EP4702101A1 - Adhesive including silica and processes for making and using a tape - Google Patents

Abstract

An adhesive includes a thermoplastic elastomeric block copolymer comprising a midblock and two or more polystyrene end blocks, a tackifying resin, and precipitated amorphous silica. A tape includes the adhesive disposed on a backing. Processes for making and using the tape are also provided.

Description

ADHESIVE INCLUDING SILICA AND PROCESSES FOR MAKING AND USING A TAPE

Cross-Reference to Related Application

This application claims priority to U.S. Provisional Application No. 63/462,726, filed April 28, 2023, the disclosure of which is incorporated by reference in its entirety herein.

Background

Styrene -conjugated diene block copolymers have been formulated to produce adhesive compositions. For example, U.S. Pat. No. 3,239,478 (Harlan), shows combinations of these block copolymers with tackifying resins and paraffinic extending oils to produce various types of adhesives. However, one of the limitations of these adhesive compositions is their relatively low service temperatures. Generally, the highest temperature at which these styrene-diene block copolymers retain useful properties and act like a vulcanized rubber is limited by the softening temperature of the styrene end block and can be about 120 °F to 180 °F (49 °C to 82 °C). U.S. SIR H1387 (Hansen et al.) and U.S. Pat. No. 4,104,323 (Hansen) propose using polyphenylene ether to improve the performance of styrene- conjugated diene block copolymer-based adhesives at relatively higher temperatures.

Heat-reactive crosslinkers have been used to improve the performance of rubber-based adhesives at elevated temperatures. Masking tapes that include rubbers and heat-reactive crosslinkers are typically made by solvent-coating a pressure sensitive adhesive composition. It is not desirable to add commonly used heat-reactive crosslinkers to the mixer when using hot melt processing of an adhesive.

In unrelated disclosures, fumed silica has been used in acrylic pressure-sensitive adhesive formulations for various purposes as reported in U.S. Pat. Nos. 4,415,615 (Esmay et al.), 4,710,536 (Klingen et al.), and 11,578,162 (Seth et al.) and Int. Pat. Appl. Pub. No. WO 95/13331 (Bennett et al.). Furthermore, U.S. Pat. No. 3,565,247 (Brochman) reports fumed silica as a nucleating and reinforcing agent in a foamed pressure -sensitive adhesive.

Summary

The present disclosure provides a thermoplastic elastomer-based adhesive useful, for example, in tapes for higher temperature (e.g., 158 °F (70 °C) to 230 °F (110 °C)) applications. Typically, and advantageously, the adhesive of the present disclosure does not require crosslinking to achieve remarkable clean-removability at such temperatures. Also typically, and advantageously, the adhesive can be easily hot-melt processed, which eliminates the need for organic solvents. In one aspect, the present disclosure provides an adhesive. The adhesive includes a thermoplastic elastomeric block copolymer comprising a midblock and two or more polystyrene end blocks, a tackifying resin, and precipitated amorphous silica.

In another aspect, the present disclosure provides a tape. The tape includes the adhesive disposed on a tape backing.

In another aspect, the present disclosure provides a process of making a tape. The process includes applying the adhesive described herein as a hot melt on a tape backing to provide the tape.

In another aspect, the present disclosure provides a process of using the tape described above. The process includes applying the tape to a surface and exposing the surface to a temperature of at least 70 °C, 80 °C, 90 °C, or 100 °C. In other words, the present disclosure provides the use of the tape at a temperature of at least 70 °C, 80 °C, 90 °C, or 100 °C.

In this application:

Terms such as "a", "an" and "the" are not intended to refer to only a singular entity but include the general class of which a specific example may be used for illustration. The terms "a", "an", and "the" are used interchangeably with the term "at least one".

The phrase "comprises at least one of' followed by a list refers to comprising any one of the items in the list and any combination of two or more items in the list. The phrase "at least one of' followed by a list refers to any one of the items in the list or any combination of two or more items in the list.

The term “polystyrene” as used herein includes polymers and copolymers of substituted styrene monomers and/or unsubstituted styrene.

The term “crosslinking” refers to joining polymer chains together by covalent chemical bonds to form a network polymer. A crosslinked polymer is generally characterized by insolubility but may be swellable in the presence of an appropriate solvent. The term “crosslinked elastomer” includes partially crosslinked elastomers.

The terms “thermoplastic elastomeric block copolymer” and “thermoplastic elastomer” may be used interchangeably.

Pressure-sensitive adhesives (PSAs) are generally known to possess the following desirable properties: (1) aggressive and permanent tack, (2) adherence with no more than finger pressure, (3) sufficient ability to hold onto an adherend, and (4) sufficient cohesive strength to be cleanly removable from the adherend. Materials that have been found to function well as PSAs are polymers designed and formulated to exhibit the requisite viscoelastic properties resulting in a desired balance of tack, peel adhesion, and shear holding power.

All numerical ranges are inclusive of their endpoints and nonintegral values between the endpoints unless otherwise stated (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, 5, etc.). Detailed Description

While PSAs are desirably cleanly removable from an adherend, clean removability can be challenging, particularly after aging at elevated temperatures. A lack of clean removability can be indicative of poor cohesive strength in the PSA (e.g., at elevated temperature) and/or poor bonding of the PSA to the backing in a PSA tape. To improve clean removal at elevated temperatures such as 200 °F (93 °C) to 230 °F (110 °C), crosslinking using chemical crosslinkers (e.g., sulfur, phenolic resins, and isocyanate) and/or radiation such as electron beam radiation have been used. However, formulating with chemical crosslinkers generally requires organic solvent, and radiation crosslinking can require specialized and/or expensive equipment. The present disclosure provides an adhesive that can be useful in a tape. Typically, and unexpectedly, clean removal of the adhesive can be achieved at elevated temperatures such as 200 °F (93 °C) to 230 °F (110 °C) without the use of chemical crosslinkers or radiation crosslinking.

The adhesive of the present disclosure includes a thermoplastic elastomeric block copolymer comprising a midblock and two or more polystyrene end blocks. The adhesive can include a single block copolymer or a mixture of two or more block copolymers. At least one block copolymer in the adhesive is a block copolymer comprising a midblock and two or more polystyrene end blocks. The midblock is generally a rubbery block (or low-Tg block), and the polystyrene end blocks are sometimes referred to as glassy blocks or high-Tg blocks.

While the present disclosure is not to be bound by theory, it is believed that at the service temperature of the adhesive, the block copolymer microphase separates into ordered nanoscale domains that include rubbery block domains and glassy block domains. When microphase separated, these copolymers form elastic, dimensionally stable solids that display significant shear strength. Unlike chemically crosslinked rubbers, the block copolymers are capable of being reversibly melted and resolidified with temperature; thus, they are known as thermoplastic elastomers. Thus, thermoplastic elastomeric block copolymers as described herein are not chemically crosslinked.

In some embodiments, the block copolymer is a linear block copolymer of general formula (S-R)_m-S where each S is independently a polystyrene block, each R is independently a rubbery block, and m is a value of at least 1. Variable m can be from 1 to 10, 1 to 5, 1 to 3, or in some embodiments, less than, equal to, or greater than 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10. In some embodiments, the linear block copolymer is a triblock copolymer wherein m is 1 and can also be represented by formula S-R-S.

In some embodiments, the block copolymer can be a star (also known as a radial or multi-arm) block copolymer of general formula (S-R)_n-Y where each R and S are the same as defined above, n is an integer equal to at least 3, and Y is the residue of a multifunctional coupling agent used in the formation of the star block copolymer. The variable n represents the number of arms in the star block copolymer and can be from 3 to 10, from 3 to 8, from 3 to 6, or in some embodiments, less than, equal to, or greater than 3, 4, 5, 6, 7, 8, 9, or 10. For each of the arms, each S and each R may have different lengths. In the block copolymer, including any of those described above, the polystyrene blocks can have the same or different molecular weights. In some embodiments, each polystyrene block independently has a weight average molecular weight of 4,000 to 50,000 grams per mole. Similarly, if there is more than one midblock (e.g., rubbery block), the midblocks can have the same or different molecular weights. In some embodiments, each midblock independently has a weight average molecular weight of 5,000 to 500,000 grams per mole.

Generally, each midblock has a glass transition temperature (T_g) that is less than ambient temperature. For example, the glass transition temperature can be less than 20°C, less than 0°C, less than -10 °C, or less than -20 °C, less than -40 °C, less than -60 °C, or in some embodiments, less than, equal to, or greater than -60 °C, -55 °C, -50 °C, -45 °C, -40 °C, -35 °C, -30 °C, -25 °C, -20 °C, -15 °C, -10 °C, -5 °C, 0 °C, 5 °C, 10 °C, 15 °C, or 20 °C. The glass transition temperature can be determined using conventional methods known in the art, including Differential Scanning Calorimetry or Dynamic Mechanical Analysis.

In some embodiments, each midblock in the block copolymer is the polymerized product of a conjugated diene, a hydrogenated derivative of a polymerized conjugated diene, or a combination thereof. The conjugated diene often contains 4 to 12 carbon atoms. Examples of useful conjugated dienes include butadiene, isoprene, 2-ethylbutadiene, 1 -phenylbutadiene, 1,3-pentadiene, 1,3 -hexadiene, 2,3-dimethyl- 1,3-butadiene, 3 -ethyl- 1,3 -hexadiene and combinations thereof. Each midblock can be a homopolymer or copolymer. The midblock may be hydrogenated. In some embodiments, the midblock comprises at least one of poly(butadiene), poly(isoprene), poly(2 -ethylbutadiene), poly(l -phenylbutadiene), poly(l,3- pentadiene), poly(l,3-hexadiene), poly(2,3-dimethyl-l,3-butadiene), poly(3-ethyl-l,3-hexadiene), poly(ethyleneZpropylene), poly(ethyleneZbutylene), or poly(isopreneZbutadiene). In some embodiments, the midblock comprises at least one of polybutadiene, polyisoprene, poly(isopreneZbutadiene), poly(ethyleneZbutylene), or poly(ethyleneZpropylene).

The glass transition temperature of each polystyrene block is generally at least 50 °C, at least 60 °C, at least 70 °C, at least 80 °C, at least 90 °C, at least 100 °C, or in some embodiments, less than, equal to, or greater than 50 °C, 55 °C, 60 °C, 65 °C, 70 °C, 75 °C, 80 °C, 85 °C, 90 °C, 95 °C, or 100 °C.

Styrene monomers useful for making the polystyrene end blocks may be unsubstituted or substituted. Useful styrene monomers at least 8 carbon atoms and in some embodiments contain at least 10 carbon atoms or at least 12 carbon atoms and up to 18 carbon atoms, up to 16 carbon atoms, or up to 14 carbon atoms. Examples of suitable styrene monomers include styrene, vinyltoluene (e.g., 2, 3, or 4- vinyltoluene), alpha-methyl styrene, 2,4-dimethyl styrene, ethyl styrene, 2,4-diethyl styrene, 3,5-diethyl styrene, alpha-2-methyl styrene, 4-tert-butyl styrene, 4-isopropyl styrene, and combinations thereof. Each polystyrene block can be a homopolymer or a copolymer. In some embodiments, the polystyrene end blocks each comprise at least one of unsubstituted polystyrene, poly (vinyltoluene), poly(alpha- methylstyrene), poly(2,4-dimethylstyrene), poly(ethylstyrene), poly(2,4-diethylstyrene), poly(3,5- diethylstyrene), poly(4-tert-butylstyrene), or poly(4-isopropyl styrene). In some embodiments, the polystyrene end blocks each comprise unsubstituted polystyrene. In some embodiments in which one or more polystyrene end blocks comprises a copolymer, at least 50 weight percent (wt%) (in some embodiments, at least 60 wt%, at least 70 wt%, at least 80 wt%, at least 90 wt%, at least 95 wt%, at least 98 wt% or at least 99 wt%) of the monomeric units are derived from styrene.

Polystyrene blocks including the polystyrene end blocks can represent from 5 wt% to 50 wt% of the block copolymer. With such an amount of polystyrene in the block copolymer, an excellent balance of cohesive strength and modulus may be achieved. The block copolymer can have a polystyrene block content of from 7 wt% to 40 wt%, 9 wt% to 33 wt%, 13 wt% to 25 wt%, or in some embodiments, less than, equal to, or greater than 7 wt%, 8 wt%, 9 wt%, 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, 15 wt%, 16 wt%, 17 wt%, 18 wt%, 19 wt%, 20 wt%, 21 wt%, 22 wt%, 23 wt%, 24 wt%, 25 wt%, 27 wt%, 30 wt%, 32 wt%, 35 wt%, 37 wt%, or 40 wt%, based on the total weight of the block copolymer.

In addition to the polystyrene blocks and the midblocks, star block copolymers include a residue of a multifunctional coupling agent Y. The coupling agent often has multiple carbon-carbon double bonds, carbon-carbon triple bonds, or other groups that can react with carbanions of a living polymer that may be used to form the star block copolymers. The multifunctional coupling agents can be aliphatic, aromatic, heterocyclic, or a combination thereof. Examples of suitable coupling agents include polyvinyl acetylene, diacetylene, di(meth)acrylates (e.g., ethylene dimethacrylate), divinyl benzene, divinyl pyridine, and divinyl thiophene. Other useful coupling agents include multi-functional silyl halide (e.g., tetrafunctional silyl halide), polyepoxides, polyisocyanates, polyketones, polyanhydrides, polyalkenyls, and dicarboxylic acid esters.

The weight average molecular weight of the block copolymer is often not more than 1,200,000 grams per mole (g/mol). In some embodiments, the weight average molecular weight is not more than 1,050,000 g/mol, 900,000 g/mol, 800,000 g/mol, 600,000 g/mol, or 500,000 g/mol. In some embodiments, the weight average molecular weight of the block copolymer is at least 75,000 g/mol, at least 100,000 g/mol, at least 200,000 g/mol, at least 300,000 g/mol, or at least 400,000 g/mol. The weight average molecular weight of the block copolymer can be from 75,000 g/mol to 1,200,000 g/mol, from 100,000 to 1,000,000 g/mol, from 100,000 to 900,000 g/mol, or from 100,000 to 500,000 g/mol.

In some embodiments, the block copolymer comprises at least one of a polystyrene-containing triblock copolymer or a polystyrene-containing star block copolymer, wherein the polystyrene-containing triblock copolymer and polystyrene-containing star block copolymer independently comprise a block of at least one of polyisoprene, polybutadiene, poly(ethylene/propylene), poly(ethylene/butylene), or polyisobutylene. In some embodiments, the block copolymer comprises at least one of a polystyrene- containing triblock copolymer or a polystyrene-containing star block copolymer, wherein the polystyrene- containing triblock copolymer and polystyrene-containing star block copolymer independently comprise a block of at least one of polyisoprene or polybutadiene. In some embodiments, the block copolymer comprises at least one of a polystyrene-polyisoprene-polystyrene triblock copolymer or a polystyrene- polybutadiene-polystyrene triblock copolymer. In some embodiments, the block copolymer comprises at least one of a polystyrene-polyisoprene-polystyrene star block copolymer or a polystyrene-polybutadiene- polystyrene star block copolymer. In some embodiments, the block copolymer comprises at least one of a polystyrene-polyisoprene-polystyrene triblock copolymer or a polystyrene-polyisoprene-polystyrene star block copolymer.

The thermoplastic elastomeric block copolymer can be present in any suitable amount in the adhesive. In some embodiments, the block copolymer is present in amount of from 30 wt% to 69 wt%, from 35 wt% to 65 wt%, from 40 wt% to 60 wt%, or 45 wt% to 60 wt%, based on the total weight of the adhesive.

In some embodiments, the adhesive of the present disclosure further includes a second block copolymer that is a diblock copolymer. The diblock copolymer generally has a single polystyrene block and a single rubbery block and can be represented here by the chemical structure S-R, wherein S and R are as defined above in any of their embodiments.

The polystyrene block content in the diblock copolymer can be from 10 wt% to 50 wt%, from 10 wt% to 40 wt%, from 15 wt% to 50 wt%, from 15 wt% to 40 wt%, from 20 wt% to 50 wt%, from 20 wt% to 40 wt%, or in some embodiments, less than, equal to, or greater than 10 wt%, 12 wt%, 15 wt%, 17 wt%, 20 wt%, 22 wt%, 25 wt%, 27 wt%, 30 wt%, 32 wt%, 35 wt%, 37 wt%, or 40 wt% relative to the overall weight of the diblock copolymer. The weight average molecular weight of the diblock copolymer can be from 75,000 g/mol to 250,000 g/mol, from 100,000 g/mol to 250,000 g/mol, from 125,000 g/mol to 250,000 g/mol, or from 125,000 g/mol to 200,000 g/mol. In some embodiments, the diblock copolymer is present in an amount of from 1 wt% to 25 wt%, from 3 wt% to 15 wt%, or from 5 wt% to 10 wt% based on the total weight of the block copolymer and the diblock copolymer.

Suitable materials for use as the block copolymer alone or in combination are commercially available, for example, under the trade designation “KRATON” (e.g., “KRATON DI 161”, “DI 118”, “Dl l 19”, “DI 126”, and “A1535”) from Kraton Performance Polymers (Houston, TX, USA), under the trade designation “SOLPRENE” (e.g., “SOLPRENE S-1205”) from Dynasol (Houston, TX, USA), under the trade designation “QUINTAC” from Zeon Chemicals (Louisville, KY, USA), and under the trade designations “VECTOR” and “TAIPOL” from TSRC Corporation (New Orleans, LA, USA).

The adhesive of the present disclosure includes a tackifying resin. Tackifying resins generally refer to materials that are compatible with the thermoplastic elastomeric block copolymer and have a number average molecular weight of up to 10,000 grams per mole. Useful tackifying resins can have a softening point of at least 70 °C as determined using a ring and ball apparatus and a glass transition temperature of at least -30 °C as measured by differential scanning calorimetry. In some embodiments, the tackifying resin has a softening point from 80 °C to 160 °C, from 100 °C to 150 °C, or from 115 °C to 145 °C. The tackifying resins are typically amorphous. In some embodiments, the number average molecular weight of the tackifying resin is up to about 5000 grams/mole, 4000 grams/mole, 2500 grams/mole, 2000 grams/mole, or 1500 grams/mole. In some embodiments, the number average molecular weight is in the range of 200 to 5000 gram/mole, in the range of 200 to 4000 grams/mole, in the range of 200 to 2000 grams/mole, or in the range of 200 to 1500 gram/mole. Number average molecular weights are determined using gel permeation chromatography according to methods known to a person skilled in the art. In some embodiments, the tackifying resin is a hydrocarbon tackifying resin.

In some embodiments, the tackifying resin comprises at least one of a polyterpene (e.g., those based on a-pinene, P-pinene, or limonene), a terpene phenolic tackifier, a rosin acid, a rosin ester, an aliphatic hydrocarbon resin (e.g., those based on cis- or trans-piperylene, isoprene, 2-methyl-but-2-ene, cyclopentadiene, dicyclopentadiene, or combinations thereof), an aromatic resin (e.g. those based on styrene, a-methyl styrene, methyl indene, indene, coumarone, or combinations thereof), or a mixed aliphatic -aromatic hydrocarbon resin. The aromatic hydrocarbon resins may be C9-type petroleum resins obtained by copolymerizing a C9 fraction produced by thermal decomposition of petroleum naphtha, and aliphatic hydrocarbon resins may be C5-type petroleum resins obtained by copolymerizing a C5 fraction produced by thermal decomposition of petroleum naphtha. Mixed aliphatic/aromatic resins may be C5/C9-type petroleum resins obtained by polymerizing a combination of a C5 fraction and C9 fraction produced by thermal decomposition of petroleum naphtha. Any of these tackifying resins may be hydrogenated (e.g., partially or completely). The term rosin, as employed herein, includes natural rosin, refined or unrefined (refined rosin will usually contain, by weight, about 90% of rosin acids and about 10% of inert material), such as natural wood rosin, natural gum rosin, and tall oil rosin; modified rosin, refined or unrefined, such as disproportionated rosin, hydrogenated rosin, and polymerized rosin; and the pure or substantially pure acids, of which rosin is comprised, alone or in admixture. In some embodiments, the rosin includes the rosin acid C19H29COOH, in some embodiments, at least one of abietic acid, neoabietic acid, palustric acid, levopimaric acid, pimaric acid, or an isopimaric acid. In some embodiments, the rosin comprises dehydro- or hydrogenated rosin acids, for example, dehydroabietic acid, dihydroabietic acid, and tetrahydroabietic acid. The tackifying resin can also include a metal rosinate (sometimes referred to in the art as a metal resinate). The metal rosinate can be metal salt (e.g., zinc, calcium, or magnesium) of any of the rosins described above.

In some embodiments, the tackifying resin is selected to be compatible with the midblock of the thermoplastic elastomeric block copolymer. The compatibility of the tackifying resin with the midblock can be determined by measuring the effect of the tackifying resin on the glass transition temperature of the midblock. If a tackifying resin is compatible, it will generally increase the glass transition temperature of the midblock as measured by Differential Scanning calorimetry or Dynamic Mechanical Analysis. In some embodiments, the tackifying resin is a hydrocarbon tackifier, an aromatic modified aliphatic tackifying resin, or a terpene tackifier. Some suitable tackifying resins are commercially available under the trade designations "ARKON" from Arakawa Chemical Industries Co., Ltd. (Osaka, Japan); "ESCOREZ" from ExxonMobil Chemical Company (Spring, Texas); "REGALREZ" and "PICCOTAC" from Eastman Chemical (Kingsport, TN); "WINGTACK" from Cray Valley (Exton, PA); and others listed in the Examples, below.

In some embodiments, the adhesive includes at least about 30 wt% and up to about 60 wt% of the tackifying resin, based on the total weight of the composition. In some embodiments, the tackifying resin is present in a range from 32 wt% to 50 wt%, 34 wt% to 48 wt%, 30 wt% to 40 wt%, 35 wt% to 50 wt%, or 35 wt% to 55 wt%, based on the total weight of the adhesive.

While aromatic tackifying resins may be useful, in some embodiments, in combination with other tackifying resins described above, in some embodiments, the adhesive of the present disclosure does not include a significant amount of aromatic resins reported to reinforce the styrene end blocks of the block copolymer. Such aromatic resins include coumarone-indene resins, poly alpha methyl styrene, polystyrene resins, vinyl toluene-a-methyl styrene copolymers, polyindene resins, and polyphenylene ether resins such as unsubstituted polyphenylene ether resins and substituted polyphenylene ether resins (e.g., poly(2,6-dimethyl-l,4-phenylene)ether). In some embodiments, the adhesive includes not more than 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0.5, or 0.1 wt% of any of these aromatic resins, except where any of these is part of a mixed aliphatic-aromatic hydrocarbon resin. In some embodiments, the adhesive is free of any one or more of these aromatic resins.

The adhesive of the present disclosure includes precipitated amorphous silica. Precipitated amorphous silica has a bulk density typically in a range from 1.9 grams per cubic centimeter (g/cc) to 2.1 g/cc and a purity of less than 99, 98, 97, or 96 percent, in some embodiments, in a range from 90 to 95 percent. In some embodiments, the precipitated amorphous silica has a Brunauer, Emmett, and Teller (BET) specific surface area in a range from 35 square meters per gram (m²/g) to 400 m²/g, 50 m²/g to 300 m²/g, 100 m²/g to 300 m²/g, 150 m²/g to 250 m²/g, or about 180 m²/g. Aggregates of precipitated amorphous silica particles can have a size in a range from one micrometer to 100 micrometers, and these aggregated particles can form agglomerates. Precipitated amorphous silica useful for practicing the present disclosure generally has a hydrophilic surface. In some embodiments, the precipitated amorphous silica is not chemically treated to install hydrophobic groups on the surface.

Precipitated amorphous silica is precipitated from a solution of sodium silicate using acid. This process of producing amorphous silica results in properties of the silica than those produced by other methods. For example, fumed silica is also known as pyrogenic silica and is produced in by pyrolyzing silicon tetrachloride, for example, in an oxygen-hydrogen flame. Fumed silica typically is a light fluffy solid with a bulk density of up to 0.19 g/cc. It forms branched aggregates with sizes in the range from 150 to 300 nanometers, which can form agglomerates. The purity of fumed silica is typically greater than 99 percent. Fumed silica requires high shear in order to be dispersed into elastomers, and such high shear can break down the elastomer and decrease its molecular weight. In comparison to fumed silica, precipitated amorphous silica typically has more surface hydroxy groups, higher density, higher moisture content, higher porosity within the particle, and lower impact on viscosity than equal weights of fumed silica. The difference between precipitated amorphous silica and fumed silica is understood by a person skilled in the art. Furthermore, precipitated amorphous silica is distinguished from colloidal silica in that the silica particles are not dispersed in water. Colloidal silica is stabilized to remain as primary particles (i.e., not aggregated particles) having a size of 1 nanometer to 100 nanometers.

Suitable precipitated amorphous silica is commercially available from a variety of sources such as PPG Silica Products, Monroeville, PA, Evonik Corporation, Parsippany, NJ, and Hifull Corporation, Yichang City, China. Sodium silicate can be obtained from a variety of sources, including green sources such as rice husk ash.

In some embodiments, the precipitated amorphous silica is present in an amount ranging from 1 wt% to 20 wt%, based on the total weight of the adhesive. In some embodiments, the precipitated amorphous silica is present in an amount ranging from 2 wt% to 18 wt%, 3 wt% to 17 wt%, 4 wt% to 16 wt%, or 5 wt% to 15 wt%, or 6 wt% to 15 wt%, based on the total weight of the adhesive.

A number of adjuvants may also be useful in the adhesive of the present disclosure. Examples of such adjuvants include antioxidants, such as hindered phenols, amines, sulfur and phosphorous hydroperoxide decomposers, and butylated hydroxytoluene (BHT)); other inorganic fdlers such as talc, zinc oxide, titanium dioxide, and aluminum oxide; and plasticizing aids such as those materials described as plasticizers in the Dictionary of Rubber, K. F. Heinisch, pp. 359, John Wiley & Sons, New York (1974); oils; elastomer oligomers; and waxes. Useful commercially available antioxidants include those available from BASF, Florham Park, NJ, under the trade designations "IRGANOX" and "IRGAFOS" such as "IRGANOX 1010" and “IRGANOX 1076”, those available from Songwon Ind. Co, Ulsan, Korea, under the trade designations “SONGNOX”, and dilaurylthiodipropionate. Useful plasticizing oils include paraffinic oils, aromatic oils, and naphthene oils such as those available, for example, from Process Oils Inc., Houston, TX. The plasticizing oil may be selected based on viscosity, for example. Adhesives of the present disclosure can also include at least one of pigments, dyes, ultraviolet absorbers, hindered amine light stabilizers, and heat stabilizers, if desired. When present, typically the antioxidant is present in the adhesive in an amount of 0. 1 to 5 parts by weight per 100 parts by weight thermoplastic elastomer, and the plasticizing aid is present in the adhesive in an amount from 10 to 30, 10 to 20, or 10 to 15 wt%, based on the total weight of the adhesive. In some embodiments, the adhesive is not foamed. In some embodiments, the adhesive does not contain a chemical blowing agent, in some embodiments, N,N'- dimethyl-N,N'-dinitrosoterephthalamide, diazoaminobenzene, benzenesulfonyl-hydrazide, or toluene-(4)- sulfonyl hydrazide, or the decomposed reaction product thereof.

In some embodiments, the adhesive of the present disclosure is disposed on a tape backing. Accordingly, in some embodiments, the present disclosure provides a tape comprising the adhesive of the present disclosure as described above in any of its embodiments. The tape backing can be any polymeric fdm material, paper, or a polymer-cloth laminate. Polymeric materials suitable for the backing include polyesters; polyolefins (e.g., polyethylene, polypropylene); ethyl cellulose film; cellulose esters (e.g., cellulose acetate, cellulose acetate butyrate, and cellulose propionate); polyvinylidene chloride-vinyl chloride and/or acrylonitrile polymers such as saran; vinyl chloride polymers (e.g., poly(vinyl chloride) and copolymers of vinyl chloride and vinyl acetate); polyfluoroethylenes (e.g., polytetrafluoroethylene and polytrifluorochloroethylene); polyvinyl alcohol; polyamides such as nylon; polystyrenes such as the copolymers of styrene and isobutylene; regenerated cellulose; benzyl cellulose; cellulose nitrate; gelatin; glycol cellulose; flexible acrylate and methacrylates; urea aldehyde films; polyvinyl acetal; polyvinyl butyral. In some embodiments, the tape backing is a polymeric film comprising at least one of a polyolefin, polyester, or poly(vinyl chloride). In some embodiments, the backing comprises polyethylene-laminated cloth. In some embodiments, the polymeric film backing comprises at least one of monoaxially oriented polypropylene, paper, or polyethylene terephthalate).

In some embodiments, the polymeric film tape backing of the tape is surface treated before the adhesive is applied. Useful surface treatments include electrical discharge in the presence of a suitable reactive or non-reactive atmosphere (e.g., plasma, glow discharge, corona discharge, dielectric barrier discharge or atmospheric pressure discharge), ultraviolet light exposure, electron beam exposure, flame discharge, and scuffing. The surface treatment can be applied as the polymeric film backing is being made or in a separate process. In some embodiments, the polymeric film backing is surface treated using corona discharge. An example of a useful corona discharge process is described in U.S. Pat. No. 5,972,176 (Kirk et al.).

In some embodiments, the tape includes optional low-adhesion backsize. Uow-adhesion backsizes are known to one of ordinary skill in the art can be made from a variety of materials (e.g., a silicone, fluorochemical, or carbamate). Some examples of low-adhesion backsizes are described, for example, in U.S. Pat. Nos. 2,532,011 (Dahlquist), 2,607,711 (Hendricks), and 3,318,852 (Dixon).

A paper backing for the tape of the present disclosure can be any suitable paper, for example, crepe paper having a weight of about 20 to 40 pounds per ream of 3000 square feet. The paper can be saturated with an aqueous emulsion of rubbers, for example, a mixture of carboxylated rubber latexes (e.g., carboxylated nitrile, styrene butadiene, and optionally acrylic rubber latexes) in a variety of ratios, optionally including polyethyleneglycol. Conventional additives such as pigments and antioxidants such as those described below can be included in the saturant. The aqueous saturant formulation may be 10% to 50% solids and may be applied to the paper at about 10% to 150% by weight, based on the weight of latex solids and dry paper weight. The saturated paper is typically then dried and cured at an elevated temperature up to about 180 °C. A conventional release coating is typically applied to one face of the impregnated paper backing. An example of a release coating formulation includes a 10:90 mixture of one acrylate (e.g., available from Dow Chemical Co., Midland, Mich., under the trade designation “RHOPLEX”) and a second acrylate (e.g., available from BASF, Florham Park, N.J., under the trade designation “ACRONAL S504”), which also contains some nitrile and butadiene rubbers. The mixture can be applied as an emulsion of about 15% to 50% solids, after which, the tape is again dried. Other suitable release coatings include water-based polyurethane/acrylic dispersions such as those from Hitac Adhesives and Coatings, Santa Fe Springs, CA, under the trade designations “HITAC RA-13W”, “HITAC RA-15W”, and “HITAC RA-42W”.

In some embodiments, the adhesive is present on the tape backing in a range from 20 grams per square meter (gsm) to 150 gsm. Useful amounts of adhesive can be, for example, 20 gsm to 60 gsm, 20 gsm to 40 gsm, or 40 gsm to 60 gsm for paper and polymeric film backings. For polymer/cloth laminates, useful amounts of adhesive can be, for example, 80 gsm to 150 gsm.

In some embodiments, the adhesive of the present disclosure is essentially free of volatile organic solvent. Volatile organic solvents are typically those have a boiling point of up to 150 °C at atmospheric pressure. Common organic solvents include aliphatic and alicyclic hydrocarbons (e.g., hexane, heptane, and cyclohexane), hydrocarbon solvents (e.g., benzene, toluene, xylenes, and d-limonene); acyclic and cyclic ketones (e.g., acetone, methyl ethyl ketone, and methyl isobutyl ketone, pentanone, hexanone, cyclopentanone, and cyclohexanone); ethers (e.g., diethyl ether, glyme, diglyme, diisopropyl ether, and tetrahydrofuran), esters (e.g., ethyl acetate and butyl acetate), sulfoxides (e.g., dimethyl sulfoxide), amides (e.g., N,N-dimethylformamide, N,N-dimethylacetamide, and N-methyl-2 -pyrrolidone), halogenated solvents (e.g., methylchloroform, l,l,2-trichloro-l,2,2-trifluoroethane, trichloroethylene, and trifluorotoluene), and alcoholic solvents (e.g., methanol, ethanol, or propanol such as isopropanol). The adhesive can be essentially free of any of these solvents. “Essentially free of volatile organic solvent” can mean that volatile organic solvent may be present (e.g., from a previous synthetic step or in a commercially available component) in an amount of up to 2.5 (in some embodiments, up to 2, 1, 0.5, 0.1, 0.05, or 0.01) wt%, based on the total weight of the adhesive.

In some embodiments, the adhesive is prepared using a hot melt process. Useful hot melt processes include hot melt mixing and melt extruding. Various components of the adhesive may be added in various zones of an extruder, if desired. U.S. Pat. No. 5,539,033 (Bredahl et al.), for example, describes a continuous compounding device and hot melt processing techniques. The continuous compounding device has a sequence of alternating conveying and processing zones. An elastomer can be continuously conveyed from one zone to another by the device. The processing zones are capable of masticating an elastomer and of mixing additives into an elastomer. The adhesive can be applied to a moving web of a backing, for example, directly from the compounding device so as to provide a continuous method for the manufacture of a PSA tape. The backing may be as described above in any of its embodiments. In some embodiments, hot melt processing of the adhesive, including applying the adhesive as a hot melt onto a tape backing to provide a tape, is carried out in a range from 150 °C to 210 °C, 160 °C to 200 °C, or 150 °C to 180 °C. Radiation-crosslinking can enhance, for example, the cohesive strength of an adhesive. Advantageously, the precipitated amorphous silica in the adhesives of the present disclosure can enhance the cohesive strength of the adhesive without the need for radiation-crosslinking. In some embodiments, the adhesive is not crosslinked, for example, by electron beam or ultraviolet radiation.

As shown in the Examples, below, in some embodiments, the tape of the present disclosure including an adhesive of the present disclosure is unexpectedly cleanly removable from a stainless-steel surface after exposure to a temperature of at least 90 °C and up to 100 °C for at least 30 minutes while comparable adhesives including the same components except for precipitated amorphous silica are not cleanly removable under the same conditions. See, for example, Examples 3Ta&b to 8Ta&b vs. Control 2Ta&b. Clean removal of tape from substrates refers to having no adhesive transfer or residue when evaluated according to the Adhesive Transfer Test described in the Examples, below. The clean removal of the tape of the present disclosure from substrates at high temperature suggests that the cohesive (internal) strength of the overall tape construction is greater than the adhesive strength between the tape and the substrate. Even at higher temperatures such as 110 °C, the incorporation of precipitated amorphous silica in the adhesive results in less adhesive being transferred during the Adhesive Transfer Test than when the adhesive includes the same components except for precipitated silica. In other embodiments, such as when the adhesive includes 85 parts tackifying resin to 100 parts of thermoplastic elastomeric block copolymer, the incorporation of precipitated amorphous silica in the adhesive results in less adhesive being transferred during the Adhesive Transfer Test than when the adhesive includes the same components except for precipitated silica. See, for example, Examples IT and 2T vs. Control IT. Furthermore, as shown in the Holding Power test and Rolling Ball Test described in the Examples, below, the addition of precipitated amorphous silica provides a tape with good holding power without compromising the initial tack of the adhesive. In addition to these advantages, the incorporation of precipitated amorphous silica in the adhesive of the present disclosure has been observed to reduce the odor of the adhesive and provide a tape with low ghosting. The presence of precipitated amorphous silica may also improve the humidity resistance of the tape.

The tape of the present disclosure may be useful for a variety of different applications that require the tape to be exposed to a variety of different temperatures or a wide range of temperature. The tape of the present disclosure can be useful, for example, as a masking tape or for any other use that requires high temperature holding power and clean removal. Because the adhesive of the present disclosure has been found to be cleanly removable from surfaces after temperature exposure, the adhesive of the present disclosure can be useful can be useful in tapes for the temporary holding and shipping of goods, such as appliances. In some embodiments, the tape is applied to a surface of an appliance, automobile, airplane, marine vessel, or electronic component. In some embodiments, the tape is a PVC tape or a box-sealing tape. The present disclosure provides of process of using the tape of the present disclosure. The process includes applying the tape to a surface and exposing the surface to a temperature of at least 70 °C, 80 °C, 90 °C, or 100 °C and up to 110 °C or higher. The surface may be a component of an appliance, an automobile, airplane, or marine vessel, for example. In some embodiments, the surface comprises at least one of glass, steel, high impact polystyrene, or a painted surface. The present disclosure provides the use of the tape of the present disclosure at a temperature of at least 70 °C, 80 °C, 90 °C, or 100 °C and up to 110 °C or higher.

Some Embodiments of the Disclosure

In a first embodiment, the present disclosure provides an adhesive comprising a thermoplastic elastomeric block copolymer comprising a midblock and two or more polystyrene end blocks, a tackifying resin, and precipitated amorphous silica. In a second embodiment, the present disclosure provides the adhesive of the first embodiment, wherein the thermoplastic elastomeric block copolymer comprises at least one of a polystyrene-containing triblock copolymer or a polystyrene-containing star block copolymer, wherein the polystyrene-containing triblock copolymer and polystyrene-containing star block copolymer independently comprise a block of at least one of polyisoprene, polybutadiene, or ethylene/butylene. In a third embodiment, the present disclosure provides the adhesive of the second embodiment, wherein the thermoplastic elastomeric block copolymer comprises at least one of a styrene- isoprene-styrene triblock copolymer or a styrene-isoprene star block copolymer. In a fourth embodiment, the present disclosure provides the adhesive of any one of the first to third embodiments, wherein the tackifying resin comprises at least one of a polyterpene, a rosin acid, a rosin ester, a metal rosinate, a C5 aliphatic hydrocarbon resin, a C9 aromatic resin, or a mixed aliphatic-aromatic hydrocarbon resin. In a fifth embodiment, the present disclosure provides the adhesive of any one of the first to third embodiments, wherein the adhesive comprises not more than 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0.5, or 0. 1 weight percent of a coumarone-indene resin, poly alpha methyl styrene, a polystyrene resin, a vinyl toluene-a- methyl styrene copolymer, or a polyindene resin, except where any of these is part of a mixed aliphatic- aromatic hydrocarbon resin. In a sixth embodiment, the present disclosure provides the adhesive of any one of the first to fifth embodiments, wherein the adhesive comprises not more than 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0.5, or 0. 1 weight percent of a poly(phenylene ether) resin. In a seventh embodiment, the present disclosure provides the adhesive of any one of the first to sixth embodiments, wherein the thermoplastic elastomeric block copolymer is present in an amount ranging from to 30 weight percent to 69 weight percent, 35 weight percent to 65 weight percent, from 40 weight percent to 60 weight percent, or 45 weight percent to 60 weight percent; wherein the tackifying resin is present in an amount ranging from 30 weight percent to 60 weight percent, 32 weight percent to 50 weight percent, 34 weight percent to 48 weight percent, 30 weight percent to 40 weight percent, 35 weight percent to 50 weight percent, or 35 weight percent to 55 weight percent; and wherein the precipitated amorphous silica is present in an amount ranging from 1 weight percent to 20 weight percent, from 2 weight percent to 18 weight percent, 3 weight percent to 17 weight percent, 4 weight percent to 16 weight percent, 5 weight percent to 15 weight percent, or 6 weight percent to 15 weight percent, based on the total weight of the adhesive.

In an eighth embodiment, the present disclosure provides the adhesive of any one of the first to seventh embodiments, wherein the adhesive is essentially free of organic solvent. In a ninth embodiment, the present disclosure provides the adhesive of any one of the first to eighth embodiments, wherein the adhesive is not foamed. In a tenth embodiment, the present disclosure provides the adhesive of any one of the first to ninth embodiments, wherein the adhesive is free of a chemical blowing agent. In an eleventh embodiment, the present disclosure provides the adhesive of any one of the first to tenth embodiments, wherein the precipitated amorphous silica is hydrophilic. In a twelfth embodiment, the present disclosure provides the adhesive of any one of the first to eleventh embodiments, wherein the precipitated amorphous silica is not chemically treated on the surface to provide hydrophobic groups. In a thirteenth embodiment, the present disclosure provides the adhesive of any one of the first to twelfth embodiments, wherein the precipitated amorphous silica has a BET specific surface area in a range from 35 square meters per gram (m²/g) to 400 m²/g, 50 m²/g to 300 m²/g, 100 m²/g to 300 m²/g, or 150 m²/g to 250 m²/g.

In a fourteenth embodiment, the present disclosure provides the adhesive of the any one of the first to thirteenth embodiments, disposed on a tape backing. This embodiment can also be referred to as a tape comprising the adhesive of the any one of the first to ninth embodiments disposed on a tape backing. In a fifteenth embodiment, the present disclosure provides the tape of any one of the fourteenth embodiment, wherein the adhesive is present in a range from 20 grams per square meter to 150 grams per square meter. In a sixteenth embodiment, the present disclosure provides the tape of the fourteenth or fifteenth embodiment, wherein the backing comprises paper, polyester, poly(vinyl chloride), polypropylene, or polyethylene laminated cloth. In a seventeenth embodiment, the present disclosure provides the tape of the sixteenth embodiment, wherein the tape backing comprises at least one of paper, poly(ethylene terephthalate), or monoaxially oriented polypropylene.

In an eighteenth embodiment, the present disclosure provides the tape of any one of the fourteenth to seventeenth embodiments, wherein the tape is cleanly removable from a surface after exposure to a temperature of at least 70 °C for at least one week. In a nineteenth embodiment, the present disclosure provides the tape of the eighteenth embodiment, wherein the surface comprises at least one of glass, steel, high impact polystyrene, or a painted surface. In a twentieth embodiment, the present disclosure provides the tape of the eighteenth or nineteenth embodiment, wherein the surface is a component of an automobile, airplane, marine vessel, or an appliance. In a twenty-first embodiment, the present disclosure provides the tape of any one of the fourteenth to twentieth embodiments, further comprising a low-adhesion backsize on a second face of the backing, opposite the first surface on which the adhesive is disposed. In a twenty-second embodiment, the present disclosure provides a process of making a tape, the process comprising applying the adhesive of any one of the first to thirteenth embodiments as a hot melt on a tape backing to provide the tape. In a twenty-third embodiment, the present disclosure provides a process of making the tape of any one of the fourteenth to twenty-first embodiments, the process comprising applying the adhesive of any one of the first to thirteenth embodiments as a hot melt on a tape backing to provide the tape. In a twenty-fourth embodiment, the present disclosure provides the process of the twenty-second or twenty-third embodiment, wherein the backing comprises paper, polyester, poly(vinyl chloride), polypropylene, polyethylene, or polyethylene laminated cloth. In a twenty-fifth embodiment, the present disclosure provides the process of the twenty-fourth embodiment, wherein the tape backing comprises at least one of paper, polyethylene terephthalate), or monoaxially oriented polypropylene. In a twenty-seventh embodiment, the present disclosure provides the process of any one of the twenty-second to twenty-sixth embodiments, wherein applying the adhesive as a hot melt is carried out at a temperature in a range from 150 °C to 210 °C, 160 °C to 200 °C, or 150 °C to 180 °C.

In a twenty-eighth embodiment, the present disclosure provides a process of using the tape of any one of the fourteenth to twenty-first embodiments, the process comprising applying the tape to a surface and exposing the surface to a temperature of at least 70 °C, 80 °C, 90 °C, or 100 °C. In a twenty-ninth embodiment, the present disclosure provides the process of the twenty-eighth embodiment, further comprising removing the tape from the surface after exposing the surface to the temperature of at least 70 °C, 80 °C, 90 °C, or 100 °C. In a thirtieth embodiment, the present disclosure provides the process of the twenty-eighth or twenty-ninth embodiment, wherein the surface comprises at least one of glass, steel, high impact polystyrene, or a painted surface. In a thirty-first embodiment, the present disclosure provides the process of any one of the twenty-eighth to thirtieth embodiments, wherein the surface is a component of an automobile, airplane, marine vessel, or an appliance. In a thirty-second embodiment, the present disclosure provides the use of the adhesive of any one of the first to thirteenth embodiments or the tape of any one of the of any one of the fourteenth to twenty-first embodiments at a temperature of at least 70 °C, 80 °C, 90 °C, or 100 °C.

Embodiments of the compositions and methods disclosed herein are further illustrated by the following examples, but the particular materials and amounts thereof recited in these examples, as well as other conditions and details, should not be construed to unduly limit this invention.

EXAMPLES

Unless otherwise noted, all parts, percentages, ratios, etc. in the Examples and the rest of the specification are by weight. The following abbreviations are used in this section: kg = kilogram, cm = centimeter, mm = millimeter, m = meter, in = inch, mb = milliliter, °C = degrees Celsius, °F = degrees Fahrenheit, Hz = Hertz, RH = relative humidity, lb = pound, g = gram, kg = kilogram, s = second, oz = ounce, r = radian, rpm = revolutions per minute, gsm = grams per square meter, W = watt, Phr = parts per hundred, Pa = Pascal, and min = minute.

Table 1 : Materials List

TEST METHODS

The instrument used for rheology testing of the adhesive was TA Instruments HR-20 Discovery Hybrid Rheometer (available from TA Instruments New Castle, Delaware). For measuring the storage modulus (G’) of the adhesive, a temperature sweep test was performed from 20°C to 120°C at 1.0 % strain, at a frequency of 1 Hz., using an 8.0-mm parallel plate for the measurements. The temperature ramp rate used was 5.0°C. Adhesive G’ values were recorded and reported at 25°C, 70°C and 100°C.

For measuring the complex viscosity of the adhesive at 380°F (193 °C), the logarithmic frequency sweep was done from 0. 1 r/s to 100 r/s using a 40-mm parallel plate. First, the sample was equilibrated at 380°F (193 °C) for 2 minutes before starting the test. Complex viscosity values of the adhesive were recorded and reported at 380°F (193 °C) and at 1Hz. Adhesion To Glass Test

Sample rolls were acclimated in a controlled temperature environment (73.4 +/- 3.6°F [23 +/- 2°C], 50 +/- 5% RH) before starting the test. The peel tester (IMASS SP200, IMASS Inc., Accord, MA) parameters were set to run at an average time of 5 seconds and testing speed of 90 in/min (229 cm/min). The 6-in by 12-in (15.24-cm by 30.48-cm) black painted glass panel (Soda Lime Glass, obtained from Northwestern Glass Fab, Fridley, MN) was secured to the peel tester platen. The glass panel was painted black using an acrylic lacquer spray paint on the “wire” side of the glass panel, not on the testing side. The “wire” side glows when put under a black light. The peel tester was then calibrated.

The black painted glass panel was cleaned with a quarter size quantity of diacetone alcohol and then wiped off with a “KIMWIPES” cleaning tissue. An additional “KIMWIPES” cleaning tissue was used to wipe the glass plate again, removing any remaining diacetone alcohol and making sure the glass surface looked clean. Finally, three N-heptane washes of less than about 1 mb were used, using a “KIMWIPES” cleaning tissue to wipe off the N-heptane from the glass plate in between each wash.

Tape samples were prepared by removing the outer 3 laps from a 1-in (2.54-cm) wide tape roll before cutting the roll to 1-in by 13-in (2.54-cm by 33-cm) long sample strips. The ends of the tape sample strip were then held in each hand. The left end of the tape sample was then touched to the left end of the black painted glass plate, and the right end of the tape sample was then touched to the right end of the glass plate. A rubber roller [per standard ASTM/PSTC 4.5 -lb (2.0- kg)] was then placed at the left end of the glass plate, sitting the rubber roller on top the tape sample.

The peel tester platen was then engaged to move at 90 in/min (229 cm/min), with the left hand guiding the rubber roller as it rolled down the tape sample onto the black painted glass panel. Once the peel tester platen stopped, the 4.5 -lb (2 -kg) rubber roller was removed from the tape sample and the platen returned to starting position. The left end of the tape sample was then attached to the wired leader with a stirrup and removed nearly all the slack by adjusting the platen. When the platen stopped, the average force was measured and recorded. The reported data was the average of three tests.

Adhesion To Steel Test or Adhesion to High Impact Polystyrene (HIPS) Test

Sample rolls were acclimated in a controlled temperature environment (73.4 +/- 3.6°F [23 +/- 2°C], 50 +/- 5% RH) before starting the test. The peel tester (INSTRON Model 3343Q8711, Norwood, MA) parameters were set to run at a crosshead speed of 12-in/min (30.5-cm/min), a jaw separation of 5 - in (12.7-cm), full-scale load of 100-oz (4.8-kg), a peel distance of 5-in (12.7-cm), and a peel force average distance set to measure between 2-in (5.1-cm) and 4-in (10.2-cm) of sample length. The peel tester was then calibrated.

A 2-in (5.1-cm) by 5-in (12.7-cm) stainless steel (Type 304) panel as prescribed in ASTM A666 with a bright annealed finish, 18-gauge ( 1 ,2-mm) thickness, and a polish finish on one side with a surface roughness height of 1.5 +/- 0.5 micro inches (0.038 +/ 0.013 micrometers) (obtained from Chemlnstruments, Fairfield, OH) or a HIPS panel 2-in (5. 1-cm) by 5-in (12.7-cm) having thickness 10- gauge (3.2-mm) thickness (obtained from Les Plastiques Folia, Inc., Granby, QC, Canada) was cleaned with a quarter size quantity of diacetone alcohol and then wiped off with “KIMWIPES” cleaning tissue. An additional “KIMWIPES” cleaning tissue was used to wipe the stainless-steel panel or HIPS panel again, removing any remaining diacetone alcohol making sure the surface looked clean. Finally, three N- heptane washes of less than about 1 mb were used, using a “KIMWIPES” cleaning tissue to wipe off the N-heptane from the stainless-steel plate in between each wash.

Tape samples were prepared by removing the outer 3 laps from a 1-in (2.54-cm) wide tape roll before cutting the roll to 1-in by 13-in (2.54-cm by 33-cm) long sample strips. The ends of the tape sample were then held in each hand. The sample was positioned above the stainless-steel panel or HIPS panel so the long edge of the sample was parallel to the long side of the panel and so the specimen was centered in the middle of the vertical direction of the panel. The tape sample was then laid onto the stainless-steel panel or HIPS panel, making sure there was 1-in (2.54-cm) of the tape sample extending from the top of the panel and that the remaining 7-in (17.8-cm) of the tape sample were extended from the bottom of the panel.

The tape sample was then rolled onto the stainless-steel panel or HIPS panel using a 4.5 -lb (2 -kg) rubber roller. The rubber roller was moved up and down the panel twice in each direction at approximately 24-in/min (61-cm/min) ensuring only to allow the weight of the roller to apply the force to the tape sample. A razor blade was used to cut, along the edge of the top of the panel, the 1-in (2.54 -cm) of the tape sample that was extended from the top of the panel. The extended 7-in (17.8-cm) tape sample was held from the bottom of the panel, and the tape sample was peeled back by hand 1-in (2.54-cm) from the bottom edge of the panel. The bottom end of the stainless-steel or HIPS panel was clamped into the lower jaw of the peel tester. The top end of the 7-in (17.8-cm) tape sample extending from the bottom of the panel was clamped into the upper jaw of the peel tester. The crosshead peel test was carried out on the peel tester, and the average peel force value was recorded. The reported data was the average of three tests.

Rolling Ball Test

Sample rolls were acclimated in a controlled temperature environment (73.4 +/- 3.6°F [23 +/- 2°C], 50 +/- 5% R.H) before starting the test. A TT100 Modified Chemlnstruments Inclined Ramp (obtained from Chemlnstruments, Fairfield, OH) and level platform were used to perform the test. The platform was leveled with an accompanying bubble level, which was set in the center of the platform. The three base screws were adjusted to align the bubble within the circle target. Both ends of the platform were secured with tape to prevent movement between tests.

A strip of 2-in (5.08-cm) wide single-liner, double coated tape obtained under the trade designation “3M FLEXOMOUNT” Plate Mounting Tape 411 from 3M Company, St. Paul, MN, was applied down the length of the platform. The 7/16-in (1.1-cm), 5.6-g stainless-steel ball bearings were cleaned with one wash of diacetone alcohol of less than about 1 mL, using a “KIMWIPES” cleaning tissue to remove the diacetone alcohol from ball bearing surface. This was followed by one dry wipe with an additional “KIMWIPES” cleaning tissue to remove any remaining diacetone alcohol from the ball bearing surface, followed by three washes with N-heptane of less than about 1 mL, using a “KIMWIPES” cleaning tissue to wipe off the remaining N-heptane from the ball bearing surface between each wash. After each ball bearing was cleaned, they were placed on an aluminum tray lined with “KIMWIPES” cleaning tissue. Nitrile rubber disposable gloves were used to place the ball bearing on the aluminum tray. After the cleaning procedure was completed, the ball bearings were allowed to sit and acclimate in a temperature-controlled environment at (73.4 +/- 3.6°F [23 +/- 2°C], 50 +/- 5% RH) for 20 minutes.

Tape samples were prepared by removing the outer 3 laps from a 1-in (2.54-cm) wide tape roll before cutting the roll to 1-in (2.54-cm) by 12-in (30.5-cm) long strips. With adhesive side facing up, the tape sample was laid on the double-coated tape on the platform base. The tape sample was secured and centered in the middle of the 2-in (5. 1-cm) wide double coated tape. It was ensured that the tape sample did not touch the tape adhesive surface but made sure it laid flat to the platform.

The TT100 Modified Chemlnstruments Inclined Ramp was placed on the left side of the level platform with the left edge of the ramp flush with the left edge of the platform with its rear touching the two guide pins located on the left side of the platform. The ramp was aligned so that it was centered on top of the surface of the 1-in (2.54-cm) wide tape sample. A McMaster Carr # 2056A23 300-mm graduated ruler was placed in the lengthwise direction of the platform along the bottom right edge of the ramp. A ball bearing, handled using the disposable gloves, was placed on top of the ramp. The ball bearing holding mechanism on the ramp was activated, allowing the ball bearing to roll freely down the ramp and on to the adhesive surface of the tape sample. The distance the ball bearing traveled was measured using the ruler. The distance to the center point of the ball bearing was measured in millimeters to determine the rolling ball tack value. The reported data was the average of three tests.

Shear to Steel Test

A stainless-steel panel 2-in (5.1-cm) by 3-in (7.6-cm) stainless steel (Type 304) as prescribed in ASTM A666 with a bright annealed finish, 18-gauge (1.2-mm) thickness, and a polish finish on one side with a surface roughness height of 1.5 +/- 0.5 micro inches (0.038 +/ 0.013 micrometers) (obtained from Chemlnstruments, Fairfield, OH) was cleaned with a quarter size quantity of diacetone alcohol and then wiped off with “KIMWIPES” cleaning tissue. An additional “KIMWIPES” cleaning tissue was used to wipe the stainless-steel panel again, removing any remaining diacetone alcohol making sure the surface looked clean. Finally, three N-heptane washes of less than about 1 mL were used, using a “KIMWIPES” cleaning tissue to wipe off the N-heptane from the stainless-steel plate in between each wash. Tape samples were prepared by cutting the roll to 0.5-in by 6.0-in (1.27-cm by 15.24-cm) long strips. The ends of the tape sample were then held in each hand. The test sample was positioned above the stainless-steel panel, so the tape sample was centered in the middle of the vertical direction of the panel. The tape sample was then laid onto the stainless-steel panel. The tape sample was then rolled onto the stainless-steel panel using a 4.5 -lb (2 -kg) rubber roller. The rubber roller was moved up and down the panel twice in each direction at approximately 24-in/min (61-cm/min) ensuring only to allow the weight of the roller to apply the force to the tape sample. A razor blade was used to cut the adhered length of the tape sample to 0.5 in (1.27 cm), so that the tape sample adhered area was 0.5-in (1.27-cm) x 0.5-in (1.27- cm).

A clamp was placed on the free end of the tape sample, ensuring that the clamp extended completely across the width of the tape sample and was aligned to uniformly distribute the load. This was then placed in the test stand so that the free end of the tape sample was vertical, ensuring that no peel forces acted on the specimen. A 1000-g mass was applied to the clamp gently so as to cause no shear impact force on the tape sample. Recorded the time elapsed in which the test sample separated completely from the test panel. The reported data was the average of three tests.

Adhesive Transfer Test

The level of adhesive transfer to a stainless-steel panel was measured after the tape samples were subjected to a bake cycle and the tape samples were removed at the bake temperature. The tape samples were tested at 3 different oven temperatures with deviation of +/- 5 °F: 200°F, 210°F, and 230°F (93 °C, 99°C, and 110°C, respectively).

A 2-in (5.1-cm) by 5-in (12.7- cm) stainless steel (Type 304) panel as prescribed in ASTM A666 with a bright annealed finish, 18-gauge ( 1 ,2-mm) thickness, and a polish finish on one side with a surface roughness height of 1.5 +/- 0.5 micro inches (0.038 +/ 0.013 micrometers), obtained from Chemlnstruments, Fairfield, OH, was cleaned with a quarter size quantity of diacetone alcohol and then wiped off with “KIMWIPES” cleaning tissue. An additional “KIMWIPES” cleaning tissue was used to wipe the stainless-steel panel again, removing any remaining diacetone alcohol making sure the surface looked clean. Finally, three N-heptane washes of less than about 1 mb were used, using a “KIMWIPES” cleaning tissue to wipe off the N-heptane from the stainless-steel plate in between each wash.

The tape samples were prepared by using a 1-in (2.54-cm) wide tape roll, removing the outer 3 laps of that roll, and acclimating the roll to room temperature of 70°F (21 °C) before starting the test. A tape sample was made by cutting the roll into 8-in (20.3-cm) long strips.

Preparing for the test started with placing 4-in by 8-in (10.16-cm by 20.3-cm) stainless steel panels on a smooth working surface. The 8-in (20.3-cm) long tape sample was applied, adhesive side down, parallel to the 4-in (20.3-cm) side edge of the steel panel at least 0.25-in (0.635-cm) to the left of the edge. A tab was left beyond the top edge of the panel for handling while a space was left at the botom end of the panel for identifying the tape sample with an affixed label. All tape samples were applied maintaining a minimum 0.25-in (0.635-cm) spacing between tape samples or from the edge of the panel.

Each tape sample was rolled down with one back and forth pass of a hand operated rubber covered roller [per standard ASTM/PSTC 4.5 -lb (2.04-kg)] at a roll down rate of approximately 2-in/s (5.08-cm/s). Next a ruler and felt tip pen were used to draw a line parallel to the long edge of the panel and 2-in (5.08-cm) down from the top of the panel. The ruler and a razor blade were then used to score the tape samples at the botom portion of the panel above the label writen on each tape sample.

Panels were placed in a circulating air type electric oven capable of maintaining from 150 to 300°F (65.6 to 149°C) +/- 5°F (Despatch LFD series Oven, Model: LFD2-11-3, Despatch Industries, Minneapolis, MN). The panels were allowed to bake for 30 +/- 2 min at desired temperature (200°F, 210°F, and 230°F (93°C, 99°C, and 110°C, respectively). At the 30 min time mark, the tape sample was peeled from the hot steel panel using an approximate 90-degree removal angle at a rate of 2-in/s (5.08- cm/s). Finally, panels were visually inspected for removal areas for adhesive transfer, and results were reported to the nearest 10%, except for none, meaning no adhesive was transferred, and not more than 5%, meaning a trace amount was transferred. The test was repeated three times at each temperature.

Adhesive Examples 1A and 2A (Ex. 1A and 2A) and Control Example (C. 1A)

Adhesive formulations used in the examples are given in Tables 2, 6, and 11. The thermoplastic elastomer block copolymer, the tackifying resin, silica filler (if present), and the antioxidant were melt blended in atwin screw extruder (Model Omega 40 from Steer America, Uniontown, OH) at 380 °F (193 °C) using 100 rpm. The composition of Ex. 1A and 2A and C. 1A are shown in Table 2, below. The storage modulus and complex viscosity of these adhesives is shown in Table 3, below.

Table 2, Composition of Ex, 1A, Ex, 2A, and C. 1A Tape Examples Control IT (C. IT) and Examples IT and 2T (Ex. IT and 2T)

The molten adhesive from C. 1A, Ex. 1A, and Ex. 2A were then coated at 350 °F (177 °C) onto PET backings using a contact die to make Tape Examples C. IT, Ex. IT, and Ex. 2T, respectively. The PET backing was first corona treated at 50.0 W/min per m². The corona treatment unit was manufactured by Enercon, Model LM5809-14PVH-25LB1B, Menomonee Falls, WI. The coating weight of the adhesive was 26.0 +/- 2 gsm. The Adhesion to Steel Test, the Rolling Ball Test, and the Shear to Steel Test were carried out on C. IT, Ex. IT, and Ex. 2T, and the results are shown in Table 4. The Adhesive Transfer Test was carried out on C. IT, Ex. IT, and Ex. 2T, and the results are shown in Table 5, below.

Table 4: Tape Test Results for C. IT, Ex, IT, and Ex, 2T

Table 5: Adhesive Transfer Test Results for C. IT, Ex, IT, and Ex, 2T

Adhesive Examples Control 2A (C. 2A) and Examples 3A to 8A (Ex. 3A to 8A)

Adhesive Examples C. 2A and Ex. 3A to 8A were prepared as described for C. 1A and Ex. 1A and Ex. 2A except using the materials shown in Table 6, below. The storage modulus and complex viscosity of these adhesives is shown in Table 7, below.

Table 6: Composition of Ex, 3A to Ex 8A and C. 2A Table 7: Rheology Data- Storage Modulus and Complex viscosity data for Ex, 3 A to Ex, 8 A and C. 2A

Tape Examples Control 2Ta&b (C. 2Ta&b) and Examples 3Ta&b to 8Ta&b (Ex. 3Ta&b to 8Ta&b) The molten adhesive from C. 2A and Ex. 3A to 8A was coated at 350 °F (177 °C) on to a paper backing using a contact die to make Tape Examples C. 2Ta and Ex. 3Ta to 8Ta, respectively. The molten adhesive from C. 2A and Ex. 3A to 8A was coated at 350 °F (177 °C) on to a PET backing using a contact die to make Tape Examples C. 2Tb and Ex. 3Tb to 8Tb, respectively. The corona treatment on PET was carried out as described for C. IT, Ex. IT, and Ex. 2T. The coating weight of the adhesive was 26.0 +/- 2 gsm. The Adhesion to Steel Test, Adhesion to Glass, the Rolling Ball Test, and the Shear to Steel Test were carried out on C. 2Ta and Ex. 3Ta to 8Ta on a paper backing, and the results are shown in Table 8. The Adhesion to Steel Test, the Rolling Ball Test, and the Shear to Steel Test were carried out on C. 2Tb and Ex. 3Tb to Ex. 8Tb on a PET backing, and the results are shown in Table 9. The Adhesive Transfer Test was carried out on C. 2Ta&b and Ex. 3Ta&b to 8Ta&b on both backings, and the results are shown in Table 10, below, and the results were the same for both backings.

Table 8: Tape Test Results C. 2Ta and Ex. 3Ta to 8Ta - Paper Backing

Table 10: Adhesive Transfer Test Results for PET Film and Paper Backed C. 2Ta&b and Ex. 3Ta&b to

8Ta&b

Adhesive Examples Control 3A (C. 3A) and Examples 9A to 11A (Ex. 9A to 11A)

Adhesive Examples C. 3A and Ex. 9A to 11A were prepared as described for C. 1A and Ex. 1A and Ex 2A except using the materials shown in Table 11, below. The storage modulus and complex viscosity of these adhesives is shown in Table 12, below.

Table 11. Composition of Ex, 9A to Ex, 11A and C. 3A

Table 12: Storage Modulus (G’) and Complex Viscosity for Ex 9A to Ex, 11A and C. 3A

Tape Examples Control 3T (C. 3T) and Examples 9T to 1 IT (Ex. 9T to 1 IT)

The molten adhesive from C. 3A and Ex. 9A to 11A was coated at 350 °F (177 °C) on to a MOPP backing using a contact die to make Tape Examples C. 3T and Ex. 9T to 1 IT, respectively. The corona treatment on MOPP was carried out as described for C. IT, Ex. IT, and 2T. The coating weight of the adhesive was 26.0 +/- 2 gsm. The Adhesion to Steel Test, Adhesion to Glass, Adhesion to HIPS, the Rolling Ball Test, and the Shear to Steel Test were carried out on C. 3T and Ex. 9T to 1 IT on a MOPP backing, and the results are shown in Table 13. Table 13: Tape Test Results - MOPP Backing for C. 3T and Ex, 9T to 11T

The Adhesive Transfer Test was carried out for Tape Examples C. 3T and Ex. 9T to 1 IT at 200 °F (93 °C). For C. 3T, 10% adhesive transfer was observed, but no adhesive transfer was observed for Ex. 9T to I IT. Various modifications and alterations of this disclosure may be made by those skilled the art without departing from the scope and spirit of the disclosure, and it should be understood that this invention is not to be unduly limited to the illustrative embodiments set forth herein.

Claims

What is claimed is:

1. An adhesive comprising: a thermoplastic elastomeric block copolymer comprising a midblock and two or more polystyrene end blocks; a tackifying resin; and precipitated amorphous silica.

2. The adhesive of claim 1, wherein the thermoplastic elastomeric block copolymer comprises at least one of a polystyrene-containing triblock copolymer or a polystyrene -containing star block copolymer, wherein the polystyrene-containing triblock copolymer and polystyrene-containing star block copolymer independently comprise a block of at least one of polyisoprene, polybutadiene, or ethylene/butylene .

3. The adhesive of claim 2, wherein the thermoplastic elastomeric block copolymer comprises at least one of a styrene-isoprene-styrene triblock copolymer or a styrene-isoprene star block copolymer.

4. The adhesive of any one of claims 1 to 3, wherein the tackifying resin comprises at least one of a polyterpene, a rosin acid, a rosin ester, a metal rosinate, a C5 aliphatic hydrocarbon resin, a C9 aromatic resin, or a mixed aliphatic-aromatic hydrocarbon resin.

5. The adhesive of any one of claims 1 to 4, wherein the thermoplastic elastomeric block copolymer is present in an amount ranging from to 30 weight percent to 69 weight percent, wherein the tackifying resin is present in an amount ranging from 30 weight percent to 60 weight percent, and wherein the precipitated amorphous silica is present in an amount ranging from 1 weight percent to 20 weight percent, based on the total weight of the adhesive.

6. The adhesive of any one of claims 1 to 5, wherein the precipitated amorphous silica BET specific surface area in a range from 35 square meters per gram to 400 square meters per gram.

7. The adhesive of any one of claims 1 to 6, wherein the adhesive is not foamed.

8. The adhesive of any one of claims 1 to 7, wherein the adhesive is essentially free of organic solvent.

9. A tape comprising the adhesive of any one of claims 1 to 8 disposed on a tape backing.

10. The tape of claim 9, wherein the tape backing comprises at least one of paper, polyester, poly(vinyl chloride), polypropylene, polyethylene, or polyethylene laminated cloth.

11. The tape of claim 10, wherein the tape backing comprises at least one of paper, polyethylene terephthalate), or monoaxially oriented polypropylene.

12. A process of using the tape of any one of claims 9 to 11, the process comprising: applying the tape to a surface; and exposing the surface to a temperature of at least 70 °C.

13. The process of claim 12, further comprising: removing the adhesive from the surface after exposing the surface to the temperature of at least 70 °C, wherein the adhesive is cleanly removed from the surface.

14. A process of making a tape, the process comprising: applying the adhesive of any one of claims 1 to 8 as a hot melt on a tape backing to provide the tape.

15. The process of claim 14, wherein applying the adhesive as a hot melt is carried out at a temperature of at least 150 °C.