Method of providing a substrate with a hydrophilic coating and substrates, particularly medical devices, provided with such coatings

A substrate such as a catheter or a guide wire is provided with a lubricous, hydrophilic abrasion-resistant coating by: a) coating said substrate with a first aqueous coating composition comprising an aqueous dispersion or emulsion of a polymer having organic acid functional groups and a polyfunctional crosslinking agent having functional groups capable of reacting with organic acid groups, and drying the coating to obtain a substantially water-insoluble coating layer having excess polyfunctional including functional groups being reactive with organic acid groups remaining, and b) contacting the dried coating layer obtained in a) with a second aqueous coating composition comprising an aqueous solution or dispersion of a hydrophilic polymer having organic acid functional groups, and drying the combined coating, the hydrophilic polymer thereby becoming bonded to the polymer of the first coating composition through the excess crosslinking agent. The drying can be carried out at ambient (room) temperature.

This invention relates to a method of providing a substrate, particularly a 
medical device or a part of such device intended for introduction in the 
human body, with a hydrophilic coating becoming lubricous when contacted 
with an aqueous fluid and substrates, particularly medical devices, 
provided with such hydrophilic coatings. 
It is generally known to provide substrates like medical devices or parts 
of such devices with a hydrophilic coating for the purpose of reducing the 
friction when the device is introduced in a humid environment like the 
human body. Such hydrophilic coatings have also been referred to as 
lubricous or "slippery" coatings. 
Catheters and other medical devices used for introduction in blood vessels, 
urethra, body conduits and the like and guide wires used with such devices 
are examples of medical devices which may be provided with hydrophilic 
coatings. Catheters for balloon angioplasty and biopsy are specific 
examples of such catheters. 
Substrates and medical articles or devices which it may be desirable to 
provide with a hydrophilic coating and methods for providing such 
substrates and articles or devices with hydrophilic coatings have been 
described in an abundant number of references, examples of which are 
mentioned in the following. 
U.S. Pat. No. 4,119,094 discloses a method of coating a substrate with a 
polyvinylpyrrolidone-polyurethane interpolymer. In the method, a 
polyisocyanate and a polyurethane in a solvent such as methyl ethyl ketone 
are applied to a substrate and the solvent evaporated after which 
polyvinylpyrrolidone in a solvent is applied to the treated substrate and 
the solvent evaporated. 
U.S. Pat. No. 5,091,205 discloses a method of providing a substrate with a 
hydrophilic lubricous coating in which the substrate is first contacted 
with a polyisocyanate solution to provide coupling, then contacted with a 
poly(carboxylic acid) solution to give a coating and then finally 
oven-dried. Methyl ethyl ketone is the preferred solvent for the 
polyisocyanates and dimethyl formamide for the poly(carboxylic acid). It 
is mentioned that the polyisocyanates can be emulsified to form an 
oil-in-water emulsion in which case, however, the reactive isocyanate 
groups need to be protected by suitable chemical groups. 
EP Patent No. 0 106 004 B1 discloses a method of forming a hydrophilic 
coating on a substrate by applying a coating from a solvent solution of a 
polyisocyanate to form a coupling coating followed by application of a 
solvent solution of a hydrophilic copolymer made from monomers selected 
from vinyl pyrrolidone, vinyl methyl ether or vinyl pyridine and a monomer 
containing active hydrogen which will react with isocyanate to form a 
covalent bond between the coupling coating and the hydrophilic copolymer. 
EP Patent No. 0 166 998 B1 discloses a method for treating the surface of a 
medical instrument. The surface is treated with a solution of a polymer 
having a reactive functional group in an organic solvent followed by 
treatment with a water-soluble polymer selected from maleic anhydride 
polymers, cellulosic polymers, polyethylene oxide polymers, and 
water-soluble nylons or derivatives thereof to covalently bond the 
reactive functional group with the water-soluble polymer after which the 
treated substrate is optionally contacted with water. 
U.S. Pat. No. 5,077,352 discloses a method in which a flexible, lubricous, 
organic polymeric coating is formed by applying a mixture of an 
isocyanate, a polyol and a poly(ethylene oxide) in a carrier liquid to a 
surface to be coated. The carrier liquid is removed and the mixture 
reacted to form a polyurethane coating with associated poly(ethylene 
oxide). Methylene chloride, chloroform, dichloroethane, acetonitrile, 
dichloroethylene, and methylene bromide are mentioned as suitable carrier 
liquids. 
International Patent Applications Nos. PCT/EP92/00918, PCT/EP92/00919, and 
PCT/DK92/00132 disclose methods for providing different medical devices 
having a polyurethane surface with a coating of a hydrophilic 
poly(meth)acrylamide. Before application of the hydrophilic coating the 
substrate is treated with a compound having functional groups capable of 
reacting with the polyurethane and the poly(meth)acrylamide, respectively, 
typically a di or higher functionality isocyanate in an organic solvent. 
A drawback of the methods according to the above-mentioned references is 
that the provision of the hydrophilic coating usually involves the use of 
organic solvents or toxic chemicals, for instance polyisocyanates, which 
can present environmental problems and/or health risks. In order to avoid 
the use of solvents some non-solvent methods have been developed. 
EP Patent Application No. 92100787.8, Publication No. EP 0 496 305 A2, 
discloses a method for preparing a shaped medical article provided with a 
lubricous coating. A coating composition comprising a blend of 
polyurethane and polyvinylpyrrolidone is co-extruded with a substrate 
polymer to give a shaped article having thereon a layer of the coating 
composition which becomes lubricous when contacted with water. 
U.S. Pat. No. 5,041,100 discloses a method for coating a substrate with a 
mixture of poly(ethylene oxide) and an aqueous dispersion of structural 
plastic material, e.g. polyurethane. As indicated in column 2, lines 
15-21, the poly(ethylene oxide) is admixed without crosslinking in 
intimately dispersed relation with the structural plastic material to 
provide a hydrophilic component to the system, which may leach to the 
surface, or which may be entrapped adjacent the surface to provide a 
hydrophilic character thereto and reduce friction, particularly when 
hydrated. 
The methods described in the above-mentioned references have the drawback 
that the interpolymer network physically attaching the hydrophilic polymer 
to the substrate often breaks down upon prolonged turbulent flow or 
soaking, and that the hydrophilic species can be washed away thereby 
rendering the article insufficiently lubricous. 
Finally, International Patent Application No. PCT/DK91/00163 discloses a 
method of providing a medical instrument with a hydrophilic, low-friction 
coating, which method comprises the steps of forming an inner layer from 
an aqueous polymer emulsion and an outer layer from an aqueous solution of 
a water-soluble hydrophilic polymer and curing the two layers 
simultaneously following application of the outer layer by heating to a 
temperature of above 100.degree. C. 
The above method eliminates the use of organic solvents and results in a 
coating which is strongly attached to the substrate. However, the use of 
curing temperatures above 100.degree. C. limits the use of the method, 
because many devices, for instance poly(ethylene terephthalate) (PET) 
balloon catheters cannot resist such temperatures. 
The present invention is directed to a method of providing a substrate, 
particularly a medical device or a part of such device intended for 
introduction in the human body, with a hydrophilic coating becoming 
lubricous when contacted with an aqueous fluid, which method among others 
makes it possible to coat devices which are sensitive to high processing 
temperatures. such as (PET) balloon catheters. The hydrophilic polymer 
becomes covalently bonded to the polymer of the first coating. 
Like the method according to PCT/DK91/00163, the method according to the 
invention uses aqueous coating compositions, but the method according to 
the present invention can be carried out at much lower temperatures, for 
instance at room temperature. 
As a further advantage the method according to the invention results in a 
very abrasion-resistant coating. 
The method according to the invention comprises 
a) coating a substrate with a first aqueous coating composition comprising 
an aqueous dispersion or emulsion of a polymer having organic acid 
functional groups and a polyfunctional crosslinking agent having 
functional groups being capable of reacting with organic acid groups, and 
drying the coating to obtain a substantially water-insoluble coating layer 
still including functional groups being reactive with organic acid groups, 
and 
b) contacting the dried coating layer obtained in a) with a second aqueous 
coating composition comprising an aqueous solution or dispersion of a 
hydrophilic polymer having organic acid functional groups, and drying the 
combined coating, the hydrophilic polymer thereby becoming bonded to the 
polymer of the first coating composition through the crosslinking agent. 
Included as an aspect of the present invention is a medical device intended 
for introduction to the body comprising a substrate suitable for 
introduction into the body, the surface of said substrate being coated 
with a cured polymeric composition, said composition comprising a first 
polymeric layer formed from at least a partial reaction of an aqueous 
dispersion or emulsion of a polymer having reactive organic acid 
functional groups present with a polyfunctional crosslinking agent capable 
of reacting with said organic acid functional groups, and a second 
hydrophilic polymeric layer having organic acid functional groups present 
and being capable of reacting with said crosslinking agent. As described 
further herein, the first polymeric layer is substantially cross-linked 
prior to the application of the second polymeric layer. Sufficient 
functional groups remain from the crosslinking agent to participate in 
covalent bonding with the second polymeric layer. This covalent bonding 
allows for excellent adhesion of the lubricous, hydrophilic layer to the 
first polymeric coating. The coating has excellent wear resistance, 
lubricity and can be applied in extremely thin layers so as not to affect 
the mechanical properties of the substrate to which it is applied. This is 
particularly important when the coating is to be applied to a thin-walled 
inflatable balloon on a balloon catheter used for angioplasty. 
Also contemplated as part of the present invention is a reactive film 
coating useful for bonding hydrophilic polymers having organic acid 
functional groups present, said film coating being the reaction product of 
an aqueous dispersion or emulsion of a polymer having organic acid 
functional groups and a polyfunctional crosslinking agent capable of 
reacting with said organic acid functional groups, whereby said reaction 
product still includes reactive functional groups from said polyfunctional 
crosslinking agent. This aspect of the invention is intended to cover that 
portion of the coating prior to further reaction with the hydrophilic, 
second coating which is applied to obtain lubricity. Thus, articles which 
have been coated only with the first coating and are prepared for the 
application of a hydrophilic coating capable of imparting lubricity when 
in contact with water is covered in this embodiment. 
A further aspect of the present invention includes a hydrophilic polymeric 
coating capable of become lubricous when in contact with an aqueous 
medium, said coating including at least two polymeric layers covalently 
bonded together to form a cross-linked network, said cross-linked network 
being the reaction product of: 
a) a first polymeric layer comprising an aqueous dispersion or emulsion of 
a polymer having organic acid functional groups and a polyfunctional 
crosslinking agent capable of reacting with said organic acid functional 
groups; and 
b) a second aqueous polymeric layer comprising an aqueous solution or 
dispersion of a hydrophilic polymer having organic acid functional groups. 
The hydrophilic polymer coating of the first polymeric layer may be 
selected from any number of polymers recited herein. Of particular 
preference, however, are the water-borne polyurethane polymers and 
polyacrylic acid polymers. The second polymeric layer may also be selected 
from a wide variety of polymers which can be covalently bonded to the 
first coating layer due to the presence of their organic acid 
functionality. Of particular preference are the polyacrylic acid polymers 
and the acrylamide-acrylic acid copolymers. 
As previously mentioned, medical devices which are at least partially 
coated with the coatings of the present invention have particular 
advantages over the prior art in that they can easily be inserted into the 
body with less frictional resistance due to the lubricous characteristics 
of the outer coating. Additionally, the adherence of the outer coating is 
improved over the prior art due to the covalent bonding which occurs 
between the two coating layers. As mentioned herein, the coating of 
angioplasty inflatable balloons which are an integral part of angioplasty 
balloon catheters is one specific application intended for the coatings of 
the present invention. Additionally, other medical devices such as guide 
wires and the like are contemplated. The devices need not necessarily be 
intended for use inside the body, and exterior uses are also contemplated. 
The present invention also contemplates a kit which includes as a first 
component an aqueous dispersion of a polymer having organic acid 
functionality, as a second component a polyfunctional crosslinking agent 
being reactive with said organic acid functionality of the first component 
and as a third component an aqueous solution or dispersion of a 
hydrophilic polymer having organic acid functionality and which when cured 
and placed in contact with water imparts lubricity. 
In the present context the term "organic acid group" is meant to include 
any groupings which contain an organic acidic ionizable hydrogen. Examples 
of functional groupings which contain organic acidic ionizable hydrogen 
are the carboxylic and sulfonic acid groups. The expression "organic acid 
functional groups" is meant to include any groups which function in a 
similar manner to organic acid groups under the reaction conditions, for 
instance metal salts of such acid groups, particularly alkali metal salts 
like lithium, sodium and potassium salts, and alkaline earth metal salts 
like calcium or magnesium salts, and quaternary amine salts of such acid 
groups, particularly quaternary ammonium salts. 
The polymer having organic acid functional groups, which is included in the 
first aqueous coating composition, will be selected duly paying regard to 
the nature of the substrate to be coated. Typically the polymer in the 
first coating composition will be selected from homo- and copolymers 
including vinylic monomer units, polyurethanes, epoxy resins and 
combinations thereof. The polymer in the first coating composition is 
preferably selected from polyurethanes, polyacrylates, polymethacrylates, 
polyisocrotonates, epoxy resins, acrylate-urethane copolymers and 
combinations thereof having organic acid functional groups. In a 
particularly preferred embodiment of the method according to the invention 
the polymer in the first coating composition is selected from homo- and 
copolymers having a substantial amount of organic acid functional groups 
in their structure, which may act as an internal emulsifier. A specific 
class of polyurethanes which may be used in the first coating composition 
are the so-called water-borne polyurethanes, among which are the so-called 
internally emulsified water-borne polyurethane containing carboxylic acid 
groups and/or sulfonic acid groups, optionally as salts of such groups, as 
internal emulsifiers are particularly preferred. 
Examples of water-borne polyurethanes are those supplied: under the 
tradename NeoRez by Zeneca Resins, for instance NeoRez-940, NeoRez-972, 
NeoRez-976 and NeoRez-981; under the tradename Sancure by Sanncor, for 
instance Sancure 2026, Sancure 2710, Sancure 1601 and Sancure 899; under 
the tradenames U21 and U21X by B. F. Goodrich; and under the tradenames 
Bayhydrol LS-2033, Bayhydrol LS-2100, Bayhydrol LS-2952 and Bayhydrol 
LS-2990 by Bayer AG. 
Another specific class of polymers which have shown particularly useful in 
the first coating composition are acrylate-urethane copolymers, for 
instance the acrylic urethane copolymer dispersions supplied under the 
tradenames NeoPac E-106, NeoPac E-121, NeoPac E-130 and NeoRez R-973 by 
Zeneca Resins. 
The concentration of the polymer in the first coating composition is 
usually from about 2 to about 60% by weight and preferably from about 5 to 
about 40% by weight calculated as solids of polymer compared to the total 
weight of the first coating composition. 
In addition to one or more polymers having organic acid functional groups, 
the first aqueous coating composition comprises one or more polyfunctional 
crosslinking agents having functional groups being capable of reacting 
with organic acid groups. Polyfunctional crosslinking agents having 
functional groups being capable of reacting with organic acid groups are 
known in the art. For instance such polyfunctional crosslinking agents 
have been used for external crosslinking of polyurethanes. 
Particularly preferred polyfunctional crosslinking agents for use in the 
method according to the invention are polyfunctional aziridines and 
polyfunctional carbodimides. 
Polyfunctional aziridines and polyfunctional carbodimides and their use as 
crosslinking agents are known in the art. 
The crosslinking agent supplied by Zeneca Resins under the tradename 
NeoCryl CX 100 and the crosslinking agent supplied by EIT Industries under 
the tradename XAMA-7 are specific examples of polyfunctional aziridine 
crosslinking agents which may be used in the method according to the 
invention, and the crosslinking agent supplied by Union Carbide under the 
tradename Ucarlink XL-29SE is a specific example of a polyfunctional 
carbodimide crosslinking agent which may be used in the method according 
to the invention. 
Among the polyfunctional aziridines useful include the trifunctional 
aziridine of the following formula: 
##STR1## 
The polyfunctional crosslinking agent is preferably a crosslinking agent 
having more than two functional groups per molecule. Furthermore, it 
should be noted that a combination of polyfunctional crosslinking agents 
may be used in the method according to the invention. 
The functional groups on the crosslinking agent serves at least two 
purposes. The first purpose is to crosslink the first polymeric coating. 
The second purpose is to participate in covalent bonding with the organic 
acid groups present in the second (hydrophilic) polymeric coating. As 
such, there must be sufficient functionality in the crosslinking agent to 
accomplish both purposes. That is, the amount of crosslinking agent used 
must be sufficient such that enough functional groups are present to 
substantially crosslink the first polymeric coating so that enough 
unreacted functional groups remain to covalently bond to the second 
hydrophilic layer. 
One indication that insufficient functionals from the crosslinking agent 
are present is the inadequate bonding of the second layer. This is 
evidenced by the lack of wear resistance and such coatings can be easily 
wiped off the substrate to which they are applied. 
The concentration of the crosslinking agent in the first coating 
composition is usually in the range from about 0.2 to about 30% by weight 
and preferably in the range from about 0.5 to about 20% by weight. 
As is known in the art the first aqueous coating composition may include 
other conventional additives like levelling agents, various stabilizers, 
pH adjustment agents, defoaming agents, cosolvents, etc. if compatible 
with the intended use of the coated substrate. 
The coating of the first aqueous coating composition is dried so as to 
obtain a substantially water-insoluble coating layer still including 
functional groups being reactive with organic acid groups. Hereafter, the 
obtained dried coating is contacted with a second aqueous coating 
composition comprising an aqueous solution or dispersion of a hydrophilic 
polymer having organic acid functional groups, after which the second 
coating is dried, the hydrophilic polymer thereby becoming bonded to the 
polymer of the first coating composition through the crosslinking agent. 
Hydrophilic polymers for use in hydrophilic lubricous coatings are known in 
the art. In the method according to the invention any hydrophilic polymer 
(homo- or copolymer or mixture of one or more of such polymers) may be 
used provided that it contains organic acid functional groups in its 
structure which can react with the polyfunctional crosslinking agent 
having functional groups being capable of reacting with organic acid 
groups to form a hydrophilic coating becoming lubricous when contacted 
with an aqueous fluid. 
The hydrophilic polymer may comprise monomer units from one or more 
monomers having organic acid functional groups. Preferred examples of such 
monomers include acrylic acid, methacrylic acid and isocrotonic acid. 
In addition to comprising monomer units from at least one monomer having 
organic acid functional groups, the hydrophilic polymer may contain 
monomer units from at least one hydrophilic monomer without any organic 
acid functional groups, such as vinylpyrrolidone and acrylamide. A 
preferred example of a copolymer for use in or as the hydrophilic polymer 
in the method according to the present invention is an acrylic 
acid-acrylamide copolymer. The acrylamide-acrylic acid copolymer supplied 
by Allied Colloids under the tradename Versicol WN 33 is a specific 
example of such a copolymer. 
The ability to become lubricous when hydrated is a critical aspect of the 
present invention. The degree of lubricity produced upon contact with 
aqueous medium will depend on a number of factors, including the type of 
hydrophilic polymer, its molecular weight, the exposure level to the 
aqueous medium, as well as the presence of agents which facilitate 
wetting. Among these, the molecular weight is the most important. The 
molecular weight range useful in the present invention will depend on the 
particular type of polymer chosen. The molecular weight of the hydrophilic 
polymer in the second coating composition will typically be in the range 
from about 100,000 to about 15 million, particularly from about 150,000 to 
about 10 million. Hydrophilic polymers having a molecular weight in the 
range from about 400,000 to about 10 million and particularly of 
approximately 7.5 million have been found particularly suitable for use in 
the method according to the invention. The aforementioned 
acrylamide-acrylic acid copolymer falls within this preferred molecular 
weight. 
The concentration of the hydrophilic polymer in the second coating 
composition will typically be from about 0.1 to 5% by weight, preferably 
from about 0.5 to about 3% by weight, calculated as solids of hydrophilic 
polymer compared to the total weight of the second coating composition. 
In a preferred embodiment of the method according to the invention the 
functional groups of the crosslinking agent are capable of reacting with 
the organic acid functional groups of the polymer in the first coating 
composition and the organic acid functional groups of the hydrophilic 
polymer at a temperature below 120.degree. C. and preferably at a 
temperature below 100.degree. C. The drying step for the second coating 
can be carried out at a temperature below 120.degree. C. and preferably at 
a temperature below 100.degree. C., although of course higher drying 
temperatures could be used if desired and compatible with the nature of 
the substrate to be coated. For instance a metal substrate could be dried 
at a higher temperature. 
However, the present invention is designed with the specific intent of 
being effective at relatively low temperatures and particularly at ambient 
or room temperature, to allow for use with heat sensitive substrates. In a 
further preferred embodiment of the method according to the invention the 
functional groups of the crosslinking agent are capable of reacting with 
the organic acid functional groups of the polymer in the first coating 
composition and the organic acid functional groups of the second coating 
(hydrophilic polymer) at a temperature in the range of 
10.degree.-70.degree. C., preferably at a temperature in the range of 
15.degree.-35.degree. C. Such reactivity of the crosslinking agent makes 
it possible to coat the substrate at a temperature in the range of 
10.degree.-70.degree. C. and preferably at a temperature in the range of 
15.degree.-35.degree. C., such as at room temperature, although of course 
higher drying temperatures can be used, if desired. 
The drying time will depend on the drying temperature, higher drying 
temperatures requiring shorter drying time and vice versa. However, it 
will be within the ordinary skill of a person skilled in the art to 
determine a suitable combination of drying temperatures and drying time 
for a specific coating. 
In many cases drying at about room temperature for about 12 hours will be 
adequate. 
Furthermore, it should be noticed that the functional groups of the 
crosslinking agent do not necessarily have to have the same reactivity 
towards the organic acid functional groups of the hydrophilic polymer and 
the organic acid functional groups of the first coating composition and 
that the drying conditions in a) and b), respectively, will be selected 
duly paying regard to said reactivities. 
The method according to the invention can be used for the coating of many 
different kinds of substrates. One field of use of particular interest is 
the coating of medical articles for use in or on the body, particularly 
catheters, guide wires or parts of such articles. 
Balloon catheters, and particularly balloon catheters for percutaneous 
angioplasty are delicate articles which have proven difficult to coat by 
known methods. An important part of a balloon catheter is the inflatable 
balloon which in a balloon catheter for percutaneous angioplasty can have 
a very thin wall thickness, i.e. on the order of about 20 .mu.m. In the 
condition in which the balloon catheter is introduced into a blood vessel 
the balloon is folded up into a multilayer construction. Therefore it is 
of great importance that a hydrophilic coating applied to the wall of such 
balloon minimize the increase in the wall thickness of the balloon. 
Furthermore, it is important that the balloon is made of a material which 
can be processed into a balloon of small wall thickness, still maintaining 
adequate strength and furthermore having the necessary biocompatibility. 
Polyethylene therephthalate (PET) possesses this combination of 
properties, but has been difficult to coat with a hydrophilic coating. 
However, in accordance with the present invention it has been disclosed 
that a PET balloon having a wall thickness of as small as about 20 .mu.m, 
can be effectively coated with a hydrophilic coating having a thickness of 
about 2-3 .mu.m without damaging the balloon, and provides the required 
lubricity. The present invention accomplishes this because the process can 
be carried out using aqueous coating compositions, as opposed to organic 
solvent based systems and drying takes place under mild conditions, e.g. 
simple air drying of the coating at room temperature. For instance, as 
previously mentioned the drying of the combined coatings can be carried 
out at room temperature for about 12 to about 24 hours. 
However, as previously mentioned the method according to the invention can 
be used for the coating of many different substrates including substrates 
selected from polymeric substrates, non-polymeric substrates and 
combinations thereof. 
For example, among the useful polymeric substrates include those selected 
from the group consisting of olefin polymers, particularly polyethylene, 
polypropylene, polyvinylchloride, polytetrafluoroethylene (PTFE), 
polyvinylacetate, and polystyrene; polyesters, particularly poly(ethylene 
terephthalate); polyurethanes; polyureas; silicone rubbers; polyamides, 
particularly nylons; polycarbonates; polyaldehydes; natural rubbers; 
polyether-ester copolymers; and styrene-butadiene copolymers. This list 
is, of course, non-limiting. 
In particular, the polymeric substrate can be selected from the group 
consisting of poly(ethylene terephthalate), polyurethanes, polyethylene, 
nylon 6, nylon 11 and polyether-ester copolymers. 
Examples of useful non-polymeric substrate include those selected from the 
group consisting of ceramics, metals, glasses and the like. 
Also, combinations of polymeric substrates and non-polymeric substrates as 
well as combinations of one or more polymeric substrates and/or one or 
more non-polymeric substrates can be coated by the method according to the 
invention. 
The invention also relates to a coated substrate as obtainable by the 
method according to the invention and a medical device, particularly a 
catheter or a guide wire provided with a coating as obtainable by the 
method according to the invention. 
A particularly preferred medical device according to the invention is a 
balloon catheter for percutaneous angioplasty having at least the balloon 
part provided with such coating.

The invention will be further illustrated in the following non-limiting 
examples representing presently preferred embodiments of the invention. 
EXAMPLE 1 
A first coating composition was prepared by adding the following 
ingredients successively to a glass beaker under proper agitation until 
thoroughly mixed. 
______________________________________ 
NeoRez R981: 250 ml 
Water: 250 ml 
0.5% Fluorad FC-129 stock solution: 
10 ml 
(prepared by diluting 1 ml Fluorad 
FC-129 in 100 ml of water) 
34% NH.sub.4 OH: 4 ml 
NeoCryl CX 100: 20 ml 
______________________________________ 
NeoRez R981 (from Zeneca Resins) is a polyester-based, aliphatic 
water-borne polyurethane containing carboxylic acid groups as internal 
emulsifier, which is stabilized by triethylamine (TEA) and has a solids 
content of 32% and a pH of 7.5-9.0 at 25.degree. C. It contains a 5.3% 
N-methyl-pyrrolidone as cosolvent. NeoCryl CX 100 (from Zeneca Resins) is 
a polyfunctional aziridine crosslinking agent. Fluorad FC-129 (from 3M) is 
added as a levelling agent. Ammonium hydroxide is used to adjust the pH of 
the solution. 
A second coating composition, as follows, was prepared: 
______________________________________ 
1.2% aqueous solution of Versicol WN23: 
400 ml 
______________________________________ 
The above solution was prepared by adding an appropriate amount of Versicol 
WN powder to water under agitation for several hours to obtain a clear 
homogeneous solution. Versicol WN23 (from Allied Colloids) is an acrylic 
acid-acrylamide copolymer having a molecular weight of 7.5.times.10.sup.6. 
A substrate was prepared by extruding a blend of two grades of 
polyether-ester block copolymer ARNITEL EM 740 and EM630 (from Akzo) with 
BaSO.sub.4, into a tube. The tube was dipped into the first coating 
composition prepared above and dried at ambient temperature (room 
temperature) for 40 minutes. Then the tube was dipped in the second 
coating composition and dried at ambient temperature over night. The 
coated surface showed very good lubricous effect when contacted with 
water. Furthermore, the coating had very good wear resistance and abrasion 
resistance, the coating being strongly retained on the surface even under 
tough force. 
EXAMPLE 2 
In the same manner as in Example 1, a first coating composition was 
prepared using the following ingredients: 
______________________________________ 
U21X: 250 ml 
Water: 100 ml 
NeoCryl CX 100: 10 ml 
______________________________________ 
U21X (from B. F. Goodrich) is a polyester-based, aliphatic polyurethane 
dispersion containing carboxylic acid groups as internal emulsifier and 
being stabilized by TEA. The dispersion has a solids content of about 30%, 
a pH of 8.5 and a viscosity of 75 cps. The dispersion includes 8.3% 
N-methylpyrrolidone as cosolvent. 
A second coating composition as follows was prepared in the same manner as 
in Example 1: 
1.2% Versicol WN23 aqueous solution 
A balloon catheter having a poly(ethylene terephthalate) (PET) balloon was 
coated with the above coating compositions in the following manner. The 
PET balloon was inflated and coated with the first coating composition by 
dipping and dried at ambient temperature for 30 minutes. Then the balloon 
was dipped in the second coating composition and dried at ambient 
temperature over night. The resultant dried coating was sterilized by 
electron beams at a dose of 2.times.25 KGray. 
The obtained coating showed excellent slipperiness and lubricity when 
contacted with saline. The wear resistance and the abrasion resistance of 
the coating was also excellent. 
EXAMPLE 3 
A first coating composition was prepared as described in Example 1 using 
the following ingredients: 
______________________________________ 
Bayhydrol LS-2033: 250 ml 
Water: 250 ml 
0.5 Fluorad FC-129 stock solution: 
10 ml 
34% NH.sub.4 OH: 4 ml 
NeoCryl CX 100: 20 ml 
______________________________________ 
Bayhydrol LS-2033 (from Bayer A. G.) is a water-borne polyurethane which is 
stabilized by sulfonate groups. The water-borne polyurethane as supplied 
has a pH of 6.5-7.5, and the sulfonate groups are in sodium salt form. The 
polyurethane has a solids content of 40%. The dispersion includes no 
cosolvent. 
A second coating composition was prepared as 25 described in Example 1 
using the following ingredients: 
______________________________________ 
Versicol WN23 solution: 
400 ml 1% (w/w) 
Versicol WN23 
NeoRez R960: 1.0 ml 
______________________________________ 
A polyurethane tube (Tecoflex EG-93A, from Themedics, Inc.) was dipped in 
the first coating composition and dried in an over at 60.degree. C. for 10 
minutes. Then the tube was dipped in the second coating composition, dried 
in an oven at 60.degree. C. for 10 minutes and dipped in the second 
coating composition once more, after which it was dried at ambient 
temperature over night. The coating showed excellent slipperiness and 
lubricity when contacted with water. 
EXAMPLE 4 
A glass slide was coated using the following coating compositions and the 
same coating procedures and drying conditions as in Example 1. 
First coating composition: 
______________________________________ 
NeoRez R-940: 100 ml 
NeoCryl CX 100: 4 ml 
______________________________________ 
NeoRez R-940 (from Zeneca Resins) is a polyether-based, aromatic 
water-borne polyurethane. 
Second coating composition: 
______________________________________ 
1.2% Versicol WN23 Aqueous solution: 
400 ml 
______________________________________ 
The coating showed excellent slipperiness and lubricity when contacted with 
water. 
EXAMPLE 5 
Using the same coating procedures as described in Example 1, a stainless 
steel substrate was coated with the following coating compositions. 
First coating composition: 
______________________________________ 
NeoPac E121: 250 ml 
Water: 100 ml 
34% NH.sub.4 OH: 
2 ml 
NeoCryl CX 100: 
16 ml 
______________________________________ 
Second coating composition: 
______________________________________ 
1% Versicol WN 23 aqueous solution: 
400 ml 
First coating composition: 
1.5 ml 
______________________________________ 
The resulting coating showed excellent slipperiness and lubricity when 
contacted with water. 
EXAMPLE 6 
Using the same coating procedures as described in Example 1, a PET 
substrate was coated with the following coating compositions: 
First coating composition: 
______________________________________ 
Bayhydrol LS 2033: 200 ml 
NeoRez R-940: 100 ml 
Triethylamine: 2 ml 
Water: 200 ml 
NeoCryl CX 100: 10 ml 
______________________________________ 
Second coating composition: 
______________________________________ 
0.8% Versicol WN23 aqueous solution: 
400 ml 
______________________________________ 
The resulting coating showed excellent slipperiness and lubricity when 
contacted with water. 
EXAMPLE 7 
A glass plate was coated with the following coating compositions as 
described in the following. 
First coating composition: 
______________________________________ 
Sancure 899: 200 ml 
NeoPac E121: 100 ml 
Acrysol TT-615: 1 ml 
(prediluted with equal weight of water) 
SAG 710: 1 ml 
34% NH.sub.4 OH: 4 ml 
______________________________________ 
Second coating composition: 
______________________________________ 
1% Versicol WN23 aqueous solution: 
400 ml 
______________________________________ 
The first coating composition was brushed onto the glass plate and dried at 
ambient temperature for 1 hour. Then the second coating composition was 
sprayed onto the precoated glass surface and dried at ambient temperature 
over night. The obtained coating showed excellent slipperiness and 
lubricity when contacted with water. 
Acrysol TT-615 is a thickener available from Rohm and Haas Company, and SAG 
710 is a defoaming agent available from OSI Specialties, Inc. 
EXAMPLE 8 
First coating composition: 
______________________________________ 
Sancure 899: 250 ml 
0.5% Fluorad FC-129 stock solution: 
10 ml 
34% NH.sub.4 OH: 4 ml 
Water: 200 ml 
Ucarlink XL-29SE: 40 ml 
______________________________________ 
Second coating composition: 
______________________________________ 
1% Versicol WN23 Aqueous solution: 
400 ml 
______________________________________ 
A balloon made from polyurethane (Impranil ELN, from Bayer A. G.) was 
dipped in the first coating composition and dried at ambient temperature 
for 40 minutes. Then the balloon was dipped in the second coating 
composition, dried at ambient temperature for 30 minutes and then dipped 
in the second coating composition once more. The coating was sterilized by 
EtO (ethylene oxide) sterilization. The coating showed excellent 
slipperiness and lubricity when contacted with water. 
Ucarlink XL-29SE is a polyfunctional carbodimide, available from Union 
Carbide. 
EXAMPLE 9 
A PET tube was coated with the following coating compositions as described 
in the following. 
First coating composition: 
______________________________________ 
NeoPac E121: 250 ml 
Water: 250 ml 
Ucarlink XL-29SE 40 ml 
______________________________________ 
Second coating composition: 
______________________________________ 
1% Versicol WN 23 aqueous solution: 
400 ml 
First coating composition: 
1 ml 
______________________________________ 
The PET tube was dipped in the first coating composition and air dried for 
30 minutes. Then the precoated tube was dipped in the second coating 
composition and air dried for 30 minutes followed by drying at 60.degree. 
C. for 24 hours. The coating showed excellent slipperiness and abrasion 
resistance when contacted with water. 
In the foregoing the invention has been described by means of specific 
embodiments, but it will be understood that various changes and 
modifications may be performed without deviating from the scope and spirit 
of the invention. 
NeoRez R-981; NeoRez R-940; NeoRez R-961; NeoRez R-972; NeoRez R-976; 
NeoRez R-973; NeoPac E-106; NeoPac E-130; NeoPac E-121; NeoCryl CX-100; 
Fluorad FC-129; U21; U21X; Versicol WN23; Bayhydrol LS-2033; Bayhydrol 
LS-2100; Bayhydrol LS-2952; Bayhydrol LS-2990; Sancure 899; Sancure 2710; 
Sancure 1601; Sancure 2026; Ucarlink XL-29SE; Acrysol TT-615 and SAG 710 
are trademarks which may be registered in one or more of the designated 
countries.