CA1215598A

CA1215598A - Process for the preparation of a hydrophilic coating

Info

Publication number: CA1215598A
Application number: CA000425828A
Authority: CA
Inventors: Hans R. Lambert
Original assignee: Astra Meditec AB
Current assignee: Astra Meditec AB
Priority date: 1982-04-22
Filing date: 1983-04-14
Publication date: 1986-12-23
Also published as: GB2119283B; EP0093094B1; ES8405826A1; DE3362494D1; IE54235B1; DK159018B; AU556350B2; FI73702C; DK159018C; DK170883D0; JPH0339753B2; GB2119283A; JPS58193766A; DK170883A; FI73702B; NO155889C; EP0093094A1; AU1326683A; SE8202524L; FI831340L

Abstract

Abstract A process for coating a polymer surface with a hydrophilic coating with low friction in wet condition. The process comprises applying to the polymer surface a solution con-taining between 0.05 to 40 % of a compound which comprises at least two unreacted isocyanate groups per molecule, evaporating the solvent, applying a solution containing between 0.5 to 50 % of polyethylene oxide to the thus treated polymer surface and then evaporating the solvent of the last mentioned solution, and curing the coating at elevated temperature. The process is preferably carried out in the presence of a catalyst for the curing of iso-cyanate.

Description

5~
LM G98-] 1 ~3-(]3-15 Process for the preparation of a hydrophilic coating The present invention relates to a process for coating a polymer surface with a hydrophilic coating which has a low coefficient of friction when wetted with a water based liquid, as well as medical articles being coated with a hydrophilic coating according to said process.

Prior Art ~ritish patent No. 1 600 963 (Biosearch Medical Products Inc.) discloses a process for applying a hydrophilic coating which coating consists of an interpolymer of polyvinyl-pyrollidone and polyurethane, said coating having a much lower coefficient of friction in wet condition than in dry condition. Such coatings are, among other things, especially useful for medical instruments intended to be entered in body cavities, because the instrument gives a good hand grip in dry condition while simultaneously becoming very slippery when it gets in contact with body liquids or wet mucuous membranesJ and thus can be inserted easily without damage to the patient. The process disclosed in said Elritish patent ; has been shown to be useful for accomplishing such coatings, but is on the other hand too complicated for being suitable Z5 for large-scale production. The process described in Example 1 in the patent thus comprises not less than ten steps, whereby one of the steps takes 6 hours to carry through.
A further disadvantage with this known process is that cracks are often formed in the coating.
Disclosure of the invention The object of the invention is to provide a process -for the preparation oF a hydrophilic coating that has a much lower coefficient of friction in wet condition and which process S5~

is more simple and more rapid to carry out than the process disclosed in the above-mentioned British patent No. 1 600 963.
Further the process also gives a coating that is free from cracks. These objects of the invention have surprisingly been achieved by applying a solution containing between 0.05-40%
(weight/volume, that is kg/litre) of a compound containing at least two unreacted isocyanate groups per molecule to a polymer surface, evaporating the solvent, applying a solution of poly-ethylene oxide containing between 0.5 to 50~ (weight/volume) to the thus treated polymer surface and then evaporating the solvent of the last mentioned solution, and curing the coating at elevated temperature.
The invention is explained in detail in the following.
The process according to the invention can be used for coating many different types of polymer surfaces, such as latex rubber, other rubbers, polyvinylchloride, other vinyl polymers, polyurethanes, polyesters and polyacrylates. The process has been found to be especially useful for latex, polyvinylchloride and polyurethanes.
The process according to the invention comprises applying to a polymer surface a compound containing at least two unreacted isocyanate groups per molecule dissolved in a solvent, by dipping, spraying or the like and then evaporating the solvent preferably by air drying. This step forms a coating w th unreacted isocyanate groups on the polymer surface. Examples of isocyanate containing compounds that may be used are poly-isocyanates such as polymethylene polyphenyl isocyanate, 4,4'-diphenylmethane diisocyanate, and 2,4-toluene diisocyanate.
Prepolymers or other addition products of isocyanates and polyols are especially useful, for example prepolymers between ~ ;
~ - 2 -S5~3 toluene diisocyanate, or hexamethylene diisocyanate, and trimethylolpropane, or trimerized hexamethylene diisocyanate biuret. Such prepolymers are commercially a~ailable under the trade mark Desmodur (Bayer AG).

- 2a -'~ .',.. .. ~ . ' , ~ 5S98 - The solvent -for the isocyanate compound is preferably one that does not react with isocyanate. The preferred solvent is methylene chloride but it is also possible to use ethyl-acetate, acetone, chloroform, methyl ethyl ketone and ethylene dichloride, for example.

The isocyanate solution may advantageously contain between 0.5 to 10 % (weight/volume) of isocyanate compound, and may preferably contain between 1 to 6 % (weight/volume) of isocyanate compound. Generally, the solution need to be in contact with the surface only briefly, for example 5 to 60 seconds. In the case of coating of for example rubber latex it is desirable with a longer period, for example 1 to 100 minutes, to obtain a strong adherence. Another method to increase the adherence is to swell the polymer surface beforehand in a suitable solvent. A still further method is ; to choose a solvent for the isocyanate, such that the solvent in itself has the ability to swell or dissolve the polymer surface which is to be coated.
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_ ... _ _ . ... .
Following the evaporation of the solvent for the isocyanate from the polymer surface, the surface is coated with poly-ethylene oxide dissolved in a solvent, whereby a hydrophilic surface is obtained which subsequent to final curing of the isocyanate normally consists of a polyethylene oxide --polyurea interpolymer. The polyethylene oxide used should have a mean molecular weight of between 104 to 107, and the preferred mean molecular weight is about 10 . Poly-ethylene oxide having such a molecular weight is commercially available, for example under the trade name POLYOX~ (Union Carbide Corporation, U.S.A.). Examples of suitable solvents for polyethylene oxide that can be used are methylene chlo-ride (preferred), ethyl acetate, acetone, chloroform, methyl ethyl ketone and ethylene dichloride. The proportion of polyethylene oxide in the solution is preferably between SS~B
'1 0.5 to 10 % (weight/volume) and most preferred between 2 to 8 % (weight/volume). The polyethylene oxide in the solvent is applied by dipping, spraying or the like for a short period of time, for example during 5 to 50 seconds. After the polyethylene oxide solution has been applied to the coated surface, the solvent is evaporated preferably by air drying. The residual traces of solvent are removed at the curing of the coating which is preferably per-Formed at a temperature of 50 to 100C, in for example an oven, and during 5 to 30 minutes. All the other steps in the process may be performed at ambient temperature.

The purpose of the curing, which is advantageously conducted in the presence of a water-containing gas such as ambient air, is to bind the isocyanate compounds together to the formation of a stable non-reactive network that binds the hydrophilic polyethylene oxide. The isocyanate groups reacts with water at the curing and yields an amine which rapidly reacts with other isocyanate groups to the formation of a urea cross-link.

According to the invention it has surprisingly been found possible to simultaneously reduce the low friction of the hydrophilic surface, to improve the adherence of the coating, and to shorten the necessary reaction times and curing times, by using some additives to the solution of isocyanate and/or the solLtion of polyethylene oxide. Such a suitable additive comprises different known catalysts for isocyanate curing.
These catalysts may be dissolved in either the isocyanate solution or the polyethylene oxide solution but are preferably dissolved in the latter. Different types of amines are espe-cially useful, for example different diamines, but also for example triethylene diamine. Preferably, an aliphatic amine is employed which is volatilizable at the drying and curing temperatures used for the coating, and which furthermore is non-toxic. Examples of suitable amines are N,N'-diethyl-ethylendiamine, hexamethylendiamine, ethylendiamine, para-diaminobenzene, 1,3-propandiol-para-aminobenzoic acid di-~s~

esther, diaminobicyclo octane, and triethanolamine. Theproportion of catalyst in the polyethylene oxide solution is suitably between 0.1 to 50 % by weight of the amount of polyethylene oxide, preferably between 0.1 to 10 % by weight.
Some of the above-mentioned amines, particularly the diamines, can also react wi-th isocyanate and thereby contribute to the crDss-linking of the isocyanate compounds that give the desired strong adherence between the hydrophilic coatin~
and the polymer surface.
Furthermore, it has surprisingly been shown to be possible to reduce the low friction for the hydrophilic surface still ; further, by way of dissolving a polymer in the isocyanate solution. Examples of suitable polymers are polyesters, polyvinyl compounds such as polyvinylchloride or polyvinyl-acetate, polyurethaneS,polyisocyanates, or copolymers of these. These otherwise substantially inert polymers are supposed to give the surprisingly reduced friction at the surface mainly because they obstruct an undesired diffusion of not yet cross-linked isocyanate compounds out into the polyethylene oxide layer. A further reason for the low friction may be that the addition of a polymer enhance the elasticity of the coating. The proportion of dissolved poly-mer in the isocyanate solution is suitably oetween 0.5 to 20 % by weight of the solution, preferably between 2 to 10 %
by weight.

The obtained hydrophilic coating evidently contains an appreciable amount of partly freely movable polyethylene oxide chains. Thus it has been shown that the coating can complex-bind a substantial amount of elemental iodine (com~
pare Example 5 ), as is also the case with free polyethylene oxide. Such a iodine containing hydrophilic and antibacterial coating is advantageous for many medical uses, for examp]e for urinary catheters which are intended for insertion in the urethra for extended periods of time and which otherwiss is a common cause of infections. The iodine containing coating is suitably prepared by final dipping in a KI/I2-solution con-~2~ 8 taining at least 1 % by weight of iodine, followed by drying, possibly preceeded by rinsin~ in a solvent. -The invention is illustrated in detail in the following Examples.

. Example 1. A pentam~r o-F toluene diisocyanate of cyanurate type (named Desmodur IL; Bayer AG) was dissolved in methylene ,~
chloride to a concentration of 2 % (weight/volume). The solution also contained a minor amount of butyl acetate. A
urinary PVC catheter was dipped in this solution during ! 30 seconds. The catheter was allowed to dry at ambient tem-perature during 30 seconds, whereupon it was dipped in a solution of 6 % (weight/volume) polyethylene oxide (type WSRN10; Union Carbide) in methylene chloride during 5 seconds. The catheter was then allowed to dry at ambient temperature during 60 secondsJ and then during 20 minutes at 70C above a bowl filled with water. The catheter was finally allowed to cool to ambient temperature during 20 minutes whereupon it was rinsed in water. The catheter had a slippery and adhering surface.

Example 2. A solution containing 0.5 % (weight/volume) of the isocyanate Desmodur IL ~compare Example 1) and 5 %
(weight/volume) of a copolymer of PVC and polyvinylacetate (20 % vinylacetate/80 ~ PVC) named LONZA~CL 4520 in methylene chloride was prepared. A PVC-catheter was dipped in this solution during 15 seconds and was then dried a-t ambient temperature during 30 seconds, whereupon it was dipped in a solution containing 6 % (weight/volume) polyethylene oxide (type WSRN10; Union Carbide; approximate mean molecular weight lOO.OOD) and 0.23 ~ ~weight/volume) triethylendiamine in methylene chloride. The catheter was dried during 60 seconds at ambient temperature and then during 20 minutes at 70C above a bowl Filled with water. It was then allowed to cool and was finally rinsed in water. The catheter had a slippery and adhering surface.
~ Q~k 5~8 Example 3. A latex catheter was swelled in methylene chloride during 30 minutes. The ca-theter was then dried at ambient temperature during 60 seconds, and was then dipped during 30 seconds in a solution containing 6 %
(weight/volume) of Desmodur L2291 (a trimerized hexa-, ~ .
methylene diisocyanate of biuret type obtainable fromBayer-AG) in methylene chloride. The catheter was dried at ambient temperature during 60 seconds and was then dipped in a solution containing 6 % (weight/volume) poly-ethylene oxide (type WSRN10~ Union Carbide) in methylenechloride. The catheter was then dried during 60 seconds at ambient temperature and finally during 20 minutes at 70C above a bowl filled with water, Example 4. The inner of a two metre long hose of PVC
(inner diameter 3 mm; outer diameter 4.5 mm) was flushed with different solutions and drying agents in the following orders and periods of time:

5 % (weight/volume) ofDesmodur IL (compare Example 1) dis-solved in methylens chloride and during 30 seconds; gaseous nitrogene of ambient temperat~re during 30 seconds; 2.5 %
(weight/volume) of polyethylene oxide (type WSRN10, Union Carbide) dissolved in methylene chloride and during 10 seconds; gaseous nitrogene of ambient temperature during 60 seconds.

The hose was then placed in an oven and gaseous nitrogene was flushed through the hose during 20 minutes. The tem-perature of the oven was 70C. The nitrogene used was firstbubbled through water. Finally the hose was taken out from the oven and water was flushed through the hose during 1 hour. The inside of the thus treated hose had a hydrophilic coating.
Example 5. A urinary catheter of latex rubber was dipped during 30 seconds in a solution containing 5 % (weight/
volume) of Desmodur~IL (compare Example 1) in methylene e ~a~rl~

iSi~B

chloride. The catheter was then dried at ambient temperature durin~ 60 seconds and was then dipped in a solution con- -tainin~ 5 ~ (weight/volume) polyethylene oxide (~ype WSRN10) in methylene chloride. The Gatheter was dried durin~ 60 seconds at ambient temperature and was then cured during 20 minutes at 70C above a bowl of water.
-After coolin~ the catheter it was rinsed in water and wasthen dipped in a saturated water solution of potassium iodide bein~ saturated with elemental iodine. Finally the catheter was rinsed in a stream of water and was allowed to dry in ambient air. The catheter had a brown colour and chemical analysis showed that it contained iodine.

.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A process for placing on a polymer surface a hydro-philic coating which has a low coefficient of friction when wetted with a water based liquid comprising: applying to the polymer surface a solution containing between 0.05 to 40% (weight to volume) of a compound which comprises at least two unreacted isocyanate groups per molecule, evaporating the solvent, applying a solution containing between 0.5 to 50% (weight to volume) of polyethylene oxide to the thus treated polymer surface and then evaporating the solvent of the last mentioned solution, and curing the coating at elevated temperature.

2. A process according to claim 1 wherein the solution of polyethylene oxide or the solution of isocyanate contains a catalyst that accelerates the curing of the isocyanate.

3. A process according to claim 2 wherein the catalyst comprises an amine, preferable a diamine or triethylene diamine.

4. A process according to claims 1, 2 or 3 wherein the isocyanate solution contains a polymer intended to reduce the diffusion of isocyanate before the curing of the coating.

5. A process according to claims 1, 2 or 3 wherein the isocyanate solution contains a polymer intended to reduce the diffusion of isocyanate before the curing of the coating and the polymer in the isocyanate solution is selected from the group consisting of polyesters, polyvinyl compounds, poly-urethanes, polyisocyanates, or copolymers of these.

6. A process according to claim 1 wherein the concluding curing is performed in the presence of a water-containing gas.

7. A process according to claim 1 wherein the polymer surface to be coated comprises a polymer selected from the group consisting of latex, polyvinylchloride, and polyurethane.

8. A process according to claim 1 wherein the obtained hydrophilic coating is made antibacterial by treatment with iodine.

9. A medical article intended for insertion in the body wherein the article is provided with a hydrophilic coating prepared according to claims 1, 2 or 3.

10. A medical article intended for insertion in the body wherein the article is provided with a hydrophilic coating prepared according to the processes claimed in claims 1, 2 or 3 in which the isocyanate solution contains a polymer intended to reduce the diffusion of isocyanate before the curing of the coating.

11. A medical article intended for insertion in the body wherein the article is provided with a hydrophilic coating prepared according to the processes claimed in claims 1, 2 or 3 in which the isocyanate solution contains a polymer intended to reduce the diffusion of isocyanate before the curing of the coating and the polymer is selected from the group consist-ing of polyesters, polyvinyl compounds, polyurethanes, poly-isocyanates or copolymers of these.

12. A medical article intended for insertion in the body wherein the article is provided with a hydrophilic coating prepared according to the processes claimed in claims 6, 7 or 8.

13. A medical article comprising a catheter which is intended for insertion in the body wherein the article is provided with a hydrophilic coating prepared according to the processes claimed in claims 1, 2 or 3.

14. A medical article comprising a catheter which is intended for insertion in the body wherein the article is provided with a hydrophilic coating prepared according to the processes claimed in claims 1, 2 or 3 in which the isocyanate solution contains a polymer intended to reduce the diffusion of isocyanate before the curing of the coating.

15. A medical article comprising a catheter which is intended for insertion in the body wherein the article is provided with a hydrophilic coating prepared according to the processes claimed in claims 1, 2 or 3 in which the isocyanate solution contains a polymer intended to reduce the diffusion of isocyanate before the curing of the coating and the polymer is selected from the group consisting of polyesters, polyvinyl compounds, polyurethanes, polyisocyanates or copolymers of these.

16. A medical article comprising a catheter which is intended for insertion in the body wherein the article is provided with a hydrophilic coating prepared according to the processes claimed in claims 6, 7 or 8.