Hydrophilic hot-melt adhesive and use thereof

Abstract

To provide a hydrophilic hot-melt adhesive composition and its use.SOLUTION: A hydrophilic hot melt adhesive composition comprising: (a) 20-70% by weight of an ethylene copolymer selected from the group consisting of ethylene vinyl acetate, ethylene n-butyl acrylate, ethylene octene, ethylene propylene, ethylene butene propylene, and mixtures thereof; (b) (i) a melting point of from 70°C to 140°C as measured according to ASTM D-127; (ii) fully saturated linear C20-C50 synthetic alcohols; (iii) an acid number of less than 100 mg KOH / g, measured according to ASTM E222; and (iv) from 1 to 25% by weight of a nonionic ethoxylate surfactant polymer emulsifier having a molecular weight of from 400 to 5000 Daltons; (c) from 20 to 70% by weight of a tackifier; and (d) 5-15% by weight of a plasticizer which is a naphthenic oil;SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a hydrophilic hot melt adhesive composition and its use. Hydrophilic hot melt adhesives improve water wettability and are particularly suitable for the production of disposable nonwoven products. [Background technology]

[0002] Nonwoven fabrics are used commercially in a variety of applications, including insulation, packaging, household wipes, surgical drapes, medical bandages, and disposable products such as diapers, adult incontinence products, and sanitary napkins.

[0003] Many of the aforementioned applications require bonding a nonwoven to another substrate or component. The second substrate can be another nonwoven, a tissue, or an unrelated material. A commonly used technique for bonding assemblies is the use of hot melt adhesives. Hot melt adhesives allow for cost- and time-efficient manufacturing because they do not require an evaporation step, as is the case with water-based or solvent-based adhesive systems. A suitable hot melt adhesive must have excellent adhesion to the substrates involved. For nonwoven applications, they must also have excellent flexibility, no smearing or bleeding, adequate viscosity, set speed and open time to function with commercially available equipment, and acceptable heat aging properties.

[0004] WO 00 / 00229 (Lindner et al.) discloses hygiene articles containing an oil-resistant, hydrophilic adhesive. However, the adhesive's formulation or durability are not disclosed. U.S. Patent No. 6,380,292 (Bostik) discloses hydrophilic hot melt adhesive compositions suitable for nonwoven disposable articles, prepared by blending various adhesive components with surfactants.

[0005] It is desirable for hot melt adhesives to have the ability to transfer liquid from a nonwoven substrate to a superabsorbent or fluff core substrate. This property is important in the construction of disposable diapers, sanitary napkins, and bed pads, where it is desired that the nonwoven, after wetting, draws moisture away from the body and into the absorbent core as quickly as possible. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 00 / 00229 [Patent Document 2] U.S. Patent No. 6,380,292 Summary of the Invention [Means for solving the problem]

[0007] The present invention provides a hydrophilic hot melt adhesive composition with improved water wettability.

[0008] In one aspect, the present invention provides a method for producing a pharmaceutical composition comprising: (a) from about 20 to about 90 weight percent of an ethylene copolymer selected from the group consisting of ethylene vinyl acetate, ethylene n-butyl acrylate, ethylene octene, ethylene propylene, ethylene butene propylene, and mixtures thereof; and (b) about 1 to about 25 wt. % of a nonionic ethoxylate surfactant polymer emulsifier having (i) a melting point of about 70°C to about 140°C as measured in accordance with ASTM D-127, (ii) a fully saturated linear C20 to C50 synthetic alcohol, (iii) an acid number of less than 100 mg KOH / g as measured in accordance with ASTM E222, and (iv) a molecular weight of about 400 to about 5000 daltons; A hydrophilic hot melt adhesive composition comprising: The subject is a hydrophilic hot melt adhesive composition having a film contact angle with distilled water of less than 70 degrees both before and after aging at 60°C for 15 days.

[0009] In another aspect, the present invention provides a method for producing a pharmaceutical composition comprising: (a) mixing the mixture at 120°C to about 190°C to form a molten mixture comprising: (i) about 20 to about 90 wt% ethylene copolymer; (ii) 1 to about 25 wt% nonionic ethoxylate surfactant polymer emulsifier; (iii) about 20 to about 70 wt% tackifier; (iv) about 20 wt% or less plasticizer; and (v) about 3 wt% or less antioxidant; (b) solidifying the hydrophilic hot melt adhesive composition by pelletizing or forming a block of the molten mixture; The present invention is directed to a method for producing a hydrophilic hot melt adhesive composition, comprising:

[0010] The ethylene copolymer is selected from the group consisting of ethylene vinyl acetate, ethylene n-butyl acrylate, ethylene octene, ethylene propylene, ethylene butene propylene, and mixtures thereof. The nonionic ethoxylate surfactant polymer emulsifier has (i) a melting point of about 70°C to about 140°C as measured in accordance with ASTM D-127, (ii) a fully saturated linear C20 to C50 synthetic alcohol, (iii) an acid number of less than 100 mg KOH / g as measured in accordance with ASTM E222, and (iv) a molecular weight of about 400 to about 5000 Daltons.

[0011] In yet another aspect, the present invention relates to an article comprising the hydrophilic hot melt adhesive composition described above and a substrate comprising film, nonwoven, wood, wood pulp, cellulose, paper, cardboard, tissue, cotton, superabsorbent particles, etc. Articles include disposable absorbent articles, masks, tissue, books, furniture, films, meat pads, animal pads, personal protective equipment, insulation, packaging, household wipes, etc. DETAILED DESCRIPTION OF THE INVENTION

[0012] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. In case of conflict, the present specification, including definitions, will control. Preferred methods and materials are described below, although methods and materials similar or equivalent to those described herein can be used in the practice or testing of this disclosure. All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety. The materials, methods, and examples disclosed herein are for illustrative purposes only and are not intended to be limiting.

[0013] As used in the specification and claims, the term "comprising" may encompass the embodiments "consisting of" and "consisting essentially of." As used herein, the terms "comprising," "including," "having," "has," "can," and "containing," and variations thereof, are intended to be open-ended transitional phrases, terms, or words that require the presence of the specified ingredients / steps and permit the presence of other ingredients / steps. However, such descriptions should also be construed as describing the composition or method as "consisting of" and "essentially consisting of" the listed ingredients / steps, which permits the presence of only the specified ingredients / steps and possible impurities resulting therefrom, and excludes other ingredients / steps.

[0014] Numerical values ​​in the specification and claims of this application, particularly when referring to polymers or polymer compositions, reflect average values ​​for compositions that may contain individual polymers of different properties. Furthermore, unless otherwise specified, numerical values ​​should be understood to include the same numerical value when converted to the same significant figures, and numerical values ​​that differ from the stated value by less than experimental error using conventional measuring techniques of the type described herein.

[0015] All ranges disclosed herein are inclusive of the recited endpoints and are independently combinable (e.g., the range "2 to 10" includes the endpoints 2 and 10, and all intermediate values). The endpoints of the ranges and any values ​​disclosed herein are not limited to the exact ranges or values. They are sufficiently imprecise to encompass values ​​that approximate those ranges and / or values. As used herein, approximation language may be applied to modify any quantitative expression that may vary without resulting in a change in the basic function involved. Thus, values ​​modified by terms such as "about" may, in some cases, not be limited to the exact value specified. In at least some instances, approximation language may correspond to the precision of the device used to measure the value. The modifier "about" should also be considered to disclose a range defined by the absolute values ​​of the two endpoints. For example, the phrase "about 2 to about 4" also discloses a range of "2 to 4." The term "about" may refer to plus or minus 10% of the indicated numerical value. For example, "about 10%" may indicate a range of 9% to 11%, and "about 1" may mean 0.9 to 1.1. Other meanings of "about" (such as rounding) will be clear from the context; for example, "about 1" may mean 0.5 to 1.4.

[0016] A particularly preferred embodiment of the hygiene product of the present invention is a disposable absorbent article.

[0017] As used herein, the term "absorbent article" refers to a device for absorbing and containing bodily exudates, and more specifically, to a device that is placed against the skin of a user to absorb and contain various exudates discharged from the user's body. Examples of disposable absorbent articles include feminine hygiene garments such as sanitary napkins and panty liners, diapers, adult incontinence devices, diaper holders, training pants, etc.

[0018] The term "disposable" is used herein to describe hygiene articles that are not intended to be laundered or otherwise restored or reused as hygiene articles after a single use.

[0019] Disposable absorbent articles typically include a liquid pervious topsheet, a liquid impervious backsheet joined to the topsheet, and an absorbent core disposed between the topsheet and the backsheet.

[0020] The topsheet is liquid pervious, permitting liquids (e.g., menses and / or urine) to readily penetrate through its thickness. Suitable topsheets can be manufactured from a wide range of materials, including woven and nonwoven materials (e.g., fibrous nonwoven webs). Suitable topsheets may be manufactured from a wide range of materials, including woven and nonwoven materials (e.g., fibrous nonwoven webs); polymeric materials such as apertured molded thermoplastic films, apertured plastic films, and hydroformed thermoplastic films; porous foams; reticulated foams; reticulated thermoplastic films; and thermoplastic scrims. Suitable woven and nonwoven materials can be composed of natural fibers (e.g., wood or cotton fibers), synthetic fibers (e.g., polymeric fibers such as polyester, polypropylene, or polyethylene fibers), or a combination of natural and synthetic fibers. When the topsheet comprises a nonwoven web, the web may be manufactured by a number of known techniques. For example, the web may be spunbonded, carded, wetlaid, meltblown, hydroentangled, a combination thereof, or the like.

[0021] Generally, absorbent cores are capable of absorbing or retaining liquids (e.g., menses, urine, and / or other bodily exudates). Absorbent cores may be manufactured in a wide variety of sizes and shapes (e.g., rectangular, oval, hourglass, "T" shaped, dogbone, asymmetrical, etc.). In addition to the absorbent composites of the present invention, absorbent cores may include any of a wide variety of liquid-absorbent materials commonly used in absorbent articles.

[0022] The backsheet is impervious to liquids (e.g., menses and / or urine) and is preferably made from a thin plastic film, although other flexible, liquid-impervious materials may also be used. The backsheet prevents exudates absorbed and contained in the absorbent core from wetting articles that contact the absorbent article, such as bed sheets, pants, pajamas, and underwear. Thus, the backsheet may comprise a woven or nonwoven material, a polymeric film such as a thermoplastic film of polyethylene or polypropylene, or a composite material such as a film-coated nonwoven material. A suitable backsheet is a polyethylene film having a thickness of about 0.012 mm (0.5 mil) to about 0.051 mm (2.0 mil). The backsheet is preferably embossed and / or matte-finished to provide a more cloth-like appearance. Furthermore, the backsheet may allow vapors to escape from the absorbent core (i.e., the backsheet is breathable) while preventing exudates from passing through the backsheet. The size of the backsheet is determined by the size of the absorbent core and the exact absorbent article design selected.

[0023] The backsheet and topsheet are positioned adjacent the garment-facing and body-facing surfaces of the absorbent core, respectively. The absorbent core is preferably joined to the topsheet, backsheet, or both in any known manner by attachment means, such as those known in the art. However, embodiments of the present invention contemplate that portions of the entire absorbent core may be unattached to the topsheet, backsheet, or both.

[0024] For example, the backsheet and / or topsheet may be secured to the absorbent core or to each other by a uniform, continuous layer of adhesive. Hot-melt adhesives are preferred for the present invention to allow for efficient manufacturing of the disposable absorbent articles of the present invention. The adhesive may be in a patterned adhesive layer or an array of discrete lines, spirals, or dots of adhesive. An exemplary attachment means for an open-pattern network of filaments includes several lines of adhesive filaments spirally wound in a helical pattern. Alternatively, the attachment means may include thermal bonding, pressure bonding, ultrasonic bonding, dynamic mechanical bonding, or any other suitable attachment means or combinations of these attachment means known in the art.

[0025] Hot melt adhesives should have moderate to excellent adhesion to the relevant substrate. Conventional hot melt adhesives are inherently hydrophobic. They typically provide a barrier between the top layer and the core, preventing the ingress of hydrophilic substances, such as moisture, water, blood, urine, and menstruation, into the core. The hydrophilic hot melt adhesives of the present invention have a low contact angle, which facilitates the permeation of aqueous materials from the top sheet into the superabsorbent core or fluff core substrate. The hydrophilic hot melt adhesive may be used as a construction adhesive between different layers or components of an article, such as between the top sheet and the acquisition layer, between the acquisition layer and the absorbent core, or between the absorbent material and the top core wrap layer. The hot melt adhesives of the present invention are also compatible with typical skin care lotions that may be present on the top sheet or used by caregivers.

[0026] The hydrophilic hot melt adhesive composition comprises (a) from about 20 to about 90 weight percent of an ethylene copolymer selected from the group consisting of ethylene vinyl acetate, ethylene n-butyl acrylate, ethylene octene, ethylene propylene, ethylene butene propylene, and mixtures thereof; and (b) about 1 to about 25 wt. % of a nonionic ethoxylate surfactant polymer emulsifier having (i) a melting point of about 70°C to about 140°C as measured in accordance with ASTM D-127, (ii) a fully saturated linear C20 to C50 synthetic alcohol, (iii) an acid number of less than 100 mg KOH / g as measured in accordance with ASTM E222, and (iv) a molecular weight of about 400 to about 5000 daltons; Includes:

[0027] This composition exhibits a film contact angle with distilled water of less than 70 degrees both before and after aging at 60°C for 15 days.

[0028] The polymer of the hydrophilic hot melt adhesive is an ethylene copolymer. The ethylene copolymer may be ethylene vinyl acetate, ethylene n-butyl acrylate, ethylene octene, ethylene propylene, ethylene butene propylene, or a mixture thereof. The ethylene monomer content may be as much as 3% by weight of the copolymer. However, ethylene homopolymer is not a preferred polymer for hydrophilic hot melt adhesives.

[0029] The ethylene copolymer is present in the hydrophilic adhesive composition in an amount of from about 20% to about 90% by weight, preferably from about 30% to about 70% by weight.

[0030] Nonionic ethoxylate surfactant polymeric emulsifiers for hydrophilic hot melt adhesives are solid polymer additives and wetting agents. They have a high molecular weight ranging from about 400 to about 5,000 daltons, preferably from about 500 to about 3,000 daltons. The melting point of the ethoxylated surfactant ranges from 70 to about 120°C, preferably from about 80 to about 100°C, and more preferably from about 85 to about 95°C. Ethoxylated surfactants are fully saturated, long-chain, linear C20-C50 synthetic alcohols. This long polymer chain facilitates incorporation into the adhesive's polymer system and significantly improves its thermal stability. The polymeric emulsifier provides bulk strength and good wetting properties. The ethoxylated surfactant polymeric emulsifier has a hydrophile-lipophile balance (HLB) number of less than 20 and is incorporated to provide a contact angle of the resulting adhesive of 70° or less, preferably less than about 50°.

[0031] Nonionic ethoxylate surfactant polymeric emulsifiers differ from traditional nonionic ethoxylated alcohols and phenols, which are R(OC2H4) n These are low molecular weight emulsifiers with short chains and much lower melting temperatures, typically melting at ambient temperatures. These conventional low molecular weight nonionic materials, such as Croda's Atmel 688, are described in WO 97 / 48779 and U.S. Patent No. 6,380,292, but do not provide low contact angles. Therefore, conventional nonionic ethoxylated alcohols and phenols are highly mobile and cannot be stabilized in the polymer matrix. As a result, they easily migrate to the surface of the polymer matrix even at room temperature and phase separate from the matrix. Furthermore, given their mobility within the system, their ability to reduce the contact angle is unstable and short-lived. Conversely, the addition of nonionic ethoxylated surfactant polymeric emulsifiers with high molecular weights, long chains, and high melting points provides stability to the polymer matrix, resulting in consistent and durable reduction in the contact angle, as evidenced by the change in contact angle after accelerated aging tests.

[0032] The nonionic ethoxylate surfactant polymer emulsifier may be present in the hydrophilic adhesive composition in an amount of from about 1% to about 25% by weight, preferably from about 1% to about 10% by weight.

[0033] Ethoxylated surfactants must be reasonably compatible with the other ingredients used in hot melt adhesives so as not to adversely affect the adhesive's application performance. On the other hand, ethoxylated surfactants must "bloom" onto the adhesive's surface to lower the contact angle and increase the adhesive's hydrophilicity. Therefore, a delicate balance of compatibility must be maintained.

[0034] The hydrophilic adhesive may further contain optional components such as a tackifier, a plasticizer, and an antioxidant.

[0035] Tackifying resins useful in the adhesive composition can be hydrocarbon resins, synthetic polyterpenes, rosin esters, natural terpenes, etc. More specifically, depending on the particular base polymer, useful tackifying resins include: (1) natural rosins and modified rosins, such as gum rosin, wood rosin, tall rosin, distilled rosin, hydrogenated rosin, dimerized rosin, and polymerized rosin; (2) glycerol and pentaerythritol esters of natural rosins and modified rosins, such as the glycerol ester of pale wood rosin, the glycerol ester of hydrogenated rosin, the glycerol ester of polymerized rosin, the pentaerythritol ester of hydrogenated rosin, and the phenol-modified pentaerythritol ester of rosin; (3) copolymers and terpolymers of natural terpenes, such as styrene / terpene and alpha-methylstyrene / terpene; (4) polyterpene resins having a softening point of about 80° C. to 150° C. as measured by ASTM method E28-58T; Terpene resins are generally obtained by polymerizing terpene hydrocarbons, such as the bicyclic monoterpene known as pinene, in the presence of a Friedel-Crafts catalyst at moderately low temperatures (including hydrogenated polyterpene resins); (5) phenol-modified terpene resins and their hydrogenated derivatives, such as resin products obtained by condensing bicyclic terpenes with phenols in an acidic medium; (6) aliphatic petroleum hydrocarbon resins having a Ball and Ring softening point of about 70°C to 135°C (the latter resins are obtained by polymerizing monomers consisting primarily of olefins and diolefins); hydrogenated aliphatic petroleum hydrocarbon resins; (7) aromatic petroleum hydrocarbon resins and their hydrogenated derivatives; and (8) alicyclic petroleum hydrocarbon resins and their hydrogenated derivatives. Some formulations may require a mixture of two or more of the above tackifying resins.

[0036] The tackifier may comprise up to about 70% of the adhesive, but is generally used in amounts of about 20-50% by weight.

[0037] To provide the desired viscosity control without substantially reducing adhesive strength, adhesive use temperature, and adhesive hydrophilicity, a plasticizer may be present in the composition of the present invention in an amount of about 20% by weight or less, preferably about 10% by weight or less, based on the total weight of the adhesive. Suitable plasticizers may be selected from the group including conventional plasticizing oils such as mineral oil, naphthenic, paraffinic, and gas-to-liquid (GTL) oils, as well as olefin oligomers and low molecular weight polymers, and vegetable and animal oils and their derivatives. Petroleum-derived oils that may be used are relatively high-boiling materials containing only small amounts of aromatic hydrocarbons. In this regard, aromatic hydrocarbons should preferably be less than 30% by weight, more specifically less than 15% by weight, of the oil. Alternatively, the oil may be completely non-aromatic. The oligomer may be polypropylene, polybutene, hydrogenated polyisoprene, hydrogenated butadiene, etc., having an average molecular weight of about 350 to about 10,000. Suitable vegetable and animal oils include glycerol esters of conventional fatty acids and their polymerization products. While any number of different plasticizers may be useful in the present invention, the inventors have found that mineral oils such as Cadle, manufactured by Witco, are particularly useful in the present invention. Benzoflex 9-88, a dipropylene glycol dibenzoate manufactured by Velsicol, has also been found to be a suitable plasticizer. Shell's gas-to-liquid oil, Lisara X409, has also been found to be suitable as a plasticizer. As will be appreciated, plasticizers have typically been used to reduce the viscosity of the overall adhesive composition without substantially reducing the adhesive's bond strength and / or service temperature. The choice of plasticizer can be useful in designing specific end uses (e.g., wet-strength core applications).

[0038] Among the applicable stabilizers or antioxidants that may be included herein are polyfunctional phenols such as high molecular weight hindered phenols and sulfur- and phosphorus-containing phenols. Representative hindered phenols include 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxyphenyl)propionate; n-octadecyl 3,5-di-tert-butyl-4-hydroxyphenyl)propionate; 4,4'-methylenebis(2,6-di-tert-butylphenol); 4,4'-thiobis(6-tert-butyl-o-cresol); 2,6-di-tert-butylphenol; phenol; 6-(4-hydroxyphenoxy)-2,4-bis(n-octylthio)-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]. When used, stabilizers are present at a level of about 0.1 to 3% by weight.

[0039] Optional additives may be incorporated into the hot melt composition to modify certain properties of the hot melt composition, including waxes, colorants such as titanium dioxide, and fillers such as talc and clay.

[0040] A low contact angle is desirable so that water, urine, or other water-based exudates "wet" rather than "bead," thereby directing the fluid into the core and away from the topsheet. The hydrophilicity of an adhesive can be quantified by measuring the adhesive's contact angle, as described below. To be suitable for the absorbent articles of the present invention, an adhesive should have a contact angle with distilled water of less than 70°, more preferably less than 50°C.

[0041] The hydrophilic hot melt adhesive compositions of the present invention may be formulated using techniques known in the art. An exemplary procedure involves placing all polymers, surfactants, tackifiers, plasticizers, and stabilizers into a jacketed mixing kettle, preferably a jacketed high-intensity mixer equipped with a rotor, and then raising the temperature from about 120°C to a range of about 120°C to about 190°C. After the resin has melted, the temperature is reduced to 100-165°C. Mixing and heating are continued until a smooth, homogeneous mass is obtained.

[0042] Hydrophilic hot melt adhesives may be applied to a variety of substrates, including films, nonwoven fabrics, cellulose or synthetic fibers, or superabsorbent particles. Hydrophilic hot melt adhesives may be used to adhere a first component, particularly a nonwoven fabric, to a second component of an absorbent article (which may be a second nonwoven fabric, cellulose fibers, superabsorbent particles, or a combination thereof). Due to their hydrophilic nature, hydrophilic hot melt adhesives facilitate the transfer of liquids, such as urine, from one component to the next during use of the article, which may take several hours and cover several liquid insults. Hydrophilic hot melt adhesives may be used, for example, to attach a topsheet to an acquisition layer, an acquisition layer to a distribution layer, or an acquisition layer or distribution layer to an absorbent core; the topsheet may be attached directly or indirectly to the absorbent core; and a core wrap, particularly the upper inner surface of the core wrap, may also be attached to the absorbent layer with the hot melt adhesive of the present invention, facilitating the transfer of liquid from the surface of the core wrap to the absorbent layer. The absorbent layer may be a mixture of cellulose fibers and superabsorbent particles, or superabsorbent particles that are substantially free of cellulose fibers. The absorbent layer, particularly an absorbent layer comprised of superabsorbent particles that are free of cellulose fibers, may be secured within the core wrap by a hot melt adhesive according to the present invention.

[0043] The hydrophilic hot melt adhesive composition may be applied onto a variety of substrates including films, nonwovens, wood, wood pulp, cellulose, paper, cardboard, tissue, cotton, superabsorbent particles, and the like.

[0044] As noted above, the resulting adhesives may be used in a wide variety of applications, as known in the art. In particular, the adhesives are useful in assembling disposable articles using multi-line, spray, or slot coating construction techniques, in which at least one liquid-permeable substrate is adhered to at least one tissue, nonwoven, polyolefin, or other soft polymeric film substrate. Additionally, the adhesives may be useful for adhering elastic materials to polyethylene, polypropylene, or nonwoven substrates to provide them with stretch-resistant gathers. The resulting adhesives, formulated with plasticizers, may be used in the assembly or construction of various disposable applications, including, but not limited to, sanitary napkins, disposable diapers, hospital gowns, bed pads, and the like. The adhesives may also be utilized in less demanding disposable structural applications, such as edge or perimeter sealing. They may be used to laminate or coat tissue and / or screen-reinforced tissue layers such as those used in wipes, tissues, labels, paper towels, toilet paper, household wipes, personal protective equipment, masks, meat pads, animal pads, furniture, and other consumer or industrial end uses, e.g., films, insulation, etc. The adhesives may be effectively utilized in a variety of packaging and carton sealing applications. The adhesives may also be used to bond multiple sheets in a wide range of bookbinding operations, insulation, and furniture.

[0045] Furthermore, the resulting adhesive can also be used as a hydrophilic coating to reduce the contact angle of a substrate and improve the hydrophilicity of the substrate surface. This hydrophilic coating has many applications. It can be applied to any surface as an anti-fog coating to flatten water droplets and prevent beading. In another example, the coating is applied to substrates that come into contact with biological systems, particularly bodily fluids. Hydrogen in bodily fluids binds to the hydrogen-bonding sites of the hydrophilic coating. It is also useful as an anti-graffiti coating because it can prevent oil adsorption. Furthermore, the hydrophilic coating can be applied to adhesive films as polymer electrolytes in batteries and ion-conducting applications.

[0046] It will be apparent to those skilled in the art that many modifications and variations of this invention can be made without departing from its spirit and scope. The specific embodiments described herein are offered by way of example only, and the invention is to be limited only by the terms of the appended claims, along with the full scope of equivalents to which such claims are entitled. [Example]

[0047] Viscosity: Viscosity was measured at 150°C using a Brookfield viscometer, spindle #27, according to ASTM 3236-88.

[0048] Contact Angle Test: When a drop of liquid contacts a solid surface, it assumes a unique shape. The shape and the time it retains that shape are determined by three interfacial forces: the force at the solid surface, the surface tension of the liquid, and the force at the solid / liquid interface. The contact angle (θ) is a relative measurement of the combined vector forces according to the following equation:

[0049]

number

[0050] where γ L is the interfacial tension of the liquid / air boundary, γ S is the interfacial tension at the solid / air boundary, γ SL is the interfacial tension of the solid / liquid boundary, and θ is the angle of the droplet.

[0051] The goniometer is equipped with a microsyringe to dispense precise droplet sizes and a camera to capture the angle at which the droplet contacts the solid surface. The contact angle is measured as the angle between the substrate and the tangent to the droplet (at the interface). The smaller the angle, the more effective the coating is at transmitting liquid through the adhesive layer. The contact angles of fresh and aged film samples are measured as follows: For new samples, create a 50-micrometer-thick film of adhesive coating on a PET film using a hot melt coater laminator (e.g., HLCL-1000, Chemi Instruments) at 120 °C (adjust the temperature as needed), then cool to ambient laboratory conditions (21–23 °C, 40–60% RH). A contact angle test is performed on the adhesive surface 24 hours after the adhesive coating is created. Aged specimens: Place new specimens in a convection oven (e.g., Blue M Convection Oven, Stabil-Therm) and age for 15 days. Set the oven temperature to 60°C. After aging, remove the specimens from the oven and allow them to condition at ambient laboratory conditions (21-23°C, 40-60% RH) for 24 hours before measuring the contact angle of the adhesive surface.

[0052] Instron Testing: Adhesion strength was evaluated with an Instron tester. Laminates bonded with hot melt adhesive were separated at the edges and placed in the jaws of a tensile tester. The samples were then pulled at a crosshead speed of 12 inches per minute, and the average peel value in grams or pounds was recorded for each product tested. If there was an adhesive failure, the type of failure was recorded instead of the peel value.

[0053] Table 1 lists the ethoxylate surfactants used in the examples and their properties.

[0054] [Table 1]

[0055] Table 2 lists all the polymers used in the examples and their properties.

[0056] [Table 2]

[0057] Table 3 shows the contact angles of various polymers and their respective formulations.

[0058] A representative tackifier used in the examples is Escoreth 5690, an aromatic modified alicyclic hydrocarbon resin with a softening point of 90.5°C manufactured by ExxonMobil.

[0059] An exemplary plasticizer used in the examples is Calsol 5550, a naphthenic oil manufactured by Calumet.

[0060] A representative antioxidant used in the examples is Evernox 10 from Everspring.

[0061] The film contact angles measured 24 hours after sample preparation ("fresh" samples) and after aging at 60°C for 15 days ("aged" samples) are shown in Table 3. Films with distilled water contact angles of less than 70° before and after aging are considered pass (P). As noted in the notes, contact angles greater than 70° are considered fail (F).

[0062] [Table 3]

[0063] All of the pure polymers have relatively high contact angles, above 80°. For example, Ateva 2842 alone in Example 1 has a contact angle of 82° in the fresh state and a contact angle of 87° after aging at 160°C for 15 days. In the absence of a nonionic ethoxylate surfactant polymeric emulsifier, the contact angle remains high (Example 4). When this polymer is mixed with an ethoxylate surfactant (Example 2), the thin film contact angle decreases substantially from 37° for the fresh sample to 34° after aging at high temperature (Aged).

[0064] Ethylene-based polymers have good compatibility with nonionic ethoxylate surfactant polymer emulsifiers, resulting in a homogeneous system that is important for stable wetting properties of edge adhesives. As shown, both fresh and aged films maintain low contact angles (<70°) with EVA (Examples 2, 3, and 5), EnBA (Example 6), PE-octene (Example 10), PP-E (Example 7), and PP / B / E (Example 9), but fail with PP-B (Example 8). PP-B is incompatible with Unitox 450 due to their poor mutual miscibility.

[0065] Table 4 shows formulations using EVA with different VA contents along with Unitox 450 and Escores 5690. As shown, different types of EVA can adjust the viscosity range, but do not substantially affect the contact angles of the systems, which are all below 70° in both the fresh and aged states.

[0066] [Table 4]

[0067] Table 5 shows the effect of ethoxylate surfactant polymer emulsifiers on contact angle. Unitox 420, 450 and 480 all have very low contact angles for the hot melt adhesives.

[0068] [Table 5]

[0069] Table 6 shows formulations containing plasticizers (Examples 17-19). The addition of plasticizers improves wetting. Ideally, the total plasticizer content is less than 20% by weight of the adhesive.

[0070] [Table 6]

[0071] Table 7 shows the bond strength of laminates made by slot or spiral coating adhesive onto a generic topsheet nonwoven and then adhering to a core nonwoven. The coat weight was 8 grams per square meter and the line speed was 300 meters per minute. Bond strength can potentially be optimized by adjusting the polymer and surfactant content.

[0072] [Table 7]

[0073] Examples 20, 21, and 22 in Table 8 demonstrate the effectiveness of a conventional low molecular weight nonionic surfactant blend (Croda International's Atmel 688) described in WO 97 / 48779 and U.S. Pat. No. 6,380,292. The film contact angles of Examples 20, 21, and 22 are all greater than 70° in both the fresh and aged states. In contrast, Examples 9 and 13, which were made with Unitox 450, an ethoxylate surfactant polymer emulsifier, have fresh contact angles less than 70°. [Table 8]

Claims

1. (a) from about 20 to about 90 weight percent of an ethylene copolymer selected from the group consisting of ethylene vinyl acetate, ethylene n-butyl acrylate, ethylene octene, ethylene propylene, ethylene butene propylene, and mixtures thereof; and (b) about 1 to about 25 wt. % of a nonionic ethoxylate surfactant polymeric emulsifier having (i) a melting point of about 70° C. to about 140° C. as measured in accordance with ASTM D-127, (ii) a fully saturated linear C20-C50 synthetic alcohol, (iii) an acid number of less than 100 mg KOH / g as measured in accordance with ASTM E222, and (iv) a molecular weight of about 400 to about 5000 daltons; A hydrophilic hot melt adhesive composition comprising: A hydrophilic hot melt adhesive composition having a film contact angle with distilled water of less than 70 degrees both before and after aging at 60°C for 15 days.

2. (a) about 30 to about 70 weight percent ethylene copolymer; and (b) up to about 20% by weight of an ethoxylated surfactant; Including, 10. The hydrophilic hot melt adhesive composition of claim 1, which exhibits a film contact angle with distilled water of less than 50 degrees.

3. 10. The hydrophilic hot melt adhesive composition of claim 1, wherein the ethylene copolymer is ethylene vinyl acetate.

4. (c) about 20 to about 70 wt. % of a tackifier; (d) up to about 20% by weight of a plasticizer; and (e) up to about 3% by weight of an antioxidant; 10. The hydrophilic hot melt adhesive composition of claim 1, further comprising:

5. 5. The hydrophilic hot melt adhesive composition of claim 4, wherein the tackifier is a hydrocarbon resin, a rosin ester resin, or a terpene resin.

6. 6. The hydrophilic hot melt adhesive composition of claim 5, wherein the hydrocarbon resin is selected from the group consisting of C5 aliphatic resins, C9 aromatic resins, dicyclopentadiene resins, C5 / C9 aliphatic / aromatic resins, and mixtures thereof.

7. 6. The hydrophilic hot melt adhesive composition according to claim 5, wherein the rosin ester resin is a rosin acid, a rosin ester, a hydrogenated rosin resin, a dimerized rosin resin, a modified rosin resin, or a mixture thereof.

8. 5. The hydrophilic hot melt adhesive composition of claim 4, wherein the plasticizer is selected from the group consisting of naphthenic oils, paraffinic oils, vegetable oils, animal oils, olefin oligomers, and derivatives thereof.

9. (a) mixing the mixture at 120°C to about 190°C to form a molten mixture comprising: (i) about 20 to about 90 wt% ethylene copolymer; (ii) 1 to about 25 wt% nonionic ethoxylate surfactant polymeric emulsifier; (iii) about 20 to about 70 wt% tackifier; (iv) up to about 20 wt% plasticizer; and (v) up to about 3 wt% antioxidant; (b) solidifying the hydrophilic hot melt adhesive composition by pelletizing or forming blocks of the molten mixture; A method for producing a hydrophilic hot melt adhesive composition, comprising:

10. (a) the ethylene copolymer is selected from the group consisting of ethylene vinyl acetate, ethylene n-butyl acrylate, ethylene octene, ethylene propylene, ethylene butene propylene, and mixtures thereof; 10. The method of claim 9, wherein (b) the nonionic ethoxylate surfactant polymer emulsifier has (i) a melting point of about 70°C to about 140°C as measured in accordance with ASTM D-127, (ii) a fully saturated linear C20-C50 synthetic alcohol, (iii) an acid number of less than 100 mg KOH / g as measured in accordance with ASTM E222, and (iv) a molecular weight of about 400 to about 5000 Daltons.

11. 10. An article comprising the hydrophilic hot melt adhesive composition of claim 1 and a substrate comprising film, nonwoven, wood, wood pulp, cellulose, paper, cardboard, tissue, or cotton.

12. 12. The article of claim 11, which is a mask, tissue, book, furniture, film, meat pad, animal pad, personal protective equipment, insulation, packaging, or household wipe.

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