Highly asymmetric triblock polymer compositions and methods for making same

Abstract

A styrenic triblock copolymer composition having a combination of excellent tensile strength and a high melt index, excellent manufacturing, finishing, and handling properties, forming stable pellets, and for use in applications including, but not limited to, adhesives, coatings, and flexographic printing. The composition comprises a first block that is a polymer of a monoalkenyl arene, a second block that is a polymer of a conjugated diene, and a third block that is a polymer of a monoalkenyl arene, wherein the third block has a peak molecular weight of about 0.06 to about 0.4 times that of the first block.

Description

[Technical Field]

[0001] <Related Applications> This application claims priority from U.S. Provisional Application No. 62 / 517,849 (filed June 9, 2017), the entire disclosure of which is incorporated herein by reference for all purposes.

[0002] The present disclosure relates to the use of styrenic block copolymers for use in applications including adhesives, flexographic printing, and paving or roofing materials. [Background technology]

[0003] Pure styrenic diblock copolymers are in high commercial demand in the adhesives industry because they can impart desirable properties such as high tack and low hot melt viscosity, allowing for more efficient conversion in the production of pressure-sensitive adhesive labels. However, styrenic diblock copolymers cannot be easily manufactured into a manageable pellet form. Typically, such products are supplied as rubber bales. Furthermore, obtaining these conventional styrenic diblock copolymers in pellet form requires investments that are sold at special prices and also suffer from excessive cold flow of the polymer. Summary of the Invention [Problem to be solved by the invention]

[0004] There remains a need to develop block copolymer compositions that have desirable processing properties. [Means for solving the problem]

[0005] In one embodiment, a composition including a styrenic triblock copolymer is disclosed, along with a method for preparing the same. The composition includes a first block that is a polymer of a monoalkenyl arene, a second block that is a polymer of a conjugated diene, and a third block that is a polymer of a monoalkenyl arene, the block copolymer having a peak molecular weight in the range of 10,000 to 500,000 g / mol, the third block having a peak molecular weight in the range of 0.06 to 0.4 times the peak molecular weight of the first block, and the composition having a total arene content in the range of 15 to 40 wt%.

[0006] In another aspect, a method for preparing a highly asymmetric triblock ("HAT") copolymer composition is disclosed. The method includes polymerizing a sufficient amount of a first monoalkyl arene to form a first polymer block (A1), adding a conjugated diene, polymerizing the conjugated diene to form a second polymer block (B) attached to the first polymer block, and adding a sufficient amount of a second monoalkyl arene to form a third polymer block attached to the second polymer block, thereby forming a HAT copolymer. The ratio of the peak molecular weight of the third block to the peak molecular weight of the first block is in the range of 0.06 to 0.4.

[0007] In yet another aspect, a method for preparing a highly asymmetric triblock ("HAT") copolymer composition via a coupling polymerization process is disclosed. The method includes polymerizing a sufficient amount of a first monoalkylarene to form a first polymer block (A2), adding a conjugated diene, polymerizing the conjugated diene to form a second polymer block (B) attached to the first polymer block, adding a sufficient amount of a second monoalkylarene to form a third polymer block (A1) attached to the second polymer block, and adding a coupling agent X to form a HAT copolymer having the formula (A2BA1)X. The ratio of the peak molecular weight of the first block (A2) to the peak molecular weight of the third block (A1) is in the range of 0.06 to 0.4.

[0008] The following terms are used throughout the specification and have the following meanings unless otherwise indicated.

[0009] "Molecular weight" refers to the true molecular weight in g / mol of a copolymer or block of a copolymer, which can be measured by gel permeation chromatography (GPC) using polystyrene calibration standards according to ASTM 5296-11. It will be understood by those skilled in the art that GPC analyses report column retention times, which are then converted to standardized molecular weights, usually using polystyrene standards. These "styrene equivalent" molecular weights are commonly used in the polymer industry. For purposes of this disclosure, peak molecular weights are reported as true molecular weights based on molar mass, rather than GPC "styrene equivalent" retention times.

[0010] Peel adhesion tests (FTM 1, peel adhesion (180°) at 300 mm / min) and loop tack tests (FTM 9, loop tack measurement) were performed using an RK K Control Coater (RK PrintCoat Instruments Ltd.) as described in Finat Technical Handbook, Test Methods, 9th edition, FINAT, Netherlands, May 2014.

[0011] Tensile strength is determined according to ASTM D412.

[0012] Melt index refers to the melt flow of a polymer measured under condition G at a temperature of 200° C. and a load of 5 kg according to ASTM D 1238. It is expressed in grams of polymer melt passing through an orifice in 10 minutes.

[0013] "Diblock copolymer" refers to the proportion of free diblock present in the composition.

[0014] "Coupling efficiency" refers to the number of coupled polymer molecules divided by the number of coupled polymer molecules plus the number of uncoupled polymer molecules. For example, if the coupling efficiency is 80%, the polymer contains 20% diblock and 80% triblock and multi-arm blocks.

[0015] "HAT" refers to a highly asymmetric triblock copolymer, and the term "highly asymmetric" refers to the differences between the polystyrene blocks of the HAT polymer. In some embodiments, HAT is blended with a second polymer or other component to form a blended HAT. The second polymer may include styrene blocks or combinations thereof. Reference to the term HAT includes HAT blends.

[0016] "Hydrogenated HAT polymer" generally refers to a HAT polymer that has been contacted with a hydrogenation catalyst for a period of time and under appropriate conditions to improve the thermal, UV, and oxidative stability, and therefore the weatherability, of the final polymer.

[0017] "Vinyl-containing" refers to a polymer product produced by polymerizing 1,3-butadiene via a 1,2-addition reaction to produce monosubstituted olefin or vinyl groups adjacent to the polymer backbone. The effect of 3,4-addition polymerization of isoprene on the final properties of any block copolymer is similar to that from the 1,2-addition of butadiene.

[0018] Disclosed herein are compositions comprising HAT polymers and HAT, and methods for their preparation. HAT polymers typically have physical properties (e.g., low cohesive strength, low melt viscosity, and improved tack) typically found in diblock copolymers over a temperature range above 150°C, and triblock copolymers similar handling properties such that pellets can be formed at other temperature ranges, e.g., below 110°C. HAT polymers can be used as components in adhesives, pressure-sensitive adhesives, flexography, paving, and roofing applications.

[0019] <HAT Polymer Composition - Triblock A1 - B - A2> In one embodiment, the HAT polymer composition is a triblock polymer called A1 - B - A2, where both A1 and A2 are monoalkenylarene blocks and B is a conjugated diene block, consisting of a smaller A2 block at the end. A1 refers to the larger of two monoalkenylarene blocks having substantially different molecular weights (MW). The peak MW of the A1 block is substantially larger than the peak MW of the A2 block, and its asymmetry can be represented as A2 = A1*X, where X ranges from about 0.06 to 0.40. In one embodiment, the peak MW of the A1 block is at least 20%, 30%, or 40% larger than the peak MW of the A2 block. In some embodiments, the composition has the formula (A2 - B - A1) n including X, where n is an integer from 2 to 6 and X is the residue of a coupling agent. Linear coupling HAT is formed when n is equal to 2. When n exceeds 2, dendritic or star-shaped coupling HAT will be formed. In the manner in which the coupled HAT polymer is coupled to the coupling agent in the A1 block, the coupled HAT has the formula (A2 - B - A1) n including X.

[0020] In one embodiment, the A1 block is formed from a monoalkenyl arene monomer that is different from the monoalkenyl arene monomer that comprises the A2 block, e.g., in one example, the A1 block comprises substantially pure styrene and the A2 block comprises substantially pure p-methylstyrene. HAT polymers that include A1 and A2 blocks composed of dissimilar monoalkenyl arenes can be referred to herein as distinct-edge HAT polymers.

[0021] In embodiments, the HAT polymer comprises, consists of, or consists essentially of a HAT, a heterocyclic HAT, a coupled HAT, a hydrogenated HAT, or a combination thereof. The term "HAT polymer" encompasses any of the HAT polymers described herein.

[0022] In the above formula, the monoalkenyl arene block comprises any polymerized monoalkenyl arene monomer. Examples include styrene, o-methylstyrene, p-methylstyrene, p-tert-butylstyrene, 2,4-dimethylstyrene, α-methylstyrene, vinylnaphthalene, vinyltoluene, and vinylxylene, or mixtures thereof. In a further aspect, the monoalkenyl arene block comprises a substantially pure monoalkenyl arene monomer. In some embodiments, the monoalkenyl arene block comprises styrene, which can be used as a substantially pure monomer. For example, styrene can be the major component in a mixture with a small proportion of a structurally related vinyl aromatic monomer. Structurally related vinyl aromatic monomers that can be used as minor components in a mixture containing styrene as the major component can be o-methylstyrene, p-methylstyrene, p-tert-butylstyrene, 2,4-dimethylstyrene, α-methylstyrene, vinylnaphthalene, vinyltoluene, vinylxylene, or combinations thereof. In some aspects, the proportion of minor vinyl aromatic monomers in a mixture containing styrene should not exceed about 10% by weight.

[0023] In embodiments, the monoalkenyl arene content of the A1 block ranges from 5 wt% to 50 wt%, alternatively from 5 to 40 wt%, alternatively from 10 to 35 wt%, based on the total weight of the HAT polymer. In embodiments, the monoalkenyl arene content of the A2 block of the HAT polymer ranges from 1 to 20 wt%, alternatively from 15 wt%, alternatively from 1 to 10 wt%, based on the total weight of the HAT polymer.

[0024] In some embodiments, the peak molecular weight of each A1 block is 5000-50,000 g / mol, alternatively 10,000-40,000 g / mol, alternatively 10,000-30,000 g / mol. In one embodiment, the peak molecular weight of each A2 block is 1000-10,000 g / mol, alternatively 1000-8000 g / mol, alternatively 1000-5000 g / mol.

[0025] In embodiments, the molecular weights of the relative A1 and A2 blocks can be expressed as a range of A2 molecular weights from (0.06)A1 to (0.4)A1, where A1 and A2 are expressed as molecular weights without regard to units.

[0026] In one embodiment, the conjugated diene block can comprise any suitable conjugated diene, or the conjugated diene has from 4 to 10 carbon atoms. In one embodiment, the conjugated diene is substantially pure monomer. butadiene It is formed from 2,3-dimethyl-1,3- butadiene , 1,3-pentadiene and 1,3-hexadiene, and 7-methyl-3-methylene-1,6-octadiene (also called myrcene), in small proportions up to 10% by weight. butadiene Alternatively, substantially pure isoprene may be utilized for the preparation of the conjugated diene block, or alternatively, substantially pure butadiene.

[0027] In some embodiments, the peak molecular weight of each conjugated diene block is from 10,000 g / mol to 500,000 g / mol, alternatively from 10,000 g / mol to 200,000 g / mol, alternatively from 10,000 g / mol to about 150,000 g / mol.

[0028] In embodiments where butadiene is the conjugated diene monomer, the vinyl content of the conjugated diene block (i.e., B block) ranges from 8 mol% to 95 mol%, alternatively from 10 mol% to 85 mol%, alternatively from 12 mol% to 65 mol%. In embodiments where isoprene is the conjugated diene monomer, the vinyl content of the B block ranges from 8 mol% to 95 mol%, alternatively from 10 mol% to 85 mol%, alternatively from 12 mol% to 65 mol%.

[0029] In one embodiment, the low vinyl B block is a conjugated diene block containing less than 15 mol% vinyl, based on the overall composition of the conjugated diene block, while the high vinyl B block is a conjugated diene block containing more than 25 mol% vinyl, based on the overall composition of the conjugated diene block.

[0030] In some embodiments, the conjugated diene block (i.e., B block) of the HAT polymer comprises a tapered vinyl content, where "tapered" refers to a distribution of vinyl content such that the end of the B block adjacent to the monoalkenyl arene block has a vinyl content of less than about 15 mol % and the opposite end of the block (distal from the monoalkenyl arene block) has a vinyl content of greater than about 25 mol %.

[0031] In one embodiment, the vinyl content of the B block increases gradually throughout the B block. In a further aspect, the B block includes regions of low vinyl content near the A1 block, followed by regions of high vinyl content distal to either the A1 or A2 block, depending on which of the two blocks is polymerized first. In some embodiments, the vinyl content of the B block starts at less than 15 mol % and gradually increases, on average, throughout the block. In a further aspect, the vinyl content at the first end of the B block ranges from 7 to 15 mol % and increases therefrom, on average, throughout the B block. At least the last 10 to 49%, or at least the last 25 to 49%, of the B block has a vinyl content greater than 25 mol %, or from 25 to 80 mol %, or from 40 to 75 mol %, or from 50 to 65 mol %.

[0032] In some embodiments, the conjugated diene block (i.e., B block) of the HAT polymer comprises a highly saturated B block in which addition of hydrogen molecules occurs at C=C moieties within the B block. Highly saturated B blocks include B blocks in which addition of hydrogen molecules occurs at greater than 92 mol %, alternatively greater than 95 mol %, or even greater than 98 mol % of the C=C moieties within the B block.

[0033] In some embodiments, the conjugated diene block (i.e., B block) of the HAT polymer comprises a partially saturated B block, wherein addition of hydrogen molecules occurs to only a portion of the C=C moieties in the B block. The partially saturated B block comprises a B block, wherein addition of hydrogen molecules occurs in the range of 20 to 90 mol %, alternatively 20 to 80, or 20 to 50 mol % of the C=C moieties in the B block.

[0034] In another embodiment, the mixed B block comprises a mixture of butadiene and isoprene, or a mixture of substantially pure butadiene and substantially pure isoprene. butadieneThe molar ratio of isoprene to isoprene is 9:1, 4:1, 3:1, 2:1, 1:1, 1:2, 1:3, 1:4, or 1:9. butadiene and the amount of butadiene in the mixed B block including isoprene is either at least 20 wt %, at least 40 wt %, at least 60 wt %, or at least 80 wt %, based on the total weight of the entire mixed B block.

[0035] In one aspect, the B block of the HAT polymer may comprise, consist of, or consist essentially of a low vinyl content, high vinyl content, or tapered vinyl content B block. In another aspect, the B block may be highly saturated, partially saturated, unsaturated, or a combination thereof, and the B block may be a mixed B block. In one embodiment, the HAT polymer may comprise a mixed midblock having the amount of two dienes in a ratio of 10:90 to 90:10, e.g., isoprene and butadiene A mixture of butadiene and myrcene. The HAT polymers may comprise, consist of, or consist essentially of any of the chemical and physical properties (e.g., melt viscosity, tensile strength, etc.) present in the individual components (e.g., coupled HAT, high vinyl content B block, etc.).

[0036] In one embodiment, the HAT polymer (A1-B-A2) has a peak MW from 10,000 to 500,000 g / mol, alternatively from 10,000 to 300,000 g / mol, alternatively from 10,000 to 100,000 g / mol.

[0037] Optional Ingredients: The HAT composition may further comprise one or more additional ingredients such as tackifiers, waxes, stabilizers (e.g., antioxidants, UV stabilizers), plasticizers (e.g., benzoates, phthalates), paraffinic oil, naphthenic oil, nucleating agents, optical brighteners, pigments, dyes, brighteners, biocides, flame retardants, antistatic agents, antislip agents, antiblocking agents, lubricants, fillers, or combinations thereof.

[0038] In some embodiments, the HAT composition may further contain a stabilizer, non-limiting examples of which include primary antioxidants and secondary antioxidants. Typically, primary antioxidants and secondary antioxidants are distinguished by their chemical structure. Hindered phenols and arylamines are examples of common primary antioxidants that scavenge alkoxy and peroxy radicals. The primary antioxidant may be present in an amount of 0.3 to 1.5 wt %, or alternatively 0.5 to 1 wt %, based on the total weight of the HAT composition.

[0039] Secondary antioxidants can also be used in conjunction with the primary antioxidants. Phosphites and thiocyanates are common secondary antioxidants that scavenge hydroperoxides produced during the autoxidation cycle of polymers exposed to heat and oxygen. Secondary antioxidants can be included in amounts of 0.5 to 2.5 wt. %, alternatively 0.5 to 2 wt. %.

[0040] Preparation Method: HAT polymers can be synthesized as A1-B-A2 or A2-B-A1. In some embodiments, the polymers are prepared by sequential polymerization: i) polymerizing a monoalkylarene block; ii) adding a conjugated diene monomer to the reaction mixture, which adds to the monoalkylarene block and subsequently polymerizes; and iii) adding a monoalkylarene monomer to the reaction mixture, which adds to the conjugated diene block and subsequently polymerizes. In the sequential HAT polymerization process, the A1 block or the A2 block can be prepared in the first step. Depending on the coupling method, the A2 block is prepared first, followed by B, A1, and final coupling reactions. In embodiments, HATs can be prepared by living anionic polymerization, as exemplified in U.S. Pat. Nos. 7,728,074 and 7,622,519.

[0041] HAT polymers can be prepared by contacting the monomers with an organic alkali metal compound in a suitable solvent at temperatures between -150°C and 300°C, or alternatively between 0°C and 100°C. Particularly effective polymerization initiators are organolithium compounds having the general formula RLi, where R is an aliphatic, alicyclic, alkyl-substituted alicyclic, aromatic, or alkyl-substituted aromatic radical having 1 to 20 carbon atoms. Suitable solvents include aliphatic, alicyclic, alkyl-substituted alicyclic, aromatic, and alkyl-substituted aromatic hydrocarbons, ethers, and mixtures. Examples of aliphatic hydrocarbons include butane, pentane, hexane, and heptane; alicyclic hydrocarbons such as cyclopentane, cyclohexane, and cycloheptane; alkyl-substituted alicyclic hydrocarbons such as methylcyclohexane and methylcycloheptane; aromatic hydrocarbons such as benzene; alkyl-substituted hydrocarbons such as toluene and xylene; and ethers such as tetrahydrofuran, diethyl ether, and di-n-butyl ether.

[0042] In embodiments, a vinyl modifier can be added to control the vinyl content of the conjugated diene block. In the case of a high-vinyl conjugated diene block prepared in the presence of a vinyl modifier, the vinyl modifier can be added simultaneously, simultaneously, or nearly simultaneously with the conjugated diene monomer. Conjugated diene blocks containing high vinyl content and their corresponding coupled counterparts can be prepared as disclosed in U.S. Pat. No. 7,125,940. Conjugated diene blocks with tapered vinyl content can be prepared by adding the conjugated diene monomer to the reaction mixture, followed by the gradual addition of the vinyl modifier in a controlled manner. Vinyl modifiers that can be used include polar compounds such as ethers, amines, and other Lewis bases, such as dialkyl ethers of glycols. Examples include dialkyl ethers of ethylene glycol containing the same or different terminal alkoxy groups and optionally having alkyl substituents on the ethylene group; (e.g., monoglyme, diglyme, diethoxyethane, 1,2-diethoxypropane, 1-ethoxy-2,2-tert-butoxyethane, or 1,2-diethoxypropane). The amount of vinyl modifier needed to achieve the desired vinyl content is determined by the chemical structure and properties of the vinyl modifier. Generally, the modifier is added in an amount of 50 to 100,000 ppm relative to the solvent.

[0043] In some embodiments, to obtain a HAT polymer with the desired chemical and physical properties required for a particular application, the HAT polymer is optionally subjected to catalytic hydrogenation. Hydrogenation methods include standard methods used to hydrogenate styrene-butadiene block copolymers. Hydrogenation can involve the use of a hydrogenation catalyst, such as a heterogeneous hydrogenation catalyst (e.g., a palladium catalyst such as Pd supported on carbon (Pd / C), a platinum catalyst such as PtO, a nickel catalyst such as Raney nickel (Ra-Ni), a rhodium catalyst, or a ruthenium catalyst). Homogeneous or colloidal hydrogenation catalysts, such as aluminum alkyl-reduced nickel octoate or similar metal complexes, can also be used. In some cases, the hydrogenation catalyst is present in an amount ranging from 0.25 wt. % to 5 wt. % based on the total weight of the HAT. The hydrogen source for hydrogenation can be hydrogen (H) or a compound capable of producing hydrogen under reaction conditions, such as formic acid, isopropanol, cyclohexene, cyclohexadiene, a diimide, or hydrazine.

[0044] The hydrogenation reaction can be carried out at elevated temperatures, elevated pressures, or a combination thereof. For example, the hydrogenation reaction can be carried out at temperatures between 120°C and 300°C and pressures between 30 and 2000 pounds per square inch (psi) or between 100 and 1000 psi.

[0045] In some embodiments, the coupled HAT can be prepared by utilizing a coupling agent selected from a group of compounds including dihaloalkanes, silicon halides, siloxanes, polyfunctional epoxides, silica compounds, esters of monohydric alcohols and carboxylic acids (e.g., methyl benzoate and dimethyl adipate), and epoxidized oils. Non-limiting examples of coupling agents include tetraalkoxysilanes such as tetramethoxysilane (TMOS) and tetraethoxysilane (TEOS); trialkoxysilanes such as methyltrimethoxysilane (MTMS); aliphatic diesters such as dimethyl adipate and diethyl adipate; and diglycidyl aromatic epoxy compounds such as diglycidyl ethers derived from the reaction of bisphenol A, epichlorohydrin, and combinations thereof. The amount of coupling agent added depends on the desired coupling efficiency and, in the case of polyfunctional coupling agents, the number of arms attached to the coupling agent. This is a stoichiometric reaction determined by the ratio of polymer chain ends to coupling agent. The coupling agent can be contacted with the HAT at any time during the preparation of the HAT. In another embodiment, contacting the coupling agent with the HAT can occur when the polymerization reaction has substantially consumed the monomer.

[0046] Properties: In one embodiment, the HAT polymer is characterized by having a tensile strength, as determined according to ASTM D412, of from 0.1 MPa to 10 MPa, alternatively from 0.1 MPa to 5 MPa, alternatively from 0.1 MPa to 4 MPa.

[0047] In one embodiment, the HAT block copolymer is characterized by a flow rate or melt index greater than 5 g / 10 min when measured according to ASTM D1238 at a temperature of 200° C. under a load of 5 kg. Alternatively, the melt index of the HAT composition may range from 5 g / 10 min to 200 g / 10 min, or alternatively, from 5 g / 10 min to 50 g / 10 min.

[0048] Application: Throughout this disclosure, references to properties of the HAT composition refer to the properties possessed by each block copolymer present in the composition (unless otherwise specified).

[0049] HAT compositions can be used in a variety of applications, including coatings, adhesives, hot melt adhesives, pressure sensitive adhesives (PSAs), and flexographic printing applications. When used in PSAs as labeling formulations, HAT compositions offer improved conversion over conventional formulations.

[0050] During PSA label manufacturing, the facestock, pressure-sensitive layer, and release liner are passed through equipment to convert the laminate into a commercially usable label. The processes involved in the conversion include printing, die-cutting, and matrix peeling to leave the label on the release liner. The cost of converting a laminate into a final product is a function of the speed at which the various processing operations are performed. While the properties of all layers of the laminate can affect the cost of conversion, the adhesive layer can be the limiting factor in the ease and cost of conversion. This is because the adhesive layer's viscoelasticity and tensile strength hinder accurate and clean die entry during the die-cutting operation and promote adhesion of the adhesive layer to the cutting blade. The strength of the adhesive also affects the matrix peeling operation that follows the die-cutting operation. The diblock-like properties of HAT in label adhesive formulations result in lower cohesive strength and better conversion.

[0051] Achieving good conversion performance does not necessarily equate to achieving excellent adhesive performance. Good general-purpose adhesives can exhibit poor conversion performance because they are difficult to cut without smearing the adhesive layer. Such adhesives can stick to the die or blade. In label manufacturing, die-cutting and matrix-peeling operations are performed at various speeds ranging from 0 to 300 meters per minute. Within this range, the adhesive can provide areas where the matrix breaks, despite the fact that matrix peeling can be successful at speeds on both sides of the area. The HAT composition can provide an adhesive system in which the adhesive cuts without smearing and the matrix peels over the entire range of operating speeds, thereby improving conversion performance over conventional PSA labeling formulations.

[0052] In some embodiments, the HAT composition is used in PSA labeling formulations. The composition features a higher melt flow rate, allowing for rapid mixing of hot-melt adhesive formulations. The PSA labeling formulation can include the HAT composition (e.g., 30% to 60% by weight), a tackifier resin (e.g., 30% to 60% by weight, e.g., Wingtack 86), a plasticizer oil (e.g., 0% to 45% by weight, e.g., Sontex 450 oil), and optionally, a stabilizer (e.g., 0% to 3% by weight, e.g., Irganox 1010), and optionally, additional polymers and / or binders. The tackifier resin can be selected from the group consisting of C5 hydrocarbon resins, C5 / C9 hydrocarbon resins, hydrogenated and partially hydrogenated C9 hydrocarbon resins, rosin esters, terpenes, and styrenated terpene resins.

[0053] Those skilled in the art will appreciate that the properties of HAT polymers are also useful in other applications requiring good finishability and pelletizability while also requiring easy blendability. For example, HAT polymers can be used to modify asphalt where good high-temperature properties are required, and can also be used in paving, roofing, waterproofing, soundproofing, or carpet backing applications. Meanwhile, ease of blending is desirable for low-shear asphalt blends. Paving applications include hot asphalt applications such as asphalt concrete paving and hot-in-place recycling, as well as emulsion applications such as fog seal, chip seal, scrub seal, cape seal, microsurfacing, cold-in-place recycling, and cold central plant recycling. Roofing applications include modified bitumen low-gradient membranes, self-adhesive underliners, and modified asphalt shingles.

[0054] Diblock copolymers tend to cold-flow and therefore cannot be easily fabricated into manageable pellets, as they are provided as rubber bales. Even after dusting, the material can rapidly cold-flow, making end-use processing difficult. For example, DYNASOL SOLPRENE 1205 is a very bulky diblock copolymer typically provided as a rubber bale. Pellets are sold at a premium price and suffer from excessive cold flow. On the other hand, the HAT compositions disclosed herein can be finished as stable pellets, which offer easier handling than even the purest diblock rubber bales in the prior art. [Example]

[0055] Example 1: The polymer structures of different examples of SIS (styrene-isoprene-styrene), SBS (styrene-butadiene-styrene), and SIBS (styrene-isoprene-butadiene-styrene) can be found in Table 1. Samples A, B, and C are continuous asymmetric triblock polymers with no detectable diblocks. They differ primarily by the size of the PS endblocks.

[0056] [Table 1]

[0057] The physical properties of these HAT SIS polymers are reported in Table 2. The PS endblocks (16 / 7.5) in Sample A were not different enough to significantly reduce tensile strength (TS). While the different endblock sizes did reduce TS, it was not enough to compensate for the absence of diblocks and the higher polystyrene content, as compared to commercially available SIS products, such as a coupled SIS with 55% diblock and 16% polystyrene content, which, based on the total amount of styrene and isoprene, had a melt flow of 24 g / 10 min (5 kg load and 200°C temperature), a tensile strength of 4.14 MPa, an elongation at break of 1500%, and a 300% modulus of 0.345 MPa.

[0058] [Table 2]

[0059] Example 2: SIS HAT polymer was formulated into an adhesive. The properties are shown in Table 3. The adhesive was approximately 180 oThe adhesive formulations were prepared using a 100% HAT SIS polymer, 49.8% Eastman Piccotac 95E resin, 10% naphthenic oil, and 0.5% Irganox 1010 antioxidant. For samples A-C, the adhesive formulation used was 39.7% HAT SIS polymer, 49.8% Eastman Piccotac 95E resin, 10% naphthenic oil, and 0.5% Irganox 1010 antioxidant. For samples E and F, the adhesive formulation used was 40% by weight SIBS HAT polymer, 50% by weight Cray Valley Wingtack 86 resin, 9.5% by weight naphthenic oil, and 0.5% Irganox 1010 antioxidant. The formulations were mixed as hot melt adhesives. The adhesive blends were dissolved in toluene at 40% solids and applied to 1 mil Mylar film using a 0.004" size doctor blade. The films were allowed to dry for 1 hour before testing, and then dried at 40°C under vacuum for 4 hours.

[0060] The samples were compared to adhesives made with a commercial SIS polymer blended with a pure diblock, such as Solprene 1205. The full sequential HAT SIS polymer behaved similarly to the high diblock SIS polymer. The adhesive made with sample C exhibited the lowest cohesive strength (due to its higher asymmetry).

[0061] [Table 3]

[0062] Example 3 - Comparative Adhesives: Comparative adhesives were formulated according to Table 4 using F1. F2 contains a commercially available high diblock SBS copolymer with 33% polystyrene content, 78% diblock content, 2 MPa tensile strength (ISO 37), and 600% elongation at break (ISO 37). F3 uses Solprene 1205 as the polymer. Comparing the results obtained with the comparative adhesives and the HAT composition, the results in Table 5 show that the HAT composition provided excellent loop tack and peel properties, indicating that this composition is useful as the sole polymer for label adhesives or, alternatively, can be blended in place of a pure diblock such as SOLPRENE 1205.

[0063] [Table 4]

[0064] [Table 5]

Claims

1. 1. A highly asymmetric triblock copolymer composition comprising: a first block A1 which is a polymer of a monoalkenyl arene; a second block B which is a mixture of butadiene and isoprene, wherein the butadiene is present in an amount of at least 20 wt %, based on the total weight of the entire second B block; and a third block A2 which is a polymer of a monoalkenyl arene, the first block A1 and the third block A2 are different from each other; the monoalkenyl arenes of the first block A1 and the third block A2 are each independently selected from the group consisting of styrene, o-methylstyrene, p-methylstyrene, p-tert-butylstyrene, 2,4-dimethylstyrene, α-methylstyrene, vinylnaphthalene, vinyltoluene, and vinylxylene, and mixtures thereof; the third block A2 has a peak molecular weight in the range of 0.06 to 0.4 of the peak molecular weight of the first block A1; and the second block B has a gradually increasing distribution of vinyl content throughout the block such that a first end of the second block B adjacent to the first block A1 of the monoalkenyl arene has a vinyl content of less than 15 mol % and the last 10-49% of the block B at the opposite second end of the second block B distal from the first block A1 has a vinyl content of more than 25 mol %; and An asymmetric triblock copolymer composition, wherein the highly asymmetric triblock copolymer composition has a peak molecular weight in the range of 10,000 to 500,000 g / mol and a total arene content in the range of 15 to 40 wt %.

2. The composition has the formula A1-B-A2 or (A2-B-A1) ｎ 2. The asymmetric triblock copolymer composition of claim 1, comprising a mixture of copolymers having X, wherein n is an integer from 2 to 6, X is a residue of a coupling agent, and block A1 has a peak molecular weight that is at least 2.5 times the peak molecular weight of block A2.

3. The composition has the formula (A2-B-A1) ｎ 3. The asymmetric triblock copolymer composition of claim 2, wherein X is a methyl group, and the copolymer is attached to a coupling agent at the A2 block.

4. 3. The asymmetric triblock copolymer composition of claim 1 or 2, wherein the asymmetric triblock copolymer is blended with at least a second polymer different from the asymmetric triblock copolymer to form a blended asymmetric triblock copolymer.

5. 3. The asymmetric triblock copolymer composition of claim 1, wherein the composition has a tensile strength of 0.1 MPa to 10 MPa, determined according to ASTM D412 or ASTM D638.

6. 3. The asymmetric triblock copolymer composition of claim 1, wherein the composition has a melt index in the range of 5 g / 10 min to 200 g / 10 min, determined according to ASTM D1238, measured at 200° C. with a mass of 5 kg.

7. 3. The asymmetric triblock copolymer composition of claim 1 or 2, wherein the conjugated diene is hydrogenated to form a hydrogenated highly asymmetric triblock copolymer.

8. A label or surface protection film formed by laminating or applying an adhesive layer comprising an adhesive composition comprising 30 to 60% by weight of the asymmetric triblock copolymer composition according to claim 1 or 2, 30 to 60% by weight of a tackifier resin, 0 to 40% by weight of an oil, and 0 to 3% by weight of an antioxidant (% by weight is based on the total weight of the adhesive composition).

9. 1. An asphalt composition or bitumen emulsion comprising: a) the asymmetric triblock copolymer composition of claim 1 or 2; b) an asphalt binder; and c) optionally a chemical crosslinker, wherein the percentage of the asymmetric triblock copolymer in the blend is 2% to 20%.

10. 1. A method for preparing a highly asymmetric triblock copolymer composition, comprising: polymerizing a sufficient amount of a first monoalkenyl arene to form a first polymer block A1; adding butadiene monomers and isoprene monomers and polymerizing the butadiene and isoprene to form a second polymer block B appended to the first polymer block A1; adding and polymerizing a sufficient amount of a second monoalkenyl arene to form a third polymer block A2 appended to said second polymer block B to form an asymmetric triblock copolymer; optionally adding a coupling agent X, the first polymer block A1 and the third polymer block A2 are different from each other; the monoalkenyl arenes of the first polymer block A1 and the third polymer block A2 are each independently selected from the group consisting of styrene, o-methylstyrene, p-methylstyrene, p-tert-butylstyrene, 2,4-dimethylstyrene, α-methylstyrene, vinylnaphthalene, vinyltoluene, and vinylxylene, and mixtures thereof; and the second polymer block B is a mixture of butadiene and isoprene, the butadiene being present in an amount of at least 20 wt. %, based on the total weight of the entire second B block; and a ratio of the peak molecular weight of the third polymer block A2 to the peak molecular weight of the first polymer block A1 is in the range of 0.06 to 0.4, and the second polymer block B has a distribution of vinyl content that gradually increases throughout the block such that a first end of the second polymer block B adjacent to the monoalkenyl arene first polymer block A1 has a vinyl content of less than 15 mol % and the last 10-49% of block B at an opposite second end of the second polymer block B distal from the first polymer block A1 has a vinyl content of greater than 25 mol %.

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