FR2612194A1 - HYDROPHILIC POLYURETHANE AND PROCESS FOR PREPARING THE SAME - Google Patents

Abstract

THE INVENTION RELATES TO A HYDROPHILIC THERMOPLASTIC POLYMER WHICH UNDERGOES DIFFERENTIAL SWELLING IN CONTACT WITH AN AQUEOUS LIQUID. ACCORDING TO THE INVENTION, A HYDROPHILIC THERMOPLASTIC POLYMER INFLATABLE IN WATER IS PROVIDED, IT IS STRETCHED TO A TEMPERATURE BEYOND ITS GLASS TRANSITION POINT TO PROMOTE THE ALIGNMENT OF ITS MOLECULES AND IT IS COOLED TO PRODUCE AN INFLATABLE POLYMER. WATER AND CONSTRAINT IN WHICH THE RATIO OF THE INFLATION ALONG THE STRETCH AXIS TO THE SIDE INFLATION IS CONTROLLED BY THE DEGREE OF STRETCH. THE INVENTION APPLIES IN PARTICULAR TO POLYMERS USEFUL IN MEDICAL, COSMETIC AND INDUSTRIAL APPLICATIONS.

Description

The present invention relates to hydrophilic polymers and

  particular to certain polyurethanes

hydrophilic inflatable in water.

  No. 3,975,350 discloses a class of polyurethanes which are formulated to provide high hydrophilicity, excellent wet-polymer properties and variations in the state of the art.

  dry in the wet state which are uniformly tolerable.

  In general, such hydrophilic polyurethanes are the product of (a) a polyfunctional resin having an equivalent weight of more than 170 and up to 2,000 and a numerical ratio of carbon to oxygen or carbon to nitrogen of up to 2 , 5: 1 to 1.2: 1 or a numerical ratio of carbon to ionic groups in said resin of 20: 1 to 6: 1 and (b) an aliphatic, alicyclic-aliphatic mixed, aliphatic-aromatic or aromatic polyfunctional isocyanate, a nitrile carbonate or mixtures thereof at a functionality of 2 or more in an amount of 0.02 over a weight of one equivalent of the isocyanate by its functionality per equivalent weight of resin by its functionality up to the equivalent weight isocyanate

to the resin.

  The above polymers are useful in medical, cosmetic and industrial applications. They are also useful as release agents for various active substances, and in the production of coatings

  hydrophilic having reduced surface friction.

  A type of polymer included in the general type described in the cited patent and which is particularly concerned by the invention is the product of a polyoxyethylene glycol and an aliphatic diisocyanate. The resulting hydrophilic polyurethane has been found to be eminently suitable for making various inserts in the body such as catheters and the like. In contact with body fluids, the polymers are swollen by the absorbed moisture, thus producing a precise fit between the insert and the tissues. In addition, the polymers are extremely slippery in the wet state. This means that medical devices or items made of them can be inserted and removed from the body with minimal discomfort to the patient.

  The swelling of these polymers occurs uniformly

  precisely, that is to say that the dilation takes place in all directions. However, uniform swelling is not always desirable. This is for example the case when a tube made of polymer is to be used as an intravenous catheter, through the needle. Here, uniform expansion results in the tube experiencing considerable elongation after insertion into a vein or artery. This may cause warping or kinking of the catheter as it adjusts to axial extension. Elongation may also make it difficult to maintain the tip of the catheter at the location

  desired in the circulatory system.

  A process has now been discovered whereby hydrophilic urethane polymers can be prepared, which undergo differential axial swelling in aqueous media and this process as well as the polymers so prepared constitute a primary objective and object of the present invention. Other objects and goals include

  the manufacture of plastic articles with these polymers.

  A particular object of the invention is a catheter which does not swell longitudinally in the presence of aqueous liquids. As understood herein, differential axial swelling means that the swelling is not uniform but will differ along the axes of a plastic article.

made with these polymers.

  The above objectives can be achieved by first forming a substantially linear hydrophilic thermoplastic polyurethane, the reaction of a

  aliphatic diisocyanate and a polyoxyethylene glycol.

  This polymer is then stretched at a temperature beyond its glass transition point to favor

  the alignment of the polymer molecules with

  cold to effect the fixation of the aligned molecules. Upon immersion in a water-based liquid, the polymer swells in which the ratio of swelling along the stretching axis to the swelling

  along the other axis is controlled by the degree of stretching.

  Thus, a tubular or rod member produced in a given polymer can be sufficiently stretched so that there is no axial extension during swelling; even axial contraction to swelling can occur with sufficient stretching. However, the stretched polymer will still have radial swelling. Such controlled directional swelling makes the polymers eminently useful in the manufacture of catheters through the needle as they do not exhibit the undesired elongation obtained.

  when the swelling occurs evenly.

  Preferred hydrophilic thermoplastic polyurethanes are prepared herein by reacting an aliphatic diisocyanate with a resin mixture containing a major amount of a polyoxyethylene glycol having a weight. molecular s between about 1,000 and about

  8,000 and a minor amount of diethylene glycol.

  Examples of polyoxyethylene glycols are the various "Carbowax" marketed in a molecular weight range by Union Carbide Corporation. Representative Carbowaxes are CARBOWAX 1450R and CARBOWAX 8000R. Examples of aliphatic diisocyanates include methylenebis (4-cyclohexyl isocyanate),

  tetramethylene diisocyanate, hexane diisocyanate

  methylene, decamethylene diisocyanate and the like.

  The invention will be illustrated in more detail

  by the following non-limiting examples.

EXAMPLE 1

  A solution of a polyoxyethylene glycol having an average molecular weight of 668 was prepared by combining 1.012.1 g (0.253 equivalents) of CARBOWAX 8000 polyoxyethylene glycol having a number average molecular weight of 8,000 and sold by Union Carbide Corporation;

  407.3 g (0.562 equivalents) of CARBOWAX 1450R, polyoxy-

  ethylene glycol having a number average molecular weight of 1450 and sold by Union Carbide Corporation; and 216.8 g (4.085 equivalents) of diethylene glycol. The components were mixed with stirring at a temperature of about C. After completion of the mixing, 633.9 g (4.802 equivalents) of methylenebis (4-cyclohexylisocyanate), commercially available under stirring, were added while maintaining stirring. the name DESMODURR W by Mobay Chemical Corporation, Pittsburg, Pennsylvania 15205, USA. During the addition, the temperature decreased to 58 ° C. At this point, 3.4 cc of a dibutyltin urethane dilaurate catalyst was added and stirring was continued for 1 to 2 minutes while the temperature reached C. The reaction mixture was then transferred to a tray and placed in an oven at 100 ° C for 1 hour and 30 minutes to ensure completion of the reaction. The polymer was removed from the oven and allowed to cool to room temperature. A sample of the polymer was placed in distilled water for 24 hours. The water content of the polymer

  The resulting hydrate amounted to 54.6% by weight.

  The above polymer was introduced into a 25.4 mm normal body thermoextruder of a type common in the medical tube extrusion industry. An assembly of a crosshead type tube die was employed, having a 1.524 mm orifice

  and a mandrel pin 0.762 mm in diameter.

  The melting temperature of the polymer was 103 C.

  As the tube exited the die, it was stretched by a strand puller until the outer diameter measured 0.813 mm. The material was then cooled to prevent relaxation at a shorter length and a larger diameter. After 24 hours of cooling, the swelling properties of the tube were examined. A number of cross-sections were taken and their dimensions were

  were measured optically using a microscope.

  Then the samples were hydrated in distilled water for 24 hours. Then, the dimensions were again measured. The tube was inflated by + 53.0% internal diameter, + 46.8% external diameter

  and only + 1.6% negligible in length.

  The 25.4 mm extruder is manufactured and sold

  by Killion Extruders, Inc. in Verona, New Jersey 07044, USA.

EXAMPLE 2

  A solution of a polyoxyethylene glycol having an average molecular weight of 2.646 was prepared by combining 2.011.6 g (0.503 equivalents) of CARBOWAX 8000 R and 56.3 g (1.060 equivalents) of diethylene glycol. The

  components were mixed with stirring at a temperature of

  After completion of mixing, 202.2 g (1.532 equivalents) were added while maintaining stirring.

  from DESMODURR W, the temperature decreased to about 60 C.

  At this point, 3.4 cc of dibutyltin dilaurate was added, and stirring was continued for about 1-2 minutes while the temperature reached C. The reaction mixture was transferred to a tray and placed in a refrigerator. oven heated to about 100 C; the polymer was kept in the oven at 100 ° C for

  1 hour to ensure the completion of the reaction.

  The tray was removed from the oven and allowed to cool

to room temperature.

  A sample of the polymer was placed in distilled water for 24 hours. The water content of the resulting hydrated polymer was determined and found to be 80.0% by weight. After hydration, the

  polymer had swelled to around 350% of its original volume

  gine. The polymer was extruded using the same equipment

  same as in Example 1 except that a rod die with an orifice of 2.54 millimeters was used and the strand was pulled until it was 0.71 mm. of diameter. As in Example 1, the material was confined to its stretched length upon cooling for 24 hours (up to room temperature). Cross-section pieces were cut for measurements

swelling.

  The diameter of the stem increased by 114.2% during hydration. The length of the samples was found to have decreased by 2.0%. The length contracted slightly because the effect of relaxation, in this case, was slightly larger in magnitude and opposite in

direction to the effect of swelling.

EXAMPLE 3

  This polymer was prepared in the manner of Example 1, using the following amounts of reagents: R CARBOWAX 1450 819.0 g (1,130 equivalents) Diethylene glycol 380.0 g (7.153 equivalents) DESMODURR W 1. 071 5 g (8,117 equivalents) 3.4 cc stannous octoate (catalyst) The resulting mixture of polyols had an average molecular weight of 289. At immersion in distilled water for 24 hours, water absorption reached 43%. , 7% by weight while the volumetric swelling was about%. A blown film of the polymer was processed on a standard blown film apparatus, but in order to obtain a large swelling ratio, a

  die smaller than usual. [Swelling ratio

  = (2 x flat dimension of the blown film) / (i x diameter of the die). The swelling ratio is the parameter

  which expresses the degree of magnification of the post-filament film.

  In the process of obtaining a blown film the enlargement

  It is obtained by extrusion of a tube, passing this tube through a pair of nip rolls which pinch the tube and form an air seal. Then, air is forced into the collapsed tube through the inside of the chuck-die. This air inflates the tube. [This looks like a balloon's swelling] In this way, very thin films can be created. Often, the tube is split and coiled to get rolls of film. In this case, a large swelling ratio has been used so that the film is strongly oriented in the direction of its circumference (or if the inflated tube has been slit,

of its width).

  A die of the blown film type of millimeters was used. The material was inflated to a flat dimension of 406 mm. The swelling ratio, therefore, was t x (406) / (4, x 50)],

  about 5: 1. The extrudate was coiled during extrusion

  and cooled on the coil for 24 hours. Samples were taken for swelling measurements. The change in width due to hydration was -34.6% (the negative value indicates that the width decreased during hydration). The measured change of

  length was + 11.3%. The thickness swelled 140.4%.

  From the foregoing, it can be seen that the swelling characteristics of various plastic forms formed with the polyurethane disclosed herein may be

  controlled by the method of the invention.

Claims (10)

R E V E N D I C A T I 0 N S   1. Hydrophilic thermoplastic polymer which undergoes differential swelling in contact with an aqueous liquid, characterized in that it is produced by the steps of: (a) forming a hydrophilic thermoplastic polymer swellable in water; (b) stretching the polymer of step (a) to a temperature beyond its glass transition point to promote alignment of the polymer molecules, and (c) cooling the stretched polymer of step (b) to producing a water-swellable and constrained polymer, wherein the ratio of swelling along the lateral swelling stretch axis is controlled by the degree stretching.   2. Polymer according to claim 1, characterized in that the hydrophilic thermoplastic polymer in water of step (a) is a polyurethane   produced by reacting a major amount of a polyoxy-   ethylene glycol having a molecular weight of about 1,000 to 10,000 and a minor amount of diethylene glycol with an aliphatic diisocyanate.   3. Polymer according to claim 2, characterized in that the aliphatic diisocyanate is the   methylenebis (4-cyclohexyl isocyanate).   4. Polymer according to claim 2, characterized in that the polyoxybethylene glycol has a weight   number average molecular weight of about 1,450.   5. Polymer according to claim 2, characterized in that the polyoxyethylene glycol has a number average molecular weight of between about 7,500. and 8,000.   6. Polymer according to claim 2, characterized in that the polyoxyethylene glycol is a mixture of polyoxyethylene glycols according to any one claims 4 or 5.   7. Polymer according to claim 1,   characterized in that it is in the form of a stretched rod.   8. Polymer according to claim 1,   characterized in that it is in the form of a stretched film.   9. Polymer according to claim 1,   characterized in that it is in the form of a stretched tube.   Polymer according to claim 9, characterized in that the tube is a catheter through the needle having substantially no elongation from swelling upon contact with an aqueous liquid.