Hot melt adhesive composition without an adhesion promoter, method of using the same, and manufactured article using the same

Abstract

The tackifier-free hot melt adhesive composition preferably has a weight average molecular weight (M w Amorphous single-site catalyzed high molecular weight propylene copolymers having a M w The hot melt adhesive comprises a semi-crystalline, single-site catalyzed, low-molecular-weight propylene copolymer having a molecular weight of less than 60,000 g / mol; and polyisobutene. The composition may optionally contain a plasticizer, a butene-rich copolymer, and an antioxidant. The hot melt adhesive is particularly useful for bonding substrates that swell or elongate significantly during use. Such applications include bonding a superabsorbent polymer to a substrate or bonding two substrates together, at least one of which contains a superabsorbent polymer, such as a layer in the absorbent core of a disposable hygiene product such as a diaper. The tackifier-free composition demonstrates adequate elongation at break, stress retention, and thermal stability, making it well-suited for stabilizing swelling species such as superabsorbent polymers.

Description

Technical Field

[0001] Field of the Invention The present invention relates to a hot melt adhesive composition without an adhesion promoter suitable for use in disposable hygiene products such as diapers and training pants. The adhesive is particularly well-suited for applications that require high elongation at break, stress retention, and thermal stability.

Background Art

[0002] Background of the Invention Hot melt adhesives typically exist as a solid mass at ambient temperature and can be converted into a fluid liquid by the application of heat. These adhesives are particularly useful in the manufacture of a variety of typically disposable products where the joining of various substrates is often required. Specific applications include disposable diapers, hospital pads, feminine sanitary napkins, panty shields, surgical drapes, and adult incontinence briefs, collectively known as disposable hygiene products or articles. Further, the adhesive can be used to manufacture preformed absorbent cores that are later inserted into disposable or reusable products. Other diverse applications include paper products, packaging materials, automotive headliners, appliances, tapes, and labels. In most of these applications, the hot melt adhesive is heated to its molten state and then applied to a substrate, often referred to as the primary substrate. A second substrate, often referred to as the secondary substrate, is then immediately brought into contact with and pressed against the first substrate. The adhesive solidifies upon cooling to form a strong bond. A major advantage of hot melt adhesives is the absence of a liquid carrier as exists in the case of water- or solvent-based adhesives, thereby eliminating the costly process associated with solvent removal and potentially harmful and / or odorous solvents.

[0003] For many applications, hot melt adhesives are often extruded directly onto a substrate in the form of a thin film or beads using a piston or gear pump device. The die temperature must be maintained well above the melting point of the adhesive to allow the molten hot melt material to flow smoothly through the coating nozzle. In most applications, particularly those found in the manufacture of food packaging and disposable nonwoven hygiene products, the bonding of delicate and heat-sensitive substrates such as thin gauge plastic films is often involved. This places an upper limit on the coating temperature for the application of hot melt adhesives. Commercially available hot melt agents today are typically formulated to have a coating temperature of less than 200°C to avoid burning or distorting the substrate. In this case, the adhesive is most typically sprayed from a nozzle at a set distance onto the target substrate or material, such as a substrate containing a superabsorbent polymer. Some indirect or non-contact coating methods have also been developed that can spray-apply the hot melt adhesive onto the substrate from a fixed distance with the aid of compressed air. These non-contact coating techniques include conventional spiral spray, Signature™, Control Coat™, UFD™, and various forms of the meltblow process. However, with indirect methods, the viscosity of the adhesive must be low enough, typically in the range of 2,000 to 30,000 mPa s, often in the range of 2,000 to 15,000 mPa s, in order to obtain an acceptable coating pattern.

[0004] Hot melt adhesives are traditionally composed of a polymer, a plasticizer, a tackifier resin (also referred to herein as a "tackifier"), and optional additives such as waxes and antioxidants. Tackifiers have long been considered a necessary component of hot melt adhesives. Traditionally, the role of tackifiers having a styrene block copolymer system is to increase tackiness by raising the glass transition temperature of the adhesive system. Tackifiers also help to suppress the viscosity of the final formulation. However, tackifiers can give an odor and volatile organic compounds (VOCs) to the adhesive formulation and thus can be viewed negatively. Therefore, it is desirable to produce a hot melt adhesive that does not contain a tackifier resin. Such adhesives are generally recognized to handle high temperatures and have less odor than other adhesives such as styrene block copolymer-based adhesives, so those based on polyolefins are desirable.

[0005] Efforts have been made to develop hot melt adhesives that do not contain a tackifier. For example, U.S. Patent No. 9,139,755 discloses a hot melt adhesive composition comprising from about 10 to 90 weight percent of an amorphous polyolefin copolymer, from about 50 to 70 weight percent of 1-butene; propene, and a comonomer comprising ethylene, 1-hexene or 1-octene and having amorphous characteristics and a crystalline block, from about 10 to 90 weight percent of a heterophasic polypropylene copolymer composition; and from about 0.1 to 30 weight percent of a polyisobutylene plasticizer produced using AlCl 3 The adhesive provides cohesion strength from the heterophasic polypropylene copolymer and adhesion strength from the amorphous polyolefin copolymer.

[0006] In addition, U.S. Patent No. 8,623,480 discloses a hot melt adhesive composition comprising at least 55 wt% of a first polymer consisting of a non-functionalized amorphous polyalphaolefin polymer containing more than about 50 wt% polypropylene, a second polymer selected from the group consisting of polypropylene homopolymers, propylene copolymers, and combinations thereof, a functionalized polypropylene wax, and a polyethylene wax. The hot melt adhesive composition preferably does not contain a tackifier.

[0007] International Patent Application WO 2013 / 039261 discloses a hot melt adhesive composition comprising (A) a propylene homopolymer having a melting point of 100°C or less obtained by polymerizing propylene using a metallocene catalyst and (B) an ethylene-based copolymer.

Summary of the Invention

[0008] In the art, there is a need for adhesives that have low tack, sufficiently high elongation at break, stress retention, and thermal stability so as to withstand significant swelling, such as swelling of superabsorbent polymers, which still have an appropriate viscosity at the desired application temperature even when wet.

[0009] Accordingly, it is advantageous to provide a hot melt adhesive that overcomes the drawbacks of the above-described prior art adhesives. In particular, it is desirable to produce a hot melt adhesive that does not contain a tackifier. Such an adhesive can withstand high temperatures and is generally recognized as having less odor and is desirably polyolefin-based. Such an adhesive has a high elongation at break and stress retention sufficient to withstand the swelling of the superabsorbent polymer when wet or swollen / expanded. Such an adhesive is particularly well-suited as a microfibered adhesive that, alone or in combination with another adhesive and / or cellulose fibers, is involved in containing superabsorbent polymer (SAP) within sanitary articles such as diapers. An adhesive that performs this function is known to provide core stabilization. The adhesive need not have a high degree of tackiness, but it is required to have very good elongation when it swells / expands because it contains SAP. The challenge in producing an adhesive that does not contain a tackifier is to develop a formulation that has good thermal stability and sufficient "strength" to meet mechanical properties such as elongation at break and stress retention.

[0010] In view of the drawbacks of the prior art, the present invention provides a hot melt adhesive composition comprising an essentially amorphous by single-site catalyst high molecular weight propylene copolymer, a semi-crystalline by single-site catalyst low molecular weight propylene copolymer, and polyisobutene, which provides a hot melt adhesive composition that does not contain a tackifier. Such a composition provides both high elongation at break and stress retention while having excellent thermal stability.

[0011] According to one embodiment of the present invention, a method of manufacturing a laminate comprises applying the hot melt adhesive composition of the present invention in a molten state to a primary substrate and joining a secondary substrate to the primary substrate by bringing the secondary substrate into contact with the adhesive composition.

[0012] According to another embodiment of the present invention, the absorbent core includes a first layer and a second layer, at least one of the first layer and the second layer includes a superabsorbent polymer, and the first layer and the second layer are adhered to each other by the hot melt adhesive composition of the present invention, and the adhesive composition adheres the superabsorbent polymer in the absorbent core.

[0013] According to another embodiment of the present invention, the disposable sanitary product includes the absorbent core of the present invention.

[0014] Detailed Description of the Invention According to one embodiment of the present invention, the hot melt adhesive composition comprises (a) an amorphous by single-site catalyst high molecular weight propylene copolymer, (b) a semi-crystalline by single-site catalyst low molecular weight propylene copolymer, and (c) polyisobutene, and the composition does not contain a tackifier. The adhesive composition may optionally include an antioxidant(s) and optionally a plasticizer(s), and an additional butene-rich polymer having a density of less than 0.908 g / cm 3 Such a composition provides both high elongation at break and stress retention while having excellent thermal stability. Thus, such an adhesive is particularly well-suited for applications that require the ability to stretch to a large extent (e.g., 350% or more) during use, and provides high stress retention (e.g., 30% or more after 10 minutes at 300% elongation) and excellent thermal stability (e.g., 90% viscosity retained after 3 days at high temperature).

[0015] Both the first and second propylene copolymers used in the present invention are single-site catalyzed. single-site catalystThe system (SSC) differs from conventional catalysts (such as Ziegler-Natta catalysts) in at least one significant aspect; they have only a single active transition metal site per catalyst molecule, and thus the activity at this metal site is the same for all catalyst molecules. One type of SSC catalyst widely used on an industrial scale today is a metallocene catalyst system consisting of a catalyst and a cocatalyst or activator. The catalyst is a transition metal complex having a metal atom located between two cyclic organic ligands, and the ligands can be the same or different derivatives of cyclopentadiene. The cocatalyst can be any compound capable of activating the metallocene catalyst by converting the metallocene complex into a catalytically active species, examples of such compounds being aluminoxanes, preferably methylaluminoxane having an average degree of oligomerization of 4 to 30. For the purposes of the present invention, other neutral or ionic activators can be used, including but not limited to various organic boron compounds such as tri(n-butyl)ammonium tetrakis(pentafluorophenyl)borate, dimethylanilinium tetrakis(pentafluorophenyl)borate, or trityl tetrakis(pentafluorophenyl)borate. Another type of SSC catalyst is a geometrically constrained catalyst (CGC).

[0016] As used herein, CGC refers to a subclass of SSC catalyst systems known as geometrically constrained catalysts. Unlike metallocenes, geometrically constrained catalysts (CGCs) are characterized by having only one cyclic ligand linked to one of the other ligands on the same metal center such that the angle at this metal between the centroid of the pi system and the additional ligand is smaller than that of a non-bridged complex with a comparable angle. More specifically, the term CGC is used for ansa-bridged cyclopentadienylamide complexes, although this definition extends well beyond this class of compounds. Thus, the term CGC is widely used to refer to ansa-bridged cyclopentadienylamide ligand systems and other ligand systems that are more or less related, whether isolobal and / or isoelectronic or not. Furthermore, the term is frequently used for related complexes having long ansa bridges that do not induce strain.

[0017] Suitable CGCs can be activators such as methylaluminoxane (MAO), perfluorinated borates, and trityl borate co-catalysts, like metallocenes. However, CGC-based catalyst systems exhibit much higher incorporation of higher alpha-olefins to a much greater extent than comparable metallocene-based systems. For olefin polymerization single-site catalyst Non-metallocene-based SSCs, also called post-metallocenes, which are used for olefin polymerization, are also known. Typical post-metallocene catalysts are characterized by bulky, neutral alpha-diimine ligands. However, these post-metallocene catalysts are frequently used for the polymerization of ethylene to produce plastomers and elastomers. They are rarely used for the polymerization of alpha-olefins such as propylene. For olefin polymerization single-site catalyst systems are well known to those skilled in the art and have been widely discussed in two symposia entitled Stereoselective Polymerization with Single-Site Catalysts (2008), edited by Lisa S. Baugh and Jo Ann M. Canich and published by CRC press, and Polyolefins: 50 Years after Ziegler and Natta II: Polyolefins by Metallocenes and Other single-site catalyst Single-Site Catalysts (2013), edited by Walter Kaminsky and published by Springer Heidelberg. single-site catalyst

[0018] Due to the progress of the SSC catalyst system described above in this specification, the production of propylene-based polymers and copolymers having various chain microstructures and specific stereochemistries has been put into practical use. Depending on the selection of the catalyst and reaction conditions, certain types of propylene polymers and copolymers can be intentionally manufactured to have, for example, a narrow molecular weight distribution, a statistically random incorporation of comonomers, a high fraction of atactic chain sequences, and an arrangement of shorter crystalline isotactic or syndiotactic chains. Macroscopically, the polymers exhibit a relatively lower melting point, a lower melting enthalpy, a lower crystallinity, and a lower density, and can show behavior more similar to elastomers than polypropylene produced by conventional catalysts. Such polymers can have various weight average molecular weight (Mw) ranges such as 1,000 g / mol to 1,000,000 g / mol, melting point ranges such as 20 °C to 150 °C well below the melting point of iPP of 170 °C, melting enthalpy ranges such as 0 J / g to 100 J / g, and density ranges such as 0.85 g / cc to 0.90 g / cc. Some of these polymers are well-suited for hot melt adhesive applications.

[0019] Both the first and second propylene copolymers are mainly composed of propylene units. This means that they contain at least 50 wt% propylene. The two propylene copolymers can be polymers of propylene with the same comonomer or different comonomers. Preferably, the high molecular weight propylene copolymer is a copolymer of propylene and a comonomer selected from the group consisting of ethylene and C 4 ~C 12 alkylene, preferably ethylene. Similarly, the low molecular weight propylene copolymer is a copolymer of propylene and a comonomer selected from the group consisting of ethylene and C 4 ~C 12It is a copolymer with a comonomer selected from the group consisting of alkylene, preferably ethylene. The first and second propylene copolymers may have the same or different comonomer contents. Preferably, the first and second propylene copolymers have an ethylene content of about 5% to about 25%, more preferably about 7% to about 20%, even more preferably about 9% to about 17%, and most preferably about 10% to about 15%.

[0020] Preferably, the high molecular weight propylene copolymer has a weight average molecular weight of at least about 80,000 g / mol, preferably at least about 95,000 g / mol, and most preferably at least about 105,000 g / mol. Preferably, the weight average molecular weight of the high molecular weight propylene copolymer is at most about 250,000 g / mol, preferably at most about 200,000 g / mol, and most preferably at most about 175,000 g / mol. When upper and lower limits of ranges of components or adhesives or other properties or concentrations are set forth herein, any range extending from any lower limit to any upper limit is contemplated by the present invention, as well as any range extending from any lower limit or any range extending from any upper limit. Accordingly, embodiments of the present invention include, by way of example, high molecular weight propylene copolymers having a weight average molecular weight of at least about 80,000 g / mol to at most about 250,000 g / mol, high molecular weight propylene copolymers having a weight average molecular weight of at least about 95,000 g / mol to at most about 250,000 g / mol, and high molecular weight propylene copolymers having a weight average molecular weight of at least about 80,000 g / mol. Preferably, the weight average molecular weight of the low molecular weight propylene copolymer is at most about 60,000 g / mol, preferably at most about 40,000 g / mol, and most preferably at most about 30,000 g / mol. Preferably, the weight average molecular weight of the low molecular weight propylene copolymer is at least about 10,000 g / mol, preferably at least about 15,000 g / mol, and most preferably at least about 17,500 g / mol. The weight average molecular weights of the two propylene copolymers described herein are characterized using high temperature size exclusion chromatography (SEC) with a polypropylene-based standard.

[0021] Preferably, the molecular weights of the two propylene copolymers are significantly offset from each other. For example, in one embodiment of the present invention, the molecular weight of the high molecular weight propylene copolymer is at least twice, preferably at least three times, and most preferably at least four times the molecular weight of the low molecular weight polypropylene copolymer.

[0022] The polydispersity index (PDI) of the propylene copolymer may vary over a wide range and may be the same or different. The polydispersity indices of the two propylene polymers are preferably at most about 5, preferably at most about 4, and most preferably at most about 3. The polydispersity indices of the two propylene polymers are preferably at least about 1.5, preferably at least about 1.8, and most preferably at least about 2. These PDI values are generally characteristic of polymers produced using single-site catalyst such as metallocene catalysts. Preferably, the propylene copolymer of the present invention is produced using a metallocene catalyst. The polydispersity index (PDI) of the propylene copolymer is determined by dividing the weight average molecular weight by the number average molecular weight (M w / M n ), and each value of M w and M n is determined using data from the same analytical method (i.e., using a polypropylene reference standard and high temperature size exclusion chromatography (SEC)).

[0023] The crystallinity of the two propylene copolymers has been found to be important for achieving the specific objectives of the present invention. According to the present invention, the high molecular weight propylene copolymer is essentially amorphous, which means that the crystallinity is relatively low or absent. Looking at the crystallinity from the perspective of the heat of fusion of the polymer, the high molecular weight propylene copolymer preferably has a heat of fusion of at most about 20 J / g, preferably at most about 15 J / g, and most preferably at most about 10 J / g. Preferably, the high molecular weight propylene copolymer preferably has a heat of fusion of at least about 0 J / g, preferably at least about 2 J / g, and most preferably at least about 5 J / g. According to an embodiment of the present invention, the low molecular weight propylene copolymer preferably has a heat of fusion of at least about 20 J / g, preferably at least about 25 J / g, and most preferably at least about 30 J / g. Preferably, the low molecular weight propylene copolymer preferably has a heat of fusion of at most about 100 J / g, preferably at most about 75 J / g, and most preferably at least about 50 J / g. The test method used to determine these heat of fusion values is ASTM E793-01, "Standard Test Method for Enthalpies of Fusion and Crystallization by Differential Scanning Calorimetry".

[0024] Preferably, the heats of fusion of the two propylene copolymers are significantly offset from each other. For example, in one embodiment of the present invention, the heat of fusion of the low molecular weight propylene copolymer is at least 2 times, preferably at least 3 times, and most preferably at least 4 times the heat of fusion of the high molecular weight polypropylene copolymer.

[0025] The melting temperature, also referred to as the melting point of the two propylene copolymers, may vary over a wide range, may be the same or may be different. Preferably, the melting temperature of the low molecular weight propylene copolymer is from about 35°C to 100°C. More preferably, the melting temperature of the low molecular weight propylene copolymer is from about 40°C to about 90°C, more preferably from about 50°C to about 80°C, and most preferably from about 55°C to about 75°C. Preferably, the melting temperature of the high molecular weight propylene copolymer is from about 70°C to about 130°C. More preferably, the melting temperature of the high molecular weight propylene copolymer is from about 75°C to about 125°C, even more preferably from about 85°C to about 115°C, and most preferably from about 90°C to about 110°C. The melting temperature described herein is measured using a differential scanning calorimeter (DSC) in accordance with ASTM E-794-01, except that one modification was made to the test by using a scanning temperature of 20°C per minute instead of 10°C per minute.

[0026] The glass transition temperatures of the two propylene copolymers may vary over a wide range, may be the same or may be different. Preferably, the glass transition temperature of each copolymer is from about -45°C to about -5°C. More preferably, the glass transition temperature is from -35°C to -15°C, even more preferably from about -32°C to -20°C, and most preferably from about -30°C to -22°C. The glass transition temperature described herein is measured using a differential scanning calorimeter (DSC) in accordance with ASTM E-794-01, except that one modification was made to the test by using a scanning temperature of 20°C per minute instead of 10°C per minute.

[0027] The melt flow rate of the high molecular weight propylene copolymer may vary over a wide range. The high molecular weight propylene copolymer may have a melt flow rate of about 1 g / 10 min to about 75 g / 10 min, preferably about 2 g / 10 min to about 50 g / 10 min, and most preferably about 5 g / 10 min to about 25 g / 10 min. The low molecular weight propylene copolymer may have a melt flow rate higher than that of the high molecular weight propylene copolymer, or it may be difficult to measure the melt flow rate. In one embodiment of the present invention, a low molecular weight propylene copolymer having a viscosity of about 500 cP to about 2,500 cP, preferably about 750 to about 2,000 cP, and most preferably about 1,000 to 1,500 cP at 190 °C is selected. As used herein, the melt flow rates of the two propylene copolymers are determined in accordance with ASTM D 1238 using a 2.16 kilogram weight at 190 °C.

[0028] Typical high molecular weight propylene copolymers suitable for use in the present invention include certain grades of VISTAMAXX™ propylene copolymers commercially available from ExxonMobil, including VISTAMAXX 6202 and 6502, and certain grades of VERSIFY™ propylene copolymers sold by The Dow Chemical Company, including VERSIFY 3000. Typical low molecular weight propylene copolymers suitable for use in the present invention include certain grades of VISTAMAXX™ propylene copolymers sold by ExxonMobil, including VISTAMAXX 8880.

[0029] In addition to the two propylene copolymers, the adhesive composition of the present invention contains polyisobutene. As used herein, polyisobutene (PIB) is produced from isobutene monomers and is -[C(CH 3 ) 2 CH 2- repeating units, referring to homopolymers or oligomers. These materials may or may not contain a certain degree of unsaturation. Generally, they have a low number average molecular weight (950 - 4,500 g / mol) and can be thin or relatively viscous liquids at room temperature. According to embodiments of the present invention, polyisobutene has a number average molecular weight of at least about 750 g / mol, preferably at least about 900 g / mol, more preferably at least about 1,500 g / mol, and most preferably at least about 2,000 g / mol. Preferably, polyisobutene has a number average molecular weight of up to about 7,500 g / mol, preferably up to about 6,000 g / mol, and most preferably up to about 4,500 g / mol. They also typically have a narrow polydispersity index (Mw / Mn < 4), which is not typically important for the present invention. Typical polyisobutenes suitable for use in the present invention include INDOPOL® H-1900 or INDOPOL® H-100 commercially available from Ineos Capital Ltd. Without being bound by any theory, polyisobutene is thought to help improve the cohesive strength of adhesives and also to plasticize propylene copolymers.

[0030] The hot melt adhesive composition of the present invention optionally includes a 1-butene copolymer. As used herein, the term "1-butene copolymer" means that the copolymer contains more than 50 mol% of butene and is produced from at least one other monomer in addition to butene. In one embodiment, the 1-butene copolymer selected can have a wide range of crystallinities (and a wide range of values of heat of fusion). Preferably, the 1-butene copolymer includes a butene-ethylene copolymer. Generally, the weight average molecular weight of the 1-butene copolymer is preferably about 15,000 - about 160,000 g / mol, and most preferably about 30,000 - about 150,000 g / mol. As used herein, when referring to the weight average molecular weight of a 1-butene copolymer, the weight average molecular weight is determined by gel permeation chromatography using a polypropylene standard. Preferably, the 1-butene copolymer has a density of about 0.907 g / cm 3, preferably up to about 0.905 g / cm 3 , more preferably up to about 0.900 g / cm 3 , and most preferably up to about 0.895 g / cm 3 and having a density of

[0031] The hot melt adhesive composition of the present invention optionally contains a plasticizer. The plasticizer can be any known compatible plasticizer, preferably selected from the group consisting of mineral oil and synthetic polyalphaolefin oil. Suitable plasticizers can also be selected from olefin oligomers and low molecular weight polymers, and plant and animal oils and their derivatives. The petroleum-derived oil that can be used is a relatively high-boiling substance containing only a small amount of aromatic hydrocarbons. In this regard, the aromatic hydrocarbons should preferably be less than 30%, more particularly less than 15% of the oil, as measured by the fraction of aromatic carbon atoms. More preferably, the oil can be essentially non-aromatic. The plasticizers useful in the present invention can be any number of different plasticizers, but mineral oil and other plasticizers having an average molecular weight of less than 5,000 daltons are particularly advantageous. As will be appreciated, plasticizers have typically been used to lower the viscosity of the entire adhesive composition, extend the open time, and improve the flexibility of the adhesive, without substantially reducing the adhesive strength and / or service temperature of the adhesive.

[0032] Embodiments of the present invention are adhesives based on mixtures of high molecular weight propylene copolymers and low molecular weight propylene copolymers, and the ratio of high molecular weight propylene copolymer to low molecular weight propylene copolymer is from about 1:1 to about 5:1, preferably from about 3:2 to about 4:1, more preferably from about 2:1 to about 7:2, and most preferably about 3:1.

[0033] The amounts of the various components can vary widely depending on the desired application temperature and other conditions of the adhesive and the desired performance characteristics. According to embodiments of the present invention, the adhesive A high molecular weight propylene copolymer in an amount of about 10% to about 60% by weight, preferably about 20% to about 50% by weight, and most preferably about 25% to about 40% by weight, based on the total weight of the composition; A low molecular weight propylene copolymer present in an amount of about 3% to about 40% by weight, preferably about 4% to about 30% by weight, and most preferably about 5% to about 20% by weight, based on the total weight of the composition; and Polyisobutene present in an amount of about 5% to about 50% by weight, preferably about 10% to about 40% by weight, and most preferably about 15% to about 30% by weight, based on the total weight of the composition is included.

[0034] The present invention includes any combination of any range of one component with any range or unlimited amount of another component, or any combination with both other components. When present, the 1-butene copolymer may be present in an amount of about 5% to about 40% by weight, preferably about 7% to about 30% by weight, and most preferably about 10% to about 25% by weight, based on the total weight of the composition. Also, when present, the plasticizer may be present in an amount of about 5% to about 60% by weight, preferably about 10% to about 50% by weight, and most preferably about 15% to about 40% by weight, based on the total weight of the composition.

[0035] The present invention may, if necessary, include an antioxidant, also referred to as a stabilizer. When included, the antioxidant may be present in the total adhesive composition in an amount of about 0.1 wt% to about 3 wt%. Preferably, about 0.2% to 2% of the antioxidant is incorporated into the composition. Antioxidants useful in the hot melt adhesive composition of the present invention are incorporated to protect the polymers described above and thereby help protect the entire adhesive system from the effects of thermal and oxidative degradation that normally occur during the manufacture and application of the adhesive and during normal exposure of the final product to the surrounding environment. Among the applicable antioxidants are high molecular weight hindered phenols and polyfunctional phenols such as sulfur- and phosphorus-containing phenols. Hindered phenols are well known to those skilled in the art and can be characterized as phenolic compounds that also contain sterically bulky radicals in proximity to their phenolic hydroxyl groups. In particular, tertiary butyl groups are generally substituted on at least one benzene ring in the ortho position relative to the phenolic hydroxyl group. The presence of these sterically bulky substituted radicals in the vicinity of the hydroxyl group serves to retard its stretching vibration frequency and correspondingly its reactivity, and thus this steric hindrance provides the phenolic compound with its stabilizing properties.Representative hindered phenols include 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene; pentaerythritol tetrakis-3(3,5-di-tert-butyl-4-hydroxyphenyl)propionate; n-octadecyl-3(3,5-di-tert-butyl-4-hydroxyphenyl)propionate; 4,4'-methylenebis(4-methyl-6-tert-butylphenol); 2,6-di-tert-butylphenol; 6-(4-hydroxyphenoxy)-2,4-bis(n-octylthio)-1,3,5-triazine; 2,3,6-tris(4-hydroxy-3,5-di-tert-butylphenoxy)-1,3,5-triazine; di-n-octadecyl-3,5-di-tert-butyl-4-hydroxybenzylphosphonate; 2-(n-octylthio)ethyl-3,5-di-tert-butyl-4-hydroxybenzoate; and sorbitol hexa-3(3,5-di-tert-butyl-4-hydroxyphenyl)propionate.

[0036] The performance of these antioxidants can be further enhanced by using them in combination with (1) synergists such as, for example, thiodipropionic acid esters and phosphites; and (2) chelating agents and metal deactivators such as, for example, ethylenediaminetetraacetic acid, its salts, and disalicylalpropylenediimine.

[0037] It should be understood that other auxiliary additives may be incorporated into the adhesive composition of the present invention to modify certain physical properties. These may include materials such as inert colorants, for example titanium dioxide, fillers, fluorescent agents, UV absorbers, surfactants, other types of polymers, etc. Typical fillers include talc, calcium carbonate, clay silica, mica, wollastonite, feldspar, aluminum silicate, alumina, alumina hydrate, glass microspheres, ceramic microspheres, thermoplastic microspheres, barite, and wood flour. Surfactants are particularly important for sanitary disposable nonwoven products because, for example, they can dramatically reduce the surface tension of the adhesive applied to the core of the diaper, thereby allowing for more rapid movement and subsequent absorption of urine by the core.

[0038] According to an embodiment of the present invention, a wax is included in the adhesive composition. Such waxes can include low molecular weight waxes, petroleum waxes such as paraffin waxes, synthetic waxes, and polyolefin waxes. Preferably, the adhesive composition is substantially wax-free, for example containing less than 1% by weight, more preferably less than 0.5% by weight, and most preferably no wax, based on the total weight of the composition.

[0039] According to an embodiment of the present invention, the hot melt adhesive composition is essentially amorphous by single-site catalyst high molecular weight propylene copolymer, semi-crystalline by single-site catalystA low molecular weight propylene copolymer, and polyisobutene, and optionally a butene-rich copolymer, and optionally consisting essentially of or consisting of one or more other optional components described herein, the adhesive not containing tackifiers. "Not containing tackifiers" means that the composition does not contain tackifiers or contains only a minimal amount of tackifiers known in the art for use in hot melt adhesives such as those disclosed in U.S. Patent No. 10,011,744 incorporated herein by reference. Classes of such tackifiers include aliphatic and alicyclic petroleum hydrocarbon resins; aromatic petroleum hydrocarbon resins and their hydrogenated derivatives; aliphatic / aromatic petroleum-derived hydrocarbon resins and their hydrogenated derivatives; aromatic-modified alicyclic resins and their hydrogenated derivatives; polyterpene resins having a softening point of about 10°C to about 140°C; copolymers and terpolymers of natural terpenes; natural and modified rosins; glycerol and pentaerythritol esters of natural and modified rosins; and phenol-modified terpene resins. According to one embodiment of the present invention, the adhesive composition does not contain non-crystalline polyalphaolefins. According to another embodiment of the present invention, the adhesive composition contains less than 40% by weight, preferably less than 25% by weight, more preferably less than 10% by weight, even more preferably less than 5% by weight, and most preferably less than 1% by weight of non-crystalline polyalphaolefins. According to another embodiment of the present invention, the adhesive composition does not contain styrene.

[0040] The flow characteristics and viscosity of the adhesive composition can be adjusted within specific parameters by methods known to those skilled in the art. The desired viscosity at a particular temperature will depend on application conditions, including, among other factors, the mode of application, the desired flow during application, the line speed, and the system used for such application. According to embodiments of the present invention, the viscosity of the composition is at most about 17,500 centipoise (cP) at about 177°C (350°F), preferably at most about 15,000 centipoise (cP) at 177°C (350°F), and most preferably at most about 12,500 centipoise (cP) at 177°C (350°F). According to embodiments of the present invention, the viscosity of the composition is at least about 1,000 centipoise (cP) at 177°C (350°F), preferably at least about 2,500 centipoise (cP) at 177°C (350°F), and most preferably at least about 5,000 centipoise (cP) at 177°C (350°F). The viscosity of the adhesive is measured with spindle 27 in accordance with ASTM D3236.

[0041] The adhesives according to embodiments of the present invention exhibit excellent mechanical properties (e.g., high elongation at break and high stress retention) and thermal stability. Due to such properties, the adhesives of the present invention are useful in sanitary, structural, and packaging applications, and in particular, are suitable for core stabilization of absorbent cores containing superabsorbent polymers that swell significantly when moisture suddenly enters. The hot melt composition of the present invention is further characterized by having an elongation at break of at least about 350%, preferably at least about 400%, more preferably at least about 450%, and most preferably at least about 475% when measured at a pull rate of 2" / min. The formulations of the present invention further meet additional mechanical properties such as the stress retained after 10 minutes at 300% elongation. Preferably, the stress retained after 10 minutes at 300% elongation is at least 30%, preferably at least about 40%, more preferably at least about 45%, and most preferably at least about 50%. In addition, embodiments of the present invention demonstrate excellent yield stress such as at least about 0.4 MPa, preferably at least about 0.5 MPa, and most preferably at least about 0.6 MPa. The hot melt adhesive composition further has excellent thermal stability such that the viscosity retained at high temperature is greater than about 85% over at least about 3 days, preferably greater than about 90% over at least about 3 days, and most preferably greater than about 90% over at least about 5 days. The methodologies for determining elongation at break, stress retention, yield stress, and thermal stability (as reflected by viscosity retention) are described in more detail in the Examples section below.

[0042] The hot melt adhesive composition of the present invention can be formulated using any mixing technique known in the art. Representative examples of the mixing procedure include putting all the components into a jacketed mixing kettle equipped with a rotor, and then raising the temperature of the mixture to the range of 150°C to 200°C to melt the contents. Any component may be pre-blended or added individually to the mixing kettle. For example, the polymer can be a pre-formed mixture or blend, or can be added individually to the mixing kettle. It should be understood that the exact temperature used in this process depends on the melting point of the specific components. Mixing is continued until a consistent and uniform mixture is formed. The contents of the kettle are protected with an inert gas such as carbon dioxide or nitrogen during the entire mixing process. Various additional and modifications can be made to the procedure for producing the hot melt composition, such as applying a vacuum to facilitate the removal of entrapped air, without infringing on the spirit of the present invention. Other devices useful for formulating the composition of the present invention include, but are not limited to, single-screw or twin-screw extruders or other modified forms of extrusion machinery, kneaders, intensive mixers, Ross (trademark) mixers, etc. The hot melt adhesive is then cooled to room temperature and formed into chubs having a protective skin formed thereon or into pellets for shipping and use.

[0043] The adhesive composition of the present invention can be used as a general-purpose hot melt adhesive in many applications, such as disposable nonwoven hygiene products, paper conversion, flexible packaging, wood processing, carton and case sealing, labeling, and other assembly applications. Particularly preferred applications include disposable diaper and feminine napkin structures incorporating a pre-formed core, reusable hygiene products incorporating a pre-formed core, diaper and adult incontinence brief elastic attachments, stabilization of the cores of diapers and napkins, lamination of the backsheet of diapers, industrial filter material conversion, surgical gown and surgical drape assembly, etc. The composition of the present invention is particularly suitable for use in core stabilization of absorbent cores having superabsorbent polymers for disposable hygiene products such as diapers, feminine care pads, and adult incontinence products.

[0044] The resulting hot melt adhesive can be applied to a substrate using various application techniques. Examples include hot melt glue guns, hot melt slot die coating, hot melt wheel coating, hot melt roller coating, melt blown coating, spiral spray, contact or non-contact strand coating with trademarks such as Signature™, Control Coat™, UFD™, etc. In a preferred embodiment, the hot melt adhesive is indirectly sprayed onto the substrate.

[0045] In one embodiment of the present invention, a method of making a laminate comprises: (1) applying the hot melt adhesive composition of the present invention in a molten state to a primary substrate; and (2) joining the secondary substrate to the primary substrate by bringing the secondary substrate into contact with the adhesive composition. In one embodiment of the present invention, the first substrate comprises a first layer (such as a bottom layer) of an absorbent core, the secondary substrate comprises a second layer (such as an upper layer) of an absorbent core, and at least one of the first layer or the second layer has a superabsorbent polymer bonded thereto. The first substrate and the secondary substrate may be a single continuous material, or may be folded such that two folds form the first and secondary substrates.

[0046] Any suitable absorbent core having a superabsorbent polymer can be used in connection with the present invention. Suitable absorbent cores are described in U.S. Patent Application Nos. 2017 / 0209616, 2017 / 0165133, and 2016 / 0270987, all of which are incorporated herein by reference. As described in U.S. Patent Application No. 2017 / 0165133, the absorbent core structure typically includes an absorbent polymer material, such as a hydrogel-forming polymer material, also referred to as an absorbent gelling material (AGM), or a superabsorbent polymer (SAP). This absorbent polymer material ensures that a large amount of body fluid, such as urine, is absorbed and confined by the absorbent article during use, providing low rewetting and good skin dryness. Thinner absorbent core structures can be manufactured by reducing or eliminating the conventional use of cellulose or cellulose fibers in the absorbent core structure. To maintain the mechanical stability of these absorbent core structures, a fibrous mesh structure, which may optionally be an adhesive, may be added to stabilize the absorbent polymer material. The absorbent core may also have additional adhesives to assist the fibrous mesh structure adhesive and / or to bond other core materials to each other and / or to other article components. The superabsorbent polymer material may be deposited or associated on the first and second substrates, and the fibrous mesh structure covers the superabsorbent polymer material on each of the first and second substrates.

[0047] In an embodiment of the present invention, the fibrillated network structure comprises the adhesive composition of the present invention. The fibrillated network structure may include other adhesives or other materials such as cellulose fibers. In another embodiment of the present invention, the only adhesive used in the fibrillated network structure is the adhesive composition of the present invention. In still another embodiment of the present invention, the fibrillated network structure consists of only one or more adhesive compositions of the present invention. In one embodiment of the present invention, the first and second absorbent layers are combined such that at least a portion of the fibrillated network structure of the first absorbent layer contacts at least a portion of the fibrillated network structure of the second absorbent layer, and the adhesive of the present invention used in the fibrillated network structure serves to adhere together the two layers to form an absorbent core. In an embodiment of the present invention, both the first and second layers of the absorbent core have a superabsorbent polymer bonded thereto. In other embodiments of the present invention, only one of these layers has a superabsorbent polymer bonded thereto.

[0048] In another embodiment of the method of manufacturing the laminate of the present invention, the primary substrate is the first layer of the absorbent core and the secondary substrate is the superabsorbent polymer. The superabsorbent polymer may be deposited on the first layer before applying the adhesive composition. In this embodiment, the adhesive may form a fibrillated network over and around the superabsorbent polymer and may be adhered to the first layer. In a further embodiment, a second layer is similarly formed and then the two layers are joined to form an absorbent core before the adhesive is cooled.

[0049] Aspects of the present invention 1. (a) An essentially amorphous by single-site catalyst high molecular weight propylene copolymer; (b) A semi-crystalline by single-site catalyst low molecular weight propylene copolymer; and (c) Polyisobutene; A hot melt adhesive composition comprising, and a hot melt adhesive composition free of tackifying agents.

[0050] 2. The high molecular weight propylene copolymer has a weight average molecular weight of at least about 80,000 g / mol, preferably at least about 95,000 g / mol, and most preferably at least about 105,000 g / mol, and a heat of fusion of at most about 20 J / g, preferably at most about 15 J / g, and most preferably at most about 10 J / g, and The low molecular weight propylene copolymer has a weight average molecular weight of at most about 60,000 g / mol, preferably at most about 40,000 g / mol, and most preferably at most about 30,000 g / mol, and a heat of fusion of at least about 20 J / g, preferably at least about 25 J / g, and most preferably at least about 30 J / g, the composition according to embodiment 1.

[0051] 3. The high molecular weight propylene copolymer has a polydispersity index of less than about 5, preferably less than about 4, and most preferably less than about 3; and The low molecular weight propylene copolymer has a polydispersity index of less than about 5, preferably less than about 4, and most preferably less than about 3, the composition according to embodiment 1 or 2.

[0052] 4. The high molecular weight propylene copolymer is a copolymer of propylene and a comonomer selected from the group consisting of ethylene and C 4 ~C 12 alkylene, preferably ethylene, and The low molecular weight propylene copolymer is a copolymer of propylene and a comonomer selected from the group consisting of ethylene and C 4 ~C 12 alkylene, preferably ethylene, the composition according to any one of embodiments 1 to 3.

[0053] 5. The polyisobutene has a number average molecular weight of at least about 750 g / mol, preferably at least about 900 g / mol, more preferably at least about 1,500 g / mol, and most preferably at least about 2,000 g / mol, the composition according to any one of embodiments 1 to 4.

[0054] 6. The high molecular weight propylene copolymer is present in an amount of about 10 wt% to about 60 wt%, preferably about 20 wt% to about 50 wt%, and most preferably about 25 wt% to about 40 wt% based on the total weight of the composition; The low molecular weight propylene copolymer is present in an amount of about 3 wt% to about 40 wt%, preferably about 4 wt% to about 30 wt%, and most preferably about 5 wt% to about 20 wt% based on the total weight of the composition; and The polyisobutene is present in an amount of about 5 wt% to about 50 wt%, preferably about 10 wt% to about 40 wt%, and most preferably about 15 wt% to about 30 wt% based on the total weight of the composition, the composition according to any one of aspects 1 to 5.

[0055] 7. The composition according to any one of aspects 1 to 6, further comprising a polymer of a 1-butene copolymer.

[0056] 8. The composition according to aspect 7, wherein the 1-butene copolymer comprises a butene-ethylene copolymer.

[0057] 9. The 1-butene copolymer has a density of at most about 0.907 g / cm 3 , preferably at most about 0.905 g / cm 3 , more preferably at most about 0.900 g / cm 3 , and most preferably at most about 0.895 g / cm 3 , the composition according to any one of aspects 7 or 8.

[0058] 10. The 1-butene copolymer is present in an amount of about 5 wt% to about 40 wt%, preferably about 7 wt% to about 30 wt%, and most preferably about 10 wt% to about 25 wt% based on the total weight of the composition, the composition according to any one of aspects 7 to 9.

[0059] 11. The composition according to any one of aspects 1 to 10, further comprising a plasticizer.

[0060] 12. The composition according to embodiment 11, wherein the plasticizer is selected from the group consisting of mineral oil, synthetic poly-alpha olefin oil, and mixtures thereof.

[0061] 13. The composition according to embodiment 11 or 12, wherein the plasticizer is present in an amount of about 5 wt% to about 60 wt%, preferably about 10 wt% to about 50 wt%, and most preferably about 15 wt% to about 40 wt% based on the total weight of the composition.

[0062] 14. The composition according to any one of embodiments 1 to 13, wherein the composition does not contain amorphous poly-alpha olefin.

[0063] 15. The composition according to any one of embodiments 1 to 14, wherein the composition does not contain wax.

[0064] 16. The composition according to any one of embodiments 1 to 15, wherein the molecular weight of the high molecular weight propylene copolymer is at least 2 times, preferably at least 3 times, and most preferably at least 4 times the molecular weight of the low molecular weight propylene copolymer.

[0065] 17. The composition according to any one of embodiments 1 to 16, wherein the heat of fusion of the low molecular weight propylene copolymer is at least 2 times, preferably at least 3 times, and most preferably at least 4 times the heat of fusion of the high molecular weight propylene copolymer.

[0066] 18. The composition according to any one of embodiments 1 to 17, wherein the viscosity of the composition is at most about 17,500 centipoises (cP) at 177 °C (350 °F), preferably at most about 15,000 centipoises (cP) at 177 °C (350 °F), and most preferably at most about 12,500 centipoises (cP) at 177 °C (350 °F).

[0067] 19. The composition according to any one of embodiments 1 to 18, further comprising an antioxidant.

[0068] 20. The composition according to any one of aspects 1 to 19, having an elongation at break of at least about 350%, preferably at least about 400%, and most preferably at least about 450%.

[0069] 21. The composition according to any one of aspects 1 to 20, having a yield stress of at least about 0.4 MPa, preferably at least about 0.5 MPa, and most preferably at least about 0.6 MPa.

[0070] 22. The composition according to any one of aspects 1 to 21, having a stress retention of at least 30%, preferably at least about 40%, and most preferably at least about 45%.

[0071] 23. The composition according to any one of aspects 1 to 22, having a viscosity that is maintained at greater than about 90% for at least 3 days, preferably greater than about 95% for at least 3 days, and most preferably greater than about 90% for at least 5 days at 177 °C.

[0072] 24. A method for manufacturing a laminate, a step of applying a hot melt adhesive composition according to any one of aspects 1 to 23 to a main substrate in a molten state; and a step of joining a secondary substrate to the main substrate by bringing the secondary substrate into contact with the adhesive composition, comprising.

[0073] 25. The method according to aspect 24, wherein the main substrate includes a first layer of an absorbent core, the secondary substrate includes a second layer of the absorbent core, and at least one of the first layer or the second layer has a superabsorbent polymer bonded thereto.

[0074] 26. An absorbent core including a first layer and a second layer, wherein at least one of the first layer and the second layer includes a superabsorbent polymer, the first layer and the second layer are adhered to each other by a hot melt adhesive composition according to any one of aspects 1 to 23, and the adhesive composition adheres the superabsorbent polymer within the absorbent core.

[0075] 27. A disposable hygiene product comprising the absorbent core according to aspect 26.

[0076] Examples The present invention will be further described by the following examples. To prepare the hot melt adhesive, all components were weighed in a single-layer aluminum paint can and heated to 177 °C under a nitrogen blanket (5 scfh). They were placed in the aluminum can with a double-blade impeller in an overhead mixer and stirred at 25 rpm until the polymer moved sufficiently. Then the speed was increased to 50 rpm until the mixture was homogeneous and at a constant temperature. The completion of the formulation was considered when the mixture looked homogeneous and no aggregates from the polymer were visible. Then, the formulation was used to test viscosity, tensile properties, and / or to produce laminates for final performance testing. Due to the excellent compatibility of the system, all components could be put together without compromising the total mixing time. This compatibility and stability resulted in a very heat-resistant system that could maintain its viscosity even after several days at 177 °C.

[0077] An adhesive was prepared using the components listed below and in Tables 1 - 3. The numerical values listed for the given raw materials are in weight % and must equal 100%.

[0078] Calsol 5500 is a naphthenic process oil available from Calumet Specialty Products.

[0079] Indopol H-1900 is an available polyisobutene oligomer with a number average molecular weight of 2,500 g / mol determined by the supplier (Ineos Capital Ltd) using gel permeation chromatography (GPC). All references in this specification to the number average molecular weight of the polyisobutene prepared are based on the same method.

[0080] Indopol H-100 is an available polyisobutene oligomer with a number average molecular weight of 910 g / mol as determined by the supplier (Ineos Capital Ltd) using gel permeation chromatography (GPC).

[0081] Irgafos 168 is tris(2,4-di-tert-butylphenyl) phosphate available from BASF Chemicals and is used as an antioxidant.

[0082] Irganox 1010 is pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate) available from BASF Corp and is used as an antioxidant.

[0083] Koattro PB M 1200M is a 1-butene copolymer with a density of 0.908 g / cm3 (tested by the supplier in accordance with ISO 1183-1) available from LyondellBasell Industries Holdings.

[0084] Koattro PB M 1500M is a 1-butene copolymer with a density of 0.890 g / cm3 (tested by the supplier in accordance with ISO 1183-1) available from LyondellBasell Industries Holdings.

[0085] Vistamaxx 6502 obtained from ExxonMobil Chemical Company, Houston, TX contains approximately 13 wt% ethylene comonomer, has a weight average molecular weight (Mw) of over 80,000 g / mol, and a density of 0.865 g / cm 3 and is an essentially amorphous poly(propylene-co-ethylene). (Reported by the supplier using ASTM D1505).

[0086] Vistamaxx 8380 obtained from ExxonMobil Chemical Company, Houston, TX is a low molecular weight, low viscosity random propylene-ethylene copolymer. It consists of approximately 12 wt% ethylene comonomer, has a weight average molecular weight (Mw) of less than 60,000 g / mol and a density of 0.864 g / cm 3 (reported by the supplier).

[0087] Vistamaxx 8880 obtained from ExxonMobil Chemical Company, Houston, TX is a semi-crystalline, low molecular weight propylene copolymer consisting of approximately 6 wt% ethylene comonomer, has a weight average molecular weight (Mw) of less than 60,000 g / mol and a density of 0.879 g / cm 3 (reported by the supplier).

[0088] Viscosity was measured at 163, 177 and 190 °C in accordance with ASTM D3236 using spindle 27. The spindle speed was adjusted so that the percent torque was between 45% and 90%. The viscosity should be low enough to result in fiber diameters between 10 and 60 μm when the adhesive is sprayed at 5 gsm using a Nordson Signature™ low flow nozzle.

[0089] The dogbones for tensile testing were made by injecting the molten adhesive into a silicone mold. As a result, the overall length of the dogbone was 3.5” × 1.0”, and when on the same plane as the mold, the thickness was 0.125”. The test area of the dogbone was 0.5” × 0.5”. The excess adhesive was scraped off from the silicone mold using a hot spatula so that the thickness of the dogbone was as close as possible to 0.125”. After cooling the samples to room temperature for at least 12 hours, they were tested for elongation at break, maximum stress, and other mechanical tests. The top and bottom of the dogbone were clamped to an Instron tensile testing machine, and only the 0.5” × 0.5” test area was exposed. The pull rate was 2” / min and continued until the specimen was destroyed. The elongation at break and maximum stress were automatically calculated in the BlueHill3 software available in Instron. The elongation at break was recorded as a percentage based on the difference between the final length and the initial length divided by the initial length, and it was determined whether the adhesive could withstand the elongation from the swelling of the SAP particles. The goal was to maintain an elongation of about 475% or more in the adhesive. Also, it was considered necessary to have good stress retention over time when held at a given elongation. The elongation value was 300%, which means that for an initial test height of 0.5”, it would elongate (at 2” / min) until the Instron jaws were a total of 2” apart. The stress or load value at 300% was recorded. Then, the test specimen was held at 300% elongation for 10 minutes before the final stress or load value was recorded. The “stress (%) held at 10 minutes, 300% elongation” seen in the following table refers to the stress after 10 minutes of holding at 300% elongation divided by the initial stress at 300% elongation and multiplied by 100, so that value is listed as the percentage of the stress maintained. This factor should be at least 30%, preferably at least about 40%, and most preferably at least about 45% or even at least about 50%.

[0090] The pattern quality was determined qualitatively and quantitatively. The adhesive was heated to about 190 °C and fed through a hose to a Signature Low Flow nozzle (Nordson Corp.) at a line speed of 200 feet per minute with a coat weight of 5 gsm. The air flow was adjusted to form the most visually fibrous-looking pattern with a minimum of agglomerates (those having a size greater than about twice the average size of the droplets) or flyaway adhesive strands (qualitatively). On average, the air pressure was about 20 psi, but this depends on the setup of each piece of the apparatus and is intended only as a reference. The nozzle head was placed 20 mm above the main substrate, which was a 33 gsm spunbond nonwoven fabric. Since the secondary substrate was a release liner, the sample could be analyzed better. Qualitative analysis was performed with a microscope to determine the diameter of the fibers generated during spray coating. The goal was to generate fiber diameters less than 60 μm, preferably less than 30 μm. Since the tensile properties of the adhesive are a function of the fiber diameter, the desired fiber diameter can vary depending on the adhesive formulation, the desired properties, and other conditions.

[0091] The thermal stability was determined by pouring approximately 150 g of the adhesive into an 8-ounce glass jar and loosely securing the lid. The jar was placed in an oven at a high temperature, namely 177 °C. The jar was removed from the oven daily to observe black charring or gelling that would indicate incompatibility. Further, 10 g slugs of the adhesive were poured out of the jar daily to determine viscosity retention. Viscosity retention was calculated by dividing the viscosity at a given temperature by the initial viscosity before thermal aging and multiplying by 100. Preferably, the viscosity retained is greater than 85% over at least 3 days. Ideally, the viscosity retained is greater than 90% over at least 3 days or even at least 5 days.

[0092]

Table 1

[0093] Table 1 demonstrates the importance of the polyisobutene (PIB) component and an optional butene-rich polymer. Example 2 shows that although the butene-rich copolymer is optional, it is preferably included as it reduces the viscosity and increases the elongation and stress retained as shown in Example 1. In Comparative Example 1 (CE1), using only naphthenic oil results in an adhesive that shows an unacceptable low elongation at break, which fails during retention at 300% elongation. Examples 1 and 2 of the present invention containing PIB had a break elongation of over 525% and retained over about 50% of their original stress after 10 minutes at 300% elongation. Example 3 containing low molecular weight PIB retained about 35% of the stress after 10 minutes at 300% elongation and had a break elongation of 463%. All examples of the present invention had a maximum stress of at least 0.61 MPa. Further, Examples 1 and 2 preferably provided an average fiber diameter of 17 μm when 5 gsm was applied at 190°C.

[0094]

Table 2

[0095] Table 2 demonstrates the role of the high molecular weight propylene copolymer component. Comparative Example 3 (CE3) replaces the high molecular weight component with an additional low molecular weight component. The loss of the high molecular weight component results in a dramatic decrease in break elongation and a complete loss of the stress retained after 10 minutes at 300% elongation.

[0096]

Table 3

[0097] Comparative Example 4 (CE4) contains a butene-rich copolymer with a specific gravity of 0.908 g / cm 3 . The resulting formulation becomes partially incompatible, resulting in a rapid decrease in break elongation and a complete loss of the stress retained after 10 minutes at 300% elongation.

[0098]

Table 4

[0099] Table 4 demonstrates excellent thermal stability through viscosity retention when placed in an oven at 177 °C for an extended period. Ideally, a hot melt adhesive is heated only for the required period, but in some cases, it may remain in a molten state for hours to days. For example, if there is a problem with the production line, the adhesive can be kept in a molten state until the line starts operating again. Additionally, some manufacturers do not produce products over the weekend and may leave the melt tank to avoid having to wait for the adhesive to remelt when restarting the line. Therefore, to enable these situations, it is advantageous to have an adhesive with excellent thermal stability. Preferably, the hot melt composition has a viscosity maintained at a temperature of at least about 85% or more over about 3 days, preferably at least about 90% or more over about 3 days, and most preferably at least about 90% or more over about 5 days.

[0100] When ranges of values are provided, it is understood that each intervening value between the upper and lower limits of that range, as well as any combination or sub - combination of the intervening values and any other defined value or intervening value within the defined range, is included within the range of the listed values. Additionally, the present invention includes ranges of components that are the lower limit of the first range and the upper limit of the second range of the components.

[0101] Unless otherwise specifically limited, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field to which this invention belongs. All publications and patents specifically mentioned herein are incorporated by reference in their entirety for all purposes including describing and disclosing the chemical substances, apparatuses, statistical analyses, and methods reported in the publications that may be used in connection with the present invention. All references cited herein should be construed as indicating the level of one of ordinary skill in the art. Nothing herein should be construed as an admission that the present invention has a right to antedate the disclosure of any prior invention.

[0102] Although described and illustrated herein with reference to specific particular embodiments, the present invention is not intended to be limited to the details shown. Rather, various changes may be made in detail within the scope of the claims and the equivalents thereof without departing from the spirit of the present invention.

Claims

1. (a) A high molecular weight propylene copolymer made by a single-site catalyst that is essentially amorphous; (b) A low molecular weight propylene copolymer made by a single-site catalyst that is semi-crystalline; (c) Polyisobutene; and (d) A polymer of a 1-butene copolymer having a density of up to 0.907 g / cm3; A hot melt adhesive composition that contains the above and does not contain a tackifier, wherein the high molecular weight propylene copolymer has a weight average molecular weight of at least 80,000 g / mol and a heat of fusion of up to 20 J / g, the low molecular weight propylene copolymer has a weight average molecular weight of up to 60,000 g / mol and a heat of fusion of at least 20 J / g, the high molecular weight propylene copolymer is present in an amount of 10% to 60% by weight based on the total weight of the composition; the low molecular weight propylene copolymer is present in an amount of 3% to 40% by weight based on the total weight of the composition; the polyisobutene is present in an amount of 5% to 50% by weight based on the total weight of the composition; the 1-butene copolymer is present in an amount of 5% to 40% by weight based on the total weight of the composition, a hot melt adhesive composition.

2. the high molecular weight propylene copolymer has a weight average molecular weight of at least 95,000 g / mol and a heat of fusion of up to 15 J / g, and the low molecular weight propylene copolymer has a weight average molecular weight of up to 40,000 g / mol and a heat of fusion of at least 25 J / g, the composition according to Claim 1.

3. the high molecular weight propylene copolymer has a polydispersity index of less than 5; and the low molecular weight propylene copolymer has a polydispersity index of less than 5, the composition according to Claim 1.

4. The high molecular weight propylene copolymer is a copolymer of propylene and a comonomer selected from the group consisting of ethylene and C ４ -C １２ alkylene, and The low molecular weight propylene copolymer is a copolymer of propylene and a comonomer selected from the group consisting of ethylene and C ４ -C １２ The composition according to claim 1, which is a copolymer with an alkylene.

5. the polyisobutene has a number average molecular weight of at least 750 g / mol, the composition according to Claim 1.

6. the high molecular weight propylene copolymer is present in an amount of 20% to 50% by weight based on the total weight of the composition; the low molecular weight propylene copolymer is present in an amount of 4% to 30% by weight based on the total weight of the composition; and the polyisobutene is present in an amount of 10% to 40% by weight based on the total weight of the composition, the composition according to Claim 1.

7. the 1-butene copolymer contains a butene-ethylene copolymer, the composition according to Claim 1.

8. The composition according to claim 1, wherein the 1-butene copolymer has a density of at most 0.905 g / cm3.

9. The composition according to claim 1, wherein the 1-butene copolymer is present in an amount of 7% to 30% by weight based on the total weight of the composition.

10. The composition according to claim 1, further comprising a plasticizer.

11. The composition according to claim 10, wherein the plasticizer is selected from the group consisting of mineral oil, synthetic polyalphaolefin oil, and mixtures thereof.

12. The composition according to claim 10, wherein the plasticizer is present in an amount of 5% to 60% by weight based on the total weight of the composition.

13. The composition according to claim 1, wherein the composition does not contain an amorphous polyalphaolefin.

14. The composition according to claim 1, wherein the composition does not contain wax.

15. The composition according to claim 1, wherein the molecular weight of the high molecular weight propylene copolymer is at least twice the molecular weight of the low molecular weight propylene copolymer.

16. The composition according to claim 1, wherein the heat of fusion of the low molecular weight propylene copolymer is at least twice the heat of fusion of the high molecular weight propylene copolymer.

17. The composition according to claim 1, wherein the viscosity of the composition is at most 17,500 centipoise (cP) at 177 °C (350 °F).

18. The composition according to claim 1, further comprising an antioxidant.

19. The composition according to claim 1, wherein the composition has an elongation at break of at least 350%.

20. The composition according to claim 1, wherein the composition has a yield stress of at least 0.4 MPa.

21. A method for manufacturing a laminate, comprising: applying a hot melt adhesive composition according to any one of claims 1 to 20 to a main substrate in a molten state; and joining a secondary substrate to the main substrate by bringing the secondary substrate into contact with the adhesive composition. A method comprising the above steps.

22. The method according to claim 21, wherein the main substrate comprises a first layer of an absorbent core, the secondary substrate comprises a second layer of the absorbent core, and at least one of the first layer or the second layer has a superabsorbent polymer bonded thereto.

23. An absorbent core comprising a first layer and a second layer, at least one of the first layer and the second layer containing a superabsorbent polymer, the first layer and the second layer being adhered to each other by the hot melt adhesive composition according to any one of claims 1 to 20, the adhesive composition being an absorbent core that adheres the superabsorbent polymer within the absorbent core.

24. A disposable sanitary product comprising the absorbent core according to claim 23.

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