Process for producing slippery, tenaciously adhering hydrogel coatings containing a polyurethane-urea polymer hydrogel commingled with a poly (n-vinylpyrrolidone) polymer hydrogel

• US 5,662,960 A
• Filed: 02/01/1995
• Issued: 09/02/1997
• Est. Priority Date: 02/01/1995
• Status: Expired due to Term

• Current Assignee: Boston Scientific Scimed, Inc. (Boston Scientific Corporation)
• Original Assignee: Schneider Electric SE
• Inventors: Forman, Michael R., Helmus, Michael N., Ding, Ni, Hostettler, Fritz, Rhum, David
• Primary Examiner(s): DUDASH, DIANA L
• Application Number:
  US08/384,711
• Time in Patent Office: 944 Days
• Field of Search: 427/2.28, 427/2.3, 427/322, 427/318, 427/301, 427/534, 427/535, 427/536
• US Class Current: 427/2.3
• CPC Class Codes: A61L 2/08 Radiation
• CPC Class Codes: A61L 29/085 Macromolecular materials
• CPC Class Codes: A61L 29/145 Hydrogels or hydrocolloids
• CPC Class Codes: A61L 31/10 Macromolecular materials
• CPC Class Codes: A61L 31/145 Hydrogels or hydrocolloids
• CPC Class Codes: B05D 7/02 to macromolecular substances, e.g. rubber treatment or coating of shaped articles made of macromolecular substances C08J7/00
• CPC Class Codes: B05D 7/16 using synthetic lacquers or varnishes
• CPC Class Codes: B05D 7/52 Two layers
• CPC Class Codes: C08G 18/10 Prepolymer processes involving reaction of isocyanates or isothiocyanates with compounds having active hydrogen in a first reaction step
• CPC Class Codes: C08G 18/302 Water
• CPC Class Codes: C08G 2210/00 Compositions for preparing hydrogels
• CPC Class Codes: C08G 2270/00 Compositions for creating interpenetrating networks
• CPC Class Codes: C08L 75/04 Polyurethanes

Abstract

A process for preparing coating compositions of a commingled hydrogel of a polyurethane-polyurea polymer hydrogel and a poly(N-vinylpyrrolidone) polymer hydrogel; a process for making materials composed of a polymeric plastic or rubber substrate or a metallic substrate, with a coating of the commingled hydrogel thereon; and a process for making medical devices with a coating of the commingled hydrogel thereon, are disclosed. The coating compositions tenaciously adhere to the substrate materials and medical devices to which they are applied due to bonding of a tie coat to a reactive substrate surface and due to the commingling of the two hydrogel components. The coating compositions and coated materials and medical devices are non-toxic and biocompatible, making them ideally suited for use in applications such as for catheters, catheter balloons and stents. In such applications, the coating compositions, coated materials, and coated medical devices made therefrom demonstrate low coefficients of friction in contact with body fluids, especially blood, as well as a high degree of wear permanence over prolonged use. The commingled hydrogel coatings are capable of being dried to facilitate storage of the devices to which they have been applied, and can be instantly reactivated for later use by exposure to water.

Claims

1. A process for producing a material bearing thereon a coating of a wet, slippery, adhering, commingled hydrogel of a hydrophilic polyurethane-polyurea polymer hydrogel and a poly(N-vinylpyrrolidone) polymer hydrogel, said process comprising:

a) affixing reactive chemical functional groups, at least some of which are amine-containing groups, to a surface of a hydrophilic or hydrophilicized hydrophobic polymer substrate or a metal substrate to make a reactive substrate surface;

b) coating the resulting reactive substrate surface of (a) with a first coating comprising a hydrophilic polyurethane-urea prepolymer intermediate, which is capable of forming a polyurethane-polyurea hydrogel-forming polymer, and which contains terminal isocyanate groups, such that at least some of said terminal isocyanate groups are reacted with and are covalently bonded to said reactive chemical functional groups on said reactive substrate surface, forming covalent polyurea bonds therewith, resulting in the formation of a tie coat of a polyurethane-polyurea hydrogel-forming polymer, which adheres to said reactive substrate surface, and wherein at least some of said terminal isocyanate groups in said polyurethane-polyurea hydrogel-forming polymer remain free to react with other species; and

c) treating said resulting tie coat of (b) with a treatment selected from the group (i-ii) consisting of;

(i) applying a second coating comprising an aqueous solution of a poly(N-vinylpyrrolidone) hydrogel-forming polymer; and

(ii) applying a second coating comprising an aqueous solution of a poly(N-vinylpyrrolidone) hydrogel-forming polymer, followed by application, in a vapor phase, of a moisture-containing substance, such that a barrier coat which is a commingled hydrogel of a hydrophilic polyurethane-polyurea polymer hydrogel and a poly(N-vinylpyrrolidone) hydrogel is formed;

wherein water of said aqueous solution or said moisture;

containing substance is bound with said polyurethane-polyurea hydrogel-forming polymer forming said polyurethane-polyurea polymer hydrogel;

wherein water of said aqueous solution or said moisture;

containing substance is bound with said poly(N-vinylpyrrolidone) hydrogel-forming polymer forming said poly(N-vinylpyrrolidone) polymer hydrogel; and

wherein said poly(N-vinylpyrrolidone) polymer hydrogel is adherent to said substrate surface as a result of being commingled with said polyurethane-polyurea polymer hydrogel.

2. The process according to claim 1 wherein said polymer substrate is a plastic or a rubber.

3. The process according to claim 2 wherein said polymer substrate is selected from the group consisting of thermoplastic polyurethanes (TPU), polyesters, nylon polymers, block copolymers of a polyether polymer and a polyester polymer, block copolymers of a polyether polyol and a compound selected from the group consisting of polyamides, polyimides, polyolefins, synthetic hydrocarbon elastomers, and natural rubber.

4. The process according to claim 3 wherein said polyester is polyethylene terephthalate (PET).

5. The process according to claim 3 wherein when said polymer substrate is a nylon polymer, said nylon polymer is selected from the group consisting of nylon-11 and nylon-12.

6. The process according to claim 3 wherein when said polymer substrate is a polyolefin, said polyolefin is selected from the group consisting of polyethylenes (PE) and polypropylenes (PP).

7. The process according to claim 3 wherein said polyether polymer is aliphatic and said polyester polymer is aromatic.

8. The process according to claim 1 wherein when said substrate is a polymer, said reactive chemical functional groups are further selected from the group consisting of hydroxyl groups, carboxyl groups, carbonyl groups, and combinations thereof.

9. The process according to claim 1 wherein said amine-containing groups are selected from the group consisting of amino groups, amido groups, urethane groups, urea groups, and combinations thereof.

10. The process according to claim 1 wherein when said substrate is a hydrophilic polymer or a hydrophilicized hydrophobic polymer, said reactive chemical functional groups are affixed to said surface of said substrate by plasma-treating said substrate with a plasma gas containing said reactive chemical functional groups.

11. The process according to claim 10 wherein when said reactive chemical functional groups are amine-containing groups, said plasma gas is a nitrogen-containing gas selected from the group consisting of ammonia, organic amines, nitrous oxide, nitrogen and combinations thereof.

12. The process according to claim 11 wherein said organic amines include primary and secondary organic amines, and combinations thereof.

13. The process according to claim 12 wherein said organic amines are selected from the group consisting of methylamine, dimethylamine, ethylamine, diethylamine, n-propylamine, allylamine, isopropylamine, n-butylamine, n-butylmethylamine, n-amylamine, n-hexylamine, 2-ethylhexylamine, ethylenediamine, 1,4-butanediamine, 1,6-hexanediamine, cyclohexylamine, n-methylcyclohexylamine, and ethyleneimine.

14. The process according to claim 12 wherein said organic amines are primary and secondary organic amines having a structure selected from the group (I-III) consisting of:

space="preserve" listing-type="equation">R.sub.1 NH.sub.2 I.,

space="preserve" listing-type="equation">R.sub.1 NHR.sub.2 II.,

and

space="preserve" listing-type="equation">H.sub.2 N--R.sub.3 --NH.sub.2 III.

wherein R₁ and R₂ are monovalent hydrocarbon radicals having from 1 to about 8 carbon atoms, and R₃ is a divalent hydrocarbon radical having from 2 to about 8 carbon atoms.

15. The process according to claim 10 wherein a radio frequency of 13.56 MHz, with a generating power of from about 0.1 to about 0.5 watts per square centimeter of plasma apparatus electrode surface, is utilized in said plasma treating of said substrate.

16. The process according to claim 15 wherein said plasma treating of said substrate is performed at a pressure of about 10^-2 Torr, at a temperature of up to about 60°

C., at a nitrogen-containing gas flow rate of from about 50 to about 2000 standard ml./min., and at a nitrogen gas-containing pressure of from about 0.01 to about 10 Torr, for a period of time of at least 30 seconds.

17. The process according to claim 10 wherein said plasma treating of said substrate is performed in a mode selected from the group consisting of batch mode and continuous mode.

18. The process according to claim 1 wherein said substrate is pre-treated, prior to making a surface thereof reactive, to clean said substrate.

19. The process according to claim 18 wherein said pre-treatment of said substrate is by a method comprising:

at least one of;

washing said substrate with at least one organic solvent; and

washing said substrate with an aqueous solution of at least one of neutral, anionic and cationic surfactants, and combinations thereof;

followed by washing said substrate with water, and drying.

20. The process according to claim 19 wherein said organic solvent is selected from the group consisting of alcohols, ketones, hydrocarbons, chlorinated hydrocarbons, ethers, petroleum ethers, cleaning spirits, and combinations thereof.

21. The process according to claim 20 wherein when said organic solvent is an alcohol, said alcohol is selected from the group consisting of methanol, ethanol, and isopropanol;

when said organic solvent is a ketone, said ketone is selected from the group consisting of acetone and methylethyl ketone;

when said organic solvent is a hydrocarbon, said hydrocarbon is selected from the group consisting of pentanes and n-hexane;

when said organic solvent is a chlorinated hydrocarbon, said chlorinated hydrocarbon is selected from the group consisting of methylene chloride and 1,1,1-trichlorethane; and

when said organic solvent is an ether, said ether is selected from the group consisting of diisopropyl ether, dioxane, and tetrahydrofuran.

22. The process according to claim 19 wherein said pre-treatment is performed for a period of time of from about 10 seconds to about 10 minutes.

23. The process according to claim 1 wherein when said substrate is a hydrophobic polymer having a nonpolar or substantially nonpolar surface, the polarity of said surface of said hydrophobic polymer substrate is first increased and said surface is made hydrophilic before making said surface reactive according to (a), by affixing reactive chemical functional groups selected from the group consisting of hydroxyl groups, carboxyl groups, carbonyl groups, and combinations thereof, to said surface of said hydrophobic polymer substrate.

24. The process according to claim 1 wherein said metal substrate is selected from the group consisting of stainless steel, titanium, alloys of steel, nickel, titanium, molybdenum, cobalt and chromium, and nitinol (nickel-titanium alloy), and vitallium (cobalt-chromium alloy).

25. The process according to claim 1 wherein when said substrate is a metal, said reactive chemical functional groups include amino-silane groups.

26. The process according to claim 25 wherein said amino-silane groups have amino terminal groups at one end and silane terminal groups at an opposite end, such that said silane terminal groups are attached to the surface of said metal substrate and said amino groups are free to react with other species.

27. The process according to claim 26 wherein lower alkyl groups having from 2 to about 8 carbons are positioned between said silane terminal groups and said amino terminal groups.

28. The process according to claim 25 wherein said amino-silane groups are affixed to said surface of said metal substrate by chemical treatment of said substrate surface.

29. The process according to claim 28 wherein said chemical treatment of said metal substrate is with a compound selected from the group consisting of γ

-aminopropyltriethoxysilane, γ

-aminopropyltrimethoxysilane, β

-aminoethyl-γ

-aminopropyltrimethoxysilane, and a prehydrolyzed aminoalkyl silanol.

30. The process according to claim 29 wherein said chemical treatment is with a composition containing from about 0.5%, by weight, to about 3%, by weight, of said compound in water.

31. The process according to claim 1 wherein said hydrophilic polyurethane-urea prepolymer intermediate is formed by reacting a water-soluble polyether polyol or copolyether polyol, and an organic polyisocyanate.

32. The process according to claim 31 wherein said organic polyisocyanate is selected from the group consisting of aliphatic, cycloaliphatic, araliphatic, aromatic and heterocyclic polyisocyanates.

33. The process according to claim 32 wherein said aliphatic, cycloaliphatic, araliphatic, aromatic or heterocyclic polyisocyanate is a diisocyanate or a trifunctional biuret or trifunctional isocyanurate derivative thereof.

34. The process according to claim 33 wherein said hydrophilic polyurethane prepolymer intermediate is formed by reacting said polyether polyol or copolyether polyol with an excess of organic polyisocyanate.

35. The process according to claim 34 wherein the hydrophilic polyurethane-urea prepolymer intermediate formation reaction is performed at temperature of up to about 90°

C.

36. The process according to claim 35 wherein the temperature is from about 50°

C. to about 70°

C.

37. The process according to claim 34 wherein the hydrophilic polyurethane-urea prepolymer intermediate formation reaction is performed in a non-aqueous solution containing a total solids content of from about 20% to about 80%, by weight.

38. The process according to claim 37 wherein a non-aqueous solvent of said solution is selected from the group consisting of aromatic hydrocarbons, ketones, ethers, esters, chlorinated alkanes, and mixtures thereof.

39. The process according to claim 38 wherein when said non-aqueous solvent is an aromatic hydrocarbon, said aromatic hydrocarbon is selected from the group consisting of benzene, toluene and xylenes;

when said non-aqueous solvent is a ketone, said ketone is methylethyl ketone;

when said non-aqueous solvent is an ether, said ether is selected from the group consisting of methyl tert. butyl ether, tetrahydrofurane and dioxane;

when said non-aqueous solvent is an ester, said ester is selected from the group consisting of methylethoxy acetate, methylisopropoxy acetate, ethyl acetate, butyl acetate, and ethyl formate; and

when said non-aqueous solvent is a chlorinated alkane, said chlorinated alkane is 1,1,1-trichloroethane.

40. The process according to claim 31 performed in the presence of a catalyst to promote reaction between said polyether polyol or said copolyether polyol and said organic polyisocyanate.

41. The process according to claim 40 wherein said catalyst is a tin-containing compound selected from the group consisting of stannous acylates, dialkyltin dicarboxylates, and dialkyltin oxides.

42. The process according to claim 41 wherein said catalyst is a tin-containing compound selected from the group consisting of stannous octoate, stannous oleate, dibutyltin dilaurate, dimethyltin dilaurate, and dioctyltin oxide.

43. The process according to claim 41 wherein said catalyst is at a concentration from about 5 ppm to about 300 ppm , based on a total weight of reaction mixture.

44. The process according to claim 1 wherein said first coating is applied to said reactive surface of said substrate as a solution containing from about 1% to about 25% by weight of coating solids in a nonaqueous solvent selected from the group consisting of aromatic hydrocarbons, ketones, ethers, tetrahydrofurane, dioxane, esters, chloroalkanes, C₅ and C₆ alkanes, methylene dichloride, acetone and mixtures thereof.

45. The process according to claim 44 wherein said polymer solids are from about 1.5% to about 8%, by weight.

46. The process according to claim 44 wherein said first coating solution is applied to said reactive surface of said substrate by a method selected from the group consisting of dip-coating, continuous coating and spray coating.

47. The process according to claim 44 further comprising removing the solvent from the first coating solution after application of said first coating solution to said substrate.

48. The process according to claim 47 wherein solvent removal is by evaporation thereof.

49. The process according to claim 1 wherein said aqueous solution of poly(N-vinylpyrrolidone) in (c)(i) or (c)(ii) further contains a water soluble polyamine dispersed therein, which reacts with and is covalently bonded to at least some of said terminal isocyanate groups of said polyurethane-polyurea hydrogel-forming polymer of said tie coat that remain free to react with other species, thereby increasing the adhesion of said poly(N-vinylpyrrolidone hydrogel and said polyurethane-polyurea hydrogel.

50. The process according to claim 49 wherein said polyamine is selected from the group consisting of ethelyenediamine, 1,2-propylenediamine, 1,3-propylenediamine, 1,4-butanediamine, 1,6-hexanediamine, diethylenetriamine, and piperazine.

51. The process according to claim 1 wherein said second coating is applied as an aqueous solution of said poly(N-vinylpyrrolidone) hydrogel-forming polymer.

52. The process according to claim 1 wherein said coating of a wet, slippery, tenaciously adhering, commingled hydrogel of a hydrophilic polyurethane-polyurea polymer hydrogel and a poly(N-vinylpyrrolidone) polymer hydrogel, has a thickness of from about 1 mil to about 5 mils.

53. The process according to claim 1 wherein (a) and (b) are completed within a period of time of two months from one another.

54. The process according to claim 1 further comprising heating said first-coated substrate surface, bearing said tie coat resulting from said first coating, to a temperature of from about 40°

C. to about 75°

C. to further promote covalent bond formation between said terminal isocyanate groups of said hydrophilic polyurethane-urea prepolymer intermediate and said terminal reactive chemical functional groups on said substrate surface, before application of said second coating.

55. The process according to claim 1 further comprising adding a slip additive to said hydrophilic polyurethane-urea prepolymer intermediate, so that said slip additive is also commingled with said commingled hydrogel.

56. The process according to claim 1 wherein said hydrogel barrier coat of a commingled hydrogel of a hydrophilic polyurethane-polyurea polymer hydrogel and a poly(N-vinylpyrrolidone) polymer hydrogel, has a water content of at least about 70% by weight.

57. The process according to claim 56 wherein said water content is from about 85% to about 90%.

58. The process according to claim 1 wherein the formation of said hydrogel barrier coat in (c) is performed in the presence of a hydrogel formation promoting catalyst.

59. The process according to claim 58 wherein said hydrogel formation promoting catalyst is a tertiary amine having a boiling point in the range of from about 3°

C. to about 305°

C.

60. The process according to claim 59 wherein said low boiling tertiary amine is selected from the group consisting of trimethylamine, triethylamine, tripropylamine, and triisopropylamine.

61. The process according to claim 58 wherein said catalyst is in aqueous solution.

62. The process according to claim 61 wherein said aqueous solution contains from about 0.03% to about 0.3% by weight of catalyst.

63. The process according to claim 1 wherein the formation of said hydrogel barrier coat in (c) is performed in the presence of a compound selected from the group consisting of aliphatic, cycloaliphatic, araliphatic, and heterocyclic diamines, and inorganic diamines, to form a chain-extended hydrogel.

64. The process according to claim 63 wherein said inorganic diamine is selected from the group consisting of hydrazine and substituted hydrazine.

65. The process according to claim 1 wherein the formation of said hydrogel barrier coat in (c) is performed in the presence of a dual catalytic and chain-extending compound containing an isocyanate reactant group and a catalytic moiety.

66. The process according to claim 65 wherein said dual compound containing an isocyanate reactant group and a catalytic moiety is an organic amine containing a tertiary amine group and at least one of a primary and a secondary amine group.

67. The process according to claim 65 wherein said dual compound is ethylenediamine.

68. The process according to claim 1 wherein the formation of said hydrogel barrier coat in (c) is performed in the presence of a basic inorganic salt selected from the group consisting of sodium carbonate, sodium bicarbonate, sodium borate, and sodium acetate, to cure said commingled hydrogel.

69. The process according to claim 68 wherein said basic inorganic salt is in an aqueous solution having a salt concentration of from about 0.05% to about 0.2% by weight.

70. The process according to claim 69 further including rinsing the resulting hydrogel coat with water to remove said inorganic salt.

71. A process for producing a material bearing thereon a dried coating of an adhering, commingled hydrogel of a hydrophilic polyurethane-polyurea polymer hydrogel and a poly(N-vinylpyrrolidone) polymer hydrogel, which is regenerable by re-exposure to moisture, said process comprising:

a) affixing reactive chemical functional groups, at least some of which are amine-containing groups, to a surface of a hydrophilic or hydrophilicized hydrophobic polymer substrate or a metal substrate to make a reactive substrate surface;

b) coating the resulting reactive surface of (a) with a first coating comprising a hydrophilic polyurethane-urea prepolymer intermediate, which is capable of forming a polyurethane-polyurea hydrogel-forming polymer, and which contains terminal isocyanate groups, such that at least some of said terminal isocyanate groups are reacted with and are covalently bonded to said reactive chemical functional groups on said substrate surface, forming covalent polyurea bonds therewith, resulting in the formation of a tie coat of a polyurethane-polyurea hydrogel-forming polymer, which adheres to said reactive substrate surface, and wherein at least some of said terminal isocyanate groups in said polyurethane-polyurea hydrogel-forming polymer remain free to react with other species;

c) treating said resulting tie coat of (b) with a treatment selected from the group (i-ii) consisting of;

(i) applying a second coating comprising an aqueous solution of a poly(N-vinylpyrrolidone) hydrogel-forming polymer;

(ii) applying a second coating comprising an aqueous solution of a poly(N-vinylpyrrolidone) hydrogel-forming polymer, followed by application, in a vapor phase, of a moisture-containing substance, such that a barrier coat which is a commingled hydrogel of a hydrophilic polyurethane-polyurea polymer hydrogel and a poly(N-vinylpyrrolidone) hydrogel is formed;

wherein water of said aqueous solution or said moisture-containing substance is bound with said polyurethane-polyurea hydrogel-forming polymer forming said polyurethane-polyurea polymer hydrogel;

wherein water of said aqueous solution or said moisture-containing substance is bound with said poly(N-vinylpyrrolidone) hydrogel-forming polymer forming said poly(N-vinylpyrrolidone) polymer hydrogel; and

wherein said poly(N-vinylpyrrolidone) polymer hydrogel is adherent to said substrate surface as a result of being commingled with said polyurethane;

polyurea polymer hydrogel; and

(d) further performing a drying of said wet, slippery, adhering, commingled hydrogel of a polyurethane-polyurea polymer hydrogel and a poly(N-vinylpyrrolidone) polymer hydrogel of (c), to form a reactivatable dried coating thereof.

72. The process according to claim 71 wherein said drying of said second coating is performed by vaccuum evaporation of wet hydrogel.

73. The process according to claim 72 wherein vacuum evaporation is performed at a pressure in the range of from about 3 Torr to about 250 Torr.

74. The process according to claim 73 wherein vacuum evaporation is performed at a temperture in the range of from about 20°

C. to about 60°

C.

75. A process for producing a material bearing thereon a coating of a wet, slippery, adhering, commingled hydrogel of a hydrophilic polyurethane-polyurea polymer hydrogel and a poly(N-vinylpyrrolidone) polymer hydrogel, wherein said coating is formed by the reactivation of a dried hydrogel coating thereof, said process comprising:

performing the process according to claim 71; and

(e) further performing a re-exposure of said dried hydrogel coating formed in (d) to a moisture-containing hydrogel-forming, substance, to reactivate said dried hydrogel coating to a wet, slippery commingled hydrogel coating.

76. The process according to claim 75 wherein said moisture-containing, hydrogel-forming, substance is selected from the group consisting of liquid water, saline solution, water vapor, and an air or gas stream having a moisture content.

77. The process according to claim 71 wherein said aqueous solution of poly(N-vinylpyrrolidone) in (c)(i) or (c)(ii) further contains a water soluble polyamine which reacts with and is covalently bonded to at least some of said terminal isocyanate groups of said polyurethane-polyurea hydrogel-forming polymer of said tie coat that remain free to react with other species, thereby increasing the adhesion of said poly(N-vinylpyrrolidone hydrogel and said polyurethane-polyurea hydrogel.

78. The process according to claim 77 wherein said polyamine is selected from the group consisting of ethelyenediamine, 1,2-propylenediamine, 1,3-propylenediamine, 1,4-butanediamine, 1,6-hexanediamine, diethylenetriamine, and piperazine.

79. A process for producing a sterilized coating of a reactivatable, dried, adhering, commingled hydrogel of a hydrophilic polyurethane-polyurea polymer hydrogel and a poly(N-vinylpyrrolidone) polymer hydrogel, on the surface of a medical device fabricated from a polymeric substrate or a metallic substrate, said process comprising:

(a) making at least a portion of an outer surface of said polymeric or metallic substrate from which said medical device is fabricated chemically reactive by affixing reactive chemical functional groups, including at least some amine-containing groups, thereto;

(b) coating the resulting reactive outer surface of said substrate with a first coating comprising a hydrophilic polyurethane-urea prepolymer intermediate, which is capable of forming a polyurethane-polyurea hydrogel-forming polymer, and which contains terminal isocyanate groups, such that at least some of said terminal isocyanate groups are reacted with and are covalently bonded to said reactive chemical functional groups on said outer surface of said polymeric or metallic substrate, forming covalent polyurea bonds therewith, resulting in the formation of a tie coat of a polyurethane-polyurea hydrogel-forming polymer, that adheres to said reactive outer surface of said substrate, and wherein at least some of said terminal isocyanate groups of said polyurethane-urea prepolymer intermediate are present in said polyurethane-polyurea hydrogel-forming polymer, such that they remain free to react with other species;

c) coating said tie coat with a second coating comprising a poly(N-vinylpyrrolidone) hydrogel-forming polymer, and a moisture-containing, hydrogel-forming substance, which also contains isocyanate-reactive chemical functional groups, such that a barrier coat of a wet, slippery, commingled hydrogel is formed upon the application of said second coating to said tie coat of said first coated substrate;

wherein said isocyanate-reactive functional groups of said hydrogel-forming substance are reacted with and are covalently bonded to at least some of said terminal isocyanate groups of said polyurethane-polyurea hydrogel-forming polymer that remain free to react with other species, to form a first hydrogel of said commingled hydrogel barrier coat, such that said first hydrogel of said commingled hydrogel barrier coat is a polyurethane-polyurea polymer hydrogel that adheres to said tie coat, and thus also adheres to said substrate surface;

wherein said moisture of said hydrogel-forming substance is bound with said poly(N-vinylpyrrolidone) hydrogel-forming polymer, to form a second hydrogel of said commingled hydrogel barrier coat, such that said second hydrogel of said commingled hydrogel barrier coat is a poly(N-vinylpyrrolidone) polymer hydrogel; and

wherein said first hydrogel of said commingled hydrogel barrier coat and said second hydrogel of said commingled hydrogel barrier coat are commingled with one another, such that said second hydrogel of said commingled hydrogel barrier coat is thereby rendered adhering to said tie coat and thus also adhering to said substrate surface;

(d) drying said wet, slippery commingled hydrogel barrier coat formed in (c) to form a dried hydrogel coating thereof; and

(e) sterilizing the resulting coated medical device, bearing said dried hydrogel coating of (d).

80. The process according to claim 79 wherein sterilization is by means of exposing said dried hydrogel-coated medical device to gamma-radiation.