Patent Description:
In the past, polybutene-<NUM> homopolymers and copolymers were made using a Ziegler-Natta catalyst. These polybutene-<NUM> polymers exhibited high melt viscosities and had to be treated with organic peroxides to decrease the molecular weight and therefore the melt viscosity of the polymers to render them suitable for use in existing hot melt adhesive applicators. The molecular weight of the resulting product was random and difficult to control and resulted in highly variable products.

The high viscosity polybutene-<NUM> polymers also were brittle at room temperature and produced adhesives that were brittle at room temperature. The brittle properties enabled the formulation of hot melt adhesives that could temporarily bond substrates together for a period of time and then allow the substrates to be easily separated without a negative aesthetic alteration of the substrate's surface. Such adhesive compositions have been used to hold pallets of packaged products together during shipping. After shipping, the packaged products can be easily separated from one another at their destination.

Recently, polybutene-<NUM> homopolymers and copolymers synthesized using metallocene catalysts have become available and have been described as being useful for incorporation into hot melt adhesive compositions that include a liquid or non-solid viscosity modifier such as plasticizing oils and greases. The presence of a non-solid viscosity modifier can the impact set time of the adhesive. Such hot melt adhesive compositions have been described as being suitable for use in manufacturing disposable hygiene articles including bonding porous substrates, such as nonwoven webs, for use in diaper constructions.

Hot melt adhesives are used in a variety of applications in the packaging industry including, e.g., case and carton sealing, tray forming and box forming. Typical substrates used in packaging applications include virgin and recycled kraft, high and low density kraft, chipboard and various types of treated and coated kraft and chipboard. To be useful, hot melt adhesive compositions must be capable of forming a fiber tearing bond to such substrates at room temperature. In addition, many packaging applications require the hot melt adhesive to exhibit a sufficient degree of adhesion to the substrate to firmly hold the resulting package together under a variety of conditions such as low temperatures, high temperatures, and stress and to be free of staining. <CIT> and <CIT> both disclose hot melt adhesive polyolefin compositions comprising metallocene catalyzed butene-<NUM>
copolymers.

There is a need for a hot melt adhesive composition that exhibits good adhesion to case and carton substrates under a variety of conditions. There is a particular need for a hot melt adhesive composition that exhibits good adhesion, under a variety of conditions, to difficult to bond substrates of the type used in case and carton sealing.

In one aspect, the invention features a hot melt adhesive composition that includes at least <NUM> % by weight metallocene-catalyzed polybutene-<NUM>, the metallocene-catalyzed polybutene-<NUM> being selected from the group consisting of polybutene-<NUM> homopolymer, polybutene-<NUM> copolymer, and combinations thereof, the metallocene-catalyzed polybutene-<NUM> comprising at least <NUM> % by weight, based on the weight of the hot melt adhesive composition, of a first metallocene-catalyzed polybutene-<NUM> having a melt flow rate of at least <NUM> grams per <NUM> minutes (g/<NUM>) at <NUM>, tackifying agent, and at least <NUM> % by weight wax as defined in claim <NUM>, the hot melt adhesive composition having a specific gravity of less than <NUM>.

In one embodiment, the hot melt adhesive composition includes at least <NUM> % by weight, or even greater than <NUM> % by weight, metallocene-catalyzed polybutene-<NUM>. In another embodiment, the hot melt adhesive composition includes at least <NUM> % by weight, or even greater than <NUM> % by weight, metallocene-catalyzed polybutene-<NUM>.

In other embodiments, the hot melt adhesive composition includes at least <NUM> % by weight metallocene-catalyzed polybutene-<NUM> and at least, or even greater than, <NUM> % by weight of a wax having a melt temperature (Tm) of at least <NUM>. In other embodiments, the hot melt adhesive composition includes at least, or even greater than, <NUM> % by weight metallocene-catalyzed polybutene-<NUM>, and at least, or even greater than, <NUM> % by weight of a wax having a Tm of at least <NUM>. In other embodiments, the hot melt adhesive composition includes at least <NUM> % by weight, or even greater than <NUM> % by weight, metallocene-catalyzed polybutene-<NUM>, and at least, or even greater than, <NUM> % by weight of a wax having a Tm of at least <NUM>.

In one embodiment, the hot melt adhesive composition includes at least <NUM> % by weight, or even greater than <NUM> % by weight, metallocene-catalyzed polybutene-<NUM> having a melt flow rate of at least <NUM>/<NUM> at <NUM> and a specific gravity of no greater than <NUM>. In another embodiment, the hot melt adhesive composition includes at least <NUM> % by weight, or even greater than <NUM> % by weight, metallocene-catalyzed polybutene-<NUM> having a melt flow rate of at least <NUM>/<NUM> at <NUM> and a specific gravity of no greater than <NUM>. In some embodiments, the hot melt adhesive composition includes from <NUM> % by weight to <NUM> % by weight metallocene-catalyzed polybutene-<NUM>. In other embodiments, the hot melt adhesive composition includes from <NUM> % by weight to <NUM> % by weight metallocene-catalyzed polybutene-<NUM>, no greater than <NUM> % by weight tackifying agent, and at least <NUM> % by weight of a wax having a melt temperature of at least, or even greater than, <NUM>.

In some embodiments, the hot melt adhesive composition includes no greater than <NUM> % by weight tackifying agent. In other embodiments, the hot melt adhesive composition includes no greater than <NUM> % by weight tackifying agent.

In some embodiments, the first metallocene-catalyzed polybutene-<NUM> has a specific gravity of no greater than <NUM>. In other embodiments, the first metallocene-catalyzed polybutene-<NUM> has a specific gravity of no greater than <NUM>.

In some embodiments, the hot melt adhesive composition has a specific gravity of no greater than <NUM>. In other embodiments, the hot melt adhesive composition has a specific gravity of no greater than <NUM>.

In another embodiment, the hot melt adhesive composition includes at least <NUM> % by weight of a wax having a Tm of at least <NUM>. In other embodiments, the hot melt adhesive composition includes greater than <NUM> % by weight of a wax having a Tm of at least <NUM>. In other embodiments, the hot melt adhesive composition includes at least, or even greater than, <NUM> % by weight of a wax having a Tm of at least <NUM>. In other embodiments, the hot melt adhesive composition includes at least, or even greater than, <NUM> % by weight of a wax having a Tm of at least, or even greater than, <NUM>. In one embodiment, the hot melt adhesive composition includes at least, or even greater than, <NUM> % by weight of a wax having a Tm at least, or even greater than, <NUM>. In another embodiment, the hot melt adhesive composition includes at least, or even greater than, <NUM> % by weight of a wax having a Tm at least, or even greater than, <NUM>.

In some embodiments, the hot melt adhesive composition has a viscosity of no greater than <NUM> mPa·s (centipoise) at <NUM>. In other embodiments, the hot melt adhesive composition has a viscosity of no greater than <NUM> mPa·s (cP) at <NUM>. In other embodiments, the hot melt adhesive composition has a viscosity of no greater than <NUM> mPa·s (cP) at <NUM>.

In other embodiments, the first metallocene-catalyzed polybutene-<NUM> has a melt flow rate greater than <NUM>/<NUM> at <NUM>.

In another embodiment, the hot melt adhesive composition further includes a second metallocene-catalyzed polybutene-<NUM> having a melt flow rate less than <NUM>/<NUM> at <NUM> and a specific gravity of less than <NUM>.

In another embodiment, the hot melt adhesive composition further includes a second metallocene-catalyzed polybutene-<NUM>, the second metallocene-catalyzed polybutene-<NUM> having a melt flow rate from <NUM>/<NUM> to <NUM>/<NUM> at <NUM>.

In other embodiments, the hot melt adhesive composition further includes a semi-crystalline polymer selected from the group consisting of propylene/ethylene copolymer, ethylene/propylene copolymer, and combinations thereof.

In one embodiment, the hot melt adhesive composition exhibits at least <NUM> % fiber tear at <NUM> when tested according to the % Fiber Tear PRATT Test Method. In another embodiment, the hot melt adhesive composition exhibits at least <NUM> % fiber tear at <NUM> when tested according to the % Fiber Tear PRATT Test Method and at least <NUM> % fiber tear at -<NUM> when tested according to the % Fiber Tear PRATT Test Method.

In other aspects, the invention features a package that includes a hot melt adhesive composition disclosed above and herein, a first substrate that includes fibers and a second substrate that includes fibers, the second substrate bonded to the first substrate through the adhesive composition.

The present invention features hot melt adhesive compositions that include relatively high levels of polybutene-<NUM> polymer and that maintain fiber tearing bonds to fibrous substrates at room temperature. The present invention also features embodiments of the hot melt adhesive composition that include relatively high levels of polybutene-<NUM> polymer and that maintain fiber tearing bonds to difficult to bond substrates at room temperature. The present invention also features embodiments of the hot melt adhesive composition that include relatively high levels of polybutene-<NUM> polymer and that maintain fiber tearing bonds to difficult to bond substrates at low temperatures. The present invention also features hot melt adhesive compositions that include relatively high levels of polybutene-<NUM> polymer and exhibit a viscosity suitable for application using hot melt applicator equipment.

Other features and advantages will be apparent from the following description of the preferred embodiments and from the claims.

In reference to the invention, these terms have the meanings set forth below:.

The hot melt adhesive composition includes metallocene-catalyzed polybutene-<NUM> having a melt flow rate of at least <NUM>/<NUM> at <NUM>, tackifying agent, and at least <NUM> % by weight wax. The hot melt adhesive composition exhibits fiber tearing bonds to fibrous packaging materials at room temperature and preferably exhibits fiber tearing bonds at high and low temperatures. The reference to fiber tear at a temperature refers to the temperature at which the test sample used to measure fiber tear is conditioned.

At <NUM>, the hot melt adhesive composition exhibits greater than <NUM> %, greater than <NUM> %, greater than <NUM> %, greater than <NUM> %, greater than <NUM> %, greater than <NUM> %, greater than <NUM> %, or even greater than <NUM> % fiber tear. At <NUM>, or even at <NUM>, the hot melt adhesive composition exhibits greater than <NUM> %, greater than <NUM> %, or even greater than <NUM> % fiber tear. At low temperatures such as <NUM>, -<NUM>, or even -<NUM>, the hot melt adhesive composition preferably exhibits greater than <NUM> %, greater than <NUM> %, or even greater than <NUM> % fiber tear. The hot melt adhesive composition can be formulated to exhibit any combination of the aforementioned fiber tear properties. The hot melt adhesive composition also can be formulated to exhibit any combination of the aforementioned fiber tear properties when measured using a relatively easy to bond substrate such as WESTROCK <NUM>-pound edge crush C flute corrugated linear board with greater than <NUM> % recycled fibers ("WESTROCK <NUM>") or even when measured using a relatively hard to bond substrate such as PRATT <NUM> pound edge crush test (ECT) with C style flute corrugated liner board ("PRATT") that includes <NUM> % recycled fibers at room temperature.

The hot melt adhesive composition also preferably has a specific gravity of less than <NUM>, no greater than <NUM>, or even no greater than <NUM>.

The hot melt adhesive composition preferably has a viscosity of less than <NUM> mPa·s (cP), less than <NUM> mPa·s (cP), no greater than <NUM> mPa·s (cP), no greater than <NUM> mPa·s (cP), no greater than <NUM> mPa·s (cP), or even no greater than <NUM> mPa·s (cP) at <NUM>, or even at <NUM>.

The hot melt adhesive composition exhibits a fast set time, and preferably exhibits a set time of no greater than <NUM> seconds, no greater than <NUM> seconds, no greater than <NUM> seconds, no greater than <NUM> seconds, no greater than <NUM> second, or even no greater than <NUM> seconds.

The hot melt adhesive composition also exhibits good heat resistance as measured by Peel Adhesion Failure Temperature (PAFT), Shear Adhesion Failure Temperature (SAFT), heat stress resistance (IOPP), or a combination thereof. Preferably the hot melt adhesive composition exhibits a PAFT of at least <NUM>, at least <NUM>, at least <NUM>, or even at least <NUM>, a SAFT of at least <NUM>, at least <NUM>, or even at least <NUM>, an IOPP of at least <NUM>, at least <NUM>, or even at least <NUM>, or a combination thereof.

A formulation of the hot melt adhesive composition that is particularly useful for maintaining a fiber tearing bond to relatively hard to bond substrates at room temperature includes a tackifying agent, at least <NUM> % by weight wax of which at least <NUM> % by weight, based on the weight of the hot melt adhesive composition, is a wax having a Tm greater than <NUM>, and greater than <NUM> % by weight of a metallocene-catalyzed polybutene-<NUM> polymer of which at least <NUM> % by weight, based on the weight of the adhesive composition, is a metallocene-catalyzed polybutene-<NUM> having melt flow rate greater than <NUM>/<NUM> at <NUM>.

Another formulation of the hot melt adhesive composition that is particularly useful for maintaining a fiber tearing bond to relatively hard to bond substrates at room temperature includes a tackifying agent, at least <NUM> % by weight wax, and greater than <NUM> % by weight of a metallocene-catalyzed polybutene-<NUM> polymer having a melt flow rate greater than <NUM>/<NUM> at <NUM>.

A formulation of the hot melt adhesive composition that is particularly useful for maintaining a fiber tearing bond to hard to bond substrates at low temperature, such as <NUM>, includes no greater than <NUM> % by weight tackifying agent, at least <NUM> % by weight of a metallocene-catalyzed polybutene-<NUM> polymer, of which at least <NUM> % by weight, based on the weight of the hot melt adhesive composition, is a metallocene-catalyzed polybutene-<NUM> polymer having a melt flow rate greater than <NUM>/<NUM> at <NUM> and a specific gravity of no greater than <NUM>, and at least <NUM> % by weight of a wax having a Tm of at least <NUM>, at least <NUM> or even at least <NUM>.

A formulation of the hot melt adhesive composition that is particularly useful for maintaining a fiber tearing bond to hard to bond substrates at low temperature, such as -<NUM>, includes no greater than <NUM> % by weight tackifying agent, at least <NUM> % by weight of a metallocene-catalyzed polybutene-<NUM> polymer, of which at least <NUM> % by weight, based on the weight of the hot melt adhesive composition, is a metallocene-catalyzed polybutene-<NUM> polymer having a melt flow rate greater than <NUM>/<NUM> at <NUM> and a specific gravity of no greater than <NUM>, and at least <NUM> % by weight of a wax having a Tm of at least <NUM> or even at least <NUM>.

The hot melt adhesive composition includes metallocene-catalyzed polybutene-<NUM>. At least <NUM> % by weight of the metallocene-catalyzed polybutene-<NUM> that is present in the hot melt adhesive composition has a melt flow rate of at least <NUM>/<NUM>, at least <NUM>/<NUM>, at least <NUM>/<NUM>, no greater than <NUM>,<NUM>/<NUM>, or even from <NUM>/<NUM> to <NUM>/<NUM> at <NUM> using a <NUM> load when tested according to ASTM D1238A. The metallocene-catalyzed polybutene-<NUM> also preferably has a specific gravity no greater than <NUM>, no greater than <NUM>, no greater than <NUM>, or even about <NUM>.

Suitable metallocene-catalyzed polybutene-<NUM> polymers include metallocene-catalyzed polybutene-<NUM> homopolymers, metallocene-catalyzed polybutene-<NUM> copolymers, and combinations thereof. Metallocene-catalyzed polybutene-<NUM> copolymers are derived from at least <NUM> % by weight butene and less than <NUM> % by weight alpha-olefin comonomer. Useful alpha-olefin comonomers include, e.g., ethylene, propylene, hexene, octene, and combinations thereof.

The metallocene-catalyzed polybutene-<NUM> optionally is a mixture of at least two different metallocene-catalyzed polybutene-<NUM> polymers including, e.g., at least one metallocene-catalyzed polybutene-<NUM> having a first melt flow rate or a first specific gravity and a metallocene-catalyzed polybutene-<NUM> having a second melt flow rate or a second specific gravity either or both of which are different from the first melt flow rate or first specific gravity. One example of a useful metallocene-catalyzed polybutene-<NUM> mixture includes a first metallocene-catalyzed polybutene-<NUM> having a melt flow rate of at least <NUM>/<NUM> and a specific gravity of no greater than <NUM> and a second metallocene-catalyzed polybutene-<NUM> having an melt flow rate of at least <NUM>/<NUM> and a specific gravity of no greater than <NUM>.

Useful metallocene-catalyzed polybutene-<NUM> polymers are commercially available under a variety of trade designations including, e.g., KOATTRO series of trade designation from LyondellBasell Industries Holdings, B. (Netherlands) including KOATTRO PB M <NUM> random polybutene-<NUM>/ethylene copolymer and KOATTRO PB M <NUM> random po lybutene-<NUM> /ethylene copolymer.

The hot melt adhesive composition includes at least <NUM> % by weight metallocene-catalyzed polybutene-<NUM>, and at least <NUM> % by weight, at least <NUM> % by weight, at least <NUM> % by weight, at least <NUM> % by weight, at least <NUM> % by weight, greater than <NUM> % by weight, at least <NUM> % by weight, greater than <NUM> % by weight, at least <NUM> % by weight, no greater than <NUM> % by weight, no greater than <NUM> % by weight, no greater than <NUM> % by weight, from <NUM> % by weight to <NUM> % by weight, from <NUM> % by weight to <NUM> % by weight, from <NUM> % by weight to <NUM> % by weight, or even from <NUM> % by weight to <NUM> % by weight, based on the weight of the hot melt adhesive composition, of a metallocene-catalyzed polybutene-<NUM> having a melt flow rate of at least <NUM>/<NUM> at <NUM>.

The metallocene-catalyzed polybutene-<NUM> optionally additionally includes a metallocene-catalyzed polybutene-<NUM> that has a melt flow rate of greater than <NUM>/<NUM> and less than <NUM>/<NUM> at <NUM>. One example of a useful commercially available metallocene-catalyzed polybutene-<NUM> that has a melt flow rate less than <NUM>/<NUM> at <NUM> is KOATTRO PB M <NUM> random polybutene-<NUM>/ethylene copolymer from LyondellBasell. The optional metallocene-catalyzed polybutene-<NUM>, when present in the hot melt adhesive composition, is present in an amount less than <NUM> % by weight, less than <NUM> % by weight, less than <NUM> % by weight, less than <NUM> % by weight, from <NUM> % by weight to <NUM> % by weight, or even from <NUM> % by weight to <NUM> % by weight.

The hot melt adhesive composition optionally includes at least one polymer other than the metallocene-catalyzed polybutene-<NUM>. The total polymer content in the hot melt adhesive composition is at least <NUM> % by weight, at least <NUM> % by weight, at least <NUM> % by weight, greater than <NUM> % by weight, at least <NUM> % by weight, at least <NUM> % by weight, no greater than <NUM> % by weight, no greater than <NUM> % by weight, or even no greater than <NUM> % by weight.

Useful additional polymers include semi-crystalline polymers such as semi-crystalline polyolefins including, e.g., semi-crystalline polypropylene, semi-crystalline propylene/alpha olefin comonomer copolymers (e.g., semi-crystalline propylene/ethylene copolymers), semi-crystalline ethylene/alpha olefin comonomer copolymers (e.g., semi-crystalline ethylene/propylene copolymers), and combinations thereof. Useful semi-crystalline polyolefins are disclosed in a number of U. Patents including, e.g., <CIT>), <CIT>) and <CIT>).

Useful semi-crystalline propylene copolymers are derived from propylene and an alpha-olefin co-monomer including, e.g., alpha-olefin monomers having at least two carbon atoms, at least four carbon atoms, from four carbon atoms to eight carbon atoms, and combinations of such monomers). Suitable alpha-olefin co-monomers include, e.g., ethylene, butene, pentene, hexene, heptene, octene, nonene, decene, dodecene, <NUM>-methyl-pentene-<NUM>, <NUM>-methyl pentene-<NUM>,<NUM>,<NUM>,<NUM>-trimethyl-hexene-<NUM>, <NUM>-ethyl-<NUM>-nonene, <NUM>,<NUM>-decadiene, and combinations thereof. Specific examples of suitable propylene-alpha-olefin copolymers include propylene-ethylene, propylene-butene, propylene-hexene, propylene-octene, and combinations thereof.

Useful semi-crystalline ethylene copolymers are derived from ethylene and an alpha-olefin co-monomer including, e.g., alpha-olefin monomers having at least three carbon atoms, at least four carbon atoms, from three carbon atoms to eight carbon atoms, and combinations of such monomers). Suitable alpha-olefin co-monomers include, e.g., propylene, butene, pentene, hexene, heptene, octene, nonene, decene, dodecene, <NUM>-methyl-pentene-<NUM>, <NUM>-methyl pentene-<NUM>,<NUM>,<NUM>,<NUM>-trimethyl-hexene-<NUM>, <NUM>-ethyl-<NUM>-nonene, <NUM>,<NUM>-decadiene, and combinations thereof. Specific examples of suitable ethylene-alpha-olefin copolymers include ethylenepropylene, ethylene-butene, ethylene-hexene, ethylene-octene, and combinations thereof.

Suitable semi-crystalline polymers are prepared using a variety of catalysts including, e.g., a single site catalyst (e.g., metallocene catalysts (e.g., metallocene-catalyzed propylene polymers)), multiple single site catalysts, non-metallocene heteroaryl catalysts, and combinations thereof.

Another useful class of additional semi-crystalline polymers is the "crystalline block composite" (CBC) polymers. CBCs are those polymers that include a crystalline ethylene-based polymer (CEP), a crystalline alpha-olefin-based polymer (CAOP), and a block copolymer having a crystalline ethylene block (CEB) and a crystalline alpha-olefin block (CAOB), where the CEB of the block copolymer is essentially the same composition as the CEP in the block composite and the CAOB of the block copolymer is essentially the same composition as the CAOP of the block composite. The compositional split between the amount of CEP and CAOP will be essentially the same as that between the corresponding blocks in the block copolymer. The block copolymers can be linear or branched. Each of the respective block segments can contain long chain branches, but the block copolymer segment is substantially linear as opposed to containing grafted or branched blocks. Useful CBC polymers exhibit a polydispersity index of from <NUM> to <NUM>, <NUM> to <NUM>, from <NUM> to <NUM>, or even from <NUM> to <NUM>.

CAOBs are highly crystalline blocks of polymerized alpha olefin units in which the monomer is present in an amount greater than <NUM> mol %, greater than <NUM> mol %, greater than <NUM> mol %, or even greater than <NUM> mol % and the comonomer content is less than <NUM> mol %, less than <NUM> mol %, less than <NUM> mol %, or even less than <NUM> mol %. CAOBs with propylene crystallinity have corresponding melting points that are at least <NUM>, at least <NUM>, at least <NUM>, or even at least <NUM>.

CEB refers to blocks of polymerized ethylene units in which the comonomer content is no greater than <NUM> mol %, from <NUM> mol % to <NUM> mol %, from <NUM> mol % to <NUM> mol %, or even from <NUM> mol % to <NUM> mol %. The CEB has a melting point of at least <NUM>, at least <NUM>, or even at least <NUM>.

Useful semi-crystalline polyolefins are commercially available under a variety of trade designations including, e.g., the VISTAMAXX series of trade designations from ExxonMobil Chemical Company (Houston, Texas) including VISTAMAXX <NUM>, VISTAMAXX <NUM>, and VISTAMAXX <NUM> propylene-ethylene copolymers, the LICOCENE series of trade designations from Clariant Int'l Ltd. (Muttenz, Switzerland) including, e.g., LICOCENE PP <NUM> TP, PP <NUM> TP, and PP <NUM> TP propylene-ethylene copolymers, and the AFFINITY series of trade designations from The Dow Chemical Company (Midland, Michigan) including AFFINITY GA1900 ethylene-octene copolymer and AFFINITY GP1570 propylene-ethylene copolymer.

The hot melt adhesive composition optionally includes from <NUM> % by weight to no greater than <NUM> % by weight, at least <NUM> % by weight, at least <NUM> % by weight, no greater than <NUM> % by weight, no greater than <NUM> % by weight, no greater than <NUM> % by weight, no greater than <NUM> % by weight, or even no greater than <NUM> % by weight optional additional semi-crystalline polymer.

Other useful classes of polymers include, e.g., amorphous polyalphaolefins including, e.g., Ziegler-Natta catalyzed amorphous polyalphaolefins (e.g., amorphous propylene homopolymers, amorphous propylene-alpha-olefin comonomer copolymers, amorphous polyethylene polymers, amorphous polyethylene-alpha-olefin comonomer copolymers and combinations thereof), elastomers including, e.g., elastomeric block copolymers (e.g., elastomeric block copolymers that includes styrene (e.g., styrene-ethylene/butene-styrene, styrene-ethylene/propylene-styrene and combinations thereof), metallocene-based elastomeric block copolymers, and combinations thereof), and functionalized versions thereof, and combinations thereof.

Useful Ziegler Natta catalyzed amorphous polyalphaolefin polymers are commercially available under a variety of trade designations including, e.g., the REXTAC series of trade designations available from Rextac LLC (Odessa, Texas) and the EASTOFLEX and AERAFIN series of trade designations from Eastman Chemical Company (Kingsport Tennessee).

Useful elastomeric block copolymers are available under a variety of trade designations including, e.g., KRATON G <NUM> styrene-ethylene/butylene-styrene block copolymer and G <NUM> styrene-ethylene/propylene-styrene block copolymer from Kraton Polymers U. LLC (Houston, Texas).

The hot melt adhesive composition optionally includes from <NUM> % by weight to no greater than <NUM> % by weight, at least <NUM> % by weight, at least <NUM> % by weight, no greater than <NUM> % by weight, no greater than <NUM> % by weight, no greater than <NUM> % by weight, no greater than <NUM> % by weight, or even no greater than <NUM> % by weight of an optional additional amorphous polyalphaolefin polymer, elastomeric polymer or combinations thereof.

The hot melt adhesive composition also includes at least one wax. Useful waxes have a heat of fusion of greater than <NUM> J/g, or even greater than <NUM> J/g. Suitable waxes preferably have a melt temperature (Tm) of at least <NUM>, at least <NUM>, at least <NUM>, at least <NUM>, at least <NUM>, at least <NUM>, at least <NUM>, or even at least <NUM>. Examples of suitable waxes include Fischer-Tropsch waxes, polyolefin waxes (e.g., polypropylene waxes and polyethylene waxes), microcrystalline waxes, metallocene waxes, and combinations thereof.

Useful Fischer-Tropsch waxes are commercially available under a variety of trade designations including, e.g., Fischer-Tropsch waxes available under the SASOLWAX series of trade designations from Sasol Wax North America Corporation (Hayward, California) including, e.g., SASOLWAX C80, SASOLWAX H1, and SASOLWAX C105, Fischer-Tropsch waxes, the BARECO series of trade designations from Baker Hughes Inc. (Sugar Land, Texas) including, e.g., BARECO PX-<NUM> Fischer-Tropsch waxes, the SHELLWAX series of trade designations from Shell Malaysia Ltd. (Kuala Lumpur, Malaysia) including, e.g., SHELLWAX SX105 Fischer-Tropsch waxes, and the VESTOWAX series of trade designations from Evonik Industries AG (Germany) including, e.g., VESTOWAX <NUM> Fischer-Tropsch wax.

Useful polyethylene waxes are commercially available under a variety of trade designations including, e.g., the EPOLENE series of trade designations from Westlake Chemical Corporation (Houston, Texas) including, e.g., EPOLENE N-<NUM> and N-<NUM> polyethylene waxes, the BARECO series of trade designations from Baker Hughes Inc. (Sugar Land, Texas) including, e.g., BARECO C4040 polyethylene wax, the AC series of trade designations from Honeywell Int'l Inc. (Morristown, New Jersey) including, e.g., A-C <NUM> and A-C <NUM> polyethylene waxes, the POLYWAX series of trade designations including POLYWAX <NUM> polyethylene wax, POLYWAX <NUM> polyethylene wax, and POLYWAX <NUM> polyethylene wax, POLYWAX <NUM> polyethylene wax and POLYWAX <NUM> polyethylene wax from Baker Hughes Inc. (Houston, Texas), and CWP <NUM> polyethylene wax from Trecora Chemical, Inc. (Pasedena, Texas).

Useful polypropylene waxes are commercially available under a variety of trade designations including, e.g., EPOLENE N-<NUM> from Westlake Chemical, HONEYWELL AC1089 from Honeywell Int'l Inc. , and LICOCENE <NUM> from Clariant Int'l Ltd. (Muttenz, Switzerland).

The total wax content in the hot melt adhesive composition is at least <NUM> % by weight, at least <NUM> % by weight, from <NUM> % by weight to <NUM> % by weight, or even from <NUM> % by weight to <NUM> % by weight. The hot melt adhesive composition preferably includes at least <NUM> % by weight, at least <NUM> % by weight, at least <NUM> % by weight, from <NUM> % by weight to <NUM> % by weight, from <NUM> % by weight to <NUM> % by weight, or even from <NUM> % by weight to <NUM> % by weight of a wax having a Tm of at least <NUM>, at least <NUM>, at least <NUM> or even at least <NUM>.

The hot melt adhesive composition also includes a tackifying agent. Useful tackifying agents have a Tg of at least <NUM>, at least <NUM>, or even at least <NUM>, and Ring and Ball softening point of at least <NUM>. Suitable classes of tackifying agents include, e.g., fully hydrogenated aliphatic and cycloaliphatic hydrocarbon resins, fully hydrogenated aromatic modified aliphatic hydrocarbon resins, and combinations thereof. Examples of useful aliphatic and cycloaliphatic petroleum hydrocarbon resins include, e.g., branched, unbranched, and cyclic C5 resins, C9 resins, and C10 resins, and combinations thereof.

Useful tackifying agents are commercially available under a variety of trade designations including, e.g., the EASTOTAC series of trade designations from Eastman Chemical Company (Kingsport, Tennessee) including, e.g., EASTOTAC H-100R, EASTOTAC H-<NUM>, and EASTOTAC H130W, the ESCOREZ series of trade designations from ExxonMobil Chemical Company (Houston, Texas) including, e.g., ESCOREZ 1310LC, ESCOREZ <NUM>, ESCOREZ <NUM>, ESCOREZ <NUM>, ESCOREZ <NUM>, ESCOREZ <NUM>, and ESCOREZ <NUM>, the WINGTACK series of trade designations from Cray Valley HSC (Exton, Pennsylvania) including, e.g., WINGTACK <NUM>, WINGTACK EXTRA, and WINGTACK <NUM>, the PICCOTAC series of trade designations from Eastman Chemical Company (Kingsport, Tennessee) including, e.g., PICCOTAC <NUM> and <NUM>, the ARKON series of trade designations from Arkawa Europe GmbH (Germany) including, e.g., ARKON P-<NUM>, and the REGALITE and REGALREZ series of trade designations from Eastman Chemical Company including, e.g., REGALITE R1125 and REGALREZ <NUM>.

The hot melt adhesive composition includes at least <NUM> % by weight, at least <NUM> % by weight, at least <NUM> % by weight, at least <NUM> % by weight, less than <NUM> % by weight, no greater than <NUM> % by weight, no greater than <NUM> % by weight, no greater than <NUM> % by weight, from <NUM> % by weight to <NUM> % by weight, from <NUM> % by weight to <NUM> % by weight, from <NUM> % by weight to <NUM> % by weight, or even from <NUM> % by weight to <NUM> % by weight tackifying agent.

The hot melt adhesive composition optionally includes a variety of additional components including, e.g., antioxidants, stabilizers, adhesion promoters, ultraviolet light stabilizers, rheology modifiers, corrosion inhibitors, colorants (e.g., pigments and dyes), fillers, flame retardants, nucleating agents, plasticizers, and combinations thereof.

Useful antioxidants include, e.g., pentaerythritol tetrakis[<NUM>,(<NUM>,<NUM>-di-tert-butyl-<NUM>-hydroxyphenyl)propionate], <NUM>,<NUM>'-methylene bis(<NUM>-methyl-<NUM>-tert-butylphenol), phosphites including, e.g., tris-(p-nonylphenyl)-phosphite (TNPP) and bis(<NUM>,<NUM>-di-tert-butylphenyl)<NUM>,<NUM>'-diphenylene-diphosphonite, di-stearyl-<NUM>,<NUM>'-thiodipropionate (DSTDP), and combinations thereof. Suitable antioxidants are commercially available under a variety of trade designations including, e.g., the IRGANOX series of trade designations including, e.g., IRGANOX <NUM>, IRGANOX <NUM>, and IRGANOX <NUM> hindered phenolic antioxidants, and IRGAFOS <NUM> phosphite antioxidant, all of which are available from BASF Corporation (Florham Park, New Jersey), and ETHYL <NUM><NUM>,<NUM>'-methylene bis(<NUM>,<NUM>-di-tert-butylphenol). When present, the adhesive composition preferably includes from about <NUM> % by weight to about <NUM> % by weight antioxidant.

The hot melt adhesive composition can be applied to or incorporated in a variety of articles including, e.g., fibers, substrates made from fibers (e.g., virgin fibers, recycled fibers, synthetic polymer fibers (e.g., nylon, rayon, polyesters, acrylics, polypropylenes, polyethylene, polyvinyl chloride, polyurethane), cellulose fibers (e.g., natural cellulose fibers such as wood pulp), natural fibers (e.g., cotton, silk and wool), and glass fibers, and combinations thereof), release liners, porous substrates, cellulose substrates, sheets (e.g., paper, and fiber sheets), paper products, woven and nonwoven webs (e.g., webs made from fibers (e.g., yarn, thread, filaments, microfibers, blown fibers, and spun fibers), perforated films, and combinations thereof), tape backings, and combinations thereof.

The hot melt adhesive composition is useful for bonding a variety of substrates including, e.g., cardboard, coated cardboard, paperboard, fiber board, virgin and recycled kraft, high and low density kraft, chipboard, treated and coated kraft and chipboard, and corrugated versions of the same, clay coated chipboard carton stock, composites, leather, fibers and substrates made from fibers (e.g., virgin fibers, recycled fibers, synthetic polymer fibers, cellulose fibers, and combinations thereof), release liners, porous substrates (e.g., woven webs, nonwoven webs, and perforated films), cellulose substrates, sheets (e.g., paper, and fiber sheets), paper products, tape backings, and combinations thereof.

The hot melt adhesive composition is useful for bonding a first substrate to a second substrate in a variety of applications and constructions including, e.g., packaging, bags, boxes, cartons, cases, trays, multi-wall bags, articles that include attachments (e.g., straws attached to drink boxes), ream wrap, cigarettes (e.g., plug wrap), filters (e.g., pleated filters and filter frames), bookbinding, paper products including, e.g., paper towels (e.g., multiple use towels), toilet paper, tissues (e.g., facial tissue), wipes, and combinations thereof.

The hot melt adhesive composition can be applied to a substrate in any useful form including, e.g., as a coating (e.g., a continuous coatings and discontinuous coatings (e.g., random, pattern, and array)), as a bead, as a film (e.g., a continuous films and discontinuous films), and combinations thereof, using any suitable application method including, e.g., slot coating, spray coating (e.g., spiral spray, random spraying, and random fiberization (e.g., melt blowing), foaming, extrusion (e.g., applying a bead, fine line extrusion, single screw extrusion, and twin screw extrusion), wheel application, noncontact coating, contacting coating (e.g., direct coating), gravure, engraved roller, roll coating, transfer coating, screen printing, flexographic, "on demand" application methods, and combinations thereof.

In on demand hot melt application systems (which are also referred to as "tank free" and "tankless" systems), hot melt compositions are fed in a solid state (e.g., pellets), to a relatively small heating vessel (relative to traditional hot melt applications systems that include a pot) where the hot melt composition is melted and, typically shortly thereafter, the molten liquid is applied to a substrate. In on demand systems, a relatively large quantity of hot melt composition typically does not remain in a molten state for an extended period of time. In many existing on demand systems, the volume of molten hot melt composition is no greater than about <NUM> liter, or even no greater than about <NUM> milliliters, and the hot melt composition is maintained in a molten state for a relatively brief period of time, including, e.g., less than two hours, less than one hour, or even less than <NUM> minutes. Suitable on demand hot melt adhesive application systems include, e.g., InvisiPac Tank-Free Hot Melt Delivery System from Graco Minnesota Inc. (Minneapolis, Minnesota) and the Freedom Hot Melt Dispensing System from Nordson Corporation (Westlake, Ohio). On demand hot melt adhesive application systems are described in <CIT>, <CIT>, <CIT>, and <CIT>, and <CIT>.

The invention will now be described by way of the following examples. All parts, ratios, percentages and amounts stated in the Examples are by weight unless otherwise specified.

Test procedures used in the examples include the following. All ratios and percentages are by weight unless otherwise indicated. The procedures are conducted at room temperature (i.e., an ambient temperature of from about <NUM> to about <NUM>) unless otherwise specified.

Melt flow rate (MFR) is determined according to ASTM D1238A at <NUM> using a <NUM> load.

Melt temperature is determined using differential scanning calorimetry (DSC). A <NUM> ± <NUM> sample is placed into a pan specific to the machine being used (e.g., TA Q2000 DSC V24. <NUM> with standard aluminum pans and lids). The sample is then covered with a specified lid and closed. A pan and lid containing no material are also closed and used as a reference sample. The sample is then loaded onto the differential scanning calorimeter posts and covered with a nitrogen blanket. The sample is then heated at a rate of <NUM> per minute (°C/min) until the sample reaches <NUM>. The sample is then put into an isothermal state for <NUM> minutes at <NUM>. The sample is then cooled at a rate of <NUM>/min until the sample reaches a temperature of -<NUM>. Then the sample is again put into an isothermal state for <NUM> minutes at -<NUM>. The sample is then heated at <NUM>/min until the sample reaches <NUM>. The resulting data is represented in graphical exothermal down format containing Heat Flow versus Temperature. The melt temperature (Tm) is the melt temperature of the peak having the greatest height.

Viscosity is determined at the specified temperature in accordance with ASTM D-<NUM> entitled, "Standard Test Method for Apparent viscosity of Hot Melt Adhesives and Coating Materials," (October <NUM>, <NUM>), using a Brookfield viscometer, a Brookfield Thermosel heated sample chamber, and a number <NUM> spindle. The results are reported in mPa·s (centipoise, cP).

The percentage fiber tear is the percentage of fiber that covers the area of the adhesive after two substrates, which have been previously bonded together through the adhesive, are separated by force. The percentage of fiber tear using WESTROCK <NUM> is determined as follows. A bead of adhesive composition measuring <NUM> (<NUM> inch) x <NUM> (<NUM> inch) is applied to a first substrate of WESTROCK <NUM>-pound edge crush C flute corrugated linear board with greater than <NUM> % recycled fibers using a ROCKTENN bond simulator at an application temperature of <NUM>. Two seconds after the bead of adhesive is applied to the first substrate, the bead of adhesive is contacted with a second substrate of WESTROCK <NUM>-pound edge crush C flute corrugated linear board with greater than <NUM> % recycled fibers, which is pressed against both the adhesive and the first substrate with a pressure of <NUM> MPa (<NUM> pounds per square inch (psi)) for a period of <NUM> seconds. The resulting construction is then conditioned at room temperature for at least <NUM> hours and then conditioned at the specified test temperature for at least <NUM> hours. The substrates of the construction are then separated from one another at the test temperature (e.g., immediately after removing the sample from the conditioning chamber) by pulling the two substrates apart from one another by hand. The surface of the adhesive composition is observed and the percentage of the surface area of the adhesive composition that is covered by fibers is determined and recorded. A minimum of five samples are prepared and tested for each hot melt adhesive composition. The results are reported in units of % fiber tear.

The percentage of fiber tear using PRATT is determined as described above in the % Fiber Tear WESTROCK <NUM> Test Method with the exception that the first and second substrates are PRATT <NUM> pound edge crush test (ECT) with C style flute corrugated liner board that includes <NUM> % recycled fibers instead of WESTROCK <NUM>-pound corrugated liner board.

Peel adhesion failure temperature (PAFT) is determined as follows. A first sheet of kraft paper is prepared by affixing two release liners on the first sheet of kraft. The release liners are separated from each other by a distance of <NUM> to form a <NUM> channel therebetween, which will accommodate the adhesive composition that is subsequently applied. A small amount of adhesive composition is applied to the channel near the top edge of the first sheet. A second sheet of kraft paper is placed on top of the adhesive composition and the first sheet of kraft paper. A draw down bar is pressed against the top edge of the second sheet, the adhesive composition, and the first sheet, and then drawn down the length of the second sheet from the top edge to the bottom edge of the second sheet of kraft paper to bond the first sheet of kraft paper to the second sheet of kraft paper through the adhesive composition. The draw down bar has a gap, which defines the thickness of the adhesive composition in the channel as the bar is drawn down the length of the sheets of kraft paper. The resulting coated adhesive composition is <NUM> (one inch) wide and from <NUM> to <NUM> (from <NUM> mils to <NUM> mils) thick. The sample is formed in such a way that a bond area of <NUM><NUM> can be tested in the failure mode. The resulting sample is conditioned at room temperature for at least <NUM> hours. The sample is positioned in an oven in the peel mode such that the top edge of the first sheet of kraft paper is held in position in the oven by a clamp, and a <NUM>-gram weight is attached to the top edge of the second sheet of kraft paper. The ambient temperature in the oven is ramped from a starting temperature of <NUM> to an ending temperature of <NUM> at a rate of <NUM>/hour. The oven automatically records the temperature at which the sample fails. A minimum of five samples are run for each sample composition. The average PAFT value of the five samples is reported in degrees Celsius.

Shear adhesion failure temperature (SAFT) is determined as follows. A first sheet of kraft paper is prepared by affixing two release liners on the first sheet of kraft. The release liners are separated from each other by a distance of <NUM> to form a <NUM> channel therebetween, which will accommodate the adhesive composition that is subsequently applied. A small amount of adhesive composition is applied to the channel near the top edge of the first sheet. A second sheet of kraft paper is placed on top of the adhesive composition and the first sheet of kraft paper. A draw down bar is pressed against the top edge of the second sheet, the adhesive composition, and the first sheet, and then drawn down the length of the second sheet from the top edge to the bottom edge of the second sheet of kraft paper to bond the first sheet of kraft paper to the second sheet of kraft paper through the adhesive composition. The draw down bar has a gap, which defines the thickness of the adhesive composition in the channel as the bar is drawn down the length of the sheets of kraft paper. The resulting coated adhesive composition is <NUM> (one inch) wide and from <NUM> to <NUM> (from <NUM> mils to <NUM> mils) thick. The sample is formed in such a way that a bond area of <NUM><NUM> can be tested in the failure mode. The resulting sample is conditioned at room temperature for at least <NUM> hours. The resulting sample is then positioned in an oven in the shear mode such that the top edge of the first sheet of kraft paper is held in position in the oven by a clamp, and a <NUM> gram weight is suspended from each sample in the shear mode, i.e., the weight is attached to the bottom edge of the second sheet of kraft paper. The ambient temperature in the oven is ramped from a starting temperature of <NUM> to an ending temperature of <NUM> at a rate of <NUM>/hour. The oven automatically records the temperature at which the sample fails. A minimum of three samples are run for each sample composition. The average SAFT value of the three samples is reported in degrees Celsius.

Set time is determined according to the following test method. A bead of adhesive composition measuring <NUM> by <NUM> is applied to a first substrate of PRATT <NUM>-pound edge crush test (ECT) C flute corrugated linear board with <NUM> % recycled fibers using a MEC ASM-15N Hot Melt Bond Simulator at <NUM>. Two seconds after the bead of adhesive is applied to the first substrate, the bead of adhesive is contacted with the second substrate of PRATT <NUM>-pound edge crush test (ECT) C flute corrugated linear board with <NUM> % recycled fibers, which is then pressed against the first substrate with a pressure of <NUM> MPa and for a period of time (referred to herein as the compression time) such that the bond area is <NUM> by <NUM>. The Bond Simulator timer is started when the substrates are compressed. After an initial compression time of <NUM> seconds, the instrument separates the two substrates by pulling on the second substrate in the Z direction and holding the first substrate in a fixed position and the force required to separate the substrates and the amount of fiber tear present on the adhesive composition is measured. Samples are run in triplicate at each compression time. If the three samples fail to exhibit greater than <NUM> % Fiber Tear for each sample, the compression time is increased by <NUM> second and the test method is repeated until greater than <NUM> % fiber tear is noted for all three samples. The <NUM> % fiber tear set time is recorded as the compression time at which the three samples achieve greater than <NUM> % fiber tear immediately upon separation. The set time is recorded in seconds.

Heat stress resistance is measured according to standard number IOPP T-<NUM> entitled, "Suggested Test Method for Determining the Heat Stress Resistance of Hot Melt Adhesives," using a starting temperature of <NUM> (<NUM> °F), a <NUM> gram load per sample, and five bonded samples per adhesive composition. After each <NUM> hour period, the number of samples that are no longer supporting the weight is recorded, and the temperature is increased by <NUM> (<NUM> °F). The pass temperature for each adhesive composition, which is defined as the maximum temperature at which <NUM> % of the samples remain bonded, is the heat stress resistance and is reported in degrees Celsius (°C).

Specific gravity is determined at room temperature according to the following method. The specific gravity of the isopropanol test solution is determined. A molten hot melt sample composition is poured into the form of three small puddles weighing <NUM> gram each. The poured sample is observed to confirm that it is well blended and free of air bubbles. If it is well blended and free of air bubbles the method is continued for that sample. The sample is allowed to cool completely. The samples are weighed to four decimal places and the value is recorded as the weight of the sample in air.

A wire support plate that includes a rectangular wire hoop is placed on a balance pan. The wire support plate includes a metal plate of a size that is capable of resting on the balance pan. The wire hoop is attached to opposite edges of the wire support plate on the same face of the plate and extends up approximately <NUM> inches from the base of the plate. A metal bridge stand that is able to straddle the balance pan without touching it is put through the wire hoop on the support plate to bridge balance pan. A beaker filled with isopropanol is centered on the wire support plate. The specific gravity of the isopropanol is a known chemical property. A small hook is then hung on the top of the wire hoop so it hangs down into the isopropanol in the beaker. The hook is then removed and pressed into the sample to attach the sample to the hook, and the hook is again hung from the wire hoop in such a way that the hot melt sample is completely submerged in the isopropanol. After approximately five seconds the weight is observed and recorded, to four decimal places, as the weight of the sample in isopropanol. The specific gravity (SG) is determined using the following equation.

The Specific Gravity (SG) of the sample = [SG of the isopropanol x weight of the sample weight in air (g)]/[(weight of the sample in air (g))-(the weight of the sample in isopropanol (g))].

The method is repeated for each sample and the average result is reported to three decimal places.

The Tm of SASOL H1 Fischer-Tropsch wax, SASOL C80 Fischer-Tropsch wax, SX <NUM> Fischer-Tropsch wax, LICOCENE <NUM> polypropylene wax, and POLYWAX <NUM> polyethylene wax were measured using the Melt Temperature Test Method. SASOL H1 was determined to have a Tm of <NUM>, SASOL C80 was determined to have a Tm of <NUM>, SX <NUM> was determined to have Tm of <NUM>, LICOCENE <NUM> was determined to have a Tm of <NUM>, and POLYWAX <NUM> was determined to have a Tm of <NUM>, POLYWAX <NUM> was determined to have a Tm of <NUM>, POLYWAX <NUM> was determined to have a Tm of <NUM>, and POLYWAX <NUM> was determined to have a Tm of <NUM>.

The components of the compositions of Comparative C1 and C2 were combined, at room temperature, in the amounts set forth in Table <NUM>, heated to <NUM> to form a melt, and then mixed at <NUM> to form the hot melt composition. The resulting compositions were tested according to the Specific Gravity, Viscosity, Set Time, % Fiber Tear PRATT, % Fiber Tear WESTROCK <NUM>, SAFT, PAFT and IOPP test methods, where indicated. The results are set forth below in Table <NUM>.

The components of the hot melt adhesive compositions of Examples E1-E29 were combined at room temperature in the amounts set forth in Tables <NUM>-<NUM> (in percent), then heated to <NUM>, and then mixed at <NUM> to form a hot melt adhesive composition. The resulting hot melt adhesive compositions were tested according to the Specific Gravity, Viscosity, Set Time, % Fiber Tear PRATT, % Fiber Tear WESTROCK <NUM>, SAFT, PAFT and IOPP test methods, where indicated. The results are set forth below in Tables <NUM>-<NUM>.

Claim 1:
A hot melt adhesive composition comprising:
at least <NUM> % by weight metallocene-catalyzed polybutene-<NUM>, the metallocene-catalyzed polybutene-<NUM> being selected from the group consisting of polybutene-<NUM> homopolymer, polybutene-<NUM> copolymer, and combinations thereof, the metallocene-catalyzed polybutene-<NUM> comprising at least <NUM> % by weight, based on the weight of the hot melt adhesive composition, of a first metallocene-catalyzed polybutene-<NUM> having a melt flow rate of at least <NUM> grams per <NUM> minutes (g/<NUM>) at <NUM> and <NUM> load;
tackifying agent; and
at least <NUM> % by weight wax having a heat of fusion greater than <NUM> Joules per gram (J/g) and a viscosity no greater than <NUM> mPa·s (centipoise, cP) at <NUM>,
the hot melt adhesive composition having a specific gravity of less than <NUM>, determined as described in the description.