Stock material or miscellaneous articles – Composite – Of polyamidoester
Reexamination Certificate
1999-09-14
2002-05-07
Copenheaver, Blaine (Department: 1773)
Stock material or miscellaneous articles
Composite
Of polyamidoester
C428S332000, C428S354000, C428S423100, C428S424200, C428S424700
Reexamination Certificate
active
06383644
ABSTRACT:
1. FIELD OF THE INVENTION
The present invention relates to a cross-linked polyurethane composition and a multilayer sheet comprising a polymeric film and a cross-linked polyurethane layer. The multilayer sheet can be used to protect a surface and can in particular be used to protect a car body. Accordingly, the present invention also relates to an automobile of which at least a part of the body is protected by the multilayer sheet. The invention also relates to a method for making the multilayer sheet.
2. BACKGROUND OF THE INVENTION
Polyurethane coatings are well known as protective coatings on various substrates to provide resistance to environmental weathering, chemical exposure, heat and abrasion. Polyurethanes are generally optically transparent and have found application in the protection of articles that have a variety of uses including both interior and exterior applications. Polyurethane coatings have further been used to cover and protect a base substrate having indicia or other decorative features thereon. Such decorative articles may have interior as well as exterior uses.
For example, WO 94/13465 describes a polyurethane based protective layer for protecting an embossed multilayer film. It is taught that a surface layer containing the reaction product of an aliphatic diisocyanate and a polyester polyol, polycarbonate polyol or polyacrylic polyol provides a good protection for interior as well as exterior uses. It is further disclosed that the polyurethane-based protective surface layer can be cross-linked or uncross-linked and can be solvent borne as well as aqueous borne.
WO 94/13496 discloses a multilayer graphic article that comprises a substrate, at least one color layer disposed thereon and a protective surface layer. The protective surface layer may comprise a polyurethane obtained from the reaction of an aromatic diisocyanate and a polyether polyol or a polyurethane obtained from the reaction of an aliphatic diisocyanate and a polyester polyol, polycarbonate polyol or polyacrylic polyol.
WO 93/24551 discloses that aqueous polyurethane dispersions can be used to produce a coating on various substrates. It is further mentioned that the they may be used for the provision of e.g. protective or decorative coatings since polyurethanes, depending on their composition, can possess many desirable properties such as good chemical resistance, water resistance, solvent resistance, toughness, abrasion resistance and durability. WO 93/24551 further discloses that polycarbonate polyol based polyurethanes can provide high performance aqueous polyurethane dispersions in terms of chemical, water, solvent and stain resistance of coatings derived therefrom. However such polycarbonate polyols are said to be expensive and the supply would not always be guaranteed.
Polyurethane protective coatings have been used on conformable films to protect parts of the body of an automobile. For example, the body of a car may need to be protected near the trunk where the body may be prone to damaging due to loading and unloading of articles. A fully satisfactory protective coating for this application has not yet been found despite the many protective coatings known in the art. Desirable properties for such a protective coating include good optical transparency, high weatherability, high heat resistance, high chemical resistance, high solvent resistance, high water resistance and high abrasion resistance. Furthermore, the protective coating desirably also has a good flexibility and can preferably be pigmented with dyes to obtain a colored protective layer without however substantially impairing the other desirable properties of the protective layer.
3. SUMMARY OF THE INVENTION
The present invention provides a multilayer sheet comprising a polymeric film having on a first major side a cross-linked polyurethane layer, the major part of said cross-linked polyurethane layer comprising a polycarbonate based polyurethane containing acid groups and cross-linked with a cross-linker, the polycarbonate based polyurethane comprising the reaction product of a polycarbonate polyol or a polycarbonate polyamine and an aliphatic polyisocyanate and the uncross-linked polycarbonate based polyurethane having a Koenig hardness of at least 150 seconds.
The multilayer sheet of the present invention has good abrasion and scratch resistance, high heat, solvent and weathering, resistance. Moreover, multilayer sheets with excellent optical properties such as clarity and transparency can be provided. Also, the polyurethane coating can be colored to provide colored versions of the multilayer sheets without substantially impairing the other desirable properties of the sheet. The multilayer sheets are useful in a variety of applications including both indoor as well as outdoor applications and they can be readily converted.
The present invention also provides a method of making a multilayer sheet comprising:
(i) coating a coating composition comprising a polycarbonate based polyurethane containing acid groups and a cross-linker on a major side of a polymeric film, and
(ii) cross-linking the thus obtained coating,
wherein the polycarbonate based polyurethane comprises the reaction product of a polycarbonate polyol or a polycarbonate polyamine and an aliphatic polyisocyanate and the uncross-linked polycarbonate based polyurethane having a Koenig hardness of at least 150 seconds.
The present invention further provides a cross-linked polyurethane composition comprising a polycarbonate based polyurethane containing acid groups and cross-linked with a cross-linker, the polycarbonate based polyurethane comprising the reaction product of a polycarbonate polyol or a polycarbonate polyamine and an aliphatic polyisocyanate and the cross-linked polycarbonate based polyurethane having a Koenig hardness of at least 150 seconds.
4. DETAILED DESCRIPTION OF THE INVENTION
The cross-linked polyurethane layer of the multilayer sheet of the present invention comprises a major amount of a cross-linked polycarbonate based polyurethane derived from the reaction of a polycarbonate polyol or a polycarbonate polyamine and an aliphatic polyisocyanate, preferably an aliphatic diisocyanate. The polycarbonate-based polyurethane further contains acid groups, preferably carboxylic acid groups, that provide the necessary cross-linking sites to the polyurethane. Preferably, the polycarbonate-based polyurethane has an acid number of at least 15 mg KOH/g and more preferably at least 18 mg KOH/g.
The polycarbonate-based polyurethane of the polyurethane layer should have a Koenig hardness of at least 150 seconds, preferably at least 175 seconds and more preferably at least 200 seconds. It has been found that if the polycarbonate-based polyurethane does not meet the Koenig hardness, the desired chemical and heat resistance as well as the desired abrasion resistance could not be achieved. It has further been found that other polyurethanes, e.g. polyester based polyurethanes, although meeting the Koenig hardness requirement of at least 150 seconds also fail to yield a protective layer that has the desired chemical and heat resistance as well as the desired abrasion resistance.
Although it is possible to blend the polycarbonate based polyurethane with other polyurethanes such as for example polyurethanes based on polyether or polyester polyols or polycarbonate based polyurethanes with a lower Koenig hardness than 150 seconds, the cross-linked polycarbonate based polyurethane should form the major part of the polyurethane layer. In accordance with the present invention, “major part” means at least 60% by weight. Preferably, the cross-linked polycarbonate polyurethane constitutes at least 80% by weight and more preferably at least 90% by weight of the total weight of the polyurethane layer. The best results can be achieved when the cross-linked polycarbonate based polyurethane constitutes about 100% by weight of the polyurethane layer.
The polycarbonate-based polyurethane is preferably an aqueous borne dispersion. Aqueous borne dispersions of polycarbonate based pol
Copenheaver Blaine
Knecht III Harold C.
Paulraj Christopher
Szymanski Brian E.
LandOfFree
Multi-layer sheet comprising a protective polyurethane layer does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Multi-layer sheet comprising a protective polyurethane layer, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Multi-layer sheet comprising a protective polyurethane layer will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2847562