Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
1999-04-09
2001-04-24
Niland, Patrick D. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C156S325000, C156S327000, C156S330000, C156S331400, C524S589000, C524S590000, C525S403000, C525S440030, C528S044000, C528S065000, C528S066000, C528S080000, C528S083000, C528S084000, C528S085000
Reexamination Certificate
active
06221978
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a moisture curable polyurethane hot melt adhesive and to a method of bonding substrates using the adhesive. In particular, this invention relates to a one component moisture curable polyurethane hot melt adhesive useful for bonding low surface energy substrates such as difficult-to-bond acrylonitrile-butadiene-styrene (ABS) substrates.
Moisture curable polyurethane hot melt adhesives are substantially solvent-free solids at room temperature that bond after application in the form of their melts by cooling and curing by the chemical reaction of isocyanate groups with moisture. Upon curing, the molecule size increases and the adhesive obtains its final characteristics.
Although suitable for many applications, moisture curable polyurethane hot melt adhesives have demonstrated limited ability to bond to certain low surface energy substrates, in particular difficult-to-bond ABS. ABS polymers are elastomeric and thermoplastic composites that exhibit excellent toughness. This property allows ABS to be used in a variety of applications making it one of the largest selling thermoplastics. A more complete description of the properties of ABS may be found in the
Encyclopedia of Polymer Science and Engineering,
Vol. 1:388-426 (Wiley, 1985).
Because of differences in its composition and production, not all grades of ABS are alike. While some ABS substrates are relatively easy to bond with moisture curable polyurethane hot melt adhesives, those skilled in the art generally recognize that many ABS substrates, referred to herein as difficult-to-bond ABS, are a challenge for polyurethane hot melt adhesives. For example, ABS substrates sold by Spartech Plastics, La Mirada, Calif. and Gage Plastics, Lake Oswego, Oreg. cannot be bonded with conventional moisture curable polyurethane hot melt adhesives.
While the reason for this shortcoming is not entirely clear, it is believed that the low surface energy of Spartech or Gage ABS renders it extremely difficult to bond with conventional polyurethane hot melt adhesives. Another possibility is that oil, mold release agent, and other possibly low molecular weight contaminants which may be used in the production process of ABS contribute to the difficulty of bonding ABS with polyurethane hot melt adhesives.
Thus, a moisture curable polyurethane hot melt adhesive that bonds to low surface energy substrates such as difficult-to-bond ABS, polyethylene, polypropylene, aluminum, and steel, as well as other substrates such as fiber-reinforced plastic, plywood, paper board, and the like, is highly desired.
SUMMARY OF THE INVENTION
It has surprisingly been discovered that moisture curable polyurethane hot melt adhesives derived from polyester polyols obtained from the reaction of diacid and diol, wherein the diacid comprises at least one aromatic diacid which is selected from the group consisting of isophthalic acid and terephthalic acid, bond well to low surface energy substrates such as difficult-to-bond ABS and corrugated polypropylene. In contrast, moisture curable polyurethane hot melt adhesives containing polyester polyols derived from the reaction product of diacid and diol, wherein the diacid comprises phthalic acid or derivatives thereof, tend to bond poorly to low surface energy substrates. The reason(s) for this are not presently understood. The inventors have discovered that the substantial exclusion of phthalic acid from the diacid utilized to fabricate the polyester polyol results in a moisture curable polyurethane hot melt adhesive that is versatile and can be used to bond a wide variety of substrate materials including fiber-reinforced plastic, plywood, paper board, and the like, and demonstrates substantially improved adhesion to low surface energy substrates such as difficult-to-bond ABS, polyethylene, polypropylene, aluminum, and steel. Accordingly, this invention relates to a moisture curable polyurethane hot melt adhesive composition which comprises a polyurethane prepolymer which is the reaction product of a polyol component and a polyisocyanate component, said polyol component comprising a polyester polyol which is the reaction product of diacid and diol, said diacid comprising at least one aromatic diacid and optionally co-monomer diacid(s), with the proviso that said diacid is substantially free of phthalic acid or derivatives thereof. This invention also relates to a method of bonding a substrate such as difficult-to-bond ABS or corrugated polypropylene, which comprises applying to a surface of such substrate the moisture curable polyurethane hot melt adhesive of this invention.
In accordance with preferred embodiments, the polyol component present in the moisture curable hot melt adhesive further comprises a crystalline polyester polyol component to improve green strength, a flexible polyol component to improve low temperature adhesion, an amorphous polyester polyol component to improve bonding to polar substrates, and/or an epoxy resin to improve adhesion to steel, aluminum, polyethylene, and polypropylene.
The phrase “substantially free” as applied to diacid(s) utilized in the preparation of polyester polyol shall be understood to refer to the possibility that minor amounts of o-phthalic acid or derivatives thereof may be present in technical grades of aromatic diacids, in particular, isophthalic acid and terephthalic acid. Such amounts are believed to represent not more than about 10 weight percent of the technical grades of such aromatic diacids. The use of such technical grades is accordingly within the scope of the invention.
The term “phthalic acid” as utilized herein shall be understood to mean ortho-phthalic acid and derivatives, e.g., the anhydride, thereof.
The term “diacid” as utilized herein shall be understood to include derivatives thereof including the anhydride, halides, and alkyl esters thereof.
The phrase “low surface energy” as utilized herein shall be understood to mean a substrate possessing a surface energy of less than 38 dyne as determined using AccuDyne® test marker pens from Diversified Enterprises, Claremont, N.H.
Other than in the examples, or where otherwise indicated, all numbers expressing quantities of ingredients or reaction conditions used herein are to be understood as modified in all instances by the term “about”.
REFERENCES:
patent: 4206299 (1980-06-01), Yamazaki et al.
patent: 4503189 (1985-03-01), Igarashi et al.
patent: 4843119 (1989-06-01), Schapira et al.
patent: 5019638 (1991-05-01), Müller et al.
patent: 5034453 (1991-07-01), Takada et al.
patent: 5115073 (1992-05-01), Meckel et al.
patent: 5166300 (1992-11-01), Rumon et al.
patent: 5232996 (1993-08-01), Shah et al.
patent: 5599895 (1997-02-01), Heider
patent: 5721311 (1998-02-01), Oien
patent: 5731090 (1998-03-01), Chen
patent: 5827926 (1998-10-01), Shimizu
patent: 5869593 (1999-02-01), Helmeke et al.
patent: 5880167 (1999-03-01), Krebs et al.
Technical Information,RUCO Polymer Corporation, Apr. 1984, 1 pg.
Rubinate® 44 Product Description,ICI Polyurethanes, Jan. 1993, 1 pg.
The Rucoflex Polyester Selector Guide,RUCO Polymer Corporation, May 1995, 9 pgs.
Fomrez® Polyester Polyols,2 pgs. (Publication Date Unknown).
Dynacoll® 7000 Copolyesters,Hüls, 10 pgs. (Publication Date Unknown).
Product Information,Dynacoll 7350-7110, Hüls, 12 pgs., May 1990.
Cain John T.
Heucher Reimar
Li Yingjie
Harper Stephen D.
Henkel Corporation
Jaeschke Wayne C.
Niland Patrick D.
LandOfFree
Moisture curable hot melt adhesive and method for bonding... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Moisture curable hot melt adhesive and method for bonding..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Moisture curable hot melt adhesive and method for bonding... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2547061