Polyisobutylene adhesives comprising multifunctional components having (meth)acryloyl or vinyl ether groups

Abstract

An adhesive composition is described that includes a polyisobutylene polymer component; and up to 30 weight percent of at least one aliphatic multifunctional component that includes at least two ethylenically unsaturated groups selected from (meth)acryloyl or vinyl ether. The monomer includes a hydrocarbon moiety having greater than 12 contiguous carbon atoms. When the hydrocarbon moiety is branched, the hydrocarbon moiety includes a side chain having at least two carbon atoms. The aliphatic multifunctional component is sufficiently compatible such that the crosslinked adhesive composition has a haze of less than 3% at a thickness of 20 micrometers. Adhesive articles are also described.

Description

Summary of the Invention

[0001] This invention describes an adhesive composition comprising a polyisobutylene polymer component and up to 30% by weight of at least one aliphatic multifunctional component, the at least one aliphatic multifunctional component comprising at least two olefinically unsaturated groups selected from (meth)acryloyl or vinyl ether. The monomer comprises a hydrocarbon moiety having more than 12 linked carbon atoms. When the hydrocarbon moiety is branched, the hydrocarbon moiety comprises a side chain having at least two carbon atoms. The aliphatic multifunctional component is sufficiently compatible such that the crosslinked adhesive composition has a haze of less than 3% at a thickness of 20 micrometers. In a typical embodiment, the polyisobutylene polymer component comprises an unfunctionalized polyisobutylene polymer, butyl rubber, or mixtures thereof. In some embodiments, the multifunctional component has a number-average molecular weight of less than 3000 g / mol as determined by nuclear magnetic resonance (NMR). In some embodiments, in addition to the unsaturated groups of (meth)acryloyl and vinyl ether, the multifunctional component comprises less than 0.08% by weight of olefinically unsaturated groups as determined by NMR. Detailed Implementation

[0002] This invention describes an adhesive composition comprising a polyisobutylene polymer component, which comprises one or more polyisobutylene polymers. Such polyisobutylene polymers can be homopolymers and / or copolymers. Unless otherwise specified, as used herein, "polyisobutylene polymer" refers to both homopolymers and copolymers.

[0003] In some embodiments, the adhesive composition is a pressure-sensitive adhesive before and / or after crosslinking the multifunctional components. Pressure-sensitive adhesives are typically characterized by a strength of less than 3 × 10⁻⁶ at a frequency of 1 Hz and an applied temperature (typically room temperature, e.g., 25°C). 5 Storage modulus (G') at 0.3 MPa. As used herein, storage modulus (G') and Tanδ refer to values ​​obtained using dynamic mechanical analysis (DMA) according to the test methods described in the examples. In some embodiments, the pressure-sensitive adhesive composition has a density of less than 2 × 10⁻⁶ Pa. 5 Pa, 1×10 5 Pa, 9×10 4 Pa, 8×10 4 Pa, 7×10 4 Pa, 6×10 4 Pa, 5×10 4 Pa, 4×10 4 Pa or 3×10 4 The storage modulus is Pa. In some embodiments, the composition has a storage modulus of at least 2 × 10⁻⁶ Pa. 4 Pa, 3×10 4Pa or 4×10 4 The energy storage modulus (G') of Pa.

[0004] In some embodiments, the pressure-sensitive adhesive has a Tanδ of no more than 0.7, 0.6, 0.5, or 0.4 at 70°C. Pressure-sensitive adhesive compositions typically have a Tanδ of at least 0.01 or 0.05 at 70°C.

[0005] Typically, pressure-sensitive adhesives are characterized by a glass transition temperature "Tg" below 25°C; while other adhesives may have a Tg of 25°C or higher, typically ranging up to 50°C. As used herein, Tg refers to a value obtained using dynamic mechanical analysis (DMA) according to the test methods described in the examples. In some embodiments, the pressure-sensitive adhesive composition has a Tg not greater than 20°C, 15°C, 10°C, 5°C, 0°C, or -5°C. The Tg of pressure-sensitive adhesives is typically at least -40°C, -35°C, -30°C, -25°C, or -20°C.

[0006] Pressure-sensitive adhesives are typically characterized as having sufficient adhesive strength. In some embodiments, the peel adhesion (e.g., peel adhesion to glass) measured according to the test methods described in the examples is at least 0.1 N / cm, 0.5 N / cm, 1 N / cm, 2 N / cm, 3 N / cm, 4 N / cm, or 5 N / cm, and ranges up to, for example, 15 N / cm, 16 N / cm, 17 N / cm, 18 N / cm, 19 N / cm, or 20 N / cm or greater.

[0007] In some embodiments, the polyisobutylene polymer component comprises a polyisobutylene polymer containing at least 90 mol%, 91 mol%, 92 mol%, 93 mol%, 94 mol%, 95 mol%, 96 mol%, 97 mol%, 98 mol%, or 99 mol% of isobutylene polymeric units.

[0008] In other embodiments, the polyisobutylene polymer component comprises a polyisobutylene copolymer containing at least 50 mol%, 55 mol%, or 60 mol% of polymeric units of polyisobutylene. In some embodiments, the copolymer also comprises polymeric units derived from 1-butene and / or 2-butene. The polymeric units derived from 1-butene and / or 2-butene are typically present in amounts ranging from at least 1 mol%, 5 mol%, 10 mol%, 15 mol%, or 20 mol% of the polyisobutylene copolymer to at most 30 wt%, 35 wt%, 40 wt%, 45 wt%, or 50 wt%. Polyisobutylene copolymers that also contain polymeric units derived from 1-butene and / or 2-butene may be characterized as "polybutene".

[0009] The polyisobutylene polymer component may contain at least two polymers, wherein the first polyisobutylene polymer contains a higher concentration of polymeric units derived from 1-butene and / or 2-butene than the second polyisobutylene polymer.

[0010] Other examples of polyisobutylene copolymers include copolymers of isobutylene and isoprene, copolymers of isobutylene and butadiene, and halogenated butyl rubbers obtained by bromination or chlorination of these copolymers. However, polyisobutylene copolymers may be free of halogenated butyl rubber, with halogen (e.g., chloride, bromide) content less than 1 mol%, 0.5 mol%, 0.25 mol%, 0.1 mol%, 0.01 mol%, or 0.001 mol% of the polyisobutylene polymer.

[0011] In some embodiments, the polyisobutylene polymer may be characterized as butyl rubber. Butyl rubber is a copolymer of isobutylene and a small amount of isoprene, thereby providing a highly saturated backbone. In some embodiments, the mol% of isoprene in the butyl rubber is at least 0.5 mol% or 1 mol%. In some embodiments, the mol% of isoprene in the butyl rubber is not greater than 3 mol%, 2.5 mol%, 2 mol%, or 1.5 mol%. In some embodiments, the Mooney viscosity ML 1+8 (ASTM D1646) of the butyl rubber at 125°C is typically at least 25, 30, 35, or 40. In some embodiments, the Mooney viscosity ML 1+8 of the butyl rubber at 125°C is typically not greater than 60 or 55. Butyl rubber is commercially available from various suppliers such as ExxonMobil.

[0012] Polyisobutylene copolymers typically do not contain structural units derived from styrene. Furthermore, polyisobutylene copolymers are generally random copolymers. In typical embodiments, the adhesive composition does not contain block copolymers such as styrene-isoprene-styrene (SIS), styrene-butadiene-styrene (SBS), and styrene-isobutylene-styrene (SIBS) block copolymers.

[0013] One or more polyisobutylene polymers may contain trace amounts of C8-C28 oligomers. The concentration of such oligomers is typically less than 0.15 wt%, 0.10 wt%, or 0.05 wt% based on the total weight of the polyisobutylene polymer.

[0014] It should be understood that one or more polyisobutylene polymers may have extremely low concentrations of residual reactive double bonds or other functional groups from the polymerization process used to prepare the polyisobutylene polymer. The concentration of such reactive double bonds or other functional groups is typically less than 5 mol%, 4 mol%, 3 mol%, or 2 mol%.

[0015] One or more polyisobutylene polymers typically have a density of 0.92 g / cc. However, depending on the content of 1-butene and / or 2-butene and / or one or more other olefin comonomers, the density can be 0.91 or lower. Furthermore, the glass transition temperature of such polymers, measured by differential scanning calorimetry (DSC), is typically between -64°C and -65°C. One or more polyisobutylene polymers are typically cold-flowed at room temperature.

[0016] Therefore, depending on the selection of one or more polyisobutylene polymers, the polyisobutylene polymer component comprises at least 50 wt%, 55 wt%, 60 wt%, 65 wt%, 70 wt%, 75 wt%, 80 wt%, 85 wt%, 90 wt%, 95 wt% or more of polyisobutylene polymer units.

[0017] Polyisobutylene polymers are commercially available from several manufacturers. Homopolymers are available, for example, under the trade name OPPANOL (e.g., OPPANOL B12, B15, B30, B50, B80, B100, B150, and B200) from BASF Corp. (Florham Park, NJ). These polymers typically have a weight-average molecular weight in the range of about 40,000 g / mol to 1,000,000 g / mol or greater. Other polyisobutylene polymers are available with a wide range of molecular weights from United Chemical Products (UCP), St. Petersburg, Russia; and from ExxonMobil Chemical Company under the trade name VISTANEX. TM Commercially available; and commercially available from BFGoodrich under the trade name "Hycar". These polyisobutylene polymers are characterized by being unfunctionalized polyisobutylene polymers that do not contain functional groups such as amines, imides, anhydrides, (meth)acrylates, and vinyl ethers.

[0018] In some embodiments, the polyisobutylene component comprises a polyisobutylene polymer having functional groups. Various functionalized PIB materials are commercially available. For example, polyisobutyleneamine with a number-average molecular weight (Mn) of about 1,000 g / mol and a molar mass distribution Mw / Mn = 1.6 can be traded under the name "Kerocom". TM "PIBA03" was purchased from BASF Corporation (Florham Park, NJ) in Florham Park, New Jersey. Additionally, polyisobutylene succinimide is available under the trade name "Kerocom".TM "PIBSI" was purchased from BASF. Anhydride-terminated polyisobutylene with a (Mn) content of approximately 1,000 g / mol is available from BASF under the trade name "Glissopal SA". Such materials may optionally be present in the adhesive composition at concentrations ranging from 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, or 10 wt%, up to a maximum of 40 wt%. Depending on the functional groups, the polyolefin copolymer may be covalently bonded to or not covalently bonded to the functionalized polyisobutylene polymer.

[0019] In other embodiments, the adhesive composition contains little or no polyisobutylene polymer having functional groups. Therefore, the concentration of one or more functionalized polyisobutylene polymers is typically less than 1% by weight of the adhesive composition.

[0020] Since the polyisobutylene in this embodiment does not contain (meth)acrylate and vinyl ether functional groups, it is presumed that the multifunctional component is not covalently bonded to the polyisobutylene polymer component.

[0021] Polyisobutylene polymers can be characterized by their molecular weight. As used herein, the weight-average molecular weight is based on gel permeation chromatography (GPC) using polystyrene standards, according to the test method described in U.S. Patent Application Serial No. 62 / 479,527, filed March 31, 2017, which was previously cited.

[0022] In some embodiments, the adhesive comprises a polyisobutylene polymer having a weight-average molecular weight of at least 25,000 g / mol; 30,000 g / mol; 35,000 g / mol; 40,000 g / mol; 45,000 g / mol; or 50,000 g / mol. In some embodiments, the polyisobutylene polymer has a weight-average molecular weight of less than 300,000 g / mol; 250,000 g / mol; 200,000 g / mol; or 150,000 g / mol.

[0023] In other embodiments, the adhesive comprises a polyisobutylene polymer (e.g., butyl rubber) having a weight-average molecular weight of at least 300,000 g / mol; 350,000 g / mol; 400,000 g / mol; 450,000 g / mol; or 500,000 g / mol. In some embodiments, the polyisobutylene polymer has a weight-average molecular weight of less than 1,000,000 g / mol or 750,000 g / mol.

[0024] In some embodiments, the polyisobutylene component comprises a blend of two or more polyisobutylene polymers, wherein each polyisobutylene polymer has a different weight-average molecular weight (Mw).

[0025] For example, in some embodiments, the polyisobutylene component comprises a blend of a high molecular weight polyisobutylene polymer (i.e., Mw greater than 300,000 g / mol) and a medium molecular weight polyisobutylene polymer (i.e., Mw less than 150,000 g / mol or 100,000 g / mol).

[0026] When a polyisobutylene component comprises two or more polyisobutylene polymers, the average weight-average molecular weight of the component can be estimated by multiplying the average molecular weight of each polyisobutylene polymer by the weight fraction of each polyisobutylene polymer in the polyisobutylene component and then summing the results. For example, if the polyisobutylene component comprises approximately 58 wt% of a first polyisobutylene polymer with a weight-average molecular weight of 75,000 and approximately 25 wt% of a second polyisobutylene polymer with a weight-average molecular weight of 500,000 g / mol, then the average weight-average molecular weight can be estimated as 75,000 × 0.58 + 500,000 × 0.25 = 168,500 g / mol. Therefore, in some embodiments, the polyisobutylene polymer component may comprise one or more polyisobutylene polymers, such that the average weight-average molecular weight (Mw) of the polyisobutylene polymer component is at least 125,000 g / mol, 150,000 g / mol, 200,000 g / mol, or 250,000 g / mol, and ranges up to 400,000 g / mol; 450,000 g / mol to 500,000 g / mol. More than one low molecular weight PIB and more than one high molecular weight PIB may be used.

[0027] The adhesive or OCA typically contains at least 40 wt%, 45 wt%, or 50 wt% of polyisobutylene component. In some embodiments, the adhesive or OCA contains at least 55 wt%, 60 wt%, 65 wt%, 70 wt%, or 75 wt% of polyisobutylene component. The polyisobutylene polymer component provides the desired water vapor transmission rate (WVTR) properties. In some embodiments, a 51-micron adhesive layer has a WVTR of less than 20 g / sq.m. / day, 15 g / sq.m. / day, or 10 g / sq.m. / day at a 40°C and 90% relative humidity gradient. In other words, the WVTR of the adhesive per micron thickness can be at least 0.2 g / sq.m. / day, 0.25 g / sq.m. / day, 0.3 g / sq.m. / day, 0.35 g / sq.m. / day, or 0.4 g / sq.m. / day. In other embodiments, the 20-micron adhesive layer exhibits a WVTR of less than 100 g / m² under 40°C and relative humidity gradients. 2 / day, 75g / m2 / day, 50g / m 2 / day, 25g / m 2 / day, 20g / m 2 / day or 15g / m 2 / sky.

[0028] Combinations of medium and high molecular weight PIB resins are particularly advantageous because they offer a wide range of desired characteristics. Medium molecular weight PIBs facilitate processing during hot melt extrusion by reducing the melt viscosity of the formulated binder mixture. In solvent processing, the medium molecular weight promotes faster solvent diffusion during drying, enabling the formation of thicker coatings. Furthermore, medium molecular weight PIBs impart conformability to OCAs, achieving stepped ink coverage and proper wetting on different surfaces—key characteristics of OCAs. High molecular weight imparts cohesiveness to the binder system, improving adhesion, shear strength, tensile strength, and dimensional stability at room and high temperatures. These properties are critical for OCAs, and different applications may require a wide range of compositions to suit the specific characteristics of each application.

[0029] The adhesive or OCA also contains a multifunctional component. This multifunctional component is typically miscible with the polyisobutylene component, allowing for a combination of higher storage modulus, lower creep compliance, or lower Tanδ and lower haze during crosslinking of the multifunctional component. In some embodiments, the creep compliance (determined by the test methods described in the examples) is less than 60 1 / Pa × 10⁻⁶. 4 55 1 / Pa×10 4 40 1 / Pa×10 4 35 1 / Pa×10 4 30 1 / Pa×10 4 25 1 / Pa×10 4 20 1 / Pa×10 4 10 1 / Pa×10 4 Or 5 1 / Pa×10 4 .

[0030] The multifunctional component is typically a monomer or oligomer with a weight-average molecular weight of no more than 10,000 g / mol or 5,000 g / mol. In some embodiments, the multifunctional component has a number-average molecular weight of less than 3,000 g / mol, 2,500 g / mol, or 1,000 g / mol as determined by NMR. In some embodiments, the multifunctional component has a number-average molecular weight of at least 200, 300, 400, 500, or 600 g / mol. When the molecular weight of the multifunctional monomer is too high, the adhesive may exhibit high haze.

[0031] The multifunctional component (e.g., an oligomer or monomer) comprises at least two (e.g., terminal) olefinic unsaturated groups selected from (meth)acryloyl or vinyl ether. The multifunctional component is aliphatic and comprises a hydrocarbon moiety having at least 12 linked carbon atoms. For oligomers with a molecular weight of 10,000 g / mol, the maximum number of carbon atoms in the hydrocarbon moiety can be in the range of up to 500 or 600. In some embodiments, the number of carbon atoms in the hydrocarbon moiety is no greater than 300, 250, or 200. In some embodiments, the number of carbon atoms is no greater than 150, 100, or 50. In some embodiments, the multifunctional component may comprise a hydrocarbon moiety with a different chain length distribution. In such embodiments, the number of carbon atoms in the hydrocarbon moiety is typically the average number of carbon atoms. The hydrocarbon moiety may be linear, cyclic, or branched. When the hydrocarbon moiety is branched, at least a portion and typically most of the side chains contain at least two carbon atoms.

[0032] The hydrocarbon moiety may contain a small amount of olefinically unsaturated groups. The amount of olefinically unsaturated groups is typically less than 0.085 wt%, 0.080 wt%, 0.075 wt%, 0.070 wt%, 0.065 wt%, 0.06 wt%, 0.055 wt%, or 0.05 wt% of the total multifunctional component (excluding olefinically unsaturated groups of (meth)acryloyl or vinyl ether groups). In some embodiments, the multifunctional component may comprise a hydrocarbon moiety with a different distribution of unsaturated groups. In such embodiments, the amount of olefinically unsaturated groups is typically the average amount of olefinically unsaturated groups. The hydrocarbon may optionally contain heteroatoms, provided that the inclusion of such heteroatoms does not increase haze by more than 3%, 2.5%, 2%, 1.5%, 1%, or 0.5% (as determined by the test methods described in the examples).

[0033] Multifunctional components typically have low acid values. Acid value can be determined by titration with a base and is defined as the amount (in milligrams) of base (e.g., potassium hydroxide) required to neutralize 1 g of polymer. When the acid value is too high, the multifunctional component may become immiscible with the polyisobutylene component, resulting in phase separation, insufficient adhesion, and / or high haze. In some embodiments, the acid value is typically no greater than 5 mg KOH / g, 4 mg KOH / g, 3 mg KOH / g, 2 mg KOH / g, 1 mg KOH / g, or 0.5 mg KOH / g.

[0034] Multifunctional homopolymers typically have low Tg and are flexible. In some embodiments, the multifunctional homopolymer has a Tg (peak value of Tanδ measured by dynamic mechanical analysis) of no more than 5°C, 10°C, or 15°C. In some embodiments, the Tg is at least 0°C. In some embodiments, the multifunctional homopolymer has an elongation of at least 5% or 10% when measured using standard tensile and elongation tests.

[0035] In some embodiments, the multifunctional component is a low-viscosity liquid at 25°C. For example, the viscosity may be less than 2000 cPs, 1500 cPs, 1000 cPs, 500 cPs, or 250 cPs. In other embodiments, the multifunctional component has a melting temperature of 50°C to 75°C, measured by DSC at a rate of 10°C / min.

[0036] In some implementations, the multifunctional component has a refractive index of 1.47 or less.

[0037] In some embodiments, the multifunctional component may be characterized as a hydrophobic acrylate. In other embodiments, the multifunctional component may be characterized as (e.g., (meth)acrylate)-functionalized poly(butadiene). The hydrocarbon moiety has a combination of unsaturated repeating units and saturated repeating units as shown in the following formula:

[0038]

[0039] The number of unsaturated repeating units is low enough that the (e.g., (meth)acrylate)-functionalized poly(butadiene) has a low concentration of the unsaturated groups described above. When the amount of unsaturated groups or the molecular weight (e.g., viscosity) is too high, the adhesive may undesirably exhibit high haze.

[0040] In some embodiments, the adhesive may also optionally contain a monofunctional component having a single (e.g., terminal) olefinic unsaturated group selected from (meth)acryloyl or vinyl ether.

[0041] In some embodiments, each olefinically unsaturated group in the polyfunctional or monofunctional component (when present) comprises at least 6, 7, 8, 9, or 10 carbon atoms. In some embodiments, each olefinically unsaturated group in the polyfunctional or monofunctional component (when present) comprises at least 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, or more carbon atoms. In some embodiments, when present, each olefinically unsaturated group in the polyfunctional or monofunctional component comprises at least 50, 100, 200, or 300 carbon atoms.

[0042] The adhesive composition may optionally contain one or more additives, such as tackifiers, plasticizers (e.g., oils, polymers that are liquid at 25°C), antioxidants (e.g., hindered phenolic compounds, phosphate esters, or derivatives thereof), UV absorbers (e.g., benzotriazole, oxazolic acid amide, benzophenone, or derivatives thereof), in-process stabilizers, corrosion inhibitors, passivators, processing aids, elastomeric polymers (e.g., block copolymers), scavenger fillers, nanoscale fillers, transparent fillers, desiccants, crosslinking agents, pigments, etc. These additives may be used alone or in combination of two or more. The total concentration of such additives ranges from 0% by weight to 60% by weight of the total adhesive composition.

[0043] When a transparent adhesive composition is desired, the adhesive typically does not contain fillers with a particle size greater than 100 nm, which could reduce the transparency of the adhesive composition. In this embodiment, the total amount of filler in the adhesive composition does not exceed 10 wt%, 9 wt%, 8 wt%, 7 wt%, 6 wt%, 5 wt%, 4 wt%, 3 wt%, or 2 wt% of the solids in the adhesive composition. In some advantageous embodiments, the adhesive composition contains no more than 1 wt%, 0.5 wt%, 0.1 wt%, or 0.05 wt% of filler.

[0044] However, in other embodiments, the adhesive composition may contain a higher amount of inorganic oxide filler (such as pyrolytic silica).

[0045] In a typical implementation, the adhesive composition does not contain acid-reactive components (such as epoxy compounds) that would cause crosslinking of acid groups.

[0046] The adhesive or OCA compositions disclosed herein may optionally contain a tackifier. The addition of a tackifier imparts greater adhesion to the composition, which is beneficial for some applications where adhesion to different substrates is a critical requirement. The addition of a tackifier increases the Tg of the composition and can reduce its storage modulus at room temperature, thereby reducing its elasticity and increasing its flowability, which is necessary, such as conforming to ink steps during lamination. However, the same addition of a tackifier may shift the viscoelastic balance too much towards viscous behavior, such as in cases where minimal creep is required and therefore less flowability is necessary. Therefore, the addition of a tackifier is optional, and its presence and concentration depend on the specific application.

[0047] Suitable tackifiers include hydrocarbon resins and hydrogenated hydrocarbon resins, such as hydrogenated alicyclic resins, hydrogenated aromatic resins, or combinations thereof. Suitable tackifiers are commercially available and include, for example, those purchased under the trade name ARKON (e.g., ARKON P or ARKON M) from Arakawa Chemical Industries Co., Ltd. (Osaka, Japan); those purchased under the trade name ESCOREZ (e.g., ESCOREZ 1315, 1310LC, 1304, 5300, 5320, 5340, 5380, 5400, 5415, 5600, 5615, 5637, and 5690) from Exxon Mobil Corporation (Houston, TX) in Houston, Texas; and those purchased under the trade name REGALREZ (e.g., REGALREZ 1085, 1094, 1126, 1139, 3102, and 6108) from Eastman Chemical Company in Kingsport, Tennessee. Those from Chemical, Kingsport, TN. Due to their low color and environmental stability, these tackifiers are particularly advantageous for OCA-type applications.

[0048] Tackifiers can have any suitable softening temperature or softening point. Softening temperatures are typically below 200°C, below 180°C, below 160°C, below 150°C, below 125°C, or below 120°C. However, in applications that tend to generate heat or where the adhesive bond is exposed to heat, tackifiers with a softening point of at least 75°C are generally selected. Such a softening point helps minimize separation of the tackifier from the rest of the adhesive composition when the adhesive composition is subjected to heat, such as from electronic devices or components. Softening temperatures of at least 80°C, at least 85°C, at least 90°C, or at least 95°C are typically selected. However, in applications that do not generate heat or where the adhesive bond is not exposed to heat, tackifiers may have a softening point less than 75°C.

[0049] In some embodiments, the adhesive composition includes a tackifier. The concentration of the tackifier can vary depending on the desired (e.g., pressure-sensitive) adhesive composition. In some embodiments, the amount of tackifier is at least 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, or 15 wt%. The maximum amount of tackifier is typically no greater than 60 wt%, 55 wt%, 50 wt%, 45 wt%, 40 wt%, 35 wt%, or 30 wt%. Increasing the concentration of the tackifier (e.g., solid at 25°C) can generally increase the Tg of the adhesive. In other embodiments, the adhesive composition contains little or no tackifier. Therefore, the concentration of the tackifier is less than 5 wt%, 4 wt%, 3 wt%, 2 wt%, 1 wt%, 0.5 wt%, or 0.1 wt%.

[0050] In addition, liquid rheology modifiers, such as plasticizers or oils, can be used. For example, mineral oil (Kaydol), naphthenic oil (Calsol 5550), and paraffin oil (Hyprene P100N) can be used. The beneficial effect of using plasticizers / oils in combination with tackifiers is that, in addition to reducing the storage modulus of the composition, it also allows for a lower glass transition temperature. This imparts higher flow characteristics to the composition, which is advantageous in applications requiring conformability to features such as ink steps, flexible connections, etc. In applications requiring defect-free lamination to cover ink steps, adhesive compositions with higher creep flexibility are known to provide better ink step coverage. Values ​​greater than 1.5 × 10⁻⁶ have been found. 4 A creep compliance of 1 / Pa is most desirable for optimal lamination coverage on the step characteristics of commercial inks.

[0051] The adhesive or OCA compositions disclosed herein may also contain UV blockers. UV-blocking packaging includes UV absorbers or combinations of UV absorbers and light stabilizers. Examples of suitable UV absorbers include, but are not limited to, benzophenone, benzotriazole, triazine, or combinations thereof. Examples of light stabilizers include, but are not limited to, hindered amine light stabilizers (HALS). The adhesive sheets of the present invention have a neutral color and low haze, which is necessary for optically transparent adhesives. The adhesive sheets of the present invention have clear UV blocking, examples of which include, but are not limited to, transmittance (T%) of less than 1.5% at 380 nm, T% of 84% at 400 nm, and T% of 96% or more at 410 nm, which effectively block UV light or even violet or blue light without causing excessive yellowing.

[0052] In some embodiments, the adhesive composition is prepared by dissolving the polyisobutylene polymer and other optional components in an organic solvent. Suitable solvents include, for example, alkanes, ethyl acetate, toluene, and tetrahydrofuran. In other embodiments, the adhesive composition may be characterized as a hot-melt adhesive. Such adhesive compositions are typically applied by melt and are solvent-free. Alternatively, a cured hot melt or dried solvent-based adhesive may be applied to or between substrates. As will be described later, the adhesive may be heated after application to the substrate.

[0053] The thickness of the adhesive layer is typically at least 10 micrometers, 15 micrometers, 20 micrometers, or 25 micrometers (1 mil), and ranges up to 500 micrometers (20 mils). In some embodiments, the thickness of the adhesive layer is no greater than 400 micrometers, 300 micrometers, 200 micrometers, or 100 micrometers. The adhesive composition can be coated as a single layer or multiple layers. These layers can be continuous or discontinuous.

[0054] Conventional coating techniques can be used to coat adhesive compositions onto a variety of flexible and non-flexible backing materials to produce single-sided or double-sided coated adhesive tapes and adhesive transfer tapes. Generally, adhesive transfer tapes comprise an adhesive layer disposed on a release liner. Such products can be formed by applying (e.g., coating, casting, or extruding) the adhesive onto the release liner and drying the adhesive (if an organic solvent is present).

[0055] The tape may also include a release material or release liner. For example, in the case of a single-sided coated tape, the side of the backing surface opposite the adhesive application is typically coated with a suitable release material. Release materials are known and include materials such as, for example, silicone, polyethylene, polyurethane, and polyacrylic acid. For a double-sided coated tape, a second layer of adhesive is applied to the opposite surface of the backing surface. The second layer may also comprise an adhesive composition as described herein or different adhesive compositions.

[0056] Flexible substrates are defined herein as any material commonly used as tape backing or that may contain any other flexible material. Examples include, but are not limited to, polymer films, woven or nonwoven fabrics (e.g., sparse cloth); metal foils, foams (e.g., polyacrylic acid, polyethylene, polyurethane, neoprene), and combinations thereof (e.g., metallized polymer films). Polymer films include, for example, polypropylene (e.g., biaxially oriented), polyethylene (e.g., high-density or low-density), polyvinyl chloride, polyurethane, polyester (polyethylene terephthalate), polycarbonate, poly(methyl methacrylate) (PMMA), polyvinyl butyral, polyimide, polyamide, fluoropolymers, cellulose acetate, cellulose triacetate, and ethyl cellulose. Woven or nonwoven fabrics may contain fibers or filaments of synthetic or natural materials such as cellulose (e.g., tissue), cotton, nylon, rayon, glass, ceramic materials, etc.

[0057] The adhesive substrate can be bonded using the adhesive composition described herein or (e.g., transfer) single-sided or double-sided coating. The substrate may include the same material as just described for the backing.

[0058] One bonding method includes providing a first substrate and bringing a surface of the first substrate into contact with an adhesive (e.g., a pressure-sensitive adhesive). In this embodiment, the opposing surfaces of the adhesive are typically temporarily covered by a release liner.

[0059] In other embodiments, the method further includes contacting the opposing surfaces of a pressure-sensitive adhesive (e.g., a layer) with a second substrate. The first and second substrates may be composed of various materials as described above, such as metals, inorganic materials (e.g., glass), organic polymer materials, or combinations thereof.

[0060] In some bonding methods, the substrate, (e.g., pressure-sensitive) adhesive composition, or a combination thereof can be heated to reduce the storage modulus (G') and thereby increase the formation of bond strength. The substrate and / or (e.g., pressure-sensitive) adhesive can be heated to temperatures of up to 30°C, or 35°C, or 40°C, or 45°C, or 50°C, or 55°C, or 60°C, or 65°C, or 70°C. In some embodiments, one or more substrates, together with the adhesive bonded to one or more substrates, are heated to a desired temperature in an oven by assessing the initial peel adhesion strength at ambient temperature (e.g., 25°C). In other embodiments, the substrate and / or (e.g., pressure-sensitive) adhesive is heated using a heat gun.

[0061] In some embodiments, the adhesive compositions described herein (e.g., pressure-sensitive) are optically transparent. Therefore, certain articles may be laminates comprising an optically transparent substrate (e.g., an optical substrate such as an optical film) and an optically transparent adhesive layer disposed on at least one main surface of the optically transparent substrate. The laminate may also include a second substrate permanently or temporarily attached to the pressure-sensitive adhesive layer, wherein the pressure-sensitive adhesive layer is positioned between the optically transparent substrate and the second substrate.

[0062] In one embodiment, the laminate can be a removable or permanent surface protective film. In some embodiments, the strip and protective film can be used for displays (e.g., lighting) that can be incorporated into household appliances, automobiles, computers (e.g., tablets), and various handheld devices (e.g., telephones). In other embodiments, the adhesive-coated film is suitable for architectural applications, window glazing (e.g., windows and windshields), and graphic film applications.

[0063] In some embodiments, the (e.g., pressure-sensitive) adhesive and the optically transparent substrate (e.g., a transparent film) have a transmittance of at least 90% for an adhesive layer with a thickness of 50 micrometers, as measured according to the test method described in the examples for visible light (410 nm). In some embodiments, the transmittance is at least 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99%.

[0064] In some exemplary laminates (where an optically transparent pressure-sensitive adhesive layer is positioned between two substrates), at least one of the substrates is an optical film, a display unit (e.g., a liquid crystal display (LCD), an organic light-emitting diode (OLED), a touch sensor, or a lens). The optical film is intended to enhance, modulate, control, maintain, transmit, reflect, refract, absorb, delay, or otherwise alter light projected onto its surface. Optical films included in the laminates include material classes with optical functions, such as polarizers, interferometric polarizers, reflective polarizers, diffusers, colored optical films, mirrors, venetian blind optical films, light control films, transparent sheets, brightness enhancement films, anti-glare and anti-reflection films, etc. The optical film used in the provided laminates may also include a delay plate, such as quarter-wavelength and half-wavelength phase-retardant optical elements. Other optically transparent films may include light-transmitting plastics (such as polyesters, cyclic olefin copolymers, light-transmitting polyimides, polycarbonate, or polymethyl methacrylate), crack-resistant films, and electromagnetic interference filters. Some films can also be used as substrates for ITO (i.e., indium tin oxide) coatings or patterning, such as those used in the manufacture of touch sensors. The low water absorption and WVTR of the adhesives described herein provide a stable low dielectric constant OCA, which can be very advantageously used in touch sensor applications to both protect the sensor and integrated conductors from environmental and corrosive effects, and to minimize electronic noise communication with the sensor. In some embodiments, the adhesives (e.g., pressure-sensitive) and tapes (e.g., transfer and double-sided coating) described herein are suitable for bonding internal or external components of optical elements such as lighting display devices, such as liquid crystal displays (“LCDs”) and light-emitting diode (“LEDs”) displays (such as battery-powered mobile phones (including smartphones), wearable (e.g., wrist) devices, car navigation systems, GPS, depth detectors, computer monitors, laptop and tablet displays). Other types of optical elements include projection (e.g., lens) components, photonic components, and polarization beam splitters.

[0065] In some embodiments, pressure-sensitive adhesives are suitable as encapsulation compositions for use in electronic devices such as those described in, for example, US2009 / 0026924, which is incorporated herein by reference.

[0066] Specifically, (e.g., pressure-sensitive) adhesives can be used as sealing components for electronic devices, such as organic devices, including organic transistors, organic memories and organic EL elements; liquid crystal displays; electronic paper; thin-film transistors; electrochromic devices; electrochemiluminescence devices; touch panels; solar cells; thermoelectric conversion devices; piezoelectric conversion devices; electrical storage devices; and so on.

[0067] In addition to various optical-related applications and / or electronic display component applications, the adhesive compositions described herein can be used in a variety of other articles. The following non-limiting examples further describe exemplary adhesives and adhesive articles of this disclosure, as well as exemplary methods for preparing such adhesives and adhesive articles. Unless otherwise specified, all percentages are by weight.

[0068] Example

[0069] The invention is described in more detail in the following examples, which are intended to be illustrative only, as many modifications and variations within the scope of the invention will be apparent to those skilled in the art. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are based on weight.

[0070] Material

[0071] Materials and their sources are listed in Table 1. Unless otherwise stated, all other reagents were obtained or purchased from fine chemical suppliers such as Sigma-Aldrich Company, St. Louis, Missouri, or synthesized by known methods.

[0072] Table 1

[0073]

[0074] Methods for haze measurement

[0075] Test samples were prepared as follows: The LCD (liquid crystal display) glass was cleaned three times with IPA (isopropyl alcohol) and the surface was completely dried with KIMWIPE (KIMTECH, supplied by Kimberly-Clark, Irving, TX). Each test sample (50 micrometers thick) was cut to a size large enough to cover the inlet port. The clear liner was removed, and the adhesive was laminated onto the LCD glass four times using a small rubber hand roller. The sample should be free of visible internal voids, particles, scratches, and defects. The test sample was then placed in a test chamber at 65°C and 90% relative humidity. Within 10 minutes, another clear liner was removed, and the background haze of the LCD glass was measured using an UltraScan Pro from Hunterlab, Reston, VA, according to ASTM D 1003-92.

[0076] A method for determining storage modulus, Tanδ, and creep compliance through dynamic mechanical analysis.

[0077] Dynamic mechanical analysis (“DMA”) of the adhesive samples was performed using a rheometer (available under the trade name “AR2000 Parallel Plate Rheometer” from TA Instruments, New Castle, DE, Newcastle, Delaware) to characterize the physical properties of each sample as a function of temperature. For each sample, 50-micron thick sheets of the polymeric adhesive sample were laminated together to obtain a 1-mm thick plate. The sample was cut from this plate using an 8-mm diameter circular punch, and then centered between 8-mm diameter parallel plates of the rheometer. The temperature was then equilibrated for 2 minutes at the test temperature under a nominal axial force of 0 g + / - 15 g. After two minutes, the axial force controller was deactivated to maintain a fixed gap for the remainder of the test.

[0078] Samples were then acquired at a temperature change rate of 3 °C / min from 25 °C to -50 °C, and then from -50 °C to 150 °C. G' at 25 °C and tanδ at 70 °C were recorded during this measurement process.

[0079] To determine creep compliance, a stress of 8,000 Pascals was applied to the sample for 300 seconds, and the creep compliance (J) was recorded at 287 seconds.

[0080] Methods for determining water vapor transmission rate (WVTR)

[0081] Water vapor transmission rate of a 50-micron thick sample of crosslinked adhesive was measured according to ASTM E398-13 using a PERMATRAN-W 1 / 50G test instrument from Mocon, Brooklyn Park, MN. Test conditions were 40°C and a 90% relative humidity gradient.

[0082] 180° peel test on glass at room temperature at 300 mm / min

[0083] Prior to testing, a single-layer pressure-sensitive adhesive film was laminated onto a 50-micrometer (μm) thick PET backing (obtained under the trade name HOSTAPHAN RN 50 from Mitsubishi Chemical Holding Groups (Wiesbaden, Germany)). The resulting pressure-sensitive adhesive strip was longitudinally cut from the pressure-sensitive adhesive film sample material to provide a test strip with a width of 25.4 mm and a length of 3050 mm. The glass panel was cleaned with a 50:50 isopropanol / water mixture prior to use.

[0084] For test sample preparation, the backing was first removed from the adhesive side, and the strip was applied to a clean test panel using gentle finger pressure. The test sample was then rolled four times at approximately 10 mm / s using a standard FINAT test roller (2.0 kg, Mecmesin Corporation, Sterling, VA) to achieve tight contact between the adhesive and the surface. After applying the pressure-sensitive adhesive strip to the test panel, the test sample was allowed to remain at ambient temperature (23°C + / - 2°C, 50% RH + / - 5%) for 24 hours before testing at 85°C or room temperature.

[0085] For the 180° peel test, the test panel is clamped in the lower movable jaws of an Instron tension tester (Instron 3365, Instron, Norwood, MA). The pressure-sensitive adhesive film strip is folded back at a 180° angle, and its free end is clamped in the upper jaws of the tension tester in the configuration commonly used for 180° measurements. The tension tester is set to a jaw separation rate of 300 mm / min. Test results are expressed in Newtons per centimeter (N / cm). The peel value is the average of three 180° peel measurements.

[0086] Preparation of Comparative Example 1 (CE 1): In CE 1, 8 g of B 15SF, 2 g of Escorez 5340, and 15 g of heptane were added to a glass vial. The vial was sealed and the contents were mixed overnight. The solution was then coated onto a 50 μm thick silicone polyester release liner RF02N (SKC Haas, Korea) using a blade coater with an 8 mil gap. The coated sample was placed in an oven at 70°C for 15 minutes. Then, a total dose of 1200 mJ / cm³ was applied. 2 The coated sample was irradiated with a UV-A H-bulb.

[0087] Other embodiments, which also contain multifunctional components, were prepared using the amounts of materials specified in Tables 2 and 3 below, in the same manner as CE 1.

[0088] Table 2

[0089]

[0090] Table 3

[0091]

[0092] Table 4

[0093]

[0094] CN308 and CN309 were analyzed by NMR. Those skilled in the art will recognize that the first step is to collect quantitative proton NMR. A deuterated solvent, essentially free of residual water, is used to ensure that the aliphatic integrated area is not artificially inflated. From the spectrum, peaks associated with acrylates, CH2O esters, unsaturated groups, and aliphatic regions can be identified and mathematically integrated. Since these materials are known to be diacrylates, the acrylate integrated value in the proton NMR can be normalized to 6. For the aliphatic integrated value, the CH2O ester signal is included. The corresponding integrated values ​​of acrylates, aliphatic groups, and unsaturated groups are normalized with an appropriate number of protons to calculate the molar number of each component. For example, the normalization number for acrylates is three, for aliphatic groups it is four, and for unsaturated groups it is two. The molar number of terminal groups (in this case, acrylates) is 2, which represents the total number of terminal groups in the sample. The average molecular weight is calculated by multiplying the molar number of this functional group by the molecular weight. For example, given the presence of 2 moles of acrylate, the value is multiplied by the molecular weight of the acrylate (72). The moles of aliphatic and unsaturated groups are also multiplied by their respective molecular weights (28 and 26, respectively). The average molecular weight is calculated by summing the weights of each component. Using this technique, CN308 was determined to have a number-average molecular weight of 3301 g / mol and 0.088 wt% unsaturated groups excluding acrylate groups. CN309 was determined to have a number-average molecular weight of 645 g / mol and 0.022 wt% unsaturated groups excluding acrylate groups.

Claims

1. An adhesive composition comprising: Polyisobutylene polymer components; and At most 30% by weight of at least one aliphatic multifunctional component, said at least one aliphatic multifunctional component comprising at least two olefinic unsaturated groups selected from (meth)acryloyl or vinyl ether, wherein, in addition to the unsaturated groups of said (meth)acryloyl and vinyl ether, said multifunctional component comprises less than 0.08% by weight of olefinic unsaturated groups as determined by NMR. The aliphatic multifunctional component comprises a straight-chain or branched hydrocarbon moiety having more than 12 linked carbon atoms, and when the hydrocarbon moiety is branched, the hydrocarbon moiety comprises a side chain having at least two carbon atoms; the multifunctional component has a number-average molecular weight of less than 3000 g / mol as determined by nuclear magnetic resonance (NMR); and the aliphatic multifunctional component is sufficiently compatible such that the crosslinked adhesive composition has a haze of less than 3% at a thickness of 20 micrometers.

2. The adhesive composition of claim 1, wherein the polyisobutylene polymer component comprises an unfunctionalized polyisobutylene polymer, butyl rubber, or a mixture thereof.

3. The adhesive composition according to claim 2, wherein the polyisobutylene polymer has a weight-average molecular weight in the range of 50,000 g / mol to 1,000,000 g / mol.

4. The adhesive composition of claim 1, wherein the adhesive composition comprises 40% to 95% by weight of a polyisobutylene polymer component.

5. The adhesive composition of claim 2, wherein the adhesive composition comprises at least 55% by weight of an unfunctionalized polyisobutylene polymer having a weight-average molecular weight in the range of 50,000 g / mol to 300,000 g / mol.

6. The adhesive composition of claim 2, wherein the adhesive composition comprises at least 55% by weight of butyl rubber having a weight-average molecular weight in the range of 300,000 g / mol to 1,000,000 g / mol.

7. The adhesive composition of claim 2, wherein the adhesive composition comprises a blend of an unfunctionalized polyisobutylene polymer and a butyl rubber, the unfunctionalized polyisobutylene polymer having a weight-average molecular weight in the range of 50,000 g / mol to 300,000 g / mol, and the butyl rubber having a weight-average molecular weight in the range of 300,000 g / mol to 1,000,000 g / mol.

8. The adhesive composition according to claim 1, wherein the multifunctional component has a density of at least 0.88 g / cc at 25°C.

9. The adhesive composition according to claim 1, wherein the multifunctional component has an acid value of 1 to 5.

10. The adhesive composition of claim 1, wherein the adhesive composition further comprises a monofunctional component comprising (meth)acrylate or vinyl ether groups.

11. The adhesive composition of claim 10, wherein each olefinic unsaturated group in the multifunctional component or the monofunctional component comprises at least 7 linked carbon atoms.

12. The adhesive composition of claim 10, wherein each olefinic unsaturated group in the multifunctional component or the monofunctional component comprises at least 11 linked carbon atoms.

13. The adhesive composition of claim 1, wherein the adhesive composition further comprises a tackifier, a plasticizer, or a combination thereof.

14. The adhesive composition of claim 13, wherein the tackifier is a non-hydrogenated or hydrogenated aliphatic hydrocarbon tackifier.

15. The adhesive composition of claim 1, wherein, when measured at a relative humidity gradient of 40°C and 90%, the adhesive composition has a thickness of less than 100 g / m² at a thickness of 50 micrometers. 2 / day WVTR.

16. An article comprising an adhesive composition according to any one of the preceding claims, wherein the adhesive composition is disposed on a substrate.

17. The article of claim 16, wherein the adhesive composition has an adhesive thickness of 0.001 mm to 1 mm.

18. The article of claim 16, wherein one or more of the substrates are release liner.

19. The article of claim 16, wherein the composition is disposed between two substrates.

20. The article of claim 16, wherein one or more of the substrates are optical films, display units, touch sensors, or lenses.

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