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
2001-10-30
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, C427S207100, C427S388400
Reexamination Certificate
active
06310125
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to adhesives and adhesive compositions, particularly to water-dispersed adhesives and adhesive compositions.
BACKGROUND OF THE INVENTION
A typical use of adhesives is for assembling articles made from different individual component parts. For example, an article may be composed of a core material that is sandwiched between a rigid outer material. The most common core materials are those that are porous and lightweight. Examples of such core materials include polystyrene and polyurethane foams and papers and metals in the form of a honeycomb mesh. Common rigid outer materials include metals such as cold rolled steel, galvanized steel, phosphate treated steel, stainless steel, and aluminum.
In a typical manufacturing process, an adhesive is applied to one or both surfaces of a core material and a rigid outer material and then pressed together under pressure. In addition, the bonded assembly may be required to meet certain performance tests. For example, the bonded assembly may be required to provide a substantial green tensile strength and a final tensile strength that is even higher.
In order to attempt to meet these requirements, adhesive formulators have provided water-based contact adhesives. In general, water-based contact adhesives are easy to use and are typically inexpensive. For example, water-based contact adhesives can be applied to substrates by spraying or roll coating. However, both surfaces of the substrates to be bonded must be coated to form an adhesive bond which limits production flexibility. Additionally, the surfaces must be joined in a relatively short period of time in order to form a bond. Moreover, once the parts have been joined together, the parts cannot easily be repositioned. Further, the coating of both substrates to be bonded, the types of substrates to be bonded, and the method of application of the contact adhesive can result in waste of adhesive. Finally, currently available water-based contact adhesives have not demonstrated adequate bond strength and temperature resistance for some applications.
Formulators have also provided water-based adhesives containing polyurethane dispersions. These adhesive compositions are typically applied to a substrate to be bonded, dried, and then bonded using heat and pressure. Such dispersions that contain dispersed polyurethanes that are primarily amorphous only possess one glass transition temperature (Tg) generally below 0° C. Such adhesives are not generally suitable for forming a thermal bond as their storage modulus (G′) over a measured temperature range tends to be relatively flat, necessitating higher temperatures to form a bond. Water dispersed adhesives containing carboxylated and sulfonated crystallizing polyester urethanes are known. Adhesives containing primarily crystallizing polyester urethanes may be relatively stiff or inflexible and typically have short open times, have limitations on drying temperatures, and have inadequate adhesion to metallic surfaces. Typically, such adhesive compositions are combined with an isocyanate to increase their thermal resistance.
SUMMARY OF THE INVENTION
In one aspect, the invention provides a water dispersed adhesive composition that comprises high modulus crystallizing polyurethane, polychloroprene, acrylic ester copolymer, a resin selected from the group consisting of thermosetting resins, thermoplastic resins, and combinations thereof, and a stabilizer system that is selected from the group consisting of branched primary amino alcohols; a combination of branched primary amino alcohol and carbodiimide; a combination of carbodiimide and dihydroxy metal compound; a combination of branched primary amino alcohol and dihydroxy metal compound; a combination of branched primary amino alcohol, carbodiimide, and magnesium oxide; a combination of magnesium oxide and carbodiimide; a combination of magnesium oxide and branched primary amino alcohol; a combination of dihydroxy metal compound, magnesium oxide, and branched primary amino alcohol; a combination of dihydroxy metal compound, magnesium oxide, and carbodiimide; and a combination of dihydroxy metal compound and magnesium oxide.
In preferred embodiments, the water dispersed adhesive compositions provide adhesives having high heat resistance, that is, can be formulated to maintain an adhesive bond up to temperatures of about 150° C. Preferably, the adhesive compositions of the invention provide 180 degree peel bond strengths of at least 18 pounds force/lineal inch (pli) (3.2 kN/m) to phosphate coated steel, and at least 16 pli (2.8 kN/m) to galvanized steel.
The term “dispersion” encompasses any form of solid dispersed in a liquid medium including, for example, latexes, emulsions, colloidal suspensions, and the like. 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 of the invention do not contain zinc oxide and are free from external plasticizers. The term “plasticizers” 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.
Other advantages of the adhesives formed from the adhesive compositions of the invention are that the adhesives bond to metals, may be roll coated, provides high green strength durable bonds, and can be formulated to maintain an adhesive bond, with heat resistance, up to temperatures of about 150° C.
The water-dispersed adhesive compositions of the invention can be easily applied to a substrate without the odor and handling issues of organic-solvent based adhesives and then dried to form a non-tacky or non-blocking adhesive (at 23° C.) that may be activated at a later time (up to about 24 hours) to form a strong, heat resistant bond.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Polychloroprene is present in the adhesives compositions at a level of from about 20 to about 285 parts per 100 parts high modulus crystallizing polyester polyurethane (as defined below), on a dry weight basis, hereinafter “phr polyurethane.” Preferably, polychloroprene is present in the adhesive compositions of the invention at a level of from about 20 to about 100 phr polyurethane, and more preferably from about 40 to about 70 phr polyurethane.
Acrylic ester copolymer is present in the adhesive compositions of the invention at a level of from about 1 to about 200 phr polyurethane, preferably from about 1 to about 50 phr polyurethane, and more preferably from about 2 to about 10 phr polyurethane.
If present, thermosetting resin may be present in the adhesive compositions of the invention at a level of from 1 to about 35 phr polyurethane, preferably from about 2 to about 15 phr polyurethane, and more preferably from about 5 to about 10 phr polyurethane.
If present, thermoplastic resin may be present in the adhesive compositions of the invention at a level of from about 5 to about 50 phr polyurethane, preferably from about 10 to about 40 phr polyurethane, and more preferably from about 20 to about 30 phr polyurethane.
If present, branched primary amino alcohol may be present in the adhesive compositions of the invention at a level of from about 0.5 to about 5, preferably about 2 to about 4, and more preferably about 2.5 to about 3.5 phr polyurethane.
If present, carbodiimide may be present in the adhesive compositions of the invention at a level of from about 0.5 to about 5, preferably about 2 to about 4, and more preferably about 2.5 to about 3.5 phr polyurethane. The ratio of branched primary amino alcohol to carbodiimide can range from 3:1 to 1:3 by weight. A preferred branched primary amino alcohol to carbodiimid
3M Innovative Properties Company
Bardell Scott A.
Rajguru U. K.
Seidleck James J.
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