Semi-crystalline polyolefin structure adhesive

Abstract

The present invention includes hot melt adhesive compositions based on polyolefin polymers that can be used for applications in disposable absorbent articles, such as construction applications. The olefin-based hot melt adhesive composition has an unexpectedly good cohesive strength.

Description

[0001] background

[0002] Adhesives are commonly used to bond substrates together to maintain a fixed relationship between two substrates. In the industrial adhesives industry, hot melt adhesives are commonly used to bond a variety of products together, including disposable absorbent products containing nonwoven substrates, such as adult incontinence products, disposable diapers, sanitary napkins, mattresses, pet pads, medical dressings, etc.

[0003] A variety of hot melt adhesives can be used in the manufacture of disposable absorbent articles. For example, in the manufacture of disposable diapers, hot melt adhesives are used for construction (e.g., bonding a backing sheet to a nonwoven fabric and optional absorbent pad), elastic attachment (e.g., bonding an elastic material to a backing sheet, such as in the leg or waist area), and core stabilization (e.g., applying an adhesive to the absorbent core to increase its strength).

[0004] Compared to rubber-based products, hot melt adhesives formulated with polyolefin polymers for construction applications tend to have lower cohesive strength. Providing olefin-based hot melt adhesives with improved cohesive strength would be useful.

[0005] Overview

[0006] In one aspect, the invention is characterized by a hot melt adhesive composition comprising a first propylene-based copolymer having a comonomer content of less than 5% by weight, a heat of fusion of 38 joules / g to 68 joules / g, and a melt flow rate of 2 g / 10 min to 40 g / 10 min when tested at 230°C / 2.16 kg according to ASTM D 1238, a second propylene-based copolymer having a comonomer content of 5% to 30% by weight, a tackifier, and a plasticizer.

[0007] In one embodiment, the first propylene copolymer has a heat of fusion of 40 joules / g to 65 joules / g. In another embodiment, the first and second propylene copolymers are metallocene-catalyzed. In a different embodiment, the second propylene copolymer has a Brookfield viscosity at 190°C of not more than 20,000 cps. In one embodiment, the hot melt adhesive composition contains at least 22% by weight of a plasticizer, or even at least 24% by weight of a plasticizer.

[0008] In one different embodiment, the hot melt adhesive composition comprises 2% to 20% by weight of a first propylene copolymer, 2% to 25% by weight of a second propylene copolymer, 30% to 60% by weight of a tackifier, and 22% to 35% by weight of a plasticizer.

[0009] In another aspect, the present invention is characterized by a hot melt adhesive composition comprising a first propylene copolymer having a comonomer content of less than 8% by weight, a heat of fusion of 38 joules / g to 68 joules / g and a melt flow rate of 2 g / 10 min to 40 g / 10 min when tested according to ASTM D 1238 at 230°C / 2.16 kg, a second propylene copolymer having a comonomer content of 8% by weight to 30% by weight and a melt flow rate of 2 g / 10 min to 50 g / 10 min when tested according to ASTM D 1238 at 230°C / 2.16 kg, a tackifier, and a plasticizer.

[0010] In one embodiment, the first propylene copolymer has a heat of fusion of 40 joules / gram to 65 joules / gram. In another embodiment, the hot melt adhesive composition comprises 3% to 12% by weight of the first propylene copolymer, 3% to 12% by weight of the second propylene copolymer, 35% to 60% by weight of the tackifier, and 25% to 35% by weight of the plasticizer.

[0011] In one embodiment, the sum of the first propylene copolymer and the second propylene copolymer constitutes 10% to 20% by weight of the hot melt adhesive composition. In a different embodiment, the sum of the first propylene copolymer and the second propylene copolymer constitutes 12% to 18% by weight of the hot melt adhesive composition.

[0012] In one embodiment, the first propylene copolymer has a melt flow rate of 2 g / 10 min to 20 g / 10 min when tested according to ASTM D 1238 at 230 °C / 2.16 kg. In a different embodiment, the first and second propylene copolymers are propylene-ethylene copolymers. In another embodiment, the tackifier is a hydrogenated hydrocarbon. In one embodiment, the tackifier has a ring and ball softening point of 90 °C to 110 °C.

[0013] In another embodiment, the plasticizer is an oil. In yet another embodiment, the hot melt adhesive composition has a heat of fusion of 6 joules / gram to 20 joules / gram.

[0014] In one different embodiment, the invention includes a disposable absorbent article made with one of the hot melt adhesive compositions of the invention. In another embodiment, the disposable absorbent article includes a first substrate, a second substrate, and the hot melt adhesive composition of the invention, wherein the hot melt adhesive composition is applied to at least one of the first substrate and the second substrate.

[0015] In one embodiment, the disposable absorbent article is selected from diapers, adult incontinence products, and hygiene products. In another embodiment, the hot melt adhesive composition of the present invention is used in disposable absorbent articles for applications selected from construction and back sheet lamination.

[0016] The hot melt adhesive composition of the present invention comprises blends of olefin polymers that work together to form physical crosslinks to produce a semi-crystalline hot melt adhesive composition capable of forming strong and durable bonds and particularly suitable for the production of disposable absorbent articles.

[0017] Vocabulary

[0018] Regarding this invention, these terms have the following meanings:

[0019] Propylene-based polymers are polymers containing at least 50% by weight of propylene.

[0020] Detailed Explanation

[0021] hot melt adhesive composition

[0022] The present invention is characterized by a hot melt adhesive composition comprising a first propylene copolymer with a unit point catalytic content of less than 5% by weight of comonomer, a heat of fusion of 40 joules / g to 65 joules / g and a melt flow rate of 2 g / 10 min to 40 g / 10 min when tested at 230°C / 2.16 kg according to ASTM D 1238, a second propylene copolymer with a comonomer content of 5% to 30% by weight, a tackifier, and a plasticizer.

[0023] The present invention is characterized by a hot melt adhesive composition comprising 4% to 20% by weight of a first propylene copolymer with a unit point catalytic content of less than 5% by weight, a heat of fusion of 40 joules / g to 65 joules / g and a melt flow rate of 2 g / 10 min to 40 g / 10 min when tested according to ASTM D1238 at 230°C / 2.16 kg, 4% to 25% by weight of a second propylene copolymer with a comonomer content of 5% to 30% by weight, 30% to 60% by weight of a tackifier, and 22% to 35% by weight of a plasticizer.

[0024] A further feature of the present invention is a hot melt adhesive composition comprising a first propylene copolymer that is catalyzed at a single point and has a comonomer content of less than 8% by weight, a heat of fusion of 40 joules / g to 65 joules / g and a melt flow rate of 2 g / 10 min to 40 g / 10 min when tested according to ASTM D 1238 at 230°C / 2.16 kg, a second propylene copolymer that is catalyzed at a single point and has a comonomer content of 8% by weight to 30% by weight and a melt flow rate of 2 g / 10 min to 50 g / 10 min when tested according to ASTM D 1238 at 230°C / 2.16 kg, a tackifier, and a plasticizer.

[0025] A further feature of the present invention is a hot melt adhesive composition comprising 3% to 12% by weight of a first propylene copolymer with a single-point catalytic content of less than 8% by weight, a heat of fusion of 40 joules / g to 65 joules / g and a melt flow rate of 2 g / 10 min to 40 g / 10 min when tested according to ASTM D 1238 at 230°C / 2.16 kg, 3% to 12% by weight of a second propylene copolymer with a single-point catalytic content of 8% to 30% by weight, a melt flow rate of 2 g / 10 min to 50 g / 10 min when tested according to ASTM D 1238 at 230°C / 2.16 kg, 35% to 60% by weight of a tackifier, and 25% to 35% by weight of a plasticizer.

[0026] The invention is further characterized by a hot melt adhesive composition comprising a first propylene copolymer that is catalyzed at a single point and has a comonomer content of less than 8% by weight, a heat of fusion of 40 joules / g to 65 joules / g and a melt flow rate of 2 g / 10 min to 40 g / 10 min when tested according to ASTM D 1238 at 230°C / 2.16 kg, a second propylene copolymer that is catalyzed at a single point and has a comonomer content of 8% to 30% by weight, and a melt flow rate of 2 g / 10 min to 50 g / 10 min when tested according to ASTM D 1238 at 230°C / 2.16 kg, a tackifier, and a plasticizer, wherein the first propylene copolymer and the second propylene copolymer constitute 10% to 20% by weight of the hot melt adhesive composition.

[0027] The first propylene copolymer is highly crystalline and has a high molecular weight. This results in a semi-crystalline hot melt adhesive composition. The inventors believe that improved cohesion of the hot melt adhesive, as demonstrated by improved static peel strength, is achieved when the crystallinity comes from the polymer rather than the wax. Although the hot melt adhesive can be semi-crystalline in the absence of wax, wax can be added to the composition in limited amounts to adjust other properties.

[0028] The hot melt adhesive composition may have a heat of fusion of 6.0 joules / g, 6.5 joules / g, 7 joules / g, 7.5 joules / g, 8 joules / g, up to 13 joules / g, 15 joules / g, 18 joules / g, 20 joules / g, 25 joules / g, or any two values ​​thereof, as tested according to the heat of fusion test method.

[0029] The hot melt adhesive composition may have a dynamic peel strength of at least 80 gf / 3 in, at least 120 gf / 3 in, at least 160 gf / 3 in, from 120 gf / 3 in to 500 gf / 3 in, or even from 300 gf / 3 in to 500 gf / 3 in, as tested according to the dynamic peel test method.

[0030] The hot melt adhesive composition may have a static peel test result of at least 5 minutes, at least 6 minutes, at least 7 minutes, at least 8 minutes, or even at least 10 minutes, as determined by the static peel test method.

[0031] The hot melt adhesive composition may have a Brookfield viscosity at 150°C of no more than 25,000 cP, no more than 20,000 cP, no more than 15,000 cP, from 250 cP to 30,000 cP, from 250 cP to 20,000 cP, or even 500 cP to 15,000 cP.

[0032] polymer

[0033] This hot melt adhesive composition comprises two different propylene-based copolymers, namely a first propylene-based copolymer and a second propylene-based copolymer. The propylene-based copolymer is a copolymer of propylene and at least one α-olefin.

[0034] Suitable propylene / α-olefin copolymers are derived from propylene and at least one α-olefin comonomer, examples of which include α-olefin comonomers having 2 to 10 carbon atoms, including, for example, ethylene, butene, 1,4-methylpentene, hexene, octene, and combinations thereof. In one embodiment, at least one propylene-based copolymer, or even two propylene-based copolymers, is a propylene-ethylene copolymer. The propylene-based copolymer can be entirely olefin-based, i.e., free of any functional groups. The propylene-based copolymer may contain at least 75% by weight of propylene or even at least 80% by weight of propylene. The propylene-based copolymer may have a polydispersity (Mw / Mn) of less than 5, less than 3, less than 2.5, or even 2 as determined by size exclusion chromatography (SEC). Available propylene-based copolymers include unit-site (e.g., metallocene) catalyzed propylene-based polymers and amorphous polyalphaolefins (APAOs).

[0035] Both the first and second propylene copolymers may have a melt index according to ASTM D1238 (230°C, 2.16 kg) ranging from 1 g / 10 min, 2 g / 10 min, 3 g / 10 min, 4 g / 10 min, 5 grams / min, 6 g / 10 min to 13 g / 10 min, 15 g / 10 min, 20 g / 10 min, 30 g / 10 min, 40 g / 10 min, 50 g / 10 min, 75 g / 10 min, or any value between any two of these values.

[0036] The total amount of the first propylene copolymer and the second propylene copolymer can be from 10 wt%, 12 wt%, 13 wt% to 20 wt%, 22 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt%, or any value between any two of these values.

[0037] First Propylene-Based Copolymer

[0038] The first propylene copolymer can be a single-point catalytic polymer. The hot melt adhesive composition may contain more than one first propylene copolymer.

[0039] The first propylene-based copolymer may be a propylene-ethylene copolymer with a single-point catalytic reaction. The first propylene-based copolymer has a comonomer content ranging from 0.5% by weight, 1% by weight, 1.5% by weight, 2% by weight to less than 5% by weight, less than 6% by weight, less than 7% by weight, less than 8% by weight, or any two of these values.

[0040] The first propylene-based copolymer has a melt index according to ASTM D1238 (230°C, 2.16 kg) of any two values ​​from 1 g / 10 min, 2 g / 10 min, 3 g / 10 min, 4 g / 10 min, 5 g / min, 6 g / 10 min to 13 g / 10 min, 15 g / 10 min, 20 g / 10 min, 30 g / 10 min, 35 g / 10 min, 40 g / 10 min, 45 g / 10 min, 50 g / 10 min, 75 g / 10 min, or any two values ​​in between.

[0041] The first propylene-based copolymer may have a Vicat softening temperature (measured by the ExxonMobil test method) of at least 80°C, at least 85°C, at least 90°C, 80°C to 120°C, 85°C to 115°C, or even 90°C to 110°C. The inventors have found that including propylene polymers with relatively high Vicat softening temperatures helps to achieve the desired cohesive strength.

[0042] The first propylene-based copolymer may have a heat of fusion tested according to the heat of fusion test method, ranging from 38 joules / g, 40 joules / g, 43 joules / g, 45 joules / g, 48 joules / g, 50 joules / g, 52 joules / g, 55 joules / g, to 60 joules / g, 62 joules / g, 64 joules / g, 65 joules / g, 66 joules / g, 68 joules / g, or any two values ​​thereof.

[0043] Commercially available first propylene copolymers include VISTAMAXX 3588 FL, which is available from ExxonMobil Chemical (Houston, Texas).

[0044] The first propylene copolymer is present in the composition in any amount from 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt% to 12 wt%, 15 wt%, 18 wt%, 20 wt%, 25 wt% or any two of these values.

[0045] Second Propylene-Based Copolymer

[0046] The second propylene-based copolymer may be selected from mono-point catalyzed polymers and Ziegler-Natta catalyzed polymers (e.g., APAO polymers). The hot melt adhesive composition may contain more than one second propylene-based copolymer. The second propylene-based copolymer may have a comonomer content ranging from 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt% to 16 wt%, 18 wt%, 20 wt%, 25 wt%, 30 wt%, or any two of these values.

[0047] The second propylene-based copolymer may have a melt index according to ASTM D1238 (230°C, 2.16 kg) of any two values ​​from 1 g / 10 min, 2 g / 10 min, 3 g / 10 min, 4 g / 10 min, 5 g / min, 6 g / 10 min to 13 g / 10 min, 15 g / 10 min, 20 g / 10 min, 30 g / 10 min, 40 g / min, 50 g / 10 min, 75 g / 10 min or between.

[0048] The second propylene copolymer can alternatively have Brookfield viscosities at 190°C of no more than 25,000 cps, no more than 20,000 cps, no more than 15,000 cps, no more than 12,000 cps, no more than 10,000 cps, 2,500 cps to 15,000 cps, or even 3,000 cps to 12,000 cps.

[0049] The second propylene copolymer may have a heat of fusion as tested according to the heat of fusion test method, ranging from 0 joules / g, 5 joules / g, 7 joules / g to 15 joules / g, 20 joules / g, 25 joules / g, 30 joules / g or any two of these values.

[0050] Available commercially available secondary polymers include VISTAMAXX 8380 and VISTAMAXX 6202 (unit-point catalytic propylene-ethylene copolymers) available from ExxonMobil Chemical (Houston, Texas) and AERAFIN 180 (APAO) and AERAFIN 75H (APAO) available from SynthomerAdhesive Technology (Kingsport, Tennessee).

[0051] The second propylene copolymer is present in the composition in any amount from 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt% to 12 wt%, 15 wt%, 18 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt% or any two of these values.

[0052] Tackifying agent

[0053] This hot melt adhesive composition contains a tackifier. The tackifier may be at least partially hydrogenated to improve the odor of the adhesive. The tackifier may be a fluid or a solid at room temperature. Suitable classes of tackifiers include, for example, aromatic, aliphatic and alicyclic hydrocarbon resins, mixed aromatic and aliphatic modified hydrocarbon resins, aromatic modified aliphatic hydrocarbon resins and their hydrogenated forms; terpenes, modified terpenes and their hydrogenated forms; natural rosins, modified rosins, rosin esters and their hydrogenated forms, and combinations thereof.

[0054] Tackifiers may have global softening points reported by suppliers of 80°C to 150°C, 90°C to 140°C, 90°C to 135°C, 90°C to 130°C, or even 90°C to 110°C.

[0055] Available tackifiers are available under various trade names, including, for example, the ESCOREZ series from Exxon Mobil Chemical Company (Houston, Texas), including ESCOREZ 2203LC, ESCOREZ 5400, and ESCOREZ 5600; the EASTOTAC series from Synthomer PLC, including EASTOTAC H-100R and EASTOTAC H-100L; the RESINALL series from Resinal Corp (Severn, NC), including RESINALL 1095S; the KOLON series from Kolon Industries, Inc. (Ulsan, Korea), including SUKOREZ SU100 and SU110; the ARKON series from Arakawa Chemical Industries, Ltd. (Osaka, Japan), including ARKON M90, ARKON M100, and ARKON P100; and from CrayValley HSC (Exton, Texas). Trade names from the WINGTACK series (Pennsylvania), including WINGTACK 86, WINGTACK EXTRA, and WINGTACK 95, and trade names from the PICCOTAC and KRISTALEX series from Synthomer LLC, including, for example, PICCOTAC 8095 and KRISTALEX 3100.

[0056] The tackifier is present in the hot melt composition in any amount from 25 wt%, 30 wt%, 35 wt%, 40 wt% to 55 wt%, 60 wt%, 65 wt% or any two of these values.

[0057] Plasticizer

[0058] This hot melt adhesive composition contains a plasticizer. Suitable plasticizers include, for example, naphthenic oils, paraffinic oils (e.g., cycloparaffin oils), mineral oils, phthalates, adipates, olefin oligomers, polybutene, polyisoprene, hydrogenated polyisoprene, polybutene, benzoates, animal oils, vegetable oils such as castor oil, soybean oil, oil derivatives, glycerides of fatty acids, and combinations thereof.

[0059] Available commercially available plasticizers include CALSOL 5550 oil from Calumet Specialty Products Partners, LP (Indianapolis, Indiana), KAYDOL OIL from Sonneborn (Tarrytown New York), PARAPOL polybutene from Exxon Mobil Chemical Company (Houston, Texas), OPPANOL polyisobutylene from BASF (Ludwigsjhafen, Germany), KRYSTOL 550 mineral oil from Petrochem Carless Limited (Surrey, England), and PURETOL 35 mineral oil from Petro Canada Lubricants Inc. (Mississauga, Ontario).

[0060] In one embodiment, the plasticizer is a naphthenic oil. The plasticizer is present in the hot melt adhesive composition in any amount between any two of the following values: at least 20% by weight, at least 22% by weight, at least 24% by weight, at least 25% by weight, or even from 15% by weight, 18% by weight, 20% by weight, 22% by weight, 24% by weight, 25% by weight, to 32% by weight, 33% by weight, 34% by weight, 35% by weight, 36% by weight, 38% by weight, 40% by weight.

[0061] wax

[0062] The hot melt adhesive composition may be wax-free or may contain wax. Available classes of waxes include, for example, paraffin waxes, microcrystalline waxes, high-density low-molecular-weight polyethylene waxes, by-product polyethylene waxes, polypropylene waxes, Fischer-Tropsch waxes, oxidized Fischer-Tropsch waxes, functionalized waxes such as acid, anhydride, and hydroxyl-modified waxes, animal waxes, plant waxes (e.g., soybean wax), and combinations thereof. Available waxes are solid at room temperature and preferably have a ring and ball softening point of 50°C to 170°C. The wax may be a propylene-based wax with a Mettler softening point (ASTM D 6092) greater than 130°C, 140°C, or even 150°C. Available waxes are available from a variety of suppliers, including trade names from Westlake Chemical Corporation (Houston, Texas) for the EPOLENEN and C series, such as EPOLENE N-21 and EPOLENE N-15, and trade names from Clariant International Ltd. (Muttenz, Switzerland) for the LICOCENE series, such as LICOCENE PP 6102, LICOCENE PP 6502 TP, and LICOCENE PP 7502 TP.

[0063] The hot melt adhesive composition may contain no more than 6% by weight, no more than 5% by weight, 0.5% by weight to 6% by weight, 0.5% by weight to 5% by weight, 0.5% by weight to 4% by weight, or even 0.5% by weight to 3% by weight of wax.

[0064] Additional components

[0065] The hot melt adhesive composition optionally includes additional components, including, for example, stabilizers, antioxidants, additional polymers (e.g., styrene block copolymers, polyethylene polymers, such as unit-point catalytic ethylene-based polymers, additional propylene-based polymers), adhesion promoters, UV stabilizers, corrosion inhibitors, colorants (e.g., pigments and dyes), fillers, surfactants, humidity indicators, superabsorbents, coatings, packaging films, and combinations thereof.

[0066] Available antioxidants include, for example, pentaerythritol tetra[3,(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 2,2'-methylenebis(4-methyl-6-tert-butylphenol), phosphites, including, for example, tri-(p-nonylphenyl)-phosphite (TNPP) and bis(2,4-di-tert-butylphenyl)4,4'-diphenyl-diphosphite, distearate-3,3'-thiodipropionate (DSTDP), and combinations thereof. Available antioxidants are available under various trade names, including, for example, the IRGANOX series, including hindered phenolic antioxidants such as IRGANOX 1010, IRGANOX 565, and IRGANOX 1076, and phosphite antioxidant IRGAFOS 168, all of which are available from BASF Corporation (Florham Park, New Jersey), as well as ETHYL 702 4,4'-methylenebis(2,6-di-tert-butylphenol). When present, the adhesive composition preferably contains 0.1% to 2% by weight of antioxidant.

[0067] Single absorbent products

[0068] The hot melt adhesive composition can be applied to (i.e., made to come into direct contact with) or incorporated into various substrates within disposable absorbent articles, including, for example, films (e.g., polyolefin films, such as polyethylene and polypropylene films), release liner, porous substrate, cellulose substrate, sheets (e.g., paper and fiber sheets), paper products, woven and nonwoven webs, fibers (e.g., synthetic polymer fibers and cellulose fibers), elastic materials, and tape backings.

[0069] This hot melt adhesive composition can also be used in a variety of applications and constructions, including, for example, disposable absorbent articles, including, for example, disposable diapers, adult incontinence products, sanitary napkins, medical dressings (e.g., wound care products), bandages, surgical pads, pet training pads (e.g., dog pads) and meat packaging products, as well as components of absorbent articles, including, for example, absorbent elements, absorbent cores, impermeable layers (e.g., backsheets), tissues (e.g., wrapping tissues), acquisition layers, and woven and nonwoven mesh layers (e.g., topsheets, absorbent tissues).

[0070] This hot melt adhesive composition can be used on substrates made of various fibers, including, for example, natural cellulose fibers such as wood pulp, cotton, silk and wool; synthetic fibers such as nylon, rayon, polyester, acrylic resins, polypropylene, polyethylene, polyvinyl chloride, polyurethane and glass; regenerated fibers; and various combinations thereof.

[0071] Various application techniques can be used to apply the hot melt adhesive composition to a substrate, including, for example, slot coating, spraying (including, for example, spiral spraying and random spraying), screen printing, foaming, engraved roller, extrusion and meltblown application techniques.

[0072] Method for manufacturing disposable absorbent products

[0073] This hot melt adhesive composition exhibits good cohesive strength. It maintains this strength at low coating weights. These properties make it suitable for use in the construction of disposable absorbent articles, core stabilization, and for elastic attachment.

[0074] This hot melt adhesive composition can be used for construction applications. In a typical construction application of disposable absorbent articles, a fluid-impermeable backsheet is bonded to a nonwoven substrate. This hot melt adhesive composition can also be used to bond at least one additional layer or material selected from absorbents, tissues, elastomers, superabsorbent polymers, and combinations thereof. For example, the adhesive can be further used in backsheet lamination, where a fluid-impermeable backsheet, typically a polyolefin film (e.g., polyethylene, polypropylene, ethylene vinyl acetate, ethylene copolymers, etc.), is bonded to a second nonwoven fabric to improve the tactile feel of the disposable article.

[0075] This hot melt adhesive can also be used to contain the absorbent core of disposable absorbent articles and / or to provide it with strength (i.e., as a core-stabilizing adhesive). The absorbent core can contain a variety of different materials, including natural cellulose fibers (such as wood pulp, fiber, cotton, fluff, etc.) and superabsorbent polymers (such as polyacrylates).

[0076] This hot melt adhesive composition can be used in elastic attachment applications, including bonding elastic materials (e.g., strands, films, etc.) to components of disposable absorbent articles. The elastic material can be coated with the hot melt adhesive composition in a stretched state and then bonded to a film (e.g., polyethylene, polypropylene, etc.) or a nonwoven substrate. The elastic material coated with the hot melt adhesive can also be bonded between two such substrates. Once the tension is removed, the process creates creep-resistant gathers.

[0077] Alternatively, the adhesive can be applied to a membrane or nonwoven substrate, and then the elastic material can be bonded to it. This hot melt adhesive can be used as an elastic attachment adhesive in the formation of tabs / protrusions in disposable absorbent articles. Alternatively, the hot melt adhesive can be further used as an elastic attachment adhesive to help make leg holes or waistbands of disposable absorbent articles elastic.

[0078] The invention will now be described by way of the following non-limiting embodiments. Unless otherwise stated, all parts, ratios, percentages and amounts specified in the embodiments are by weight.

[0079] Example

[0080] Test Procedure

[0081] Unless otherwise stated, the test procedures used in the embodiments and throughout the specification include the following.

[0082] Viscosity test method

[0083] Viscosities were determined using a Brookfield Thermoset viscometer, model RVDV 2, and rotor #27, according to ASTM D-3236, entitled "Standard Test Method for Apparent viscosity of Adhesives and Coating Materials" (October 31, 1988). Results were reported in centipoises (cps).

[0084] Heat of fusion determined by dynamic scanning calorimetry

[0085] DSC measurements were performed on a Mettler Toledo DSC 3. Samples were evaluated in a hermetically sealed aluminum pan. Sample sizes ranged from 9 to 12 mg. Each adhesive sample was acclimated at 180°C for 10 minutes. The samples were then cooled at 20°C / min and aged at 25°C for 10 minutes. After aging, the samples were rapidly cooled to -50°C and then ramped up at 10°C / min until a temperature of 200°C was reached. The heat of fusion (reported here in J / g) was taken from this second heating ramp.

[0086] Preparation of peel test samples

[0087] Using a 3-inch (76.2 mm) wide slot coater and laminator set to an application temperature of 157°C, without a bonding roll or end-sealing unit, apply 3 grams per square meter (m²). 2 Apply coating weight and minimum rewind and unwind tension to prevent stretching of the web.

[0088] The hot melt adhesive composition was continuously applied to a surface with a thickness of 0.1 mm and a strength of 15 g / m². 2A nonwoven polypropylene web of base weight is applied. The nonwoven web is passed through an applicator at a speed of 190 m / min to 250 m / min with a deflection of 5 mm. Then, an impermeable laminated polyethylene film with a thickness of 0.23 mm, traveling at the same speed as the nonwoven web, is adhered to the nonwoven web with an adhesive composition to form a laminate. The time between applying the adhesive to the nonwoven web and adhering it to the polyethylene film is 0.3–0.4 seconds.

[0089] Dynamic Peel Adhesion Test Method

[0090] Dynamic peel strength was determined according to ASTM D1876-01, entitled "Test Method for Determining Peel Resistance of Adhesive (T-Peel Test Method)," but with eight replicates. Test samples were run on an IMASS Spec type testing instrument. Test samples were prepared according to the sample preparation method described in the peel test sample preparation instructions. Eight test samples were prepared for each sample composition, and the test samples were tested 24 hours after preparation. The average peel value within 10 seconds of peeling was recorded, and the results were reported in grams per 3 inches (gf / 3 in).

[0091] Static Peel Adhesion Test Method

[0092] Static peel was determined by suspending a 150 g weight transversely (e.g., perpendicular to the web path of the laminator) over a 2-inch wide laminate. Samples were tested in a controlled temperature and humidity chamber set at 25°C and 50% relative humidity. The suspension time of the weight was measured in minutes. Eight test samples were prepared for each sample composition, and the test samples were tested 24 hours after preparation. The average suspension time was reported.

[0093] Table 1 – Polymer Properties

[0094] NA (Not Applicable)

[0095]

[0096] Table 2 – Examples

[0097] NT (Untested)

[0098]

[0099] Other embodiments are described in the claims.

Claims

1. A hot melt adhesive composition comprising: a. A first propylene-based copolymer having a comonomer content of less than 5% by weight, a heat of fusion of 40 joules / g to 65 joules / g, and a melt flow rate of 2 g / 10 min to 40 g / 10 min when tested at 230°C / 2.16 kg according to ASTM D 1238. b. A second propylene-based copolymer having a comonomer content of 5% to 30% by weight, c. Tackifiers; and d. Plasticizers.

2. The hot melt adhesive composition according to claim 1, wherein the first propylene copolymer and the second propylene copolymer are metallocene-catalyzed propylene-ethylene copolymers.

3. The hot melt adhesive composition according to any one of the preceding claims, wherein the second propylene copolymer has a Brookfield viscosity at 190°C of not more than 20,000 cps.

4. The hot melt adhesive composition according to any one of the preceding claims, comprising at least 22% by weight of a plasticizer.

5. The hot melt adhesive composition according to any one of the preceding claims, comprising: a. 4% to 20% by weight of the first propylene copolymer, b. 4% to 25% by weight of the second propylene copolymer, c. 30% to 60% by weight of the aforementioned tackifier, and d. 22% to 35% by weight of the plasticizer.

6. The hot melt adhesive composition according to any one of the preceding claims, wherein the second propylene copolymer has a comonomer content of 8% to 30% by weight and a melt flow rate of 2 g / 10 min to 50 g / 10 min when tested at 230 °C / 2.16 kg according to ASTM D 1238.

7. The hot melt adhesive composition according to any one of the preceding claims, wherein the sum of the first propylene copolymer and the second propylene copolymer constitutes 10% to 20% by weight of the hot melt adhesive composition.

8. The hot melt adhesive composition according to any one of the preceding claims, wherein the first propylene copolymer has a melt flow rate of 2 g / 10 min to 20 g / 10 min when tested at 230 °C / 2.16 kg according to ASTM D 1238.

9. The hot melt adhesive composition according to any one of the preceding claims, wherein the first propylene copolymer has a heat of fusion of 45 joules / gram to 65 joules / gram.

10. The hot melt adhesive composition according to any one of the preceding claims, wherein the tackifier is a hydrogenated hydrocarbon having a ring and ball softening point of 90°C to 110°C.

11. The hot melt adhesive composition according to any one of the preceding claims, further comprising wax.

12. The hot melt adhesive composition according to any one of the preceding claims, having a heat of fusion of 6 joules / gram to 20 joules / gram.

13. A disposable absorbent article comprising the hot melt adhesive composition according to claim 1.

14. The disposable absorbent article of claim 13, wherein the hot melt adhesive composition is used in the disposable absorbent article for applications selected from construction and backsheet lamination.

15. A hot melt adhesive composition comprising: a. 4% to 20% by weight of a first propylene-based copolymer, which is mono-point catalyzed, has a comonomer content of less than 5% by weight, a heat of fusion of 40 joules / g to 65 joules / g, and a melt flow rate of 2 g / 10 min to 40 g / 10 min when tested at 230 °C / 2.16 kg according to ASTM D 1238. b. 4% to 25% by weight of a second propylene-based copolymer having a comonomer content of 5% to 30% by weight, c. 30% to 60% by weight of tackifier and d. 22% to 35% by weight of plasticizer.

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