrier. To this end, a pressure-sensitive adhesive composition is applied on one side to a specially siliconized release film 4, thereby forming a pressure-sensitive adhesive layer 2. The pressure-sensitive adhesive application amount is typically between 20 and 500 g / m². If necessary, this pressure-sensitive adhesive layer 2 is covered with another specially siliconized release film on its second side. To use the self-adhesive tape, the specially siliconized release film is then removed.

[0199] As an alternative to a specially siliconized release film, for example, a specially siliconized release paper can be used. In this case, however, the surface roughness of the specially siliconized release paper should be reduced in order to achieve a pressure-sensitive adhesive composition side that is as smooth as possible.

[0200] Test Method

[0201] Unless expressly stated otherwise, the measurements are carried out under test conditions of 23±1° C. and 50±5% relative air humidity.

[0202] Test 1 - Molar Mass (GPC)

[0203] (a) Molar mass distribution of nitrile rubber

[0204] The molar mass distribution was determined by gel permeation chromatography (GPC). The eluent used was THF. The measurement was performed at 23°C. The preparative column used was PSS-SDV, 5 µm, 10³Å, ID 8.0 mm x 50 mm. For the separation, the columns used were PSS-SDV, 5 µm, 10³Å and 10 4 Å and 10 6 Å, each with an ID of 8.0 mm x 300 mm. The sample concentration was 4 g / l and the flow rate was 1.0 ml / min. Calibration was performed using the ReadyCal kit Poly(styrene) high, commercially available from PSS Polymer Standard Service GmbH, Mainz (µ = µm; 1 Å = 10-10 m). For the molar mass distribution, the number average Mn and the weight average Mw are determined, from which the dispersion index Mw / Mn can be calculated.

[0205] (b) Weight average molar mass of plasticizers and tackifying resins in particular

[0206] The weight-average molar mass Mw was determined by gel permeation chromatography (GPC). The eluent used was THF. The measurement was performed at 23°C. The preparative column used was PSS-SDV, 5 µm, 10³Å, ID 8.0 mm x 50 mm. For the separation, the columns used were PSS-SDV, 5 µm, 10³Å and 10 4 Å and 10 6 Å, each with an ID of 8.0 mm x 300 mm. The sample concentration was 4 g / l and the flow rate was 1.0 ml / min. Calibration was performed using the ReadyCal kit Poly(styrene) high, commercially available from PSS Polymer Standard Service GmbH, Mainz.

[0207] Test II - Adhesion to Steel

[0208] The adhesive force was determined (according to AFERA ​​5001) as follows. A polished steel plate with a thickness of 2 mm was used as the designated adhesive substrate. Unless otherwise specified, the adhesive sheet to be investigated (50 g / m² pressure-sensitive adhesive layer, 36 µm etched polyester foil) was cut to a width of 20 mm and a length of approximately 25 cm, a handle was provided, and immediately thereafter, a 4 kg steel roller was pressed back and forth five times at a speed of 10 m / min onto the corresponding selected adhesive substrate. Immediately thereafter, the adhesive sheet was pulled away from the adhesive substrate at an angle of 180° using a tensile testing machine (from Zwick) at a speed of v = 300 mm / min, and the force required for this was measured at room temperature. The measured values ​​were obtained as the average value from three individual measurements (in N / cm).

[0209] To determine the chemical resistance (tolerance), self-adhesive tape samples were stored in a 75:25 (volume %) mixture of isopropanol and water at 65°C and 90% relative humidity. For storage in isopropanol / water, a sealable container was used to prevent evaporative loss of the isopropanol. After storage, the samples were first rinsed with distilled water and then stored at 23°C and 50% relative humidity for 24 hours. The adhesion was then measured as described above.

[0210] Test III - Dynamic Shear Strength

[0211] A 25 mm x 25 mm section of the transfer tape sample was pasted between two steel plates (polished stainless steel, 2 mm thick). For reproducible component production, a pressure of 652 N was achieved for 60 seconds. After storage for 72 hours at 23 ° C and 50% relative humidity, the components were separated at 50 mm / min in a tensile testing machine (Zwick) at 23 ° C and 50% relative humidity, so that the two steel plates were pulled apart at an angle of 180 ° and the maximum force was determined in N / cm 2 The results are the average of three separate measurements.

[0212] Test IV - Softening Temperature of Tackifying Resins

[0213] For the individual substances: The (tackified) resin softening temperature (softening point; Erw-point) was determined according to the so-called ring and ball method and standardized to ASTM E28.

[0214] Testing V-DAPC

[0215] 5.0 g of the test substance (tackifying resin sample to be tested) are weighed into a dry test tube, and 5.0 g of xylene (isomer mixture, CAS [1330-20-7], ≥98.5%, Sigma-Aldrich #320579 or equivalent) are added. The test substance is dissolved at 130°C, and the solution is then cooled to 80°C. If xylene escapes, it is replenished with additional xylene until 5.0 g of xylene are present again. 5.0 g of diacetone alcohol (4-hydroxy-4-methyl-2-pentanone, CAS [123-42-2], 99%, Aldrich #H41544 or equivalent) are then added. The test tube is shaken until the test substance has completely dissolved. To this end, the solution is heated to 100°C. The test tube containing the resin solution is then placed in a Chemotronic Cool cloud point measuring instrument from Novomatics and heated to 110°C. Cooling is carried out at a cooling rate of 1.0 K / min. The turbidity point is determined optically. To do this, the temperature at which the solution reaches 70% turbidity is recorded. The results are reported in °C. The lower the DACP, the more polar the test substance.

[0216] Testing VI-MMAP

[0217] 5.0 g of the test substance (tackifying resin sample to be tested) are weighed into a dry test tube, and 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) are added. The test tube is shaken until the test substance has completely dissolved. To do this, the solution is heated to 100°C. The test tube containing the resin solution is then introduced into a Chemotronic Cool cloud point measuring instrument from Novomatics and heated to 110°C. Cooling is carried out at a cooling rate of 1.0 K / min. The cloud point is determined optically. To this end, the temperature at which the solution reaches 70% turbidity is recorded. The result is reported in °C. The lower the MMAP, the more aromatic the test substance.

[0218] Hereinafter, the present invention will be explained in more detail by means of further examples, without wishing to unnecessarily limit the present invention thereby.

[0219] Production of pressure-sensitive adhesive compositions

[0220] All ingredients required for the target formulation were weighed into a sample cup and mixed with the solvent. 2-Butanone was used in such a ratio to the other ingredients that a solids content of 25% by weight (all ingredients required for the target formulation) was obtained. The mixture was placed on a roller table at room temperature for 48 hours.

[0221] Preparation of samples

[0222] The pressure-sensitive adhesive composition solution is applied to a siliconized polyester substrate using a coating knife on a commercial laboratory coating station (e.g., from SMO (Sondermaschinen Oschersleben GmbH)). Butanone is evaporated in a circulating air drying cabinet at 105°C for 10 minutes. The gap width during coating is adjusted so that after evaporation of the solvent, a pressure of 50 g / m² is achieved. 2 The solvent-free films were subsequently covered with another layer of siliconized PET foil and stored at 23°C and 50% relative humidity until further testing.

[0223] The pressure-sensitive adhesive composition provided with microspheres was applied in the same manner and foamed between two liners at 172°C for 30 seconds.

[0224] Some of the coating samples were also crosslinked using electron beams. Here, irradiation was performed on the polyester liner-pressure-sensitive adhesive layer-polyester liner assembly. An accelerating voltage of 30 kV and a dose of 30 kGy were used. The irradiation was performed on one side.

[0225] For adhesion tests and storage in isopropyl alcohol / water to determine chemical resistance, coated specimens with a 50 g / m² layer of the pressure-sensitive adhesive composition were laminated onto 36 µm etched polyester foil.

[0226] I. Raw Materials Used

[0227] Table 2: Chemicals used

[0228]

[0229] Table 3: Solids weight [%] means in each case [% by weight]

[0230]

[0231] Table 4

[0232]

[0233] Solids weight [%] means in each case [% by weight]

[0234] Furthermore, Example 4 of WO2007012656 A1 was replicated. However, this example did not result in a pressure-sensitive adhesive tape. The adhesion at room temperature was less than 0.5 N / cm. The dynamic shear strength could not be determined.

[0235] As can be seen from the table, the use of the pressure-sensitive adhesive composition according to the invention surprisingly achieves an improvement in the performance profile including adhesion and dynamic shear strength. Thus, the pressure-sensitive adhesive composition according to the invention is at an improved level in terms of the conflicting objectives of adhesion and cohesion.

[0236] Meanwhile, it can be seen from the adhesion after storage in isopropyl alcohol / water that the examples according to the present invention still have good chemical resistance.

[0237] Reference Signs List

[0238] 1 self-adhesive tape

[0239] 2 pressure-sensitive adhesive layers

[0240] 3 carriers

[0241] 4 Release film

Claims

1. A pressure-sensitive adhesive composition comprising: (a) a nitrile rubber component; and (b) a tackifying resin component; wherein the nitrile rubber component (a) comprises at least one first nitrile rubber N1 having an acrylonitrile content of at least 14 wt % and at most 22 wt % and at least one second nitrile rubber N2 having an acrylonitrile content of at least 25 wt % and at most 32 wt %, and the fraction of the nitrile rubbers N1 and N2 is at least 90 wt %, based on the nitrile rubber component (a); and The tackifying resin component (b) comprises at least one tackifying resin having aromatic structural units, said tackifying resin having an MMAP of at most 40° C. (according to test VI) and a softening point of at least 85° C. and at most 135° C. (according to test IV).

2. The pressure-sensitive adhesive composition according to claim 1, characterized in that The pressure-sensitive adhesive composition comprises at least 38.0 wt % and at most 60.0 wt %, preferably at least 42.0 wt % and at most 55.0 wt % of the nitrile rubber component (a), based on the total weight of the pressure-sensitive adhesive composition.

3. The pressure-sensitive adhesive composition according to claim 1, characterized in that The fraction of the nitrile rubbers N1 and N2 is at least 95% by weight, preferably 100% by weight, based on the nitrile rubber component (a).

4. The pressure-sensitive adhesive composition according to claim 1, characterized in that Each nitrile rubber N1 has an acrylonitrile content of 16 to 21% by weight and / or each nitrile rubber N2 has an acrylonitrile content of 26 to 30% by weight.

5. The pressure-sensitive adhesive composition according to claim 1, characterized in that Each nitrile rubber N1 has a Mooney viscosity (ML (1+4) 100° C.) of 45 to 80 MU and / or each nitrile rubber N2 has a Mooney viscosity (ML (1+4) 100° C.) of 35 to 65 MU.

6. The pressure-sensitive adhesive composition according to claim 1, characterized in that The tackifying resin (b) is contained in an amount of 40.0 wt % to 62.0 wt %, preferably 40.0 wt % to 55.0 wt %, based on the total weight of the pressure-sensitive adhesive composition.

7. The pressure-sensitive adhesive composition according to claim 1, characterized in that The at least one tackifying resin of the tackifying resin component (b) is selected from tackifying resins having aromatic structural units, in particular based on C9 monomer streams, and polymers of pure C8 or C9 aromatic compounds, aliphatically modified aromatic resins, so-called C9 / C5 resins.

8. The pressure-sensitive adhesive composition according to claim 1, characterized in that The pressure-sensitive adhesive composition is foamed.

9. The pressure-sensitive adhesive composition according to claim 1, characterized in that The pressure-sensitive adhesive composition comprises one or more fillers.

10. The pressure-sensitive adhesive composition according to claim 1, characterized in that The pressure-sensitive adhesive composition is crosslinked, wherein crosslinking is preferably performed by irradiation with electron radiation in a preferred dose of at least 20 kGy and at most 60 kGy, and an acceleration voltage of preferably 1.8 kV to 2.4 kV per 1 μm layer thickness.

11. Self-adhesive tape comprising at least one pressure-sensitive adhesive composition according to any one of claims 1 to 10.

12. Use of the pressure-sensitive adhesive composition according to any one of claims 1 to 10 or the self-adhesive tape according to claim 11 for bonding electronic, optical or precision mechanical devices and bonding therein and for bonding labels or tags, in particular for bonding in mobile devices.

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