Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2001-07-27
2004-07-13
Niland, Patrick D. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C427S372200, C427S385500, C428S423100, C524S589000
Reexamination Certificate
active
06762243
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a multilayer coating system comprising a thick, gel-like base layer and a topcoat of polyurethane coating, and their production and use (application).
2. Description of the Prior Art
In the automobile industry it is standard practice for, e.g., the instrument panel
to use an uncoated plastic material (cheap solution with poor optical and haptic properties and poor resistance to environmental influences),
to apply a composite structure based on polyurethane foam and coating, textile material or leather as decorative layer by means of adhesive bonding (good haptic properties, but high costs due to complicated production),
subsequently to coat the employed plastic materials, e.g., using a two-component polyurethane-based 50 &mgr;m thin soft-feel coating (average haptic properties, good resistance properties, average price).
This also applies as appropriate to the other areas of use of plastic materials that come into direct contact with human skin. The soft effect of the thin soft-feel coating layers can be enhanced only within certain limits (e.g. by increasing the layer thickness to 100 &mgr;m), and also the resistance properties and optical properties of the coating are generally impaired.
The composite structure based on carrier/foam/coating also has a number of disadvantages:
The production costs are high and accordingly such systems are expensive.
The light-fastness is often not adequate.
The use of plasticizers in the films contributes significantly to fogging.
Anhydrous gel compositions such as those described in EP-A 0 057 838 and EP-A 0 057 839 have become widely available on the market and are manufactured and used according to the processes described in these publications. These applications relate to anhydrous gel compositions, gel compositions with a depôt effect optionally containing active substances, based on a polyurethane matrix and high molecular weight polyols as dispersing agents and optionally active substances, as well as to a process for the production of the gel compositions, optionally in the presence of the active substances. Biocides, pharmaceuticals, ethereal oils, fragrances, coloring agents, cleaning agents, anti-aging agents, lubricants and antistatics, and other materials may be used as active substances. The gel compositions may be employed as casting or pouring compositions or as moldings containing active substances having a depôt effect of the active substances. These gels are used as such and are covered with films or textile materials in order to permit use as a block gel.
Water-based gels have been used for some years in many technical sectors (see for example R. L. Whistler, Industrial Gums, Academic Press, Inc., New York, 1973 and DE-A 2 347 299). A particularly interesting property of the gels is that they possess a high casting accuracy. This is utilized in order to duplicate moldings. In this case the body to be cast is recast with the gel-forming composition. The molding is removed after the gel formation. A gel mold is obtained whose cavity corresponds to the shape of the molding.
An agar-gel is used as duplicating composition, for example in the dental sector. Such compositions have a number of disadvantages however:
a) the gelling takes a long time and has to be carried out under specific process conditions,
b) the elasticity of the gel is not sufficiently high for the demolding of thin crosspieces and undercuts,
c) the dimensional stability is unsatisfactory, and
d) if the gel mold is kept in the open air the dimensions change even after a very short time as a result of evaporation of water.
Anhydrous casting compositions are also known, for example, based on silicone. They are produced by mixing a prepolymer with a small amount of crosslinking agent. The model to be cast is poured together with this reaction mixture and removed after the mixture has hardened. A mold is obtained having a cavity in which castings of the model can then be produced. Anhydrous casting compositions have the following disadvantages however:
a) too high a viscosity for the casting of very fine depressions and undercuts in the surface of the model, and
b) excessive reaction times—reducing the reaction time by increasing the amount of the crosslinking agent results in excessive shrinkage of the mold.
Gel compositions containing active substances with a depôt effect, in which the active substances are released to the surrounding medium over a period of weeks to months, are known for example from U.S. Pat. Nos. 3,822,238 and 3,975,350. Also, it is known from DE-A 25 21 265 that water-containing and/or alcohol-containing polyurethane-polyurea gels can be produced in the presence of fragrances.
Carrier materials based on water-containing gels are described, which may contain a very wide variety of agents, e.g. pharmaceuticals, biocides or fragrances. Such water-based gels have the disadvantage however that many agents, for example biocides, may be relatively rapidly decomposed due to the presence of the water and, thus, the time of effectiveness of these gels, i.e. the depôt effect, is greatly reduced. It is also known to incorporate solid and/or foamed high molecular weight polyurethanes as active substances (CH-A 289 915).
Such high molecular weight polyurethanes have the disadvantage, however, that a large proportion of the incorporated liquid agents remains in the polyurethane as a result of the universally high molecular weight structure and/or too high a proportion of rigid material, and are thus lost for the depôt effect. Solid active agents can be used only to a very limited extent; non-volatile solid substances do not migrate out and highly volatile solid substances can diffuse out only for a very short time and in very small amounts.
EP-A 0 057 838 and EP-A 57 839 describe gels based on polyols that have a high casting accuracy without suffering from the aforementioned disadvantages. These gels are obtained by reacting one or more higher functional, high molecular weight polyols in the presence of catalysts and optionally fillers and additives with organic diisocyanates and/or polyisocyanates at an isocyanate index of about 15-60. The term “isocyanate index” denotes the equivalent ratio (NCO/OH)×100. As has been found, elastic gels according to the invention that are synthesized from a covalently crosslinked polyurethane matrix and one or more polyols rigidly bound therein (i.e. without the danger of an interfering exudation) are obtained only if the isocyanate and polyol components reacting with one another have a certain minimum functionality and if the polyol or polyols are substantially free from fractions with an OH number of more than 112 or with a molecular weight below 800, preferably below 1000.
It was then also found that gel compositions with improved depôt effect, uniform release of active substances, high active substance concentrations, good stability of the active substance additives and good migration ability of the active substances are obtained if active substances are dissolved or dispersed, as additives, in high molecular weight polyols in the polyurethane-forming reaction, and diisocyanates and/or polyisocyanates as well as catalysts and optionally conventional additives are mixed in.
The advantages of these gel compositions is that a high proportion of high molecular weight polyols is present in the only partially crosslinked polyurethane matrix, which permits and regulates the migration and release of the active substances to the outside.
The disadvantage however is the surface of these gels, which is too rubbery and therefore sensitive to dirt, and does not have a good feel (is too tacky) and accordingly has unsatisfactory haptic properties. Either a film or textile material is therefore applied as protective layer. The films are also necessary in order to be able to handle the gel at all. Initially, this is expensive and also permits only a restricted use, or even no use at all of the gel in various applications where this film inte
Kobusch Claus
Küttner Wolfram
Stender Adolf
Bayer Aktiengesellschaft
Gil Joseph C.
Matz Gary F.
Niland Patrick D.
Roy Thomas W.
LandOfFree
Multilayer coating systems containing a gel-like base 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 Multilayer coating systems containing a gel-like base layer..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Multilayer coating systems containing a gel-like base layer... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3222737