Stock material or miscellaneous articles – Composite – Of polyamidoester
Reexamination Certificate
1999-03-31
2001-11-13
Copenheaver, Blaine (Department: 1773)
Stock material or miscellaneous articles
Composite
Of polyamidoester
Reexamination Certificate
active
06316108
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to polyurethane latexes, processes for preparing them, polymers prepared therewith, and substrates coated therewith. This invention particularly relates to coating substrates having polar surfaces with polyurethane latexes.
Latex polymers are known to be useful in many applications such as paints, sealants, and films. Polyurethane latexes are less widely used due to inherent difficulties in preparing stable aqueous polyurethane latexes. For example, polyurethane formulation components, such as polyisocyanates can be reactive with water. Polyurethane prepolymers useful for forming latexes are often not low viscosity liquids at ambient conditions. These and other properties can cause polyurethane latexes to be unstable, that is to form a dispersion which separates from the continuous aqueous phase of the latex, which is often not desirable in an industrial venue.
Recently, there have been several advances in the art of preparing stable, organic solvent free, polyurethane latexes. For example, U.S. application Ser. No. 09/039,976 filed Mar. 16, 1998, the teachings of which published as WO 98/41554 on Sep. 24, 1998, discloses preparing such polyurethane latexes. U.S. application Ser No. 09/039,978 filed Mar. 16, 1998, now abandoned in favor of its divisional application, U.S. application Ser. No. 09/551,400 filed Apr. 19, 2000, discloses preparing carpets using polyurethane latexes. As these latexes become more available and widely used, it will be desirable to improve their performance, particularly in regard to physical properties.
It would be desirable in the art of coating substrates with polyurethane latexes to be able to coat substrates having polar surfaces with a polyurethane latex having good adhesion thereon. It would be particularly desirable if the polyurethane latex which has good adhesion on polar surfaces was an aqueous, organic solvent free, polyurethane latex.
SUMMARY OF THE INVENTION
In one aspect, the present invention is an article of manufacture comprising a substrate having a polar surface, and adherent thereto, a polyurethane polymer prepared from a latex herein: (A) the polyurethane latex is. prepared from a polyurethane repolymer which has a polymer backbone substantially free of ionic groups and is prepared from a prepolymer formulation which includes polyols having an average ethylene oxide content of less than 80 weight percent, (B) the prepolymer is chain extended with an aminoethyl ethanolamine (AEEA) chain extender, and (C) the prepolymer and latex are prepared in the substantial absence of an organic solvent.
In another aspect, the present invention is a process for preparing a latex coated substrate comprising applying a polyurethane latex to a polar surface of a substrate having a polar surface wherein: (A) the polyurethane latex is prepared from a polyurethane prepolymer which has a polymer backbone substantially free of ionic groups and is prepared from a prepolymer formulation which includes polyols having an average ethylene oxide content of less than 80 weight percent, (B) the prepolymer is chain extended with an AEEA chain extender, and (C) the prepolymer and latex are prepared in the substantial absence of an organic solvent.
In still an another aspect, the present invention is a polyurethane latex which can be used to prepare a polyurethane polymer having improved adhesion properties comprising a polyurethane latex wherein: (A) the polyurethane latex is prepared from a polyurethane prepolymer which has a polymer backbone substantially free of ionic groups and is prepared from a prepolymer formulation which includes polyols having an average ethylene oxide content of less than 80 weight percent, (B) the prepolymer is chain extended with an AEEA chain extender, and (C) the prepolymer and latex are prepared in the substantial absence of an organic solvent.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
In preparing embodiments of the present invention, a polyurethane latex is formed. For the purposes of the present invention, the term “polyurethane” is defined to include the compounds known in the art as “polyureas”. The terms polyurea and polyurethane are well known in the art of preparing polymers, but for clarity, these terms are defined as follows. A “polyurethane” is a polymer having a structure similar to that of a polymer prepared by reacting a polyisocyanate and a poly-alcohol. A “polyurea” is a polymer having a structure similar to that of a polymer prepared by reacting a polyisocyanate with a polyamine. It is further recognized in the art of preparing polyurethanes that either material can have some linkages other than the named primary linkage. For example, a polyurethane prepared using a base polyol but also an amine chain extender would have some urea linkages but would still be a polyurethane. Likewise a polyurea prepared using a base polyamine but also using a glycol chain extender would have some urethane linkages but would still be a polyurea, but may be referred to herein also as a polyurethane.
The polymers of the present invention are prepared by applying a latex to a substrate. The latex can be applied by means of painting or spraying. For purposes of the present invention, painting is defined as applying a material, such as a polyurethane latex, to a brush or other applicator, and then depositing the polyurethane latex on a substrate, or, in alternative, the material can be puddled or pooled on a substrate and then spread over the substrate using a brush or other spreading means. Also for the purposes of the present invention, spraying is defined as applying a material, such as a polyurethane latex, by atomizing the material and ejecting the atomized material onto the substrate.
Another process useful with the present invention for applying a polyurethane latex to a substrate is dipping. In a dipping process, a substrate is lowered into a pool of latex and then removed. The latex which is retained on the substrate can be allowed to dry as is or can be further spread to make a more even application. Parts of the substrate can be masked to avoid getting polyurethane latex on the entire surface of the dipped substrate.
Still another process for applying a latex to substrate useful with the present invention is application by means of a transfer process. In a transfer process, a polyurethane latex is applied to a material which has very little ability to adhere to the polymer which forms upon dehydration. This “transfer” material is brought into contact with another substrate which has a higher adhesive affinity for the polymer. The transfer material is removed and the polymer is retained on the substrate. While the above processes for applying a latex to a substrate are preferred, any process known to be useful to one of ordinary skill in the art for applying a polyurethane latex to a substrate can be used with the present invention.
The polyurethane latexes of the present invention have improved adhesion to polar surfaces. For the purposes of the present invention, a polar surface is one having a critical surface tension of wetting (CST) greater than 33 dynes/cm. Preferably the CST is from 33 to 2,000 dynes/cm. More preferably from 35 to 1,800 dynes/cm. Examples of materials having polar surfaces include, but are not limited to: steel, polyethylene terephthalate, polyvinyl chloride, polyurethane, nylon-6, polyvinylidene chloride, and polycarbonate. Examples of materials having nonpolar substrates include polyethylene, polypropylene and polytetrafluoroethylene.
After being applied, a polyurethane latex of the present invention is dried to produce a polymer. Any means of drying the polyurethane latex can be used which is known to be useful to those of ordinary skill in the art. For example, the polyurethane latex coating can be air dried at ambient conditions or it can be dried at elevated temperatures, optionally in reduced humidity or with forced air. The two considerations of choosing drying conditions for the present invention are 1) not to exceed the temperature tolerance of
Tabor Rick L.
Willkomm Wayne R.
Copenheaver Blaine
Paulraj Christopher
The Dow Chemical Company
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