Self-lubricating polymer composition

Abstract

A polymer resin composition is disclosed including a chemically attached lubricant structure to produce a self-lubricating medical device thereby eliminating the need of a secondary lubrication step currently required which is useful in medical and surgical devices.

Claims

1. A polyurethane resin of Formula I: ##STR00003## wherein the repeating unit of m is in the range from 5 to 2000; the repeating unit of n is in the range from 1 to 40, and the polyurethane resin comprises a weight average molecular weight (M.sub.w) in the range of from about 67,000 g/mole to 110,000 g/mol, and a number average molecular weight (M.sub.n) in the range of from about 30,000 g/mol to 50,000 g/mol; and “ran” refers to random; wherein the polysiloxane is present in an amount ranging from about 1 to about 3 weight percent of the polyurethane resin.

2. A medical article molded from the self-lubricating polyurethane of claim 1.

3. The medical article of claim 2, wherein the medical article is a component of a cannula, catheter, wedge, tipping, blood control actuator, stopper or syringe.

4. The polyurethane resin of claim 1, wherein the resin is effective as a self-lubricating polyurethane for infusion therapy and upon formation of a medical article molded from the polyurethane resin, a kinetic coefficient of friction of the medical article is 0.215 or less.

5. The polyurethane resin of claim 1 comprising a polydispersity in the range of from 1.8 to 2.3.

Description

DETAILED DESCRIPTION OF THE INVENTION

(1) Before describing several exemplary embodiments of the invention, it is to be understood that the invention is not limited to the details of construction or process steps set forth in the following description. The invention is capable of other embodiments and of being practiced or being carried out in various ways.

(2) The present invention relates to a polyurethane resin having an incorporated lubricant structure which may be used to produce a self-lubricating medical device or component of a medical device. The resin of the present invention eliminates the required secondary lubrication step currently found in the manufacture of many medical device components. Due to the lower surface energy of an incorporated lubricant, the incorporated lubricant has a propensity for migration to the surface both during the catheter fabrication process and as a function of time post-production.

(3) In one or more embodiments of the present invention, a lubricant is attached chemically to a polyurethane resin. In one or more embodiments, existing lubricants, such as polydimethylsiloxane or fluorinated lubricants, may be used. The lubricants are chemically reacted to attach with or be incorporated into a desired polyurethane resin of interest. In one or more embodiments, the lubricant is covalently attached or incorporated into the backbone structure of the resin. The lubricant may be attached chemically to a desired polyurethane resin using several techniques. One technique to chemically attach the lubricant to the desired polyurethane is the modification of the urethane monomer prior to polymerization of the monomer into a polyurethane polymer. In one embodiment, isocyante monomers are reacted with polyols to create polyurethane. The isocyante monomers can be modified to contain a lubricating moiety and the reaction with polyols will continue to create self-lubricating polyurethane.

(4) Another technique to chemically attach the lubricant to the desired polyurethane is to graft a lubricant onto the resin backbone of an existing resin using controlled chemistry such as ATRP, functional group reactions, or plasma modification of the resin surface followed by grafting of the lubricant onto the surface of the resin.

(5) Another technique to chemically attach the lubricant to the desired polyurethane is to utilize the functional groups on the lubricating chemicals to co-polymerize it with the monomers into a co-polymer thereby adding the lubricating moiety directly into the backbone of the polymer. For example, a lubricant, such as PDMS, can be made with alcohol or “OH” functional groups, which is an essential reactive group to the polyurethane synthesis. The structure of PDMS with the —OH functional group will co-react with the isocyanate to incorporate PDMS chains into polyurethane creating the self-lubricating polymer.

(6) It is intended that the chemical modification process to functionalize the lubricant onto the resin would still enable the resin to be suitable for use in Class II medical devices.

(7) During and after the fabrication process of the medical device component, the lubricant blooms to the surface due to the lower surface energies of the silicone or fluorinated groups. Due to the chemical linkage of the lubricant to the polymer chain of the bulk material, an additional lubrication process step to obtain the lubrication performance required is eliminated.

(8) In another aspect of the present invention, the synthesis technique may also be utilized to incorporate anti-microbial chemicals or anti-thrombogenic chemicals into a polymer resin composition of the present invention including a lubricant structure.

(9) The resin of the present invention may be used in polymer based medical devices which require lubrication such as the injection syringe barrel and/or stopper. The resin of the present invention may also be used in syringes which are prefilled with saline or other solutions which further dissolve the lubricant off the surface of the syringe barrel and carry it into the patient's bloodstream.

Example 1

PDMS-Polyurethane (Self-Lubricating Urethane)

(10) A series of polyurethane resins of Formula I as follows were prepared:

(11) ##STR00002##
wherein the repeating unit of m is in the range from 5 to 2000. The repeating unit of n is in the range from 1 to 40. The overall molecular weight of the polyurethane resins is between 15,000 g/mole to 130,000 g/mol.

(12) The polyurethane resins of Formula I were prepared from 400 g/mol to 77,000 g/mol of silicone fluid such as Gelest DMS-S31, polyols such as DuPont Tetrathane T-1000, 4,4-diphenyl methane diisocyanate (MDI), and 1,4 butanediol (BDO). The diols, i.e., DMS-S31, Tetrathane T-1000, and BDO were mixed, heated to 65±3° C. The MDI then was added and the mixture was stirred to prevent phase separation of the liquid mixture. After about 1 to 3 minutes, the temperature increased to about 80° C. The liquid mixture then was poured into polytetrafluoroethylene lined trays and heated to 100° C. overnight to complete the polymerization. After cooling to ambient temperature, the resins were chipped and extruded into film for measurement of physical properties. The results are showed in Table 1. As a control, sample #1 “0% PDMS”, was prepared in which the DMS-S31 fluid was omitted and replaced with a like quantity of polyols. The results are also included in Table 1.

(13) TABLE-US-00001 TABLE 1 Molecular Weight Number Avg. Weighted Avg. MW Polydispersity MW (Mn, g/mol) (Mw, g/mol) (PDI = Mw/Mn) 0% PDMS 27,303 50,960 1.87 1% PDMS 34,007 67,837 1.99 2% PDMS 31,020 67,567 2.18 3% PDMS 48,640 110,300 2.27 4% PDMS 15,990 30,613 1.91 5% PDMS 15,887 28,647 1.80 6% PDMS 24,073 50,060 2.08 7% PDMS 24,510 41,273 1.68 10% PDMS  15,683 27,707 1.77

(14) TABLE-US-00002 TABLE 2 Tensile Properties Avg. Tensile at break (Psi) Std. dev. 0% PDMS 5887 1951 1% PDMS 5684 965 2% PDMS 6565 1645 3% PDMS 6396 800 4% PDMS 3574 457 5% PDMS 2650 582 6% PDMS N/A N/A 7% PDMS 2157 582 10% PDMS  1538 417

(15) TABLE-US-00003 TABLE 3 Coefficient of Friction (CoF) Avg. Kinetic CoF 0% PDMS 0.295 0% PDMS dipped into 5% silicone 0.214 catheter lube 1% PDMS 0.215 2% PDMS 0.174 3% PDMS 0.197 4% PDMS 0.202 5% PDMS 0.190 6% PDMS 0.204 7% PDMS 0.286 10% PDMS 0.190

(16) TABLE-US-00004 TABLE 4 Thermal Analysis Tc (° C.) Tc Enthalpy (J/g) Td (° C.) 0% PDMS 161.5 16.7 305 1% PDMS ND ND 309 2% PDMS ND ND 308 3% PDMS ND ND 308 4% PDMS ND ND 306 5% PDMS ND ND 304 6% PDMS ND ND 307 7% PDMS ND ND 301 10% PDMS  ND ND 309 ND is defined as “not detected”.

(17) As shown in Tables 1-4, various Polyurethane/Polysiloxane resins were tested for various attributes such as number average molecular weight, weighted average molecular weight, polydispersity, average tensile at break, coefficient of friction and thermal analysis, the results are shown in Tables 1-4.

(18) As shown from the results in Table 3, the addition of 3% by weight of co-polymer PDMS into the polyurethane synthesis, achieved the same if not lower coefficient of friction as currently lubricated polyurethane material. The current lubrication of polyurethane required an additional coating of 5% by weight addition of PDMS. This method of co-polymerizing lubrication functionality into polyurethane is more efficient at achieving lower coefficient of friction than simply coating an additional layer of PDMS.

(19) As shown in Table 4, co-polymerization of PDMS into the resin backbone disrupted the crystallization of the hard segment but did not disturb the tensile properties.

(20) Silicone diols, such as those disclosed in U.S. Pat. No. 4,647,643 are known products which can be prepared by synthetic methods reported in the art may be used as lubricants in the present invention. Non-silicone diols, for example fluorinated diols, such as those marketed as “Krytox” diols commercially available from Dupont may be used as lubricants in the present invention.

(21) From consideration of the synthesis, those skilled in the art will appreciate that the silicone diol may include a mixture of functional R-groups such as a combination of ethylene and butylene groups.

(22) A presently preferred silicone diol for use in the invention is a polydimethylsiloxane diol with molecular weight in range of 400 g/mole to 139,000 g/mol.

(23) As a general rule, the polyurethanes of the present invention are easily prepared by forming a diol mixture containing the short chain diol, a long chain polyether or polyester diol and the silicone diol of formula and adding the diisocyanate to the diol mixture. Catalysts conventionally used in the synthesis of polyurethanes, such as dibutyltin dilaurate, tertiary amines (i.e. 1,4-diazabicyclo[2.2.2]octane), and metallic compounds (i.e. dibutyltin dilaurate or bismuth octanoate) may be used.

(24) Polyether diols which can be used in the present invention include the polyalkylene glycols. Two polyether diols that are presently preferred for use in the present invention are poly(tetramethylene ether) glycols having molecular weights in the range of 650 to about 2000. Such polyols are commercially available as Polymeg 1000 (Quaker Oats Co., Chemical Division) and Terathane T-1000 (DuPont).

(25) The diol included in the polyurethane resins of the invention may include ethylene glycol, 1,3-propylene glycol, 1,4-butane diol, neopentyl glycol, etc. Other diols which can be employed are alicyclic glycols having up to 10 carbon atoms, e.g., 1,4-cyclohexane diol, 1,4-dimethylol cyclohexane, etc.

(26) Representative diisocyanates useful in the present invention include aromatic and alicyclic diisocyanates, such as 4,4-diphenyl methane diisocyanate (MDI), toluene diisocyanate (TDI), isophorone diisocyanate (IPDI), methylene bis (4-cyclohexyl isocyanate) (HMDI), etc. Of these, MDI and HMDI are presently preferred.

(27) The diisocyanate and the diols are included in an amount of 1 to 10 weight percent of the product. In one or more embodiments, the diisocyanate range from 40% to 75% by weight. In one or more embodiments, silicone diol may be added in 1 to 10 weight %. In general, the ratio of OH to isocyanate functional group is about a 1:1 ratio.

(28) The long chain polyether diol or the long chain polyether diol or a mixture of the two diols constitutes the balance of the polyurethane resin.

(29) The polyurethane resins of the invention can be fabricated into film, tubing and other forms by conventional thermoplastic fabricating techniques including solution casting, extrusion molding, etc. The resin may have incorporated therein, as desired, conventional stabilizers and other additives. The amounts of these materials will vary depending upon the application of the polyurethane, but they are typically present in amounts ranging from about 0.2 to 50 weight percent of the polymer.

(30) The polyurethane-polysiloxane resin may include polydimethylsilioxane (PDMS).

(31) In one or more embodiments, it is envisioned that anti-microbial chemicals or anti-thrombogenic chemicals may be covalently bound to the resin.

(32) The present invention also allows for the ability to injection mold catheters using a one shot mold without having to sacrifice optical clarity.

(33) Reference throughout this specification to “one embodiment,” “certain embodiments,” “one or more embodiments” or “an embodiment” means that a particular feature, structure, material, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. Thus, the appearances of the phrases such as “in one or more embodiments,” “in certain embodiments,” “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily referring to the same embodiment of the invention. Furthermore, the particular features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments.

(34) Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It will be apparent to those skilled in the art that various modifications and variations can be made to the method and apparatus of the present invention without departing from the spirit and scope of the invention. Thus, it is intended that the present invention include modifications and variations that are within the scope of the appended claims and their equivalents.