Enteral feeding tubes

An enteral feeding tube includes a unitary, molded weighted bolus insert molded to a preformed tubular stem. The bolus and stem are each formed from a polymeric composition including a thermoplastic elastomeric block copolymer, e.g. styrene-ethylene-butylene-styrene, and an essentially linear polysiloxane having a kinematic viscosity at room temperature of 20 to 10.sup.6 centistokes, and optionally, polypropylene and/or mineral oil. The bolus is weighted with tungsten powder mixed into the polymeric composition. The bolus includes a central bore extending over at least a portion of its length and communicating with the interior of the stem and to the exterior of the bolus.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to enteral feeding tubes. More specifically, 
this invention relates to enteral feeding tubes formed of a polymeric 
composition comprising a block copolymer and a polysiloxane, and a unique 
weighted bolus for use therewith. 
2. Description of the Prior Art 
Enteral feeding (stomach and intestinal feeding) is commonly used to 
nourish patients who, for a variety of reasons, cannot consume food 
normally. Compared with intravenous (parenteral) feeding, enteral feeding 
is a more natural way to supply the patient with nutrition while helping 
to reduce possible infection and vein damage. 
Conventional enteral feeding tubes are made of polyvinylchloride, 
elastomeric silicone or polyurethane. These materials have been found to 
be unsatisfactory for the following reasons. For polyvinylchloride, 
stomach acids can leach out the plasticizer from the polyvinylchloride. If 
the tube is left in the stomach for an extended period of time, the 
leached tube hardens and becomes brittle and distorted. As is apparent, 
this causes patient discomfort and can make removal of the tube difficult 
and painful. On the other hand, elastomeric silicone tubing is much softer 
and resists hardening. However, because of its limpness, an elastomeric 
silicone tubing is extremely difficult to insert and position in the 
stomach. Although polyurethane tubes have intermediate flexibility and are 
easier to insert than silicone, they are still difficult to insert and 
position. 
In general, an enteral feeding tube comprises an elongated stem (tube body) 
having two ends--a distal end which ultimately is positioned within the 
stomach or intestines of a patient and a proximal end which remains out of 
the patient and preferably is equipped with a connector for attachment to 
a nutritional support system. The distal end may be joined to a weighted 
terminal (bolus) and the proximal end may have a female connector with an 
integrally formed closure plug. The connector and bolus usually are 
connected to the stem by bonding agents or adhesives. As a result of the 
use of these bonding agents, a secure bond may not be achieved and 
additional foreign substances are introduced into the body of the patient. 
The weighted bolus normally comprises a pouch containing therein a heavy 
material. Mercury has been most often used as the weighted material. 
However, inasmuch as mercury is a highly toxic material and can cause much 
harm to the patient should the pouch burst, a substitute therefor should 
be used. 
In order to administer nutrients to the patient through the enteral feeding 
tubes, current tubes have openings formed in the wall of the tube body 
proximally of the weighted bolus. These openings create weakened areas in 
the tube body which may cause the tubes to kink and, thus, to occlude the 
tube and obstruct the flow of nutrient. Because of the use of mercury or 
other such materials in the bolus, it heretofore has been impossible or 
impractical to provide the openings in the bolus itself where the 
likelihood of kinking would be greatly reduced or totally eliminated. 
Thus there is a need for an enteral feeding tube formed of a material which 
is easy to handle because of the desired degree of flexibility, can 
withstand the action of stomach acid and have a smooth surface which will 
not irritate the patient's tissues. Moreover, there is a need to eliminate 
the hazards associated with the use of mercury and other unbonded 
substances in the weighted bolus and also to eliminate or greatly reduce 
the possibility of kinking and its associated problems. The present 
invention was made with the objective of overcoming the known shortcomings 
of conventional enteral feeding tubes. 
SUMMARY OF THE INVENTION 
The present invention provides an enteral feeding tube formed of a 
polymeric composition comprising a thermoplastic elastomeric hydrocarbon 
block copolymer and a polysiloxane. The block copolymer comprises blocks 
of styrene-ethylene-butylene-styrene wherein the styrene blocks have a 
molecular weight of 5,000 to 40,000 and the ethylene-butylene block, 
20,000 to 500,000. The polysiloxane has a kinematic viscosity of 20 to 
10.sup.6 centistokes at room temperature. 
In one embodiment of the invention, the distal end of the enteral feeding 
tube is provided with a weighted bolus formed from a unique formulation of 
a polymeric composition and tungsten. The tungsten is a heavy material 
that, when compounded with the polymeric composition, may be molded into a 
variety of configurations and, preferably, it may be insert molded 
directly onto the distal end of the tube body. This eliminates the 
necessity of using bonding agents to secure the bolus to the tube. 
Also, the unique compounded bolus formulation may be molded or otherwise 
formed into a hollow configuration which permits the formation of openings 
directly in the bolus, thus, avoiding the requirement of having the 
openings in the tube body where kinking may occur. 
As a further advantage of the present invention, because of the 
compatibility of materials utilized in the construction of the tubing stem 
and the connector, these components also may be firmly secured together 
during the insert molding of the connector directly onto the proximal end 
of the tubing without the use of bonding agents.

DETAILED DESCRIPTION OF THE INVENTION 
The present invention provides enteral feeding tubings formed of a 
composition comprising a substantially uniform mixture of an elastomeric 
thermoplastic hydrocarbon block copolymer and a polysiloxane. The 
composition, which may contain more than one hydrocarbon block copolymer, 
possesses physical and surface properties which avoid all of the 
above-described problems found in conventional enteral feeding tubes. 
In its simplest form, the composition comprises from about 0.1 to 12 
percent, by weight, of the polysiloxane, the remainder being the block 
copolymer. This represents an unusual result primarily because of the 
dissimilar nature of the polysiloxane molecule compared to the hydrocarbon 
backbone of the elastomeric macromolecule. 
The polysiloxane content of the composition becomes even more unusual where 
the latter includes an appreciable amount of mineral oil. In fact, the 
mineral oil may even represent 60 percent of the composition's total 
weight. Nonetheless, the composition appears able to take up an 
appreciable amount of polysiloxane and achieve the beneficial results. 
The composition may include other additives such as polypropylene, 
generally in an amount less than 45 per cent of the total weight of the 
composition. In addition, antioxidants and radiopaque materials may be 
included in the composition. 
The block copolymer which preferably comprises from about 23 to 73 percent 
by weight of the total weight of the composition may have an A - B, 
preferably A - B - A, configuration in which A takes the form of a 
monovinyl arene polymer block. To provide the elastomeric properties, B 
may be a hydrogenated or nonhydrogenated conjugated diene polymer block. 
The copolymer may contain more than two or three blocks suggested above. 
It may have several interspersed A and B blocks linearly interconnected as 
A - B - A - B - A - B. Alternately or additionally, the block copolymer 
may have blocks with a branched connection to the main chain as 
##STR1## 
For the present invention, the A - B - A structure will be used to 
encompass all of these variations in polymer block structure. 
The styrene-ethylene-butylene-styrene macromolecule represents a prime 
example of this type of block copolymer, wherein the styrene blocks 
typically constitute about 20 to 50 percent of the copolymer's weight 
while the ethylene-butylene block provides the remaining 50 to 80 percent. 
The styrene blocks themselves normally have a molecular weight in the 
range of 5,000 to 40,000. The ethylene-butylene block has a molecular 
weight greatly exceeding that of the styrene blocks and falling within the 
approximate range of 20,000 to 500,000. The total molecular weight of the 
copolymer typically ranges from 50,000 to 600,000. By molecular weight, it 
is meant either the weight average or number average molecular weight, 
since for the block copolymers useful in the present invention there is 
little difference between these molecular weights. 
When more than one block copolymer is used to prepare the polymeric 
composition, the block copolymers have different contents of terminal A 
blocks and middle B blocks. 
The polysiloxane, which is an essentially linear polysiloxane, has a 
kinematic viscosity within the range of about 20 to 10.sup.6, preferably 
about 200 to 13,000, centistokes at room temperature (20.degree. to 
25.degree. C.). A typical example of the polysiloxane is silicone oil. The 
polysiloxane has the repeating structure: 
##STR2## 
wherein R.sub.1, R.sub.2 =H, 
##STR3## 
with CH.sub.3 being preferred, and n is a positive integer having a value 
ranging from 10 to 20,000. 
Examples of such block copolymers are described in a series of U.S. patents 
issued to the Shell Chemical Company namely: U.S. Pat. Nos. 3,485,787; 
3,830,767; 4,006,116; 4,039,629; and 3,041,103. 
Adding a polysiloxane, preferably silicone oil, to one or more elastomeric, 
thermoplastic hydrocarbon block copolymers accomplishes several distinct 
and desirable results. Initially, the composition displays a substantial 
improvement in its processability. This has particular importance when the 
material is formed into thin webs. Without the polysiloxane, the material 
appears to have flow and surface properties which cause the molten plastic 
to form globules, thus a rough surface. 
The surface effects produced by the polysiloxane appear to derive from a 
slightly increased concentration of silicone molecules at the 
composition's surface. The processing techniques discussed below should 
typically result in a uniform dispersement of the polysiloxane throughout 
the composition. However, a slight migration of the silicone molecules to 
the material's surface may occur. As a result, the material's surface, to 
a depth of about 5.0 to 20.0 nm, appears to have a concentration of 
silicone molecules approximately twice that of the bulk of the material. 
The thinness of this layer, of course, prevents the greater concentration 
there from affecting the bulk concentration of the polysiloxane throughout 
the material. Consequently, on a macroscopic scale, the material has a 
substantially uniform dispersement of the polysiloxane. This gives the 
surface substantially different properties than the hydrocarbon block 
copolymer without the polysiloxane. 
Typically, the middle or B, block of the A - B - A elastomeric hydrocarbon 
block copolymer provides the molecule with its elastomeric properties; the 
B blocks themselves possess the rubber qualities. Polymers formed from 
conjugated dienes have found favor in this role. Butadiene and isoprene 
represent monomers which, after polymerization, have provided the middle, 
elastomeric block. 
The resulting block copolymer typically has its mechanical properties 
determined primarily by the elastomeric B block. Accordingly, the middle 
block should provide at least a majority of the block copolymer's total 
molecular weight. In fact, it usually provides 50 to 80 percent of the 
molecular weight of the final product. The molecular weight of the middle 
B block usually falls within the range of 20,000 to 500,000 and typically 
comes within the narrower range of 20,000 to 200,000. 
The terminal, or A, blocks of the copolymer provide the cohesiveness 
between the individual macromolecules in the thermoplastic rubber. These 
terminal blocks themselves behave as a thermoplastic. They do not usually 
display any elastomeric quality. However, representing a minority of the 
weight of the final elastomer, they do not impart their own mechanical 
properties to the product. 
The thermoplastic adherence between molecules of the A blocks replaces the 
vulcanization of the natural, latex, or silicone rubbers. In 
vulcanization, actual chemical bonds develop between the macromolecules 
constituting the rubber. These crosslinking reactions generally occur at 
elevated temperatures and thus impart the name "thermoset" to the 
materials. These rubbers generally require extensive periods of time to 
"cure": or undergo the required crosslinking. The crosslinking does not 
represent a reversible process. As a consequence, the nonthermoplastic 
rubbers, once cured to a particular form, cannot melt to adopt a different 
form. At elevated temperatures they only oxidize or, in more extreme 
cases, burn. 
The terminal A blocks of the block copolymer adhere to each other through 
physical attraction bonds characteristic of all thermoplastics. Thus, when 
in the solid form, the terminal blocks of several molecules adhere to each 
other to provide the required cohesiveness throughout the material. These 
particles serve to bind the sundry macromolecules in the mass into an 
integral whole. 
At elevated temperatures, these "particles" of physically bonded terminal 
blocks of different macromolecules actually melt. The entire mass of 
material then assumes the liquid or molten state and can undergo the usual 
processing techniques such as injection molding. When cooled, the terminal 
blocks of different macromolecules again physically bond to each other and 
form particles. The material then generally retains the shape it possessed 
when the particles formed by the terminal A blocks coalesced into the 
solid state. 
The class of molecules labeled monovinylarenes have provided suitable 
thermoplastic terminal A blocks for these polymers. Examples of the 
monomers which can polymerize into the terminal blocks include isoprene 
and alphamethyl isoprene. The former of these two has generally received 
greater use. 
The terminal A blocks generally have a molecular weight within the range of 
5,000 to 40,000, and most fall within the range of 8,000 to 20,000. The 
terminal blocks constitute about 20 to 50 percent of the total weight of 
the macromolecule. 
As discussed above, the elastomeric block copolymer molecule may include 
more than two or three blocks suggested by the A - B - A formula. The 
macromolecule may contain additional blocks arranged in either the linear 
or branched fashion. In this eventuality, the thermoplastic A block may 
not actually represent the terminal blocks at all ends of the molecule. In 
any event, the macromolecule generally has a total molecular weight 
falling within the range of 50,000 to 600,000. 
As mentioned previously, one or more of the block copolymers may be used in 
forming the composition. When more than one block copolymer is used, the 
block copolymers differ from each other with respect to the amounts of 
terminal A blocks and middle B blocks present therein. For instance, a 
mixture of a first block copolymer containing about 28 percent by weight 
styrene block A (e.g., Shell Kraton G 1650) and a second block copolymer 
containing about 33 percent by weight styrene block A (e.g., Shell Kraton 
G 1651) can be used. The weight ratio of the first : second block 
copolymer can vary from 15:85 to 50:50. 
The polysiloxane has the following repeating structure: 
##STR4## 
where R.sub.1, R.sub.2 =H, 
##STR5## 
and n is a positive integer between 10 and 20,000. The readily available 
silicone oils generally employ the methyl group for both of the radicals 
R.sub.1 and R.sub.2. The polysiloxane is essentially linear as shown in 
the above formula. A preferred example of the polysiloxane is silicone 
oil. 
The viscosity of the polysiloxane should permit its facile coating of and 
mixing with the crumbs or pellets of the elastomer. This results in a 
general requirement that the kinematic viscosity be within the range of 
about 20 to 1,000,000 centistokes at room temperature. At the lower end of 
the above range, the polysiloxane encounters some difficulty in coating 
the polymer pellets. As a preferred embodiment, silicone oil having a 
kinematic viscosity of 200 to 13,000 centistokes works well without 
complication. 
For the present invention, a medical grade polysiloxane should be employed. 
Furthermore, devolatilizing the polysiloxane prior to its introduction to 
the block copolymer removes very low molecular weight elements that could 
leach and irritate the patient's tissues. 
The polysiloxane generally constitutes about 0.1 to 12 percent of the total 
weight of the elastomeric composition, preferably from 1 to 7 percent. The 
ability of the hydrocarbon to take up this amount of the polysiloxane is 
surprising; the hydrocarbon backbone of the polymer has a drastically 
disparate nature as compared to the silicone structure of the 
polysiloxane. 
The surprise becomes even greater for polymeric compositions that already 
include substantial amounts of mineral oil as a lubricant. Mineral oil, if 
present, may account for up to 60 percent of the total weight of the 
composition. Typically, the mineral oil constitutes from 25 to 50 percent 
of the composition's total weight. 
Furthermore, the mineral oil and the polysiloxane also have distinctly 
different chemical properties. The former has a hydrocarbon composition as 
compared to the silicone of the polysiloxane. Moreover, the mineral oil 
fills the spaces that would presumably accommodate the polysiloxane. Yet, 
a composition having 50 percent of mineral oil can still assimilate 
several percent of the polysiloxane to produce a drastically different 
elastomer. 
Adding polypropylene as a binder to the present elastomeric composition 
produces a stiffening effect upon the elastomeric composition. The 
polypropylene also reduces its elasticity slightly. The amount of added 
polypropylene generally remains less than 45 percent of the composition's 
total weight. It more usually falls within the range of 2 to 20 percent or 
in the narrower range of 5 to 10 percent. The addition of bismuth 
oxychloride or barium sulfate provides the polymeric composition with an 
opacity to X-rays. Titanium dioxide pigment can also be added to affect 
the polymer's visual appearance. 
The following represents a summary of the weight percentages of the 
components in the present polymeric composition 
______________________________________ 
Weight % 
Component Broad Preferred 
______________________________________ 
Polysiloxane 0.1-12 1-7 
Polypropylene 0-45 1-30 
Mineral Oil 0-60 25-50 
Block copolymer balance 20-73 
______________________________________ 
The block copolymer is, by nature, a hydrophobic composition and its 
surface remains unwetted. Water absorption by the copolymer is low as 
indicated by ASTM-D-570. Scanning electron micrographs of the surface of 
the copolymer show a smooth, closed surface, free of surface interruptions 
or defects. Qualitative observation of the copolymer surface when wet with 
water indicates that the surface tends to have a slick and lubricious 
feel. No coating is used to obtain this surface characteristic which is 
believed to be inherent in the silicone nature of the surface. 
Both the surface smoothness and concentration of polysiloxane portend a 
blood and tissue compatibility of the material. Both factors reduce the 
likelihood of the attachment and clotting of blood components to the 
polymer. 
Preparing the elastomeric composition with the dispersed polysiloxane 
begins with the hydrocarbon block copolymer. The techniques for preparing 
the elastomeric thermoplastics appear in many references including the 
patents referenced above. The inclusion of the usual additives also 
appears in these discussions. 
Mixing the crumbs or pellets of one or more of the elastomeric copolymers, 
having different amounts of the constituent blocks, with the polysiloxane 
should result in a coating of the former with the latter. To do so, the 
pellets or crumbs and the polysiloxane may be mixed in a tumbler. Any 
additional ingredients, such as polypropylene, polystyrene, and/or 
stabilizer may also be added to the mixture at this point. 
The coated elastomer pellets or crumbs next receive sufficient heat to 
induce their melting. Applying a shearing pressure to the melted coated 
crumbs or pellets appears to induce a substantially uniform dispersement 
of the polysiloxane in the mixture. The heat required to effectuate the 
melting, of course, depends upon the individual elastomer. Typically, it 
ranges from 160.degree. C. to 225.degree. C. 
After melting the block copolymer by heating, the mixture comprising the 
block copolymer, the polysiloxane and other suitable ingredients described 
above may be optionally fed through a plurality of calender rolls to form 
sheets of the mixture. Thereafter, the sheets are subjected to shearing 
pressure by feeding the cut strips of sheets to an extruder or a 
compression molding machine for better dispersement of the polysiloxane. 
To ensure adequate dispersement of the polysiloxane, the composition is 
subjected to an appropriate amount of of pressure, usually about 1,500 
p.s.i. However, it has been found that by increasing the pressure, further 
improved properties of the product are obtained. Thus, the molten mixture 
may be subjected to pressures of 2,500 p.s.i., 3,000 p.s.i., or higher. 
An extruder provides the most convenient means of achieving the 
temperatures and pressures required to disperse the polysiloxane within 
the composition. An extruder typically has several temperature zones and 
thus can pass the crumbs or pellets of the polymer through the temperature 
stages required for melting. FIG. 1 shows an extruder screw generally at 
20 modified to apply a greater shearing pressure to the resin material. 
The screw 20 has the four zones characteristic of most extruder screws. The 
first section 21, known as the feed zone, initiates the melting of the 
polymer pellets and moves them along to the compression or transition zone 
22. In zone 22, the polymer generally completely melts and undergoes a 
sufficient shearing stress to cause thorough mixing of the ingredients. 
The metering section 23 usually provides the melted resin to the die at a 
known rate and pressure. Working section 30 allows mixing of the polymer 
melt. 
The screw shown in FIG. 1 has a length-to-diameter ("L/D") ratio of 24:1. 
In this type of screw, the metering section 23 typically has about 20 to 
25 percent of the total flights, or pitch lengths, of the entire screw. On 
the modified screw 20 shown in FIG. 1, the metering section 23 has ten 
flights 24 of the screw's total of 24.62 flights; the feed section 21 has 
6.62 flights 27, and the transition section 22 has eight flights. Thus, 
for the screw 20, the metering section 23 has 40 percent of the total 
flights. This large fraction of the flights increases the length of time 
that the resin remains in the metering section 23 and the amount of 
pressure applied to it. 
Furthermore, as shown in FIG. 1a, the flights 24 of the metering section 23 
have a much smaller cross-sectional area than the flights 27 of the feed 
section 21. In fact, the depth 28 of the feed-section flight 27 amounts to 
four times the depth 29 of the metering-section flight 24. This high 
compression ratio of 4:1 drastically increases the pressure applied to the 
material in the metering section 23. To increase the pressure even 
further, the compression ratio of the feedsection flights 21 to those in 
the metering section 23 may even go to 5:1 or higher. As this ratio 
increases, the material becomes squeezed into the smaller flights 24 and, 
thus experiences a greater shearing pressure. 
Naturally, the pressure experienced by the polymer in the flights 24 also 
depends upon the size of the orifice through which it passes when 
departing the extruder. At the small orifice sizes of 0.015, 0.010, or 
even 0.005 inch, only a small amount of resin leaves the extruder over a 
period of time. The remainder backs up against the orifice opening and 
maintains the pressure upon the polymer in the pump section 23. 
Larger orifices, of course, allow the pressure in the metering section 23 
to dissipate. However, placing a screen, called a breaker plate, adjacent 
to the screw's working section 30 can retain a sufficient back pressure on 
the metering section 23. This screen can have a mesh of 100 or finer. 
Placing additional obstacles in the path of the molten polymer beyond the 
breaker plate can also increase the pressure experienced in the metering 
section 23. Furthermore, a longer land, which is the distance along which 
the bore of the extruder narrows down to the orifice size, can also retain 
the desired pressure in the flights 24. A pressure blender and a mixing 
head can also give increased pressure. An extruder with the appropriate 
modification can deliver the resin to its die under a pressure of 3,000 
p.s.i. at the breaker plate. 
Once produced, the material, as a thermoplastic, will submit to the usual 
product-forming techniques. Thus, it can undergo further extrusion to a 
particular shape, if not achieved in the original extrusion. Moreover, its 
thermoplastic nature allows the reuse of scraps of material and of 
rejected parts. 
FIG. 2 illustrates one embodiment of the present invention. Enteral feeding 
tube, generally designated by the numeral 40, comprises a stem 42 having 
one end (proximal end) connected to female connector 44 integrally formed 
with plug 46 and the other end (distal end) connected to weighted bolus 
48. Both the connector 44 and weighted bolus 48 are attached to the stem 
42 by insert molding to be described below. 
In FIGS. 3-5, only the distal end of the enteral feeding tube is shown. It 
is understood that the proximal end of the tube is connected to a female 
connector with plug as shown in FIG. 2. 
FIG. 3 illustrates in further detail the bolus and stem. Bolus 50 is 
generally cylindrically shaped, having end 50a connected to stem 52 and 
the other end 50b being rounded or devoid of sharp edges to avoid injuring 
the patient. Disposed within bolus 50 is a central bore 54 which extends 
longitudinally from end 50a through almost the entire length of bolus 50. 
Bore 54 terminates at a distance from end 50b so as to define a closed 
end. A plurality of openings 56 connect bore 54 with the exterior of bolus 
50. Although four openings are shown in FIG. 3, this number is not 
critical as long as one or more openings are used. End 50a is joined to 
stem 52 which is in the form of a tube. Thus, liquid nutrient can be fed 
to a patient through the enteral feeding tube after the bolus has been 
inserted into the patient's stomach or intestines. Conversely, stomach 
fluids can be drained from the patient's stomach by using the enteral 
feeding tube. 
FIG. 4 shows another embodiment of the present invention. The construction 
of the bolus 60 is similar to that shown in FIG. 3, with the exception 
that central bore 62 extends through the entire length of the bolus. Thus, 
bolus 60 is provided with end opening 64 and side openings 66. 
FIG. 5 illustrates a further embodiment of the present invention. As shown 
in FIG. 5, enteral feeding tube 70 comprises only stem 72, no bolus being 
connected thereto. The distal end of stem 72 is provided with a plurality 
of openings 74 including end opening 76. 
In the above described embodiments, the stem is formed of the polymeric 
composition described hereinabove. More specifically, the formulation 
shown in Table I is most preferred. As shown in Table I, two block 
copolymers having different amounts of terminal A blocks and middle B 
blocks are used in forming the stem. 
TABLE I 
______________________________________ 
Material Components 
Weight % 
______________________________________ 
Kraton G-1651 15-20 
Shell Oil Co. 
Kraton G-1650 3-6 
Shell Oil Co. 
Polypropylene #5520 
1-5 
Shell Oil Co. 
Polypropylene #5820 
20-25 
Shell Oil Co. 
Polypropylene #467DP 
1-3 
Eastman Corp. 
Silicone Oil, #360 
3-5 
Dow Corning 
Mineral Oil 40-50 
Witco Chem Co. 
Stabilizer 0.01-0.1 
Irganox #1010 
Ciba Geigy Corp. 
______________________________________ 
In forming the stem, it may be desirable to add to the formulation a 
radiopaque material such as bismuth oxychloride or barium sulfate. In such 
an event, the amount of radiopaque material added usually constitutes 5% 
to 50% by weight of the resulting mixture. Generally, when bismuth 
oxychloride is used, this compound together with the polymeric composition 
are added to the extruder to form an extrudate containing about 5 to 20 
weight percent bismuth oxychloride. Alternatively, barium sulfate may be 
co-extruded as a stripe in the stem. In such an event, the amount of 
barium sulfate used constitutes about 10 to 50 weight percent of the 
resulting product. 
With reference to the weighted bolus, this is formed by mixing the 
polymeric composition with a heavy material such as tungsten particles. 
Since tungsten is non-toxic, its presence in the bolus does not adversely 
affect the health of the patient. The polymeric composition may comprise 
one or more of the thermoplastic elastomeric block copolymers having 
different amounts of terminal A blocks and middle B blocks. Other 
ingredients which may be present in the composition include polypropylene 
and mineral oil. The tungsten particles typically have an average particle 
diameter of about 2 to 6 microns (150 mesh). The material for the bolus 
comprises from about 10 to 20 weight percent of the polymeric composition 
containing the thermoplastic elastomeric hydrocarbon block copolymer and 
from about 80 to 90 weight percent of the tungsten powder. 
A typical formulation for the bolus is shown in Table II. 
TABLE II 
______________________________________ 
Material Components Weight % 
______________________________________ 
Tungsten powder, 150 mesh 
85-90 
Kraton G-1651 4-6 
Shell Oil Co. 
Kraton G-1650 1-2 
Shell Oil Co. 
Polypropylene #467DP 
0.3-0.5 
Eastman Corp. 
Polypropylene #5520 0.1-0.2 
Shell Oil Co. 
Polypropylene #5820 0.2-0.6 
Shell Oil Co. 
Silicone Oil #360 0.3-0.7 
Dow Corning 
Mineral Oil 4-6 
Witco Chem Co. 
Stabilizer, Irganox #1010 
0.006 
Ciba-Geigy Corp. 
______________________________________ 
As to the integrally formed female connector and plug, these are made of 
the above-described thermoplastic elastomeric hydrocarbon block copolymer. 
For easy identification, the connector and plug are usually colored. Thus, 
a typical formulation for the connector and plug is shown in Table III. 
Both the female connector with plug and weighted bolus are directly 
conected to the stem by insert molding. Since all of the parts are made of 
the same general polymeric composition, a very firm bond is obtained. 
It has been found that the stem can be most conveniently formed by 
extrusion. The female connector with plug and weighted bolus are then 
formed onto the stem by injection molding. 
TABLE III 
______________________________________ 
Material Components 
Weight % 
______________________________________ 
Kraton G-2705 97.00 
Shell Oil Co. 
Silicone Oil #360 1.98 
Dow Corning 
Colorant .991 
______________________________________ 
The present invention is further illustrated in the following examples. 
Since the examples are for illustration, they are not to be construed as 
limiting. 
EXAMPLE 1 
This example illustrates the formation of the stem portion of the present 
enteral feeding tube. 
20 lbs of a polymer composition having the following formulation is mixed 
with 2 lbs of barium sulfate and fed to the hopper of a 1" Killion 
extruder. 
______________________________________ 
Material Components 
Weight % 
______________________________________ 
Kraton G-1651 18.4 
Shell Oil Co. 
Kraton G-1650 4.6 
Shell Oil Co. 
Polypropylene #5520, 
3.0 
Shell Oil Co. 
Polypropylene #5520 
23.0 
Shell Oil Co. 
Polypropylene #467DP 
2.0 
Eastman Corp. 
Silicone Oil #360 4.0 
Dow Corning 
Mineral Oil 45.0 
Witco Chem Co. 
Stabilizer, Irganox #1010 
0.05 
Ciba Geigy Corp. 
Total 100.05 
______________________________________ 
The mixture is extruded into a tubing under the conditions set forth below. 
______________________________________ 
Feed Zone temperature 
300.degree. F. 
Transition Zone temperature 
350.degree. F. 
Metering Zone temperature 
355.degree. F. 
Working Zone (die) temperature 
360.degree. F. 
Screen packs 40-60-80 mesh 
Extruder speed 23 ft./min. 
______________________________________ 
The tubing is cut to 351/2 inch length and marked at 19.7 inch from one 
end. 
EXAMPLE 2 
This example shows the preparation of the polymeric composition used for 
forming the weighted bolus. 
0.069 lb of a block copolymer A-30 and 0.056 lb. of a block cololymer A-50, 
the formulations for both A-30 and A-50 being shown below, are prepared. 
______________________________________ 
Material Components 
Weight % 
______________________________________ 
Block copolymer A-30 
Kraton G-1651 32.2 
Shell Oil Co. 
Kraton G-1650 13.8 
Shell Oil Co. 
Polypropylene #467DP 
5.0 
Eastman Corp. 
Silicone Oil #360 4.0 
Dow Corning 
Mineral Oil 45.0 
Stabilizer, Irganox #1010 
0.05 
Ciba Geigy Corp. 
Total 100.05 
Block copolymer A-50 
Kraton G-1651 30.4 
Shell Oil Co. 
Kraton G-1650 7.6 
Shell Oil Co. 
Polypropylene #5520 
3.0 
Shell Oil Co. 
Polypropylene #5820 
8.0 
Shell Oil Co. 
Polypropylene #467DP 
2.0 
Eastman Corp. 
Silicone Oil #360 4.0 
Dow Corning 
Mineral Oil 45.0 
Witco Chem Co. 
Stabilizer, Irganox #1010 
0.05 
Ciba Geigy 
Total 100.05 
______________________________________ 
0.875 lb. of tungsten powder, 150 mesh, having an average diameter of 2 to 
6 microns, is divided into three approximately equal portions. 
The copolymers which are in pellet form are fed to a Banbury mixer 
operating at 50 rpm, Sterlco Banbury temperature (.degree.F.) of 400/300, 
drop temperature (.degree.F.) of 320/340 with a total mixing time of 25-35 
minutes. The copolymers are mixed for about 6-9 minutes. The first portion 
of the tungsten powder is added, with the mixture being mixed for about 
4-6 minutes. Thereafter, the second portion of tungsten powder is added 
and mixed for about 7-9 minutes. The last portion of the tungsten powder 
is then added and mixed for about 10 to 12 minutes. 
The mixture is removed from the Banbury mixer, placed on a two-roll mill 
and rolled into a sheet having a thickness of about 0.075 to 0.250 inch. 
The formed sheet is permitted to cool at room temperature for about 10 to 
30 minutes, after which it is granulated. 
Although it is shown in this Example that two separate block copolymer 
formulations A-30 and A-50 are mixed, it is understood that a single 
formation having the identical composition as the combined formulations 
can be used. Since there is no reaction among the ingredients forming the 
block copolymer, the sequence of mixing of the ingredients is immaterial. 
EXAMPLE 3 
This example illustrates the formation of a colored female connector and 
plug which are joined to the stem of Example 1. 
0.99 lb. of block copolymer A-50M described below is mixed with 0.01 lb. of 
orange colorant. 
______________________________________ 
Material Components 
Weight % 
______________________________________ 
Kraton G-2705 98 
Shell Oil Co. 
Silicone Oil #360 2 
Dow Corning 
______________________________________ 
The mixture is then added to a Banbury mixer which is operated under the 
following conditions: 
______________________________________ 
Drop temperature, .degree. F. 
310 
Sterlco Banbury temperature, .degree.F. 
410/320 
Screw speed 50 rpm 
Mix time 15 minutes 
______________________________________ 
Thereafter, the mixture is placed on a two-roll mill at a speed setting of 
15 ft./min. and formed into a sheet which is then granulated. 
To form the female connector onto the stem of Example 1, a 15-ton Boy press 
is used and operated under the following conditions: 
______________________________________ 
Mold temperature, both halves, .degree.F. 
120.degree. F. 
Nozzle heat set at 60 on Variac 
Front zone temperature, .degree.F. 
450 
Rear zone temperature, .degree.F. 
430 
Injection speed full open 
Screw RPM 200 
Mold open time 1 sec. 
Injection time 3.5 sec. 
Cool time 15 sec. 
Shot size setting 13 
Cushion 1/8 inch 
______________________________________ 
The mold is opened and the tubing is placed on to the core pin; care is 
exercised to insure placement of the tubing into the tubing channel. The 
core pin is placed into the mold. The mold is closed and the 
copolymer/colorant mixture is injected to form the connector. When the 
mold opens, the formed product is removed from the core pin and inspected 
for major molding flaws such as sinks and short-shot. 
The weighted bolus is then insert molded onto the marked other end of the 
stem using a 15 ton Boy press under the same conditions. The polymeric 
material injected is that shown in Example 2.