HOT-MELT ADHESIVE COMPOSITIONS

Abstract: Hot-melt adhesive compositions comprising a hydroxy-functionalized polyether which is not the reaction product of a dicarboxylic acid with a diglycidyl ether, optionally in combination with a compatible tackifier, a compatible plasticizer and a comptatible diluent.

Description: HOT-MELT ADHESIVE COMPOSITIONS The present invention relates to hot-melt adhesive compositions. Hot-melt adhesives are adhesives with a thermoplastic character, that is, they flow at an elevated temperature and are solid at a lower temperature. Such adhesives are well-known and are typically applied by extruding the heated adhesive between two articles to be bonded and then allowing the adhesive to cool. As the adhesive cools, it forms a more rigid bond between the articles. See generally, A.J. Kinloch, Adhesion and Adhesives Science and Technology, Chapman and Hall (London, 1990), pages 175-176. The major advantage of hot-melt adhesives is the lack of a carrier fluid which eliminates the need for drying the adhesive film once it is applied to the substrate. This elimination of the drying step overcomes hazards associated with solvent usage and also allows for faster production line speeds and lower costs. The ability to modify the properties of the adhesive composition with the addition of various resins, oils, waxes and other additives, makes hot-melt adhesives commercially useful in a wide variety of applications. U.S. Patents 5,574,076 and 5,583,187 describe hot-melt adhesive compositions comprising thermoplastic methylol polyesters as the base polymer or main functional adhesive material. These polyesters are prepared from the reaction of at least one dicarboxylic acid with a diglycidyl ether, a diglycidyl ester or a combination thereof. WO 97/23564 discloses compositions of (1 ) a polysaccharide, a modified polysaccharide, or a naturally-occurring fiber or particulate filler and (2) a thermoplastic hydroxy-functional polyether derived from monomers containing 1 or more epoxy groups are suitable for, among other things, adhesives. It would be desirable to provide a hot-melt adhesive composition wherein the base polymer is a hydroxy functionalized polymer which does not contain ester linkages labile to hydrolytic degradation. In one aspect, the present invention is the use as a hot melt adhesive, of a composition comprising a thermoplastic hydroxy-functionalized polyether which is essentially free of ester linkages labile to hydrolytic degradation. In another aspect, the present invention is a hot-melt adhesive composition comprising a thermoplastic hydroxy-functionalized polyether which is not the reaction product of a dicarboxylic acid with a diglycidyl ether, optionally in combination with a compatible tackifier, a compatible plasticizer and a compatible diluent. In another aspect, the present invention is a method of adhering a first substrate to at least one other substrate which may be of the same or different material as the first substrate, comprising contacting the first substrate and the at least one other substrate with an effective amount of a hot-melt adhesive composition comprising a thermoplastic hydroxy-functionalized polyether which is not the reaction product of a dicarboxylic acid with a diglycidyl ether, at a temperature and pressure sufficient to flow the hot-melt adhesive composition onto a portion of each substrate; bringing adjacent portions of adhesive-coated substrates into contact with each other and applying sufficient pressure to form a joint (which may be a laminate) and cooling the joint to resolidify the hot-melt adhesive composition. The hot-melt adhesive compositions of the present invention may be employed in a wide variety of uses as are known in the art, such as, for example, packaging and carton sealing operations, bookbinding operations, metal bonding assembly such as in automotive or appliance applications, and assembly of wood articles. They may also be employed for laminating tissue and/or screen-reinforced tissue layers such as are used in individual or roll use applications as in wipers, paper towel, toilet tissue and other consumer or industrial end uses. When formulated with plasticizers, the resultant adhesives may be useful in the assembly or construction of various disposable articles, such as sanitary napkins, disposable diapers, hospital gowns, and bed pads. These adhesives may also be useful for the assembly of disposable articles using spray or multi-line construction techniques wherein at least one flexible film substrate is bonded to at least one tissue, non- woven, polyolefin or other flexible polymeric film substrate. In addition, the adhesives may also be useful in the bonding of elastic materials to polyethylene, polypropylene or non- woven substrate so as, for example, to impart elongation resistant gathers thereto. The adhesives may also be useful in less demanding disposable construction applications such as for end or perimeter sealing. Preferably, the base polymer of the hot-melt adhesive composition of the present invention comprises any one of the following hydroxy-functional polyethers: (1) poly(hydroxy ethers) having repeating units represented by the formula: (2) poly(hydroxy amino ethers) having repeating units represented by the formula: OH OH -0— CH 2 -C— CH 2 - A— CH 2 -C— CH 2 -0— B- I I R R n (3) poly(hydroxy ether sulfonamides) having repeating units represented by the formula: OH R 1 0 0 R 1 OH I I II 2 II I I -OCH 2 CCH 2 N— S— R— S— NCH 2 CCH 2 OB- I l ia I II II I R 0 0 R or OH OH I I -OCH 2 CCH 2 NCH 2 CCH 2 OB- I llb R S0 2 R R l 3 (4) poly(hydroxy ether sulfides) having repeating units represented by the formula: IV (5) poly(hydroxy amide ethers) having repeating units represented independently by any one of the formulas: OH o o I 2 II • OCH 2 CCH 2 OAr— NHC— R CNHAr— j- Va R or OH 0 -OCH 2 C 1 CH 2 OArC "NHAr- - Vc I R n or (6) poly(hydroxy amide ethers) having repeating units represented by any one of the formulas: H 2 OAr V Ib or OH 0 OH -OCH 2 CCH 2 OAr — CNH— Ar OCH 2 CCH 2 OAr _--— VI c R R wherein R is alkyl or hydrogen; R 1 and R 3 are independently a substituted or an unsubstituted alkyl or aryl wherein the substituent(s) is a monovalent moiety which is inert in the reactions used to prepare the hydroxy-functionalized polyethers, such as cyano, halo, amido, hydroxy and hydroxyalkyl; Ar is a divalent aromatic moiety; A is a diamino moiety or a combination of different amine moieties; B, R 2 , and R 4 are independently a divalent organic moiety which is predominantly hydrocarbylene; and n is an integer from 5 to 1000. The term "predominantly hydrocarbylene" means a divalent radical which is predominantly hydrocarbon, but which optionally contains a minor amount of heteroatomic moiety such as oxygen, sulfur, imino, sulfonyl, and sulfoxyl. In the preferred embodiment of the present invention, R is hydrogen; R 1 and R 3 are independently methyl, ethyl, propyl, butyl, 2-hydroxyethyl or phenyl; Ar, B, R 2 and R 4 are independently 1 ,3-phenylene, 1 ,4-phenylene, sulfonyldiphenylene, oxydiphenylene, thiodiphenylene or isopropylidenediphenylene; A is 2-hydroxyethylimino, 2-hydroxypropylimino, piperazenyl or N,N'-bis(2-hydroxyethyl)-1 ,2-ethylenediimino. The hydroxy-functional polyethers having repeating units represented by Formula I are prepared, for example, by contacting a diglycidyl ether or a combination of diglycidyl ethers with a dihydric phenol or combination of dihydric phenols using the process described in U.S. Patent 5,164,472. Alternatively, the poly(hydroxy ethers) are obtained by allowing a dihydric phenol or a combination of dihydric phenols to react with an epihalohydrin by the process described by Reinking, Bamabeo, and Hale in the Journal of Applied Polymer Science. Volume 7, page 2135 (1963). Preferably the poly(hydroxy ether of Formula I is a poly(hydroxy phenoxyether) The polyetheramines having repeating units represented by Formula II are prepared by contacting one or more of the diglycidyl ethers of a dihydric phenol with a difunctional amine (an amine having two amine hydrogens) under conditions sufficient to cause the amine moieties to react with epoxy moieties to form a polymer backbone having amine linkages, ether linkages and pendant hydroxyl moieties. These polyetheramines are described in U.S. Patent 5,275,853. The polyetheramines can also be prepared by contacting a diglycidyl ether or an epihalohydrin with a difunctional amine. The hydroxy-functional poly(ether sulfonamides) having repeating units represented by Formulas Ilia and 1Mb are prepared, for example, by polymerizing an N,N'-dialkyl or N,N'-diaryldisulfonamide with a diglycidyl ether as described in U.S. Patent 5,149,768. The hydroxy-functional polyethers having repeating units represented by Formula IV are prepared by reacting a diglycidyl ether and a dithiol as described in U.S. Patents 4,048,141 and 4,171 ,420. The poly(hydroxy amide ethers) represented by Formula V are prepared by contacting a bis(hydroxyphenylamido)alkane or arene, or a combination of 2 or more of these compounds, such as N,N'-bis(3-hydroxyphenyl)adipamide or N,N'-bis(3- hydroxyphenyl)glutaramide, with an epihalohydrin as described in U.S. Patent 5,134,218. The poly(hydroxy amide ethers) represented by Formula VI are preferably prepared by contacting an N,N'-bis(hydroxyphenylamido)alkane or arene with a diglycidyl ether as described in U.S. Patents 5,089,588 and 5,143,998. The hydroxy-functional polyethers available from Phenoxy Associates, Inc. are also suitable for use as the base polymer in the practice of the present invention. These polymers and the process for preparing them are described in U.S. Patent 3,305,528 and 5,401 ,814. Optionally, the hydroxy-functionalized polyether has a multimodal molecular weight distribution. The term "multimodal molecular weight distribution," as used herein, means that the base polymer has a molecular weight distribution determined by size exclusion chromatography that contains more than one peak value. The base polymer of this invention also can be a mixture of hydroxy-functionalized polyethers of the same or different primary structures with different molecular weights. The tackifiers which can be employed in the practice of the present invention for preparing the hot-melt adhesive composition include terpene phenolic resins and benzoates, such as, for example, sucrose benzoate. The amount of the tackifier most advantageously incorporated into the hydroxy-functionalized polyether is dependent on a variety of factors including the specific components used to form the hot-melt adhesive composition as well as its desired properties. Typical amounts can range from 0 to 90 weight percent based on the weight of the total composition. Generally, the hot-melt adhesive composition comprises at least about 0.1 , preferably about 1 , more preferably about 2, and most preferably about 4 weight percent and less than about 80, preferably about 60, more preferably about 50 weight percent of the tackifier based on the total weight of the composition. The plasticizers which can be employed in the practice of the present invention for preparing the hot-melt adhesive composition include phthalate plasticizers, such as dioctyl phthalate; liquid polyesters such as Dynacol 720 from Hϋls; benzoate plasticizers such as diethylene glycol dibenzoate (for example, Benzoflex 50 available from Velsicol) and diethylene glycol benzoate where the mole fraction of hydroxyl groups which have been esterified ranges from 0.5 to 0.95 (for example, Benzoflex 2-45 High Hydroxy from Velsicol); phosphate plasticizer such as t-butylphenyl diphenyl phosphate (for example, Santicizer 154 commercially available from Monsanto); polyalkylene glycols such as the phenyl ether of poly(ethylene glycol) (for example, Pycal 94 available commercially from ICI); as well as liquid rosin derivatives having Ring and Ball melting points below about 60°C, such as the methyl ester of hydrogenated rosin (for example, Hercolyn D from Hercules); as well as vegetable and animal oils such as glyceryl esters of fatty acids and polymerization products thereof. If used, the plasticizer is generally present in amounts up to about 90 percent by weight, preferably 10 to 40 percent by weight. Other applications conventionally employing hot-melt adhesives may require the use of wax diluents in order to reduce the melt viscosity or cohesive characteristics of the hot-melt adhesive composition without appreciably decreasing their adhesive bonding characteristics. These waxes are often used in adhesives which do not exhibit pressure sensitive properties. If present, the waxes are used in an amount up to 90 percent by weight, preferably 5 to 35 percent by weight. Suitable waxes include N-(2-hydroxyethyl)-12- hydroxystearamanide wax, hydrogenated castor oil, oxidized synthetic waxes, poly(ethylene oxide) having a weight average molecular weight of above about 1000 and functionalized synthetic waxes such as carbonyl-containing Escomer H101 from Exxon. Mixtures of one or more of such materials may be employed. It should be recognized that some adhesive formulations described herein may contain both wax and plasticizer components so that the presence of one or the other is not mutually exclusive. Other optional additives may be incorporated into the hot-melt adhesive compositions in order to modify certain properties thereof. Among these additives are antioxidants or stabilizers, colorants such as titanium dioxide; and fillers, such as talc and clay. There may also be present in the adhesive composition certain thermoplastic and/or hydrophilic polymers as are conventionally used in this class of adhesive to impart flexibility, toughness, strength and/or water sensitivity. Suitable thermoplastic polymers include ethylene vinyl acetate, ethylene acrylic acid, ethylene methyl acrylate, and ethylene n-butyl acrylate copolymers containing 12 to 50 percent vinyl or acrylate monomers. Suitable hydrophilic polymers include polyvinyl alcohol, hydroxyethyl cellulose, hydroxypropyl cellulose, polyvinyl methyl ether, poly(ethylene oxide), and polyvinyl pyrrolidone. Among the applicable stabilizers or antioxidants which may be included herein are high molecular weight hindered phenols such as sulfur and phosphorus-containing phenols. In general, the hot-melt adhesive composition of the present invention can be prepared using techniques known in the art. An exemplary procedure involves placing approximately 40 percent of the total tackifying resin concentration with all the polymer, wax, plasticizers and stabilizers in a jacketed mixing kettle, preferably in a jacketed heavy duty mixer, which is equipped with rotors and thereupon raising the temperature to a range of up to about 190°C. After the resin has melted, the temperature is lowered to 150°C to 165°C. Mixing and heating are continued until a smooth, homogeneous mass is obtained whereupon the remainder of the tackifying resin is thoroughly and uniformly admixed therewith. Techniques for melt-blending of a polymer with additives of all types are known in the art and can typically be used in the practice of this invention. Typically, in a melt blending operation useful in the practice of the present invention, the hydroxy-functionalized polyether is heated to a temperature sufficient to form a polymer melt and combined with the desired amount of the other components in a suitable mixer, such as an extruder, a Banbury mixer, a Brabender mixer, or a continuous mixer. A physical mixture of the different components may also be heated simultaneously and blended using one of the previously mentioned mixers. In the practice of the present invention, the melt blending is preferably carried out in the absence of air, as for example, in the presence of an inert gas, such as argon, neon, or nitrogen. However, the present invention may be practiced in the presence of air. The melt blending operation can be conducted in a batch or discontinuous fashion but is more preferably conducted in a continuous fashion in one or more processing zones such as in an extruder from which air is largely or completely excluded. The extrusion can be conducted in one zone or step or in a plurality of reaction zones in series or parallel. A hydroxy-functionalized polyether melt containing the other hot-melt adhesive components may also be formed by reactive melt processing in which the other components are initially dispersed in a liquid or solid monomer or cross-linking agent which will form or be used to form the hot-melt adhesive composition. This dispersion can be injected into a polymer melt containing one or more polymers in an extruder or other mixing device. The injected liquid may result in new polymer or in chain extension, grafting or even cross-linking of the polymer initially in the melt. The hot-melt adhesive composition of the present invention can also be formed by mixing the monomer used in forming the hydroxy-functionalized polyether with the other components in the presence or absence of a solvent and subsequently polymerizing the monomer to form the hydroxy-functionalized polyether component of the composition. After polymerization, any solvent that is used is removed by conventional means. Alternatively, the polymer may be granulated and dry-mixed with the other components of the hot-melt adhesive composition and the composition heated in a mixer until the hydroxy-functionalized polyether is melted to form a flowable mixture. This flowable mixture can then be subjected to a shear in a mixer sufficient to form the desired composition. The hydroxy-functionalized polyether may also be heated in the mixer to form a flowable mixture prior to the addition of the other components of the hot-melt adhesive composition. The hydroxy-functionalized polyether and the other components are then subjected to a shear sufficient to form the desired hot-melt adhesive composition. The following working examples are given to illustrate the invention and should not be construed as limiting its scope. Unless otherwise indicated, all parts and percentages are by weight. Examples Lap shear test specimens were prepared by compression molding a 1 inch (2.54 cm) by 0.5 inch (1.27 cm) film of the selected hydroxy-functional polyethers between 0.062 inch (1.575 mm) thick cold-rolled steel test plates (1" (2.54 cm) x 4" (10.2 cm) x 0.062" (1.575 mm), 1/2 hard, ground one side), obtained from Q-Panel, Cleveland, Ohio and used without surface cleaning or treatment. Molding temperature was 100°C above the measured glass transition temperature of the respective polymer, and the following molding pressure and time profile was used. The samples were equilibrated in the press for 10 minutes at 5000 psi (3.447 x 10 7 Pa) at the molding temperature, then for 4 minutes at 80,000 psi (5.516 x 10 8 Pa), and the press was allowed to cool to 120 S F (50 9 C) under 80,000 psi (5.516 x 10 8 Pa) force for 5 minutes. The samples were removed and testing using an Instron testing frame at a crosshead speed of 0.05 inches (0.13 cm) per minute, following ASTM test method D-1002. Test results are shown in Table I below. Lap Shear Strength data in psi are converted to pascal by multiplying by 6.894757 x 10 3 and rounding. In the Failure Mode observation column, AF denotes visual observation of apparent adhesive failure, CF denotes apparent cohesive failure, and %CF the apparent percent of cohesive failure in tests where there was apparent partial cohesive failure. Table Table I (continued) Table I (continued) Table I (continued) Table I (continued) Table I (continued)

Claims: CLAIMS: 1. A hot-melt adhesive composition comprising a thermoplastic hydroxy- functionalized polyether which is not the reaction product of a dicarboxylic acid with a diglycidyl ether, optionally in combination with a compatible tackifier, a compatible plasticizer and a compatible diluent. 2. The hot-melt adhesive composition of Claim 1 wherein the hydroxy- functionalized polyether has a multimodal molecular weight distribution or is a mixture of two or more hydroxy-functionalized polyethers having different molecular weights. 3. The hot-melt adhesive composition of Claim 1 wherein the hydroxy- functionalized polyether is a poly(hydroxy ether) having repeating units represented by the formula: wherein B is a divalent organic moiety which is predominantly hydrocarbylene, R is alkyl or hydrogen, and n is an integer from 5 to 1000. 4. The hot-melt adhesive composition of Claim 3 wherein the hydroxy- functionalized polyether is prepared by the reaction of a diglycidylether or epihalohydrin with a bisphenol. 5. The hot-melt adhesive composition of Claim 1 wherein the hydroxy- functionalized polyether is a poly(hydroxy amino ether) having repeating units represented by the formula: OH OH I -O— CH 2 -C — CH 2 - A — CH 2 -C— CH 2 -0— B- I I R R n wherein A is a diamino moiety or a combination of different amine moieties; B is a divalent organic moiety which is predominantly hydrocarbylene; R is alkyl or hydrogen; and n is an integer from 5 to 1000. 6. The hot-melt adhesive composition of Claim 5 wherein the hydroxy- functionalized polyether is prepared by the reaction of a diglycidyl ether with a difunctional amine. 7. The hot-melt adhesive composition of Claim 1 wherein the hydroxy- functionalized polyether is a hydroxy-functional poly(hydroxy ether sulfonamide) having repeating units represented by any one of the formulas: wherein R is hydrogen or alkyl, R 1 and R 3 are independently a substituted or an unsubstituted alkyl or aryl wherein the substituent(s) is a monovalent moiety which is inert in the reactions used to prepare the hydroxy-functionalized polyether; B and R 2 are independently a divalent organic moiety which is predominantly hydrocarbylene, and n is an integer from 5 to 1000. 8. The hot-melt adhesive of Claim 7 wherein the hydroxy-functionalized polyether is prepared by the reaction of a diglycidyl ether and a difunctional sulfonamide. 9. The hot-melt adhesive of Claim 1 wherein the hydroxy-functionalized polyether has repeating units represented by the formula: wherein R is hydrogen or alkyl, R 4 and B are independently a divalent organic moiety which is predominantly hydrocarbylene and n is an integer of 5 to 1000. 10. The hot-melt adhesive of Claim 9 wherein the hydroxy-functionalized polyether is prepared by the reaction of a diglycidyl ether and a dithiol. 11. The hot-melt adhesive of Claim 3 wherein the hydroxy-functionalized polyether is a poly(hydroxy amide ether) having repeating units represented independently by any one of the formulas: or a poly(hydroxy amide ether) having repeating units represented by any one of the formulas: OH 0 O OH -OCH p CCH p OAr— CNH— R 2 NHC— Ar— OCH 2 CCH 2 OAr -J— V Ib I I R R n or OH 0 OH -OCH 2 CCH 2 OAr — CNH — Ar OCH 2 CCH 2 OAr _i_ VIc R R wherein R is alkyl or hydrogen, and Ar is a divalent aromatic moiety, R 2 is a divalent organic moiety which is predominantly hydrocarbylene, and n is an integer from 5 to 1000. 12. The hot-melt adhesive of Claim 1 wherein the tackifier is a terpene phenolic resin or a benzoate in an amount of from 0.1 to 80 percent by weight. 13. The hot-melt adhesive of Claim 1 wherein the plasticizer is a phthalate plasticizer, benzoate plasticizer, a liquid polyester, a phosphate plasticizer, a polyalkylene glycol, a vegetable oil, or an animal oil in an amount of from 10 to 40 percent by weight. 14. The hot-melt adhesive of Claim 1 wherein the diluent is a wax in an amount of from 5 to 35 percent by weight. 15. The hot-melt adhesive of Claim 14 wherein the wax is N-(2- hydroxyethyl)-12-hydroxystearamanide wax, hydrogenated castor oil or an oxidized synthetic wax. 16. Use as a hot melt adhesive, of a composition comprising a thermoplastic hydroxy-functionalized polyether which is essentially free of ester linkages labile to hydrolytic degradation. 17. A method of adhering a first substrate to at least one other substrate which may be of the same or different material as the first substrate, in which the first substrate and the at least one other substrate are contacted with an effective amount of a hot-melt adhesive composition at a temperature and pressure sufficient to flow the hot-melt adhesive composition onto at least a portion of each substrate, adjacent portions of the adhesive-coated substrates are brought into contact with each other under sufficient pressure to form a joint and the joint is cooled to resolidify the hot-melt adhesive composition, characterized in that the hot-melt adhesive composition is a thermoplastic hydroxy-functionalized polyether which is not the reaction product of a dicarboxylic acid with a diglycidyl ether. 18. The method of Claim 17 wherein the thermoplastic hydroxy- functionalized polyether is selected from (1) at least one poly(hydroxy ether) having repeating units represented by the formula: (2) at least one poly(hydroxy amino ether) having repeating units represented by the formula: I I (3) at least one poly(hydroxy ether sulfonamide) having repeating units represented by the formula: OH OH I I -OCH 2 CCH 2 NCH 2 CCH 2 OB- I llb R S0 2 R R I s (4) at least one poly(hydroxy ether sulfide) having repeating units represented by the formula: .OCH 2 IV (5) at least one poly(hydroxy amide ether) having repeating units represented independently by any one of the formulas: or OH 0 -OCH 2 C 1 CH 2 OArC "NHAr- — Vc I R and (6) a poly(hydroxy amide ether) having repeating units represented by any one of the formulas: OH O 0 OH ■OCH 2 CCH 2 OAr— CNH— R 2 NHC— Ar— OCH 2 CCH 2 OAr -| — vib R R or -OCH 2 VIc wherein R is alkyl or hydrogen, R 1 and R 3 are independently a substituted or an unsubstituted alkyl or aryl wherein the substituent(s) is a monovalent moiety which is inert in the reactions used to prepare the hydroxy-functionalized polyethers; Ar is a divalent aromatic moiety; A is a diamino moiety or a combination of different amine moieties; B, R 2 and R 4 are independently a divalent organic moiety which is predominantly hydrocarbylene; and n is an integer from 5 to 1000. 19. The method of Claim 18 in which the hot-melt adhesive includes at least one of a tackifier, a compatible plasticizer and a compatible diluent. 20. The method of Claim 18 wherein at least one substrate is a flexible polymeric film substrate, a non-woven substrate, paper, cardboard, wood or a metal substrate. 21. The method of Claim 20 wherein the at least one substrate is cold- rolled steel. 22. The method of Claim 20 wherein the hot-melt adhesive includes at least one of a tackifier, a compatible plasticizer and a compatible solvent.

Inventors: MANG MICHAEL N, WHITE JERRY E, MANG, MICHAEL, N., WHITE, JERRY, E.
Applicants: DOW CHEMICAL CO, THE DOW CHEMICAL COMPANY
Application year: 1999
Main classification: C09J171
IPC codes: C08G65, C09J7, C09J171