HOT MELT PRESSURE SENSITIVE ADHESIVE COMPOSITIONS AND METHODS OF

MAKING THE SAME

FIELD

[0001] The present disclosure relates to hot melt adhesive compositions and methods of forming the same In particular, this disclosure relates to pressure sensitive hot melt adhesive compositions and methods of forming them.

BACKGROUND

[0002] Hot melt adhesive compositions are used in a variety of applications that require bonding two substrates together A hot melt adhesive composition is generally applied in a liquid or molten state and forms a bond as it cools and solidifies. Hot melt adhesive compositions can be applied by extruding the adhesive composition at elevated temperatures directly onto a substrate to form a structural bond with another substrate as the temperature of the adhesive composition cools.

[0003] Hot melt adhesive compositions may be used in packaging applications (e.g for bonding cardboard and corrugated boards), for nonwoven applications (e.g., disposable articles such as diapers), bookbinding, and footwear manufacturing, among other applications.

[0004] In certain applications, it is desired to have a hot melt adhesive that is pressure sensitive. In certain applications, it is desired to have a hot melt adhesive that is pressure sensitive, and that exhibits cohesion to a wide range of substrates and in a wide variety of applications. In certain applications, it is desired to have a hot melt adhesive that is pressure sensitive, and that exhibits superior holding power at elevated temperatures.

SUMMARY

[0005] Various aspects of the present disclosure provide a hot melt pressure sensitive adhesive composition. In a first aspect, the hot melt pressure sensitive adhesive comprises an isocyanate-group terminated compound, a plasticizer, a thermoplastic polymer; and a tackifying agent. At least one of the plasticizer or tackifying agent contains isocyanate reactive groups. In some aspects, the hot melt pressure sensitive adhesive composition of the first aspect further comprises a polyurethane-curing catalyst. In some aspects, the hot melt pressure sensitive adhesive composition further comprises a non-reactive tackifying agent.

[0006] In some aspects, both the plasticizer and the tackifying agent contain hydroxyl groups. In some aspects, the hot melt pressure sensitive adhesive composition comprises a second plasticizer that is not hydroxyl modified.

[0007] In some aspects, the combined weight percent of the isocyanate-group terminated compound, the plasticizer, the thermoplastic polymer, and the tackifying agent is at least 90% based on the total weight of the adhesive composition. In some aspects, the combined weight percent of the isocyanate-group terminated compound, the plasticizer, the thermoplastic polymer, and the tackifying agent is at least 95% based on the total weight of the adhesive composition.

[0008] In some aspects, the tackifying agent is at least one of an aliphatic hydrocarbon resin, an aromatic hydrocarbon resin, or an aliphatic-aromatic hydrocarbon resin. In some aspects, the tackifying agent is at least one of an aliphatic resin, an aromatic modified resin, a cycloaliphatic resin, a hydroxyl modified resin, or hydrogenated versions thereof. In some aspects, the tackifying agent is at least one of a rosin or a terpene resin.

[0009] In some aspects, the thermoplastic polymer is at least one of a block copolymer, or a polyolefin. In some aspects, the thermoplastic polymer is at least one of a propylene-rich polyolefin, a butene-rich polyolefin, or an ethylene-rich polyolefin. In some aspects, the thermoplastic polymer may be a styrene block copolymer. In some aspects, the thermoplastic polymer is an SIS block copolymer.

[0010] In some aspects, the plasticizer is at least one of an oil, a liquid resin, or a liquid polymer. In some aspects, the plasticizer is polybutene. In some aspects, the hot melt pressure sensitive adhesive composition contains a first plasticizer that does not contain hydroxyl groups and is at least one of an oil, a liquid resin, or a liquid polymer, and a second plasticizer that contains hydroxyl groups.

[0011] In some aspects, the isocyanate-group terminated compound may be a monomeric diisocyanate. In some aspects, the isocyanate-group terminated compound may be at least one of methylene diphenyl diisocyanate (MDI), methylene bis diphenyl isocyanate, hydrogenated methylene diphenyl isocyanate (HMDI), hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), polymeric methylene diphenyl diisocyanate, toluene diisocyanate (TDI), poiymethylene polyphenyl diisocyanate, naphthalene diisocyanate (NDI), or polymethylene polyphenyl isocyanate (PAPI).

[0012] In some aspects, the hot melt pressure sensitive adhesive composition is tacky at room temperature.

[0013] In some aspects, the isocyanate-group terminated compound is present in an amount of from about 1 wt.% to about 20 wt.% based on the total weight of the hot melt pressure sensitive adhesive composition. In some aspects, the thermoplastic polymer is present in an amount of from about 5 wt.% to about 70 wt.% based on the total weight of the hot melt pressure sensitive adhesive composition. In some aspects, the tackifying agent is present in an amount greater than 0.0 wt.% to about 50 wt.% based on the total weight of the hot melt pressure sensitive adhesive composition. In some aspects, the tackifying agent is present in an amount of from about 5 wt.% to about 30 wt.% based on the total weight of the hot melt pressure sensitive adhesive composition. In some aspects, the plasticizer is present in an amount greater than 0.0 wt.% to about 50 wt.% based on the total weight of the hot melt pressure sensitive adhesive composition.

[0014] In some aspects, the hot melt pressure sensitive adhesive composition comprises the isocyanate-group terminated compound in an amount of from about 5 wt.% to about 20 wt.%, the thermoplastic polymer in an amount of from about 15 wt.% to about 40 wt.%, the tackifying agent in an amount of from about 10 wt.% to about 50 wt.%, the plasticizer in an amount of from about 15 wt.% to about 30 wt.%, and about 0.2 wt.% a polyurethane-curing catalyst, all based on the total wei ght of the hot melt pressure sensiti ve adhesi ve composition .

[0015] Also disclosed herein, in a second aspect, is a hot melt pressure sensitive adhesive composition comprising the reaction product of an isocyanate compound, a plasticizer, and a tackifying agent; with a thermoplastic polymer. At least one of the plasticizer or the tackifying agent is hydroxyl terminated.

[0016] In some aspects, the isocyanate compound is at least one of an aromatic diisocyanate, an aliphatic diisocyanate, or an oligomer; the thermoplastic polymer is at least one of styrene- ethylene-butylene-styrene (SEBS), styrene-isoprene-styrene (SIS), or styrene-butadiene-styrene (SBS); the tackifying agent is rosin, a terpene resin, a phenolic resin, or a terpene phenolic resin; and the plasticizer is at least one of mineral oil, a resin, or a liquid polymer. [0017] In some aspects, the hot melt pressure sensitive adhesive composition of the second aspect contains the isocyanate compound in an amount of from about 5 wt.% to about 20 wt.%, the thermoplastic polymer in an amount of from about 15 wt.% to about 40 wt.%, the tackifying agent in an amount of from about 10 wt.% to about 40 wt.%, the plasticizer in an amount of from about 15 wt.% to about 25 wt.%, and about 0.2 wt.% a polyurethane-curing catalyst, all based on the total weight of the hot melt pressure sensitive adhesive composition.

[0018] In some aspects, the tackifying agent has a softening point at a temperature from about 60°C to about 160°C. In some aspects, the tackifying agent has at least one of a number- average molecular weight from about 100 to about 1000, an OH value from about 1 to about 400, or a softening point at a temperature between about 60°C to about 160°C.

[0019] In some aspects, the hot melt pressure sensitive adhesive composition has a 180° peel strength of at least 5 N/cm (13 N/in.) after curing.

[0020] In some aspects, the hot melt pressure sensitive adhesive composition has a shear strength of at least 23 N/cm ² (150 N/in. ² ) after curing.

[0021] In some aspects, the hot melt pressure sensitive adhesive composition has a holding time of greater than one minute at temperatures greater than 40°C about one week after curing.

[0022] In some aspects, the hot melt pressure sensitive adhesive composition exhibits crosslinking between the components of the hot melt pressure sensitive adhesive composition after curing.

[0023] Also disclosed herein is a method of forming a hot melt pressure sensitive adhesive composition. In some aspects, the method comprises combining a thermoplastic polymer, a plasticizer, and a tackifying agent to form a first mixture, and adding an isocyanate compound to the first mixture to form a hot melt pressure sensitive adhesive composition. In some aspects, the combined weight percent of the thermoplastic polymer, the plasticizer, the tackifying agent, and the isocyanate compound is at least 90 wt.%, based on the total weight of the hot melt pressure sensitive adhesive composition. At least one of the plasticizer or the tackifying agent contains - OH groups. In some aspects, the method further includes adding a catalyst.

[0024] In some aspects, the method includes maintaining the thermoplastic polymer, the plasticizer, and the hydroxyl-containing tackifying agent at a first temperature during the combining step, and carrying out the adding step at a second temperature that is lower than the first temperature. In some aspects, the thermoplastic polymer, the plasticizer, and the hydroxyl- containing tackifying agent are at a first temperature of from about 100°C to about 200°C during the combining step. In some aspects, the adding step is carried out at a second temperature of from about 80°C to about 130°C.

[0025] In some aspects, the method further includes maintaining a pressure that is lower than atmospheric pressure on the thermoplastic polymer, the plasticizer, and the hydroxyl-containing tackifying agent for from about 2 to about 3 hours. In some aspects, the method includes maintaining a pressure of less than or equal to -l.OMPa relative to atmospheric pressure on the thermoplastic polymer, the plasticizer, and the hydroxyl-containing tackifying agent for from about 2 to about 3 hours. In some aspects the adding step includes maintaining a pressure that is lower than atmospheric pressure for from about 0 5 to about 2 hours. In some aspects, the method includes maintaining a pressure of less than or equal to -l.OMPa relative to atmospheric pressure for from about 0.5 to about 2 hours during the adding step.

[0026] While multiple embodiments are disclosed, still other embodiments of the present disclosure will become apparent to those skilled in the art from the following detailed description, which shows and describes illustrative embodiments of the disclosure. Accordingly, the drawings and detailed description are to be regarded as illustrative in nature and not restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] FIG. 1 is a graph showing experimental results of various compositions according to embodiments described herein.

DETAILED DESCRIPTION

[0028] Disclosed herein is a hot melt pressure sensitive adhesive composition that includes a thermoplastic polymer, an isocyanate compound, a tackifying agent, and a plasticizer. The hot melt pressure sensitive adhesive composition may include the reaction product of an isocyanate compound with a tackifying agent and/or a plasticizer, and a thermoplastic polymer having sufficient structural integrity to provide cohesive strength. In some embodiments, the hot melt pressure sensitive adhesive composition includes one or more of each component. For example, the adhesive composition may include one or more isocyanate-group terminated compounds, one or more thermoplastic polymers, one or more tackifying agents, and/or one or more plasticizers. In some embodiments, the hot melt pressure sensitive adhesive composition further includes additional components, such as a catalyst and/or an antioxidant. In some embodiments, the hot melt pressure sensitive adhesi ve contains no more than 15 % by weight of polyester or polyether polyols, no more than 10 % by weight, no more than 5 %, or even is free of them.

[0029] The hot melt pressure sensitive adhesive composition is tacky to the touch at room temperature.

[0030] The hot melt pressure sensitive adhesive composition exhibits a 180° peel strength of from about 3.9 N/cm (10 N/inch), about 5.9 N/cm (15 N/inch), about 7.9 N/cm (20 N/'inch) or about 9.8 N/cm (25 N/inch), to about 21.7 N/cm (55 N/inch), about 23.6 N/cm (60 N/inch), about 25.6 N/cm (65 N/inch), or about 27.6 N/cm (70 N/'inch), or a 180° peel strength between any pair of the foregoing values, after curing. For example, the hot melt pressure sensitive adhesive composition exhibits a 180° peel strength between any pair of the foregoing values after being held for about one week in a CTH (constant temperature and humidity) room. In some embodiments, the hot melt pressure sensitive adhesive composition has a 180° peel strength of greater than 10.2 N/cm (26 N/inch) after curing. In some embodiments, the hot melt pressure sensitive adhesive composition has a 180° peel strength of at least 25 6 N/cm (65 N/inch) after curing.

[0031] The hot melt pressure sensitive adhesive composition exhibits a sheer strength of from about 10 N/cm ² (65 N/inch ² ), about 15 N/cm ² (95 N/inch ² ), about 51.2 N/cm ² (330

N/inch ² ), about 52.7 N/cm ² (340 N/inch ), about 54.3 N/cm ² (350 N/inch ² ), or about 55.8 N/cm ² (360 N/inch ² ), to about 60.5 N/cm ² (390 N/inch ² ), about 62.0 N/cm ² (400 N/inch ² ), about 63.6 N/cm ² (410 N/'inch ² ), about 75 N/cm ² (484 N/inch ² ), or about 100 N/cm ² (645 N/inch ² ), or a sheer strength between any pair of the foregoing values after c uring. In some embodiments, the hot melt pressure sensitive adhesive composition has a sheer strength of greater than 22.9 N/cm ² (148 N/inch ² ) after curing. In some embodiments, the hot melt pressure sensitive adhesive composition has a sheer strength of at least 63.1 N/cm ² (407 N/inch ² ) after curing.

[0032] The hot melt pressure sensitive adhesive composition exhibits thermal stability over a wide range of temperatures. The hot melt pressure sensitive adhesive composition exhibits a holding time of greater than one minute at temperatures of about 40°C about one week after being applied. In some embodiments, the hot melt pressure sensitive adhesive composition exhibits a holding time of from about one minute, about 10 minutes, or about 20 minutes, to about 30 minutes, or about 40 minutes at temperatures as great as 60°C, or a time between any pair of the foregoing values, after about one week of curing. In some embodiments, the hot melt pressure sensi tive adhesi ve composition exhibits a holding time of from about one minute, about 40 minutes, or about one hour, to about two hours, about three hours, or about four hours at temperatures as great as 75°C, or a time between any pair of the foregoing values, after about one week of curing. In some embodiments, the hot melt pressure sensitive adhesive composition exhibits a holding time of greater than about 40 minutes at temperatures of about 60°C, after about one week of curing ln some embodiments, the hot melt pressure sensitive adhesive composition exhibits a holding time of greater than four hours at a temperature of about 75°C, after about one week of curing. In some embodiments, the hot melt pressure sensitive adhesive composition exhibits an absolute holding power at temperatures as great as about 100°C, after about one week of curing. For example, the adhesive composition bond does not fail when held for at least six days at temperatures of as great as 10G ^C 'C, after about one week of curing. In some embodiments, the hot melt pressure sensitive adhesive composition exhibits an absolute holding power throughout a range of temperatures. For example, the adhesive composition bond does not fail when held at temperatures as great as 40°C, then held at temperatures as great as 60°C, then held at temperatures as great as 75°C, and then held at temperatures or as great as 100°C, after about one week of curing.

[0033] The hot melt pressure sensitive adhesive composition exhibits viscosity stability over a wide range of temperatures. For example, the adhesive composition maintains viscosity stability at temperatures of as great as about 120°C, about ! 30°C, about 140°C, or about ! 50°C. In some embodiments, the hot melt pressure sensitive adhesive composition has a viscosity growth of no greater than about 0.8% per hour, no greater than about 0.9% per hour, or no greater than about 1.0% per hour at temperatures of about 150°C. In some embodiments, the hot melt pressure sensitive adhesive composition has a viscosity growth of less than about 6% per hour, at temperatures of about 150°C. In some instances, the hot melt pressure sensitive adhesive composition has a viscosity no greater than about 21 ,000 centipoise (cp), no greater than about 20,000 cp, no greater than about 19,000 cp, no greater than about 8,000 cp, no greater than about 7,500 ep, no greater than about 7,000 cp, no greater than about 3,000 cp, no greater than about 2,900 cp, or no greater than about 2,800 cp, at temperatures of about 150°C. [0034] The hot melt pressure sensitive adhesive composition is cured after it has cooled to room temperature (from about 25°C to about 35°C). Solidification or curing of the hot melt pressure sensitive adhesive composition may occur when the liquid adhesive composition cools from its application temperature to room temperature (e.g. 25°C to 35°C) and forms bonds between the components of the adhesive composition. In some embodiments, the hot melt pressure sensitive adhesive composition exhibits crosslinking between the components of the hot melt pressure sensitive adhesive composition after curing. This crosslinking helps provide the hot melt pressure sensitive adhesive composition with superior holding power at elevated temperatures

[0035] The adhesive composition has suitable green strength to form initial bonds to a substrate. The hot melt pressure sensitive adhesive compositions disclosed herein exhibit adhesion to substrates formed from a wide range of materials. Some examples of materials that the hot melt pressure sensitive adhesive composition exhibit good adhesion to include, but are not limited to, polycarbonate (PC), polypropylene (PP), polyethylene (PE), polyethylene terephthalate (PET), acrylonitrile butadiene styrene (ABS), polyvinyl chloride (PVC), and polyamide (PA), although additional materials are further contemplated. The hot melt pressure sensitive adhesive compositions disclosed herein exhibit good tack, cohesive strength, peel strength, and holding power to substrates formed from the materials disclosed herein. The hot melt adhesive composition exhibits thermal stability, green bond strength, pot stability, a cured bond strength, and that can be used in a wide range of applications in production and use.

[0036] As used herein, pressure sensitive refers to the characteristic wherein a material is tacky at room temperature. The hot melt pressure sensitive adhesive may be tacky to the touch after being applied and cooling to room temperature. The adhesive composition may be tacky to the touch both before the hot melt pressure sensitive adhesive composition has cured and after the adhesive composition has cured.

10037] As used herein, tacky or tackiness describes the characteristic of a material, such as an adhesive composition, to adhere to a substrate after coming in contact with the substrate. For example, an adhesive composition disposed on a surface of a first substrate may adhere to a second substrate that comes in contact with the adhesive material that is attached to the first substrate, such that separating the first substrate and second substrate requires a greater amount of force than would be required to separate the first substrate and second substrate without the adhesive material between them.

Thermoplastic Polymer

[0038] The hot melt pressure sensitive adhesive composition contains one or more thermoplastic polymers. In some embodiments, the thermoplastic polymer is at least one of a homopolymer, copolymer or a higher order polymer. For example, the thermoplastic polymer may be a block copolymer and/or a terpolymer. The thermoplastic polymer can be an elastomer.

[0039] Suitable polymers that may form the thermoplastic polymer include, but are not limited to, block copolymers such as A-B diblock copolymers, A-B-A triblock copolymers, radial A-B-type block copolymers, multiblock copolymers, Y block copolymers, linear A-(B- A)n -B block copolymer, or an amorphous or semi-crystalline polyolefin polymer.

[0040] In some embodiments, such as an A-B-A block copolymer, a radial A-B-type block copolymer, or a linear A-(B-A) _n -B block copolymer, the A component may comprise a polystyrene block and the B component may comprise a rubbery block, such as a polyolefin block. Further suitable A components include polymers that have aromatic monomers and glassy endblock units such as polyalphamethylstyrene, and other similar polymers. Suitable B components include, but are not limited to, polymers or monomers that can generate rubbery polymeric blocks such as isoprene, butadiene, and mixtures thereof. Suitable B components may include hydrogenated and/or nonhydrogenated polymers or monomers. Suitable block copolymers that may form the thermoplastic polymer include styrene block copolymers, including but not limited to, styrene-ethylene -butylene-styrene (SEBS), styrene-isoprene-styrene (SIS), styrene-butadiene-styrene (SBS), styrene-butadiene rubber (SBR), or hydrogenated SIS (SETS), and combinations thereof.

[0041] Suitable block copolymers that may form the thermoplastic polymer include styrene block copolymers containing styrene at a weight percent from about 10%, about 15%, or about 20%, to about 40%, about 45%, or about 50% based on the total weight of the block copolymer, or a weight percent between any pair of the foregoing values. Suitable examples of block copolymers that may form the thermoplastic polymer include styrene-isoprene-styrene (SIS) block copolymers having a number average molecular weight of from about 50,000, about 70,000, or about 90,000, to about 150,000, about 180,000, about 200,000, or about 500,000, and containing from about 10 wt.%, about 15 wt.%, or about 20 wt.%, to about 40 wt.%, about 50 wt.%, or about 60 wt.% styrene, based on the total weight of the copolymer. Further suitable examples of block copolymers that may form the thermoplastic polymer include styrene- butadiene-styrene (SBS) block copolymers having a molecular weight of about 50,000, about 70,000, or about 90,000, to about 150,000, about 180,000, or about 200,000, or about 500,000, and from about 10 wt.%, about 15 wt.%, or about 20 wt.%, to about 40 wt.%, about 50 wt.%, or about 60 wt.% styrene.

100421 Further suitable examples of block copolymers that may form the thermoplastic polymer include styrene hydrogenated butadiene styrene block copolymers (i.e styrene- ethylene -butylene-styrene block copolymers) having a molecular weight of about 30,000, about 50,000, or about 70,000, to about 90,000, about 100,000, or about 120,000, or about 500,000, and from about 10 wt.%, about 15 wt.%, or about 20 wt.%, to about 40 wt.%, about 50 wt.%, or about 60 wt.% styrene, although additional block copolymers of further molecular weights and compositions are contemplated. In some embodiments, the thermoplastic polymer may include a mixture of copolymers having a ratio of di-block polymer to tri-block polymers from about 0.1:1, about 0.2:1, about 0.3:1, to about 0.8:1, about 0 9:1 , or about 1:1, or a ratio between any pair of the foregoing values.

[0043] Further examples of suitable thermoplastic polymers include polybutadienes, including the hydroxylated versions thereof, for example hydroxyl-terminated polybutadiene. Further examples of other suitable thermoplastic polymers include polyolefins. For example, the thermoplastic polymer may be at least one of a propylene-rich polyolefin, a butene -rich polyolefin, or an ethylene-rich polyolefin. It is envisioned that in some embodiments, suitable thermoplastic polymers may include acrylates or acetates (e.g. EVA).

[0044] In some embodiments, the thermoplastic polymer has a softening point at a temperature from about 60°C, about 70°C, about 80°C, or about 90°C, to about 160°C, about 170°C, about 180°C, or about 190°C, or a temperature between any pair of the forgoing values, as measured by the ASTM Ring and Ball softening point test, although thermoplastic polymers with alternative softening points are contemplated.

[0045] Examples of suitable commercially available thermoplastic polymers include styrene block copolymers such as those sold under the product designations SIS 1105 or SIS 1 124 (both available from Guangzhou Tongshen Chemical Co., located in Quanzhou City, China), KRATON D1126 or other styrene block copolymers sold under the trade designations KRATON and KRATON G (available from Kraton Corp., located in Houston, TX). Examples of suitable olefin block copolymers include those sold under the trade designation INFUSE (available from The Dow Chemical Co., located in Midland, MI). Examples of suitable propylene-rich polyolefins include those sold under the trade designation VISTAMAXX 6202 (available from ExxonMobil Chemical Company, of Houston, TX).

[0046] The thermoplastic polymer is present in the hot melt pressure sensitive adhesive composition in an amount from about five wt.%, about 10 wt.%, about 15 wt.%, about 20 wt.%, or about 25 wt.%, to about 50 wt.%, about 55 wt.%, about 60 wt.%, about 65 wt.%, or about 70 wt. %, based on the total weight of the hot melt pressure sensitive adhesive composition, or an amount between any pair of the foregoing values, although additional amounts are contemplated. In embodiments having more than one thermoplastic polymer, the total amount of the more than one thermoplastic polymer in the hot melt pressure sensitive adhesive composition may be from about five wt.%, about 10 wt.%, about 15 wt.%, about 20 wt.%, or about 25 wt.% to about 50 wt.%, about 55 wt.%, about 60 wd.%, about 65 wt.%, or about 70 wt %, based on the total weight of the hot melt pressure sensitive adhesive composition, or an amount between any pair of the foregoing values. The thermoplastic polymer can combine with the remaining components of the adhesive composition to provide initial green strength and cured strength to the adhesive composition.

Isocyanate Compound

[0047] The hot melt pressure sensitive adhesive composition includes one or more isocyanate compounds. As used herein, the term "isocyanate compound" indicates a compound having two or more -NCO groups. The isocyanate compound may he an isocyanate-group terminated compound. The isocyanate compound can be selected from the group consisting of a monomeric isocyanate and an isocyanate terminated oligomer.

[0048] Some examples of suitable isocyanate compounds include, but are not limited to aromatic isocyanates such as aromatic diisocyanates, aliphatic isocyanates such as aliphatic diisocyanates. In some examples, an isocyanate compound may be used to form a prepolymer composition for use in the hot melt pressure sensitive adhesive.

I I [0049] Suitable isocyanate compounds that may be used to form the hot melt pressure sensitive adhesive composition include aliphatic and aromatic isocyanate compounds having an isocyanate functionality of about two or more. In some embodiments, the isocyanate compound has from one to 10 aliphatic or aromatic groups substituted by the isocyanate group. The isocyanate compound may also contain other substituents which do not substantially adversely affect the viscosity of the isocyanate prepolymers, the adhesive properties of the hot melt pressure sensiti ve adhesi ve composition, or the reactivity of the -NC() groups during the formation of the adhesive composition. The isocyanate compound can also comprise mixtures of both aromatic and aliphatic isocyanates and isocyanate compounds having both aliphatic and aromatic character.

[0050] Suitable isocyanate compounds include methylene diphenyl isocyanate compounds such as diphenyl methane diisocyanate including its isomers, methylene diphenyl diisocyanate (MDI), carbodiimide modified MDI, hydrogenated methylene diphenyl isocyanate (HMDI), hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), polymeric methylene diphenyl isocyanate, diphenylmethane-4,4'-diisocyanate, diphenylmethane-2,2'-diisocyanate, diphenylmethane-2,4'-diisocyanate, and other oligomeric methylene isocyanates; toluene diisocyanate compounds (TDI) including isomers thereof, tetramethyl xylene diisocyanate (TMXDI), isomers of naphthylene diisocyanate, isomers of triphenylme thane triisocyanate, and mixtures thereof, although additional isocyanates are further contemplated. In some instances, aliphatic di, tri, and polyisocyanates are also suitable isocyanate compounds, including, for example, hydrogenated aromatic diisocyanates, aliphatic polyisocyanates, or cycloaliphatic polyisocyanates, although additional isocyanates are further contemplated.

[0051 ! The isocyanate compound is present in the hot melt pressure sensitive adhesive composition in an amount from about one wt.%, about two wt.%, about four wt.%, about five wt.%, to about 14 wt.%, about 16 wt.%, about 18 wt.%, or about 20 wt. %, based on the total weight of the hot melt pressure sensitive adhesive composition, or an amount between any pair of the foregoing values, although additional values are contemplated. In embodiments having more than one isocyanate compound, the total amount of the isocyanate compounds present in the hot melt pressure sensitive adhesive composition may be from about one wt.%, about two wt.%, about four wt.%, about six wt.%, to about 14 wt.%, about 16 wt.%, about 18 wt.%, or about 20 wt. %, based on the total weight of the hot melt pressure sensitive adhesive composition, or an amount between any pair of the foregoing values, although additional values are contemplated. In some embodiments, the isocyanate compound is present in the hot melt pressure sensitive adhesive composition in an amount of about five wt.%, about 10 wt.%, or about 15 wt.%, based on the total weight of the hot melt pressure sensitive adhesive composition, although additional amounts are contemplated.

Tackifying Agent

[0052] The hot melt pressure sensitive adhesive composition includes one or more tackifying agents.

[0053] In some embodiments, suitable tackifying agents for use in the adhesive composition are those containing isocyanate reactive groups (e.g. active hydrogen containing groups, for example, hydroxyl, amine, thiol, etc., groups) which can react with the isocyanate component of the hot melt pressure sensitive adhesive composition. In some embodiments, the hot melt pressure sensitive adhesive composition may further include one or more non-reactive tackifying agents.

[0054] Suitable tackifying agents that may be used to form the adhesive composition include those having a softening point at a temperature from about 60°C to about 160°C, as measured by the A STM Ring and Ball softening point test. For example, suitable tackifydng agents include those having a softening point of greater than 60°C and less than about 160° C, less than about 150° C, or less than about 140° C. In some instances, tackifying agents suitable for use in forming the adhesive composition have a softening point at a temperature from about 60°C, about 80°C, about !00°C, to about !20°C, about 140°C, or about !60°C, or a softening point between any pair of the foregoing temperatures, although additional tackifying agents are further contemplated.

[0055] In some embodiments, the tackifying agent has a number-average molecular w'eight from about 80, about 100, or about 120, to about 900, about 1000, or about 1100, or a molecular weight between any pair of the foregoing values, although additional molecular weights are contemplated.

[0056] In some embodiments, the tackifying agent is a hydroxyl modified tackifying agent (an -OH modified tackifying agent), such as a hydroxyl terminated tackifying agent. In some embodiments, the tackifying agent has a hydroxyl (OH) number from about one, about five, about 10, about 15, about 20, about 25, about 30, about 50 to about 100, about 140, about 160, about 200, about 250, about 300, about 380, about 400, or about 420, or an OH value between any pair of the foregoing values

[0057] Suitable tackifying agents for use in forming the hot melt pressure sensitive adhesive composition include, aromatic, aliphatic and cycloaliphatic hydrocarbon resins, mixed aromatic and aliphatic modified hydrocarbon resins, hydroxyl modified resins, aromatic modified aliphatic hydrocarbon resins, and hydrogenated versions thereof. Further suitable examples of tackifying agents include terpenes, modified terpenes and hydrogenated versions thereof

[0058] In some embodiments, suitable tackifying agents include rosins, terpene resins, phenolic resins (e.g. terpene phenolic resins, phenol modified aromatic hydrocarbon resins, etc.) and hydrogenated version thereof. In some embodiments, suitable tackifying agents include natural rosins, modified rosins, rosin esters, and hydrogenated versions thereof; low molecular weight polylactic acid, and combinations thereof. Examples of suitable natural and modified rosins include gum rosin, wood rosin, tall oil rosin, distilled rosin, hydrogenated rosin, dimerized rosin, and polymerized rosin. Examples of suitable tackifying agents include rosin esters, including glycerol esters of rosin, methyl esters of rosin, glycerol esters of hydrogenated rosin, glycerol esters of polymerized rosin, pentaerythritol esters of natural and modified rosins including pentaerythritol esters of rosin, pentaerythritol esters of hydrogenated rosin,

pentaerythritol esters of tall oil rosin, phenolic-modified pentaerythritol esters of rosin, and combinations thereof

[0059] Further examples of suitable tackifying agents include copolymers and terpo!ymers of natural terpenes, for example, styrene-terpene, alpha-methyl styrene-terpene and vinyl toluene - terpene, and combinations thereof. Examples of suitable aliphatic and cycloaliphatic petroleum hydrocarbon resins include aliphatic and cycloaliphatic petroleum hydrocarbon resins, the hydrogenated derivatives thereof, and combinations thereof Suitable aliphatic and cycloaliphatic petroleum hydrocarbon resins include, e.g , branched, unbranched, and cyclic C5 resins, C9 resins, and CIO resins.

[0060] Examples of suitable commercially available tackifying agents that may be used in forming the hot melt pressure sensitive adhesive composition include those sold under a variety of trade designations including certain of the ESCOREZ series of trade designations (available from ExxonMobil Chemical Co., located in Houston, TX) including ESCOREZ 5400, ESCOREZ 5415, ESCOREZ 5600, ESCOREZ 5615, and ESCOREZ 5690, the EASTOTAC series of trade designations (available from Eastman Chemical Co., located in Kingsport, TN) including EASTOTAC H-100R, EASTOTAC H-100L, EASTOTAC H 130W, and EASTOTAC H142, the WINGTACK series of trade deignations (available from Cray Valley HSC, located in Exton, PA) including WINGTACK 86, WINGTACK EXTRA, and WINGTACK 95, the PICCOTAC series of trade names (a vailable from Eastman Chemical Co.) including PICCOTAC 8095, the ARKON series of trade names (available from Arkawa Europe GmbH, located in Germany) including ARKON P-125, and those sold under the REGALITE series of trade designations (available from Eastman Chemical Co.) including, e.g., REGALITE R1125.

[0061] Suitable tackifying agents for forming the hot melt pressure sensitive adhesive composition include, phenol modified terpene resins such as those sold under the trade designation SYLVARES TP (available from KRATON Corp , of Houston, TX) and phenol modified C9 aromatic hydrocarbon resins such as those sold under the trade designation

HIKOTACK P (available from Kolon Chemical Company LTD, located in Kwacheon City, Korea). Further suitable tackifying agents useful for forming the hot melt pressure sensitive adhesive composition include modified aliphatic resins such as those sold under the trade designation LUHOREZ M90 (available from Zibo Luha Hongjin New Material Co., Ltd., located in Zibo, China).

[0062] The tackifying agent is present in the hot melt pressure sensitive adhesive

composition in an amount from about one wt.%, about five wt.%, about 10 wt.%, or about 15 wt.%, to about 30 wt.%, about 40 wt.%, about 50 wt.%, or about 60 wt.%, based on the total weight of the adhesive composition, or an amount between any pair of the foregoing values, although additional values are contemplated. In some embodiments, the one or more tackifying agents is present in the hot melt pressure sensitive adhesive composition in an amount of about 10 wt.%, about 12 wt.%, or about 20 wt.%, based on the total weight of the hot melt pressure sensitive adhesive composition, although additional weight percentages are contemplated. Plasticizer

[0063] The hot melt pressure sensitive adhesive composition includes one or more plasticizers. In some embodiments, the plasticizer is at least one of an oil, a liquid resin, or a liquid polymer. Liquid resins include resins that are liquid at room temperature (e.g. from about 25°C to about 35°C).

[0064] Suitable plasticizers for use forming in the hot melt pressure sensitive adhesive composition include, mineral oils, paraffin oils, naphthenic oils, synthetic liquid oligomers of polyolefins (e.g., polybutene and polypropylene), hydrocarbon fluids, vegetable oils, and combinations thereof. In some embodiments, a suitable plasticizer may have number average molecular weight (Mn) from about 1 ,000, about 2,000 to about 6,000 or about 10,000, or a molecular weight between any pair of the foregoing values.

[0065] In some embodiments, the plasticizer may be modified (e.g. hydroxyl modified (-OH modified)). Suitable hydroxyl modified plasticizers include those containing -OH at a weight percent from about 0.5 wt.%, about one wt.%, or about two wt.%, to about seven wt.%, about eight wt.%, or about nine wt.%, based on the total weight of the plasticizer, or a weight percent between any pair of the foregoing values. In some embodiments, the plasticizer may by a hydroxylated compound that is reactive with the isocyanate compound. In some embodiments, the plasticizer may be unmodified (e.g not hydroxyl modified). In some embodiments, the hot melt pressure sensitive adhesive composition includes a first plasticizer that is hydroxyl modified and a second plasticizer that is not hydroxyl modified.

[0066] In some embodiments, the plasticizer may be a liquid resin that is modified (e.g. hydroxyl modified). The plasticizer may be a liquid resin that is unmodified. In some embodiments, the plasticizer may be a hydroxylated compound such as a hydroxyl-terminated polybutene, a hydroxyl-modified liquid resin, or a combination thereof.

[0067] . In some embodiments, a suitable plasticizer is liquid polybutene (e.g. liquid at room temperature). Suitable plasticizers include liquid polybutene having a viscosity range from about 500 centipoise (cp), about 2,000 cp, or about 6,000 cp, to about 10,000 cp, about 50,000 cp, or about 70,000 cp, or a viscosity between any pair of the foregoing values at a temperature from about 25°C to about 35°C. [0068] Suitable commercially available plasticizers may include those sold under the series of trade designations NYFLEX (a vailable from Nynas Corp., located in Houston, TX) including, for example, NYFLEX 222B, oils such as those sold under the trade designation KAYDOL (available from Sonneborn, LLC, located in Parsippany, NJ), mineral oil such as those sold under the trade designation KRYSTOL such as KRYSTOL 550 (available from Petrochem Carless Ltd , located in Surrey, England), oils such as those sold under the trade designation CALSOL 550 (available from Calumet Specialty Products Partners, LP., located in Indianapolis, IN), rubber oils such as those sold under the product designation KN4010 (available from Fuda Petrochemical Co., Ltd, located in Hangzhou, China), and polyalphaolefins such those under the SPECTRASYN series of trade designations (available from ExxonMobil Chemical Co., located in Houston, TX), including, for example, SPECTRASYN 4 and 40.

[0069] Suitable plasticizers may include certain commercially available liquid hydrocarbon resins, such as those sold under the trade designation REGALITE C8010 (available from

Eastman Chemical Co., located in Kingsport, TN), and certain examples of those sold under the trade designation ESCOREZ such as ESCOREZ 5040 (available from ExxonMobil Chemical Co., located in Houston, TX) Further suitable -OH modified liquid resins that may be used as a plasticizer include those sold under the trade designation NOV ARES (available from RUTGERS Germany GmbH, of Germany) including, for example, those in the NOV ARES series such as LA, LC, HA, TNA, CA, or LS series.

[0070] Suitable plasticizers may include liquid polybutene sold under the RICQN series trade designation (available from Cray Valley, of Exton, PA), such as R!CON 130, 142, or 150. Suitable polybutenes may be those sold under the INDOPOL series trade designation (available from INEOS of London, England). Further suitable plasticizers include -OH modified liquid polybutene sold under the KRASOL trade designation series (available from Cray Valley, of Exton, PA), such as KRASOL LBH-2000, 3000, or 5000.

10071] The plasticizer is present in the hot melt pressure sensitive adhesive composition in an amount from about one wt.%, about five wt.%, about 10 wt.%, or about 15 wt.%, to about 30 wt.%, about 40 wt.%, or about 50 wt.%, based on the total weight of the adhesive composition, or an amount between any pair of the foregoing values, although additional values are contemplated. In embodiments having more than one plasticizer, the total amount of the one or more plasticizers present in the hot melt pressure sensitive adhesive may be about one wt.%, about five wt.%, about 10 wt.%, or about 15 wt.%, to about 30 wt.%, about 40 wt.%, or about 50 wt.%, based on the total weight of the adhesive composition, or an amount between any pair of the foregoing values, although additional values are contemplated.

Additional Components

[0072] In some embodiments, the hot melt pressure sensitive adhesive composition optionally includes one or more of a variety of additional components including, for example, stabilizers, antioxidants, adhesion promoters, ultraviolet light stabilizers, rheology modifiers, biocides, corrosion inhibitors, dehydrators, colorants (e.g., pigments and dyes), fillers, surfactants, flame retardants, waxes, additional polymers, and mixtures and combinations thereof.

[0073] ln some embodiments, the hot melt pressure sensitive adhesive composition includes one or more antioxidant. In some embodiments, suitable antioxidants include but are not limited to pentaerythritol tetrakis [3,(3 ,5 -di-tert-butyl-4-hydroxyphenyl)propionate] , 2 ,2 '-methylene bis(4-methyl-6-tert-butylphenol), phosphites including, e.g. , tris-(p-nonylphenyl)-phosphite (TNPP) and bis(2,4-di-tert-butylphenyl)4,4'-diphenylene-diphosphonite, di-stearyl-3,3'- thiodipropionate (DSTDP), and combinations thereof. Useful antioxidants are commercially available under a variety of trade designations including, for example, hindered phenolic antioxidants sold under the IRGANQX series of trade designations (available from BASF Corporation, Florham Park, N.J.) including, e.g., IRGANQX 1010, IRGANQX 565, IRGANQX 1076, phosphite antioxidants sold under the trade designation IRGAFOS such as IRGAFOS 168 (available from BASF, of Ludwigshafen, Germany) and 4,4'-methylene bis(2,6-di-tert- butylphenoi) available under the common name Ethyl 702.

[0074] In some embodiments, the hot melt pressure sensitive adhesive composition includes one or more catalysts. In some embodiments, suitable catalysts may be selected for improving the reaction, forming, and/or curing of the remaining components of the hot melt pressure sensitive adhesive composition. For example, the adhesive composition may include a curing catalyst such as a polyurethane-curing catalyst. Suitable curing catalysts that may be used to form the hot melt pressure sensitive adhesive composition include 2,2’ dimorphohnodiethylether (DMDEE) for examples, those sold under the trade designation JEFFCCAT (available from Hunstman Performance Products, located in The Woodland, TX). Method of Forming Hot Melt Pressure Sensitive Adhesive

[00751 In some embodiments, a method of forming the hot melt pressure sensitive adhesive composition includes combining the thermoplastic polymer, plasticizer, tackifying agent, and isocyanate compound to form the hot melt pressure sensitive adhesive composition.

[0076] In some embodiments, a method of forming the hot melt pressure sensitive adhesive composition includes combining the thermoplastic polymer, plasticizer, tackifying agent, and then adding the isocyanate compound to form the hot melt pressure sensitive adhesive composition. For example, a method of forming a hot melt pressure sensitive adhesive composition may include, in a first step, combining the thermoplastic polymer with the tackifying agent and plasticizer, followed by a second step of adding the isocyanate compound.

In some embodiments, in the second step a catalyst is added to the thermoplastic polymer, plasticizer, hydroxyl-containing tackifying agent and isocyanate compound to help form the hot melt pressure sensitive adhesive composition.

[0077] ln some embodiments, in a first step, the thermoplastic polymer, the plasticizer, and the tackifying agent are maintained at a first temperature while these components are combined. In some embodiments, in a second step, the isocyanate compound is added to the components that were combined in the first step, and the components combined in the second step are maintained at a second temperature that may be higher than, lower than, or equal to the first temperature. In a preferred embodiment, the second temperature is lower than the first temperature. For example, the first temperature may be from about 100°C, about 120°C, or about 140°C, to about 160°C, about 180°C, or about 20G ^C C, or a temperature between any pair of the foregoing values, although additional temperatures are further contemplated. In some

embodiments, the second temperature may ^? be about 70°C, about 80°C, about 90°C, or about 100°C, to about 120°C, about 130°C, or about 140°C, or a temperature between any pair of the foregoing values, although additional temperatures are further contemplated.

[0078] The components of the hot melt pressure sensitive adhesive composition may be combined in a vessel that can be pressure controlled, for example, a vessel that can maintain a pressure inside the vessel that is higher than, equal to, or less than the pressure outside the vessel, such as atmospheric pressure. As an example, the components of the hot melt pressure sensitive adhesive composition may be combined in a vessel, and the inside of the vessel may be maintained at a pressure that is lower than atmospheric pressure during the first step and/or the second step. In some embodiments, the first step includes combining the thermoplastic polymer, plasticizer, tackifying agent in a vessel for from about one hour, about two hours, to about three hours, about four hours, or about five hours, or a time between any pair of the foregoing values, whi le maintaining the pressure inside the vessel at a pressure lower than atmospheric pressure.

In some embodiments, the second step includes combining the components combined in the first step with the isocyanate compound, and optionally the catalyst, in a vessel for from about 0.5 hour, about one hours, to about two hours, about three hours, or about four hours, or a time between any pair of the foregoing values, while maintaining the pressure inside the vessel at a pressure lower than atmospheric pressure. In some embodiments, the first step and/or the second step may include maintaining a pressure inside the vessel of about -0.5 MPa, about -1.0 MPa, about -1.5 MPa, or about -2.0 MPa relative to atmospheric pressure.

Sample Procedure for Forming Hot Melt Pressure Sensitive Adhesive

[0079] In some embodiments, a process for forming a hot melt pressure sensitive adhesive composition includes, in a first step, adding to a vessel a thermoplastic polymer in an amount of from about 5 wt.% to about 70 wt.%, a tackifying agent in an amount greater than 0 0 wt.% to about 80 wt.%, and a plasticizer in an amount of from about 15 wt.% to about 25 wt.%, all based on the total final weight of the hot melt pressure sensitive adhesive composition. The components combined in the first step may be mixed in the vessel for about 2 to 3 hours. The pressure inside the vessel may be maintained at about -1.0 MPa relative to atmospheric pressure. The components of the vessel may be maintained at a temperature from about 100°C to about 200°C during the first step.

[0080] In some embodiments, in a second step, an isocyanate compound in an amount of from about 1 wt.% to about 20 wt.% and a catalyst in an amount of about 0 2 wt.%, all based on the total final weight of the hot melt pressure sensitive adhesive composition, are added to the components combined in the first step. In some examples, the total weight percent of the thermoplastic polymer, the tackifying agent, the plasticizer, the isocyanate compound and the catalyst comprise at least 90 wt.% of the final weight of the hot melt pressure sensitive adhesive composition. In some examples, the total weight percent of the thermoplastic polymer, the tackifying agent, the plasticizer, the isocyanate compound and the catalyst comprise at least 95 wt.% of the final weight of the hot melt pressure sensitive adhesive composition. The components combined in the second step may be mixed in the vessel for about 0.5 to about 2 hours to form the hot melt pressure sensitive adhesive composition. The pressure inside the vessel may be maintained at about -1.0 MPa relative to atmospheric pressure. The components of the vessel may be maintained at a temperature from about 80°C to about 130°C during the second step.

[0081] In a preferred embodiment, a process for forming a hot melt pressure sensitive adhesive composition includes, in a first step, adding to a vessel a thermoplastic polymer in an amount of from about 15 wt.% to about 40 wt.%, a tackifying agent in an amount of from about 10 wt.% to about 40 wt.%, and a plasticizer in an amount of from about 20 wt.% to about 25 wt.%, all based on the total final weight of the hot melt pressure sensitive adhesive composition. The components combined in the first step may be mixed in the vessel for about 2 to 3 hours.

The pressure inside the vessel may be maintained at about -1.0 MPa relative to atmospheric pressure. The components of the vessel may be maintained at a temperature from about 100°C to about 200°C, during the first step.

[0082] In some embodiments, in a second step, an isocyanate compound in an amount of from about five wt.% to about 10 wt.% and a polymrethane-curing catalyst in an amount of about 0.2 wt.%, all based on the total final weight of the hot melt pressure sensitive adhesive composition, are added to the components combined in the first step. In some examples, the total weight percent of the thermoplastic polymer, the tackifying agent, the plasticizer, the isocyanate compound and the catalyst comprise at least 90 wt.% of the final weight of the hot melt pressure sensitive adhesive composition. In some examples, the total weight percent of the thermoplastic polymer, the tackifying agent, the plasticizer, the isocyanate compound and the catalyst comprise at least 95 wt.% of the final weight of the hot melt pressure sensitive adhesive composition. The components combined in the second step may be mixed in the vessel for about 0.5 to about two hours to form the hot melt pressure sensitive adhesive composition. The pressure inside the vessel may be maintained at about -1.0 MPa relative to atmospheric pressure. The components of the vessel may be maintained at a temperature from about 80°C to about 130°C during the second step. [0083] Typically, using a block copolymer that includes segments having a low glass transition temperature (Tg) as a polymer backbone in a hot melt adhesive can provide useful levels of tack and adhesion in some instances, due to the low weight molecular of certain materials in hot melt adhesives, for example certain oils or tackifying agents, cohesion under certain conditions and high temperature performance may be limited. It can also be difficult in some instances to product a hot melt adhesive that includes isocyanate group terminated chemicals that are compatible with a polyolefin or rubber or similar components in forming a hot melt pressure sensitive adhesive. It has been found that in some instances, a certain degree of crosslinking between the components of the hot melt pressure sensitive adhesive can help increase the cohesive strength of the adhesive composition and increase the range of substrates that the adhesive can adhere to. In some instances, tailoring the percentage of the thermoplastic polymer content in the hot melt pressure sensitive adhesive composition can help to further tune the cohesion level, and the materials that the hot melt adhesive can adhere to.

[0084] Additionally or alternatively, a hot melt adhesive composition may be formed to have certain pressure sensitive characteristics. For example, it has been found that adding hydroxyl- containing compounds to a hot melt adhesive can be used to help add pressure sensitive characteristics to the hot melt adhesive composition. Some other techniques include adding certain plasticizers and/or tackifying agents that help add pressure sensitive characteristics, without compromising other desired properties. In some instances, the process used to form a hot melt pressure sensitive adhesive can be chosen such that it helps impart desired cohesive properties to the adhesive. For example, first mixing the thermoplastic polymer, tackifying agent, and plasticizer followed by adding the isocyanate compound such as MDI, may produce a hot melt adhesive that is pressure sensitive that can cure by reacting with moisture in the air.

[0085] It has been found that in some instances, forming a hot melt pressure sensitive adhesive composition by selecting components of the hot melt pressure sensitive adhesive composition such that the adhesive composition exhibits crosslinking between the components of the adhesi ve composition after the adhesi ve composition has cured may be preferable. For example, it has been found that certain type of tackifying agents, such as those with hydroxyl groups, may be favorable. As an example, tackifying agents for example resins having hydroxyl groups can be polymerized with an isocyanate compound, for example MDI, to form a hot melt pressure sensitive adhesive composition. When the hot melt pressure sensitive adhesive composition is exposed to air, it may be cured by moisture, for example by ambient moisture in the air, to form a cured adhesive exhibiting a certain degree of crosslinking In some examples, adding a plasticizer that can react with the other components of the adhesive composition may help crosslinking of the components of the adhesive composition, and may help increase the cohesion. For example, adding a hydroxyl-containing plasticizer may increase the cohesion of the cured adhesive composition.

[0086] It has been found that the hot melt pressure sensitive adhesive compositions disclosed herein have good stability, such as viscosity stability and viscosity growth rate stability, up to high temperatures, such as about 150°C. Good viscosity stability allows the hot melt pressure sensitive adhesive compositions disclosed herein to be useful in a wide range of applications. It has been found that in some compositions, controlling certain levels of MDI can tune the viscosity stability which can enable the adhesive composition to be tuned to fit various kinds of manufacturing processes. For example, the hot melt pressure sensitive adhesive composition can maintain viscosity stability at temperatures that are used for melting and applying the adhesive composition as a liquid under manufacturing conditions.

[0087] The hot melt pressure sensitive adhesive compositions disclosed herein have been found to be suitable for bonding a wide range of substrates formed from materials such as PC,

PE, PET, PVC, PP, ABS, PA, among others. The hot melt pressure sensitive adhesive

compositions disclosed herein have been found to have good tack, good cohesion strength, good peel strength and good holding power The hot melt pressure sensitive adhesive compositions disclosed herein maintain these characteristics at high temperatures, such as between room temperature and for example at temperatures as great as 1G0°C.

[0088] It has been found that the hot melt pressure sensitive adhesive compositions disclosed herein also exhibit pressure sensitive characteristics after the adhesive composition has cured.

The adhesive composition may be tacky at room temperature (e.g. 25°C to 35°C) and at temperatures above room temperature, for example temperatures between room temperature and l00°C. The adhesive composition also is flexible, even after being cured

[0089] In some examples, the hot melt pressure sensitive adhesive compositions disclosed herein can be applied as a liquid to a first substrate. The viscosity stability allows the adhesive composition to remain as a liquid as the adhesive composition is delivered and applied to the first substrate, for example as the adhesive composition is delivered through a tube, and/or through a nozzle, at high temperatures. In some applications, a second substrate may be attached to the first substrate by bringing the second substrate in contact with the adhesive composition that has been applied to the first substrate. For example, the second substrate may be brought in contact with the first substrate before or after the adhesive composition has cured. The pressure sensitive characteristics may help the second substrate to be positioned in relation to the first substrate while the adhesive composition is curing, and/or after it has cured. The features and

characteristics of the hot melt pressure sensitive adhesive compositions, including but not limited to those described herein, provides a user with a wide range of applications, and a range of conditions that the adhesive composition can be applied under.

[0090] ln some examples, the adhesive composition can be applied as a film for example, to a first substrate, and then after the adhesive composition has cured, to attach the first substrate to a second substrate ln certain instances, the adhesive composition can be used to form tape, such as removable tape. In certain instances, the adhesive composition can be coated to a substrate to form labels. The adhesive composition may be used to make tape with high temperature performance as the adhesive composition can maintain tackiness at high temperatures, such as above room temperature. In some instances, the crosslinking of the componen ts of the adhesi ve composition helps to improve and maintain the cohesion strength of the adhesive composition, even at high temperatures. For example, a tape formed using the hot melt adhesive compositions disclosed herein may be applied to a substrate at about room temperature and maintain its level of tackiness as the tape is heated to temperatures above room temperature.

[0091] The hot melt pressure sensitive adhesive compositions disclosed herein are useful in the manufacture of articles and/or for bonding to substrates made of a wide variety _" of materials, including but not limited to wood, cardboard, paper, metal, plastics, rubbers, glass, nonwovens, and textiles. Further examples include consumer products and in specialized industrial applications. Markets where the hot melt pressure sensitive adhesive compositions are useful include disposable items, such as diapers or feminine hygiene products, textiles such as carpet and clothing, food packaging, footwear, consumer electronics, construction, furniture, automotive and aircraft. Various applications include but are not limited to use in marine and automotive applications, windows, use in the manufacture of doors including entry _" doors, garage doors and the like, use in the manufacture of architectural panels, use in bonding components on the exterior of vehicles, such as headlamps and the like. [0092] The hot melt pressure sensitive adhesive compositions disclosed herein may be used to bond articles together by" applying the adhesive compositions in a liquid or molten form to a surface of a first article, bringing a second article in contact with the adhesive compositions applied to the first article, and subjecting the applied adhesive composition to conditions which will allow the adhesive composition to cool and cure to a solid form. In some instances, the conditions for the adhesive compositions to cool and cure may include environments that contain ambient moisture, which may" react with the components of the adhesive composi tion to cure the adhesive.

[0093] The adhesive compositions may be distributed and stored in a solid form, and stored in the absence of moisture. When the adhesive composition is ready" for use, the solid adhesive composition may be heated and melted prior to application.

EXAMPLES

[0094] The fol lowing non-limiting examples are included to further illustrate various embodiments of the present disclosure and are not intended to limit the scope of the present disclosure.

TEST METHODS

Viscosity Test Method

[0095] Viscosity was determined using a Brookfield DV2T viscometer and a spindle number 27 rotating at five to ten rpm on a composition to be tested that has been heated to 150°C.

[0096] Viscosity stability was determined by measuring the viscosity" according to the Viscosity Test Method of ASTM D445 (ISO 3104) on an hourly" basis and calculating the increase as a percentage of the initial viscosity. The sample was aged in the viscometer.

Tack Test Method

[0097] The tack or tackiness test may be carried out by" placing a sample of adhesive composition onto a firs t substrate, and bringing a second substrate, such as a piece of paper, a piece of pl astic, or a finger, in contact with the sample of adhesi ve composition. The samples of adhesive composition were formed into a film 0.15 millimeter (mm) thick and 2.5 centimeter (cm) (one inch) wide. The samples were applied at a temperature of 150°C. The samples w'ere measured at a temperature of 25°C after one week of curing. No increase in the amount of force needed to remove the second substrate from the adhesive composition would indicate no tack or tackiness. Low tack or low tackiness would be found if the second substrate would remain in place at the position along the first substrate where the second substrate is in contact with the adhesive composition, but can be separated from the first substrate with minimal force and without deforming the sample of adhesive composition. Medium tack or moderate tack may be found if the second substrate is contacted with the adhesive composition and there is a change in the shape of the surface of the adhesive composition as the second substrate is separated from the first substrate. Moderate tack may be found in substances such as gums or tree sap. High tack or high tackiness is found when separating the second substrate from the portion of the first substrate having the adhesive composition causes a change in the shape of the sample of adhesive composition or the shape of either the first or second substrate, including but not requiring damage to the first and/or second substrate (e.g. difficulty removing plywood or plastic, tearing the surface of cardboard or paper, adhesive composition remaining on the skin of a finger when removing the finger from the adhesive composition ). High tack is typically comparable to house hold tapes, for example packing tapes or duct tapes.

Shear and Peel Test Method

[0098] The shear test was conducted by laminating a first three mm thick polycarbonate (PC) substrate with an adhesive composition to form a film of the adhesive composition with a thickness of 0 15 mm. The applied adhesive composition was then then contacted with a second three mm thick polycarbonate (PC) substrate after about five to 20 minutes of the adhesive composition being laminated onto the PC substrate. The shear tests were conducted after the samples were prepared and then maintained for one week in a constant temperature and humidity room set at 25°C and 50% relative humidity.

[0099] Test samples for the shear tests were cut with each sample having dimensions of one inch (2.54 cm) by four inches (10.2 cm), and three mm thick using standard polycarbonate (PC) lap-shears, with a 1/2 inch ² (3.2 cm ² ) area of overlap and 0.005 inch (0.0127 cm) spacer

[0100] Test samples for the peel sample were cut, with each sample having dimensions of one inch (2.54 cm) by four inches (10.2 cm), and three mm thick using standard PC lap-shears. The samples for the peel test were formed by laminating a three mm thick polycarbonate (PC) substrate with an adhesive composition to form a film of adhesive composition with a thickness of 0.15 mm. The applied adhesive composition was then contacted with a 0.05 mm thick polyethylene terephthalate (PET) film after about five to 20 minutes of the adhesive composition being laminated onto the PC substrate. The peel tests were conducted after the samples were prepared and then maintained for one week in a constant temperature and humidity room set at 25°C and 50% relative humidity.

[0101] The travel speed of the shear and peel testing machine was 50 mm/min. All data was measured at 25°C and 60% humidity, using a tester available under the trade designation

INSTRON (model LEGEND 2369 available from Illinois Tool Works Inc., in Norwood, MA). Holding Power Test Method

[0102] Test samples for the holding power tests were cut with each sample having dimensions of one inch (2.54 cm) by four inches (10.2 cm), and three mm thick using standard polycarbonate (PC) lap-shears, with a 1/2 inch ² (3.23 cm ² ) area of overlap and 0.005 inch (0.0127 cm) spacer.

[0103] The holding power test was conducted by laminating a first three mm thick PC substrate with the adhesive composition to form a film of the adhesi ve composition with a thickness of 0.15 mm. The applied adhesive composition was then then contacted with a second three mm thick PC substrate within fi ve to 20 minutes of being laminated onto the PC substrate.

[0104] Holding power tests w ^? ere conducted one week after the samples were formed and then maintained for one week in a constant temperature and humidity room set at 25°C and 50% relative humidity.

[0105] To test the samples, each sample was hung vertically in an oven. The top side of each sample was fixed while the bottom side was loaded with a one kg weight. The test samples were placed in an oven for about one hour to raise the adhesive composition to the test temperature. The time when the weighted sampled dropped, after being heated to the test temperature, was recorded.

[0106] EXAMPLE 1

[0107] In a first exemplary sample, an S1S block copolymer (SIS 1 105, available from Grand Petrochemical Co., Ltd., in Ningbo, China), a first tackifying agent (SYLVARES TP 300, a terpene phenolic resin available from KRATON, Corp., Houston, TX), a second tackifying agent (LUHOREZ M90, available from Luhua Hongjin New Material Co., Ltd, Zibo, China), and a plasticizer in the form of a naphthenic oil (KN4010, available from Fuda Petrochemical Co., Ltd, located in Hangzhou, China) were combined in a first step in a vessel. The components of the vessel combined in the first step were maintained at a temperature from about 100°C to about 200°C while the components were combined. A vacuum was drawn inside the vessel and the pressure inside the vessel was maintained at less than or equal to -0.9 MPa relative to

atmospheric pressure for about two to three hours as the components in the vessel were mixed.

At the end of the first step, the components that were combined in the first step were allowed to cool to a temperature from about 80°C to about 130°C.

[0108] After the first step, in a second step, MDI (DESMODUR 44 C Fused, from Covestro, of Leverkusen, Germany) and a catalyst, 2,2' dimorpholinodiethylether (JEFFCAT DMDEE, from HUNSTMAN, of The Woodlands, TX), were added to the components that were combined in the vessel in the first step. The components of the vessel in the second step were maintained at a temperature from about 80°C to about 130°C during the second step. A vacuum was drawn inside the vessel and the pressure inside the vessel was maintained at less than or equal to -0.9 MPa relative to atmospheric pressure for about half an hour to about two hours as the

components were mixed. At the conclusion of the second step, a hot melt pressure sensitive adhesive was produced. Table l show's the weight in grams of the components of the first exemplary sample, Sample A2, which is listed in Table 1 and various tested parameters.

[0109] A first comparative sample was produced to compare to Sample A2. The components used to form the first comparative example are shown in Table 1 and the sample is titled Sample Al. Generally, the same steps used to make Sample A2 were used to make Sample Al.

However, no MDI was added to form Sample Al in step 2.

[0110] EXAMPLE 2

[0111 ] In a second exemplary example, the same steps used to form the hot melt pressure sensitive adhesive of Sample A2 were used to make Sample B2. However, in Sample B2, the SIS block copolymer was replaced with an SIS copolymer available under the product designation SIS 1126 (from Grand Petrochemical Co., Ltd., in Ningbo, China), and the first tackifying resin was replaced with resin available under the trade designation SYLYARES TP 96 (from

KRATON, Corp., Houston, TX). The amounts of the components in Sample B2 are shown in Table 1, along with various tested parameters.

[0112] A second comparative sample was produced to compare to Sample B2. The first comparative example is included in Table 1 and is titled Sample Bl. The same steps used to make Sample B2 were used to make Sample B l . However, no MDI was added to form Sample B! . The amounts of the components used to make Sample B l are included in Table 1.

[0113] EXAMPLE 3

[0114] In a third exemplary example, the same steps used to form the hot melt pressure sensitive adhesive of Samples A2 and B2 were used to make Sample C2. However, in Sample C2, the SIS block copolymer was replaced with a SIS copolymer available under the product designation Dl 124 (from K RATON. Corp , Houston, TX), and the first tackifying resin was replaced with a resin available under the trade designation SYLVARES TP 105 (from

KRATON, Corp., Houston, TX) The amounts of the components in Sample C2 are shown in Table 1, along with various tested parameters

[0115] A third comparative sample was produced to compare to Sample C2. The third comparative example is included in Table 1 and is titled Sample Cl . The same steps used to make Sample C2 were used to make Sample Cl However, no MDI was added to form Sample Cl The amounts of the components used to make Sample Cl are included in Table 1.

[0116] As shown in Table 1, comparing Sample A2 to Sample Al, Sample B2 to Bl, and Sample C2 to Cl, adding MD1 increases the peel strength above that of the corresponding comparative sample that does not have MDI. As shown, in Sample A2, the peel strength was more than 6 times greater than in Sample Al without MDI. Also shown is an increase in shear strength in the exemplary examples above that of the corresponding comparative sample that does not have MDI. In some examples, such as Sample B2 and Sample C2, adding the MDI led to an increase in the shear strength by about four times greater than in the corresponding comparative sample which does not have MDI.

[0117] FIG. 1 is a graph showing the holding time of the samples contained in Table 1 at various temperatures. As shown in FIG. 1 and as tabulated in Table 1, at 40°C the Sample Al holding time 2, Sample Bl holding time 4, and Sample Cl holding time 6 were all less than one minute. As shown in FIG. 1 and in Table 1, Sample A2 was first exposed to a temperature of about 40°C for about one hour. After about one hour at 40°C, Sample A2 had not failed and the temperature was then increased to 60°C. After this thermal history, and then at a temperature of about 60°C, the Sample A2 holding time 10 was about forty minutes. As shown in FIG. 1 and in Table 1, Sample C2 was first exposed to a temperature of about 40°C for about one hour. After about one hour, the temperature was increased to 60°C. After about 18 hours at 60°C, Sample C2 had not failed, and was then exposed to a higher temperature of 75°C. After the previous thermal history, at 75°C the Sample C2 holding time 12 was about four hours and ten minutes. As shown in FIG. 1 and in Table 1 , Sample B2 was exposed to a temperature of about 40°C for about one hour, then exposed to a temperature of about 60 ^C C for about 18 hours, then exposed to a temperature of about 75°C for about 30 hours, then exposed to a temperature of about 85°C for about 70 hours, and then exposed to a temperature of 100°C, and the bond did not fail. That is, Sample B2 was exposed to an ever increasing temperature of 40°C, then 60°C, then 75°C, then 85°C, and 100°C. After the total Sample B2 holding time 14 was over 145 hours, the Sample B2 bond had not failed.

[0118] As shown in Table 1, the level of tack or tackiness in the adhesive composition both before and after curing can be tuned by adjusting the amount of the thermoplastic polymer that is used to form the hot melt pressure sensitive adhesive composition. It has been observed that high tack can be attained when the amount of thermoplastic polymer used is relatively low, for example at weight percentages of about 17% or 18%. When the thermoplastic polymer (e.g. styrene block copolymer) content in the hot melt pressures sensitive adhesive composition is higher, for example at about 42 wt.%, the level of tack may be lower. For example, comparing Samples A2 and C2, where C2 has more than twice as much thermoplastic polymer content, in some instances the level of tack in the adhesive composition is lower in adhesive compositions with higher amounts of thermoplastic polymer. As shown with Sample C2, in adhesive compositions having higher amounts of thermoplastic polymer, the level of tack may be lower after the adhesive composition has cured than before it is cured.

[0119] As also shown in Table 1, cohesive strength can be about three times greater by tuning the amount of MDI in the adhesive composition. For example, reading the shear strengths and peel strengths shown in Table 1, the effect of the MDI on these properties is shown by comparing Samples A2, B2, and C2. In general, greater amounts of MDI is believed to provide a higher level of crosslinking, such that the polymer network throughout the adhesive composition is enhanced and helps to tune the shear and peel strength. Further, the level of tack after curing and the holding time at elevated temperatures can also be tuned by finding a suitable amount of MDI for a desired value.

[0120] Various modifications and additions can be made to the exemplary embodiments discussed without departing from the scope of the present invention. For example, while the embodiments described above refer to particular features, the scope of this invention also includes embodiments having different combinations of features and embodiments that do not include all of the above described features.