Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2000-04-05
2003-04-01
Reddick, Judy M. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C428S304400, C428S314800, C428S319700, C428S319900, C428S344000, C428S346000, C428S349000, C428S412000, C428S423100, C428S423300, C428S423500, C428S423700, C428S424200, C428S425800, C524S247000, C524S249000
Reexamination Certificate
active
06541550
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to water-dispersed adhesive compositions and particularly to water-dispersed adhesive compositions that form adhesives that can be thermally activated at low temperatures.
BACKGROUND OF THE INVENTION
In the manufacture of office or automobile seating, a fabric is typically bonded to a contoured foam surface. The cloth-covered foam may then also be bonded to a support material such as wood or plastic. The contoured foam is typically bonded to the fabric by an adhesive. The adhesive may be applied when the part is needed or may be applied, allowed to dry, and then bonded at a later time depending upon the characteristics of the particular adhesive.
Adhesives such as sprayable hot melts, solvent based adhesives, and water-based contact adhesives have been used for such applications. Sprayable hot melt adhesives typically require specialized spray and storage equipment and have a short open time. Hot melt adhesives may also require re-heating at relatively high temperatures, for example, 265° F.-350° F. (130° C.-177° C.) to re-melt the adhesive and form a bond. Solvent-based adhesives are available with a wide range of solvated polymers, including crystallizing polyurethanes. However, the use of materials containing organic solvents in the workplace has raised emission and exposure concerns.
Water-dispersed adhesives are known in the art. These adhesives have gained commercial success in general because they are typically easily applied to substrates and do not contain appreciable amounts of organic solvents.
However, water-dispersed adhesives currently available may not provide adequate adhesion to all substrates. One example of a substrate that can be difficult to bond is flexible foam, in particular, molded foam. Molded foams, typically made using urethanes, are difficult to bond because the surface of the foam is smooth and relatively non-porous and often has mold release residue dispersed about its surface. Such foams are generally more difficult to bond because the combination of a smooth surface and any additional mold-release residue provides a surface that has a lower surface energy than a foam that does not have a molded surface.
SUMMARY OF THE INVENTION
In one aspect, the present invention provides low temperature activatable water-dispersed adhesive compositions. The adhesive compositions of the invention comprise low modulus crystallizing polyester polyurethane, acrylic ester copolymer, one or more hydrophobically-modified associative polyurethanes, and a stabilizer system comprising a combination of carbodiimide and branched primary amino alcohol.
In another aspect, the invention provides adhesives made from the adhesive compositions described in this application.
The term “water dispersed” means that the carrier is primarily water. However, incidental organic solvents, such as those present in additives and commercially available components, may be present. Thus, the adhesive compositions of the invention are at least substantially free of organic solvents. Preferably, however, “water-dispersed” refers to a 100% water carrier.
The term “dispersion” encompasses any form of solid dispersed in a liquid medium including, for example, latexes, emulsions, colloidal suspensions, and the like.
The adhesive compositions or the adhesives of the invention contain no external plasticizer or zinc oxide. The adhesive compositions of the invention also preferably contain no polychloroprene resins or dispersions.
The term “plasticizer” as used herein means compounds from the following classes: phthalates including alkyl benzyl phthalates; adipates including dialkyl adipates; phosphates including alkyl aryl phosphates and triaryl phosphates; alkyl and aryl sulfonamides; and hydrogenated terphenyls.
The term “low temperature activatable adhesive” means adhesives of the invention that are capable of bonding substrates at a bondline temperature of as low as 43° C.
The term “low modulus” means a storage modulus (G′) not more than 3×10
6
dynes/cm
2
at 60° C., and preferably not more than 1×10
9
dynes/cm
2
at 20° C., as measured by dynamic mechanical analysis (DMA) at a frequency of 1 Hertz.
The term “crystallizing polyester polyurethane” means a polyester polyurethane polymer that has at least one measurable glass transition temperature (Tg) above 20° C. as measured by DMA.
The term “adhesive composition” means a mixture of adhesive components dispersed in water. The term “adhesive” means a mixture of adhesive components wherein water has been removed.
The adhesives of the invention after coating onto a substrate may be formulated to be non-blocking at ambient temperature (23° C.), and then can be thermally activated to form a bond.
The adhesives of the invention also provide open times of at least 3 days at ambient conditions. The term “open time” means the time that an effective adhesive bond can still be made, after the adhesive has been applied to a substrate and dried.
Other advantages of the adhesive compositions of the invention include the adhesive compositions are sprayable, can be bonded at low pressures (1-3 psi (0.048-0.14 kPa)), provide high green strength durable bonds, that is, bonds that maintain or increase in bond strength and are environmentally resistant, for example, at 52° C. and 80% RH, for 48 hours, the adhesives can be bonded greater than 24 hours after drying (non-blocking), and the adhesive compositions of the invention have low penetration into porous surfaces.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The water-dispersed adhesive compositions of the invention comprise one or more low modulus crystallizing polyester polyurethanes, acrylic ester copolymer, one or more hydrophobically-modified associative polyurethanes, and a stabilizer system. The water-dispersed adhesive compositions optionally, but preferably, contain one or more antioxidants.
Acrylic ester copolymer is generally present in the adhesive compositions of the invention in an amount of from about 60 to about 400 parts per 100 parts low modulus crystallizing polyester polyurethanes on a dry weight basis, or “phr urethane.” Acrylic ester copolymer is preferably present in the adhesive compositions of the invention in an amount of from about 70 to about 230 phr urethane and more preferably present in an amount of from about 80 to about 160 phr urethane.
Hydrophobically-modified associative polyurethane is generally present in the adhesive compositions of the invention in an amount of from about 0.05 to about 2, preferably from about 0.07 to about 1, and more preferably from about 0.07 to about 0.5 phr urethane.
The adhesive compositions of the invention contain a stabilizer system. The stabilizer system is a combination of carbodiimide and branched primary amino alcohol. Carbodiimide is present in the adhesive compositions of the invention in an amount of from about 1 to about 8 phr, preferably from about 1.5 to about 7 phr, more preferably from about 2.0 to about 6.5 phr urethane. Branched primary amino alcohol is present in the adhesive compositions of the invention in an amount from about 1.5 to about 7 phr, preferably from about 2 to about 4 phr, more preferably from about 2.3 to about 3.5 phr urethane. Generally, the ratio of carbodiimide to branched primary amino alcohol ranges from about 2 to 0.5 to about 0.5 to 2 by weight with a ratio of about 2 to 1 preferred.
If present, antioxidant is provided in the adhesive composition of the invention in an amount of from about 1.5 to about 7.0, preferably, about 2.0 to about 5.0, more preferably, about 2.4 to about 2.8 phr urethane.
The water-dispersed adhesive compositions of the invention contain one or more low modulus crystallizing polyester polyurethane, preferably in the form of a water dispersion. The low modulus crystallizing polyester polyurethane provides the adhesives of the invention with high hot tack, a rapid crystallization rate resulting in high green strength, a high solids content (>50%), an extended bond range capability of at least 3 days, and moderate
McCarthy Arianne E.
Rayner Terry J.
3M Innovative Properties Company
Bardell Scott A.
Reddick Judy M.
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