阅读说明：本技术 基于丙烯腈-丁二烯橡胶的压敏胶粘剂 (Pressure-sensitive adhesive based on acrylonitrile-butadiene rubber ) 是由 任焱杰 S.班伯格 T.克拉温克尔 于 2021-04-09 设计创作，主要内容包括：本发明涉及基于丙烯腈-丁二烯橡胶的压敏胶粘剂,所述压敏胶粘剂具有与胶粘剂从基材的可容易移除性组合的良好耐冲击性。这通过包括以下的压敏胶粘剂得以解决：-至少一种丙烯腈-丁二烯橡胶；和-至少一种增粘剂树脂,且其特征在于丙烯腈橡胶的丙烯腈含量小于30重量％；压敏胶粘剂包括至少一种松香树脂作为增粘剂树脂；并且所有增粘剂树脂整体具有6-150的酸值。本发明还涉及根据本发明的压敏胶粘剂用于粘合移动电子设备中的部件的用途。(The present invention relates to pressure-sensitive adhesives based on acrylonitrile-butadiene rubber, which have good impact resistance combined with easy removability of the adhesive from a substrate. This is solved by a pressure sensitive adhesive comprising: -at least one acrylonitrile-butadiene rubber; and-at least one tackifier resin, and characterized in that the acrylonitrile rubber has an acrylonitrile content of less than 30% by weight; the pressure-sensitive adhesive comprises at least one rosin resin as a tackifier resin; and all tackifier resins have an acid number of 6 to 150 as a whole. The invention also relates to the use of the pressure sensitive adhesive according to the invention for bonding components in mobile electronic devices.)

1. A pressure sensitive adhesive comprising:

-at least one acrylonitrile-butadiene rubber; and

-at least one tackifier resin,

it is characterized in that

The acrylonitrile rubber has an acrylonitrile content of less than 30 wt%;

the pressure-sensitive adhesive comprises at least one rosin resin as a tackifier resin; and is

The entirety of all tackifier resins had an acid number of 6 to 150.

2. A pressure-sensitive adhesive according to claim 1, characterized in that the acrylonitrile content of the acrylonitrile-butadiene rubber is at least 10% by weight.

3. A pressure-sensitive adhesive according to claim 1 or 2, characterized in that the pressure-sensitive adhesive comprises a total amount of tackifier resin of up to 40-70 wt. -%, based on the total weight of the pressure-sensitive adhesive.

4. A pressure sensitive adhesive according to any one of the preceding claims, characterized in that the acrylonitrile rubber is a solid acrylonitrile rubber.

5. The pressure-sensitive adhesive according to claim 4, wherein the pressure-sensitive adhesive further comprises at least one liquid acrylonitrile-butadiene rubber, the liquid acrylonitrile-butadiene rubber having an acrylonitrile content of at least 10% by weight and less than 30% by weight.

6. A pressure sensitive adhesive according to any one of the preceding claims, characterized in that the entirety of all tackifier resins has an acid number of at least 9.

7. A pressure sensitive adhesive according to any of the preceding claims, characterized in that the pressure sensitive adhesive is free of oils and plasticizers.

8. Use of a pressure sensitive adhesive according to any of the preceding claims for bonding parts in a mobile electronic device.

Technical Field

The present invention is in the field of pressure sensitive adhesives as they are used to temporarily or permanently bond a wide variety of substrates. More particularly, the invention relates to pressure-sensitive adhesives based on acrylonitrile-butadiene rubber and their use.

Background

Pressure Sensitive Adhesives (PSAs) have long been known. PSAs are adhesives that allow for durable adhesion to substrates even under relatively weak applied pressure. A variety of compounds are suitable as bases for PSA.

Nowadays, tapes equipped with PSA (known as pressure sensitive tapes) have found widespread use in the industrial and domestic fields. Pressure-sensitive adhesive tapes generally consist of a carrier film fitted with a PSA on one or both sides. There are also pressure-sensitive adhesive tapes which consist only of PSA layers and therefore do not comprise a carrier film, these being referred to as transfer tapes. The composition of the pressure sensitive adhesive tape can vary greatly and follow the specific requirements of various applications. The support is usually composed of a polymer film, for example polypropylene, polyethylene or polyester, or of paper, textile or nonwoven.

Self-adhesive or pressure-sensitive adhesive compositions are typically composed of acrylate copolymers, silicones, natural rubber, synthetic rubber, styrene block copolymers, or polyurethanes.

Acrylonitrile-butadiene rubber, NBR, is derived from nitrile butadiene rubber, and means a synthetic rubber obtained by copolymerizing acrylonitrile and butadiene-1, 3-diene in a mass ratio of about 52:48 to 10: 90. It is produced almost exclusively in aqueous emulsions. The resulting emulsion is used as such (NBR latex) or processed to solid rubber. The properties of the nitrile rubber depend on the ratio of the initial monomers and their molar mass. Vulcanizates obtainable from nitrile rubbers have a high resistance to fuels, oils, fats and hydrocarbons and are distinguished by more favourable ageing behaviour, lower wear and reduced gas permeability compared to their natural rubber counterparts. On the other hand, it is considerably insufficient in weather resistance.

Acrylonitrile-butadiene rubber is widely available. In addition to the acrylonitrile content, the various types are distinguished in particular by the viscosity of the rubber. This is usually illustrated by the Mooney viscosity. The viscosity is determined on the one hand by the number of branches in the polymer and on the other hand by the molecular weight. With regard to polymerization, a distinction is made in principle between so-called cold polymerization and hot polymerization. In contrast to hot polymerization, which is usually carried out at from 30 to 40 ℃, cold polymerization is usually carried out at from 5 to 15 ℃, resulting in a lower number of branches.

NBR rubber is available from many manufacturers, such as Nitriflex, Zeon, LG Chemicals, and Lanxess.

Carboxylated NBR grades (grades) are produced by: acrylonitrile and butadiene are terpolymerized with a small portion of (meth) acrylic acid in an emulsion. They are known for high strength. The selective hydrogenation of the C, C double bonds in NBR leads to hydrogenated nitrile rubbers (H-NBR) which have an increased temperature (up to 150 ℃ in hot air or ozone) or improved stability towards swelling agents (e.g.sulfur-containing crude oils, brake fluids and/or hydraulic oils). Vulcanization is accomplished with conventional sulfur crosslinking agents, peroxides, or with the aid of high energy radiation.

In addition to carboxylated or hydrogenated NBR rubbers, liquid NBR rubbers are also present. These rubbers are limited in their molecular weight during polymerization by the addition of chain transfer agents and are therefore obtained as liquid rubbers.

In order to adjust the properties associated with the application, the PSA may be modified by blending tackifier resins, plasticizers, crosslinking agents, fillers, or the like.

Among them, the PSA may include a so-called plasticizer. Well-known plasticizers are, for example, low molecular weight polyacrylates, plasticizing resins, phosphates or polyphosphates, paraffinic and naphthenic oils, oligomers such as oligopolybutadienes and oligoisoprenes, liquid terpene resins, vegetable and animal oils and fats. Plasticizing resins may have the same chemical base as some tackifier resins, but generally differ from these in their softening point (<40 ℃).

The field of application of electronic devices increases as they expand. This has also led to increased demands regarding the properties and manufacture of such products. Electronic devices of interest in the technical field of the present invention are, for example, smart phones (cell phones), tablet computers, notebook computers, cameras, video cameras, keyboards, touch pads, etc.

For the purposes of the present description, electronic, optical and precision mechanical devices are in particular devices classified in category 9 of the international classification (nis classification), 10 th edition (NCL (10-2013)) for goods and services for trademark registration, insofar as they are electronic, optical or precision mechanical devices; and timepieces and timekeeping devices according to category 14(NCL (10-2013)),

for example, in particular

Scientific, marine, measuring, photographic, cinematic, optical, weighing, metering, signalling, monitoring, life saving and teaching instruments and instruments;

instruments and instruments for conducting, switching, converting, storing, regulating and monitoring electricity;

image recording, processing, transmission, and reproduction devices, such as televisions and the like;

acoustic recording, processing, transmitting, and reproducing devices, such as broadcasting devices and the like;

computers, calculators and data processing devices, mathematical devices and instruments, computer accessories, office instruments (e.g., printers, facsimile machines, copiers, word processors), data storage devices;

telecommunication devices and multifunctional devices with telecommunication functions, e.g. telephones and answering machines

Chemical and physical measurement devices, control devices and instruments, such as battery chargers, multimeters, lamps, and tachometers;

marine equipment and instruments;

optical devices and instruments;

those for medical devices and instruments and sportsmen;

clocks and chronometers;

solar cell modules, such as electrochemical dye-sensitized solar cells, organic solar cells, thin film cells;

fire extinguishing equipment.

The technical development is more and more directed towards the following devices: they are becoming smaller and lighter in design, allowing them to be carried by their owners at any time and generally by the general public. This is typically done by achieving a low weight and/or suitable size of such devices. For the purposes of this specification, such devices are also referred to as mobile devices or portable devices. In this trend, precision mechanical and optical devices are (also) increasingly being provided with electronic components, thereby increasing the possibility of miniaturization. As mobile devices are carried, they are subjected to increased loads, in particular mechanical and chemical loads, for example by edge impacts, by dropping, by contact with other hard objects in a bag, or simply by the long movements involved in being carried itself. However, mobile devices are also subject to loads to a greater extent due to moisture exposure, temperature effects, etc., than those "non-mobile" devices that are typically installed indoors and move little or not at all.

Listed below are a number of portable devices in which the pressure-sensitive adhesives of the present invention may be advantageously employed.

Cameras, digital cameras, photographic accessories (such as exposure meters, flashes, diaphragms, camera housings, lenses, etc.), film cameras, video cameras, mini-computers (mobile, palmtop), laptop, notebook, netbook, ultrabook, tablet, handheld devices, electronic organizers and organizers (so-called "electronic organizer" or "personal digital assistant", PDA, palmtop), modem

Computer fittings and operating units for electronic devices, e.g. mouse

Drawing pad, drawing board, microphone, speaker, game console, joystick

Remote controller, touch pad

Monitor, display, screen, touch-sensitive screen (sensor screen, touch-screen device), projector

Electronic book (e-book) reading device

Mini-tv, pocket tv, device for playing movies, video player, radio (including mini-radio and pocket radio), walkman, compact disc walkman (displays), music player (for e.g. CD, DVD, blue light, tape, USB, MP3), earphone, cordless phone, cell phone, smart phone, interphone (two-way radio), hands-free device, pager (pager )

Mobile defibrillator, blood glucose meter, blood pressure monitor, pedometer, pulse meter

Torch, laser pointer

Motion detector, optical amplifier, distance vision device, night vision device, GPS device, navigation device, portable interface device for satellite communication

Data storage device (USB stick, external hard drive, memory card)

Watch, electronic watch, pocket watch, linked list, stopwatch.

For installation applications in electronic devices (not only portable devices), reworkability of expensive components becomes increasingly important. Therefore, the adhesive tape used to adhere such components needs to be removable and should therefore exhibit a low separating force when removed from the respective surface. It is desirable that the adhesive tape can be removed in a residue-free manner, since any further cleaning steps that may further damage the highly sensitive components of the device should be avoided.

EP 1426407A 1 discloses an adhesive polymer composite comprising at least one optionally hydrogenated nitrile rubber polymer having a Mooney viscosity (ML [email protected] ℃ C.) below 30, optionally at least one filler and optionally at least one crosslinking agent.

WO 2017/025492 a1 relates to a pressure-sensitive adhesive material comprising as base polymer at least one solid acrylonitrile butadiene rubber and an adhesive resin, wherein the proportion of adhesive resin is in the range of 30 to 130phr and the acrylonitrile content in the solid acrylonitrile butadiene rubber is 10 to 30% by weight.

US 2003/0134112 a1 describes a tape comprising a highly extensible, substantially non-recyclable backing bearing on at least one major surface thereof a layer of pressure sensitive adhesive. The tape is capable of being removed from the substrate surface after being stretched from the substrate surface only at an angle of no greater than about 35 °.

WO 2014/067667 a1 discloses a heat-debondable tape having a base adhesive layer and at least one heat-peelable adhesive layer comprising an adhesive and heat-expandable particles. The base adhesive layer has an adhesion of less than 2N/20mm at the expansion temperature of the thermally expandable particles and an adhesion of more than 10N/20mm at 20 ℃.

WO 97/46631 a1 discloses a temperature responsive (temperature sensitive) adhesive article comprising:

(a) a temperature responsive support capable of changing its shape at a first transition temperature; and

(b) a heat-deformable pressure-sensitive adhesive on at least a portion of at least one surface of the carrier,

the heat deformable pressure sensitive adhesive is capable of changing its shape at a second transition temperature. The article can be designed to provide a wide variety of bonding and debonding properties.

WO 2014/066195 a1 describes a pressure sensitive adhesive composition suitable for selective debonding, the pressure sensitive adhesive composition comprising:

a continuous first phase comprising a pressure sensitive adhesive matrix; and

a discontinuous second phase comprising crosslinked silicone gel particles dispersed in a pressure sensitive adhesive matrix, the properties being such that upon exposure to a debonding agent, the particles undergo a change in at least one of shape and volume.

There are various limitations in the debonding properties of the adhesive tapes known to date. "stretch releasing" tapes require die cut shapes to apply stretch, which in many cases cannot be achieved in all applications due to complex layouts. Thermal-based de-bonding typically requires temperatures up to 110 ℃. In some cases, there are highly sensitive components that will be damaged by such temperatures.

Disclosure of Invention

It is an object of the present invention to provide pressure-sensitive adhesives based on acrylonitrile-butadiene rubber which are useful in technical applications, said adhesives exhibiting the property profile of conventional PSAs with good impact resistance combined with the easy removability of the adhesive from the substrate.

Accordingly, the present invention provides a pressure sensitive adhesive comprising:

-at least one acrylonitrile-butadiene rubber; and

-at least one tackifier resin,

and is characterized in that

The acrylonitrile rubber has an acrylonitrile content of less than 30 wt%;

the pressure-sensitive adhesive comprises at least one rosin resin as a tackifier resin; and is

The entirety of all tackifier resins had an acid number of 6 to 150.

Such pressure sensitive adhesives have been demonstrated to exhibit good impact resistance, as well as significantly improved removability from a substrate upon treatment with ethanol.

Detailed Description

The pressure sensitive adhesive of the present invention may comprise one (single) or more acrylonitrile-butadiene rubbers. Hereinafter, "acrylonitrile-butadiene rubber" is meant to include also the case where only one (single) acrylonitrile-butadiene rubber is present in the pressure-sensitive adhesive. Likewise, the term "all acrylonitrile-butadiene rubber as a whole" includes the case where only one (single) acrylonitrile-butadiene rubber is present in the pressure-sensitive adhesive.

Preferably, the acrylonitrile content in the acrylonitrile-butadiene rubber is at least 10 wt.%. More preferably, the acrylonitrile-butadiene rubber has an acrylonitrile content of 12 to 25 wt.%, more preferably 15 to 22 wt.%. If the pressure-sensitive adhesive of the present invention comprises a plurality of acrylonitrile-butadiene rubbers, this preferably applies to all acrylonitrile-butadiene rubbers of the pressure-sensitive adhesive.

The acrylonitrile-butadiene rubber can be blended with an inert release aid, preferably selected from talc, silicates (talc, clay, mica), zinc stearate and PVC powder, more particularly on the order of 3phr, based on the entirety of all acrylonitrile-butadiene rubber of the pressure-sensitive adhesive.

Preferably, the at least one acrylonitrile-butadiene rubber is a solid acrylonitrile-butadiene rubber. In one embodiment of the invention, all of the acrylonitrile-butadiene rubber of the pressure sensitive adhesive is solid acrylonitrile-butadiene rubber. In another embodiment, the at least one acrylonitrile-butadiene rubber is a solid acrylonitrile-butadiene rubber, and the pressure sensitive adhesive further comprises at least one liquid acrylonitrile-butadiene rubber having an acrylonitrile content of at least 10 wt% and less than 30 wt%. The pressure sensitive adhesive of the present invention may comprise one (single) or more of such liquid acrylonitrile-butadiene rubbers. The fraction of all liquid acrylonitrile-butadiene rubber as a whole is preferably up to 20% by weight, more preferably between 1 and 15% by weight, more preferably between 2 and 10% by weight, based on the total weight of the pressure-sensitive adhesive.

Liquid acrylonitrile-butadiene rubbers are distinguished from solid acrylonitrile-butadiene rubbers in that they have a softening point of <40 ℃.

Softening point T of oligomer and polymer compounds as used herein_SIs based on the ring and ball method according to DIN EN 1427:2007, with the provisions applied accordingly (investigating oligomer or polymer samples instead of bitumen and retaining the procedure otherwise); the measurements were performed in a glycerol bath.

The polymer base of the pressure-sensitive adhesive (PSA) according to the invention preferably consists of solid, or solid and liquid acrylonitrile-butadiene rubber. More preferably, no other polymers are present in the PSA other than acrylonitrile-butadiene rubber. Preferably, the pressure sensitive adhesive comprises acrylonitrile-butadiene rubber in a total amount of up to 30 to 75 wt.%, more preferably 40 to 65 wt.%, based on the total weight of the pressure sensitive adhesive.

In one embodiment of the invention, the PSA consists of: solid and liquid acrylonitrile-butadiene rubber, one or more tackifier resins, at least one aging inhibitor, and optionally at least one release aid. In further embodiments, the PSA may further include at least one plasticizer, at least one filler, and/or at least one dye.

The term "tackifier resin" is understood by the skilled person to mean a resin-based substance that increases the tack of a PSA compared to a PSA of the same composition that does not comprise a tackifier resin.

The pressure sensitive adhesive includes at least one rosin resin as a tackifier resin. Rosin resins are also known as "rosin resins". The term "rosin resin" includes both natural rosins and modified rosins. Rosin resins include, for example, natural rosin; dimerizing rosin; partially hydrogenated rosin; fully hydrogenated rosin; esterified products of these kinds of rosins such as glycerol esters, pentaerythritol esters, ethylene glycol esters and methyl esters; and rosin derivatives such as disproportionated rosin, fumaric acid-modified rosin, and lime-modified rosin.

Further, all of the tackifier resins of the pressure-sensitive adhesive according to the present invention have an acid value of 6 to 150 as a whole. Preferably, all tackifier resins of the pressure-sensitive adhesive according to the present invention have an acid value of at least 9 in their entirety.

Acid number, also known as acid number (or neutralization number or acidity), is the mass of potassium hydroxide (KOH) in milligrams required to neutralize 1 gram of chemical. Acid number is a measure of the number of carboxylic acid groups in a compound or in a mixture of compounds. In a typical procedure, a known amount of a sample dissolved in an organic solvent, often isopropanol, is titrated with a known concentration of potassium hydroxide (KOH) solution using phenolphthalein as a color indicator.

Acid number is used to quantify the acidity of a material. It is the amount of base (expressed as milligrams of potassium hydroxide) required to neutralize the acidic components in 1 gram of sample.

The acid number can be calculated using the following equation:

A N＝[(V_eq-b_eq)*N*(56.1g mol^–1)]/W_{sample (I)}

Wherein AN is the acid value, V_eqVolume of titrant (ml) consumed at the equivalence point for the sample and 1ml of standard solution, b_eqIs the volume (ml) of titrant consumed at the equivalence point for 1ml of standard solution, N is the molar concentration of titrant, and 56.1g/mol is the molecular weight of KOH. W_{Sample (I)}The mass of the sample in grams.

Generally, resins containing OH-and COOH-groups are preferred tackifier resins for pressure sensitive adhesives. Thus, preferably at least 50 wt.%, more preferably at least 70 wt.%, particularly preferably at least 90 wt.% of the total of all tackifier resins of the pressure-sensitive adhesive according to the invention is a tackifier resin comprising OH-and COOH-groups. In particular, all tackifier resins of the pressure-sensitive adhesive according to the invention are tackifier resins comprising OH-and COOH-groups. The preferred OH-group containing tackifier resin of the pressure sensitive adhesive is a terpene-phenolic resin.

Preferably, at least 50 wt.%, more preferably at least 70 wt.%, particularly preferably at least 90 wt.% of the total of all tackifier resins of the pressure-sensitive adhesive according to the invention is a rosin resin or a mixture of a rosin resin and a terpene-phenolic resin. In particular, all tackifier resins of the pressure-sensitive adhesive according to the invention are rosin resins or a mixture of rosin resins and terpene-phenolic resins.

Still preferably, at least 50 wt.%, more preferably at least 70 wt.%, particularly preferably at least 90 wt.% of all tackifier resins of the pressure-sensitive adhesive according to the invention as a whole are rosin resins. In particular, all tackifier resins of the pressure-sensitive adhesive according to the present invention are rosin resins.

Preferably, the pressure sensitive adhesive according to the present invention comprises tackifier resins in a total amount of 35 to 65 wt.%, more preferably 40 to 60 wt.%, based on the total weight of the pressure sensitive adhesive.

Further preferably, the pressure sensitive adhesive according to the present invention does not contain any hydrocarbon resin. This has been observed to result in a beneficial effect on the removability of the adhesive.

Preferably, the pressure sensitive adhesive of the present invention comprises at least one primary antioxidant, more preferably at least one sterically hindered phenol; and/or at least one secondary antioxidant, more preferably at least one secondary antioxidant selected from phosphites, thioethers and C-radical scavengers. Furthermore, it is preferred that the pressure-sensitive adhesive of the present invention comprises at least one light stabilizer, in particular at least one UV absorber and/or sterically hindered amine.

These substances advantageously provide stabilization of the adhesive against environmental and aging effects.

Further additives which may be included by the pressure-sensitive adhesive according to the invention are, for example, fillers and dyes. The filler may be a reinforcing or non-reinforcing filler. Preferably, the filler is selected from silica, in particular spherical, acicular and irregular silica; a layered silicate; calcium carbonate; zinc oxide; titanium dioxide; alumina; and alumina hydroxide.

Preferably, the pressure sensitive adhesive according to the present invention does not contain any plasticizers and oils. This has been observed to have a beneficial effect on the impact resistance of the adhesive.

The maximum fraction of the entirety of all additives (i.e., all substances except the acrylonitrile-butadiene rubber and the tackifier resin) is preferably 15% by weight, more preferably 5% by weight, and particularly preferably 2% by weight, based on the total weight of the pressure-sensitive adhesive.

To enhance the cohesive properties of the pressure-sensitive adhesive, it may also be crosslinked, in particular by addition of peroxides or by high-energy radiation. This may have a beneficial effect on properties such as shear resistance. The pressure sensitive adhesives of the present invention are preferably crosslinked.

The PSA is preferably used to assemble a carrier to provide an adhesive tape. Therefore, another subject of the present invention is an adhesive tape comprising a layer of a pressure-sensitive adhesive according to the present invention.

In the sense of the present invention, adhesive tape shall encompass all sheet-like or tape-like carrier constructions coated on one or both sides with adhesive, and therefore, besides conventional tapes, also decals, cut sheets, die-cut pieces (punched sheet-like carrier constructions coated with adhesive), two-dimensionally extending structures (e.g. sheets), etc., as well as multi-layer arrangements.

Furthermore, the expression "adhesive tape" also includes so-called "transfer tapes", in other words tapes consisting only of pressure-sensitive adhesive substances. In the case of transfer tapes, the adhesive may be applied before application between flexible liners provided with a release layer and/or having anti-adhesive properties. For applications, typically, the first liner is removed, an adhesive is applied, and then the second liner is removed.

The tape may be provided in a fixed length, for example in the form of a meter-length product, or as a continuous product on a roll (archimedes spiral) or even cross-wound shaft.

The coating weight (coating thickness) of a pressure-sensitive adhesive layer according to the invention in the adhesive tape is preferably between 10 and 150g/m²More preferablyAt 15 and 120g/m²In the meantime. For the transfer tape, the coating weight is particularly preferably 30 to 100g/m²(ii) a For the adhesive tape further comprising at least a carrier layer, it is particularly preferably 50 to 80g/m²。

In one embodiment of the invention, the adhesive tape further comprises a carrier layer. The carrier material is preferably selected from paper; weaving a fabric; a nonwoven fabric; and films made from polyesters such as polyethylene terephthalate (PET), polyethylene, polypropylene, polyurethane, oriented polypropylene, polyvinyl chloride, polylactic acid, cellulose, modified starch, and polyhydroxyalkanoates. The woven fabric may be made from renewable resources, preferably from cotton, hemp, jute or stinging nettle fibers. Particularly preferably, the carrier material is made of PET or polyurethane.

The carrier material may be equipped with PSA on one or both sides. Furthermore, the carrier layer may be provided with one or more coatings. Also, only one side of the pressure sensitive tape may be equipped with a PSA of the present invention, and a different PSA may be used on the other side.

The adhesive tape is formed by applying the adhesive to the carrier partially or over the entire area. The coating can also be carried out in the form of one or more strips in the longitudinal (machine) direction, optionally in the transverse (cross direction), but more particularly the coating is over the entire area. Furthermore, the pressure-sensitive adhesive can be applied in the form of patterned dots by means of screen printing, in which case the dots of adhesive can also differ in size and/or distribution, or by gravure printing of lines joining in the longitudinal and transverse directions, by printing with engraved rollers, or by flexographic printing. The adhesive may be in the form of a dome (produced by screen printing) or in other patterns such as a grid, stripes, zigzag lines. Furthermore, the PSA may also be applied by spraying, for example, creating a more or less irregular pattern.

In one embodiment, the adhesive tape further comprises an adhesion promoter, also referred to as a primer layer, between the carrier layer and the pressure sensitive adhesive layer. Such a primer layer may improve interlayer adhesion strength between the adhesive and the support.

The primer is preferably based on a dispersion or solvent system of isoprene or butadiene containing rubbers, acrylate rubbers, polyvinyl, polyvinylidene and/or ring rubbers. It may further include an isocyanate or epoxy resin, which may improve the adhesion of the PSA and in some cases may also increase the shear strength of the PSA. The adhesion promoter can likewise be applied as a coextruded layer on one side of the support layer.

In another embodiment, the surface of the carrier layer that is in contact with the pressure sensitive adhesive has been subjected to a physical pretreatment prior to bringing the carrier layer into contact with the PSA. Suitable physical surface treatments include flame treatment and corona or plasma treatment.

Furthermore, in a single-sided adhesive tape, the surface of the carrier layer opposite to the surface contacting the pressure-sensitive adhesive may have been subjected to an anti-adhesive physical treatment or coating, and more particularly may be equipped with a release layer.

Suitable release layers may be based on compounds having a linear or branched alkyl or alkenyl group with a C-number of at least 10, for example stearyl compounds such as polyvinylstearyl carbamate; stearyl compounds of transition metals such as Cr or Zr, ureas formed from polyethyleneimine and stearyl isocyanate, stearyl sulfosuccinate and stearyl sulfosuccinamate; c₁₄-C₂₈Chromium complexes of fatty acids; acrylic polymers having perfluorinated alkyl groups; and silicones such as poly (dimethylsiloxane) or fluorosilicone compounds.

The adhesive tape may likewise have been laminated with a release liner, which typically comprises a base material of polyethylene, polypropylene, polyester or paper that has been coated on one or both sides with a silicone system.

The adhesive tape of the invention can be produced by any method known to the skilled person. Thus, the PSA including additives dissolved in a suitable solvent can be applied to the support or release film by means of engraved roll application, comma bar coating, multi-roll coating or in a printing process, after which the solvent can be removed in a drying tunnel or oven. Alternatively, the carrier material or the release film can also be coated in a solvent-free process. For this purpose, the acrylonitrile-butadiene rubber can be heated and melted in an extruder. Further process steps can be carried out in the extruder, for example mixing with the above-mentioned additives, filtration or degassing. The melt can then be coated on a carrier layer or release film by means of a calender.

The pressure-sensitive adhesive tape of the invention is used at 50g/m²Preferably has a peel adhesion to the steel substrate of at least 4.0N/cm, more preferably at least 6.0N/cm.

Examples

Test method

Unless otherwise stated, measurements were made under test conditions of 23. + -. 1 ℃ and 50. + -. 5% relative humidity.

Impact resistance; z plane (DuPont test)

A square sample having the shape of a box (outer dimension 33mmx33 mm; frame width 2.0 mm; inner dimension (window cut) 29mmx29mm) was cut from the tape to be investigated. The sample was adhered to a Polycarbonate (PC) frame (outer dimension 45mmx45 mm; border width 10 mm; inner dimension (window cutout) 25mmx25 mm; thickness 3 mm). On the other side of the double-sided tape, a PC window of size 35mmx35mm was adhered. The gluing of the PC frame, the adhesive tape frame and the PC window is carried out in such a way that the geometric center and the diagonal lie on top of each other in each case (diagonal corners). The bonding area is 248mm². The adhesive was pressed at 10 bar for 5 seconds and stored for 24 hours with conditioning at 23 ℃/50% relative humidity.

Immediately after storage, the adhesive assembly of PC frame, tape and PC window with the protruding edge of the PC frame was clamped in the sample holder in such a way that the assembly was oriented horizontally and the PC window was below the frame. The sample holder is then inserted centrally into the intended receiver of the DuPont impact tester. A punch weighing 150g was inserted so that a circular impact geometry with a diameter of 24mm struck centrally on and flush with the window side of the PC window.

A weight having a mass of 150g, guided on two guide rods, was dropped vertically from a height of 5cm onto the assembly thus arranged by the sample holder, sample and punch (measurement conditions 23 ℃, 50% relative humidity). The height of the falling weight was increased in steps of 5cm until the impact energy introduced caused the destruction of the sample as a result of the impact stress, and the PC window was separated from the PC frame.

To be able to compare experiments with different samples, the energy was calculated as follows:

E[J]height [ m]Mass weight [ kg]*9.81kg/m*s²

For each product, five samples were tested and the average energy value was reported as a characteristic value of impact resistance. A value of at least 0.45J is considered to indicate good impact resistance.

Push out Strength (z plane)

The push-out test provides information about the degree of resistance of adhesion of components in the frame body, such as a display or a window in the housing.

Rectangular frame-like samples (outer dimension 33mmx33 mm; frame width 2.0mm in each case; inner dimension (window opening) 29mmx29 mm; bonding area 248mm on each of the upper and lower sides) were cut out of the adhesive tape to be investigated²). The sample was adhered to a rectangular PC plastic frame (PC ═ polycarbonate) (outer dimension 40mmx40 mm; border width of the long side in each case 8 mm; border width of the short side in each case 10 mm; inner dimension (window opening) 24mmx24 mm; thickness 3 mm). Adhered to the other side of the double-sided tape sample was a rectangular PC sheet having a size of 35mmx35 mm. The full bonding area of the available tape is used. The PC frame, tape sample and PC window were bonded so that the geometric center of the rectangle, the bisector of the acute diagonal and the bisector of the obtuse diagonal each lie above one another (corner on corner, long side on long side and short side on short side). The bonding area is 248mm². The adhesive was pressed at 248N for 5 seconds and stored for 24 hours with conditioning at 23 ℃/50% relative humidity.

Immediately after storage, the adhesive assembly consisting of PC frame, tape and PC sheet was placed on the frame structure (sample holder) with the protruding edge of the PC frame such that the assembly was oriented horizontally and the PC sheet was pointing downwards, hanging freely.

The plunger was then moved vertically from above through the window of the PC frame at a constant speed of 10 mm/sec so that it was pressed centrally onto the PC board and as a slaveThe corresponding force (determined by the corresponding pressure and the contact area between the piston and the plate) was recorded as a function of the time from the first contact of the piston with the PC plate until shortly after the plate was dropped (measurement conditions 23 ℃, 50% relative humidity). Force acting immediately before adhesive bond failure between PC board and PC frame (maximum force F in N in force-time diagram_{Maximum of}) Recorded as an answer to the push-out test.

Push-out Strength for removability (EtOH/Water)

To determine the removability of the tape under the influence of EtOH/water, the specimens made for the push-out strength test as described previously were stored in a 75:25 (vol%) mixture of ethanol and water at 65 ℃ and 90% relative humidity. For ethanol/water storage, a closable container is used to prevent loss of ethanol by evaporation. After storage, the samples were first rinsed with distilled water and then stored at 23 ℃ and 50% relative humidity for 24 hours. Only then the above-described extrapolated strength test is repeated.

Giving the maximum force F in%_{Maximum of}As a result of the decrease (rate of decrease); a high drop (at least 35%) indicates good removability of the tape.

Preparation of PSA

The pressure-sensitive adhesives (PSAs) listed in the examples were homogenized to a solvent-based composition in a kneading apparatus with double sigma kneading hooks. The solvent used is butanone (methyl ethyl ketone, 2-butanone). The kneading apparatus was cooled by means of water cooling.

In the first step, solid acrylonitrile-butadiene rubber is preswollen with the same amount of butanone for 12 hours at 23 ℃. The preliminary batch was then kneaded for 2 hours. Subsequently, again, the above-selected amount of butanone and optionally liquid NBR rubber were added in two steps with kneading for 10 minutes in each case. The tackifier resin was then added as a solution in butanone with a solids content of 50%, and uniform kneading was continued for 20 minutes or more. The final solids content was adjusted to 30% by weight by addition of butanone.

Production of test specimens

In a commercial laboratory coating station (Sondermaschen Oschers)leben GmbH) was coated with PSA by means of a coating knife on a 23 μm thick and trifluoroacetic acid etched PET film. Butanone was evaporated in a forced air oven at 105 ℃ for 10 minutes. The gap width during coating was adjusted to reach 50g/m after evaporation of the solvent²Coating weight of (c). The solvent-free film was then lined with siliconized PET film and stored at 23 ℃ and 50% relative humidity for further testing.

Examples

Table 1: acrylonitrile-butadiene rubber used

Table 2: tackifier resins used

Table 3: plasticizers used

Table 4: compositions according to embodiments of the invention

Table 5: composition of comparative example

Table 6: test results according to embodiments of the present invention

Table 7: test results of comparative example