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
2001-10-23
Seidleck, James J. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S175000, C524S204000, C524S217000
Reexamination Certificate
active
06306942
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 350° F. (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-based contact adhesives containing polychloroprene typically have a short open time, for example, not more than about 4 hours. Such water-based adhesives also tend to release chlorine over time which can be detrimental to the fabric bonded to the foam core. Additionally, some contact-adhesives are fast breaking dispersions which require immediate bond formation after application and may require moderate pressure (>3 psi (>0.14 kPa)) to effect a bond. Water-based contact adhesives also tend to exhibit auto adhesion, which prevents stacking of adhesive-coated parts.
SUMMARY OF THE INVENTION
In one aspect, the present invention provides adhesive compositions which comprise low temperature thermally activatable water-dispersed adhesive composition comprising low modulus crystallizing polyester polyurethane, acrylic ester copolymer, thermoplastic resin selected from the group consisting of terpene-phenolics, resin esters, acrylate-acrylonitrile copolymers, acrylate-styrene-acrylonitrile terpolymers, and combinations thereof, 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 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, latexes, 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 thermally activatable adhesive” means adhesives of the invention that are capable of bonding substrates at a bondline temperature of as low as 109° F. (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 68° F. (20° C.) as by 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.
Adhesives of the invention after coating onto a substrate are also non-blocking.
Adhesives of the invention also have a long open time, that is, the adhesives of the invention can be bonded more than 24 hours after drying (non-blocking). Adhesives of the invention can also be bonded at low pressures, that is, pressures on the order of 1-3 psi (0.048-0.14 kPa) are required to effect a bond having adequate strength.
Other advantages of the adhesive compositions of the invention include the adhesive compositions are sprayable, they provide high green strength environmentally resistant bonds, 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, thermoplastic resin, hydrophobically-modified associative polyurethane, 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 2 to about 15 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 4 to about 12 phr urethane and more preferably present in an amount of from about 6 to about 10 phr urethane.
Thermoplastic resin is present in the adhesive compositions of the invention in an amount of from about 10 to about 30, preferably from about 15 to about 25, and more preferably from about 18 to about 22 phr urethane.
Hydrophobically-modified associative polyurethane is present in the adhesive compositions of the invention in an amount of from about 0.05 to about 3, preferably from about 0.05 to about 2.0, and more preferably from about 0.05 to about 1.0 phr urethane.
The adhesive compositions of the invention contain a stabilizer system. The stabilizer system comprises 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 1.0 to about 3.0, preferably from about 1.4 to about 2.4, more preferably from about 1.6 to 2.0 phr urethane. Branched primary amino alcohol is present in the adhesive compositions of the invention in an amount from about 1.0 to about 3.0, preferably from about 1.4 to about 2.4, more preferably from about 1.6 to 2.0 phr urethane. Generally, the ratio of carbodiimide to branched primary amino alcohol ranges from about 0.5 to 1 to about 1 to 0.5 by weight with a ratio of about 1 to 1 preferred.
If present, antioxidant is provided in the adhesive composition of the invention in an amount of from about 1.0 to about 3.0, preferably about 1.4 to about 2.5, more preferably about 1.6 to about 2.2 phr urethane.
The adhesive compositions of the invention contain one or more low modulus crystallizing polyester polyurethanes, 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 (50-60%), an extended bond range capability (up to four days), and moderate heat resistance. The low modulus crystallizing polyester polyurethane can either be carboxylated or sulfonated, but is preferably carboxylated. Low modulus crystallizing polyester polyurethanes can be generally made by methods described in PCT Publication WO 99/26993. Useful low modulus crystallizing polye
McCarthy Arianne E.
Rayner Terry J.
3M Innovative Properties Company
Bardell Scott A.
Rajguru U. K.
Seidleck James J.
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