MXPA98010530A - Adhesive hydrofly fusion in calie - Google Patents

Abstract

A hot melt hydrophilic adhesive compositions, characterized in that it comprises the following components: 10-50% of n polymer, 40-80% of a viscous resin, 0-40% of a plasticizer, 0.1-2% of an antioxidant; and 0.1-30% of a surfactant, which has an HLB of less than 15, the surfactant is selected from the group consisting of a fatty acid ester, a co-polymer of ethylene oxide / propylene oxide, 2,4,7,9-tetramethyl- 5-decin-4,7-diol, an alkylphenol ethocylate, an alcohol ethoxylate and an alkylaminic ethoxylate, the total constituting 100% of the components by weight, and wherein the adhesive has a contact angle of 75 ° or men

Description

HOT FUSING HYDROPHILIC ADHESIVE BACKGROUND OF THE INVENTION The present invention relates to hot melt adhesives, and more specifically to hot melt adhesives having improved hydrophilic properties and which find utility in the manufacture of disposable non-woven articles. Nonwoven consists of a mesh of interlocking fibers, and is employed in the construction of disposable products. Specific applications of non-woven materials include disposable diapers, sanitary napkins, surgical curtains, hospital cushions and adult incontinence products In such applications it is generally necessary to adhere nonwoven material, paper or absorbent fluff or the like to another substrate. This second substrate may be another non-woven material, or a material such as a polyolefin, eg a polyethylene or polypropylene layer.A hot melt adhesive has typically been used to bond such materials because there is no need to an evaporation step during manufacturing, as would be the case with water-based adhesives or solvents The appropriate hot-melt adhesives must have adequate bond strength to bond the relevant substrates, and must also possess good flexibility, it must not be stained or allowed to leak, it must have an appropriate viscosity and an adequate opening time for to be used in commercial equipment, acceptable stability under storage conditions, and acceptable thermal stability under normal application conditions. Many different polymers have been used in hot melt adhesives used in the construction of disposable nonwoven products. In this respect, typical hot melt adhesives have employed polymers including S-I-S (styrene-isoprene-styrene); SBS (styrene-butadiene-styrene); SEBS (styrene-ethylene butylene-styrene); EVA (ethylene acetate vinyl); and APAO (amorphous poly alpha olefin). While these polymers, when properly mixed, provide acceptable adhesion between most substrates employed in the typical construction of non-woven materials, such as diapers, and also provide acceptable adhesion under dry conditions, they have several deficiencies that reduce their usefulness. . One of the most notable deficiencies in hot melt adhesives of the prior art concerns the manner in which the adhesive, which is typically very hydrophobic, reacts when exposed to liquids, such as water, urine, or the like. Normally, one would expect the hydrophobic character of hot melt adhesives to be an advantage because such adhesives provide good dry bonds and normally sustain an acceptable bond strength when wet. However, manufacturers of disposable articles of non-woven materials such as diapers have attempted to manufacture products that are much thinner in profile and overall thickness and that incorporate super-absorbent materials in place of the lint that is normally present in the core. Therefore, it is extremely important in such non-woven constructions to ensure that water, urine or other water flows or solutions are directed immediately towards the absorbent core and that any material that can prevent such action is eliminated or at least minimized. As a result, one can easily understand why the hydrophobicity of typical hot melt adhesives is undesirable because it is a characteristic that inherently prevents the transfer of fluids to the core of such articles. Therefore, it has been recognized for a long time that it would be desirable to have a hot melt adhesive which is useful for bonding substrates which are typically employed in the construction of non-woven articles, such as polyethylene, polypropylene, non-woven materials, absorbent paper, or lint, and which also maintains an acceptable wet adhesion force when exposed for prolonged periods to water, urine or similar substances. At the same time, such adhesives should be more hydrophilic so as not to impede the transfer of fluids to the absorbent core of such articles.

SUMMARY OF THE INVENTION Therefore, it is an object of the present invention to provide an improved hot melt adhesive which is useful in the manufacture of disposable articles of nonwoven materials. A further object of the present invention is to provide a hot melt adhesive which can be used as a construction adhesive, and which would also be sufficiently hydrophilic to assist in the transfer of fluid to the absorbent core of the nonwoven disposable article. In order to realize the above mentioned objects, the present invention provides a hot melt adhesive having the following composition: (by weight): about 10-50% of a polymer; about 40-80% of a viscous resin; about 0-40% of a plasticizer; about 0.1-2% of an antioxidant; and about 0.1-30% of a surfactant, constituting 100% of the components by weight. The surfactant has a hydrophilic-lipophilic balance (HLB) of less than 15, and is incorporated into the composition in an amount such that the resulting adhesive has a contact angle of 75 ° or less, and preferably less than about 40 °. A low contact angle is desirable for water, urine or other liquid flows to spread out instead of forming globules, causing fluids to move away from the adhesive. The surfactant should be reasonably compatible with the other raw materials used in the hot melt adhesive so as not to adversely affect the function of the construction or the thermal stability of the adhesive. On the other hand, the surfactant must "bloom" on the surface of the adhesive to lower the contact angle and make the adhesive more hydrophilic. Therefore, it is necessary to maintain a delicate balance of compatibility. The surfactant should not contain any water or other solvents, making it workable in hot melt mixers, and should not be toxic to the user. The adhesive of the present invention has the advantage over hydrophilic adhesives of the prior art that it is not soluble in water. A water-soluble adhesive has little wet strength, and thus loses its usefulness after initial contact with liquids. Also, once dissolved, a water soluble adhesive can form a dilute solution that can make contact with the user's skin, causing undesirable side effects. The adhesive of the present invention will significantly increase the absorption of fluid in the core of non-woven articles, such as diapers, and thus improve the efficiency of the core. It will also decrease the opportunity for fluid filtration of such articles and will help improve absorption in articles filled with thinner superabsorbents by directing the fluid more rapidly to the core. This is done by applying the hot melt hydrophilic adhesive of the present invention to a substrate of a disposable article of absorbent nonwoven material in a configuration such that that fluid is directed, or conveyed to a desired absorbent location on one of the substrates. For example, if the disposable article is a diaper, the adhesive could be applied in a rectangular pattern in the mid-crotch region of a non-woven substrate. This would result in the urine being directed towards the absorbent core in the crotch region, rather than towards the edge of the diaper in the area of the leg. The adhesives of the present invention are especially suitable for use in absorbent products such as diapers, training underpants, incontinence products, feminine sanitary products, and medical products. With all these products there is a need to consolidate the layers or substrates of the article, and hot melt is frequently used as discussed. Commonly, the core area of the article is formed by spraying a layer of adhesive on a non-woven substrate and adhering it to an absorbent core. In many cases, a layer of woven material is placed between the non-woven layer and the core, sometimes totally enveloping the core and in other cases simply covering the top layer. Another layer of adhesive can be used to bond the absorbent fluff from the core to the fabric and, in addition, another layer of adhesive can bind the fabric or fluff to the backing layer (which frequently consists of polyethylene or a laminate). Then there is at least one and frequently a number of hot melt spray layers applied to join the core in place. If there is no good contact between the nonwoven top layer and the core, it can result in distortion of the non-woven material, dramatically reducing absorption. In addition, the adhesive holds the core in place and can help prevent cracking of the core. Kernel fissuring can impede the proper flow of liquids within the core itself and cause leakage. To improve the resistance to loosening and cracking of the core, a different kind of hot melt has been unpacked having a high wet strength that represents an improvement over conventional adhesives, because a good bond to both the fabric and the core is maintained. when being wet. Unfortunately, the process of placing hot melt sprayed layers in the core area can, in fact, decrease the fluid uptake, because the adhesive itself is quite hydrophobic. Although the new class of high strength wet adhesive mentioned above is resistant to peeling under wet conditions, they are also hydrophobic. The adhesives of the present invention are very hydrophilic and eliminate this point, improving, even, the acquisition of core fluid, compared to conditions without the use of adhesives (see Examples 2-3). They can also be formulated to be hydrophilic and have improved peel strength under wet conditions, such as the new class of adhesives mentioned above (see Example 4). These adhesives show an obvious utility in the core area which consolidates the layers in a particular absorbent article without inhibiting the absorbency of the structure. The absorbent cores can be found in articles such as diapers, incontinence products, feminine health products, medical devices and the like. Frequently, superabsorbent materials (SAP) are used in absorbent articles to improve the degree and retention power of the absorbent cellulose material in the core. These SAPS are sometimes held in place by hot melt. As can be easily appreciated, these hot melts may retard the absorbency rate of the SAP due to its hydrophobic nature. The hydrophilic adhesives of this invention could also be used in this application.

The top layer of absorbent articles needs to allow the easy passage of fluids. This layer is often a non-woven material or some type of polymer-based material such as polyethylene or polypropylene. While these perforated materials and films serve well as cover layers, they will be recognized to be hydrophobic in nature. A drop of liquid placed on these materials will not easily pass through the material even if it has many open pores. To solve this problem, the manufacturers of these materials have had to treat them to make them more hydrophilic (often by a surface treatment). In other cases, manufacturers of absorbent articles have sprayed surfactants or other materials on the products during processing. Spraying these materials causes occupational problems in the manufacturing line and the atomized materials can fill the air and cause irritation in the operators. In addition, these materials have no other use apart from the preparation of the hydrophilic cover layer. In addition, the surfactants can migrate to other parts of the article and cause the release of the hot melt. It will be noted that the adhesives of this invention could be used both to join the article and to allow use of standard hydrophobic cover layers. The hydrophilic character could be taken to the article to treat certain areas selectively, allowing greater freedom in the design of absorbent articles. There are other applications where it is desirable to make a breathable material, that is, to allow moisture (such as sweat) to flow through a laminate. This can be useful both in articles such as diapers and in medical articles. This invention could also be used to improve the flow over typical hydrophobic hot fusions in such applications.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a bar diagram comparing the percentage of water that passed through a laminate of nonwoven material bonded to a fabric and that was absorbed by a towel where the laminate was adhered with an adhesive hydrophobic hot melt typical of the prior art having a contact angle of 85 ° in one test, against a hot melt hydrophilic adhesive formulated according to the present invention in a second test; Figure 2 is a bar diagram comparing the average peel strength and contact angle for various hot melt adhesives; Figure 3 is a schematic, enlarged, and perspective view of a disposable diaper incorporating a hydrophilic hot melt adhesive of the current invention; Fig. 4 is a schematic cross-sectional view of the diaper of Fig. 3; Fig. 5 is a schematic cross-sectional view of a feminine care sanitary napkin incorporating a hot melt hydrophilic adhesive of the current invention; and Figure 6 is a schematic perspective view, enlarged, of a disposable diaper similar to that of Fig. 1, incorporating a hydrophilic hot melt adhesive of the present invention applied to the cover layer of nonwoven material in such a condition. way that provides the transport of fluids to the center of the diaper DETAILED DESCRIPTION OF THE PREFERRED MODALD3AD A hot melt hydrophilic adhesive composition having ingredients in the following ranges provides advantages over current technology when evaluated for wettability. More particularly, the adhesive composition of the present invention has the following ingredients by weight; about 10-50% of a polymer; about 40-80% of a viscous resin; about 0-40% of a plasticizer; about 0.1-2% of an antioxidant; and about 0.1-30% of some surfactants, adding 100% by weight of the components. Any of a variety of available thermoplastic materials can be used as the polymer in the compositions of the invention in an amount of from about 10% to about 50% by weight, preferably from about 15% to about 25%. Examples of such materials include polymers based on ethylene, including ethylene / vinyl acetate, ethylene acrylate, ethylene methacrylate, ethylene methyl acrylate, ethylene methyl methacrylate, polybutylene, high and low density polyethylene, polyethylene and polyethylene blends. chemically modified, copolymers of ethylene and monomers 1-6 mono- or di-unsaturated, polyamides, polybutadiene rubber, poly esters such as polyethylene terephthalate, polybutylene terephthalate; thermoplastic polycarbonates, atactic polyalphaolefins, including atactic polypropylene, and others; thermoplastic polyacrylamides, polyacrylonitrile, acrylonitrile copolymers and other monomers, such as butadiene styrene; polymethyl pentene, polyphenylene sulfide, aromatic polyurethanes; styrene acrylonitrile, acrylonitrile-butadiene styrene, styrene-butadiene rubbers, polyethylene terephthalate, acrylonitrile-butadiene styrene elastomers, polyphenylene sulfide, block polymers AB, ABA, A- (BA) nB, (AB) nY where A comprises an aromatic polyvinyl block, block B comprises an elastic medium block which can be partially hydrogenated, and mixtures thereof. Preferred polymers for use in the adhesives of this invention comprise EVA, APP, polybutylene, ABA linear block copolymers, linear multiple block copolymers A- (BA) nB, and radioblock or teleblock copolymers of the formula (AB) nY wherein A comprises a polystyrene block, B comprises a substantially elastic polybutadiene or polyisoprene block, Y comprises a polyvalent compound, and n is an integer of at least 3. The middle blocks can be post-treated to improve their thermal stability by Hydrogenation or other subsequent treatment that eliminates residual unsaturation. The size and amount of blocks A or terminal blocks in the structure of block copolymers A-B-A can reach up to 15-51 percent by weight of the polymer. While the total styrene content in the polymers can reach up to 51% by weight of the polymer, and since the polymers can have more than two A blocks for optimum performance, the total of block A must be less than or equal to about 45% by weight of the polymer, and, more preferably, less than or equal to 35% by weight of the polymer. In an S-B-S (styrene-butadiene-styrene) copolymer, the preferred molecular weight is about 50,000 to 120,000, and the preferred styrene content is about 20 to 45% by weight. In an S-I-S (styrene-isoprene-styrene) copolymer, the preferred molecular weight is about 100,000 to 200,000 and the preferred styrene content is about 14-35% by weight. Hydrogenation of the butadiene-media blocks produces elastic half-blocks that are typically considered ethylene-butylene-middle blocks. Such block copolymers are available from Shell Chemical Company, Enichem, Fina and Dexco; Copolymers of multiple block or tapered block (of type A- (B-A) n -B) are available from Firestone. The viscous resins which are used in the hot-melt construction adhesives of the present invention are those which extend the adhesive properties and improve the specific adhesion of the polymer. In the present invention, the term "viscous resin" includes: (a) natural and modified resin such as, for example, gumorresin, wood resin, tall oil resin, distilled resin, hydrogenated resin, dimerized resin and polymerized resin; (b) glycerol and pentaerythritol esters of natural and modified resins, such as, for example, pale wood resin glycerol ester, hydrogenated resin glycerol ester, polymerized resin glycerol ester, wood resin pentaerythritol ester pale, the pentaerythritol ester of hydrogenated resin, the pentaerythritol ester of high oil resin and the pentaerythritol ester of resin modified by phenol; (c) polyterpene resins having a softening point, determined by the method ASTM E28-58T, of from about 60 ° C to 140 ° C, resulting in the last polyterpene resins generally from the polymerization of terpene hydrocarbons, such as the monoterpene known as "pinene", in the presence of Friedel-Crafts catalysts at moderately low temperatures; Also included are the hydrogenated polyterpene resins; (d) copolymers and terpolymers of natural terpenes, eg, styrene-terpene, a-methyl styrene / terpene and vinyl toluene / terpene; . (e) phenol-modified terpene resins such as, for example, the resin product resulting from the condensation, in an acidic medium, of a terpene and a phenol; (f) Aliphatic petroleum hydrocarbon resins having Ring and Ball softening points of from about 60 ° to 140 ° C, resulting in the subsequent resins of the polymerization of monomers consisting primarily of olefins and diolefins; also included are hydrogenated hydrocarbon petroleum aliphatic resins; examples of such commercially available resins and based on a Cs-olefin fraction of this type are the viscous resins' Wingtack 95"and 'Wingtack 115' sold by Goodyear Tire and Rubber Company; (g) petroleum aromatic hydrocarbons and the hydrogenated derivatives thereof; (h) the aliphatic / aromatic petroleum derived from hydrocarbons and the hydrogenated derivatives thereof. Mixtures of two or more of the viscous resins described above may be required for some formulations. Although a range of 40-80% by weight of viscose resin can be used, the preferred range is 50% to 65%. An example of a commercially available viscose resin that is useful for the current invention includes the resin that is identified by the trade designation Unitac R100L. This resin is a high oil resin ester based on pentacritritol, available from Union Camp. A plasticizer may be present in the composition of the present invention in amounts of from about 0% to about 40% by weight, preferably from about 10% to about 30%, in order to provide the desired viscosity control without decrease the adhesive strength or the service temperature of the adhesive. A suitable plasticizer can be selected from the group which includes not only normal plasticizing oils, such as mineral oil, but also olefin oligomers and low molecular weight polymers, as well as vegetable and animal oils and derivatives thereof. The petroleum-derived oils that can be employed are relatively high boiling temperature materials that contain only a minimal proportion of aromatic hydrocarbons. In this regard, the aromatic hydrocarbons should preferably comprise less than 30%, and more particularly less than 15% by weight, of the oil. Alternatively, the oil may be totally non-aromatic. The oligomers may be polypropylenes, polybutenes, hydrogenated polyisoprene, hydrogenated butadiene, or the like having average molecular weights of between about 350 and about 10,000. Suitable vegetable and animal oils include glycerol esters of the usual fatty acids and the products of the polymerization thereof. The plasticizer which finds utility in the present invention can be any of a variety of plasticizers but the inventors have discovered that mineral oil, such as Kaydol manufactured by Witco, is particularly useful in the present invention. Benzoflex 9-88, a dipropylene glycol dibenzoate manufactured by Velsicol, is also considered a suitable plasticizer. As will be appreciated, plasticizers have typically been employed to lower the viscosity of the total adhesive composition without too lowering the adhesive strength and / or the service temperature of the adhesive. The choice of a plasticizer can be useful in the formulation of specific end uses (such as applications for high wet strength cores).

The waxes in the composition of the present invention are used to reduce the melt viscosity in the construction of hot melt adhesives without appreciably diminishing their adhesive bonding characteristics. These waxes are also used to reduce the opening time of the composition without affecting the temperature function. Among the useful waxes are: (1) .- polyethylene of low molecular weight, that is, 1000-6000, having a hardness value, according to the method ASTM D-1321, of from about 0.1 to 120, and points of ASTM softening from about 150 ° to 250 ° F (60 to 120 ° C):. . . . . . (2) - petroleum waxes, such as paraffin, having a melting point of from about 130 ° to 170 ° F (54.4 to 80 ° C) and microcrystalline wax having a melting point of from about 135 ° to 200 ° F (57 to 93.3 C), the subsequent melting points being determined by the method ASTM D127-60; (3) - atactic polypropylene having a Ring and Ball softening point of from about 120 ° to 160 ° C; (4) - synthetic waxes made by the polymerization of carbon monoxide and hydrogen such as Fischer-Tropsch wax; and (5) - polyolefin waxes. According to the present invention, the term "polyolefin wax" refers to those polymeric or long chain entities composed of olefinic monomer units. These materials are commercially available from Eastman Chemical Co. under the trade name "Epolene." Preferred materials for use in the compositions of the current invention have a Ring and Ball softening point of 200 ° F to 350 ° F. (93.3 to 180 ° C). It should be understood that each of these wax solvents is a solid at room temperature. Other useful substances include hydrogenated fats and oils of animals, fish and vegetables such as hydrogenated tallow, lard, soybean oil, cottonseed oil, castor oil, fish oil, cod liver oil, etc., and which are solid at room temperature by virtue of being hydrogenated, have also been found useful with respect to their function as equivalents of wax solvents. These hydrogenated materials are often called, in the adhesive industry, "animal or vegetable waxes." In addition, hydrocarbon oils, especially naphthenic or paraffinic process oils, can also be used as wax solvents. The current invention includes a stabilizer or antioxidant in an amount of from about 0.1% to about 2% by weight, but preferably from about 0.1% to 1%. The stabilizers that are useful in the hot melt adhesive compositions of the current invention are incorporated to help protect the above-noted polymers, and thus the total adhesive system, from the effects of thermal and oxidative degradation that normally occurs during the manufacture and application of the adhesive, as well as the ordinary exposure of the final product to the environment. Such degradation is commonly manifested by a deterioration in the appearance, physical characteristics and performance characteristics of the adhesive. A particularly preferred antioxidant is Irganox 1010, a methane of tetrakis (methylene (3,5-di-tert-butyl-4-hydroxyhydrocinnamate)) manufactured by Ciba-Geigy: Among the applicable stabilizers are hindered phenols by high molecular weight and polyfunctional phenols , such as phenols containing sulfur and phosphorus. Hindered phenols are well known to those skilled in the art and can be characterized as phenolic compounds that also contain sterically bulky radicals close to the same phenolic hydroxyl group. In particular, tertiary butyl groups are generally substituted on the benzene ring in at least one of the ortho positions relative to the phenolic hydroxyl group. The presence of these sterically bulked radicals substituted in the vicinity of the hydroxyl group serves to retard its elongation frequency and accordingly, its reactivity; this steric hindrance thus provides the phenolic compound with its stabilizing properties. Representative hindered phenols include: 1-, 3,5-trimethyl-2,4,6-tri (3-5-di-tert-butyl-4-hydroxy-benzy-lo) benzene; pentaerythritol tetrakis-3 (3,5-di-tert-butyl-4-hydroxyphenyl) propionate; n-octadecyl-3 (3,5-ditert-butyl-4-hydroxyphenyl) propionate; 4,4'-methylene bis (4-methyl-6-tert butylphenol); 4,4'-thiobis (6-tert-butyl-o-cresol); 2,6-di-tert-butylphenol; 6- (4-hydroxyphenoxy) -2,4-bis (n-ocitltio) -l, 3,5-triazine; 2,4,6-tri (4-hydroxy-3,5-di-tert-butyl-phenoxy) -l, 3,5-triazine; di-n-octadecy 1-3, 5-di-tert-butyl-4-hydroxybenzylphosphonate; 2- (n-octylthio) ethyl-3,5-di-tert-butyl-4-hydroxybenzoate; and sorbitol propionate hexa- (3,3,5-di-tert-butyl-4-hydroxy-phenyl). Especially preferred as a stabilizer is pentaerythritol tetrakis-3 (3,5-di-tert-butyl-4-hydroxyphenol) propionate. The operation of these stabilizers can be improved by using, in conjunction with it; (1) synergists, such as, for example, thiodipropionate esters and phosphites; and (2) chelating agents and metal deactivators, such as, for example, ethylenediaminetetraacetic acid, salts thereof, and disalicylalpropylenediimine. The hot melt adhesive composition of the instant invention can be formulated using any of the techniques known in the art. A representative example of the prior art process involves the placement of all the substances in an isolated mixer vessel, and preferably in a Baker-Perkins or Day industrial type isolated mixer equipped with rotors, then increasing the temperature of this mixture to a range from around 250 ° F to 350 ° F (120 to 180 ° C). It should be understood that the precise temperature to be used in this step would depend on the melting point of the particular ingredients. The resulting adhesive composition is stirred until the polymers are completely dissolved. A vacuum is then applied to remove trapped air. Optional additives can be incorporated into hot melt adhesive constructions in order to modify particular physical properties. These additives may include colorants, such as titanium dioxide and fillers such as talc and clay. The surfactant may be present in the composition of the present invention in amounts of from about 0.1% to about 30%, by weight, and preferably from about 1% to about 10% in order to make the adhesive more hydrophilic. The surfactant has a hydrophilic-lipophilic balance number (HLB) of less than 15, and is incorporated into the composition in an amount such that the resulting adhesive has a contact angle of 75 ° or less, and preferably less than about 40 °. °. A low contact angle is desirable for water, urine or other liquid flow to extend instead of forming globules, causing fluids to move away from the adhesive. The HLB of a surfactant is an expression of its hydrophilic-lipophilic balance, that is, the balance between size and strength of groups of hydrophilic (attracts water, or polar) and lipophilic (attracts oil, or non-polar) surfactants . All surfactants consist of a molecule that combines both groups: hydrophilic and lipophilic. The surfactant should be reasonably compatible with the other raw materials used in the hot melt adhesive so that it does not adversely affect the construction of the adhesive. On the other hand, the surfactant must "bloom" to the surface of the adhesive to lower the contact angle and make the adhesive more hydrophilic. Therefore, we must maintain a delicate balance of compatibility. The surfactant must not contain water or any other solvent, making it workable in hot melt mixers and non-toxic for the end user. The surfactant must also be sufficiently stable and non-volatile to allow processing in hot melt equipment and applications without affecting the adhesive. Gomo is used in the present, the term "surfactant" or "active surface agent" refers to any compound that reduces the surface tension when dissolved in water or water solutions, or that reduces the interfacial tension between two liquids, or between a liquid and a solid . Examples of suitable surfactants include, but are not limited to, the following: (1) - fatty acid esters such as glycerol esters, PEG esters and sorbitan, including ethylene glycol distearate, ethylene glycol monostearate, mono- and / or di- glycerol oleate, PEG dioleate, PEG monolaurate, sorbitan monolaurate, sorbitan trioleate, etc. These surfactants are available from ICI, Rhone Poulenc, and other sources. (2) - Non-ionic ethoxylates, such as alkylphenol ethoxylates, alcohol ethoxylates, alkylamino ethoxylates, etc., including octylphenol ethoxylate, nonylphenol ethoxylate, alkylamine ethoxylates, etc. These surfactants are available from Rhone-Poulenc, Union Carbide and other sources. (3) - Non-ionic surfactants such as 2,4,7,9-tetrametu-5-decin-4,7-diol available from Air Products. (4) - Ethylene oxide / propylene oxide copolymers available from Union Carbide, BASF, etc. It should be noted that these and other surfactants can be combined, if necessary, to produce the best mix of hydrophilic performance characteristics. It has been found that Atmer 688, a mixture of non-ionic surfactant, and Alkamuls GMS-C, a glycerol monostearate, both manufactured by ICI Americas Inc., are the preferred surfactants for use in the present adhesive composition. Contact angle measurements of liquid droplets on substrate surfaces are used to characterize the wettability of the surface. The lower the contact angle, the more hydrophilic the adhesive becomes. The contact angle is defined as the angle between the support surface of the substrate and the line tangent to the point of contact of the liquid droplet with the substrate. The value of the contact angle of the liquid droplet will depend on the surface energy of the substrate and the surface tension of the liquid. If there is complete wetting between the liquid and the surface of the substrate, the droplet will spread over the substrate and the contact angle will approach zero, and if the wetting is partial, the resulting contact angle will lie in the range of 0 to 180 degrees. Both the contact angles reported in Fig. 1 and 2, like those in Table 1, were determined using a CAM-FILM angle meter available from Tantee, Inc. using the half-angle measurement method described in U.S. Patent No. 5,268,733. Referring now to Fig. 1, a bar diagram comparing the percentage of water absorbed through a laminate in a towel that was covered by the laminate is shown. The laminate was a non-woven substrate bonded to a fabric layer. The joint was formed with a hydrophobic hot melt adhesive of the prior art having a contact angle of 85 degrees, or a hydrophilic hot melt adhesive (XO) having a contact angle of 50 degrees formulated according to the invention current. Each adhesive was tested at three different levels of aggregate, namely 1 mg / in2 (1 mg / 6.4516 cm2), 3 mg / in2 (3 mg / 6.4516 cm2) and 10 mg in2 (1 mg / 6.4516 cm2). The test was performed by placing a towel on a flat support, covering the towel with the laminate, and then lifting one of the edges of the support so that the towel and laminate were raised at an angle of 30 degrees. 3 grams of water were poured into the laminate. The weight of the wet towel was measured and compared to its original dry weight to determine the percentage of water absorbed. As illustrated, the hydrophilic adhesive of the current invention is clearly superior to the hydrophobic adhesive of the prior art in wettability. The percentage of water absorbed by the towel ranged from 65% -71% using the current hydrophilic adhesive (XO), when the absorption was only 25% -50% using the hydrophobic adhesive of the prior art. Therefore, the hydrophilic adhesive (XO) allowed significantly greater fluid absorption by the towel. Fig. 2 illustrates a bap diagram comparing the average peel strength and contact angles for various hot melt adhesives. Fig. 2 demonstrates that hydrophilic adhesives made in accordance with the present invention, of which all have a contact angle less than 75 °, retain sufficient peel strength to be used as construction adhesives in non-woven articles, such as diapers In these tests, the laminates were formed using polyethylene (PE) and nonwoven substrates (NW) bonded with the designated adhesive having an aggregate of 3 mg / 6.4516 cm2. The contact angle was determined for each adhesive and hatched as shown by the solid line. The samples were tested for resistance to Instron detachment at a crosshead speed of 12 inches / minute (30 cm./minute), and is the average of five tests. Also, it should be noted that the term "high" in Fig. 2 refers to the amount of surfactant added to the adhesive, which was 15%. The term "medium" refers to the addition of 10% surfactant to the adhesive formula while "low" refers to the use of 5% surfactant in the formula. Referring now to Figs. 3 and 4, there is illustrated in Fig. 3 an enlarged view of various substrates comprising a diaper 10 in its extended and unfolded state, showing portions of the structure schematically to more clearly demonstrate the construction of the diaper 10. Fig. 4 illustrates schematically, in cross section, the multiple layers or substrates of the diaper 10. As used herein, the term "diaper" refers to an absorbent article typically worn by infants, young children and incontinent persons. As is readily understood, the absorbent article is placed around the lower torso and held in place on the user's hips. However, it should be understood that the present invention is also applicable to other absorbent articles, such as training underpants, incontinence products such as underpants and underwear, feminine care products, such as sanitary napkins, intimate pads, and medical products, such as surgical curtains, and the like. Here, the term "absorbent article" refers to the device or product that absorbs and retains body fluids and exudates such as urine. More specifically, this term refers to such devices or articles that make contact with or are in proximity to the body of the user to absorb and retain various fluids and body exudates. The term "disposable" is used herein to describe absorbent articles that are intended to be discarded after a single use. Such articles are not intended to be washed or reused as an absorbent article. Preferred embodiments of absorbent articles of the Present invention are the diaper 10 shown schematically shown in Fig. 3 and the feminine care sanitary towel 11 schematically illustrated in Fig. 5. As shown in Figs. 3 and 4, the diaper 10 comprises multiple layers of laminate material or substrates bonded to form the absorbent article. More specifically, the diaper 10 includes a top layer 12 of fluid permeable nonwoven material and a fluid impenetrable backing layer 13 (typically made of polyethylene) bonded to the top layer 12. An absorbent core 14 is located between the top layer 12 and the backing layer 13. The absorbent core 14 may comprise lint 8 and a super absorbent material (SAP) 15, centrally disposed. The diaper 10 may also include a top fabric layer 16 disposed between the top layer 12 and the core 14, as well as a bottom fabric layer 17 disposed between the backing layer 13 and the core 14. As best shown in FIG. Fig. 4, each substrate is joined to an adjacent substrate by a layer of adhesive formulated according to the current invention. For example, the upper layer of non-woven material 12 is adhered to the upper fabric layer 16 by means of a layer of adhesive 18 applied to the lower part of the upper layer 12 .. In turn, the upper fabric layer 16 is adhered to the core 14 by a layer of adhesive 19. The core 14 adheres to the lower fabric layer 17 by a layer of adhesive and the lower fabric layer 17 in turn is adhered to the backing layer 13 by a layer of adhesive 21 applied to the upper surface of the backing layer 13. The adhesive can be spirally sprayed or applied to the backing layer 13. flange, depending on the location and type of union desired. As best shown in Fig. 3, the diaper 10 includes a pair of opposed waist panels 22, 23 interconnecting a crotch portion 24. crotch portion 24 includes, in turn, a pair of openings for legs 25, 26 with elastic seams. The waist panels 22, 23 are joined when the diaper 10 is being worn by a wearer by a fastening syswhich is illustrated in Fig. 3 as a pair of removable adhesive tape tabs 27, 28. Referring now to the Fig. 5, there is shown an absorbent article that manifests a typical feminine care towel 11. The towel 11 comprises multiple layers of laminate material or substrates bonded to form the - absorbent article. More particularly, the towel 11 includes a layer of fluid-permeable nonwoven material 29 and a fluid-impermeable backing layer 30 (typically made of polyethylene) bonded to the top layer 29. An absorbent core 31 is located between the upper layer 29 and the backing layer 30. The absorbent core 31 may be comprised of lint and / or a super-absorbent material (SAP). The towel 11 may also include a top fabric layer 32 disposed between the top layer 29 and the core 31. As shown in Fig. 5, each substrate is adhered to an adjacent substrate by means of a layer of adhesive formulated in accordance with the invention. with the current invention. For example, the upper layer 29 of nonwoven material is adhered to the upper fabric layer 32 by a layer of adhesive 33 applied to the underside of the layer 29. In turn, the upper fabric layer 32 is attached to the core. 31 by means of a layer of adhesive 34. Finally, the core 31 is adhered to the backing layer 30 by means of a layer of adhesive 35 applied to the upper surface of the backing layer 30. In the embodiment shown in FIG. 5, there is also a layer of adhesive 36 applied to the underside of the backing layer 30 and release paper 37 covering the adhesive 36. In this way, when the release paper 37 is removed to expose the adhesive 36, it can be used the adhesive layer 36 to secure the towel 11 to the underwear worn by the wearer, as is conventional and well known in the art. Referring now to Fig. 6, a diaper 38 similar to diaper 10 shown in Figs. 3 and 4. Accordingly, the same numbers are used in Fig. 6 to indicate similar components, with the exception of the designation of an "a" following the number. The diaper 38, however, incorporates a hot melt hydrophilic adhesive melt adhesive formulated in accordance with the present invention and applied to the upper layer of nonwoven material 12a in such a manner as to provide for the transportation of fluids to the diaper center 38 In order to do this, Fig. 6 illustrates a rectangular configuration 39 of adhesive applied to the underside of the top layer 12a in the crotch area 24a. The selective application of the adhesive in this portion of diaper 38 improves the penetration of fluid into the crotch area 24a over other areas, such as the fastening panels 22a, 23a and the seams of the leg openings 25a, 26a of the top layer 12a. This is due to the hydrophilic characteristic of the adhesive in the configuration 39. Although shown here in a rectangular configuration, other configurations could be employed, such as oval shapes, football shapes, figure eight, circular shapes and the like, all of which they would be employed to direct the fluid to a desired absorbent location in one of the substrates of an absorbent article, such as a sanitary napkin or towel. The invention is further illustrated by means of the examples set forth below: EXAMPLES 1-5 The following adhesive mixtures were prepared according to the percentages shown in Sample 1. Example 1 is a typical hydrophobic adhesive of the prior art. without the addition of a surfactant. Examples 2-4 were formulated using various amounts of surfactant according to the present invention. When tested, the formulations of Examples 2-4 demonstrated sufficient peel strength to function as construction adhesives, while providing a reduced contact angle resulting in hydrophilic characteristics sufficient to provide wettability. SAMPLE 1 Raw materials Unitac R1OOL 100 ° C mp, PE high oil resin ester, Union Camp Stereon 840A SBS block copolymer, Firestone SolT193B SIS block copolymer, Enichem Kaydol Mineral oil, Witco Benzoflex 9-88 dipropylene glycol dibenzoate, Velsicol Atmer 688 non-ionic surfactant blend, ICI Alkamuls GMS / C glycerol monostearate, Rhone-Poulenc Irganox 1010 methane tetrakis (methylene (3,5-di-tert-butyl-4-hydroxyhydrocinnamate)), Ciba-Geigy Coating conditions: PE laminates to non-wovens, 3.0 mg / 6.4516 cm2, Spiral Spray, 0.5 sec. Opening time, adhesive 163 ° C, air 200 ° C. Instron resistance to detachment: Average resistance to detachment at 30 cm / minute

Claims (22)

1. CLAIMS 1.- A hot melt hydrophilic adhesive composition, characterized in that it comprises the following components: about 10-50% of a polymer; about 40-80% of a viscous resin; about 0-40% of a plasticizer; about 0.1-2% of an antioxidant; and about 0.1-30% of a surfactant, the total constituting 100% of the components by weight, and wherein the adhesive has a contact angle of less than about 75 °.
2. 2. The composition according to claim 1, characterized in that the adhesive has a contact angle of less than about 50 °.
3. 3. The composition according to claim 1, characterized in that the surfactant has an HLB of less than 15.
4. 4. The composition according to claim 1, characterized in that the plasticizer is mineral oil.
5. 5. The composition according to claim 1, characterized in that the surfactant is selected from the groups consisting of esters of fatty acids, non-ionic ethoxylates and copolymers of ethylene oxide / propylene oxide.
6. 6. The composition according to claim 1, characterized in that the polymer is selected from the group consisting of ethylene-based polymers, including ethylene / vinyl acetate, ethylene acrylate, ethylene methacrylate, ethylenemethyl acrylate, ethylenemethyl methacrylate, polybutylene, polyethylene high and low density, mixtures of polyethylene and chemically modified polyethylene, copolymers of ethylene and monomers 1-6 mono- or di-unsaturated, polyamides, polybutadiene rubber, polyesters such as polyethylene terephthalate, polybutylene terephthalate; thermoplastic polycarbonates, atactic polyalphaolefins, including atactic polypropylene, and others; thermoplastic polyacrylamides, polyacrylonitrile, acrylonitrile copolymers and other monomers, such as butadiene styrene; polymethyl pentene, polyphenylene sulfide, aromatic polyurethanes; styrene acrylonitrile, acrylonitrile-butadiene styrene, styrene-butadiene rubbers, polyethylene terephthalate, acrylonitrile-butadiene styrene elastomers, polyphenylene sulfide, block polymers AB, ABA, A- (BA) nB, (AB) nY where A comprises an aromatic polyvinyl block, block B comprises an elastic medium block which can be partially hydrogenated, and mixtures thereof.
7. 7. The composition according to claim 1, characterized in that the antioxidant is hindered phenol.
8. 8. The composition according to claim 1, characterized in that the viscous resin is selected from aliphatic petroleum hydrocarbon resins, petroleum hydrocarbon aromatic resins, hydrogenated petroleum hydrocarbon aliphatic resins or resin esters.
9. 9. A hot melt hydrophilic adhesive composition characterized in that it comprises the following components: about 18-25% of a polymer; about 50-60% of a viscous resin; about 12-25% of a plasticizer; about 1% of an antioxidant; and about 2-15% of a surfactant, the total constituting 100% of the components by weight, and wherein the adhesive has a contact angle of less than about 50 °.
10. 10. - The composition according to claim 9, characterized in that the surfactant has an HLB of less than 15.
11. 11. The composition according to claim 9, characterized in that the plasticizer is mineral oil.
12. 12. The composition according to claim 9, characterized in that the surfactant is selected from the groups consisting of esters of fatty acids, non-ionic ethoxylates and copolymers of ethylene oxide / propylene oxide.
13. 13. The composition according to claim 9, characterized in that the polymer is selected from the group consisting of ethylene-based polymers, including ethylene / vinyl acetate, ethylene acrylate, ethylene methacrylate, ethylenemethyl acrylate, ethylenemethyl methacrylate, polybutylene, polyethylene. high and low density, mixtures of polyethylene and chemically modified polyethylene, copolymers of ethylene and monomers 1-6 mono- or di-unsaturated, polyamides, polybutadiene rubber, polyesters such as polyethylene terephthalate, polybutylene terephthalate; thermoplastic polycarbonates, atactic polyalphaolefins, including atactic polypropylene, and others; thermoplastic polyacrylamides, polyacrylonitrile, acrylonitrile copolymers and other monomers, such as butadiene styrene; polymethyl pentene, polyphenylene sulfide, aromatic polyurethanes; styrene acrylonitrile, acrylonitrile-butadiene styrene, styrene-butadiene rubbers, polyethylene terephthalate, acrylonitrile-butadiene styrene elastomers, polyphenylene sulfide, block polymers AB, ABA, A- (BA) nB, (AB) aY wherein A comprises an aromatic polyvinyl block, the block B comprises an elastic medium block which can be partially hydrogenated, and mixtures thereof.
14. 14. The composition according to claim 9, characterized in that the antioxidant is hindered phenol.
15. 15. The composition according to claim 9, characterized in that the viscous resin is selected from aliphatic petroleum hydrocarbon resins, petroleum hydrocarbon aromatic resins, hydrogenated petroleum hydrocarbon aliphatic resins or resin esters.
16. 16. A method for manufacturing an absorbent and disposable article of nonwoven material, characterized in that it comprises the steps of: providing a first layer of material comprising a substrate of an absorbent and disposable article of nonwoven material; providing a second layer of material comprising a second substrate of an article and disposable of nonwoven material; applying a hydrophilic hot melt adhesive to one of the first or second layers of material in a configuration such that the fluid contacting the adhesive is directed towards a desired absorbent location in the first or second layer; and joining said first and second layers.
17. 17. The method according to claim 16, characterized in that the first layer of material is a nonwoven substrate and the second layer of material is a tissue substrate.
18. 18. The method according to claim 17 characterized in that the absorbent and disposable article of non-woven material is a diaper.
19. 19. The method according to claim 17, characterized in that the absorbent and disposable article of nonwoven material is a sanitary napkin.
20. 20. The method according to claim 17, characterized in that the configuration comprises a rectangular model of the adhesive applied to the nonwoven substrate.
21. 21. - The method according to claim 16 characterized in that said hydrophilic hot melt adhesive comprises the following components: about 10-50% of a polymer; about 40-80% of a viscous resin; about 0-40% of a plasticizer; about 0.1'2% of an antioxidant; and about 0.1-30% of a surfactant, the total constituting 100% of the components by weight, and wherein the adhesive has a contact angle of less than about 75 °.
22. 22. The method according to claim 16, characterized in that the hot melt hydrophilic adhesive comprises the following components: about 18-25% of a polymer; about 50-60% of a viscous resin; about 12-25% of a plasticizer; about 1% of an antioxidant; and about 2-15% of a surfactant, the total constituting 100% of the components by weight, and wherein the adhesive has a contact angle of less than about 50 °. HOT FUSION HYDROPHYL ADHESIVE SUMMARY OF THE INVENTION Hydrophilic hot melt adhesive compositions suitable for a variety of applications, especially disposable nonwoven articles, are prepared by mixing various adhesive components with a surfactant. The surfactant has a hydrophilic-lipophilic balance number (HLB) of less than 15, and is incorporated into the composition in an amount such that the resulting adhesive has a contact angle of 75 ° or less, and preferably less than about 40 °. . A low contact angle is desirable so that water, urine or other aqueous flow, upon contact with a laminate bonded by the adhesive, extends instead of forming globules, causing the fluid to move away from the adhesive and toward the adhesive. Absorbent core of the disposable article.