FR2516928A1 - COMPOSITIONS OF HYDROCARBON SEQUENCE COPOLYMER AND DISPERSE POLYSILOXANE AND INFLATABLE BALLOON FOR MEDICAL PROBE MADE OF SUCH COMPOSITIONS - Google Patents

Abstract

THE INVENTION CONCERNS COMPOSITIONS OF HYDROCARBON SEQUENCE COPOLYMER AND DISPERSE POLYSILOXANE AND AN INFLATABLE BALLOON FOR A MEDICAL PROBE MADE OF SUCH COMPOSITIONS; THE COMPOSITIONS CONSTITUTE A PRACTICALLY UNIFORM MIXTURE OF A THERMOPLASTIC ELASTOMER HYDROCARBON SEQUENCE COPOLYMER AND OF 0.1 TO 12 WITH RESPECT TO THE WEIGHT OF THE COMPOSITION OF A POLYSILOXANE; PREFERREDLY, A MINERAL OIL AND POLYPROPYLENE ARE DISPERSED IN THE COMPOSITION; THE COMPOSITION ALLOWS ARTICLES WITH A SMOOTH SURFACE ON MICROSCOPIC EXAMINATION AND IN PARTICULAR INFLATABLE BALLOONS FOR MEDICAL PROBES.

Description

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  The present invention relates to compositions of block hydrocarbon copolymer and dispersed polysiloxane and

  an inflatable balloon for medical probe made of such compositions.

  The modification of the compositions of different polymer materials gives them markedly different properties. The modification of a particular molecular composition can

  allow the production of a material with specific properties

  required for a particular job.

  Recent work has investigated the possibility of producing

  a thermoplastic material having elastomeric properties

  elastomers are thermosetting as opposed to thermoplastic polymers For example, natural and artificial rubbers undergo a necessary stage of vulcanization during their production The crosslinked mass obtained cannot melt

  under the effect of heat On the contrary, it simply burns.

  Silicone rubbers having a polysiloxane structure also undergo crosslinking to acquire their properties.

  elastomers Also, they do not melt when hot.

  In the United States patent series No. 3,485,787, No. 3,830,767, No. 4,006,116, No. 4,039,629 and No. 4,041,103, the Shell Oil Company has attempted to providing an elastomer having thermoplastic properties by using block copolymer compositions Typically, a block copolymer has the formula

A B A (1)

  In thermoplastic elastomers, the central block B of the copolymer

  has the desired elastomeric properties.

  However, unlike the rubbery materials commonly used, the central elastomeric blocks do not crosslink in the material to form a unitary mass. On the contrary, it is the terminal blocks A which confer the required cohesion between the macromolecules. Apparently, these terminal blocks unite as usual for thermoplastics In Shell material, the terminal thermoplastic blocks constitute

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  a small portion of the total weight of the macromolecules Consequently, they adhere to each other in the form of relatively small particles incorporated in the elastomeric mass of the central blocks B. Typically, Shell uses as terminal blocks A polymers formed from monoalkenyl arenes whose

  styrene is a typical example.

  As central block B, Shell uses a polymer conjugated diene. Butadiene and isoprene are examples of

elastomeric central blocks.

  The copolymer can contain more than the three blocks suggested by the formula (1) above. There can exist several interlocking blocks A and B joined together in a linear fashion such that

A B A B A B (2)

  Otherwise or in addition, the block copolymer may comprise blocks forming a branching of the main chain such as

A B A A A B A

  B A Otherwise, it can have a simple structure A B In the description which

  follows, the simple formula (1) encompasses all these variants o B represented

  smells the elastomeric block The letter A designates the thermoplastic bonding block constituting the terminal blocks of a three-block molecule The block copolymers can contain various other

  ingredients such as mineral oil, polystyrene, polypro-

pylene and antioxidants.

  In U.S. Patent No. 3,485,787,

  a mineral oil is incorporated to dilute the block copolymer.

  In this particular patent, the central elastomer block undergoes hydrogenation to produce an ethylene-butylene block from a butadiene block. To avoid the exudation of the dilution oil, it is incorporated in the United States patent from America 3,830,767 a block copolymer petroleum hydrocarbon wax.

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  In US Patents NO 4,006,116 and NO 4,039,629, blends of styrene-ethylene-butylene estyrene block copolymers having different molecular weights are formed for the styrene end blocks and the ethylene center blocks. -butylene These mixtures apparently form a product having superior characteristics in the application to

  shoes for which they are intended.

  In US Patent No. 4,041,103, a block copolymer of styrene-ethylene-butylene-styrene is mixed with a polyamide polymer. This patent indicates that the product has

  improved dimensional stability at elevated temperatures.

  Despite various efforts to produce a high quality thermoplastic elastomer, the materials obtained are

  lacking many of the qualities associated with rubber materials

  usual teuses For example, when extruded, thermoplastic elastomers do not have the smooth surface or the elasticity of

  natural, artificial or silicone-based rubbers.

  A particular need for improved thermoplastic material, in particular with regard to elastomeric properties,

  appears in the medical field Despite the range of plas-

  available, the problems of toxicity, incompatibility, surface roughness, lack of flexibility and others have not

  received a completely satisfactory solution.

  U.S. Patent No. 4,123,409 relates to a thermoplastic elastomer primarily designed to seal a mouth through human tissue.

  uses a block copolymer having thermoplastic end blocks

  ticks and an elastomeric intermediate block The copolymer receives an equal amount of a high molecular weight oil compatible and associable with the elastomeric block of the copolymer Therefore, to obtain the desired improvement, a hydrocarbon mineral oil is incorporated into a copolymer having a block hydrocarbon elastomer Similarly, when the elastomer block consists of a polysiloxane, a silicone oil is part of the final product The materials obtained according to this patent have an increase in flexibility as well

  than the ability to wet the skin.

  In US Patent No. 3,034,509, about 0.15 to 1.00% by weight of a silicone oil is added to a polyethylene used in surgical tubing. silicone reduces the toxic reaction of blood to the tubing It also helps to slow coagulation when the tube comes into contact with living tissue for extended periods. The endotracheal tube is another medical article to which much time and effort has been spent improving. The problems associated with an endotracheal tube are discussed by W Wu et al in Critical Care Medicine 1, 197 (1973), U Nordin in Acta Otorlaryngol suppl, 345, 7 (1975) and by WN Bernhard et al in Anesthesiology, 48, 413 (1978) These articles relate in particular to the inflatable balloon which surrounds the tube of the endotracheal tube The balloon subjects the endotracheal tube in the patient's trachea at the location determined by the anesthesiologist In addition, the balloon must be completely closed at

  minus a portion of the trachea to prevent suction fluids

  ration such as saliva does not cross the trachea to reach

the patient's lungs.

  Two types of balloons are currently used with endotracheal tubes The least preferred balloon is made of a relatively inflexible material or with low elasticity When it is deflated, it has a small residual volume The balloon with "low volume" requires a significant internal swelling pressure for

  that its walls move apart and come into contact with the trachea.

  Any swelling beyond this minimum point of contact exerts

  usually a very high pressure against the tracheal wall.

  This strong pressure against the side wall can damage

  -30 strongly the trachea to the point of causing the death of the patient.

  The second type of endotracheal tube uses a balloon with a high elasticity which, when deflated, has a large residual volume. A process for forming this balloon with large volume consists in placing a balloon with low volume, formed of polyvinyl chloride, in boiling water The swelling

  forced transforms the low volume balloon into a large balloon.

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  Excessive swelling of the endotracheal tube with a large volume balloon exerts less lateral pressure on the trachea than the type of low volume balloon However, the endotracheal tube with large volume can still seriously damage the patient's trachea. , as the balloon comes into contact with a larger surface of the trachea, it has more extensive detrimental effects on the trachea

  than the model whose balloon has a lower volume.

  In addition, the deflation of the large volume balloon folds its wall When it expands in the trachea, the large volume balloon does not normally reach its maximum dimensions If it did, it would have the same harmful effects as the balloon. at low volume However, as the balloon does not expand to its maximum volume, its walls retain at least a few folds These folds constitute passages through which the suction liquids reach the lungs of the patient The wrinkles also leave

  deep grooves in the tracheal mucosa.

  Generally, the endotracheal tube balloons are made of a polyvinyl chloride composition whose rough surface can irritate the patient's windpipe. In addition, polyvinyl chloride contains plasticizers which can be

  leaches and cause toxic reactions.

  Other endotracheal tube balloons are made of a latex or silicone rubber composition. These are two thermosetting materials that require long-term immersion and curing. Therefore, these two materials have non-uniform surfaces that can also irritate the trachea In addition, they may show pitting and generally the rate of disposal of the final product is high In addition, as is the case with thermoset plastics, an article of

  waste cannot be recovered and reused.

  In addition, each product must undergo extensive testing to ensure that it meets the necessary criteria. Even in the case of a perfect product, the rubber materials have a high gas permeability.

  internal pressure of the balloon can increase or decrease depending on the atmos-

  surrounding sphere in the trachea These two types of variation have of course unfortunate consequences The increase in pressure increases the irritation of the trachea; lowering pressure

  can allow the passage of suction liquids around the balloon.

  U.S. Patent No. 4,154,244 suggests using a block copolymer similar to the above Shell materials for the probe tube and balloon. More particularly in this patent, different compositions of the copolymer are used. sequenced by styrene-ethylene-butylene-styrene so that the inflatable balloon has properties different from those of the fairly rigid tube In addition, the material has a rough surface which can irritate

  the patient's trachea Also, the component cannot be extruded

  sition in extremely thin sections to give the balloon the high degree of flexibility desired Therefore, we continue to

  look for improved materials for endotracheal tubes.

  The invention relates to a composition comprising a practically uniform mixture of an elastomeric thermoplastic hydrocarbon block copolymer and a polysiloxane. The composition, which may contain several hydrocarbon block copolymers, has physical and surface properties which were previously obtained only with vulcanized or crosslinked rubbers The present composition consisting of the polysiloxane and of the copolymer can be used and extruded with a very small thickness which it was previously impossible to obtain with the elastomers

  thermoplastic hydrocarbon block copolymers.

  The dispersion of the polysiloxane in a thermoplastic elastomeric hydrocarbon provides a composition which can have a remarkably smooth surface. In particular, the surface can, on a microscopic scale, be as smooth as that of a rubber.

silicone.

  Typically, the composition comprises from 0.1 to 12% by weight or more of the polysiloxane. This constitutes an unexpected result mainly due to the different nature of the molecule.

  polysiloxane relative to the hydrocarbon skeleton of the macromole-

elastomeric cule.

  The polysiloxane content of the composition is even more unusual when the latter comprises an appreciable amount of a mineral oil In fact, the mineral oil can even represent 607 of the total weight of the composition Nevertheless, the composition is capable of containing an amount appreciable poly-

  siloxane and provide advantageous results.

  The composition can contain up to 25% of polystyrene and also other additives such as polypropylene generally at a rate of less than 45% of the total weight of the composition Barium sulphate can be added to make the composition opaque to X-rays Also, foaming agents allow the composition to take the form of a cellular product. It is also possible to incorporate

antioxidants in the composition.

  The block copolymer may have a configuration A B or preferably A B A in which A is a block of monovinylarene polymer To confer the elastomeric properties, B may

  Be a block of hydrogenated or non-hydrogenated conjugated diene polymer.

  The styrene-ethylene-butylene-styrene macromolecule is an excellent example of this type of block copolymer, where the styrene blocks typically constitute about 20 to 50% of the weight of the copolymer, while the ethylene-butylene block constitutes the remaining 50 to 80% The styrene blocks themselves normally have a molecular weight in the range of 5,000 to 40,000 The ethylenebutylene block has a molecular weight much higher than that of the styrene blocks including in the range approximately 000 to 500,000 Typically, the total molecular weight of the

  copolymer is between 50,000 and 600,000.

  When using multiple block copolymers to prepare the present composition, the block copolymers have

  different contents in terminal A blocks and central B blocks.

  Polysiloxane, which is an essentially linear polysiloxane, has a kinematic viscosity in the range of from about to about 106 and preferably from about 200 to 13,000 c St at ordinary temperature (20 to 25 C). A typical example of polysiloxane is silicone oil The polysiloxane consists of units of formula:

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  if 0 o R 1 and R 2 represent H, CH or preferably C and n is a positive integer with a value between 10 and 000. The elastomer composition containing the polysiloxane can be used in various types of medical articles Thanks to the polysiloxane, the elastomer lends itself better to prolonged contact with human tissue The balloon of a medical device such as a Foley catheter or an endotracheal tube can advantageously be

  made from a composition of an elastic hydrocarbon block copolymer

  thermoplastic tomère in which is distributed almost uniformly

  mement an essentially linear polysiloxane.

  The block copolymer with polysiloxane appears to be extremely inert to human tissue. Therefore, the inflatable balloon of an endotracheal tube can remain in contact with the wall of the trachea without irritation due to

toxic reactions.

  In addition, thanks to the great elasticity of the thin sections made of such a material, they can be inflated beyond the pressure at which they seal against the trachea This material which minimizes the lateral pressure against the wall avoids much complications from other probes

  commonly used endotracheal tubes.

  The high elasticity of this copolymer containing polysiloxane as well as the small residual volume of the balloon allow a uniform swelling against the wall of the trachea to form a complete joint This avoids the aspiration of liquid in the lungs

of the patient.

  In addition, the elasticity of the wall of the balloon allows, after deflation, that it contracts by tightening on the tube without it forming folds. Also, the material has a surface

  extremely smooth All of these characteristics prevent damage

  mage the tracheal wall during placement, use

  and removal of the medical device.

  Other characteristics and advantages of the invention

  will be better understood on reading the description which follows

  of several exemplary embodiments and with reference to the accompanying drawings, in which

  FIG. 1 represents an electro-photomicrograph

  nique with a magnification of 2000 x the surface of an elastomeric thermoplastic hydrocarbon block copolymer containing 3% by weight of dispersed polysiloxane;

  FIG. 2 represents an electro-photomicrograph

  also nicks with a magnification of 2000 x the surface of a plasticized polyvinyl chloride commonly used to form the balloons of the endotracheal tubes; FIG. 3 illustrates the surface with a 2000 × magnification of a latex rubber; and

  FIG. 4 represents an electro-photomicrograph

  pic with a magnification of 2000 x the surface of a rubber

silicone.

  According to the invention, the addition of a polysiloxane, preferably a silicone oil to one or more elastomeric thermoplastic hydrocarbon block copolymers, makes it possible to obtain

  several distinct and desirable outcomes First, the ability

  study in the implementation of the material is clearly improved This is particularly important when the material has to be extruded into thin sheets In the absence of polysiloxane, the material has flow properties and surface properties which make the molten plastic material forms globules and therefore has a

  rough surface at the exit of the extruder orifice.

  The tendency of the molten material to agglomerate hinders its implementation in various ways First of all, the extruded material cannot have a very smooth surface As the molten material tends to form globules, the surface is characterized by ridges, furrows and even craters Polysiloxane apparently reducing the surface energy of the material

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  melt allows the extruded plastic to solidify with

a very smooth surface.

  Figure 1 shows an electronic photomicrograph of the surface of a thermoplastic elastomeric block copolymer with dispersed polysiloxane The photomicrograph shows with a magnification of 2000 x dust particles on the surface of the elastomer The material illustrated in Figure 1 is composed of an ABA block copolymer in which the terminal blocks are made of polystyrene and the central block is made of an ethylene-butylene copolymer It also includes

  about 50% by weight of mineral oil, 5% of polypropylene,

  polystyrene and various antioxidants Shelll Chemical

  Company of Houston, Texas, sells base polymer without poly-

  siloxane under the name of Kraton G 2705 The polysiloxane which constitutes approximately 37 of the weight of the final composition is dispersed in the block copolymer The Dow Corning Company of Midland, Michigan, supplies the polysiloxane in the form of the silicone oil freed from volatile matter 360 Medical Grade Among antioxidants

  suitable, figure the Irganox which is a product of Ciba-Geigy Corpo-

ration.

  Comparable microphotographs illustrating other materials commonly used in the medical field, in particular for forming the balloons of the endotrachdal probes, are illustrated in FIGS. 2 to 4 Each of these figures has the same magnification

than Figure 1.

  More particularly, Figure 2 shows the surface of an endotracheal probe balloon made of plasticized polyvinyl chloride This composition is commonly used in endotracheal tubes The photomicrograph shows significant surface irregularities This roughness of the surface irritates and damages the

patient's mucosa.

  Figure 3 illustrates with a magnification of 2000 x the surface of a latex rubber In this case also, the roughness

  of the surface has an irritating effect on the patient.

  Figure 4 shows the surface of an endo-

  tracheal made of silicone rubber The photograph shows that rubber has a certain tendency to form globules Besides, the surface seems relatively smooth Comparison of

  FIGS. 1 and 4 show that the thermo-hydrocarbon sequenced copolymer

  plastic with dispersed polysiloxane has a smooth surface comparable to or better than silicone rubber. The surface effects produced by polysiloxane

  appear to be due to a slight increase in the concentration of

  silicone cules on the surface of the composition The processing technique typically causes a uniform dispersion of the polysiloxane in the composition However, there is a slight migration of the silicone molecules on the surface of the material Consequently, the surface of the material to a depth of about 5.0 to 20.0 nm seems to have a concentration of silicone molecules about double that of the whole The thinness of

  this layer of course prevents this increase in the con-

  centration modifies the overall concentration of the polysiloxane in the material Consequently, on a macroscopic scale, the polysiloxane is dispersed practically uniformly in the material The surface therefore has properties clearly different from those of the copolymer

  hydrocarbon block not containing polysiloxane.

  The smooth surface and the concentration of the polysiloxane suggest the compatibility of the material with the blood These two factors reduce the tendency to fixation and coagulation

  blood components on the polymer.

  Shell's patents, previously cited, provide

  a general overview of thermo-hydrocarbon block copolymers

  elastomeric plastics The information found in these references as well as in the United States patent Reissue No. 27 145 applies generally to the disclosure relating to

  following thermoplastic rubbers.

  Typically, the central block or block B of the elastomeric hydrocarbon block copolymer A B A gives the molecule its elastomeric properties; the blocks B have in themselves the qualities of rubbers The polymers formed from conjugated dienes have proved advantageous in this regard Butadiene and isoprene constitute monomers which, after polymerization, provide the central elastomer block In addition, the block of butadiene can be

  hydrogenated to form an elastomeric block of ethylene copolymer-

  butylene. Typically, the mechanical properties of the block copolymer obtained are mainly determined by the elastomer block B Consequently, the central block must constitute at least the majority of the total molecular weight of the block copolymer In practice, it generally constitutes 50 to 80% molecular weight

  of the final product The molecular weight of the central block B is generally

  typically in the range of 20,000 to 500,000 and typically

  in the narrower range from 20,000 to 200,000.

  The terminal blocks or blocks A of the copolymer provide the cohesiveness between the individual macromolecules of the thermoplastic rubber These terminal blocks behave as a thermoplastic material Generally, they have no elastomeric character However, since they constitute only a small portion of the weight of the final elastomer, they do not impart their own

  mechanical properties to the product.

  The thermoplastic adhesion between the molecules of the blocks A replaces the vulcanization of natural latex or silicone rubbers During vulcanization, chemical bonds are formed between the macromolecules constituting the rubber These

  cross-linking reactions are generally carried out at temperatures

  high tures and the materials are therefore called "thermoset" These rubbers generally require significant periods of time to "harden" or present the required crosslinking Crosslinking is not a reversible process Consequently rubbers

  non-thermoplastic, once they have hardened to a particular form

  cannot melt to take a different shape.

  At high temperatures, they only oxidize or, in cases

extreme, burn.

  The terminal blocks A of the block copolymer adhere to each other by physical attraction bonds characteristic of all thermoplastic materials. Therefore, when they are in the solid state, the terminal blocks of several molecules adhere to each other to provide the required cohesiveness to matter blocks

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  adhering terminals form small groups or "particles" incorporated

  porés in the predominant elastomeric portions of the material.

  These particles are used to bind the various macromolecules in the form

of a unit mass.

  At high temperatures, these "particles" of blocks

  physically linked terminals of different macromolecules melt.

  The whole mass then takes a liquid or molten state and can be subjected to conventional implementation techniques such as

  extrusion, blow molding or injection molding After cooling

  the terminal blocks of the different macromolecules

  again physically unite with each other and form particles.

  The material then generally retains the shape it had when the particles formed by the terminal blocks A have

united in the solid state.

  The category of molecules called monovinylarenes

  has been found to provide suitable thermoplastic terminal blocks A

  required for these polymers Examples of monomers that can be

  polymerize in terminal blocks include isoprene and α-methyl isoprene The first of these monomers has generally been used more.

  Terminal blocks A generally have a molecular weight

  laire in the range of 5,000 to 40,000 and most have a molecular weight in the range of 8,000 to 20,000 The blocks

  terminals constitute approximately 20 to 50% of the total weight of the macro

  molecule. As previously indicated, the elastomeric block copolymer molecule may contain more than two or three blocks suggested by the formula ABA The macromolecule may contain additional blocks having the linear or branched arrangements suggested by the formulas (2) and (3) In this case , all the terminal blocks of the molecule may not consist of the thermoplastic block A In all cases, the macromolecule generally has

  a total molecular weight in the range of 50,000 to 600,000.

  As previously indicated, one or more block copolymers can be used to form the composition When more than one block copolymer is used, the block copolymers differ from one another by the quantities of terminal blocks A

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  and of intermediate blocks B which they contain For example, a mixture of a first block copolymer containing approximately 28% by weight of blocks A of styrene (for example Kraton G 1650 from Shell) and a second block copolymer containing about 33% by weight of blocks A of styrene (for example Kraton G 1651 from Shell). The weight ratio of the first block copolymer to the second can

vary between 15/85 and 50/50.

  The polysiloxane consists of the following units:

If 0-

  R 2 n o R 1 and R 2 represent H, CH 3 or and N is a positive integer between 10 and 20,000 In the silicone oils which it

  is easy to obtain, the symbols R 1 and R 2 represent gener

  each methyl radical Polysiloxane is essential-

  linear as shown in the formula above An example

  The preferred polysiloxane is silicone oil.

  The viscosity of the polysiloxane can allow it to easily coat grains and pellets with the elastomer and to mix with them. It is therefore generally necessary for the kinematic viscosity to be in the range of approximately 20 to 1,000,000 c St. A the lower end of the above range, the polysiloxane has some difficulties in coating the polymer pellets. In a preferred embodiment, a silicone oil having a kinematic viscosity of 200 to 13,000 is used satisfactorily and without complications. c St. When the final product is used for medical purposes, a medical grade polysiloxane must be used. In addition, the removal of volatile matter from the polysiloxane before its introduction into the block copolymer eliminates the elements of very low molecular weight which could be leached out. and irritate the patient's tissue.

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  Generally, the polysiloxane constitutes approximately 0.1 to 12% of the total weight of the elastomer composition, preferably 1 to 7%. The capacity to fix this quantity of polysiloxane which the hydrocarbon exhibits is surprising; the hydrocarbon backbone of the polymer has a very disparate structure compared to the structure

polysiloxane silicone.

  This possibility is even more surprising in the case of polymer compositions which already contain quantities

  important mineral oil as lubricant Mineral oil even

  if present may constitute up to 60% of the total weight of the composition Typically, the mineral oil constitutes 25 to 50% of the

total weight of the composition.

  In addition, mineral oil and polysiloxane also have markedly different chemical properties.The first is

  composed of a hydrocarbon, while the polysiloxane is a sili-

  cone In addition, the mineral oil fills the spaces that would be likely to receive the polysiloxane However, a composition

  containing 50% mineral oil can still receive several pour-

  cents of the polysiloxane to produce a significantly different elastomer.

  The addition of polypropylene as a binder to the present elastomer composition has a reinforcing effect on the elastomer composition Polypropylene also slightly reduces the elasticity The amount of polypropylene added generally remains less than% of the total weight of the composition It is more generally understood in the range of 2 to 20% or in the narrower range of

at 10%.

  The addition of barium sulfate also strengthens the polymer composition Of course, barium sulfate also makes the polymer composition opaque to X-rays Titanium dioxide

  pigment can also change the appearance of the polymer Poly-

  styrene can improve the rheological properties of the polymer.

  The addition of a foaming agent to the polymer during its preparation leads to a clearly different type of product. Instead of a practically solid material, a cellular product filled with air is obtained with a considerably reduced density. This cellular thermoplastic elastomer has generally the consistency of a sponge The use of a non-toxic foaming agent makes it possible to use the product obtained in the medical field One of these non-toxic foaming agents is azobisformamide Added at a rate of approximately 2% , it releases gaseous carbon dioxide The gas bubbles covered with the molten elastomer produce the spongy material after solidification This cellular product can be useful as a compress for

wounds.

  A medical device balloon such as a probe

  tracheal made of this thermoplastic elastomer with poly-

  dispersed siloxane can expand to 12 times its original size without bursting It can easily be inflated to 8 to 10 times its original diameter without undesirable effects This allows it to expand to the necessary size when used in a abnormally large trachea It becomes safe to inflate the balloon until it

  comes into contact with the wall of the trachea and it provides a watertight

  complete shea with the trachea without risk of bursting or

lesion other than negligible.

  In addition, the high elasticity of the material requires only a minimal increase in the internal pressure of the balloon when its

  volume increases So when the balloon reaches a sufficient size

  health to come into contact with the tracheal wall, it exerts only a minimal pressure against this wall Consequently, a reduced range of sizes of endotracheal tubes is enough for all the patients of a hospital So the hospital can store less of

sizes and reduce inventory.

  In addition, the elasticity of the material makes it possible to exert only a slight pressure against the tracheal wall when the balloon is inflated to a volume sufficient to seal with the trachea This low pressure avoids the injuries caused by

  conventional balloons which exert significant lateral pressure.

  In addition, the present material has a smooth and flexible surface when swollen. This property also has the effect of reducing irritation and alterations of the mucous membrane.

of the patient's tracheal wall.

  The low pressure necessary for the balloon to seal against the wall of the trachea and the inherent flexibility of the present material allow easy flexion This property is important because the artificial respiration apparatus often causes slight pulsations of the endotracheal tube in the direction of the patient's trachea The flexible balloon absorbs these movements Consequently, the balloon does not rub against the tracheal wall On the contrary, polyvinyl chloride balloons do not have this flexibility and elasticity When the artificial respiration device causes pulsations,

  polyvinyl chloride balloons rub against the tracheal wall.

* As their surface is rough, they can damage the windpipe

  patient and in practice they harm it.

  The present composition can also be used for the manufacture of balloon catheters known in the art such as Foley catheters. The composition can also be used to form the entire catheter or only the balloon of the catheter. In the following examples, a polystyrene-ethylene-butylenepolystyrene (SEBS) polymer is used with a lubricating mineral oil sold under the name of Kraton G 2705 by Shell Chemical Company The silicone oil used as polysiloxane is slowly added to the polymer pellets and we mix the whole

  in the barrel until the pellets have a uniform coating

  oil form At this time, we sprinkle the mixture of ingredients

  any additional such as barium sulfate or polypro-

  pylene The mixture of all the ingredients is then introduced into the hopper of the extruder so that they are brought to the

power section.

  In the following examples, the quantities of ingredients are expressed in percentages by weight. In addition, to determine the tensile strengths, standard samples in the form of dumbbells, die cut, are subjected to tests at ordinary temperature. , with an Instron device with a speed of

displacement of 50 cm / min.

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EXAMPLES 1 to 7

  A mixture of SEBS Kraton G 2705 resin pellets and 2 to 5% of silicone oil is introduced into a Brabender extruder. The particular oil used has a kinematic viscosity of 350 c St at ordinary temperature and has been freed of volatile products. before use This oil is supplied by Dow

  Corning Company of Michigan as 360 Medical Grade.

  To prepare an elastomer containing 2% of polysiloxane, 1.36 kg of SEBS pellets are mixed with 27.21 g of silicone oil. The extruded material has a thickness of between 0.40 and

  0.46 mm and has a 100% modulus of elasticity of 19.3 bars.

  The values of the elongation and the tensile strength of this product at 2% are shown in table 1 below with the corresponding values of elastomers containing 3, 4 and 5%.

  silicone oil In the latter examples, respective

  40.82 g and 54.43 g and 68.04 g of silicone oil at 1.36 kg

elastomer pellets.

  Examples 2, 4 and 7 were not carried out at the same time as the other examples in Table 1 The differences in the results obtained with these materials may indicate a difference in pressure in the extruder In these examples, the material has a

  1007% modulus of elasticity of 20.7 bars.

TABLE 1

  Example Silicone oil Elongation Resistance at (%) (tensile (bars)

1 _ 2,800 144.0

2 2,710 158.0

3 3,650 133.0

4 3,700 135.0

4,560,124.0

6 5,590 116.4

7 5 710 115.8

  In hot-joint tearing tests carried out with a material having a nominal dimension of 12.7 mm, at the speed of 5 cm / min, the composition of Example 2 with 2% silicone oil was tested at 0.72 da N / cm and 8.9 bars The material of Example 4 at 3% of polysiloxane was tested at 0.51 da N / cm and

4.8 bars.

  EXAMPLES 8 and 9 In these examples, in addition to the silicone oil, the SEBS pellets are mixed with 5% polypropylene having a melt index of 12 according to standard ASTM D-1238-70 and sold by Shell under the designation 5820 In the first of these tests, the same Brabender extruder is fed with a mixture comprising 1.36 kg of SEBS pellets, 40.82 g of the silicone oil described above and 58.04 g of polypropylene La extruded material has a thickness between 0.38 and 0.43 mm and has a modulus

  100% elasticity of 20.7 bars.

  When the amount of silicone oil is increased from 3 to% (54.43 g), a material with increased elongation and the same tensile strength is obtained. The results are shown in the

table 2 following.

TABLE 2

  % of polypropylene Example Silicone oil Elongation Resistance to (%) (%) traction (bars)

8 3,620 144.0

9 4 690 144.0

EXAMPLES 10 to 12

  In these examples, mixtures consisting of 1.36 kg of SEBS resin pellets and 204.12 g (15%) of barium sulfate are prepared. The amount of silicone oil in these mixtures is 3% (40.82 g), 4% (54.82 g) or 5% (58.04 g) The sheets produced by extrusion of these mixtures have a thickness of between 0.36

2-516928

  and 0.40 mm and a modulus of elasticity at 1007 of 21.4 bars.

  the tensile strength of these products are listed in

the following table 3.

TABLE 3

  15% Ba SO 4 Example Silicone oil Elongation Resistance to (M) (M) tensile (bars)

3,580 105.4

il 4 650 114,4

12 5 640 102.7

EXAMPLES 13 to 15

  We use an HPM extruder with a 63.5 mm screw to produce a material with optimal properties The screw has a compression factor of 4/1 and rotates at 10 rpm The three zones of the extruder operate at 1850 C , 1930 C and 1990 C, the die temperature being 204.50 C. The extruder is fed with a mixture consisting of 2% (45.36 g) of the silicone oil used previously and 2.27 kg of Kraton G 2705 pellets from Shell On extrudes the product

  tubular in several tests with different wall thicknesses.

  The material has a 100% elastic modulus of 17.2 bars.

  To obtain a 0.254 mm thick tubular wall, a 12.14 mm diameter die and a 11.58 mm needle are used with the extruder. The material is slightly stretched after extrusion. The percentage of elongation and resistance in tension are shown in the following table 4 for tubes having

  a wall thickness of 0.102 to 0.127 mm and 0.064 to 0.127 mm.

  As shown in Table 4, the decrease in thickness of the

  wall reduces the elongation and the tensile strength of the tube.

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TABLE 4

  The above examples suggest that the polymer formed from Shell's SEBS Kraton G 2705 elastomer with about 2-4% silicone oil has the optimal strength combination

  high mechanical, low modulus and maximum elongation The addi-

  5% polypropylene does not change the tensile strength

of the material produced.

  The addition of 15% barium sulfate reduces the resistance

  tensile strength of the elastomer obtained However, the elongation clings Barium sulfate in compositions containing 3 to 4% of silicone oil also causes a slight increase in the

rigidity of the elastomer obtained.

EXAMPLE 16

  A mixture is prepared having the composition Components Kraton G-1651 (product of Shell Co) Kraton G-1650 (product of Shell Co) Polypropylene n 5820 (product of Shell Co) Polypropylene n 467 DP (product of Eastman Chem Co) Antioxidant ( Irganox # 1010, product of Ciba-Geigy Corp) Silicone oil # 360 (product of Dow Corning) 1 Mineral oil (product of Witco Chemical Co) 2 Weight (g), 3 38.7, 0 9.0 0.15 next:% ponderal, 8 12.89 4.99 2.99 o 005 o 12.0, 0

300.15

  4.00, 00, 00 1 Kinematic viscosity = 12,500 c Ts 2 Viscosity = 350 c P 2% silicone oil Example Thickness (mm) Elongation (%) Tensile strength (bars)

13 0.254 920 159.8

14 0.102 0.127 810 113.0

0.064 0.127 610 77.2

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  In the above mixture, the weight ratio of Kraton G-1651 to Kraton G-1650 is 70/30. It is mixed dry and then mixed in the molten state in a Banbury mixer at the maximum vapor pressure of 49, 9 bars for 3 to 5 min The melt is then transformed into a sheet with a rubber mill at the maximum steam pressure (49.9 bars) for 1 to 2 min. The sheets obtained are then compression molded or extruded from cut strips. Samples of razor cut strips measuring 76.2 x 6.35 x 1.78 mm are prepared and tested to determine the following physical properties: Shore A hardness 46 Elongation (%) 750 Tensile strength, bars 55.8

EXAMPLE 17

  Example 16 is repeated with a similar composition, except that 96.9 g of Kraton G-1651, 17.1 g of Kraton G-1650 and 150 g of mineral oil are used, the amounts of other components are unchanged In this mixture, the weight ratio of Kraton

  G-1651 at Kraton G-1650 is 85/15 This mixture provides a

  sition with the following properties Shore A hardness 44 Elongation (%) 880 Tensile strength, bars 68.9

EXAMPLE 18

  Example 16 is repeated with a similar composition, except that 57 g of Kraton G-1651, 57 g of Kraton G-1650 and 30 g of polypropylene NO 5820 are used, the amounts of the other components being unchanged In this mixture, the weight ratio of Kraton G-1651 to Kraton G-1650 is 50/50 This mixture provides a composition having the following properties Shore hardness A 56 Elongation (%) 605 Tensile strength, bars 36.5

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  The results of Examples 16 to 18 show that

  blends of block copolymers also produce compounds

  sitions with excellent properties.

  Of course, various modifications can be made by those skilled in the art to the devices or methods which have just been described only by way of nonlimiting examples.

  without departing from the scope of the invention.

Claims (17)

R E V E N D I C A T I O N S   1 Composition, characterized in that it consists of a practically uniform mixture of (A) a block copolymer   elastomeric thermoplastic hydrocarbon and (B) a polysiloxane.   2 Composition according to claim 1, characterized in   that said polysiloxane is an essentially linear polysiloxane.   3 Composition according to claim 2, characterized in that said polysiloxane has a kinematic viscosity comprised in   the range of about 20 to 1,000,000 c St at room temperature.   4 Composition according to claim 3, characterized in that said block copolymer is a block copolymer of styrene-ethylenebutylene-styrene. Composition according to Claim 4, characterized in that the styrene blocks of said copolymer have a molecular weight of approximately 5,000 to 40,000 and the ethylene-butylene block of said copolymer   has a molecular weight of about 20,000 to 500,000.   6 Composition according to Claim 5, characterized in that the said polysiloxane constitutes approximately 0.1 to 12% of the total weight of the composition.   7 Composition according to claim 6, characterized in that said polysiloxane comprises the units: R 1 Si O R 2   o R 1 and R 2 represent H, CH 3 or and N is an integer.   positive with a value between 10 and 20,000.   8 Composition according to Claim 7, characterized in that the said polysiloxane has a kinematic viscosity of approximately 200 to 13,000 c St. 9 Composition according to the claim 5, characterized in that it comprises at least one additional elastomeric thermoplastic hydrocarbon block copolymer having quantities of styrene blocks and ethylene-butylene blocks different from those of the copolymer (A). Composition, characterized in that it consists of a practically uniform mixture of:   (A) at least one thermo-hydrocarbon block copolymer   elastomeric plastic, said copolymer having a total molecular weight of about 50,000 to 600,000; (B) an essentially linear polysiloxane having a kinematic viscosity of about 20 to 1,000,000 c St at room temperature and constituting about 0.1 to 12% of the total weight of said composition; and (C) a mineral oil constituting less than about 60%   the total weight of said composition.   11 Composition according to claim 10, characterized in that it further comprises polypropylene which constitutes less   about 45% of the total weight of said composition.   12 Composition according to Claim 11, characterized in that the said block copolymer has a configuration A B A o A is a block of monovinylarene polymer and B is a block of   hydrogenated or non-hydrogenated conjugated diene polymer.   13 Composition according to claim 12, characterized in that: (A) said block copolymer is a block copolymer of styrene-ethylenebutylene-styrene; (B) said polysiloxane constitutes approximately 0.1 to 12% of the total weight of said composition; (C) said mineral oil constitutes about 25 to 50% of the total weight of said composition; and (D) said polypropylene constitutes approximately 5 to 10% of the total weight of said composition.   14 Composition, characterized in that it consists of a practically uniform mixture of: (A) at least one elastomeric thermoplastic block copolymer ABA o A is a block of monovinylarene polymer and B is a block of hydrogenated conjugated diene polymer or not hydrogenated; (B) an essentially linear polysiloxane having a kinematic viscosity of about 20 to 1,000,000 c St at room temperature and constituting about 0.1 to 12% of the total weight of said composition; and (C) a mineral oil constituting less than about 60%   the total weight of said composition.   Composition according to Claim 14, characterized in that it also comprises polypropylene constituting less   about 45% of the total weight of said composition.   16 Composition according to claim 15, characterized in that: (A) said block copolymer is a styrene-ethylenebutylene-styrene block copolymer; (B) said polysiloxane constitutes approximately 0.1 to 12% of the total weight of said composition; (C) said mineral oil constitutes about 25 to 50% 7 of the total weight of said composition; and (D) said polypropylene constitutes approximately 5 to 10% of the total weight of said composition.   17 Inflatable balloon for medical probe, characterized in that it is formed of a composition comprising a practically uniform mixture of:   (A) at least one thermo-hydrocarbon block copolymer   elastomeric plastic, said copolymer having a total molecular weight of about 50,000 to 600,000; (B) an essentially linear polysiloxane having a kinematic viscosity of about 20 to 1,000,000 c St at room temperature and constituting about 0.1 to 12% of the total weight of said composition; and (C) a mineral oil constituting less than about 60%   the total weight of said composition.   18 Balloon according to claim 17, characterized in that the composition further comprises (D) polypropylene which   constitutes less than about 45% of the total weight of said composition.   19 Balloon according to claim 18, characterized in that said block copolymer has a configuration A B A o A is a block of monovinylarene polymer and B is a block of polymer   of hydrogenated or non-hydrogenated conjugated diene.   Balloon according to claim 19, characterized in   that the block copolymer (A) is a block copolymer of styrene-   ethylene-butylene-styrene, said polysiloxane (B) constitutes approximately 1 to 12% of the total weight of said composition, said mineral oil constitutes approximately 25 to 50% of the total weight of said composition and said polypropylene (D) constitutes approximately 5 to 10 % of the total weight of said composition.   21 Balloon according to claim 20, characterized in that the styrene blocks of said copolymer have a molecular weight of approximately 8,000 to 20,000 and constitute approximately 20 to 50% of the total weight of said copolymer and the ethylene-butylene block has a molecular weight of around 20,000 to 500,000 and constitutes 50 to 80% of the total weight of said copolymer.   22 Balloon according to claim 21, characterized in that said composition further comprises at least one block copolymer of additional styrene-ethylene-butylene-styrene having a   different content of styrene blocks.