JPH10114814A - Fiber-forming polyurethane solution - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a fiber-forming polyurethane soln. excellent in spinnability by dissolving, in a polar solvent, a segmented polyurethane obtd. by reacting a high-mol.-wt. glycol, a chain extender, and a diisocyanate in a specified equivalent ratio. SOLUTION: A diisocyanate (e.g. 4,4'-diphenylmethane diisocyanate) is charged into a reactor, and a high-mol.-wt. glycol having terminal hydroxyl groups (e.g. polytetramethylene glycol) is heated and added to the diisocyanate under stirring by nitrogen blowing. The resultant prepolymer is thermally mixed and reacted with a chain extender (e.g. 1,4-butanediol) dissolved in a polar solvent (e.g. dimethylacetamide) in an equivalent ratio of isocyanate group to the sum of hydroxyl and amino groups lower than 1 to give a segmented polyurethane having a mol.wt. of about 50,000-300,000 Dalton. A fiber can be formed by passing a polyurethane soln. adjusted to a solid content of 50% and a soln. viscosity of about 500,000-3,000,000 through an orifice in the air.

Description

DETAILED DESCRIPTION OF THE INVENTION

BACKGROUND OF THE INVENTION AND DESCRIPTION The present invention relates generally to polyurethanes, and more particularly to polyurethane homopolymers that can be spun in air. If a polyurethane homopolymer that can be spun in air is desired, the equivalent ratio of the reactants can be tailored to be hydroxy-excess.

[0002] Over the years, numerous approaches have been taken to provide polymers suitable for spinning or molding. Some of these approaches involve the use and development of polyurethane materials that tend to have desirable properties such as toughness, good abrasion resistance, generally beneficial flexibility, and good adhesion. The significance of such properties and many of the many beneficial properties will depend on whether the polyurethane is manufactured as a fiber, molding resin, paint, elastomer or foam. For example, polyurethane typically has a high modulus, good electrical resistance,
Provide fibers with high moisture resistance and advantageous crystalline structure. Many of these properties are useful in forming so-called spandex fibers containing segmented polyurethane materials. Often they are in the form of poly (urea-urethane) which is very elastic and cannot be easily annealed. Further, they typically must be spun under water or other liquid. Also, in order to spin significant transmissions of the knit when knitting such fibers under tension, they are typically wrapped around the spandex fibers to provide lubricity during knitting to minimize the consequences of these tensions. Dacron or nylon fibers are wound. At times, it provides fibers that are not as or more resilient than typical spandex segmented polyurethanes, can be knitted with less tension, and can be annealed to remove residual tension if desired. It is desirable. This type of property is particularly desirable for the production of artificial blood vessels from spun fibers.

The present invention can be tailored for use as a material that can be spun in air, including the ability to spin into fibers that are sufficiently thin to be suitable for spinning vascular grafts and non-woven vascular grafts. Along these lines, including capabilities, generally provide improved polyurethanes. The spinable homopolymeric urethane polymer component is formed from a reactant charge that is slightly hydroxy-excessive and not isocyanate-excessive.

It is therefore a general object of the present invention to provide an improved polyurethane material and a method for its polymerization and production.

Another object of the present invention is to provide an improved polyurethane which can be spun into very fine filaments in air.

Another object of the present invention is to spin in water if it is simply wound on a bobbin, but the movement of the fiber along the length of the vascular prosthesis results in excessive stretching and cutting, and An object of the present invention is to provide an improved polyurethane which cannot be spun into a nonwoven artificial blood vessel.

It is another object of the present invention to provide an improved fiber-forming segmented polyurethane that can be spun in combination with the generation of an electrostatic field.

It is another object of the present invention to provide an improved polyurethane material suitable for spinning into vascular prostheses and the like.

[0009] These and other objects, features, and advantages of the present invention will become more apparent with consideration of the following detailed description.

The polymers according to the present invention can be generally classified as polyurethanes, since the backbone contains urethane groups and often urea groups, and those groups are repeating units within the polymer backbone. In its most preferred form, the polymer is a segmented polyurethane homopolymer. Such homopolymers are preferably soluble in polar organic solvents and when subjected to stress conditions and stretched immediately after leaving the orifice, such as those that occur when winding a fiber extrudate under tension on a mandrel. It can be extruded through a fine orifice into an elongated continuous fiber or strand strong enough to minimize its cutting. By properly controlling the reactant charge to form a high molecular weight urethane polymer, it is formulated to be fiber-forming or spinnable in air.

The formation of the polyurethane part according to the invention comprises:
This includes reacting a hydroxyl group of a macroglycol (hereinafter referred to as a high molecular weight glycol) with an isocyanate group of a diisocyanate compound to form a prepolymer.

The complete polymerization of the prepolymer is achieved by the addition of the desired chain extender. Prepolymerization and chain extension are typically performed in the presence of a suitable solvent and under suitable reaction conditions.

Although the polymers of the present invention can be prepared in non-solvent systems as is known in the art, they are not suitable for fiber spinning applications, especially from high viscosity solvent solutions such as biocompatible vascular prostheses. When intended to be used for fiber spinning of porous tubes, it is desirable to produce the polymer in a solvent system. When prepared in a solvent, the polymer is usually synthesized with a solids content of less than 60%. Above 60% solids, the polymer is difficult to mix due to its high viscosity. The polymer can be synthesized in a single step rather than a multi-step approach of producing a prepolymer and then polymerizing it further with a chain extender. In general, one-step polymerizations form polymers that are uncontrolled in their structure and crystallize differently than polymers prepared by a two-step approach.

Suitable macroglycols for preparing the polymers according to the invention are those of the general formula HO-R-, such as polyesteramides, polycaprolactone or polyacrylates.
It is a hydroxy-terminated compound having OH. Wherein R
Is a polyester, polyether, polyolefin, or polycarbonate. Examples of macro glycols are tetramethylene glycol, polyethylene glycol, polypropylene glycol, polyester diol and polycarbonate diol.

The other polyester moiety (R moiety) of these macroglycols generally contains the reaction product of a dihydric alcohol and a dibasic carboxylic acid. Instead of the free dicarboxylic acids, the corresponding dicarboxylic anhydrides or the corresponding lower alcohol esters of dicarboxylic acids or mixtures thereof can also be used for the preparation of the polyester polyol part. The dicarboxylic acids may be aliphatic, cycloaliphatic, aromatic and / or heterocyclic, and may be optionally substituted. Dihydric alcohols which can be used are, for example, ethylene glycol, propylene glycol, hexane-1,6-diol and diethylene glycol.

The polycaprolactone portion of these macroglycols is prepared by polymerization of a lactone such as, for example, ε-caprolactone, or by condensation of a hydroxycarboxylic acid, for example, ε-hydroxycaproic acid, with a starting material containing a hydroxyl group. Including polyester. Representative polyether macroglycol moieties include polyethers made from ethylene oxide, propylene oxide, butylene oxide, tetrahydrofuran, and mixtures thereof. Exemplary polyacrylate macroglycol moieties include dihydroxy functional acrylic copolymers. Representative polyesteramide macroglycol moieties are made by replacing a small amount of the diol used to make the described polyesters with compounds such as ethanolamine, isopropanolamine, ethylenediamine and 1,6-hexamethylenediamine.

The diisocyanate reactant according to the present invention has the general formula OCN-R'-NCO, where R 'is a hydrocarbon which may contain aromatic or non-aromatic structures, including aliphatic and alicyclic structures. is there. An exemplary isocyanate is MD
I, that is, 4,4-methylenebiphenyl isocyanate or 4,4'-diphenylmethane diisocyanate. Other exemplary isocyanates are tolylene diisocyanate, such as hexamethylene diisocyanate and 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate, 4,4'-tolidine diisocyanate, m-phenylene diisocyanate, 4-chloro- 1,3-phenylene diisocyanate, 1,4-tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate, 1,10-decamethylene diisocyanate, 1,4-cyclohexylene diisocyanate, 4,4′-methylene bis (cyclohexyl isocyanate), Includes 3,3'-dimethyl-4,4'-diphenylmethane diisocyanate, 1,5-tetrahydronaphthalenediisocyanate, and mixtures of such diisocyanates.

The chain extender to complete the polymerization of the prepolymer must have two or more functional groups. Preferred and well-known chain extenders are 1,
4-butanediol. Generally speaking, ethylene glycol, propylene glycol, ethylenediamine,
Most diols or diamines, including methylene dianiline and the like, are suitable.

As regards the solvent, a polar solvent such as dimethylacetamide is included to ensure a complete and homogeneous reaction. Other suitable solvents of generally polar nature include dimethylformamide, tetrahydrofuran, cyclohexanone and 2-pyrrolidone.

Although other components such as catalysts, antioxidants, and extruders can be included, there is a tendency or preference to exclude such components when a medical grade polymer is desired. In this regard, preferred amine-containing solvents, such as dimethylacetamide, tend to catalyze the reaction and nothing else. Such additives may be necessary when the polyurethane is not solution polymerized.

When it is desired to provide a polyurethane homopolymer, which is a high molecular weight plastic fiber-forming polymer soluble in polar solvents, the diisocyanate component is based on the sum of the equivalents of the hydroxyl and amino group-containing components (active hydrogen equivalent). The equivalent ratio should generally be less than one. This equivalence ratio results from a reaction charge of active hydrogen excess, not isocyanate excess. This ratio represents the relative ratio of isocyanate equivalents (from diisocyanate) to total equivalents (from combination with macroglycol) of hydroxyl groups present during the reaction charge. In practice, this ratio is conveniently determined by formulating a reaction charge having a ratio of about 1 or a slight isocyanate excess such that gelation is observed. The charge is then reduced slightly by small increments of the isocyanate charge, and such repetition is continued until gelation is no longer seen.

The ratio of chain extender to macroglycol determines the hardness and modulus of the polyurethane homopolymer. At very low ratios, such as below 0.1, the product is gummy, and at very high ratios, for example, above 10, the product is very crystalline and non-elastomeric.

Polyurethanes prepared according to the present invention to a 50% solids content are from about 500,000 to 3,000
Gives a polymer solution viscosity of 000 centipoise.
The molecular weight of the polyurethane varies primarily with the ratio of macroglycol to chain extender, with higher ratios of macroglycol to chain extender yielding higher molecular weights within limits. A typical molecular weight range for the polyurethane homopolymer according to the present invention is from about 50,000 to about 300,000 daltons, preferably about 15
On the order of 000 daltons or more,
Such a molecular weight is determined by measurement with polystyrene standards.

EXAMPLE A flask containing polytetramethylene glycol (having a molecular weight of about 650) and a sintered glass boiling chip was heated to 100-120 ° C. with stirring for 1 hour and then heated to 0.1-0.3 mmHg. The taste was dried by reducing the pressure. Dry nitrogen was periodically released into the flask to drive off the water vapor. An aliquot of 1,4-butanediol was also dried, but at a temperature below 100 ° C. These dried reactants were stored at room temperature in sealed containers under molecular sieves and dry nitrogen. The alcohol content was determined by titration. The water content was also determined by titration and was kept below 200 ppm.

[0025] 50 sealed drums of frozen MDI
Thawed in a １００100 ° C. water bath and transferred the dissolved isocyanate to a clean dry round bottom flask under nitrogen. Prior to charging the isocyanate to the reaction vessel, the isocyanate content percetone was determined.

The prepolymer polymerization was first heated (70
C.) A 500 ml round bottom flask is charged with 53.55 g (approximately 4.5 equivalents) of MDI, and then a hot solution (95 to 1 equivalent) containing 31.10 g (approximately 1 equivalent) of polytetramethylene glycol.
(00 ° C.). The addition was always carried out immediately with stirring and nitrogen blowing. The reaction mixture was exothermicly mixed at ambient temperature and the exothermic temperature was 120 ° C.
(High exothermic temperatures should be avoided as the solution may turn yellow and decompose.) After mixing the prepolymer for one hour, the 1,4-butanediol chain in 85 g of well-dried dimethylacetamide The finished polymerization was achieved by adding a hot solution (95-100 ° C) containing 15.07 g (about 3.5 equivalents) of extender. Put the solution under nitrogen
The mixture was further mixed for an hour and the concentrated polyurethane solution was transferred from the mixer to an oven where the reaction was maintained at 65 ° C. for 24 hours. The polyurethane solution was filtered into a dispersion gel and the particles were removed.

In order to form the polyurethane solution into a plurality of fibers in the air and wrap it around a mandrel so as to form it conveniently into a non-woven vascular graft, a plurality of micro-orifices in the shape of a syringe are added to the polyurethane solution. To insert the device into a device for forming an artificial blood vessel on a mandrel. The equivalent ratio of isocyanate to alcohol of this segmented polyurethane that forms fibers in air was 0.990 to 0.999.

It will be understood that the described embodiments of the invention are illustrative of some of the applications of the principles of the present invention. Numerous modifications are possible by those skilled in the art without departing from the spirit and scope of the invention.

Claims (8)

[Claims] 1. An equivalent ratio of an isocyanate group of a high molecular weight glycol reactant having a terminal hydroxyl group, a chain extender, and a diisocyanate having a terminal isocyanate group to the total of hydroxyl groups and amino groups in all reaction components. 1. A fiber-forming polyurethane solution in air comprising a solution in which a segmented polyurethane, which is a reaction product obtained by reacting at less than, is dissolved in a polar solvent. 2. The fiber-forming polyurethane solution of claim 1, wherein said chain extender is selected from the group consisting of diols and diamines. 3. The segmented polyurethane is from 50,000 to 300,0, as measured by polystyrene standards.
3. The fiber-forming polyurethane solution of claim 1 or 2 having a molecular weight of 00 Daltons. 4. The fiber-forming solution according to claim 3, wherein said molecular weight is at least 150,000 daltons. 5. The fiber-forming polyurethane solution according to claim 1, which has a solid content of not more than 60% by weight. 6. The method of claim 1 wherein said polyurethane solution is treated to disperse a gel that exhibits pseudocrosslinking by allophanate formation so that it can be extruded through an orifice into elongated continuous fibers. Fiber-forming polyurethane solution. 7. A fiber obtained by extruding and spinning the fiber-forming polyurethane solution according to claim 1 in air. 8. The fiber-forming polyurethane solution of claim 1 wherein the solution is extruded through an orifice in air to form elongated fibers, wherein the fibers continuously promote tissue growth therein. Winding the pre-elongated fibers onto a mandrel to form a plurality of turns forming a non-woven cylinder having overlapping fibers that contact and adhere to each other to form a surface, comprising: A method of manufacturing a biocompatible vascular prosthesis, comprising removing a nonwoven polyurethane cylinder from a mandrel to provide.