FR2612120A1 - HYDROPHILIC COATING AND COATED SUBSTRATE - Google Patents

Abstract

THE INVENTION RELATES TO A MANUFACTURING ARTICLE HAVING A COATING WHICH INFLATES IN THE PRESENCE OF AQUEOUS MEDIA WITH A CONCOMITANT REDUCTION OF THE FRICTION COEFFICIENT. ACCORDING TO THE INVENTION, AN ADHESIVE COATING CONTAINING FREE ISOCYANATE GROUPS IS APPLIED TO A SUBSTRATE; A SECOND COATING OF A VINYL COPOLYMER HAVING A MAJOR POLYMERIC COMPONENT DERIVED FROM N-VINYLPYRROLIDONE AND A MINOR POLYMERIC COMPONENT DERIVED FROM A MONOMER WITH ETHYLPYLPYRROLIDONE INSATURATION DERIVED FROM AN ETHYLPYLPYRROLIDONE AND A MINOR POLYMERIC COMPONENT DERIVED FROM A MONOMER WITH ETHYLPYLPYRROLIDONE INSATURATION DERIVED FROM AN ETHYLPYLPYLPYRROLIDONE UNSATURATED MONOMER AND REHYAUFFENIC SUBSTATURATED HYHYLASTRANT AND REHYAUDENIC SUBSTATURATED MONOMER FROM REHYAUFFENIC AND REHYAUDENIC SUBSTATURATED HYHYLPYLPYRROLIDONE AND SUBSTRATE MONOMER FROM THE REHYAUFFENIC REQUIRED COATINGS. TO REACTION BETWEEN ACTIVE HYDROGENS AND ISOCYANATE GROUPS AND THUS CHEMICALLY BINDING THE COPOLYMER COATING TO THE ADHERENT ISOCYANATE COATING. THE INVENTION APPLIES IN PARTICULAR TO THE PRODUCTION OF CATHETERS, DEVICES FORMING IMPLANTS, CONTACT LENSES, CHAMBERS FOR PERISTALTIC PUMPS, CONDOMS, ARTERIOVENOUS BRIDGES, GASTRO-ENTERAL FEEDING TUBES OR OF ENDOTRACHEAL TUBES.

Description

The present invention relates to hydrophilic coatings having a

lower coefficient of friction in the wet state than in the dry state. The invention also relates to a process for preparing such coatings and to the coated articles produced therefrom. Hydrophilic coatings which absorb aqueous fluids to form hydrated coatings having

a lower coefficient of friction than coatings

dry precursors are known. Such coatings have various uses, in particular in the field of medicine. For example, coatings can. be applied to devices or instruments intended for insertion into tissues or cavities of the body. On contact with bodily fluids or moist mucous membranes, the coatings undergo hydration, becoming very

slippery thanks to the reduction of the friction coefficient

is lying. In this condition, coated objects can

be easily inserted or removed from the body without damaging it

mediate or cause discomfort to the patient. However, when dry, coated objects are not slippery and can easily be gripped by hand and generally

handled in a normally practical manner.

An example of the above hydrophilic coatings is given in British Pat. No. 1,600,963 to Biomedical Medical Products, Inc. According to that patent,

the coatings include a polyvinyl interpolymer

pyrrolidone-polyurethane. They are produced by first applying a polyisocyanate and a polyurethane in a solvent to a suitable substrate and then the solvent is evaporated, leaving a surface layer of polyurethane with unreacted isocyanate groups. The substrate thus treated is then coated with polyvinylpyrrolidone to

forming the polyvinylpyrrolidone-polyurethane interpolymer.

Although exhibiting an increased slippery nature in the wet state, the hydrophilic coatings of the patent

Britain have not been fully satisfactory.

This is not surprising since, according to subsequently published US Patent No. 4,487,808, which describes these coatings, their manufacture is too complicated for large-scale production and, moreover, the coatings have been found to be susceptible to cracking. Another disadvantage is the presence of unreacted polyvinylpyrrolidone which can leak from the coating for

its use.

Hydrophilic polyvinylpyrrolidone coatings

have now been discovered which represent an improvement

The ratio to those of the prior art above and the formation of such coatings, the substrates coated therewith, and the vinylpyrrolidone polymers used to produce such coatings constitute the primary object and purpose of the invention. Other objects and

goals will emerge subsequently.

The hydrophilic coatings of the invention are produced by applying to a substrate having free isocyanate groups a copolymer of vinylpyrrolidone with an ethylenically unsaturated monomer containing

the active hydrogen being able to react with the iso- groups

free cyanates attached to the substrate. A chemical reaction is then caused to take place between the isocyanate groups and the reactive hydrogens in the copolymer, thus firmly bonding the latter to the substrate. As far as can be determined, polyvinylpyrrolidone does not leak from the present coatings when contacted with polar solutions such as alcohol or aqueous media. It is believed that the strong chemical union between the isocyanate groups in the substrate and the reactive hydrogens in the ethylenic monomer prevents the leakage of the polyvinylpyrrolidone. In the reference coatings, on the other hand, the polyvinylpyrrolidone is apparently rather weakly bound to the intermediate layer.

of polyurethane / polyisocyanate on the substrate. We consider

states that this is because the polyvinylpyrrolidone is bonded to the intermediate layer by physical rather than chemical forces; indeed, there is no reaction

chemical of polyvinylpyrrolidone with an isocyanate.

But whatever the explanation, the fact remains that benchmark coatings are leaking from

polyvinylpyrrolidone.

The N-vinylpyrrolidone copolymers of the invention

tion are obtained by the copolymerization of N-vinyl-

pyrrolidone and an ethylenically unsaturated monomer having active hydrogens of the reactive type with an organic isocyanate. The polymerization is carried out in the known manner. Typically, the monomers are

dissolved in a solvent containing a polymer initiator

The solution is heated to moderately high temperatures, generally between about C and about 100 C. Completion of the reaction is effected by heating for a few hours, usually about 2 to 8 hours. The copolymer is

recovered by removing the solvent which, desirably

table, is an organic liquid boiling between about C and about 130 C. Examples of such solvents include methyl alcohol, ethyl alcohol, tetrahydrofuran, isopropyl ether, chloroform, methylene chloride, acetone , methyl ethyl ketone and the like. Suitable polymerization initiators include any source of free radicals such as, for example, azobisisobutyronitrile, peroxygen compounds such as hydrocarbon peroxide, diisopropyl percarbonate, benzoyl peroxide and the like. As previously noted, the

N-vinylpyrrolidone copolymers of the invention contain

generate active hydrogens which react with isocyanate groups in the substrate. This results in chemical bonding of the coatings prepared from the N-vinylpyrrolidone copolymers to the substrate. The

reactive hydrogens have the form of functional substituents.

tional attached to an ethylenically unsaturated monomer.

In general terms, the amount of ethylenic monomer required to properly bond the copolymer to the substrate is relatively minor compared to N-vinylpyrrolidone which constitutes the major part of the copolymer. A satisfactory number ratio of monomers for the preparation of the copolymers is from about 2% to about 10% ethylenic monomer and from about 90% to about 98% N-vinylpyrrolidone.

Hydrogens active in the monomer are present

both typically in functional entities such as -OH, = NH, -COOH and -SH. Examples of the above ethylenic monomers include allyl alcohol, methallyl alcohol, acrylic acid and their lower hydroxyalkyl esters such as 2-hydroxyethyl acrylate, methacrylic acid and their hydroxyalkyls.

lower esters such as 2-hydroxy- methacrylate

ethyl, 2-hydroxyethylthioacrylate, N-hydroxyethyl-

acrylamide, 2-butene-1-carboxylic acid,

2-hydroxyethyl ester and the like.

The substrate can be any material of the interior.

structure required but is commonly a metal or a polymer such as polyurethane, a vinyl resin represented by polyvinyl chloride, a polyacrylate such as polymethyl methacrylate, a polycarbonate, a polyester such as polyethylene terephthalate, polyethylene terephthalate. polybutylene, polytetramethylene terephthalate as well as various rubbery polymers such as polyisoprene and latex. Isocyanate groups are applied to the substrate by coating it with a solution of a polyisocyanate by known coating techniques such as dipping, spraying or the like and then evaporating the solvent, preferably by air drying leaving a film. polyisocyanate on the surface. Examples of

polyisocyanates are polyphenyl ioscyanate, 4,4'-

diphenylmethane diisocyanate and 2,4-toluene diisocyanate.

Desirably, the polyisocyanate coating solution contains a film-forming material to improve the strength and adhesion of the coating.

dried polyisocyanate. However, more desirably

Generally, the coating is formed from a polyurethane prepolymer of the type obtained by condensing a resin having active hydrogens with an excess of a polyisocyanate. Such isocyanate terminated prepolymers are well known in the polyurethane art and their

description including their preparation and use

as coating materials are widely documented in the patent and technical literature; see "The Development and Use of Polyurethane Products" by E. N. Doyle (1971) published by McGrawHill, Inc.

As an example of resins used for the preparation

ration of polyurethane prepolymers, mention may be made of polyether polyols such as polyethylene glycol,

polypropylene glycol, polylactones and the like.

A particularly large class of hydrogen polyols

active are polyol polyesters which can be generated

Generally described as the reaction product of a polycarboxylic acid and a polyhydroxy compound. Examples of the polyhydroxy compounds include ethylene glycol, propylene glycol, tetramethylene glycol, glycerin and the like. Polycarboxylic acid is commonly a dicarboxylic acid, particularly an aliphatic acid of 5 to 8 carbon atoms, adipic acid being a typical component which is often employed in the manufacture of polyol polyesters. In some cases, a small amount of a low molecular weight diol, for example 1,4-butanediol, can be added to the polyol resin in the preparation of the polyurethane prepolymers. A preferred isocyanate terminated prepolymer derived from a polyether polyol is obtained by reacting a major amount of a polyoxyethylene glycol having a molecular weight of between about 1,000 and about 8,000 or its mixtures, a minor amount of diethylene glycol and excess polyisocyanate

such as DESMODUR WR (Mobay). Examples of polyoxy-

ethylene glycols are the various commercially available "Carbowaxes"

read by Union Carbide Corporation in a range of molecular weights. Representative Carbowaxes are PEG (CARBOWAX 1450R) and PEG (CARBOWAX 8000R) where numbers indicate molecular weights. Such simple diols serve as chain extenders and modifiers. For further details regarding the manufacture and use of urethane polymers, see "The Development and Use of Polyurethane

Products "" cited above.

The isocyanate is applied to the substrate in a

solvent which does not react with isocyanate groups.

Suitable solvents include alkyl chlorides such as methylene chloride, ethylene chloride; ethyl acetate, acetone, methyl ethyl ketone and alkyl ethers. The solvent is desirably a liquid at ordinary temperatures and pressures. The isocyanate solution can be of any concentration but is conveniently applied to the substrate at a solids content of between about

2% and 15% by weight, generally about 3 to about 7%.

The application of the isocyanate solution is by

usual processes, commonly by immersion or spraying

tion. The coating is air dried to effect evaporation of the solvent. Normally the times of

drying time is between about 5 and 60 minutes.

The adhesion of the isocyanate to certain substrates such as

that a rubber latex can be improved by pre-

treatment with a swelling solvent or iso-

cyanate can be dissolved in a solvent which exhibits

a swelling action on the surface.

After evaporation of the isocyanate solvent, a strong and adherent film of isocyanate remains on the surface of the substrate. The latter is then covered by immersion or spraying with a solution of the N-vinylpyrrolidone copolymer and the substrate thus coated is subjected to drying in air until the solvent has evaporated. The solvent for the Nvinylpyrrolidone copolymer is desirably an organic liquid which evaporates relatively easily at room temperature or at slightly elevated temperatures. Examples of copolymer solvents are chlorinated alkanes such as dichloroethane and methylene chloride. Following removal of the solvent, an outer film of the copolymer remains on the isocyanate coated substrate.

of N-vinylpyrrolidone.

The above coated substrate is heated to curing temperatures, preferably between about 50 C and 110 C, so that the free isocyanate groups in the inner coating react with the active hydrogen in the ethylenic monomer units of the N-vinylpyrrolidone copolymer. This chemical union firmly binds the outer polyvinylpyrrolidone to the inner isocyanate coating. In contact with aqueous media, the outer surface of the substrate undergoes hydration with the concomitant increase in the coefficient of friction of the wetted surface. There was no leakage of the coating ingredients to

aqueous media.

The substrates coated according to the invention are useful as catheters, devices forming implants, contact lenses, peristaltic pump chambers,

condoms, arteriovenous bypass, feeding tubes

gastroenteric tion, endotracheal tubes and the like.

The invention will be better illustrated by the examples

which follow o the amounts are in parts by weight.

EXAMPLE 1

111.0 parts of N-vinylpyrrolidone and 2.06 parts of hydroxyethyl methacrylate were dissolved in 300 parts of methyl alcohol in a reaction vessel, equipped with a stirrer and a reflux condenser. The reaction mixture was brought to 68 C-69 C

under nitrogen and 0.5 part of azobisisobutyro-

nitrile (polymerization initiator).

The reaction mixture was refluxed for 6 hours with constant stirring. The conversion to polymer was found to be 99.2%.

EXAMPLE 2

The polymer solution of Example 1 was extracted from 200 parts of methyl alcohol at 400 ° C under vacuum. 200 parts of dimethylformamide were added to the solution and the remaining alcohol was extracted at 40 ° C under vacuum. The viscosity of the final polymer solution

in DMF (dimethylformamide) was 920 cP at 25 C.

EXAMPLE 3

120 parts of N-vinylpyrrolidone and 4.6 parts of allyl alcohol were dissolved in 200 parts of tetrahydrofuran in a reaction vessel, equipped with a stirrer and a reflux condenser. The reaction mixture was heated to 400C under a blanket of nitrogen, and 0.6 part of diisopropyl percarbonate was added. The reaction was allowed to take place at 40 C

for 5 hours.

The conversion to polymer was found to be

99.1%; the viscosity of the solution is 550 cP at 25 C.

EXAMPLE 4

86 parts of N-vinylpyrrolidone and 3 parts of hydroxypropyl acrylate were dissolved in 160 parts of ethyl alcohol and 60 parts of acetone in a reaction vessel equipped with a stirrer and a reflux condenser. The reaction mixture was brought to 40 ° C under a nitrogen blanket, 0.5 part of diisopropyl percarbonate was added and the reaction was carried out.

for 6 hours.

The conversion to polymer was found to be 98.5% and the viscosity of the solution was 480 cP

at 25 C.

EXAMPLE 5

A latex tube (urological catheter) was dipped in a solution containing 2 parts of Pellethane 2363 (Dow) and 1 part of a diisocyanate prepolymer, containing 20% -22% free isocyanate (Boscodur 4 from Bostik ) in 97 parts of dichloroethane. The solution was air dried for 10 minutes and the coated tube was dipped in a polymer solution of Example 2 and allowed to air dry for 10 minutes. The coatings have

cured at 100 C for 20 minutes.

The final coating had a wet kinetic friction coefficient of 0.024, in

measuring according to the method of ASTM D-1894-75.

EXAMPLE 6

A prepolymer was prepared by reacting 48.79 parts of CARBOWAX 1450R (Union Carbide), 7.73 parts of diethylene glycol and 43.48 parts of methylene-bis (dicyclohexylisocyanate) (DESMODURR W, Mobay) with 0, 2 part of stannous octoate (catalyst

reaction).

The polymer was dissolved as 5%

solids in chloroform.

EXAMPLE 7

A prepolymer was prepared by reacting

76.10 parts of CARBOWAX 8000R (Union Carbide), 2.59 per

parts of diethylene glycol and 21.31 parts of DESMODURR W

(Mobay) with 0.2 part of stanous octoate.

The polymer was dissolved as 3%

solids in dimethylformamide.

EXAMPLE 8

An extruded PVC (polyvinyl chloride) tube was dipped in a solution of a prepolymer of Example 6 and air dried for 5 minutes. It was then dipped in 1 part of the polymer solution of Example 3 and 2 parts of dichloroethane, and air dried for 5 minutes. Both

Coatings were cured at 80 C for 1 hour.

The final coating had excellent adhesion to the substrate, which did not decrease after prolonged swelling in water at 37 C, exhibited a high slippery condition with no leakage of low molecular weight compounds.

EXAMPLE 9

An extruded polyurethane tube (Pellethane 2363, Dow) was dip coated, using the prepolymer solution of Example 7 and air dried for 10 minutes. The outer coating was dip coated, using the polymer solution of Example 4, air dried for 10 minutes and both coatings were cured at 100 C for

minutes.

The final coating in the swollen state had the coefficient of kinetic friction of 0.031 and all

the other advantages mentioned in Example 8.

2612 120

Claims (15)

R E V E N D I C A T I ONS 1.- Manufacture article covered with a coating which swells in the presence of aqueous media with concomitant reduction in the coefficient of friction, characterized in that it is produced by: applying, to a substrate, an adherent coating containing groups free isocyanates; applying to the substrate thus coated a second coating of a vinyl copolymer having a major polymeric component derived from N-vinylpyrrolidone and a minor polymeric component derived from an ethylenically unsaturated monomer containing reactive hydrogens, and heating the coated substrate at curing temperatures to effect the reaction between active hydrogens and isocyanate groups and thereby chemically bond the coating of the copolymer to the coating of adherent isocyanate. 2.- Article according to claim 1, characterized in that the adherent isocyanate coating is a prepolymer terminated in diisocyanate produced by reaction of a resin having reactive hydrogens with an excess. of diisocyanate. 3.- Article according to claim 1, characterized in that the resin is a polyether polyol. 4.- Article according to claim 1, characterized in that the ethylenic monomer is 2-hydroxyethyl methacrylate. 5.- Article according to claim 1, characterized in that the ethylenic monomer is hydroxypropyl acrylate. 6.- Article according to claim 1, characterized in that the ethylenic monomer is allyl alcohol. 7.- Article according to claim 1, characterized in that the substrate is a polymer. 8.- Article according to claim 1, characterized in that the substrate is a catheter. 9.- Article according to claim 1, characterized in that the substrate is an implant device. 10.- Article according to claim 1, characterized in that the substrate is a contact lens. 11.- Article according to claim 1, characterized in that the substrate is a peristal pump chamber tick. 12.- Article according to claim 1, characterized in that the substrate is a preservative. 13.- Article according to claim 1, characterized in that the substrate is an arteriovenous bypass. 14.- Article according to claim 1, characterized in that the substrate is a gastro-feeding tube enteric. 15.- Article according to claim 1, characterized in that the substrate is an endotracheal tube